Frequency of pain crises in sickle cell anemia and its relationship with the sympatho-vagal balance, blood viscosity and inflammation.

BACKGROUND: Recent evidence suggests that autonomic nervous system activity could be involved in the pathophysiology of sickle cell disease, but it is unclear whether differences in autonomic nervous system activity are detectable during steady state in patients with mild and severe disease. The aim of the present study was to compare the autonomic nervous system activity, blood rheology, and inflammation in patients with sickle cell anemia according to the frequency of acute pain crisis. DESIGN AND METHODS: Twenty-four healthy volunteers, 20 patients with sickle cell anemia with milder disease, and 15 patients with sickle cell anemia with more severe disease were recruited. Milder disease was defined as having no pain crisis within the previous year. More severe disease was defined as having had within the previous year three or more pain crises which were documented by a physician and required treatment with narcotics. The autonomic nervous system activity was determined by spectral analysis of nocturnal heart rate variability. Blood viscosity determination and measurements of several inflammatory markers (interleukin-6, soluble vascular cell adhesion molecule-1, soluble CD40 ligand and sL-selectin) were made on blood samples collected in steady-state conditions. RESULTS: Results showed that: 1) patients who had suffered more frequent pain crises had lower parasympathetic activity and greater sympatho-vagal imbalance than both controls and patients with milder disease. However, when adjusted for age, no significant difference was detected between the two sickle cell anemia patient groups; 2) patients who had suffered more frequent pain crises had higher blood viscosity than patients with milder disease, and this was not dependent on age. CONCLUSIONS: Results from the present study indicate that both the autonomic nervous system activity and blood viscosity are impaired in patients with sickle cell anemia exhibiting high frequency of pain crisis in comparison with those who did not experience a crisis within the previous year.

Hemorheology and heart rate variability: is there a relationship?

The aim of the present study was to test the relationships between hemorheology and autonomic nervous system (ANS) activity in 23 sickle cell trait (SCT) carriers and 17 control subjects. Hemorheological parameters were assessed at rest. Nocturnal ANS activity was calculated from heart rate variability indices. Impairment was observed in both domains in SCT carriers as they showed higher blood viscosity, higher red blood cell rigidity and a lower index of oxygen supply to tissues, as well as lower ANS activity. The index of oxygen supply to tissues was positively correlated with some of the indices of parasympathetic activity and global ANS activity. Negative correlations were found between blood viscosity and the very low frequency of the spectrum (VLF) that contains partial parasympathetic activity and between red blood cell rigidity and the percentage of differences between adjacent normal RR intervals more than 50 ms (PNN50), which also describes parasympathetic activity. These results support the hypothesis that autonomic nervous system equilibrium is affected by perturbations in blood rheology. Mechanisms have yet to be elucidated.