Case of the Month #28: Opioid-induced hyperalgesia by Dr Nofil Mulla

A collaborative patient-physician relationship is key. In the preoperative period, opioid education, chronic opioid cessation or tapering and risk assessment are imperative. Preoperative patient education regarding opioid use can decrease opioid consumption and improve postoperative opioid cessation.

Intraoperative analegsics

High doses of intra-operative fentanyl and remifentanil are known to be associated with an increased likelihood of OIH. Surgeries requiring short-term exposure to high potency opioids should utilise the lowest possible infusion doses (remifentanil <0.2 μg/kg/min), which need to be tapered prior to infusion cessation. Non-opioid analgesics are known to assist with opioid dose reduction. As the central glutaminergic system and NMDA receptor activation are thought to be important drivers of OIH, Ketamine and Methadone are often prescribed to prevent and treat OIH. α-2-receptor agonists, Clonidine and Dexmedetomidine have been used to treat OIH. Use of two or more non-opioid analgesics can reduce both opioid analgesic requirements and adverse opioid side effects including respiratory depression. A total daily opioid dose decrease may be accomplished by a 10–20% reduction per week. Although, tapering as high as 50% per week may be necessary in some cases, further research is needed to determine whether it is associated with increased non-compliance. As incomplete cross-tolerance exists among various opioids, the total daily dose of opioids could be decreased by 30–50% with opioid rotation which is likely to prevent OIH.

Regional analgesia and local anaesthetic techniques

Regional anaesthesia may impact central sensitisation and decrease hyperalgesia after surgery. Besides lessening acute postoperative pain, local anaesthetics are known to decrease acute inflammation, cytokine production and central markers of pain sensitisation. Neuraxial techniques are known to reduce the occurrence of OIH as well as facilitate early discharge and recovery.

Non-pharmacological techniques

Enhanced recovery after surgery (ERAS) protocols consisting of early mobilisation, optimising caloric intake, and patient education are known to improve pain outcomes. Exercise is helpful in the prevention of OIH in animal models via a descending modulatory-mediated mechanism. Perioperative patient education regarding opioid related risk and guidance on managing pain without opioids can decrease postoperative opioid consumption. Analgesic strategies can include passive range or motion, moist heat, or ice therapy. Relaxation, behavioural instruction, and other psychological support strategies should be considered to prevent OIH.