Heterotopic splenic autotransplantation in prevention of overwhelming postsplenectomy infection.

An experimental study was undertaken to evaluate the protective effect of heterotopic splenic autotransplantation in weanling rats. Rats were divided into three experimental groups: splenectomy, control, and splenic autotransplantation. Rats were challenged with i.v. type I pneumococcus. Bacterial bloodstream clearance and survival were determined. Splenic bacterial uptake was measured by determining the isotopic activity of technetium-99m-labeled pneumococci. Autoradiographs and material stained with hematoxylin and eosin and Gram strains were examined for histologic features. All autografts survived and were histologically compatible with normal splenic tissue. Bloodstream clearance of pneumococci was significantly greater in rats with splenic autotransplantation. Splenic autografts had 10 to 30 times greater uptake of pneumocci than did the liver. Rats with autotransplantation had a prolonged survival time. Heterotopic splenic autotransplantation may prove to be an important adjunctive surgical measure in the treatment of children undergoing splenectomy.     

Infectious Sequelae in the Use of Polyglycolic Acid Mesh for Splenic Salvage with Intraperitoneal Contamination

Salvage of the injured spleen is important in the trauma patient. Loss of the spleen can result in both early and late infectious complications due to immunologic and phagocytic deficits. Splenic salvage techniques include the use of polyglycolic acid (PGA) mesh to wrap and tamponade the damaged and bleeding spleen. However, the use of mesh may increase the incidence of infection in the presence of intraperitoneal contamination. We examined whether mesh in the contaminated field increases the infection rate compared to splenectomy in a murine model. Sixty male Sprague–Dawley rats were divided into three groups of 20 each: splenectomy, splenic wrap with PGA, and control (with splenic mobilization). All rats were subjected to a standard inoculum of enteric bacteria at the time of celiotomy. Sixteen (80%) of the splenectomy rats, 10 (50%) of the PGA mesh wrapped rats, and four (20%) of the control rats expired (P< 0.5). In surviving rats, necropsy at 7 days demonstrated abscess formation in all four (100%) of splenectomy, four of 10 (40%) in PGA mesh wrapped, and two of 16 (13%) of control rats. All of the abscesses in the wrap group involved the mesh. Overall infection rates (including fatal peritonitis, abscess formation, and empyema) were 100% for splenectomy, 75% for PGA mesh wrapped, and 30% for control rats (P< 0.05). We conclude in this experimental model that the use of PGA mesh wrap does increase susceptibility to infection, but much less so than splenectomy in the presence of intraperitoneal contamination.     

Relative merits of partial splenectomy, splenic reimplantation, and immunization in preventing postsplenectomy infection.

Partial splenectomy, splenic autotransplantation, and immunization with pneumococcal vaccine have been reported to protect patients against overwhelming postsplenectomy infection, and this study was undertaken to evaluate these therapeutic alternatives. For this purpose 136 rats were divided into experimental groups: 34 controls, 34 splenectomy, 34 partial splenectomy, and 34 splenic autotransplantation animals. Five weeks after operation, two-thirds of the animals were immunized with killed pneumococci. The effects of operation and immunization were studied by challenging the animals intravenously with pneumococci. Pneumococcal antibody titers were determined, and phagocytic uptake of pneumococci by the spleen and liver was measured. Immunization impressively increased the survival rate in all groups. At low-challenge doses autotransplantation prolonged survival. At higher-challenge doses only partial splenectomy increased survival. Partial splenectomy and control animals had higher antibody titers than did splenectomy and autotransplantation rats. Animals with the highest antibody titers had the greatest splenic and hepatic phagocytic uptake of pneumococci. Partial splenectomy was more efficient in removing pneumococci than was autotransplantation. Thus immunization is one of the most important factors contributing to survival after splenectomy. Partial splenectomy is preferable to splenic autotransplantation because it is associated with higher antibody titers after immunization, better pneumococcal splenic uptake, and improved survival rates.     

Role of the liver in host defense to pneumococcus following splenectomy

Splenectomy is associated with increased susceptibility to bacterial infection, and this is thought to be primarily due to a decrease in clearance of bacteria from the blood. The purpose of the present study was to determine if splenectomy could increase susceptibility to pneumococcus type 3, which is cleared primarily by the liver in rats, and if hepatic function is altered by splenectomy. Splenectomy increased the mortality of rats challenged iv with pneumococcus. Heat-killed, 51Cr-labeled pneumococci were rapidly cleared by the liver and splenectomy did not alter the initial clearance rate or the initial hepatic uptake of bacteria. Injection of viable pneumococci showed that blood levels were unchanged at 30 min but were much greater 5 hr after challenge in splenectomized animals. Hepatic uptake of viable pneumococcus was also not changed at 30 min after injection but at 5 hr the number of bacteria in the liver was greater in the splenectomized animals. This suggests an impairment in hepatic bactericidal function. Another contributing factor may have been that the hepatic bactericidal capacity was overwhelmed by the pneumococci which would normally have been killed by the spleen. Lung localization of viable bacteria was increased initially but there was no decrease in pulmonary bactericidal function. Thus, splenectomy increased susceptibility to a bacteria cleared primarily by the liver which was attributed to an impairment of hepatic bactericidal function and/or an inability of the liver to compensate for the loss of splenic function due to a saturation of the bactericidal system.     

Overwhelming pneumococcal infection in rats immediately after splenectomy

A rat model was used to evaluate the possibility that a nonspecific factor of splenic origin, promoting opsonization and/or antibody production, could affect the susceptibility to pneumococci after splenectomy. Streptococcus pneumoniae type 1 4 × 10³ CFU was injected intravenously in Sprague-Dawley rats. In Experiment I, two groups of previously splenectomized rats (15 at 7 weeks and 15 at 14 weeks of age) were challenged with pneumococci at the age of 15 weeks. All these rats succumbed with no difference in survival time between the two groups. In contrast, the entire control group of 10 nonsplenectomized (sham-operated) rats challenged peroperatively with pneumococci survived. In experiment II, 62 animals were divided into two equal groups. One group was splenectomized when 9 weeks old, and the other was subjected to omental resection (sham operation) at the same time. Two weeks later splenectomy was performed on previously oment-resected animals and the remaining animals were sham-operated. At the second operation all animals were challenged with pneumococci. In each group 74% died and survival times did not show any difference between the two groups. In experiment III splenectomy was performed on 37 9-week-old rats. Two weeks later 20 of these were subjected to omental resection, and in the remaining 17, intraabdominal deposition of homologous dispersed splenic tissue was carried out. Peroperatively, pneumococci were injected intravenously. No difference between the two groups as regards mortality rate or survival times was registered. These experiments revealed no factor remaining briefly after splenectomy that could affect the susceptibility to intravenous injection of Streptococcus pneumoniae type 1.     

Assessment of post-splenectomy residual splenic function. Splenic autotransplants

Splenectomy increases the risk of fulminant sepsis. The present study assesses residual splenic function in patients splenectomized due to traumatic rupture of the spleen; and six cases with splenic autotransplants. Splenic tissue was observed in only 48% of the splenectomized patients and 100% of the autotransplant cases. The two most reliable analytical parameters to assess the presence of functional splenic tissue, were the absence of Howell-Jolly bodies and normal IgM blood levels. In cases where total splenectomy is indicated, it has proved useful to perform autotransplantation of splenic tissue at omentum major level.     

The effects of splenectomy and splenic implantation on alveolar macrophage function

The effect of splenectomy on the ability of alveolar macrophages of young and adult rats to phagocytize Pneumococci, Types 3 and 14, and Pseudomonas aeruginosa was studied. Young animals showed a significant (15%) decrease in the phagocytosis of pneumococci type 14, 4 weeks after splenectomy. This depression increased to 30% in 6 weeks' time. Such depression was also noted when young splenectomized rat alveolar macrophages were challenged with Pseudomonas aeruginosa but not with type 3 pneumococci 6 weeks postsplenectomy. Three months following splenectomy in young animals, the rats were grown and they seemed to regain their normal phagocytic activity against pneumococci type 14. Adult rats also showed no alteration in their phagocytic activity against type 3 pneumococci. Autoimplantation of the spleen had a protective effect on the phagocytosis of type 14 pneumococci, and a nonsignificant effect on that of type 3. The present study postulates a modulatory role of the spleen on alveolar macrophage function. Splenectomy may cause the impairment of local lower respiratory immune function, making lungs vulnerable to specific bacterial invasion. Such splenic modulatory effect on alveolar macrophage phagocytic function seems to be age and antigen specific.     

Intraportal splenic autotransplantation in rats: Feasibility and effectiveness

This experiment was designed to see whether or not normal host resistance to infection could be reestablished in splenectomized animals by intraportal autotransplantation of homogenized splenic tissue. Part I studied the feasibility of the technique. Within 1 hr of splenectomy, 16 adult Lewis rats received an intraportal injection of autogenous splenic tissue which had been passed through a 500-μm screen. Five rats died acutely from hemorrhage at the site of injection. The others tolerated the infusion well, both acutely and chronically. The animals developed only transient elevations in liver enzymes; chronic portal hypertension did not occur. Histologically, splenic tissue could be demonstrated within terminal portal venules. Part II assessed the effectiveness of intraportal splenic autotransplantation. Eight to twelve months after splenectomy, autotransplantation, or sham operation, 103 Sprague-Dawley rats were challenged with intravenous boluses of 10⁵ to 10⁸ pneumococci. Mortality was 91% for splenectomized animals, 88% for animals bearing autotransplants, and 59% for controls. Thus intraportal splenic autotransplantation is technically feasible in rats. The grafts are well tolerated by the liver, and splenic tissue is preserved in intimate contact with the blood stream. Even after 8 to 12 months, however, such autografts are not capable of providing normal protection against massive pneumococcemia.     

Increased susceptibility to pulmonary infection in alloxan diabetic mice

Pulmonary infections in diabetics have received little attention clinically or experimentally despite an impression that diabetics are more prone to pulmonary infections and do poorly with these and all infections. In a mouse model, aerosolized pneumococci were used in order to mimic the natural portal of entry of pneumococci, to investigate susceptibility to pneumococcal infection in alloxan diabetic and normal mice, and to test the hypothesis that insulin therapy would have a protective effect. When exposed to an aerosol created from 10⁸ type III Streptococcus pneumoniae (PnIII)/ml, nondiabetic mice had a higher survival rate than uncontrolled diabetic mice (P < 0.001) and insulin-treated diabetic mice (P < 0.001). Insulin-treated diabetic mice had a significantly decreased death rate compared to untreated diabetic mice (P < 0.05). The data show that alloxan diabetic mice are more likely to succumb to infection from aerosolized pneumococci than are normal mice. Insulin therapy appeared to decrease this susceptibility. A possible clinical inference is that insulin therapy is beneficial in diabetic patients with pulmonary infections.     

Regeneration of splenic remnants after partial splenectomy in rats

Splenic regeneration in the rat was measured after removal of 25, 50, or 75% of the spleen, 50% of the spleen with autotransplantation of the excised portion, and splenectomy with autotransplantation of 50% of the spleen. Splenic growth in rats undergoing sham splenectomies served as a control. Splenic mass at 6 weeks and 4 months after surgery was directly related to the remnant size. “Normalized” spleen weights (measured as grams of splenic tissue per 100 grams of rat weight) after 25, 50, and 75% splenectomy were 57, 41, and 38% of controls at 6 weeks, and 77, 71, and 44% of controls at 4 months. All differences were significant at P < 0.03 except those between 50 and 75% splenectomy at 6 weeks, and between 25 and 50% splenectomy at 4 months. A comparison of autotransplanted splenic mass after total splenectomy with that after 50% splenectomy (0.042 ± 0.005 and 0.025 ± 0.004, respectively, at 6 weeks) demonstrated that an intact subtotal spleen inhibited significantly regeneration of the autotransplanted spleen. The effect of autotransplanted splenic tissue on regeneration of a splenic remnant was little to none at 4 months.     

Autotransplantation of splenic tissue after splenectomy in rats offers partial protection against intravenous pneumococcal challenge

Thirty-six splenectomized Sprague-Dawley rats with omental implants of splenic tissue were challenged with intravenous pneumococci. The mortality rate in this group was compared to 31 similarly challenged splenectomized and 28 normosplenic rats. The results showed that while rats with implanted splenic tissue had a better survival rate (p = 0.04) than splenectomized rats, their survival was poorer than that of rats with normal spleens (p = 0.02) (Fischer's exact test).     

Pulmonary antipneumococcal defenses after hemisplenectomy

Conservative splenic surgery such as partial splenectomy is advocated for splenic injuries, since splenectomy predisposes individuals to overwhelming sepsis with encapsulated organisms, of which Streptococcus pneumoniae is the most frequently isolated. The respiratory route is argued to be the most likely portal of entry of pneumococci; however, little data exist on the interaction of the spleen and pulmonary defense mechanisms against pneumococcal invasion. We studied the effect of splenectomy, 50% splenectomy (hemisplenectomy), 25% splenectomy, and sham operation on in vivo clearance of live pneumococci from the lungs of male CD-1 mice following an aerosol challenge of pneumococci. Splenectomy impaired pneumococcal clearance from mouse lung pairs and allowed for increased translocation of live pneumococci to tracheobronchial lymph nodes compared to sham-operated controls. Preservation of splenic mass by partial splenectomy improved lung clearance and allowed for fewer bacteria to be cultured from tracheobronchial lymph nodes compared to splenectomized animals. Clearance of live pneumococci from the lungs and survival were directly proportional to the amount of splenic tissue remaining. Splenic factors probably exist which regulate reticuloendothelial cell function throughout the host. Maintaining adequate splenic mass, therefore, is an important consideration when operating for splenic trauma.     

The effect of site and technique of splenic tissue reimplantation on pneumococcal clearance from the blood

The technique and site of reimplantation of splenic tissue influences survival of laboratory animals following intravenous injection of pneumococci. Splenic tissue was prepared by slicing, mincing, or grating the spleen. The tissue was placed subcutaneously, intraperitoneally, retroperitoneally, or in an omental pouch. This study was designed to determine the rate of pneumococcal clearance from the blood stream 16 weeks following splenic reimplantation by four different methods. All animals were challenged with an intravenous 1 mL bolus containing 10(7) bacteria. The New Zealand white rabbits were divided into six groups: intact spleen; splenectomized; spleen slices in an omental pouch; minced spleen in an omental pouch; splenic tissue implanted subcutaneously; and bits of spleen dropped into the peritoneal cavity. Animals with an intact spleen and those with spleen slices implanted into an omental pouch cleared bacteria during the first hour and all bacteria had disappeared at three hours. Bacteremia persisted longer than three hours in the other groups. Splenic tissue had regenerated in all animals with omental pouch implants, in four of six with minced spleen dropped into the peritoneal cavity but in only one with a subcutaneous implant. Reimplanted splenic tissue clears pneumococci from the blood stream best when thin slices of spleen are placed in an omental pouch. This technique also assures successful regeneration of splenic tissue.     

Implications in the burn neutrophil of serum and cellular zinc levels

A parabolic correlation between leukocyte zinc content and phagocytic capacity apparent in clinical studies has been tested in a rat model. Dietary zinc restriction decreased average serum zinc levels from control values of 1.65 ± 0.41 to 0.70 ± 0.28 μg/ml during the first 13 weeks of restriction (P < 0.0005) and to 0.56 ± 0.23 μg/ml during the second 13 weeks (P < 0.0005). A parabolic variation in latex phagocytosis was observed in rat neutrophils during 33 weeks of zinc restriction. During study Weeks 12 through 21 a trend toward improved neutrophil antibacterial activity corresponded with a period of increased phagocytic activity in zinc-deficient rats. After Week 27 an opposite trend of impaired antibacterial activity corresponded to significantly decreased phagocytosis relative to controls (P < 0.0005). This study suggests that acquired neutrophil functional defects may be corrected by replacement of specific nutritional components.     

Inefficient substrate utilization: A mechanism of cachexia in cancer

Definition of mechanisms of cachexia and inanition in cancer should improve treatment. To determine the interrelationships between tumor substrate metabolism, caloric intake, and body weight, 24 Buffalo rats were studied. Twelve rats had Morris 7777 tumors implanted and twelve were controls. Animals had daily weights and rat chow intake measured. When tumor-bearing animals lost significant weight (P < 0.05, t test), they were sacrificed with a control animal. The liver from experimental and control animals and the hepatoma from the thigh were excised, homogenized, and mitochondria were isolated. The adenosine diphosphate (ADP)-stimulated respiratory activity (state 3) and ADP-independent respiratory activity (state 4) of mitochondria were determined. The Respiratory Control Index (RCI) was calculated as the most sensitive indicator of mitochondrial oxygen-substrate metabolism. Tumor-burdened rats and controls had statistically equivalent chow consumption (P > 0.05). Tumor mitochondria demonstrated reduced rates of state 3 and state 4 oxygen consumption and RCIs were statistically less than control liver tissue (P < 0.05). From these data we conclude: (1) weight loss in this tumor model is not due to inadequate intake; (2) hepatoma mitochondria are inefficient in use of substrates; and (3) exhaustion of substrates in an inefficient manner may contribute to the catabolism of cancer.     

The effect of protein deficiency on growth and response of primary and metastatic hepatoma

Although protein-energy malnutrition is common in the cancer patient, the efficacy of aggressive nutritional therapy is unclear. This study evaluates the effects of protein deficiency on tumor growth, response, and chemotherapy complications in primary and metastatic rat hepatoma. Seventy-two ACI rats (200–250 g) with implanted Morris hepatoma were divided into four groups (N = 18 for each group): 1, regular diet; 2, regular diet plus cyclophosphamide (CPM) (100 mg/kg/ip); 3, protein-free diet; and 4, protein-free diet + CPM. Forty additional rats in similar groups (5–8, ten in each group) underwent intravenous injection of 6 × 10³ tumor cells to produce pulmonary metastases. Animals were assessed for survival, tumor size, serum albumin, number of pulmonary metastases, and hemorrhagic cystitis at 2 weeks. Survival was 50% in groups 4 and 8, and 100% in the others. Serum albumin was significantly lower in rats on protein free diets (2.59 ± 0.37 vs 3.35 ± 0.40 g%, P < 0.01). Tumor volume was significantly reduced by CPM (26.0 ± 4.2 cm³ vs 1.2 ± 0.4 cm³, P < 0.01). Protein-free diets resulted in lower total body weight, and reduced tumor volume without, but not with CPM (14 ± 1.6 cm³P < 0.05, 1.1 ± 0.3 cm³, P < 0.05 vs above controls). CPM reduced the number of pulmonary metastases in regular diet groups (307.2 ± 108.3 vs 36 ± 11, P < 0.01), while protein free diets did not significantly affect metastases, without or with CPM (251.7 ± 71.4 and 22.3 ± 12.4, P > 0.05 vs controls). Hemorrhagic cystitis was much more common in protein free groups compared to rats on regular diets (55 vs 11%, P < 0.01). These data indicate that protein deficiency did not affect response to chemotherapy in a primary or metastatic rat hepatoma model. However, protein deficiency results in a significantly increased rate of mortality, weight loss, and hemorrhagic cystitis which may lead to delay or cessation of cancer therapy.     

Splenic resection or heterotopic transplantation of splenic tissue as alternatives to splenectomy. Regeneration and protective effect against pneumococcal septicemia

In 82 male Sprague-Dawley rats, divided into eight groups according to surgical procedure performed (total splenectomy, sham operation and six different modes of splenic conservation), resistance to intravenous injection of 4 X 10(3) CFU of Streptococcus pneumoniae type I was evaluated 16 weeks after the surgical procedures. Significant regeneration of the spleen and almost normal resistance to pneumococci was seen 16 weeks after a two-thirds resection. Pieces of the spleen, implanted subcutaneously or into the greater omentum, also showed marked regeneration; though survival time was prolonged, the mortality among these animals following injection with pneumococci did not, however, differ from that of totally splenectomized animals. Dispersed splenic tissue, injected subcutaneously, intramuscularly, or retroperitoneally, showed less sign of regeneration and had no effect on mortality or survival time in partially vis-à-vis totally splenectomized rats.     

The impact of splenic artery embolization on the management of splenic trauma: an 8-year review

Background

Splenic artery embolization (SAE) is an adjunct to nonoperative management (NOM) of splenic injuries. We reviewed our experience with SAE to identify its impact on splenic operations.

Methods

Patients admitted with splenic injuries over an 8-year period were identified and the initial method of management noted (simple observation, SAE, or splenic surgery). The first 4 years (period 1) during which SAE was introduced was compared with the latter 4 years (period 2) when it was used frequently.

Results

There were 304 patients in period 1 and 416 in period 2. NOM was initial management in 59.9% in period 1% and 60.1% in period 2 (P = 1.0) and failure rates were 5.3% versus 2.9%, respectively (P = .12). More SAE procedures were performed in period 2—13.7% versus 4.9% (P ≤.001)—and there was a reduction in the proportion of splenic operations—35.2% versus 26.2% (P <.01).

Conclusions

SAE is associated with a reduction in splenic operations, although it did not alter the failure rate of NOM.     

Comparison of omental splenic autotransplant to partial splenectomy. Protective effect against septic death

The possible benefit of either partial splenectomy or splenic autotransplantation as protection against post-splenectomy sepsis was investigated. Sprague-Dawley rats were challenged with intravenous Streptococcus pneumoniae and the incidence of bacteremia and mortality were recorded. Animals were divided into four groups based upon the amount of splenic tissue conserved: total splenectomy (0%), partial splenectomy (62%), splenic autotransplantation (27%), or sham celiotomy (100%). A statistically significant (P 0.05) decrease in the incidence of septic death was seen in comparing the total splenectomized animals (63%) to the autotransplant group (27%), the partial splenectomy (4%) and the control group (4%). This diminishing mortality is inversely proportional to the amount of splenic remnant in the respective groups. There was a similar, parallel relationship in the incidence of Streptococcus pneumoniae bacteremia. Thus, the greater the amount of remaining splenic tissue, the lower the incidence of bacteremia and subsequent mortality, implying the preservation of immunologic function with splenic conservation.     

Serum antibody responses to pneumococcal vaccine after splenic autotransplantation

Immunization with pneumococcal capsular polysaccharide vaccines is advocated after splenectomy; however, experimental and clinical data suggest an impaired antibody response in splenectomized individuals. This study examined the value of splenic autotransplantation at various sites in augmenting the antibody response to Type III pneumococcal capsular polysaccharide in mice immunized 3 months after operation. Splenectomy resulted in impaired antibody responses compared to sham-operated mice (p less than 0.001) using an enzyme-linked immunosorbent assay. Mice with intraperitoneal splenic autotransplants, but not mice with subcutaneous or intramuscular transplants, had greater antibody responses compared to splenectomized mice (p less than 0.05). Antibody responses were elevated only in mice autotransplanted with 50% or more of the original splenic mass. Since autotransplantation of splenic tissue augments the antibody response to pneumococcal capsular polysaccharides, the combination of splenic autotransplantation and pneumococcal vaccination may confer more protection than either modality alone in individuals who must undergo splenectomy.