Cardiopulmonary changes associated with abdominal insufflation of carbon dioxide in mechanically ventilated, dorsally recumbent, halothane anaesthetised horses.

The researchers studied the effects of abdominal insufflation with carbon dioxide (CO2) on the heart and lung functions in anesthetized, lying down horses that underwent laparoscopic surgery. They observed that this procedure led to significant alterations in the horses’ cardiopulmonary parameters which may increase the risk of postoperative complications.

Research Methodology

• The study involved six horses that were anaesthetized with halothane in oxygen and subjected to laparoscopic colopexy, a surgical procedure involving the fixation of parts of the large intestine.
• The abdomen of these horses was inflated with carbon dioxide (CO2) to a pressure of 15 mmHg.
• The vaporiser settings were adjusted to maintain a fractional halothane expired of 1.5 MAC and an acceptable depth of anaesthesia.
• The ventilation was regulated to maintain an ETCO2 (End Tidal CO2) of 35 mmHg before abdominal insufflation and kept constant thereafter.
• Cardiopulmonary data were collected at various time intervals namely, before, at 30 and 60 minutes during, and 30 minutes after CO2 insufflation.
• The changes in cardiopulmonary variables were evaluated using ANOVA for repeated measures and Tukey’s protected t-test.

Key Findings

• The researchers observed that oxygen partial pressure and pH of arterial blood, tidal volume, and systemic vascular resistance decreased during abdominal insufflation and laparoscopic surgery.
• Conversely, they noted that the mean arterial blood pressure, right atrial pressure, cardiac index, stroke index, CO2 partial pressure in arterial blood, end tidal respiratory gases, and calculated physiological shunt increased significantly during the procedure.
• It was found that only the systemic vascular resistance returned to the pre-insufflation level after desufflation, indicating lasting changes in the other parameters.

Conclusion

• The study concluded that the hypercapnia (excessive CO2 in the bloodstream), acidosis (excessive acid in the body fluids), and the apparent increase in cardiac work during CO2 pneumoperitoneum for laparoscopic surgery might put an anesthetized horse at an added risk of perioperative complications.
• This research highlights the need to carefully consider these risks and perhaps develop mitigation strategies when performing such procedures on horses.