Midazolam desaturation

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. 

A 61-year-old woman was given 15 ml of lidocaine solution 2% and lidocaine spray 4% for topical anesthesia of the throat and oropharynx before upper gastrointestinal endoscopy. She was also sedated with intravenous midazolam 2 mg and pethidine 75 mg. She became cyanosed and desaturated (Sp02 78%) immediately after the procedure. Her Sp02 did not recover, despite 100% oxygen. Her methemoglobin concentration was 37%. 

An 84-year-old woman weighing 74 kg had a past history of hypertension, emphysema, and ischemic heart disease. She had an infraclavicular brachial plexus block with 40 ml (400 mg) of prilocaine 1% and 10 ml (75 mg) of ropivacaine 0.75%, and 20 minutes later developed difficulty in breathing and became desaturated. She had received midazolam 2 mg before the block. 

Midazolam was used in a wide range of doses (0.03-0.6 mg/kg) in 91 children undergoing diagnostic or minor operative procedures with intravenous midazolam sedation (7). Opioids were co-administered in 84% and oxygen desaturation occurred in 32%, most of whom had received high doses of opioids in addition to the midazolam. Other adverse events included airway obstruction (n = 3) and vomiting (n = 1). The presence of independent appropriate trained personnel not directly involved in performing the procedure, appropriate resuscitation... 

Observational studies In a prospective study of 516 children undergoing CT scans, who received midazolam 0.212 mg/kg, there was adequate sedation in 5.9 minutes and only a few patients required additional boluses [22 ]. There were adverse effects in 9.1% of patients, including desaturation in 6.9%, all of whom were treated successfully with oxygen, hiccups in 1.4%, and agitation in 0.79%. All the adverse effects were self-limitmg. 

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