Postoperative pain in patients with opioid tolerance: the importance of therapeutic individualisation

Abstract

Background: patients with chronic cancer pain are often treated with opioids for pain relief. However, their exposure leads to tolerance and alterations in the nociceptive signal, requiring increased doses to achieve the same pain control. This is one of the reasons why this group is considered difficult to manage in anaesthesiology. In addition, the lack of specific studies and protocols for this population results in poorer analgesic management and an increase in postoperative complications compared with opioid-naïve patients. Objective: the main objective is to compare the effect of individualizing the intravenous morphine rescue dose in PCA (Patient-Controlled Analgesia) devices based on preoperative opioid dose on the proportion of patients achieving acceptable pain control (Numerical Rating Scale ≤3 at rest, 24 h postoperatively) compared with a standard PCA morphine dose, in opioid-tolerant patients undergoing laparoscopic abdominal oncologic surgery. Study design and participants: this trial is a randomised, double-blind, multicentre, prospective, controlled trial that will study 336 patients (≥18 years) exposed to ≥60 mg oral morphine equivalent for ≥7 days, scheduled for laparoscopic oncologic abdominal surgery at Hospital Universitari Doctor Josep Trueta or Bellvitge University Hospital over one year. Methods: participating patients who have provided informed consent will be randomised 1:1 into two groups: standard PCA morphine rescue dose according to the institutional protocol or individualised PCA morphine dose adjusted to the patient's preoperative oral morphine equivalent (OME). During the postoperative stay in the Post-Anaesthesia Care Unit (PACU), patients will be controlled during the first 24 hours, where they will receive multimodal analgesia according to the protocol. At 24 hours, the proportion of patients with acceptable pain at rest (NRS ≤3) will be measured

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