Letters to the Editor
I read with fascination the case report by Wells and Rasch (1), in which they described emergence delirium and paranoid delusions in one adult and three children recovering from sevoflurane anesthesia. Like most pediatric anesthesiologists, I have observed this phenomenon countless times, and like many pediatric anesthesiologists, I have abandoned sevoflurane as an anesthetic for the maintenance of general anesthesia; however, it has been retained as the best inhaled anesthetic for induction of anesthesia. Wells’ and Rasch’s description of the delirium is very consistent with my observations of children behaving irrationally, psychotically, and often aggressively, and like the authors, I have found that premedication does not prevent this side effect, nor can anything treat it short of re-induction of sleep, be that with opioids, benzodiazepines, or propofol. After arousal for the second time, recovery is typically uneventful.
What is going on here? Unfortunately, we must conjecture at this time, but herein lies a rare opportunity to demonstrate an anatomical basis for Freud’s theories and rescue his practice from the dreary unimaginative realm of modern psychiatric theories: It is well recognized that washout of inhaled anesthetics from the central nervous system occurs with variable time constants, a phenomenon to which the “isoflurane shakes” is attributed (rapid recovery of the spinal cord compared with slower recovery of descending inhibition of spinal cord reflexes). My observations of sevoflurane (and desflurane) delirium is consistent with rapid washout of insoluble agents from, and therefore early arousal of the id, while the ego and superego remain anesthetized and inactive in inhibiting animalistic and delusional behavior. Positron emission tomography may be one method by which the brains of patients can be serially imaged during washout of insoluble agents, allowing us to finally pinpoint the anatomical nexus of the id (rapid washout), and the ego and superego (slower washout). Perhaps combined with carefully performed psychiatric interviews during recovery and combining these data with positron emission tomography imaging, we could further differentiate the nexi of the superego and ego. The possibilities for further research then become endless.
Elliot Krane MD
1. Wells LT, Rasch DK. Emergence “ delerium” after sevoflurane anesthesia: a paranoid delusion? Anesth Analg 1999; 88:1308–10.