Abstract 20557: Therapeutic Hypothermia at 33C is Superior to 35C After Ischemia
Introduction: Therapeutic hypothermia is the most potent neuroprotectant ever studied in animal models of focal or global cerebral ischemia. Although various studies have shown a protective effect of hypothermia between 30°C and 36° C, a strong debate remains regarding the efficacy of hypothermia in stroke or cardiac arrest patients, especially the ideal depth: 33°C or 36°C.
Hypothesis: The present study aimed to compare directly 33°C vs. 35°C hypothermia using various durations and treatment delay times.
Methods: We studied primary cultured neurons and astrocytes in an oxygen glucose deprivation (OGD) model of ischemia and hypoxia. Neurons and astrocytes were cultured from E19 and after 7 days exposed to OGD (neurons: 2h duration, astrocytes: 10h). Then, hypothermia at 33°C or 36°C began 0, 30, 60 or 90min after the OGD and lasted for 2, 4 or 24 hours. After 24h, cell viability was measured using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT).
Results: Cell viability was significantly improved in neurons by hypothermia for 2h, 6h and 24h duration when begun immediately after OGD. Target-depth 33°C was significantly better than 35°C (p<0.001 ***). When hypothermia was initiated 30, 60, or 90min after OGD ended, we again found 33°C hypothermia provided significant neuroprotection compared to 35°C hypothermia (p< 0.001 ***). In astrocytes exposed to OGD, 33°C hypothermia showed significant cell viability when compared to normothermia (37°C) for various durations. In contrast, 35°C hypothermia, showed no significant improvements in cell viability compared to normothermia (37°C).
Conclusions: Our data confirm the superiority of 33°C compared to 35°C but both temperatures are superior to normothermia. These data powerfully inform the current debate over ideal target-depth of therapeutic hypothermia.
Author Disclosures: P. Rajput: None. J. Bai: None. J. Lamb: None. P. Lyden: None.
- © 2014 by American Heart Association, Inc.