Metabolic and hemodynamic evaluation of two long term sedation protocols in dogs

ABSTRACT We aimed to determine the hemodynamic and metabolic parameters of two sedative protocols for long-term ventilation in dogs. Twelve dogs, were randomly allocated in two groups (n=6) who received constant rate infusion (CRI) of midazolam (0,5mg/kg/h), fentanyl (10µg/kg/h) and propofol (18mg/kg/h) in GMF or ketamine (0,6 mg/kg/h), morphine (0,26mg/kg/h) and propofol (18mg/kg/h) in GCM, during 24 hours. The dogs were mechanically ventilated to normocapnia with FiO2 of 40%. Heart rate decreased 32% in GMF and 34% in GCM during infusion time reducing CI in 24% at GMF and 29% at GCM. CaO2, CmvO2, DO2 and VO2 decreased in GCM (5%, 16%, 31% and 7% respectively) and GMF (4%, 19%, 26% and 15% respectively). Extraction ratio increased 32% in GMF and 36% in GCM without differences between groups; however, decreased VO2, evaluated for indirect calorimetry, suggests minimization of DO2 reduction. No differences between time to extubation, sternal recumbency and total recovery time were observed between groups, with an average of 33,8±15,9, 134,8±60,7 e 208±77,5 minutes respectively. We conclude that both protocols allowed mechanical ventilation with IC and DO2 reduction without metabolic and hemodynamic impairment, and can be safely used in healthy dogs.

摘要
本研究旨在明确两种用于犬长期通气的镇静方案的血流动力学与代谢参数。12只犬被随机分为两组，每组6只：GMF组接受咪达唑仑（0.5mg/kg/h）、芬太尼（10μg/kg/h）与丙泊酚（18mg/kg/h）的恒速输注（constant rate infusion, CRI），GCM组接受氯胺酮（0.6mg/kg/h）、吗啡（0.26mg/kg/h）与丙泊酚（18mg/kg/h）的恒速输注，整个干预过程持续24小时。所有犬均采用机械通气维持正常碳酸血症，吸入氧分数（FiO2）设置为40%。输注期间，GMF组心率下降32%，GCM组下降34%；两组心指数（Cardiac Index, CI）分别下降24%与29%。GCM组的动脉血氧含量（arterial oxygen content, CaO2）、混合静脉血氧含量（mixed venous oxygen content, CmvO2）、氧供（oxygen delivery, DO2）及氧耗（oxygen consumption, VO2）分别下降5%、16%、31%与7%，GMF组则分别下降4%、19%、26%与15%。氧提取率在GMF组升高32%，GCM组升高36%，两组间无显著差异；不过经间接量热法评估的氧耗下降，提示氧供下降所带来的负面影响得到了缓解。两组的拔管时间、恢复至胸骨卧位时间及总苏醒时间均无显著差异，平均时长分别为33.8±15.9、134.8±60.7及208±77.5分钟。本研究认为，两种镇静方案均可在实现心指数与氧供下降的同时，不会造成代谢与血流动力学损伤，可安全应用于健康犬。