Hemodynamic Alterations in Normotensive and Hypertensive Subjects during the Pyrogenic Reaction.

It is well known that toxic substances, probably derivatives of bacterial protein ( 1), frequently appear in improperly distilled water. A dramatic and often potentially dangerous syndrome of chill and fever (pyrogenic reaction), occasionally complicated by peripheral circulatory collapse, follows the intravenous administration of solutions contaminated with these substances. A marked increase in renal blood flow (2), a reduction in arterial pressure (3) and an increase in cardiac output (4) have been observed during the pyrogenic reaction in normal man, indicating a marked reduction in over-all peripheral resistance. Three stages of arterial pressure change have been described (3): namely, (a) a short period of elevated pressure during the chill and initial rise in temperature, (b) a phase characterized by a moderate fall in blood pressure, coinciding approximately with the appearance of renal hyperemia, and (c) a marked reduction in blood pressure with a narrowing of the pulse pressure some 4 or 5 hours after the administration of the pyrogen. Although antipyretics, such as amidopyrine, when given in adequate doses prior to injection of the pyrogen, will prevent chill and fever, they do not affect renal hyperemia or phases (b) and (c). The reduction of arterial pressure (c) is usually greater among hypertensive than among normal subjects and may be so profound as to result in a shocklike state, even in the absence of fever. It is not known whether the late reduction in blood pressure is a result of widespread vasodilation, reduced cardiac output or a combination of the two. Nor is it known whether there is any fundamental difference in response on the part of hypertensive as compared with normotensive individuals. The present study was undertaken to evaluate the hemodynamic factors involved in this reduction. METHODS