Left ventricular ejection fraction during anaesthetic induction: comparison of rapid-sequence and elective induction.

Abstract

A randomized clinical trial was conducted in 14 women, aged 24-60 years, to compare the effects of rapid-sequence induction of anaesthesia and elective induction on heart rate, blood pressure and left ventricular ejection fraction (LVEF). None of the patients suffered from heart or lung diseases, and all were scheduled for hysterectomy. Cuff blood pressure was measured repeatedly by an automatic recording device, and heart rate and LVEF were monitored by a portable nonimaging nuclear probe. In seven patients, a rapid-sequence induction was performed following preoxygenation and with simultaneous injection of thiopentone (5 mg X kg-1) and succinylcholine, without starting manual ventilation until the airway was secured with the endotracheal tube. In another seven patients, elective induction was carried out by sequential administration of the same drugs. Forty seconds after laryngoscopy and intubation mean blood pressure had increased by 38 per cent and heart rate by 29 per cent from preintubation values in the rapid sequence induction group, compared to 30 and 12 per cent respectively, in the elective induction group (p less than 0.05). Similar decreases in LVEF was observed in both groups, from 0.60 to 0.42 in the elective induction group, and from 0.60 to 0.41 in the rapid-sequence induction group. The equal depression of LVEF indicates that laryngoscopy and intubation produce, with both induction regimens, sudden impairment of cardiac function. The more pronounced hypertension and tachycardia observed during rapid-sequence induction suggests a higher myocardial oxygen consumption which may represent a serious additional burden for the poorly perfused heart.