Blood Pressure measurements are site dependent in a cohort of patients with neurological illness

Abstract

Blood pressure (BP) management is a crucial part of critical care that directly affects morbidity and mortality. While BP has become a mainstay in patient care, the accuracy and precision of BP measures across commonly used sites (left upper arm, right upper arm, etc.) and methods have not been established. This study begins to fill this gap in literature by testing the null hypothesis that BP measurement does not vary according to site. this is a prospective, non-randomized, cross-sectional study of 80 neurocritical care unit patients. Near simultaneous non-invasive blood pressure (NIBP) readings from 4 different locations (bilateral upper arm, bilateral wrist) and, when available, intraarterial blood pressure readings (IABP) were included. Pearson correlation coefficients and one-way repeated measures ANOVA were used to observe the systolic, diastolic, and mean arterial pressure (MAp) correlations. the Bp measured at the four most common sites (left upper arm, left wrist, right upper arm, right wrist) had adequate correlation coefficients but were statistically significantly different and highly unpredictable. The median inter-site systolic variability was 10 mmHg (IQR 2 to 10 mmHg). The median inter-site MAP variability was 6mmHg with an interquartile range (IQR) of 3 to 9 mmHg. As expected, the values correlated to show that patients with high Bp in one site tended to have high Bp in another site. However, the unpredictable inter-site variability is concerning within the clinical setting where oftentimes BP measurement site is not standardized but resulting values are nevertheless used for treatment. There is prominent inter-site variability of BP measured across the 4 most common measurement sites. The variability persists across non-invasive (NIBP) and invasive (IABP) methods of assessment. Blood pressure (BP) monitoring is essential to neuroscience intensive care unit (NSICU) patient management. Adequate cerebral perfusion is dependent upon central BP control, maintained through the modulation of various factors such as cardiac output, vascular tone, systemic vascular resistance, and intravascular volume. Although BP can be measured at multiple sites (e.g., upper arm, wrist, thigh), there is no gold standard for site selection. Inconsistencies in BP readings may occur due to inter-observer variability, technical issues, or methods and locations for measurement. The true value of a patient's BP cannot be measured with total precision, owing to its natural variability over time, as well as the limitations of the methods used to measure BP 1. Moreover, BP measurement is influenced by other physiological factors, such as position changes (e.g., orthostatic stress due to gravitational blood volume shift) and external factors, such as the measurement site used for the non-invasive blood pressure (NIBP) machine 2. This variability lends ambiguity to BP measurements in the critical care setting, where accuracy is paramount as a basis for medical interventions. It is particularly crucial in the NSICU setting, where...

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