Page 1304 - Hall et al (2015) Principles of Critical Care-McGraw-Hill

CHAPTER 96: Sickle Cell Disease 911

FIGURE 96-6. Radiographic findings of pulmonary hypertension in an 18-year-old sickle cell patient. A. The central pulmonary artery (PA) is enlarged and significantly larger than the
adjacent ascending aorta (AA) indicating a PA/AA ratio >1. B and C illustrate the relative increase in segmental artery size relative to adjacent bronchus (arrows) as well as loss of peripheral
vascularity. D. Right ventricular (RV) and right atrium (RA) are dilated. All images illustrate the finding of mosaic perfusion pattern of parenchymal attenuation.

pulmonary thromboembolic disease may also contribute to pulmonary overt or subclinical in nature. Population screening with transcranial
hypertension in subgroup of sickle cell patients. Doppler ultrasonography is performed prospectively to identify those
■ SEPSIS AND MENINGITIS at high risk for strokes because prophylactic transfusion therapy can
prevent these strokes. Patients at risk are those with time-averaged
Due primarily to splenic dysfunction, patients with sickle cell disease mean blood flow velocity over 200 cm/s in the internal or middle carotid
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are at particular risk for sepsis. Children younger than 6 years are at arteries. Clinical strokes can manifest during acute illness or as isolated
greatest risk, especially for meningitis. Advances in conjugate vaccines neurologic events. Children with acute neurologic events should be
are improving these risks, but these patients remain at higher risk for rapidly assessed clinically for the likelihood of ischemic stroke versus
sepsis and meningitis than the general population. Although sepsis and bacterial meningitis, with the latter normally presenting with features of
meningitis may be caused by any organisms pathogenic in the general sepsis. Ischemic clinical stroke mandates rapid treatment with exchange
population, patients with sickle cell disease are particularly susceptible transfusion to limit the extent of the infarction and prevent recurrences.
to infection with encapsulated organisms, especially Streptococcus pneu- Emergency exchange transfusion should be considered in children with
moniae. This organism may be resistant to β-lactam antibiotics due to sickle cell disease and acute neurologic disability even before neuro-
long-term penicillin prophylaxis or recurrent courses of empiric antibi- imaging studies. Without continued chronic transfusion, two of three
otics. Empiric antibiotic coverage with ceftriaxone or cefotaxime should patients will have a recurrence. The required duration of long-term
be considered for fever in children younger than 6 years and in patients transfusion remains unclear, although most children with stroke are
of all ages who appear toxic or have fever with high-grade leukocytosis. transfused into adulthood. Issues in stroke in sickle cell disease have
These antibiotics have rarely been associated with immune-mediated recently been reviewed. 43
hemolytic anemia, and appropriate caution and monitoring should be Ischemic stroke generally predominates over hemorrhagic stroke, but
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undertaken. Cerebrospinal fluid pleocytosis or strongly suspected bacte- during the third decade of life, stroke is more commonly hemorrhagic.
rial meningitis should be treated initially with vancomycin in addition These are usually intracerebral hemorrhages but may occur as subarach-
to large doses of ceftriaxone or cefotaxime. Antimicrobial management noid hemorrhages, with the latter often following rupture of aneurysms.
of ACS was discussed earlier. Hemorrhages occur apparently due to chronic vasculopathy, and there
■ STROKE fied by transfusion therapy. Unfortunately, there is a dearth of published
is no published evidence to indicate whether or not its course is modi-
Approximately 7% of patients with sickle cell disease will develop clini- experience to guide therapy in these patients, and treatment is largely
supportive, with consideration of exchange transfusion. Surgical inter-
cally detected cerebral infarction, with much of this risk occurring in vention may be indicated for aneurysms.
early childhood. Young children are at risk of ischemic stroke, with a
adults older than 53 years. These strokes are commonly in large vessel ■ SPLENIC SEQUESTRATION AND INFARCTION
peak incidence between ages 2 and 5 years, and another peak is seen in
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distributions, in contrast to the microvascular infarcts incurred in other Splenic sequestration involves acute engorgement of the spleen, presum-
organs. The infarctions are commonly multifocal and can be clinically ably due to obstruction of its venous outflow by sickled erythrocytes.
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