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| |  ESRA: Diamorphine/Bupivacine Combination Best Anesthetic Bet for Patients Undergoing Cardiac Surgery By Cameron Johnston Special to DG News
WARSAW, POLAND -- September 20, 2001 -- There is a significant difference in post-operative side effects that result from use of various epidural mixtures in cardiac surgery patients. In a presentation today at the annual meeting of the European Society for Regional Anesthesia, in Warsaw, Poland, Dr. Manuel Sanchez del Agulla, of the Manchester Royal Infirmary, in Manchester, England, discussed these findings. The researchers enrolled four groups of 10 patients, who were hospitalized for cardiac artery by-pass grafting (CABG), and treated them with different epidural mixtures during and after cardiac surgery. The anesthesia in each group was standardized and consisted of either ropivacaine 0.2% (Naropin, AstraZeneca), or bupivacaine 0.125% (Carbostesin, AstraZeneca), combined with either diamorphine 50 (µg/mL), or fentanyl (12 µg/mL). According to Dr. del Aguila, epidural anesthesia is well established as useful in cardiac surgery. However, post-operative pain, and in particular, the ESSAM (epidural scoring scale for arm movements) scale indicate that epidurals before their surgery leave patients with significant limitations in movement post-operatively. Specifically, the ESSAM score measures strength of hand-grip, wrist flexion and elbow flexion, rating all of these on a scale of 0-4, with 0 being no limitations, and four being total immobility (Elrazek at al, Anaesthesia 1999, 54:1097-1109). Sedation, pain scores, infusion rates, respiratory response rates and complications rates were recorded throughout the study. According to Dr. del Aguila, the average length of the infusion was 51 hours, delivered through an epidural catheter placed at T2/3 (between the second and third thoracic vertebrae) at an average depth of 5.6 cm. No differences in respiratory response rates, or rates of complication related to the epidural itself were observed. However, there were significant differences in the degree of motor blockade that was seen. The two ropivacaine mixtures were associated with a much greater degree of motor blockade (p=0.004) while those patients receiving the ropivacaine/fentanyl mixture had the highest pain scores (4.6 as compared with 2.9 in the bupivacaine/fentanyl cohort, and 0.8 and 0.2 in the ropivacaine/diamorphine and bupivacaine/diamorphine groups, respectively). The infusion rate, the pain score at rest, and the pain score on movement rates were all lower among both groups receiving diamorphine. The greater muscle relaxation seen in the ripovacaine group could not be explained by the dose of the local anaesthetic, the investigators said, because the same responses were not seen in the bupivacaine/fentanyl groups, despite the higher infusion rate in that group. The lower infusion rates observed in the two groups receiving diamorphine could be explained by its metabolism to morphine inside the spinal cord, and could illustrate the importance of using opiates that are lipid soluable to minimize rostral spread, the researcher said. Respiratory depression was low in all groups, which the investigators noted was important, since the epidurals were inserted fairly high up, and the rate of infusion in the fentanyl groups was considered high (13.3 in the fentanyl/ropivacaine group and 14.8 in the fentanyl/bupivacaine group). The maximum anesthetic response rates, and minimum response rates were similar between all four groups.
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