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机械通气的镇静方案的血流动力学与代谢参数。将12只犬随机分为两组（每组n=6）：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）的恒速静脉输注（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）的恒速静脉输注，持续给药24小时。所有受试犬均以吸入氧分数（Fraction of Inspired Oxygen, FiO2）为40%的参数实施机械通气，以维持正常碳酸血症。给药期间，GMF组与GCM组的心率分别下降32%与34%，两组的心指数（Cardiac Index, CI）分别较基线下降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）、氧输送（Oxygen Delivery, DO2）与氧消耗（Oxygen Consumption, VO2）分别较基线下降5%、16%、31%与7%；GMF组上述指标分别下降4%、19%、26%与15%。两组的氧摄取率分别升高32%与36%，组间无统计学差异；但通过间接测热法（indirect calorimetry）评估的氧消耗下降提示，氧输送的降低效应已被最小化。两组的拔管时间、恢复至胸骨卧位的时间与总恢复时间均无统计学差异，平均时长分别为33.8±15.9、134.8±60.7与208±77.5分钟。本研究表明，两种镇静方案均可在维持正常碳酸血症的前提下实施机械通气，虽可导致氧输送下降，但不会造成代谢与血流动力学损伤，可安全应用于健康犬。