Perioperative lung ultrasonography in healthy horses undergoing general anesthesia for elective surgery

Incidence and risk factors for complications associated with equine general anaesthesia for elective magnetic resonance imaging

BACKGROUND

Complications are a practical consideration for elective magnetic resonance imaging (MRI) studies performed under general anaesthesia but relatively little is known about their distribution and risk factors.

OBJECTIVES

To describe the incidence of complications associated with MRI performed under general anaesthesia at a large referral facility and evaluate potential risk factors for these complications.

STUDY DESIGN

Retrospective case-control study.

METHODS

Patient information and details of the MRI procedure were collected retrospectively from medical records of all horses that had undergone an MRI under general anaesthesia at the University of Pennsylvania, New Bolton Center, between September 2005 and April 2012. Complications and categorical variables were examined by chi-squared or Fisher's exact tests as appropriate. A mixed-effects logistic regression approach was used to evaluate associations between explanatory variables and the outcome variable (complications or pyrexia). A univariable screen was used to select variables (likelihood ratio test p < 0.2) for inclusion in the multivariable analysis. Statistical significance was inferred when p ≤ 0.05.

RESULTS

Complications were noted after MRI in 51 (17.4%) of 293 events eligible for inclusion. Complications included pyrexia (n = 35), pneumonia (n = 14), colic (n = 10), facial/nerve paralysis (n = 6), diarrhoea (n = 4), and other (n = 3). The odds of developing a post-anaesthetic complication were significantly decreased in horses that received peri-anaesthetic antimicrobials (OR 0.29, 95% CI 0.14-0.63, p = 0.002). Increased age (OR 0.87, 95% CI, 0.76-0.99, p = 0.03) and peri-anaesthetic antimicrobial administration (OR 0.23, 95% CI 0.08-0.65, p = 0.005) were associated with a decreased odds of developing pyrexia.

MAIN LIMITATIONS

Single centre retrospective design.

CONCLUSIONS

Potential complications including pyrexia, pneumonia and colic should be recognised when pursuing MRI under general anaesthesia. The administration of peri-anaesthetic antimicrobials decreased the odds of a complication and warrants consideration, particularly in horses that might be classified as high risk.

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.

Decision Making in Severe Equine Asthma-Diagnosis and Monitoring

Decision making consists of gathering quality data in order to correctly assess a situation and determine the best course of action. This process is a fundamental part of medicine and is what enables practitioners to accurately diagnose diseases and select appropriate treatment protocols. Despite severe equine asthma (SEA) being a highly prevalent lower respiratory disease amongst equids, clinicians still struggle with the optimization of routine diagnostic procedures. The use of several ancillary diagnostic tests has been reported for disease identification and monitoring, but many are only suitable for research purposes or lack practicality for everyday use. The aim of this paper is to assist the equine veterinarian in the process of decision making associated with managing SEA-affected patients. This review will focus on disease diagnosis and monitoring, while also presenting a flow-chart which includes the basic data that the clinician must obtain in order to accurately identify severely asthmatic horses in their everyday routine practice. It is important to note that European and American board-certified specialists on equine internal medicine can provide assistance in the diagnosis and treatment plan of SEA-affected horses.