Anesthesia and analgesia
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Anesthesia and analgesia · Nov 1988
Clinical Trial Controlled Clinical TrialA dose-response study of intrathecal morphine: efficacy, duration, optimal dose, and side effects.
We performed a double-blind study of the dose-response relationship of intrathecal morphine (0, 0.3, 1, and 2.5 mg) for postoperative pain relief in 33 subjects who underwent total knee or hip replacement surgery. Assessments commenced 1 hour after the opioid injection, which was given at the end of surgery, and continued for 24 hours. Pain measurements, supplementary analgesia requirements, and adverse effects were recorded. ⋯ Pruritus was unique to intrathecal morphine administration, but nausea, vomiting, and urinary retention were common in all the groups. We conclude that no ideal dose of intrathecal morphine exists because, even with small quantities, minor adverse effects are evident. Doses between 0.3 and 1 mg, however, should provide good analgesia free from the major complication, respiratory depression.
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Anesthesia and analgesia · Nov 1988
Comparative StudyComparative pharmacokinetics of bupivacaine and ropivacaine, a new amide local anesthetic.
The pharmacokinetics of ropivacaine, a new amide local anesthetic, and bupivacaine were determined in dogs after IV and epidural administration. After 15-minute IV infusions of 3.0 mg/kg ropivacaine (n = 6) and 3.4 mg/kg bupivacaine (n = 4), the maximum arterial concentrations (Cmax) of ropivacaine averaged 2.41 +/- 0.52 micrograms/ml compared with 3.35 +/- 0.16 micrograms/ml of bupivacaine. The elimination half life (t 1/2 beta) of ropivacaine (25.9 +/- 1.7 min) was significantly shorter than for bupivacaine (39.1 +/- 13.3 min) after IV infusion. ⋯ No differences existed between t 1/2 beta values for ropivacaine and bupivacaine after epidural administration. Total body clearance of both agents tended to be lower after epidural administration, particularly when epinephrine-containing solutions were employed. Little difference existed between the two drugs when equivalent solutions were administered.(ABSTRACT TRUNCATED AT 250 WORDS)
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Anesthesia and analgesia · Nov 1988
Comparative StudyComparative motor-blocking effects of bupivacaine and ropivacaine, a new amino amide local anesthetic, in the rat and dog.
Ropivacaine (S-(-)-1-propyl-2',6'-pipecoloxylidide) is a new local anesthetic that is structurally related to mepivacaine and bupivacaine. The comparative effects of ropivacaine and bupivacaine on motor function were assessed in the laboratory rat and dog. (It was not possible to accurately evaluate sensory blockade in these models.) Several concentrations of both agents were injected in the region of the sciatic nerve of the rat and into the lumbar epidural or subarachoid space in the dog. Epidural blockade was also performed utilizing solutions of ropivacaine and bupivacaine which contained epinephrine (1:200,000). ⋯ In the epidural and spinal studies in the dog, ropivacaine was less potent and had a shorter duration of motor blockade than did bupivacaine at equal drug concentrations. A 1.0% solution of ropivacaine produced epidural motor blockade similar in onset and duration to that achieved with a 0.75% solution of bupivacaine. Epinephrine did not significantly prolong the duration of motor blockade of either agent after epidural administration.
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Anesthesia and analgesia · Nov 1988
Combined depressant effects of diltiazem and volatile anesthetics on contractility in isolated ventricular myocardium.
Because the volatile anesthetics depress the entry of calcium (Ca) into myocardial cells and also alter release of intracellular Ca stores, additional pharmacologic blockade of Ca entry could potentially enhance anesthetic-induced depression. The depressant effects of the calcium entry blocker diltiazem combined with the volatile anesthetics halothane, enflurane, or isoflurane were investigated in isolated guinea pig papillary muscle. Muscle contractions were studied in normal Tyrode solution after rest and at stimulation rates of 0.1, 0.25, 0.5, 1, 2, and 3 Hz. ⋯ Similar frequency-dependent differences in depression by approximately 2 MAC anesthetics were observed in the presence of 1 microM diltiazem. The patterns of depressant action by the volatile anesthetics were similar to those previously observed in the absence of diltiazem. Furthermore, when the volatile anesthetic depression of contractions was combined with the depression due to diltiazem-induced blockade of Ca entry, the resulting contractile depression did not differ significantly from a prediction that assumed simply additive effects.