PROPHYLACTIC ESMOLOL BOLUS TO SUPPRESS SY MPATHOADRENERGIC REACTIONS TO INDUCTION OF ANESTHESIA

In addition to laryngoscopy, endotracheal intubation and other stressf ul intraoperative phases, hypertension occurs during recovery from ana esthesia, provoking post-operative complications like bleeding and inc reased intracranial or intraocular pressure. Furthermore, these hypert ensive 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 si ngle bolus for preventing the increases in blood pressure and heart ra te during recovery from anaesthesia and extubation in patients with hy pertension was investigated. Patients and Methods. Sixty-three patient s with a history of hypertension over a period of more than 6 months a nd blood pressure (BP) more than 150/90 mm Hg undergoing intervertebra l-disc, otolaryngologic, or eye surgery were included in the study. Th e operations were performed during thiopentone-induced isoflurane anae sthesia with relaxation by atracurium. The patients were assigned to t hree groups after giving witnessed oral informed consent. During the s tudy period they received the study drug twice: (A) 30-90 s before tur ning of the nitrous oxide; and (B) 20-90 s before extubation. Group I (placebo) received placebo each time, group II (100 mg esmolol) placeb o at A and 100 mg esmolol i.v. at B, and group III (200 mg esmolol) 10 0 mg esmolol i.v. each time. After each medication the cardiovascular parameters were measured noninvasively over a period of 10 min every m inute and in the following 2 h every 15 min. Results. After the first medication systolic and diastolic BP, heart rate (HR), and rate-pressu re product (RPP) were lower in patients receiving 100 mg esmolol (Grou p III) than in groups I and II. After the second injection the blood p ressure 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 [chiBAR(2min +/- 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 drop ped below 60.min-1, but in none of these patients did the BP become in stable. Conclusions. The sympathoadrenergic reaction during recovery f rom anaesthesia and extubation can be treated by beta-blocking agents, but such therapy is not without risk because of the long half-life an d effects of the therapy on other factors such as postoperative loss o f intravascular volume. Esmolol is a new, short-acting, cardioselectiv e beta-blocker with a very short plasma distribution time and eliminat ion half-life of 9.2 min. Thus, the potential risks of beta-blockers d ue to half-life are minimised. The results of this study show that a d angerous increase in BP and HR with increased myocardial oxygen consum ption 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 p atients might indicate a risk of cardiac instability, the systolic BP did not fall below 100 mm Hg, and the episode of bradycardia was so sh ort that there was no risk to the patients.