Comparison between invasive radial and femoral arterial pressures and carotid tonometry in ICU patients: A physiological study.

BACKGROUND: Peripheral arterial pressure is used to guide hemodynamic management in intensive care unit (ICU) patients and for estimating various parameters of left ventricular afterload and function. Nevertheless, there is a physiological amplification of pressure from central to peripheral arteries, that remains to be documented in ICU patients. Our aim was to compare central to peripheral pressure amplification at the radial and femoral artery levels in ICU patients.

METHODS: In this prospective, observational and single-center study, we included consecutive spontaneously breathing patients already equipped with an arterial catheter. Carotid systolic arterial pressure obtained by carotid tonometry was considered a surrogate of aortic systolic pressure. We calculated pulse pressure amplification (PPAMP, difference between femoral or radial PP and carotid PP), systolic pressure amplification (SPAMP, difference between femoral or radial SP and carotid SP), PP ratio and SP ratio. The primary endpoint was the difference in PPAMP and SPAMP between the femoral and radial arteries. Secondary endpoints were the difference between peripheral and central estimates of cardiac power output (CPO), total arterial stiffness and effective arterial elastance (Ea).

RESULTS: 98 patients were included: 68(69%) were men, with a mean age of 62 ± 16 years, and 42(43%) had a history of arterial hypertension. The arterial catheter was located in the radial artery in 59(60%) patients and the femoral artery in 39(40%) patients. Femoral and radial SAP and PP were higher than carotid SAP and PP (p < 0.001). The PPAMP and the SPAMP (12 ± 11 vs. 8 ± 10 mmHg p = 0.04 for both), the PP ratio (p = 0.03) and the SP ratio (p = 0.04) were higher at the radial than at the femoral artery level. Femoral and radial estimates of CPO overestimated centrally-derived CPO, with more marked overestimation at the radial than femoral artery level (9 ± 9 vs. 5 ± 7%, p = 0.04). The amount of overestimation was correlated to PPAMP and SPAMP (r = 0.85for both), PP ratio (r = 0.77) and SP ratio (r = 0.85) (all p < 0.001). Similar results were found for total arterial stiffness and Ea.

CONCLUSIONS: The pressure amplification was lower at the femoral than radial artery level and should not be neglected in ICU patients when interpreting arterial pressures and estimating hemodynamic variables.