Cardiopulmonary effects and recovery characteristics associated with 2 sedative protocols for assisted ventilation in healthy neonatal foals

Neonatal foals may require prolonged sedation to permit ventilatory support in the first few days of life. The objective of this study was to evaluate and compare the cardiopulmonary effects and clinical recovery characteristics of 2 sedative/analgesia protocols in healthy foals receiving assisted ventilation. Foals were randomized to receive dexmedetomidine, butorphanol, and propofol (DBP) or midazolam, butorphanol, and propofol (MBP) during a 24-hour period. Infusion rates of dexmedetomidine, midazolam, and propofol were adjusted and propofol boluses administered according to set protocols to maintain optimal sedation and muscle relaxation. Ventilatory support variables were adjusted to preset targets. Physiologic variables were recorded, cardiac output (CO) measured (thermodilution), and arterial and mixed venous blood collected for gas analysis at intervals up to 24 hours. Foals in group DBP received dexmedetomidine [2.4 ± 0.5 μg/kg body weight (BW) per hour], butorphanol (13 μg/kg BW per hour), and propofol (6.97 ± 0.86 mg/kg BW per hour), whereas foals in group MBP received midazolam (0.14 ± 0.04 mg/kg BW per hour), butorphanol (13 μg/kg BW per hour), and propofol (5.98 ± 1.33 mg/kg BW per hour). Foals in the DBP group received significantly more propofol boluses (9.0 ± 3.0) than those in the MBP group (4.0 ± 2.0). Although physiologic variables remained within acceptable limits, heart rate (HR), mean arterial pressure (MAP), and cardiac index (CI) were lower in foals in the DBP group than in the MBP group. Times to sternal recumbency, standing, and nursing were significantly shorter in the DBP than MBP group. We found that MBP and DBP protocols are suitable to assist ventilatory support in neonatal foals, although MBP results in a prolonged recovery compared to DBP.