Colloid osmotic pressures, plasma volume and interstitial fluid volume in patients with heart failure

In 13 patients with heart failure colloid osmotic pressure in plasma (IIp) and in subcutaneous interstitial fluid from thorax (IIi) (wick technique), plasma volume (PV) and interstitial fluid volume (IFV) were measured and correlated to haemodynamic parameters (cardiac index (CI) and right atrial pressure (RAP]. In seven patients with anasarca measurements of IIp, IIi, PV and IFV were repeated after fluid withdrawal (mean 7786 ml) by ultrafiltration. In the patients, IIi was reduced compared with normal subjects (11.5 +/- 3.4 versus 15.8 +/- 2.7 mmHg, p less than 0.01 (mean +/- SD] and transcapillary colloid osmotic gradient (IIp - IIi) increased (14.6 +/- 2.3 versus 12.8 +/- 2.7 mmHg, p less than 0.05). The IFV in the patients was increased to 137% of values in normal subjects (p less than 0.01) and the ratio PV/IFV significantly reduced. Correlations were found between IIi and CI (r = 0.69, p less than 0.01) and IIi and RAP (r = 0.78, p less than 0.01). Ultrafiltration led to a parallel decrease in PV and IFV and increase in IIp. The results indicate that reduced IIi is an important factor limiting peripheral oedema in heart failure and the reduction is more pronounced in severe heart failure. The reduction of IIi is due to both dilution of interstitial proteins and to reduction of interstitial protein mass by lymphatic wash-out.