Different cardiovascular responses to hemodialysis-induced fluid depletion and blood pressure compliance

On the basis of cardiovascular compliance, hemodialysis (HD) patients can be classified as hypotension prone (HP) or hypotension resistant (HR).

We compare the hemodynamic behavior and myocardial performances in 6 HP and 6 HR patients before and after an isolated ultrafiltration (IU) session removing 3% of total body water.

HP show higher basal plasma angiotensin II levels during IU (p<0.01), whereas angiotensin II remained unchanged in HR patients (p<0.001 between groups). The percentage changes of plasma volume (PV) was similar in the 2 groups. A significant reduction of cardiac index was observed only in the HP group (p<0.001 between groups). The mean values of heart rate remained significantly higher, whereas total peripheral resistances significantly fell in the HP in comparison with the HR group (p<0.001 between groups). During IU, the mean arterial pressure (MAP) changes were -10 +/- 3 mm Hg in the HP vs. -3.3 +/- 2 mm Hg in the HR group (p<0.001). Echocardiography data were collected before and after IU. All enrolled patients presented left ventricular hypertrophy; following IU, HP patients showed a reduction of mean left ventricular diameter (p<0.01), left atrial diameters and right atrial diameter, and a change in percentage of right atrium ejection fraction (p<0.001, p<0.01).

In comparison with HR patients, HP patients before and after IU showed a defective arteriovenous tone adjustment to the PV changes, with a hemodynamic picture of abnormal sympathetic stimulation. Moreover, a reduced cardiac preload with both atrial and ventricular underfilling in these patients is at risk for a sudden drop in MAP.