Abstract
Background/AimAlthough it has been hypothesized that muscle metabolism and fatigability could be impaired in sickle cell patients, no study has addressed this issue.MethodsWe compared muscle metabolism and function (muscle microvascular oxygenation, microvascular blood flow, muscle oxygen consumption and muscle microvascular oxygenation variability, which reflects vasomotion activity, maximal muscle force and local muscle fatigability) and the hemorheological profile at rest between 16 healthy subjects (AA), 20 sickle cell-hemoglobin C disease (SC) patients and 16 sickle cell anemia (SS) patients.ResultsMuscle microvascular oxygenation was reduced in SS patients compared to the SC and AA groups and this reduction was not related to hemorhelogical abnormalities. No difference was observed between the three groups for oxygen consumption and vasomotion activity. Muscle microvascular blood flow was higher in SS patients compared to the AA group, and tended to be higher compared to the SC group. Multivariate analysis revealed that muscle oxygen consumption was independently associated with muscle microvascular blood flow in the two sickle cell groups (SC and SS). Finally, despite reduced muscle force in sickle cell patients, their local muscle fatigability was similar to that of the healthy subjects.ConclusionsSickle cell patients have normal resting muscle oxygen consumption and fatigability despite hemorheological alterations and, for SS patients only, reduced muscle microvascular oxygenation and increased microvascular blood flow. Two alternative mechanisms can be proposed for SS patients: 1) the increased muscle microvascular blood flow is a way to compensate for the lower muscle microvascular oxygenation to maintain muscle oxygen consumption to normal values or 2) the reduced microvascular oxygenation coupled with a normal resting muscle oxygen consumption could indicate that there is slight hypoxia within the muscle which is not sufficient to limit mitochondrial respiration but increases muscle microvascular blood flow.
Highlights
Patients with sickle cell disease (SCD) are characterized by anemia and altered blood rheology which may impair blood flow [1], trigger vaso-occlusive crisis, cause tissue ischemia [2,3,4] and limit exercise capacity [5].Few studies investigated baseline microvascular oxygenation at the cerebral level in SCD patients and reported reduced values suggesting a certain degree of chronic cerebral hypoxia [6,7,8].But, it is unknown whether it is the case in other organs
We demonstrated that sickle cell patients have normal resting muscle oxygen consumption and fatigability despite hemorheological alterations and, for SS patients only, reduced muscle microvascular oxygenation
The platelets count was higher in the SS group than in the AA group and no difference was observed between sickle cell-hemoglobin C disease (SC) patients and AA subjects or SS patients
Summary
Few studies investigated baseline microvascular oxygenation at the cerebral level in SCD patients and reported reduced values suggesting a certain degree of chronic cerebral hypoxia [6,7,8]. It is unknown whether it is the case in other organs. Callahan et al [9] previously suggested that muscle function could be altered in some patients with SCD It has been proposed [10] that reduced red blood cell (RBC) deformability in rat cremaster muscle could severely affects capillary recruitment and tissue oxygenation. One may suggest that the reduced RBC deformability in SCD, in association with the other blood rheological abnormalities, could reduce muscle microcirculatory oxygenation, muscle oxygen consumption and impair muscle function in this population
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