The effects of intraoperative intravenous clonidine on gastric intramucosal PCO2.

To investigate the effects of clonidine given as an anesthetic adjunct on splanchnic perfusion, we determined intramucosal gastric PCO2 using gastric tonometry in 60 patients scheduled for large intestine surgery. After induction of anesthesia, patients were randomly assigned to four groups. Patients in Group 1 received an IV infusion of sufentanil (0.2 microg x kg(-1) x h(-1)); patients in Group 2 received an IV infusion of clonidine (4 microg/kg in 20 min followed by 2 microg x kg(-1) x h(-1)); patients in Group 3 received an IV infusion of ketamine (0.5 mg/kg followed by 0.25 mg x kg(-1) x h(-1)); patients in Group 4 received an epidural infusion of bupivacaine (7 mL of 0.5% followed by 5 mL/h of 0.25%). Gastric intramucosal PCO2 was assessed immediately before skin incision and every hour during surgery using a nasogastric tube. A last measurement was taken after skin closure. An arterial sample was collected simultaneously to measure arterial PCO2. Oxygen consumption (VO2/min) was continuously recorded. Gastric intramucosal PCO2 significantly increased during surgery in all groups independent of the anesthetic technique considered (P < 0.01) and was not related to metabolic changes or blood pressure variations. This increase, however, remains in the physiologic range. In conclusion, our results demonstrate that clonidine given as an anesthetic adjutant at the dose used has no deleterious effect on splanchnic perfusion during colonic surgery. IMPLICATIONS: IV clonidine given as an anesthetic adjunct at a dose of 4 microg/kg in 20 min, followed by 2 microg x kg(-1) x h(-1), has no deleterious effect on splanchnic perfusion during colonic surgery.