Surface oximetry of healthy and ischemic equine intestine.

This research study focuses on gathering measurements of oxygen tension in different sections of the intestines in horses to understand how oxygen levels change under conditions of healthy function versus induced intestinal ischemia. This process involves an oxygen detection method involving a nonheated miniature oxygen polarographic electrode and maintaining specific physiological parameters in the horses throughout the procedure.

Methodology

• The research involved gathering measurements of oxygen tension in three sections of the equine intestine – the jejunum, ileum, and the large colon’s pelvic flexure. These areas were examined in horses that were anesthetized with halothane.
• The horses were given assisted ventilation with 100% oxygen to maintain the partial pressure of carbon dioxide (PaCO2) at a consistent level of 50 +/- 8 mmHg. Simultaneously, researchers ensured the mean arterial blood pressure was 70 mm of Hg or greater.
• The equipment used by the researchers to gather the measurements was a nonheated miniature oxygen polarographic electrode, which measures oxygen tension.

Findings

• The research uncovered that mean oxygen tension for the respective intestinal fields were as follows: For jejunum it was 71 +/- 20 mm of Hg, for ileum it was 61 +/- 8 mm of Hg, and for the pelvic flexure of the large colon, it was 55 +/- 13 mm of Hg.
• To study the response of these tissue areas to ischemia or insufficient blood supply, they induced various types of vascular occlusion in the large colon of twelve more anesthetized horses. The induced occlusions included venous, arterial and venous, venous and intramural (within the wall of the organ), and arterial, venous, and intramural obstructions.
• These obstructions created significant drops in the oxygen tension, the values of which varied based on the type of occlusion induced. For example, the tension dropped as low as 8 +/- 7 mm of Hg for venous obstruction and down to 4 +/- 3 mm of Hg for arterial and venous obstruction. In instances of intramural and arterial and venous obstruction, the tension fell to 3 +/- 0 mm Hg.
• Following the removal of the obstructions, a period of thirty minutes saw the oxygen tension rise to at least half the value prior to the occlusion in the large colon.