Crystalloid or colloid fluid loading and pulmonary permeability, edema, and injury in septic and nonseptic critically ill patients with hypovolemia

OBJECTIVE: To compare crystalloid and colloid fluids in their effect on pulmonary edema in hypovolemic septic and nonseptic patients with or at risk for acute lung injury/acute respiratory distress syndrome. We hypothesized that 1) crystalloid loading results in more edema formation than colloid loading and 2) the differences among the types of fluid decreases at high permeability.

DESIGN, SETTING, AND PATIENTS: Prospective randomized clinical trial on the effect of fluids in 24 septic and 24 nonseptic mechanically ventilated patients with clinical hypovolemia.

INTERVENTIONS: Patients were assigned to NaCl 0.9%, gelatin 4%, hydroxyethyl starch 6%, or albumin 5% loading for 90 minutes according to changes in filling pressures.

MEASUREMENTS AND MAIN RESULTS: Twenty-three septic and 10 nonseptic patients had acute lung injury/acute respiratory distress syndrome (p < 0.001). Septic patients had greater pulmonary capillary permeability, edema, and severity of lung injury than nonseptic patients (p < 0.01), as measured by the pulmonary leak index (PLI) for Gallium-labeled transferrin, extravascular lung water (EVLW), and lung injury score (LIS), respectively. Colloids increased plasma volume, cardiac index, and central venous pressure (CVP) more than crystalloids (p < 0.05), although more crystalloids were infused (p < 0.05). Colloid osmotic pressure (COP) increased in colloid and decreased in crystalloid groups (p < 0.001). Irrespective of fluid type or underlying disease, the pulmonary leak index increased by median 5% (p < 0.05). Regardless of fluid type or underlying disease, EVLW and LIS did not change during fluid loading and EVLW related to COP-CVP (rs = -.40, p < 0.01).

CONCLUSIONS: Pulmonary edema and LIS are not affected by the type of fluid loading in the steep part of the cardiac function curve in both septic and nonseptic patients. Then, pulmonary capillary permeability may be a smaller determinant of pulmonary edema than COP and CVP. Safety factors may have prevented edema during a small filtration pressure-induced rise in pulmonary protein and thus fluid transport.