Sickle Cell Disease

Anna D. Jarvis

Melanie Kirby

Introduction

A group of genetic disorders in which a single point mutation results in substitution of valine for glutamic acid at the sixth position on the β-hemoglobin chain
Common sickle cell syndromes include hemoglobin SS disease, hemoglobin S-hemoglobin C disease, hemoglobin S-β thalassemia disease
High risk of infection due to splenic dysfunction: overactive reservoir function and ineffective filtration
Splenomegaly may be present by 4-5 months of age
Spleen is palpable in 50% by 12 months of age

Sickle Cell Emergencies

Vaso-occlusive Crisis (VOC)

Cause

Ischemic tissue injury results from obstructed blood flow by sickled RBCs
Precipitants: infection, fever, acidosis, hypoxia, dehydration, extremes of heat and cold

Clinical Presentation

Individual patients often have a recurrent pattern of pain
Pain can be symmetrical, asymmetrical, or migratory
Any area of the body may be affected:
- Infants: dactylitis (hand/foot syndrome)
- Others: limb pain, abdominal pain, back pain
Bone pain is the most frequent VOC and may be accompanied by low-grade fever, redness, and warmth
History should include:
- Nature, duration, and severity of pain
- Comparison to previous painful crises
- Analgesics already taken for current episode
- Previous experience with analgesics/side effects
- Associated symptoms (e.g., fever/dyspnea)
- Consider other etiologies (e.g., osteomyelitis)

Management

± Oxygen
Maintain hydration and adequate pain control
Hydration: 1.5 × maintenance normal saline
Rule out other pathologies and concurrent sickle crises
Measure pain intensity with age and developmentally appropriate tools (see Ch. 64, Pain Management)
Check with caregivers for child’s usual response to pain
Children with chronic pain syndromes develop coping mechanisms and may not appear as distressed
- Mild to moderate pain: acetaminophen (15 mg/kg) with codeine (1 mg/kg) q 4 h
- Moderate to severe pain: morphine 0.1 mg/kg IV
May require morphine infusion 10-40 mcg/kg/h ½ child’s weight in kg = morphine in mg added to 50 mL D5W, 1 mL/hr = 10 mcg/kg/hr
Transfuse if hemoglobin 15 g/L or more below baseline

Aplastic Crisis

Cause

Parvovirus B19, other viruses
- Parvovirus B19 is a common cause of aplastic crisis, highly contagious
- Infected pregnant healthcare providers have risk of fetal complications
- Family contacts with SCD at high risk of developing aplastic crises

Clinical Presentation

Rapid fall in hemoglobin to 30-50 g/L
Reticulocytes < 0.1%
Usually lasts 7-10 days
Marrow recovery is heralded by the presence of many nucleated RBCs in the peripheral blood smear
Less severe in SC or sickle β-thalassemia
Presentation may be subtle: “fatigue, less active”

Management

Transfuse to Hb 80-90 g/L:
- Caution as transfusion may precipitate congestive cardiac failure
Partial exchange transfusion may be needed
Monitor cardiovascular status closely
Monitor family members with SCD

Splenic Sequestration Crisis

Sequestration of half or more of a child’s blood volume may occur over hours
Results in sharp fall in hemoglobin ± platelets
Can occur in older children with HbSC disease, sickle β-thalassemia, or SS patients with persistent splenomegaly

Cause

Clinical Presentation

Management

PRBC transfusion
Splenectomy for patients > 2 years age
Chronic transfusion program if < 2 years age
Monitor closely for congestive cardiac failure during PRBC transfusion
Platelet infusions may be indicated
Although a viral etiology is most likely in young febrile patients, cover for bacterial infections (see Fever Sepsis Syndrome below)