Comparison of the efficacy of epidural morphine given by intermittent injection or continuous infusion for the management of postoperative pain.

BACKGROUND AND OBJECTIVES: To compare the effectiveness and side effects of epidural morphine sulfate (MSO4), delivered by continual infusion or intermittent bolus. METHODS: Thirty patients undergoing upper abdominal surgery were randomized into two equal groups to receive MSO4 through a thoracic epidural catheter by one of two methods. Group 1 patients received an initial bolus of morphine (0.07 mg/kg) at the end of surgery, followed by injections of 2-5 mg morphine into the epidural catheter on demand. Patients in group 2 received an initial bolus of morphine (0.03 mg/kg) during surgical peritoneal closure and were immediately started on an infusion of 0.01% morphine at 5 mL/hour (0.5 mg/hour). The infusion dose was titrated from 0.2 to 1.0 mg/hour, dependent on side effects. Outcome measurements included pulmonary function studies, arterial blood gases, morphine plasma levels, pain relief scores, global evaluations, and side effects. RESULTS: No difference existed between groups in forced vital capacity, forced expiratory volume in 1 second, or in arterial blood gas measurements. Side effects were similar in both groups. Respiratory depression was not seen in either group. Group 2 reported significantly better analgesia than group 1 on postoperative days 1 and 2 (P < .01). Peak plasma morphine levels for group 1 were significantly higher than the steady state plasma morphine levels for group 2 (P < .05). CONCLUSIONS: Continuous epidural infusion provides better analgesia without increased side effects for postoperative pain when compared with an intermittent (or demand) bolus technique.

Continuous epidural methadone for the management of postoperative pain after lower abdominal surgery.

BACKGROUND AND OBJECTIVES: The efficacy of methadone administered by continuous epidural infusion for 24 hours for the management of postoperative pain has been reported. The pharmacokinetic characteristics of methadone predict that significant accumulation would occur if infusions were continued for longer than 24 hours and that this accumulation could result in serum concentrations above the threshold associated with systemic analgesia. METHODS: We tested this hypothesis by measuring serum methadone concentrations, pain scores, and side effects in 18 patients receiving continuous epidural infusions of methadone for the relief of postoperative pain after lower abdominal surgery over 3 days. RESULTS: Twelve of 18 patients completed the study. Persistent inadequate analgesia required a change in the infusion mixture in 5 of these patients by the second postoperative day. The sixth patient suffered a fatal pulmonary embolus (judged to be unrelated to the study) on the morning of the first postoperative day. Methadone concentrations increased significantly from 20 +/- 18 ng/ml (median +/- quartile) on postoperative Day 1 to 70 +/- 47 ng/ml on Day 3. Pain relief scores steadily increased from 50 +/- 5 at 2 hours postoperatively to 83 +/- 5 by Day 3. The only side effects noted in the present study were nausea and sedation. CONCLUSION: The accumulation of serum concentrations reported here argue that the risks of thoracic epidural placement may outweigh the potential benefits when methadone is administered alone by continuous infusion for longer than 24 hours.

Pharmacodynamics and pharmacokinetics of epidural ropivacaine in humans.

The purpose of this study was to characterize the pharmacodynamics and pharmacokinetics of three concentrations of the new long-acting amide local anesthetic, ropivacaine, given epidurally in 15 physical status ASA I or II patients for elective lower-extremity orthopedic procedures using a nonrandomized open-label design. Three groups of five patients each received either 0.5%, 0.75%, or 1.0% ropivacaine. Upper and lower levels of analgesia to pinprick were determined at frequent intervals until normal sensation had completely returned. Motor blockade was assessed by use of a modified Bromage scale after each determination of level of analgesia. Fifteen venous blood samples were collected over 12 h after ropivacaine injection. Pharmacokinetic parameters were derived using serum concentration-time data. No significant differences were found between the three groups in terms of onset or recovery of motor and sensory blockade. Median maximum thoracic levels of analgesia achieved were 8, 6, and 5 for the 0.5%, 0.75%, and 1.0% groups, respectively, and occurred at 29 +/- 11, 37 +/- 21, and 30 +/- 9 min. Respective times to two-segment regression were 2.8 +/- 1.0, 3.0 +/- 0.5, and 2.9 +/- 0.6 h. Total durations of sensory blockade were 5.4 +/- 0.7, 6.5 +/- 0.4, and 6.8 +/- 0.8 h, respectively. No statistically significant differences were noted between the three groups in terms of clearance (CL). The mean residence time (MRT) was significantly longer for the 0.5% group when compared with the 1% group. The peak concentration (Cmax) for the 0.5% group was found to be significantly lower than for either the 0.75% or 1% groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of continuous epidural infusion of a local anesthetic and administration of systemic narcotics in the management of pain after total knee replacement surgery.

Continuous bupivacaine epidural analgesia was compared with conventional methods of systemic analgesic administration in the management of postoperative pain in 30 patients for 3 days following total knee replacement surgery. Patients given continuous epidural analgesia had significantly better pain relief (visual analogue scale, global evaluation), needed significantly fewer supplementary analgesics, and had significantly fewer side effects. In the epidural group, sensory block averaged six dermatomes on day 1 and four dermatomes on day 3. The number of patients with complete (or almost complete) motor block of the lower limbs decreased from eight on day 1 to five on day 3. The mean dosage of bupivacaine decreased from 21.0 +/- 5.7 (SD) mg/hr on day 1 to 15.1 +/- 8.5 mg/hr on day 3. No signs of accumulation of or toxic reactions to bupivacaine were seen.