Lower Transcranial Doppler Flow Velocities in Sickle Cell Anemia Patients on Hydroxyurea: Myth or Fact

Associations Between Transcranial Doppler Flow Velocities, Laboratory Parameters, and Clinical Features in Turkish Children With Sickle Cell Disease

OBJECTIVE

Stroke is one of the major complications of sickle cell disease (SCD). Stroke features either occlusion of, or stenosis at, the origin of one of the large intracerebral arteries, the internal carotid artery (ICA), and/or the middle cerebral artery (MCA).

PURPOSE

We sought correlations between cerebral blood flow velocities and the laboratory and clinical findings of patients with SCD.

MATERIALS AND METHODS

Fifty-three pediatric SCD patients (39 with HbSS, 14 with HbSβ0) were analyzed. The mean patient age was 12.9±3.9 years. The control group contained 24 healthy individuals. The time-averaged maximum mean velocity (TAMMV) and resistive index (RI) of the MCA, the TAMMVs of the ICA and vertebral artery (VA), and the diameter of the VA were estimated through transcranial Doppler ultrasonography using a 2.5 MHz transducer, in accordance with the Stroke Prevention Trial in Sickle Cell Anemia (STOP) protocol. We evaluated the relationships between the TAMMVs, laboratory parameters, and clinical findings.

RESULTS

The mean±SD MCA TAMMV was 161.2±35.4 cm/s in patients with HbSS and 185.8±62.9 cm/s in patients with HbSβ0. The mean MCA TAMMV, RI, ICA TAMMV, VA TAMMV, and VA diameter were 168.5±43.9 cm/s, 0.63±0.06, 116.8±25.5 cm/s, 69.2±18.5 cm/s, and 3.5±0.61 mm for all SCD patients, respectively. In the control group, the mean MCA TAMMV, RI, ICA TAMMV, VA TAMMV, and VA diameter were 103.8±28.8 cm/s, 0.53±0.04, 96.4±27.8 cm/s, 40.3±12.1 cm/s, and 3.4±0.6 mm, respectively. Although the differences were not significant, TAMMVs were higher in HbSβ0 patients taking hydroxyurea; those with hemoglobin levels <8 g/dL, ferritin levels >1000 ng/dL, mean platelet volume >12 fL, or red cell distribution width >18%; or required chelation, or were below the third percentiles of weight and height. The TAMMV was significantly higher only in SCD patients who complained of headache.

CONCLUSIONS

High ferritin and low hemoglobin levels, a high mean platelet volume, a high red cell distribution width, low weight (below the third percentile), and a short height (below the third percentile) may be associated with elevated cerebral blood flow velocities and an increased stroke risk in children with SCD. Children with such features should be closely followed-up through transcranial Doppler ultrasonography examination.

Transcranial Doppler screening in Nigerian children with sickle cell disease: A 10-year longitudinal study on the SPPIBA cohort

BACKGROUND

Primary stroke prevention programmes for children with sickle cell disease (SCD) have been shown to be feasible interventions in resource-poor countries. Different hydroxyurea (HU) regimens have been utilised in ameliorating the severity of SCD.

OBJECTIVE

To determine the long-term outcomes of the stroke prevention programme for children with SCD in Ibadan (SPPIBA), Nigeria.

METHODS

A longitudinal study of 396 children with haemoglobin SS disease who had been on the stroke prevention programme for a minimum period of 5 years. All enrollees had nonimaging TCD performed at baseline and thereafter 3-monthly or annually. Children with TCD velocities ≥170 cm/s were treated with HU by dose-escalation regimen.

RESULTS

The mean age at first TCD examination was 102 ± 46.7 months and the period of follow-up ranged from 5 to 10 years (mean = 7.2 ± 1.7). Time to significant decline in TCD velocities ranged from 5 to 35 months, (median = 10.0 months). The minimum dose of HU required to achieve significant decline in TCD velocities ranged from 15 to 31 mg/kg/day, mean 23.7 (±3.9). HU dose escalation beyond 20 mg/kg/day was required to attain significant reductions in the time-averaged mean of maximal velocities (TAMMV) in 69.1% of the cases. Two stroke events occurred giving a stroke incidence of 0.08 per 100 patient-years.

CONCLUSION

The majority of Nigerian children with SCD and elevated TCD velocities achieved significant decline in TAMMV within the first year of HU therapy but on higher doses of HU. It might be important to individualise HU doses for optimal outcomes in primary stroke prevention.

Pattern of cerebral blood flow and the interrelationship of vascular parameters of transcranial Doppler imaging in children with sickle cell disease

PURPOSE

We assessed the pattern of cerebral blood flow and the relationship between the different transcranial Doppler imaging (TCDI) vascular parameters in children with sickle cell disease (SCD).

METHODS

Forty-three SCD pediatric patients with a stable condition (21 HbSS, 19 HbSβ⁰ Thal, and 3 HbSD), aged 10.1 ± 3.9 years were studied. A control group of 26 with age and sex-matched, were included for comparison. TCDI scanning was carried out using a phased array transducer of 1-3 MHz through the trans-temporal window. Peak systolic velocity (PSV), end diastolic velocity (EDV), time-averaged mean of the maximum velocity (TAMxV), pulsatility index (PI), and resistive index (RI) were in the anterior circle of Willis vessels and posterior cerebral artery.

RESULTS

The highest mean ± SD values for the middle cerebral artery PSV, EDV, TAMxV, PI, and RI were 130.30 + 26.5, 145.0 ± 21.9; 58.60 + 13.70, 67.90 ± 13.3; 84.90 + 14.50, 94.80 ± 17.9; 0.95 + 0.20, 0.80 ± 0.20; 0.58 + 0.09, 0.50 ± 0.10 in the control and SCD groups, respectively. Independent t-test showed significant difference (P < .05) for all vascular parameters in all vessels in each side between both groups. There was a positive significant correlation between TAMxV, PSV, and EDV (P = .001, r = .96), and a negative significant correlation between TAMxV and PI in the SCD group (P = .001, r = -.46) but not in the control group (P > .05, r = -.62).

CONCLUSIONS

There was a direct relationship between TAMxV and PSV and EDV, and an inverse relationship between TAMxV and PI in a group of SCD patients with normal TCDI values.