Reduced defense of central blood volume during acute hypovolemic circulatory stress in aging women

• Elderly men respond with decreased defense of central blood volume during hypovolemic stress, but this response has not been evaluated with age in women. The aim was to examine the compensatory mechanisms to defend central blood volume during experimental hypovolemia in elderly compared to young women. Cardiovascular responses in 34 women, 12 elderly (66.4±1.4 yr) and 22 young (23.1±0.4 yr) were studied during experimental hypovolemic circulatory stress induced by lower body negative pressure (LBNP) of 11-44 mmHg. Volumetric technique was used to assess the capacitance response (redistribution of peripheral venous blood to the central circulation) as well as to assess net capillary fluid transfer from tissue to blood in the arm. LBNP created comparable hypovolemia in elderly and young women. Heart rate increased less in elderly women (LBNP of 44 mmHg: 20±2 vs. 37±4 %, P < 0.01), but with similar decrease in forearm vascular conductance (FVC). Mobilization of capacitance blood from the peripheral circulation was both slower and decreased by ~60 % in elderly, and net capillary fluid absorption from surrounding tissues was reduced by ~40 % (LBNP of 44 mmHg). In conclusion, during acute hypovolemic circulatory stress elderly women responded with less increase in heart rate but with an equal change in FVC, implying decreased cardiovagal baroreceptor sensitivity. Furthermore, both capacitance response and net capillary fluid absorption were reduced, indicating less efficiency to defend central blood volume in elderly than in young women.

Nyckelord

Female

trauma

baroreceptor sensitivity

orthostatic tolerance

adrenergic receptor response

MEDICINE

MEDICIN

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