Infection in splenectomized sickle cell disease patients

[Splenic dysfunction in sickle cell disease: An update]

The spleen filters blood cells and contributes to the immune defense. The red pulp clears the blood from altered red blood cells via its unique microcirculatory network ; while the white pulp is a secondary lymphoid organ, directly connected to the bloodstream, whose specificity is the defense against encapsulated bacteria through the production of "natural" IgM in the marginal zone. Various health conditions can cause acquired impairment of the splenic function (or hyposplenism) directly and/or through therapeutic splenectomy. Hypo/asplenia is complicated by an increased susceptibility to encapsulated germ infections, but an increased risk of thrombosis and pulmonary hypertension has also been reported after surgical splenectomy. Homozygous sickle cell disease is the most common disease associated with functional asplenia. The latter appears early in childhood likely through repeated ischemic alterations caused by the sickling of red blood cells. In addition, specific complications such as hypersplenism and acute splenic sequestration can occur and may be life-threatening. We provide here an update on the role and physiology of the spleen, which will allow a better understanding of the pathophysiology of spleen damage and its consequences in sickle cell disease.

Risk of infection and death among post-splenectomy patients

OBJECTIVES

The true incidence of post-splenectomy sepsis remains undetermined.

METHODS

An English literature review on post-splenectomy sepsis was undertaken by means of databases of MEDLINE for the period 1966-96. The data registered included age at splenectomy, indication for splenectomy, incidence of infection and death, interval between splenectomy and infection, and microbial aetiology.

RESULTS

The reports include 19 680 patients having undergone splenectomy with a median follow up of 6.9 years. The incidence of infection after splenectomy was 3.2% and the mortality rate was 1.4%. Only 6942 reports were sufficiently detailed to allow useful analysis. The incidence of infection among children and adults was similar, 3.3% and 3.2%, respectively. However, the death rates among children were higher than adults (1.7% vs. 1.3%). The incidence of infection was highest among patients with thalassemia major (8.2%), and sickle-cell anaemia (7.3%). The highest mortality rates were observed among patients with thalassaemia major (5.1%), and sickle-cell anaemia (4.8%).

CONCLUSION

The incidence of sepsis among post-splenectomy patients is low, however, it carries a high mortality rate especially among children with hematological disorders.

Duration of penicillin prophylaxis in sickle cell anemia: issues and controversies

Functional asplenia occurs in 94% of patients with homozygous sickle cell anemia by 5 years of age and may result in fatal septicemia due to encapsulated microorganisms such as Streptococcus pneumoniae. Penicillin prophylaxis in these patients significantly reduces the risk of septicemia; however, continuation of prophylaxis beyond 5 years of age is controversial, since the risk of developing septicemia is reduced after this age and prolonged prophylaxis may lead to emergence of penicillin resistance. Although reports of penicillin-resistant pneumococci in patients receiving penicillin prophylaxis are conflicting, the prevalence of these organisms in the general population in North America increased from 5% in 1989 to more than 35% in 1997. Discontinuation of prophylaxis after age 5 years may be recommended because of lack of benefit, difficulty maintaining compliance, reduced risk of developing pneumococcal bacteremia after that age, and increase in prevalence of penicillin-resistant pneumococci worldwide.

Surgical management of children with hemoglobinopathies

Sickle hemoglobinopathies include sickle cell disease, sickle-C disease, and sickle-beta thalassemia. Patients with these disorders commonly suffer a multitude of destructive events to vital organs, especially to the central nervous system, the spleen, the kidney, the lung, and the heart as a result of microvascular plugging by the sickled erythrocytes. Thoughtful preparation for anesthesia and operation, especially when directed by experienced individuals, can greatly reduce the hazard of inducing the sickle crises that formerly plagued individuals with sickle hemoglobinopathies who faced major operations under general anesthesia. The patient must be free of any acute illness, especially one involving the respiratory system. Adequate hydration preoperatively combined with avoiding perioperative hypoxia, hypothermia, and acidosis, the triggers for sickling, will go far toward avoiding sickle-induced complications. Modern transfusion therapy, consisting of multiple small transfusions of Hb A erythrocytes administered over several weeks prior to the operation, not only corrects the chronic anemia but suppresses erythropoiesis of cells containing Hb S in the patient's bone marrow and leaves him or her with a majority of cells containing Hb A. This provides a safety net in case a sickle-inducing insult occurs despite the best efforts to avoid one. Individuals with sickle hemoglobinopathies may require any of the operations common to all children, for example, herniorrhaphy, appendectomy, tonsillectomy, and circumcision, but a significant number will develop calcium bilirubinate cholelithiasis and possibly cholecystitis as a result of the continual increased load of bile salts resulting from the shortened lifespan of the cells containing Hb S. Also, although most individuals with Hb S will gradually suffer splenic infarction by late childhood, a significant number of infants will experience acute splenic sequestration crisis, a life-threatening entity, the recurrence of which is prevented by splenectomy. Several publications have demonstrated that such surgical procedures can be performed in large numbers of patients with sickle hemoglobinopathies without deaths and with minimal morbidity.

Acute splenic sequestration crisis in sickle cell disease: early detection and treatment

Acute splenic sequestration crisis (ASSC) in children with various forms of sickle cell disease can result in life-threatening circulatory collapse due to the loss of circulating blood volume. Over a 6-year period we have treated 12 patients ranging in age from 5 1/2 months to 7 years presenting with acute sequestration crisis. Eleven had homozygous sickle cell disease and the other had sickle-thalassemia. One patient died of acute circulatory collapse. Eight patients underwent splenectomy after a major episode of sequestration with no serious infectious complications up to 5 years following splenectomy. Three patients with minor episodes have been followed with no recurrences. To foster early detection of this potentially lethal complication of sickle cell disease, an educational program in our Comprehensive Sickle Cell Center instructs the parents to examine the spleen and bring their child in for evaluation if the spleen enlarges. A newly developed videotape describes the common symptoms of ASSC and illustrates the technique of palpating the spleen. With early detection of sickle cell disease by neonatal screening and the educational program, the morbidity and mortality from this complication of sickle cell disease can be reduced.

Long-term management of splenic sequestration in children with sickle cell disease

We describe our experience with 23 children with sickle cell disease and splenic sequestration crisis, emphasizing our management approaches and the patients' subsequent clinical courses. Our data illustrate that sequestration crisis may occur despite a reduction in hemoglobin S concentration to less than 30% of the total hemoglobin mass. In addition, the risk of recurrent splenic sequestration was similar for patients who received transfusion therapy and for those who were simply observed. We conclude that a short-term transfusion program to prevent recurrent splenic sequestration is of limited benefit.