Bettschart-Wolfensberger R, Bowen I M, Freeman S L, Weller R, Clarke K W
Department of Farm Animal and Equine Medical Surgery, The Royal Veterinary College, University of London, Hatfield, UK.
Equine Vet J. 2003 May;35(3):308-13. doi: 10.2746/042516403776148354.
To search for long-term total i.v. anaesthesia techniques as a potential alternative to inhalation anaesthesia.
To determine cardiopulmonary effects and anaesthesia quality of medetomidine-ketamine anaesthesia induction followed by 4 h of medetomidine-propofol anaesthesia in 6 ponies.
Sedation consisted of 7 microg/kg bwt medetomidine i.v. followed after 10 min by 2 mg/kg bwt i.v. ketamine. Anaesthesia was maintained for 4 h with 3.5 microg/kg bwt/h medetomidine and propofol at minimum infusion dose rates determined by application of supramaximal electrical pain stimuli. Ventilation was spontaneous (F(I)O2 > 0.9). Cardiopulmonary measurements were always taken before electrical stimulation, 15 mins after anaesthesia induction and at 25 min intervals.
Anaesthesia induction was excellent and movements after pain stimuli were subsequently gentle. Mean propofol infusion rates were 0.89-0.1 mg/kg bwt/min. No changes in cardiopulmonary variables occured over time. Range of mean values recorded was: respiratory rate 13.0-15.8 breaths/min; PaO2 29.1-37.9 kPa; PaCO2 6.2-6.9 kPa; heart rate 31.2-40.8 beats/min; mean arterial pressure 90.0-120.8 mmHg; cardiac index 44.1-59.8 ml/kg bwt/min; mean pulmonary arterial pressure 11.8-16.4 mmHg. Recovery to standing was an average of 31.1 mins and ponies stood within one or 2 attempts.
In this paper, ketamine anaesthesia induction avoided the problems encountered previously with propofol. Cardiovascular function was remarkably stable. Hypoxaemia did not occur but, despite F(I)O2 of > 0.9, minimal PaO2 in one pony after 4 h anaesthesia was 8.5 kPa.
The described regime might offer a good, practicable alternative to inhalation anaesthesia and has potential for reducing the fatality rate in horses.
寻找长期静脉内麻醉技术，作为吸入麻醉的一种潜在替代方法。
确定6匹小马在接受咪达唑仑 - 氯胺酮麻醉诱导后，再进行4小时咪达唑仑 - 丙泊酚麻醉时的心肺效应和麻醉质量。
镇静采用静脉注射7μg/kg体重的咪达唑仑，10分钟后静脉注射2mg/kg体重的氯胺酮。通过施加超强电疼痛刺激确定最低输注速率，以3.5μg/kg体重/小时的咪达唑仑和丙泊酚维持麻醉4小时。通气为自主呼吸（F(I)O2>0.9）。心肺测量总是在电刺激前、麻醉诱导后15分钟以及每隔25分钟进行一次。
麻醉诱导效果极佳，疼痛刺激后的动作随后很轻柔。丙泊酚的平均输注速率为0.89 - 0.1mg/kg体重/分钟。心肺变量随时间未发生变化。记录的平均值范围为：呼吸频率13.0 - 15.8次/分钟；PaO2 29.1 - 37.9kPa；PaCO2 6.2 - 6.9kPa；心率31.2 - 40.8次/分钟；平均动脉压90.0 - 120.8mmHg；心脏指数44.1 - 59.8ml/kg体重/分钟；平均肺动脉压11.8 - 16.4mmHg。恢复站立平均用时31.1分钟，小马在一两次尝试内就能站立。
在本文中，氯胺酮麻醉诱导避免了先前使用丙泊酚时遇到的问题。心血管功能非常稳定。未发生低氧血症，但尽管F(I)O2>0.9，一匹小马在麻醉4小时后的最低PaO2为8.5kPa。
所描述的方案可能为吸入麻醉提供一种良好、可行的替代方法，并且有可能降低马匹的死亡率。
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