Abstract P100: Role of Neutrophils and Preventive Effect of Dexamethasone on Pulmonary Complications during Hypothermic Therapy for Brain-Injured Patients
To study differences in the rate of occurrence of pneumonia and the time-course changes in oxygenation in brain-injured patients with or without dexamethasone (D), a neutrophil attenuator, during hypothermic or normothermic therapy.
For exploring the mechanism of pulmonary complications during hypothermic therapy, to examine the effect of decreasing the culture temperature as well as steroid application on phagocytic and bactericidal functions in neutrophils harvested from normal volunteers.
Design: A retrospective observational study and in vitro human neutrophil studies.
Setting: Two university hospitals.
Subjects and Methods: Brain-injured patients (GCS<8) treated with hypothermic (N=23, 32–33°C) or normothermic (N=16, 36 –37.5°C) therapy were studied. Hypothermic therapy including the rewarming phase usually lasted for seven days. Normothermic therapy also was done for the same period. Their PaO2/FIO2 (P/F) ratios and C-reactive protein (CRP) levels were reviewed. D at the dose of 0.16 mg/kg for 7 days was given to patients in both groups (17 patients in hypothermia; 11 in normothermia). The data were analyzed using ANOVA, the Mann-Whitney U-test or the chi-squared test (p<0.05). IRB approval was obtained before starting in vitro studies.
Results: Although the overall rate of occurrence of pneumonia did not differ between the hypothermic and the normothermic groups, the rate in the hypothermic patients not receiving D was greater than that in the hypothermic patients being given D. The hypothermic patients without D showed more severe deterioration in their P/F ratios along with CRP elevation especially during and after the rewarming. The in vitro phagocytic neutrophil function was reduced while the culure temperature was below 33°C, but increased when the temperature reached 35°C and above, a level simulated in the rewarming phase in the clinical settings. Such neutrophil function was reduced by steroid application at 37°C.
Conclusion: This report poses hypotheses:
neutrophils play a role in pulmonary complications during hypothermic therapy, especially during the rewarming phase, for brain-injured patients;
dexamethasone exerts preventive effects on the sequelae.