title: An evaluation of apnea or spontaneous ventilation in early recovery following mechanical ventilation in the anesthetized horse.
abstract: OBJECTIVE
  To compare arterial oxygen and carbon dioxide tensions in apneic and spontaneously ventilating horses recovering from anesthesia.
  
  
  METHODS
  Randomized clinical trial.
  
  
  METHODS
  Forty-two healthy horses averaging 466 ± 106 kg and 6 ± 5 years of age.
  
  
  METHODS
  Anesthetized horses undergoing a variety of surgical procedures and receiving positive pressure ventilation (IPPV) were divided into two equal groups. One group was allowed to return to spontaneous ventilation prior to disconnection from the anesthetic circuit (weaned). The other group remained apneic during transport to a recovery stall. Arterial blood gas data were collected at five time points: 20 minutes before moving to a recovery stall (t = - 20); at the time the anesthetic circuit was disconncted (t = 0); at 3 and 5 minutes post-disconnection (t = 3 and t = 5) and at the time of the first spontaneous breath (t = sv). The data were analyzed using an anova method for repeated measures and paired, two-tailed t-tests. Significance was assumed when p < 0.05.
  
  
  RESULTS
  The apneic group took a mean of 5 minutes 18 seconds (± 135 seconds) before starting spontaneous ventilation. This group maintained significantly higher PaO2levels at intermediate time points (t = 0 and t = 3) but no difference was noted after 5 minutes. PaCO2levels were higher in the weaned group at time 0 minutes, returning to a comparable level to the apneic group at t = 3 minutes.
  
  
  CONCLUSIONS
  Horses can survive a short period of apnea during transport from the surgery suite to recovery stall and may benefit from a reduced incidence of transient hypoxemia compared with spontaneously ventilating horses. This information has practical implications for the anesthetist evaluating the options for discontinuing IPPV when horses are moved to a recovery stall.
authors.affiliation: University of California School of Veterinary Medicine, Department of Surgical and Radiological Sciences, Davis, CA, USA.
authors.forename: Bonnie D
authors.initials: BD
authors.lastname: Wright
authors.affiliation: University of California School of Veterinary Medicine, Department of Surgical and Radiological Sciences, Davis, CA, USA.
authors.forename: Susan V
authors.initials: SV
authors.lastname: Hildebrand
keywords: Anesthesia; apnea; equine; oxygenation; recovery; ventilation