Circulatory and respiratory adaptation in man to acute withdrawal and reinfusion of blood

Abstract

In eight healthy men 950 g of blood (12.2 17.6% of the blood volume) was withdrawn and reinfused after about half an hour. Respiration and circulation were studied by analyses of expiratory gas, blood gases and data from right heart catheterization. On hemorrhage oxygen uptake and cardiac output decreased by 10 and 28%, repectively; both varied indirectly with the blood loss. The pressures in the right ventricle, pulmonary and systemic arteries fell without relation to the cardiac output. Mean heart rate did not change significantly, but a moderate positive covariation (P less than 0.05) between heart rate and arterial blood pressure was found during bleeding. This result was confirmed by the relative bradycardia noted in the period prior to reinfusion. On refilling of the bood the oxygen uptake and the pulmonary arterial pressures increased above the initial value. The heart rate varied directly with the arterial pressure also during reinfusion. The observations demonstrate a depression of the metabolism and circulation on moderate hemorrhage. Part of these effects is tentatively referred to a lowered set point of the arterial baroreflexes.

Bradycardia During Reversible Hypovolaemic Shock: Associated Neural Reflex Mechanisms and Clinical Implications

“…A low HR has also been demonstrated in volunteers after bleeding approximately 1 L (Ebert et al 1941;Wallace & Sharpey-Schafer 1941;Barcroft et al 1944;Shenkin et al 1944;Barcroft & Edholm 1945;Price et al 1966;Bergenwald et al 1975Bergenwald et al , 1977, in patients with a blood loss of approximately 2 L (Hoffman 1972;Hyun et al 1972;Jansen 1978;Secher et al 1984;Sander-Jensen et al 1986b;Barriot & Riou 1987), and even during haemorrhage in anaesthetized patients (Rwsgaard & Secher 1986). The finding that patients appear to have a larger blood loss than volunteers at the time when a low HR appears reflects the fact that fluid therapy, albeit inadequate, delays the response in the patients.…”

Lower body negative pressure as a model to study progression to acute hemorrhagic shock in humans

“…Acute hemorrhage decreases cardiac output, stroke volume, left ventricular work, mean arterial pressure, and central venous pressure (103) and, therefore, constitutes a challenge to cardiovascular homeostasis. Reduction of ϳ15% of the total blood volume (Х750 ml) decreases cardiac output by 30% (11). During mild-to-moderate hemorrhage, arterial pressure is maintained through sympathoexcitation that increases peripheral vascular resistance and heart rate, but cardiac output falls progressively.…”

Cardiovascular Function and Arterial Blood Gases during Isolated Ultrafiltration in Healthy Man

“…An unchanged heart rate, in spite of a diminished stroke volume and car diac filling pressures and even a fall in blood pressure, has also been reported in non-uremic subjects when hypovolemia was induced by experimental hemorrhage. Thus, Bergenwald et al [9] found that a reduction in blood volume through blood letting (12.2-17.6% of blood volume during 24-41 min) in healthy volunteers reduced stroke volume and cardiac output by about one third. The significant fall in arterial blood pressures was countered by a systemic vasoconstric tion but without any change in heart rate.…”

“…The significant fall in arterial blood pressures was countered by a systemic vasoconstric tion but without any change in heart rate. Bergenwald et al [9] suggested that the un changed heart rate might be due to a lower ing of the set point of the arterial baroreflexes through interaction with baroreceptors in the low-pressure region. During plas ma-exchange treatment with an intermittent cell separator, Coli et al [16] found a fall in arterial and pulmonary blood pressures and cardiac index, an increased total peripheral resistance, but an unchanged heart rate after the first plasma-exchange cycle before 300 ml of fresh frozen plasma was infused for replacement.…”

“…However, it has also been ob served that rapid isolated ultrafiltration in volves the risk of hypotensive episodes with out reflex tachycardia [8], Hence, in uremic patients tachycardia cannot be used as a sign of impending hypovolemia during ultrafil tration. This raises the question whether the absence of a heart rate response is the result of the uremic state with autonomic neuropa thy or a normal physiological phenomenon where changes in the central blood volume interfere with arterial baroreceptor function [9). The aim of the present investigation was to study the hemodynamic adaptation to iso lated ultrafiltration in healthy man and thus exclude possible effects of the uremic state.…”