Analgesia in Intensive Care

Pain in intensive care is common, often under-treated, and is assessed with a behavioural tool (the Critical-Care Pain Observation Tool or the Behavioural Pain Scale) when the patient cannot self-report. Analgesia comes first, then sedation, and a multimodal plan lowers opioid use.

Assessment. Score pain at rest and during care, at least every 4 hours, and before and after each intervention.

Opioid risks. Respiratory depression, ileus, delirium, tolerance and, with morphine, accumulation of active metabolites in kidney failure.

Opioid of choice. Fentanyl for most patients. Remifentanil for short-acting control and rapid awakening. Hydromorphone and oxycodone are alternatives. Avoid morphine in kidney failure.

Non-opioid adjuncts.

• Paracetamol regularly.

• Ketamine at low dose for opioid-sparing.

• Gabapentin or pregabalin (with kidney adjustment) for neuropathic pain.

• Lidocaine infusion for selected patients.

• Regional techniques, such as thoracic epidural or fascial plane block for rib fractures and surgery.

• Avoid NSAIDs in shock, kidney injury and bleeding risk.

Special groups.

• Opioid-tolerant patients: continue the baseline opioid and add to it.

• Children: weight-based dosing and age-appropriate pain scores.

• Pregnancy: opioids are acceptable at the lowest dose, with neonatal teams informed near delivery.

• East Africa: where fentanyl is not available, give morphine at reduced dose and longer interval in kidney impairment, with close monitoring.

• Fentanyl: bolus 25 to 100 micrograms intravenously, then infusion 25 to 200 micrograms/h (0.7 to 10 micrograms/kg/h).

• Morphine: bolus 2 to 4 mg intravenously, infusion 1 to 5 mg/h in normal kidney function.

• Hydromorphone: bolus 0.2 to 0.6 mg intravenously.

• Remifentanil: 0.025 to 0.2 micrograms/kg/min.

• Paracetamol: 1 g every 6 hours, maximum 4 g daily (15 mg/kg, maximum 60 mg/kg daily if under 50 kg).

• Ketamine: 0.05 to 0.2 mg/kg/h.

Monitoring. Pain and sedation scores every 4 hours, respiratory rate and capnography in non-ventilated patients, bowel function with a daily laxative, and review of opioid dose daily.

Stop rules. Reduce opioid dose for oversedation, respiratory depression or ileus. Reverse life-threatening depression with naloxone 0.04 to 0.4 mg intravenously in small repeated doses.

Referral and escalation. Refer to the pain team for pain not controlled by two opioids, for neuropathic pain, and for regional techniques. Involve palliative care for end-of-life symptom control.

Common errors. Not assessing pain in sedated patients, using morphine in kidney failure, continuing high opioid doses after recovery, and forgetting a laxative.