Direct Peritoneal Resuscitation for Trauma

Direct peritoneal resuscitation (DPR) has been found to be a useful adjunct in the management of critically ill trauma patients. DPR is performed following damage control surgery by leaving a surgical drain in the mesentery, placing a temporary abdominal closure, and postoperatively running peritoneal dialysis solution through the surgical drain with removal through the temporary closure. In the original animal models, the peritoneal dialysate infusion was found to augment visceral microcirculatory blood flow reducing the ischemic insult that occurs following hemorrhagic shock. DPR was also found to minimize the aberrant immune response that occurs secondary to shock and contributes to multisystem organ dysfunction. In the subsequent human trials, performing DPR had significant effects in several key categories. Traumatically injured patients who received DPR had a significantly shorter time to definitive fascial closure, had a higher likelihood of achieving primary fascial closure, and experienced fewer abdominal complications. The use of DPR has been further expanded as a useful adjunct for emergency general surgery patients and in the pretransplant care of human cadaver organ donors.

Water removal during automated peritoneal dialysis assessed by remote patient monitoring and modelling of peritoneal tissue hydration

Water removal which is a key treatment goal of automated peritoneal dialysis (APD) can be assessed cycle-by-cycle using remote patient monitoring (RPM). We analysed ultrafiltration patterns during night APD following a dry day (APD_DD; no daytime fluid exchange) or wet day (APD_WD; daytime exchange). Ultrafiltration for each APD exchange were recorded for 16 days using RPM in 14 patients. The distributed model of fluid and solute transport was applied to simulate APD and to explore the impact of changes in peritoneal tissue hydration on ultrafiltration. We found lower ultrafiltration (mL, median [first quartile, third quartile]) during first and second vs. consecutive exchanges in APD_DD (−61 [−148, 27], 170 [78, 228] vs. 213 [126, 275] mL; p < 0.001), but not in APD_WD (81 [−8, 176], 81 [−4, 192] vs. 115 [4, 219] mL; NS). Simulations in a virtual patient showed that lower ultrafiltration (by 114 mL) was related to increased peritoneal tissue hydration caused by inflow of 187 mL of water during the first APD_DD exchange. The observed phenomenon of lower ultrafiltration during initial exchanges of dialysis fluid in patients undergoing APD_DD appears to be due to water inflow into the peritoneal tissue, re-establishing a state of increased hydration typical for peritoneal dialysis.

On the change of transport parameters with dwell time during peritoneal dialysis

The transitory change of fluid and solute transport parameters occurring during the initial phase of a peritoneal dialysis dwell is a well-documented phenomenon; however, its physiological interpretation is rather hypothetical and has been disputed. Two different explanations were proposed: (1) the prevailing view-supported by several experimental and clinical studies-is that a vasodilatory effect of dialysis fluid affects the capillary surface area available for dialysis, and (2) a recently presented alternative explanation is that the molecular radius of glucose increases due to the high glucose concentration in fresh dialysis fluid and that this change affects peritoneal transport parameters. The experimental bases for both phenomena are discussed as well as the problem of the accuracy necessary for a satisfactory description of clinical data when the three-pore model of peritoneal transport is applied. We show that the correction for the change of transport parameters with dwell time provides a better fit with clinical data when applying the three-pore model. Our conclusion is in favor of the traditional interpretation namely that the transitory change of transport parameters with dwell time during peritoneal dialysis is primarily due to the vasodilatory effect of dialysis fluids.

Influence of dialysate temperature on creatinine peritoneal clearance in peritoneal dialysis patients: a randomized trial

BACKGROUND

Patients on continuous ambulatory peritoneal dialysis (PD) are encouraged to warm dialysate to 37 °C before peritoneal infusion; main international PD guidelines do not provide specific recommendation, and patients generally warm dialysate batches partially or do not warm them at all. Warming of dialysate is a time-consuming procedure, not free from potential risks (i.e. degradation of glucose), and should be justified by a clear clinical benefit.

METHODS

We designed a single blind randomized controlled trial where 18 stable PD patients were randomized to receive a peritoneal equilibration test either with dialysate at a controlled temperature of 37 °C (intervention group) or with dialysate warmed with conventional methods (control group). Primary end-point was a higher peritoneal creatinine clearance in patients in the intervention group.

RESULTS

Patients in the intervention group did not show a significantly higher peritoneal creatinine clearance when compared to the control group (6.38 ± 0.52 ml/min vs 5.65 ± 0.37 ml/min, p = 0.2682). Similar results were obtained for urea peritoneal clearance, mass transfer area coefficient of creatinine and urea. There were no significant differences in total abdominal discomfort questionnaire score, blood pressure and body temperature between the two groups.

CONCLUSIONS

Using peritoneal dialysate at different temperatures without causing significant side effects to patients appears feasible. We report a lack of benefit of warming peritoneal dialysate to 37 °C on peritoneal clearances; future PD guidelines should not reinforce this recommendation.

TRIAL REGISTRATION

NCT04302649, ClinicalTrials.gov ; date of registration 10/3/2020 (retrospectively registered).

Dialysate copeptin and peritoneal transport in incident peritoneal dialysis patients

Purpose

Systemic and intraperitoneal inflammation are characteristic features of patients with end-stage renal disease undergoing chronic peritoneal dialysis (PD). Arginine vasopressin (AVP) and its surrogate marker copeptin play important roles in many pathophysiological processes in chronic kidney disease. The aim of this study was to assess if copeptin concentrations in plasma and dialysate were related to peritoneal transport parameters and residual renal function (RRF) in incident PD patients.

Methods

In 37 clinically stable incident PD patients (mean age 50 years, 68% women, 32% diabetes), a 4 h peritoneal equilibration test (PET) was performed 4–6 weeks after the onset of PD. Plasma (at 2 h of PET) and dialysate (at 4 h) concentrations of copeptin, high-sensitivity C-reactive protein and interleukin-6 (IL-6) were determined.

Results

Plasma (80.7 ± 37.3 pg/mL) and dialysate (33.2 ± 18.0 pg/mL) concentrations of copeptin were correlated (Rs = 0.52, p = 0.001). Plasma and dialysate copeptin concentrations were negatively correlated with renal function as assessed by renal Kt/V (Rs = − 0.38; p = 0.021 and Rs = − 0.33; p = 0.047, respectively). At PET, dialysate copeptin negatively correlated with D/P creatinine (Rs = − 0.35, p = 0.033), and positively with D/D0 glucose (Rs = 0.33, p = 0.045) and ultrafiltration (Rs = 0.37, p = 0.024). Multivariate analysis showed that low dialysate copeptin (β = –0.30, p = 0.049) and high dialysate IL-6 (β = + 0.40, p = 0.012) were independent determinants of higher D/P creatinine.

Conclusions

Dialysate copeptin was negatively associated with D/P creatinine in incident PD patients suggesting a potential influence of copeptin or AVP on peritoneal solute transport rate that might involve vasoactive mechanisms.

Direct peritoneal resuscitation reduces intestinal permeability after brain death

BACKGROUND

The profound inflammatory response associated with brain death is frequently cited as the reason organs procured from brain dead donors are associated with worse graft function. The intestine releases inflammatory mediators in other types of shock, but its role is brain death has not been well-studied. Direct peritoneal resuscitation (DPR) improves visceral organ blood flow and reduces inflammation after hemorrhagic shock. We hypothesized that use of DPR would maintain intestinal integrity and reduce circulating inflammatory mediators after brain death.

METHODS

Brain death was induced in male Sprague-Dawley rats by inserting a 4F Fogarty catheter into the epidural space and slowly inflating it. After herniation, rats were resuscitated with normal saline to maintain a mean arterial pressure of 80 mm Hg and killed with tissue collected immediately (time 0), or 2 hours, 4 hours, or 6 hours after brain death. Randomly selected animals received DPR via an intraperitoneal injection of 30-mL commercial peritoneal dialysis solution.

RESULTS

Levels of proinflammatory cytokines, including IL-1β and IL-6, as well as high-mobility group box 1 protein and heat shock protein 70, were all increased after brain death and decreased with DPR. Fatty acid binding protein and lipopolysaccharide, both markers of intestinal injury, were increased in the serum after brain death and decreased with DPR. Immunohistochemistry staining for zona occludin-1 showed decreased intestinal tight junction integrity after brain death, which improved with DPR.

CONCLUSIONS

Intestinal permeability increases after brain death, and this contributes to the increased inflammation seen throughout the body. Using DPR prevents intestinal ischemia and helps preserve intestinal integrity. This suggests that using this novel therapy as an adjunct to the resuscitation of brain dead donors has the potential to reduce inflammation and potentially improve the quality of transplanted organs.

The vasodilating effect of glucose differs among vessels at different branching level in the porcine retina ex vivo

Diabetic retinopathy is characterized by retinal lesions related to disturbances in retinal blood flow. The metabolic dysregulation in diabetes involves hyperglycemia which in both clinical and experimental studies has been shown to induce dilatation of larger retinal vessels, which has been suggested to be mediated by nitric oxide (NO). However, the effects of glucose on the diameter of smaller retinal vessels that are the site of development of diabetic retinopathy are unknown. Diameter changes in porcine retinal arterioles, pre-capillary arterioles and capillaries were studied ex vivo during acute changes in intraluminal glucose concentrations that mimicked changes in plasma glucose in diabetic patients. The experiments were repeated during blocking of NO-synthesis. Intravascular application of 2 mM glucose dilated arterioles and capillaries significantly, while 20 mM glucose dilated precapillary arterioles significantly. Intravascular application of 20 mM glucose dilated precapillary arterioles previously exposed to 2 mM glucose, while no significant diameter changes were observed after application of 2 mM glucose in vessels previously exposed to 20 mM glucose. No diameter changes were observed after application of 5.5 mM glucose in vessels previously exposed to both 2 mM and 20 mM glucose in either order. There was no significant difference between the diameter responses in the absence and presence of NO-synthesis blocker. Glucose induced dilatation of porcine precapillary arterioles ex vivo differs from the response in larger arterioles and capillaries, and the response is unaffected by the blocking of NO-synthesis. This may have implications for understanding the pathophysiology of diseases in the retinal microcirculation, such as diabetic retinopathy.

Functional vascular anatomy of the peritoneum in health and disease

The peritoneum consists of a layer of mesothelial cells on a connective tissue base which is perfused with circulatory and lymphatic vessels. Total effective blood flow to the human peritoneum is estimated between 60 and 100 mL/min, representing 1-2 % of the cardiac outflow. The parietal peritoneum accounts for about 30 % of the peritoneal surface (anterior abdominal wall 4 %) and is vascularized from the circumflex, iliac, lumbar, intercostal, and epigastric arteries, giving rise to a quadrangular network of large, parallel blood vessels and their perpendicular offshoots. Parietal vessels drain into the inferior vena cava. The visceral peritoneum accounts for 70 % of the peritoneal surface and derives its blood supply from the three major arteries that supply the splanchnic organs, celiac and superior and inferior mesenteric. These vessels give rise to smaller arteries that anastomose extensively. The visceral peritoneum drains into the portal vein. Drugs absorbed are subject to first-pass hepatic metabolism. Peritoneal inflammation and cancer invasion induce neoangiogenesis, leading to the development of an important microvascular network. Anatomy of neovessels is abnormal and characterized by large size, varying diameter, convolution and blood extravasation. Neovessels have a defective ultrastructure: formation of large "mother vessels" requires degradation of venular and capillary basement membranes. Mother vessels give birth to numerous "daughter vessels". Diffuse neoangiogenesis can be observed before appearance of macroscopic peritoneal metastasis. Multiplication of the peritoneal capillary surface by neoangiogenesis surface increases the part of cardiac outflow directed to the peritoneum.

Peritoneal Fluid Transport rather than Peritoneal Solute Transport Associates with Dialysis Vintage and Age of Peritoneal Dialysis Patients

During peritoneal dialysis (PD), the peritoneal membrane undergoes ageing processes that affect its function. Here we analyzed associations of patient age and dialysis vintage with parameters of peritoneal transport of fluid and solutes, directly measured and estimated based on the pore model, for individual patients. Thirty-three patients (15 females; age 60 (21–87) years; median time on PD 19 (3–100) months) underwent sequential peritoneal equilibration test. Dialysis vintage and patient age did not correlate. Estimation of parameters of the two-pore model of peritoneal transport was performed. The estimated fluid transport parameters, including hydraulic permeability (LpS), fraction of ultrasmall pores (α_u), osmotic conductance for glucose (OCG), and peritoneal absorption, were generally independent of solute transport parameters (diffusive mass transport parameters). Fluid transport parameters correlated whereas transport parameters for small solutes and proteins did not correlate with dialysis vintage and patient age. Although LpS and OCG were lower for older patients and those with long dialysis vintage, α_u was higher. Thus, fluid transport parameters—rather than solute transport parameters—are linked to dialysis vintage and patient age and should therefore be included when monitoring processes linked to ageing of the peritoneal membrane.

Peritoneal fluid transport: mechanisms, pathways, methods of assessment

Fluid removal during peritoneal dialysis is controlled by many mutually dependent factors and therefore its analysis is more complex than that of the removal of small solutes used as markers of dialysis adequacy. Many new tests have been proposed to assess quantitatively different components of fluid transport (transcapillary ultrafiltration, peritoneal absorption, free water, etc.) and to estimate the factors that influence the rate of fluid transport (osmotic conductance). These tests provide detailed information about indices and parameters that describe fluid transport, especially those concerning the problem of the permanent loss of ultrafiltration capacity (ultrafiltration failure). Different theories and respective mathematical models of mechanisms and pathways of fluid transport are presently discussed and applied, and some fluid transport issues are still debated.

Peritoneal equilibration test with conventional 'low pH/high glucose degradation product' or with biocompatible 'normal pH/low glucose degradation product' dialysates: does it matter?

BACKGROUND

The evaluation of the peritoneal transport characteristics is mandatory in peritoneal dialysis (PD) patients. This is usually performed in routine clinical practice with a peritoneal equilibration test (PET) using conventional dialysates, with low pH and high glucose degradation product (GDP) concentrations. An increasing proportion of patients are now treated with biocompatible dialysates, i.e. with physiological pH and lower GDP concentrations. This questions the appropriateness to perform a PET with conventional solutions in those patients. The aim of our study is to compare the results of the PET using biocompatible and conventional dialysates, respectively.

METHODS

Nineteen stable PD patients (13 males, 6 females; mean age: 67.95±2.36 years, mean body surface area: 1.83±0.04 m2, dialysis vintage: 2.95±0.19 years) were included, among which 10 were usually treated with biocompatible and 9 with conventional solutions. Two PETs were performed, within a 2-week interval, in each patient. PET sequence (conventional solution first or biocompatible solution first) was randomized in order to avoid 'time bias'. Small (urea, creatinine and glucose), middle (beta-2-microglobulin) and large molecules' (albumin and alpha-2-macroglobulin) dialysate/plasma (D/P) concentration ratios and clearances were measured during each PET. Ultrafiltration (UF) and sodium filtration were also recorded. Results of both tests were compared by the Wilcoxon paired test.

RESULTS

No statistical difference was found between both dialysates for small molecule transport rates or for sodium filtration and UF. However, a few patients were not similarly classified for small-solute transport characteristics within the PET categories. Beta-2-microglobulin and albumin D/P ratios at different time points of the PET were significantly higher with the biocompatible, when compared with the conventional, solutions: 0.10±0.03 versus 0.08±0.02 (P<0.01) and 0.008±0.003 versus 0.007±0.003 (P=0.01), respectively. A similar difference was also observed for beta-2-microglobulin that was higher with biocompatible dialysates (1.04±0.32 versus 0.93±0.32 mL/min, respectively).

CONCLUSION

Peritoneal transport of water and small solutes is independent of the type of dialysate which is used. This is not the case for the transport of beta-2-microglobulin and albumin that is higher under biocompatible dialysates. Vascular tonus modification could potentially explain such differences. The PET should therefore always be carried out with the same dialysate to make longitudinal comparisons possible.

Intestinal Microcirculatory Flow Alterations in Necrotizing Enterocolitis are Improved by Direct Peritoneal Resuscitation

Vasoconstriction of the neonatal intestinal microvasculature is a central mechanistic event in development of necrotizing enterocolitis. We hypothesized that topical treatment of the intestine with dialysate fluid would ameliorate the vasoconstriction in necrotizing enterocolitis (NEC). NEC was induced in experimental groups. Control animals were delivered vaginally and dam-fed (control group). Neonatal pups underwent laser Doppler flow study of the terminal ileum to determine real-time blood flow in the intestinal microvasculature. After baseline flow was determined, dialysis solution was added to the peritoneal cavity and alterations in microcirculation were recorded. Baseline ileal blood flow in the control group was significantly higher than in NEC rat pups at 48 hours post delivery ( P < 0.05), but not at 24 hours ( P = NS). Ileal blood flow increased in all groups after adding dialysate ( P < 0.05), improving ileal blood flow in the 48-hour NEC group and reaching the baseline level of the 48-hour control group ( P < 0.05). Our data shows blood flow to be higher in 48-hour controls as compared with 24-hour controls suggesting a time-dependency in the development of intestinal vasoregulatory processes. All groups had an increase in blood flow with dialysate treatment. This may represent a novel initial therapy to improve intestinal ischemia in human necrotizing enterocolitis.

Computer simulations of osmotic ultrafiltration and small-solute transport in peritoneal dialysis: a spatially distributed approach

The aim of this study was to simulate clinically observed intraperitoneal kinetics of dialysis fluid volume and solute concentrations during peritoneal dialysis. We were also interested in analyzing relationships between processes in the peritoneal cavity and processes occurring in the peritoneal tissue and microcirculation. A spatially distributed model was formulated for the combined description of volume and solute mass balances in the peritoneal cavity and flows across the interstitium and the capillary wall. Tissue local parameters were assumed dependent on the interstitial hydration and vasodilatation induced by glucose. The model was fitted to the average volume and solute concentration profiles from dwell studies in 40 clinically stable patients on chronic ambulatory peritoneal dialysis using a 3.86% glucose dialysis solution. The model was able to describe the clinical data with high accuracy. An increase in the local interstitial pressure and tissue hydration within the distance of 2.5 mm from the peritoneal surface of the tissue was observed. The penetration of glucose into the tissue and removal of urea, creatinine, and sodium from the tissue were restricted to a layer located within 2 mm from the peritoneal surface. The initial decline of sodium concentration (sodium dip) was observed not only in intraperitoneal fluid but also in the tissue. The distributed model can provide a precise description of the relationship between changes in the peritoneal tissue and intraperitoneal dialysate volume and solute concentration kinetics. Computer simulations suggest that only a thin layer of the tissue within 2-3 mm from the peritoneal surface participates in the exchange of fluid and small solutes between the intraperitoneal dialysate and blood.

Free water transport in children on peritoneal dialysis is higher with more biocompatible dialysis solutions, higher with older age and declines with time

BACKGROUND

Water transport in peritoneal dialysis occurs through small pores and aquaporins. Free water transport (FWT) occurs through aquaporins only and gives a reflection of peritoneal aquaporin function. In this study, FWT in children was calculated for the first time in different settings.

METHODS

A prospective cohort study was performed; 87 peritoneal equilibrium tests (PETs) were analysed in 65 patients. Three subgroups were analysed: patients with their first PET; patients in their second year on dialysis; patients in their third year on dialysis or thereafter. Patients using 3.86% glucose solution with low pH/high glucose degradation products (GDP) were compared to patients using 3.86% glucose solution with neutral pH/low GDP. Sixteen patients using neutral pH/low GDP solution were followed longitudinally. FWT was calculated using the dialysate/plasma ratio of sodium.

RESULTS

The proportional contribution of FWT was significantly higher in patients using dialysis solution with neutral pH/low GDP solution compared to patients using solutions with low pH/high GDP (50 versus 40%). Transcapillary ultrafiltration (TCUF) showed the same trend but was not statistically significant. Total FWT was higher as well. Higher FWT was observed with older age. In the longitudinal group, TCUF and water transport through small pores declined, while FWT remained stable in the first 1.5 years. The contribution of FWT increased in this period (48-61%), then slowly declined again to baseline level during the third year.

CONCLUSIONS

Total FWT and relative contribution of FWT were significantly higher with neutral pH/low GDP solution. This can reflect a better preservation of aquaporins. The decline in the contribution of FWT in long-term dialysis could hypothetically implicate aquaporin dysfunction or different trafficking of aquaporins.

Preliminary resuscitation for perforated necrotizing enterocolitis: 2 cases treated with initial direct peritoneal resuscitation

We used peritoneal infusions of 2.5% dextrose solution as an adjunct to resuscitation of 2 very low-birth-weight infants having perforated necrotizing enterocolitis. This was repeated every 12 hours for 7 days before and 1 day after extensive bowel resection. The designation of this research method has been termed direct peritoneal resuscitation. We discuss our observations and the evolution of this technique from studies in the animal laboratory to a recent trial in patients with abdominal trauma. We propose that the early response benefit of this preoperative resuscitation seen in our 2 cases be investigated by others. Prospective controlled trials could then be considered for those high-risk patients having diffuse disease and shock.