Haemodynamic response to induction of anaesthesia with ketamine/midazolam

Abstract

The haemodynamic responses following induction of anaesthesia with ketamine and midazolam have not been determined previously. Twenty adult patients for elective myocardial revascularization were randomized to two regimens for induction of anaesthesia. Patients in Group I received ketamine, 2 mg·kg-1, and midazolam, 0.2 mg·kg-1 and those in Group II received ketamine, 2 mg·kg-1, and midazolam, 0.4 mg·kg-1. Measurements were recorded at baseline, 1 min postinduction, and at one, three, five and ten minutes after tracheal intubation. Tachycardia and hypertension (>20% increases from awake baseline values) were treated with esmolol, 250 μg·kg-1. There were 11 patients in Group I and nine patients in Group II. There were no significant intergroup differences in demographic or haemodynamic variables. Both groups had decreases (P<0.05), in stroke volume, pulmonary capillary wedge pressure, and right ventricular end-diastolic volume at multiple study intervals following anaesthetic induction. None of these changes required clinical intervention. Five patients (all in Group Il) had hypertensive responses to tracheal intubation. Preoperative hypertension (mean arterial pressure ≥100 mmHg) was a predictor (P<0.05) of a hypertensive response to intubation, independent of the midazolam dose. Intravenous ketamine and midazolam was associated with a high incidence (25%) of haemodynamic responses to tracheal intubation. The higher dose of midazolam did not provide any haemodynamic advantage. © 1991 Canadian Anesthesiologists.