EPIDEMIOLOGY OF THE ADVERSE HEMODYNAMIC EVENTS OCCURRING DURING CLONIDINE ANESTHESIA - A PROSPECTIVE OPEN TRIAL OF INTRAOPERATIVE

Study Objective: Determine the hemodynamic consequences of intraoperative clonidine during major abdominal surgery. Design: Prospective open trial. Setting: Teaching hospital. Patients: 402 consecutive patients scheduled for major abdominal surgery. Interventions: 350 consecutive patients received intravenous (IV) clonidine (loading dose of 4 mu g/kg in 20 minutes at anesthesia induction, followed by a continuous infusion of 2 mu g/kg/h until the end of surgery). Fifty-two additional patients served as controls. Anesthetic technique consisted of balanced anesthesia (isoflurane, fentanyl, atracurium). ECG, invasive arterial blood pressure (BP), expiratory PCO2 and pulse oximetry were continuously recorded. Hemodynamic events (HEs) were defined as moderate for a 20% reduction of the baseline systolic blood pressure (SBP) or a heart rate (HR) decreasing between 50 beats per minute (bpm) and 40 bpm. A 30% reduction of the baseline SBP or a HR below 40 bpm was considered an important HE. The rate and duration of these events were recorded from induction to recovery. HEs requiring a specific treatment were noted. Central venous pressure, volume of fluid infused, and urinary output were also recorded. Measurements and Main Results: 21% of control patients and 31% of clonidine patients had no adverse HEs. A moderate reduction of the baseline BP was the most common episode in both groups. The incidence of the HEs (moderate and important) was similar in both groups but the duration HEs was significantly longer in the clonidine patients (p < 0.05). 40% of the control patients and 13% of the clonidine patients required specific management for their HEs (p < 0.05), the most common of which was hypotension without bradycardia. Neither coexisting pathology nor preoperative medications influenced the incidence of HEs. Conclusion: IV clonidine can be used routinely during anesthesia for major abdominal surgery.