Horses undergoing abdominal exploratory procedures are susceptible to both hypotension and inadequate tissue perfusion. Mean arterial pressure (MAP) is often considered an indicator of sufficient tissue blood flow, although systemic measures may not accurately mirror microcirculatory dynamics. This investigation assessed MAP, cardiac index, lactate concentration, and four microcirculatory indices in six healthy, anesthetized adult horses undergoing planned laparotomies. Microcirculatory data were collected at three gastrointestinal sites (oral mucosa, colonic serosa, and rectal mucosa) using dark-field microscopy. All macro- and microcirculatory values were recorded during normotension, induced hypotension, and after normotension was re-established through dobutamine administration. Hypotension was generated by increasing the inhaled isoflurane concentration. The induced hypotensive state did not produce consistent or predictable variations in systemic or microvascular perfusion across any of the three intestinal locations examined. Normal blood pressure was successfully restored with dobutamine, but systemic and microvascular perfusion indices remained largely unchanged. These observations indicate that relying solely on mean arterial pressure as a measure of adequate perfusion may not always be reliable.
