A comparison of target-controlled infusion versus volatile inhalant anesthesia for heart rate, respiratory rate, and recovery time in a rat model.

We conducted this study to determine whether heart rate, respiratory rate, and recovery time differed significantly between rats receiving target-controlled infusion (TCI) and those under volatile inhalant anesthesia. TCI rats received intravenous propofol at an average effect site concentration of 11.3 microg/ml or propofol plus ketamine (5 mg/ml of propofol) at an average effect site concentration of 8.7 microg/ml. Inhalant anesthesia rats received isoflurane (average, 1.8%) delivered in medical-grade air. We used a tail-clamp response test to determine when a surgical plane of anesthesia was attained. Anesthesia was continued for 1 h from the first negative tail-clamp test. During this time the test was repeated every 10 min to confirm that a surgical plane of anesthesia was being maintained. Anesthesia then was discontinued, and the animals were monitored continuously until they recovered. Average heart rate was higher for rats during anesthesia with isoflurane compared with TCI propofol-ketamine (P =0.0053). Average respiratory rate was higher for TCI regimens compared with isoflurane anesthesia, with male rats having consistently faster respiratory rates than females (P <0.001). Recovery time was longer for both TCI regimens compared with isoflurane (P <0.001). Once venous access was accomplished, TCI anesthesia with propofol or propofol combined with a low dose of ketamine was comparable to an isoflurane inhalant regimen in ease of administration and control of the anesthetic event when used in rats for procedures of 1-h duration. Respiratory rate was increased and recovery time was longer for rats receiving the TCI regimens.