Olsen H, Vernersson E, Länne T
Department of Endocrinology, Lund University, Malmö University Hospital, S-205 02 Malmö, Sweden.
Am J Physiol Heart Circ Physiol. 2000 Jan;278(1):H222-32. doi: 10.1152/ajpheart.2000.278.1.H222.
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.
研究发现，老年男性腿部静脉顺应性降低，下垂部位血液蓄积（容量反应）减少，这可能导致对体位性低血压期间压力感受器功能的年龄相关变化产生误解。在33名健康男性[18名年轻人（平均年龄22岁）和15名老年人（平均年龄65岁）]中，借助60 cmH₂O的下体负压（LBNP）研究了对低血容量循环应激的血流动力学反应。在研究小腿和手臂的容量反应以及手臂的跨毛细血管液体吸收时使用了容积技术。LBNP导致老年受试者心率增加幅度较小（P < 0.001）和外周阻力增加幅度较小（P < 0.01），且手臂的跨毛细血管液体吸收减少（P < 0.05）。然而，老年受试者小腿的血液蓄积减少（1.66±0.10 vs. 2.17±0.13 ml/100 ml组织；P < 0.01）。因此，在小腿血液蓄积相似时（老年受试者LBNP 80 cmH₂O），未发现心血管反射反应随年龄变化。然而，手臂的容量反应（外周血液向中心循环的动员）仍然降低（0.67±0.10 vs. 1.37±0.11 ml/100 ml组织；P < 0.01）。因此，老年人在体位性应激期间发现的心血管反射反应降低似乎是由于随着年龄增长腿部容量反应降低以及随之而来的中心低血容量刺激较小，而不是反射反应效率降低。在相似的低血容量循环应激下，心血管反射反应未见随年龄变化。然而，老年人手臂的容量反应（外周血液向中心循环的动员）减少了约50%。这可能严重妨碍急性失血时的生存可能性。
