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.

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.

The small intestine plays an important role in upregulating CGRP during sepsis.

Although studies have indicated that calcitonin gene-related peptide (CGRP), a potent vasodilatory peptide, is upregulated after endotoxic shock, it remains controversial whether this peptide increases during sepsis and, if so, whether the gut is a significant source of CGRP under such conditions. To study this, polymicrobial sepsis was induced by cecal ligation and puncture (CLP) followed by fluid resuscitation. Plasma levels of CGRP were measured at 2, 5, and 10 h after CLP (i.e., early, hyperdynamic sepsis) and at 20 h after CLP (late, hypodynamic sepsis). The results indicate that plasma CGRP did not increase at 2--5 h but increased by 177% at 10 h after CLP (P < 0.05). At 20 h after the onset of sepsis, however, the elevated plasma CGRP returned to the sham level. To determine the source of the increased plasma CGRP, the liver, spleen, small intestine, lungs, and heart were harvested, and tissue CGRP was assayed at 10 h after CLP in additional animals. Only the small intestine showed a significant increase in tissue levels of CGRP (by 129%, P < 0.05). Determination of portal vs. systemic levels of CGRP indicates that portal CGRP was 65.7 +/- 22.7% higher than the systemic level at 10 h after CLP, whereas portal CGRP in sham-operated rats was only 4.9 +/- 2.1% higher. Immunohistochemistry examination revealed that CGRP-positive stainings increased in the intestinal tissue but not in the liver at 10 h after the onset of sepsis. The distribution of CGRP stainings was associated with intestinal nerve fibers. These results, taken together, demonstrate that upregulation of CGRP occurs transiently during the progression of sepsis (at the late phase of the hyperdynamic sepsis), and the gut appears to be a major source of such an increase in circulating levels of this peptide.

Does early infusion of red blood cells after trauma and hemorrhage improve organ functions?

OBJECTIVE: Early management of trauma victims includes control of bleeding and rapid restoration of intravascular volume. However, it remains controversial whether infusion of blood products is superior to crystalloids alone. Therefore, it was the aim of the present study to determine whether resuscitation with red blood cells plus lactated Ringer's solution (RL) is more effective than RL alone in improving the cardiovascular and hepatocellular functions after trauma and severe hemorrhage. DESIGN: Prospective study. SETTING: Laboratory. SUBJECTS: Sprague-Dawley rats. INTERVENTIONS AND MEASUREMENTS: Male adult rats were anesthetized and underwent a laparotomy to induce tissue trauma before hemorrhage. The animals were then bled to and maintained at a mean arterial pressure of 40 mm Hg until 40% of the maximal bleed-out (MB) volume was returned in the form of RL, and were then resuscitated with either four times the volume of MB with RL or washed red blood cells (RBC) (-45% the volume of MB) in three times the volume of RL over 60 mins. Various in vivo heart performance variables, cardiac output, and hepatocellular function (ie, the maximum velocity and the overall efficiency of indocyanine green clearance) were determined at 4 hrs after resuscitation. Hemoglobin, systemic oxygen delivery, circulating blood volume, and plasma levels of interleukin-6 were also measured. MAIN RESULTS: At 4 hrs after RL resuscitation, heart performance, cardiac output and hepatocellular function were significantly depressed and plasma levels of interleukin-6 were significantly increased. Although infusion of RBC significantly increased mean arterial pressure, hemoglobin, and oxygen delivery compared with animals resuscitated with RL only, infusion of RBC did not further improve the depressed cardiovascular and hepatocellular functions under such conditions. CONCLUSION: Because infusion of RBC and RL resuscitation do not improve organ functions compared with RL resuscitation without RBC, it appears that pharmacologic agents in addition to fluid resuscitation are needed to restore cardiovascular and hepatocellular functions after trauma and hemorrhage.

Testosterone receptor blockade after trauma and hemorrhage attenuates depressed adrenal function.

Although the testosterone receptor antagonist flutamide restores the depressed immune function in males after trauma and hemorrhage, it remains unknown whether this agent has any salutary effects on adrenal function. To study this, male rats underwent laparotomy and were bled to and maintained at a blood pressure of 40 mmHg until 40% of the shed blood volume was returned in the form of Ringer lactate. Animals were then resuscitated and flutamide (25 mg/kg body wt) was administered subcutaneously. Plasma adrenocorticotropic hormone (ACTH) and corticosterone, as well as adrenal corticosterone and cAMP were measured 20 h after resuscitation. In additional animals, ACTH was administered and ACTH-induced corticosterone release and adrenal cAMP were determined. The results indicate that adrenal contents of corticosterone and cAMP were significantly decreased and morphology was altered after hemorrhage. Administration of flutamide improved corticosterone content, restored cAMP content, and attenuated adrenal morphological alterations. Flutamide also improved the diminished ACTH-induced corticosterone release and adrenal cAMP response at 20 h after hemorrhage and resuscitation. Furthermore, the diminished corticosterone response to ACTH stimulation in the isolated adrenal preparation was improved with flutamide. These results suggest that flutamide is a useful adjunct for improving adrenal function in males following trauma and hemorrhage.

Alterations in tissue oxygen consumption and extraction after trauma and hemorrhagic shock.

OBJECTIVES: Although trauma and hemorrhage are associated with tissue hypoperfusion and hypoxemia, changes in oxygen delivery (DO2), oxygen consumption VO2), and oxygen extraction at the organ level in a small animal (such as the rat) model of trauma and hemorrhage have not been examined. Therefore, the objectives of this study were to determine whether blood flow, DO2, VO2, and oxygen extraction ratio in various organs are differentially altered after trauma-hemorrhagic shock and acute resuscitation in the rat. DESIGN: Prospective, randomized animal study. SETTING: A university research laboratory. SUBJECTS: Male Sprague-Dawley rats (n = 6-7 animals/group) weighing 275-325 g. INTERVENTIONS: Male rats underwent laparotomy (i.e., soft tissue trauma) and were bled to and maintained at a blood pressure of 40 mm Hg until 40% of shed blood volume was returned in the form of lactated Ringer's solution. They were then resuscitated with four times the volume of shed blood with lactated Ringer's solution for 60 mins. At 1.5 hrs postresuscitation, cardiac output and blood flow were determined by using strontium-85 microspheres. Blood samples (0.15 mL each) were collected from the femoral artery and vein and the hepatic, portal, and renal veins to determine total hemoglobin and oxygen content. Systemic and regional DO2, VO2, and oxygen extraction ratio were then calculated. MEASUREMENTS AND MAIN RESULTS: Both the systemic hemoglobin and systemic arterial oxygen content in hemorrhaged animals at 1.5 hrs postresuscitation were >50% lower as compared with sham-operated controls. Cardiac output and blood flow in the liver, small intestine, and kidneys decreased significantly, but blood flow in the brain and heart remained unaltered after hemorrhage and resuscitation. Systemic DO2 and VO2 were 73% and 54% lower, respectively, than controls at 1.5 hrs after resuscitation. Similarly, regional DO2 and VO2 in the liver, small intestine, and kidneys decreased significantly under such conditions. In addition, the liver had the most severe reduction in VO2 (76%) among the tested organs. However, the oxygen extraction ratio in the liver of sham animals was the highest (72%) and remained unchanged after hemorrhage and resuscitation. CONCLUSION: Because the liver experienced the most severe reduction in VO2 associated with an unchanged oxygen extraction capacity, this organ appears to be more vulnerable to hypoxic insult after hemorrhagic shock.

Is prostacyclin responsible for producing the hyperdynamic response during early sepsis?

OBJECTIVE: Although polymicrobial sepsis is characterized by an early hyperdynamic phase (2-10 hrs after cecal ligation and puncture [CLP]), followed by a late hypodynamic phase (20 hrs after CLP), it remains unknown whether prostacyclin or prostaglandin I2 (PGI2) plays a significant role in modulating the hyperdynamic state during early sepsis. The aim of this study was to determine whether inhibition of PGI2 synthesis prevents the occurrence of the hyperdynamic response during early sepsis. DESIGN: Prospective, controlled animal study. SETTING: A university research laboratory. SUBJECTS: Adult male Sprague-Dawley rats were subjected to sepsis by CLP. INTERVENTIONS AND MEASUREMENTS: Blood samples were collected at 2, 5, 10, or 20 hrs after CLP, and plasma concentrations of PGI2, in the form of its stable product 6-keto-PGF1alpha, were measured by radioimmunoassay. In additional studies, a PGI2 synthase inhibitor, tranylcypromine, was administered subcutaneously at the time of CLP and again at 3 hrs after CLP. At 5 hrs after the onset of sepsis, the maximal rates of the left ventricular pressure rise (+dP/dtmax) and fall (-dP/dtmax) were determined by an in vivo heart performance analyzer. Microvascular blood flow in the liver, small intestine, and spleen was assessed by laser Doppler flowmetry. MAIN RESULTS: Plasma concentrations of 6-keto-PGF1alpha increased significantly at 2-20 hrs after CLP. At 5 hrs after the onset of sepsis, +/-dP/dt(max) and microvascular blood flow in the tested tissues increased significantly. Inhibition of PGI2 synthase activity did not prevent the occurrence of hypercardiovascular responses under such conditions. Moreover, the administration of tranylcypromine significantly reduced circulating concentrations of 6-keto-PGF1alpha at 5 hrs after CLP. CONCLUSIONS: Because inhibition of PGI2 production did not prevent the occurrence of the hyperdynamic and hypercardiovascular response during the early stage of sepsis, mediators other than PGI2 appear to play a major role in producing the hyperdynamic response under such conditions.

Reduction in vascular responsiveness to adrenomedullin during sepsis.

BACKGROUND: Although sepsis is characterized by an early, hyperdynamic phase followed by a late, hypodynamic phase, the mechanism responsible for the transition from the hyperdynamic to the hypodynamic state remains unknown. Since recent studies have shown that adrenomedullin (ADM), a novel potent vasodilatory peptide, is upregulated during sepsis, the aim of this study was to determine whether the reduced vascular responsiveness to ADM is associated with the transition from the hyperdynamic phase to the hypodynamic phase of sepsis. MATERIALS AND METHODS: Adult male Sprague-Dawley rats were subjected to sepsis by cecal ligation and puncture (CLP). At 5 and 10 h (i.e., the hyperdynamic phase of sepsis) or 20 h (the hypodynamic phase) after CLP, the thoracic aorta or small intestine was harvested and preconstricted with norepinephrine. Adrenomedullin (10(-7) M) was applied and the percentage of ADM-induced vascular relaxation in the aortic ring and isolated small intestine was determined. RESULTS: The responsiveness to ADM in the thoracic aorta was not altered at 5-10 h, but decreased significantly at 20 h after CLP. Although ADM-induced relaxation in resistance blood vessels of the small intestine did not change at 5 h, it decreased markedly at 10 and 20 h after the onset of sepsis. CONCLUSIONS: Since the transition from hyperdynamic to hypodynamic sepsis takes place between 10 and 20 h after CLP, it is likely that reduced vascular responsiveness to ADM may be responsible for such an event during the course of polymicrobial sepsis. In view of this, maintenance of vascular ADM responsiveness by pharmacologic agents appears to be a novel approach for preventing or delaying the occurrence of hypodynamic sepsis and septic shock.

Salutary effects of ATP-MgCl2 on the depressed endothelium-dependent relaxation during hyperdynamic sepsis.

OBJECTIVES: Studies have shown that endothelium-dependent relaxation (mediated by endothelium-derived nitric oxide) is depressed during the early, hyperdynamic stage of sepsis. Although it is known that ATP-MgCl2 produces beneficial effects following various adverse circulatory conditions, it remains unknown whether this agent attenuates the depressed endothelium-dependent relaxation during early sepsis. The aim of this study, therefore, was to determine whether or not the administration of ATP-MgCl2 early after the onset of sepsis improves or maintains endothelium-dependent relaxation. DESIGN: Prospective, controlled animals study. SETTING: A university research laboratory. SUBJECTS: Adult male Sprague-Dawley rats were subjected to polymicrobial sepsis by cecal ligation and puncture (CLP), followed by administration of 3 mL/100 g body weight normal saline to these and sham-operated rats. INTERVENTIONS: At 1 hr after CLP, ATP-MgCl2 (50 micromol/kg body weight) or an equivalent volume of normal saline was infused intravenously over 90 mins. MEASUREMENTS AND MAIN RESULTS: At 5 hrs or 10 hrs after CLP (i.e., the early, hyperdynamic stage of sepsis), the thoracic aorta was isolated, cut into rings, and placed in organ chambers. Norepinephrine was used to preconstrict vessel rings. Dose responses for an endothelium-dependent vasodilator, acetylcholine (ACh, via endothelium-dependent nitric oxide), and an endothelium-independent vasodilator, nitroglycerin, were determined. These results indicate that endothelium-dependent relaxation induced by ACh was significantly depressed at 5 and 10 hrs after CLP. Administration of ATP-MgCl2 after the onset of sepsis, however, maintained ACh-induced vascular relaxation. In contrast, no significant difference in nitroglycerin-induced vascular relaxation as well as norepinephrine-induced contraction was observed, irrespective of administration of ATP-MgCl2. CONCLUSION: Since administration of ATP-MgCl2 prevents the impaired vascular relaxation to the endothelium-dependent vasodilator ACh, this agent may be a useful adjunct for maintaining endothelial cell function during the hyperdynamic stage of sepsis.

Mechanism of adrenal insufficiency following trauma and severe hemorrhage: role of hepatic 11beta-hydroxysteroid dehydrogenase.

BACKGROUND: Although adrenal insufficiency may not occur with moderate hypotension, it does occur with severe hemorrhage. Since hepatocellular function is depressed following severe hemorrhage, it remains unknown whether the liver plays any role in regulating adrenal function after trauma and hemorrhagic shock. HYPOTHESIS: Hepatic 11beta-hydroxysteroid dehydrogenase (11beta-HSD), a microsomal enzyme responsible for the degradation of bioactive corticosterone, plays a major role in the development of adrenal insufficiency following trauma and severe hemorrhage. DESIGN, INTERVENTIONS, AND MAIN OUTCOME MEASURES: Male rats underwent laparotomy to induce trauma before hemorrhage. They were then bled to and maintained at a blood pressure of 40 mm Hg until 40% of the maximal bleed-out volume was returned in the form of Ringer lactate. The rats were then resuscitated with 4 times the volume of maximal bleed-out with Ringer lactate during a 60-minute period. Plasma levels of corticosterone and corticotropin were measured at various intervals. In additional groups, corticotropin-induced corticosterone release, adrenal contents of corticosterone and cyclic adenosine monophosphate (cAMP), hepatic 11beta-HSD activity, and plasma levels of corticosterone-binding globulin were determined at 1.5 hours after resuscitation. Moreover, a model of moderate hypotension (blood pressure, 80 mm Hg) was used to determine whether adrenal function is depressed under such conditions. RESULTS: At the time of maximal bleed-out, plasma corticosterone and corticotropin levels increased by 245% (P<.001) and 293% (P<.001), respectively. Despite corticotropin levels being similar to those of the animals undergoing sham operation after resuscitation, corticosterone levels in hemorrhaged animals remained elevated up to 4 hours after resuscitation (by 158%-207%; P<.001). In addition, corticotropin-induced corticosterone release decreased by 78% at 1.5 hours after resuscitation (P = .009). In contrast, moderate hypotension did not reduce corticotropin-induced corticosterone release. Adrenal corticosterone content and cAMP levels (i.e., the second messenger of corticotropin action) decreased by 55% (P<.001) and 25% (P = .03), respectively. Hepatic 11beta-HSD activity decreased significantly at 1.5 hours after resuscitation (P<.001). CONCLUSIONS: Sustained increase in plasma corticosterone levels following hemorrhage and resuscitation may be, in part, due to the decreased hepatic 11beta-HSD activity. The high level of corticosterone negatively regulates corticotropin release, further reducing adrenal responsiveness to corticotropin stimulation. Thus, the liver appears to play an important role in regulating adrenal function following trauma and severe hemorrhage.

The pivotal role of adrenomedullin in producing hyperdynamic circulation during the early stage of sepsis.

BACKGROUND: Initial cardiovascular responses during sepsis are characterized by hyperdynamic circulation. Although studies have shown that a novel potent vasodilatory peptide, adrenomedullin (ADM), is up-regulated under such conditions, it remains unknown whether ADM is responsible for initiating the hyperdynamic response. OBJECTIVE: To determine whether increased ADM release during early sepsis plays any major role in producing hyperdynamic circulation. DESIGN, INTERVENTION, AND MAIN OUTCOME MEASURE: Synthetic rat ADM (8.5 microg/kg of body weight) was infused intravenously in normal rats for 15 minutes at a constant rate. Cardiac output, stroke volume, and microvascular blood flow in various organs were determined immediately as well as 30 minutes after ADM infusion. At 30 minutes after infusion, plasma ADM level was also measured. In additional groups, rats were subjected to sepsis by cecal ligation and puncture. At 1.5 hours after cecal ligation and puncture, specific anti-rat ADM antibodies were infused, which completely neutralized the circulating ADM. Various hemodynamic variables were measured 5 hours after cecal ligation and puncture (ie, the early stage of sepsis). RESULTS: Cardiac output, stroke volume, and microvascular blood flow in the liver, small intestine, kidney, and spleen increased, and total peripheral resistance decreased 0 and 30 minutes after ADM infusion. In addition, plasma levels of ADM increased from the preinfusion level of 92.7+/-5.3 to 691.1+/-28.2 pg/mL 30 minutes after ADM infusion, which was similar to ADM levels observed during early sepsis. Moreover, 5 hours after the onset of sepsis, cardiac output, stroke volume, and microvascular blood flow in various organs increased and total peripheral resistance decreased. Administration of anti-ADM antibodies, however, prevented the occurrence of the hyperdynamic response. CONCLUSIONS: The results suggest that increased ADM production and/or release plays a major role in producing hyperdynamic responses during early sepsis. Since our previous studies have shown that vascular responsiveness to ADM decreases in late sepsis, maintenance of ADM vascular responsiveness by pharmacological agents during the course of sepsis may prevent transition from the hyperdynamic to the hypodynamic state.

Upregulation of Kupffer cell beta-adrenoceptors and cAMP levels during the late stage of sepsis.

Although a burst of immunoresponsiveness may occur during the early stage of sepsis, late sepsis is characterized by severe immunodepression. In addition, although studies have shown that stimulation of macrophage beta-adrenoceptors results in an increase in cAMP and an associated reduction in macrophage phagocytic activity, it remains unknown whether Kupffer cell beta-adrenoceptor characteristics and cAMP levels are altered during polymicrobial sepsis. To study this, Sprague-Dawley rats were subjected to sepsis by cecal ligation and puncture (CLP). At 5 h (i.e., the early stage of sepsis) or 20 h (late sepsis) after CLP or sham operation, the liver was perfused with collagenase solution and Kupffer cells were isolated. beta-Adrenoceptor characteristics of the isolated Kupffer cells were determined using [125I]iodopindolol, and basal levels of cAMP were measured by radioimmunoassay. The results indicate that while maximum binding capacity (Bmax) of Kupffer cell beta-adrenoceptors was not altered at 5 h, it increased significantly at 20 h after CLP. Similarly, basal levels of cAMP in Kupffer cells did not change at 5 h but increased markedly at 20 h after the onset of sepsis. In contrast, the dissociation constant (Kd, 1/affinity) of Kupffer cell beta-adrenoceptors was not significantly affected by sepsis at both 5 h and 20 h after CLP. Thus, upregulation of beta-adrenoceptors and increase in cAMP levels in Kupffer cells occur during the late stage of polymicrobial sepsis, and this may contribute to the depression of macrophage phagocytic function under such conditions.

Up-regulation of a novel potent vasodilatory peptide adrenomedullin during polymicrobial sepsis.

A large number of studies have been and are being carried out to examine the role of nitric oxide in the hyperdynamic and hypodynamic stages of sepsis. It remains unknown, however, whether adrenomedullin (ADM), a novel potent vasodilatory peptide, is up-regulated during hyperdynamic sepsis and, if so, whether its production is sustained during hypodynamic sepsis. To determine this, rats were subjected to sepsis by cecal ligation and puncture (CLP), followed by administration of 3 mL/100 g body weight normal saline to these and sham-operated animals. Blood samples were taken at 1, 1.5, 2, 5, and 10 h (2-10 h post-CLP represents the hyperdynamic stage of sepsis) or at 20 and 30 h after CLP (i.e., the hypodynamic stage). Plasma levels of ADM were measured by radioimmunoassay. Adrenomedullin gene expression in various tissues was examined at 2, 10, or 20 h after CLP by reverse transcription-polymerase chain reaction (RT-PCR). The results indicated that plasma levels of ADM did not increase at 1 and 1.5 h after CLP but increased significantly at 2 h after the onset of sepsis. Moreover, circulating ADM increased progressively at 5-20 h and remained elevated at 30 h after CLP. The increased levels of plasma ADM during sepsis were correlated with up-regulation of ADM mRNA in the small intestine, left ventricle, and thoracic aorta. In contrast, ADM gene expression in renal and hepatic tissues was not significantly altered following the onset of sepsis. The association between the up-regulated ADM and the occurrence of hyperdynamic circulation during the early stage of sepsis (both occur at 2 h after CLP) may indicate a possible cause and effect relationship between the two events. Since we have previously shown that ADM-induced vascular relaxation decreased at 20 h after CLP, it appears that the down-regulation of ADM receptors may be responsible for the transition from the hyperdynamic stage to the hypodynamic stage of sepsis.

Is gut the "motor" for producing hepatocellular dysfunction after trauma and hemorrhagic shock?

BACKGROUND: Although studies suggest that the gut may be the "motor" responsible for producing sepsis and multiple organ failure after injury, it is not known whether enterectomy prior to the onset of hemorrhage alters proinflammatory cytokines TNF and IL-6 and, if so, whether hepatocellular dysfunction and damage are prevented or attenuated under such conditions. MATERIALS AND METHODS: Under methoxyflurane anesthesia, an enterectomy in the rat was performed by excision of the duodenum, jejunum, and ileum. The rats were then 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. The animals were then resuscitated with four times the volume of shed blood with Ringer's lactate over 1 h. At 1.5 h after the completion of resuscitation, hepatocellular function [i.e., the maximal velocity (Vmax) and transport efficiency (Km) of indocyanine green (ICG) clearance] was assessed by an in vivo ICG clearance technique. Blood samples were taken for the measurement of TNF, IL-6, and liver enzymes (i.e., SGPT and SGOT). Cardiac output and microvascular blood flow were determined by ICG dilution and laser Doppler flowmetry, respectively. RESULTS: The increase in circulating levels of TNF but not IL-6 was prevented by enterectomy prior to hemorrhage. The reduced Vmax and K(m) and elevated SGPT and SGOT following hemorrhage and resuscitation, however, were not significantly affected by prior enterectomy. Moreover, enterectomy before hemorrhage further reduced hepatic perfusion. CONCLUSION: Since enterectomy prior to the onset of hemorrhage does not prevent or attenuate the reduced ICG clearance and elevated liver enzymes despite downregulation of TNF production, it appears that the small intestine does not play a significant role in producing hepatocellular dysfunction and injury following trauma and hemorrhagic shock.

Hepatocellular dysfunction after severe hypotension in the absence of blood loss is associated with the increased IL-6 and PGE2.

Although hepatocellular dysfunction occurs following trauma and hemorrhagic shock, whether severe hypotension even in the absence of blood loss depresses hepatocellular function remains unknown. The aim of this study, therefore, was to determine whether chemically induced severe hypotension causes hepatocellular dysfunction and, if so, whether IL-6 and PGE2 are associated with this dysfunction. To study this, hypotension was induced in adult male rats by intravenous infusion of a high dosage of ATP-MgCl2 solution (3.2 +/- 0.45 micromol/min/kg body wt) for 60 min. Blood pressure decreased from 108 +/- 6 mm Hg to an average of 43 mm Hg during the infusion period and returned to normal levels immediately after the completion of ATP-MgCl2 infusion. At 0 and 4 h after hypotension, hepatocellular function [i.e., maximum velocity of indocyanine green clearance (Vmax) and its efficiency (Km)] was measured using a fiberoptic catheter and in vivo hemoreflectometer. Cardiac output was determined by dye dilution. Microvascular blood flow was assessed by laser Doppler flowmetry. Plasma levels of PGE2 and IL-6 were measured by radioimmunoassay and bioassay, respectively. The results indicate that severe hypotension in the absence of any blood loss depresses hepatocellular function (i.e., decreased Vmax and Km) despite stable cardiac output and hepatic perfusion at 0 and 4 h after the completion of hypotension. Moreover, severe hypotension resulted in significantly increased plasma levels of PGE2 (only at 0 h) and IL-6. Thus, chemically induced severe hypotension in the absence of any blood loss, which does not significantly reduce cardiac output and hepatic perfusion, depresses hepatocellular function and upregulates IL-6 and PGE2 production.

Severe hypoxemia in the absence of blood loss depresses hepatocellular function and up-regulates IL-6 and PGE2.

Although hepatocellular function is depressed early after trauma and hemorrhage (which are associated with low flow conditions and tissue hypoxemia), it remains unknown whether hypoxemia without blood loss, produces hepatocellular dysfunction and, if so, whether IL-6 and PGE2 are associated with this dysfunction. To study this, rats were placed in a plastic box which was flushed with a gas mixture containing 6.3% O2:93.7% N2 or room air for 60 min, followed by their return to room air. At 0 and 4 h after hypoxemia, hepatocellular function (i.e., maximum velocity of indocyanine green clearance (Vmax) and the efficiency of the transport (Km)) was measured using an in vivo hemoreflectometer. Cardiac output was assessed by dye dilution technique. Tissue microvascular blood flow was determined by laser Doppler flowmetry. Plasma IL-6 and PGE2 were measured by bioassay and radioimmunoassay, respectively. The results indicate that hypoxemia produced a depression in hepatocellular function (i.e., decreased Vmax by 44-50% and Km by 55-68%) despite stable cardiac output and hepatic microcirculation at 0 and 4 h after hypoxemia. Moreover, hypoxemia resulted in a significant increase in plasma IL-6 (by 372%-389%) as well as PGE2 (by 38% at 0 h post-hypoxemia). Thus, hypoxemia observed after trauma and hemorrhagic shock appears to be responsible for producing hepatocellular dysfunction possibly through the up-regulation of IL-6 and PGE2. In view of this, long-lasting hypoxemia in trauma victims should be avoided, perhaps by early intubation and ventilation so that the potential additional proinflammatory cytokine and PGE2 release can be prevented.

Mechanism of hepatocellular dysfunction during early sepsis. Key role of increased gene expression and release of proinflammatory cytokines tumor necrosis factor and interleukin-6.

BACKGROUND: Hepatocellular dysfunction occurs at 1.5 hours after cecal ligation and puncture (CLP [ie, sepsis model]), despite normal cardiac output and hepatic perfusion. OBJECTIVE: To determine whether proinflammatory cytokines such as tumor necrosis factor (TNF) and interleukin-6 (IL-6) are up-regulated before the occurrence of hepatocellular dysfunction during sepsis. DESIGN, INTERVENTION, AND MAIN OUTCOME MEASURE: Rats were subjected to sepsis by CLP, followed by administration of normal saline solution, 3 mL/100 g of body weight, to these and animals undergoing sham operation. At 0.5, 1, 1.5, or 2 hours after CLP, circulating levels of TNF and IL-6 were measured by enzyme-linked immunosorbent assay and bioassay, respectively. In additional animals, Kupffer cells were isolated at 1, 2, or 5 hours after CLP or sham operation. Kupffer cell TNF and IL-6 messenger RNA levels were determined by reverse-transcription polymerase chain reaction technique. RESULTS: Plasma levels of TNF and IL-6 increased significantly at 1.5 hours and persisted at 2 hours after CLP. Levels of TNF and IL-6 messenger RNA in Kupffer cells increased as early as 1 hour after CLP. The up-regulated gene expression also persisted at 2 and 5 hours after the onset of sepsis. CONCLUSIONS: We have previously shown that TNF-alpha infusion produces hepatocellular dysfunction and that pharmacological inhibition of TNF production prevents it. Since the present study demonstrated that upregulation of proinflammatory cytokine gene expression occurs before hepatocellular dysfunction during sepsis, TNF and/or IL-6 may be responsible for producing hepatocellular dysfunction. Thus, administration of pharmacologic agents that selectively block or inhibit proinflammatory cytokine release may be useful in preventing cellular dysfunction during early sepsis.

Pentoxifylline maintains hepatocellular function and improves cardiac performance during early sepsis.

BACKGROUND AND OBJECTIVE: Although pentoxifylline (PTX) produces various beneficial effects after endotoxemia, it remains unknown whether this agent attenuates the depressed hepatocellular function and improves heart performance during early sepsis. The aim of this study, therefore, was to determine whether PTX maintains hepatocellular function and improves cardiac function during the early hyperdynamic stages of polymicrobial sepsis. DESIGN, MATERIALS, AND METHODS: Rats were subjected to sepsis by cecal ligation and puncture (CLP). At 1 hour after CLP, PTX (50 mg/kg body weight), or an equal volume of saline, was infused intravenously over 30 minutes. At 2 or 5 hours after CLP (i.e., early hyperdynamic stages of sepsis), hepatocellular function was assessed by in vivo indocyanine green clearance. Cardiac output was determined by dye dilution. Left ventricular performance parameters such as maximal rates of left ventricular pressure rise and fall (+/-dP/dtmax), ventricular peak systemic pressure, etc., were determined using a heart performance analyzer. RESULTS: The results indicate that hepatocellular function was significantly depressed at 2 and 5 hours after CLP. Administration of PTX, however, maintained hepatocellular function to sham levels. Although cardiac output increased after CLP with or without PTX treatment, this agent markedly improved cardiac performance as evidenced by significantly higher + dP/dtmax and ventricular peak systemic pressure as well as other heart performance parameters. CONCLUSIONS: Pentoxifylline appears to be a useful adjunct for maintaining hepatocellular function and improving cardiac performance during the early hyperdynamic stages of polymicrobial sepsis.

Liver endothelial cell function is depressed only during hypodynamic sepsis.

Although studies have indicated that hepatocellular function is depressed early after the onset of sepsis, it remains unknown whether liver endothelial cell function is also compromised under such conditions. To study this, male rats were subjected to polymicrobial sepsis by cecal ligation and puncture (CLP), followed by administration of 3 ml/100 g body wt normal saline subcutaneously to these and to sham-operated animals. Blood samples (0.2-ml aliquots) were taken from the carotid artery, portal vein, and hepatic vein at 2, 5, 10 (i.e., hyperdynamic sepsis), or 20 hr (hypodynamic sepsis) after CLP, and plasma hyaluronic acid (HA) was determined using a Pharmacia assay kit. In addition, HA clearance was assessed at 5, 10, or 20 hr after CLP by injecting 30 micrograms/100 g body wt HA intravenously. Plasma HA was determined at 2-40 min after the administration of HA. The results indicate that plasma levels of HA in blood from three different sites did not increase significantly until 10 hr after CLP. Clearance of HA decreased only at 20 hr after CLP, compared to sham-operated animals. These results suggest that the increased plasma levels of HA at 10 hr after the onset of sepsis are solely due to the increased release/production of the polysaccharide. Since circulating HA is cleared exclusively by the liver endothelial cell, the results demonstrate that liver endothelial cell dysfunction (i.e., the increased circulating HA levels and decreased HA clearance) occurs only during the late, hypodynamic stage of polymicrobial sepsis.