Mean Arterial Pressure in Acute Ischemic Stroke Study

Background. There is little, if any, evidence available on the validation of blood pressure (BP) measurements obtained in the acute care setting. Despite this, acute stroke practitioners trust and rely on non-invasive blood pressure (NIBP) devices to guide acute ischemic stroke (AIS) patients’ treatment. Although systolic blood pressure (SBP) has been found to be the most unreliable measurement displayed on NIBP devices, treatment decisions for AIS are based on them. Today, 25 years after the FDA’s approval of alteplase, practitioners continue to use BP parameters of 185/110 and 180/105 to guide the initiation of alteplase bolus and infusion, although the shift to the use of NIBP devices challenges the validity of these dated parameters. Theoretically, by inserting the inclusion and exclusion systolic and diastolic blood pressure thresholds into the mean arterial pressure (MAP) equation, one could deduce the exclusion threshold for MAP to be > 130. Furthermore, if a MAP of 130 mmHg were to be adopted as the threshold for treatment, many patients who would otherwise be excluded, would receive alteplase treatment. A clear understanding of MAP in relation to SBP and diastolic blood pressure (DBP) in patients with AIS, which is now exclusively measured with NIBP devices, is critical for safe and effective alteplase management. Study Aims. To understand agreement between SBP, DBP, and MAP measured by NIBP and measured manually in alteplase-treated AIS patients. An additional secondary study aim was to investigate the relationship between MAP and outcomes in alteplase-treated AIS patients. Methods. Two trained examiners from three comprehensive stroke centers and four primary stroke centers measured five sets of manual-derived BP and NIBP-derived SBP, DBP, and MAP in 95 acute ischemic stroke patients treated with alteplase for a total of 475 paired sets of measures. The two examiners used a dual-auditory stethoscope to ensure accuracy of the manual measures. To avoid interruption of acute stroke care, all measurements occurred during the 24 hours following the alteplase infusion. The data was analyzed using Bland-Altman analysis for measures of agreement. Results. Our study found no agreement in SBP, DBP, and MAP for 475 paired manual and NIBP measurements, with SBP and MAP manual and NIBP measures showing the least agreement between methods. Although DBP-paired measures did not agree, they were in closer agreement than SBP and MAP measures on Bland-Altman (BA) analysis for measures of agreement, and 44% of DBP measures fell within 5 mmHg of each other. NIBP measures were consistently higher than manual measurements and differed from manual measurements as much as 50 mmHg for SBP, 40 mmHg for DBP, and 44 mmHg for MAP. We found that the higher the systolic blood pressure, the greater the disagreement. Additionally, we analyzed the percentage of measurements that fell within a difference of 5, 10, 15, and 20 mmHg for SBP, DBP, and MAP separately. For SBP, 39% of the 475 sets of measures fell within 5 mmHg and 62% fell within 10 mmHg. For DBP, 44% fell within 5mmHg and 72% fell within 10 mmHg. For MAP, 34% fell within 5 mmHg and 62% fell within 10 mmHg. Conclusion. Despite the widespread use of NIBP devices, few clinicians are familiar with their fundamental operating principles and the potential for inaccuracies and disagreement between manual and NIBP measurements. Clinically acceptable limits of agreement for SBP, DBP, and MAP in AIS patients should be defined a priori based on clinical necessity, biological considerations, and treatment goals. Additionally, our study takes an important first step in reframing AIS treatment context toward consideration of MAP as a key measure to guide the initiation of alteplase treatment and ongoing patient management. It is likely that stroke guidelines are silent regarding MAP because the information to understand safe MAP levels in AIS patients during and after alteplase administration is lacking. The safe MAP for AIS patients receiving alteplase treatment is not yet known, but work must continue in this area. Document Type Dissertation Degree Name Doctor of Philosophy (PhD) Program Nursing Science Research Advisor Anne W. Alexandrov, Ph.D.