Peroperative depth of anaesthesia may influence postoperative opioid requirements.
BACKGROUND
Studies on monitoring the depth of anaesthesia have shown that with the use of these monitors the peroperative consumption of anaesthetics can be reduced. Studies have also indicated that the peroperative depth of anaesthesia may affect the postoperative course. The purpose of this study was to evaluate a possible relation between the depths of anaesthesia and the postoperative pain score and consumption of morphine.


METHODS
We used middle latency auditory evoked potentials (MLAEPs) for monitoring the depth of anaesthesia. The study was prospective, observer blinded and included 50 women scheduled for elective abdominal hysterectomy. Anaesthesia was induced using propofol and remifentanil. Before leaving the recovery room the patients were provided with a programmed patient-controlled pump (PCA), which was only activated on demand. Auditory evoked potentials were registered from just before induction of anaesthesia and during the whole procedure, but the anaesthetist did not have access to the monitor.


RESULTS
Fifty patients were included and seven were excluded. The remaining 43 patients were divided into two groups: Group High (n=12) with an AAI>28 for >5% of the registration time and Group Low (n=31) with an AAI>28 for <5% of the registration time. Group High had significantly higher morphine requirements in the recovery and activated the PCA-pump more frequently during the first 24 postoperative hours.


CONCLUSIONS
The results indicate that the peroperative depth of anaesthesia may have effects on the postoperative analgesic requirements.
Henneberg
S W
SW
Department of Anaesthesia, The Juliane Marie Centre, Rigshospitalet, Copenhagen, Denmark. steenhenneberg@rh.dk
Rosenborg
D
D
Weber Jensen
E
E
Ahn
P
P
Burgdorff
B
B
Thomsen
L L
LL
D000328:Adult; D016058:Analgesia, Patient-Controlled / Q000379:methods; D000701:Analgesics, Opioid / Q000008:administration & dosage / Q000627:therapeutic use*; D000758:Anesthesia / Q000379:methods*; D018686:Anesthetics, Intravenous / Q000627:therapeutic use; D005072:Evoked Potentials, Auditory / Q000187:drug effects; D005260:Female; D006801:Humans; D007044:Hysterectomy / Q000379:methods; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods; D009020:Morphine / Q000008:administration & dosage / Q000627:therapeutic use*; D010147:Pain Measurement / Q000379:methods; D010149:Postoperative Pain / Q000517:prevention & control; D019990:Perioperative Care / Q000379:methods*; D010865:Pilot Projects; D010880:Piperidines / Q000627:therapeutic use; D011182:Postoperative Care / Q000379:methods*; D015742:Propofol / Q000627:therapeutic use; D011446:Prospective Studies; D000077208:Remifentanil; D016037:Single-Blind Method
D000701:Analgesics, Opioid; D018686:Anesthetics, Intravenous; D010880:Piperidines; D009020:Morphine; D000077208:Remifentanil; D015742:Propofol