RADIAL ARTERY PRESSURE MONITORING UNDERESTIMATES CENTRAL ARTERIAL-PRESSURE DURING VASOPRESSOR THERAPY IN CRITICALLY ILL SURGICAL PATIENTS

Objectives: Radial artery pressure is known to differ from central art erial pressure in normal patients (distal pulse amplification) and in the early postcardiopulmonary bypass period. The adequacy of the radia l artery as a site for blood pressure monitoring in critically ill pat ients receiving high dose vasopressors has not been carefully examined . Design: Prospective observational study comparing simultaneous intra arterial measurements of radial (peripheral) and femoral artery (cent ral) pressures. Setting: Clinical investigation in a university based surgical intensive care unit. Patients: Fourteen critically ill patien ts with presumed sepsis who received norepinephrine infusions at a rat e of greater than or equal to 5 mu g/min. Interventions: All patients were managed in accordance with our standard practice for presumed sep sis, which consisted of intravascular volume repletion followed by vas opressor administration titrated to a mean arterial pressure of greate r than or equal to 60 mm Hg. Measurements and Main Results: Systolic a nd mean arterial pressures were significantly higher when measured fro m the femoral vs, radial site (p <.005). The higher mean arterial pres sures enabled an immediate reduction in norepinephrine infusions in 11 of the 14 patients. No change in cardiac output or pulmonary artery o cclusion pressure was noted after dose reduction. In the two patients in whom simultaneous recordings were made after discontinuation of nor epinephrine infusions, equalization of mean arterial pressures was obs erved. Conclusions: Radial artery pressure underestimates central pres sure in hypotensive septic patients receiving high dose vaso presser t herapy. Clinical management, based on radial pressures, may lead to ex cessive vasopressor administration. Awareness of this phenomena may he lp minimize adverse effects of these potent agents by enabling dosage reduction.