Tucker Laura, Almeida Daniel, Wendt-Hornickle Erin, Baldo Caroline F, Allweiler Sandra, Guedes Alonso G P
Veterinary Clinical Sciences Department, College of Veterinary Medicine, University of Minnesota, St. Paul, MN 55108, USA.
Department of Clinical Studies, Ontario Veterinary College, University of Guelph, Guelph, ON N1G 2W1, Canada.
Animals (Basel). 2022 Feb 1;12(3):353. doi: 10.3390/ani12030353.
Lower than expected arterial oxygen tension (PaO) continues to be an unresolved problem in equine anesthesia. The aim of this randomized, crossover, and prospective study using six adult horses is to determine if a 15° reverse Trendelenburg position (RTP) increases PaO during inhalation anesthesia. Under constant-dose isoflurane anesthesia, dorsally recumbent horses were positioned either horizontally (HP) or in a 15° RTP for 2 h. Lungs were mechanically ventilated (15 mL/kg, 6 breaths/min). Arterial carbon dioxide tension (PaCO), PaO, inspired oxygen fraction (FiO), and end-tidal carbon dioxide tension (EtCO) were determined every 30 min during anesthesia. Indices of dead-space ventilation (Vd/Vt), oxygenation (P-F ratio), and perfusion (F-shunt) were calculated. Dobutamine and phenylephrine were used to support mean arterial pressure (MAP). Data are presented as median and range. In one horse, which was deemed an outlier due to its thoracic dimensions and body conformation, indices of oxygenation worsened in RTP compared to HP (median PaO 438 vs. 568 mmHg; P-F ratio 454 vs. 586 mmHg, and F-shunt 13.0 vs. 5.7 mmHg). This horse was excluded from calculations. In the remaining five horses they were significantly better with RTP compared to HP. Results in remaining five horses showed that PaO (502, 467-575 vs. 437, 395-445 mmHg), P-F ratio (518, 484-598 vs. 455, 407-458 mmHg), and F-shunt (10.1, 4.2-11.7 vs. 14.2, 13.8-16.0 mmHg) were significantly different between RTP and HP ( = 0.03). Other variables were not significantly different. In conclusion, the 15° RTP resulted in better oxygenation than HP in dorsally recumbent, isoflurane-anesthetized horses, although worsening of oxygenation may occur in individual horses. A study detailing the cardiovascular consequences of RTP is necessary before it can be recommended for clinical practice.
低于预期的动脉血氧分压（PaO）在马的麻醉中仍然是一个未解决的问题。本项随机、交叉、前瞻性研究以6匹成年马为对象，旨在确定在吸入麻醉期间，15°头高脚低卧位（RTP）是否会提高PaO。在恒定剂量异氟烷麻醉下，背卧位的马被置于水平位（HP）或15°RTP 2小时。肺进行机械通气（15 mL/kg，6次/分钟）。麻醉期间每30分钟测定动脉二氧化碳分压（PaCO）、PaO、吸入氧分数（FiO）和呼气末二氧化碳分压（EtCO）。计算无效腔通气指数（Vd/Vt）、氧合指数（P-F比值）和灌注指数（F-分流）。使用多巴酚丁胺和去氧肾上腺素维持平均动脉压（MAP）。数据以中位数和范围表示。一匹马因其胸廓尺寸和体型被视为异常值，与HP相比，其在RTP时氧合指数恶化（PaO中位数438 vs. 568 mmHg；P-F比值454 vs. 586 mmHg，F-分流13.0 vs. 5.7 mmHg）。这匹马被排除在计算之外。在其余5匹马中，与HP相比，RTP时情况明显更好。其余5匹马的结果显示，RTP和HP之间的PaO（502, 467 - 575 vs. 437, 395 - 445 mmHg）、P-F比值（518, 484 - 598 vs. 455, 407 - 458 mmHg）和F-分流（10.1, 4.2 - 11.7 vs. 14.2, 13.8 - 16.0 mmHg）有显著差异（P = 0.03）。其他变量无显著差异。总之，在背卧位、异氟烷麻醉的马中，15°RTP比HP能带来更好的氧合，尽管个别马可能出现氧合恶化。在推荐其用于临床实践之前，有必要进行一项详细研究RTP对心血管影响的研究。
