The antinociceptive effect of epidural lignocaine and fentanyl during lithotripsy

To determine the antinociceptive effect of combining epidural fentanyl with lignocaine during non-immersion lithotripsy, 56 healthy patients were enrolled into a prospective, randomized, double-blind study. Epidural anaesthesia was induced with either lignocaine 300 mg alone, or lignocaine 300 mg, or 200 mg in combination with fentanyl 100 micrograms. Throughout the procedure analgesia was assessed by comparing the incidence of (a) spontaneous complaints of pain, (b) patients' attempts to withdraw from the painful stimulus, (c) supplemental epidural lignocaine requirements, (d) the haemodynamic response to lithotripsy and (e) the time to first postoperative pain. The patients who received the fentanyl-lignocaine 300 mg combination required no supplemental lignocaine, experienced marginally less intraoperative pain and recorded lower mean arterial blood pressures when compared with lignocaine 300 mg alone. However, when the combination of lignocaine 200 mg and fentanyl 100 micrograms was administered, patients experienced significantly more pain, withdrew from the painful stimulus more often and received more supplemental lignocaine when compared with the other two treatment groups. No difference was found in the time to the first complaint of postoperative pain. Similarly, discharge times were unaffected by treatment modality. We conclude that despite the addition of fentanyl, adequate analgesia during lithotripsy is dependent upon the dose of local anaesthetic administered.