Titration of intravenous anesthetics for cardioversion

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Abstract
To compare propofol, methohexital, and midazolam administered as titrated infusions for sedation during electrical cardioversion. A prospective, randomized, single-blind comparative study. Coronary care unit in a military teaching hospital. Thirty adult patients with atrial fibrillation, atrial flutter, or paroxysmal supraventricular tachycardia. Each patient required electrical cardioversion. Patients were randomized to receive one of the three study drugs. Ten patients composed one drug group. Demographic variables were similar between groups. Patients were randomized to receive propofol (10 mg/mL), methohexital (5 mg/mL), or midazolam (0.5 mg/mL) administered at 10 mL/min until the patients failed to follow verbal commands and demonstrated a degradation of the lid response to stimulation. Dose requirements (mean +/- SD) were propofol 1.69 +/- 0.46 mg/kg, methohexital 1.07 +/- 0.34 mg/kg, and midazolam 0.16 +/- 0.06 mg/kg. Hemodynamic assessment at baseline, after induction, after cardioversion, and at recovery demonstrated no difference in mean arterial pressure between the three groups. The time to awakening was significantly prolonged in the group that received midazolam (33 +/- 11 mins, p < .05) as compared with the times of the groups that received propofol (11 +/- 4 mins) and methohexital (9 +/- 3 min). Side-effects were similar between groups, with the exception of an increase in pain on injection with propofol and an increased frequency of confusion in those patients receiving midazolam. Recall of the electrical discharges at one hour after the procedure occurred in two patients in the propofol group. In both cases, there were technical problems which caused the duration of the procedure to extend into the anticipated recovery period. Unit dose costs at our institution for a 70-kg patient are: methohexitol, $3.14 (500-mg bottle); medazolam, $14.88 (5-mg vials x 3); and propofol, $6.60 (200-mg ampule). All three drugs are acceptable choices for use during elective direct-current cardioversion. Titration of the agent results in a total drug dose which is usually less than the typical induction dose. There were no significant differences in the hemodynamic actions of these drugs at any time interval. Both propofol and methohexital proved superior in their ability to provide a more rapid anesthetic onset and recovery as compared with midazolam. Propofol offers the advantage of requiring no premixing or dilution, and it is not a controlled substance, although it does result in more pain on injection.

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