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Cardiopulmonary effects associated with head-down position in halothane-anesthetized ponies with or without
Tanya Duke1, Antonio M Cruz1, J Ignacio Cruz1
1Department of Veterinary Anesthesiology, Radiology and Surgery, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
Veterinary Anaesthesia and Analgesia
|April 14, 2017
Summary
The head-down position in horses increases carbon dioxide and decreases oxygen levels, with capnoperitoneum potentially preserving blood pressure but worsening ventilation-perfusion mismatch.
Area of Science:
- Veterinary Anesthesiology
- Equine Physiology
- Surgical Positioning
Background:
- The head-down position is used in equine surgery.
- Cardiopulmonary effects of this position, especially with capnoperitoneum, require investigation.
Purpose of the Study:
- To compare cardiopulmonary effects of the head-down position with and without capnoperitoneum in halothane-anesthetized horses.
Main Methods:
- Prospective randomized study in five ponies under halothane anesthesia.
- Ponies were placed in a head-down 30° position for 60 minutes, with or without capnoperitoneum (12 mm Hg).
- Cardiopulmonary variables were monitored throughout.
Main Results:
- Head-down position decreased PaO2 and increased PaCO2, right atrial pressure, and Vd/Vt and Qs/Qt ratios in both groups.
- Capnoperitoneum (INS) group showed earlier ventilation-perfusion mismatch and longer recovery than controls (CON).
- Cardiac index and systemic blood pressure were preserved in INS during head-down tilt.
Conclusions:
- Head-down position with capnoperitoneum in horses can preserve cardiac index and blood pressure.
- However, it leads to earlier ventilation-perfusion mismatch and prolonged recovery.
- Healthy ponies tolerate capnoperitoneum at 12 mm Hg in the head-down position.