A group of anesthesiologists familiar with international disaster relief operations wrote, "There is a danger of the modern practitioner becoming an ‘anesthetic dinosaur,' unable to survive except in a sophisticated technological environment."1 Inexperience with ketamine, ether, and halothane, anesthetics commonly used in developing countries, may come to haunt those trying to deliver inhalational anesthesia in austere circumstances. Ketamine is an easy and safe anesthetic to give, even by non-anesthetists; ether is extremely safe, portable, and deliverable by improvised means. Modern anesthetists often lack a familiarity with halothane. Therefore, a description of these three anesthetics will help clinicians deliver safe anesthesia.
Ketamine merits a detailed discussion because of its wide spectrum of safe uses (e.g., sedation, regional and general anesthesia, analgesia, and psychiatry) and its availability throughout the world, even in areas with resource scarcities. (A discussion of ketamine use for C-sections is in Chapter 15, Sedation and General Anesthesia.)
"Ketamine is remarkably safe and is certainly the safest anesthetic if you are inexperienced."2 Not surprisingly, in some hospitals without a trained anesthetist, up to 90% of the operations are done under ketamine.3
Ketamine is unique, producing hypnosis (sleep), analgesia (pain relief), and amnesia (short-term memory loss).4 Patients given ketamine rapidly go into a trance-like "dissociative" state, becoming detached from their surroundings. Patients' eyes are wide open, and they have a slow nystagmus, preserve their corneal and light reflexes, and make reflexive movements.5,6 A major benefit of using ketamine is that, unless high doses are used or smaller doses are given rapidly, the patient's airway remains open and he breathes spontaneously.2,5 Even if transient apnea occurs, brief bag-valve-mask (BVM) ventilation suffices until spontaneous respirations return. Another major benefit is that patients maintain their blood pressure (BP), even in shock.7 Laryngeal spasm is an extremely rare complication.2
Being water and lipid soluble, ketamine can be administered intravenously, intramuscularly (IM), orally, rectally, subcutaneously, transnasally, transdermally, and via an epidural block. Ketamine has a slower onset than other intravenous (IV) anesthetic agents after an IV bolus (1 to 5 minutes), and its duration of action depends on the route of administration (20 to 30 minutes for IM; 10 to 15 minutes for IV).6
Ketamine comes in three concentrations: 10 mg/mL, 50 mg/mL, and 100 mg/mL. If only one strength is to be kept in a hospital, the 50-mg/mL ampoule is the best compromise, since it can be used for IM injections or may be diluted down to 10 mg/mL for IV use. Protect the medication from light when stored. Ketamine's physiological effects are shown in Table 16-1.
Table 16-1 Ketamine's Physiological Effects ||Download (.pdf)
Table 16-1 Ketamine's Physiological Effects
Baroreceptors: Normal function