Does normothermia during cardiopulmonary bypass increase neutrophil-endothelium interactions?

BACKGROUND

The use of warm blood cardioplegia is usually associated with that of warm cardiopulmonary bypass (CPB). Little is known, however, about the effect of temperature during bypass on neutrophil-endothelium interactions, which are currently considered a key component of the inflammatory response to CPB.

METHODS AND RESULTS

Twenty-five patients operated on under CPB were studied. Core temperature during bypass was kept normothermic (33.5 degrees C to 37 degrees C) in 14 and lowered to 28 degrees C to 30 degrees C in the 11 remaining patients. The two groups were otherwise comparable. Arterial blood samples were collected before CPB and 30 minutes, 4 hours, and 24 hours thereafter. Samples were assayed for interleukin-1 receptor antagonist (IL-1ra), soluble intercellular adhesion molecule 1 (sICAM-1), and elastase, which are markers of cytokine production, cytokine-upregulated endothelial ligands for neutrophil adhesion molecules, and degranulation secondary to adhesion of neutrophils to endothelial cells, respectively. IL-1ra levels (mean +/- SEM) peaked 4 hours after bypass and were significantly higher in the warm group (87,926 +/- 24,067 versus 18,090 +/- 5798 mg/L, P < .02). Peak values of sICAM-1, which occurred 24 hours after bypass, were correspondingly higher in warm patients (414 +/- 74 versus 298 +/- 23 micrograms/L in cold patients). In keeping with these data, warm patients released significantly more elastase at both the 30-minute (703 +/- 101 versus 349 +/- 55 micrograms/L, P < .01) and 4-hour (627 +/- 116 versus 324 +/- 31 micrograms/L, P < .03) post-CPB study points.

CONCLUSIONS

Temperature profoundly affects neutrophil-endothelium interactions, which leads one to question the use of systemic normothermia in patients at higher risk of suffering from postbypass inflammation-mediated organ damage.