Administration of ketamine or Innovar by the microdrip technic: a double blind study

This study of 40 healthy adults undergoing elective gynecologic procedures was undertaken to evaluate the microdrip technic of administering ketamine or Innovar slowly to induce anesthesia and to supplement N2O anesthesia. All patients were managed by the same anesthetist and surgeons and received 10 mg of diazepam and 0.4 mg of atropine IM for premedication. After injection of 10 mg of diazepam, anesthesia was induced by infusions containing either ketamine (2 mg/ml) or Innovar (0.1 ml/ml), at an average rate of 10 ml/min. The infusions were assigned to the patients randomly and their nature was disguised from the staff. After tracheal intubation, ventilation was mechanically supported and anesthesia maintained with N2O-O2 (2:1), by drip at a rate adjusted to the patient's vital signs, and by intermitten injections of 3 to 6 mg of d-tubocurarine. Special forms coded to suit computer use were used to collect data during induction, maintenance, and recovery, and standard mathematical tests were used for analysis. Results showed that (a) ketamine effects could not be differentiated clinically from those of Innovar; (b) ketamine dosage could be reduced to 0.3 to 0.5 the recommended bolus dosage; (c) pulse rates and incidence of mental aberrations during induction or recovery were equal in both groups; (d) blood pressure showed a modest but significant increase (10% from basal values) until 20 minutes of tracheal intubation only in the ketamine group; (e) mean Pao2 determined 30 minutes after tracheal intubation was significantly higher in the ketamine group; (f) ketamine administration by the slow (20 mg/min) microdrip technic reduces the incidence of side effects.