Causes and outcomes of the acute chest syndrome in sickle cell disease. National Acute Chest Syndrome Study Group

BACKGROUND

The acute chest syndrome is the leading cause of death among patients with sickle cell disease. Since its cause is largely unknown, therapy is supportive. Pilot studies with improved diagnostic techniques suggest that infection and fat embolism are underdiagnosed in patients with the syndrome.

METHODS

In a 30-center study, we analyzed 671 episodes of the acute chest syndrome in 538 patients with sickle cell disease to determine the cause, outcome, and response to therapy. We evaluated a treatment protocol that included matched transfusions, bronchodilators, and bronchoscopy. Samples of blood and respiratory tract secretions were sent to central laboratories for antibody testing, culture, DNA testing, and histopathological analyses.

RESULTS

Nearly half the patients were initially admitted for another reason, mainly pain. When the acute chest syndrome was diagnosed, patients had hypoxia, decreasing hemoglobin values, and progressive multilobar pneumonia. The mean length of hospitalization was 10.5 days. Thirteen percent of patients required mechanical ventilation, and 3 percent died. Patients who were 20 or more years of age had a more severe course than those who were younger. Neurologic events occurred in 11 percent of patients, among whom 46 percent had respiratory failure. Treatment with phenotypically matched transfusions improved oxygenation, with a 1 percent rate of alloimmunization. One fifth of the patients who were treated with bronchodilators had clinical improvement. Eighty-one percent of patients who required mechanical ventilation recovered. A specific cause of the acute chest syndrome was identified in 38 percent of all episodes and 70 percent of episodes with complete data. Among the specific causes were pulmonary fat embolism and 27 different infectious pathogens. Eighteen patients died, and the most common causes of death were pulmonary emboli and infectious bronchopneumonia. Infection was a contributing factor in 56 percent of the deaths.

CONCLUSIONS

Among patients with sickle cell disease, the acute chest syndrome is commonly precipitated by fat embolism and infection, especially community-acquired pneumonia. Among older patients and those with neurologic symptoms, the syndrome often progresses to respiratory failure. Treatment with transfusions and bronchodilators improves oxygenation, and with aggressive treatment, most patients who have respiratory failure recover.

Internal carotid artery occlusion in a child with sickle cell disease: case report and immunohistochemical study

PURPOSE

The purpose of this report is to describe the clinical and pathologic features of a patient with acute thrombosis of both internal carotid arteries leading to death.

METHODS

This is a case report of special interest because of extensive brain vessel pathologic examination.

RESULTS

The analysis of this case showed that the brain had suffered massive infarction and cerebral edema. The internal carotid arteries (ICAs) were occluded by acute thrombus. The arterial wall of the left ICA, studied at its distal segment, showed a small amount of intimal hyperplasia which did not cause encroachment on the lumen. Immunohistochemical stains indicated that this lesion was formed by proliferative vascular smooth muscle rather than incremental thrombus formation.

CONCLUSION

Acute thrombus formation can occur in the large cerebral arteries of children with sickle cell disease in the presence of only minimal intimal hyperplasia. The intimal hyperplasia which forms the sickle related vasculopathy seen on angiography or detected by Transcranial Doppler may be more related to stimulation of smooth muscle cells than dysregulation of thromboregulation at the endothelial surface. Implications for preventive treatment are discussed.

Sickle cell disease and tonsillectomy. Preoperative management and postoperative complications

BACKGROUND

Patients with sickle cell disease are recognized as having a relatively higher risk for postoperative complications, including fever, atelectasis, pneumonia, or sickle cell vas-occlusion.

OBJECTIVE

To present a protocol for preoperative management of patients with sickle cell disease undergoing tonsillectomy, including the use of transfusions and intravenous hydration.

DESIGN

Retrospective chart review.

SETTING

Academic, tertiary care referral medical center.

PATIENTS

Seventy-five patients with sickle cell disease who underwent tonsillectomy with or without adenoidectomy were included for review. Preoperative management was documented, and risk factors were assessed. Intraoperative management was reviewed, and postoperative complications were identified and compared with preoperative data and management.

RESULTS

Preoperative management consisted of transfusions to a hemoglobin S ratio (hemoglobin S-total hemoglobin) less than 40% or a hemoglobin level greater than 100 g/L. Aggressive intravenous hydration of 1.5 times the maintenance fluid was given 24 hours before surgery. Increased complications were associated with a preoperative hemoglobin S ratio greater than 40% (P < .05) and an age younger than 4 years (P < .05). Operative time, technique, and blood loss were not statistically significant risk factors. The average length of hospitalization was 4.8 days.

CONCLUSIONS

Children with sickle cell disease presenting for elective tonsillectomy should be given a transfusion to a hemoglobin S ratio less than 40% in an attempt to reduce postoperative complications. Additional factors, such as age and presence of obstructive sleep apnea, only increase the potential risks.

Reverse dot-blot detection of the African-American beta-thalassemia mutations

DNA-based diagnosis of the beta thalassemias provides accuracy to newborn screening genetic counseling, and prenatal diagnosis. However, the use of polymerase chain reaction (PCR)-based methods is challenged by the great number of different-beta-thalassemia mutations that exist even within defined ethnic groups. In this regard, the reverse dot-blot method offers a means of screening for several mutations with a single hybridization reaction. We have applied the reverse dot-blot method to the detection of the beta-thalassemia mutations of African-Americans. We used two biotin-labeled primer pairs in a duplex reaction to amplify and label two beta-globin target DNA fragments that encompass all known African-American beta-thalassemia mutations. The PCR products were denatured and hybridized to polyT-tailed, membrane-fixed, allele-specific probe pairs for the hemoglobin (Hb) S, Hb C, and 14 beta-thalassemia mutations and their corresponding wild-type sequences. Seven common mutations plus Hb S and Hb C were included on one diagnostic strip, and seven less common beta-thalassemia mutations were included on another strip. Carefully controlled, high stringency hybridization allowed accurate distinction of these alleles. Reverse dot-blot diagnosis of the less common beta-thalassemia mutations precludes the need for alternative, more technically challenging methods. This method provides a rapid, accurate method for diagnosis of beta thalassemia among African-Americans and other ethnic groups in which beta thalassemia occurs.

Risk of recurrent stroke in patients with sickle cell disease treated with erythrocyte transfusions

OBJECTIVE

To determine the effect of a transfusion program on risk of stroke recurrence in children with sickle cell disease.

DESIGN

The clinical course and experience with transfusion therapy at eight centers were reviewed for subjects whose initial stroke occurred after January 1988.

RESULTS

Sixty subjects were observed for 191.7 patient-years. Eight had a single recurrent stroke (two intracranial hemorrhages and six infarctions) for a prevalence of 13.3%, or one recurrence for each 24 patient-years of observation. Thirteen subjects had 15 transient neurologic events; two of these had subsequent strokes, but the overall risk was similar for those who did and those did not have transient events. Hemoglobin S levels were greater than the desired maximum of 30% at the time of 7 of 16 transient events and five of six recurrent infarctions. The stroke recurrence rate was similar to those in previous reports of children receiving long-term transfusion therapy but significantly less than that reported for children who did not receive transfusions (p < 0.001).

CONCLUSIONS

We conclude that maintenance of hemoglobin S at a level less than 30% appears to be effective in reducing the rate of recurrent infarction but does not prevent transient neurologic events. Transient neurologic events are common but do not appear to be related to recurrent stroke.

Alpha thalassemia and stroke risk in sickle cell anemia

In an effort to identify possible risk factors for stroke in Sickle Cell Anemia (Hb SS), we analyzed the distribution of alpha-globin gene deletions in a group of Hb SS patients with and without stroke. The group with stroke consisted of 44 patients, (27 male, 17 female) with a mean of 7.5 years at time of stroke. The control group (non-stroke) had 256 Hb SS patients (126 male, 130 female) with a mean age of 7.7 years. There were 9 patients with heterozygous alpha-thalassemia in the stroke group (20.5%). In the control group, there were 93 patients with heterozygous alpha-thalassemia and 5 with homozygous alpha-thalassemia. The incidence of alpha-thalassemia in Hb SS patients without stroke (38%) was comparable to that reported for the African-American population in general. The incidence in the stroke population (20.5%) was significantly lower (P = 0.02) These results indicate that alpha-thalassemia is associated with a lower risk of stroke in Hb SS. This observation should be confirmed in studies involving larger numbers of patients. Possible protective effects of alpha-thalassemia are unknown but may be related to decreased hemolysis and more favorable rheologic properties of red blood cells.

Transcranial Doppler correlation with cerebral angiography in sickle cell disease

BACKGROUND AND PURPOSE

Cerebral infarction in sickle cell disease is associated with arterial narrowing or occlusions of intracranial arteries. Primary stroke prevention would be feasible if a noninvasive screening test could be developed to detect intracranial disease in patients before symptoms develop.

METHODS

To determine the sensitivity and specificity of transcranial Doppler in detecting significant (greater than or equal to 50% lumen diameter reduction) intracranial arterial lesions, we compared transcranial Doppler and cerebral angiography in a primarily young, symptomatic group of 33 patients (18 males and 15 females) with sickle cell disease.

RESULTS

From a total of 34 examinations, transcranial Doppler detected significant abnormalities in 26 of 29 (sensitivity 90%, specificity 100%). Five were normal by both techniques. The transorbital examination detected abnormalities in two patients whose studies were otherwise unremarkable.

CONCLUSIONS

Transcranial Doppler is sensitive and specific for the detection of arterial vasculopathy of sickle cell disease. Screening should include a transorbital examination of the distal internal carotid artery as well as examination using the transtemporal approach.

The use of transcranial ultrasonography to predict stroke in sickle cell disease

BACKGROUND

Stroke, especially cerebral infarction, is a major cause of morbidity and mortality in children with sickle cell disease. Primary prevention of stroke by transfusion therapy may be feasible if there is a way to identify the patients at greatest risk. Transcranial Doppler ultrasonography can measure flow velocity in the large intracranial arteries. The narrowing of these arteries, which leads to cerebral infarction, is characterized by an increased velocity of flow.

METHODS

Using transcranial Doppler ultrasonography, we prospectively measured the velocity of cerebral blood flow in children and young adults being followed because of sickle cell disease. The results were classified as either normal or abnormal on the basis of the highest velocity of flow in the middle cerebral artery. Abnormal velocity was defined as a flow greater than or equal to 170 cm per second, a definition determined by post hoc analysis to maximize the predictive success of the test. The end point was a clinically apparent first cerebral infarction.

RESULTS

Two hundred eighty-three transcranial ultrasound examinations were performed in 190 patients with sickle cell disease (age at entry, 3 to 18 years). After an average follow-up of 29 months, cerebral infarction was diagnosed in seven patients. In 23 patients the results of the ultrasound examinations were abnormal, and in 167 patients they were normal. The clinical and hematologic characteristics of the two groups were similar, but six of the seven strokes occurred among the 23 patients with abnormal ultrasound results (P less than 0.00001 by Fisher's exact test). In this group, the relative risk of stroke was 44 (95 percent confidence interval, 5.5 to 346).

CONCLUSIONS

Transcranial ultrasonography can identify the children with sickle cell disease who are at highest risk for cerebral infarction. Periodic ultrasound examinations and the selective use of transfusion therapy could make the primary prevention of stroke an achievable goal.

Splenic phagocytic function in children with sickle cell anemia receiving long-term hypertransfusion therapy

To determine the effects of blood transfusions on splenic function in older patients with sickle cell anemia, we investigated splenic function in 12 patients who had had cerebrovascular accidents and who were being treated at two collaborating centers using different transfusion protocols. Splenic function was assessed by radionuclide scan and pocked erythrocyte count. Patients were 6 to 18 years of age and had been receiving transfusions for 7 months to 10 years (median 4.2 years). Of the 12 children, five had normal or increased splenic size and function (normal scan and normal or minimally elevated pocked erythrocyte count). All were receiving intensive transfusion therapy, with the aim of maintaining the hemoglobin S level at less than 20%. The other seven patients had abnormal splenic function (absent radionuclide uptake and elevated pocked erythrocyte count); each was receiving less intensive transfusion therapy, with the pretransfusion hemoglobin S level usually at 30% to 40%. No patient developed bacterial septicemia while receiving hypertransfusion therapy. We conclude that splenic function during a long-term transfusion program is variable, depending in part on the "intensity" of transfusion therapy. Apparent splenic involution and fibrosis may be a reversible event in some patients.

Cerebral infarction in sickle cell anemia: mechanism based on CT and MRI

We studied 25 patients with sickle cell anemia and cerebral infarction. We classified lesions as to probable mechanism (large versus small vessel disease) based on the CT/MRI appearance of established infarction. Most patients had CT/MRI patterns of major cerebral vessel occlusion (41%) or border-zone (distal insufficiency) infarcts (31%) best explained by large cerebral vessel vasculopathy. Seven of 25 (28%) had either isolated subcortical (12%) or small cortical branch occlusion (16%) consistent with other mechanisms such as small vessel occlusion or embolism. These results suggest that most clinically recognized cerebral infarctions in sickle cell anemia are caused by large vessel disease, but this mechanism may not account for symptoms of cerebral ischemia in all cases.

Detection of cerebral vasculopathy in sickle cell disease using transcranial Doppler ultrasonography and magnetic resonance imaging. Case report

We describe a case of homozygous sickle cell anemia in which noninvasive transcranial Doppler ultrasonography and magnetic resonance imaging were used to detect angiographically documented occlusive lesions of intracranial arteries.

MR and CT investigation of cerebrovascular disease in sickle cell patients

Stroke is a common complication of sickle cell disease. Using MR and CT, we studied 10 patients with sickle cell disease and a history of stroke and compared these findings with those of 10 sickle cell patients without stroke. The purpose was to determine if MR could visualize the large vessel vasculopathy previously seen on angiography and to estimate the incidence of asymptomatic abnormalities in the nonstroke group. MR consistently demonstrated the major intracranial arteries and showed three cases with occlusion and three with stenosis of either the internal carotid or middle cerebral arteries. Infarctions were better delineated on MR but were also seen on CT. Seven cases with and two without stroke had high-signal white matter lesions on MR. Further research using cranial MR to develop noninvasive means of identifying sickle cell patients at risk for stroke is warranted.

The rare alpha-thalassemia-1 of blacks is a zeta alpha-thalassemia-1 associated with deletion of all alpha- and zeta-globin genes

Restriction endonuclease mapping with alpha and zeta-globin gene probes showed differences between the alpha-thalassemia-1 (alpha-thal-1) condition in two patients with HbH disease. One patient had the rare black type of alpha-thal-1 together with alpha-thal-2 and HbS heterozygosities. The second patient was a Laotian child with HbE, Hb Constant Spring (alpha-thal-2), and alpha-thal-1 heterozygosities. The diagnoses were based on clinical, hematologic, and biochemical data. Whereas DNA fragments hybridizing to a zeta-probe were obtained from the Laotian type of alpha-thal-1, neither alpha nor zeta-gene fragments could be identified deriving from the black type of alpha-thal-1. Therefore, the black type of alpha-thal-1 is associated with a deletion of the entire zeta 2-psi zeta-psi alpha-alpha 2-alpha 1 gene complex and can be considered a zeta alpha-thal-1. It is likely that homozygosity for such a condition will lead to embryonic wastage, explaining the absence of hydrops fetalis in blacks.