An evaluation of apnea or spontaneous ventilation in early recovery following mechanical ventilation in the anesthetized horse.

This research evaluates the effects of apnea (temporary cessation of breathing) versus spontaneous ventilation during the recovery phase after anesthesia in horses. The results indicate that horses can survive a short period of apnea and may even benefit by experiencing less transient hypoxemia, a condition characterized by low oxygen level in blood.

Methods and Scope of the Study

• 42 healthy horses, with an average weight of 466 kg and age of 6 years, were studied.
• These horses were undergoing various surgical procedures and were put under anesthesia with positive pressure ventilation (IPPV), a technique to mechanically assist or replace spontaneous breathing.
• The horses were grouped into two equal fractions; the first group was allowed to return to spontaneous breathing before being disconnected from the anesthesia circuit (weaned group), while the second group stopped breathing (apnea) during the transfer to recovery.
• Arterial blood gas data were collected at different time points before and after disconnection from the anesthesia circuit to monitor the levels of oxygen (PaO) and carbon dioxide (PaCO).
• The collected data was then analyzed using analysis of variance (anova) method for repeated measures and paired, two-tailed t-tests to look for statistically significant differences between the two groups.

Results of the Study

• The horses in the apneic group took a mean time of around 5 minutes to start spontaneous breathing.
• These horses demonstrated significantly higher levels of oxygen in the blood at intermediate points (at disconnection and 3 minutes post the disconnection) as compared to the weaned group.
• The level of carbon dioxide was found to be higher in the weaned group at disconnection but equaled that in the apneic group after 3 minutes.

Conclusions and Implications

• According to the study, horses can tolerate a short period of paused breathing and may even potentially benefit by having a reduced rate of short-lived hypoxemia than those that start spontaneous breathing early.
• These findings could help anesthesia professionals in making crucial decisions about discontinuing IPPV when horses are being moved to recovery after anesthesia, and possibly reducing the incidences of hypoxemia.