Cerebral tissue hemoglobin saturation in children with sickle cell disease
Division of Hematology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio. . Pediatric Blood & Cancer
(Impact Factor: 2.39).
11/2012; 59(5):881-7. DOI: 10.1002/pbc.24227
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.
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.
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.
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. Pediatr Blood Cancer 2012; 59: 881-887. © 2012 Wiley Periodicals, Inc.
Available from: Enrico M Novelli
- "Prior research, however, shows that although the oxygen affinity of haemoglobin S is decreased in its polymerised state and in hypoxic conditions, it is near normal in its tetrameric state and in patients in normoxia (Abdu et al., 2008; Fabry et al., 2001), like the steady state SCA patients in our study. In children, lower peripheral oxygen saturation was positively correlated with cerebral desaturation (Quinn and Dowling, 2012). In adults, however, when the oxygen saturation of venous blood of HbSS patients was directly tested, it was found to be similar to that of HbAA controls, probably because increased blood flow in SCA leads to relatively lower oxygen extraction (Gladwin et al., 1999). "
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ABSTRACT: Sickle cell anaemia (SCA) is a hereditary hemoglobinopathy characterised by extensive vascular dysfunction that stems from inflammation, thrombosis and occlusion of post-capillary venules. Cognitive impairment is a neurological complication of SCA whose pathogenesis is unknown. We hypothesised that cerebral venular abnormalities are linked to cognitive impairment in SCA. Thus, we employed 7T magnetic resonance imaging (MRI) to examine the association between venular density and cognitive function in homozygous SCA. We quantified the density of total, long, and short venules in pre-defined regions of interest between the frontal and occipital cornu on each hemisphere. Cognitive function was assessed using the Hopkins Verbal Learning Test - Revised (HVLT-R) test of learning and memory. Patients (n=11) were compared with race, age and gender-equated controls (n=7). Compared to controls, patients had an overall venular rarefaction, with significantly lower density of long venules and greater density of short venules which was inversely related to HVLT-R performance and haemoglobin. To our knowledge, this is the first 7T MRI study in SCA and first report of associations between cerebral venular patterns and cognitive performance and haemoglobin. Future studies should examine whether these novel neuroimaging markers predict cognitive impairment longitudinally and are mechanistically linked to severity of anaemia.
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Available from: Aurélien Pichon
Available from: Aurélien Pichon
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ABSTRACT: Sickle cell anemia (SS) is characterized by a reduced cerebral microvascular oxygen saturation (cerebral TOI), which is not associated with hemoglobin concentration. Cerebral TOI has never been studied in sickle cell-hemoglobin C disease (SC). We focused on the relationships between hemorheological alterations and cerebral TOI in sickle cell patients with no cerebral vasculopathy and on the usefulness of TOI variability to assess the cerebral vasomotion activity. The blood rheological profile, the level of cerebral TOI (spatial resolved spectroscopy) and the cerebral TOI variability, which reflects vasomotion activity, were compared between 20 healthy subjects (AA), 21 SC patients, and 21 SS patients. Cerebral TOI exhibited the following order: AA > SC > SS. The low cerebral TOI in SS patients was related to red blood cell aggregation and deformability properties. The cerebral TOI variability of SS and SC patients was increased above healthy values and vasomotion activity was negatively associated with the reduced cerebral TOI in SS patients. We demonstrated that (1) blood rheology could be involved in the reduced cerebral TOI in SS patients but not in SC patients; (2) vasomotion activity is increased in SS and SC patients to compensate for the reduced cerebral TOI. Am. J. Hematol. 2012. © 2012 Wiley Periodicals, Inc.
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