Cardiovascular system assessment and multiple organ dysfunction in horses with acute gastrointestinal disease
McConachie, Erin Lynn
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Acute gastrointestinal disease, or colic, is a common condition afflicting horses of all ages, breeds and disciplines. Substantial morbidity and mortality for horses treated surgically persists despite improvements in the management, diagnosis and surgical correction of colic over the past few decades. While the causes for morbidity and mortality are multifactorial, horses with clinical evidence of endotoxemia or the systemic inflammatory response syndrome (SIRS) are at an increased risk for complications, such as the development of the multiple organ dysfunction syndrome (MODS) and mortality. The main objectives of the studies presented herein were to elucidate the role the cardiovascular system plays in systemic inflammatory conditions, such as SIRS, in horses with colic in the post-operative period and to develop criteria to describe MODS in horses with colic. First, a non-invasive 2-Dimensional echocardiographic method for cardiac output estimation was validated in healthy adult horses. This study revealed that three 2-D echocardiographic methods had acceptable agreement with the reference measurement. Second, heart rate variability (HRV) analysis was performed in the post-operative period in horses with acute surgical colic and healthy horses that underwent an elective procedure to assess the difference between HRV in these groups and a potential association between HRV and survival. This study illustrated that horses with colic have reduced HRV compared to healthy horses and that time domain measures of HRV were associated with non-survival. A multifaceted approach to cardiovascular system assessment, consisting of hemodynamic monitoring, electrocardiography, and cardiac troponin (cTnI) measurement, was then performed on healthy horses and those with acute surgical colic to detect cardiovascular dysfunction. The results from this investigation demonstrated cardiovascular system abnormalities in horses with colic, particularly those with ischemic gastrointestinal lesions, characterized by reduced HRV, increased cTnI concentration, reduced stroke volume index and increased frequency of pathologic arrhythmias. Finally, through incorporation of what was discovered in the first three studies, a review of the literature and the use of clinical judgment a scoring system for MODS in horses with acute gastrointestinal disease was developed and validated.