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.

Can we trust radial artery pressure monitoring for cardiac surgery?

“…8,15 Indeed, a radial artery diameter of less than 1.8 mm has been associated with 48% risk of an RFAPG. 10 Those gradients have been reported not only in cardiac surgery but also in cardiac arrest, 16 septic shock, 14,17,18 liver transplantation, [19][20][21] critically ill patients, 22,23 and severe vasodilator intoxications. 24 How can we explain these gradients?…”

“…The second mechanism is a result of downstream vasodilatation beyond the radial artery leading to decreased vascular resistance. (B) To detect or suspect an RFAPG, several methods can be used, including radial AP waveform analysis, the use of NIBP of the upper extremity, 23,39 and ultrasound techniques using two-dimensional measurement and Doppler. Unreliable radial arterial pressure should be suspected if two-dimensional ultrasound measurement of the radial artery diameter is less than 1.8 mm, 10 if the change of pressure over time (dP/dt) of the radial artery does not correlate with cardiac function, 6,42 if the estimated dP/dt and the PG calculated from the MR Doppler signal is higher than the radial artery pressure 18,43 or if there is no triphasic arterial signal using Doppler interrogation of a radial or brachial artery.…”

“…18 Noninvasive measurement of blood pressure in the upper extremity using a blood pressure cuff can also be used to detect such gradients. In the intensive care unit, Jacquet-Lagre `ze et al 23 were able to identify significant RFAPG with a specificity of 92% (95% confidence interval [CI], 67 to 100) and a sensitivity of 100% (95% CI, 83 to 100). A simple method to potentially confirm an RFAPG is to compress the radial artery or the wrist distal to the point of insertion of the catheter.…”

“…8,15 De fait, un diame `tre d'arte `re radiale infe ´rieur a `1,8 mm a e ´te ´associe ´a `48 % de risque de survenue d'un RFAPG. 10 Ces gradients n'ont pas e ´te ´de ´crits que dans le cadre de la chirurgie cardiaque, mais aussi en cas d'arre ˆt cardiaque, 16 de choc septique, 14,17,18 de transplantation he ´patique, [19][20][21] chez des patients dans un e ´tat critique 22,23 et en cas d'intoxication se ´ve `re avec des vasodilatateurs. 24 Comment pouvons-nous expliquer ces gradients?…”

“…18 La mesure non invasive de la pression arte ´rielle au niveau du bras au moyen d'un brassard a `tension peut e ´galement servir a `la de ´tection de ces gradients. Jacquet-Lagre `ze et al 23 ont pu identifier, dans une unite ´de soins intensifs, des RFAPG significatifs avec une spe ´cificite ´de 92 % (intervalle de confiance [IC] a `95 % : 67 a `100) et une sensibilite ´de 100 % (IC a `95 % : 83 a `100). Une me ´thode simple de confirmation potentielle d'un RFAPG consiste a `comprimer l'arte `re radiale ou le poignet en position distale par rapport au point d'insertion du cathe ´ter.…”