As with many conditions, the course of sickle cell anemia and the number and types of crises that pregnant patients experience closely parallels their course outside of pregnancy with the exception that some pregnant women experience an increase in vaso-occlusive crises. Patients may be particularly vulnerable to a vaso-occlusive crisis in the immediate postpartum period due to the large hemodynamic changes that occur at that time. The management of a crisis does not differ substantially in pregnancy or the postpartum period from that recommended outside of pregnancy.
There are several types of sickle cell crises (Table 28-4). The most common crisis is a vaso-occlusive crisis in which the patient experiences severe pain, typically in the long bones or joints and probably as the result of the low oxygen environment of the marrow. The most common sites are the humerus, tibia, and femur. About 60% of patients with sickle cell anemia have at least one vaso-occlusive crisis a year. A crisis may last from several days to weeks and is precipitated by many factors including infection, infarction, dehydration, acidosis, stress, drug or alcohol use, exposure to cold, and pregnancy. As many as a third of crises are due to infection. However, most crises occur without a clear precipitating event. Although bone pain is most commonly due to a vaso-occlusive crisis, it can also be a presentation of osteomyelitis. Both will have pain, increased warmth, swelling, and a leukocytosis. The distinction can usually be made based on the temperature and white blood cell count. Generally both are much higher in osteomyelitis. Other orthopedic complications are common (Table 28-5).
TABLE 28-4.Types of Sickle Cell Crisis
TABLE 28-5.Common Orthopedic Complications in Sickle Cell Anemia ||Download (.pdf) TABLE 28-5. Common Orthopedic Complications in Sickle Cell Anemia
Vaso-occlusive crisis resulting in bone pain
Osteonecrosis of humeral or femoral head
Dactylitis (painful swelling of fingers and toes)
Although the pain of a vaso-occlusive crisis occurs most often in long bones it can also occur in the chest, abdomen, and back. Pain may be localized or migratory. It is common to have pain in several sites simultaneously. The pain of a vaso-occlusive crisis has been described as constant or throbbing as well as sharp, dull, pounding, and cutting. Many patients describe a prodromal period of 1 to 2 days prior to a full-blown crisis in which they feel parenthesis, numbness, or a dull ache in areas which subsequently become much more painful. Up to 20% of patients have had a recent hospitalization for a crisis. Recovery from a crisis predisposes patients to a high risk of thromboembolic disorders as the patients have increased erythropoiesis, elevated levels of fibrinogen, and increased plasma viscosity. It can be difficult to distinguish the pain of a vaso-occlusive crisis from that of other abdominal etiologies such as cholelithiasis or appendicitis. One must be careful to consider all etiologies and not simply attribute abdominal pain to a sickle cell crisis. Generally, patients in a vaso-occlusive crisis who have abdominal pain still have bowel sounds. The absence of bowel sounds should prompt consideration of another cause of the abdominal pain such as appendicitis or cholecystitis.
In addition to the vaso-occlusive pain, many patients have chronic pain as a result of leg ulcers, bone conditions, or neuropathies. Some patients will never be entirely pain free.
The acute chest syndrome (ACS) is a type of crisis in which the patient presents with fever, chest pain, tachypnea, an increase white blood cell count, and infiltrates on chest x-ray. This common complication is due to infection or infarction of lung tissue and is seen more often in patients who are asthmatic. The most common organisms are Chlamydia, Mycoplasma, Parvovirus B19, and various respiratory viruses. It can also be due to Staphylococcus and Streptococcus pneumoniae. ACS can also occur because of an underlying rib infarction as patients hypoventilate and develop atelectasis due to the pain of respiration. It can be difficult to distinguish ACS from pneumonia or a pulmonary embolism.
A megaloblastic crisis occurs in the setting of folate depletion when insufficient folate levels leads to a cessation of erythropoiesis. Folate deficiency is common in sickle cell anemia due to the rapid turnover of cells. A megaloblastic crisis can occur with poor oral intake, alcoholism, or with increased demands for folate such as that which occurs in pregnancy.
Several types of crisis are more commonly seen in children. These are splenic sequestration crisis, an aplastic crisis, and a hyperhemolytic crisis. By adulthood most patients are functionally asplenic so splenic sequestration is not typically seen in pregnancy. Many aplastic crises have been reported in association with a Parvovirus B19 infection. A hyperhemolytic crisis is defined by a 2-g drop in hemoglobin associated with an enlarged spleen. As with a splenic sequestration crisis, a hyperhemolytic crisis is generally confined to childhood as adults are functionally asplenic. A hyperhemolytic crisis can occur in conjunction with mycoplasma infections, hereditary spherocytosis, and medications, especially in patients with glucose-6-phosphate deficiency (G6PD). However, since G6PD is an X-linked disorder, this is rarely seen in females.