Is a Cuff Enough?
/Haber EN, Sonti R, Simkovich SM, Pike CW, Boxley CL, Fong A, Weintraub WS, Cobb NK. Accuracy of Noninvasive Blood Pressure Monitoring in Critically Ill Adults. J Intensive Care Med. 2024 Jan 12:8850666231225173. doi: 10.1177/08850666231225173. Epub ahead of print. PMID: 38215002.
P: 1852 patients admitted to tertiary care MICU with a variety of precipitating conditions
I: Invasive blood pressure monitoring
C: Noninvasive blood pressure monitoring
O: 67 % of measurements in agreement using 10 % MAP difference as the cutoff
Background
Sepsis is a leading cause of mortality for hospitalized patient’s both worldwide and in the United States. The surviving sepsis guidelines weakly recommend invasive arterial blood pressure monitoring (IABP) over noninvasive blood pressure monitoring (NIBP) with a blood pressure cuff supported by low quality evidence.(1) Data comparing the accuracy between IABP and NIBP measurements are limited. The largest analysis of 736 critically ill patients found a mean difference of 1 mmHg which was not statistically significant, however, there was only one measurement recorded per patient.(2) Arterial lines have several drawbacks compared with non-invasive methods such as: training requirements for caregivers, potential for pain and increased pain medications, limitation of participation in physical therapy, risk of digital ischemia, and risk of iatrogenic infection.(3)
Methods
This study was a retrospective observational study at a single academic tertiary care facility in their medical intensive care unit (MICU). They recorded data on all patients admitted to the MICU over a 27-month period with concurrent IABP and NIBP measurements. The primary outcome was defined as agreement of less than 10 % of the mean arterial pressure (MAP) between simultaneously recorded IABP and NIBP measurements. This more stringent measurement was selected as small changes in MAP can alter clinical care in the ICU setting such as by effecting vasopressor titration. The following variables were chosen for analysis as potential predictors of discrepancy: patient demographics (age, BMI, comorbidities), need for continuous renal replacement therapy (CRRT), mechanical ventilation, illness severity (as approximated by SOFA score), norepinephrine dose, and arterial line location, among others. Continuous data were analyzed using a student T-test and Wilcoxon rank-sum test and categorical data were analyzed via X2 test.
Results
They studied 1852 patients in the MICU with the most common admission diagnoses being respiratory failure (34 %), sepsis (23 %), and primary CNS disease such as stroke or hemorrhage (23 %). Of these, 43 % were female, 46 % identified as black, 39 % identified as white, and they had a median age of 63. 53286 measurement pairs were recorded with a median of 13 measurements per patient. These were primarily recorded on radial arterial line (81 %). Just over half (54 %) of the patients were mechanically ventilated, 19 % were on CRRT, and 36 % were on norepinephrine drips.
They found an average IABP MAP of 77 (interquartile range of 68-90) and NIBP MAP of 84 (interquartile range of 76-95). Sixty-seven percent of measurements agreed within the 10 % cutoff with 7.2 % of the paired measurements being identical. The median difference between IABP and NIBP MAP was 6 mm Hg. Of their pre-determined variables the following were independent predictors of discrepancy: increasing NE doses (aOR 1.10 [1.08-1.12, p=0.03]), lower MAP value (aOR 0.98 [0.98-0.99 P<0.01]), higher BMI (aOR 1.04 [1.01-1.09 P=0.01]), increasing patient age (aOR 1.31 [1.30-1.37 p<0.01]), radial arterial line location (aOR 1.74 [1.16-2.47 P=0.04]).
Discussion
There was general agreement between NIBP and IABP MAP measurement for a variety of illness severity. IABP MAP measurements tended to have a lower diastolic blood pressure measurement, which caused much of the discrepancy between NIBP and IABP measurement, although the clinical significance of this is not well understood.(4) Although several independent variables were found to predict discordance, the adjusted odds ratios for these variables were small, suggesting a mild ability to predict discordance. Of these, radial arterial line placement had the strongest predictive value for discordance. This has been theorized to be due to the smaller diameter of the catheter used in a radial arterial line versus a femoral or axillary arterial line, thus under-estimating the MAP. Interestingly, illness severity, as estimated by SOFA sores, were not predictive of disagreement. Ultimately, the presented data is likely no sufficient to suggest that IABP measurements are not needed; rather, it suggests that further research into specific protocols in which invasive blood pressure measurements are not needed is required.
Limitations & strengths
This was a single center retrospective study wherein data was gathered due to caregiver preference, chance, or change in patient status and not due to study protocol. Patients with discordant measurements could have had their NIBP measured with altered frequency, as there was no requirement to perform a NIBP measurement in patients with an intra-arterial catheter. Additionally, arterial line access may have been established for purposes other than blood pressure measurement, such as frequent blood draws.
Takeaway
There is correlation between IABP and NIBP monitoring in the majority of critically ill patients requiring care in the medical ICU setting; a quarter of patients had no discrepant measurements at all. Factors that correlate with increased discrepancy between IABP and NIBP measurements, listed in order of predictive strength, include: radial location, increasing age, increasing norepinephrine dose, and increasing BMI. Further research is needed into patient-centered outcomes such as mortality, end-organ dysfunction, and length of hospital stay to better understand the risks and benefits of intra-arterial catheter placement for blood pressure monitoring. Ultimately, this article is unlikely to significantly change my practice pattern in the ED, where patients tend to be undifferentiated with rapidly evolving clinical presentations.
References
Evans L, Rhodes A, Alhazzani W, et al. Surviving sepsis campaign: International Guidelines for Management of Sepsis and Septic Shock 2021. Crit Care Med. 2021;49:e1063-e1143.
Kaufmann T, Cox EGM, Wiersema R, et al. Non-invasive oscillometric versus invasive arterial blood pressure measurements in critically ill patients: a post hoc analysis of a prospective observational study. J Crit Care. 2020;57:118-123.
Lucet J, Bouadma L, Zahar J, et al. Infectious risk associated with arterial catheters compared with central venous catheters. Crit Care Med. 2010;38:1030-1035.
Araghi A, Bander J, Guzman J. Arterial blood pressure monitoring in overweight critically ill patients: invasive or noninvasive? Crit Care. 2006;10:R64.
Authorship
Written by Jeremy Sobocinski, MD, PGY-3 University of Cincinnati Department of Emergency Medicine
Posting, Editing, Audio Editing by Jeffery Hill, MD MEd, Associate Professor, University of Cincinnati Department of Emergency Medicine
Cite As: Sobocinski, J., Hill, J. Is a Cuff Enough. TamingtheSRU. www.tamingthesru.com/blog/journal-club/cuff. 4/17/2024
