Hemodynamic alterations of heat stroke in the elderly.

Serial hemodynamic alterations were investigated in seven elderly patients with heat stroke. Their mean age was 72 +/- 6 years. The circulatory response to heat stroke was either hyperdynamic of hypodynamic. Two patients had increased cardiac index (4.3 and 4.4 L/min/m2), increased right atrial pressure (10 and 12 mm Hg), normal pulmonary capillary wedge pressure (10 and 12 mm Hg), and decreased systemic vascular resistance (542 and 738 dyne.sec.cm-5). Five patients had decreased cardiac index (mean 2.3 +/- 0.2 L/min/m2), decreased right atrial pressure (mean 2 +/- 1 mm Hg), normal pulmonary capillary wedge pressure (mean 6 +/- 3 mm Hg), and increased systemic vascular resistance (mean 2020 +/- 204 dyne.sec.cm-5). Circulatory failure appears to be secondary to peripheral pooling of blood or hypovolemia. The inability to compensate hemodynamically when stressed by heat may predispose certain elderly individuals to develop heat stroke.