Hypertonic saline resuscitation restores hemorrhage-induced immunosuppression by decreasing prostaglandin E2 and interleukin-4 production

Modeling the two-hit hypothesis for evaluating strategies to prevent organ injury after shock/resuscitation

The major cause of late death in patients sustaining major trauma relates to the development of progressive organ failure. Recent studies suggest that trauma victims are rendered susceptible to the development of organ failure because antecedent shock/resuscitation renders them susceptible to an exaggerated immune response to late inflammatory stimuli, the so-called two-hit hypothesis. In this article, the rationale underlying the use of a "two-hit" model in trauma research is reviewed and a specific example is cited. Importantly, these models permit investigation aimed at understanding the cellular and molecular mechanisms of disease after shock/resuscitation. Interventions such as antioxidant therapy and hypertonic saline resuscitation have a rational basis for use and have been shown to be effective in a rodent two-hit lung injury model. These studies suggest potential use in the critically ill trauma patient population.

Hypertonic resuscitation: physiologic mechanisms and recommendations for trauma care

Hypertonic saline solutions, with or without added colloid, have received extensive evaluation as volume expanders in both animal studies and clinical trials. Most studies have used 7.5% NaCl/6% dextran 70 (HSD). HSD's primary mechanism of action is rapid osmotic mobilization of cellular water into the blood volume. The measured volume expansion efficiency of HSD is equal to 10 times that of lactated Ringer's solution. Part of HSD's effectiveness is because of the hyperosmotic vasodilation of both systemic and pulmonary vessels. Increased cardiac effectiveness occurs because of the combination of increased preload (venous return) and reduced afterload (vasodilation). Increased cardiac contractility also has been reported in several studies and may play a role, but other studies refute a direct effect on contractility. HSD has been shown to be effective and safe with preexisting dehydration. Animal studies of immune function suggest that increased osmolarity prevents T-cell depression and decreases neutrophil activation. Several perioperative and eight randomized, blinded trauma trials have shown safety and reduced volume needs and suggest increased survival, particularly in head- and penetrating-injury patients. Infusion rates for HSD of 10 to 20 minutes may be recommended for the initial resuscitation of hypotensive trauma.

Hypertonic saline dextran alleviates hepatic injury in hypovolemic rats undergoing porta hepatis occlusion

To monitor the ischemic and/or reperfusion injury after porta hepatis occlusion (Pringle maneuver) in livers subjected to hypotension, serum alanine amino transferase (ALT), liver malondialdehyde (MDA), and liver glutathione (GSH) levels were measured. MDA is a by-product of oxidant-induced lipid peroxidation, and GSH is an endogenous antioxidant. The effects of lactated Ringer's (LR) and hypertonic saline (7.5%)/Dextran (6%; HSD) resuscitation on liver injury, if any, was investigated. Rats in sham (S, n = 8) and five other groups (n = 8) underwent femoral artery and vein catheterization and laparotomy. The hemorrhage and ischemia (HI) group was bled 30% of their blood volume and had their porta hepatis occluded for 30 min. The HI, LR, and HSD groups underwent both hemorrhage and occlusion. Thirty minutes after hemorrhage, the LR and HSD groups received either LR (equivalent to three times the shed blood) or HSD (10 mL/kg) resuscitation over 30 min. Both LR and HSD resuscitation lowered the increased ALT and liver tissue MDA seen in the HI group. ALT was decreased from 348 +/- 93 IU/L in the HI group to 200 +/- 98 IU/L in the LR and 139 +/- 74 IU/L in the HSD groups. Liver tissue MDA was 353 +/- 22 nmol/g/tissue in the HI group and LR decreased it to 261 +/- 17 nmol/g/tissue, whereas HSD decreased it to 273 +/- 20 nmol/g/tissue. The decrease in ALT and the increase in liver GSH were more pronounced with HSD resuscitation (P < 0.05). HSD seems to be more effective than LR in decreasing the liver tissue damage produced by total hepatic inflow occlusion under hypovolemic conditions.

Hypertonic saline resuscitation limits neutrophil activation after trauma-hemorrhagic shock

There is evidence suggesting that the ischemic gut is a major source of factors that lead to neutrophil activation, and that neutrophil activation can be reduced by hypertonic saline resuscitation. Thus, we tested whether trauma-hemorrhagic shock-induced neutrophil activation can be reduced by hypertonic saline resuscitation, as well as whether hypertonic saline reduces the ability of mesenteric lymph from shocked animals to activate neutrophils. Male Sprague-Dawley rats subjected to trauma (laparotomy), plus 90 min of shock [mean arterial pressure (MAP) MAP = 30 mmHg] or sham shock were resuscitated with Ringer's lactate or 7.5% hypertonic saline at an equivalent sodium load. Whole blood samples were collected before shock as well as at 1 and 2 h after the end of the shock period for neutrophil CD11b and CD18 expression measurements. In a second set of experiments, mesenteric lymph samples collected from rats subjected to trauma plus hemorrhagic shock (T/HS) or trauma plus sham-shock (T/SS) and resuscitated with Ringer's lactate or hypertonic saline were tested for their ability to modulate PMN CD11b, CD18, or L-selectin expression, as well as prime PMN for an augmented respiratory burst. To avoid confounding results due to interspecies differences, while at the same time looking at potential human responses, both naive rat and human PMN were tested. Both CD11b and CD18 expression were increased in PMN harvested from rats subjected to T/HS and resuscitated with Ringer's lactate solution, but not in T/HS rats resuscitated with hypertonic saline. These results indicate that PMN activation is increased to a greater extent in Ringer's lactate-resuscitated than hypertonic saline-resuscitated animals. Likewise, mesenteric lymph from the T/HS rats resuscitated with Ringer's lactate increased naive rat and human PMN CD11b and CD18 expression to a greater extent than did T/HS lymph from the hypertonic saline-treated rats. Additionally, T/HS lymph from the Ringer's lactate- but not the hypertonic saline-treated rats induced PMN L-selectin shedding. Lastly, T/HS lymph from the Ringer's lactate-treated rats induced the greatest PMN respiratory burst. These results indicate that resuscitation from T/HS with hypertonic saline is associated with less PMN activation than resuscitation with Ringer's lactate, and that factors produced or released by the postischemic intestine and carried in the mesenteric lymph contribute to neutrophil activation after an episode of T/HS.

Hemorrhagic shock resuscitation with a low molecular weight starch reduces neutrophil-endothelial interactions and vessel leakage in vivo

BACKGROUND

The polymorphonuclear neutrophil (PMN) has been implicated in the pathogenesis of endothelial cell (EC) damage and organ injury following hemorrhagic shock. Pentastarch (PTS), a low substituted medium molecular weight (MW) colloid, improves hemodynamics in hypovolemic shock and cardiac surgery. No data exist comparing the immunomodulation of PTS and Ringer's lactate (RL) on the activation of PMN in hemorrhagic shock in vivo.

METHODS

Using an in vivo murine hemorrhagic shock model (blood withdrawal to maintain 50 mmHg x 45 min), circulating PMN were observed every 15 minutes using intravital microscopy on cremaster muscle. EC-PMN interactions (videorecorded and subsequently analyzed blindly), vessel leakage (live epifluorescence after injection of 50 mg/kg fluorescent albumin) and PMN expression of L-selectin (immunofluorescent monoclonal antibodies and flow cytometry) were evaluated in three resuscitation groups: PTS (7.14 mL/kg 10% pentastarch/0.9% NaCl + shed blood, n = 13), RL (RL [2 x shed blood volume] + shed blood, n = 13) and SHAM (0 hemorrhage, 0 resuscitation, n = 9). Significance was evaluated by ANOVA with Bonferroni correction.

RESULTS

PMN rolling was significantly diminished in PTS and SHAM as compared to RL animals at all time points. Similar differences were found in PMN adherence to EC at most time points onwards from 15 minutes following resuscitation. In vivo vessel permeability was lowest in SHAM and PTS animals (mean 0.274 +/- 0.07 and 0.356 +/- 0.15, respectively, p > 0.05) and highest in RL animals (0.667 +/- 0.09, p < 0.001 vs PTS or SHAM). PMN L-selectin expression tended to be higher in the RL group than either SHAM and PTS groups. There were no flow-mechanics differences between groups (vessel diameter, mean red cell velocity, shear stress, shear rate).

CONCLUSIONS

10% pentastarch reduces RL-associated EC-PMN interactions and vessel leakage following hemorrhagic shock. These results support the use of low MW starches to resuscitate hemorrhagic shock, potentially reducing PMN-mediated tissue injury.

Hypertonic saline resuscitation attenuates neutrophil lung sequestration and transmigration by diminishing leukocyte-endothelial interactions in a two-hit model of hemorrhagic shock and infection

BACKGROUND

Hypertonic saline (HTS) attenuates polymorphonuclear neutrophil (PMN)-mediated tissue injury after hemorrhagic shock. We hypothesized that HTS resuscitation reduces early in vivo endothelial cell (EC)-PMN interactions and late lung PMN sequestration in a two-hit model of hemorrhagic shock followed by mimicked infection.

METHODS

Thirty-two mice were hemorrhaged (40 mm Hg) for 60 minutes and then given intratracheal lipopolysaccharide (10 microg) 1 hour after resuscitation with shed blood and either HTS (4 mL/kg 7.5% NaCl) or Ringer's lactate (RL) (twice shed blood volume). Eleven controls were not manipulated. Cremaster intravital microscopy quantified 5-hour EC-PMN adherence, myeloperoxidase assay assessed lung PMN content (2 1/2 and 24 hours), and lung histology determined 24-hour PMN transmigration.

RESULTS

Compared with RL, HTS animals displayed 55% less 5-hour EC-PMN adherence (p = 0.01), 61% lower 24-hour lung myeloperoxidase ( p= 0.007), and 57% lower mean 24-hour lung histologic score ( p= 0.027).

CONCLUSION

Compared with RL, HTS resuscitation attenuates early EC-PMN adhesion and late lung PMN accumulation in hemorrhagic shock followed by inflammation. HTS resuscitation may attenuate PMN-mediated organ damage.

Hypertonic saline resuscitation of hemorrhagic shock diminishes neutrophil rolling and adherence to endothelium and reduces in vivo vascular leakage

OBJECTIVE

To evaluate the in vivo effects of hypertonic saline (HTS) resuscitation on the interactions of endothelial cells (ECs) and polymorphonuclear neutrophils (PMNs) and vascular permeability after hemorrhagic shock.

SUMMARY BACKGROUND DATA

The PMN has been implicated in the pathogenesis of EC damage and organ injury following hemorrhagic shock. Compared to Ringer's lactate (RL), HTS resuscitation diminishes PMN and EC adhesion molecule expression and organ sequestration of PMNs.

METHODS

In a murine model of hemorrhagic shock (50 mmHg for 45 minutes followed by resuscitation) using intravital microscopy on cremaster muscle, the authors studied PMN-EC interactions and vascular leakage (epifluorescence after 50 mg/kg fluorescent albumin) in three resuscitation groups: HTS (shed blood + 4 cc/kg 7.5% HTS, n = 12), RL (shed blood + RL [2x shed blood volume], n = 12), and sham (no hemorrhage or resuscitation, n = 9). EC ICAM-1 expression was evaluated by immunohistochemistry. Data, presented as mean +/- SEM, were evaluated by analysis of variance with Bonferroni correction.

RESULTS

There were no differences between groups in flow mechanics. Compared to RL, HTS animals (t = 90 minutes) displayed diminished PMN rolling and PMN adhesion to EC at time intervals beyond t = 0. There were no differences between the sham and HTS groups. Vascular leakage was 45% lower in HTS than in RL-resuscitated animals. Cremaster EC ICAM-1 expression was similar in the two groups.

CONCLUSIONS

Using HTS instead of RL to resuscitate hemorrhagic shock diminishes vascular permeability in vivo by altering PMN-EC interactions. HTS could serve as a novel means of immunomodulation in hemorrhagic shock victims, potentially reducing PMN-mediated tissue injury.

Hypertonic saline resuscitation of hemorrhagic shock diminishes neutrophil rolling and adherence to endothelium and reduces in vivo vascular leakage

OBJECTIVE

To evaluate the in vivo effects of hypertonic saline (HTS) resuscitation on the interactions of endothelial cells (ECs) and polymorphonuclear neutrophils (PMNs) and vascular permeability after hemorrhagic shock.

SUMMARY BACKGROUND DATA

The PMN has been implicated in the pathogenesis of EC damage and organ injury following hemorrhagic shock. Compared to Ringer's lactate (RL), HTS resuscitation diminishes PMN and EC adhesion molecule expression and organ sequestration of PMNs.

METHODS

In a murine model of hemorrhagic shock (50 mmHg for 45 minutes followed by resuscitation) using intravital microscopy on cremaster muscle, the authors studied PMN-EC interactions and vascular leakage (epifluorescence after 50 mg/kg fluorescent albumin) in three resuscitation groups: HTS (shed blood + 4 cc/kg 7.5% HTS, n = 12), RL (shed blood + RL [2x shed blood volume], n = 12), and sham (no hemorrhage or resuscitation, n = 9). EC ICAM-1 expression was evaluated by immunohistochemistry. Data, presented as mean +/- SEM, were evaluated by analysis of variance with Bonferroni correction.

RESULTS

There were no differences between groups in flow mechanics. Compared to RL, HTS animals (t = 90 minutes) displayed diminished PMN rolling and PMN adhesion to EC at time intervals beyond t = 0. There were no differences between the sham and HTS groups. Vascular leakage was 45% lower in HTS than in RL-resuscitated animals. Cremaster EC ICAM-1 expression was similar in the two groups.

CONCLUSIONS

Using HTS instead of RL to resuscitate hemorrhagic shock diminishes vascular permeability in vivo by altering PMN-EC interactions. HTS could serve as a novel means of immunomodulation in hemorrhagic shock victims, potentially reducing PMN-mediated tissue injury.

Influence of beta-adrenoceptor antagonists on hemorrhage-induced cellular immune suppression

Hemorrhagic shock is associated with increasing catecholamine plasma concentrations. Plasma catecholamines are known to affect cellular immune functions. We therefore, investigated the effect of endogenously released catecholamines on lymphocyte distribution (CD4+ lymphocytes, CD8+ lymphocytes, and natural killer (NK) cells), splenocyte apoptosis (Annexin V binding), tumor necrosis factor-alpha (TNF-alpha), and interleukin 10 (IL-10) release during a volume-controlled hemorrhagic shock in mice. Mice received either saline (HEM), the non-selective beta-adrenoceptor antagonist propranolol (PROP; 2 mg/kg i.p.), or the beta1-adrenoceptor antagonist metoprolol (MET; 2 mg/kg i.p.) before induction of hemorrhage. Mice were sacrificed to obtain the spleen and whole blood 1 h after hemorrhage, 1 h after fluid resuscitation, and 24 h after hemorrhage. Flow cytometric analysis revealed an increase in circulating NK cells in the HEM group. This effect was completely abolished by pretreatment with propranolol or metoprolol. Furthermore, administration of either beta-adrenoceptor antagonist led to a decrease of circulating CD8+ lymphocyte numbers. Monitoring of splenocyte apoptosis by determination of Annexin V binding revealed an increase in splenocyte apoptosis 24 h after hemorrhage in the HEM group but not in the animals pretreated with propranolol or metoprolol. Induction of hemorrhage did not affect TNF-alpha or IL-10 plasma concentrations in either experimental group. We conclude that plasma catecholamines affect cellular immunity in the early phase of trauma via a beta-adrenergic pathway.

Hypertonic saline improves intestinal mucosa barrier function and lung injury after trauma-hemorrhagic shock

Our objective was to test the hypotheses that small volume hypertonic saline (HTS) resuscitation protects against trauma-hemorrhagic shock (T/HS)-induced intestinal and lung injury better than standard volume resuscitation with Ringer's lactate (RL), and that the degree of lung injury correlates with the degree of gut injury after therapy. Male Sprague-Dawley rats were subjected to laparotomy (trauma) and 90 min of T/HS or sham shock (T/SS), and were then resuscitated with RL or 7.5% NaCl solution at an equivalent sodium load. Intestinal and lung injury was assessed at 3 and 24 h after resuscitation. Lung permeability, pulmonary myeloperoxidase (MPO) levels, and the bronchoalveolar lavage fluid (BALF) protein to plasma protein ratio were increased after T/HS, but were significantly lower in HTS-resuscitated than RL-treated rats. The incidence of bacterial translocation (BT) was not different between the groups, but the magnitude of BT after T/HS was less after HTS than RL resuscitation. Barrier function of intestinal segments was impaired only in the T/HS rats resuscitated with RL and histological analysis demonstrated fewer injured villi in the T/HS rats resuscitated with HTS than RL. Linear regression analysis revealed direct correlations between the percent of injured villi, increased lung permeability, and pulmonary neutrophil sequestration. Resuscitation with HTS ameliorated T/HS-induced gut and lung injury seen with RL resuscitation. These results, together with the direct correlation found between gut and lung injury, suggest that lung injury after T/HS may be mediated by gut injury.

Clinical review: Hypertonic saline resuscitation in sepsis

The present review discusses the hemodynamic effects of hypertonic saline in experimental shock and in patients with sepsis. We comment on the mechanisms of action of hypertonic saline, calling upon data in hemorrhagic and septic shock. Specific actions of hypertonic saline in severe sepsis and septic shock are highlighted. Data are available that support potential benefits of hypertonic saline infusion in various aspects of the pathophysiology of sepsis, including tissue hypoperfusion, decreased oxygen consumption, endothelial dysfunction, cardiac depression, and the presence of a broad array of proinflammatory cytokines and various oxidant species. The goal of research in this field is to identify reliable therapies to prevent ischemia and inflammation, and to reduce mortality.

Use of hypertonic saline solutions in treatment of cerebral edema and intracranial hypertension

OBJECTIVES

To review the literature on the use of hypertonic saline (HS) in treating cerebral edema and intracranial hypertension.

DATA SOURCES

Review of scientific and clinical literature retrieved from a computerized MEDLINE search from January 1965 through November 1999.

STUDY SELECTION

Pertinent literature is referenced, including clinical and laboratory investigations, to demonstrate principles and efficacy of treatment with HS in patients with intracranial space-occupying pathology.

DATA EXTRACTION

The literature was reviewed to summarize the mechanisms of action, efficacy, adverse effects, systemic effects, and comparisons with standard treatments in both clinical and laboratory settings.

DATA SYNTHESIS

HS has an osmotic effect on the brain because of its high tonicity and ability to effectively remain outside the bloodbrain barrier. Numerous animal studies have suggested that fluid resuscitation with HS bolus after hemorrhagic shock prevents the intracranial pressure (ICP) increase that follows resuscitation with standard fluids. There may be a minimal benefit in restoring cerebral blood flow, which is thought to be mitigated through local effects of HS on cerebral microvasculature. In animal models with cerebral injury, the maximum benefit is observed in animals with focal injury associated with vasogenic edema (cryogenic injury). The ICP reduction is seen for < or =2 hrs and may be maintained for longer periods by using a continuous infusion of HS. The ICP reduction is thought to be caused by a reduction in water content in areas of the brain with intact blood-brain barrier such as the nonlesioned hemisphere and cerebellum. Most comparisons with mannitol suggest almost equal efficacy in reducing ICP, but there is a suggestion that mannitol may have a longer duration of action. Human studies published to date reporting on the use of HS in treating cerebral edema and elevated ICP include case reports, case series, and small controlled trials. Results from studies directly comparing HS with standard treatment in regard to safety and efficacy are inconclusive. However, the low frequency of side effects and a definite reduction of ICP observed with use of HS in these studies are very promising. Systemic effects include transient volume expansion, natriuresis, hemodilution, immunomodulation, and improved pulmonary gas exchange. Adverse effects include electrolyte abnormalities, cardiac failure, bleeding diathesis, and phlebitis. Although unproven, a potential for central pontine myelinolysis and rebound intracranial hypertension exists with uncontrolled administration.

CONCLUSIONS

HS demonstrates a favorable effect on both systemic hemodynamics and intracranial pressure in both laboratory and clinical settings. Preliminary evidence supports the need for controlled clinical trials evaluating its use as resuscitative fluid in brain-injured patients with hemorrhagic shock, as therapy for intracranial hypertension resistant to standard therapy, as firstline therapy for intracranial hypertension in certain intracranial pathologies, as small volume fluid resuscitation during spinal shock, and as maintenance intravenous fluid in neurocritical care units.

Hypertonic saline solution induces prostacyclin production by increasing cyclooxygenase-2 expression

BACKGROUND

Previously, we demonstrated that hypertonic saline solution (HTS) and endotoxin (lipopolysaccharide [LPS]) induce prostacyclin (PGI(2)) production in human endothelial cells. Here, we hypothesized that HTS and LPS may induce PGI(2) production by increasing cyclooxygenase (COX) expression. We further examined the activation of p38 and extracellular signal-regulated kinases (ERK) and questioned whether these transduction cascades might mediate COX expression.

METHODS

Human umbilical vein endothelial cells were stimulated with varying concentrations of NaCl or LPS.

RESULTS

HTS and LPS induced prompt activation of both p38 and ERKs that peaked at 30 minutes. HTS and LPS also induced a dose-related increase in COX-2 with maximal expression within 4 to 6 hours; there was no change in COX-1. This correlated with an increase in supernatant PGI(2) levels, which became statistically significant for NaCl of more than 40 mmol/L and for all LPS doses. The inhibition of p38 with SB202190 abrogated the osmotic and LPS-induced COX-2 expression and PGI(2) production. Inhibition of ERK activation had no effect on COX-2 expression.

CONCLUSIONS

Hyperosmolarity and LPS induce, in chronologic order, p38 and ERK activation, COX-2 expression, and PGI(2) production. Because COX is the rate-limiting enzyme in prostaglandin synthesis, it is likely that the increase in PGI(2) production is due to, at least in part, the increased COX-2 expression. The data also suggest that p38 mitogen-activated protein kinase is involved in the signaling cascade for COX-2 expression.

Effects of blood resuscitation versus dextran resuscitation after hemorrhage on intrinsic myocardial function

BACKGROUND

Myocardial function is altered by many factors present in hemorrhaged and resuscitated animals. The purpose of this study was to determine whether resuscitation after a short period of hemorrhagic shock, which by itself did not alter intrinsic cardiac function, causes dysfunction.

METHODS

Guinea pigs were instrumented to measure blood pressure and cardiac output, and several days later 50% of their blood volume was removed at a rate of 1 mL/min. Some animals were resuscitated with the shed blood and some with 6% dextran. Hearts were studied 1 or 24 hours after resuscitation.

RESULTS

Isolated hearts from animals after 1 hour of resuscitation demonstrated dysfunction whether resuscitated with blood or dextran, although dysfunction was more severe with blood resuscitation. By 24 hours, dysfunction was essentially reversed.

CONCLUSIONS

Resuscitation after hemorrhagic shock caused injury to the myocardium independent of the hemorrhage. Blood resuscitation resulted in greater dysfunction than did resuscitation with dextran.

The effects of interleukin-10 in hemorrhagic shock

BACKGROUND

Interleukin-10 (IL-10) counteracts the effects of the proinflammatory cytokines interleukin-1 (IL-1), interleukin-6 (IL-6), and tumor necrosis factor (TNF). Experimental data suggest that inhibition of these proinflammatory cytokines improves outcome in sepsis, endotoxemia, necrotizing pancreatitis, and other severe inflammatory states. We hypothesized that the administration of IL-10 would attenuate the release of proinflammatory cytokines after severe hemorrhagic shock.

METHODS

To test our hypothesis, male Sprague-Dawley rats (N = 20) were divided into control and experimental groups. We induced hemorrhagic shock by removing a sufficient quantity of blood to maintain a mean arterial pressure of 50 mm Hg or less for 120 min. The animals were then resuscitated with shed blood and an equal volume of 0.9% saline. The experimental group received 10,000 units of IL-10 at the initiation of shock. Serum IL-1, IL-6, TNF, and lactate were measured at baseline, after 120 min of shock, and 60 min after resuscitation. The rats were followed for 72 h to calculate survival.

RESULTS

Similar levels of hypoperfusion were obtained in both groups as demonstrated by lactate levels and amount of shed blood. The survival rate (70%) was the same in both groups. Serum levels of IL-1 and IL-6 were not significantly different between the two groups, although there was a trend toward IL-6 suppression. TNF, however, was significantly lower in the IL-10-treated group at the end of shock (Wilcoxon test, P < 0. 025).

CONCLUSION

Administration of IL-10 suppresses the TNF surge observed after severe hemorrhagic shock.

[Vascular loading in the first 24 hours following severe head injuries]

The main goal at the acute phase of head injury is to prevent a decrease in blood pressure, which promotes cerebral ischemia. Volume loading is therefore frequently indicated. A normal or increased plasma osmolarity should be maintained. Thus hypotonic fluids should be avoided. Hyperglycaemia is also a risk factor for brain injury and glucose use has to be restricted in the first hours after trauma. Isotonic saline 0.9% is the first solution to be infused. Lactated Ringer solutions are mildly hypotonic as approximately 114 mL of free water is contained in each litre of the solution. Isotonic colloids are indicated to replace blood losses, but have no advantage over cristalloids, concerning the development of cerebral oedema. Fluid restriction minimally affects cerebral edema. Because of the severe consequences of hypovolaemia and hypotension, fluids should not be restricted until haemodynamic stability is achieved. Hypertonic fluids rapidly restore intravascular volume and decrease intracranial pressure. Although they probably have a place in prehospital intensive therapy, the demonstration of their benefit is still lacking. Monitoring of intravascular volume is essential. Continuous arterial pressure and central venous pressure monitoring are mandatory. New monitoring techniques as the measurement of systolic pressure variations or transoesophageal Doppler echocardiography will probably find a place in the management of trauma patients in the near future.

Reversal of sexual dimorphism in splenic T lymphocyte responses after trauma-hemorrhage with aging

Previous studies have demonstrated that hemorrhagic shock produces immunodepression in young male mice, whereas the immunoresponsiveness in young proestrus female mice is enhanced under such conditions. This sexually dimorphic immune response to hemorrhage appears to be related to high estrogen and testosterone levels in females and males, respectively. Nonetheless, it is unknown what impact the age-related decline in the sex steroid levels has on the immune response after hemorrhage. To study this, young (2-3 mo) and aged (18-19 mo) male and female CBA/J NIA mice were subjected to laparotomy (i.e., soft tissue trauma) and hemorrhage (35 +/- 5 mmHg for 90 min and fluid resuscitation) or sham operation. Twenty-four hours later, splenocyte responses were assessed in vitro. Splenic T lymphocyte responses [i.e., proliferation, interleukin-2 (IL-2) and interferon-gamma (IFN-gamma) release] were depressed in young males and enhanced in young females after trauma-hemorrhage. In contrast, in the aged male and female groups these parameters of splenocyte function were reversed after trauma-hemorrhage (i.e., increased proliferation and IL-2 release in aged males compared with suppressed proliferation and IFN-gamma release in aged females). Furthermore, the release of the immunosuppressive cytokine IL-10 inversely correlated with the age- and gender-related changes in splenocyte responses after trauma-hemorrhage. Thus the sexually dimorphic immune response in young males and females to trauma-hemorrhage appears to reverse as sex hormone levels decline with age.

Immune dysfunction following trauma-haemorrhage: influence of gender and age

Recent studies indicate that young female proestrus mice show an enhanced immune response following trauma-haemorrhage, as opposed to the immunodepression observed in males of comparable age. Testosterone is suggested as the cause of immunodepression in males, whereas oestradiol seems to be responsible for the enhanced immune response in females, however, sex hormone levels decrease with age. To determine if the sexual dimorphism in immune responses observed in young mice following trauma-haemorrhage changes with age, young (2-3 months) and aged (18-19 months) male and female CBA/J NIA mice were subjected to soft-tissue trauma (laparatomy) and haemorrhage (35+5 mmHg for 90 min and fluid resuscitation) or sham operation. Mice were killed 24 h later, and whole blood, as well as splenic and peritoneal macrophages (Mstraight phi) obtained. Plasma 17beta-oestradiol and free testosterone decreased in aged females and males, respectively. Mstraight phi from young females had enhanced IL-1beta and suppressed IL-10 production following trauma-haemorrhage, while aged females had unchanged production IL-1beta and IL-6 production and enhanced IL-10 release. In contrast, IL-1beta and IL-6 production by Mbeta from young males was suppressed and IL-10 production enhanced following trauma-haemorrhage, whereas Mstraight phi from aged males produced elevated levels of IL-1beta and IL-6 and suppressed levels of IL-10 following trauma-haemorrhage. Thus, the gender-related changes in the immune response to trauma-haemorrhage were reversed in aged mice.

Immune dysfunction in trauma

This article documents that all immunomodulation strategies for patients sustaining traumatic injury are still under intense investigation. Although we can speculate that combination strategies may be more beneficial than single-agent immunomodulation approaches, comprehensive clinical studies are required to determine efficacious immune therapy for trauma patients. The only strategy available to clinicians caring for trauma patients is immunonutrition, and this should be strongly considered as a rational approach to improve immune function and reduce septic complications in critically ill or injured patients.

Hypertonic saline induces prostacyclin production via extracellular signal-regulated kinase (ERK) activation

BACKGROUND

Hypertonic saline (HTS) resuscitation exerts protective effects in reperfusion injury including a decrease in pulmonary vascular resistance and an increase in microvascular perfusion and cerebral blood flow; however, the mediators of these effects are unknown. Prostacyclin (PGI2) is a paracrine mediator with two main effects, vasodilation and inhibition of platelet aggregation. We hypothesized that HTS may induce PGI2 production by endothelial cells.

METHODS

Human umbilical vein endothelial cells (HUVECs) were treated with varying concentrations of NaCl. After 12 h of incubation, the supernatant was assayed for 6-keto-prostaglandin F1, a stable metabolite of PGI2, by ELISA. Phospho-specific ERK-1 and ERK-2 mitogen-activated protein kinase (MAPK) antibody, which recognizes only activated ERK, was used to determine ERK activation status by Western blotting.

RESULTS

Addition of 20-100 mM NaCl or endotoxin [lipopolysaccharide (LPS)] induced PGI2 production by HUVECs. HTS and LPS induced ERK-1 and ERK-2 activation. PGI2 production was inhibited when the HUVECs were pretreated with PD 98059, a specific inhibitor of ERK phosphorylation.

CONCLUSION

These data suggest that HTS induces PGI2 production in HUVECs. In addition, HTS and LPS induce activation of ERK which is required for PGI2 production. HTS resuscitation may improve microvascular circulation and decrease reperfusion injury via induction of PGI2 production by endothelial cells.

Do different rates of fluid resuscitation adversely or beneficially influence immune responses after trauma-hemorrhage?

BACKGROUND

Although rapid fluid resuscitation continues to be an important component of the initial therapy for trauma patients, it remains unknown whether the rate of fluid administration after trauma-hemorrhage has any deleterious or beneficial effects on immunity.

METHODS

Male C3H/HeN mice were subjected to sham operation or soft-tissue trauma (midline laparotomy) and hemorrhagic shock (mean arterial blood pressure of 35+/-5 mm Hg for 90 minutes) followed by resuscitation with four times the volume of shed blood in the form of lactated Ringer's solution over 30 minutes (rapid rate), 60 minutes (moderate rate), or 120 minutes (slow rate). The animals were killed at either 4 hours or 4 days after the end of trauma-hemorrhage. Spleens were harvested and splenocyte interleukin (IL)-3 and interferon-gamma (IFN-gamma) release as well as splenic macrophage IL-1beta and IL-6 release were determined.

RESULTS

The results indicate that at 4 hours after trauma-hemorrhage, splenocyte IL-3 and IFN-gamma release were significantly depressed in all animals subjected to trauma-hemorrhage compared with sham-operated animals. At 4 days after trauma-hemorrhage, splenocyte IL-3 and IFN-gamma release were restored in mice resuscitated with the slow rate of resuscitation; however, the release of these cytokines remained significantly depressed in animals resuscitated with the moderate or rapid rates. Splenic macrophage IL-1beta and IL-6 release were significantly depressed at 4 hours after trauma-hemorrhage. At 4 days after trauma-hemorrhage, the release of these proinflammatory cytokines was still depressed in animals resuscitated with the rapid rate. In contrast, splenic macrophage IL-1beta and IL-6 release were restored in mice receiving the slow rate of resuscitation.

CONCLUSION

These results suggest that a slower rate of fluid resuscitation after trauma-hemorrhage leads to a faster restoration of the depressed cell-mediated immunity, whereas rapid fluid resuscitation produces a prolonged depression of immune responses. In view of this, we propose that a prospective clinical study of this type must be performed in a select group of trauma patients to determine whether or not a slower rate of fluid resuscitation also improves immune responses in trauma patients.

Resuscitation with hypertonic saline dextran reduces endothelial cell swelling and improves hepatic microvascular perfusion and function after hemorrhagic shock

BACKGROUND

Hemorrhagic shock severely compromises hepatic microcirculation and function with tendency to promote hepatic insufficiency and multiple organ failure.

MATERIAL AND METHODS

The aim of the study was to evaluate the effects of small volume resuscitation on liver microcirculation (intravital fluorescence microscopy and electron microscopy) and function (arterial ketone body ratio (AKBR) and bile flow), in a rat model of traumatic-hemorrhagic shock. One hour after hemorrhage (MAP 40 mm Hg) the rats were resuscitated with HSD (7.2% NaCl/10% dextran 60, 10% of shed blood/2 min, n = 8); DEX (6% dextran 60, 100% of shed blood/5 min, n = 8); or RL (Ringer lactate, 400% of shed blood/20 min, n = 6).

RESULTS

HSD yielded a better recovery of sinusoidal perfusion (17.8 +/- 0.8% nonperfused sinusoids) than DEX (21.8 +/- 0. 7%, P < 0.05) and RL (23.9 +/- 0.9%, P < 0.01). Hemorrhagic shock produced a moderate increase of mean sinusoidal endothelial cell thickness, which was further enhanced by DEX and RL (P < 0.05 vs baseline), whereas HSD reduced the mean endothelial cell thickness toward baseline (P < 0.05 vs DEX and RL). Both AKBR and bile flow were profoundly reduced after 1 h shock. Resuscitation with DEX and RL produced a weak recovery, still remaining at shock level, while HSD infusion allowed a significant improvement of AKBR and bile flow (P < 0.05 vs shock).

CONCLUSION

Reduction of mean endothelial cell thickness after HSD is very likely the mechanism for the amelioration of sinusoidal perfusion, resulting in a significant improvement of hepatic energetic status and excretory function.

Hypertonic saline resuscitation reduces neutrophil margination by suppressing neutrophil L selectin expression

Hypertonic saline (HS) reduces hemorrhage-induced lung injury by suppressing the neutrophil oxidative burst and reducing lung neutrophil influx. This study investigated whether this is caused by the effects of HS on endothelial adhesion molecule expression, the production of chemoattractants in the lung, or a direct effect of HS on neutrophil selectin expression.

METHODS

BALB/c mice were made to hemorrhage to 40 mm Hg for 1 hour and resuscitated with shed blood and either 4 mL/kg 7.5% HS or two times the shed blood volume of lactated Ringer's solution (LRS). Neutrophil L selectin expression was determined by flow cytometry, total neutrophil counts were obtained by differential staining, and pulmonary endothelial P and E selectin expression was evaluated by immunohistochemistry. Chemoattractants in lung lavages were determined with a modified Boyden chamber migration assay.

RESULTS

Chemotactic activity of lavage fluid of HS-treated animals was not significantly different from that of LRS-treated animals, and endothelial P and E selectin expression was not altered by HS resuscitation. Neutrophils of HS-treated animals, however, expressed significantly less L selectin than those of LRS-treated mice. Concomitantly, circulating neutrophil counts of LRS-treated animals were significantly decreased compared with those of HS-treated mice.

CONCLUSION

HS had little effect on endothelial selectin expression and chemoattractant production in the lung. HS significantly decreased neutrophil L selectin expression, however. This suggests that HS resuscitation may reduce lung injury by preventing neutrophil L selectin expression and endothelial adhesion.

Hypertonic saline resuscitation decreases susceptibility to sepsis after hemorrhagic shock

BACKGROUND

We hypothesized that improvements in cellular immune function after hypertonic saline (HTS) resuscitation will alter the outcome of sepsis after hemorrhage.

METHODS

To test this hypothesis, a two-hit model was used. Hemorrhage was induced in BALB/c mice by catheterizing the femoral artery and bleeding until a mean arterial pressure = 35 mm Hg was reached and maintained for 1 hour. Resuscitation was performed with HTS (NaCl 7.5%, 4 mL/kg) or lactated Ringer's (LR, twice the shed blood volume), plus the shed blood. Cecal ligation and puncture (CLP) was performed 24 hours after hemorrhage. Mortality was assessed for 72 hours, comparing HTS (n = 14) and LR (n = 13) resuscitation. Another set of animals (n = 10 in each group at each time point) were killed at 2 and 24 hours after blood collection. Liver and blood were cultured for the presence of bacteria, and lung and liver samples were scored on a scale from 0 (normal) to 4 (most severe) in a blind fashion by a pathologist.

RESULTS

Mortality 72 hours after CLP was 14.3% in HTS and 76.9% in LR treated animals (p < 0.002). At 24 hours after CLP, 44% of HTS, but 77% of LR treated animals had > 1,000 colony forming units/mL of blood. Positive liver cultures (> 100,000 colony forming units/g) also showed the same trend (HTS = 30%, LR = 60%). Autopsies revealed a better containment of the infection (abscess formation) in the HTS group. At 2 hours, lung scores were 1.2 +/- 0.25 and 2.6 +/- 0.31 for HTS and LR, respectively (p < 0.002). At 24 hours, HTS treated animals showed marked improvement of lung injury, while the scores in the LR group remained high. A significant difference was also observed regarding liver injury. At 2 hours, scores were 0.4 +/- 0.22 and 2.3 +/- 0.16 for HTS and LR, respectively (p < 0.002). At 24 hours, HTS treated animals showed normal hepatic architecture, although mild injury was still observed in the LR group.

CONCLUSION

HTS resuscitation leads to increased survival after hemorrhage and CLP. Marked improvements were observed in lung and liver injury compared with isotonic resuscitation. The better containment of the infection observed with HTS resuscitation corresponds to a marked decreased in bacteremia. HTS resuscitation stands as an alternative resuscitation regimen with immunomodulatory potential.

Hypertonic saline activates protein tyrosine kinases and mitogen-activated protein kinase p38 in T-cells

OBJECTIVES

In previous in vitro studies, we have found that hypertonic saline (HTS) can augment T-cell proliferation and restore the function of suppressed T-cells. Our animal models have shown that HTS resuscitation reverses immunosuppression after hemorrhage and reduces mortality from sepsis. In the present study, we investigated if and how HTS may influence T-cell signaling and function on a subcellular level.

DESIGN

Human peripheral blood mononuclear cells (PBMC) were used to determine the effect of HTS on T-cell interleukin 2 (IL-2) production and proliferation. Human Jurkat T-cells were used to study the effects of HTS on T-cell signal transduction, IL-2 mRNA transcription, and IL-2 expression.

MATERIAL AND METHODS

The effect of HTS on T-cell proliferation and IL-2 production was measured with PBMC and Jurkat T-cells. IL-2 mRNA transcription in HTS-treated Jurkat cells was measured by reverse transcriptase polymerase chain reaction. HTS-induced protein tyrosine phosphorylation in Jurkat T-cells was determined by immunoblotting with anti-phosphotyrosine antibodies. Expression in Jurkat cells of the mitogen-activated protein kinase p38 (MAPK p38), a signal transduction protein that is activated by osmotic stress, was determined by immunoblotting with anti-MAPK p38 antibodies. HTS-induced MAPK p38 activation in Jurkat cells was measured with an immune-complex kinase assay using ATF-2 as a substrate.

MEASUREMENTS AND MAIN RESULTS

Proliferation of activated human PBMC increased significantly upon addition of HTS to the culture medium. This effect of HTS was paralleled by enhanced IL-2 production of activated PBMC and Jurkat cells and IL-2 mRNA transcription of Jurkat cells. HTS exposure of Jurkat cells caused tyrosine phosphorylation of a number of cellular proteins. We found that Jurkat T-cells expressed MAPK p38 and that it was activated in the presence of HTS. All these effects of HTS on T-cell signaling and function were observed at NaCl concentrations that were within physiologically relevant levels (20-100 mmol/L hypertonicity).

CONCLUSIONS

In T-cells, HTS triggers a signaling pathway that includes increased tyrosine phosphorylation of several cellular proteins and activation of MAPK p38. HTS alone does not result in IL-2 mRNA transcription, IL-2 expression, or T-cell proliferation. However, in combination with other stimuli, HTS augments T-cell IL-2 expression and proliferation. We speculate that HTS could "resuscitate" suppressed T-cells in trauma patients by circumvention of, or substituting for, blocked signaling pathways.