..... Infection

Patients with SCD are at increased risk of infection as a

result of the loss of splenic function secondary to recurrent

splenic infarcts. Children as young as 6 months of age may

be functionally asplenic, and most patients with SCD are

by the age of 5 or 6 years. This makes them more vulnera ­

ble to infections with encapsulated organisms such as S.

pneumoniae and H. influenzae.S. aureus, Escherichia coli,

and Salmonella typhimurium are also common pathogens.

Bone, pulmonary, and central nervous system (CNS)

infections are common and must be considered in any

febrile patient with SCD.

..... Neurologic

Patients with SCD are at increased risk for cerebrovascular

accident (CVA), ischemic and hemorrhagic, as well as s ubarachnoid hemorrhage. Approximately 10% of patients

will have a CVA by the age of 20 years. Vasoocclusion, as

well as endothelial damage, are believed to play a role in

development of CVA.

..... Splenic Sequestration

The abnormal sickled cells become trapped in the spleen

(splenic sequestration), leading to a rapid decrease in

steady state hemoglobin and an enlarged spleen. A rapid

decrease in hemoglobin can lead to hemodynamic instability and altered mental status. Splenic sequestration is a

serious complication seen more commonly in children

than adults and carries a significant morbidity and mortality potential.

..... Aplastic Crisis

Aplastic crisis arises when bone marrow production of

RBCs stops or falls below the rate of destruction. Aplastic

crisis is also associated with reticulocytopenia. Aplastic

crisis in patients with SCD has been linked to infection

with parvovirus as well as folic acid deficiency.

..... Hemolytic Anemia

Chronic hemolysis is a problem for all patients with

SCD due to the deformed RBC. Hemoglobin levels

range from 6-9 g/dL. Patients will also have an increased

reticulocyte count due to increase RBC destruction.

Under stress (eg, infection), hemolysis rates may

increase and patients my have a decrease in hemoglobin

from their baseline.

..... Priapism

Priapism, a painful failure of penile detumescence secondary to corpus cavernosum obstruction by sickled cells, has

a bimodal peak (5-13 years and 2 1-29 years of age).

Prolonged priapism can lead to impotence due to fibrosis

and vascular damage.

CLINICAL PRESENTATION

..... History

Patients will present with pain that is usually moderate to

severe and most commonly involves the extremities, back,

chest, and abdomen. Important historical considerations

include possible precipitants, previous complications,

home analgesic regimen, and routine medical care.

Common precipitants of a pain crisis include infection,

cold, and dehydration. Determine whether the patient's

pain is typical or atypical in relation to previous episodes in

an effort to determine whether more than a simple vasoocclusive pain crisis is occurring. The presence of fever, chest

pain, shortness of breath, joint swelling, or redness should

prompt the clinician to look beyond a simple pain crisis.

..... Physical Examination

Note the presence of abnormal vital signs (VS), particu ­

larly fever, tachycardia, tachypnea, hypoxia and hypotension, which may indicate complications of SCD or another

acute process. Although most patients with an acute vaseocclusive crisis will have a low-grade temperature, a fever

greater than 38.3°C (100.9 F) should prompt a search for

an infectious precipitant. In addition, acute chest syn ­

drome should be suspected in patients with chest pain,

shortness of breath, fever, and cough. Determination of

hydration status is critical. Rehydrating the patient in crisis

not only reduces sickling of the cells, but also increases the

intravascular volume, thereby helping to relieve vasoocclusion. In addition to rapid and accurate VS measurements

and determination of hydration status, several key organ

systems must be assessed .

The general appearance of the patient should be noted

for signs of respiratory distress, physical pain, and lethargy.

Because of the increased rate of hemolysis, patients with

SCD may have j aundice or scleral icterus. Pallor may indicate a significant drop in hemoglobin. The skin should be

examined for signs of infection. Pallor, left upper quadrant

pain, and splenomegaly are all concerning for splenic

sequestration. Chest auscultation should be done to note

any rales, rhonchi, or wheezing. The abdominal exam

should note the presence of focal tenderness, especially the

right or left upper quadrants. The presence of splenomeg ­

aly or hepatomegaly, or the presence of guarding or

rebound tenderness, should alert the practitioner to an

intra-abdominal process beyond that associated with pain

crisis. Extremities and joints should be examined for focal

tenderness, joint erythema, or swelling, all of which may

indicate osteomyelitis or septic arthritis and not simply

bone pain associated with a crisis. Patients with SCD

require a thorough examination of the extremities, and it

should be performed on an undressed patient to rule out

these serious complications. A full neurologic exam including cranial nerves and cerebellar signs should be per ­

formed to assess for any new neurologic deficits in a

patient with acute complaints.

SICKLE CELL EMERGENCIES

DIAGNOSTIC STUDIES

..... Laboratory

Initial laboratory studies in patients s uspected of having vasaocclusive crisis include complete blood count and reticulocyte

count. The Hb level is usually between 6 and 9 g!dL, but

should be compared with previous levels for any acute

decreases that would be consistent with rapid hemolysis,

splenic sequestration, or aplastic crisis. The r eticulocyte count

should be elevated during a typical acute vasoocclusive pain

crisis to compensate for increased RBC turnover. A reticulocyte count less than 2% would be concerning for aplastic crisis. Leukocytosis (12-20 K/mm) is common and does not

necessarily indicate infection. Infection should not be

excluded solely on the basis of white blood c ell (WBC) count.

Liver function tests are indicated in patients with abdominal

pain or jaundice to further evaluate evidence of hemolysis,

gall bladder, or liver end-organ damage. Urinalysis is needed

to assess for infection as a precipitant for the acute pain crisis.

Blood and urine cultures are only needed in patients in whom

infection is suspected.