What’s New in Intravenous Anesthetics?

Abstract

Summary It is obvious that many of the goals desirable in an ideal IV induction agent have not been achieved with the currently available drugs. An ideal drug for induction of anesthesia would provide for a rapid and pleasant loss of consciousness, no cardiorespiratory changes, good operating conditions, and a rapid recovery without side effects. Although they are not ideal induction agents, the newer IV anesthetics possess some unique pharmacologic properties that may offer advantages over thiopental (Table 10). Premedication with sedative-anxiolytic drugs (for example, midazolam, diazepam) can minimize preinduction anxiety and thereby, decrease the induction dosage requirements. In achieving a smooth induction of anesthesia, it is desirable to minimize myocardial oxygen demand and to maximize myocardial oxygen supply. Use of an induction technique that rapidly achieves an adequate level of anesthesia (hypnosis) and analgesia without producing hypotension or tachycardia is important in maintaining the crucial balance between oxygen supply and demand. If an adequate “depth of anesthesia” is not achieved during induction of anesthesia, larynogoscopy, and tracheal intubation will produce reflex sympathetic stimulation (that is, tachycardia, hypertension, arrhythmias), which may be extremely deleterious to the critically ill patient. Thiopental remains the most widely used IV anesthetic even though it is unstable in solution, produces significant cardiovascular and respiratory depression, lacks analgesic properties, readily crosses the placental barrier, and is associated with a high incidence of postoperative drowsiness and sedation. Unfortunately, the other available IV anesthetic agents are also capable of producing adverse reactions when used for induction of anesthesia. Although the newer IV agents should prove to be extremely useful for both induction and maintenance of anesthesia, thiopental will likely remain the drug of choice for routine induction of general anesthesia. In conclusion, the rational use of two or more rapid and relatively short-acting IV drugs possessing mutually complementary pharmacologic properties (for example, sufentanil-thiopental, alfentanil-propofol, or midazolam-ketamine) will allow the anesthetist to achieve a rapid and smooth induction, cardiovascular stability during the maintenance period, and a rapid recovery without adverse side effects. The availability of more rapid-acting and “controllable” IV anesthetics and analgesics should further enhance our ability to achieve optimal surgical conditions during general anesthesia.