Techniques to Induce General Anesthesia

Key Points

• Neuromuscular blockade has been shown to improve the ability to face-mask ventilate and perform laryngoscopy.

• A ketamine induction is likely to preserve spontaneous ventilation; however, apnea has been reported, and airway obstruction is always possible.

• Succinylcholine, despite its side effects, is still recommended as the neuromuscular blocking drug of choice for rapid sequence induction and intubation (RSI) over rocuronium because of the advantages of its quick offset. However, the recent wider availability of sugammadex may change this recommendation.

• Although cricoid pressure (CP) may be important in reducing the risk of aspiration during airway management, it has been shown to result in greater difficulty with face-mask ventilation and to impair laryngoscopy, laryngeal mask airway (LMA) insertion, ventilation via an LMA, and intubation via an LMA.

• Inhalational induction can be performed using either vital capacity “single breath” or conventional breathing techniques.

• Pediatric patients experience a more rapid induction of anesthesia than adults with inhalational anesthetics because of a higher alveolar ventilation to functional residual capacity ratio.

• Spontaneous ventilation may be maintained with inhalational induction, but recovery from airway obstruction is highly variable and may require a prolonged period of time.

Introduction

Airway management usually requires some form of anesthesia to blunt airway reflexes, attenuate the hemodynamic response to airway instrumentation, and provide patient comfort. When clinically indicated, an “awake” technique, utilizing local anesthesia of the airway with or without sedation, can be used to meet these goals (see Chapter 12 ). In emergency settings where the patient is obtunded or comatose, such as during acute respiratory or cardiac arrest, anesthesia may not be required at all. Most commonly, however, airway management is performed after induction of general anesthesia.

Induction of general anesthesia is often achieved with anesthetic agents that produce airway obstruction and some degree of central apnea as a side effect; the addition of neuromuscular blocking drugs (NMBDs) to an intravenous (IV) induction guarantees apnea. Although it is not within the scope of this chapter, induction of general anesthesia should only be performed after careful consideration and prediction of the ability to manage the patient’s airway once apnea ensues (see Chapter 13 ). This chapter reviews common strategies to induce general anesthesia and their implications on airway management. Techniques that ablate spontaneous ventilation are discussed first, followed by techniques that are more likely to preserve spontaneous ventilation.