Metabolic networks in a porcine model of trauma and hemorrhagic shock demonstrate different control mechanism with carbohydrate pre-feed.

BACKGROUND: Treatment with oral carbohydrate prior to trauma and hemorrhage confers a survival benefit in small animal models. The impact of fed states on survival in traumatically injured humans is unknown. This work uses regulatory networks to examine the effect of carbohydrate pre-feeding on metabolic response to polytrauma and hemorrhagic shock in a clinically-relevant large animal model. METHODS: Male Yorkshire pigs were fasted overnight (n = 64). Pre-fed animals (n = 32) received an oral bolus of Karo\textregistered\syrup before sedation. All animals underwent a standardized trauma, hemorrhage, and resuscitation protocol. Serum samples were obtained at set timepoints. Proton NMR was used to identify and quantify serum metabolites. Metabolic regulatory networks were constructed from metabolite concentrations and rates of change in those concentrations to identify controlled nodes and controlling nodes of the network. RESULTS: Oral carbohydrate pre-treatment was not associated with survival benefit. Six metabolites were identified as controlled nodes in both groups: adenosine, cytidine, glycerol, hypoxanthine, lactate, and uridine. Distinct groups of controlling nodes were associated with controlled nodes; however, the composition of these groups depended on feeding status. CONCLUSIONS: A common metabolic output, typically associated with injury and hypoxia, results from trauma and hemorrhagic shock. However, this output is directed by different metabolic inputs depending upon the feeding status of the subject. Nodes of the network that are related to mortality can potentially be manipulated for therapeutic effect; however, these nodes differ depending upon feeding status.

Hypercoagulability in porcine hemorrhagic shock is present early after trauma and resuscitation.

INTRODUCTION: The understanding of coagulopathy associated with trauma continues to evolve. Trauma patients are frequently coagulopathic early after injury and become hypercoagulable within days of injury. Thrombelastography (TEG) allows real-time evaluation of the coagulation status of patients. We hypothesized that TEG will identify post-traumatic hypercoagulable state in our porcine model of hemorrhagic shock and resuscitation. METHODS: Fourteen male Yorkshire pigs were sedated, instrumented, and splenectomized via laparotomy. Eight of these animals underwent a shock protocol consisting of a pulmonary contusion via captive bolt gun, 35% hemorrhage and two liver fractures. Vitals, hemodynamics, physiologic parameters and TEG were measured at baseline, after shock and at intervals after injury thru 72 h post-injury. RESULTS: Animals undergoing surgery and instrumentation demonstrated the same hypercoagulable patterns as animals that received shock, injury, and resuscitation. In this model, hypercoagulability was present in both groups at 4 h after injury and continued for 72 h post-injury (increased angle and maximum amplitude, P < 0.05, compared to baseline). Statistically significant differences between the groups were noted at both 16 and 48 h post-injury. CONCLUSIONS: Hypercoagulability is present early after surgical intervention and trauma. This finding has implications for use of deep venous thrombosis (DVT) prophylaxis in trauma patients.

Analysis of biomarkers characteristic of porcine liver injury--from biomolecular logic gates to an animal model.

A biocatalytic cascade for the analysis of the simultaneous increase in the concentration of two biomarkers characteristic of liver injury (alanine transaminase, ALT, and lactate dehydrogenase, LDH) was tested on real samples acquired from an animal model (domestic pigs, Sus scrofa domesticus) suffering from traumatic liver injury. A two-step reaction biocatalyzed in the presence of both enzyme-biomarkers resulted in the oxidation of NADH followed by optical absorbance measurements. A simple qualitative, YES/NO, test allowed for distinction between animals with and without the presence of liver injury with the probability of 92%. These data represent the first demonstration of applying binary logic systems for the analysis of real biomedical samples.

Perioperative Coagulation Changes in Total Pancreatectomy and Islet Autotransplantation.

OBJECTIVES: Thrombotic complications after total pancreatectomy with islet autotransplantation (TPIAT) are common. However, the systemic changes to coagulation in the perioperative period have not been well studied. Our objective was to evaluate the derangements in coagulation in the perioperative period for this procedure. METHODS: This was a prospective observational study of patients undergoing elective TPIAT for chronic pancreatitis. Multiple methods of evaluating coagulation, including 2 viscoelastic assays and standard laboratory assays were obtained at defined intraoperative and postoperative intervals. RESULTS: Fifteen patients were enrolled. Laboratory values demonstrated initial intraoperative hypercoagulability before significant systemic anticoagulation after islet infusion with heparin. Hypercoagulability is again seen at postoperative days 3 and 7. Subgroup analysis did not identify any major coagulation parameters associated with portal vein thrombosis formation. CONCLUSIONS: Apart from the immediate period after islet cell and heparin infusion, patients undergoing TPIAT are generally hypercoagulable leading to a high rate of thrombotic complications. Portal vein thrombosis development had minimal association with systemic derangements in coagulation as it is likely driven by localized inflammation at the time of islet cell infusion. This study may provide the groundwork for future studies to identify improvements in thrombotic complications.

MG53 as a Novel Therapeutic Protein to Treat Acute Lung Injury.

INTRODUCTION: Lung injury has several inciting etiologies ranging from trauma (contusion and hemorrhage) to ischemia reperfusion injury. Reflective of the injury, tissue and cellular injury increases proportionally with the injury stress and is an area of potential intervention to mitigate the injury. This study aims to evaluate the therapeutic benefits of recombinant human MG53 (rhMG53) protein in porcine models of acute lung injury (ALI). MATERIALS AND METHODS: We utilized live cell imaging to monitor the movement of MG53 in cultured human bronchial epithelial cells following mechanical injury. The in vivo efficacy of rhMG53 was evaluated in a porcine model of hemorrhagic shock/contusive lung injury. Varying doses of rhMG53 (0, 0.2, or 1 mg/kg) were administered intravenously to pigs after induction of hemorrhagic shock/contusive induced ALI. Ex vivo lung perfusion system enabled assessment of the isolated porcine lung after a warm ischemic induced injury with rhMG53 supplementation in the perfusate (1 mg/mL). RESULTS: MG53-mediated cell membrane repair is preserved in human bronchial epithelial cells. rhMG53 mitigates lung injury in the porcine model of combined hemorrhagic shock/contusive lung injury. Ex vivo lung perfusion administration of rhMG53 reduces warm ischemia-induced injury to the isolated porcine lung. CONCLUSIONS: MG53 is an endogenous protein that circulates in the bloodstream. Therapeutic treatment with exogenous rhMG53 may be part of a strategy to restore (partially or completely) structural morphology and/or functional lung integrity. Systemic administration of rhMG53 constitutes a potential effective therapeutic means to combat ALI.

Liver metabolomic changes identify biochemical pathways in hemorrhagic shock.

BACKGROUND: Despite ongoing advances in treatment, thousands of patients still die annually from complications due to hemorrhagic shock, a condition causing dramatic physiologic and metabolic changes as cells switch to anaerobic metabolism in response to oxygen deprivation. As the shift from aerobic to anaerobic metabolism occurs in the peripheral tissues during shock, the liver must increase production of endogenous glucose as well as process excess lactate produced in the periphery. This places the liver at the center of metabolic regulation in the body during hemorrhagic shock. Therefore, we hypothesized that liver tissue from pigs during an in vivo model of hemorrhagic shock (n = 6) would reflect resultant metabolic changes. MATERIALS AND METHODS: The in vivo model of shock consisted of 45 min of shock followed by 8 h of hypotensive resuscitation (80 mmHg) and subsequent normotensive resuscitation (90 mmHg) ending 48 h after the shock period. Control groups of pigs (n = 3) (1) shock with no resuscitation, and (2) only anesthesia and instrumentation, also were included. Metabolic changes within the liver after shock and during resuscitation were investigated using both proton ((1)H) and phosphorous ((31)P) nuclear magnetic resonance (NMR) spectroscopy. RESULTS: Concentrations of glycerylphosphorylcholine (GPC) and glycerylphosphorylethanolamine (GPE) were significantly lower at 8 h after shock, with recovery to baseline by 23 and 48 h after shock. Uridine diphosphate-glucose (UDP-glucose), and phosphoenolpyruvate (PEP) were elevated 23 h after shock. CONCLUSIONS: These results indicate that (1)H and (31)P NMR spectroscopy can be used to identify differences in liver metabolites in an in vivo model of hemorrhagic shock, indicating that metabolomic analysis can be used to elucidate biochemical events occurring during this complex disease process.

Noninvasive tissue oxygen saturation measurements identify supply dependency.

BACKGROUND: Hemorrhagic shock can lead to multiple organ failure and death. We have previously shown that noninvasive measurement of tissue oxygen saturation (StO(2)) has predictive value for outcomes in patients suffering hemorrhagic shock. Our study objectives were twofold: (1) to compare invasive and noninvasive measurements of local and systemic tissue hemoglobin oxygenation and (2) to compare the effects of various physiologic conditions seen in patients in hemorrhagic shock on tissue hemoglobin oxygenation. MATERIALS AND METHODS: We studied pigs in controlled conditions mimicking shock induced by one of the following: hypothermia, isovolemic hemodilution, or manipulations of vascular tone. We obtained both invasive and noninvasive measurements in a hind limb of StO(2), tissue hemoglobin index, femoral artery and venous flows, blood pressures, temperature, pH, pO(2), pCO(2), oxygen saturation, lactate, hemoglobin, and base excess. In all cases, we measured baseline values in both experimental and control hind limbs. RESULTS: We found that tissue hemoglobin oxygenation did not vary significantly over relevant physiologic temperatures. Under all physiologic conditions tested, we found supply-dependent oxygen consumption at oxygen levels less than 7 mL O(2)/min/kg. Similarly, we found that local oxygen delivery in animals subjected to varying degrees of isovolemic hemodilution or altered vascular tone was correlated with supply-dependent oxygen consumption, as measured by local noninvasive StO(2). CONCLUSIONS: Noninvasive StO(2) measurements are valid and durable over a wide range of physiologic conditions and correlate with invasively-measured oxygen delivery.

Hypothermia is associated with improved outcomes in a porcine model of hemorrhagic shock.

BACKGROUND: : Hypothermia after trauma is, in current medical practice, both avoided and aggressively treated. However, the effects of environmental hypothermia during early resuscitation after hemorrhagic shock have been only poorly characterized. METHODS: : The objective of our study was to compare normothermia versus mild and severe levels of hypothermia in a porcine model of hemorrhagic shock. In a prospective survival study, we anesthetized 19 juvenile male pigs (Yorkshire-Landrace, 15-25 kg) and caused them to hemorrhage until their systolic blood pressure was 45 mm Hg to 55 mm Hg for a duration of 45 minutes. Then, we randomized them into three groups (all of which underwent an 8-hour limited resuscitation period) as follows: normothermic (39 degrees C), mildly hypothermic (36 degrees C), and severely hypothermic (33 degrees C). We used ice packs to achieve surface cooling that mimicked environmental hypothermia. After 8 hours, we rewarmed the pigs and fully resuscitated them for 16 hours. We extubated the survivors and observed them for an additional 24 hours, before killing them. RESULTS: : Surface cooling resulted in significant reduction in core body temperature. The mortality rate was significantly higher in the normothermic group (60%) than in the two hypothermic groups combined (7%) (p = 0.015) or in the severely hypothermic group (0%) (p = 0.023). Hypothermic animals had significantly lower levels of creatinine kinase, lactate dehydrogenase, and lactate in addition to a lower base deficit after shock. However, severely hypothermic animals required greater volumes of colloid infusion and whole blood transfusion to maintain our target systolic blood pressure and hemoglobin levels when compared with normothermic animals. We saw a strong trend toward decreased oxygen consumption with hypothermia. CONCLUSIONS: : In our porcine model, we found that simulating mild and severe levels of environmental hypothermia during early resuscitation after hemorrhage was associated with a significantly decreased mortality rate. Furthermore, markers of cellular stress and organ dysfunction, including lactate levels and the base deficit, were lower in hypothermic animals. Decreasing oxygen consumption with hypothermia may, in part, explain the protective effects observed with hypothermia.

Alterations in Enteroendocrine Hormones After Total Pancreatectomy With Islet Autotransplantation.

OBJECTIVE: When total pancreatectomy with islet autotransplantation (TPIAT) is performed for chronic pancreatitis, the pancreas and most of the duodenum are removed, with Roux-en-Y reconstruction of the gastrointestinal tract. Enteroendocrine cells in the intestines and pancreas secrete hormones coordinating digestion and motility, but anatomic reconstruction alters transit of nutrients to these cells. We hypothesized that TPIAT leads to changes in enteroendocrine hormones. METHODS: Glucagon-like peptide 1 (GLP-1), peptide YY (PYY), and pancreatic polypeptide (PP) were measured from mixed-meal tolerance tests of 34 clinical trial participants before and 18 months after TPIAT. Area under the curve of GLP-1 and PYY-stimulated responses were calculated by trapezoidal method, and the PP response was measured as the stimulated max minus baseline (ΔPP). RESULTS: Area under the curve of GLP-1 and PYY increased significantly after TPIAT (GLP-1 average +553.1 pg/mL per minute, P = 0.004; PYY average +4647.9 pg/mL per minute, P = 0.02). ΔPP trended toward lower after TPIAT (average, -52.2 pg/mL, P = 0.06). CONCLUSIONS: In this novel study of enteroendocrine hormones in TPIAT patients, stimulated levels of GLP-1 and PYY were significantly higher after versus before TPIAT. ΔPP was lower after TPIAT, but not significantly. These hormone changes have potential clinical implications that warrant further research.

Tissue hemoglobin index: a non-invasive optical measure of total tissue hemoglobin.

INTRODUCTION: The tissue hemoglobin index (THI) is a hemoglobin signal strength metric provided on the InSpectra StO2 Tissue Oxygenation Monitor, Model 650. There is growing interest regarding the physiologic meaning of THI and whether a clinically useful correlation between THI and blood hemoglobin concentration exists. A series of in vitro and in vivo experiments was performed to evaluate whether THI has potential utility beyond its primary purpose of helping InSpectra device users optimally position a StO2 sensor over muscle tissue. METHODS: The THI and tissue hemoglobin oxygen saturation (StO2) were measured using the InSpectra StO2 Tissue Oxygenation Monitor, Model 650, with a 15 mm optical sensor. A THI normal reference range was established in the thenar eminence (hand) for 434 nonhospitalized human volunteers. In 30 subjects, the thenar THI was also evaluated during 5-minute arterial and venous blood flow occlusions, and with blood volume exsanguination in the hand induced with an Esmarch bandage. In addition, correlation of the THI to blood total hemoglobin concentration (Hbt) was studied in five pigs whose Hbt was isovolumetrically diluted from 13 to 4 g/dl systemically and 0.5 g/dl locally in the hind limb. The sensitivity and specificity of the THI to measure tissue hemoglobin concentration (THC) were characterized in vitro using isolated blood tissue phantoms. RESULTS: In human thenar tissue, the average THI was 14.1 +/- 1.6 (mean +/- standard deviation). The THI extrapolated to 100% blood volume exsanguination was 3.7 +/- 2.0 units presumably from myoglobin. On average, the THI increased 1.5 +/- 1.0 units with venous occlusion and decreased 4.0 +/- 2.0 units with arterial occlusion. In porcine hind limbs, the THI weakly correlated with Hbt (r2 = 0.26) while DeltaTHI during venous occlusion had a stronger correlation (r2 = 0.62). In vitro tests indicated that THI strongly correlated (r2 > 0.99) to phantom THC and was insensitive to StO2 changes. CONCLUSIONS: Steady-state THI values do not reliably indicate Hbt. The THI is a reproducible quantitative index for THC, and THI trends can discriminate between arterial or venous blood flow occlusions. The THI magnitude permits the estimation of myoglobin's contribution to StO2.

Eight hours of hypotensive versus normotensive resuscitation in a porcine model of controlled hemorrhagic shock.

OBJECTIVES: The aim of this study was to compare hypotensive and normotensive resuscitation in a porcine model of hemorrhagic shock. METHODS: This was a prospective, comparative, randomized survival study of controlled hemorrhagic shock using 28 male Yorkshire-Landrace pigs (15 to 25 kg). In 24 splenectomized pigs, the authors induced hemorrhagic shock to a systolic blood pressure (sBP) of 48 to 58 mm Hg (approximately 35% bleed). Pigs were randomized to undergo normotensive resuscitation (sBP of 90 mm Hg, n = 7), mild hypotensive resuscitation (sBP of 80 mm Hg, n = 7), severe hypotensive resuscitation (sBP of 65 mm Hg, n = 6), or no resuscitation (n = 4). The authors also included a sham group of animals that were instrumented and splenectomized, but that did not undergo hemorrhagic shock (n = 4). After the initial 8 hours of randomized pressure-targeted resuscitation, all animals were resuscitated to a sBP of 90 mm Hg for 16 hours. RESULTS: Animals that underwent severe hypotensive resuscitation were less likely to survive, compared with animals that underwent normotensive resuscitation. Mean arterial pressure (MAP) decreased with hemorrhage and increased appropriately with pressure-targeted resuscitation. Base excess (BE) and tissue oxygen saturation (StO2) decreased in all animals that underwent hemorrhagic shock. This decrease persisted only in animals that were pressure target resuscitated to a sBP of 65 mm Hg. CONCLUSIONS: In this model of controlled hemorrhagic shock, initial severe hypotensive pressure-targeted resuscitation for 8 hours was associated with an increased mortality rate and led to a persistent base deficit (BD) and to decreased StO2, suggesting persistent metabolic stress and tissue hypoxia. However, mild hypotensive resuscitation did not lead to a persistent BD or to decreased StO2, suggesting less metabolic stress and less tissue hypoxia.

Near-infrared spectroscopy in patients with severe sepsis: correlation with invasive hemodynamic measurements.

BACKGROUND: Clinicians have begun using near-infrared spectroscopy (NIRS) to monitor tissue perfusion in hemorrhagic shock, as the technique allows continuous noninvasive monitoring of tissue hemoglobin oxygen saturation (StO(2)) and the tissue hemoglobin index (THI). We hypothesized that StO(2) measurements in patients with severe sepsis would be associated with the severity of their illness and would correlate with invasive hemodynamic measurements. METHODS: We measured mean arterial pressure (MAP), serum lactate concentration, blood hemoglobin concentration, StO(2), and THI in nine healthy volunteers and ten patients with septic shock in a surgical intensive care unit (ICU). Enrolled patients had a pulmonary artery catheter, and had family able to give informed consent. The average Acute Physiology and Chronic Health Evaluation (APACHE) II score at enrollment for the patients was 19 +/- 5 (standard deviation) points. Volunteers and patients were similar with respect to age and sex. To collect NIRS data, we used the InSpectra Tissue Spectrometer, Model 325 (Hutchinson Technology, Inc., Hutchinson, MN). For three consecutive days, we obtained invasive hemodynamic measurements three times daily, simultaneously with NIRS measurements, and metabolic cart measurements once daily. RESULTS: Patients with severe sepsis had significantly lower thenar muscle StO(2) values (p = 0.031) than healthy volunteers. Near-infrared spectroscopy-derived mixed venous oxygen saturation (NIRSvO(2)) and StO(2) measured from the thenar eminence in patients with severe sepsis correlated with SvO(2) from the pulmonary artery catheter (p < 0.05). In this group of patients, StO(2) did not correlate significantly with lactate concentration, base deficit, or APACHE II score. CONCLUSIONS: Near-infrared spectroscopic measurements of StO(2) correlated with invasive hemodynamic measurements in patients with severe sepsis but did not correlate with severity of illness. These findings suggest that NIRStO(2) may be a clinically useful measurement in monitoring patients with severe sepsis. Further study of this device in early resuscitation of patients with sepsis is necessary.

Plasma metabolomics pilot study suggests age and sex-based differences in the metabolic response to traumatic injury.

INTRODUCTION: Age and sex affect outcomes from trauma. Older patients tend to be under-triaged, consume more healthcare resources, and experience worse outcomes relative to younger patients. Sex has also been associated with different outcomes, with women experiencing better outcomes than men. While baseline metabolism differs with both age and sex, no study has examined how these differences affect the response to trauma. We used high-throughput metabolomics to assess metabolic differences associated with blunt trauma according to age and sex. METHODS: Metabolic profiles were constructed using nuclear magnetic resonance spectroscopy for trauma patients age 21-40 years (n = 20, 55% male) and >65 years (n = 22, 41% male) from plasma samples obtained on Day 1 and Day 3 of each patient's hospital stay. These were compared to profiles constructed from plasma obtained from healthy controls of the same age (21-40: n = 23, 61% male; 65+: n = 26, 50% male). Differences in metabolic profiles were assessed with partial least squares discriminant analysis. RESULTS: Trauma elicits an overwhelming global stress response that includes more subtle differences in metabolism related to age and gender. Significant differences due to normal aging were also identified. Many of the metabolites measured were present in similar levels in healthy controls age 65+ as they were in trauma patients of all ages. Sex-based differences in metabolism were observed in younger trauma patients on Day 3 but not in older patients. CONCLUSIONS: Differences in energy metabolism and oxidative stress were implicated in the response to trauma in all patients. Older trauma patients may enter the trauma state with pre-existing oxidative stress and energy deficits that complicate recovery. Sex-based differences in recovery from trauma support the large body of work demonstrating the role of sex in recovery from trauma.

Evaluation of novel formulations of d-ß-hydroxybutyrate and melatonin in a rat model of hemorrhagic shock.

d-ß-hydroxybutyrate and melatonin (BHB/MLT) infusion improves survival in hemorrhagic shock models. The original BHB/MLT formulation contains dimethyl sulfoxide (DMSO) to increase melatonin solubility. We formulated BHB/MLT solutions wherein DMSO was replaced either with 10% polyvinylpyrrolidone (BHB/MLT/PVP) or with 5% hydroxypropyl-ß-cyclodextrin/2.5% PVP/2.5% polyethylene glycol 400 (BHB/MLT/CD). Safety and efficacy of the new and the original BHB/MLT solution were tested in a lethal rat hemorrhagic shock model, with seven groups: 1) sham, 2) shock, untreated, 3) shock, lactated Ringer's solution (LR), 4) shock, 4 M BHB/MLT/DMSO, 5) shock, 2 M BHB/MLT/DMSO, 6) shock, BHB/MLT/PVP and 7) shock, BHB/MLT/CD. BHB/MLT/DMSO was given at full strength and 1:1 dilution to match the concentration of the novel formulations. Rats were anesthetized, instrumented, and 40% of the total blood volume was withdrawn in three steps, followed by four-hour long shock. Treatment boluses were infused half-way throughout hemorrhage. Survival was highest in BHB/MLT/CD-treated rats (8/10), followed by the BHB/MLT/PVP (6/10), 4 M BHB/MLT/DMSO (5/10) or 2 M BHB/MLT/DMSO (5/10), LR (3/10) and the untreated group (0/11). Survival did not differ significantly between BHB/MLT groups (p > 0.05), but was significantly higher in BHB/MLT/CD than in LR-treated animals (p = 0.018). BHB/MLT/PVP and BHB/MLT/CD constitute promising candidates for clinical hemorrhagic shock treatment.

Assessment of prehospital hemorrhage and airway care using a simulation model.

BACKGROUND: The quality of prehospital care impacts patient outcomes. Military efforts have focused on training revision and the creation of high-fidelity simulation models to address potentially survivable injuries. We sought to investigate the applicability of models emphasizing hemorrhage control and airway management to a civilian population. METHODS: Prehospital health care providers (PHPs) undergoing their annual training were enrolled. A trauma scenario was simulated with two modules: hemorrhage control and airway management. Experienced raters used a validated tool to assess performance. Pearson correlation, logistic regression, and χ tests were used for analysis. RESULTS: Ninety-five PHPs participated with a mean experience of 15.9 ± 8.3 years, and 7.4% reported past military training. The PHPs' overall execution rate of the six hemorrhage control measures varied from 38.9% to 88.4%. The median blood loss was 1,700 mL (interquartile range, 1,043-2,000), and the mean global rater score was 25.0 ± 7.4 (scale, 5-40). There was a significant relationship between PHP profession and past military experience to their consideration of blood transfusion and tranexamic acid. An inverse relationship between blood loss and global rater score was found (r = -0.59, n = 88, p = 1.93 × 10). After simulated direct laryngoscope failure in the airway module, 58% of PHPs selected video laryngoscopy over placement of a supraglottic airway. Eighty-six percent of participants achieved bilateral chest rise in the manikin regardless of management method. Participants reported improved comfort with skills after simulation. CONCLUSION: Our data reveal marginal performance in hemorrhage control regardless of the PHP's prior experience. The majority of PHPs were able to secure an advanced airway if direct laryngoscope was unavailable with a predisposition for video laryngoscopy over supraglottic airway. Our findings support the need for continued training for PHPs highlighting hemorrhage control maneuvers and increased familiarity with airway management options. Improved participant confidence posttraining gives credence to simulation training. LEVEL OF EVIDENCE: Prognostic/epidemiological study, level III.

Dynamic near-infrared spectroscopy measurements in patients with severe sepsis.

This study evaluated near-infrared spectroscopy (NIRS)-derived measurements in hemodynamically stable patients with severe sepsis, as compared with similar measurements in healthy age-matched volunteers. Prospective, preliminary, observational study in a surgical intensive care unit and clinical research center at a university health center. We enrolled 10 patients with severe sepsis and 9 healthy age-matched volunteers. For patients with severe sepsis, we obtained pulmonary artery catheter and laboratory values three times daily for 3 days and oxygen consumption values via metabolic cart once daily for 3 days. For healthy volunteers, we obtained all noninvasive measurements during a single session. We found lower values in patients with severe sepsis (versus healthy volunteers), in tissue oxygen saturation (StO2), in the StO2 recovery slope, in the tissue hemoglobin index, and in the total tissue hemoglobin increase on venous occlusion. Patients with severe sepsis had longer StO2 recovery times and lower NIRS-derived local oxygen consumption values versus healthy volunteers. In our preliminary study, NIRS provides a noninvasive continuous method to evaluate peripheral tissue oxygen metabolism in hemodynamically stable patients with severe sepsis. Further research is needed to demonstrate whether these values apply to broader populations of patients with systemic inflammatory response syndrome, sepsis, severe sepsis, and septic shock.

Increased poly(ADP-ribose) polymerase activity during porcine hemorrhagic shock is transient and predictive of mortality.

AIM OF THE STUDY: The aim of our study was to compare poly(ADP-ribose) polymerase (PARP) activity levels in a porcine model of hemorrhagic shock and resuscitation. MATERIALS AND METHODS: We designed a prospective, comparative randomized survival study of hemorrhagic shock using 20 male Yorkshire-Landrace pigs (15-25 kg). In 16 pigs after splenectomy, we induced hemorrhagic shock to a mean arterial pressure of 50 mm Hg ( approximately 35% bleed). Pigs were randomized to receive normotensive resuscitation (SBP 90 mm Hg), mild hypotensive resuscitation (SBP 80 mm Hg), moderate hypotensive resuscitation (SBP 65 mm Hg), or no resuscitation (n=4 in each group). We also included a group of sham animals that were instrumented and had a splenectomy but not bled (n=4). Muscle and liver biopsies were taken prior to hemorrhage, after 45 min of shock, and 8, 24, and 48 h after resuscitation. PARP activity levels in biopsies were measured using chemical quantitation of NAD+. RESULTS: Irrespective of our resuscitation strategy or outcome, both muscle and liver PARP activity levels rose after 45 min of shock and then returned to baseline. Excluding our control animals, PARP activity levels were significantly higher during shock in non-survivors compared to survivors. CONCLUSIONS: In our model of porcine hemorrhagic shock, PARP activity levels increased during hemorrhagic shock. However, this increase in PARP activity levels was transient as they returned to baseline regardless of resuscitation strategy. Interestingly, PARP activity levels were significantly higher during hemorrhagic shock in non-survivors compared to survivors. These findings suggest that PARP activity may be a part of initial pathways leading from hemorrhagic shock to death.

D-ß-Hydroxybutyrate and melatonin for treatment of porcine hemorrhagic shock and injury: a melatonin dose-ranging study.

OBJECTIVE: Treatment with a combination of D-ß-hydroxybutyrate (BHB) and melatonin (M) improves survival in hemorrhagic shock models. Our objective was to find the most effective melatonin concentration in combination with 4 molar BHB (4 M BHB). Survival and markers of organ injury were analyzed in pigs exposed to pulmonary contusion, liver crush injury, and hemorrhagic shock and treated with lactated Ringer's solution; 4 M BHB/43 mM M; 4 M BHB/20 mM M; 4 M BHB/10 mM M; 4 M BHB/4.3 mM M; or 4 M BHB/0.43 mM M. This work is an extension of a previously published research study. RESULTS: Survival was highest in pigs receiving 4 M BHB/43 mM M (13/14), followed by lactated Ringer's solution (11/16) and BHB/M with decreased melatonin concentrations (4 M BHB/20 mM M 3/6, 4 M BHB/10 mM M 2/6, 4 M BHB/4.3 mM M 3/6, 4 M BHB/0.43 mM M 1/6, p = 0.011). High mortality was associated with increases in serum lactate, higher liver and muscle injury markers and decreases in PaO2:FiO2 ratios. Our study indicates that treatment with 4 M BHB and melatonin concentrations below 43 mM lack the survival benefit observed from 4 M BHB/43 mM melatonin in pigs experiencing hemorrhagic shock and polytrauma.

Metabolomic analysis of survival in carbohydrate pre-fed pigs subjected to shock and polytrauma.

Hemorrhagic shock, a result of extensive blood loss, is a dominant factor in battlefield morbidity and mortality. Early rodent studies in hemorrhagic shock reported carbohydrate feeding prior to the induction of hemorrhagic shock decreased mortality. When repeated in our laboratory with a porcine model, carbohydrate pre-feed resulted in a 60% increase in death rate following hemorrhagic shock with trauma when compared to fasted animals (15/32 or 47% vs. 9/32 or 28%). In an attempt to explain the unexpected death rate for pre-fed animals, we further investigated the metabolic profiles of pre-fed non-survivors (n = 15) across 4 compartments (liver, muscle, serum, and urine) at specific time intervals (pre-shock, shock, and resuscitation) and compared them to pre-fed survivors (n = 17). As hypothesized, pre-fed pigs that died as a result of hemorrhage and trauma showed differences in their metabolic and physiologic profiles at all time intervals and in all compartments when compared to pre-fed survivors. Our data suggest that, although all animals were subjected to the same shock and trauma protocol, non-survivors exhibited altered carbohydrate processing as early as the pre-shock sampling point. This was evident in (for example) the higher levels of ATP and markers of greater anabolic activity in the muscle at the pre-shock time point. Based on the metabolic findings, we propose two mechanisms that connect pre-fed status to a higher death rate: (1) animals that die are more susceptible to opening of the mitochondrial permeability transition pore, a major factor in ischemia/reperfusion injury; and (2) loss of fasting-associated survival mechanisms in pre-fed animals.

Ringer's ethyl pyruvate in hemorrhagic shock and resuscitation does not improve early hemodynamics or tissue energetics.

Reactive oxygen species (ROS) have been implicated in the pathogenesis of hemorrhagic shock. Ethyl pyruvate, a derivative of pyruvate and a proposed oxygen radical scavenger, is attractive as a possible resuscitation fluid. We investigated whether resuscitation with lactated Ringer's (LR) containing ethyl pyruvate (REP) had any hemodynamic or tissue energetic benefits compared with LR alone for hemorrhagic shock. Hemorrhagic shock was induced in splenectomized pigs via inferior vena cava cannula. After 90 min of shock, animals were resuscitated in a stepwise fashion with LR or REP (30 mg/kg/dose, given as 1.5 mg/mL in LR) at 20 cc/kg/step for four steps. Data collected during this experiment included physiologic and hemodynamic parameters, near-infrared reflectance spectroscopy measurements of tissue hemoglobin oxygen (StO(2)) of the stomach, liver, and hind limb, and nuclear magnetic resonance phosphorus spectra of the liver and hind limb at each time point. In both resuscitative groups, heart rate, and lactate and pyruvate values increased during shock and began to drop toward baseline values during resuscitation. Mean arterial pressure, oxygen delivery, and oxygen consumption decreased during shock and increased toward baseline levels during the resuscitative process. There were no significant changes in physiologic parameters between the LR- and REP-resuscitated animals. There was a significantly lower stomach StO(2) and hind limb cellular cytoplasmic pH during later resuscitative endpoints in REP-resuscitated animals. The clinical significance of these findings are unclear. There is no short-term hemodynamic or tissue energetic advantage to using REP as a resuscitation fluid when compared with LR. Long-term outcome studies are needed to further evaluate any potential benefits of use of REP in hemorrhagic shock.