Lorazepam in Open-Heart Surgery — Plasma concentrations before, during and after bypass following different dose regimens

Abstract

Thirty-six patients (29 males and 7 females) undergoing open-heart surgery received one of three different dose regimens of lorazepam. All received a weight-related oral dose (2 mg, 3 mg or 4 mg) pre-operatively for night sedation. Twenty-four patients had an additional weight-related dose (2 mg, 3 mg or 4 mg intravenously) either as part of the induction (12 patients) or just prior to connection of the heart-lung machine (12 patients). Plasma concentrations of lorazepam were measured 20 minutes after induction, immediately before bypass, 30 and 60 on bypass and 30 minutes after bypass. Only when additional intravenous lorazepam was given prior to connection to the heart-lung machine were plasma lorazepam concentrations obtained compatible with complete amnesia.

The pharmacokinetics of anesthetic drugs and adjuvants during cardiopulmonary bypass

“…References for data presented in the fig. : Propofol ( 36) ( 38) ( 35), Etomidate ( 41), Thiopentone ( 43), Methohexitone ( 7), Ketamine ( 45), Lorazepam ( 52), Midazolam ( 56) ( 33), Propranolol ( 96) ( 95), Digoxin ( 102) ( 103), Diltiazem ( 99), Lidocaine ( 88) ( 90).…”

“…Lorazepam disposition was studied by Boscoe et al ( 52) and Aaltonen et al ( 53), both of whom demonstrated a decrease in plasma concentration on starting bypass with a subsequent increase post bypass. In the study performed by Boscoe et al, lorazepam was administered the night before morning surgery.…”