March 1, 1998Open Access
View Full PaperHemodilution Reduces Clinic and Ambulatory Blood Pressure in Polycythemic Patients
Key Result
Isovolumic hemodilution significantly reduced clinic systolic blood pressure from 144.3 to 136.0 mm Hg and diastolic from 87.0 to 82.1 mm Hg (P<0.05 for both) in patients with polycythemia.
Structured PICO
Does isovolumic hemodilution reduce clinic and ambulatory blood pressure in patients with polycythemia?
P
Population
22 normotensive and hypertensive patients with polycythemia evaluated before and 7 to 10 days after isovolumic hemodilution.
I
Intervention
Isovolumic hemodilution (withdrawal of 400 to 700 mL of blood, with concomitant infusion of an equivalent volume of saline-albumin solution)
C
Comparator
Baseline (before hemodilution)
O
Outcome
Clinic and 24-hour ambulatory blood pressure (BP) values at 7 to 10 dayssurrogate
Isovolumic hemodilution significantly reduces both clinic and 24-hour ambulatory blood pressure in patients with polycythemia, particularly those with hypertension.
Main Result
p-value: p=<.05
Abstract
Limited information is available for humans on whether blood viscosity affects total peripheral resistance and, hence, blood pressure. Our study was aimed at assessing the effects of acute changes in blood viscosity on both clinic and 24-hour ambulatory blood pressure (BP) values. In 22 normotensive and hypertensive patients with polycythemia, clinic and 24-hour ambulatory BPs were measured before and 7 to 10 days after isovolumic hemodilution; this was performed through the withdrawal of 400 to 700 mL of blood, with concomitant infusion of an equivalent volume of saline-albumin solution. Hematocrit, plasma renin activity, plasma endothelin-1, right atrial diameter (echocardiography), and blood viscosity were measured under both conditions. Plasma renin activity and right atrial diameter were used as indirect markers of blood volume changes. Plasma endothelin-1 was used to obtain information on a vasomotor substance possibly stimulated by our intervention, which could counteract vasomotor effects. Isovolumic hemodilution reduced hematocrit from 0.53+/-0.05 to 0.49+/-0.05 (P<.01). Plasma renin activity, plasma endothelin-1 and right atrial diameter were unchanged. Clinic blood pressure was reduced by hemodilution (systolic, 144.3+/-5.4 to 136.0+/-3.9 mm Hgmean+/-SEM; diastolic, 87.0+/-2.8 to 82.1+/-2.6 mm Hg, P<.05 for both) and a reduction was observed also for 24-hour average ABP (systolic, 133.6+/-2.9 to 129.5+/-2.7 mm Hg; diastolic, 80.0+/-2.0 to 77.3+/-1.7 mm Hg, P<.05 for both). The reduction was consistent in hypertensive patients (n = 12), whereas in normotensive patients (n = 10) it was small and not significant. Both clinic and 24-hour average heart rates were unaffected by the hemodilution. Thus, in polycythemia, reduction in blood viscosity without changing blood volume causes a significant fall in both clinic and 24-hour ambulatory BPs; this is particularly true when, as can often happen, blood pressure is elevated. This emphasizes the importance this variable may have in the determination of blood pressure and the potential therapeutic value of its correction when altered.