Sickle cell disease (SCD), an inherited disorder due to
homozygosity for the abnormal
hemoglobin, hemoglobin S (HbS).
Hemoglobin S (HbS), results from the substitution of a
valine for glutamic acid as the sixth amino acid of the
beta globin chain, which produces a hemoglobin
tetramer (alpha2/beta S2) that is poorly soluble when
Major Clinical Menifestations
Episodes of ischemic pain (i.e., painful crises)
Ischemic malfunction or frank infarction in the
central nervous system,
Acute severe anemia
There are three settings in which an acute fall in
hemoglobin concentration may be superimposed upon the
1.Splenic sequestration crisis
Vaso-occlusive crisis & its effects
Acute painful episodes
Multi organ failure
Effect on growth and
Bone ischemia &
Effects on pregnancy
Acute Chest Syndrome
The acute chest syndrome (ACS) is the most common form
of acute pulmonary disease in patients with
SCD, occurring in almost one-half of patients.
It is the most frequently reported cause of death in
adults, and is a risk factor for early mortality.
Definition of Acute Chest
Presence of a new pulmonary infiltrate, not due to
Involving at least one complete lung segment
Tachypnea, wheezing, or cough
Causes can be listed as:
1. Unknown cause
2. Pulmonary infarction
4.Chlamydia pneumoniae infection
5.Mycoplasma pneumoniae infection
Patients with ACS present with
Examination of the chest may reveal local tenderness
over the ribs or sternum; findings of pulmonary
consolidation may also be noted.
Common laboratory findings
Thrombocytopenia or thrombocytosis
Falling hemoglobin concentration
Elevations in lactate dehydrogenase
High Bilirubin levels
Diagnosis of Acute Chest
No current laboratory or radiographic finding permits the
differentiation of ACS from other acute pulmonary
manifestations of SCD, including pneumonia and
The finding of pulmonary infiltrate should be treated as
infectious pneumonia (assume both are present) until
Pulmonary infarction due to PE or ACS?
This differentiation remains problematic.
Lack of evidence for DVT
Abnormal ventilation-perfusion scans
Inability to safely perform contrast studies in
these patients because of the possible
association with further sickling.
Investigations for ACS
Steady state Hb% & Hb electrophoresis
CBC, Retics & peripheral film
Urine microscopy & cultures
Blood group & antibody screening
ABGs & Pulse oxymetry
Clinical severity of Acute Chest Syndrome is broad.
Close monitoring of progressive pulmonary changes and
escalating severity because the clinical status of these
patients can quickly deteriorate if the underlying
pulmonary insult is not reversed.
The goals of therapy are
To correct underlying factors that contribute
to deoxygenation of hemoglobin including
dehydration & Infections
To control pain
To support the patient’s respiratory &
If dehydration is present, it should be corrected as
hypovolemia can contribute to increase sickling.
Once it is corrected, euvolemia should be
Overhydration or rapid hydration should be avoided
Weights should be monitored daily along with
intake/output for assessment of the fluid status and
management of the patient
Broad spectrum empiric coverage with
a third generation cephalosporin (eg, cefotaxime or
ceftriaxone) for common bacterial coverage and
a macrolide (eg, azithromycin or erythromycin) for
coverage of atypical organisms (such as mycoplasma and
should be initiated immediately on admission.
Oxygen supplementation should be provided to maintain
arterial oxygen saturation ≥ 92 percent.
Incentive spirometry, preferably supervised by a clinical
worker, should be employed at least every two hours to
prevent atelectasis from hypoventilation.
Patients with poor respiratory effort or rising
Use of positive pressure ventilation devices such as
nasal mask continuous positive airway pressure
(CPAP) or bilevel positive airway pressure (BiPAP)
may be useful.
Patients with respiratory failure and acute
respiratory distress syndrome
Conventional or high-frequency oscillatory mechanical
ventilation can be used.
Other respiratory interventions
Inhaled nitric oxide
Extra corporeal membrane oxygenation
(Bronchoscopy with bronchoalveolar lavage (BAL), usually reserved for
patients with severe or progressive infiltrates, provides both diagnostic and
therapeutic benefits. Bronchial samples can be examined for lipid content in
alveolar macrophage as evidence for pulmonary fat embolism and also sent
for culture. In intubated patients, bronchoscopy with suction and removal of
bronchial casts has been reported to improve patient ventilation)
In patients with ACS, transfusion therapy should be
considered early in the course of the disease.
The goal of simple transfusion is to increase the
hematocrit (Hct) to 30 percent or hemoglobin (Hgb) to 11
To improve oxygenation
For accentuated anemia
For patients with clinical or radiological progression
of disease but not impending respiratory failure.
For patients in whom exchange transfusion will be