Venugopalan C S, Holmes E, O'Malley N A
Department of Veterinary Physiology, Pharmacology and Toxicology, School of Veterinary Medicine, Louisiana State University, Baton Rouge 70803.
Am J Vet Res. 1989 Nov;50(11):1872-6.
The arrhythmogenic dose of epinephrine (ADE) was determined in heartworm-infected and noninfected (control) dogs during thiamylal-induced and halothane-maintained anesthesia to assess the myocardial sensitization. The ADE in heartworm-infected dogs (2.42 +/- 0.26 micrograms/kg of body weight) was significantly lower than that for the controls (3.36 +/- 0.29 micrograms/kg). After 2 weeks, ADE was determined again in these dogs after atropine treatment. Atropine treatment lowered the ADE to 1.76 +/- 0.33 micrograms/kg and 1.77 +/- 0.19 micrograms/kg in heartworm-positive and -negative dogs, respectively. After 2 weeks more, the ADE was determined after administration of prazosin, an alpha 1-antagonist. Only 2 of 6 controls and 3 of 6 heartworm-positive dogs had arrhythmias after a threefold increase of ADE. The mean ADE in the dogs that responded to treatment were 7.4 micrograms/kg and 7.2 micrograms/kg for heartworm-positive and -negative dogs, respectively. The finding of this study indicated that ADE in heartworm-infected dogs were lower than those in the control dogs, which makes the heartworm-infected dogs more vulnerable to arrhythmia during anesthesia. Atropine did not protect the dogs of either group. However, prazosin protected the dogs of both groups by significantly increasing the threshold of the ADE. On the basis of our findings, to reduce the risk of arrhythmia, we suggest that routine screening of dogs for heartworm infection be done before anesthetics are used.
在硫喷妥钠诱导和氟烷维持麻醉期间，测定感染心丝虫和未感染（对照）犬的肾上腺素致心律失常剂量（ADE），以评估心肌敏感性。感染心丝虫犬的ADE（2.42±0.26微克/千克体重）显著低于对照组（3.36±0.29微克/千克）。2周后，对这些犬进行阿托品治疗，然后再次测定ADE。阿托品治疗使感染心丝虫阳性和阴性犬的ADE分别降至1.76±0.33微克/千克和1.77±0.19微克/千克。再过2周，给予α1拮抗剂哌唑嗪后测定ADE。在ADE增加三倍后，6只对照犬中只有2只、6只感染心丝虫阳性犬中只有3只出现心律失常。对治疗有反应的犬中，感染心丝虫阳性和阴性犬的平均ADE分别为7.4微克/千克和7.2微克/千克。本研究结果表明，感染心丝虫犬的ADE低于对照犬，这使得感染心丝虫犬在麻醉期间更容易发生心律失常。阿托品对两组犬均无保护作用。然而，哌唑嗪通过显著提高ADE阈值对两组犬均有保护作用。基于我们的研究结果，为降低心律失常风险,我们建议在使用麻醉剂前对犬进行心丝虫感染的常规筛查。
