Comparative Systemic Toxicity of Ropivacaine and Bupivacaine in Nonpregnant and Pregnant Ewes

Anesthesiology - Tập 82 Số 3 - Trang 734-740 - 1995
Alan C. Santos1, Richard G. Arthur2, David Wlody3, Pedro De Armas4, Hisayo O. Morishima5, Mieczyslaw Finster
1Associate Professor of Anesthesiology, Obstetrics and Gynecology, School of Medicine, State University of New York at Stony Brook, Stony Brook, New York.
2Associate Professor of Anaesthesia, Department of Anaesthesia, Harvard Medical School, Brigham and Women's Hospital, Boston, Massachusetts.
3Clinical Associate Professor of Anesthesiology, Department of Anesthesiology, Health Sciences Center—Brooklyn, Brooklyn, New York.
4Instructor of Clinical Medicine, Department of Medicine, College of Physicians and Surgeons of Columbia University, New York, New York.
5Professor of Anesthesiology, Obstetrics and Gynecology, College of Physicians and Surgeons of Columbia University, New York, New York.

Tóm tắt

Background Ropivacaine is a new amide local anesthetic, having therapeutic properties similar to those of bupivacaine but with a wider margin of safety. Bupivacaine is probably the most commonly used drug in obstetric epidural analgesia, even though laboratory studies have suggested that pregnancy increases the cardiotoxicity of bupivacaine but not of other local anesthetics. The current study was designed to reevaluate, in a random and blinded fashion, the systemic toxicity of bupivacaine and ropivacaine in nonpregnant and pregnant sheep. Methods Chronically prepared nonpregnant and pregnant ewes were randomized to receive an intravenous infusion of ropivacaine or bupivacaine at a constant rate of 0.5 mg.kg-1.min-1 until circulatory collapse. The investigators were blinded to the identity of local anesthetic. Heart rate, arterial blood pressure, and cardiac rhythm were monitored throughout the study. Arterial blood samples were obtained before infusion and at the onset of toxic manifestations, which appeared in the following sequence: convulsions, hypotension, apnea, and circulatory collapse. Serum drug concentrations and protein binding were determined. Blood pH and gas tensions were measured. Results There were no significant differences between non-pregnant and pregnant animals in the doses or serum concentrations of either drug required to elicit toxic manifestations. In nonpregnant animals, similar doses and serum concentrations of ropivacaine and bupivacaine were associated with the onset of convulsions and circulatory collapse. In pregnant ewes, greater doses of ropivacaine as compared to bupivacaine were required to produce convulsions (7.5 +/- 0.5 vs. 5.0 +/- 0.6 mg.kg-1) and circulatory collapse (12.9 +/- 0.8 vs. 8.5 +/- 1.2 mg.kg-1). The corresponding serum concentrations of ropivacaine were similar to those of bupivacaine. Pregnancy did not affect the serum protein binding of either drug. The proportion of animals manifesting a malignant ventricular arrhythmia as the terminal event was similar among all groups. Conclusions The systemic toxicity of ropivacaine or bupivacaine is not enhanced by gestation in sheep. This is in contrast to an earlier study in which the cardiotoxicity of bupivacaine was enhanced during ovine pregnancy. Greater doses of ropivacaine, as compared to bupivacaine, are needed to produce toxic manifestations in pregnant animals.

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Anesthesiology

Tập 82 Số 3

734-740

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