Lower airway ultrasonographic, endoscopic, and cytological changes in horses undergoing inhalation anesthesia with controlled ventilation for minor elective surgeries.

This research study investigates how general anesthesia with controlled ventilation affects the respiratory systems of horses undergoing minor elective surgeries. The researchers found that the process can induce inflammation in the trachea and changes in the lungs, discovered using ultrasound imaging and tracheal examinations.

Study Design and Methodology

• The investigation was designed as a prospective observational study and utilized eleven client-owned horses which were being prepared for elective surgeries.
• Prior to anesthesia and 24 hours after, a series of evaluations were carried out on each horse. These examinations included a physical exam, auscultation with a rebreathing bag, complete blood cell count, lung ultrasound imaging, tracheal endoscopy imaging and a transendoscopic tracheal wash.
• Lung ultrasound imaging was also repeated immediately after each horse had fully recovered from the anesthesia.

Main Findings and Implications

• The results clearly indicated a significant increase in blood neutrophil count between pre- and post-anesthesia.
• Ultrasonographic score of the lungs was found to have increased at recovery for both the left and right sides of the lungs.
• Moreover, the score of the dependent lung was higher than the independent lung at recovery time. However, no difference between the two was observed 24 hours after anesthesia.
• The researchers noted that the tracheal mucus score was higher after anesthesia. They also observed severe local inflammation in several horses at the site of the endotracheal tube cuff.
• Neutrophil count was significantly higher on tracheal wash fluid cytology after anesthesia, without any significant changes noticed on bacterial load.
• The increase in tracheal mucus score and neutrophil count in tracheal wash samples were observed after general anesthesia in healthy horses that showed no clinical evidence of pneumonia, such as fever or cough. Therefore, the investigators attributed these increased scores and counts to the inflammation triggered by endotracheal intubation and cuff inflation.
• This suggests that even a minor elective surgery with no complications could result in inflammation of the trachea and changes in the ultrasound images of the lungs in otherwise healthy horses. This is an important note, particularly for veterinarians and medical personnel when evaluating the respiratory system of horses post general anesthesia.