Post splenectomy infection Dr. M. Shahparianpour

Spleen

consists of the capsule and trabeculae which enclose the pulp. 3 zones of the pulp a. White pulp – lymph node; contains lymphocytes, macrophages, and plasma cells in a reticular network b. Red pulp – consists of the cord and sinuses; contains the cellular elements of the blood c. Marginal zone – poorly defined vascular space between pulps; contains sequestered foreign material and plasma as well as abnormal cellular elements

histology

The role of the spleen in the prevention of bacterial infections

It acts as an endothelial filtration organ for bacteria and other foreign material through: phagocytosis and the production of opsonins including antigen-specific IgM, alternate complement components, properdin, and tuftsin One of its most important immune functions is responding to blood-borne particulate antigens in the nonimmune host. The spleen provides the most effective primary IgM response to encapsulated bacteria

There also seems to be a relationship between the quantity and quality of spleen and protection against sepsis: splenic function after subtotal splenectomy for splenic injury is preserved and may be adequate to prevent severe postsplenectomy sepsis The propensity for pneumococcal infections in patients with sickle cell disease underscores the importance of qualitative splenic function to protect against sepsis

Etiology of asplenia and hyposplenia

Asplenia refers to the absence of the spleen. The most common cause of asplenia is surgical removal of the spleen: Hypersplenism accounts for up to 50% of splenectomies, whereas trauma accounts for 10% to 30%

Hyposplenism refers to a poorly functioning, but intact spleen A rare cause of asplenia is congenital agenesis of the spleen. This may occur as an isolated finding or as part of a syndrome often associated with cardiovascular abnormalities, such as Ivemark’s syndrome. Hyposplenism refers to a poorly functioning, but intact spleen

Functional asplenia Autoimmune Disease PBC SLE Sjogrens Intestinal Disorder Celiac disease Crohn’s UC Haematological Disease Sickle cell Essential thrombocytopenia Infiltrative Disease Amyloid Sarcoidosis Neoplasia Breast Cancer Haematological malignancy Miscellaneous Alcoholism BMT TPN Splenic Thrombosis

The risk of developing severe infection remains a significant complication of asplenia (surgical splenectomy or congenital asplenia) and hyposplenia, especially in children under the age of 5 years

Splenic salvage methods (eg, partial splenectomy) are practiced with specific indications, the goal being to preserve some of the splenic immune function. Whether partial splenectomy renders the same risk of developing overwhelming postsplenectomy sepsis (OPSS) as total splenectomy and whether the same preventative measures should be taken, remain unclear.

Definition of OPSI OPSI may have a short prodrome with non-specific symptoms Evolve into septic shock and DIC Clinical course measured in hours rather than days Fever most common – most report rigors 1 - 2 days prior to presentation In adults OPSI usually cryptic infection without primary source

It is well known that asplenia or hyposplenia convey an increased lifetime risk of developing severe infections to an affected individual, regardless of: age, the cause of asplenia or hyposplenia, in the case of splenectomy, the duration of time from removal of the spleen

the incidence seems to be related to age and underlying disease : Splenectomized children under the age of 15 years are at greater risk of developing OPSS than adults The incidence of OPSS is higher in children with underlying hemoglobinopathies (thalassemia major and sickle cell disease) and hereditary spherocytosis than in those who undergo splenectomy because of trauma

Low risk Intermediate risk High risk Risk of OPSI can be stratified according to underlying disease Low risk Trauma Intermediate risk Spherocytosis ITP Portal Hypertension High risk Thalassaemia sickle cell disease Hodgkin's Disease Malignancy

Risk of post splenectomy sepsis low but carries high risk of death (50-80%) If patients are educated to seek attention immediately may be reduced to about 10% More than 50% who die do so within 48 hours of admission

Children: 1/175 patient years Adults: 1/400~500 patient years Highest risk at first few years 1/3 at first year 1/2 at first 2 years However, 1/3 after first 5 years Can happen even 20 years after splenectomy

Clinical manifestations Fever Any fever must be viewed as possible PSS Bacteremia Coagulopathy Purpura, petechiae Meningitis Headache, neck stiffness, seizure Respiratory symptoms Cough, dyspnea, respiratory failure GI symptoms Nausea, vomiting, diarrhea, GI bleeding Shock

The mortality rate of sepsis associated with asplenia or hyposplenia remains high; death occurs in 50% to 70% of those afflicted Mortality rates are also age related, with the highest rates reported in those children less than 2 years of age

Common pathogens Encapsulated pathogen Streptococcus pneumoniae(50~60 %) No particular serotype is more common Haemophilus influezae(20~30 %) Neisseria spp.(10~20 %) Other uncommon pathogens: Capnocytophaga canimorsus Common flora in oral cavity of dogs and cats Bordetella holmesii

Capnocytophaga canimorsus

LAB CBC Blood smear DIC profile Lumbar puncture CXR Blood culture

Management Braod-spectrum antibiotics General suggestion Based on expert opinion Must cover: penicillin-resistant pneucoccus beta-lactamase producing H.influenzae General suggestion Ceftriaxone + Vancomycin Levofloxacin + Vancomycin Life-support measures H/D or CVVH for ARF Ventilator Inotropic agents Fluid

Prevention Avoid unnecessary splenectomy Immunization Timing 14 days before splenectomy 14 days after splenectomy (not immediately) Pneumococcal vaccine PPV-23 for adults PCPV-7 for children and some adults Haemophilus B vaccine Meningococcal vaccine Re-immunization Other vaccines: influenza vaccine

Antibiotic prophylaxis Daily penicillin Reduce incidence by half Reduce mortality by 80 percents Life-long or 3~5years? Post PSS patients Abx for fever On hand Empirical: Augmentin, Cefuroxine, fluoroquinolones When fever, Take the drug and go to doctor without delay Abx for dental procedures Not recommended for no obvious advantage

Absent or dysfunctional spleen in adults Immunisation Travel † Antibiotics Antibiotic prophylaxis (adult dose) Penicillin V 500mg b.d. Amoxycillin 500mg bd (Erythromycin 250mg od if penicillin allergy) HiB Vaccine Previously non immunised adults should receive a single dose of vaccine. Pneumococcal vaccine Polysaccharide vaccine (Pneumovax). Avoid in pregnancy. Meningitis C vaccine Previously non immunised adults should receive a single dose of vaccine Influenza Annual vaccine Anti-malarials if travelling to endemic areas Meningitis A+C,W135,Y if appropriate Antibiotics‡ Check antibodies 4/52 post vaccination Antibiotic cover 3 day supply of Amoxycillin should be kept by the patient with instructions to take 1gm at first sign of infection and 500mg tds thereafter and to seek immediate medical attention. Poor response revaccinate and re-test at 4/52 Good response recheck antibody titre in 1 year If poor response give conjugate (Prevenar) if not already given. †Discuss with Adult Infectious Disease team ‡Antibiotic prophylaxis may need altering depending upon local resistance.

Lack of splenic clearance of leads to high parasitaemia Malaria Lack of splenic clearance of leads to high parasitaemia Increased risk of fulminant malaria

Antibiotic Prophylaxis 1. All patients, regardless of underlying condition, should be on lifelong antibiotic prophylaxis. This should be either Penicillin V or Amoxycillin, with a preference for Penicillin V. Adult doses: Penicillin V 500 mg b.d. Amoxycillin 500 mg o.d.   2. For penicillin allergic patients, Erythromycin 250 mg b.d. should be used. 3. Patients travelling to areas where penicillin-resistant pneumococci have been identified should be switched from Penicillin V to Amoxycillin before travelling and for one week after return.

Immunization 4. Asplenia in itself is not a contraindication to routine immunization. Normal inoculations, including live vaccines, can be given safely to adults with absent or dysfunctional spleens. 5. All splenectomised patients and those with functional hyposplenism should receive pneumococcal immunisation; Haemophilus influenzae type B [Hib] conjugate vaccine and conjugated meningococcal C vaccine [MenC] as soon as possible. For pneumococcal vaccination the 23-polyvalent pneumococcal vaccine [Pneumovax] should be used.

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