Hypertonic saline and pentoxifylline reduces hemorrhagic shock resuscitation-induced pulmonary inflammation through attenuation of neutrophil degranulation and proinflammatory mediator synthesis

Fluid therapy and traumatic brain injury: A narrative review

Traumatic brain injury (TBI) is an important health and social problem. The mechanism of damage of this entity could be divided into two phases: (1) a primary acute injury because of the traumatic event; and (2) a secondary injury due to the hypotension and hypoxia generated by the previous lesion, which leads to ischemia and necrosis of neural cells. Cerebral edema is one of the most important prognosis markers observed in TBI. In the early stages of TBI, the cerebrospinal fluid compensates the cerebral edema. However, if edema increases, this mechanism fails, increasing intracranial pressure. To avoid this chain effect, several treatments are applied in the clinical practice, including elevation of the head of the bed, maintenance of normothermia, pain and sedation drugs, mechanical ventilation, neuromuscular blockade, controlled hyperventilation, and fluid therapy (FT). The goal of FT is to improve the circulatory system to avoid the lack of oxygen to organs. Therefore, rapid and early infusion of large volumes of crystalloids is performed in clinical practice to restore blood volume and blood pressure. Despite the relevance of FT in the early management of TBI, there are few clinical trials regarding which solution is better to apply. The aim of this study is to provide a narrative review about the role of the different types of FT used in the daily clinical practice on the management of TBI. To achieve this objective, a physiopathological approach to this entity will be also performed, summarizing why the different types of FT are used.

Immunomodulatory Effect of Hypertonic Saline Solution in Traumatic Brain-Injured Patients and Intracranial Hypertension

Traumatic brain injury (TBI) is often associated with an increase in the intracranial pressure (ICP). This increase in ICP can cross the physiological range and lead to a reduction in cerebral perfusion pressure (CPP) and the resultant cerebral blood flow (CBF). It is this reduction in the CBF that leads to the secondary damage to the neural parenchyma along with the physical axonal and neuronal damage caused by the mass effect. In certain cases, a surgical intervention may be required to either remove the mass lesion (hematoma of contusion evacuation) or provide more space to the insulted brain to expand (decompressive craniectomy). Whether or not a surgical intervention is performed, all these patients require some form of pharmaceutical antiedema agents to bring down the raised ICP. These agents have been broadly classified as colloids (e.g., mannitol, glycerol, urea) and crystalloids (e.g., hypertonic saline), and have been used since decades. Even though mannitol has been the workhorse for ICP reduction owing to its unique properties, crystalloids have been found to be the preferred agents, especially when long-term use is warranted. The safest and most widely used agent is hypertonic saline in various concentrations. Whatever be the concentration, hypertonic saline has created special interest among physicians owing to its additional property of immunomodulation and neuroprotection. In this review, we summarize and understand the various mechanism by which hypertonic saline exerts its immunomodulatory effects that helps in neuroprotection after TBI.

Adjuncts to Resuscitation

Damage control resuscitation has been increasingly adopted and practiced over the last decade. The concepts used are not new to this era of medicine but are novel in combination. This chapter will focus on adjuncts to damage control resuscitation (DCR) including massive transfusion protocols, the “other” tenets of damage control resuscitation, hypertonic saline, tranexamic acid, pharmacologic resuscitation, Factor VIIa, and prothrombin complex, and viscoelastic testing.

The Impact of Pre-Hospital Administration of Lactated Ringer's Solution versus Normal Saline in Patients with Traumatic Brain Injury

Lactated Ringer's (LR) and normal saline (NS) are both used for resuscitation of injured patients. NS has been associated with increased resuscitation volume, blood loss, acidosis, and coagulopathy compared with LR. We sought to determine if pre-hospital LR is associated with improved outcome compared with NS in patients with and without traumatic brain injury (TBI). We included patients receiving pre-hospital LR or NS from the PRospective Observational Multicenter Major Trauma Transfusion (PROMMTT) study. Patients with TBI (Abbreviated Injury Scale [AIS] head ≥3) and without TBI (AIS head ≤2) were compared. Cox proportional hazards models including Injury Severity Score (ISS), AIS head, AIS extremity, age, fluids, intubation status, and hospital site were generated for prediction of mortality. Linear regression models were generated for prediction of red blood cell (RBC) and crystalloid requirement, and admission biochemical/physiological parameters. Seven hundred ninety-one patients received either LR (n = 117) or NS (n = 674). Median ISS, AIS head, AIS extremity, and pre-hospital fluid volume were higher in TBI and non-TBI patients receiving LR compared with NS (p < 0.01). In patients with TBI (n = 308), LR was associated with higher adjusted mortality compared with NS (hazard rate [HR] = 1.78, confidence interval [CI] 1.04-3.04, p = 0.035). In patients without TBI (n = 483), no difference in mortality was demonstrated (HR = 1.49, CI 0.757-2.95, p = 0.247). Fluid type had no effect on admission biochemical or physiological parameters, 6-hour RBC, or crystalloid requirement in either group. LR was associated with increased mortality compared with NS in patients with TBI. These results underscore the need for a prospective randomized trial comparing pre-hospital LR with NS in patients with TBI.

Hypertonic Saline Dextran Ameliorates Organ Damage in Beagle Hemorrhagic Shock

OBJECTIVE

The goal of this study was to investigate the effect of hypertonic saline with 6% Dextran-70 (HSD) resuscitation on organ damage and the resuscitation efficiency of the combination of HSD and lactated ringers (LR) in a model of hemorrhage shock in dogs.

METHODS

Beagles were bled to hold their mean arterial pressure (MAP) at 50 ± 5 mmHg for 1 h. After hemorrhage, beagles were divided into three groups (n = 7) to receive pre-hospital resuscitation for 1 h (R1): HSD (4 ml/kg), LR (40 ml/kg), and HSD+LR (a combination of 4 ml/kg HSD and 40 ml/kg LR). Next, LR was transfused into all groups as in-hospital resuscitation (R2). After two hours of observation (R3), autologous blood was transfused. Hemodynamic responses and systemic oxygenation were measured at predetermined phases. Three days after resuscitation, the animals were sacrificed and tissues including kidney, lung, liver and intestinal were obtained for pathological analysis.

RESULTS

Although the initial resuscitation with HSD was shown to be faster than LR with regard to an ascending MAP, the HSD group showed a similar hemodynamic performance compared to the LR group throughout the experiment. Compared with the LR group, the systemic oxygenation performance in the HSD group was similar but showed a lower venous-to-arterial CO2 gradient (Pv-aCO2) at R3 (p < 0.05). Additionally, the histology score of the kidneys, lungs and liver were significantly lower in the HSD group than in the LR group (p < 0.05). The HSD+LR group showed a superior hemodynamic response but higher extravascular lung water (EVLW) and lower arterial oxygen tension (PaO2) than the other groups (p < 0.05). The HSD+LR group showed a marginally improved systemic oxygenation performance and lower histology score than other groups.

CONCLUSIONS

Resuscitation after hemorrhagic shock with a bolus of HSD showed a similar hemodynamic response compared with LR at ten times the volume of HSD, but HSD showed superior efficacy in organ protection. Our findings suggest that resuscitation with the combination of HSD and LR in the pre-hospital setting is an effective treatment.

Effect of 200 mEq/L Na+ hypertonic saline resuscitation on systemic inflammatory response and oxidative stress in severely burned rats

BACKGROUND

Excessive release of inflammatory mediators and oxidative stress play important roles in the increased vascular permeability and systemic edema during the early stage of severe burn. This study investigates the effect of 200 mEq/L Na(+) hypertonic saline (HS) on systemic inflammatory response and oxidative stress in severely burned rats.

MATERIALS AND METHODS

Sprague-Dawley rats were divided into three groups: sham group, burn plus lactated Ringer's group, and burn plus HS group. Lung edema was assessed in terms of wet-weight-to-dry-weight ratio. Tumor necrosis factor α and interleukin 6 concentrations in serum were examined by enzyme-linked immunosorbent assay. Peripheral blood mononuclear cells were isolated and the expression of p38 mitogen-activated protein kinase was determined by Western blot analysis. The lung and intestinal concentrations of malondialdehyde, an indicator of oxidative stress, were also measured.

RESULTS

Resuscitation with 200 mEq/L Na(+) HS significantly decreased the lung wet-weight-to-dry-weight ratio and abolished hyponatremia induced by burn injury. HS treatment also prevented the increases of myeloperoxidase activity and malondialdehyde content in the lung and intestine of severely burned rats. However, there were no significant differences, either in serum tumor necrosis factor α and interleukin 6 concentrations or with respect to the p38 mitogen-activated protein kinase expression in peripheral blood mononuclear cells, between the burn plus lactated Ringer's group and burn plus HS group (P > 0.05).

CONCLUSIONS

Initial resuscitation with 200 mEq/L Na(+) HS after severe burn injury decreases pulmonary edema, prevents hyponatremia, and attenuates oxidative stress, but is not capable of inhibiting the systemic inflammatory response.

Uncovering the neuroenteric-pulmonary axis: vagal nerve stimulation prevents acute lung injury following hemorrhagic shock

AIMS

Trauma/hemorrhagic shock (T/HS) induced gut injury is known to initiate a systemic inflammatory response which can lead to secondary lung injury. We have shown that vagal nerve stimulation (VNS) protects intestinal epithelial integrity after a severe burn insult. We hypothesize that VNS will protect the lung from injury following T/HS by preventing intestinal barrier failure.

MAIN METHODS

Male Balb/c mice were subjected to a T/HS model with and without cervical VNS. Intestinal injury was evaluated by measuring changes in gut barrier function and tight junction protein localization. Lung injury was evaluated using histology and markers of lung inflammation. Using NF-kB-luciferase (NF-kB-luc) transgenic mice, NF-kb-DNA binding was measured by photon emission analysis at 4 after injury.

KEY FINDINGS

T/HS is associated gut injury characterized by histologic injury, increased epithelial permeability, and altered localization of gut tight junction proteins. Cervical VNS prevented the T/HS-induced changes in gut barrier integrity. Gut injury after T/HS was associated with acute lung injury at 24 h characterized by histologic injury, increased number of MPO positive stained cells and MPO enzymatic activity, and increased ICAM-1 expression in lung endothelium. VNS decreased T/HS-induced lung injury with a marked decrease in lung inflammation compared to T/HS alone. Lungs harvested from NF-kB-luc mice at 4h post VNS+T/HS demonstrated decreased DNA binding of NF-kB compared to T/HS alone as measured by changes in bioluminescence.

SIGNIFICANCE

VNS is effective in protecting against acute lung injury caused by hemorrhagic shock through its ability to prevent gut barrier dysfunction.

What's new in resuscitation strategies for the patient with multiple trauma?

The last decade has seen a sea change in the management of major haemorrhage following traumatic injury. Damage control resuscitation (DCR), a strategy combining the techniques of permissive hypotension, haemostatic resuscitation and damage control surgery has been widely adopted as the preferred method of resuscitation in patients with haemorrhagic shock. The over-riding goals of DCR are to mitigate metabolic acidosis, hypothermia and coagulopathy and stabilise the patient as early as possible in a critical care setting. This narrative review examines the background to these changes in resuscitation practice, discusses the central importance of traumatic coagulopathy in driving these changes particularly in relation to the use of high FFP:RBC ratio and explores methods of predicting, diagnosing and treating the coagulopathy with massive transfusion protocols as well as newer coagulation factor concentrates. We discuss other areas of trauma haemorrhage management including the role of hypertonic saline and interventional radiology. Throughout this review we specifically examine whether the available evidence supports these newer practices.

Period of irreversible therapeutic intervention during sepsis correlates with phase of innate immune dysfunction

Sepsis is a major health problem in the United States with high incidence and elevated patient care cost. Using an animal model of sepsis, cecum ligation, and puncture, we observed that mice became rapidly hypothermic reaching a threshold temperature of 28 °C within 5-10 h after initiation of the insult, resulting in a reliable predictor of mortality, which occurred within 30-72 h of the initial procedure. We also observed that the inflammatory gene expression in lung and liver developed early within 1-2 h of the insult, reaching maximum levels at 6 h, followed by a decline, approaching basal conditions within 20 h. This decrease in inflammatory gene expression at 20 h after cecal ligation and puncture was not due to resolution of the insult but rather was an immune dysfunction stage that was demonstrated by the inability of the animal to respond to a secondary external inflammatory stimulus. Removal of the injury source, ligated cecum, within 6 h of the initial insult resulted in increased survival, but not after 20 h of cecal ligation and puncture. We concluded that the therapeutic window for resolving sepsis is early after the initial insult and coincides with a stage of hyperinflammation that is followed by a condition of innate immune dysfunction in which reversion of the outcome is no longer possible.

The role of toll-like receptor-4 in the development of multi-organ failure following traumatic haemorrhagic shock and resuscitation

Haemorrhagic shock and resuscitation (HS/R) following major trauma results in a global ischaemia and reperfusion injury that may lead to multiple organ dysfunction syndrome (MODS). Systemic activation of the immune system is fundamental to the development of MODS in this context, and shares many features in common with the systemic inflammatory response syndrome (SIRS) that complicates sepsis. An important advancement in the understanding of the innate response to infection involved the identification of mammalian toll-like receptors (TLRs) expressed on cells of the immune system. Ten TLR homologues have been identified in humans and toll-like receptor-4 (TLR4) has been studied most intensively. Initially found to recognise bacterial lipopolysaccharide (LPS), it has also recently been discovered that TLR4 is capable of activation by endogenous 'danger signal' molecules released following cellular injury; this has since implicated TLR4 in several non-infectious pathophysiologic processes, including HS/R. The exact events leading to multi-organ dysfunction following HS/R have not yet been clearly defined, although TLR4 is believed to play a central role as has been shown to be expressed at sites including the liver, lungs and myocardium following HS/R. Multi-organ dysfunction syndrome remains an important cause of morbidity and mortality in trauma patients, and current therapy is based on supportive care. Understanding the pathophysiology of HS/R will allow for the development of targeted therapeutic strategies aimed at minimising organ dysfunction and improving patient outcomes following traumatic haemorrhage. A review of the pathogenesis of haemorrhagic shock is presented, and the complex, yet critical role of TLR4 as both a key mediator and therapeutic target is discussed.

Influence of preoperative 7.5% hypertonic saline on neutrophil activation after reamed intramedullary nailing of femur shaft fractures: a prospective randomized pilot study

OBJECTIVES

Femoral reaming and intramedullary nailing (IMN) primes polymorphonuclear leukocytes (PMNL) and thereby increases the posttraumatic systemic inflammatory response. Resuscitation with hypertonic saline (HTS) attenuates PMNL activation after trauma-hemorrhage. We hypothesized that preoperative administration of 7.5% HTS attenuates PMNL priming after IMN of unilateral femur shaft fractures compared with 0.9% normal saline.

DESIGN

Prospective, randomized, double-blind study.

SETTING

Level I trauma center.

PATIENTS

Twenty patients between 18 and 80 years of age with an Injury Severity Score less than 25 and a unilateral femur shaft fracture amenable to IMN fixation within 24 hours after injury.

INTERVENTION

Patients were allocated to equally sized HTS or normal saline treatment groups (n = 10) before surgery. Solutions were administered in a blinded bag as a single bolus of 4 mL/kg body weight immediately before surgery. Whole blood samples were collected directly before saline application (t0) and at 6, 12, and 24 hours after surgery.

MAIN OUTCOME MEASUREMENTS

PMNL surface expression of CD11b and CD62L, as determined by flow cytometry analysis.

RESULTS

Demographic characteristics of both treatment groups were comparable. Baseline expression of CD11b and CD62L cell markers was in a similar range in the two cohorts. The expression levels of CD11b were comparable between the two groups throughout the observation time, whereas CD62L levels were significantly higher in the HTS group at 6 and 24 hours after surgery.

CONCLUSION AND SIGNIFICANCE

Preoperative infusion of HTS appears to exert an anti-inflammatory effect by attenuating the extent of postoperative PMNL activation after reamed IMN for femoral shaft fractures.

Resuscitative effect of hyperoxia fluid on high-altitude hemorrhagic shock in rats and antishock mechanisms

Pathophysiological characteristics of hemorrhagic shock at high altitude are different from that at plain which involve severe injury, high mortality, difficult treatment and compromised liquid tolerance. High-altitude pulmonary/cerebral edema and multiple-organ dysfunction render the conventional treatment ineffective. Herein, we evaluated the resuscitation effects of hyperoxia solution on high-altitude hemorrhagic shock in rats. For this purpose, a rat model of high-altitude (3,658 m) hemorrhagic shock was established on the plateau and hyperoxia solution (4 ml/kg) was infused through external jugular vein for resuscitation at 60 min post-hemorrhage. Blood pressure, blood gas, left and right ventricular pressure, lung and brain water content, survival time, survival rate at 2 h, levels of inflammatory cytokines and free oxygen radicals in blood and tissue were determined. After resuscitation with hyperoxia solution, blood pressure, arterial oxygen partial pressure, left and right ventricular systolic pressure, ±dp/dt max, survival time and rate were significantly increased. Lung and brain water content were unchanged, malondialdehyde activity in lung, brain and plasma and levels of TNF-α, IL-1, IL-6, and endothelin were significantly decreased. Besides, CGRP was elevated with reduced injury and improved lung and kidney functions. Concludingly, resuscitation with hyperoxia solution is feasible and more effective than other classical liquids, making it the first choice of treatment for high-altitude hemorrhagic shock.

Fluid resuscitation in multiple trauma patients

PURPOSE OF REVIEW

Fluid resuscitation in trauma patients with hemorrhagic shock is controversially discussed in the literature. The coincidence of brain injury complicates management of these patients. This article summarizes the current knowledge on nonblood component fluid resuscitation and choice of fluids in patients with multiple trauma.

RECENT FINDINGS

Whereas current evidence suggests the efficacy of fluid therapy in hemorrhagic shock without active bleeding, experimental and clinical data demonstrate that aggressive volume challenge may be futile or even deleterious in the setting of uncontrolled hemorrhage. Large amounts of isotonic crystalloids may be associated with hypothermia, acidosis and inflammation. In patients with traumatic brain injury hypertonic solutions may positively influence inflammation and intracranial pressure without affecting neurologic outcome or mortality.

SUMMARY

To date no large-scale clinical studies exist to either support or refute the use of nonblood component fluid resuscitation of hemorrhagic shock in trauma patients. The optimal choice of fluid remains to be determined, but existing evidence suggests avoiding crystalloids in favor of hypertonic solutions. The role of modern, iso-oncotic colloids in the treatment of hemorrhagic shock has not yet been sufficiently defined. In patients with concomitant brain injury, arterial hypotension must be avoided and infusion of hypotonic solutions is obsolete, whereas administration of hypertonic solutions may exert beneficial effects beyond hemodynamic stabilization.

Treatment with pentoxifylline reduces ischemia/reperfusion-induced liver injury in rats with severe hemorrhagic shock

AIM: To investigate the effects of treatment with pentoxifylline (PTX) on ischemia/reperfusion-induced liver injury in rats with severe hemorrhagic shock.

METHODS: Forty-eight Sprague-Dawley rats were randomly and equally divided into four groups: control group, shock group (NR group), Lactated Ringer's (LR) solution-treated group (LR group), LR solution plus PTX group (LR-PTX group). A rat model of severe hemorrhagic shock was generated, and arterial blood pressure (MAP) was determined continuously. Blood specimens were collected before shock and 1 and 4 h after resuscitation for determination of serum AST and ALT levels. The rats of the NR group were killed 1 h after shock to collect liver samples. The rats of the LR and LR-PTX groups were resuscitated with LR and LR-PTX (25 mg/kg, three times the volume of shed blood), respectively, and then killed 4 h after resuscitation to collect liver samples to determine the expression of TNF-α, NF-κB and MIP-2 proteins and MPO activity. Liver injury was examined by light microscopy and electron microscopy.

RESULTS: Compared with the control group, MAP (mmHg) decreased significantly 1 h after shock in the other groups (37.3 ± 2.1, 37.0 ± 2.0, 37.6 ± 2.2 vs 106.0 ± 2.6, all P < 0.05). After resuscitation, MAP rose initially but decreased at 3 and 4 h in the LR and LR-PTX groups (88.3 ± 3.0, 87.6 ± 4.3 vs 105.0 ± 2.9; 69.0 ± 2.0, 66.7 ± 2.1 vs 102.1 ± 1.1, P < 0.05). Serum AST and ALT levels at 1 h after shock and 4 h after resuscitation in the NR, LR and LR-PTX groups were significantly higher than those in the control group (142.0 ± 8.3, 144.1 ± 7.6, 147.2 ± 8.1 vs 45.1 ± 6.3; 427.0 ± 12.5, 365.3 ± 8.0 vs 51.1 ± 6.3, all P < 0.01; 86.3 ± 7.8, 88.3 ± 6.6, 89.1 ± 5.9 vs 53.6 ± 6.1; 342.9 ± 4.7, 280.4 ± 9.1 vs 50.6 ± 7.6, all P < 0.05). The expression of NF-κB, TNF-α and MIP-2 proteins and MPO activity in the liver were significantly increased and pathologic injury was more significant in the NR, LR and LR-PTX groups compared with the control group (all P < 0.05). Compared with the LR group, serum AST and ALT levels at 4 h after resuscitation were significantly lower in the LR-PTX group (P < 0.05). The expression levels of NF-κB, TNF-α and MIP-2 proteins and MPO activity in the liver were significantly lower (all P < 0.05) and pathologic injury was milder in the LR-PTX group than in the LR group.

CONCLUSION: Treatment with PTX can protect against ischemia/reperfusion-induced liver injury in rats with severe hemorrhagic shock by inhibiting TNF-α release and NF-κB activation and decreasing the expression of inflammatory mediators.

Key Words: Hemorrhagic shock; Liver injury; Resuscitation; Pentoxifylline

Hypertonic saline and reduced peroxynitrite formation in experimental pancreatitis

OBJECTIVES

In this study, we tested the hypothesis that hypertonic saline exerts anti-inflammatory effects by modulating hepatic oxidative stress in pancreatitis.

INTRODUCTION

The incidence of hepatic injury is related to severe pancreatitis, and hypertonic saline reduces pancreatic injury and mortality in pancreatitis.

METHODS

Wistar rats were divided into four groups: control (not subjected to treatment), untreated pancreatitis (NT, pancreatitis induced by a retrograde transduodenal infusion of 2.5% sodium taurocholate into the pancreatic duct with no further treatment administered), pancreatitis with normal saline (NS, pancreatitis induced as described above and followed by resuscitation with 0.9% NaCl), and pancreatitis with hypertonic saline (HS, pancreatitis induced as described above and followed by resuscitation with 7.5% NaCl). At 4, 12, and 24 h after pancreatitis induction, liver levels of inducible nitric oxide synthase (iNOS), heat-shock protein 70, nitrotyrosine (formation of peroxynitrite), nitrite/nitrate production, lipid peroxidation, and alanine aminotransferase (ALT) release were determined.

RESULTS

Twelve hours after pancreatitis induction, animals in the HS group presented significantly lower iNOS expression (P<0.01 vs. NS), nitrite/nitrate levels (P<0.01 vs. NS), lipid peroxidation (P<0.05 vs. NT), and ALT release (P<0.01 vs. NS). Twenty-four hours after pancreatitis induction, nitrotyrosine expression was significantly lower in the HS group than in the NS group (P<0.05).

DISCUSSION

The protective effect of hypertonic saline was related to the establishment of a superoxide-NO balance that was unfavorable to nitrotyrosine formation.

CONCLUSIONS

Hypertonic saline decreases hepatic oxidative stress and thereby minimizes liver damage in pancreatitis.

High tidal volume ventilation is not deleterious in infant rats exposed to severe hemorrhage

BACKGROUND

Both high tidal volume (V(T)) ventilation and hemorrhage induce acute lung injury in adult rodents. It is not known whether injurious ventilation augments lung injury in infant rats exposed to severe hemorrhage.

METHODS

Two-week-old rats were allocated for ventilation with VT 7 mL/kg and positive end-expiratory pressure (PEEP) 5 cm H₂O (low V(T)) or V(T) 21 mL/kg and PEEP 1 (high V(T)) for 4 hours. Additional rats were subjected to volume-controlled hemorrhage and delayed saline resuscitation, followed by low V(T) or high V(T) ventilation for 4 hours. Nonventilated control groups were also included. Airway resistance and the coefficient of tissue elastance were derived from respiratory input impedance measurements using the low-frequency forced oscillation technique. Pressure-volume curves were obtained at baseline and at the end of the study. Interleukin-6, macrophage inflammatory protein-2, and tumor necrosis factor alpha were determined in bronchoalveolar lavage fluid (BALF) and serum.

RESULTS

In both healthy and hemorrhage-exposed animals, high V(T) resulted in reduced elastance (better lung compliance) and increased transcutaneous oxygen saturation. Interleukin-6 in BALF was greater in ventilated animals when compared with nonventilated controls, but not different among ventilated groups. No significant differences were found for all other inflammatory mediators, total protein concentration in BALF, and histology.

CONCLUSION

High V(T) ventilation with low PEEP improves respiratory system mechanics without causing additional damage to healthy and hemorrhage-exposed infant rats after 4 hours of ventilation. This study highlights the tolerance to high V(T) ventilation in infant rats and underscores the need for age-specific animal models.

A novel fluid resuscitation strategy modulates pulmonary transcription factor activation in a murine model of hemorrhagic shock

INTRODUCTION

Combining the hemodynamic and immune benefits of hypertonic saline with the anti-inflammatory effects of the phosphodiesterase inhibitor pentoxifylline (HSPTX) as a hemorrhagic shock resuscitation strategy reduces lung injury when compared with the effects of Ringer's lactate (RL). We hypothesized that HSPTX exerts its anti-inflammatory effects by interfering with nuclear factor kappa B/cAMP response element-binding protein (NF-kappaB-CREB) competition for the coactivator CREB-binding protein (CBP) in lung tissue, thus affecting pro-inflammatory mediator production.

METHODS

Male Sprague-Dawley rats underwent 60 minutes of hemorrhagic shock to reach a mean arterial blood pressure of 35 mmHg followed by resuscitation with either RL or HSPTX (7.5% HS + 25 mg/kg PTX). After four hours, lung samples were collected. NF-kappaB activation was assessed by measuring the levels of phosphorylated cytoplasmic inhibitor of kappa B (I-kappaB) and nuclear NF-kappaB p65 by western blot. NF-kappaB and CREB DNA-binding activity were measured by electrophoretic mobility shift assay (EMSA). Competition between NF-kappaB and CREB for the coactivator CBP was determined by immunoprecipitation. Interleukin-8 (IL-8) levels in the lung were measured by ELISA.

RESULTS

RL resuscitation produced significantly higher levels of lung IL-8 levels, I-kappaB phosphorylation, p65 phosphorylation, and NF-kappaB DNA binding compared with HSPTX. NF-kappaB-CBP-binding activity was similar in both groups, whereas CREB-CBP-binding activity was significantly increased with HSPTX. CREB-DNA binding-activity increased to a greater level with HSPTX compared with RL.

DISCUSSION

HSPTX decreases lung inflammation following hemorrhagic shock compared with conventional resuscitation using RL through attenuation of NF-kappaB signaling and increased CREB-DNA binding activity. HSPTX may have therapeutic potential in the attenuation of ischemia-reperfusion injury observed after severe hemorrhagic shock.

Optimal fluid resuscitation: timing and composition of intravenous fluids

BACKGROUND

Recent data suggest that the timing of fluid resuscitation and the type of fluid used to treat hemorrhagic shock contribute to the inflammatory response as well as cell death.

METHODS

Rats were bled of 40% of their total blood volume and then resuscitated in either early or delayed fashion. Treatment was assigned randomly and consisted of lactated Ringer's solution, normal saline, bicarbonate Ringer's solution, hypertonic saline, or no resuscitation. The first four groups were subdivided into early and late resuscitation. After a 5-h observation period, lung and liver samples were evaluated for apoptosis, and blood was collected for measurements of the cytokines interleukin (IL)-6, IL-10, and IL-1beta.

RESULTS

The rats that were not resuscitated had significantly more apoptosis in liver tissue. In the lung, bicarbonate Ringer's solution, when given early, was associated with significantly less apoptosis. Non-resuscitated rats had significantly higher IL-6 concentrations than all other groups. Animals receiving hypertonic saline early had significantly higher IL-6 concentrations than those given any other fluid. The concentration of IL-1beta was significantly higher in the non-resuscitated rats than in those receiving bicarbonate Ringer's, lactated Ringer's, or normal saline for early resuscitation. Interleukin-10 was elevated significantly in non-resuscitated rats.

CONCLUSIONS

Cellular destruction and a pro-inflammatory response follow hemorrhagic shock. Early resuscitation with isotonic crystalloid fluids decreases these responses.

Current trends in resuscitation strategy for the multiply injured patient

The ideal resuscitation strategy for multiply injured patients remains a topic of ongoing debate. At present, no consensus has been reached on the ideal fluid for early resuscitation and on the threshold for blood product transfusions. The concept of "permissive hypotension" for bleeding trauma patients furthermore contributes to the controversy in the field, particularly as it relates to blunt trauma and to patients with associated head injuries. Finally, postinjury coagulopathy is a poorly defined entity, and current resuscitation strategies lack strong evidence-based scientific support. This review article provides a brief overview of the existing resuscitation protocols for multiply injured patients, including ATLS and "damage control", and will address developing controversies in the field.

Toll-like receptor 4 regulates heme oxygenase-1 expression after hemorrhagic shock induced acute lung injury in mice: requirement of p38 mitogen-activated protein kinase activation

Acute lung injury (ALI) leading to respiratory distress is a common sequela of shock or trauma. The toll-like receptors (TLRs) stand at the interface of innate immune activation in the settings of both infection and sterile injury by responding to a variety of microbial and endogenous ligands alike. This work explored the effects of TLR-4 on hemorrhage-induced ALI and characterizes the signaling pathways and the mechanisms involved in noninfectious ALI. Mice underwent hemorrhagic shock and resuscitation (HSR). Arterial blood gases; expressions of TLR-4, heme oxygenase 1 (HO-1), and p38 mitogen-activated protein kinase (p38MAPK); myeloperoxidase activity; lung wet/dry ratios; and IL-10 levels in lung tissues were obtained at 6, 24, and 48 h after HSR. Hemorrhagic shock and resuscitation induced significant expressions of TLR-4, HO-1, and p38MAPK in C3H/HeN mice. IL-10 and myeloperoxidase were markedly increased at 24 h after HSR, and C3H/HeN mice had ALI with PaO2/fraction of inspired oxygen less than 300 mmHg. The induced amount of each cytokine level and the expressions of TLR-4, HO-1, and p38MAPK of C3H/HeN mice were significantly higher compared with C3H/HeJ mice. This study demonstrated that lung p38MAPK is activated after HSR, and p38MAPK inhibitor FR167653 suppresses HO-1 induction after ALI. We concluded that TLR-4 might induce HO-1 messenger RNA expression, which is probably involved in p38MAPK activation in the development of the lung dysfunction after HSR.

Burn-induced gut barrier injury is attenuated by phosphodiesterase inhibition: effects on tight junction structural proteins

Loss of intestinal barrier function after burn injury allows movement of intraluminal contents across the mucosa, which can lead to the development of distant organ injury and multiple organ failure. Tight junction function is highly regulated by membrane-associated proteins including occludin and zonula occludens protein 1 (ZO-1), which can be modulated by systemic inflammation. We hypothesized that (1) burn injury leads to gut barrier injury, and (2) phosphodiesterase inhibition will attenuate these burn-induced changes. Male balb/c mice undergoing a 30% steam burn were randomized to resuscitation with normal saline or normal saline + pentoxifylline (PTX; 12.5 mg/kg). Intestinal injury was assessed by histological diagnosis and TNF-alpha levels using enzyme-linked immunosorbent assay. Intestinal permeability was assessed by measuring the plasma concentration of fluorescein isothiocyanate-dextran after intraluminal injection in the distal ileum. Occludin and ZO-1 levels were analyzed by immunoblotting and immunohistochemistry. Thirty percent total body surface area (TBSA) burn results in a significant increase in intestinal permeability. Treatment with PTX after burn attenuates intestinal permeability to sham levels. Burn injury resulted in a marked decrease in the levels of tight junction proteins occludin and ZO-1 at 6 and 24 h. The use of PTX after burn significantly decreases the breakdown of occludin and ZO-1. Pentoxifylline also attenuates the burn-induced increase in plasma and intestinal TNF-alpha. Confocal microscopy demonstrates that PTX attenuates the burn-induced reorganization of occludin and ZO-1 away from the tight junction. Pentoxifylline attenuates burn-induced intestinal permeability and decreases the breakdown and reorganization of intestinal occludin and ZO-1. Therefore, phosphodiesterase inhibition may be a useful adjunct strategy in the attenuation of burn-induced gut barrier injury.

Pentoxifylline modulates intestinal tight junction signaling after burn injury: effects on myosin light chain kinase

BACKGROUND

Burn injury can result in loss of intestinal barrier function, leading to systemic inflammatory response syndrome and multiorgan failure. Myosin light chain kinase (MLCK), a tight junction protein involved in the regulation of barrier function, increases intestinal epithelial permeability when activated. Prior studies have shown that tumor necrosis factor (TNF)-alpha activates MLCK, in part through a nuclear factor (NF)-kappa B-dependent pathway. We have previously shown that pentoxifylline (PTX) decreases both TNF-alpha synthesis and NF-kappaB activation in models of shock. Therefore, we postulate that PTX will attenuate activation of the tight junction protein MLCK, which may decrease intestinal tight junction permeability after severe burn.

METHODS

Male balb/c mice undergoing a severe burn were randomized to resuscitation with normal saline (NS) or NS + PTX (12.5 mg/kg). Intestinal TNF-alpha levels were evaluated using enzyme linked immunosorbent assay. Gut extracts were obtained to assess MLCK, phosphorylated IKK, IkappaB-alpha, and NF-kappaB p65 levels by immunoblotting.

RESULTS

Burn injury increased intestinal MLCK protein levels threefold in animals resuscitated with NS, whereas those receiving PTX had MLCK levels similar to control (p < 0.01). Treatment with PTX attenuated burn-induced intestinal permeability. PTX decreased cytoplasmic IKK, IkappaB-alpha phosphorylation, and nuclear NF-kappaB p65 translocation to sham levels (p < 0.05 vs. NS).

CONCLUSION

Treatment with PTX attenuates activation of the tight junction protein MLCK, likely through its ability to decrease local TNF-alpha synthesis and NF-kappaB activation after burn. PTX may have therapeutic utility by decreasing intestinal barrier breakdown after burn.

Pentoxifylline modulates intestinal tight junction signaling after burn injury: effects on myosin light chain kinase

BACKGROUND

Burn injury can result in loss of intestinal barrier function, leading to systemic inflammatory response syndrome and multiorgan failure. Myosin light chain kinase (MLCK), a tight junction protein involved in the regulation of barrier function, increases intestinal epithelial permeability when activated. Prior studies have shown that tumor necrosis factor (TNF)-alpha activates MLCK, in part through a nuclear factor (NF)-kappa B-dependent pathway. We have previously shown that pentoxifylline (PTX) decreases both TNF-alpha synthesis and NF-kappaB activation in models of shock. Therefore, we postulate that PTX will attenuate activation of the tight junction protein MLCK, which may decrease intestinal tight junction permeability after severe burn.

METHODS

Male balb/c mice undergoing a severe burn were randomized to resuscitation with normal saline (NS) or NS + PTX (12.5 mg/kg). Intestinal TNF-alpha levels were evaluated using enzyme linked immunosorbent assay. Gut extracts were obtained to assess MLCK, phosphorylated IKK, IkappaB-alpha, and NF-kappaB p65 levels by immunoblotting.

RESULTS

Burn injury increased intestinal MLCK protein levels threefold in animals resuscitated with NS, whereas those receiving PTX had MLCK levels similar to control (p < 0.01). Treatment with PTX attenuated burn-induced intestinal permeability. PTX decreased cytoplasmic IKK, IkappaB-alpha phosphorylation, and nuclear NF-kappaB p65 translocation to sham levels (p < 0.05 vs. NS).

CONCLUSION

Treatment with PTX attenuates activation of the tight junction protein MLCK, likely through its ability to decrease local TNF-alpha synthesis and NF-kappaB activation after burn. PTX may have therapeutic utility by decreasing intestinal barrier breakdown after burn.

Phosphodiesterase inhibition attenuates alterations to the tight junction proteins occludin and ZO-1 in immunostimulated Caco-2 intestinal monolayers

AIMS

Under normal conditions, the intestinal mucosa acts as a local barrier to prevent the influx of luminal contents. The intestinal epithelial tight junction is comprised of several membrane associated proteins, including zonula occludens-1 (ZO-1) and occludin. Disruption of this barrier can lead to the production of pro-inflammatory mediators and ultimately multiple organ failure. We have previously shown that Pentoxifylline (PTX) decreases histologic gut injury and pro-inflammatory mediator synthesis. We hypothesize that PTX prevents the breakdown of ZO-1 and occludin in an in vitro model of immunostimulated intestinal cell monolayers.

MAIN METHODS

Caco-2 human enterocytes were grown as confluent monolayers and incubated under control conditions, or with PTX (2 mM), Cytomix (TNF-alpha, IFN-gamma, IL-1), or Cytomix+PTX for 24 h. Occludin and ZO-1 protein levels were analyzed by Western blot. Confocal microscopy was used to assess the cytoplasmic localization of ZO-1 and occludin.

KEY FINDINGS

Cytomix stimulation of Caco-2 cells resulted in a 50% decrease in both occludin and ZO-1 protein. Treatment with Cytomix+PTX restored both occludin and ZO-1 protein to control levels. Confocal microscopy images show that Cytomix caused an irregular, undulating appearance of ZO-1 and occludin at the cell junctions. Treatment with PTX prevented the Cytomix-induced changes in ZO-1 and occludin localization.

SIGNIFICANCE

Treatment with PTX decreases the pro-inflammatory cytokine induced changes in the intestinal tight junction proteins occludin and ZO-1. Pentoxifylline may be a useful adjunct in the treatment of sepsis and shock by attenuating intestinal barrier breakdown.

Hepatic transcription factor activation and proinflammatory mediator production is attenuated by hypertonic saline and pentoxifylline resuscitation after hemorrhagic shock

BACKGROUND

Fluid resuscitation can contribute to postshock inflammation and the development of end organ injury. We have previously observed an attenuation in pulmonary and ileal inflammation when hypertonic saline and pentoxifylline (HSPTX) were concomitantly administered after hemorrhage. We hypothesized that the attenuation in hepatic injury observed with HSPTX is associated with the reduction of transcription factor activation and proinflammatory mediator production when compared with Ringer's lactate (RL).

METHODS

Male Sprague-Dawley rats were resuscitated with racemic RL (32 mL/kg) or HSPTX (4 mL/kg 7.5% NaCl + PTX 25 mg/kg) and killed at 4 hours and 24 hours after resuscitation. Liver injury was determined by histology and serum aminotransferases. Nitrite, tumor necrosis factor-alpha, interleukin (IL)-1beta, and IL-6 were measured with enzyme-linked immunosorbent assay. High mobility group box 1, inducible nitric oxide synthase, nuclear factor (NF)-kappaB phosphorylation, and signal transducers and activators of transcription-3 phosphorylation were determined by Western blot. Transcription factor activation was verified with Electrophoretic Mobility Shift Assay.

RESULTS

RL resuscitation led to significant increases all measured parameters when compared with control. In contrast, HSPTX did not induce elevations in histologic liver injury or alanine aminotransferase levels. HSPTX attenuated inducible nitric oxide synthase by 23% (p < 0.01), nitrite by 25% (p < 0.05), tumor necrosis factor-alpha by 25% (p < 0.05), IL-1 by 63% (p < 0.01), IL-6 by 35% (p < 0.05), and high mobility group box 1 by 39% (p < 0.05) when compared with RL. HSPTX reduced IkappaB-alpha phosphorylation by 34% (p < 0.05), NF-kappaB p65 phosphorylation by 75% (p < 0.01), and signal transducers and activators of transcription-3 phosphorylation by 52% (p < 0.01).

CONCLUSIONS

The reduction in liver injury observed with HSPTX resuscitation after hemorrhage is associated with attenuation transcription factor activation and proinflammatory mediators. HSPTX has the potential to be a superior resuscitation fluid with significant immunomodulatory properties.

Hypertonic saline and pentoxifylline attenuates gut injury after hemorrhagic shock: the kinder, gentler resuscitation

BACKGROUND

We have previously demonstrated that postshock resuscitation with Hypertonic saline and Pentoxifylline (HSPTX) attenuates pulmonary and histologic gut injury when compared with Ringer's lactate (RL). In this study, we hypothesized that the decrease in gut injury observed with HSPTX is associated with the attenuation of inducible nitric oxide synthase (iNOS) activity and production of ileal proinflammatory mediators after hemorrhagic shock.

METHODS

In a rat model of hemorrhagic shock, resuscitation was conducted with RL (32 mL/kg; n = 7) or HSPTX (4 mL/kg 7.5% NaCl + PTX 25 mg/kg; n = 7). Sham animals that did not undergo shock were also studied. Four hours after resuscitation, the terminal ileum was collected for evaluation of nitrite, tumor necrosis factor (TNF)-alpha, Interleukin (IL)-6, and cytokine-induced neutrophil chemoattractant (CINC) by enzyme immunoassay. Heme oxygenase-1 (HO-1), iNOS, cytoplasmic inhibitor of kappa B (Ikappa B) phosphorylation, and nuclear factor (NF)kappa B p65 nuclear translocation were determined by Western blot.

RESULTS

HSPTX resuscitation resulted in a 49% decrease in iNOS when compared with RL (p < 0.05). Similar results were obtained when examining nitrite (882 +/- 59 vs. 1,435 +/- 177 micromol/L; p < 0.01), and HO-1 content (p < 0.05). RL resuscitation resulted in markedly higher levels of TNF-alpha (83 +/- 27 vs. 9 +/- 5 pg/mL; p < 0.01), IL-6 (329 +/- 58 vs. 118 +/- 43 pg/mL; p < 0.05), and CINC (0.43 +/- .06 vs. 0.19 +/- .08 ng/mL; p < 0.05) than HSPTX. The increase in cytokines observed with RL was also associated with an increase in I-kappaB phosphorylation (p < 0.01) and NF-kappaB p65 nuclear translocation (p < 0.001).

CONCLUSION

The attenuation in gut injury after postshock resuscitation with HSPTX is associated with downregulation of iNOS activity and subsequent proinflammatory mediator synthesis. HSPTX has the potential to be a superior resuscitation fluid with significant immunomodulatory properties.