Evaluation of an oscillometric blood pressure monitor in anesthetized dogs: Agreement with direct measurements and ability to detect hypotension

We evaluated the agreement between oscillometric and direct blood pressure monitors in anesthetized dogs and evaluated the ability of the oscillometric method to detect MAP <60 mmHg. Forty client-owned dogs, three months to 14 years old, 4.6-50.2 kg, under general anesthesia were studied. Systolic (SAP), mean (MAP) and diastolic (DAP) arterial pressures were measured directly via an arterial catheter and with an oscillometric cuff (Cardell Touch monitor). Paired values were compared with mixed effect models. Bias and limits of agreement (LOA) were calculated. The sensitivity and false negative rate to detect hypotension (invasive MAP <60 mmHg) using an oscillometric MAP <60 and < 70 mmHg were calculated. A receiver operating characteristics (ROC) curve was constructed and the area under the curve calculated. SAP and DAP differed between methods (both P < 0.001), but MAP did not (P = 0.5). Bland-Altman plots showed small biases but wide LOA for all variables. The sensitivity to detect hypotension was 40% with a false negative rate of 60% when using an oscillometric MAP <60 mmHg, and 68% and 32%, respectively, with a MAP <70 mmHg. The area under the ROC curve for MAP was 0.82. While the oscillometric MAP did not differ from invasive values, the device failed to recognize hypotensive events when 60 mmHg was used as the threshold to detect hypotension. Higher MAP values increased the ability to correctly recognize hypotension, but at the expense of a higher incidence of false positives.