Chapter 099. Disorders of Hemoglobin (Part 7)

Clinical Manifestations of Sickle Cell Trait Sickle cell trait is usually asymptomatic. Anemia and painful crises are exceedingly rare. An uncommon but highly distinctive symptom is painless hematuria often occurring in adolescent males, probably due to papillary necrosis. Isosthenuria is a more common manifestation of the same process. Sloughing of papillae with urethral obstruction has been reported, as have isolated cases of massive sickling or sudden death due to exposure to high altitudes or extremes of exercise and dehydration.DiagnosisSickle cell syndromes are suspected on the basis of hemolytic anemia, RBC morphology (Fig. 99-4), and intermittent episodes of ischemic pain....
Nội dung trích xuất từ tài liệu:
Chapter 099. Disorders of Hemoglobin (Part 7) Chapter 099. Disorders of Hemoglobin (Part 7) Clinical Manifestations of Sickle Cell Trait Sickle cell trait is usually asymptomatic. Anemia and painful crises areexceedingly rare. An uncommon but highly distinctive symptom is painlesshematuria often occurring in adolescent males, probably due to papillary necrosis.Isosthenuria is a more common manifestation of the same process. Sloughing ofpapillae with urethral obstruction has been reported, as have isolated cases ofmassive sickling or sudden death due to exposure to high altitudes or extremes ofexercise and dehydration. Diagnosis Sickle cell syndromes are suspected on the basis of hemolytic anemia, RBCmorphology (Fig. 99-4), and intermittent episodes of ischemic pain. Diagnosis isconfirmed by hemoglobin electrophoresis and the sickling tests already discussed.Thorough characterization of the exact hemoglobin profile of the patient isimportant, because sickle thalassemia and hemoglobin SC disease have distinctprognoses or clinical features. Diagnosis is usually established in childhood, butoccasional patients, often with compound heterozygous states, do not developsymptoms until the onset of puberty, pregnancy, or early adult life. Genotyping offamily members and potential parental partners is critical for genetic counseling.Details of the childhood history establish prognosis and need for aggressive orexperimental therapies. Factors associated with increased morbidity and reducedsurvival are more than three crises requiring hospitalization per year, chronicneutrophilia, a history of splenic sequestration or hand-foot syndrome, and secondepisodes of acute chest syndrome. Patients with a history of cerebrovascularaccidents are at higher risk for repeated episodes and require especially closemonitoring using Doppler carotid flow measurements. Patients with severe orrepeated episodes of acute chest syndrome may need lifelong transfusion support,utilizing partial exchange transfusion, if possible. Figure 99-4 Sickle cell anemia. The elongated and crescent-shaped red blood cells seenon this smear represent circulating irreversibly sickled cells. Target cells and anucleated red blood cell are also seen. Sickle Cell Syndromes: Treatment Patients with sickle cell syndromes require ongoing continuity of care.Familiarity with the pattern of symptoms provides the best safeguard againstexcessive use of the emergency room, hospitalization, and habituation to addictivenarcotics. Additional preventive measures include regular slit-lamp examinationsto monitor development of retinopathy; antibiotic prophylaxis appropriate forsplenectomized patients during dental or other invasive procedures; and vigorousoral hydration during or in anticipation of periods of extreme exercise, exposure toheat or cold, emotional stress, or infection. Pneumococcal and Haemophilusinfluenzae vaccines are less effective in splenectomized individuals. Thus, patientswith sickle cell anemia should be vaccinated early in life. The management of acute painful crisis includes vigorous hydration,thorough evaluation for underlying causes (such as infection), and aggressiveanalgesia administered by a standing order and/or patient-controlled analgesia(PCA) pump. Morphine (0.1–0.15 mg/kg every 3–4 h) or meperidine (0.75–1.5mg/kg every 2–4 h) should control severe pain. Meperidine should be used onlyfor acute short-term pain control; as a chronic analgesic, it is unsuitable. Bone painmay respond as well to ketorolac (30–60 mg initial dose, then 15–30 mg every 6–8h). Inhalation of nitrous oxide can provide short-term pain relief, but great caremust be exercised to avoid hypoxia and respiratory depression. Nitrous oxide alsoelevates O2 affinity, reducing O2 delivery to tissues. Its use should be restricted toexperts. Many crises can be managed at home with oral hydration and oralanalgesia. Use of the emergency room should be reserved for especially severesymptoms or circumstances in which other processes, e.g., infection, are stronglysuspected. Nasal oxygen should be employed as appropriate to protect arterialsaturation. Most crises resolve in 1–7 days. Use of blood transfusion should bereserved for extreme cases: transfusions do not shorten the duration of the crisis. No tests are definitive to diagnose acute painful crisis. Critical to goodmanagement is an approach that recognizes that most patients reporting crisissymptoms do indeed have crisis or another significant medical problem. Diligentdiagnostic evaluation for underlying causes is imperative, even though these arefound infrequently. In adults, the possibility of aseptic necrosis or sicklearthropathy ...