Effect of extracorporeal membrane oxygenation on neutrophil function in neonates.

OBJECTIVE

To study the effect of long-term extracorporeal membrane oxygenation (ECMO) support on neutrophil function.

DESIGN

A prospective, clinical investigation.

SETTING

A pediatric intensive care unit.

PATIENTS

Four groups of patients: ECMO group 1, newborns after 1 day of ECMO support (n = 10); ECMO group 2, newborns after 5 days of ECMO support (n = 6); group 3, normal newborns (n = 20); group 4, normal adults (n = 30).

INTERVENTIONS

Two mL of heparinized blood was obtained from patients in each group. A modification of the Smith and Rommel technique was used to measure neutrophil phagocytosis and killing utilizing live Candida tropicalis as the test organism. Neutrophils were incubated for 90 mins in normal adult serum with live Candida. Viability of Candida after phagocytosis was tested by vital fluorochrome staining. Phagocytic index (the number of neutrophils with intracytoplasmic Candida divided by the total neutrophils) and candidicidal ratio (neutrophils with dead Candida divided by total neutrophils with Candida) were determined daily.

MEASUREMENTS AND MAIN RESULTS

Neutrophils from ECMO group 1 (day 1) and ECMO group 2 (day 5) patients had significantly higher phagocytosis indices (72.8 +/- 20 and 76 +/- 18) and candidicidal ratios (0.15 +/- 0.1 and 0.16 +/- 0.09) compared with neutrophils from group 3 patients (normal neonates) (64 +/- 7 and 0.06 +/- 0.04). The phagocytosis indices were significantly lower in neutrophils from ECMO group 1 (day 1) and ECMO group 2 (day 5) patients compared with group 4 (adults) patients (86 +/- 9). However, the candidicidal ratios in neutrophils from ECMO groups 1 and 2 (ECMO day 1 and day 5) patients were equal to that value in group 4 (adults) (0.10 +/- 0.04). ECMO support for 5 days (ECMO group 2 vs. group 1) did not significantly change either the phagocytosis index or candidicidal ratio.

CONCLUSIONS

Phagocytosis and intracellular killing by neutrophils of ECMO-supported neonates were significantly greater than those values found in normal newborns. ECMO support for 5 days produced no significant changes in neutrophil phagocytosis or killing.