Chapter 5 Anesthesia for the Surgeon
INTRODUCTION
Perioperative management has changed significantly since the early 1980s. Specifically, many operations that historically required preoperative hospitalization are now performed as same-day admission, outpatient, or office-based procedures. An estimated 400,000 outpatient surgical procedures were performed in 1984, compared with 8.3 million procedures in 2000.1 Because of this, surgeons must be familiar with anesthesia techniques, risks, and pitfalls.
Persons older than age 65 make up the fastest-growing segment of the population in the United States and are expected to account for 20% of the population by 2025.2 As expected, this segment of the population has many comorbidites that must be accounted for when evaluating perioperative risk and the safety of outpatient procedures requiring conscious sedation. Familiarity with methods used to assess operative risk can make preoperative evaluation and preparation smooth and cost effective.
OUTPATIENT AND OFFICE-BASED ANESTHETIC PITFALLS
Neurologic System
Tables 5-1 and 5-2 list many of the commonly used analgesic and amnestic/anxiolytic agents, their doses, and reversal agents.
Meperidine-Related Seizure
• Consequence
• Repair
• Prevention
Local Anesthetic–Related Seizure
• Consequence
Table 5-3 Commonly Used Local Anesthetics
Agent | Max Dose (Interstitial) | Duration |
---|---|---|
Lidocaine (plain) | 5 mg/kg | 30–60 min |
Lidocaine with 100 mcg epinephrine* | 7 mg/kg | 1.5–2 hr |
Bupivacaine (Marcaine/Sensorcaine) | 3 mg/kg | 3–4 hr |
Chloroprocaine† | 15 mg/kg | 30–60 min |
Tetracaine† | 2 mg/kg | 3 hr |
* Contraindicated in organs supplied by end-arterioles.
† Ester class agent that can cause allergic reaction in patients allergic to para-aminobenzoic acid (PABA).
From Rutter T, Tremper K. Anesthesiology and pain management. In Greenfield L, Mulholland M, Oldham K, et al (eds): Surgery: Scientific Principles and Practice, 2nd ed. Philadelphia: Lippincott-Raven, 1997; pp 438–454; and Salam GA. Regional anesthesia for office procedures: part I: head and neck surgeries. Am Fam Physician 2004;69:585–590.
• Repair
• Prevention
Inadequate Analgesia
• Consequence
• Prevention
Inadequate Amnesia/Anxiolysis
• Consequence
• Prevention
Respiratory System
One of the most common serious adverse events associated with surgeon-delivered anesthesia is airway compromise.8 This is most commonly seen in patients receiving conscious sedation.
Delay in Control of the Airway and Failure to Recognize Respiratory Compromise
• Consequence
• Repair
• Prevention
It is important for the surgeon to assess the adequacy of the patient’s airway and pulmonary reserve prior to administering a sedative or analgesic agent. Assessment of the airway should include the Mallampati score (ability to visualize the tonsillar pillars), ability to open the mouth fully, submental distance, degree of neck mobility, and presence of facial hair. It has been shown that increasing Mallampati score, inability to open the mouth more than two finger widths, and submental distance less than three finger widths are associated with difficulty with orotracheal intubation.9 Furthermore, facial hair can make bag-mask ventilation difficult by preventing the mask from sealing around the mouth adequately.
Medication-Related Respiratory Depression
• Consequence
• Repair
• Prevention
Cardiovascular System
Hypotension
• Consequence
• Prevention
End-Organ Ischemia
• Consequence
Bupivacaine-Induced Arrhythmia
• Consequence
• Prevention
Hematologic System
Methemoglobinemia
A common anesthetic pitfall that can acutely affect the surgical patient hematologically is methemoglobinemia resulting from aerosolized anesthetic used for endoscopic procedures. Lidocaine; benzocaine, tetracaine, and butamben (Cetacaine); have been associated with methemoglobinemia, with Cetacaine implicated most often.10,11
• Consequence
• Repair
PITFALLS FOR SPECIFIC BLOCKS13
The landmarks for each of the blocks discussed later are summarized in Table 5-4. In addition, Figures 5-1 to 5-4 depict the anatomic location for each injection.
Table 5-4 Landmarks for Regional Blocks
Type of Block | Landmarks | Comments |
---|---|---|
Finger | 1 cm distal to the webspace, along the radial and ulnar sides of the finger | Epinephrine-containing anesthetics are contraindicated |
Median nerve | Deep to the flexor retinaculum, between the tendons of the flexor carpi radialis and the palmaris longus or just lateral to the tendon of the flexor carpi radialis | Aspirate prior to injection to avoid inadvertent arterial injection |
Ulnar nerve | Deep to the flexor retinaculum, medial to the tendon flexor carpi ulnaris tendon, and also along the styloid process of the ulna | Usually requires two separate injections to anesthetize the dorsal and volar branches |
Radial nerve | Wide area extending from the snuff box toward the ulnar aspect of the wrist | |
Posterior ankle | 1 cm above the posterior aspect of the medial and lateral malleoli, deep to the flexor retinaculum | Anesthetizes sole of foot. Aspirate prior to injection to avoid injection into the posterior tibial artery/vein |
Anterior ankle | 1 cm above the anterior aspect of the medial and lateral malleoli | Anesthetizes the dorsum of the foot |
From Salam GA. Regional anesthesia for office procedures: part II: extremity and inguinal area surgeries. Am Fam Physician 2004;69:896–900.
Ilioinguinal Nerve Block
The addition of ilioinguinal nerve block to the anesthetic regimen used for inguinal herniorrhaphy is associated with a lower cost and higher patient satisfaction score than those of general anesthesia or systemic sedation with local anesthesia alone.14,15 A 10- to 20-ml mixture of 0.25% bupivacaine and 1% lidocaine is injected through all layers of the anterior abdominal wall approximately 1.5 cm medial to the anterior superior iliac spine (see Fig. 5-1). This block is not intended to be used as the sole modality for analgesia during inguinal herniorrhaphy; rather, it is meant to supplement an overall regimen so as to provide better postoperative pain control and facilitate discharge from the recovery area.
• Consequence
• Repair and Prevention
Inadvertent Femoral Nerve Block
• Consequence
• Prevention
Finger Block
Two nerves travel on each side of each finger. The needle is inserted 1 cm distal to the webspace at the medial and radial sides of the digit (see Fig. 5-2). One milliliter to 2 ml of 1% lidocaine or 0.25% to 0.5% bupivacaine is injected.
Intravascular or Intraneural Injection
• Consequence
• Prevention
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