Diazepam general anesthesia

Frequently, a preoperative sedative is given to a patient 1 to 2 hours before the administration of general anesthesia.2,36 Sedatives are usually administered orally or by intramuscular injection, and are given while the patient is still in his or her room. This approach serves to relax the patient and reduce anxiety when arriving at the operating room. Commonly used preoperative sedatives include barbiturates (secobarbital, pentobarbital), opioids (butorphanol, meperidine), and benzodiazepines (diazepam, lorazepam) (Table 11-2). Different sedatives are selected depending on the patient, the type of general anesthesia used, and the preference of the physician. 

Nevertheless, some interactions of benzodiazepines with muscle relaxants used in anesthesia have been described. Diazepam has been reported to potentiate the effects of tubocurare (163) and gallamine (164) and to reduce the effects of suxamethonium (164). However, in 113 patients undergoing general anesthesia, intravenous diazepam 20 mg, lorazepam 5 mg, and lormetaze-pam 2 mg did not potentiate the neuromuscular blocking effects of vecuronium or atracurium (162). 

In 113 patients undergoing general anesthesia, intravenous midazolam 15 mg slowed recovery of the twitch height after vecuronium and atracurium compared with diazepam. The recovery index was not altered (162). However, in another study in 20 patients, midazolam 0.3 mg/kg did not affect the duration of blockade, recovery time, intensity of fasciculations, or adequacy of relaxation for tracheal intubation produced by suxamethonium 1 mg/kg, nor the duration of blockade and adequacy of relaxation for tracheal intubation produced by pancuronium 0.025 mg/kg in incremental doses until 99% depression of muscle-twitch tension was obtained (161). Furthermore, in 60 patients undergoing maintenance anesthesia randomly assigned to one of six regimens (etomidate, fentanyl, midazolam, propofol, thiopental plus nitrous oxide, or isoflurane plus nitrous oxide), midazolam did not alter rocuronium dosage requirements (165). 

Inomata S, Nagashima A, Itagaki F, et al. CYP2C19 genotype affects diazepam pharmacokinetics and emergence from general anesthesia. Clin Pharmacol Ther 2005 78 647-55. 

Most BZs are completely absorbed from the gastrointestinal (GI) tract. The one exception is clorazepate, a pro-drug that undergoes acid hydrolysis in the stomach and is decarboxylated to form N-desmethyl-diazepam, which is then completely absorbed into the bloodstream (Bellantuono et ak, 1980 Hobbs et ak, 1996 Chouinard et ak, 1999). In contrast, most BZs, with the exception of lorazepam and midazolam, are not consistently absorbed from intramuscular injection (Chouinard et ak, 1999). Lorazepam is available as a sublingual form that reaches clinical effect at the same rate as an oral dose. In general, intravenous administration is used only for anesthesia or for the acute management of seizures. When BZs are given via this route, the onset of action is almost immediate (Chouinard et ak, 1999). 

Benzodiazepines—including diazepam, lorazepam, and midazolam—are used intravenously in anesthesia (see Chapter 25), often in combination with other agents. Not surprisingly, benzodiazepines given in large doses as adjuncts to general anesthetics may contribute to a persistent postanesthetic respiratory depression. This is probably related to their relatively long half-lives and the formation of active metabolites. However, such depressant actions of the benzodiazepines are usually reversible with flumazenil. 

General anesthetics are rarely given alone. In addition to the analgesic agents just mentioned, benzodiazepines (midazolam, Versed diazepam, Valium ) are commonly used as adjuncts for the relief of anxiety, amnesia, and sedation prior to induction of anesthesia. Neuromuscular blockers (e.g., succinylcholine or pancuronium) can also be administered during the induction of anesthesia to relax skeletal muscles. 

Indications Clinical uses include treatment of epileptic seizures and as a component of anesthesia. Benzodiazepines are usually preferred to barbiturates for treatment of anxiety. Antipsychotics are preferred for treatment of neurotic states. Indications Generally, benzodiazepines are used for treatment of anxiety and neurotic states, nervous tension, agitation, psychosomatic illness, delerium tremens. Also used for skeletal muscle relaxant, anticonvulsant, and sedative properties. Diazepam is the benzodiazepine of choice for muscle relaxation and intractable seizures. 

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