Studies on the circulation in normotensive febrile patients

Normotensive febrile patients were studied in a constant-temperature room during stable fever, They were restudied later while afebrile and after heating the trunk. Finger and forearm blood flow were measured by venous occlusion plethysmography. The ability of cutaneous vessels to constrict on dependence of the limb was measured by laser Doppler flowmetry. The volume, velocity and acceleration of the blood in the ascending aorta were determined using pulsed Doppler ultrasound with a probe in the supra-sternal notch; measurements of systolic time intervals were made. While febrile, patients had a tachycardia and shortened systolic ejection times; cardiac output and total peripheral resistance were unchanged on average as compared to when afebrile. There was no evidence of any change in left ventricular contractility during fever from measurements of the peak velocity, maximum acceleration of blood or from the systolic time intervals. As compared to when heated, febrile patients had a skin blood flow that was relatively reduced for their skin temperature and had preservation of postural vasoconstriction.