Epidural catheter analgesia for the management of postoperative pain
Since its introduction to North America in 1942, the use of epidural catheter analgesia has increased dramatically. Improved equipment, methods and medications have broadened its application to include among others, surgical anesthesia, chronic pain relief and the management of postoperative pain. Numerous techniques for epidural puncture and insertion of the catheter have been described. Although complications have been associated with placement of an epidural catheter, these are rare when performed by an experienced anesthesiologist. Epidural analgesia was first accomplished by blockade with local anesthetics. Bupivacaine has been called the local anesthetic of choice for epidural infusion. Bolus administration of epidural local anesthetics gives effective analgesia; however, its use is limited by brief duration and occasionally severe hypotension. Epidural local anesthetics have been administered by continuous infusion in an attempt to minimize side effects. Nevertheless, hypotension, as well as motor block, numbness, nausea and urinary retention have occurred. Epidural analgesia with local anesthetics is effective in relieving postoperative pain, but its safety and feasibility have been questioned because of the frequent, potentially serious side effects. These problems led to trials of epidural narcotics for postoperative pain management. The exact site of action of epidural narcotic analgesics is debatable; however, the bulk of evidence supports a direct spinal action. Epidural narcotics appear to specifically inhibit nociceptive stimuli. The prolonged and profound analgesia that occurs with epidural narcotics relative to parenteral administration is due to a higher concentration of drug reaching the CSF through the epidural route. Since nervous transmission is not completely blocked this technique cannot provide anesthesia during operation. Morphine has been the most frequently used narcotic for epidural analgesia. Results of several recent, randomized double-blind studies have shown that epidural narcotics give adequate analgesia comparable with that observed with epidural bupivacaine. Epidural morphine provides a greater duration of analgesia and may cause fewer side effects. Improved analgesia has been reported when epidural narcotics are used in combination with local anesthetics. Continuous administration of low dosage epidural narcotics has been shown to have less frequent side effects than bolus administration. Nevertheless, pruritus, urinary retention, hypotension and severe respiratory depression have been reported with both methods.(ABSTRACT TRUNCATED AT 400 WORDS)
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ABSTRACT: Twenty-one patients who underwent elective cholecystectomy were studied with regard to the effect of intrapleural administration of bupivacaine-adrenaline solution on postoperative pain and ventilatory capacity. Administration of 10 or 20 ml of 2.5 mg/ml or 5 mg/ml bupivacaine solution resulted in complete analgesia in 143 of 159 administrations. Most patients experienced the maximal pain-relieving effect within 1-2 min and analgesia persisted as a rule for 3-5 h. Forced vital capacity and forced expiratory volume in 1 s increased after intrapleural analgesia on average by 56% and 46%, respectively, on the first postoperative day and by 35% and 51%, respectively, on the second day. There was no significant difference in the analgesic effect or in the effect on the ventilatory capacity between the 2.5 mg/ml or the 5 mg/ml solution, in either the 10 ml or the 20 ml dose. Placebo (NaCl) given intrapleurally had no effect on pain or on the ventilatory capacity. The plasma concentration of bupivacaine after intrapleural administration showed a wide interindividual variation, with considerably higher average values when the 5 mg/ml solution had been used than for the 2.5 mg/ml solution. Although no toxic effects were noted, a 2.5 mg/ml solution, which can be given in an initial dose of 20 ml and top-up doses of 10 ml at 3-6 h intervals, is recommended. In four patients minor pneumothorax developed when the catheter was introduced. The pneumothorax was easily evacuated, but underlines the need for great care when introducing the catheter.
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ABSTRACT: Improvement in postoperative pulmonary mechanics with epidural analgesia has been described. Data on the hemodynamic effects of this technique are absent from the surgical literature. To provide such data we have evaluated two groups of patients undergoing aortic reconstruction: group I (n = 25), general anesthesia and group II (n = 6), general anesthesia with adjunctive epidural analgesia. The groups were comparable preoperatively as judged by the incidence of cardiac history, preoperative ejection fraction, and measured hemodynamic parameters. Postoperatively there were no significant differences in the pressure-related parameters; however, rate-related factors including heart rate and double product were significantly decreased in group II with no reduction in cardiac index. Postoperative increases in total body oxygen consumption were also markedly attenuated by epidural analgesia. Epidural analgesia reduces the hemodynamic demands on the heart after major surgery and is a useful adjunct, especially in patients with coronary artery disease.
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