Cerebral tissue hemoglobin saturation in children with sickle cell disease.

BACKGROUND: Desaturation of hemoglobin (Hb) in cerebral tissue, a physiologic marker of brain vulnerable to ischemic injury, can be detected non-invasively by transcranial oximetry. Absolute cerebral oximetry has not been studied in sickle cell disease (SCD), a group at very high risk of cerebral infarction in whom prevention of brain injury is key. PROCEDURE: We measured absolute Hb saturation in cerebral tissue (S(CT)O(2)) in children with SCD using near-infrared spectrophotometry and investigated the contributions of peripheral Hb saturation (S(P)O(2)), hematologic measures, cerebral arterial blood flow velocity, and cerebral arterial stenosis to S(CT)O(2). We also assessed the effects of transfusion.
RESULTS: We studied 149 children with SCD (112 HbSS/Sβ(0); 37 HbSC/Sβ(+)). S(CT)O(2) was abnormally low in 75% of HbSS/Sβ(0) and 35% of HbSC/Sβ(+) patients. S(CT)O(2) (mean ± SD) was 53.2 ± 14.2 in HbSS/Sβ(0) and 66.1 ± 9.2% in SC/Sβ(+) patients. S(CT)O(2) correlated with age, sex, Hb concentration, reticulocytes, Hb F, and S(P)O(2), but not transcranial Doppler arterial blood flow velocities as continuous measures. In multivariable models, S(P)O(2), Hb concentration, and age were significant independent determinants of S(CT)O(2). Cerebral vasculopathy was associated with ipsilateral cerebral desaturation. Transfusion increased S(CT)O(2) and minimized the inter-hemispheric differences in S(CT)O(2) due to vasculopathy.
CONCLUSIONS: Cerebral desaturation, a physiologic marker of at-risk brain, is common in SCD, more severe in HbSS/Sβ(0) patients, and associated with peripheral desaturation, more severe anemia, and increasing age. Cerebral oximetry has the potential to improve the identification of children with SCD at highest risk of neurologic injury and possibly serve as a physiologic guide for neuroprotective therapy.