Taylor P M, Kirby J J, Shrimpton D J, Johnson C B
Department of Clinical Veterinary Medicine, University of Cambridge, UK.
Equine Vet J. 1998 Jul;30(4):304-9. doi: 10.1111/j.2042-3306.1998.tb04102.x.
Sixteen colts were premedicated with acepromazine and anaesthesia was induced with detomidine and ketamine. Ponies were randomly allocated to receive halothane (HAL) or infusion of detomidine, ketamine and guaiphenesin (DKG) to maintain anaesthesia. Heart and respiratory rate, ECG, mean arterial blood pressure (MABP), cardiac index (CI), blood gases and plasma cortisol, ketamine and guaiphenesin were measured. Surgical castration took place between 45 and 75 min and anaesthesia lasted 90 min. MABP with DKG was significantly higher than with HAL, and, with HAL, MABP increased from pre-surgery (64 +/- 6 mmHg) to mid-surgery (80 +/- 5 mmHg) but did not change with DKG. At 30 min, CI was similar in both groups (57 +/- 7 ml/kg bwt/min); it decreased during surgery with HAL and remained low, but it increased slightly with DKG, and was higher than with HAL at 60 and 90 min. Plasma cortisol decreased in both groups until 40 min then increased with HAL only during surgery. Ketamine concentration reached a plateau (1.3-1.8 microg/ml) between 20 and 90 min and guaiphenesin concentration between 60 and 90 min (99-101 microg/ml). Recovery was generally smooth in both groups. This study demonstrated that during HAL the increase in blood pressure associated with surgical stimulus is accompanied by decreased CI; this did not occur during DKG which is likely to lead to better tissue perfusion than HAL. The adrenocortical activity seen during HAL was absent during DKG which may result from pituitary depression, analgesic effects of total intravenous anaesthesia (TIVA) or better perfusion.
16 匹小马驹用乙酰丙嗪进行术前用药，并用右美托咪定和氯胺酮诱导麻醉。将小马随机分配接受氟烷（HAL）或输注右美托咪定、氯胺酮和愈创甘油醚（DKG）以维持麻醉。测量心率、呼吸频率、心电图、平均动脉血压（MABP）、心脏指数（CI）、血气以及血浆皮质醇、氯胺酮和愈创甘油醚的水平。手术去势在45至75分钟之间进行，麻醉持续90分钟。使用DKG时的MABP显著高于使用HAL时，并且使用HAL时，MABP从术前（64±6 mmHg）增加到手术中（80±5 mmHg），但使用DKG时未发生变化。在30分钟时，两组的CI相似（57±7 ml/kg体重/分钟）；在使用HAL的手术过程中CI降低并保持在较低水平，但使用DKG时CI略有增加，并且在60和90分钟时高于使用HAL时。两组的血浆皮质醇在40分钟前均下降，然后仅在使用HAL的手术过程中升高。氯胺酮浓度在20至90分钟之间达到平台期（1.3 - 1.8 μg/ml），愈创甘油醚浓度在60至90分钟之间达到平台期（99 - 101 μg/ml）。两组的恢复总体上都很顺利。本研究表明，在使用HAL期间，与手术刺激相关的血压升高伴随着CI降低；而在使用DKG期间未出现这种情况，这可能导致比HAL更好的组织灌注。在使用HAL期间出现的肾上腺皮质活动在使用DKG期间未出现，这可能是由于垂体抑制、全静脉麻醉（TIVA）的镇痛作用或更好的灌注所致。
