Increased glomerular filtration rate in patients after reconstructive surgery on the abdominal aorta

Fifty-three patients undergoing elective reconstructive surgery on the abdominal aorta were included in a prospective study to obtain information on postoperative glomerular filtration rate (GFR) in relation to increased fluid and sodium intake and decreased plasma colloid osmotic pressure (COP). GFR, extracellular fluid volume (ECV) and COP were measured before operation and on the first and fourth day after surgery. GFR and ECV were measured by means of the single injection residue detection method using the inulin analogue polyfructosan-S as marker. The compiled GFR values increased from 92.3 to 103.7 ml min−1 1.73m−2 (P < 0.002) on the first day, and to 105.3 ml min−1 1.73m−2 (P < 0.001) on the fourth day after surgery. Concomitantly, ECV increased from 8.9 litres 1.73m−2 before operation to 9.5 litres 1.73m−2 (P < 0.05) and 9.6 litres 1.73m−2 (P < 0.025) respectively. Positive linear correlation was found on the first postoperative day between GFR per 1.73m2 and ECV per 1.73m2 (r = 0.33, P < 0.05) and between GFR per 1.73m2 and extracellular sodium content per 1.73m2 (r = 0.38, P < 0.01). COP was not correlated to GFR per 1.73m2. The postoperative increase in GFR found in this study is most likely to be the result of increased ECV and renal plasma flow. Whether other factors are also involved remains unknown.