Anesthesiology
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Comparative Study
Comparative effects of bupivacaine and ropivacaine on intracellular calcium transients and tension in ferret ventricular muscle.
Recent evidence suggests that ropivacaine exerts markedly less cardiotoxicity compared with bupivacaine; however, the mechanisms are not fully understood at the molecular level. ⋯ The cardiodepressant effect of bupivacaine is approximately twofold greater than that of ropivacaine. Bupivacaine suppresses Ca transients more markedly than does ropivacaine and reduces myofibrillar activation, which may at least in part underlie the greater inhibitory effect of bupivacaine on cardiac contractions. These results suggest that ropivacaine has a more favorable profile as a local anesthetic in the clinical settings.
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Opioid receptors mediate cardiac ischemic preconditioning. Remifentanil is a new, potent ultra-short-acting phenylpiperidine opioid used in high doses for anesthesia. The authors hypothesize that pretreatment with this drug confers cardioprotection. ⋯ Remifentanil mimics cardioprotection via all three opioid receptors. This differs from ischemic preconditioning, which confers cardioprotection via kappa- and Delta-, but not mu-opioid receptors. Part of the protective effect of remifentanil may be produced by mu-agonist activity outside the heart.
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Continuous positive-pressure ventilation in acute respiratory failure. By Kumar A, Falke KJ, Geffin B, Aldredge CF, Laver MB, Lowentein E, Pontoppidan H. N Engl J Med 1970; 283:1430-6. ⋯ Prevention of air-space collapse during expiration and an increase in functional residual capacity probably explain improved oxygenation with continuous positive-pressure ventilation. In four patients, subcutaneous emphysema or pneumothorax developed. Weighed against the effects of prolonged hypoxemia, these complications were not severe enough to warrant cessation of continuous positive-pressure ventilation.
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Comment Letter
Three arguments regarding a paradigm of general anesthesia.