A dose-response study of phenylephrine in critically ill, septic surgical patients

Objective: To determine the response of haemodynamic and oxygen-transport parameters to phenylephrine in a dose-response fashion in septic non-hypotensive, vasodilated surgical intensive care unit (ICU) patients. Design: Prospective study. Setting: Surgical ICU of a tertiary care, university medical centre. Patients: Ten septic non-hypotensive, vasodilated surgical ICU patients. Interventions: Routine ICU monitoring, including pulmonary and radial artery catheters. Measurements: Haemodynamic and oxygen-transport measurements were taken at baseline and during therapy. Phenylephrine was infused intravenously for 3 h at progressively increasing doses of 0.5, 1.0, 2.0, 3.0, 4.0, and 8.0 μg · kg⁻¹ · min⁻¹ at 30-min intervals. Measurements were taken after each dose. Results: Mean arterial pressure (MAP) and systemic vascular resistance (SVRI) increased linearly with phenylephrine dose. Cardiac index and pulmonary artery occlusion pressures did not change. Statistically significant changes were observed in heart rate, MAP, stroke index, and systemic and pulmonary vascular resistance. Eight patients had a clinically significant increase (>15%) in oxygen consumption (VO₂I). Oxygen delivery (D₂OI) increased in only three patients. Serum lactate concentrations were unchanged or lower at the end of the study in all eight pateints, who displayed a 15% increase in VO₂I. Conclusions: Treatment with phenylephrine increased expected haemodynamic parameters in a linear fashion; however, clinical changes in VO₂I occurred at variable doses. Dose-response trials are needed to determine the optimal dose of phenylephrine. Further study is needed to evaluate the clinical effects of phenylephrine in septic patients. Received: 12 December 1995 / Accepted in revised form: 19 August 1996