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Cardiovascular response to acute hypovolemia in relation to age. Implications for orthostasis and hemorrhage

In English

Författare

Summary, in English

Venous compliance in the legs of aging man has been found to be reduced with decreased blood pooling (capacitance response) in dependent regions, and this might lead to misinterpretations of age-related changes in baroreceptor function during orthostasis. The hemodynamic response to hypovolemic circulatory stress was studied with the aid of lower-body negative pressure (LBNP) of 60 cmH(2)O in 33 healthy men [18 young (mean age 22 yr) and 15 old (mean age 65 yr)]. Volumetric technique was used in the study of capacitance responses in the calf and arm as well as transcapillary fluid absorption in the arm. LBNP led to smaller increase in heart rate (P < 0.001) and peripheral resistance (P < 0.01) and reduced transcapillary fluid absorption in the arm (P < 0.05) in old subjects. However, blood pooling in the calf was reduced in old subjects (1.66 +/- 0.10 vs. 2.17 +/- 0.13 ml/100 ml tissue; P < 0. 01). Accordingly, during similar blood pooling in the calf (LBNP 80 cmH(2)O in old subjects), no changes in cardiovascular reflex responses with age were found. The capacitance response in the arm (mobilization of peripheral blood to the central circulation) was still reduced, however (0.67 +/- 0.10 vs. 1.37 +/- 0.11 ml/100 ml tissue; P < 0.01). Thus the reduced cardiovascular reflex response found in the elderly during orthostatic stress seems to be caused by a reduced capacitance response in the legs with age and a concomitant smaller central hypovolemic stimulus rather than a reduced efficiency of the reflex response. With similar hypovolemic circulatory stress, no changes in cardiovascular reflex responses are seen with age. The capacitance response in the arm (mobilization of peripheral blood toward the central circulation) is reduced, however, by approximately 50% in the elderly. This might seriously impede the possibility of survival of an acute blood loss.

Publiceringsår

2000-01

Språk

Engelska

Sidor

32-222

Publikation/Tidskrift/Serie

American Journal of Physiology - Heart and Circulatory Physiology

Volym

278

Issue

1

Dokumenttyp

Artikel i tidskrift

Förlag

American Physiological Society

Ämne

  • Physiology and Anatomy
  • Cardiology and Cardiovascular Disease

Nyckelord

  • Acute Disease
  • Adult
  • Aged
  • Aging/physiology
  • Baroreflex/physiology
  • Capillary Permeability
  • Cardiovascular System/physiopathology
  • Compliance
  • Hemodynamics
  • Hemorrhage/physiopathology
  • Humans
  • Hypovolemia/physiopathology
  • Lower Body Negative Pressure
  • Male
  • Middle Aged
  • Posture/physiology
  • Vascular Capacitance
  • Veins/physiopathology

Aktiv

Published

Forskningsgrupp

  • Endocrine
  • Anaesthesiology and Intensive Care Medicine

ISBN/ISSN/Övrigt

  • ISSN: 0363-6135