A multidisciplinary approach to hemodialysis access: prospective evaluation.

Dialysis access procedures and complications represent a major cause of morbidity, hospitalization and cost for chronic dialysis patients. To improve outcomes and reduce the cost of hemodialysis access procedures we developed a multidisciplinary approach, involving nephrologists, access surgeons, and radiologists. A full-time dialysis access coordinator scheduled all access procedures with the surgeons and radiologists, and tracked outcomes. A computerized database was developed for prospective documentation of procedures and complications. Confidential, detailed analyses and recommendations for improvements were provided periodically to the surgeons and radiologists. The major changes arising from the multidisciplinary approach were as follows: (1) The approach to clotted grafts evolved from an inpatient surgical procedure to an outpatient radiologic procedure. The immediate technical success rate of graft declots increased from 48% to 69%. (2) Elective placement of arteriovenous (A-V) grafts evolved from a three-day inpatient hospitalization to a largely outpatient procedure. The proportion of A-V grafts placed as same day surgery or outpatient surgery increased from 16% to 81%. (3) Surgical complications of new A-V graft surgery decreased from 25% to 11%. (4) Aggressive detection and correction of graft stenosis decreased the incidence of graft thrombosis by 60%, from 0.70 to 0.28 events per patient-year. (5) The proportion of native A-V fistula construction in new dialysis patients increased from 33% to 69%. In conclusion, an integrated multidisciplinary approach markedly reduced surgical complications of access surgery and decreased access failures. These improvements occurred despite a marked decrease in hospitalization for access procedures, with a substantial cost saving.

Molecular conjugate-mediated gene transfer into isolated human and transplanted rat kidneys.

Technically, renal transplantation has been feasible for over four decades. However, immunological injury to the transplanted kidney continues to be the leading cause of graft loss. While current immunosuppressive protocols yield a 1-year graft survival of > 90%, the trade off is increased risks from nephrotoxicity to manifestations of long-term immunosuppression. We have developed techniques which would allow genetic manipulation of the donor kidney while utilizing current procurement and preservation protocols.

Molecular conjugate-mediated gene transfer into isolated human kidneys.

Advances in systemic immunosuppressive therapy for solid organ transplantation have done little to decrease the percentage of allografts that eventually will develop chronic rejection. However, one of the promises of modern molecular biology includes the ability to introduce new genetic information into mammalian hosts. The ability to deliver genes and control their expression in the adult kidney has been described in appropriate animal models. Consequently, gene transfer technology represents a realistic therapeutic approach to modify the allogeneic kidney before engraftment in an effort to decrease the incidence of posttransplant dysfunction. To bridge the gap between animal studies and the clinical application of this technology, we report the first genetic transfection of isolated human kidneys under conditions of organ preservation. Polymerase chain reaction, reversed transcription polymerase chain reaction, and in situ hybridization techniques demonstrated that an adenovirus-polylysine-deoxyribonucleic acid (DNA) complex can be used to insert a complementary DNA expression vector encoding beta-galactosidase into the intact human kidney. Immunohistochemical and in situ enzymatic analyses determined further that gene delivery and expression were localized in proximal tubular epithelial cells. Consequently, targeting of genes to perturb mediators of the local inflammatory response may represent a rational therapeutic interventional strategy in chronic rejection of the kidney.

Thromboxane synthetase inhibition and thromboxane receptor blockade preserve pulmonary and circulatory function in a porcine burn sepsis model.

BACKGROUND: Thromboxane A2 (TxA2) is a key mediator in the pathophysiology of severe burns and sepsis. This study was performed to assess the potential benefits of TxA2 synthetase inhibition and TxA2 receptor blockade in sepsis after severe thermal injury. STUDY DESIGN: Pigs with left atrial, aortic, and pulmonary artery catheters received a 40 percent third-degree burn and, 24 hours later, 100 micrograms per kg Escherichia coli endotoxin. The antagonist treatment (BM) group was treated with the TxA2 receptor antagonist BM 13.177, the synthetase treatment (OKY) group with the TxA2 synthetase inhibitor OKY-046, and the control group received saline solution placebo. Another group without burn or endotoxin was used to assess the side effects of BM 13.177. RESULTS: Both drugs significantly attenuated the changes in pulmonary vascular resistance index, cardiac index, arterial PO2, shunt, oxygen delivery, and oxygen consumption seen after endotoxin. However, cardiac index was significantly decreased in group BM before endotoxin. In healthy pigs, BM 13.177 decreased cardiac index and oxygen delivery and increased the pulmonary vascular resistance index. CONCLUSIONS: TxA2 synthetase inhibitors and TxA2 receptor blockers are potentially useful in sepsis after severe burns. Comparison between drugs was complicated by the adverse effects of the antagonist, and further investigation with other antagonists is needed.

Postburn gastrointestinal vasoconstriction increases bacterial and endotoxin translocation.

Splanchnic ischemia has been associated with bacterial translocation and increased endotoxin absorption from the gut. To study the effects of major burn on splanchnic circulation, minipigs were randomized to receive 40% flame burn and Parkland resuscitation or sham burn and maintenance fluids. Total and fractionated blood flow, O2 delivery and consumption, mucosal pH of the intestine, and endotoxin levels in the superior mesenteric vein were measured for 48 h, and then abdominal organs were harvested for bacteriological culture and histopathological analysis. Total mesenteric blood flow and fractionated blood flow to the mucosa-submucosa of the jejunum, cecum, and colon decreased 2 and 4 h postburn. Although mesenteric O2 consumption was unchanged, mesenteric O2 delivery and intestinal mucosal pH were decreased during the early postburn period. Concomitantly, endotoxin levels in the superior mesenteric vein were significantly elevated during the first 8 h postburn. The bacteriological cultures of the systemic tissue samples showed increased bacterial translocation in the burn group. After major burns, there is a transient selective splanchnic vasoconstriction, which is associated with intestinal mucosal acidosis and increased incidence of bacterial translocation and endotoxin absorption from the gut.

Bacterial translocation after thermal injury.

OBJECTIVES: To review the mechanisms responsible for bacterial translocation after thermal injury. Areas investigated were the rate of bacterial translocation, blood flow to the gastrointestinal tract, potential of reversibility of mesenteric vasoconstriction, specific vasomediators responsible for postburn mesenteric vasoconstriction, potential reversal of gut mucosal atrophy with decreased translocation, and evidence of gut mucosal damage after thermal injury. DESIGN: Using three different animal models consisting of rats, sheep, and minipigs, the objectives were defined. Using the sheep model, the relationship of decreased mesenteric blood flow after thermal injury was defined along with rates of translocation, and the potential reversibility of the postburn mesenteric vasoconstriction and its effect on translocation. The effect of smoke inhalation and the combination of thermal injury and inhalation injury on rates of translocation are explained. Using minipigs, the role that thromboxane A2 plays on the postburn mesenteric vasoconstriction was defined by blocking thromboxane A2 synthesis with OKY046, a specific thromboxane synthetase inhibitor. Evidence of gut mucosal injury was determined using ornithine decarboxylase as an indicator of gut mucosal damage and subsequent repair in the minipig model. The rat model was used to demonstrate gut mucosal atrophy after thermal injury and the potential for reversal of atrophy with the use of bombesin, a specific gut mucosal growth stimulator. RESULTS: After thermal injury, there were significant decreases in mesenteric blood flow. There was also an increase in bacterial translocation. Selective infusion of nitroprusside into the cephalic mesenteric artery prevented the post-burn mesenteric vasoconstriction and attenuated bacterial translocation. Smoke inhalation and smoke inhalation with thermal injury resulted in mesenteric vasoconstriction and increased rates of bacterial translocation. OKY046 infusion prevented the postburn increase in mesenteric vascular resistance. There were increased concentrations of ornithine decarboxylase within the colonic mucosa, indicating a previous injury and the presence of ongoing repair. Likewise, there was gut mucosal atrophy after thermal injury with bacterial translocation. Treating with bombesin attenuates the postburn mucosal atrophy and prevents bacterial translocation. CONCLUSIONS: Thermal injury is associated with mesenteric vasoconstriction. This postburn mesenteric vasoconstriction results in damage to gut mucosa and allows for increases in bacterial translocation. The postburn mesenteric ischemia can be ameliorated with nitroprusside infusion, thus preventing translocation. Thromboxane A2 appears to be a major mediator of the postburn decrease in mesenteric blood flow. Likewise, prevention of postburn gut mucosal atrophy with bombesin attenuates bacterial translocation.

Effects of hypertonic saline dextran resuscitation on oxygen delivery, oxygen consumption, and lipid peroxidation after burn injury.

We compared the effects of lactated Ringer's (LR) and hypertonic saline dextran (HSD) on postburn cardiovascular function, O2 consumption, lipid peroxidation, and bacterial translocation. Miniature pigs with 40% total body surface area (TBSA), third-degree burns received, 30 minutes postburn, either Parkland resuscitation (LR group, n = 8) or HSD, 10 mL/kg/30 minutes, followed by LR, 4 mL/kg/%burn over the next 23 hours (HSD group, n = 8). The HSD prevented the early decrease in cardiac index (CI); the early increase in the resistance of the systemic, mesenteric, celiac, and renal vascular beds; and the decrease in mesenteric O2 consumption seen after burns when LR alone is used for resuscitation. The HSD also moderated the systemic and mesenteric lipid peroxidation. Bacterial translocation was less in the HSD group (3 of 8 animals) compared with the LR group (5 of 8 animals), but was not statistically different. Hypertonic saline dextran may be beneficial in improving the postburn microcirculation and attenuating postburn oxidant-induced lipid peroxidation in the systemic tissues and the gut.

Mesenteric lymphadenectomy prevents postburn systemic spread of translocated bacteria.

We investigated the role of mesenteric lymph nodes in postburn systemic spread of intestinal bacteria. Group 1 minipigs (n=8) had a 40% third-degree burn. Group 2 minipigs (n=7) had the same burn injury, but their mesenteric lymph nodes were removed immediately after burn. Group 3 minipigs (n=8) had sham burn, and group 4 minipigs (n=6) had mesenteric lymph node removal under anesthesia. All minipigs were killed at 48 hours, and tissues were harvested for bacteriological culture. Group 1 showed a large number of positive cultures from several of the systemic organs. Group 2 demonstrated no positive cultures in any of the tissues except the peritoneal fluid. These data suggest that bacterial translocation occurs mainly via mesenteric lymphatics to mesenteric lymph nodes and, thence, into other systemic tissue. After major burns, mesenteric lymph nodes may become an additional focus of infection.

Influence of burn size on the incidence of contamination of burn wounds by fecal organisms.

Ischemia and reperfusion injury of the gut mucosa after severe injury have been shown to allow endogenous gastrointestinal tract microorganisms to pass into systemic areas (bacterial translocation); this has been hypothesized as a source of burn-wound contamination. To study this phenomenon, 53 pediatric patients with burns underwent routine fecal culture at the time of admission. These cultures were compared with wound cultures that were obtained at the time of admission and throughout their hospitalization. Patients were grouped according to burn size: Small (1% to 20% total body surface area burned), Moderate (21% to 50%), and Severe (greater than 50%). The incidence of corresponding isolates was determined for each group and compared by analysis of variance. No difference in the frequency of corresponding isolates could be demonstrated between the Small (4.0%) and Moderate (7.7%) groups, whereas the Severe group (53.3%) demonstrated a significantly larger incidence of corresponding isolates (p less than 0.0001). Translocation of gut flora after severe burn injury may account for some instances of burn-wound contamination.

Effects of anesthesia, surgery, fluid resuscitation, and endotoxin administration on postburn bacterial translocation.

The aim of the study reported here was to assess the effects of some clinically relevant factors on the incidence and outcome of postburn bacterial translocation. Miniature pigs in 8 groups (n = 6 in each) underwent: (1) general anesthesia (GA); (2) operation (insertion of Swan-Ganz, arterial, and portal catheters) under GA; (3) burn (40% total body surface area, third degree, under GA); (4) burn and operation; (5) burn, operation, and resuscitation (Parkland); (6) burn, operation, and resuscitation plus endotoxin (100 micrograms/kg IV bolus, 2nd day). Groups 1-6 were killed at 48 hours and tissue samples were harvested for bacteriologic culture. Groups 7 and 8 were the same as 2 and 5, respectively, but were killed at 96 hours. Resuscitation and endotoxin increased postburn bacterial translocation but only endotoxin promoted systemic sepsis. In the absence of additional trauma, translocated bacteria were cleared by 96 hours postburn.

Inositol trisphosphate enhances calcium release in skinned cardiac and skeletal muscle.

Experiments from other laboratories suggest that inositol trisphosphate (InsP3) may be involved in the excitation-contraction coupling (ECC) process of cardiac and skeletal muscle. Our results support this hypothesis. Studying fiber bundles (less than 200-microns diameter) from guinea pig papillary muscles skinned with saponin and mechanically skinned single fibers from frog semitendinosus muscle, we find that calcium-induced force oscillations (observed in solutions containing low ethyleneglycol-bis(beta-aminoethylether)-N,N'-tetraacetic acid and pCa 7.0) are enhanced in magnitude and frequency by InsP3 at concentrations as low as 1 microM. InsP3 at 10 microM can often induce such oscillations in mechanically skinned frog skeletal muscle. In skinned cardiac fibers, InsP3 increases the magnitude of caffeine contractures at submaximal caffeine concentrations to a greater extent than at near-maximal caffeine concentrations. InsP3 (30 microM) has no effect on either the calcium sensitivity or maximal force generated by the contractile apparatus of skinned cardiac muscle. We conclude that InsP3 has no direct effect on the contractile machinery but that it can modulate ECC by enhancing the calcium-induced release of calcium from the sarcoplasmic reticulum, possibly from the same pool and through the same mechanism as caffeine.