Diuretic responses to Ringer's solution and 20% albumin at different arterial pressures

Intravenous volume loading is a common treatment when hypovolemia is a potential cause of oliguria. We studied whether the effectiveness of Ringer's solution and 20% albumin in inducing diuresis differs depending on the mean arterial pressure (MAP). For this purpose, volume kinetic analysis was performed based on urine output and hemoglobin-derived plasma dilution obtained during and after 136 infusions of Ringer and 85 infusions of 20% albumin. Covariance analysis quantified the diuretic response at different arterial pressures. The results show that the diuretic response to a known plasma volume expansion was greater for Ringer's solution above a MAP of 70 mmHg, while 20% albumin was significantly more effective at lower pressures (p < 0.03). Simulations of the urinary output in response to infusion of a predefined fluid volume yielded superior efficacy for 20% albumin when the MAP was low, while Ringer's was similarly effective when the MAP averaged 100 mmHg. In conclusion, urine output in response to plasma volume expansion with 20% albumin was similar to, or even stronger, than that of Ringer's solution when the MAP was below 70 mmHg.