Teixeira Neto Francisco J, McDonell Wayne N, Black William D, Moraes Aury N, Duronghphongtorn Sumit
Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada, N1G 2W1.
Am J Vet Res. 2004 Apr;65(4):464-72. doi: 10.2460/ajvr.2004.65.464.
To evaluate the cardiorespiratory and intestinal effects of the muscarinic type-2 (M2) antagonist, methoctramine, in anesthetized horses.
6 horses.
Horses were allocated to 2 treatments in a randomized complete block design. Anesthesia was maintained with halothane (1% end-tidal concentration) combined with a constant-rate infusion of xylazine hydrochloride (1 mg/kg/h, i.v.) and mechanical ventilation. Hemodynamic variables were monitored after induction of anesthesia and for 120 minutes after administration of methoctramine or saline (0.9% NaCl) solution (control treatment). Methoctramine was given at 10-minute intervals (10 microg/kg, i.v.) until heart rate (HR) increased at least 30% above baseline values or until a maximum cumulative dose of 30 microg/kg had been administered. Recovery characteristics, intestinal auscultation scores, and intestinal transit determined by use of chromium oxide were assessed during the postanesthetic period.
Methoctramine was given at a total cumulative dose of 30 microg/kg to 4 horses, whereas 2 horses received 10 microg/kg. Administration of methoctramine resulted in increases in HR, cardiac output, arterial blood pressure, and tissue oxygen delivery. Intestinal auscultation scores and intestinal transit time (interval to first and last detection of chromium oxide in the feces) did not differ between treatment groups.
Methoctramine improved hemodynamic function in horses anesthetized by use of halothane and xylazine without causing a clinically detectable delay in the return to normal intestinal motility during the postanesthetic period. Because of their selective positive chronotropic effects, M2 antagonists may represent a safe alternative for treatment of horses with intraoperative bradycardia.
评估毒蕈碱2型（M2）拮抗剂甲戊氨酯对麻醉马匹心肺及肠道的影响。
6匹马。
采用随机完全区组设计将马匹分为2组。用氟烷（呼气末浓度1%）联合持续静脉输注盐酸赛拉嗪（1毫克/千克/小时）及机械通气维持麻醉。在麻醉诱导后以及给予甲戊氨酯或生理盐水（0.9%氯化钠溶液，对照处理）后120分钟监测血流动力学变量。每隔10分钟静脉注射甲戊氨酯（10微克/千克），直至心率（HR）比基线值至少增加30%，或直至给予最大累积剂量30微克/千克。在麻醉后阶段评估恢复特征、肠道听诊评分以及使用氧化铬测定的肠道转运情况。
4匹马接受的甲戊氨酯总累积剂量为30微克/千克，而2匹马接受10微克/千克。给予甲戊氨酯导致心率、心输出量、动脉血压和组织氧输送增加。各处理组之间的肠道听诊评分和肠道转运时间（粪便中首次和最后检测到氧化铬的间隔时间）无差异。
甲戊氨酯改善了使用氟烷和赛拉嗪麻醉的马匹的血流动力学功能，且在麻醉后阶段未导致临床上可检测到的恢复正常肠道蠕动的延迟。由于其选择性正性变时作用，M2拮抗剂可能是治疗术中出现心动过缓马匹的一种安全替代药物。
