Sedation-induction midazolam

Midazolam (Versed), a short-acting benzodiazepine CNS depressant, is used as a preanesthetic drug to relieve anxiety for induction of anesthesia for conscious sedation before minor procedures, such as endoscopic procedures and to supplement nitrous oxide and oxygen for short surgical procedures. When the drug is used for induction anesthesia, the patient gradually loses consciousness during a period of 1 to 2 minutes. 

Recovery is sufficiently rapid with most intravenous drugs to permit their use for short ambulatory (outpatient) surgical procedures. In the case of propofol, recovery times are similar to those seen with sevoflurane and desflurane. Although most intravenous anesthetics lack antinociceptive (analgesic) properties, their potency is adequate for short superficial surgical procedures when combined with nitrous oxide or local anesthetics, or both. Adjunctive use of potent opioids (eg, fentanyl, sufentanil or remifentanil see Chapter 31) contributes to improved cardiovascular stability, enhanced sedation, and perioperative analgesia. However, opioid compounds also enhance the ventilatory depressant effects of the intravenous agents and increase postoperative emesis. Benzodiazepines (eg, midazolam, diazepam) have a slower onset and slower recovery than the barbiturates or propofol and are rarely used for induction of anesthesia. However, preanesthetic administration of benzodiazepines (eg, midazolam) can be used to provide anxiolysis, sedation, and amnesia when used as part of an inhalational, intravenous, or balanced anesthetic technique. 

Adjunctive use of potent opioids (eg, fentanyl and related compounds) contributes cardiovascular stability, enhanced sedation, and profound analgesia. Other intravenous agents such as the benzodiazepines (eg, midazolam, diazepam) have slower onset and recovery features and are rarely used for induction of anesthesia. However, preanesthetic administration of benzodiazepines can be used to provide a basal level of sedation and amnesia when used in conjunction with other anesthetic agents. 

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. 

The pharmacology and adverse effects of midazolam in infants and children have been reviewed (4). The optimal dose of intramuscular midazolam for preoperative sedation has been studied in a double-blind prospective study of 600 patients who were age-stratified (51). The patients received intramuscular atropine 0.6 mg and one of five doses of midazolam 15 minutes before induction of anesthesia. For the age groups 20-39, 40-59, and 60-79 years, the optimal sedative and amnesic effects of midazolam were 0.10, 0.08, and 0.04 mg/kg respectively. The frequency with which the undesirable adverse effects of reduced blood pressure, oxygen desaturation, oversedation, loss of eyelash reflex, and tongue root depression occurred increased with age, and optimal doses for a low incidence of adverse effects were 0.08, 0.06, and 0.04 mg/ kg in the same age groups respectively. 

Midazolam. Give 0.05 mg/kg (up to 0.35 mg/kg for anesthesia induction) IV over 20-30 seconds (usual adult doses vary 1 mg to maximum of 5 mg given in increments of 2.5 mg every 2 minutes lower dose in geriatric patients with maximum at 3.5 mg) or 0.07-0.1 mg/kg IM. Repeat after 10-20 minutes if needed. Continuous infusions have also been used to maintain effect with initial rates of 0.02-0.1 mg/kg/h (usual adult dose 1-7 mg/h children 1-2 mcg/kg/min) and then titrated to effect. Caution There have been several reports of respiratory arrest and hypotension after rapid intravenous injection, especially when midazolam is given in combination with opioids. Prolonged continuous infusion may lead to persistent sedation after the dmg is discontinued because midazolam accumulates in tissues. 

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