DOI: 10.1097/CCM.0000000000000387
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PMID: 24933050
Issn Print: 0090-3493
Publication Date: 2014/07/01
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Excerpt
Understandably, sickle cell anemia is widely viewed through a jaundiced eye by intensivists, emergency physicians, hospitalists, trainees, students, and, in fact, most physicians. They do not appreciate that the patients they repetitively care for represent a minority of the sickle cell population; less than one fourth patients of sickle cell patients comprise the majority of emergency room visits and hospitalizations (1). Most physicians seldom interact with the large proportion of patients who may go years (or even decades) between hospital encounters for sickle-related problems. The explanation for such phenotypic disparity remains elusive. While modifying socioeconomic and genetic factors have been identified (such as coinherited α thalassemia and baseline hemoglobin F levels), these known variables barely scratch the surface of explaining the wide variation in disease manifestations.
Median survival in homozygous sickle cell anemia (the predominant form of clinical disease) has been about 45 years in developed countries (2–4). Advances over the last dozen years appear to be improving on this. Childhood mortality is being impacted by penicillin prophylaxis, pneumococcal vaccination, and routine Doppler screening with pre-emptive therapy for those at high risk of ischemic stroke (4–6). In adults with moderate-to-severe symptoms, hydroxyurea reduces painful crises, hospital admissions, and acute chest syndrome (ACS) and appears to increase longevity (7).
Infection remains a major problem for these usually functionally asplenic people, but ACS has emerged as the most common cause of death, especially for young adults (8). In children, overt ischemic stroke has affected 10%, with an equal number suffering “silent” brain infarcts by imaging (9); sequestration syndrome is another risk. Those escaping early fatal complications remain at risk for these in middle age or may fall victim to the toll extracted from chronic microcirculatory insults to organ function (10, 11). Susceptible are the heart, lungs, kidneys, brain, and liver. Morbidities occur from avascular necrosis of joints (even in young adults), retinopathy (particularly in sickle cell [SC] disease), and erectile dysfunction.
The signature complication of sickling disorders is acute vaso-occlusive pain crisis. Beyond pain relief and hydration, management must focus on monitoring for emergent complications. In this issue of Critical Care Medicine, Cecchini et al (12) confirm that most sickle cell patients in ICU do not initially present with ACS or multiple organ failure but rather deteriorate during hospitalization. Confirmed are previous observations that patients with “milder” sickling disorders are at equal or higher risk for life-threatening complications when they do suffer a vaso-occlusive crisis (13). (Hemoglobin SC disease and S-β thalassemia are milder than homozygous hemoglobin SS disease in that hemoglobin is higher, pain episodes less frequent, and mean longevity longer.)
Expanding on small prior studies (14), Cecchini et al (12) looked for predictors of “complicated outcome” (CO), defined as the need for vital support (mechanical ventilation, vasopressors, and hemodialysis) or death. CO occurred in 20% and death in 7% of 138 consecutive ICU admissions. Not surprisingly, CO correlated with more rapid deterioration in the 48 hours prior to ICU transfer, specifically higher respiratory rate, progressive renal injury, and rapidly declining hemoglobin. Perhaps, surprising is the lack of correlation of CO with attributes indicative of more severe chronic disease, such as recent hospital admission or transfusion, hydroxyurea use, or (reassuringly) iron chelation therapy.
ACS is defined as fever and/or respiratory symptoms accompanied by a new infiltrate on chest radiograph (15).
