ACID-BASE DERANGEMENTS DURING SORBENT REGENERATIVE HEMODIALYSIS IN MECHANICALLY VENTILATED PATIENTS

Objective: To assess acid-base derangements during sorbent regenerative hemodialysis in mechanically ventilated patients. Design: Consecutive case series; prospective study. Setting: An ICU in a university hospital. Patients: Seven patients undergoing hemodialysis for acute renal failure who required mechanical ventilation for acute respiratory failure. Interventions: Pulmonary and systemic hemodynamics, pH, and gas tensions in dialysate, arterial and mixed venous blood, and blood entering and leaving the dialyzer, were measured before, during, and after hemodialysis. Measurements and Main Results: During the first 2 hrs of hemodialysis, dialysate pH decreased from 6.91 +/- 0.14 to 6.06 +/- 0.37 and Pco2 increased to 437 +/- 111 torr (58.2 +/- 14.8 kPa). Simultaneously, the patients lost bicarbonate into the bath. As a result, pHa decreased from 7.38 +/- 0.02 to 7.31 +/- 0.02. At the end of dialysis, pHa returned to normal. Conclusion: Sorbent hemodialysis in mechanically ventilated patients is accompanied by acidosis that may contribute to hemodynamic instability.