Evaluation of an Esophageal Stethoscope as an Early Predictor of Serious Cardiovascular Insufficiency in the Dog

Accuracy of an esophageal stethoscope combined with a vital signs monitor (VSM) was evaluated as an early predictor of cardiovascular failure during anesthesia. In 10 anesthetized dogs, hypotension and reduction in cardiac output were induced by gradually increasing the inspired halothane concentration. Cardiovascular performance and intensity of heart sounds recorded by the esophageal stethoscope and amplified by the VSM were assessed as depth of anesthesia was increased. Halothane concentration was increased until cardiovascular performance was reduced to a point where heart sounds were no longer audible from the VSM. The esophageal stethoscope in combination with the VSM was easy to use and the unit had an excellent signal to noise ratio. However, usefulness of the esophageal stethoscope as an early predictor of serious cardiovascular depression could not be substantiated. In three dogs, cardiac arrest occurred simultaneously with the loss of heart sounds and in the remaining seven dogs, sound loss occurred when the degree of cardiovascular depression was life threatening.