[Effects of clonidine and midazolam on postoperative shivering, nausea, and vomiting]

Postoperative shivering, nausea, and vomiting are common problems after general anesthesia. We compared the effects of clonidine and those of midazolam on postoperative shivering, nausea and vomiting in elderly patients.

We studied 40 elderly patients (age > 60 yr) undergoing elective surgery under general anesthesia combined with epidural anesthesia. Patients were allocated randomly to receive oral clonidine 3-4 microg x kg(-1) (clonidine group) or intramuscular midazolam 0.04-0.05 mg x kg(-1) (midazolam group). Anesthesia was maintained with sevoflurane in a nitrous oxide and oxygen mixture, and fentanyl as needed, combined with epidural anesthesia with mepivacaine. Shivering, nausea, and vomiting were recorded at recovery from anesthesia, 3 h after the transference to the ward, and the next morning. Shivering was graded by using a three-point rating scale, whereas nausea and vomiting were assessed by means of a four-point rating.

The incidence of shivering was lower at recovery from anesthesia in the clonidine group (P < 0.05). Likewise, the incidence of nausea was lower at recovery from anesthesia in the clonidine group (P < 0.05). There were no differences in shivering and nausea at other recording points. One patient in each group had vomiting.

Clonidine premedication is effective for preventing shivering and nausea after general anesthesia combined with epidural anesthesia.