Randomized controlled trial of the effect of depth of anaesthesia on postoperative pain

• Published in: British journal of anaesthesia : BJA Vol. 112; no. 4; pp. 675 - 680
• Main Authors: Law, C.J., Jacobson, G.M., Kluger, M., Chaddock, M., Scott, M., Sleigh, J.W.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01-04-2014
• Subjects: Adolescent; Adult; Aged; Analgesia, Patient-Controlled - methods; Analgesics, Opioid - administration & dosage; Analgesics, Opioid - blood; Anesthesia, General - methods; Anesthetics, Inhalation - administration & dosage; depth of anaesthesia; Double-Blind Method; Drug Administration Schedule; Electroencephalography - methods; Female; Fentanyl - administration & dosage; Fentanyl - blood; Humans; Isoflurane - administration & dosage; Isoflurane - analogs & derivatives; Male; Middle Aged; Monitoring, Intraoperative - methods; Morphine - administration & dosage; Pain Measurement - methods; Pain, Postoperative - prevention & control; postoperative pain; Young Adult; depth of anaesthesia; postoperative pain
• ISSN: 0007-0912; 1471-6771
• DOI: 10.1093/bja/aet419

Our hypothesis was that deep anaesthesia, as estimated by a low target bispectral index (BIS) of 30–40, would result in less postoperative pain than that achieved at a conventional depth of anaesthesia.
We undertook a randomized double-blind controlled study at two tertiary teaching hospitals in New Zealand (2010–1) recruiting 135 adult patients ASA I–II presenting for non-emergent surgery under general anaesthesia requiring tracheal intubation. Anaesthesia was maintained with desflurane and a multimodal analgesia regimen comprising fentanyl infusion, i.v. paracetamol, and parecoxib. Patients were randomly assigned to either a low BIS (30–40) group or a high BIS (45–60) group. Desflurane concentrations were titrated to achieve these targets. Postoperative pain was assessed by: the pain on awakening (0–10, verbal rating scale, VRSawake) in the post-anaesthetic care unit; pain on activity at 20–24 h after operation (VRSd1A); and the rate of morphine patient-controlled analgesia (PCA) usage over the first 24 h.
There was no statistically significant difference between the two groups for any of the pain scores. The median [inter-quartile range (IQR)] VRSawake was 4.0 (0–8) for the low and 4.0 (0–8) for the high BIS groups (P=0.56). The median (IQR) VRSd1A was 3.0 (1–5) for the low and 3.0 (1.5–4.5) for the high BIS groups (P=0.83). The median PCA morphine consumption in the low BIS group was 0.61 mg h−1 (0.04–1.5) vs 0.43 mg h−1 (0–1.59) in the high BIS group (P=0.98).
We conclude that there is no clinically useful analgesic effect of a deep anaesthesia regimen.