Orotracheal intubation in the horse – Is bigger better?

Prevalence and degree of orotracheal intubation-related tracheal lesions in horses

BACKGROUND

Orotracheal intubation is commonly performed for inhalation anaesthesia in horses to ensure safe and reliable administration of volatile anaesthetics and to secure the airways. In human and equine medicine, the occurrence of intubation-associated complications has been described, which can range from mild mucosal irritation to severe necrosis. However, there are only sparse descriptions of mucosal alterations and the course of healing after elective surgery in horses.

OBJECTIVE

To investigate the prevalence and severity of tracheal lesions following endotracheal intubation associated with general anaesthesia in equine patients.

STUDY DESIGN

Prospective, clinical study.

METHODS

Forty adult Warmblood horses, weighing 400-600 kg, presented for elective surgery under general anaesthesia were included. For orotracheal intubation, a silicone tube was used and inflated until a cuff pressure of 40 cmH2O was confirmed. In all horses, endoscopic examination of the trachea with video documentation was performed prior to intubation and immediately after extubation, as well as 1, 3, 5 and 7 days after general anaesthesia. The type (redness, secretion, bleeding, erosions) and degree (0 = non-existent to 4 = severe) of corresponding lesions were assessed and scored. The occurrences of clinical signs were recorded. Statistical evaluation was performed using Friedman's test and Pearson correlation.

RESULTS

The median score immediately after recovery from anaesthesia was 6 (2-12) and increased significantly to 11 (4-15) after 1 day (p = 0.021). At day 7, the median score was 0 (0-2) with only four horses showing signs of mild tracheitis, and clinical signs were not observed throughout this time period. The duration of intubation correlated with the degree of tracheal damage (r2 = 0.67, p < 0.001).

MAIN LIMITATIONS

Clinical, non-randomised study without a control group.

CONCLUSION

Although orotracheal intubation was accompanied by focal inflammation of the trachea, in the present study no horses showed clinical signs and lesions healed within a week.

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

Effects of general anesthesia with controlled ventilation on the respiratory system have had limited evaluation in horses. A prospective observational study was performed with eleven client-owned horses undergoing elective surgery. Physical examination, auscultation with a rebreathing bag, complete blood cell count, lung ultrasound imaging, tracheal endoscopy imaging and transendoscopic tracheal wash were conducted before and 24 hours after anesthesia. Lung ultrasound imaging was also repeated just after recovery. A significant increase in blood neutrophil count between pre- and post-anesthesia (P=0.004) was observed. There was an increase in ultrasonographic score of the lungs at recovery (left P=0.007, right P=0.017). The score of the dependent lung was higher than the independent lung at recovery time (P=0.026) but no difference was observed 24 hours after anesthesia. The tracheal mucus score was higher after anesthesia (P=0.001); severe local inflammation was present in several horses at the site of endotracheal tube cuff. Neutrophil count was significantly higher on tracheal wash fluid cytology after anesthesia (P=0.016), without any significant changes on bacterial load. Increased tracheal mucus score and neutrophil count in tracheal wash samples were observed after general anesthesia in healthy horses without clinical evidence of pneumonia (fever, cough). Tracheal inflammation secondary to endotracheal intubation and cuff inflation was, therefore, suspected. Elective surgery without complications can induce inflammation of the trachea and changes in ultrasound images of the lungs in healthy horses and should be considered when evaluating respiratory system after a general anesthesia.