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.     

Chronic resuscitation after trauma-hemorrhage and acute fluid replacement improves hepatocellular function and cardiac output.

OBJECTIVE: To determine whether prolonged (chronic) resuscitation has any beneficial effects on cardiac output and hepatocellular function after trauma-hemorrhage and acute fluid replacement. BACKGROUND DATA: Acute fluid resuscitation after trauma-hemorrhage restores but does not maintain the depressed hepatocellular function and cardiac output. METHODS: Male Sprague-Dawley rats underwent a 5-cm laparotomy (i.e., trauma was induced) and were bled to and maintained at a mean arterial pressure of 40 mmHg until 40% of maximal bleed-out volume was returned in the form of Ringer's lactate (RL). The animals were acutely resuscitated with RL using 4 times the volume of maximum bleed-out over 60 minutes, followed by chronic resuscitation of 0, 5, or 10 mL/kg/hr RL for 20 hours. Hepatocellular function was determined by an in vivo indocyanine green clearance technique. Hepatic microvascular blood flow was assessed by laser Doppler flowmetry. Plasma levels of interleukin-6 (IL-6) were determined by bioassay. RESULTS: Chronic resuscitation with 5 mL/kg/hr RL, but not with 0 or 10 mL/kg/hr RL, restored cardiac output, hepatocellular function, and hepatic microvascular blood flow at 20 hours after hemorrhage. The regimen above also reduced plasma IL-6 levels. CONCLUSION: Because chronic resuscitation with 5 mL/kg/hr RL after trauma-hemorrhage and acute fluid replacement restored hepatocellular function and hepatic microvascular blood flow and decreased plasma levels of IL-6, we propose that chronic fluid resuscitation in addition to acute fluid replacement should be routinely used in experimental studies of trauma-hemorrhage.     

Testosterone: the crucial hormone responsible for depressing myocardial function in males after trauma-hemorrhage.

OBJECTIVE: To determine whether testosterone depletion in males before trauma-hemorrhage has any salutary effects on cardiac performance after hemorrhage and resuscitation. SUMMARY BACKGROUND DATA: Studies indicate that castration of male mice before trauma-hemorrhage prevents the immunodepression seen after hemorrhage and resuscitation. However, the effect of precastration on cardiac performance under such conditions remains unknown. METHODS: Male rats were castrated or sham-castrated 14 days before the experiment. After laparotomy (i.e., induction of trauma), the rats were bled to and maintained at a mean arterial pressure of 40 mm Hg until 40% of the maximal shed volume was returned in the form of Ringer's lactate solution. The animals were then resuscitated with four times the shed blood volume with Ringer's lactate solution over 60 minutes. Heart performance was measured using a left ventricular catheter connected to an in vivo heart performance analyzer. Indices of left ventricular performance (i.e., maximal rate of the pressure increase [+dP/dt(max)] and decrease [-dP/dt(max)) were measured up to 4 hours after trauma, hemorrhagic shock, and resuscitation. RESULTS: In sham-castrated animals, trauma-hemorrhage and resuscitation decreased the in vivo heart performance as evidenced by the reduced values of +dP/dt(max) and -dP/dt(max). Precastrated animals, however, showed significantly higher values of +dP/dt(max) and -dP/dt(max) than sham-castrated animals after trauma-hemorrhage and resuscitation. CONCLUSIONS: Testosterone antagonism in males might be an effective approach for maintaining myocardial function after adverse circulatory conditions. Although testosterone depletion in male trauma victims is neither practical nor advocated, testosterone receptor blockade after trauma may represent a novel and useful adjunct for maintaining normal myocardial performance under those conditions.     

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.     

Estradiol administration improves splanchnic perfusion following trauma-hemorrhage and sepsis.

HYPOTHESIS: The female sex steroid 17beta-estradiol improves immune functions following trauma-hemorrhage in rodent models. Therefore, we hypothesized that 17beta-estradiol administration following trauma-hemorrhage would also improve cardiac output, splanchnic perfusion, and oxygen utilization, even after the induction of subsequent sepsis. SETTING: A university laboratory. INTERVENTION: Male rats underwent midline laparotomy (ie, soft tissue injury). They were bled to a mean arterial pressure of 35 to 40 mm Hg for 90 minutes and resuscitated over 60 minutes with lactated Ringer solution. At the beginning of resuscitation, 17beta-estradiol (l mg/kg) or a vehicle was administered. At 20 hours after resuscitation, polymicrobial sepsis was induced by cecal ligation and puncture (CLP). MAIN OUTCOME MEASURES: At 5 hours after CLP, cardiac performance (via a left ventricular catheter), cardiac output, and organ blood flow were determined using strontium 85 microspheres. Blood samples were collected from the femoral artery and jugular, portal, and renal veins to determine systemic and regional oxygen delivery and consumption. Moreover, circulating levels of 17beta-estradiol, its adrenal precursor dehydroepiandrosterone (DHEA), and corticosterone were assessed by enzyme-linked immunosorbent assay. RESULTS: Hemorrhage and subsequent sepsis significantly depressed cardiac performance, cardiac output, organ perfusion, and oxygen consumption. Estrogen did not restore cardiac output or systemic oxygen consumption; nonetheless, it restored the depressed intestinal perfusion. Rats treated with estrogen had significantly elevated levels of plasma 17beta-estradiol, but the levels of DHEA or corticosterone were not affected. CONCLUSIONS: The increase in gut perfusion could represent a potential mechanism for the salutary effects of 17beta-estradiol following trauma-hemorrhage. Because 17beta-estradiol improves systemic and intestinal perfusion after trauma-hemorrhage and induction of subsequent sepsis, this agent appears to be a promising adjunct for the treatment of trauma victims.     

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.     

Should normothermia be restored and maintained during resuscitation after trauma and hemorrhage?

BACKGROUND: Although hypothermia often occurs after trauma and has protective effects during ischemia and organ preservation, it remains unknown whether maintenance of hypothermia or restoring the body temperature to normothermia during resuscitation has any deleterious or beneficial effects on heart performance and organ blood flow after trauma-hemorrhage. METHODS: Male rats underwent laparotomy (i.e., induced trauma) and were exsanguinated to and maintained at a mean arterial pressure of 40 mm Hg until 40% of the maximum shed volume was returned in the form of Ringer's lactate. Body temperature decreased from approximately 36.5 degrees C to below 32 degrees C. The animals were then resuscitated with four times the volume of maximal bleedout with Ringer's lactate. In one group, body temperature was rewarmed to 37 degrees C during resuscitation. In another group, 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 as well as during resuscitation. Left ventricle performance parameters such as maximal rate of left ventricular pressure increase and decrease (+/-dP/dt(max)) were measured up to 4 hours. Cardiac output and regional blood flow were determined by radioactive microspheres at 4 hours after the completion of resuscitation. RESULTS: The maintenance of normothermia during hemor. rhage or prolonged hypothermia after resuscitation depressed the left ventricular performance parameters, cardiac output, and regional blood flow in various organs. Rewarming the body to normothermia during resuscitation, however, significantly increased heart performance, cardiac output (from hypothermia 16.2 +/- 1.4 to 22.3 +/- 1.4 mL/min per 100 g body weight,p < 0.05) and total hepatic blood flow (from hypothermia 117.5 +/- 5.3 to 166.0 +/- 9.3 mL/min per 100 g tissue, p < .05). CONCLUSION: Our data indicate that restoration of normothermia during resuscitation improves cardiac function and hepatic blood flow compared with hypothermia.     

Mechanism of the beneficial effects of pentoxifylline on hepatocellular function after trauma hemorrhage and resuscitation.

BACKGROUND. The purpose of this study was to determine whether pentoxifylline administration restores the depressed hepatocellular function after trauma hemorrhage and crystalloid resuscitation and, if so, whether this is the result of the down-regulation of inflammatory cytokines, tumor necrosis factor (TNF) and interleukin-6 (IL-6). METHODS. After laparotomy rats were bled to and maintained at a mean arterial pressure of 40 mm Hg until 40% of maximum shed blood volume was returned in the form of Ringer's lactate. They were then resuscitated with Ringer's lactate to four times the shed blood volume. Pentoxifylline (50 mg/kg body weight) or saline solution was infused intravenously for 95 minutes during and after resuscitation. One and a half hours and 4 hours after resuscitation, hepatocellular function (maximal velocity [Vmax] and the efficiency of the active transport [Km] of indocyanine green clearance) and plasma. TNF and IL-6 levels were determined with in vivo hemoreflectometer and cellular assays, respectively. RESULTS. Circulating TNF and IL-6 levels increased significantly after hemorrhage and resuscitation. Pentoxifylline treatment, however, markedly decreased the levels of these cytokines, and the values were similar to those of sham rats. The decreased Vmax and Km values were also restored by pentoxifylline treatment. Moreover, there was a significant correlation between Vmax and TNF or IL-6 levels. CONCLUSIONS. The down-regulation of inflammatory cytokines by pentoxifylline may be the mechanism by which this agent restores the depressed hepatocellular function after trauma hemorrhage and resuscitation.     

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.     

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.     

Estradiol's effect on portal response to endothelin-1 after trauma-hemorrhage

BACKGROUND: The fine balance between vasoconstrictors and vasodilators maintains portal circulation. Studies have shown that portal response to endothelin-1 (ET-1), a potent vasoconstrictor, is enhanced following hemorrhagic-shock, which subsequently leads to the impaired hepatic circulation and hepatic damage. Although protective effects of 17beta-estradiol (E(2)) against hepatic damage following trauma-hemorrhage have been observed, it remains unknown whether E(2) directly improves hepatic circulation. We hypothesized that the salutary effects of E(2) are mediated, at least in part, by the attenuation of portal response to ET-1 following trauma-hemorrhage. MATERIALS AND METHODS: Male adult Sprague-Dawley rats were randomly assigned to sham operation or trauma-hemorrhage with or without in vivo E(2) treatment. Trauma-hemorrhage included midline laparotomy and approximately 90 min of hemorrhagic shock (35 mmHg), then resuscitation with four times the shed blood volume with Ringer's lactate solution over 60 min. For the E(2) treatment group, 1 mg/kg of E(2) was added to the Ringer's lactate solution. At 5 h after the end of resuscitation, the liver was isolated and perfused in vitro to measure portal pressure responses to exogenous ET-1 (60 pmol in 150 ml perfusate, bolus) with or without E(2) (1,500 pg/ml). RESULTS: Peak portal pressure after the administration of ET-1 was significantly higher in vehicle-treated trauma-hemorrhage group compared with the sham group. This effect was significantly attenuated in the E(2) treatment group. Furthermore, E(2) treatment restored bile production and prevented hepatic damage following trauma-hemorrhage. CONCLUSIONS: The beneficial effects of estradiol observed following trauma-hemorrhage, at least partly, are caused by the attenuation of portal pressure response to increased ET-1.     

Female Sex Hormones Regulate Macrophage Function After Trauma-Hemorrhage and Prevent Increased Death Rate From Subsequent Sepsis

OBJECTIVE: To determine whether reduction of circulating female sex hormones by ovariectomy causes suppression of macrophage (Mphi) function after trauma-hemorrhage and increases susceptibility to subsequent sepsis. SUMMARY BACKGROUND DATA: Studies indicate that immune functions are markedly depressed in males but not in proestrus females after trauma-hemorrhage. Although male sex steroids are immunosuppressive, it remains unknown whether female sex hormones are immunoprotective after trauma-hemorrhage. METHODS: Circulating female sex hormones were reduced by ovariectomy of 8-week-old female CBA/J mice. Two weeks afterward, ovariectomy and proestrus sham-ovariectomy mice were subjected to laparotomy (i.e., soft tissue trauma) and hemorrhagic shock (35 +/- 5 mm Hg for 90 minutes, then resuscitated) or sham operation. Two hours afterward, splenic and peritoneal Mphi and Kupffer cells were isolated and cytokine production was assessed. In a second series of experiments, animals were subjected to sepsis by cecal ligation and puncture at 24 hours after trauma-hemorrhage or sham operation, and survival was assessed. RESULTS: Release of interleukin-1 and interleukin-6 by splenic and peritoneal Mphi from proestrus mice was maintained after trauma-hemorrhage, whereas release of interleukin-1 and interleukin-6 by Mphi from ovariectomized mice was depressed by approximately 50%. In contrast, trauma-hemorrhage resulted in a fourfold increase of Kupffer cell release of tumor necrosis factor-alpha in ovariectomized females and a fivefold increase in plasma concentrations of tumor necrosis factor-alpha. Release of tumor necrosis factor-alpha and plasma concentrations were unchanged in proestrus mice under such conditions. When proestrus and ovariectomized animals were subjected to sepsis by cecal ligation and puncture at 24 hours after trauma-hemorrhage or sham operation, ovariectomized mice had a significantly higher death rate than proestrus mice. CONCLUSIONS: These findings suggest that female sex hormones play a critical role in maintaining immune responses after trauma-hemorrhage by suppressing the elaboration of tumor necrosis factor-alpha and prevent the increased lethality from subsequent sepsis. Thus, female sex hormones may be a useful adjunct in preventing trauma-induced immunodepression and increased susceptibility to subsequent sepsis.     

Adequate crystalloid resuscitation restores but fails to maintain the active hepatocellular function following hemorrhagic shock

Studies have shown that active hepatocellular function is depressed early after trauma-hemorrhage and persists despite resuscitation with two or three times (x) the volume of maximum bleedout (MB) with lactated Ringer's solution (LR). However, it is not known if a larger volume of fluid resuscitation corrects this dysfunction. To study this, rats were bled to and maintained at a mean arterial pressure of 40 mm Hg until 40% of the MB volume was returned in the form of LR, and then resuscitated with 4x or 5x the volume of MB with LR. Three doses of indocyanine green (ICG) were given intravenously and [ICG] measured in vivo using an in-vivo hemoreflectometer. The initial velocity of the clearance of ICG was calculated. Maximal velocity of the clearance (Vmax: the number of functional ICG receptors) and kinetic constant (Km: the efficiency of the active transport) were determined from the Lineweaver-Burk plot. Vmax decreased during hemorrhage, was restored to control levels at 0-4 hours after resuscitation, but decreased at 4-8 hours after resuscitation despite restoration of cardiac output following resuscitation with 5x LR. This could be the result of increased TNF release. The Km also decreased during hemorrhage, but increased at 0-1.5 hours and remained at control levels even 4-8 hours after resuscitation. Thus the failure of Vmax to remain at control levels following adequate fluid resuscitation may form the basis of cellular dysfunction and multiple organ failure after severe hemorrhagic shock.     

Mild hypothermia increases survival from severe pressure-controlled hemorrhagic shock in rats

BACKGROUND: In previous studies, mild hypothermia (34 degrees C) during uncontrolled hemorrhagic shock (HS) increased survival. Hypothermia also increased mean arterial pressure (MAP), which may have contributed to its beneficial effect. We hypothesized that hypothermia would improve survival in a pressure-controlled HS model and that prolonged hypothermia would further improve survival. METHODS: Thirty rats were prepared under light nitrous oxide/halothane anesthesia with spontaneous breathing. The rats underwent HS with an initial blood withdrawal of 2 mL/100 g over 10 minutes and pressure-controlled HS at a MAP of 40 mm Hg over 90 minutes (without anticoagulation), followed by return of shed blood and additional lactated Ringer's solution to achieve normotension. Hemodynamic monitoring and anesthesia were continued to 1 hour, temperature control to 12 hours, and observation without anesthesia to 72 hours. After HS of 15 minutes, 10 rats each were randomized to group 1, with normothermia (38 degrees C) throughout; group 2, with brief mild hypothermia (34 degrees C during HS 15-90 minutes plus 30 minutes after reperfusion); and group 3, with prolonged mild hypothermia (same as group 2, then 35 degrees C [possible without shivering] from 30 minutes after reperfusion to 12 hours). RESULTS: MAP during HS and initial resuscitation was the same in all three groups, but was higher in the hypothermia groups 2 and 3, compared with the normothermia group 1, at 45 and 60 minutes after reperfusion. Group 1 required less blood withdrawal to maintain MAP 40 mm Hg during HS and more lactated Ringer's solution for resuscitation. At end of HS, lactate levels were higher in group 1 than in groups 2 and 3 (p < 0.02). Temperatures were according to protocol. Survival to 72 hours was achieved in group 1 by 3 of 10 rats, in group 2 by 7 of 10 rats (p = 0.18 vs. group 1), and in group 3 by 9 of 10 rats (p = 0.02 vs. group 1, p = 0.58 vs. group 2). Survival time was longer in group 2 (p = 0.09) and group 3 (p = 0.007) compared with group 1. CONCLUSION: Brief hypothermia had physiologic benefit and a trend toward improved survival. Prolonged mild hypothermia significantly increased survival after severe HS even with controlled MAP. Extending the duration of hypothermia beyond the acute phases of shock and resuscitation may be needed to ensure improved outcome after prolonged HS.     

Hepatocellular dysfunction persists during early sepsis despite increased volume of crystalloid resuscitation.

Although hepatocellular dysfunction occurs early in sepsis despite fluid resuscitation, it is unknown if an increased volume of resuscitation protects hepatocellular function. To study this, rats were subjected to sepsis by cecal ligation and puncture (CLP). These and sham-treated rats then received either 3 or 6 mL/100 g BW normal saline subcutaneously. Studies were performed at 5 hours (i.e., early sepsis) or 20 hours (late sepsis) after CLP. Hepatic blood flow was determined by radioactive microspheres, 3H-galactose clearance technique, and laser Doppler flowmetry in both groups. Active hepatocellular function (i.e., Vmax and Km) was assessed by an in vivo indocyanine green clearance technique. The results indicate that: (1) hepatic blood flow increased markedly in early sepsis; (2) Vmax and Km decreased significantly at 5 hours and 20 hours after CLP; and (3) the increased volume of fluid resuscitation did not improve the depressed active hepatocellular function 5 hours following CLP. Cardiac output and hepatic microcirculation, however, were significantly increased in early sepsis. These results confirm the notion that the depression in hepatocellular function in early sepsis is not the result of any reduction of hepatic perfusion. The dissociation of increased hepatic blood flow from depressed hepatocellular function remains despite the larger volume of resuscitation. The hepatocellular dysfunction that occurs even in early sepsis cannot be corrected simply by increasing the volume of crystalloid resuscitation.     

After spontaneous hypothermia during hemorrhagic shock,continuing mild hypothermia (34 degrees C) improves early but not late survival in rats

BACKGROUND: Spontaneous hypothermia is common in victims of severe trauma. Laboratory studies have shown benefit of induced (therapeutic) mild hypothermia (34 degrees C) during hemorrhagic shock (HS). Clinical data, however, suggest that hypothermia, which often occurs spontaneously in trauma patients, is detrimental. Because critically ill trauma patients are usually cool, the clinical question, which has not been explored in the laboratory with long-term outcome, is whether maintaining hypothermia or actively rewarming the patient improves outcome. We hypothesized that after spontaneous cooling during HS, continuing mild therapeutic hypothermia during resuscitation is beneficial compared with active rewarming. METHODS: In study A, under light isoflurane anesthesia, 24 Sprague-Dawley rats were bled over 10 minutes to, and maintained at, mean arterial pressure (MAP) of 40 mm Hg until reuptake of 30% of maximal shed blood volume was needed. Rectal temperature (Tr) decreased spontaneously to, and was then maintained at, 35 degrees C during HS. Fluid resuscitation included the remaining shed blood and up to 400 mL/kg of lactated Ringer's solution with 5% dextrose over 4 hours. During resuscitation, three groups (n = 8 each) were studied: normothermia (rapid rewarming to Tr 37.5 degrees C at the beginning of resuscitation); hypothermia-2 h (cooling to Tr 34 degrees C to resuscitation time 2 hours); and hypothermia-12 h (cooling to Tr 34 degrees C to 12 hours). Rats were observed to 72 hours. In study B, more severe HS than in study A was studied. HS was induced with 3 mL/100 g blood withdrawal over 15 minutes followed by maintenance of MAP of 40 mm Hg until 50% of maximal shed blood volume was needed. Two groups (n = 8 each) were studied: normothermia and hypothermia-12 h. Data are presented as mean +/- SD or median (range). RESULTS: In study A, both hypothermia groups had higher MAP and lower heart rates during resuscitation than the normothermia group (p < 0.01). Survival to 72 hours was achieved in three of eight rats in the normothermia group and two of eight in each hypothermia group. Thirteen of 17 deaths occurred after 24 hours. In study B, for resuscitation, the hypothermia group needed less fluid (53 +/- 6 mL vs. 79 +/- 32 mL, p < 0.05), but had higher MAP (p < 0.01), lower heart rate (p < 0.01), and lower lactate level (p = 0.06). All rats died before 72 hours. The hypothermia group had longer survival time (24.5 [13-48.5] hours) than the normothermia group (7.5 [1.5-19] hours) (p = 0.003 by life table analysis). CONCLUSION: After spontaneous cooling during moderately severe HS, mild, controlled hypothermia during resuscitation does not seem to affect long-term survival. After more severe HS, hypothermia increases survival time. Hypothermia supports arterial pressure during resuscitation from severe HS.     

Differential alterations in intestinal permeability after trauma-hemorrhage

BACKGROUND: Recent studies have shown that the intestinal barrier function is altered and macromolecules can translocate after trauma and hemorrhagic shock. The translocated molecules are absorbed from the lymphatic tissue or directly enter the circulation in the gut. However, it remains unknown to what degree these compartments contribute to the clearance of the macromolecules. METHODS: Male Sprague-Dawley rats (350-400 g) underwent a 5-cm midline laparotomy (i.e., soft tissue injury), were bled to a mean arterial pressure of 35 mmHg and maintained for approximately 90 min, and then resuscitated with Ringer's lactate (4x the shed blood volume) over 60 min. At 2 h after resuscitation, a solution containing 51Cr-EDTA, FITC-dextran-4 kDa, and rhodamine B-dextran-40 kDa was instilled into a jejunal blind loop and their concentrations were determined in mesenteric lymph and blood samples harvested between 2 h and 4 h after resuscitation. RESULTS: Trauma-hemorrhage and crystalloid resuscitation significantly increased mesenteric lymph flow and the mucosal permeability for the three marker molecules. There was no difference in the concentrations of 51Cr-EDTA between the blood and lymph compartment after trauma-hemorrhage. However, the high molecular weight marker (rhodamine-B-dextran-40 kDa) accumulated in significantly higher concentrations in the mesenteric lymph than in the plasma under such conditions. CONCLUSIONS: The accumulation of macromolecules in the mesenteric lymph suggests that this compartment plays an important role in the altered gut barrier function after trauma-hemorrhage.     

Ischemia-reperfusion decreases protein tyrosine phosphorylation and p38 mitogen-activated protein kinase phosphorylation in rat lung transplants.

BACKGROUND: Dramatic alterations of protein tyrosine phosphorylation have been found during the ischemia-reperfusion (IR) period of human lung transplantation. IR also induces activation of p38 mitogen-activated protein kinase (p38) in the heart and kidney. The objective of the present study was to determine whether these changes exist in a rat single-lung transplant model for further mechanistic investigations. METHODS: Isogeneic lung transplantation was performed from Lewis (LEW) to LEW rats, whereas allogeneic transplantation was from LEW to Brown Norway (BN) rats. Blood gases and peak airway pressure were monitored. Lung tissues were collected after 6 hours of cold ischemic preservation, after 30 minutes of warm ischemia for lung implantation, and after 2 hours of reperfusion. Protein tyrosine kinase (PTK) and phosphatase (PTP) activities were measured. Protein tyrosine phosphorylation, Src PTK and p38 expression and p38 phosphorylation were examined by western blotting. RESULTS: In both iso- and allografts, the lung function of transplants was very well preserved. Protein tyrosine phosphorylation, PTK and PTP activities were decreased significantly after 2 hours of reperfusion. Src protein level and phosphorylation of p38 were reduced after 2 hours of reperfusion. CONCLUSIONS: During the early IR period of lung transplantation, decreased protein tyrosine phosphorylation may be involved in apoptosis and other biologic changes. The lack of p38 activation suggests that activity of mitogen-activated protein kinase pathways in the lung transplantation setting may be different from other IR processes.     

Attenuation of vascular endothelial dysfunction by testosterone receptor blockade after trauma and hemorrhagic shock

HYPOTHESIS: The salutary effects of the testosterone receptor antagonist flutamide on the depressed immune and cardiovascular functions after hemorrhage and resuscitation are related to improved endothelial cell function, which can subsequently lead to an increase in organ blood flow, oxygen delivery, and tissue oxygen consumption. DESIGN, INTERVENTIONS, AND MAIN OUTCOME MEASURES: Male adult rats underwent a 5-cm midline laparotomy (ie, trauma) and were bled to and maintained at a mean systemic arterial pressure of 40 mm Hg until 40% maximal blood-out volume was returned in the form of Ringer lactate). The animals were then resuscitated with 4 times the total volume of shed blood with Ringer lactate for 60 minutes. Flutamide (25 mg/kg) or an equivalent volume of the vehicle propanediol was injected subcutaneously 15 minutes before the end of resuscitation. At 20 hours after resuscitation, aortic rings (approximately 2.5 mm in length) were isolated and mounted in an organ chamber. Dose responses for an endothelium-dependent vasodilator (acetylcholine chloride) and endothelium-independent vasodilator (nitroglycerine) were determined. Organ blood flow was measured using strontium 85-labeled microspheres. Total hemoglobin and oxygen content in the femoral artery and portal, hepatic, and renal veins were determined. Oxygen delivery and consumption in liver, small intestine, and kidneys were calculated. RESULTS: Administration of flutamide after trauma-hemorrhage attenuated the depressed endothelial function. Furthermore, flutamide treatment restored the reduced blood flow and oxygen delivery and consumption in all organs tested after trauma-hemorrhage and resuscitation. CONCLUSION: Flutamide appears to be a useful adjunct for improving vascular endothelial function and regional hemodynamics after trauma-hemorrhage and resuscitation.     

Salutary effects of androstenediol on hepatic function after trauma-hemorrhage are mediated via peroxisome proliferators-activated receptor gamma

BACKGROUND: A recent study suggested that administration of androstenediol (Adiol) after trauma-hemorrhage (T-H) improves hepatic functions; however, the mechanism responsible for the salutary effect of Adiol remains unknown. Although studies indicate similarities and association between the anti-inflammatory properties of Adiol and peroxisome proliferator-activated receptor gamma (PPARgamma), whether the salutary effects of Adiol are mediated via upregulation of PPARgamma remains unclear. METHODS: Male Sprague-Dawley rats underwent laparotomy and approximately 90 minutes of hemorrhagic shock (40 mm Hg), followed by resuscitation with 4 times the shed blood volume in the form of Ringer's lactate. Adiol (1 mg per kilogram of body weight, iv) was administered at the end of resuscitation. An additional group of rats were treated with PPARgamma antagonist (GW9662, 1 mg/kg ip) along with Adiol and the rats were sacrificed 5 hours thereafter. RESULTS: Hepatic functions were markedly depressed and plasma tumor necrosis factor-alpha, C-reactive protein and endothelin-1 were markedly increased after T-H. DNA-binding activity of nuclear factor kappa B and AP-1, and gene expressions of inducible nitric oxide synthase and endothelin-1 in the liver also increased significantly. These parameters were attenuated by Adiol treatment. These effects were accompanied an increased DNA-binding activity of PPARgamma in T-H-Adiol-treated rats. Treatment of rats with GW9662 prevented the salutary effects of Adiol after T-H. CONCLUSIONS: Since blockade of PPARgamma prevented the salutary effects of Adiol on hepatic functions and proinflammatory factors, this finding suggests that Adiol mediated its salutary effects after T-H via the PPARgamma-related pathways.