Speculations on neurogenic pulmonary edema (NPE).

Evidence suggests the following pathogenesis for neurogenic pulmonary edema. The initial phase results from a centrally mediated, massive, sympathetic discharge. This produces intense, generalized, but transient, vasoconstriction with a resultant shift of blood from the high-resistance systemic circulation to the lowresistance pulmonary circulation. Marked increases in pulmonary vascular pressures and marked increases in pulmonary blood volume then produce pulmonary edema because of the hydrostatic effect of increased pulmonary capillary pressure. In addition, pulmonary hypertension and hypervolemia injure pulmonary blood vessels, altering pulmonary capillary permeability and producing lung hemorrhage. After the transient systemic and pulmonary vascular hypertension subside, the patient is left with abnormal pulmonary capillary permeability, so that pulmonary edema persists in the face of normal hemodynamics and normal cardia function.