Pain control after liver transplantation surgery

Although post-liver transplantation pain is not as severe as expected from the size of the surgical incision, optimal pain control becomes crucial to aid compliance with the ventilator, improve respiratory function, and facilitate an early weaning from mechanical ventilation.

Because the majority of analgesics are primarily metabolized and excreted by the hepatobiliary system, a poor recovery of graft function will result in a decrease in clearance and reduced elimination of the drug. On the other hand, if the liver is working well, the metabolism of analgesics improves significantly with minimal accumulation. Morphine-based analgesia has been associated with a higher risk of sedation and respiratory depression compared with major abdominal surgical procedures. Fentanyl and sufentanil in continuous intravenous infusion may be preferred in the presence of hemodynamic instability or bronchospasm. Sufentanil produces shorter-lasting respiratory depression and long-lasting analgesia than does fentanyl.

The provision of potent continuous analgesia, independent of the duration of infusion, and the unique pharmacokinetics, not significantly affected by the functional status of the graft, make remifentanil appropriate for the majority of liver-transplanted patients. Unlike for patients with very severe pain after major abdominal surgery, liver transplant recipients usually benefit from tramadol, either in repeated intravenous boluses or continuous intravenous infusion. Paracetamol has been included as adjuvant (or sole agent, rarely) in the analgesic treatment of mild to moderate postoperative pain. The combination treatment (paracetamol plus tramadol) is a reasonable, safe option with improved analgesia and concurrent reduction in the incidence of some opioid-related side effects.

Frequent review of the patient's response is mandatory when potent opioids are used because dose-dependent respiratory depression is a serious and potentially life-threatening adverse effect. The benefits provided by epidural analgesia in this particular setting should be weighed against the risks because in the presence of markedly deranged perioperative blood clotting, the development of epidural hematoma represents a disastrous complication.