Page 708 - Hematology_ Basic Principles and Practice ( PDFDrive )

600 Part V Red Blood Cells

Pulmonary Complications 60

Pulmonary disease is the leading cause of death in patients with Pain
16
SCD. Both acute and chronic pulmonary complications are 50 Fever
common. The common acute complications are pneumonia and
acute chest syndrome, and the common chronic complication is
pulmonary hypertension. 40
Pneumonia 30
Pneumonia is defined as chest infiltrates on chest radiography or chest Percentage of patients
CT scan associated with fever and an identified infectious etiology.
The risk for and increased frequency of S. pneumoniae infections is 20
discussed under Infections earlier. In addition, Mycoplasma pneu-
moniae, Chlamydia pneumoniae, and Legionella spp. are also relatively
common causes of pneumonia in patients with SCD. Antibiotic 10
therapy for pneumonia or acute chest syndrome should cover these
agents in addition to pneumococcus and H. influenzae. When anti-
biotics are used to treat the acute chest syndrome, they should cover 0
S. pneumoniae, H. influenzae type b, M. pneumoniae, and C. pneu- 0 <2 2–4 5–9 10–19 20+
moniae. The combination of cefuroxime and erythromycin is Age (yr)
recommended. Fig. 42.12 AGE-SPECIFIC ASSOCIATED EVENTS WITHIN 2 WEEKS

Acute Chest Syndrome PRECEDING ACUTE CHEST SYNDROME. (Adapted with permission from
Vichinsky EP, Styles LA, Colangelo LH, et al: Acute chest syndrome in sickle cell disease:
182
Acute chest syndrome occurs in approximately 30% of patients. Clinical presentation and course. Cooperative Study of Sickle Cell Disease. Blood
Acute chest syndrome is defined as a new infiltrate on chest radiog- 89:1787, 1997.)
raphy or chest CT scan associated with one or more new symptoms,
which include fever, chest pain, cough, sputum production, dyspnea,
and hypoxia. This entity is included in discussions of SCD because
processes other than infection, such as vasoocclusion, could also of NO through scavenging by free Hb may have an important role
lead to pulmonary symptoms, signs, and chest radiographic changes. in the pathophysiology of this disease. 187,191 Pulmonary hypertension
However, it should be borne in mind that the usual etiology might usually occurs in adults and carries a poor prognosis. 192
be both vasoocclusion and infection simultaneously, and in almost The association with early death and the emerging availability of
all cases of acute chest syndrome, antibiotics should be administered. candidate treatments suggest that efforts should be made to diagnose
Many episodes in which common pathogens are not cultured are this condition in all patients with SCD. 187,191 The feasibility of an
caused by “atypical” agents (Mycoplasma, Legionella, and Chlamydia echocardiogram-determined tricuspid regurgitant jet (TR-jet) veloc-
spp.), suggesting that antibiotic therapy include agents directed at ity measurement of 2.5 m/s to make the diagnosis was suggested by
186
atypical agents. Pulmonary fat embolus, evidenced by stainable fat selective cardiac catheterization in a cohort of 195 patients;
in pulmonary macrophages obtained by bronchoalveolar lavage or however, the sensitivity and specificity of this test may have limita-
191
sputum induction, is found in 44% to 60% of cases of acute chest tions. Elevations in BNP levels correlate with an increased TR-jet
183
syndrome. Acute chest syndrome caused by pulmonary fat embolus and risk of early death.
is associated with more severe hematologic and clinical abnormalities. In a 16-week, double-blind, placebo-controlled trial of sildenafil
In adults, the mortality rate is four times higher than in children. 3,184 to treat patients with SCD with increased TR-jet velocity and a low
Acute chest syndrome is often preceded by febrile episodes in exercise capacity, sildenafil increased hospitalization rates for pain
184
193
children and by vasoocclusive pain crisis in adults (Fig. 42.12). without evidence of improvement in TR-jet velocity or BNP levels.
Elevation of serum phospholipase A2 was detected in patients admit- If such patients have chronic relative reticulocytopenia, measures to
ted with vasoocclusive pain crisis 24–48 hours before acute chest increase total Hb could be a consideration requiring evaluation in
185
syndrome was clinically diagnosed. Pulmonary fat embolus is often clinical trials (see Basic Management and Disease Modification).
preceded by an acute painful episode. Some patients have a rapidly
progressive course associated with a precipitous decrease in arterial Other Pulmonary Complications
oxygen tension; they may require intensive care treatment. If there Other findings include restrictive and obstructive lung disease and
194
are clinical signs of respiratory distress or when arterial oxygen tension hypoxemia. High-resolution, thin-section CT scanning of the
cannot be maintained above 70 mmHg with inhaled oxygen, partial- lungs may show chronic interstitial fibrosis. Airway hyperreactivity
exchange transfusion is indicated. Artificial ventilation may be occurs in nearly two-thirds of children with SCD not diagnosed as
required. having asthma. Thirty-six percent of 53 children with SCD were
In patients with pneumonia or chest syndrome, antibiotics should found to have sleep-related upper airway obstruction, 16% had
cover S. pneumoniae, M. pneumoniae, Chlamydia pneumoniae, H. hypoxemia, and all 15 who underwent adenotonsillectomy improved
195
influenzae, and Legionella spp. symptomatically and had improved hypoxemia. Sleep apnea may
be associated with surgically reversible exacerbations of painful epi-
Pulmonary Hypertension sodes and strokes. Blood gas and pulmonary function measurements
Chronic complications such as pulmonary hypertension occur in as should be obtained as baseline data for all patients.
many as 60% of patients. 186–188 There does not appear to be an
187
association with the occurrence of acute chest syndrome, emphasiz-
ing that the pathophysiology of these two conditions may differ in Hepatobiliary Complications
some key features. The pathophysiology may involve thrombi in large
and small arteries, 189,190 cardiac decompensation from progressive Hepatobiliary complications in patients with SCD include choleli-
anemia, and potentially reversible increases in vascular tone from NO thiasis, cholecystitis, acute hepatic cell crisis, acute hepatic sequestra-
196
190
depletion and medial and intimal hypertrophy. The recognition tion crisis, and sickle cell intrahepatic cholestasis. Chronic
that pulmonary hypertension is a feature of hemolytic syndromes transfusion also places patients at risk for infection with hepatitis
other than sickle cell and that markers of hemolysis correlate with viruses and for transfusional hemosiderosis. Nontransfusion-related
the risk of pulmonary hypertension supports the idea that depletion hepatic hemosiderosis can also be seen.