Estradiol administration after trauma-hemorrhage improves cardiovascular and hepatocellular functions in male animals

OBJECTIVE: To determine whether female sex steroids have any salutary effects on the depressed cardiovascular and hepatocellular functions following trauma and hemorrhage in male animals. SUMMARY BACKGROUND DATA: Studies indicate that gender difference exists in the immune and cardiovascular responses to trauma-hemorrhage, and that male sex steroids appear to be responsible for producing immune and organ dysfunction, but it remains unknown if female sex steroids produce any salutary effects on the depressed cellular and organ functions in males following trauma and hemorrhage. METHOD: Adult male Sprague-Dawley rats underwent a midline laparotomy (i.e., trauma induction), and were bled to and maintained at a mean arterial pressure of 40 mmHg until 40% of the maximum bleed-out volume was returned in the form of Ringer's lactate (RL). Animals were then resuscitated with RL at 4 times the shed blood over 60 minutes. 17beta-estradiol (50 microg/kg) or an equal volume of vehicle was injected subcutaneously 15 minutes before the end of resuscitation. The maximal rate of ventricular pressure increase or decrease (+/-dP/dtmax), cardiac output, and hepatocellular function (i.e., maximal velocity and overall efficiency of in vivo indocyanine green clearance) were assessed at 24 hours after hemorrhage and resuscitation. Plasma levels of interleukin (IL)-6 were also measured. RESULTS: Left ventricular performance, cardiac output, and hepatocellular function decreased significantly at 24 hours after trauma-hemorrhage and resuscitation. Plasma levels of IL-6 were elevated. Administration of 17beta-estradiol significantly improved cardiac performance, cardiac output, and hepatocellular function, and attenuated the increase in plasma IL-6 levels. CONCLUSION: Administration of estrogen appears to be a useful adjunct for restoring cardiovascular and hepatocellular functions after trauma-hemorrhage in male rats.     

Continuous resuscitation after hemorrhage and acute fluid replacement improves cardiovascular responses

BACKGROUND: Although acute fluid replacement after trauma and severe hemorrhage remains the cornerstone in the management of trauma victims, it remains unknown whether continuous resuscitation after trauma-hemorrhage and acute fluid replacement produces salutary effects on cardiovascular function and reduces proinflammatory cytokine release. METHODS: Adult male rats underwent laparotomy (ie, soft tissue trauma) and were bled to and maintained at a mean arterial pressure of 40 mm Hg until 40% of the shed blood volume was returned in the form of Ringer's lactate (RL). The animals were then resuscitated with 4 times the volume of shed blood with RL for 60 minutes, followed by continuous resuscitation with RL at 5 mL/h/kg for 48 hours after the acute fluid replacement. At 48 hours after hemorrhage, mean arterial pressure, cardiac output, and left ventricular contractility parameters, such as the maximal rates of ventricular pressure increase (+dP/dt(max)) and decrease (-dP/dt(max)), were determined. Microvascular blood flow in the intestine and kidney was assessed by laser Doppler flowmetry. In addition, plasma levels of TNF-alpha were assayed by enzyme-linked immunosorbent assay. RESULTS: The mean arterial pressure and cardiac output were decreased by 34% and 18%, respectively, at 48 hours after hemorrhage and acute resuscitation. Continuous resuscitation, however, markedly improved these parameters. Similarly, +dP/dt(max) and -dP/dt(max) decreased significantly after hemorrhage and acute fluid replacement but was restored to sham values after continuous resuscitation. Microvascular blood flow in the gut and kidneys was decreased after hemorrhage and acute resuscitation by 34% and 35%, respectively. However, intestinal and renal perfusion was maintained at the sham levels at 48 hours after continuous resuscitation. In addition, the upregulated TNF-alpha after acute resuscitation alone was reduced after continuous resuscitation. CONCLUSIONS: Continuous resuscitation after acute fluid replacement appears to be a useful approach for restoring and maintaining cardiovascular function and organ perfusion after trauma and severe hemorrhage.     

Restoration of body temperature to normothermia during resuscitation following trauma-hemorrhage improves the depressed cardiovascular and hepatocellular functions

HYPOTHESIS: Rewarming the body to 37 degrees C during resuscitation following trauma-hemorrhage has salutary effects on cardiovascular and hepatocellular functions. DESIGN, INTERVENTIONS, AND MAIN OUTCOME MEASURES: Male rats underwent laparotomy (trauma induced) and were then bled to and maintained at a mean arterial pressure of 40 mm Hg until 40% of the maximum shed blood volume was returned in the form of Ringer lactate solution. Rats were exposed to ambient temperature and allowed to become hypothermic during hemorrhage. The animals were then resuscitated with 4 times the volume of shed blood with Ringer lactate solution for 60 minutes. In 1 group, the body temperature was rewarmed to 37 degrees C during resuscitation. In another group, the body temperature was maintained at hypothermia (32 degrees C) for 4 hours after resuscitation. In an additional group, the body temperature was kept at 37 degrees C during hemorrhage and resuscitation. At 4 hours after resuscitation, the rats were returned to a room with ambient temperature. Various in vivo heart performance variables (maximal rate of pressure increase and decrease), cardiac output, hepatocellular function, and plasma IL-6 level were determined at 24 hours after resuscitation. RESULTS: Either maintenance of normothermia during hemorrhage or prolonged hypothermia following resuscitation had deleterious effects on cardiovascular variables and hepatocellular function and up-regulated plasma IL-6 levels. In contrast, rewarming the body to 37 degrees C during resuscitation improved cardiac contractility, cardiac output, and hepatocellular function and reduced plasma IL-6 level. CONCLUSION: Since rewarming the body temperature to normothermia during resuscitation improved depressed cardiovascular and hepatocellular functions, this should be considered as a useful adjunct to fluid resuscitation after trauma-hemorrhage.     

Critical role of oxygen radicals in the initiation of hepatic depression after trauma hemorrhage

BACKGROUND: Although depression in hepatocellular function occurs early after trauma and severe hemorrhage and persists despite fluid resuscitation, it remains unknown whether reactive oxygen species (ROS) play any role in the initiation of hepatocellular depression and damage under those conditions. We hypothesized that administration of a ROS scavenger at the beginning of resuscitation will attenuate organ injury after severe shock. METHODS: Male Sprague-Dawley rats (275-325 g) underwent laparotomy (i.e., induction of soft tissue trauma) and were then bled to and maintained at a mean arterial pressure of 40 mm Hg until 40% of the maximal bleed-out volume was returned in the form of Ringer's lactate. The animals were then resuscitated with four times the volume of maximal bleed-out with RL over 60 minutes. The ROS scavenger 2-mercaptopropionyl glycine (30 mg/kg) or vehicle was administered intravenously as a bolus at the beginning of resuscitation. At 2 hours after the completion of crystalloid resuscitation or the equivalent interval after sham-operation, cardiac index was measured by a dye dilution technique. Hepatocellular function, i.e., the maximum velocity of indocyanine green clearance (Vmax) and the efficiency of the active transport (Km), was determined using an in vivo hemoreflectometer. Serum levels of tumor necrosis factor (TNF)-alpha and alanine aminotransferase were determined with ELISA and colorimetrically, respectively. RESULTS: The results indicate that at 2 hours after trauma hemorrhage and resuscitation, cardiac index and hepatocellular function were markedly depressed with concomitantly increased serum levels of TNF-alpha and alanine aminotransferase (p < 0.05). Administration of 2-mercaptopropionyl glycine, however, restored the depressed cardiac and hepatic function and markedly attenuated liver enzyme release and serum levels of TNF-alpha (p < 0.05). CONCLUSION: Our data suggest that ROS play a role in producing the depression in organ functions after severe hemorrhagic shock. Thus, adjuncts that attenuate the detrimental effects of ROS may be useful for improving the depressed cardiac and hepatocellular functions after trauma hemorrhage and resuscitation.     

Mechanism of the beneficial effects of ATP-MgCl2 following trauma-hemorrhage and resuscitation: downregulation of inflammatory cytokine (TNF, IL-6) release.

Although ATP-MgCl2 improves hepatocellular function in a nonheparinized model of trauma-hemorrhage and crystalloid resuscitation, it remains unknown whether the beneficial effects of this agent are due to downregulation of the release of the inflammatory cytokines, tumor necrosis factor (TNF), and interleukin-6 (IL-6) under those conditions. To study this, rats underwent a 5-cm laparotomy (i.e., trauma induced) and were bled to and maintained at a mean arterial pressure of 40 mm Hg until 40% of maximum bleedout volume was returned in the form of Ringer's lactate (RL). The animals were then resuscitated with four times the volume of shed blood with RL over 60 min. ATP-MgCl2 (50 mumoles/kg body weight each) or an equivalent volume of normal saline was infused intravenously for 95 min. This infusion was started during the last 15 min of RL resuscitation. Plasma levels of TNF and IL-6 were measured at 1.5 hr after the completion of resuscitation by cytokine-dependent cellular assays. Hepatic blood flow was determined by in vivo indocyanine green clearance (corrected by hepatic extraction ratio for indocyanine green), radioactive microspheres, and [3H]-galactose clearance techniques. The results indicate that the levels of circulating TNF and IL-6 increased significantly in the hemorrhaged-resuscitated animals. ATP-MgCl2 treatment, however, markedly decreased the synthesis and/or release of these cytokines to levels similar to the sham group. The markedly decreased hepatic blood flow (as determined by three different methods) and hepatic extraction ratio for indocyanine green were also restored by ATP-MgCl2 treatment.(ABSTRACT TRUNCATED AT 250 WORDS)     

Insight into the mechanism by which estradiol improves organ functions after trauma-hemorrhage

BACKGROUND: Recent studies have indicated that female rodents with high levels of estradiol (proestrus) have better organ functions after trauma-hemorrhage than females with low estradiol levels (estrus) or male animals. However, the precise role of estrogens in maintaining organ function after hemorrhage remains unknown. METHODS: Adult female Sprague-Dawley rats were ovariectomized 14 days before the experiment to decrease circulating levels of estradiol. Animals underwent laparotomy to induce tissue trauma and were then bled to and maintained at a mean arterial pressure of 40 mm Hg until 40% of the maximal bleed-out volume was returned in the form of Ringer's lactate. Resuscitation was carried out with 4 times the volume of maximal bleed-out with Ringer's lactate during a period of 1 hour. 17beta-Estradiol (E2, 1 mg/kg body weight intravenously) with or without a specific estrogen receptor antagonist ICI 182,780 (3 mg/kg body weight intraperitoneally) was given at the beginning of resuscitation. At 24 hours after hemorrhage and resuscitation, cardiovascular and hepatocellular functions (ie, the maximal velocity and overall efficiency of indocyanine green clearance) were determined. Plasma E2 was also assayed. The effects of ovariectomy and E2 administration on uterine weight were measured in additional groups of animals. RESULTS: The results indicate that cardiovascular and hepatocellular organ functions were significantly depressed after trauma-hemorrhage and were restored in animals receiving E2. However, simultaneous administration of its specific receptor antagonist abolished the salutary effects of E2 treatment despite high circulating levels of E2. Uterine weight decreased at 14 days after ovariectomy, which was partially restored with a single dose of E2. CONCLUSIONS: Administration of 17beta-estradiol should be considered a novel and safe adjunct for ameliorating hemorrhage-induced organ dysfunctions in ovariectomized and postmenopausal women because of their low estradiol levels.     

Effect of fluid resuscitation with and without endothelin A receptor blockade on hemoconcentration and organ function in experimental pancreatitis

BACKGROUND: Intravascular fluid loss contributes to pancreatitis-associated multiple organ dysfunction and is thus a major target for therapy in this life-threatening disease. AIM: To evaluate intravascular fluid loss and extravascular fluid sequestration together with cardiorespiratory and renal function in a well-established rat model of severe acute pancreatitis (AP) and to investigate the effect of fluid resuscitation with and without endothelin receptor A blockade on these parameters. METHOD: Induction of AP in rats by a standardized bile salt infusion into the pancreatic duct and intravenous cerulein hyperstimulation. Six hours after AP induction, animals were randomized into 4 groups to receive (1) no therapy; (2) 4 ml/kg/h Ringer's lactate (RL) i.v.; (3) 8 ml/kg/h RL i.v., or (4) 4 ml/kg/h RL plus an endothelin receptor antagonist. Target parameters measured before and after AP induction and during the 24-hour observation period included: mean arterial blood pressure, heart rate, hematocrit, arterial blood gases, urine production, ascites and pleural effusions. RESULTS: After 6 h, all animals presented with severe hemoconcentration (hematocrit >57%) and oliguria (<0.5 ml/6 h). Cardiorespiratory parameters were within the normal range. Up to 12 h after AP induction, animals without therapy had an increased hematocrit and oliguria and developed metabolic acidosis. Animals receiving fluid resuscitation had a significant drop in hematocrit and maintained compensated blood gas values. A significant increase in urine production was only observed in animals given 8 mg/kg/h RL. Between 12 and 24 h, urine production significantly increased with fluid resuscitation and respiratory parameters stabilized except for animals treated with 8 ml/kg/h RL which developed arterial hypoxia and hypercapnia. CONCLUSIONS: Intravascular fluid loss and extravascular fluid sequestration together with decreased urine production characterize the early phase of this model of severe AP. Massive fluid resuscitation necessary for increasing urine output may lead to respiratory distress. Reduction of intravascular fluid loss by endothelin receptor blockade is associated with improved renal and respiratory function.     

Cardiovascular effect of 7.5% sodium chloride-dextran infusion after thermal injury.

HYPOTHESIS: Clinical study can help determine the safety and cardiovascular and systemic effects of an early infusion of 7.5% sodium chloride in 6% dextran-70 (hypertonic saline-dextran-70 [HSD]) given as an adjuvant to a standard resuscitation with lactated Ringer (RL) solution following severe thermal injury. DESIGN: Prospective clinical study. SETTING: Intensive care unit of tertiary referral burn care center. PATIENTS: Eighteen patients with thermal injury over more than 35% of the total body surface area (TBSA) (range, 36%-71%) were studied. INTERVENTIONS: Eight patients (mean +/- SEM, 48.2% +/- 2% TBSA) received a 4-mL/kg HSD infusion approximately 3.5 hours (range, 1.5-5.0 hours) after thermal injury in addition to routine RL resuscitation. Ten patients (46.0% +/- 6% TBSA) received RL resuscitation alone. MAIN OUTCOME MEASURES: Pulmonary artery catheters were employed to monitor cardiac function, while hemodynamic, metabolic, and biochemical measurements were taken for 24 hours. RESULTS: Serum troponin I levels, while detectable in all patients, were significantly lower after HSD compared with RL alone (mean +/- SEM, 0.45 +/- 0.32 vs 1.35 +/- 0.35 microg/L at 8 hours, 0.88 +/- 0.55 vs 2.21 +/- 0.35 microg/L at 12 hours). While cardiac output increased proportionately between 4 and 24 hours in both groups (from 5.79 +/- 0.8 to 9.45 +/- 1.1 L/min [mean +/- SEM] for HSD vs from 5.4 +/- 0.4 to 9.46 +/- 1.22 L/min for RL), filling pressure (central venous pressure and pulmonary capillary wedge pressure) remained low for 12 hours after HSD infusion (P = .048). Total fluid requirements at 8 hours (2.76 +/- 0.7 mL/kg per each 1% TBSA burned [mean +/- SEM] for HSD vs 2.67 +/- 0.24 mL/kg per each 1% TBSA burned for RL) and 24 hours (6.11 +/- 4.4 vs 6.76 +/- 0.75 mL/kg per each 1% TBSA burned) were similar. Blood pressure remained unchanged, and serum sodium levels did not exceed 150 +/- 2 mmol/L (mean +/- SD) in either group. CONCLUSIONS: The absence of deleterious hemodynamic or metabolic side effects following HSD infusion in patients with major thermal injury confirms the safety of this resuscitation strategy. Postburn cardiac dysfunction was demonstrated in all burn patients through the use of cardiospecific serum markers and pulmonary artery catheter monitoring. Early administration of HSD after a severe thermal injury may reduce burn-related cardiac dysfunction, but it had no effect on the volume of resuscitation or serum biochemistry values.     

Administration of progesterone after trauma and hemorrhagic shock prevents hepatocellular injury

HYPOTHESIS: Administration of a single dose of progesterone following trauma and hemorrhage in progesterone-deficient rats would ameliorate the inflammatory response and hepatocellular damage. SETTING: A university laboratory. INTERVENTIONS: Ovariectomized female Sprague-Dawley rats (250-350 g; Charles River Laboratories, Wilmington, Mass) underwent a 5-cm midline laparotomy (ie, induction of soft tissue trauma), were bled to a mean arterial blood pressure of 35 mm Hg for about 90 minutes, and then were resuscitated using Ringer lactate solution. Progesterone (25 mg/kg of body weight) or vehicle was administered subcutaneously at the end of resuscitation. In additional animals, Kupffer cells were isolated following trauma, hemorrhage, and resuscitation and treated in vitro with progesterone, lipopolysaccharide, or both. MAIN OUTCOME MEASURES: Six hours following resuscitation, plasma tumor necrosis factor alpha (TNF-alpha) and interleukin 6 (IL-6) levels and liver myeloperoxidase activity were determined. Hepatocellular function (maximum velocity of indocyanine green clearance [Vmax] and the efficiency of the active transport or Michaelis-Menten constant [Km]) and plasma levels of transaminases were measured 20 hours after resuscitation. Kupffer cell IL-6 and TNF-alpha production were assessed. RESULTS: Plasma levels of TNF-alpha, IL-6, aspartate aminotransferase, and alanine aminotransferase, as well as hepatic myeloperoxidase activity were increased, whereas indocyanine green clearance was depressed in vehicle-treated rats following trauma-hemorrhage. Animals treated with progesterone showed significantly reduced levels of the TNF-alpha, IL-6, and transaminases as well as reduced myeloperoxidase activity in the liver. Progesterone-treated animals showed increased Vmax and Kmax values for indocyanine green. In vitro treatment of Kupffer cells with progesterone decreased TNF-alpha production but did not affect the production of IL-6. CONCLUSION: Progesterone administration following trauma-hemorrhage ameliorates the proinflammatory response and, subsequently, the hepatocellular injury via direct action on immunocompetent cells.     

HSPTX protects against hemorrhagic shock resuscitation-induced tissue injury: an attractive alternative to Ringer's lactate

BACKGROUND: Conventional fluid resuscitation with Ringer's lactated (RL) activates neutrophils and causes end-organ damage. We have previously shown that HSPTX, a combination of small volume hypertonic saline (HS) and pentoxifylline (PTX), a phosphodiesterase-inhibitor, downregulates in vitro neutrophil activation and proinflammatory mediator synthesis. Herein, we hypothesized that HSPTX decreases end-organ injury when compared with RL in an animal model of hemorrhagic shock. METHODS: Sprague-Dawley rats were bled to a mean arterial pressure of 35 mm Hg for 1 hour. Animals were divided into 3 groups: sham (no shock, no resuscitation, n = 7), RL (32 mL/kg, n = 7), and HSPTX (7.5% NaCl 4 mL/kg + PTX 25 mg/kg; n = 7). Shed blood was infused after fluid resuscitation. Blood pressure was monitored until the end of resuscitation. Animals were sacrificed at 24 hour after resuscitation. Bronchoalveolar lavage fluid (BALF) was obtained for white cell count (total and differential) and TNF-alpha and IL-1beta levels were measured by ELISA. Lung and intestinal injury at 24 hour were evaluated by histopathology. Organ damage was graded by a pathologist and a score was created (0 = no injury; 3 = severe). Lung neutrophil infiltration was evaluated by MPO immune staining. RESULTS: There were no differences in mean arterial pressure between groups. At 24 hours, BALF leukocyte count was decreased by 30% in HSPTX animals (p < 0.01). TNF-alpha and IL-1beta levels were markedly decreased in HSPTX-resuscitated animals compared with their RL counterparts (p < 0.01). HSPTX-resuscitated animals (lung injury score = 1.0 +/- 0.4) had markedly decreased acute lung injury compared with RL-treated animals (2.5 +/- 0.3) (p < 0.01). RL resuscitation led to a two-fold increase in lung neutrophil infiltration whereas in HSPTX-treated animals, the number of MPO + cells was similar to sham animals (p < 0.001). Intestinal injury was markedly attenuated by HSPTX (1.1 +/- 0.3) compared with RL animals (2.6 +/- 0.4) (p < 0.001). CONCLUSIONS: HSPTX, a small volume resuscitation strategy with marked immunomodulatory potential led to a marked decrease in end-organ damage. HSPTX is an attractive alternative to RL in hemorrhagic shock resuscitation.     

Dehydroepiandrosterone restores hepatocellular function and prevents liver damage in estrogen-deficient females following trauma and hemorrhage

INTRODUCTION: Recent studies have shown that administration of the sex steroid dehydroepiandrosterone (DHEA) in males following trauma-hemorrhagic shock has salutary effects on the depressed cardiovascular and immunological functions under those conditions. Since the effects of sex steroids are gender specific, we examined whether administration of DHEA has any beneficial effects on hepatocellular function in female rats with low estrogen levels following trauma-hemorrhage. METHODS: Ovariectomy was performed in female Sprague-Dawley rats 14 days prior to the experiments. The animals then underwent a 5-cm midline laparotomy and were subjected to hemorrhagic shock (40 mm Hg for 90 min). This was followed by fluid resuscitation (Ringer's lactate over 60 min) and administration of DHEA (30 mg/kg BW) or vehicle subcutaneously at the end of resuscitation. At 24 h after resuscitation hepatocellular function, i.e., clearance of indocyanine green (ICG), and hepatocyte damage (serum alanine aminotransferase) were measured. Plasma levels of DHEA and 17beta-estradiol were also assayed. RESULTS: Vehicle-treated rats had significantly reduced hepatocellular function, increased ALT activity, and decreased levels of 17beta-estradiol following trauma-hemorrhage compared to sham-operated animals (P < 0.05, ANOVA and Student-Newman-Keuls test). In animals receiving DHEA following trauma-hemorrhage, hepatocellular function and ALT activity were similar to those of shams. However, administration of DHEA did not influence the plasma levels of 17beta-estradiol. CONCLUSIONS: Administration of DHEA following trauma-hemorrhage restored hepatocellular function and reduced hepatic damage that was observed in ovariectomized female rats under such conditions. This salutary effect of DHEA did not appear to be due to elevated levels of plasma 17beta-estradiol. We therefore propose that DHEA should be considered a novel, safe, and useful adjunct in the treatment of trauma-induced hepatocellular dysfunction in ovariectomized and postmenopausal females.     

The PI3K/Akt pathway mediates the nongenomic cardioprotective effects of estrogen following trauma-hemorrhage

OBJECTIVE: To determine whether the nongenomic actions of E2 have any beneficial effect on cardiac function following trauma-hemorrhage and whether those effects are mediated via the PI3K/Akt pathway. SUMMARY BACKGROUND DATA: Since studies suggest that both genomic and nongenomic pathways are involved in mediating the salutary effects of 17beta-estradiol (estradiol) following trauma-hemorrhage, we examined if the nongenomic effects of estradiol on cardiac function after trauma-hemorrhage involve the PI3K/Akt pathway. METHODS: Male Sprague-Dawley rats ( approximately 300 g) underwent trauma-hemorrhage (mean blood pressure, 40 mm Hg for 90 min, then resuscitation). Estradiol conjugated to bovine serum albumin (BSA) (estradiol-BSA; 1 mg/kg estradiol) with or without estrogen receptor antagonist (ICI 182,780), PI3K inhibitor (Wortmannin), or vehicle was injected intravenously during resuscitation. At 2 hours after trauma-hemorrhage or sham operation, cardiac output, stroke volume, heart rate, mean arterial pressure, and +/-dP/dt were measured. Cardiomyocyte PI3K, p-Akt, Akt protein expressions and apoptosis were also determined. One-way ANOVA and Tukey's test were used for statistical analysis. RESULTS: Cardiac output, stroke volume, and +/-dP/dt decreased significantly after trauma-hemorrhage. Administration of estradiol or estradiol-BSA significantly improved these parameters of cardiac function. Although trauma-hemorrhage decreased cardiomyocyte PI3K protein expression and Akt phosphorylation (p-Akt), estradiol or estradiol-BSA treatment following trauma-hemorrhage prevented such decreases in cardiomyocyte PI3K protein expressions and p-Akt. The increase in cardiomyocyte apoptosis was also prevented in rats receiving estradiol-BSA. Co-administration of ICI 182,780 or Wortmannin abolished beneficial effects of estradiol-BSA on cardiac functions following trauma-hemorrhage. CONCLUSION: The PI3K/Akt pathway plays a critical role in mediating the nongenomic salutary effects of estradiol on cardiac function following trauma-hemorrhage.     

The effect of hypertonic saline resuscitation on responses to severe hemorrhagic shock by the skeletal muscle, intestinal, and renal microcirculation systems: seeing is believing

BACKGROUND: Decompensated hemorrhagic shock is often refractory to resuscitation, and we show here that it is associated with loss of vascular tone in skeletal muscle precapillary arterioles. We tested the hypothesis that microvascular derangements in the skeletal muscle, intestinal, and renal microcirculation systems would be reversed by initial hypertonic saline-dextran infusion. METHODS: Male Sprague-Dawley rats underwent precollicular brain stem transection without anesthesia for study. Parameters measured by in vivo videomicroscopy included cardiac output, mean arterial pressure, and microvascular responses in the skeletal muscle, ileum, and renal (i.e., the hydronephrotic kidney) microcirculation systems. Hemorrhaged was induced to a mean arterial pressure of 50 mmHg until decompensation occurred. The rats were then initially resuscitated with (1) 4 mL/kg 7.5% NaCl in 6% dextran 70, (2) 33 mL/kg .9% NaCl in 6% dextran 70, or (3) 33 mL/kg .9% NaCl. Twenty minutes later they received shed blood plus 33 mL/kg .9% NaCl to maintain mean arterial pressure at baseline levels. RESULTS: Decompensated hemorrhagic shock decreased cardiac output to between 24% and 35% of baseline values and profoundly decreased microvascular blood flow to between 10% and 19% of baseline. At the completion of resuscitation cardiac output increased to greater than baseline in all groups. Microvascular blood flow increased toward baseline transiently but then progressively deteriorated to between 36% and 69% of baseline in the 3 tissues. There was no significant difference between the three resuscitative fluids. CONCLUSIONS: Despite return of cardiac output to greater than baseline levels, muscle, intestinal, and renal microvascular blood flows remained significantly depressed. Hypertonic saline and/or dextran did not improve these deficits.     

Pentoxifylline but not saralasin restores hepatic blood flow after resuscitation from hemorrhagic shock

After determining that hepatic blood flow remains impaired after resuscitation from hemorrhagic shock, we used the angiotensin II receptor antagonist saralasin and pentoxifylline to investigate their respective effects on hepatic blood flow responses after resuscitation from hemorrhagic shock. Rats were bled to 50% of baseline blood pressure for 60 min and resuscitated with shed blood and an equal volume of lactated Ringer's solution. Saralasin [10 micrograms/kg per min (n = 6)], pentoxifylline [25 mg/kg bolus and 12.5 mg/kg per hr (n = 7)], or saline (n = 11) were started with the onset of resuscitation. Total hepatic blood flow measured by ultrasonic transit time flow meter, effective nutrient hepatic blood flow measured by galactose clearance, mean arterial pressure, and cardiac output were recorded at 15-min intervals for 2 hr after resuscitation. Hemorrhage decreased cardiac output 57% below baseline and decreased total hepatic blood flow 64% below baseline. Resuscitation restored cardiac output to baseline levels in all three groups. Despite restoration of cardiac output, total hepatic and effective hepatic blood flow remained significantly below baseline in the saline control and saralasin groups but was restored to baseline levels in the pentoxifylline group. These data indicate that angiotensin II does not contribute significantly to the hepatic blood flow impairment after resuscitation from hemorrhagic shock. Improvement in flow with pentoxifylline implies that hemorrhage and resuscitation impair hepatic microvascular hemorrheology and that addition of pentoxifylline to standard resuscitation corrects the impairment.     

A role of PPAR-gamma in androstenediol-mediated salutary effects on cardiac function following trauma-hemorrhage

OBJECTIVE: To examine the mechanism by which androstenediol improves cardiac function following trauma-hemorrhage (T-H). SUMMARY BACKGROUND DATA: Androstenediol administration improves cardiovascular function and attenuates proinflammatory cytokine production following T-H. Activation of the peroxisome proliferator-activated receptor-gamma (PPAR-gamma) has been shown to be protective following ischemic conditions. We hypothesized that PPAR-gamma activation plays a role in the androstenediol-mediated salutary effects on cardiac function following T-H. METHODS: Male rats underwent laparotomy and hemorrhagic shock (40 mm Hg for 90 minutes), followed by resuscitation with 4 times the shed blood volume in the form of Ringer's lactate. Androstenediol (1 mg/kg body weight, i.v.) was administrated at the end of resuscitation. In a separate group of animals, a PPAR-gamma antagonist (GW9662) was administered simultaneously with androstenediol and animals were killed at 5 hours thereafter. RESULTS: A decrease in cardiac function and an increase in IL-6 and iNOS gene expression were observed following T-H. Androstenediol treatment normalized cardiac function, increased PPAR-gamma DNA binding activity, attenuated IL-6 and iNOS gene expressions, and reduced plasma IL-6. Plasma 15-deoxy-Delta12, 14-prostaglandin J2 (PGJ2, an endogenous PPAR-gamma agonist) levels were also increased in androstenediol-treated T-H rats, but these levels were lower than those observed in shams. Coadministration of PPAR-gamma antagonist along with androstenediol, however, prevented the androstenediol-mediated reduction in cardiac iNOS and IL-6 expressions and abolished the improvements in cardiac function. CONCLUSION: The androstenediol-mediated salutary effects on cardiac function following T-H appear to be mediated at least in part via PPAR-gamma activation, which down-regulates IL-6 and iNOS gene expression in the heart.     

Pulmonary microvascular changes following fluid resuscitation in an ovine model of endotoxemia

Fluid resuscitation is complicated in hypotensive septic patients by their susceptibility to pulmonary edema. This problem was evaluated in the ovine model of endotoxemia with a chronic lung lymph fistula. Escherichia coli endotoxin (lipopolysaccharide, 1.5 micrograms/kg) was given intravenously over 30 minutes. Group M (n = 9) continued to receive baseline fluids (2 mL/kg/h), while group R (n = 6) received 7 mL/kg/h of Ringer's lactate. After an initial drop in cardiac index, animals in both groups developed a hyperdynamic state. The fall in mean arterial pressure seen in group M was absent from group R. The higher fluid volume resulted in a rise in left atrial pressure and pulmonary microvascular pressure. The lung lymph flow and permeability index were elevated in both groups but were higher in group R. The calculated filtration coefficient showed a threefold increase in both groups. Augmented fluid resuscitation during endotoxemia resulted in an elevated interstitial fluid flux and permeability index secondary to an increase in pulmonary microvascular pressure and greater surface area of the injured microvascular beds being perfused.     

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.     

Hepatocellular dysfunction occurs early after hemorrhage and persists despite fluid resuscitation

The liver is a major organ involved in multiple organ failure (MOF) following hemorrhage and trauma. However, it is not known if active hepatocellular membrane transport, measured by in vivo indocyanine green (ICG) clearance, is depressed after hemorrhage and if it persists after resuscitation. To study this, rats were bled to and maintained at a mean BP of 40 mm Hg until 40% of maximum bleedout (MB) volume was returned in the form of Ringer's lactate (RL). The rats were then resuscitated with 2X or 3X the volume of MB with RL and hepatocellular function was determined at various intervals. ICG, two to four doses (0.167-1.667 mg/kg BW), was given intravenously and [ICG] was continuously recorded without the need of blood sampling, using an in vivo hemoreflectometer with computer-assisted data acquisition. Initial velocity of clearance (V0) was calculated from [ICG] vs time (t) according to [ICG] = e (a + bt + ct 2), where eab is V0. Maximal velocity of clearance (Vmax) and Km, a kinetic constant representing the efficiency of the active transport process, were determined from the Lineweaver-Burk plot. The results indicate that Vmax decreased by 66% at MB and remained depressed despite fluid resuscitation. Km, decreased by 58% at MB, returned to prehemorrhage level after 3X RL but was not maintained and it decreased by 60% at 4 hr after resuscitation. This in vivo study demonstrates that active hepatocellular function is significantly depressed early after hemorrhage and persists despite resuscitation with RL and may form the basis of the MOF observed after severe and prolonged hemorrhage.     

A comparison of hypertonic to isotonic fluid in the resuscitation of brain injury and hemorrhagic shock

We studied the early and late effects of hypertonic resuscitation (HR) on the injured brain using a porcine model of hemorrhagic shock and focal cryogenic brain injury. After shock, swine were randomly assigned to receive a bolus (4 cc/kg) of either Ringers lactate (RL) or 7.5% hypertonic saline in 6% Dextran 70, followed by either RL or hypertonic sodium lactate to restore mean arterial pressure to baseline. All animals were studied for 24 hr after the start of resuscitation. Bolus HR improved cerebral blood flow (CBF) with a lower intracranial pressure (ICP) than RL. Continued hypertonic resuscitation prolonged the period of improved CBF and low ICP. At 24 hr CBF had deteriorated in the region of injury in all study groups and in the uninjured hemisphere in swine receiving RL. These data suggest that rapid resuscitation without increasing ICP for up to 6 hr as seen with hypertonic fluid could conceivably allow adequate time for surgical evacuation of mass lesions and effectively prevent secondary brain injury. This work underscores the importance of prolonged periods of study when evaluating brain resuscitation from traumatic shock.     

The effect of resuscitation on inhalation injury

Eighteen chronically instrumented sheep with lung-lymph catheters were studied. Inhalation injury was produced in 12 animals under halothane anesthesia and then studied for 24 hours. Six of the animals received 70 ml/m2/hr body surface area of 5% dextrose in Ringer's lactated solution (normal maintenance fluid requirements for sheep), and six received 140 ml/m2/hr (twice normal maintenance fluid requirements for sheep). Six additional animals were anesthetized, insufflated with air instead of smoke, and received 70 ml/m2/hr of resuscitation fluid (sham group). Twelve hours after injury, the recorded variables from the animals that were smoked and had received a high fluid resuscitation were not different from the sham group whereas the group with low-volume fluid resuscitation had a much higher lung-lymph flow and lymph-to-plasma protein concentration ratio and a lower cardiac output. The lung microvascular permeability changes seen with smoke inhalation are made worse by inadequate fluid resuscitation.