Mean arterial pressure (MAP): An alternative and preferable measurement to systolic blood pressure (SBP) in patients for hypotension detection during hemapheresis

Current protocols utilize systolic blood pressure (SBP) of less than 80 mmHg as objective evidence of hypotension during hemapheresis. However, tissue hypoperfusion is the pathophysiologic endpoint of low blood pressure, and mean arterial pressure (MAP), rather than SBP, is the physiologic driving force behind blood flow to organs and tissues. It is thus hypothesized that MAP is more appropriate than SBP in the assessment of hypotension and that a threshold MAP can be utilized as a sensitive indicator of hypotension during hemapheresis. Thirty-one patients who experienced hypotension during hemapheresis over a 4.5 year period reflecting forty-four hypotensive episodes were selected. The initial phase of each hemapheresis procedure provided baseline MAP and blood pressure (BP) measurements as control values. BP and MAP were then determined at the onset of subjective hypotension and compared to one another by using regression and sensitivity analyses. Correlation coefficients between SBP and MAP were found to be 0.8097 in baseline normotensive patients and 0.7725 in hypotensive patients. Sensitivity in the detection of hypotension was 0.09% for SBP equal to 80 mmHg and 56.81% for MAP equal to 70 mmHg. An SBP of 80 mmHg or less was therefore concluded to be a less sensitive and physiologically less appropriate measurement of hypotension than MAP. As a single value less than 70 mmHg or a series of successive measurements trending downward toward 70 mmHg, MAP provides an objective assessment of hypotension that may precede hemodynamic decompensation.