INFLUENCE OF ANESTHESIA, POSTANESTHETIC STATE, AND RESTRAINT ON SUPERIOR MESENTERIC ARTERIAL FLOW IN NORMAL RATS

To exclude possible confounding effects of anesthesia on splanchnic hemodynamics, two different awake postanesthetic models (PAM), restrained and unrestrained, have been used. However critical analysis of the splanchnic hemodynamic state in these models is not available. We conducted experiments using chronically implanted pulsed-Doppler flow probes on the superior mesenteric artery (SMA) in ketamine-anesthetized and in postanesthetic restrained and unrestrained normal rats. Baseline values of mean SMA flow were compared with those under anesthesia (30 min), PAM (restrained or unrestrained at 90 and 150 min), and reanesthesia. Sham-anesthetized unrestrained animals provided control values. The same animals (n = 7) underwent the restrained, unrestrained, and control experiments at least 5 days apart. Ketamine anesthesia did not significantly alter mean SMA flow (89 +/- 9% of baseline) compared with sham-anesthetized controls (99 +/- 9%). Mean SMA flow in both PAM, restrained and unrestrained, had a significant (P < 0.05) decrease at 90 min (78 +/- 8 and 83 +/- 12%) and at 150 min (68 +/- 14 and 78 +/- 14%) when compared with baseline and control. Reanesthesia returned SMA flows to baseline values (91 +/- 16%). The variability of mean SMA flow was significantly increased in both PAM. Maximum variability was observed in the restrained model (69 +/- 32%). These results indicate 1) that ketamine anesthesia does not significantly alter SMA flow and 2) that both the restrained and unrestrained PAM exhibit significant alterations of the splanchnic circulation for at least 2 h after complete recovery from anesthesia. Thus, in the absence of critical evaluation, results of splanchnic hemodynamic studies with these models should be questioned. Ketamine anesthesia administered intra-muscularly may be preferred to the awake PAM for the study of the splanchnic circulation.