Intensive Care Unit, Royal Adelaide Hospital & St Andrew’s Hospital, Adelaide, SA, Australia
Intensive Care Unit, The Alfred Hospital, Melbourne, VIC, Australia
Royal Adelaide Hospital, University of Adelaide, L5 Eleanor Harrald Building, North Terrace, 5000 Adelaide, SA, Australia
Brendon J. Coventry
Patients with increasing illness severity and complexity are particularly susceptible to more severe complications and tolerate complications less well due to a diminished physiologic reserve. Such patients may require intensive care unit (ICU) admission simply for their condition alone, and many certainly do once they suffer a complication. As such, complications arising in the postoperative period are more frequent within the ICU than the general ward. ICU patients often have multiple comorbidities, and this commonly contributes to prolonged stay and other problems. In addition to postoperative care, ICU is commonly used for a period of preoperative care within the ICU, often for optimization of their condition. Finally, complications may in fact arise directly from the treatments and time in the ICU (e.g., tracheostomy, pulmonary infection, or perforation of a peptic ulcer).
When considering “risks,” “complications,” or “consequences” associated with ICU stays, it is important to recognize that some of the most difficult and complex cases and surgical problems that can arise are managed by ICU staff. Risks can still be reduced, and substantial advances are being continuously made to improve the situation. Despite this, morbidity and mortality remain high in relative terms for patients admitted to ICU.
The purpose of this chapter is to raise awareness of the potential problems that can occur in ICU patients of differing types in order to predict and potentially act to avert complications from arising. This may also prevent a “chain” of other complications from arising and so maximize potential reversibility and recovery. The best intensive care treatment is often a matter of simply and safely supporting the patient through the problems that can arise postoperatively. If complications are averted in this critical period, the patient stands an excellent chance of success in the longer term.
It is on this broad understanding and background that the following chapter is written.
Over the last six decades, intensive care has evolved out of the early postoperative recovery units for patients requiring extended recovery and support following complicated surgery (Calvin et al. 1997) and the mechanical ventilation units developed for poliomyelitis sufferers (Judson and Fisher 2006). With extensive technological, pharmaceutical, scientific, and procedural advances, modern intensive care units (ICUs) care for complex medical, surgical, burns, and trauma patients. These units may be combined or separated into these specialties.
Despite advances, overall ICU mortality remains high. Figures vary widely due to heterogeneity of patients and units; however in some hospitals up to 30 % of all patients admitted to ICU die before leaving hospital. The severity of illness of ICU patients that contributes to such a high mortality is also reflected in the complications suffered by survivors. Many of the deaths occur despite ICU care, yet some may die as a result of complications of ICU care itself. Iatrogenic complications have previously been correlated with (1) patients age over 65 years, (2) two or more established organ system failures, (3) human errors, and (4) high or excessive nursing workload (Giraud et al. 1993; Memtsoudis et al. 2007). As such, ICU patients suffer iatrogenic complications at a rate as high as 30 %, some of which contribute to morbidity and even death. Training, staffing, and monitoring form part of every ICU in order to reduce these risks (Zapol 1993).
Complications Associated with Intensive Care Support
Admission of surgical patients to ICU may be elective or planned, or it may occur as an emergency admission following surgical or anesthetic complication or progression of the underlying condition. Admissions may sometimes be preoperative for surgical optimization but are usually postoperative in order to avert, detect, monitor, and manage pathological and physiologic aberrations and organ failures and to improve morbidity and mortality. This support often means patients survive when they may not have in the past or can undergo more “dangerous” surgery than previously was possible. For many others, this support may help to avoid or curtail complications of their surgery, underlying surgical condition, and medical comorbidities.
Many elective admissions to the intensive care unit (ICU) are relatively short term and are not associated with significant complications. The elective nature means these patients should be informed and consented for their ICU admission. However, some admissions may be more prolonged and are associated with exposure to higher risks; many of these may not be predicted. It is useful to warn patients and relatives preoperatively of the possibility of an ICU admission, to prepare them and avoid unnecessary anxiety. In the event of unplanned ICU admission and support, informed consent is often not possible or practicable. In any case clear and ongoing communication with the patient and/or family is essential.
Complications associated with intensive care for surgical patients may be categorized as:
Complications occurring in ICU but associated with the acuity or severity of their underlying condition, surgery, or comorbidities
Complications resulting directly from devices/procedures and other therapies undertaken as part of ICU support
Many complications associated with ICU support are a consequence of the preexisting comorbidities and acute pathology that a patient has, together with the type and complexity of the surgical procedure performed. In addition, significant comorbidities and the performance of complex surgery are associated with increased risk of complications, which often necessitate or prolong an ICU stay. This inevitably exposes these patients to a greater risk of complications resulting directly from intensive care itself. For example, prolongation of the ICU stay increases the risks from immobility, sedation, nosocomial infection, and utilization of long-term indwelling devices for ventilation, vascular access, monitoring, nutrition, or drainage.
Given the broad range of surgical patients and conditions, therapies, and procedures undertaken in ICU, complications are common and diverse. This chapter will outline some of the important complications more specifically to intensive care. Although it is easier to consider these within individual organ systems as we do here, complications encountered in ICU patients often coexist and are frequently additive. Increasing numbers of organ system failures have been clearly shown to increase mortality and morbidity.
Critical illness itself frequently leads to central and peripheral neurologic complications (Barlas et al. 2001). These complications may also arise from a constellation of ICU procedures and therapy, medical or surgical conditions, or simply an underlying primary neurologic disease. Such complications may go unrecognized, as critically ill patients are often intubated, sedated, and/or receiving neuromuscular-blocking agents. Encephalopathy remains the most common neurologic complication in ICU and is usually multifactorial in origin. Sepsis is the condition with the highest incidence of neurologic complications. Severe weakness termed “critical illness polymyoneuropathy” is another frequent complication of critical illness and its treatment. Neurologic complications are associated with increased disability, longer hospital stay, and increased mortality. Minor neural deficits may go entirely unnoticed due to the subtle nature of many of these, such that the range and frequency of neurologic complications is often underreported and underappreciated but may be discernable to those who know the patient well, for example, family members or close friends, who may notice cognitive impairment(s). If fact, the more we study these post-ICU patients, especially the severely unwell and prolonged stay cases, the more appreciation we are gaining for the more subtle deficits that are acquired, either by the disease(s), the ICU care, or both. Avoidance of hypotension, to preserve cerebral perfusion, where possible, is a major factor in averting this range of complications. Of course, the scope of neurologic deficits, especially the more minor ones, needs to be sensibly balanced against the often higher risks from not admitting the patient to ICU. See Table 6.1.
Neurologic and psychiatric complications in intensive care
Encephalopathy (sepsis, drugs, uremia, hepatic, hypercarbic, hypoxic metabolic – Na, Ca, glucose, etc.)
Up to 70 % ICU pts, 23.5 % hypoxic/ischemic
Critical illness polyneuropathy (CIP) and myopathy
79 % (of sepsis/MSOF)
Risk factors – sepsis, gentamicin, steroids, respiratory disease, multiorgan failure, acidosis, β-agonist (inotropes, salbutamol), neuromuscular-blocking drugs, transplant (lung > liver > renal)
Stroke (ischemic and hemorrhagic)
Sleep disorders and ICU psychosis, anxiety, depression, PTSD (family and patient)
8–28 % overall. 0.8–4 % new onset. 8 % of comatose pts. Up to 50 % of trauma pts
Neurologic complications of procedures
Central cord syndrome, lingual/hypoglossal nerve damage (hyperextension for intubation)
Changes in ICP due to ventilation and altered pCO2/pH
CNS infection – after lumbar puncture, external ventricular drain (EVD), or ICP monitor
Radiculopathy/neuropraxia associated with procedures – e.g., central venous catheter placement – especially cervical and femoral sites
Acute and chronic pain syndromes worsened by lack of autonomy and independence
Some complications are associated with the procedure and anesthetic required to intubate or extubate a patient’s trachea (Table 6.2), drain pleural spaces, or create a tracheostomy in ICU patients. However, the most frequent complications are associated with invasive ventilation, and the risk increases with time duration on mechanical ventilation. Significant complications include (Figs. 6.1 and 6.2):
Complications of tracheal intubation
During intubation (range between 13 and 30 %)
1. Hypotension or hypertension
2. Upper airway trauma – perforation or laceration of the pharynx, larynx, trachea, false passage, etc.
3. Intubation of the right main bronchus
4. Regurgitation with aspiration
7. Esophageal intubation
8. Inability to intubate or ventilate – resulting in hypoxia and death
9. Myocardial ischemia
10. Elevation of ICP
11. Spinal cord injury
15. Malfunction of endotracheal tube (partial dislodgement, inappropriate tube length, cuff laceration, occlusion, cuff leak)
16. Prolonged intubation attempt
3. Tube blockage or kinking
2. Subglottic stenosis
3. Tracheoesophageal fistula
4. Vocal cord paralysis
6. Granuloma formation
8. Late aspiration of gastric or oral secretions
More common than complications of intubation (Asai et al. 1998)
4. Hypoventilation (hypercapnia)
8. Airway obstruction
9. Sore throat, hoarseness, poor cough
10. Pulmonary edema
1. Positive-pressure ventilation complications – e.g., hyper-/hypocapnia, barotrauma, pneumothorax, ARDS
2. Cuff leak – immediate or late, requiring reintubation, possible aspiration
3. Accidental extubation
4. Agitation and need for ongoing sedation/paralysis with its own complications
Ventilator-associated pneumonia (common – 8–28 % of mechanically ventilated patients (Chastre and Fagon 2002))
Acute respiratory distress syndrome (ARDS – mortality 43–46 % (de Hemptinne et al. 2009))
Ventilator-induced lung injury (VILI) including barotrauma, volutrauma, pneumothorax/pneumomediastinum/pneumopericardium, and venous air embolism
Prolonged intubation – tracheal stenosis, abnormal swallowing, and recurrent aspiration
Failure to wean (prolonged need for mechanical ventilation)
Need for sedation and paralysis, with inherent complications
Adverse pulmonary and systemic hemodynamic effects of positive intrathoracic pressure
Cardiovascular monitoring and support is a common reason for a surgical patient to require ICU care. One-third of all postoperative complications and more than half of the deaths are due to cardiac complications (Devereaux et al. 2005a). Up to 50 % of perioperative myocardial infarctions (MIs) may be unrecognized, if physicians rely solely on clinical symptoms and signs (Devereaux et al. 2005b); 15–25 % of patients experiencing a MI following noncardiac surgery die during that admission. Furthermore, while in ICU patients may suffer complications of underlying cardiac disease brought on by the stressed and critically ill state, such as decompensated heart failure or acute myocardial ischemia. Even in the absence of underlying cardiac disease, cardiac function is often depressed in patients with severe sepsis and other multiorgan dysfunction syndromes. Some echocardiographic studies suggest up to half of patients with prolonged septic shock develop myocardial depression (defined by reduced ejection fraction) and that 25 % of septic patients without shock have impaired ventricular function (Rudiger and Singer 2007). Many of the other complications in ICU relate to drugs and procedures that either impair cardiac function or contribute to arrhythmias. Some examples include:
Acute myocardial ischemia or infarction
Cardiac failure (RV or LV or both)
Shock – multiple etiologies
Pulmonary emboli – obstructive shock
Pericarditis +/− effusion and tamponade (e.g., uremia, trauma)
Arrhythmias (e.g., from electrolyte abnormalities, ischemia, central venous/pulmonary artery catheter)
Myocardial perforation (e.g., from pacing wires or central venous catheters)
Noncardiac complications of cardiac procedures and monitoring (Francis 1999)
The kidneys normally require about 20 % of cardiac output and perfusion with blood at about 400 ml/min/100 g (kidney) in normal states and are highly sensitive to low cardiac output, low mean arterial pressure, and hypoxia. These conditions often contribute to the renal dysfunction and failure, commonly encountered in surgical patients in ICU. In approximately 6 % of ICU patients, this can be severe enough to require renal replacement therapy (dialysis) (Bagshaw et al. 2008; Uchino et al. 2005). Development of acute renal failure in ICU is associated with a mortality ranging from 50 to 70 %, especially when requiring dialysis or associated with other organ failures (Brivet et al, 1996; Briglia and Paganini 1999). Of the survivors, 5–20 % remain dialysis dependent at hospital discharge (Hoste and Schurgers 2008). Sepsis, burns, trauma, and acute respiratory failure often result in renal failure. Although usually multifactorial, the most frequent causes of renal failure in surgical ICU patients are shock, aminoglycoside therapy, and intravenous contrast media. Other conditions and therapies in ICU further contribute to the burden of renal complications. Methods for preventing or treating acute renal failure remain unclear; however, it is important to maintain circulation and to avoid the use of nephrotoxic substances such as contrast media, aminoglycosides, and nonsteroidal anti-inflammatory drugs. The concentration of these drugs should be measured and perhaps avoided or alternatives chosen, if possible. Renal replacement therapies (most commonly hemofiltration and/or hemodialysis) are delivered in ICU when required but have specific complications particularly associated with vascular access catheters and extracorporeal circuits. Some important and common complications include:
Contrast-induced nephropathy (intravenous contrast)
Acute renal failure (Table 6.3)
Acute renal failure: ICU-related causes
Renal (approx 79 %) (Coulter and Wiedemann 1999)
Drugs/toxins (especially aminoglycosides, nonsteroidal anti-inflammatory drugs (NSAIDs), contrast media, ACE inhibitors, myoglobin, amphotericin, B-lactam antibiotics)
Sepsis (48 % overall)
Prerenal (approx 17 %)
Abdominal compartment syndrome (also renal and post-renal contribution)
Post-renal (obstructive – rare 1–4 %)
Decompensation of chronic renal failure (any cause)
Complications of renal replacement therapy (disequilibrium syndromes, bleeding, hypotension, sepsis, fluid, electrolyte, and thermal homeostasis errors)
Hepatobiliary problems occur during the treatment of other systemic disorders in ICU and are frequent sequelae of sepsis, shock, and cardiac low-flow states. Although hepatic problems are principally either prehepatic, intrahepatic (hepatocellular), or posthepatic (cholestatic), in practice and in serious unwell ICU patient, mixed etiologies are usual. Unless the primary problem is with the liver, hepatic dysfunction usually corrects if the underlying problem (e.g., sepsis or shock) is corrected.
Examples of types and causes include:
TPN-related hepatobiliary complications ranging from mildly elevated liver enzyme values to steatosis, steatohepatitis, cholestasis, fibrosis, and cirrhosis. Total parenteral nutrition-related hepatobiliary complications have been reported to be very common, with incidence ranging from 20 to 75 % in adults (Guglielmi et al. 2006).
Drug-induced hepatic dysfunction or hepatitis, occasionally leading to fulminant hepatic failure.
Cholecystitis (including acalculous, especially in diabetics).
Hepatic abscess (multiple etiologies – including direct extension of infection, biliary tract disease, trauma, septicemia, inflammatory bowel disease with portal venous bacteremia).
Hepatic synthetic dysfunction from nutritional and perfusion inadequacy.
Nutrition is important for ICU survival and surgical recovery. Intravenous (total parenteral) nutrition has been shown for years to be inferior to enteric feeding and associated with greater complications (Moore et al. 1992). When gastrointestinal complications occur, as they frequently do in ICU patients, not only is the gut itself compromised, but so too is the ability for the patient to receive sufficient enteral nutrition.
Diagnosis of any gastrointestinal complication is often difficult and delayed due to paucity of signs and reported symptoms (often due to sedation and analgesia) in the ICU patient. Although gastrointestinal bleeding (GIB) is common (up to 91 % of some ICU patient groups) (Peura and Johnson 1985), overt bleeding requiring transfusion occurs in only 1–2 % (Cook et al. 1996). This must be weighed against the risk and cost of prophylaxis with gastric acid suppression, which is expensive; contributes to bacterial colonization of the upper GI tract; is associated with increased incidence of ventilator-acquired pneumonia; and can interact with other medications. Enteral feeding reduces the incidence of GIB while providing nutrition and maintaining bowel mucosal integrity so should be given early to all patients without a contraindication.
Common GI complications include:
Esophageal reflux (common in comatose patients, leading to esophagitis and aspiration)
Peptic ulceration – stress ulceration/ischemia
Abdominal compartment syndrome
Colitis (clostridial and other infective causes, antibiotics, ischemic, etc.)
Complications of enteral and parenteral nutrition
Constipation and fecal impaction or loading
Gut perforation (esophageal, gastric, duodenal, small bowel, colonic, stercoral)
Regulatory functions of the body are commonly impacted by the stresses of surgery and critical illness. As such, metabolic and endocrine abnormalities are frequently present on admission and during ICU admissions. Although the clinical significance of some of these conditions remains to be understood, many, such as hyperglycemia, have been shown to be associated with morbidity and mortality (Wah Cheung et al. 2005), so detection and treatment is important. Some of the more common abnormalities include:
Altered glucose metabolism (frequent hyper- and hypoglycemia and insulin resistance)
Adrenal insufficiency (primary adrenal failure or secondary insufficiency most commonly due to withdrawal of exogenous glucocorticoids or to hypothalamic or pituitary dysfunction)
Thyroid (hyper-, hypo-, or sick euthyroid)
Acid–base disturbances (e.g., dialysis with lactate-buffered solutions, metabolic alkalosis with furosemide therapy/contraction alkalosis, respiratory acidosis with ARDS ventilation)
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