emDOCs Podcast – Episode 75: Asplenia

Today on the emDOCs cast with Brit Long, MD (@long_brit), we look at asplenia and its complications.

Episode 75: Asplenia

Definitions

• Asplenia is complete loss of the spleen’s function.
  • Anatomic splenectomy:  spleen has been surgically removed.
  • Functional splenectomy: spleen is present but not working.
    • The classic example is sickle cell disease (SCD).
    • Patients with SCD develop functional asplenia by 3-5 years of age.
• Hyposplenia is reduced splenic function.
  • Numerous chronic medical conditions can cause this:  chronic liver disease, HIV, malignancies, thalassemia, celiac disease, ulcerative colitis, sarcoidosis, amyloidosis, lupus, and rheumatoid arthritis.

Epidemiology

• 1 million people in the U.S. are asplenic, and 22,000 splenectomies are performed annually.

Spleen Anatomy and Physiology:

• Immune and hematologic functions are carried out in the red and white pulp.
  • White pulp
    • Largest number of B cells in the body, which are important for antibody production.
    • Releases components of alternate complement pathway, makes neutrophils, natural killer cells, monocytes, serum opsonins and cytokines, all of which help in removing harmful bacteria.
  • Red pulp
    • Filters and removes old blood cells and harmful microorganisms.
• The one organ capable of removing encapsulated organisms.
  • Streptococcus pneumonia, H. influenza, Neisseria, Capnocytophaga, E. coli, Pseudomonas
• Primary site of serum IgM antibody production.
• Plays important roles in cytokine production and the complement cascade.

Identifying Asplenic Patients

• Anatomically asplenic patients should wear a medical bracelet and carry an ID card.
  • If they are unable to provide a history:
    • Look for Howell-Jolly bodies on peripheral smear.
    • Look for depressions on RBC membranes. These suggest hyposplenism if over 4% of RBCs have this feature.
    • Ultrasound can be used to evaluate for presence/absence of a spleen.

Clinical Issues for Patients with Asplenia

• Infection
  • 2-3 times increased risk of infection, sepsis, and mortality.
  • Pneumonia, meningitis, sepsis, and atypical infections are all more common.
  • If an asplenic patient develops an infection, they are at 6x higher risk for a subsequent infection for the next 3 years.
• Overwhelming Post-Splenectomy Infection (OPSI)
  • Risk is highest in anatomically asplenic patients, but can occur in functional or hyposplenic patients.
    • OPSI occurs in 0.5% of asplenic patients.
    • Most common in the first 2 years after splenectomy.
    • Mortality rate is 10-70%.
  • Source of infection varies.
    • May be a common location (UTI, pneumonia), or could involve multiple systems.
    • OPSI may be associated with an atypical location such as septic arthritis or a spinal epidural abscess.
    • Most common causative organism is S. Pneumoniae.  
    • Others include Haemophilus influenzae type b, Neisseria meningitidis,  Capnocytophaga canimorsus, Capnocytophaga cynodegmi, Escherichia coli, and Staphylococcus aureus.
  • OPSI presentation:
    • Presents similar to a viral infection or gastroenteritis initially (fever, chills, myalgias, nausea/vomiting, diarrhea).
    • Patients can become septic and decompensate in hours, developing hypotension, septic shock, ARDS, DIC.
  • Suspected OPSI evaluation:
    • Approach like a patient with neutropenia or septic shock.
      • CBC, CMP, UA
      • Lactate
      • Blood cultures
      • Evaluate for end-organ damage
      • DIC workup with fibrinogen and coagulation panel
      • CXR
      • LP if signs of meningitis
  • OPSI Management:
    • Initiate broad spectrum antibiotics while completing the evaluation.
      • Consider a later generation cephalosporin or carbapenem plus vancomycin or vancomycin plus piperacillin tazobactam and/or azithromycin for atypical pneumonia.
    • Fluids and vasopressors
      • Patients are at risk for adrenal insufficiency. Consider stress dose steroids if the blood pressure does not improve with fluids and vasopressors.
    • For patients with focal infection that are otherwise well appearing, consider hematology consult and have a low threshold for admission.
• Infection prevention:
  • Vaccines
    • All patients should receive pneumococcal, meningococcal, haemophilus B.
      • Ideally, started 10-12 weeks before elective surgery and completed 2-3 weeks before surgery.
    • For emergency splenectomy, vaccines should be given 2 weeks after surgery.
    • For patients with functional asplenia, vaccines given as soon as possible.
  • Prophylactic antibiotics
    • Daily antibiotic prophylaxis is given for ~1 year after splenectomy.
    • Daily prophylaxis is offered to hyposplenic children <5 years of age.
    • Daily (often lifelong) prophylaxis is offered to those thought to be at high risk:  concurrent immunocompromising conditions or history of sepsis/other severe infection caused by encapsulated organisms.
    • Penicillin and amoxicillin are the preferred agents.
• Emergency antibiotics for infectious symptoms
  • Patients will have a supply of antibiotics to be used if they develop symptoms of infection such as fever, chills, rigors, etc.
• Thrombus:
  • Asplenic patients have a higher risk of atherosclerosis, CAD, stroke, limb ischemia, MI, DVT, PE, and portal vein thrombosis.
    • Incidence of thrombotic events is 10-37%
  • Patients post splenectomy are at highest risk in the months following surgery.
  • Functional asplenia also carries an increased risk of thrombosis.
  • Evaluation and treatment similar to those with normal spleen function.
• Pulmonary Hypertension (PH)
  • Elevated pulmonary arterial pressures are found in 8-11.5% of asplenic patients. Incidence is higher in patients who have chronic disease states like SCD or thalassemia.
  • Presentation: non-specific symptoms including dyspnea, fatigue, chest pain, syncope, and peripheral edema.
  • Diagnosis: ECG, ultrasound, CT.
  • Management:
    • Delicate balance of improving RV function and systemic perfusion while avoiding hypoxia, hypercarbia, hypotension, and mechanical ventilation if possible.
    • Optimize fluid status with diuresis or small fluid boluses and vasopressors.
  • Consider ICU admission and involving pulmonology/critical care colleagues.

References:

1. Long B, Koyfman A, Gottlieb M. Complications in the adult asplenic patient: A review for the emergency clinician. Am J Emerg Med. 2021 Jun;44:452-457. PMID: 32247651.