Hemodynamic Effects of Active Standing in the Middle Age and the Old Age Subjects

Abstract

Hemodynamic effects of the active sitting and standing from the supine position were investigated in the middle age group (8 males and l female, 51±2 years old) and the old age group (13 males and 17 females, 80±7 years old). Blood pressure was determined by a recording of intra-arterial pressure, and cardiac output was determined by dye-dilution ear-piece method. Total peripheral resistance was calculated from measured cardiac output and blood pressure (formula: blood pressure=cardiac output×total peripheral resistance). In the supine position, blood pressure was 112/57 and 150/65mmHg, heart rate 66 and 65 beats/min, cardiac index 4.3 and 3.4l/min/m², stroke index 63 and 57ml/beat/m² and total peripheral vascular resistance 1439 and 2324 dyn·sec·cm^-5·m² in the middle age group and the old age group, respectively. The active sitting from the supine position induced a fall of blood pressure 12/4 and 18/5mmHg, and the active standing caused a fall of 6/2 and 6/-3mmHg in the middle age group and the old age group, respectively. The standing induced a 32% and a 25% increase in heart rate, in the middle age group and the old age group, respectively. The keeping of standing position for 30sec induced a 14% and a 19% increase in heart rate form control values of the supine position, a 10% and 4% reduction of stroke volume, a 5% reduction and a 16% increased in cardiac output, and a 20% increase and no change in total peripheral vascular resistance, in the middle age group and the old age group, respectively. The increase of cardiac output was significantly correlated with the reduction of total peripheral vascular resistance. The standing position elevated total peipheral vascular resistance in the middle age group, but not in the old age group. The increase in concentration of plasma catecholamines by the standing was no difference between the middle age group and the old age group. Blood pressure change induced by the active standing was controled by the elevation of total peripheral vascular resistance in the middle age group, in contrast the change was controled by the increase in cardiac output in the old age group. Orthostatic hypotension was observed in the old age, which could not increase cardiac output during standing position.