RISK: All post splenectomy patients have an increased risk of overwhelming bacterial infection. Certain factors however do influence the degree of risk:
· Age: Younger patients have greater risk
· Underlying disease: Risk with underlying immunodeficiency > thalassemia > sickle cell anemia > traumatic splenectomy
· Time since splenectomy: Recent splenectomy has greater risk than many years post-operatively
PATHOGENS: The most common cause of overwhelming post-splenectomy sepsis is S. pneumoniae, however all of the pathogens listed below can be a source of serious infection in these patients:
· Encapsulated bacteria: S. pneumoniae, H. influenza, N. meningitidis
· S. aureus
· Numerous gram negatives including E. coli, K. pneumoniae, Salmonella sp. and Capnotcytophagia sp. (the latter usually acquired from a dog bite)
· Babesia (acquired from ticks in the Eastern seaboard particularly Cape Cod, Martha’s Vineyard, Nantucket, Block Island)
Individuals undergoing splenectomy should receive the age appropriate (see below) pneumococcal vaccine, H. influenza and quadrivalent meningococcal vaccine (the latter for those > 2 years of age) if possible up to three weeks prior to removal of the spleen to optimize the immune response. When this is not feasible and for emergency splenectomy, vaccination should be initiated as soon as possible after the patient’s recuperation.
There are currently 2 licensed pneumococcal vaccine:
1) a 23-valent Pnemococcal Polysaccharide Vaccine, PPV-23 (Pneumovax®). This vaccine is immunogenic only in those > 2 years of age and provides protection against the greatest number of clinically relevant seroptypes.
2) a 7-valent Protein-Conjugated Vaccine, PCV-7 (Prevnar®), which is immunogenic and safe beginning at 6 weeks of age. It has not been well studied in older patients and provides protection against only 7 serotypes.
Current recommendations for this use of these vaccines post splenectomy are as follows:
· Children less than 2 years of age should receive PCV-7 at the usual ages recommended for children their age: 2, 4, 6 and 12-15 months of age. These children should be given PPV-23 at 2 years of age.
· Children 2 to 5 years of age should receive two doses of PCV-7 given 2 months apart, followed > 2 months later by a dose of PPV-23.
· Older children and adults should receive the PPV23. (These recommendations may change as more safety and efficacy data becomes available in older patients.)
· A booster PPV23 should be given approximately 5 years after the initial vaccine/series.
· Quadrivalent conjugated meningococcal vaccine should be given to all asplenic individuals > 2 years of age. (Also subject to change as new vaccines become available)
· Hemophilus influenza vaccine should be given once to all individuals > 2 years of age and at the time of routine vaccination for younger children.
The issue of antibiotic prophylaxis in these patients is controversial for several reasons. The risk of disease, while lifelong is variable, depending on the factors listed above. The only regimen which has been studied is penicillin prophylaxis for patients with functional asplenia from sickle cell anemia. Resistance to penicillin (and other antibiotics) is a growing concern, so it’s efficacy is currently presumed to be lower. In addition, compliance with an indefinite daily regimen is extremely difficult. The patients who are most likely to benefit from prophylaxis are:
· Children < 5 years of age,
· Individuals who have had splenectomy within the past year,
· Those with an underlying immunodeficiency in addition to splenectomy
Regimens for children: (though there is limited data re: efficacy in the current era of increasing pneumococcal resistance)
· Penicillin G: Pediatrics: 250 mg. p.o. b.i.d. (less than 5 years, 125 mg. p.o., b.i.d.)
· Alternatives: Amoxicillin: Pediatrics: 20mg/kg/day divided b.i.d.
· As there are currently no ideal second line oral agents, allergy to the penicillins should be assessed carefully.
No data are available in adults and antibiotic prophylaxis is generally not recommended this population. As always, patients need to be evaluated on an individual basis.
· Be sure that patients understand the need for prompt medical evaluation for all febrile illnesses
· Patients who do not have rapid access to medical care should be advised to develop resources for the local availability of appropriate antibiotics.
· Patients need to be aware of the increased risk posed by dog bites, and tick and mosquito bites in areas endemic for babesia and malaria respectively.
The adult and pediatric infectious disease services remain available to assist with individualizing patient-specific issues.