Risk of Stroke in Children with Sickle Cell Disease after Splenectomy

Background

Stroke and splenic sequestration are known complications associated with sickle cell disease in children. The cerebral blood flow velocity measured by transcranial doppler ultrasonography (TCD) is a screening tool to identify patients who are at increased risk of stroke. Children with critical time-average maximum velocity (TAMV) are started on chronic blood transfusion program to prevent stroke. Iron overload, inhibitor development and risk of infection are some of the complications associated with chronic blood transfusions. The objective of this study was to assess the changes in cerebral blood flow and the need for chronic blood transfusions after splenectomy performed in children with splenic sequestration.

Methods

A retrospective chart review of sickle cell disease children splenectomized between 1999 and 2014 at the University of South Alabama was performed. In addition to demographic data, results of routine screening TCDs for up to 15 years were obtained and compared to pre-splenectomy TCDs by using the paired t-test. We also compared the TAMV and blood counts in splenectomized and non-splenectomized patients of the same sickle cell disease variant that were age- and sex-matched. The cases were also compared to a non-splenectomized cohort control group comprising of children with sickle cell disease using the independent t-test.

Results

A total of 40 patients (36 with Hemoglobin SS disease and 4 with S-Beta Thalassemia Zero) received splenectomy during the study period at a mean age of 2.5 years (1.5 to 18 years). The mean TAMV before splenectomy was 129 cm/sec, which increased to 157 cm/sec and decreased back to 137 cm/sec at two and five years post-splenectomy, respectively. When comparing these changes using the paired t-test, the difference was not statistically significant. Four (10%) of these patients needed to be started on chronic blood transfusions due to critical TCDs. Another patient had a critical TCD before splenectomy and was continued on chronic transfusions post-splenectomy. The mean TAMV in our sickle cell patients without splenectomy at age 14 years was 123 cm/sec (n=107). Five (4.7%) of these patients were receiving chronic blood transfusions for critical TCDs. The odds ratio of having a critical TCD in splenectomized patients versus non-splenectomized patients was 2.3:1.

The TAMV in patients at 2 years post-splenectomy was 157 cm/sec compared to 139 cm/sec in age- and sex-matched non-splenectomized controls (p = 0.035). The mean platelet count prior to splenectomy was 301/m³. It increased to 536/m³ one year post-splenectomy and remained elevated at 510/m³ four years post-splenectomy. The differences in platelet counts were statistically significant. The mean platelet count in non-splenectomized patients at 14 years of age was 387/m³. Prevalence of treatment with Hydroxyurea was 45% (18 patients) in splenectomized patients and 18% (19 patients) in the non-splenectomized control group.

Conclusion

We conclude that the mean cerebral blood flow velocity was increased after splenectomy. When comparing cases to matched controls, the biggest difference in TAMVs was found at two years post-splenectomy. Splenectomy is effective in preventing life threatening sequestration events. However, in our patient cohort, the risk of requiring chronic blood transfusions for a critical TCD (≥200 cm/s) doubled after splenectomy.