Anesthetic techniques

In this chapter, we will discuss the following anesthetic techniques: general anesthesia, monitored anesthesia care (MAC), and local anesthesia, specifically tailored to ambulatory surgery. The emphasis will be on the goals of the ideal ambulatory anesthetic, quick recovery with minimal adverse effects, and short times to discharge readiness. (Also see Chapter 7.) Preoperative logistics The techniques and agents discussed in this chapter will therefore focus on short-acting agents, agents with minimal or easily treatable side effects, and the use of a combination of agents (multimodal) to minimize adverse effects and maximize therapeutic effects. General anesthesia General anesthesia is a medically induced reversible coma accomplished by administering a combination of anesthetic drugs and agents for achieving amnesia, analgesia, hypnosis, and skeletal muscle relaxation. General anesthesia consists of the following phases. Induction This could be inhalational or intravenous. Inhalational induction Inhalational induction may be achieved with a mixture of oxygen/nitrous oxide (30/70) with added sevoflurane, all administered via a face mask to the patient until loss of consciousness. The airway and ventilation are supported as needed. Sevoflurane is non-irritating and has a low solubility which makes it the anesthetic of choice for inhalational induction. One option is to start with a nitrous oxide induction, wait for 1–2 min and then introduce sevoflurane 8%. Another option is to start both simultaneously, or eventually sevoflurane 8% may be used as the only agent. There are no major documented benefits or drawbacks to any of these options, and the choice of one may depend on local tradition and experience. Inhalational induction is typically used in infants and children, or in the needle-phobic adult who will not allow the placement of an intravenous line preoperatively. After loss of consciousness and placement of an IV, the airway device of choice is inserted. At this point, the patient may be given IV propofol (1 mg/kg) to achieve an adequate depth of anesthetic for insertion of a laryngeal mask airway (LMA). The advantages of inhalational induction are ease of administration and widespread acceptance in the pediatric population. Disadvantages include unpleasant odor, claustrophobia, and prolonged induction in larger and older patients with the potential for complications such as breath-holding or laryngospasm and increased incidence of PONV.