Interstitial fluid volume, plasma volume and colloid osmotic pressure in patients with nephrotic syndrome

Abstract

Colloid osmotic pressure in plasma (II_p) and in subcutaneous interstitial fluid (11) (wick technique), plasma volume (PV) and interstitial fluid volume (IFV) were measured in nephrotic patients (n = 11) and in healthy controls. Six of the patients were treated with ultrafiltration and the parameters were measured before and after withdrawal of mean 7460 ml (total ultrafiltrate in two sessions). In the nephrotic patients mean II II_p, was 11.6 mmHg and II II_i was 3.9 mmHg compared to 28.6 mmHg and 15.8 mmHg. respectively, in healthy controls. PV was in the normal-to-high range and IFV was increased to 150%, of the values in controls. No statistically significant change in PV, II II_p or II II_i was found after ultrafiltration and IFV was reduced by 20%. The results indicate that reduction in II_i is an important oedema-preventing factor and that the reduction in interstitial protein mass is more than proportional compared to the degree of hypoproteinaemia. Ultrafiltration in the rate and magnitude we have used, leads to reduction in IFV but small changes in PV, II II_p, or II II_i.

Key Words:

• colloid osmotic pressure
• interstitial fluid volume
• nephrotic syndrome
• oedema-preventing mechanism
• plasma volume
• ultrafiltration