LETTERS TO THE EDITOR: Letters & Announcements
Hypnosis First, Then Dissociation
In this study, postoperative confusion occurred in 5 (14%) of schizophrenic patients (Group A) with small-dose ketamine and in 8 (23%) of schizophrenic patients (Group B) without ketamine. Hallucinations occurred in 1 (3%) of Group A and in 2 (6%). There was no significant difference in incidence of postoperative hallucinations between Groups A and B. The incidence of confusion, such as hallucinations, after large-dose ketamine (>2 mg kg−1) is 5–30%(1). However, small-dose ketamine does not cause hallucinations or impairment of cognitive functioning (2). Therefore, propofol anesthesia with small-dose ketamine might not increase the occurrence of postoperative hallucinations in depressed patients. However, propofol might block the hallucinations from ketamine. Friedberg (3) reported that 1264 patients with ketamine-propofol anesthesia experienced no hallucinations. In this study, anesthesia was induced with 1.0 mg · kg−1 ketamine, 1.5 mg · kg−1 propofol, and 2 μg · kg−1 fentanyl. The method of induction can decrease to 40–70 in bispectral index (BIS) monitor. Therefore, propofol may contribute to blocking hallucinations from ketamine.
Akira Kudoh, MD
1. White PF, Way WL, Trevor AL. Ketamine: its pharmacology and therapeutic uses. Anesthesiology 1982; 56: 119–36.
2. Krystal JH, Karper LP, Seibyl JP, et al. Subanesthetic effects of the noncompetitive NMDA antagonist, ketamine, in humans: psychotomimetic, perceptual, cognitive, and neuroendocrine responses. Arch Gen Psychiatry 1994; 51: 199–214.
© 2003 International Anesthesia Research Society
3. Friedberg BL. Propofol-ketamine technique: dissociative anesthesia for office surgery: a 5-year review of 1264 cases. Anesthetic Plast Surg 1999; 23: 70–5.