Non-invasive detection of a femoral-to-radial arterial pressure gradient in intensive care patients with vasoactive agents

Abstract

Background: In patient requiring vasopressors, the radial artery pressure may underestimate the true central aortic pressure leading to unnecessary interventions. When using a femoral and a radial arterial line, this femoral-to-radial arterial pressure gradient (FR-APG) can be detected. Our main objective was to assess the accuracy of non-invasive blood pressure (NIBP) measures; specifically, measuring the gradient between the NIBP obtained at the brachial artery and the radial artery pressure and calculating the non-invasive brachial-to-radial arterial pressure gradient (NIBR-APG) to detect an FR-APG. The secondary objective was to assess the prevalence of the FR-APG in a targeted sample of critically ill patients.

Methods: Adult patients in an intensive care unit requiring vasopressors and instrumented with a femoral and a radial artery line were selected. We recorded invasive radial and femoral arterial pressure, and brachial NIBP. Measurements were repeated each hour for 2 h. A significant FR-APG (our reference standard) was defined by either a mean arterial pressure (MAP) difference of more than 10 mmHg or a systolic arterial pressure (SAP) difference of more than 25 mmHg. The diagnostic accuracy of the NIBR-APG (our index test) to detect a significant FR-APG was estimated and the prevalence of an FR-APG was measured and correlated with the NIBR-APG.

Results: Eighty-one patients aged 68 [IQR 58-75] years and an SAPS2 score of 35 (SD 7) were included from which 228 measurements were obtained. A significant FR-APG occurred in 15 patients with a prevalence of 18.5% [95%CI 10.8-28.7%]. Diabetes was significantly associated with a significant FR-APG. The use of a 11 mmHg difference in MAP between the NIBP at the brachial artery and the MAP of the radial artery led to a specificity of 92% [67; 100], a sensitivity of 100% [95%CI 83; 100] and an AUC ROC of 0.93 [95%CI 0.81-0.99] to detect a significant FR-APG. SAP and MAP FR-APG correlated with SAP (r² = 0.36; p < 0.001) and MAP (r² = 0.34; p < 0.001) NIBR-APG.

Conclusion: NIBR-APG assessment can be used to detect a significant FR-APG which occur in one in every five critically ill patients requiring vasoactive agents.

Keywords: Aorto-radial gradient; Diagnostic study; Femoro-radial gradient; Vasoplegia.

Fig. 1

Flow chart. FR-APG femoral-to-radial arterial pressure gradient; NIBR-APG non-invasive brachial-to-radial arterial pressure gradient. The index test is the average NIBR-APG mean arterial pressure (MAP) measured three times (T1, T2, T3) with non-invasive cuff at the two arms at the brachial level and with an invasive radial artery cannulae. The “final diagnostic or reference standard” is defined as FR-APG of more than 10 mmHg of MAP measured with invasive femoral and radial cannulae

Fig. 2

Receiver operating characteristics curves using three non-invasive methods to estimate the femoral-to-radial arterial pressure gradient (FR-APG) defined in terms of mean arterial pressure (MAP). The first method (purple) is using the average of the three non-invasive measurements (T1, T2 and T3) of the two upper limbs. The second method (orange) is using only non-invasive MAP value at T1. The third method (green) is using only non-invasive systolic arterial pressure (SAP) value at T1. NIBR-APG non-invasive brachial-to-radial arterial pressure gradient; FR-APG is defined as an FR-APG of more than 10 mmHg MAP measured with invasive femoral and radial cannulae

Fig. 3

Scatter plot of the femoral-to-radial arterial pressure gradient (FR-APG) versus non-invasive brachial-to-radial arterial pressure gradient (NIBR-APG). The correlation between the FR-APG in mean arterial pressure (MAP) and the NIBR-APG in MAP was r² = 0.32 (p < 0.001)