Page 1300 - Hall et al (2015) Principles of Critical Care-McGraw-Hill

CHAPTER 96: Sickle Cell Disease 907

cardiac enzyme release, coronary atherosclerosis is essentially non- frequently encountered, which very rarely cause bone sepsis in patients
existent in patients with sickle cell disease for reasons that are poorly without sickle cell disease. Joint effusions and occasionally hemarthro-
understood, possibly owing to low levels of low-density lipoprotein sis may be seen adjacent to infarcted bones. Septic arthritis is seen less
cholesterol, early mortality of males, and increased heme oxygenase-1 commonly.
activity. Cardiomegaly and biventricular chamber dilation are nearly
universal due to a long-term high cardiac output state as compensa- ■ SKIN
tion for severe chronic anemia. High-output cardiac failure, diastolic Leg ulcers, a clinical feature of this and other hemolytic disorders, are
dysfunction, and pulmonary hypertension are common cardiac com- usually limited to adolescence and adulthood. They usually heal very
plications of sickle cell disease (see Tables 96-3 and 96-4). slowly and can cause very severe pain. They rarely develop acute cellu-
■ HEPATOBILIARY litis or osteomyelitis. They are best treated with scrupulous wound care
rather than antibiotics.
Up to 42% of patients with sickle cell disease have calcium bilirubinate
gallstones by age 18 years, although only a fraction of these patients are SPECIAL PROBLEMS IN THE ICU
symptomatic. Stones develop due to hemolytic anemia and the very high
rate of bilirubin excretion in bile as a breakdown product of hemoglobin The demographics of adult patients with sickle cell disease admitted to
turnover. In cases of acute cholecystitis, awaiting its resolution decreases the medical ICU at a single institution over a 10-year span are presented
perioperative complications. Acute vaso-occlusion in the liver can cause in Table 96-5. Specific issues in management of patients with sickle cell
pain, elevated transaminases, and extreme hyperbilirubinemia, gener- disease admitted to the ICU are discussed in detail below.
sequester peripheral blood cells, clinically analogous to splenic seques- ■ ACUTE CHEST SYNDROME
ally responding well to supportive care. Rarely, the liver may acutely
tration syndrome (see Special Problems in the ICU). The ACS of sickle cell disease is an all-inclusive acute lung injury (ALI)
■ SPLENIC syndrome, akin to ARDS. The largest clinical study of ACS defined
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ACS on the basis of the finding of a new pulmonary infiltrate involv-
Nearly all patients with sickle cell disease develop progressive loss of ing at least one complete lung segment that was consistent with the
splenic function secondary to its microvascular vaso-occlusion and presence of alveolar consolidation but excluding atelectasis. In addi-
infarction, beginning at birth and complete by age 10 years. This mani- tion, the case definition required chest pain, a temperature higher than
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fests primarily as a marked susceptibility to sepsis and meningitis due to 38.5°C, tachypnea, wheezing, or cough. Implicit in this definition is
encapsulated organisms, particularly in children younger than 5 years. the acknowledgment that lung injury from a wide variety of causes can
The incidence of serious infection is dramatically decreased by penicillin induce pulmonary microvascular sickling to a greater or lesser extent.
prophylaxis and conjugate vaccines against Haemophilus influenzae and Identified etiologies of the ACS include infection, vascular infarction,
Streptococcus pneumoniae. However, splenic dysfunction still causes a and fat emboli (Table 96-6). Vichinsky and colleagues found that infec-
modest lifelong risk of overwhelming sepsis. The spleen is atrophic and tions account for about one-half of cases with identified etiologies, with
nonfunctional in 98% of adults with homozygous SS sickle cell anemia identified pathogens in order of frequency: Chlamydia, Mycoplasma,
(see calcified spleen in Fig. 96-3B). A dramatic acute complication of respiratory syncytial virus, Staphylococcus aureus, Streptococcus pneu-
sickle cell disease is splenic sequestration crisis, described in detail in the moniae, and Parvovirus (Table 96-7). Approximately one-third of cases
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section on special problems in the ICU. This complication occurs fre- were presumed due to pulmonary infarction from vaso-occlusion.
quently in pediatric patients with functioning spleens, primarily young Some of these cases may have resulted from pulmonary atelectasis due to
children with homozygous SS disease, and adults with hemoglobin SC hypoventilation caused by painful infarction of ribs or vertebrae. Localized
sickle cell disease or S-β -thalassemia because approximately 50% of hypoxemia due to ventilation-perfusion mismatch of any cause may result
+
these patients retain their spleen into adulthood. It is conceivable that in intrapulmonary sickling and vaso-occlusion (see Table 96-6).
hydroxyurea therapy in children with sickle cell disease might lead to Fat embolism appears to play a large role in episodes of ACS develop-
prolongation of splenic function. ing after the onset of a pain crisis. In the study by Vichinsky et al, oil
droplets in pulmonary macrophages were found in bronchoalveolar
■ RENAL lavage fluid from approximately one-sixth of all cases, indicative of
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Isosthenuria or hyposthenuria (decreased urine osmolarity) develops fat embolism. The mechanism appears to involve infarction of bone
marrow, with sloughing of fat droplets from necrotic marrow into
in most patients by age 10 years, resulting in increased maintenance the venous circulation, resulting in pulmonary fat emboli resembling
fluid and sodium requirements. Hematuria due to papillary necrosis is
an occasional complication, usually self-resolving. A nephropathy with
nephrotic grade proteinuria can gradually progress to uremia. Early
signs include the normally low serum creatinine exceeding 0.6 mg/dL, TABLE 96-5 Demographics of MICU Admissions for Patients With SCD a
progressively severe anemia, and a rise in the serum uric acid level. SCD hospitalizations resulting in MICU admission (range) 1.5%-2.9%
Angiotensin-converting enzyme inhibitors can decrease proteinuria
and potentially slow progression of renal insufficiency. Uremia has been MICU stay, days (mean ± standard deviation) 5.0 ± 6.5
treated with dialysis and with renal transplantation. MICU mortality rate 13%
■ SKELETAL MICU diagnosis: 43%
Acute chest syndrome (including pneumonia)
Bone marrow infarcts are frequent causes of pain. These may be Severe anemia 36%
detected on magnetic resonance imaging or radionuclide imaging with
technetium sulfur colloid, although it is not normally clinically helpful Sepsis 20%
to ascertain these by imaging. The heads of the femur and humerus Pulmonary hypertension 9%
are susceptible to avascular necrosis, a potential source of constant Left heart failure 4%
pain and disability, sometimes requiring joint replacement. Ischemic
bone becomes susceptible to bacterial osteomyelitis; however, this is Multiorgan failure 3%
quite rare in adult patients. Staphylococcus aureus is the most common a Chart survey between 1983 and 1994 at Howard University Hospital in Washington, DC.
organism in sickle cell osteomyelitis episodes. Salmonella species are MICU, medical intensive care unit; SCD, sickle cell disease.

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