Minimizing emergence phenomena: subdissociative dosage of ketamine in balanced surgical anesthesia

Three hundred twelve patients, ranging in age from 14 to 89 years and undergoing various major and minor surgical procedures, were anesthetized by oxygen, nitrous oxide, and ketamine in sequence. Anesthesia was induced with thiopental (5.8 mg./kg.). The first 212 patients received an initial dose of ketamine of 1.6 mg./kg. lean body mass; 100 other patients, an initial (subdissociative) dose of ketamine of 0.4 mg./kg. body weight. Subsequent doses of ketamine, one-half the initial dose, were given 20 to 40 minutes apart, as needed. Postoperative subjective reactions were limited to slight confusion on emergence, with some disorientation to time, and occurred in 10 patients (5 percent) in the first group and 4 (4 percent) in the latter group. No psychotomimetic reactions were noted in either group. The latter group unanimously found the anesthetic technic acceptable for future use.