Continuous arteriovenous hemofiltration countercurrent dialysis (CAVH-D) in acute respiratory failure (ARDS)

The balance between intravascular volume, oxygen transport, and arterial oxygenation is delicate in patients with adult respiratory distress syndrome (ARDS). Recently, we used continuous arteriovenous countercurrent hemodialysis (CAVH-D) in 14 nonoliguric patients who had severe ARDS. The cause of the ARDS was pancreatitis in 1 patient, trauma in 10 patients, and postoperative in 4 patients. All patients were edematous, in marked positive fluid balance but not intravascularly overloaded before institution of CAVH-D. Transfemoral CAVH-D was instituted and managed by the SICU staff. Patients underwent CAVH-D for a mean of 65.2 hours (range, 12-140 hours) and cleared a mean of 480 mL/h of filtrate. The only complication was one patient who bled from a loose tubing connection. Three patients were grossly unstable when CAVH-D was begun. Their mean cardiac index (CI) was 2.3 L/min/m2 despite maximal inotropes. Their CAVH-D filters cleared a mean of 600 mL/h, but they required constant fluid resuscitation and died of cardiogenic shock and ARDS within 3 days. The other 11 patients had significant improvement in their respiratory function. Mean FI02 was weaned from 0.73 to 0.45 (p less than 0.005) and PEEP from 14.3 cm to 8.9 cm (p less than 0.005). Peak airway pressures fell from a mean of 60 mm Hg to 45 mm Hg (p less than 0.01). There was no significant change in CI or wedge pressure, but oxygen consumption rose from a mean of 279 to 409 mL/m (p less than 0.05). The technique of CAVH-D offers an alternative to patients with ARDS who do not have large on-going fluid requirements. It is safe, can be managed by the surgical staff, and is associated with a significant improvement in respiratory variables without requiring a drop in filling pressures that might potentially compromise oxygen transport.