Clonidine en prémédication et anesthésie à l'isoflurane pour la réduction du saignement en chirurgie otologique

Abstract

Seventy-seven ASA 1 patients scheduled for ear surgery were premedicated orally, 90 min before anaesthesia. They were randomly assigned to two groups, according to the drug used : hydroxyzine alone (group T, n = 39) or combined with clonidine (4.9 ± 0,3 μg · kg −1) (group C, n = 38). Anaesthesia was induced with midazolam (0.3 mg · kg −1) and alfentanil (30 μg · kg −1). Ventilation was controlled with a 50/50 v/v mixture of oxygen and nitrous oxide (F etCO 2 = 4 to 4.5 %), and anaesthesia was maintained with repeated injections of alfentanil (15 μg · kg −1 at the start of surgery, and then every 15 min) and with isoflurane (mean end-expiratory concentration 0.6 ± 0.3 vol %). Surgical bleeding was assessed every ten minutes on a numerical scale with four values. A bloodless surgical field was obtained by adjusting the isoflurane concentration up to 2 MAC, and by using a trinitrine infusion as required. Cardiovascular monitoring included an electrocardioscope and automatic blood pressure measurements. Before induction of anaesthesia, the blood pressure was lower in group C (84.7 ± 11.2 vs. 95.9 ± 106 mmHg) (p < 0.001); the difference in heart rate was not significant (65 ± 15 vs. 70.6 ± 14 b · min −1). Moderate stable intraoperative hypotension was obtained in both groups. However, mean arterial blood pressure (C : 65.8 ± 7.8 mmHg ; T : 73 ± 9.4 mmHg) and heart rate (C : 53.4 ± 6.8 b · min −1; T : 60.4 ± 8 b · min −1) were significantly lower in the patients premedicated with clonidine (p < 0.001). There were more periods of sinus bradycardia (heart rate ≤ 50 b · min −1), mostly seen before the beginning of surgery, in group C patients (p < 0.01); atropine was also required more often (when the heart rate was ≤ 40 b · min −1) in this group of patients (NS). The comparative assessment of surgical field quality was in favour of group C (no troublesome bleeding) as opposed to the control group (16 % troublesome bleeding) ; there were also more bloodless surgical fields in the former group (73.7 % vs. 48.7 % in group T, p < 0.05). This study therefore demonstrated that clonidine premedication before anaesthesia with isoflurane was helpful in decreasing bleeding during ear surgery.