Alveolar-arterial oxygen gradient in acute chest syndrome of sickle cell disease

Acute Chest Syndrome in Children with Sickle Cell Disease

Acute chest syndrome (ACS) is a frequent cause of acute lung disease in children with sickle cell disease (SCD). Patients may present with ACS or may develop this complication during the course of a hospitalization for acute vaso-occlusive crises (VOC). ACS is associated with prolonged hospitalization, increased risk of respiratory failure, and the potential for developing chronic lung disease. ACS in SCD is defined as the presence of fever and/or new respiratory symptoms accompanied by the presence of a new pulmonary infiltrate on chest X-ray. The spectrum of clinical manifestations can range from mild respiratory illness to acute respiratory distress syndrome. The presence of severe hypoxemia is a useful predictor of severity and outcome. The etiology of ACS is often multifactorial. One of the proposed mechanisms involves increased adhesion of sickle red cells to pulmonary microvasculature in the presence of hypoxia. Other commonly associated etiologies include infection, pulmonary fat embolism, and infarction. Infection is a common cause in children, whereas adults usually present with pain crises. Several risk factors have been identified in children to be associated with increased incidence of ACS. These include younger age, severe SCD genotypes (SS or Sβ⁰ thalassemia), lower fetal hemoglobin concentrations, higher steady-state hemoglobin levels, higher steady-state white blood cell counts, history of asthma, and tobacco smoke exposure. Opiate overdose and resulting hypoventilation can also trigger ACS. Prompt diagnosis and management with intravenous fluids, analgesics, aggressive incentive spirometry, supplemental oxygen or respiratory support, antibiotics, and transfusion therapy, are key to the prevention of clinical deterioration. Bronchodilators should be considered if there is history of asthma or in the presence of acute bronchospasm. Treatment with hydroxyurea should be considered for prevention of recurrent episodes. This review evaluates the etiology, pathophysiology, risk factors, clinical presentation of ACS, and preventive and treatment strategies for effective management of ACS.

Acute Chest Syndrome in Sickle Cell Disease: Pathophysiology and Management

Acute chest syndrome (ACS) is defined as the development of a new pulmonary infiltrate and respiratory symptoms in a patient with sickle cell disease (SCD). One of the most serious complications of SCD, ACS is the leading cause of mortality in patients with SCD. ACS is age dependent, with children having milder disease that often is infectious. Adults often have more severe disease, with pulmonary fat embolism secondary to preceding long bone infarction frequently as a contributing factor. Rapid diagnosis and a high index of suspicion are crucial since this syndrome may have a high mortality rate. A high white blood cell count and a felling hemoglobin tend to be associated with this illness. Patients are often febrile, but may not have positive blood or sputum cultures. Appropriate therapy includes judicious fluids, close attention to respiratory care, antibiotics, and transfusion therapy. Use of the drug, hydroxyurea, has been shown to decrease the incidence of ACS. Patients with repeated episodes are at risk for the development of chronic lung disease and pulmonary hypertension. New treatment strategies such as inhibitors of cytokines and pulmonary vasodilators such as nitric oxide may reduce the high mortality of ACS.

How I treat acute chest syndrome in children with sickle cell disease

Acute chest syndrome describes new respiratory symptoms and findings, often severe and progressive, in a child with sickle cell disease and a new pulmonary infiltrate. It may be community-acquired or arise in children hospitalized for pain or other complications. Recognized etiologies include infection, most commonly with atypical bacteria, and pulmonary fat embolism (PFE); the cause is often obscure and may be multifactorial. Initiation of therapy should be based on clinical findings. Management includes macrolide antibiotics, supplemental oxygen, modest hydration and often simple transfusion. Partial exchange transfusion should be reserved for children with only mild anemia (Hb > 9 g/dL) but deteriorating respiratory status. Therapy with corticosteroids may be of value; safety, efficacy and optimal dosing strategy need prospective appraisal in a clinical trial. On recovery, treatment with hydroxyurea should be discussed to reduce the likelihood of recurrent episodes.

Managing acute chest syndrome of sickle cell disease in an African setting

Despite the fact that acute chest syndrome contributes immensely to morbidity and mortality in patients with sickle cell anaemia, its exact aetiopathogenesis is very complex and not yet well understood. Therefore, a high index of suspicion is needed in its diagnosis, and appropriate treatment should be commenced as soon as possible to prevent lethal complications of this condition, especially in Nigeria where appropriate diagnostic and therapeutic facilities may not be readily available. This is very important, as it may even develop on hospital admission. There is a need to further investigate preventive measures such as the use of hydroxyurea and the newly introduced Nicosan, especially in those people with recurrent disease, in order to reduce both short- and long-term complications of this syndrome among sickle cell patients in Nigeria.

Corticosteroids and increased risk of readmission after acute chest syndrome in children with sickle cell disease

BACKGROUND

Acute chest syndrome (ACS) is a frequent cause of hospitalization and mortality in children with sickle cell disease. Transfusion is often required to prevent respiratory failure and treatment with dexamethasone may reduce the length of admission and the need for transfusions. We performed a retrospective cohort study to evaluate risk factors for readmission and prolonged hospitalization after different treatments for ACS.

PROCEDURE

We identified patients <22 years of age hospitalized with ACS at Johns Hopkins Hospital from January 1998 to April 2004 using the hospitals discharge database and by reviewing dictated summaries.

RESULTS

We identified 65 patients with 129 episodes of ACS (mean age 12.5 years, range 1.2-21.9 years). Thirty-nine episodes were treated with corticosteroids and 51 with transfusions. Patients were readmitted within 14 days after 23 episodes (18%). Readmission was strongly associated with report of an inhaler or nebulizer at home [odds ratio (OR) 6.0, P < 0.05], diastolic BP at 48 hr (OR 1.8 per 10 mm increase, P<0.01), corticosteroids (OR 20, P < 0.005), or transfusion (OR 0.03, P < 0.05). Treatment with corticosteroids alone (P < 0.05) and older age (P < 0.001) were associated with longer hospitalization.

CONCLUSIONS

These results demonstrate a greatly elevated independent risk of readmission after ACS in children with asthma and after treatment with corticosteroids and a protective effect of transfusion. Although dexamethasone has documented efficacy for reducing the duration of ACS, the substantial risk of readmission for pain should limit its use.

Sickle acute lung injury: role of prevention and early aggressive intervention strategies on outcome

Acute chest syndrome in sickle cell disease is a form of acute lung injury that may progress to acute respiratory distress syndrome and death. Despite recent advances in diagnosis and treatment that have resulted in improved survival in sickle cell disease, acute chest syndrome remains the most common cause of death in this population. The current standards of treatment for acute chest syndrome have been reviewed. Biomedical re-search forms the basis for sound clinical decision making and implementation of interventions that target prevention, diagnosis, and effective treatment options. Although current clinical trials are ongoing to address several new potential therapeutic options,more research using preventative and interventional strategies in sickle acute lung injury is warranted.

The acute chest syndrome

Recent large clinical studies of the acute chest syndrome (ACS) have improved our understanding of its pathophysiology and epidemiology. However, there is still a need for better methods of distinguishing vaso-occlusion from fibrin or fat embolism, for rapid diagnostic tests to make positive identifications of microbial infection, for adjunctive therapies that would affect prognosis, and for identification of factors that influence prognosis. The difference in clinical course and severity between children and adults supports the results of current studies indicating multiple causes for ACS. The mainstay of successful treatment remains high-quality supportive care. The judicious use of transfusion therapy has a major role in preventing mortality in the absence of a specific therapy that consistently improves the clinical course.

Chronic transfusion therapy for children with sickle cell disease and recurrent acute chest syndrome

The objective was to study the effects of chronic transfusion therapy (CTX) on the prevention of new episodes of acute chest syndrome (ACS) in children with sickle cell disease (SCD) and recurrent or unusually severe ACS. A retrospective chart review was performed of patients given CTX for recurrent or severe ACS. Frequency, median severity score, and median hospital stay for ACS episodes were determined. Differences in these values before and during CTX were analyzed. Twenty-seven patients were identified. Before treatment, the ACS incidence was 1.3 episodes per patient-year; during treatment, it decreased to 0.1 episodes per patient-year (P < 0.0001). The median severity score for ACS episodes was 0.8 (range 0-5) before CTX and 0.5 (0-3) during CTX (P = 0.84). The median hospital stay was 5 days (range 3-15 days) before CTX and 3 days (2-7 days) during CTX (P = 0.38). CTX significantly reduces the incidence of ACS events among patients with a history of recurrent or severe episodes but does not significantly decrease their severity. The effectiveness of CTX should be prospectively compared with that of hydroxyurea and stem cell transplantation.

Safety of purified poloxamer 188 in sickle cell disease: phase I study of a non-ionic surfactant in the management of acute chest syndrome

Acute chest syndrome (ACS) is the most common cause of death in patients with sickle cell anemia. Its management is primarily palliative. We performed a Phase I evaluation of purified poloxamer 188 (a non-ionic surfactant) in the management of ACS. Forty-three patients with sickle cell disease and ACS were treated with doses as high as 2960 mg/day by continuous intravenous (IV) infusion. The maximum tolerated dose has not been identified. No evidence of renal toxicity or other limiting adverse events were found. One adult patient died due to sepsis and adult respiratory distress syndrome, which were unrelated to treatment. Poloxamer 188 is safe to administer to patients with ACS, and preliminary data suggest that it may shorten its duration and the length of hospitalization in a dose related manner. Children appeared to benefit more than adults. The data and safety profile justify further studies with purified poloxamer 188 in the treatment of ACS.

Anaesthetic management of the child with sickle cell disease

Sickle cell disease (SCD) is a relatively common inherited disorder of haemoglobin with significant morbidity and mortality. This review describes the epidemiology and pathophysiology of the disease, and discusses the clinical manifestations found in children with SCD. A discussion of the evidence concerning the perioperative management of such children is presented.

Breathing patterns during vaso-occlusive crisis of sickle cell disease

STUDY OBJECTIVES

To determine the effect of sickle cell pain and its treatment on patients' breathing patterns, and to compare the effect of thoracic cage pain to pain at other sites.

DESIGN

Prospective, observational study.

SETTING

Sickle Cell Center Day Hospital.

PATIENTS

Twenty-five patients with sickle cell disease admitted to the Sickle Cell Center Day Hospital for treatment of vaso-occlusive crisis (VOC) [10 patients with chest (thoracic cage) pain].

INTERVENTIONS

Breathing patterns were measured by respiratory inductive plethysmography. Tidal breathing data, including respiratory rate, tidal volume (VT), minute ventilation, and the rib cage contribution to VT, were collected at baseline and then following treatment with opioid analgesia.

MEASUREMENTS AND RESULTS

The patients with chest pain had smaller V(Ts) at baseline than those with pain at other sites (355 +/- 37 mL vs 508 +/- 141 mL, p = 0.003), and higher respiratory rates (23.2 +/- 8.2 breaths/min vs 17.6 breaths/min, p = 0.03). These differences became insignificant following opioid treatment. Six patients had respiratory alternans (four patients in the chest pain group, and two patients with pain at other sites). All cases of respiratory alternans resolved following opioid administration.

CONCLUSIONS

Patients with VOC and chest pain have more shallow, rapid breathing than patients with pain elsewhere. Analgesia reduces these differences. As pain-associated shallow breathing and maldistribution of ventilation may contribute to the pathogenesis of acute chest syndrome, these results support the need for adequate pain relief and monitoring of ventilatory patterns during the treatment of VOC.

Acute chest syndrome in sickle cell disease in Saudi Arab Children in the Eastern Province

BACKGROUND

This study was conducted to define the clinical features and outcome of acute chest syndrome (ACS) in sickle cell disease (SCD) patients in the Eastern Province of Saudi Arabia.

PATIENTS AND METHODS

This was a prospective study involving patients who were 12 years or younger, admitted to Qatif Central Hospital with ACS (or developed ACS during hospitalization) between July 1992 and July 1997. Chest x-ray, CBC, cultures (blood, sputum and throat), mycoplasma titers and blood gases were performed at the onset of ACS. Oxygen therapy, antibiotics, blood transfusion and mechanical ventilation were used as required.

RESULTS

One hundred and thirty-two patients with episodes of ACS (154 admissions which accounted for 7.7% of SCD admissions) were studied. Fever, cough and chest pain were the most common symptoms. Raised temperature, tachypnea and tachycardia were the most common findings. ACS was associated with painful crisis (46.8%) and infections (13%). It was mild in 31.2%, moderate in 57.1% and severe in 11.7% of admissions. Radiological studies revealed unilateral infiltrate in 69.5%, bilateral infiltrate in 20.8% and pleural effusion in 3.3%. There was a significant drop in Hb and platelets, and a rise in WBC. Significant hypoxia was found in 10.4% and bacteremia was found in 7.1%. Cephalosporine was required for 37%, simple blood transfusion for 74%, exchange transfusion for 2%, and mechanical ventilation for 0.7% of admissions. None of our patients died. Mean duration of hospitalization was 6.7 days.

CONCLUSION

Acute chest syndrome in children with sickle cell disease in the Eastern Province of Saudi Arabia is relatively mild and infrequent, and rarely associated with bacteremia.

Principles and problems of transfusion in sickle cell disease

Sickle cell disease (SCD) is associated with red blood cell (RBC) abnormalities and moderate to severe anemia, and blood transfusion is naturally a mainstay of treatment. However, transfusion therapy for SCD may incur special and distinctive adverse effects. Thus, it is important to understand the indications for and goals of transfusion therapy and to be aware of the potential side effects of therapy. Years of unsystematic clinical observations, followed by more carefully designed and in some cases randomized studies, have contributed substantially to our knowledge of transfusion therapy in SCD. However, much remains unknown and areas of controversy persist. In addition, serologic barriers pose enduring roadblocks to the optimization of transfusion therapy for patients with SCD, and the syndrome of massive hemolytic transfusion reactions and hyperhemolysis in SCD persists as a life-threatening complication for which appropriate clinical management is not yet defined.

[Respiratory distress and drepanocytosis]

Acute chest syndrome (ACS) is characterized by chest pain with dyspnea and recent radiologic abnormalities, and is an acute lung complication whose problem is one of etiology. Alveolar hypoventilation linked to infarcts of the thoracic ribs, thoracoabdominal trauma, subdiaphragmatic pain, the administration of analgesics causing respiratory depression, or sleep disturbance, is a frequent cause of ACS. Bronchoalveolar lavage has revealed the frequency of fat embolism following infarcts in the long bones. Pulmonary vascular occlusion, due to thrombosis or emboli, is rare, as are the infectious pneumonia and pulmonary edema. The pathogenetic mechanisms consist of an alteration of the rheological properties of the blood, the existence of an hypercoagulability state, specific interactions between the abnormal sickle cells and the vascular endothelium, and a dysregulation of the vascular reactivity. Research centered around NO biology has led to an expanded understanding of the critical interdependence of NO, hemoglobin, and the microvasculature. An anemic patient with ACS suffers from loss of pulmonary scavenging and hypoxic pulmonary vasoconstriction and loss of peripheral NO delivery. Interruption of this cycle by transfusing normal (hemoglobin A-containing) erythrocytes might improve all the abnormalities.

Measurement of hemoglobin saturation by oxygen in children and adolescents with sickle cell disease

Pulse oximetry is a noninvasive method of measuring oxyhemoglobin saturation. The validity of pulse oximetry in sickle cell disease (SCD) has been questioned. We evaluated pulse oximetry, arterial blood gas analysis, and co-oximetry in patients with SCD, and we assessed the effect of dyshemoglobin and altered blood-oxygen affinity on their accuracy. Sixteen patients with SCD aged 7-21 years had arterial and venous blood drawn and transcutaneous pulse oximetry performed. Oxyhemoglobin dissociation curves were plotted from the venous blood of 15 patients. Oxyhemoglobin saturation estimated by arterial blood gas analysis (SaO(2)) and measured by pulse oximetry (SpO(2)) were both higher than the saturation by co-oximetry (FO(2)Hb) (mean +/- SD = 96.3 +/- 1.6%, 94 +/- 3.1%, and 89.1 +/- 3.8%, respectively). There was a significant, positive correlation between SpO(2) and FO(2)Hb (r = 0.7, P = 0.002). The patients had elevated levels of methemoglobin (MetHb) and carboxyhemoglobin (COHb) (2.3 +/- 1.4% and 4.7 +/- 1.3%, respectively). The oxyhemoglobin dissociation curves were frequently shifted to the right with oxygen tensions elevated when hemoglobin was 50% saturated with oxygen (P(50)) (32.5 +/- 4.5 mm Hg). There was a strong correlation between the amounts of dyshemoglobin (MetHb + COHb) and the difference between SaO(2) and FO(2)Hb (r = 0.7, P = 0.002). There was no correlation between the difference between SaO(2) and FO(2)Hb and the P(50) (r = 0.27, P = 0.33) There was also a strong positive correlation between SaO(2)-SpO(2) and dyshemoglobin fraction (r = 0.77, P = 0.001). We conclude that pulse oximetry and arterial blood gas analysis overestimate oxygen saturation when compared to co-oximetry, but that SpO(2) is consistently closer than SaO(2) to FO(2)Hb. SpO(2) is partially affected by MetHb and COHb. The discrepancy between SaO(2) and FO(2)Hb is due to the presence of dyshemoglobin and a shifted oxyhemoglobin dissociation curve, but the effect from dyshemoglobin predominates.

Pulmonary complications

The management of patients with acute chest syndrome is changing as its etiology and pathophysiology are being defined. Current management should include aggressive evaluation and monitoring, and treatment should be tailored to each patient's clinical course. New therapies show promise in reducing morbidity of acute chest syndrome in the future.

Systemic fat embolism and pulmonary hypertension in sickle cell disease

Systemic fat embolism, a relatively rare complication of sickle cell disease, is difficult to diagnose and it is often fatal. A high index of suspicion and early transfusion therapy may provide the best chance for recovery. Sickle cell-related pulmonary hypertension can be documented by cardiac catheterization but has no proven treatment. Patients with this complication are usually adults, have a poor prognosis, and may be considered for hydroxyurea treatment. Administration of vasodilators, anticoagulation, or oxygen may be beneficial in selected individuals.

Effect of transfusion in acute chest syndrome of sickle cell disease

OBJECTIVE

To study the effects of transfusion on the clinical course and oxygenation indexes of children with sickle cell disease and acute chest syndrome.

METHODS

During a 2-year period, 36 children with sickle cell disease admitted with a total of 40 episodes of acute chest syndrome were examined. Patients were given a clinical severity score indicative of the degree of respiratory distress. Arterial blood gas values were determined 4 to 24 hours before and 12 to 24 hours after transfusion, and indexes of oxygenation were calculated; six patients who were not given transfusions also had blood gases measured on admission and approximately 24 hours later for comparison.

RESULTS

Blood transfusion was administered during 27 episodes (67.5%); 20 children received a simple packed cell transfusion, four had a partial packed cell exchange transfusion, and three had a simple transfusion followed by whole blood exchange transfusion because of worsening clinical symptoms. Although there was no significant change in oxygenation indexes for the six patients not treated with transfusion, there was significant improvement in all indexes after transfusion. The transfused group had more severe disease on admission, but there was no significant difference in duration of fever, tachypnea, retractions, or hospital stay between the transfusion and the nontransfusion groups.

CONCLUSION

Blood transfusion, even simple transfusion of packed erythrocytes, significantly improves oxygenation in children with acute chest syndrome and is a valuable adjunct to therapy.