Epidural Opiates for Relief of Cancer Pain

Summary

Epidural catheters externalized subcutaneously at a distance of 8 cm from the point of insertion were placed in 75 patients suffering from pain associated with a variety of abdominal cancers. Different opiates were administered epidurally. There were no significant differences in the degree of pain reduction after approximately equianalgetic doses, the mean pain reduction being 42% after 10 min, 60% after 30 min and 63% after 60 min. The duration of analgesia was: saline (10 ml) < bupivacaine (0.25%, 2×5 ml) < pethidine (50 mg) < fentanyl (0.1 mg) < morphine (0.05 mg/kg) < morphine (5 mg). The combination of morphine (0.05 mg/kg) and bupivacaine (0.5%, 5 ml) was highly effective (pain reduction 60 min after epidural application 100%) and duration of analgesia was even longer as after epidural morphine alone. Different diluents (saline 0.9% and dextrose 5%) and different volumes of dilution (10 ml and 0.1 ml/cm body length) had no influence on degree and duration of pain reduction. Patients, who had previously received systemic opiate therapy, showed a reduced effect (reduction of duration of analgesia by 45%) of epidural morphine. In these patients repeated administration of epidural morphine resulted in a progressive diminution in duration of effectiveness (-12.5% on the 10th day of epidural treatment), which finally led to complete tolerance after about 3 weeks in 5 patients. Tolerance was reversible after an intermediate period of epidural application of local anaesthetics.

Epidural morphine had no influence on heart rate and blood pressure and led to a slight decrease in respiratory rate and increase in P_aCO₂, during the first hour after epidural administration. VC, MBC, FEY₁and MF were not significantly affected during the first 8 hours after epidural administration. There were no changes in local blood flow of the lower extremities. Most patients experienced side-effects like tiredness (10%), nausea (16%), vomiting (6%), pruritus (53%), urinary retention (48%). Most of the patients with preceeding systemic opiate therapy showed slight withdrawal symptoms, starting 3 to 4 hours after the epidural morphine injection. After a period of 2 to 3 weeks of epidural treatment no contamination of the epidural catheter could be detected.