Donna Knarr

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.

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 0.57%, 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 ums 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 ± 23, 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 term 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. Mean (± SD) values of the pharmacokinetic parmeters for the 0.5%, 0.75%, and 1.0% groups were, respectively, MRT: 9.9 ± 3.6, 7.5 ± 2.6, and 4.5 ± 0.8 h; CL: 0.35 ± 0.21, 0.34 ± 0.24, and 0.52 ± 0.11 L·kg−1·h−1; Cmax: 0.53 ± 0.19, 1.07 ± 0.57, and 1.53 ± 0.60 μg/mL; and tmax: 1.6 ± 1.4, 0.66 ± 0.19, and 0.65 ± 0.16 h. Pharmacokinetic and pharmacodynamic characteristics of epidural ropivacaine are similar to those of epidural bupivacaine in humans.

Continuous intravenous infusion of methadone for control of burn pain.

Seventeen patients with acute, severe burns were treated with a two-stage continuous, intravenous infusion of methadone to control pain. An initial loading infusion was run for 2 hours at 0.1 mg/kg/hr of methadone; then a maintenance infusion was continued at 0.01 mg/kg/hr of methadone. Median visual analog scale scores were 70% pain relief after the 2-hour loading infusion and 80% after 24 hours. Cardiovascular parameters were stable. There was a significant decrease in the respiratory rate of the patients. It appears that continuous intravenous methadone is an effective analgesic agent for the patient with acute, severe burns. Administration of the drug should be on an individualized basis with conservative dosing in a well-monitored environment because somnolence and respiratory depression can occur.

COMPARISON OF THE EFFICACY OF EPIDURAL MORPHINE GIVEN BY INTERMITTENT INFECTION 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.

A double blind comparison of 0.5% bupivacaine and 0.5% ropivacaine given epidurally in humans

AIM OF INVESTIGATION : In this study we compare the effectiveness of interpleural bupivacaine with that of intravenous meperidine for the management of pain after cholecystectomy. We also investigate the effect of pIi-adjustment of bupivacaine using sodium bicarbonate on the onset and quality of analgesia. METHODS : Fifteen patients undergoing elective cholecystectomy and requiring postoperative analgesia were randomly assigned to three groups: group one received interpleural bupivacaine 0.5% 2Occ with epinephrine 1:200,000; group two received interpleural bupivacaine 0.5% 2Occ with epinephrine 1:200,000 and sodium bicarbonate 8.4% ml/20cc bupivacaine); (0.2

Comparative side effects of epidural morphine and meperidine

AIM OF -IGATION: To assess the degree of respiratory depression caused by a new opioid, tramado hydrochloride, and to compare this with morphine and placebo. METHODS: Double blind, placebo controlled study using three doses of tramado (0.5mg/kg, lmgkg, 2mg/kg), and morphine (O.l43mg/kg) in anaesthetised patients breathing 1% halothane prior to surgery. Following induction of anaesthesia, endotracheal intubation and return of spontaneous ventilation, patients were changed to a breathing circuit from which continuous recordings were made of respiratory rate, tidal volume, minute volume and end-tidal C02. When these had reached a ‘steady state’ (respiratory rate and ETCO2 constant), baseline measurements were recorded, the test drug administered and further recordings made at 5,10,15,20,25 and30 minutes. WS: Little change occurred in all measured respiratory parameters in the placebo group, demonstrating that breathing halothane alone caused little or no increase in respiratory depression over the measurement period. Tramadol, in all three doses, produced a small dose-dependent drop in respiratory rate within 5 minutes of injection. However, even with the highest dose of Tramadol the fall was much less marked than with morphine. Tidal volume was decreased equally in all treatment groups (including placebo) and over the same time course. Most importantly, end-tidal CO2 did not change significantly in any of the Tramaal groups, but increased markedly in the morphine group. CO CLUSIONS; Tramadol in doses up to 2mg/kg reduces respiratory rate but significantly less than morphine O.l43mg/kg. Tidal volume and end-tidal CO2 are not demonstrably affected by tramadol, although both are significantly altered by morphine. A recent parallel study in our unit in an on-demand system has shown tramadol to be equipotent with pethidine. Thus the 2mg/kg dose would correspond to 140mg intravenous bolus of pethidine in a 70kg man. Using the accepted morphine:pethidine potent y ratio of 1: 12, the failure to demonstrate clinically significant respiratory depression with 2mg/kg of Tramadol would suggest a much higher therapeutic index for this drug.

Difference in analgesia following epidural blockade in patients with postoperative or chronic low back pain

&NA; Subjective responses of continuous epidural analgesia with bupivacaine were compared in 30 patients with acute (postoperative) or chronic (low back) pain. In the acute pain patients, sensory block was 4 dermatomes at 9 h and 6 dermatomes at 64 h. Corresponding values in the chronic pain patients were 8 and 6 dermatomes respectively. Motor blockade of the lower limbs was more profound in the acute pain group. The acute pain patients had significantly better pain relief (VAS: 85–96% vs. 55–70%) and a significantly higher proportion of these patients reported a global score of 3 (excellent; 80% vs. 7%). The mean dosage of bupivacaine decreased in the acute pain group from 21.0 ± 5.7 (mean ± S.D.) mg/h at 9 h to 15.1 ± 8.5 mg/h at 64 h. Corresponding values for the chronic pain group were 20.7 ± 5.9 and 12.0 ± 6.0 mg/h respectively. Mean plasma concentration of bupivacaine increased from 1.2 ± 0.8 &mgr;g/ml at 9 h to 2.1 ±1.4 &mgr;g/ml at 64 h in the acute pain patients and was 0.8 ± 0.3 &mgr;m/ml at 9 h to 1.0 ± 1.0 &mgr;g/ml at 64 h in the chronic pain patients. The incidence of side effects was approximately the same in both groups. No signs of accumulation or toxic reactions to bupivacaine were seen.