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June 1997 Late intraoperative clonidine administration prevents postanesthetic shivering after total intravenous or volatile anesthesia.Horn E-P, Werner C, Sessler DI, Steinfath M, Schulte am Esch J;Anesthesia & Analgesia 1997; 84:613-7. [ see abstract below ] Post anesthetic shivering develops in up to 60% of patients recovering from general anesthesia. Central adrenergic receptors appear to modulate postanesthetic shivering. Previous studies utilizing clonidine suggest that its effect is related to the time, dose, and duration of its administration. In this study, patients were given either intravenous saline placebo or 3 µg/kg clonidine at the end of anesthesia maintained with either isoflurane and nitrous oxide or a continuous infusion of propofol. Groups were demographically similar and procedures lasted approximately one hour. After discontinuation of the anesthetic, the times to respond to command were similar between the groups: 9-12 minutes. Patients treated with clonidine experienced significantly less postoperative pain when first measured 15 minutes after extubation. Pain scores were 59 and 57 mm on a 100-mm scale in the isoflurane/saline and propofol/saline groups and were 19 and 24 mm in the isoflurane/clonidine and propofol/clonidine groups, respectively. The time to first analgesia administration was also significantly longer in the clonidine groups, 28 minutes vs. 10 minutes. The incidence of postanesthetic shivering was significantly reduced in both clonidine groups. 53% of isoflurane/saline patients and 13% propofol patients shivered, whereas no patient who received clonidine shivered with either anesthetic. Other potential side effects of the administration of clonidine are hypotension, bradycardia and sedation. Sedation during recovery was not measured in this study. The administration of clonidine prevented the mild arterial blood pressure increase seen at fifteen minutes after extubation in the saline groups. After clonidine administration, with both isoflurane and propofol, mean arterial blood pressure remained nearly constant and a 10 bpm decrease in heart rate was seen. The optimal dose of clonidine administered at the end of anesthesia which will both decrease post-procedural pain and decrease postanesthetic shivering, while avoiding the associated side effects of cardiovascular depression and sedation for ambulatory surgery patients remains to be further elucidated in additional studies. Return to the Current Literature Review Front Page, or read the abstract: ABSTRACT Postoperative administration of clonidine is an effective treatment for shivering. However, the ability of this drug to stop postanesthetic shivering when administered intraoperatively remains controversial. Furthermore, the relative efficacy of clonidine during isoflurane and propofol anesthesia remains unknown. We therefore evaluated the incidence of postanesthetic shivering in patients given clonidine during nitrous oxide/isoflurane or propofol anesthesia. Because clonidine is an analgesic, we also evaluated postoperative pain and analgesic requirements. We studied 60 patients undergoing elective ear or nose surgery. General anesthesia was induced with 2.0 mg/kg propofol, 1.5 micrograms/kg fentanyl, and 0.1 mg/kg vecuronium. General anesthesia was maintained with isoflurane and 70% nitrous oxide in one group of patients; in the other, a continuous infusion of propofol (8 mg.kg-1.h-1) was administered (without nitrous oxide). Five minutes before tracheal extubation, patients in each group were randomly assigned to receive saline, placebo, or 3 micrograms/kg clonidine intravenously. Postanesthetic shivering was evaluated by a blind investigator. Postoperative pain was assessed using a visual analog scale. Postoperative shivering was observed in 53% of the patients given isoflurane without clonidine and in 13% of the patients given propofol without clonidine. No patient given clonidine shivered. Clonidine administration significantly reduced postoperative pain. The incidence of postanesthetic shivering was significantly less after propofol anesthesia than after isoflurane/nitrous oxide anesthesia. However, a late intraoperative bolus administration of 3 micrograms/kg clonidine prevents postoperative shivering in patients given either type of anesthesia. |
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