Cardiovascular responses to phlebotomy and sitting in middle-aged and elderly subjects

Responding appropriately to hypotensive challenges is an important determinant of health and functional independence in elderly individuals. Cardiovascular responses to phlebotomy and postural change were evaluated using a large database developed in a study designed to establish the safety of blood donation by older individuals.

The groups studied included 464 subjects aged 65 years and younger (range, 52 to 65 years) and 532 subjects more than 65 years old (range, 66 to 78 years old). Blood pressure and pulse rate measurements were followed by the withdrawal of 500 mL of blood. These measurements were repeated, first in the supine and then in the sitting position.

Nearly all individuals studied remained hemodynamically stable after these two challenges. Age was not an independent predictor of blood pressure change after either phlebotomy or postural change. Large decreases in diastolic blood pressure were equally rare in both age groups. However, more older subjects (15.2%) exhibited a decline of 20 mm Hg or more in systolic blood pressure following phlebotomy, compared with the middle-aged group (6.9%). These age-related differences did not persist after controlling for the higher initial systolic blood pressures observed in the older subjects. Postphlebotomy postural change to the sitting position had little additional effect.

These results indicate that the ability to respond to hypovolemia and postural change remains relatively intact in healthy elderly individuals. The higher prevalence of a significant drop in systolic blood pressure after phlebotomy, orthostasis, and possibly other homeostatic challenges in older subjects is probably due to the presence of higher basal blood pressure readings, including hypertension. In spite of these differences, blood donation is appropriate and should be encouraged in healthy elderly individuals in this age group.