Arterial oxygen tension and pulmonary ventilation in horses placed in the Anderson Sling suspension system after a period of lateral recumbency and anaesthetised with constant rate infusions of romifidine and ketamine.

The research investigates whether suspension in an Anderson Sling (AS), a device used to help sedated horses stand, improves their heart and lung functions and recovery quality after being in a right lateral recumbency (RLR) position under anaesthesia. The results suggest that the AS improves these functions and therefore should be considered for use in helping horses recover from hypoxia (low oxygen levels).

Research Methodology

• The experiment involved six Standardbred horses that were anaesthetised twice. Catheters were inserted into each horse’s right jugular vein and the left carotid artery.
• The horses were first treated with the sedative romifidine. They were then induced into anaesthesia with the drugs diazepam and ketamine.
• Each horse was placed in right lateral recumbency (RLR), or lying on its right side, for 50 minutes. After this period, they were either maintained in the same RLR position or placed in the Anderson Sling (AS) for an additional 60 minutes.
• During the entire procedure, vital signs such as heart rate, respiratory rate, arterial pressure, tidal volume, and carbon dioxide levels were continuously monitored.
• Blood samples were taken several times throughout the procedure to measure lactate concentration (an indicator of muscle stress), creatine kinase activity (a marker for muscle damage) and perform blood gas analysis.

Results

• The RLR group experienced lower arterial oxygen tensions, higher alveolar-arterial oxygen tension gradients, higher respiratory rates, and higher minute volumes than the AS group during the second 40-100 minute anaesthetic period (P2). These findings suggest that the sling might improve lung oxygenation and reduce the effort associated with breathing.
• On the contrary, arterial carbon dioxide tension and mean arterial pressure increased in the AS group during P2. This implies that while the horses were better oxygenated, they suffered from higher blood pressure levels.
• Following recovery, horses in the AS group showed an improved recovery process compared to those in the RLR group, suggesting better overall recovery from anaesthesia.
• In the RLR group, lactate levels were higher than in the AS group during recovery. This suggests there might be an increased muscular stress in horses kept in the RLR position.
• Creatine kinase activities, indicating muscle damage, were higher in the AS group 24 hours after the procedure, suggesting potential strain from using the sling.

Conclusions

• Overall, the Anderson Sling suspension seemed to improve cardiopulmonary function and recovery quality in horses after a period of being lying on their side under anaesthesia.
• However, there were higher creatine kinase activities observed in the AS group 24 hours after the experiment, indicating potential muscle damage from being in the sling.
• The researchers conclude that the benefits of improved cardiopulmonary function and recovery would warrant the use of the Anderson Sling in recovering hypoxic horses, but further research is likely needed to confirm these results and mitigate any potential drawbacks.