Superior Survival Outcomes of a Polyethylene Glycol-20k Based Resuscitation Solution in a Preclinical Porcine Model of Lethal Hemorrhagic Shock.

OBJECTIVE: To compare early outcomes and 24-hour survival after LVR with the novel polyethylene glycol-20k-based crystalloid (PEG-20k), WB, or hextend in a preclinical model of lethal HS. BACKGROUND: Posttraumatic HS is a major cause of preventable death. current resuscitation strategies focus on restoring oxygen-carrying capacity (OCC) and coagulation with blood products. Our lab shows that PEG-20k is an effective non-sanguineous, LVR solution in acute models of HS through mechanisms targeting cell swelling-induced microcirculatory failure. METHODS: Male pigs underwent splenectomy followed by controlled hemorrhage until lactate reached 7.5-8.5 mmol/L. They were randomized to receive LVR with PEG-20k, WB, or Hextend. Surviving animals were recovered 4 hours post-LVR. Outcomes included 24-hour survival rates, mean arterial pressure, lactate, hemoglobin, and estimated intravascular volume changes. RESULTS: Twenty-four-hour survival rates were 100%, 16.7%, and 0% in the PEG-20k, WB, and Hextend groups, respectively (P= 0.001). PEG-20k significantly restored mean arterial press, intravascular volume, and capillary perfusion to baseline, compared to other groups. This caused complete lactate clearance despite decreased OCC. Neurological function was normal after next-day recovery in PEG-20k resuscitated pigs. CONCLUSION: Superior early and 24-hour outcomes were observed with PEG-20k LVR compared to WB and Hextend in a preclinical porcine model of lethal HS, despite decreased OCC from substantial volume-expansion. These findings demonstrate the importance of enhancing microcirculatory perfusion in early resuscitation strategies.

Acute resuscitation with polyethylene glycol-20k: A thromboelastographic analysis.

BACKGROUND: Previous ex vivo studies have shown that polyethylene glycol-20,000 Da (PEG-20k), a novel synthetic polymer that is highly effective for resuscitation, has a hypocoagulable effect on human blood. This study's objective was to determine the in vivo effects of PEG-20k-based resuscitation solutions on coagulation and platelet function in a porcine model of hemorrhagic shock. METHODS: Anesthetized pigs underwent controlled hemorrhage until the lactate reached 7 mmol/L or 50% to 55% of their estimated blood volume was removed. A laparotomy was performed to simulate tissue injury. Low volume resuscitation (LVR) was given with fluorescein isothiocyanate-labeled 10% PEG-20k solution (100 mg/mL) or Lactated Ringers, both delivered at volumes equal to 10% of the estimated blood volume (n = 5). Thromboelastography was performed after surgery (baseline), after hemorrhage, and 15 minutes, 120 minutes, and 240 minutes postresuscitation. Hemoglobin was measured to determine changes in plasma volume. Plasma PEG-20k concentration was measured by indicator dilution. RESULTS: Pigs given PEG-20k survived 2.6-fold longer than controls (p < 0.001) and had a significant increase in plasma volume demonstrated by the sustained drop in hemoglobin, relative to controls. Pigs resuscitated with LR died from hypotension an average of 90 minutes after resuscitation compared to the PEG-20k pigs, which all survived 240 minutes and were then euthanized with normal blood pressure and lactate. Administration of PEG-20k primarily decreased the thromboelastograph maximum amplitude, however this began to return toward baseline by 240 minutes. Peak plasma concentration of PEG-20k after LVR were 40% lower than predicted, based on simple dilution (5.7 mg/mL vs. 10 mg/mL) and the half-life was 59.6 minutes. CONCLUSION: These data demonstrate that acute resuscitation with PEG-20k significantly improves tolerance to hypovolemia but also decreases platelet function in the coagulation cascade, which was due, in part, to its volume expanding effects.

Low-volume resuscitation using polyethylene glycol-20k in a preclinical porcine model of hemorrhagic shock.

INTRODUCTION: Polyethylene glycol-20k (PEG-20k) is highly effective for low-volume resuscitation (LVR) by increasing tolerance to the low-volume state. In our rodent shock model, PEG-20k increased survival and expanded the "golden hour" 16-fold compared to saline. The molecular mechanism is largely attributed to normalizations in cell and tissue fluid shifts after low-flow ischemia resulting in efficient microvascular exchange. The objective of this study was to evaluate PEG-20k as an LVR solution for hemorrhagic shock in a preclinical model. METHODS: Anesthetized male Yorkshire pigs (30-40 kg) were hemorrhaged to a mean arterial pressure (MAP) of 35 to 40 mm Hg. Once lactate reached 7 mmol/L, either saline (n = 5) or 10% PEG-20k (n = 5) was rapidly infused at 10% calculated blood volume. The primary outcome was LVR time, defined by the time from LVR administration to the time when lactate again reached 7 mmol/L. Other outcomes measured included MAP, heart rate, cardiac output, mixed venous oxygen saturation, splanchnic blood flow, and hemoglobin. RESULTS: Relative to saline, PEG-20k given after controlled hemorrhage increased LVR time by 16-fold, a conservative estimate given that the lactate never rose after LVR in the PEG-20k group. Survival was 80% for PEG-20k LVR compared to 0% for the saline controls (p < 0.05). Polyethylene glycol-20k also significantly decreased heart rate after hemorrhage and increased cardiac output, MAP, splanchnic flow, and mixed venous oxygen saturation. Falling hemoglobin concentrations suggested sizable hemodilution from fluid shifts into the intravascular compartment. CONCLUSIONS: In a preclinical model of controlled hemorrhagic shock, PEG-20k-based LVR solution increased tolerance to the shock state 16-fold compared to saline. Polyethylene glycol-20k is a superior crystalloid for LVR that may increase safe transport times in the prehospital setting and find use in hospital emergency departments and operating rooms for patients awaiting volume replacement or normalization of cell, tissue, and compartment fluid volumes.

Comparison of a new hemostatic agent to current combat hemostatic agents in a Swine model of lethal extremity arterial hemorrhage.

BACKGROUND: Gaining hemostatic control of lethal vascular injuries sustained in combat using topical agents remains a challenge. Recent animal testing using a lethal arterial injury model has demonstrated that QuikClot zeolite granules (QCG) and the HemCon chitosan bandage (HC) are not capable of providing hemostasis and improving survival over the Army gauze field bandage (AFB). We have developed a new hemostatic agent consisting of a granular combination of a smectite mineral and a polymer (WoundStat) capable of producing hemostasis in the face of high-pressure arterial bleeding. We compared the performance of WoundStat (WS) to QCG, HC, AFB, and the new QuikClot zeolite Advance Clotting Sponge (ACS) in a lethal vascular injury model. METHODS: Hemostatic agents were tested using a lethal femoral artery vascular injury model. Twenty-five (5 per group) male swine (42 kg +/- 3 kg) were anesthetized, instrumented, and splenectomized. A lethal femoral artery injury was produced by creating a 6-mm arteriotomy in the vessel. After 45 seconds of hemorrhage, animals were randomized to be treated with AFB (control group), HC, QCG, ACS, or WS. Pressure (200 mm Hg) was applied over the product in the wound for 3 minutes. A second application and 3 additional minutes of pressure was provided if hemostasis was not achieved. Fluid resuscitation was begun at the time of application with 500 mL of Hextend, followed by lactated Ringer's solution at 100 mL/min to achieve and maintain a postapplication mean arterial blood pressure of 65 mm Hg. Animals were observed for 180 minutes or until death. Primary endpoints were survival, survival time, post-treatment blood loss, and amount of resuscitation fluid. RESULTS: All animals treated with WS survived to 180 minutes and required only a single application. No animal in the AFB, QCG, or ACS group survived. One animal in the HC group survived. Survival (p < 0.05) and survival times (p < 0.0001) for WS animals were significantly greater than for all other groups. No significant difference in survival or survival time existed between the AFB, QCG, ACS, or HC groups. Post-treatment blood loss (p = 0.0099) and postresuscitation fluid volume (p = 0.006) was significantly less for animals treated with WS than for all other groups. No significant difference in these parameters existed between the AFB, QCG, ACS, and HC groups. CONCLUSION: WS was superior to the other hemostatic agents tested in this study of lethal arterial vascular injury. Additional study is warranted on this agent to determine its potential for use in combat and civilian trauma.

Amplified cytokine response and lung injury by sequential hemorrhagic shock and abdominal compartment syndrome in a laboratory model of ischemia-reperfusion.

BACKGROUND: Increased intra-abdominal pressure has been shown to result in a myriad of physiologic aberrations that result in the abdominal compartment syndrome (ACS). The clinically relevant combination of hemorrhagic shock and resuscitation and subsequent ACS, however, has not been studied in detail. We hypothesized that sequential hemorrhagic shock (HS) and ACS would result in greater cytokine activation and polymorphonuclear neutrophil (PMN)-mediated lung injury than with either insult alone. METHODS: Twenty Yorkshire swine (20-30 kg) were studied. Group 1 (n = 5) was hemorrhaged to a mean arterial pressure of 25 to 30 mm Hg for 60 minutes and resuscitated to baseline mean arterial pressure. Intra-abdominal pressure was then increased to 30 mm Hg above baseline and maintained for 60 minutes. Group 2 (n = 5) was subjected to HS alone and Group 3 (n = 5) to ACS alone. Group 4 (n = 5) had sham experiment without HS or ACS. Central and portal venous interleukin-1beta, interleukin-8, and tumor necrosis factor-alpha levels were serially measured. Bronchoalveolar lavage (BAL) for protein and PMNs was performed at baseline and 24 hours after resuscitation. Lung myeloperoxidase was evaluated at 24 hours after resuscitation. RESULTS: Portal and central vein cytokine levels were equivalent but were significantly higher in Group 1 than in other groups. BAL PMNs were higher (p < 0.05) in Group 1 (4.1 +/- 2.0 x 106) than in the other groups (0.6 +/- 0.5, 1.4 +/- 1.3, and 0.1 +/- 0.0 x 106, respectively) and lung myeloperoxidase activity was higher (p < 0.05) in Group 1 (134.6 +/- 57.6 x 106/g) than in the other groups (40.3 +/- 14.7, 46.1 +/- 22.4, and 7.73 +/- 4.4 x 106/g, respectively). BAL protein was higher (p < 0.01) in Group 1 (0.92 +/- 0.32 mg/mL) compared with the other groups (0.22 +/- 0.08, 0.29 +/- 0.11, and 0.08 +/- 0.06 mg/mL, respectively). CONCLUSION: In this clinically relevant model, sequential insults of ischemia-reperfusion (HS and resuscitation) and ACS were associated with significantly increased portal and central venous cytokine levels and more severe lung injury than HS or ACS alone.

The effects of hemodynamic shock and increased intra-abdominal pressure on bacterial translocation.

BACKGROUND: We hypothesized that hemorrhagic shock followed by the abdominal compartment syndrome (ACS) resulted in bacterial translocation (BT) from the gastrointestinal (GI) tract. METHODS: Nineteen Yorkshire swine (20-30 kg) were divided into two groups. In the experimental group, group 1 (n = 10), animals were hemorrhaged to a mean arterial pressure (MAP) of 25-30 mm Hg for a period of 30 minutes and resuscitated to baseline MAP. Subsequently, intra-abdominal pressure (IAP) was increased to 30 mm Hg above baseline by instilling sterile normal saline into the peritoneal cavity. The IAP was maintained at this level for 60 minutes. Acid/base status, gastric mucosal ph (pHi), superior mesenteric artery (SMA) blood flow, and hemodynamic parameters were measured and recorded. Blood samples were analyzed by polymerase chain reaction (PCR) for the presence of bacteria. Spleen, lymph node, and portal venous blood cultures were obtained at 24 hours. Results were analyzed by ANOVA and are reported as mean +/- SEM. The second group was the control. These animals did not have the hemorrhage, resuscitation, or intra-abdominal hypertension (IAH) but were otherwise similar to the experimental group in terms of laparotomy and measured parameters. RESULTS: SMA blood flow in group 1 (baseline of 0.87 +/- 0.10 l/min) decreased in response to hemorrhage (0.53 +/- 0.10 l/min, p = 0.0001) and remained decreased with IAH (0.63 l/min +/- 0.10, p = 0.0006) as compared to control and returned towards baseline (1.01 +/- 0.5 l/min) on relief of IAH. pHi (baseline of 7.21 +/- 0.03) was significantly decreased with hemorrhage (7.04 +/- 0.03, p = 0.0003) and decreased further after IAH (6.99 +/- 0.03, p = 0.0001) in group 1 compared to control, but returned toward baseline at 24 hours (7.28 +/- 0.04). The mean arterial pH decreased significantly from 7.43 +/- 0.01 at baseline to 7.27 +/- 0.01 at its nadir within group 1 (p = 0.0001) as well as when compared to control (p = 0.0001). Base excess was also significantly decreased between groups 1 and 2 during hemorrhage (3.30 +/- 0.71 vs. 0.06 +/- 0.60, p = 0.001) and IAH (3.08 +/- 0.71 vs. -1.17 +/- 0.60, p = 0.0001). In group 1, 8 of the 10 animals had positive lymph node cultures, 2 of the 10 had positive spleen cultures, and 2 of the 10 had positive portal venous blood cultures for gram-negative enteric bacteria. Only 2 of the 10 animals had a positive PCR. In group 2, five of the nine animals had positive lymph node cultures, zero of the nine had positive spleen cultures, and one of the nine had positive portal venous blood cultures. Two of the nine animals had positive PCRs. There was no significant difference in cultures or PCR results between the two groups (Fisher's exact test, p = 0.3). CONCLUSION: In this study, hemorrhage followed by reperfusion and a subsequent insult of IAH caused significant GI mucosal acidosis, hypoperfusion, as well as systemic acidosis. These changes did not appear to be associated with a significant bacterial translocation as judged by PCR measurements, tissue, or blood cultures.