Cardiorespiratory effects of a 7° reverse Trendelenburg position in anaesthetized horses: a randomized clinical trial.

The research article conducts a clinical trial to assess the impact of a 7-degree reverse Trendelenburg position (an inclined position with the head higher than the feet) on the cardiorespiratory conditions in anaesthetized horses of different weight categories. The study suggests that while there are minor differences across weight classes, overall, there aren’t any significant changes in gas exchange or cardiovascular function due to the positioning.

Methodology

• The study was conducted as a randomized, non-blinded clinical trial with 125 horses that were about to undergo elective surgery while lying on their back (dorsal recumbency).
• The horses were divided into three different weight classes and randomly positioned either horizontally or at a 7° reverse Trendelenburg position.
• All horses were anesthetized using a combination of isoflurane in oxygen and a constant rate of romifidine infusion. They were also mechanically ventilated throughout anaesthesia.
• Every 15 minutes, arterial blood gas analyses and routine cardiovascular monitoring were conducted, and relevant data were computed.
• Data from the first hour of anesthesia were evaluated between both positions using mixed model analysis of variance.

Results

• The outcomes showed a significant interaction between the positioning and weight class for the alveolar to arterial oxygen tension gradient and F-shunt.
• In the two lower weight classes, these values were lesser in the reverse Trendelenburg position than in the horizontal position, and the converse was recorded in the heaviest weight class.
• Arterial oxygen tension and oxygenation indices showed a significant decline with horses in higher weight classes.

Conclusion

• The 7° reverse Trendelenburg position did not lead to any notable differences in gas exchange or cardiovascular function.
• The study found that horses with a higher body weight are more likely to suffer from hypoxaemia when in dorsal recumbency during anesthesia.