TABLE 1331 Types of Sickle Cell Crises

Vasoocclusive crises are the classic "sickle crises" characterized by painful events, often involving the back, chest, extremities or abdomen. They are the most common reason for emergency department (ED) visits by children with SCD. These vasoocclusive events account for more of the morbidity and hospitalizations than any other set of complications. The episodes are highly variable from patient to patient, with many patients reporting no crises at all, whereas others experience them on a regular basis, varying in location, duration, and severity. Typical sickle cell patients average about four severe attacks per year; with few patients reporting crises daily.

Some of these vasoocclusive crises seem to have "triggers." Stress (emotional or physical), cold water immersion/exposure (especially as associated with shivering postexposure), dehydration, high altitudes/hypoxia, or infection (bacterial or viral, with the latter being the most common trigger in children under the age of 10).

Most vasoocclusive crises occur without any obvious cause. They result from the classic mechanism of sludging of sickled red blood cells into the microcirculation, resulting in tissue hypoxia and infarction. The associated pain may recur in the same location(s), but it can be anywhere in the body. Young children tend to have pain in the limbs, whereas adolescents more commonly complain of abdominal pain. Overall musculoskeletal (first) and abdominal pain (second) are the two most common types of vasoocclusive crises.

With musculoskeletal pain, the location can be anywhere but mostly involves the long bones—i.e.,the femur, tibia, and humerus. Lumbosacral pain is also commonly reported. Often there are no demonstrative physical findings but point tenderness may be found in the painful locations. Inguinal pain with difficulty in weight bearing and walking should raise the suspicion of avascular necrosis of the femoral head. Radiographs and/or a bone scan will aid in the diagnosis.

Infants may present with sickle dactylitis, also known as hand and foot syndrome. This occurs secondary to ischemia and infarction in the bone marrow of the extremities. Nutrient arteries that supply the metacarpals and the metatarsals become occluded and cause avascular necrosis. Clinically one sees swelling and pain of the hands and feet, often with an accompanying low-grade fever (i.e., less than 38.6°C or 101.5°F). One or all four extremities may be involved. Dactylitis is usually seen in children under the age of 2 and is rare after the age of 5.

Abdominal pain is the next most common type of vasoocclusive crisis seen in children with SCD. It is characterized by its abrupt onset, lack of localization, and recurrence. Patients often complain of diffuse, generalized abdominal pain, typically in the absence of significant peritoneal signs. Bowel sounds usually remain present and auscultate normally during these attacks. It can be extremely difficult to differentiate whether the pain is caused by vasoocclusive crisis or by a more common type of surgically correctable condition. While peritoneal signs are often absent in crisis, abdominal guarding and rebound tenderness may be present to cloud the diagnosis. Mesenteric infarction as well as splenic and hepatic infarction are the most likely causes of the pain, but the differential also should include pancreatitis, hepatitis, appendicitis, perforated viscus, and pelvic inflammatory disease/gynecologic pathology. It is important to determine if the abdominal pain in SCD patients has substantially changed in character, quality, duration, severity, and associated symptoms. If such changes are present, infection or other related diagnoses should be explored.

Because of the rapid turnover of red blood cells bilirubin gallstones commonly form. This can result in biliary colic and/or cholecystitis with a secondary gallstone ileus ["right-upper-quadrant (RUQ) syndrome"]. Any sickle cell patient in crisis with RUQ pain should be carefully evaluated for this possibility. Approximately 75 percent of sickle patients have demonstrable bilirubin gallstones; fortunately only about 10 percent become symptomatic.

RUQ syndrome is characterized by the sudden onset of RUQ pain, anorexia, extreme hyperbilirubinemia (greater than 50 mg/dL), and progressive hepatomegaly. RUQ syndrome is usually benign and self-limiting in the pediatric patient population. It is felt to result from intrahepatic cholestasis and seems reversible with intravenous fluids and other supportive measures. However, in a small number of adult patients, this syndrome can progress to liver failure.

With all of the aforementioned conditions, ultrasound examination and/or computed tomography (CT) of the abdomen and pelvis may be useful. Prompt surgical consultation is initiated in patients in whom the diagnosis cannot be clarified.

Infections can cause vasoocclusive crises; therefore, determining the presence of an infectious process is critical. Painful crises are often associated with a low-grade fever and leukocytosis, but any temperature above 101°F/38.4°C (or an absolute band count greater than 300 cells per cubic millimeter) is more likely to represent an infectious etiology than tissue ischemia.

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