A study of cardiovascular function under controlled and spontaneous ventilation in isoflurane-medetomidine anaesthetized horses.

The research investigates potential differences in cardiovascular function in horses anesthetized with isoflurane-medetomidine and subjected to either spontaneous ventilation or intermittent positive pressure ventilation during elective surgery. Results show no significant difference in cardiovascular function between the two groups.

Background of the Study

• The research is a prospective randomized clinical study conducted on sixty horses under two categories: spontaneous ventilation (SV) and intermittent positive pressure ventilation (IPPV).
• All the horses in the study were undergoing elective surgical procedures under general anesthesia and classified under ASA I or ASA II, indicating they had a mild systemic disease.

Methods and Procedures

• The horses were initially sedated with medetomidine and anesthesia was then induced using ketamine and diazepam.
• Anesthesia was maintained with a continuous infusion of isoflurane and medetomidine.
• Horses in the IPPV group were kept mildly hypercapnic, maintaining a specific arterial partial pressure of carbon dioxide.
• Parameters like heart rate, respiratory rate, arterial blood pressure along with inspiratory and expiratory gases were continuously monitored.
• Cardiac output was checked using lithium dilution. If horses showed nystagmus, a symptom of involuntary eye movement, a bolus of ketamine was administered.

Results and Findings

• There were no significant differences found between the two groups when it came to factors like age, weight, body position during anesthesia, and anaesthetic duration.
• The respiratory rate was found to be higher in the IPPV group and more horses in this group received supplemental ketamine.
• All horses recovered from anesthesia without complications, regardless of the group they were in.

Conclusion of the Study

• The conclusion drawn from this study was that there was no significant difference in cardiovascular function in horses undergoing elective surgery during isoflurane-medetomidine anesthesia when comparing SV and IPPV, as long as the horses are kept mildly hypercapnic.
• The results thus suggest that the cardiovascular function under general anesthesia in horses with health status ASA I and II is equal, whether they’re under IPPV or not, if the PaCO(2) is maintained at 50-60 mmHg.