Diltiazem treatment in newborn canine endotoxic shock

The mortality of sepsis/septic shock continues to be high in newborns. However, there is no established method in its treatment. Although calcium channel blockers ameliorate the hemodynamic deterioration of adult circulatory shock, their effects on newborn endotoxic shock have not been elucidated. This study was performed in newborn dogs to investigate the effects of diltiazem on newborn endotoxic shock. Endotoxic shock was induced in newborn dogs (2-10 days old, 300-800 g) by an intravenous injection of E. coli lipopolysaccharide (LPS; 1.5 mg/kg), and diltiazem (DZ) at the dose of 300, 600 or 1200 micrograms/kg was administered intravenously 20 min prior to LPS injection. Hemodynamic changes were serially observed until 120 min after LPS injection. The heart rate, mean arterial pressure and cardiac output decreased after LPS injection, and systemic vascular resistance decreased. DZ at the dose of 600 micrograms/kg attenuated the decreases of MAP and cardiac output, but 300 and 1200 micrograms/kg of DZ exacerbated them. DZ at the dose of 1200 micrograms/kg decreased the heart rate, and DZ at all three doses attenuated the increase of systemic vascular resistance. Therefore, 600 micrograms/kg of DZ is beneficial in the treatment of endotoxic shock in newborn dogs.     

Beta-adrenergic drug therapy in newborn canine endotoxic shock

The mortality of septic shock remains high in newborns. Although the effectiveness of adrenergic drug therapy continues to be controversial, adrenergic drugs have been used for the treatment of newborn endotoxic shock. To elucidate the effects of beta-adrenergic drugs on the fulminant hemodynamic deterioration of newborn endotoxic shock, newborn dogs (2-10-day-old, 264-800 g) were given Escherichia coli lipopolysaccharide (LPS; 10 mg/kg iv) and treated with isoproterenol (0.1 micrograms/kg/min) or dopamine (5 micrograms/kg/min) infusion from 5 to 120 min after LPS injection. Isoproterenol attenuated the effects of LPS by increasing the mean arterial pressure (32 +/- 2 vs. 13 +/- 1 mmHg at 120 min), cardiac output (183 +/- 29 vs. 118 +/- 23 ml/min/kg at 120 min), and the survival time (5.3 vs 2.9 hr). However, dopamine did not improve the hemodynamic deterioration. As dopamine-beta-hydroxylase activity in the blood was significantly lower in newborn dogs than in adult dogs, inadequate response of newborn dogs to dopamine was thought to be in part due to enzymatic immaturity.     

Benoxaprofen attenuation of lethal canine endotoxic shock

Our prior work demonstrated in a canine endotoxic shock model (LD100) that the cyclooxygenase inhibitor ibuprofen given 60 minutes after endotoxin administration could improve hemodynamics but not survival over control animals. The present study was designed to examine the effect of benoxaprofen, a dual lipoxygenase and cyclooxygenase inhibitor, in the same canine endotoxic model (LD100) and compare it to ibuprofen treatment. After thiopental anesthesia (25 mg/kg IV), animals were instrumented to measure various cardiovascular parameters. Endotoxic shock was induced by injecting Escherichia coli (0111:B4) endotoxin (1 mg/kg IV). Benoxaprofen (10 mg/kg IV; N = 13), ibuprofen (12.5 mg/kg; N = 6), or saline (N = 12) was injected 60 minutes after endotoxin administration. During the treatment period, both benoxaprofen and ibuprofen increased mean arterial pressure, heart rate, and vascular resistance to the same degree over the control animals. Benoxaprofen did increase dP/dtmax while ibuprofen did not. Twenty-four-hour survival was 0% for the control animals (N = 12), 0% for the ibuprofen group (N = 6), and 61.5% for the benoxaprofen group (N = 13). In an additional set of experiments, benoxaprofen (N = 8) was given 120 minutes after endotoxin administration and demonstrated similar improvements in hemodynamics and survival. These data demonstrate that benoxaprofen could improve survival in an otherwise lethal endotoxic model and suggest that the products of the lipoxygenase pathway may contribute to the lethality of an LD100 endotoxic shock model.     

Prophylaxis and treatment of newborn endotoxic shock with anti-lipid A monoclonal antibodies.

The newborn is very susceptible to gram-negative sepsis/septic shock. The mortality of newborn endotoxic shock continues to be high. Since lipid A is responsible for the toxic effects of lipopolysaccharide, anti-lipid A antibodies may prevent endotoxic shock in the newborn. This study showed that both anti-lipid A monoclonal IgG (A78S1) and anti-lipid A monoclonal IgM (A523) decreased the mortality of endotoxic shock in 10 day old rats. Prophylactic administration of A78S1 and A523 to the pregnant rat decreased the mortality of endotoxic shock in their 0-day-old offspring. Prophylaxis was due to transplacental passage of A78S1 treatment. The mechanism of prophylaxis remains unclear in A523 treatment.     

Intrahepatocellular erythrocyte inclusions and increased calcium precipitation in canine endotoxic shock

Aims: To investigate the electron microscopic lozalization of membrane-bound and exchangeable calcium with specific calcium precipitation techniques during endotoxic shock in the dog.Methods: Ten pentobarbital anesthetized, mechanically ventilated, and paralyzed dogs were studied. Six dogs received 2 mg/kg E.coli endotoxin i.v. followed by a continuous 0.9% saline infusion to restore and maintain baseline cardiac filling pressures. Four dogs served as time-matched controls. Each experiment lasted for 3 h. After the completion of study, the livers of four endotoxic and two control dogs were fixed by perfusion of 3% glutaraldehyde via the portal vein. Liver sections were then prepared for electron microscopy and calcium localization studies.Results: Hepatocytes of endotoxic animals completely lost their plasma membrane-bound calcium. The most severely damaged cells cells showed extensive “blebbing” of the plasma membrane and contained numerous cytoplasmic erythrocyte inclusions. Endotoxin administration also caused excessive calcium precipitation inside hepatocytes in areas with pronounced sinusoidal damage.Conclusions: In this acute model of fluid-resuscitated endotoxic shock in dogs, the use of specific calcium localization techniques enables the demonstration of disturbances in hepatocellular calcium handling, which appear to be closely related to structural alterations of the hepatocyte cell membrane. Erythrocyte uptake by hepatocytes is a previously undescribed phenomenon in canine endotoxic shock and may serve as an additional histologic marker of ultrastructural cell (membrane) damage.     

Cardiovascular response in canine endotoxic shock: effect of ibuprofen pretreatment.

Ibuprofen pretreatment increases arterial pressure and reduces mortality in endotoxic dogs. The increase in arterial pressure may be caused by increases in arterial resistance, arterial sphincter tone, or both. Thus it is not clear if ibuprofen pretreatment prevents the hemodynamic effects of endotoxemia or merely masks such effects by producing concomitant increases in arterial resistance. Accordingly, this study was performed to determine the effects of ibuprofen pretreatment on arterial pressure-flow relations and other measures of cardiovascular function in a canine model of endotoxic shock. In 19 pentobarbital-anesthetized and splenectomized, closed-chest dogs, biventricular stroke volumes were measured with electromagnetic flow probes, and intrathoracic vascular and pleural pressures were measured with catheters. Instantaneous venous return curves (see Pinsky MR, J Appl Physiol 56:765, 1984) were generated during positive-pressure ventilation, and steady-state arterial pressure-flow relations, left ventricular function, peripheral vascular compliance, oxygen consumption/oxygen delivery ratio, and arterial blood lactate levels were measured during two sequential volume loading and removal (20 ml/kg) sequences. All but two dogs received a bolus infusion of Escherichia coli endotoxin (2 mg/kg) between the two fluid challenge runs. Eleven of the 17 endotoxic dogs also received ibuprofen (15 mg/kg) immediately before the initial fluid challenge. Ibuprofen pretreatment abolished all hemodynamic effects of endotoxin, whereas in the untreated group endotoxin caused decreases in calculated arterial outflow pressure and in peripheral vascular capacitance. Oxygen consumption remained constant despite changes in oxygen delivery in the nonendotoxic dogs and in the ibuprofen-pretreated dogs, whereas oxygen consumption covaried with oxygen delivery in the endotoxic dogs not pretreated with ibuprofen. Arterial lactate levels were higher after endotoxin infusion (2.1 +/- 0.5 to 3.1 +/- 0.6 mmol/liter; P less than 0.05 pre- to postvolume) but were not different between treatment groups. These data suggest that ibuprofen alters many, but not all, of the hemodynamic effects of endotoxin infusion in the dog.     

Hemodynamic and renal advantages of dual cyclooxygenase and leukotriene blockade during canine endotoxic shock

The decline in mean arterial pressure (MAP), cardiac output (CQ), and renal blood flow (RBF) that accompany endotoxic shock is partly ameliorated by cyclooxygenase or leukotriene blockade. This study determined whether dual cyclooxygenase and leukotriene blockade provided greater hemodynamic protection than either single blockade alone. Mongrel dogs were pretreated with either ibuprofen or LY171883 alone or dual blockade consisting of ibuprofen combined with LY171883 or propylgallate, then given Escherichia coli endotoxin, and monitored for 10 hr. Postendotoxemic MAP was equally maintained with dual blockade and with ibuprofen. For the first 5 hr postendotoxin, CQ was best maintained by dual blockade. However, by 9 hr postendotoxin, CQ in LY171883-treated animals was 88 +/- 8% of control. LY171883 provided the greatest protection of RBF, while dual blockade provided the least protection for both RBF and urine flow rates (V). Ibuprofen-treated dogs required less NaHCO3 for acid-base maintenance than did dual-blocked animals. In summary, dual cyclooxygenase and leukotriene blockade was advantageous in protecting MAP and CQ during the early phases of shock but provided no greater protection of RBF, GFR, V or acid-base balance than did single blockade. Overall, LY171883 provided the best protection from circulatory dysfunction.     

Verapamil treatment of canine hemorrhagic shock

The entry of calcium (Ca++) into ischemic cells is the first of a series of steps leading to irreversible cellular damage. This study examined the ability of verapamil, which may delay or diminish the injury-induced influx of Ca++, to prolong survival in three groups of chronically instrumented dogs subjected to a single, rapid hemorrhage. In untreated animals (group 1, N = 6), hemorrhage decreased mean arterial blood pressure from 101 +/- 3 mm Hg to 23 +/- 2 mm Hg. Following hemorrhage, arterial pressure recovered to 61 +/- 5 mm Hg before the secondary fall (decompensation) occurred. As decompensation progressed, arterial pressure fell to 25 mm Hg, and the animals were euthanized. In group 2 (N = 6), verapamil treatment (2 mg bolus, 1 mg/hr infusion) was initiated 30 minutes before the hemorrhage. This treatment significantly increased both the time to decompensation (184 +/- 15 minutes vs 72 +/- 9 minutes) and survival time (262 +/- 20 minutes vs 128 +/- 8 minutes). Arterial pressure recovery during the first 60 minutes following hemorrhage, however, was not affected by the verapamil pretreatment. Verapamil treatment immediately after the hemorrhage (group 3, N = 4) increased the survival rate to 75% (three of four animals). These results indicate that calcium channel blockade may be a useful initial intervention in the treatment of hemorrhagic shock.     

Adrenal gland function in reversible endotoxic shock

Because adrenal participation in the defense mechanisms against endotoxic shock is essential for survival, adrenal gland function during reversible endotoxicosis was studied. The injection of E. coli LPS into rats produces an increase in plasma corticosteroids (maximum at 2-4 hr post-endotoxin injection) and ACTH levels (maximum at 2 hr post-endotoxin injection), which return to control values at the recovery phase. Nevertheless, ACTH-induced steroidogenesis in cells isolated from adrenal glands of endotoxemic rats is clearly impaired, even at 2 hr post-endotoxin injection when corticosteroid levels are maximal. During reversible endotoxic shock there is also a depletion of adrenal ascorbic acid (maximum at 2-4 hr post-endotoxin injection) and a decrease in adrenal cytochrome P-450 levels. These data suggest that impairment of the adrenal gland function could involve mechanisms at the receptor level (desensitization by the high plasma ACTH levels or a direct effect of LPS) and/or at post-receptor steps (decrease in adrenal cytochrome P-450 levels related to the diminution in adrenal ascorbic acid content).     

Central nervous system is involved in the cardiovascular responses to naloxone in canine endotoxic but not hemorrhagic shock

We used naloxone to investigate the role of central nervous system opiate receptors in the cardiovascular depression of canine hemorrhagic and endotoxic shock. Shock was induced by bleeding dogs into a reservoir to achieve and maintain a mean arterial pressure (MAP) of 45 mmHg for 30 min; at 30 min the reservoir was clamped and the animals were treated with intracerebroventricular (ICV) perfusion of naloxone 0.1 mg/kg (n = 5) or artificial CSF (n = 5) for 30 min. Endotoxemic shock was induced by the iv injection of E. coli endotoxin 1 mg/kg; 15 min later the animals were given naloxone 0.1 mg/kg (n = 5) or artificial CSF (n = 5) ICV for 30 min. ICV naloxone significantly increased MAP, cardiac output (CO), and left ventricular performance (LV dP/dt max) compared to artificial CSF in canine endotoxic shock but not hemorrhagic shock. Naloxone 0.1 mg/kg (n = 5) given into the cisterna magna failed to significantly improve MAP, CO, or LV dP/dt max in dogs subjected to reservoir hemorrhagic shock for 60 min compared to artificial CSF (n = 5). These results are compatible with opiate-receptor-mediated central cardiovascular depression in endotoxic shock and peripheral cardiovascular depression in hemorrhagic shock. Accordingly, the sites of action of naloxone are mainly central in endotoxic shock and peripheral in hemorrhagic shock.     

Fluid resuscitation with hypertonic saline in endotoxic shock

Hypertonic saline has been used in the treatment of hypovolemic or burn shock for its rapid volemic effects. Hypertonic solutions could also improve cardiac performance and protect cellular metabolism in acute circulatory failure. We therefore studied the hemodynamic effects of continuous hypertonic saline infusion in the treatment of severe endotoxic shock in the dog. Thirty minutes after slow injection of 3 mg/kg of Escherichia coli endotoxin, fluid resuscitation with either hypertonic saline containing 1,200 mOsm of NaCl/liter (eight dogs) or normotonic saline solution (eight dogs) was started and titrated to maintain left-sided filling pressures at control level. For the next 210 min, the total amount of fluid administered was 64.5 +/- 7.8 ml/kg in the hypertonic group and 83.6 +/- 10.3 ml/kg in the normotonic group. These differences were not statistically significant. Intravascular pressures were similar in the two groups, but cardiac output, stroke volume, and oxygen consumption were significantly higher in the hypertonic group. These results therefore indicate that hypertonic saline can rapidly restore oxygen transport and tissue oxygen consumption in septic shock. The duration of these hemodynamic effects, however, remains to be determined.     

Role of leukocyte-derived pro-opiomelanocortin peptides in endotoxic shock.

The immune and neuroendocrine systems communicate and maintain homeostasis through various mechanisms, including the use of common signal and recognition molecules and the use of similar processes. This type of integrated network has profound effects on the onset and outcome of certain disease states, including endotoxic shock, in which a cascade of mediators influence the pathophysiologic responses. We have found that some of the common signal molecules shared between the immune and neuroendocrine systems are the peptide hormones adrenocorticotropin (ACTH) and endorphins (END). Our investigations have shown that these molecules are produced in vitro by cells of the immune system treated with various stimuli, including immunological stimuli such as bacterial lipopolysaccharide (LPS; endotoxin), virus infection (Newcastle virus; NDV), and the more classical neuroendocrine stimuli corticotropin-releasing hormone (CRH). We have proposed that the production of END by the peripheral immune system contributes to the pool of opioid peptides associated with the pathophysiology of endotoxic shock. Lymphocytes from LPS-sensitive C3HeB/FeJ mice but not LPS-resistant C3H/HeJ mice produce END and ACTH both in vitro and in vivo after treatment with LPS. Purification of the in vitro produced LPS-induced END from B-lymphocyte spleen cells followed by injections into both LPS-sensitive and -resistant mice elicits changes in body temperature and respiration rate. The spleen cells from the LPS-sensitive mice process ACTH and END differently depending on the stimulus for induction and the cell type in which the processing takes place. CRH or virus induce ACTH 1-39 and beta-END, whereas inductions with LPS yield major products of ACTH 1-22 to 1-26 and gamma-END, products that are for the most part unique to the immune system. We have shown that LPS induces a novel protease that functions optimally at pH 5 to cleave ACTH 1-39 into ACTH 1-22 to 1-26. This enzyme is present in LPS, but not mock or CRH-induced B cells from LPS-sensitive mice. The LPS-resistant mice did not possess this enzyme and therefore produced only the high-molecular-weight pro-opiomelanocortin (POMC)-like molecule. The inability to produce ACTH and END, presumably by their inability to process the precursor, may account, in part, for their lack of response to the LPS. The POMC peptides also may play an indirect role in orchestrating the pathophysiologic response, since both ACTH and END were shown to induce tumor necrosis factor (TNF). Our data strongly suggest that lymphocyte POMC peptides ACTH and END are important mediators in the overall response to endotoxin.     

Leukocyte response and hypoglycemia in superlethal endotoxic shock.

This laboratory has documented a progressively developing hypoglycemia associated with systemic hypotension, hepatosplanchnic pathology, and death in endotoxin-shocked dogs. Recent data documented accelerated uptake of glucose in blood following endotoxin, with certain components of the buffy coat responsible for the increased uptake. The present study utilizing the awake dog assayed a possible protective role of leukocytes against the lethal effects of endotoxin. Animals were divided into paired groups: saline controls (Group I) and endotoxin experimentals (Group II). Group II animals were injected intravenously with sublethal doses of E. coli endotoxin on 2 successive days (Days 1 and 2), LD100 on the third day, and 2 X LD100 on Day 4. The control group received equal volumes of saline on Days 1, 2, and 3, but on Day 4 received a superlethal dose of endotoxin identical to the experimental group. The awake dog became febrile and exhibited initial leukopenia with subsequent marked leukocytosis in response to endotoxin. Lethal hypoglycemia was not seen in animals demonstrating initial leukocytosis (zero time) on the day of superlethal endotoxin challenge, while animals with initial normal leukocyte counts died with low glucose concentrations (mean, 40 mg%). Results suggest that an initial leukocytosis and sustained gluconeogenic function are important factors in survivability to endotoxin shock.     

Effect of temperature on naloxone treatment in canine hemorrhagic shock

The effects of temperature on naloxone treatment in canine hemorrhagic shock were examined in 24 dogs hemorrhaged to a mean arterial blood pressure of 35 mm Hg (ambient temperature, 21 degrees C). After two hours of hypotension, the blood reservoir was clamped with no return of shed blood. Dogs were divided into three groups: Control (n = 8) received normal saline (0.5 cc/kg/hr); naloxone-cold (n = 8) and -warm (n = 8) received naloxone (2 mg/kg bolus and 2 mg/kg/hr constant infusion). Body temperature was maintained in four dogs with a warming blanket, and four dogs received no external warming. Rectal temperature fell to 34.2 +/- 0.9 degrees C in naloxone-cold animals; naloxone-warm animals were maintained at 38.6 +/- 0.1 degrees C by external warming. Control dogs rapidly deteriorated after reservoir clamping (survival, 18.6 +/- 5 min). Naloxone infusion significantly increased survival regardless of body temperature (cold, 125 +/- 21 min; warm, 199 +/- 13 min). Naloxone transiently increased mean arterial pressure and dP/dt in the colder dogs, while coronary perfusion, myocardial oxygen metabolism, and plasma beta-endorphin levels were unchanged. In the warmer dogs, naloxone significantly improved hemodynamic function and myocardial perfusion as indicated by the increased mean arterial pressure, cardiac output, stroke volume, dP/dt, and coronary blood flow. Furthermore, naloxone reduced plasma beta-endorphin levels and corrected the metabolic derangements of shock in this group. Our data indicate hypothermia significantly diminished the beneficial effects of naloxone treatment in canine hemorrhagic shock.     

Melatonin as a therapeutic agent in experimental endotoxic shock

Abstract: We demonstrated that the pineal neurohormone melatonin exerts immunoregulatory effects via T-helper 2 (Th2) cell products. Th2 products may modulate the secretion and/or action of inflammatory cytokines, which play an important role in the development of septic shock associated with endotoxemia. Here we report that a single melatonin injection protects mice treated with a lethal dose of lipolysaccharide (LPS) especially when melatonin was injected 3 to 6 hr after LPS. This effect did not apparently involve Th cells or inhibition of inflammatory cytokines or macrophage nitric oxide (NO) generation. Nevertheless, plasma nitrate concentration, which reflects the rate of NO synthesis, showed a significant reduction at 18 and 24 hr after LPS administration. Melatonin is being studied in humans for cancer immunotherapy. The data presented here identify melatonin as potential therapy for septic shock.     

Effect of fibronectin supplementation in endotoxic shock in the dog

An earlier study by our group demonstrated significant amelioration of hypotension, hypoglycemia, and acidosis in dogs treated with purified human plasma fibronectin prior to induction of endotoxic shock. The present study was completed to determine whether treatment with purified human plasma fibronectin 1 hr after induction of endotoxic shock would provide similar benefits. To this end, selected hemodynamic, pulmonary, acid-base, metabolic, hematological, and serum chemistry parameters were monitored for 6 hours in two groups of anesthetized dogs in Escherichia coli endotoxic shock. One group was given an intravenous injection of purified human plasma fibronectin, and the other received an equal volume of saline 1 hr after shock induction. Between-group analysis of the data revealed no significant differences between any parameter excepting modest differences in plasma glucose, albumin, alkaline phosphatase, and BUN concentrations. However, even these differences, although statistically significant, were sporadic and unimpressive. This study suggested that treatment of dogs with fibronectin during gram-negative endotoxic shock was not efficacious.