Splenic sequestration

• Splenic sequestration, or intrasplenic trapping of RBCs, is a major cause of morbidity and mortality in SCD. It is more common in children who have not yet undergone splenic auto-infarction.
  
• It results in a sudden enlargement of the spleen accompanied by an acute fall in the hemoglobin level.
  
• Symptoms include fatigue, abdominal fullness, and left upper quadrant abdominal pain.
  
• Physical examination may reveal tachycardia, pallor, and splenomegaly.
  
• Patients can rapidly deteriorate and develop altered mental status, hypotension, and cardiovascular collapse secondary to anemia and hypovolemic shock. The condition can be fatal within hours.

Stroke

• Stroke is one of the most devastating complications of SCD.
  
• Children with SCD have a 200-fold higher risk of stroke than those without SCD. Approximately 10% of patients experience a stroke before the age of 20 years.
  
• Patients with ischemic stroke typically present with hemiparesis or focal deficits. Vague symptoms consistent with a transient ischemic attack may be warning signs of an impending stroke.
  
• Patients with hemorrhagic stroke may exhibit headache, vomiting, or altered mental status.

Eye trauma

• Even minor trauma to the eye can cause hemorrhage (hyphema) into the anterior chamber in patients with sickle cell disease. Patients with sickle cell trait are also at increased risk for hyphema and its complications.
  
• When hyphema develops, sickled RBCs may clog the trabecular meshwork resulting in acute angle-closure glaucoma.
  
• Patients with SCD are also more susceptible to rebleeding and delayed complications such as optic nerve atrophy and central retinal artery occlusion.
  
• Symptoms include pain and decreased visual acuity in the affected eye.
  
• Physical examination may reveal hyphema and elevated intraocular pressure.

Diagnosis and evaluation

• Obtain a complete blood count to assess the degree of anemia.
  
• A reticulocyte count can help to differentiate between splenic sequestration and transient red cell aplasia (Table 52.2).
  
• Elevations in indirect bilirubin, alanine aminotransferase, and lactate dehydrogenase are consistent with hemolysis.
  
• Perform blood typing and screening if there is concern that the patient may need a transfusion.
  
• Patients with a fever should be evaluated for infection (Table 52.3).
  
• An elevated white blood cell count >20 000/microliter with an increased number of bands suggests the presence of an infection. Many patients with SCD have a baseline leukocytosis.
  
• Obtain cardiac biomarkers if acute coronary syndrome is suspected.
  
• Chest radiographs can identify the presence of a new infiltrate. The lower lobes are most commonly involved, but any lobe can be affected.
  
• Emergent head computed tomography (CT) should be performed in patients with suspected acute stroke.

Table 52.2. Differentiating common causes of acute anemia in sickle cell disease

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Critical management

Vaso-occlusive crisis

• Initial management includes aggressive pain management and rehydration.
  
• Treatment of pain usually requires opioids. Morphine, fentanyl, and hydromorphone are all acceptable options. Meperidine should be avoided because its metabolite can cause neurotoxicity.
  
• In the absence of intravenous (IV) access, oral administration is preferred over the intramuscular route due to concerns for hematoma formation.
  
• Careful monitoring is required to prevent over-sedation and hypoventilation.
  
• Use acetaminophen as adjuvant analgesic pharmacotherapy.
  
• NSAIDs should be used sparingly and with caution as patients with sickle cell disease have some degree of renal dysfunction (from microinfarction and chronic anemia).
  
• Fluid rehydration should be performed judiciously. Use boluses of IV crystalloids if there is overt hypovolemia (sepsis, vomiting, diarrhea). Otherwise, infuse a hypotonic solution such as 5% dextrose in half-normal saline.
  
• IV fluid therapy should not exceed 1.5 times maintenance to avoid pulmonary edema or atelectasis, which may lead to acute chest syndrome.
  
• Transfusion has not been shown to be effective for routine acute VOC and should be reserved for other complications of SCD.
  
• Supplemental oxygen is recommended only if the patient’s oxygen saturation falls below 92%.

Transient red cell aplasia

• Patients should be transfused only if they develop symptomatic anemia.
  
• Intravenous immunoglobulin may be administered once the diagnosis is made.
  
• Because parvovirus B19 is highly communicable, patients with aplastic crisis should be isolated from pregnant or immunocompromised individuals.

Priapism

• Patients with priapism for less than 2 hours duration should receive conservative treatment with IV fluids and analgesics.
  
• If priapism has been present for more than 2 hours, first-line therapy includes drainage of the corpus cavernosa followed by irrigation with a 1:1 000 000 solution of epinephrine in saline. If drainage and irrigation fail, consider exchange transfusion.

Infection

• Patients who are systemically ill must be treated promptly with broad-spectrum IV antibiotics. Once a causative organism is identified, therapy can be tailored according to its antibiotic sensitivity.
  
• Septic patients should be treated by implementation of the early goal-directed therapy protocol.

Acute chest syndrome

• Treatment of ACS parallels that of VOC, including analgesia, IV fluids, and supplemental oxygen.
  
• All patients with ACS should receive antibiotics to cover both typical and atypical organisms. A full course of antibiotics is recommended regardless of culture results.
  
• Bronchospasm may accompany ACS. Administer bronchodilators to all patients regardless of the presence or absence of audible wheezes and continue the treatment if a response is elicited.
  
• Transfusion therapy may be life-saving in ACS. Exchange transfusion is preferred over simple transfusion in patients with deteriorating conditions, particularly in those with relatively high hemoglobin (>9 g/dL). The goal for exchange transfusion therapy is to decrease the hemoglobin S concentration to <30%.
  
• Inhaled nitric oxide may reduce pulmonary pressures and improve ventilation–perfusion matching.
  
• Steroids are not recommended in ACS unless there is a concurrent asthma exacerbation.

Splenic sequestration

• All patients with acute splenic sequestration should immediately be transfused with packed red blood cells (PRBCs).
  
• Serial hemoglobin measurements should be performed to evaluate the adequacy of transfusion.

Stroke

• Exchange transfusion is the treatment of choice for children with acute ischemic stroke. Thrombolysis is contraindicated.
  
• Adults with SCD who present with stroke symptoms should receive conventional therapy for stroke, including thrombolysis with tissue plasminogen activator if indicated.

Eye trauma

• Patients who sustain eye trauma with or without hyphema require emergent evaluation by an ophthalmologist for evaluation of intraocular pressure.
  
• Treatment of hyphema includes head-of-bed elevation to 30 degrees and topical medications for lowering intraocular pressure (such as timolol).
  
• Mannitol and acetazolamide should be avoided because of their potential to promote sickling.
  
• All patients with sickle cell disease or sickle cell trait presenting with hyphema should be admitted for medical therapy and serial intraocular pressure measurements.

Sudden deterioration

Respiratory distress

• Causes of acute respiratory distress include pneumonia, pulmonary edema, pulmonary embolism, and fat embolism.
  
• Chest radiography should be obtained to help identify the etiology of the patient’s respiratory compromise.
  
• A chest CT may be necessary if the chest radiograph does not provide a clear explanation for the patient’s deterioration.
  
• Noninvasive positive-pressure ventilation improves oxygenation and ventilation in patients with pulmonary edema and decreases the need for intubation.
  
• Patients with impending respiratory failure should be emergently intubated.

Hypotension

• Splenic sequestration, pulmonary embolism, and septic shock can all cause a precipitous drop in blood pressure.
  
• Patients may require central venous access or invasive hemodynamic monitoring.
  
• Bedside ultrasound can be used to assess volume status (inferior vena cava collapse) and identify signs of pulmonary embolism (right heart strain).
  
• Inotropic support may be necessary in patients with persistent hypotension despite aggressive fluid resuscitation and PRBCs transfusion.
  
• Hypotension associated with sepsis should be managed according to early goal-directed therapy after the early administration of broad-spectrum antibiotics.

Altered mental status

• Patients with focal neurological deficits should undergo emergent head CT to evaluate for ischemic or hemorrhagic stroke.
  
• Altered mental status may be an ominous sign in patients with splenic sequestration. Emergent RBC transfusion is imperative.
  
• Patients with VOC may develop a depressed level of consciousness as a result of excessive opiate use. Intravenous naloxone may be used to reverse the respiratory depression. Patients with persistent respiratory compromise will require orotracheal intubation.

Vasopressor of choice: Patients presenting with septic physiology should receive norepinephrine as first-line vasopressor.

References

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