To study whether the circulatory changes of human septic shock are mediated in part by nitric oxide.Design
Open-label, nonrandomized clinical trial on the effects of methylene blue, an inhibitor of nitric oxide action.Setting
Intensive care unit of a teaching hospital.Patients
Nine consecutive patients with documented septic shock and a pulmonary artery catheter in place, after initial resuscitation with fluids, sympathomimetics, and mechanical ventilation.Interventions
Hemodynamic and metabolic variables were measured before and then 15, 30, 60, and 120 mins after the start of a 20-min infusion of 2 mg/kg of methylene blue.Measurements and Main Results
Patients had a hyperdynamic circulation, and methylene blue increased (p < .01) mean arterial pressure from 84 +/- 18 to 109 +/- 31 mm Hg and cardiac index from 4.7 +/- 0.9 to 5.6 +/- 1.2 L/min/m2, before and 30 mins after starting the methylene blue infusion, respectively. Cardiac filling pressures did not change. In the same time interval, the subnormal systemic vascular resistance index increased (p = .09) and arterial compliance decreased (p < .05). Oxygen delivery and oxygen uptake increased (p <.05) from 714 +/- 188 to 865 +/- 250 mL/min/m2 and from 160 +/- 39 to 186 +/- 44 mL/min/m2, respectively. Except for heart rate, which increased by 11 +/- 8 beats/min (p < .01), variables returned to baseline values at time = 120 mins.Conclusions
After initial resuscitation from human septic shock, a single dose of methylene blue transiently increases mean arterial pressure and oxygen uptake, associated with a decrease in arterial compliance and increases in myocardial function and oxygen delivery. Hence, nitric oxide may be a mediator of the circulatory changes of human septic shock.