Fluid management and plasma renin activity in organ donors

Fluid management and assessment of organ perfusion in organ donors with hypotonic polyuria remain poorly investigated problems. In our protocol, urinary losses (565 +/- 202 ml/h) were replaced volume for volume by 3.3% dextrose/0.3% natrium chloride solution (Baxter) with 20 mmol/l potassium chloride. Concentrated red blood cells were administered to maintain hematocrit at about 30%, and volume expansion (central venous pressure above 6 mmHg) was obtained by gelatin (haemaccel) infusion. In all donors (n = 9), plasma electrolytes remained within normal limits despite hypotonic polyuria. Suppression of initial plasma renin activity (PRA: 9.7 +/- 3.6 ng/ml per hour) was obtained by subacute volume expansion. In eight donors the hemodynamic status improved, dopamine administration, when used, was discontinued, and PRA decreased (2.3 +/- 0.7 ng/ml per hour; P less than 0.05). The only donor who failed to respond to fluid therapy had increased PRA (24.2 ng/ml per hour). During fluid challenge, an inverse relationship was demonstrated between mean arterial pressure and PRA in all nine donors (r = -0.61; P less than 0.001), while there were no significant changes in blood urea. creatinine, or urine output. It is concluded that in organ donors, proper maintenance of the hemodynamic status and suppression of the renin stress response may be obtained by an adequate fluid management, involving both qualitative restoration and expansion of intravascular volume.