Human neutrophil degranulation during extracorporeal circulation

Abstract

Cardiopulmonary bypass, especially when prolonged, may result in hemostatic failure and pulmonary dysfunction, which has been attributed to changes in platelets and leukocytes, respectively. It has been well documented that contact of blood with synthetic surfaces causes platelet activation. In this report, we explore mechanisms of the activation of neutrophils during simulated in vitro extracorporeal circulation and document the release of neutrophil lactoferrin and elastase during clinical cardiopulmonary bypass (CCB). Inhibition in the simulated circuit by prostaglandin E1 (PGE1) and lidocaine suggests different mechanisms for release of neutrophil-specific proteins. During CCB with a bubble oxygenator it was observed that platelet counts fell to 42% ± 2% of baseline. In addition, ß-thromboglobulin antigen (ßTG), a platelet-specific, a-granule protein marker reflecting the release reaction, increased from 0.15 ± 0.05 to 0.84 ± 0.11 µg/mL. Neutrophil counts decreased to 67% ± 7% of prebypass levels but then gradually rose as bypass continued. Both lactoferrin, a neutrophil-specific granule marker, and neutrophil elastase, an azurophilic granule marker, increased in plasma threefold to 1.66 ± 0.33 µg/mL and 1.65 ± 0.68 µg/mL, respectively, just before bypass was stopped. When fresh heparinized human blood was recirculated within an extracorporeal membrane oxygenator bypass circuit for 120 minutes, plasma ß-TG rose to 5.13 µg/mL, lactoferrin increased from 0.13 ± 0.04 to 1.62 ± 0.22 µg/mL, and neutrophil elastase rose from 0.05 ± 0.02 to 1.86 ± 0.41 µg/mL. At 120 minutes, lidocaine (100 µmol/L), which inhibits neutrophil activation, delayed release of lactoferrin (1.33 ± 0.26 µg/mL) and markedly inhibited release of elastase (0.24 ± 0.05 µg/mL) but did not inhibit release of ß-TG antigen (5.66 µg/mL at 120 minutes). PGE1 (0.3 µmol/L) inhibited significantly the release of ß-TG (0.31 µg/mL) and elastase (0.52 ± 0.11 µg/mL) and attenuated the release of lactoferrin (1.57 ± 0.45 µg/mL).