Body as a Whole
2B01
Key word: Adjuvant Treatment of Colon Cancer
Author: Ibrahim Sultan, MD
Editor: Elizabeth C. Wick, MD
A 60-year-old man undergoes a right hemicolectomy for colon adenocarcinoma. The pathology revealed a tumor with negative microscopic margins, well-differentiated histology, and 10 lymph nodes in the specimen. He was found to have a stage II (T2N0M0) tumor. Which of the following characteristics place him at a higher risk, thus making him a potential candidate for adjuvant therapy?
Age
Highly differentiated histology
Location of the tumor
Number of sampled lymph nodes
T2 lesionView Answer
Answer: (D) Number of sampled lymph nodes
Rationale:
Adjuvant therapy is typically reserved for patients with stage III colon adenocarcinoma. The advantage of adjuvant therapy for patients with node negative disease has not been clearly proven, but there may be a survival advantage of 2% to 5% in 5 years for certain groups of patients. Specific characteristics of stage II or node negative patients that may indicate a benefit with adjuvant therapy include T4 lesions, inadequate nodal sampling (<12), lymphovascular invasion, poorly differentiated histology, and bowel perforation.
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References:
Compton C, Hawk E, Grochow L, et al. Colon cancer. In: Abeloff MD, Armitage JO, Niederhuber JE, Kastan MB, McKenna WG, eds. Abeloff’s Clinical Oncology. 4th ed. Philadelphia, PA: Churchill Livingstone Elsevier; 2008: 1477-1524.
Morris A. Colorectal cancer. In: Mulholland MW, Lillemoe KD, Doherty GM, Maier RV, Simeone DM, Upchurch GR, eds. Greenfield’s Surgery: Scientific Principles and Practice. 5th ed. Philadelphia, PA: Lippincott Williams and Wilkins; 2011.
Saltz LB. Adjuvant therapy for colon cancer. Surg Onc Clin N Am. 2010;19:819-827.
2B02
Key word: Antibiotic Prophylaxis of Surgical Site Infection
Author: Joshua C. Grimm, MD
Editor: Elizabeth C. Wick, MD
A 65-year-old male is undergoing an elective left inguinal hernia repair. With regard to his risk of surgical site infection, which of the following is true?
A surgical site infection is defined as one occurring within 60 days of the procedure or within 6 months if an implant is left in place
Administration of most preoperative antibiotics should be within 1 hour of incision
Antibiotics are given postoperatively because there is documented proof that they decrease the risk of surgical site infection after wound closure
If the procedure necessitates drain placement, studies have shown a decrease in infection rates if antibiotics are continued until they are removed
Routine use of vancomycin for antibiotic prophylaxis is recommendedView Answer
Answer: (B) Administration of most preoperative antibiotics should be within 1 hour of incision.
Rationale:
In order to curb the increasing prevalence of surgical site infections, the Surgical Care Improvement Project (SCIP) was designed and implemented. It outlines six infection prevention measures, including the timing of preoperative antibiotic administration, duration of therapy, and appropriate selection depending on the case type to ensure adequate coverage. Most antibiotics should be given within 1 hour of incision (vancomycin and some fluoroquinolones being the exception due to prolonged infusion times). A surgical site infection is defined as an infection occurring within 30 days of the procedure date or within 1 year if an implant is left in place. The antibiotic chosen should cover the most likely infective agent encountered during the given operation but need not cover every potential pathogen. Preoperative antibiotics should be used in every clean-contaminated procedure and selectively in clean procedures. Routine use of vancomycin is not recommended, but it can be implemented in patients with beta-lactam allergy or in institutions with a preponderance of methicillin-resistant Staphylococcus aureus. There is no benefit in prolongation of antibiotic therapy for greater than 24 hours after the procedure. Some cardiothoracic surgeons advocate antibiotic use for 48 hours due to the impact of cardiopulmonary bypass on immune modulation and pharmacokinetics, however. While some surgeons continue antibiotics until surgical drains are removed, there is no evidence to support such actions on the basis of decreasing wound infections, and this practice should not be continued.
References:
Bosco JA 3rd, Slover JD, Haas JP. Perioperative strategies for decreasing infection: a comprehensive evidence-based approach. J Bone Joint Surg Am. 2010;92(1):232-239.
Edwards FH, Engelman RM, Houck P, et al. The Society of Thoracic Surgeons practice guideline series: antibiotic prophylaxis in cardiac surgery, part I: duration. Ann Thorac Surg. 2006;81(1):397-404.
Horan TC, Gaynes RP, Martone WJ, et al. CDC definitions of nosocomial surgical site infections, 1992: a modification of CDC definitions of surgical wound infections. Infect Control Hosp Epidemiol. 1992;13(10):606-608.
Mangram AJ, Horan TC, Pearson ML, et al. Guideline for prevention of surgical site infection, 1999. Hospital Infection Control Practices Advisory Committee. Infect Control Hosp Epidemiol. 1999;20(4):250-278.
2B03
Key word: Characteristics of Early Excision of 40% Total Body Surface Area Burns
Author: Joshua C. Grimm, MD
Editor: Pamela A. Lipsett, MD, MHPE, FACS, FCCM
A 27-year-old man was injured in a chemical plant explosion and presented to the hospital with burns covering over 50% of his total body surface area (TBSA). Early excision is planned. Which of the following statements is true concerning his condition?
Early excision of burns prolongs the inflammatory phase of healing
Early excision of burns results in a decreased risk of infection
Hypertrophic scarring is a complication of early excision
Early excision should occur in one procedure in extensive burns (>40% TBSA)
With improved burn care, infection no longer carries significant morbidityView Answer
Answer: (B) Early excision of burns results in a decreased risk of infection
Rationale:
Early surgical excision and grafting of burns has been an ongoing area of focus and debate. Until recently, however, the morbidity and mortality associated with early excision created a surgical dilemma. Advances in the care of critically ill burn patients in the intensive care unit setting have now afforded surgeons the ability to undertake early, aggressive treatment in burn injuries.
Burn wound excision should occur within the first few days of the injury and results in improved survival. The goals of this strategy are to reduce the period of inflammation (which results in greater function and improved cosmetic result by decreasing the incidence of hypertrophic scaring) and to diminish the risk of infection (which carries a significant morbidity). Despite these benefits, several studies have demonstrated reduced complications when less than 20% of burned surfaces are removed in a single procedure. Therefore, large body surface area burns should be excised with serial procedures.
References:
Barret JP, Herndon DN. Modulation of inflammatory and catabolic responses in severely burned children by early burn wound excision in the first 24 hours. Arch Surg. 2003;138:127-132.
Deitch EA, Wheelahan TM, Rose MP, et al. Hypertrophic burn scars: analysis of variables. J Trauma. 1983;23:895-898.
Engrav LH, Heimbach DM, Reus JL, Harnar TJ, et al. Early excision and grafting vs. nonoperative treatment of burns of indeterminate depth: a randomized prospective study. J Trauma. 1983;23:1001-1004.
2B04
Key word: Characteristics of Epidural Analgesia
Author: Brenessa M. Lindeman, MD
Editor: Asad Latif, MBBS, MPH
Which of the following is most likely to occur with use of local anesthetics administered via an epidural catheter for pain control following thoracic surgery?
Regional vasodilation
Renal toxicity
Respiratory depression
Temporary leg weakness
Urinary retentionView Answer
Answer: (A) Regional vasodilation
Rationale:
Epidural catheters are a method of regional anesthesia and utilize local anesthetic agents either alone or in combination with other drugs such as opioids. Autonomic nerves are the most sensitive to the effects of local anesthetics, followed by sensory nerves and then, motor nerves. This sensitivity pattern can lead to loss of sympathetic vasomotor tone and subsequently hypotension, particularly in dehydrated or hemodynamically unstable patients. Epidural catheters are intended to provide analgesia only to the body region where an operation is performed. With a thoracic epidural, the coverage area of the block does not routinely extend to the lumbar spine. This coverage means that urinary retention and leg weakness should not occur, unlike when an epidural catheter is placed in the lumbar region. Renal toxicity and muscle tremors are not associated with epidural anesthesia. Respiratory depression is possible when opioids are also administered via the epidural catheter, although this side effect is infrequent given the relatively small doses of opioid that are typically used.
Reference:
Catterall WA, Mackie K. Local anesthetics. In: Brunton LL, Chabner BA, Knollmann BC, eds. Goodman & Gilman’s Pharmacologic Basis of Therapeutics. 12th ed. New York, NY: McGraw-Hill; 2011. http://www.accessanesthesiology. com/content/16665256. Accessed May 20, 2013.
2B05
Key word: Immunosuppressant Side Effects
Author: Isaac Howley, MD
Editor: Andrew M. Cameron, MD, PhD
A 59-year-old male presents to clinic 2 years after a deceased donor kidney transplant for diabetic nephropathy. His creatinine is now 1.7 mg/dL, up from a stable baseline of 1.1 mg/dL following his transplant. His blood glucose levels have been well controlled, with HbA1c of 6.2%. You perform a percutaneous core-needle biopsy, which shows no evidence of rejection. Which of the following immunosuppression medications is most likely contributing to this patient’s increasing renal insufficiency?
Azathioprine
Mycophenolate mofetil (MMF)
Prednisone
Sirolimus
TacrolimusView Answer
Answer: (E) Tacrolimus
Rationale:
All immunosuppressive agents currently in use have clinically significant side effects. Medications differ both in their mechanisms of action, side effect profiles, and drug interactions. Most patients following abdominal organ transplantation require a three-drug maintenance regimen, most typically consisting of a corticosteroid (prednisone), an antiproliferative agent (azathioprine or MMF), and a T-cell directed immunosuppressant (tacrolimus, cyclosporine, or sirolimus). Determining the most appropriate immunosuppressive regimen for a given patient is contingent on a balance of these factors.
Glucocorticoids such as prednisone work through inhibiting macrophage and T-cell cytokine production, inhibiting macrophage activation, and suppressing prostaglandin synthesis. Side effects may be significant and include hypertension, hyperglycemia, truncal obesity, mood lability, cataract formation, pancreatitis, and osteoporosis.
MMF is perhaps the least toxic of the standard immunosuppressant medications. It interferes with purine metabolism and therefore with lymphocyte proliferation. It may cause leukopenia, but the most common side effect is diarrhea, which may be mitigated by administering the drug in divided doses or in enteric-coated formulations. Azathioprine is a purine analogue that has essentially been supplanted by MMF due to its improved efficacy. Azathioprine may cause leukopenia and hepatic insufficiency.
Tacrolimus and sirolimus inhibit the production of IL-2 via binding to FK binding protein, which then blocks the phosphatase activity of calcineurin, an upstream regulator of IL-2 transcription. These medications therefore have potent antilymphocyte activity without affecting other cell lines. Tacrolimus is associated with alopecia, post-transplant diabetes, hypertension, nephrotoxicity, and neurotoxicity. Compared to tacrolimus, sirolimus causes less significant nephrotoxicity, although it may cause hypertriglyceridemia, proteinuria, thrombocytopenia, anemia, and profound impairment of wound healing.
Reference:
Granger DK, Ildstad ST. Transplantation immunology and immunosuppression. In: Townsend CM, Beauchamp RD, Evers BM, Mattox KL, eds. Sabiston Textbook of Surgery. 18th ed. Philadelphia, PA: Saunders Elsevier; 2008:655-691.
2B06
Key word: Characteristics of Necrotizing Soft Tissue Infections
Author: Robert A. Meguid, MD, MPH
Editor: Pamela A. Lipsett, MD, MHPE, FACS, FCCM
A 34-year-old HIV-positive man presents with a swollen, erythematous, and painful left forearm. He reports that the redness began after injecting heroin into his left hand web spaces 2 days prior. On examination, the skin overlying his arm is blistered, he is unable to flex his hand or wrist, and you palpate crepitus along his forearm. Which of the following is true regarding these types of infections?
Antibiotic therapy is the primary management modality
Clostridium perfringens is the most frequently cultured organism in necrotizing soft tissue infections
Group A β-hemolytic Streptococcus is more common than Clostridium perfringens in monomicrobial infections
Most necrotizing soft tissue infections are polymicrobial
Surgical debridement should be performed 48 hours after presentation to provide adequate interval for response to antibioticsView Answer
Answer: (D) Most necrotizing soft tissue infections are polymicrobial
Rationale:
Immunocompromised patients are more susceptible to necrotizing soft tissue infections than the general population. Approximately 75% of necrotizing soft tissue infections are due to polymicrobial infections, with the most frequently cultured species of organisms being Streptococcus and Bacteroides. However, in cases in which a single pathogen is cultured (monomicrobial infections), anaerobic bacteria (such as Clostridium species) are more commonly identified than aerobic bacteria.
Patients often present with a recent history of an identifiable inoculation with microorganisms, such as intravenous drug administration, trauma, cutaneous infections, or insect bites. Characteristic findings on physical examination include erythema, tenderness, tense edema, bullae, crepitus, and skin necrosis. Liquefactive necrosis of the fascia and adjacent soft tissue produces a characteristic dish-water-like drainage. Patients may rapidly progress to septic shock.
Treatment relies on early diagnosis based on a high index of suspicion for necrotizing soft tissue infection. In addition to administration of broad-spectrum antibiotics, surgical debridement should be performed immediately. Debridement entails wide resection of infected tissue to reach uninfected margins. Serial debridement is often necessary to ensure thorough resection of infected tissue. Delay in surgical debridement beyond 24 hours is associated with a doubling of mortality. Supportive therapy such as intensive monitoring and hemodynamic resuscitation are important, given the high rate of sepsis associated with necrotizing soft tissue infections.
References:
Dellinger EP. Surgical Infections. In: Mulholland MW, Lillemoe KD, Doherty GM, Maier RV, Upchurch GR, eds. Greenfield’s Surgery: Scientific Principles and Practice. 5th ed. 132-146. Philadelphia, PA: Lippincott Williams and Wilkins; 2011.
Manahan MA, Milner SM, Freeswick P, et al. Necrotizing skin and soft tissue infection. In: Cameron JL, ed. Current Surgical Therapy. 9th ed. Philadelphia, PA: Mosby; 2008:1128-1131.
2B07
Key word: Characterization of Process Measures
Author: Brenessa M. Lindeman, MD
Editor: Martin A. Makary, MD, MPH
Which of the following is the definition of a process measure as utilized in health care?
A health state of a patient resulting from health care used to assess the extent that health care services influence the likelihood of desired outcomes
A measurement of patients’ perspective of their experience in the hospital
A summary of performance obtained by combining information from more than one individual measure
An indicator that assesses a health care service provided to, or on behalf of, a patient often used to assess adherence to recommendations for clinical practice based on evidence or consensus
The percentage of patients who had a good medical outcomeView Answer
Answer: (D) An indicator that assesses a health care service provided to, or on behalf of, a patient often used to assess adherence to recommendations for clinical practice based on evidence or consensus.
Rationale:
Measures used to assess and compare the quality of care provided to patients are classified as structure, process, and outcomes measures. Structure measures examine physical equipment, facilities, and available personnel. Process measures assess whether patients receive specific health care services, which are known to be good care based on their condition. For example, if one was examining the quality of care received by patients with diabetes, one might assess the proportion of diabetic patients who had undergone an annual fundoscopic examination by an ophthalmologist. Such measures are used because research has demonstrated a link between those processes and important outcomes.
Outcome measures, on the other hand, attempt to assess the effects of medical care on the health status of patients (e.g., an improvement in symptoms, morbidity, or mortality). Outcome measures therefore attempt to measure the sum of multiple health care services/processes provided to an individual. Together process and outcome measures provide a more comprehensive view of the quality of health care compared to either one alone.
A national initiative to improve outcomes for patients having surgery is the Surgical Care Improvement Project, or SCIP. SCIP is a collaborative partnership between surgeons, anesthesiologists, nurses, pharmacists and others to reduce preventable surgical morbidity and mortality. Begun in 2003, the measures primarily focus on care processes and center around prevention of surgical site infection (e.g., appropriate antibiotics, given within 1 hour of incision, and discontinued within 24 hours of the procedure), venous thromboembolism (e.g., appropriate prophylaxis ordered and continued postoperatively), cardiac events (e.g., appropriate administration of perioperative beta-blockers), or prevention of respiratory complications (e.g., elevation of the head of the bed to at least 30 degrees for patients receiving mechanical ventilation, appropriate stress ulcer disease prophylaxis, etc.).
Answer (A) is the definition of outcome measures. Answer (B) is the definition of patient experience measures. Answer (C) is the definition of composite measures. Answer (E) is an outcome measure.
References:
Bratzler DW, Hunt DR. The surgical infection prevention and surgical care improvement projects: national initiatives to improve outcomes for patients having surgery. Clin Infect Dis. 2006;43(3):322-330.
Brook RH, McGlynn EA, Cleary PD. Quality of health care. Part 2: measuring quality of care. N Engl J Med. 1996; 335(13):966-970.
Donabedian A. The quality of care. How can it be assessed? JAMA. 1988;260(12):1743-1748.
2B08
Key word: Definition of Active and Latent Error
Author: Raja Mohan, MD
Editor: Martin A. Makary, MD, MPH
When a physician places an order for a medication in an electronic ordering system, the system checks to see if the patient has an allergy to that medication. In addition, a pharmacist checks the dose and type of medication to ensure that it is appropriate for the patient. Afterwards, a nurse administers the medication and has to scan the patient’s ID badge before doing so. In one isolated case, a nurse administered the medication without checking the patient’s name, and the patient experienced an adverse reaction to the medication. This scenario is an example of which of the following?
Active error
Close call
Latent error
Near-miss
Systems errorView Answer
Answer: (A) Active error
Rationale:
Errors in prescribing, dispensing and administering medications are common in health care and result in significant human and financial cost. A report issued by the U.S. Institute of Medicine concluded that medication-related adverse events are the single leading cause of injury, harming at least 1.5 million people every year and causing extra medical costs of up to $3.5 billion per year. It is estimated that up to 7,000 people die annually from medication errors.
Human errors can be classified as “latent errors” and “active errors.” Latent errors refer to failures of routines or systems that either contribute to the occurrence of errors or allow them to cause harm. In other words, latent errors are “accidents waiting to happen.” Latent errors are synonymous with systems errors. Causes of latent errors can be ambiguous drug references, drug storage issues, lack of independent double checks, or incomplete patient information, such as a missing allergy. On the other hand, active errors are the unsafe acts committed by people who are in direct contact with the patient. They can be caused by a variety of reasons, such as mistakes, lapses in judgment, or procedural violations. Nearmisses and close calls are errors that occur but do not cause an adverse event.
References:
Bates DW. Preventing medication errors: a summary. Am J Health Syst Pharm. 2007;64(14 Suppl 9):S3-S9, quiz S24-S26.
Glavin RJ. Drug errors: consequences, mechanisms, and avoidance. Br J Anaesth. 2010;105(1):76-82.
Reason J. Human error: models and management. BMJ. 2000;320(7237):768-770.
2B09
Key word: Diagnosis of Incarcerated Femoral Hernia
Author: Kyle J. Van Arendonk, MD, PhD
Editor: Barish H. Edil, MD
A 57-year-old woman with no past medical or surgical history presents to the emergency room with pain in her groin. She reports that the pain has become so severe that she is nauseous and has vomited multiple times over the past day. On physical examination, her abdomen is distended, and a small, irreducible mass is palpated inferior and lateral to the pubic tubercle. Which of the following statements is correct?
Incarceration and strangulation rarely occur with this condition
The presence of a preformed peritoneal sac causes this congenital condition
This condition typically requires a laparotomy to obtain adequate exposure
This diagnosis is seen most commonly in middle-aged and older women
Watchful waiting is appropriate if reduction can be achievedView Answer
Answer: (D) This diagnosis is seen most commonly in middleaged and older women
Rationale:
Hernia is the third most common cause of intestinal obstruction after adhesions and cancer. Examination of a patient with intestinal obstruction should therefore include a careful examination of the entire abdominal wall and groin to look for the presence of any hernias. Femoral hernias are relatively rare compared to inguinal hernias, accounting for approximately 10% of all groin hernias. They most commonly occur in women and in patients of age 40 to 70 years old.
The femoral canal is just medial to the femoral vessels and normally just contains lymphatics and adipose tissue and ends blindly. With femoral hernias, however, preperitoneal fat, bladder, or peritoneal sac (with or without intraperitoneal contents) passes through the femoral ring and through the femoral canal, becoming clinically evident when passing distally through the femoral orifice, which is bound posteriorly by the pectineal fascia, laterally by the femoral sheath, anteriorly by the fascia lata, and medially by the iliopubic tract. The etiology of femoral hernias is thought to be acquired, rather than congenital, and caused by persistently elevated intra-abdominal pressure.
Differentiating between a femoral and inguinal hernia through physical examination can be somewhat difficult, and often definitive diagnosis is not obtained until surgery. On examination, the pubic tubercle is typically palpable superior and medial to a femoral hernia but inferior and lateral to an inguinal hernia. In addition, if the hernia is reduced, a finger can be placed over the medial end of the inguinal ligament: With Valsalva, a femoral hernia should then appear inferior
to the finger, while an inguinal hernia should appear superior to the finger.
to the finger, while an inguinal hernia should appear superior to the finger.
Femoral hernias have a propensity to incarcerate and therefore more frequently require emergency surgery and bowel resection compared to inguinal hernias. All femoral hernias require surgical repair and can be corrected via a femoral, inguinal, or preperitoneal approach with suture, mesh, or both. Each approach has its advantages and disadvantages, and any technique can be applied in the absence of incarceration or strangulation. With incarcerated or strangulated femoral hernias, the femoral and laparoscopic totally extraperitoneal (TEP) repairs should be avoided. In cases of strangulation, prosthetic mesh should not be used, but biologic mesh can still be considered.
Reference:
Swartz DE, Felix EL. Femoral hernia. In: Yeo CJ, ed. Shackelford’s Surgery of the Alimentary Tract. 7th ed. Philadelphia, PA: Saunders Elsevier; 2013:547-555.
2B10
Key word: Diagnosis of Paradoxic Aciduria
Author: Jens U. Berli, MD
Editor: Pamela A. Lipsett, MD, MHPE, FACS, FCCM
You are called to the emergency department to assess a 17-year-old female with abdominal pain and suspicion of an incarcerated inguinal hernia. She has bulimia and has had several admissions to the psychiatric ward. The hernia is nonreducible, and you schedule her for surgery. Her laboratory values come back as follows:
WBC 11,000/mm3
Hbg 11.0 g/dL
Lactic acid 3.1 mg/dL
Na 140 mEq/L
Cl 96 mEq/L
K 2.9 mEq/L
Blood pH 7.49
Urine pH 6.1
The medical student asks you why her urine is acidotic in the setting of a metabolic alkalosis. Your answer is:
The patient has a renal tubular acidosis leading to low pH of the urine
The patient likely has a urinary tract infection with acidproducing bacteria
The patient’s gastrointestinal losses stimulate the renin-angiotensin-aldosterone axis, decreasing HCO3– excretion into the urine
The patient’s gastrointestinal losses stimulate the renin—angiotensin-aldosterone axis, increasing H+ excretion into the urine
To help with weight loss, the patient is taking a diuretic that acidified the urineView Answer
Answer: (D) The patient’s gastrointestinal losses stimulate the renin—angiotensin-aldosterone axis, increasing H+ excretion
Rationale:
The patient described above is suffering from loss of gastric fluid rich in chloride and to a lesser degree hydrogen ion (H+) and potassium. This leads to an overall net loss of H+ causing a metabolic alkalosis. The body’s ability to correct a metabolic alkalosis is limited as respiratory and renal compensation are inefficient. Instead, the hypovolemia and electrolyte losses lead to activation of the renin—angiotensin-aldosterone system, in which aldosterone acts to reabsorb sodium in exchange for potassium. This also leads to water reabsorption. Potassium is then exchanged for H+ leading to the paradoxical aciduria in the setting of contraction alkalosis. The release of antidiuretic hormone is also stimulated, which assists in absorption of free water.
Renal tubular acidosis leads to a normal anion gap metabolic acidosis and alkalotic urine. Bacteria (urinary tract infection) can lead to alkalotic urine due to splitting of urea into ammonia.
References:
Galla JH. Metabolic alkalosis. J Am Soc Nephrol. 2000;11(2): 369-375.
Marino PL. Metabolic alkalosis. The ICU book. 3rd ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2006:565-576.
2B11
Key word: Diagnosis of Refeeding Syndrome
Author: Said C. Azoury, MD
Editor: Elliott R. Haut, MD, FACS
A cachectic-appearing 45-year-old female with a history of long-term alcoholism is admitted for recurrent small bowel obstruction after multiple episodes of nausea and vomiting for the past 5 days. She is managed conservatively with a nasogastric tube, NPO status, intravenous fluids, and total parenteral nutrition (TPN). The best way to prevent the development of refeeding syndrome in this patient is:
Avoid hyponatremia by adjusting the sodium amount in the TPN bag on a daily basis
Follow daily nutritional laboratory values such as prealbumin and triglycerides to ensure that the nutritional needs of the patient are being met
Institute caloric repletion rapidly, at 40 kcal/kg/day and slowly increase rate after the first week
Monitor closely for hypoglycemia, a common paradoxical effect of excessive parenteral feeding of severely malnourished patients
Strictly monitor vital signs and fluid balance and replete electrolytes as neededView Answer
Answer: (E) Strictly monitor vital signs and fluid balance and replete electrolytes as needed
Rationale:
Refeeding syndrome (RFS) may be described as the metabolic disturbances, clinical manifestations, and complications that occur with excessive and rapid feeding of patients with severe underlying malnutrition. RFS was first recognized and described in World War II when victims of starvation were noted to experience cardiac or neurologic dysfunction after being reintroduced to food. RFS can result in serious harm and death. The hallmark biochemical feature of refeeding syndrome is hypophosphatemia. However, hypokalemia, hypomagnesemia, and changes in sodium, fluid balance, glucose, protein, and fat metabolism may also be seen. Electrolyte disturbances occur within 12 to 72 hours of refeeding and can continue for the next 2 to 7 days. Cardiac complications can develop within the first week, most commonly within the first 24 to 48 hours, while neurologic signs and symptoms develop somewhat later.
The pathophysiology of RFS relies on the fact that during starvation, secretion of insulin is decreased in response to the reduced intake of carbohydrates. Fat and protein stores are instead used to produce energy. This leads to intracellular loss of electrolytes, in particular, phosphate. Malnourished patients can have depleted intracellular phosphate stores despite normal serum phosphate concentrations. With reintroduction of nutrition to a malnourished individual, a sudden shift from fat to carbohydrate metabolism occurs, leading to increased insulin secretion. Insulin stimulates cellular uptake of phosphate, potassium, and magnesium, thus
leading to hypophosphatemia, hypokalemia, and hypomagnesemia. The electrolyte disturbances and fluid overload that result with refeeding can produce the clinical features of RFS, which include rhabdomyolysis, respiratory failure, cardiac failure, arrhythmias, hypotension, seizures, coma, and sudden death. Early clinical features of RFS are nonspecific and may go unrecognized; therefore high clinical suspicion is critical in order to recognize and treat the syndrome. Postoperative patients and patients with anorexia nervosa, chronic alcoholism, and cancer are known to be at high risk for RFS and should be followed carefully.
leading to hypophosphatemia, hypokalemia, and hypomagnesemia. The electrolyte disturbances and fluid overload that result with refeeding can produce the clinical features of RFS, which include rhabdomyolysis, respiratory failure, cardiac failure, arrhythmias, hypotension, seizures, coma, and sudden death. Early clinical features of RFS are nonspecific and may go unrecognized; therefore high clinical suspicion is critical in order to recognize and treat the syndrome. Postoperative patients and patients with anorexia nervosa, chronic alcoholism, and cancer are known to be at high risk for RFS and should be followed carefully.
RFS can occur with both enteral and parenteral feeding. Prevention is the key to successful management. RFS can be avoided by identifying patients at risk early, restarting feeding at a reduced calorific rate (i.e, “permissive underfeeding” with 25% to 50% of estimated requirements), avoiding rapid increases in the amount of daily calories ingested for 3 to 7 days, and closely monitoring the patients during the refeeding process. Correction of electrolyte abnormalities, especially magnesium and potassium, and fluid imbalances is performed alongside feeding. If the syndrome is detected, the rate of feeding should be slowed, and essential electrolytes should be repleted. The cardiovascular system should be evaluated closely, and the fluids provided should be limited. Most fatalities are due to cardiac complications since atrophy of the heart during starvation renders the patient more vulnerable to fluid overload and heart failure.
References:
Mehanna HM, Moledina J, Travis J. Refeeding syndrome: what it is, and how to prevent and treat it. BMJ. 2008; 336:1495-1498.
Shires GT. Fluid and electrolyte management of the surgical patient. In: Brunicardi FC, Andersen DK, Billiar TR, Dunn DL, Hunter JG, Matthews JB, Pollock RE, eds. Schwartz’s Principles of Surgery. 9th ed. New York, NY: McGraw-Hill; 2010. http://www.accessmedicine.com/content.aspx? aID=5011700. Accessed April 14, 2013.
2B12
Key word: Diagnosis of Syndrome of Inappropriate Antidiuretic Hormone
Author: Emmanouil Pappou, MD
Editor: Pamela A. Lipsett, MD, MHPE, FACS, FCCM
The following laboratory finding is most consistent with the diagnosis of the syndrome of inappropriate antidiuretic hormone secretion (SIADH):
Plasma ADH level of 0.2 µUnits/mL
Serum osmolality of 320 mOsmol/kg
Serum sodium of 149 mEq/L
Urine osmolality of 52 mOsmol/kg
Urine sodium of 60 mEq/LView Answer
Answer: (E) Urine sodium of 60 mEq/L
Rationale:
Syndrome of inappropriate antidiuretic hormone secretion (SIADH) is characterized by an inappropriately high secretion of antidiuretic hormone (ADH), which leads to water retention and ensuing hyponatremia. Hyponatremia, defined as a serum sodium concentration of less than 135 mEq/L, occurs in approximately 10% to 15% of patients at some time during their hospital stay. Although history (heart failure, cirrhosis, renal failure, hypothyroidism, adrenal insufficiency, recent fluid infusion, diarrhea, and diuretics) and physical examination (edema and ascites) often provide important clues to the cause of hyponatremia, laboratory testing is almost always required to establish the diagnosis.
The three most important laboratory tests in the evaluation of hyponatremia are serum osmolality, urine osmolality, and urine sodium concentration. Serum osmolality (Sosm), which normally ranges from 280 to 300 mOsmol/kg, is reduced in most hyponatremic patients. Hyper-osmolar (Sosm >300 mOsmol/kg) hyponatremia occurs in patients with marked hyperglycemia, where glucose acts as an osmotically active solute. Iso-osmolar hyponatremia is seen with conditions such as hyperlipidemia or hyperglobulinemia (e.g., multiple myeloma). However, these cases are laboratory artifacts and are often referred to as pseudohyponatremia since the sodium concentration in the plasma water remains normal.
In patients with hypo-osmolar hyponatremia, urine osmolality is typically high (>100 mOsmol/kg) due to impaired water excretion. Values below 100 mOsmol/kg may be seen with primary polydipsia, where maximally dilute urine is excreted because of excessive water-drinking.
Measurement of urine sodium is helpful in the diagnosis of hyponatremia, particularly when the volume status of the patient is hard to assess clinically. Urine sodium is usually low (<20 mEq/L) in most patients with a low circulating volume (hypovolemia, congestive heart failure, liver cirrhosis), whereas patients with SIADH will typically have high levels (>20 mEq/L). In a retrospective study, the ability to distinguish hypovolemia and SIADH using the urine sodium
concentration alone was found to be reasonably high (82%) when a cutoff of 50 mEq/L was used.
concentration alone was found to be reasonably high (82%) when a cutoff of 50 mEq/L was used.
SIADH is a diagnosis of exclusion and can usually be made with routine history, physical examination, and laboratory confirmation with hyponatremia, hypo-osmolality, a urine osmolality above 100 mOsmol/kg, and a urine sodium concentration above 20 mEq/L. Plasma ADH levels tend to be high or inappropriately normal in most types of hyponatremia and are currently of limited diagnostic value.
Management of SIADH includes treatment of the underlying cause (cancer, infection, drugs, central nervous system disease, etc.), fluid restriction, diuretics, intravenous infusion of saline, and/or medications (e.g., demeclocycline).
References:
Decaux G, Musch W. Clinical laboratory evaluation of the syndrome of inappropriate secretion of antidiuretic hormone. Clin J Am Soc Nephrol. 2008;3(4):1175-1184.
Hato T, Ng R. Diagnostic value of urine sodium concentration in hyponatremia due to syndrome of inappropriate antidiuretic hormone secretion versus hypovolemia. Hawaii Med J. 2010;69(11):264-267.
Vaidya C, Ho W, Freda BJ. Management of hyponatremia: providing treatment and avoiding harm. Cleve Clin J Med. 2010;77(10):715-726.
2B13
Key word: Diagnosis of Vitamin K Deficiency
Author: Robert A. Meguid, MD, MPH
Editor: Pamela A. Lipsett, MD, MHPE, FACS, FCCM
Which of the following is associated with vitamin K deficiency?
Glossitis
Megaloblastic anemia
Prolonged prothrombin time
Rickets
ScurvyView Answer
Answer: (C) Prolonged prothrombin time
Rationale:
Vitamin K is a lipid-soluble vitamin produced by bacteria within the small intestine, where it is absorbed. In the liver, vitamin K is necessary for the carboxylation and subsequent activation of the vitamin K-dependent coagulation pathway Factors II, VII, IX, X, Protein C, and Protein S. Warfarin inhibits the activity of these factors by competitively binding vitamin K receptor sites in the liver. Vitamin K deficiency can result from dietary insufficiency, or more commonly, following administration of broad-spectrum antibiotics resulting in inhibition of bacteria producing vitamin K and subsequent bacterial overgrowth of the small intestine.
Vitamin K deficiency results in a lack of the active forms of Factors II, VII, IX, X, Protein C, and Protein S, which can lead to increased bleeding. Specifically, active Factor VII with a half life of 4 hours becomes depleted first, resulting in prolonged prothrombin time (PT) as the first clinical manifestation of vitamin K deficiency.
Glossitis, dermatitis, mucositis, and neuropathy are due to vitamin B2 (riboflavin) deficiency. Megaloblastic anemia is due to vitamin B12 deficiency and folate deficiency. Vitamin B12 deficiency is also associated with peripheral neuropathy. Vitamin D deficiency results in rickets, or softening of the bones in children with immature skeletal development, and osteomalacia in adults. Scurvy is caused by vitamin C (ascorbic acid) deficiency, resulting in failure to cross-link collagen. Ascorbic acid is required for the hydroxylation of lysine and proline into hydroxylysine and hydroxyproline, which in turn cross-link collagen into a stable construct.
References:
Ansell J, Hirsh J, Hylek E, et al. Pharmacology and management of the vitamin K antagonists: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition). Chest. 2008;133(6 Suppl):160S-198S.
Heneke PK, Wakefield TW. Hemostasis. In: Mulholland MW, Lillemoe KD, Doherty GM, Maier RV, Upchurch GR, eds. Greenfield’s Surgery: Scientific Principles and Practice. 5th ed. Philadelphia, PA: Lippincott Williams and Wilkins; 2011.
Reilly JJ, Jr. Principles of surgical nutrition. In: Simmons RL, Steed DL, eds. Basic Science Review for Surgeons. St. Louis, MO: W.B. Saunders; 1992.
Steed DL. Hemostasis and coagulation. In: Simmons RL, Steed DL, eds. Basic Science Review for Surgeons. St. Louis, MO: W.B. Saunders; 1992.
2B14
Key word: Effect of Use of Iodine Drapes
Author: Kyle J. Van Arendonk, MD, PhD
Editor: Martin A. Makary, MD, MPH
Your medical student wants to know why yellow adhesive drapes were applied to a patient’s skin prior to incision. Which of the following would be a correct reply regarding the use of iodine-impregnated drapes?
Iodine-impregnated drapes are a required component of the Surgical Care Improvement Project (SCIP)
Iodine-impregnated drapes are most beneficial when used for contaminated and clean-contaminated cases
Iodine-impregnated drapes can be used alone in place of other skin preparations
Iodine-impregnated drapes can reduce microbial counts on the skin
Iodine-impregnated drapes have been shown to reduce the incidence of surgical site infections (SSIs)View Answer
Answer: (D) Iodine-impregnated drapes can reduce microbial counts on the skin
Rationale:
SSIs are a common preventable adverse event associated with considerable morbidity, extended hospital stay, and financial cost. Evidence-based practices for prevention of SSIs include the initial administration of perioperative antibiotics within 1 hour before surgery, the preoperative use of electric hair clippers or no hair removal (as opposed to razor shaving of hair), and the maintenance of normothermia during surgery.
For many SSIs, the pathogen originates from the patient’s skin. Povidone-iodine is a potent, rapid, and persistent bactericidal with broad-spectrum activity. Iodine-impregnated drapes have therefore been used in attempt to further prevent SSIs by decreasing microbial counts on the skin and by acting as a microbial barrier. However, a meta-analysis of two studies comparing iodine-impregnated adhesive drapes with no adhesive drapes found that iodine-impregnated drapes did not in fact significantly reduce the risk of SSI.
References:
Bratzler DW, Hunt DR. The surgical infection prevention and surgical care improvement projects: national initiatives to improve outcomes for patients having surgery. Clin Infect Dis. 2006;43(3):322-330.
Webster J, Alghamdi AA. Use of plastic adhesive drapes during surgery for preventing surgical site infection. Cochrane Database Syst Rev. 2007;(4):CD006353.
2B15
Key word: Effect of Use of Isolation Gowns
Author: Andrew P. Dhanasopon, MD
Editor: Martin A. Makary, MD, MPH
Which of the following scenarios represents appropriate use of isolation gowns when entering the room of a patient infected with Clostridium difficile?
Using the same isolation gown for two different patients in two different rooms as long as both are infected with Clostridium difficile
Wearing an isolation gown is not necessary if one wears a laboratory coat
Wearing an isolation gown only if contact with the patient is anticipated
Wearing an isolation gown that covers the body from the neck to mid-thigh including the entire back and arms
When removing the gown, turning the contaminated side inward, rolled into a bundle, and discarding the gown in any container outside the patient’s roomView Answer
Answer: (D) Wearing an isolation gown that covers the body from the neck to mid-thigh including the entire back and arms
Rationale:
Isolation gowns protect the health care worker’s neck, arms, torso, and upper thigh to prevent contamination of clothing with blood, body fluids, and other potentially infectious materials. When contact precautions are used, as in the case of this patient with Clostridium difficile, donning of a gown regardless of anticipated interaction with the patient prevents unintentional contact with contaminated environmental surfaces. When removing the gown, one must discard it before leaving the patient’s room to prevent contaminating the environment outside of the patient’s room. Clinical and laboratory coats or jackets worn over personal clothing are not considered Personal Protective Equipment. The same isolation gown must not be used for two different patients.
Reference:
Siegel JD, Rhinehart E, Jackson M, et al. 2007 guideline for isolation precautions: Preventing transmission of infectious agents in health care settings. Am J Infect Control. 2007;35(10 Suppl 2):S65-S164.
2B16
Key word: Etiology of Grand Mal Seizure after Lidocaine Administration
Author: Brenessa M. Lindeman, MD
Editor: Bradford D. Winters, MD, PhD
A 59-year-old man weighing approximately 65 kg and having a long history of hepatitis C presents with a 7-cm skin laceration. For anesthesia, 20 mL of 2% lidocaine is infiltrated into the wound bed. While suturing the wound, the patient begins to have generalized convulsions. Which of the following confers an increased risk for lidocaine toxicity?
Active bacterial infection
Coronary artery disease
Hepatic impairment
Immunodeficiency
Renal impairmentView Answer
Answer: (C) Hepatic impairment
Rationale:
Lidocaine is an amide local anesthetic. Doses of 4 to 5 mg/kg of plain lidocaine and up to 7 mg/kg of lidocaine with epinephrine are safe in healthy patients without producing toxicity. Lidocaine is usually given as a 1% solution (10 mg/mL). Higher concentrations beyond 1% do not improve onset or duration of analgesia and may in fact increase the risk of toxicity.
The central nervous system (CNS) and cardiovascular system are the major sites of lidocaine toxicity. The CNS is more sensitive to local anesthetic toxicity than the cardiovascular system, and therefore CNS intoxication usually manifests before signs of cardiovascular compromise. CNS symptoms of lidocaine toxicity include perioral numbness, tinnitus, and grand mal seizures. Cardiovascular effects include bradycardia, hypotension, arrhythmias, and cardiac arrest.
Approximately 90% of lidocaine is metabolized by the microsomal enzyme system in the liver, and less than 10% is excreted unchanged in the urine. Thus patients with compromised hepatic function are at increased risk for lidocaine toxicity. Dosage reductions by two- to three fold are highly recommended, especially in patients with moderate to severe cirrhosis. The patient in this case received 20 mL of 2% lidocaine (20 mg/mL) for a total dose of 400 mg, which is approximately 6 mg/kg and clearly excessive given his hepatic impairment.
Reference:
DeToledo JC. Lidocaine and seizures. Therapeutic Drug Monitoring. 2000;22(3):320-322.
2B17
Key word: Etiology of Hypotension after Blunt Trauma
Author: Lisa M. Kodadek, MD
Editors: Elliott R. Haut, MD, FACS, and F. Dylan Stewart, MD, FACS
An 8-year-old pedestrian struck by a motor vehicle presents in extremis with a closed left femur fracture and severe right craniofacial injury. The patient is intubated and bilateral chest tubes are placed with return of 150 mL of blood from the left chest tube and 100 mL of blood from the right chest tube. As the patient is fluid-resuscitated, Focused Abdominal Sonography for Trauma (FAST) examination is performed and is negative. The patient remains hypotensive and unresponsive to initial fluid resuscitation. The most likely source of this patient’s hypotension is injury to the:
Femur
Heart
Lung
Spleen
StomachView Answer
Answer: (D) Spleen
Rationale:
This pediatric patient presents with a pattern of injuries known as Waddell’s triad. This triad is seen in pedestrians stuck by motor vehicles and consists of (1) tibiofibular or femur fracture, (2) truncal injury, and (3) craniofacial injury. Most often, the initial impact causes the bony injury and ipsilateral intrathoracic and intra-abdominal injury, while subsequent injury to the contralateral face and cranium is sustained after the child is thrown following initial impact.
The liver and spleen are the most commonly injured intra-abdominal organs after blunt abdominal trauma. In this scenario, splenic injury is the most likely etiology of hypotension given the presenting injury pattern. It is important to remember that the FAST examination is relatively insensitive in children because of the frequency of solid-organ injury seen without associated hemoperitoneum.
The patient has bilateral chest tubes without a dramatic initial return of blood. Lung injury would be more likely if chest tube output was higher. In adults, initial chest tube output greater than 1,500 mL or greater than 200 mL/hr for 4 hours is an indication for thoracotomy. In children, these numbers must be adjusted. Initial chest tube output greater than approximately 15 to 20 mL/kg or ongoing output of greater than approximately 5 mL/kg is considered an indication for thoracotomy in the pediatric trauma setting. Stomach injuries occur in less than 1% of blunt abdominal trauma patients. Cardiac injury would be less plausible in this scenario and is often recognized during FAST examination of the pericardium.
References:
Holmes JF, Gladman A, Chang CH. Performance of abdominal ultrasonography in pediatric blunt trauma patients: a meta-analysis. J Pediatr Surg. 2007;42(9):1588-1594.
Hoyt DB, Coimbra R, Acosta J. Management of acute trauma. In: Townsend CM, Beauchamp RD, Evers MB, Mattox KL, eds. Sabiston Textbook of Surgery. 18th ed. Philadelphia, PA: Elsevier Saunders; 2008:477-520.
Piper GL, Peitzman AB. Blunt abdominal trauma. In: Cameron JL, Cameron AM, eds. Current Surgical Therapy. 10th ed. Philadelphia, PA: Elsevier Saunders; 2011:918-923.
2B18
Key word: Etiology of Paresthesias after Thyroid Surgery
Author: Brenessa M. Lindeman, MD
Editor: Anthony P. Tufaro, DDS, MD, FACS
Which of the following neck procedures puts a patient most at risk for paresthesias in the postoperative period?
Central neck dissection
Parathyroid autotransplantation
Parathyroidectomy
Thyroid lobectomy
Total thyroidectomyView Answer
Answer: (E) Total thyroidectomy
Rationale:
Hypoparathyroidism leading to digital or perioral paresthesia is a known side effect of surgical procedures in the neck. The risk of hypoparathyroidism is increased with bilateral neck procedures, specifically total thyroidectomy, and in the presence of malignancy. It is routine practice to check a calcium level following total thyroidectomy to screen for the presence of hypoparathyroidism and determine the need for postoperative calcium supplementation. Most cases of hypoparathyroidism are transient, but up to 2% may be permanent.
Reference:
Borman KA, Rabaglia JL. Thyroid diseases. In: Souba WW, Fink MP, Jurkovich GJ, Kaiser LR, Pearce WH, Pemberton JH, Soper NJ, eds. ACS Surgery: Principles and Practice. Decker Intellectual Properties; 2011.
2B19
Key word: Extrapyramidal Effects of Antiemetics
Author: Said C. Azoury, MD
Editor: Bradford D. Winters, MD, PhD
A postoperative patient with nausea and abdominal discomfort is discharged on both promethazine and metoclopramide. The patient has also been taking another antiemetic at home for several months, since initiating chemotherapy for her underlying malignancy, but she cannot recall the name of the drug. Two days later, the patient calls reporting a tremor and a feeling of stiffness in her extremities. Which of the following is the most appropriate next step?
Continue both promethazine and metoclopramide and prescribe diphenhydramine for symptomatic relief
Increase the dose of metoclopramide, switch promethazine to ondansetron, and have the patient return if symptoms persist or worsen
Increase the dose of promethazine, switch metoclopramide to ondansetron, and have the patient return if symptoms persist or worsen
Obtain an urgent EEG to rule out seizure activity because antiemetics may lower seizure threshold
Stop all current antiemetics, prescribe a serotonin receptor inhibitor such as ondansetron, and have the patient return if symptoms persist or worsenView Answer
Answer: (E) Stop all current antiemetics, prescribe a serotonin receptor inhibitor such as ondansetron, and have the patient return if symptoms persist or worsen
Rationale:
Postoperative nausea and vomiting is the most common complication in postanesthesia care units, ranging between 10% and 30%, and a major concern for both patients and health care providers. There are several different kinds of antiemetics prescribed for the postoperative patient and for chemotherapy-induced emesis prophylaxis, with varying mechanisms of action.
Promethazine is a phenothiazine derivative that blocks postsynaptic mesolimbic dopamine receptors in the brain. It also antagonizes H1- and muscarinic receptors in the central nervous system, both of which are responsible for its sedating properties. The muscarinic-blocking effect may in fact be the one responsible for its antiemetic activity. Promethazine may cause extrapyramidal symptoms, including acute dystonic reactions, akathisia, pseudoparkinsonism, and tardive dyskinesia.
Metoclopramide blocks dopamine and serotonin receptors in the chemoreceptor trigger zone of the central nervous system. It is used to increase gastric motility and gut motility by enhancing the tissue response to acetylcholine in the upper gastrointestinal tract, and this prokinetic effect itself may contribute to its antiemetic properties. Metoclopramide, like promethazine, has been associated with extrapyramidal symptoms. Coadministration of metoclopramide with neuroleptics/antipsychotics or with phenothiazines such as promethazine may increase the frequency and severity of extrapyramidal reactions.
Acute dystonic reactions most typically manifest within the initial 24 to 48 hours of use, whereas pseudoparkinsonism (bradykinesia, tremor, rigidity) or tardive dyskinesia may occur after several months of therapy. Tardive dyskinesia is a hyperkinetic movement disorder manifested as chorea, athetosis, dystonia, akathisia, stereotyped behaviors, and tremor and may be irreversible. Treatment of extrapyramidal symptoms includes antimuscarinic agents such as benztropine or diphenhydramine and dopamine agonists such as pramipexole.
Ondansetron is a selective 5-HT3 receptor antagonist, blocking serotonin both peripherally on vagal nerve terminals and centrally in the chemoreceptor trigger zone. Ondansetron has not been associated with extrapyramidal symptoms.
References:
Ganzini L, Casey DE, Hoffman WF, et al. The prevalence of metoclopramide induced tardive Dyskinesia and acute extrapyramidal movement disorders. Arch Intern Med. 1993;153:1469.
Tarsy D, Baldessarinin RJ. Tardive dyskinesia. Annu Rev Med. 1984;35:605.
2B20
Key word: Fluid Requirement with 30% TBSA Flame Burn
Author: Ibrahim Sultan, MD
Editor: F. Dylan Stewart, MD, FACS
A 25-year-old man weighing 80 kg suffers partial-thickness flame burns to his entire left and right upper extremities and to his entire left lower extremity. He is brought to the emergency room 4 hours after the injury. His airway is secured for a depressed Glasgow Coma Scale (GCS) score, and two large bore intravenous lines are placed. What rate of intravenous fluid administration is this patient expected to need over the next 4 hours in order to achieve adequate resuscitation?
Lactated Ringer at 1,440 mL/hr
Lactated Ringer at 2,500 mL/hr
Lactated Ringer at 721 mL/hr
Normal saline at 1,440 mL/hr
Normal saline at 721 mL/hrView Answer
Answer: (A) Lactated Ringer 1,440 mL/hr
Rationale:
The man in the vignette has sustained nearly 36% burns to his body according to the “rule of nines” used to estimate total body surface area (TBSA) involved in burns. According to this rule, each upper extremity represents 9% TBSA and each lower extremity represents 18% TBSA. The Parkland formula is employed to calculate resuscitation in patients who sustain greater than 15% TBSA burns. According to the Parkland formula, fluid resuscitation over the first 24 hours = 4 mL × body weight (in kilograms) × % TBSA. Thus, for the patient in this vignette, 4 mL × 80 kg × 36% = 11,520 mL. Half of this volume (5,760 mL) is given in the first 8 hours beginning immediately after the thermal injury, and the other half is given over the next 16 hours. In this instance, it took 4 hours for the patient to reach the emergency room, making it such that the first half of fluids needs to be administered over the next 4 hours, making the hourly resuscitation volume for these 4 hours 5,760 mL/4 hr = 1,440 mL/hr. In addition, lactated Ringer is the fluid of choice for patients with thermal burns because of the massive amount of volume they require. Large amounts of normal saline can cause a nongap metabolic acidosis.
References:
Gallagher JJ, Wolf SE, Herndon DN. Burns. In: Townsend CM, Beauchamp RD, Evers BM, Mattox KL, eds. Sabiston Textbook of Surgery. 18th ed. Philadelphia, PA: Elsevier; 2008: 559-585.
Phillips BJ. Burns: fluids, nutrition and metabolics. In: Cameron JL, Cameron AM, eds. Current Surgical Therapy. 10th ed. Philadelphia, PA: Elsevier; 2011: 1036-1042.
2B21
Key word: Hair Removal in Contaminated Laceration Repair
Author: Brenessa M. Lindeman, MD
Editor: Martin A. Makary, MD, MPH
A 20-year-old woman presents with a 3-cm laceration on the parietal region of her scalp after tripping on a sidewalk. On physical examination, you note a linear wound with clean edges in the center of hair-bearing scalp that continues to ooze. Which of the following repair options is recommended?
Clean the wound, allow to heal by secondary intention
Clean the wound, clip surrounding hair, suture closed
Clean the wound, leave surrounding hair in place, suture closed
Clean the wound, shave surrounding hair, apply skin glue
Clean the wound, shave surrounding hair, suture closedView Answer
Answer: (C) Clean the wound, leave surrounding hair in place, suture closed
Rationale:
For many years, the advice regarding how to manage hair surrounding a laceration has been in flux. Initial advice was to shave the hair, but evidence revealed that this led to an increased incidence of wound infection. Clipping hair then became the standard of care, but several studies have shown that this step is not necessary provided that the wound can be appropriately cleaned. An emergency medicine study from 1988 revealed no infections in 68 lacerations when hair was neither clipped nor shaved, after a mean follow-up time of 5 days. In addition, a randomized trial from the otolaryngology literature showed no difference in wound infection rate of skull base surgery when hair was removed versus not.
References:
Gil Z, Cohen JT, Spektor S, et al. The role of hair shaving in skull base surgery. Otolaryngol Head Neck Surg. 2003; 128(1):43-47.
Howell JM, Morgan JA. Scalp laceration repair without prior hair removal. Am J Emerg Med. 1988;6(1):7-10.
2B22
Key word: Hemodynamic Findings in Septic Shock
Author: Lisa M. Kodadek, MD
Editor: Mark D. Duncan, MD, FACS
A 65-year-old man with a history of congestive heart failure and coronary artery disease underwent abdominoperineal resection 7 days ago for rectal adenocarcinoma. On morning rounds, the patient is confused, tachycardic, and hypotensive with an elevated white blood cell count. Purulent drainage from his perineal wound is present. Fluids are given. The patient is most likely to have which of the following sets of hemodynamic findings?
|
View Answer
Answer: (C)
|
Rationale:
Early septic shock is associated with increased cardiac output, decreased vascular resistance, increased myocardial oxygen consumption, and variable or unchanged right heart filling pressure. Answer (A) is typical of hypovolemic shock. Answer (B) is typical of cardiogenic shock. Answer (D) is typical of spinal/neurogenic shock. Answer (E) is a pattern of hemodynamic findings not seen in shock states.
Reference:
Cuschieri J. Shock. In: Mulholland MW, Lillemoe KD, Doherty GM, Maier RM, Simeone DM, Upchurch GR, eds. Greenfield’s Surgery: Scientific Principles and Practice. 5th ed. Philadelphia, PA: Lippincott Williams amd Wilkins; 2011.
2B23
Key word: Indication for Antibiotics with 40% TBSA Burns
Author: Andrew P. Dhanasopon, MD
Editor: F. Dylan Stewart, MD, FACS
A 52-year-old hospital maintenance worker is admitted to the Emergency Department after sustaining burn injuries from a ruptured steam pipe. On physical examination, he has circumferential deep burns involving his torso, back, and both arms and hands. The patient is intubated and placed on appropriate IV fluids and brought to the operating room for urgent escharotomy. Prior to incision for escharotomy, the appropriate treatment would be:
No antibiotics
Silver sulfadiazine
Systemic prophylactic antibiotics alone
Topical and systemic prophylactic antibiotics
Topical antibiotics to all affected tissuesView Answer
Answer: (C) Systemic prophylactic antibiotics alone
Rationale:
Burn wounds begin to be colonized over the first 2 days by skin flora and later by gastrointestinal flora. Aggressive wound care, early excision and grafting, and topical antibiotics are associated with a significant decline in the incidence of burn wound infections. Topical antibiotics and other topical antimicrobials such as silver sulfadiazine are therefore indicated in this patient postoperatively but are not necessary prior to incision.
Systemic antibiotics are indicated for burn wounds with a documented infection (defined as >105 organisms per gram of tissue via wound biopsy) or in systemically ill patients presumed to have sepsis or other sources of infection (urinary tract infection, pneumonia, etc.). Prophylactic administration of systemic antibiotics are generally recommended only for the perioperative period for severe burns with total body surface area (TBSA) >40% that require escharotomy, excision, and/or skin grafting. Systemic prophylactic antibiotics have no benefit prior to routine debridements or skin grafting for small burns.
References:
Avni T, Levcovich A, Ad-El DD, et al. Prophylactic antibiotics for burns patients: systematic review and meta-analysis. BMJ. 2010;340:c241.
Church D, Elsayed S, Reid O, et al. Burn wound infections. Clin Microbiol Rev. 2006;19(2):403-434.
D’Avignon LC, Chung KK, Saffle JR, et al. (The Prevention of Combat-Related Infections Guidelines Panel). Prevention of infections associated with combat-related burn injuries. J Trauma. 2011;71(2 Supplement 2):S282-S289.
Mozingo DW, McManus AT, Kim SH, et al. Incidence of bacteremia after burn wound manipulation in the early postburn period. J Trauma. 1997;42(6):1006-1011.
2B24
Key word: Effective Pain Control
Author: Jens U. Berli, MD
Editor: Bradford D. Winters, MD, PhD
Which of the following parenteral analgesics is contraindicated for critically ill patients or patients with known opiate abuse due to its potential side effects?
Acetaminophen
Buprenorphine
Fentanyl
Hydromorphone
KetorolacView Answer
Answer: (B) Buprenorphine
Rationale:
Some opioids are not recommended for routine use in critically ill patients. Buprenorphine is a partial mu opiate receptor agonist and a weak kappa opiate receptor antagonist that has less euphoric and respiratory depression effects than typical opiate agonists. Because it is a partial antagonist, buprenorphine in moderate to high doses (e.g., infusion in critical care setting) can precipitate an extremely intense form of opioid withdrawal called “precipitated withdrawal” in opioid-dependent patients or after prolonged opiate administration. Other agents with the same properties as buprenorphine are butorphanol, dezocine, nalbuphine, and pentazocine.
Fentanyl and hydromorphone are amongst the most frequently used opioids in the inpatient setting. Fentanyl is a synthetic derivative of morphine with a rapid onset of action due to its better penetration through the blood-brain barrier. Hydromorphone has a faster onset compared to morphine, and unlike morphine, it does not have active metabolites that extend its effect. Both fentanyl and hydromorphone are commonly used as continuous intravenous infusions in critically ill patients.
Ketorolac may be used in critically ill patients as a short-term adjunct, although all nonsteroidal anti-inflammatory drugs should be used with caution, especially in elderly patients, in those with preexisting renal insufficiency, or in states of hypoperfusion as they are associated with renal events (nephritis, kidney failure), bleeding, an increased risk of cardiovascular thrombotic events including myocardial infarction and stroke, and gastrointestinal events such as bleeding or ulceration. When used, treatment should not exceed 5 days.
Acetaminophen in parenteral form has been widely used in Europe in the past and has recently been approved by the FDA for use in the United States. It is a good analgesic for patients with normal liver function.
Reference:
Schumacher MA, Basbaum AI, Way WL. Opioid analgesics & antagonists. In: Katzung BG, Masters SB, Trevor AJ, eds. Basic & Clinical Pharmacology. 11th ed. New York, NY: McGraw-Hill; 2011.
2B25
Key word: Initial Treatment of Ischemic Orchitis after Hernia Repair
Author: Andrew P. Dhanasopon, MD
Editor: Mohamad E. Allaf, MD
A 25-year-old man is evaluated 7 days after an open right inguinal hernia repair with mesh. Intraoperatively the patient had a large hernia sac that required extensive dissection and handling of the spermatic cord. He now reports fevers and 3 days of progressive pain and swelling in his right testicle. He denies dysuria, hematuria, or recent trauma. Physical examination demonstrates a tender, enlarged right testicle without discoloration. Ultrasonography reveals no fluid collection but reduced echogenicity of the right testicle and decreased intratesticular flow on color Doppler. What is the management of this complication?
Emergent orchiectomy
Reassurance, comfort measures, and NSAIDs
Urgent surgical re-exploration to loosen the internal ring
Urgent surgical re-exploration with neurectomy of the ilioinguinal and iliohypogastric nerves
Urgent surgical re-exploration with removal of the meshView Answer
Answer: (B) Reassurance, comfort measures, and NSAIDs
Rationale:
This patient presents with ischemic orchitis after inguinal hernia repair. This complication occurs in <1% of all herniorrhaphies and is more frequent after recurrent inguinal hernia repair. Patients usually present within the first week after hernia repair. Typical symptoms include low-grade fever and testicular pain, tenderness, and enlargement. Ultrasound usually reveals hypoechogenicity and reduced flow to the testicle using color Doppler. Risk factors include a large hernia sac, a hernia sac that extends into the scrotum, extensive dissection of the hernia sac off the spermatic cord, and extensive handling of the spermatic cord. These risk factors may also lead to hematoma formation; the scrotum would then typically have a blue-black discoloration, and ultrasound would reveal a fluid collection.
Ischemic orchitis is thought to be due to injury and thrombosis of the veins in the pampiniform plexus, not injury to the testicular artery. This injury is self-limited, and long-term effects are rare. Management is expectant: reassurance, comfort measures, and NSAIDs. Surgical re-exploration is not helpful and will increase the patient’s risk of additional complications. Neurectomy is the treatment for chronic neuropathic groin pain that has failed conservative management following herniorrhaphy. Emergent orchiectomy is rarely indicated and reserved for testicular necrosis.
References:
Holloway BJ, Belcher HE, Letourneau JG, et al. Scrotal sonography: a valuable tool in the evaluation of complications following inguinal hernia repair. J Clin Ultrasound. 1998;26(7):341-344.
Sherman V, Macho JR, Brunicardi FC. Inguinal hernias. In: Brunicardi FC, Andersen DK, Billiar TR, Dunn DL, Hunter JG, Matthews JB, Pollock RE, eds. Schwartz’s Principles of Surgery. 9th ed. New York, NY: McGraw-Hill; 2010. http://www.accesssurgery.com/content.aspx?aID=5031117. Accessed May 10, 2013.
2B26
Key word: Most Common Side Effect of Mycophenolate
Author: Babak J. Orandi, MD, MSc
Editor: Dorry L. Segev, MD, PhD
Of the following, which is the most common side effect of mycophenolate mofetil (MMF)?
Diarrhea
Gingival hyperplasia
Hyperglycemia
Nephrotoxicity
TremorView Answer
Answer: (A) Diarrhea
Rationale:
MMF, which acts by blocking de novo purine synthesis, preventing formation of DNA and RNA and therefore B- and T-cell proliferation, is a frequently used immunosuppressive drug in transplant patients. MMF is a fundamental component of many post-transplant immunosuppressive regimens, as it has been shown to reduce the incidence of acute rejection.
The most common side effects are gastrointestinal in nature, particularly diarrhea. About 40% to 50% of patients on MMF experience one or more gastrointestinal complications within the first 6 months post-transplant, which may lead to MMF dose reduction or withdrawal in about half of these cases. Other side effects of MMF include bone marrow suppression, infectious complications, and neurologic effects such as headache and fatigue. In the transplant patient, it is critically important to differentiate medication-induced diarrhea from other causes of diarrhea, particularly infectious diarrhea. If MMF proves to be the causative agent, more frequent administration with a lower dose is often effective in minimizing this side effect; in some cases, the overall dose also needs to be decreased. The clinician must exercise caution in adjusting and in particular decreasing immunosuppression, as there is a delicate balance between resolving symptoms and maintaining sufficient immunosuppression to protect the graft.
Nephrotoxicity and tremors are most strongly associated with calcineurin inhibitors such as cyclosporine and tacrolimus. Steroids cause a hyperglycemic state. Gingival hyperplasia is a side effect of cyclosporine.
References:
Mourad M, Malaise J, Eddour DC, et al. Correlation of mycophenolic acid pharmacokinetic parameters with side effects in kidney transplant patients treated with mycophenolate mofetil. Clin Chem. 2001;47:88-94.
Platt JL, Cascalho M. Transplantation immunology. In: Mulholland MW, Lillemoe KD, Doherty GM, Maier RV, Upchurch GR, eds. Greenfield’s Surgery: Scientific Principles and Practice. 5th ed. Philadelphia, PA: Lippincott Williams and Wilkins; 2011.
2B27
Key word: Risks of Long-term Immunosuppression
Author: Babak J. Orandi, MD, MSc
Editor: Dorry L. Segev, MD, PhD
A 52-year-old male who had a deceased donor renal transplant 6 months ago presents to clinic with a low-grade fever, fatigue, a 4.54 kg (10 lb) weight loss, and a serum creatinine of 2.3 mg/dL, an increase from his baseline post-transplant level of 1.4 mg/dL. Transplant biopsy shows no evidence of acute rejection. Measurement of serum Epstein-Barr virus (EBV) DNA by polymerase chain reaction (PCR) demonstrates a high viral load. The patient will most likely display clinical improvement with the following:
Broad-spectrum intravenous antibiotics
Further increase in immunosuppression
Intravenous ganciclovir
Plasmapheresis
Reduction of immunosuppressionView Answer
Answer: (E) Reduction of immunosuppression
Rationale:
This scenario likely represents post-transplant lymphoproliferative disease (PTLD), which complicates up to 15% of solid organ transplants. PTLD represents a spectrum of disease that ranges from an indolent, EBV-positive polyclonal lymphoproliferation that is usually seen early post-transplant and often resolves with reduction of immunosuppression, to a malignant and aggressive lymphoma that is rapidly fatal without combination chemotherapy. PTLD has myriad presentations but often presents with fever, lymphadenopathy, pharyngitis, fatigue, weight loss, sweat, and/or allograft dysfunction. It may occur at any time after transplantation; however, the risk appears to be greatest within the first year post-transplantation, with a median time to presentation of 6 months. Empiric treatment of allograft dysfunction as acute rejection may actually lead to worsened allograft function and worsening of PTLD, so careful workup is required. A variety of treatment paradigms for PTLD have been proposed, most of which are poorly studied. It is generally accepted that first-line treatment is the reduction of immunosuppression. Surgical excision and/or radiation therapy can also be used for localized disease. Prompt recognition and treatment is imperative because mortality rates have been reported to be as high as 70%.
References:
Gottschalk S, Rooney CM, Heslop HE. Post-transplant lymphoproliferative disorders. Annu Rev Med. 2005;56:29-44.
Tsai DE, Loren AW. Post-transplant lymphoproliferative disorder. Clin Chest Med. 2005;26:631-645.
2B28
Key word: Treatment of Bleeding Associated with Clopidogrel
Author: Babak J. Orandi, MD, MSc
Editor: Ying Wei Lum, MD
A 64-year-old woman undergoes an emergent cardiac catheterization for unstable angina. She is given 300 mg of clopidogrel before the procedure; however, the cardiologist is unable to revascularize a near-total obstructing lesion of the left anterior descending artery. The patient is therefore referred for emergent coronary artery bypass grafting. Postoperatively she has high-volume sanguinous output from her chest tube. The most appropriate treatment for the correction of clopidogrelassociated coagulopathy is:
Administration of cryoprecipitate
Administration of desmopressin
Administration of protamine
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