Starling pressures in the human arm and their alteration in postmastectomy oedema.

1. Surgery and radiotherapy to axillary lymph nodes during breast cancer treatment is often followed, commonly years later, by chronic postmastectomy oedema (PMO). PMO is considered a 'high protein' oedema due to reduced axillary lymph drainage. Since oedema formation also depends on fluid input (capillary filtration), we studied the Starling pressures in the affected and contralateral arm. Colloid osmotic pressure was measured in patient serum (pi p) and interstitial fluid (pi i). Subcutis fluid was collected from PMO arms by both wick and aspiration methods, and from the control arm by the wick method only. Interstitial hydraulic pressure (P(i)) was measured by the wick-in-needle method. 2. Oedema pi i was 19.2 +/- 4.1 cmH2O (n = 13, wick) to 16.3 +/- 4.4 cmH2O (n = 41, aspirate; difference not significant; mean +/- S.D. throughout). This was significantly lower than pi i in the control arm (21.4 +/- 3.8 cmH2O, n = 14, P < 0.01, analysis of variance). Also, there was a negative correlation between oedema pi i and the percentage increase in arm volume (correlation coefficient r = -0.35, P < 0.05) in contrast to conventional expectation. 3. Oedema P(i) (1.9 +/- 2.0 cmH2O, n = 28) exceeded the subatmospheric control P(i) (-2.8 +/- 3.0 cmH2O; P < 0.01). Venous and arterial pressures were normal but pi p was subnormal (31.1 +/- 2.7 cmH2O, n = 47). 4. Net pressure opposing capillary blood pressure, P(o), was calculated as P(i) + sigma (pi p-pi i) for a reflection coefficient, sigma, of 0.90-0.99.(ABSTRACT TRUNCATED AT 250 WORDS)