Intraperitoneal resuscitation improves intestinal blood flow following hemorrhagic shock

Advantages of pyruvate-based fluids in preclinical shock resuscitation-A narrative review

This review focuses on the innate beneficial effects of sodium pyruvate-based fluids, including pyruvate in intravenous solutions, oral rehydration solutions, and peritoneal dialysis solutions, on shock resuscitation with various animal models relative to current commercial fluids over the last two decades. Due to its superior pharmacological properties, pyruvate effectively sustains cytosolic glycolytic pathways and mitochondrial oxidative phosphorylation by restoration of redox potentials and reactivation of pyruvate dehydrogenase in hypoxia, even anoxia, and diabetes, reversing the Warburg effect and diabetic glucometabolic aberration. Pyruvate has been demonstrated to protect against multiorgan dysfunction and metabolic disturbance in numerous preclinical studies with various pathogenic injuries. The unique features of pyruvate potential clinical benefits encompass to efficiently correct lethal lactic acidosis via metabolically rapid consumption of intracellular [H⁺] and robustly protect multiorgan metabolism and function, particularly visceral organs in addition to the heart and brain, significantly prolonging survival in various animal models. Pyruvate protection of red blood cell function and preservation of the partial pressure of arterial oxygen should be highly concerned in further studies. Pyruvate is much advantageous over existing anions such as acetate, bicarbonate, chloride, and lactate in commercial fluids. Pyruvate-based fluids act as a therapeutic agent without causing iatrogenic resuscitation injury in addition to being a volume expander, indicating a potential novel generation of resuscitation fluids, including crystalloids and colloids. Pyruvate-based fluids have an enormous potential appeal for clinicians who face the ongoing fluid debate to readily select as the first resuscitation fluid. Clinical trials with pyruvate-based fluids in shock resuscitation are urgently warranted.

Centhaquine Restores Renal Blood Flow and Protects Tissue Damage After Hemorrhagic Shock and Renal Ischemia

Background: Centhaquine (CQ) (Lyfaquin®) is in late stage clinical development as a safe and effective first-in-class resuscitative agent for hemorrhagic shock patients (NCT02408731, NCT04056065, and NCT04045327). Acute kidney injury (AKI) is known to be associated with hemorrhagic shock. Hence, effect of CQ on protection of kidneys from damage due to hemorrhagic shock was investigated. Methods: To assess effect of CQ on AKI in shock, we created a rat model with hemorrhagic shock and AKI. Renal arteries were clamped and de-clamped to induce AKI like ischemia/reperfusion model and hemorrhage was carried out by withdrawing blood for 30 min. Rats were resuscitated with CQ (0.02 mg/kg) for 10 min. MAP, heart rate (HR), and renal blood flow (RBF) were monitored for 120 min. Results: CQ produced a significant improvement in RBF compared to vehicle (p< 0.003) even though MAP and HR was similar in CQ and vehicle groups. Blood lactate level was lower (p = 0.0064) in CQ than vehicle at 120 min post-resuscitation. Histopathological analysis of tissues indicated greater renal damage in vehicle than CQ. Western blots showed higher HIF-1α (p = 0.0152) and lower NGAL (p = 0.01626) levels in CQ vs vehicle. Immunofluorescence in the kidney cortex and medulla showed significantly higher (p< 0.045) expression of HIF-1α and lower expression of Bax (p< 0.044) in CQ. Expression of PHD 3 (p< 0.0001) was higher, while the expression of Cytochrome C (p = 0.01429) was lower in the cortex of CQ than vehicle. Conclusion: Results show CQ (Lyfaquin®) increased renal blood flow, augmented hypoxia response, decreased tissue damage and apoptosis following hemorrhagic shock induced AKI, and may be explored to prevent/treat AKI. Translational Statement: Centhaquine (CQ) is safe for human use and currently in late stage clinical development as a first-in-class resuscitative agent to treat hemorrhagic shock. In the current study, we have explored a novel role of CQ in protection from hemorrhagic shock induced AKI, indicating its potential to treat/prevent AKI.

Direct Peritoneal Resuscitation Improves Survival in a Murine Model of Combined Hemorrhage and Burn Injury

INTRODUCTION

Combined burn injury and hemorrhagic shock are a common cause of injury in wounded warfighters. Current protocols for resuscitation for isolated burn injury and isolated hemorrhagic shock are well defined, but the optimal strategy for combined injury is not fully established. Direct peritoneal resuscitation (DPR) has been shown to improve survival in rats after hemorrhagic shock, but its role in a combined burn/hemorrhage injury is unknown. We hypothesized that DPR would improve survival in mice subjected to combined burn injury and hemorrhage.

MATERIALS AND METHODS

Male C57/BL6J mice aged 8 weeks were subjected to a 7-second 30% total body surface area scald in a 90°C water bath. Following the scald, mice received DPR with 1.5 mL normal saline or 1.5 mL peritoneal dialysis solution (Delflex). Control mice received no peritoneal solution. Mice underwent a controlled hemorrhage shock via femoral artery cannulation to a systolic blood pressure of 25 mm Hg for 30 minutes. Mice were then resuscitated to a target blood pressure with either lactated Ringer's (LR) or a 1:1 ratio of packed red blood cells (pRBCs) and fresh frozen plasma (FFP). Mice were observed for 24 hours following injury.

RESULTS

Median survival time for mice with no DPR was 1.47 hours in combination with intravascular LR resuscitation and 2.08 hours with 1:1 pRBC:FFP. Median survival time significantly improved with the addition of intraperitoneal normal saline or Delflex. Mice that received DPR followed by 1:1 pRBC:FFP required less intravascular volume than mice that received DPR with LR, pRBC:FFP alone, and LR alone. Intraperitoneal Delflex was associated with higher levels of tumor necrosis factor alpha and macrophage inflammatory protein 1 alpha and lower levels of interleukin 10 and intestinal fatty acid binding protein. Intraperitoneal normal saline resulted in less lung injury 1 hour postresuscitation, but increased to similar severity of Delflex at 4 hours.

CONCLUSIONS

After a combined burn injury and hemorrhage, DPR leads to increased survival in mice. Survival was similar with the use of normal saline or Delflex. DPR with normal saline reduced the inflammatory response seen with Delflex and delayed the progression of acute lung injury. DPR may be a valuable strategy in the treatment of patients with combined burn injury and hemorrhage.

Plasma resuscitation with adjunctive peritoneal resuscitation reduces ischemic intestinal injury following hemorrhagic shock

INTRODUCTION

Impaired intestinal microvascular perfusion following resuscitated hemorrhagic shock (HS) leads to ischemia-reperfusion injury, microvascular dysfunction, and intestinal epithelial injury, which contribute to the development of multiple organ dysfunction syndrome in some trauma patients. Restoration of central hemodynamics with traditional methods alone often fails to fully restore microvascular perfusion and does not protect against ischemia-reperfusion injury. We hypothesized that resuscitation (RES) with fresh frozen plasma (FFP) alone or combined with direct peritoneal resuscitation (DPR) with 2.5% Delflex solution might improve blood flow and decrease intestinal injury compared with conventional RES or RES with DPR alone.

METHODS

Sprague-Dawley rats underwent HS (40% mean arterial pressure) for 60 minutes and were randomly assigned to a RES group (n = 8): sham, HS-crystalloid resuscitation (CR) (shed blood + two volumes CR), HS-CR-DPR (intraperitoneal 2.5% peritoneal dialysis fluid), HS-FFP (shed blood + two volumes FFP), and HS-DPR-FFP (intraperitoneal dialysis fluid + two volumes FFP). Laser Doppler flowmeter evaluation of the ileum, serum samples for fatty acid binding protein enzyme-linked immunosorbent assay, and hematoxylin and eosin (H&E) staining were used to assess intestinal injury and blood flow. p Values of <0.05 were considered significant.

RESULTS

Following HS, the addition of DPR to either RES modality improved intestinal blood flow. Four hours after resuscitated HS, FABP-2 (intestinal) and FABP-6 (ileal) were elevated in the CR group but reduced in the FFP and DPR groups. The H&E staining demonstrated disrupted intestinal villi in the FFP and CR groups, most significantly in the CR group. Combination therapy with FFP and DPR demonstrated negligible cellular injury in H&E graded samples and a significant reduction in fatty acid binding protein levels.

CONCLUSION

Hemorrhagic shock leads to ischemic-reperfusion injury of the intestine, and both FFP and DPR alone attenuated intestinal damage; combination FFP-DPR therapy alleviated most signs of organ injury. Resuscitation with FFP-DPR to restore intestinal blood flow following shock could be an essential method of reducing morbidity and mortality after trauma.

Involvement of TRPV1-containing peripheral sensory efferents in hemodynamic responses in a rat hemorrhagic shock model

BACKGROUND

Mechanisms underlying hemodynamic disturbance in hemorrhagic shock are not completely understood. Transient receptor potential vanilloid 1-expressing afferents are involved in hemorrhagic shock pathology, and transient receptor potential vanilloid 1 antagonist, capsazepine, acts on the central nervous system to improve mortality in a rat hemorrhagic shock model. In contrast, transient receptor potential vanilloid 1-positive efferents promote vasoactive reactions through the release of neuropeptides, including calcitonin gene-related peptides. This study aimed to investigate whether transient receptor potential vanilloid 1-positive peripheral sensory efferents are involved in hemodynamic responses after hemorrhagic shock.

METHODS

Male rats underwent hemorrhagic shock (mean arterial pressure 30 mm Hg for 90 min, followed by resuscitation for 30 min) and received capsazepine (5 μM/kg) 30 min after shock induction. A separate cohort of rats subjected to hemorrhagic shock received hCGRP_8-37 (300 μg/kg), a calcitonin gene-related peptide receptor antagonist, at 30, 60, or 90 minutes after shock induction. The 24-hour survival rate, mean arterial pressure, heart rate, arterial blood gas, and plasma calcitonin gene-related peptide levels were measured. Tissue blood flow and oxygenation both in the mesentery and skeletal muscle were also assessed.

RESULTS

Capsazepine treatment prevented the hemorrhagic shock-induced increase in plasma calcitonin gene-related peptide levels, and hCGRP_8-37 treatment improved the 24-h survival rates after hemorrhagic shock at a time-dependent manner. The hCGRP_8-37- or capsazepine-treated rats exhibited tissue oxygenation and metabolic conditions comparable to those in control rats at the end of the experiment.

CONCLUSION

Transient receptor potential vanilloid 1 plays a crucial role in hemodynamic responses to hemorrhagic shock, partly via calcitonin gene-related peptide release, involved in its peripheral sensory-efferent functions. The hCGRP_8-37 appears to improve peripheral circulatory failure, which may be useful as adjunct treatment after hemorrhagic shock.

Direct Peritoneal Resuscitation Alters Leukocyte Infiltration in the Lung After Acute Brain Death

BACKGROUND

Brain death is associated with significant lung injury and inflammation. This has been associated with worse long-term outcomes for transplanted lungs. Direct peritoneal resuscitation (DPR) reduces systemic inflammation in brain death and improves lung procurement rate. The effect of DPR on macrophage and neutrophil infiltration in the lungs is not known.

METHODS

Male Sprague-Dawley rats had a 4F Fogarty catheter inserted into the skull and the balloon inflated until brain death was achieved. Rats were resuscitated with normal saline to maintain a mean arterial pressure of 80 mmHg (targeted intravenous fluid, TIVF) and DPR animals received an intraperitoneal injection of commercial peritoneal dialysis solution. Rats were sacrificed at 0, 2, 4, and 6 h after brain death. Protein levels were assessed using quantitative ELISA. Leukocytes were quantified using flow cytometry and immunohistochemistry.

RESULTS

At all time points, DPR downregulated multiple inflammatory cytokines including IFN-γ, TNF-α, IL-1α, and IL-6. Adhesion molecules ICAM, E-selectin, and P-selectin were increased above sham at 4 and 6 h after brain death and reduced with DPR, whereas VCAM was reduced at 2 and 6 h. Infiltration of macrophages and neutrophils were trended downward at 6 h with DPR, though this difference was not statistically significant.

CONCLUSIONS

Animals that received TIVF alone had significant increases in inflammatory cytokines within the lung tissue, leading to adhesion molecule expression and ultimately leukocyte infiltration. Each stage of inflammation was affected by DPR. Using DPR in brain dead organ donors shows promise as a way to reduce lung injury and inflammation.

Intestinal microcirculation and necrotizing enterocolitis: The vascular endothelial growth factor system

Necrotizing enterocolitis (NEC), a leading cause of morbidity and mortality in preterm neonates, is a devastating disease characterized by intestinal tissue inflammation and necrosis. NEC pathogenesis is multifactorial but remains unclear. Translocation of bacteria and/or bacterial products across a weak intestinal barrier in the setting of impaired mucosal immunity leads to an exaggerated inflammatory response and secondary mucosal epithelial injury. In addition to prematurity, other risk factors for NEC include congenital heart disease, maternal pre-eclampsia with placental vascular insufficiency, severe anemia and blood transfusion - all conditions that predispose the intestine to ischemia. We recently found that maldevelopment of the intestinal microvasculature plays an important role in NEC pathogenesis. Here we review the evidence supporting a role for defective development of the intestinal mucosal microvasculature and perturbations of intestinal blood flow in NEC, emphasizing the importance of vascular endothelial growth factor (VEGF) and the VEGF receptor-2 signaling pathway.

Direct peritoneal resuscitation reduces inflammation in the kidney after acute brain death

Brain death is associated with significant inflammation within the kidneys, which may contribute to reduced graft survival. Direct peritoneal resuscitation (DPR) has been shown to reduce systemic inflammation after brain death. To determine its effects, brain dead rats were resuscitated with normal saline (targeted intravenous fluid) to maintain a mean arterial pressure of 80 mmHg; DPR animals also received 30 cc of intraperitoneal peritoneal dialysis solution. Rats were euthanized at 0, 2, 4, and 6 h after brain death. Pro-inflammatory cytokines were measured using ELISA. Levels of IL-1β, TNF-α, and IL-6 in the kidney were significantly increased as early as 2 h after brain death and significantly decreased with DPR. Levels of leukocyte adhesion molecules ICAM and VCAM increased after brain death and were decreased with DPR (ICAM 2.33 ± 0.14 vs. 0.42 ± 0.04, P = 0.002; VCAM 82.6 ± 5.8 vs. 37.3 ± 1.9, P = 0.002 at 4 h) as were E-selectin and P-selectin (E-selectin 25,605 vs. 16,144, P = 0.005; P-selectin 82.5 ± 3.3 vs. 71.0 ± 2.3, P = 0.009 at 4 h). Use of DPR reduces inflammation and adhesion molecule expression in the kidneys, and is associated with reduced macrophages and neutrophils on immunohistochemistry. Using DPR in brain dead donors has the potential to reduce the immunologic activity of transplanted kidneys and could improve graft survival.

Randomized Controlled Trial Evaluating the Efficacy of Peritoneal Resuscitation in the Management of Trauma Patients Undergoing Damage Control Surgery

BACKGROUND

Peritoneal resuscitation (PR) represents a unique modality of treatment for severely injured trauma patients requiring damage control surgery. These data represent the outcomes of a single institution randomized controlled trial into the efficacy of PR as a management option in these patients.

STUDY DESIGN

From 2011 to 2015, one hundred and three patients were enrolled in a prospective randomized controlled trial evaluating the use of PR in the treatment of patients undergoing damage control surgery compared with conventional resuscitation (CR) alone. Patient demographics, clinical variables, and outcomes were collected. Univariate and multivariate analysis was performed with a priori significance at p ≤ 0.05.

RESULTS

After initial screening, 52 patients were randomized to the PR group and 51 to the CR group. Age, sex, initial pH, and mechanism of injury were used for randomization. Method of abdominal closure was standardized across groups. Time to definitive abdominal closure was reduced in the PR group compared with the CR group (4.1 ± 2.2 days vs 5.9 ± 3.5 days; p ≤ 0.002). Volume of resuscitation and blood products transfused in the initial 24 hours was not different between the groups. Primary fascial closure rate was higher in the PR group (83% vs 66%; p ≤ 0.05). Intra-abdominal complications were lower in the PR compared with the CR group (8% vs 18%), with abscess formation rate (3% vs 14%; p < 0.05) being significant. Patients in the PR group had a lower 30-day mortality rate, despite similar Injury Severity Scores (13% vs 28%; p = 0.06).

CONCLUSIONS

Peritoneal resuscitation enhances management of damage control surgery patients by reducing time to definitive abdominal closure, intra-abdominal infections, and mortality rates.

Direct Peritoneal Resuscitation Alters Hepatic miRNA Expression after Hemorrhagic Shock

BACKGROUND

MicroRNAs (miRNAs) are small segments of noncoding RNA that regulate gene expression and protein function, and therefore are key regulators of cellular processes including those of the inflammatory cascade after hemorrhagic shock (HS). We have previously shown that direct peritoneal resuscitation (DPR), as an adjunct to traditional IV fluid resuscitation, improves visceral blood flow and reduces pro-inflammatory cytokines released during HS. The effects of DPR on hepatic miRNA (miR) expression patterns after resuscitated HS are not known.

STUDY DESIGN

Male Sprague-Dawley rats were divided into 3 groups: sham (no HS); conventional resuscitation (CR; HS, then resuscitated with shed blood and 2 volumes of saline); and DPR (CR plus 30 mL peritoneal dialysis solution). Animals were sacrificed at 4 hours, and miRNAs were measured using reverse transcription polymerase chain reaction.

RESULTS

Use of DPR downregulated 68 of 92 hepatic miRNAs compared with only 2 of 92 upregulated when compared with CR alone, p < 0.01). Specifically, miR-9-5p, miR-122-5p, and miR-146, which regulate NFκB, were downregulated 4.1-, 3.4-, and 0.86-fold, respectively; miR-29a and miR-126 were upregulated 0.88- and 3.7-fold when DPR was compared with CR.

CONCLUSIONS

Adding DPR downregulated most hepatic miRNAs compared with CR alone. Some miRNAs were affected more significantly, suggesting that although this clinical intervention causes a near-global downregulation of hepatic miRNA, it still targets specific inflammatory pathways. Use of DPR for resuscitation of patients in HS may reduce hepatic inflammation to improve patient outcomes after hemorrhage.

Management of the lower gastrointestinal system in burn: A comprehensive review

BACKGROUND

Burn produces complex gastrointestinal (GI) responses. Treatment, including large volume fluid resuscitation and opioid analgesia, may exacerbate GI dysfunction. Complications include constipation and opioid-induced bowel dysfunction (OBD), acute colonic pseudo-obstruction (ACPO), bacterial translocation and sepsis, and abdominal compartment syndrome (ACS). Contamination of perineal burns contributes to delayed healing, skin graft failure and sepsis and may impact upon morbidity and mortality. The authors carried out a literature review on management of the lower GI system in burn. This study aimed to explain: current prevention and treatment modalities; drawbacks and complications associated with available treatments, and to provide direction for development of best practice guidelines. ACS is associated with high mortality and should be treated with careful fluid resuscitation and diuresis, to minimise and remove oedema.

METHODS

A comprehensive search of English language literature was performed on PubMed, Medline and Embase. Both MeSH and keywords searches were used.

RESULTS

Evidence available on the management of lower gastrointestinal system in burn is summarised. Levels of evidence available are generally low (level III-IV).

CONCLUSION

Structured, graded interventions are required for prevention and treatment of constipation and OBD. Correction of electrolyte imbalance, adequate enteral intake and mobilisation are pre-requisites. Laxatives should be used according to World Gastroenterology Organisation recommendations. Resistant constipation may respond to changes in medication, but ACPO should be suspected and treated when present. Other complications, such as bacterial translocation and ACS are common in major burns. There is evidence that selective digestive tract decontamination reduces mortality and infectious episodes in major burns. ACS is associated with high mortality and should be treated with careful fluid resuscitation and diuresis. Surgery is reserved for non-responsive and severe cases. Perineal burns present challenges in wound and bowel management. Faecal management systems and negative pressure wound therapy (NPWT) may improve wound control and hygiene, but diversion colostomy will still be beneficial in some cases. There is a clear need for rigorous studies to guide practice more effectively in these challenging conditions.

Preservation of hepatic blood flow by direct peritoneal resuscitation improves survival and prevents hepatic inflammation following hemorrhagic shock

Conventional resuscitation (CR) from hemorrhagic shock (HS) results in gut and liver hypoperfusion, organ and cellular edema, and vital organ injury. Adjunct direct peritoneal resuscitation (DPR) with dialysate prevents gut vasoconstriction, hypoperfusion, and injury. We hypothesized that DPR might also improve hepatocellular edema, inflammation, and injury. Anesthetized male SD rats were assigned to groups (n = 8/group): 1) sham (no HS); 2) HS (40% MAP/60 min) + intravenous fluid conventional resuscitation [CR; shed blood + 2 vol saline (SAL)/30 min]; 3) HS+CR+DPR (30 ml ip 2.5% glucose dialysate); or 4) HS+CR+SAL (30 ml ip saline). Histopathology showed lung and liver injury in HS+CR and HS+CR+SAL up to 24-h postresuscitation (post-RES) that was not in shams and which was prevented by adjunct DPR. Wet-to-dry weight ratios in HS+CR revealed organ edema formation that was prevented by adjunct DPR. HS+CR and HS+CR+SAL had 34% mortality by 24-h post-RES, which was absent with DPR (0%). Liver IFN-γ and IL-6 levels were elevated in CR compared with DPR or shams. TNF-α mRNA was upregulated in CR/sham and DPR/sham. IL-17 was downregulated in DPR/sham. CXCL10 mRNA was upregulated in CR/sham but downregulated in DPR/sham. Despite restored central hemodynamic performance after CR of HS, liver blood flow was compromised up to 24 h post-RES, and the addition of DPR restores and maintains liver perfusion at 24-h post-RES. DPR prevented liver injury, histological damage, and edema formation compared with CR alone. DPR provided a mitigating anti-inflammatory dampening of the systemic inflammatory response. In all, these effects likely account for improved survivorship in the DPR-treated group.

Direct peritoneal resuscitation augments ileal blood flow in necrotizing enterocolitis via a novel mechanism

PURPOSE

Endothelin-1, prostaglandins (PGs), and nitric oxide (NO) have been implicated in the intestinal microvascular dysfunction of necrotizing enterocolitis (NEC). We hypothesized that direct peritoneal resuscitation (DPR) dilates the intestinal microvasculature and improves blood flow independent of these mechanisms.

METHODS

Rat pups were assigned by litter to experimental NEC or CONTROL groups. Laser Doppler flowmetry evaluation of intestinal microvascular blood flow was studied at baseline, with mediator blockade (endothelin-A receptor, endothelin-B receptor, PG synthesis, or NO synthase) and with DPR. Repeated-measures analysis of variance test was applied with Tukey-Kramer honestly significant difference test (P < .05).

RESULTS

At baseline, NEC animals demonstrated significantly decreased ileal blood flow as compared with CONTROLs (P < .05). Endothelin-A receptor and PG inhibition increased flow in the intestinal microvasculature, but this was significantly augmented by the addition of DPR (P < .05). Blockade of NO synthase decreased intestinal blood flow, which was overcome with addition of DPR (P < .05).

CONCLUSION

Ileal blood flow was significantly reduced in NEC animals as compared with CONTROLs. The addition of DPR to the peritoneum increased ileal blood flow significantly in all groups in spite of blockade of these known vasoactive mechanisms. Direct peritoneal resuscitation may be a novel strategy to improve intestinal blood flow in NEC.

The beneficial effect of direct peritoneal resuscitation on septic shock in rats

The high mortality associated with conventionally resuscitated septic shock and the subsequent multiple-organ failure remain a very significant and costly clinical problem. Conventional simple intravenous resuscitation (CR) from septic shock often fails to restore the progressive splanchnic vasoconstriction and hypoperfusion, and fails to reverse gut-derived systemic inflammatory response and fluid sequestration. Numerous interventions have been used to protect organ systems and cellular viability from the lethal injury accompanying hypoperfusion and ischemia but none of these efforts have been sufficient to halt or reverse the main course of the pathophysiology noted with conventional resuscitated shock. Recently, some studies have found that in hemorrhagic shock, direct peritoneal resuscitation (DPR) not only produces sustained hyperperfusion in viscera but also has immunomodulatory and anti-fluid sequestration effects. Although the etiology and pathogenesis of septic shock and hemorrhagic shock differ, both kinds of shock result in hypoperfusion of the intestines and other internal organs. In this paper, we seek to determine whether DPR has a similar therapeutic effect on septic shock/resuscitation.

Altered intestinal microcirculation is the critical event in the development of necrotizing enterocolitis

PURPOSE

The pathophysiology of necrotizing enterocolitis (NEC) includes prematurity, enteral feeds, hypoxia, and hypothermia. We hypothesized that vasoconstriction of the neonatal intestinal microvasculature is the essential mechanistic event in NEC and that these microvascular changes correlate with alterations in mediators of inflammation.

METHODS

Sprague-Dawley rat pups were separated into groups by litter. Necrotizing enterocolitis was induced in experimental groups, whereas control animals were delivered vaginally and dam fed. Neonatal pups underwent intravital videomicroscopy of the terminal ileum with particular attention to the inflow and premucosal arterioles. Reverse transcriptase-polymerase chain reaction was performed to evaluate for messenger RNA of mediators of inflammation.

RESULTS

Necrotizing enterocolitis animals demonstrated statistically significant smaller inflow and premucosal arterioles than control animals (P < .05). Necrotizing enterocolitis animals had an altered intestinal arteriolar flow with a distinct "stop-and-go" pattern, suggesting severe vascular dysfunction. Reverse transcriptase-polymerase chain reaction confirmed elevation of Toll-like receptor 4 (P = .01) and high-mobility group box protein 1 (P = .001) in the ileum of animals with NEC.

CONCLUSION

Intestinal arterioles were significantly smaller at baseline in animals with NEC compared with controls, and expression of inflammatory mediators was increased in animals with NEC. This represents a novel method of defining the pathophysiology of NEC and allows real-time evaluation of novel vasoactive strategies to treat NEC.

Hemorrhage-induced hepatic injury and hypoperfusion can be prevented by direct peritoneal resuscitation

BACKGROUND

Crystalloid fluid resuscitation after hemorrhagic shock (HS) that restores/maintains central hemodynamics often culminates in multi-system organ failure and death due to persistent/progressive splanchnic hypoperfusion and end-organ damage. Adjunctive direct peritoneal resuscitation (DPR) using peritoneal dialysis solution reverses HS-induced splanchnic hypoperfusion and improves survival. We examined HS-mediated hepatic perfusion (galactose clearance), tissue injury (histopathology), and dysfunction (liver enzymes).

METHODS

Anesthetized rats were randomly assigned (n = 8/group): (1) sham (no HS); (2) HS (40% mean arterial pressure for 60 min) plus conventional i.v. fluid resuscitation (CR; shed blood + 2 volumes saline); (3) HS + CR + 30 mL intraperitoneal (IP) DPR; or (4) HS + CR + 30 mL IP saline. Hemodynamics and hepatic blood flow were measured for 2 h after CR completion. In duplicate animals, liver and splanchnic tissues were harvested for histopathology (blinded, graded), hepatocellular function (liver enzymes), and tissue edema (wet-dry ratio).

RESULTS

Group 2 decreased liver blood flow, caused liver injuries (focal to submassive necrosis, zones 2 and 3) and tissue edema, and elevated liver enzymes (alanine aminotransferase (ALT), 149 +/- 28 microg/mL and aspartate aminotransferase (AST), 234 +/- 24 microg/mL; p < 0.05) compared to group 1 (73 +/- 9 and 119 +/- 10 microg/mL, respectively). Minimal/no injuries were observed in group 3; enzymes were normalized (ALT 89 +/- 9 microg/mL and AST 150 +/- 17 microg/mL), and tissue edema was similar to sham.

CONCLUSIONS

CR from HS restored and maintained central hemodynamics but did not restore or maintain liver perfusion and was associated with significant hepatocellular injury and dysfunction. DPR added to conventional resuscitation (blood and crystalloid) restored and maintained liver perfusion, prevented hepatocellular injury and edema, and preserved liver function.

Hemorrhagic shock and resuscitation-mediated tissue water distribution is normalized by adjunctive peritoneal resuscitation

BACKGROUND

Adjunctive direct peritoneal resuscitation (DPR) from hemorrhagic shock (HS) improves intestinal blood flow and abrogates postresuscitation edema. HS causes water shifts as a result of sodium redistribution and changes in transcapillary Starling forces. Conventional resuscitation (CR) with crystalloid aggravates water sequestration. We examined the compartment pattern of organ tissue water after HS and CR, and modulation of tissue edema by adjunctive DPR.

STUDY DESIGN

Rats were hemorrhaged (40% mean arterial pressure for 60 minutes) and assigned to four groups (n = 7): sham, no HS; HS no resuscitation; HS+CR (shed blood plus 2 volumes Ringer's lactate); and HS+CR+DPR (20 mL clinical intraperitoneal (IP) dialysis fluid). Isotopic markers determined equilibrium distribution volumes [V(D)] in gut, liver, lung, and muscle by quantitative autoradiography (2-hour postresuscitation). Total tissue water (TTW) was determined by wet-dry weights. Extracellular water was measured from (14)C-mannitol V(D), and intravascular volume (IVV) from (131)I-labeled IgG V(D). Cellular and interstitial water volumes were calculated.

RESULTS

HS alone decreased IVV in all tissues and TTW in gut, lung, and muscle, but not liver, compared with shams. IVV remained decreased with all resuscitations despite restoration of central hemodynamics. CR caused interstitial edema in gut, liver, and muscle, and cellular edema in lung. DPR reduced (liver, muscle) or prevented (gut, lung) these volume shifts.

CONCLUSIONS

HS decreases IVV. HS-induced water shifts are organ-specific and prominent in gut, lung, and muscle. CR restores central hemodynamics, does not restore IVV, and alters organ-specific TTW distribution. Adjunctive DPR with IP dialysis fluid normalizes TTW and water compartment distribution and prevents edema. Combined effect of DPR and intravascular fluid replacement appears to prevent global tissue edema and improve outcomes from HS.

Postresuscitation tissue neutrophil infiltration is time-dependent and organ-specific

BACKGROUND

Hemorrhagic shock with conventional resuscitation (CR) primes circulating neutrophils and activates vascular endothelium for increased systemic inflammation, superoxide release, and end-organ damage. Adjunctive direct peritoneal resuscitation (DPR) with intraperitoneal instillation of a clinical peritoneal dialysis solution decreases systemic inflammation and edema formation by enhancing tissue perfusion. The aim of this study is to determine the effect of adjunctive DPR on neutrophil and fluid sequestration.

METHODS

Anesthetized rats were hemorrhaged to 40% mean arterial pressure for 60 min. Animals were randomized for CR with the return of the shed blood plus two volumes of saline, or CR plus adjunctive DPR with 30 mL of intraperitoneal injection of a clinical peritoneal dialysis solution. Tissue myeloperoxidase (MPO) level, a marker of neutrophil sequestration, and total water content were assessed in the gut, lung, and liver in sham animals and at time-points 1, 2, 4, and 24 h postresuscitation.

RESULTS

Resuscitation from hemorrhagic shock increases MPO level in all tissues in a near-linear fashion during the first 4 h following resuscitation. This occurs irrespective of the resuscitation regimen used. Tissue MPO level returned to baseline at 24 h following resuscitation except in the liver where CR and not adjunctive DPR caused a significant rebound increase. Adjunctive DPR prevented the CR-mediated obligatory fluid sequestration in the gut and lung and maintained a relative normal tissue water in these organs compared with CR alone (n = 7, F = 10.1, P < 0.01).

CONCLUSION

Hemorrhagic shock and resuscitation produces time-dependent organ-specific trends of neutrophil sequestration as measured with tissue levels of myeloperoxidase, a marker of neutrophil infiltration. Modulation of the splanchnic blood flow by direct peritoneal resuscitation did not alter the time-dependent neutrophil infiltration in end-organs, suggesting a subordinate role of blood rheology in the hemorrhage-induced neutrophil sequestration. Vulnerable window for neutrophil-mediated tissue damage exists during the first 4 h following resuscitation from hemorrhagic shock in rats. Direct peritoneal resuscitation prevents the early obligatory fluid sequestration and promotes early fluid mobilization.

Cellular edema regulates tissue capillary perfusion after hemorrhage resuscitation

BACKGROUND

Hemorrhage-induced activation of endothelial cell Na+/H+ -exchanger results in cellular swelling, which physically impedes capillary filling and compromises gut perfusion. We hypothesized that correction of the vascular volume deficit by conventional resuscitation does not improve capillary filling unless cellular swelling is prevented. Also, we hypothesized that adjunctive direct peritoneal resuscitation (DPR) with topical peritoneal dialysis solution (Delflex; Fresenius USA, Inc., Ogden, Ut) enhances capillary filling and gut perfusion by mechanisms that are independent of the Na+/H+ function.

METHODS

In vivo intravital videomicroscopy and Doppler velocimeter were used by us to measure microvascular diameter and flow, capillary filling (index of functional capillary density, FCD), and endothelial cell function in the terminal ileum of anesthetized rats. Rats were bled to 50% mean arterial pressure for 60 min and resuscitated with the shed blood plus 2 volumes of saline (conventional resuscitation). Prevention of endothelial cell swelling was achieved with topical amiloride (specific Na+/H+ inhibitor) in the tissue bath before hemorrhage or simultaneously with conventional resuscitation. DPR was simulated by instillation of Delflex in the tissue bath as adjunctive to conventional resuscitation. Sham no hemorrhage group and a simulated DPR group that received topical amiloride treatment served as controls.

RESULTS

Conventional resuscitation from hemorrhagic shock restored and maintained central hemodynamics but caused progressive and persistent intestinal vasoconstriction and hypoperfusion associated with low FCD and endothelial cell dysfunction. Prevention of endothelial cell swelling when combined with conventional resuscitation, preserved endothelial cell function, and restored local intestinal microvascular variables to near-prehemorrhage levels. Simulated adjunctive DPR produced rapid, sustained, and generalized vasodilation associated with restoration of endothelial cell function, and maximum recruitment of FCD independent of the Na+/H+ -exchanger function.

CONCLUSIONS

Paradoxical endothelial cell swelling occurs early during hemorrhagic shock because of activation of the Na+/H+ exchanger. This cellular edema, which is not resolved by correction of the vascular volume deficit, explains the persistent postresuscitation endothelial cell dysfunction and gut hypoperfusion. Simulated adjunctive DPR in this study reversed endothelial cell swelling and enhanced gut perfusion by mechanisms that are independent of the Na+/H+ exchanger activity.

Mechanisms of direct peritoneal resuscitation-mediated splanchnic hyperperfusion following hemorrhagic shock

Conventional resuscitation (CR) from hemorrhagic shock causes a persistent and progressive splanchnic vasoconstriction and hypoperfusion despite hemodynamic restoration with intravenous fluid therapy. Adjunctive direct peritoneal resuscitation (DPR) with a clinical peritoneal dialysis solution instilled into the peritoneal cavity has been shown to restore splanchnic tissue perfusion, down-regulate the gut-derived exaggerated systemic inflammatory response, promote early fluid mobilization, and improve overall outcome. This study was conducted to define the molecular mechanisms of DPR-induced gut hyperperfusion after hemorrhagic shock. Male rats were bled to 50% baseline mean arterial pressure and resuscitated with the shed blood plus two volumes of saline (CR). In vivo videomicroscopy and Doppler velocimetry were used to assess terminal ileal microvascular diameters and blood flow. Direct peritoneal resuscitation animals received CR and topical application of a clinical glucose-based peritoneal dialysis solution (Delflex). Inhibitors, glibenclamide (K(+)ATP channels), N-monomethyl-L-arginine (L-NMMA) (nitric oxide synthase), 8-cyclopentyl-1,3-diprophylxanthine (DPCPX) (A1 adenosine receptor), tetrabutylammonium (K(+)Ca2+ channels), and mefenamic acid (cyclooxygenase) were topically applied (individually or in combination) with DPR according to protocol; BQ-123 (endothelin A receptor antagonist) and BQ-788 (endothelin B receptor antagonist) were used topically with CR to define the mechanism of post-CR vasoconstriction and hypoperfusion. Conventional resuscitation caused a persistent progressive intestinal vasoconstriction and hypoperfusion that can be abolished with endothelin antagonists. In contrast, adjunctive DPR caused an instantaneous sustained vasodilation and hyperperfusion. Glibenclamide or L-NMMA partially attenuated DPR-induced vasodilation, whereas the addition of DPCPX to the two inhibitors eliminated the dilation. Cyclooxygenase and K(+)Ca2+channels were not active in DPR-mediated microvascular effects. In conclusion, DPR improves splanchnic tissue perfusion by endothelium-dependent mechanisms mediated by activations of glibenclamide-sensitive K(+) channels (KATP), adenosine A1 receptor subtype activation, and nitric oxide release. Direct peritoneal resuscitation preserves endothelial dilatory functions, thereby overriding any endothelium-derived constrictor response triggered by hemorrhagic shock and CR.

Clinical peritoneal dialysis solutions modulate white blood cell-intestinal vascular endothelium interaction

BACKGROUND

Hemorrhagic shock (HS) with conventional resuscitation (CR) (HSCR) primes neutrophils and modulates leukocyte (WBC)-endothelium interaction as part of an exaggerated systemic inflammatory response. We hypothesize that topical application of clinical peritoneal dialysis solutions (PD) modulates such interaction.

METHODS

Intestinal intravital microscopy was used to measure WBC rolling in terminal ileum post capillary venules (V2 and V3) in sham-operated animals, and in animals that underwent fixed pressure hemorrhage (50% mean arterial pressure for 60 minutes), followed by conventional resuscitation with the return of the shed blood and 2 vol of saline. Number of rolling WBCs per thirty seconds in selected V2 and V3, bathed in either Kreb's solution or a 2.5% clinical peritoneal dialysis solution (PD) was quantified. Diameters were measured for the in-flow arterioles (A1), and out-flow venules (V1), for calculation of local blood flow with optical Doppler velocimetry.

RESULTS

The PD solution significantly (P < .05, n = 11) attenuated WBC-endothelium interaction in sham-operated animals while no significant difference was elicited in HSCR (P > .05, n = 9 Kreb's, n = 7 PD). In addition, the PD solution produced an instantaneous dilation at all levels of the intestinal arterioles in both sham and HSCR. While intestinal venular blood outflow was increased by the PD solution, venular diameters changed very little.

CONCLUSION

Superfusion of the gut with glucose-based peritoneal dialysis solutions decreases the concentration of rolling leukocytes along the venular vascular endothelium by a vasodilation-mediated increase in arteriolar inflow and venous outflow mechanism. Hemorrhagic shock and conventional resuscitation enhance the concentration of rolling leukocytes presumably by mechanisms related to upregulation of the adhesion molecules and the low-flow state. Hemorrhage and resuscitation-enhanced leukocytes rolling was not reversed by adjunctive DPR despite the associated marked increase in arterial inflow and venous outflow. The status of the endothelium and the level of leukocyte priming in low-flow states are stronger predictors of leukocyte-endothelium interaction than rheology factors.

Direct energy delivery improves tissue perfusion after resuscitated shock

BACKGROUND

Conventional resuscitation (CR) from hemorrhagic shock (HS) does not restore intestinal blood flow. Indicators of anaerobic metabolism suggest that cellular energy production also is compromised. We hypothesize that the direct intravenous delivery of lipid-encapsulated high-energy phosphates to cells improves intestinal perfusion during HS and resuscitation (RES).

METHODS

MAP (MAP) was monitored in male rats (200 g), terminal ileum microvessel diameters were measured by in vivo videomicroscopy, and blood flow (Doppler velocimetry) was calculated. Cellular energy delivery was accomplished by intravenous infusion during RES of fusogenic unilamellar lipid vesicles that contain adenosine triphosphate (ATP; VitaSol). Our protocol was HS to 50% baseline MAP for 60 minutes, 30 minutes of RES, and continued microscopy observation for 120 minutes. Experimental groups (n=8 each) were HS+CR (group I); HS+CR+ VitaSol (group II); HS+CR+Vehicle, Vehicle is the phospholipid vesicles without magnesium ATP, (group III); HS+ VitaSol (group IV); sham-operated control+VitaSol (group V); and a time-matched sham-operated control (group VI). The survival outcome and total tissue water from wet weight/dry weight ratio as a function of adjunct VitaSol resuscitation were evaluated in separate intact animal experiments.

RESULTS

HS caused a selective vasoconstriction of the intestinal inflow arterioles (100 microm), which was not seen in the smaller intestinal premucosal arterioles (7-15 microm). CR, which restored baseline hemodynamics, resulted in an initial restoration of intestinal microvascular diameters at all arteriolar levels. However, this was followed by a progressive vasoconstriction and hypoperfusion in premucosal vessels at 120 minutes after RES (-20.48% +/- 2.95% from baseline diameters). In contrast, VitaSol with CR caused enhanced premucosal dilation (+34.27% +/- 4.62%) and augmented flow (+20.50% +/- 10.70%) above prehemorrhage baseline. Vesicles alone had no effect, and VitaSol alone caused only a modest dilation. CR of moderate HS (40% of baseline MAP for 60 minutes, n=10) caused 20% mortality, whereas adjunct VitaSol resuscitation had a 100% survival and less tissue water content.

CONCLUSIONS

Our data confirms that CR causes progressive intestinal hypoperfusion. Cellular resuscitation with direct intravenous energy delivery improves intestinal perfusion after CR and results in improved survival and less tissue edema.

Peritoneal resuscitation

BACKGROUND

After resuscitation from hemorrhagic shock, intestinal microvessels constrict leading to impaired mucosal blood flow. This occurs despite restoration of central hemodynamics. We review studies on the use of peritoneal dialysis fluid as an adjunct treatment in amelioration of this gut hypoperfusion.

METHODS

Using in vivo microscopy of the intestinal microcirculation, the effects of topically applied dextrose-based peritoneal dialysis fluid was measured. In other words, animal experiments, the survival benefits, the morbidity, blood flow distribution, and the postresuscitation inflammatory response to direct peritoneal resuscitation (DPR) were determined.

RESULTS

Simulated DPR caused a dramatic vasodilation compared with a progressive vasoconstriction when used during conventional resuscitation (CR) from hemorrhagic shock. It also reversed established vasoconstriction 2 and 4 hours after CR. In CR animals, there was a 40% mortality compared with 100% survival in DPR animals. DPR resulted in a downregulation of the gut-associated proinflammatory response noted after CR and similarly prevented edema formation.

CONCLUSION

DPR enhances organ blood flow to organs incited in the pathogenesis of multiple organ failure and improves survival after severe hemorrhage and CR.

Direct peritoneal resuscitation from hemorrhagic shock: effect of time delay in therapy initiation

BACKGROUND

After conventional resuscitation from hemorrhagic shock, splanchnic microvessels progressively constrict, leading to impairment of blood flow. This occurs despite restoration and maintenance of central hemodynamics. The authors' recent studies have demonstrated that topical and continuous ex vivo exposure of the gut microvasculature to a glucose-based clinical peritoneal dialysis solution (Delflex), as a technique of direct peritoneal resuscitation (DPR), can prevent these postresuscitation events when initiated simultaneously with conventional resuscitation. This study aimed to determine whether DPR applied after conventional resuscitation reverses the established postresuscitation intestinal vasoconstriction and hypoperfusion.

METHODS

Male Sprague-Dawley rats were bled to 50% of baseline mean arterial pressure and resuscitated intravenously over 30 minutes with the shed blood returned plus two times the shed blood volume of saline. Initiation of ex vivo, topical DPR was delayed to 2 hours (group 1, n = 8), or to 4 hours (group 2, n = 8), respectively, after conventional resuscitation. Intravital microscopy and Doppler velocimetry were used to measure terminal ileal microvascular diameters of inflow A1 and premucosal A3 (proximal pA3, distal dA3) arterioles and blood flow in the A1 arteriole, respectively. Maximum arteriolar dilation capacity was obtained from the topical application, in the tissue bath, of the endothelium-independent nitric oxide-donor sodium nitroprusside (10M).

RESULTS

Hemorrhagic shock caused a selective vasoconstriction of A1 (-24.1% +/- 2.15%) arterioles from baseline, which was not seen in A3 vessels. This caused A1 blood flow to drop by -68.6% of the prehemorrhage value. Conventional resuscitation restored and maintained hemodynamics in all the animals without additional fluid therapy. In contrast, there was a generalized and progressive postresuscitation vasoconstriction of A1 (-21.7%), pA3 (-18.5%), and dA3 (-18.7%) vessels. The average postresuscitation A1 blood flow was -49.5% of the prehemorrhage value, indicating a persistent postresuscitation hypoperfusion. Direct peritoneal resuscitation reversed the postresuscitation vasoconstriction by 40.9% and enhanced A1 blood flow by 112.9% of the respective postresuscitation values.

CONCLUSIONS

Delayed DPR reverses the gut postresuscitation vasoconstriction and hypoperfusion regardless of the initiation time. This occurs without adverse effects on hemodynamics. Direct peritoneal resuscitation-mediated enhancement of tissue perfusion results from the local effects from the vasoactive components of the Delflex solution, which are hyperosmolality, lactate buffer anion, and, to a lesser extent, low pH. The molecular mechanism of this vasodilation effect needs further investigation.

A novel method of peritoneal resuscitation improves organ perfusion after hemorrhagic shock

BACKGROUND

After resuscitation from hemorrhagic shock, intestinal microvessels constrict leading to impairment of blood flow. This occurs despite restoration and maintenance of central hemodynamics. Our recent studies have demonstrated that topical and continuous exposure of the gut microvasculature to a clinical solution (Delflex; Fresenius Medical Care), as a technique of direct peritoneal resuscitation (DPR), reverses the postresuscitation vasoconstriction and hypoperfusion to a sustained dilation and hyperperfusion. We hypothesize that initiation of DPR simultaneously with resuscitation from hemorrhagic shock enhance organ blood flow to all tissues surrounding the peritoneal cavity as well as distant organs.

METHODS

Male Sprague-Dawley rats were anesthetized, intubated and cannulated for monitoring of hemodynamics and for withdrawal of blood. Rats were hemorrhaged to 50% of mean blood pressure for 60 minutes prior to resuscitation with shed blood plus 2 volumes of saline. Animals were randomized for intraperitoneal therapy with 30 mL saline (group 1, n = 9), or Delflex (group 2, n = 9). Whole organ blood flow was measured by colorimetric microsphere technique with phantom organ at baseline, after completion of resuscitation, and at 120 minutes postresuscitation. Replenishment of the dwelling intraperitoneal saline or Delflex was performed in (group 3, n = 8), and (group 4, n = 8), respectively at 90 minutes postresuscitation, and a single whole organ blood flow was performed at 120 minutes postresuscitation.

RESULTS

Direct peritoneal resuscitation caused a significant increase in blood flow to the jejunum (35%), ileum (33%), spleen (48%), and pancreas (57%), whereas a marked increase in blood flow was detected in the lung (111%), psoas major muscle (115%), and diaphragm (132%), as compared with the saline treated animals in group 1. At 120 minutes postresuscitation, organ blood flow returned to the prehemorrhagic shock baseline level in all organs irrespective of peritoneal therapy. Replenishment of the intraperitoneal solution in group 3 and 4, enhanced blood flow to the liver, kidneys, and diaphragm.

CONCLUSIONS

Direct peritoneal resuscitation enhanced blood flow to organs incited in the pathogenesis of multiple organ failure that follows hemorrhagic shock.