JOURNAL ARTICLE
RANDOMIZED CONTROLLED TRIAL

[Esmolol as a bolus for prevention of sympathetic adrenergic reactions following induction of anesthesia]

J Schäffer, C Karg, S Piepenbrock
Der Anaesthesist 1994, 43 (11): 723-9
7840400
In addition to laryngoscopy, endotracheal intubation, and other stressful intraoperative phases, hypertension occurs during recovery from anaesthesia, provoking post-operative complications like bleeding and increased intracranial or intraocular pressure. Furthermore, these hypertensive reactions result in life-threatening complications, especially in patients with pre-existing cardiovascular diseases. In this study, the effect of the new, short-acting beta-blocker esmolol given as a single bolus for preventing the increases in blood pressure and heart rate during recovery from anaesthesia and extubation in patients with hypertension was investigated. PATIENTS AND METHODS. Sixty-three patients with a history of hypertension over a period of more than 6 months and blood pressure (BP) more than 150/90 mm Hg undergoing intervertebral-disc, otolaryngologic, or eye surgery were included in the study. The operations were performed during thiopentone-induced isoflurane anaesthesia with relaxation by atracurium. The patients were assigned to three groups after giving witnessed oral informed consent. During the study period they received the study drug twice: (A) 30-90 s before turning off the nitrous oxide; and (B) 20-90 s before extubation. Group I (placebo) received placebo each time, group II (100 mg esmolol) placebo at A and 100 mg esmolol i.v. at B, and group III (200 mg esmolol) 100 mg esmolol i.v. each time. After each medication the cardiovascular parameters were measured noninvasively over a period of 10 min every minute and in the following 2 h every 15 min. RESULTS. After the first medication systolic and diastolic BP, heart rate (HR), and rate-pressure product (RPP) were lower in patients receiving 100 mg esmolol (Group III) than in groups I and II. After the second injection the blood pressure was lower in the two groups receiving 100 mg esmolol, than the placebo group (I: 180.1 +/- 7.4/100.7 +/- 3.6; II: 152.8 +/- 5.8/87.9 +/- 3.4; III: 157.9 +/- 5.3/91.5 +/- 3.6 mm Hg [mean 2 min +/- SEM]). The changes in HR (I: 88.2 +/- 3.8; II: 75.6 +/- 2.6; III: 72 +/- 3.1 min-1) and RPP (I: 15,800 +/- 900; II: 11,700 +/- 700; III: 11,400 +/- 600) were similar. In 8 of the 20 patients in group III the HR dropped below 60.min-1, but in none of these patients did the BP become instable. CONCLUSIONS. The sympathoadrenergic reaction during recovery from anaesthesia and extubation can be treated by beta-blocking agents, but such therapy is not without risk because of the long half-life and effects of the therapy on other factors such as postoperative loss of intravascular volume. Esmolol is a new, short-acting, cardioselective beta-blocker with a very short plasma distribution time and a elimination half-life of 9.2 min. Thus, the potential risks of beta-blockers due to half-life are minimised. The results of this study show that a dangerous increase in BP and HR with increased myocardial oxygen consumption can be prevented by a single bolus, and better by a double bolus of 100 mg esmolol. Although bradycardia with HR below 50.min-1 in 8 patients might indicate a risk of cardiac instability, the systolic BP did not fall below 100 mm Hg, and the episode of bradycardia was so short that there was no risk to the patients.

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