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Chapter 48. Anesthesia: Choices and Complications

Aeron Doyle, MD, MDCM, FRCPC

Hospitalists are often involved in perioperative patient care and should be familiar with techniques and complications of anesthesia, as well as preoperative and postoperative considerations. Current modalities include general anesthetics, neuraxial techniques (spinal and epidural), regional anesthetics (nerve blocks), and monitored anesthetic care (MAC), or so-called conscious sedation. Each mode of anesthesia has benefits and risks that must be weighed in view of the operative procedure and the condition and comorbidities of each patient. The administration of regional or local anesthetics does not preclude the necessity for general anesthesia in the event of unforeseen events or complications. Therefore, patients undergoing all but the most minor procedures should be assessed as potential candidates for general anesthesia.

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Cardiovascular and psychiatric medications in the perioperative period

  • Beta-blockers, calcium channel blockers, and amiodarone should be continued in the perioperative period. Patients who receive perioperative angiotensin-converting enzyme inhibitors and angiotensin receptor blockers may be at greater risk of intraoperative hypotension. Some authorities recommend holding these drugs on the day of surgery, particularly for operations with significant fluid shifts or using techniques associated with systemic inflammatory responses, such as cardiopulmonary bypass. It is traditionally recommended to stop monoamine oxidase inhibitors (MAOIs) two weeks prior to surgery. Patients who take MAOIs perioperatively are at risk of serotonergic toxicity and hypertension, especially with vasopressor use, as well as excessive sedation from inhibition of opioid metabolism by MAOIs. Some anesthesiologists continue MAOIs perioperatively, avoiding indirect-acting sympathomimetics such as ephedrine, and using narcotics such as morphine with lesser degrees of interaction with MAOIs, instead of meperidine. Tricyclic antidepressants (TCAs) and selective serotonin reuptake inhibitors (SSRIs) may be continued perioperatively. TCAs have rarely been associated with intraoperative hypotension, requiring norepinephrine for reversal. SSRIs are occasionally implicated in perioperative serotonin syndrome, particularly when given with serotonin 5-HT3 receptor antagonists such as ondansetron, and phenylpiperidine opioids such as fentanyl.

General anesthesia is usually induced with a short-acting intravenous agent such as propofol and maintained with inhaled halogenated ethers or intravenous propofol. The mechanism of action of inhalational anesthetics remains unclear and may be a membrane effect, a receptor effect, or both. These agents may be used in conjunction with narcotics and muscle relaxants to achieve balanced anesthesia and may also be supplemented with inhaled nitrous oxide. Airway protection may be obtained by endotracheal intubation; airway patency, but not protection, may be ensured with a laryngeal mask airway, or oropharyngeal airway with mask.

Complications of general anesthesia include postoperative nausea and vomiting (PONV); aspiration; complications of intubation, such as dental, mucosal, or laryngeal trauma; atelectasis and complications of positive pressure ventilation, such as barotrauma; complications of positioning during surgery; and allergic or idiosyncratic reactions to anesthetic agents. Additionally, ischemic or thromboembolic events may occur perioperatively because of physiologic stresses from surgery or anesthesia.

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Side effects of anesthesia induction...

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