Sevoflurane impairs post-operative olfactory memory but preserves olfactory function.
OBJECTIVE
The effect of anaesthesia on olfaction has not been systematically studied. Our aim is to compare the effects of general and regional anaesthesia on olfactory acuity and memory in the immediate post-operative period.


METHODS
Sixty adult patients with the American Society of Anesthesiologists I and II status scheduled for elective minor surgery were included. Exclusion criteria were smoking, alcoholism, psychiatric disease and recent or past airway infection with resulting hyposmia. Patients were randomly allocated to one of three groups (in the analysis, n = 16 in each group): epidural anaesthesia (group E), general anaesthesia with propofol (group P) and general anaesthesia with sevoflurane (group S) of 40-120 min duration. The evening before surgery, at 0.5 and at 3 h post-operatively olfactory acuity and memory were tested, along with blood sampling to measure plasma melatonin and oxytocin levels. Olfactory acuity was tested with successive dilutions of n-butyl-alcohol, and olfactory memory (interpretation of odours) with the University of Pennsylvania Smell Identification Test.


RESULTS
Patient characteristics did not differ between groups. Olfactory acuity was intact in all patients, before and after anaesthesia. Olfactory memory deteriorated in group S compared to groups P and E at both post-operative time-points. This was accompanied by a significant post-operative reduction of plasma melatonin levels in group S. Oxytocin levels remained constant in all groups.


CONCLUSIONS
Our results manifest a specific effect of sevoflurane on olfactory memory, not observed with neuraxial or total intravenous anaesthesia. The misinterpretation of odours in the immediate post-operative period by sevoflurane could be mediated by the decreased levels of melatonin.
2nd Department of Anaesthesiology, School of Medicine, University of Athens, Attikon Hospital, Athens, Greece.
Georgia
G
Kostopanagiotou
Konstantinos
K
Kalimeris
Kyriakos
K
Kesidis
Paraskevi
P
Matsota
Cleanthi
C
Dima
Maria
M
Economou
Charalambos
C
Papageorgiou
D000328:Adult; D000767:Anesthesia, Epidural / Q000009:adverse effects / Q000379:methods; D018685:Anesthetics, Inhalation / Q000009:adverse effects* / Q000627:therapeutic use; D005260:Female; D006801:Humans; D008297:Male; D008550:Melatonin / Q000097:blood; D008738:Methyl Ethers / Q000009:adverse effects* / Q000627:therapeutic use; D008875:Middle Aged; D000857:Olfaction Disorders / Q000139:chemically induced*; D055696:Olfactory Perception / Q000187:drug effects*; D010121:Oxytocin / Q000097:blood; D015742:Propofol / Q000009:adverse effects / Q000627:therapeutic use; D000077149:Sevoflurane; D013997:Time Factors
D018685:Anesthetics, Inhalation; D008738:Methyl Ethers; D000077149:Sevoflurane; D010121:Oxytocin; D008550:Melatonin; D015742:Propofol