ACUTE CHEST SYNDROME

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ACUTE CHEST SYNDROME

• Dr.Padma Gadde
• Dr. Dora Alvarez

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ACUTE CHEST SYNDROME

• Acute chest syndrome" (ACS) broadly describes a
  disease
• leading cause of death
• second most common cause of hospitalization in
  patients with sickle cell disease

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ACUTE CHEST SYNDROME

• Its rapid clinical course, with or without fever,
  is characterized by chest pain, cough,
  progressive anemia, hypoxemia, and the presence
  of new pulmonary infiltrates on chest radiographs

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Learning Objectives

• To identify the causes of acute chest syndrome
  (ACS) in patients with sickle cell disease
• To understand the pathophysiology of ACS
• To recognize elements that are important in
  appropriate management of ACS

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ACUTE CHEST SYNDROME

• The approach to diagnosis, monitoring, and
  treatment requires
• recognition of the complication,
• correction, if possible, of inciting factors,
• maintenance of euvolemia,
• pain control, and
• use of transfusions and
• administration of oxygen, if needed.

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ACUTE CHEST SYNDROMERisk factors

• Younger age
• Homozygous sickle cell or sickle cell-beta
  thalassemia genotype
• Winter months
• Fever

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ACUTE CHEST SYNDROMERisk factors

• Surgery
• Avascular necrosis of bone
• Previous pulmonary events
• High hemoglobin levels
• High steady-state leukocyte counts
• Low fetal hemoglobin concentration

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Pathophysiology

• The pathogenesis of parenchymal lung infiltrates
  in ACS is incompletely understood.
• Pulmonary infiltrates may result from either one
  process or a combination of several interacting
  processes, which may include
• atelectasis,
• infection,
• fat embolism,
• thromboembolism and,
• most commonly, in situ microvascular occlusion
  within the pulmonary vasculature by sickled
  erythrocytes

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Pathophysiology

• The importance of nonembolic microvascular
  occlusion in causing ACS is demonstrated by
  findings on thin-cut computed tomographic scans
  Arterioles and venules are either absent or
  diminished in number, and ground-glass opacities
  appear in a mosaic, patchy, or multifocal
  distribution

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pathophysiology

• Fat embolism from bone marrow necrosis seems to
  be an important and often unrecognized cause of
  ACS

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pathophysiology

• Patients with pulmonary fat embolism are more
  likely than others to have severe bone and chest
  pain, changes in mental status, and a prolonged
  hospital course.
• A complete blood cell count in these patients
  shows more severe anemia and thrombocytopenia
  than in patients without pulmonary fat embolism,
  and chest radiographs reveal more multilobar
  infiltrates

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pathophysiology

• sPLA2 liberates free fatty acids from
  phospholipids.
• Measurement of secretory phospholipase A2 (sPLA2)
  levels may be helpful, because they have recently
  been found to be elevated in patients with sickle
  cell disease and ACS from pulmonary fat embolism

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pathophysiology

• An early rise in these levels precedes the
  development of ACS and thus may be a useful
  marker in predicting its occurrence.
• Furthermore, sPLA2 levels correlate with disease
  severity.

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Mechanisms of hypoxemia

• Hypoventilation due to
• Direct chest-wall splinting from either rib and
  sternal infarctions or abdominal crisis
• Excessive sedation from narcotic analgesics,
  leading to decreased oxygen exchange

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Mechanisms of hypoxemia

• Ventilation-perfusion mismatch possibly caused by
  diseases that underlie or result from acute chest
  syndrome
• Pneumonia
• Mucous plugging
• Aspiration
• Bronchospasm
• Pulmonary hypertension
• Cor pulmonale

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Mechanisms of hypoxemia

• Impaired oxygen diffusion from repetitive
  episodes of acute chest syndrome that ultimately
  result in restrictive lung disease (2,3)

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Evaluation

• ACS is more severe in adolescents and adults than
  in children.
• Patients most commonly present with shortness of
  breath, chills, and pleuritic chest pain, but no
  fever

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Evaluation

• In some cases, physical signs of disease are
  delayed and are first noted during
  hospitalization.

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Evaluation

• These include
• chest-wall tenderness secondary to rib
  infarction.
• dullness to percussion caused by pleural
  effusion.
• and auscultatory rales from pulmonary
  consolidation.

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Evaluation

• Results of laboratory studies may show
• anemia with thrombocytopenia
• or thrombocytosis,
• leukocytosis,
• and evidence of hemolysis,
• including elevated LDH
• bilirubin levels

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Evaluation

• Findings on chest radiographs, although not
  pathognomonic, include
• patchy lower-lobe involvement in a segmental,
  lobar, or multilobar distribution, with or
  without pleural effusion.
• Correlation between the extent of consolidation
  found on chest radiographs and the severity of
  hypoxemia is poor

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Evaluation

• The presence of bilateral pulmonary infiltrates,
  however, identifies a subset of patients who are
  more likely to have serious illness.
• Their clinical course is characterized by
  tachycardia, protracted hypoxemia, longer
  duration of fever, and a greater fall in
  hemoglobin levels

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Diagnostic tests for acute chest syndrome

• Sputum analysis for Gram's stain
• Blood cultures
• Chest radiographs
• Thin-cut computed tomographic scan of chest
• Serial measurement of arterial blood gases
• Ultrasound or impedance plethysmography
• Bone scan
• Flexible bronchoscopy with bronchoalveolar lavage
  

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Management of acute chest syndrome in patients
with sickle cell disease

• Identify and treat all underlying precipitating
  factors
• Maintain adequate oxygenation, improve
  oxygen-carrying capacity, and improve tissue
  oxygen deliveryAdminister supplemental oxygen to
  maintain PaO2 in 70-100 mm Hg range

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Management of acute chest syndrome in patients
with sickle cell disease

• Give simple or exchange transfusion to enhance
  oxygen capacity or reduce hemoglobin S
  concentration to reverse episodes
• For severe respiratory failure, use mechanical
  ventilation with positive end-expiratory pressure
  (PEEP) or continuous positive airway pressure
  (CPAP

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Management of acute chest syndrome in patients
with SSD

• Prevent further alveolar collapse by using
  incentive spirometry, CPAP, and PEEP
• Maintain adequate fluid volumeGive hypotonic
  saline (D5W or 5 dextrose in 0.25 normal
  saline) to maintain normovolemic state

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Management of acute chest syndrome in patients
with SSD

• Control painGive adequate amounts of narcotic
  analgesics to alleviate pain, avoiding
  hypoventilation from excessive sedation
• Nonsteroidal anti-inflammatory medications (if
  not contraindicated by underlying peptic ulcer or
  renal disease)
• Morphine sulfate, 0.1-0.15 mg/kg every 3-4 hours
  intravenously, through fixed scheduling or
  patient-controlled analgesia

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Management of acute chest syndrome in patients
with SSD

• Treat underlying infectionProvide empirical
  coverage for community-acquired pneumonia,
  pending results from other studies use second-
  or third-generation cephalosporin or selected
  beta-lactam/beta-lactamase inhibitor in
  combination with macrolide
• Prescribe bronchodilatorUse albuterol (Airet,
  Proventil, Ventolin) through metered-dose inhaler
  or nebulizer

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Management of acute chest syndrome in patients
with SSD

• Fluid administrationIf the patient is unable to
  consume fluids orally, 5 dextrose in water or 5
  dextrose in 0.25 normal saline solution should
  be administered intravenously to maintain
  euvolemia once any existing volume deficits have
  been corrected.

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Management of acute chest syndrome in patients
with SSD

• Dehydration must be remedied, because it can
  result in increased plasma osmolarity and
  intracellular dehydration of red blood cells.
• Under those conditions, erythrocytes are more
  likely to sickle. Hypotonic saline solutions are
  used because free water enters the relatively
  hypertonic red blood cells.
• This process causes osmotic swelling, decreased
  mean corpuscular hemoglobin concentration and,
  consequently, a reduced tendency for sickling.

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Management of acute chest syndrome in patients
with SSD

• Decisions regarding transfusion are best guided
  by the patient's clinical condition.
• Simple transfusion is indicated for patients with
  mild to moderate ACS the goal is a hemoglobin
  value of 10 g/dL
• Exchange transfusions should be reserved for
  severe crises, when it is important to decrease
  the hemoglobin S concentration rapidly.
• Unlike simple transfusions, exchange transfusions
  avoid the problems related to increased blood
  volume and viscosity. It is suggested that a PaO2
  of less than 60 mm Hg, clinical deterioration, or
  a worsening condition seen on chest radiographs
  should prompt exchange transfusion.

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Management of acute chest syndrome in patients
with SSD

• The goal is to reduce the hemoglobin S
  concentration to 20 to 30 and the hematocrit to
  30 (5). Patients with recurrent episodes of ACS
  may also benefit from regular exchange
  transfusions to maintain the hemoglobin S
  concentration below 30.

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