ObjectiveTo describe the clinical characteristics of a group of patients infected with the newly recognized hantavirus in the Southwestern United States.DesignCase series.SettingTertiary referral center.PatientsAll patients with confirmed hantavirus infection admitted to the University of New Mexico Hospital between May 1, 1993 and January 1, 1994.InterventionsRecords of patients with hantavirus infection were reviewed to collect all pertinent clinical data.Measurements and Main ResultsPulmonary disease in these patients was characterized by hypoxemia covering a wide range of severity. The cause of hypoxemia was an increased permeability (noncardiac) pulmonary edema which could be differentiated from hydrostatic (cardiac) pulmonary edema by its association with low pulmonary artery occlusion pressures and increased protein content of edema fluid. Hemodynamic measurements in severe cases showed a shock state characterized by a low cardiac index (range 1.6 to 3.0 L/min/m2), a low stroke volume index (range 10.5 to 29 mL/m2), and high systemic vascular resistance index (range 1653 to 2997 dyne centered dot sec/cm5centered dot m2). Progression to death was associated with worsening cardiac dysfunction unresponsive to treatment and causing oxygen debt and lactic acidosis.ConclusionsThe two major life-threatening pathophysiologic changes in Hantavirus Pulmonary Syndrome are increased permeability pulmonary edema, and an atypical form of septic shock caused by myocardial depression and hypovolemia.(Crit Care Med 1996; 24:252-258)