The liver is an important organ in the metabolism of asymmetrical dimethylarginine (ADMA)

BACKGROUND AND AIMS

Asymmetrical dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide (NO) synthase enzymes, whereas symmetrical dimethylarginine (SDMA) competes with arginine transport. Although both dimethylarginines may be important regulators of the arginine-NO pathway, their metabolism is largely unknown. Both dimethylarginines are removed from the body by urinary excretion. However, ADMA is also subject to enzymatic degradation by the enzyme dimethylarginine dimethylaminohydrolase (DDAH), which is highly expressed in the liver. To elucidate the role of the liver in the metabolism of ADMA, we aimed to investigate dimethylarginine handling of the liver in detail.

METHODS

Ten male Wistar rats were used for this study. Blood flow was measured using radiolabeled microspheres according to the reference sample method. Concentrations of dimethylarginines were measured by HPLC. The combination of arteriovenous concentration difference and organ blood flow allowed calculation of net organ fluxes and fractional extraction rates.

RESULTS

Both the liver (0.89+/-0.11) and the kidney (0.68+/-0.06) showed a high net uptake (nmol/100 g body weight (BW)/min) of ADMA, whereas a significant net uptake of SDMA was only observed in the kidney (0.34+/-0.04). For the liver, fractional extraction rates were 29.5% +/-3.0 for ADMA and 0.0%+/-3.7 for SDMA. Fractional extraction rates of ADMA and SDMA for the kidney were 36.0%+/-2.7 and 31.6%+/-3.8, respectively.

CONCLUSIONS

The liver plays an important role in the metabolism of ADMA by taking up large amounts of ADMA from the systemic circulation.

Renal arginine synthesis is impaired after experimental ischaemia–reperfusion

Background

Endogenous arginine synthesis is important for maintaining normal plasma levels of arginine. Recently it was shown that low plasma levels of arginine are the drive for renal arginine synthesis. In chronic renal insufficiency low plasma levels of arginine are common. To evaluate renal arginine synthesis in acute renal injury, as seen after periods of ischaemia during major vascular surgery, ischaemia–reperfusion of one kidney was performed in a rat model.

Methods

In this model of unilateral renal ischaemia–reperfusion male Wistar rats were used. Arginase infusion (ASE) was used to lower arginine plasma levels to 50 per cent of normal and control rats received saline infusion (SAL). After an ischaemic period of 90 min, the kidney was perfused for 150 min (IR kidney). The contralateral kidney was left in situ and served as a control (CL kidney). Blood flow measurement was performed at the end of the experiment using radiolabelled microspheres. Blood samples were taken for amino acid analysis (high-pressure liquid chromatography). Uptake or release of arginine (flux) was calculated from flow and the arteriovenous concentration difference.

Results

Infusion of arginase efficiently decreased arginine plasma levels (ASE: mean(s.d.) 45·3(4·8) μmol/dm3 versus SAL: 107·5(6·0); P < 0·0001). In SAL rats, in both IR and CL kidneys a net uptake of arginine was observed (arginine flux CL kidney: + 12·5(4·9), IR kidney: + 23·6(5·8) μmol/dm3; P not significant). Lowering arginine plasma levels by arginase resulted in production of arginine in the (non-ischaemic) CL kidney. In contrast, in the IR kidney a net uptake of arginine was seen (arginine flux CL kidney: − 5·3(2·2) μmol/dm3, IR kidney: + 10·3(3·7) μmol/dm3; P < 0·01).

Conclusion

Synthesis of arginine by the kidney was impaired after a period of acute ischaemia–reperfusion. Ischaemia–reperfusion injury of the kidney is a condition often seen after major vascular reconstruction and impaired arginine synthesis might limit substrate for the l-arginine nitric oxide pathway.

Impairment of renal blood flow after renal ischaemia–reperfusion is not aggravated by low plasma levels of arginine

Background

The fundamental role of the l-arginine–nitric oxide pathway has not been established for maintaining renal blood flow. Plasma levels of arginine appear to be rate limiting for nitric oxide synthesis in various cell types. Low plasma levels of arginine are seen after major surgery, trauma and sepsis. The present study was designed to establish the effects of low arginine plasma levels on renal blood flow during the initial phase of renal ischaemia–reperfusion.

Methods

In this unilateral renal ischaemia–reperfusion model, male Wistar rats were used. Arginase infusion (ASE) was used to lower arginine plasma levels to 50 per cent of normal; control rats received saline infusion (SAL). After an ischaemic period of 90 min, the kidney was perfused for 150 min (IR kidney). The contralateral kidney was left in situ and served as a control (CL kidney). Blood flow measurement was performed at the end of the experiment using radiolabelled microspheres. Blood samples were taken for amino acid analysis (high-pressure liquid chromatography).

Results

Infusion of arginase efficiently decreased plasma levels of arginine (ASE mean(s.d.) 45·3(4·8) μmol/dm3 versus SAL 107·5(6·0) μmol/dm3; P < 0·0001). In both SAL and ASE rats, a significantly lower blood flow was found in the IR kidney compared with the (non-ischaemic) CL kidney. Lowering arginine plasma levels by arginase did not influence renal blood flow compared with SAL, in both IR and CL kidneys.

Conclusion

In this acute, unilateral renal ischaemia–reperfusion model, low arginine plasma levels did not further aggravate renal blood flow.

The role of inducible nitric oxide synthase in lipopolysaccharide-mediated hyporeactivity to vasoconstrictors differs among isolated rat arteries

We investigated whether organ-specific differences exist in the role of inducible nitric oxide synthase (iNOS) in hyporeactivity to vasoconstrictors following 20 h in vitro exposure of isolated superior mesenteric, renal, hepatic and coronary arteries from the rat to bacterial lipopolysaccharide (LPS). LPS attenuated contraction in response to depolarizing KCl in all arteries. Maximum contractile responses to noradrenaline were attenuated in superior mesenteric and hepatic arteries, and those to the thromboxane A(2) analogue U46619 were attenuated in coronary arteries. LPS shifted the concentration-response curve to noradrenaline in renal arteries to the right. Removal of extracellular L-arginine improved the response to noradrenaline in superior mesenteric and renal arteries only. Addition of the iNOS inhibitor aminoguanidine resulted in full recovery of the responses to noradrenaline in superior mesenteric, renal and hepatic arteries. Contractile responses in coronary arteries did not improve after inhibition of iNOS activity. Therefore the pattern of the LPS-induced changes in vascular reactivity, as well as the contribution of iNOS to impaired vascular constriction, differed among vascular beds. These differences are likely to represent a contributory factor in the sepsis-associated redistribution of cardiac output.

Low arginine plasma levels do not aggravate renal blood flow after experimental renal ischaemia/reperfusion

BACKGROUND

Ischaemic renal dysfunction is present in many clinical settings, including cardiovascular surgery. Renal hypoperfusion seems to be the most important pathophysiologic mechanism. Arginine plasma levels are rate limiting for NO synthesis, and low arginine plasma levels are seen after major vascular surgery.

OBJECTIVE

to establish the effects of low arginine plasma levels on renal blood flow after renal ischaemia/reperfusion.

DESIGN

Wistar rats were used in this unilateral renal ischaemia/reperfusion model. After 70 min of ischaemia, the kidney was reperfused for 150 min. Arginase infusion was used to lower arginine plasma levels. Blood flow measurement was performed at the end of the experiment using radiolabelled microspheres. Additional experiments were performed for histopathology.

RESULTS

Arginase efficiently decreased arginine plasma levels to about 50% of normal. There was a lower blood flow in the ischaemic kidney than the contralateral (non-ischaemic) kidney. Lowering arginine plasma levels did not reduce renal blood flow in the ischaemic kidney. Renal histopathology was not influenced by lowered arginine plasma levels.

CONCLUSIONS

Lowering arginine plasma levels did not affect blood flow or histology following renal ischaemia and reperfusion.

The effect of mild endotoxemia during low arginine plasma levels on organ blood flow in rats

OBJECTIVE

Arginine is the sole precursor in the generation of the vasodilating agent nitric oxide. Arginine plasma levels are low in situations associated with endotoxemia such as major trauma, sepsis, and experimental obstructive jaundice. The aim of the study was to evaluate hemodynamics at low arginine plasma levels during a low-grade endotoxemia.

DESIGN

Randomized, placebo-controlled animal laboratory investigation.

SUBJECTS

Male Wistar rats (n = 29), anesthetized.

INTERVENTIONS

Rats were randomly assigned to receive (at t = 0 mins) an intravenous infusion of 1.5 mL of 0.9% NaCl (SAL, n = 12) or 1.5 mL of an arginase (3200 IU) solution (ASE, n = 17) over a 20-min period. After the SAL or ASE infusion, rats were randomly assigned to receive an intravenous endotoxin (lipopolysaccharide [LPS], 150 microg/kg in 1.0 mL of 0.9% NaCl; ASE/LPS, n = 10 and SAL/LPS, n = 6) challenge or a control infusion (1.0 mL of 0.9% NaCl; ASE/SAL, n = 7 and SAL/SAL, n = 6) at t = 30 mins.

MEASUREMENTS AND MAIN RESULTS

Organ blood flow was measured at t = 270 mins, using radiolabeled microspheres. At this time point, arginine plasma levels were lower in the ASE-treated rats (ASE/SAL vs. SAL/SAL and ASE/LPS vs. SAL/LPS, both p < .005, respectively). Cardiac output, mean arterial pressure, and therefore total peripheral resistance were similar for all groups. In the LPS-treated animals (SAL/LPS and ASE/LPS), cardiac output was maintained by a higher heart rate compensating the lower stroke volume. Organ blood flow to the small intestine and splanchnic blood flow was lower in the ASE/LPS-treated rats (both p < .05 when compared with other groups). Total liver blood flow was similar for all groups; the lower splanchnic blood flow was compensated for by a higher hepatic arterial blood flow.

CONCLUSION

The present study shows that low arginine plasma levels do not influence organ blood flow, whereas, during a low-grade endotoxemia, low arginine plasma levels result in reduced blood flow to the small intestine.

Kupffer cell depletion by CI2MDP-liposomes alters hepatic cytokine expression and delays liver regeneration after partial hepatectomy

BACKGROUND

Although Kupffer cells (KCs) are capable of producing important growth-stimulating cytokines, their role in liver regeneration following partial hepatectomy (PH) remains poorly understood.

METHODS

In the present study liver regeneration was studied after KC-depletion by intravenous administration of liposome-encapsulated dichloromethylene-diphosphonate (C12MDP), a method known to physically eliminate KCs. Furthermore, splenectomy was performed one week prior to PH to exclude the effect of C12MDP-liposomes on macrophage populations in the spleen.

RESULTS

KC-depletion was confirmed in cryostat liver sections stained with the monoclonal antibody ED2, a marker for resident tissue macrophages. Forty-eight hours after PH, the cumulative hepatocyte DNA synthesis, as determined in liver sections by the hepatocyte bromodeoxyuridine labeling index, was significantly decreased in KC-depleted rats when compared to control-rats. The weight of the remnant liver, expressed as a percentage of the initial liver weight, was significantly less at 96 h after PH in KC-depleted rats. KC-depletion abolished the hepatic interleukin-6 (IL-6) and interleukin-10 (IL-10) mRNA synthesis and decreased hepatic expression of tumor necrosis factor-alpha (TNF-alpha), hepatocyte growth factor (HGF) and transforming growth factor-beta1(TGF-beta1) mRNA after PH, as was assessed by reverse-transcriptase polymerase chain reaction (RT-PCR). Moreover, at 4 h after PH the systemic release of IL-6 was significantly decreased in KC-depleted rats.

CONCLUSION

We conclude that KCs are important for hepatocyte regeneration after PH. Delayed liver regeneration in KC-depleted rats can be explained, at least in part, by an imbalanced hepatic cytokine expression, thereby suppressing important growth-stimulating cytokines.

Reduced arginine plasma levels are the drive for arginine production by the kidney in the rat

In bile duct ligated rats, arginase (ASE) release from damaged hepatocytes results in low arginine (ARG) levels despite maximal renal ARG production. Plasma ARG levels were restored by reducing gut-derived endotoxemia that lowered circulating ASE activity although maintaining increased renal production. From this it was not clear if the higher renal ARG production was induced by the low grade endotoxemia or the low arginine plasma levels. The separate and combined influence of both factors on ARG metabolism was studied in the rat. Male Wistar rats received either bovine liver ASE, to lower ARG levels, or saline (SAL). Following the ASE or SAL infusion, rats were randomized to receive a low dose endotoxin (LPS) or SAL infusion. In ASE/SAL- and ASE/LPS-treated rats, ARG levels were lower compared with SAL/SAL (p<.005) and SAL/LPS (p<.005). The increased ARG production by the kidneys and gut proved to be independent of LPS but related to reduced ARG plasma levels (both p<.05 when compared with SAL/SAL and SAL/LPS). Metabolism of related amino acids was not explanatory. The study concluded that a low grade endotoxemia did not influence the metabolism of ARG by the gut, kidney, and liver. Reductions in ARG plasma by ASE treatment, irrespective a low dose endotoxin, were the drive for ARG production by the gut and the kidney.

Paradoxical changes in organ blood flow after arginase infusion in the non-stressed rat

Arginine (ARG) is the precursor of nitric oxide (NO), a potent vasodilator. Arginase (ASE) is released following hepatocellular damage, resulting in low plasma ARG levels. The effect of ASE infusion on hemodynamics was studied. Rats received a 20 min ASE or saline infusion, and systemic hemodynamics and organ blood flow were studied, at 30 and 270 min, using radiolabeled microspheres. Compared with control, ASE resulted (30 min) in 1) undetectable ARG levels; 2) higher mean arterial pressure and total peripheral resistance (both p < .05); 3) higher blood flow to the heart, kidneys, stomach, small intestine (all p < .05), and spleen (p < .001); and 4) lower vascular resistance in the heart, kidneys, stomach, and small intestine (all p < .05) and in the spleen (p < .005). At 270 min, ASE rats had similar organ blood flow and higher nitrate levels in urine and plasma (both p < .05) compared with control. We conclude that ASE reduces ARG levels with simultaneous increase in mean arterial pressure and total peripheral resistance. Higher nitrate production, suggesting higher NO formation in the presence of low ARG plasma levels, is paradoxical but could explain the higher blood flow in some organs. The increased total peripheral resistance during higher nitrate formation suggests regional differences in dependency of NO production on plasma ARG levels.

Gut endotoxin restriction improves postoperative hemodynamics in the bile duct-ligated rat

BACKGROUND

Postoperative hemodynamic disturbances in obstructive jaundice are associated with complications such as shock and renal failure. Gut-derived endotoxemia may underlie these complications. Recently, we have shown that cholestyramine treatment prevents gut-derived endotoxemia in bile duct-ligated (BDL) rats (Houdijk APJ, Boermeester MA, Wesdorp RIC, Hack CE, van Leeuwen PAM: Tumor necrosis factor unresponsiveness following surgery in bile duct-ligated rats. Am J Physiol 271: G980-G986, 1996).

METHODS

The effect of cholestyramine on systemic hemodynamics and organ blood flows after a laparotomy was studied in 2 wk BDL rats using radioactive microspheres.

RESULTS

Compared with sham-operated rats, postoperative BDL rats had 1) lower blood pressure (p < .05) and heart rate (p < .001) with higher cardiac output (p < .05), 2) lower splanchnic blood flow (p < .05), 3) lower renal blood flow (p < .01), and 4) higher splanchnic organ and renal-vascular resistances. Cholestyramine treatment in BDL rats prevented the postoperative decrease in blood pressure by increasing cardiac output (p < .01). In addition, cholestyramine maintained splanchnic blood flow at sham levels (p < .05). Furthermore, cholestyramine also prevented the fall in renal blood flow after surgery in BDL rats.

CONCLUSION

Gut endotoxin restriction using cholestyramine treatment maintained normal blood pressure, improved splanchnic blood flow, and completely prevented the fall in renal blood flow in BDL rats. Reducing the gut load of endotoxin in patients with obstructive jaundice scheduled for abdominal surgery may prevent postoperative hemodynamic complications.

Soluble glucan protects against endotoxin shock in the rat: the role of the scavenger receptor

Soluble carboxymethyl-b-1,3-glucan (CMG), a possible ligand for scavenger receptors, has macrophage-activating action but lacks the granulomatose inflammatory side effect: it is a promising immunomodulator that may mitigate the severity of sepsis. This motivated us to study in rats the effect of CMG (25 mg/kg), injected into the tail vein at 48 and 24 h prior to the administration of 5 mg/kg Escherichia coli 0127.B8 endotoxin on survival, hemodynamic condition, and, in vitro, on the chemiluminescence of PMNs and macrophages, and on macrophagal tumor necrosis factor (TNF) production. Acetylated low density lipoprotein (AcLDL) clearance in vivo and in vitro binding to macrophages was used to study scavenger receptor function. In the nonpretreated group 9 of 10 rats died during the first 24 h after endotoxin, but all CMG-pretreated rats survived. CMG-pretreatment prevented severe decreases in cardiac output and blood pressure after endotoxin. Chemiluminescence of macrophages and PMNs from CMG-pretreated rats was about two times less (p < .05) than that from nonpretreated ones; the endotoxin induced TNF production by macrophages also decreased. Pretreatment with CMG increased, but coinjection of CMG and AcLDL decreased the AcLDL clearance, while coinjection of endotoxin and AcLDL decreased the survival rate. In vitro AcLDL uptake by macrophages decreased after coinjection with CMG. Our results thus showed that CMG was protective in rat endotoxin shock, which seemed partly connected with enhancement of endotoxin clearance through scavenger receptors and to decreased TNF production.

Arginine deficiency in bile duct-ligated rats after surgery: the role of plasma arginase and gut endotoxin restriction

BACKGROUND & AIMS

Arginine deficiency may underlie the cellular immune depression after surgery in obstructive jaundice, which is associated with gut-derived endotoxemia. The aim of this study was to study arginine metabolism in the bile duct-ligated rat (BDL) after laparotomy.

METHODS

Treatment with cholestyramine, a known endotoxin binder, was used to evaluate the role of gut-derived endotoxemia.

RESULTS

In BDL rats, arginine levels were lower compared with those in sham-operated controls (P < 0.005), despite a three-fold increase in renal arginine release (P < 0.01). Liver and gut arginine handling also could not explain the reduced arginine levels. Higher plasma arginase activity (P < 0.0001) was measured in BDL rats, explaining both the lower arginine levels (r = 0.73, P < 0.01) and the increase in arginase product levels: ornithine (P < 0.005 and r = 0.72; P < 0.01) and urea (P < 0.01). Cholestyramine treatment prevented the decrease in postoperative arginine deficiency by reducing plasma arginase activity by 43% (P < 0.005). In addition, it significantly lowered plasma levels of the other liver enzymes (aspartate transaminase, alanine transaminase, gamma-glutamyl transpeptidase, and alkaline phosphatase; P < 0.05) in BDL rats.

CONCLUSIONS

The study concluded that arginine deficiency in BDL rats after surgery is caused by high plasma liver arginase activity. Cholestyramine prevented the arginine deficiency by reducing plasma arginase activity through the inhibition of additional endotoxin-mediated hepatocellular damage after surgery in BDL rats.

Influence of fluid resuscitation on renal function in bacteremic and endotoxemic rats

PURPOSE

Fluid resuscitation, which is the most important primary therapy in sepsis, is not always able to prevent acute renal failure. In this study, we investigated in two different rat models of distributive shock whether fluid resuscitation would increase renal plasma flow (RPF) and subsequently glomerular filtration rate (GFR).

MATERIALS AND METHODS

In pentobarbital anesthetized wistar rats Haemaccel (Behring Pharma, Hoechst, the Netherlands) infusion (1.2 mL/100 g/h for 3 hours) was started immediately during either bacteremia (bolus of living Escherichia coli bacteria, 10(9) or endotoxemia (1 hour infusion of E. coli endotoxin, 8 mg/kg), as well as in time-matched healthy controls.

RESULTS

After 3 hours, this treatment had increased RPF (clearance of 131I-hippurate) above normal in control (+67%) and bacteremic rats (+75%), whereas in endotoxemic animals, the significantly decreased RPF was normalized. On the other hand, in bacteremic animals, the lowered GFR (clearance of creatinine; x44%) was normalized, whereas in endotoxemic animals GFR remained depressed (x30%). The lack of improvement in GFR during endotoxemia was also indicated by a profound fall in urine flow, which by contrast steadily increased in control and bacteremic rats owing to volume loading. In both shocked groups, the decreased renal oxygen delivery was normalized, but the higher renal oxygen consumption than expected on the basis of the work needed for sodium reabsorption was not influenced by Haemaccel treatment, despite the fact that it caused this work load to rise in bacteremic but not in endotoxemic rats. In both shock models, renal cortical adenosine triphosphate content did not differ from healthy controls and was not influenced by volume loading.

CONCLUSIONS

In conclusion, our study suggests that a decrease in GFR caused by live bacteria in the circulation may benefit from fluid resuscitation, while during endotoxemia this therapy could not prevent acute renal failure.

Renal function and oxygen consumption during bacteraemia and endotoxaemia in rats

BACKGROUND

The hypothesis that renal failure during septic shock may occur as a result of hypoxia-related cell dysfunction was investigated in two rat models of distributive shock.

METHODS

Pentobarbitone-anaesthetized rats received either a bolus (1 ml) of living Escherichia coli bacteria (hospital-acquired strain, 1 x 10(9) CFU/ml; BA-group, n = 7), or a 1-h infusion of endotoxin (E. coli O127.B8: 8 mg/kg; ET-group, n = 7), or saline to serve as time matched controls (C-group, n = 7).

RESULTS

Urine flow in the BA- and ET-group reached a nadir at 1 h, but thereafter increased and reached values higher than control at 3 h. At this time point, renal oxygen delivery had decreased, in the BA-group mainly due to a fall in arterial oxygen content and in the ET-group to a fall in renal plasma flow (clearance of 131I-hippurate). However, renal oxygen extraction had significantly increased, by 31% in the BA and by 59% in the ET group, while renal oxygen consumption remained the same. Net tubular sodium reabsorption had decreased by 55% in the BA and by 25% in the ET group, due to a fall in glomerular filtration rate (clearance of creatinine). Hence, an excess oxygen consumption was found which was caused neither by an increased renal glucose release nor by the presence of an increased number of leukocytes stuck in the glomeruli. Renal tubular cells showed normal morphology. An indication that proximal tubular function in the BA and ET group remained largely intact were normal ATP levels, absence of urinary glucose, and a normal fractional excretion of sodium. However, since urine flow had increased in shocked rats at 3 h, water appeared selectively lost.

CONCLUSIONS

Our data indicate that in rat models of septic shock renal failure is not caused by cortical hypoxia or a shortage of cellular energy supply.

Laparotomy and renal function during endotoxin shock in rats

Despite the wide use of laparotomy to study kidney function, the possible influence of this procedure on systemic and renal parameters in septic rats is unknown. We studied this in anesthetized Wistar rats with and without endotoxin shock (1 h Escherichia coli O 127.B8: 8 mg.kg-1 infusion). We also compared clearance of creatinine and inulin to measure glomerular filtration rate (GFR). Laparotomy attenuated the endotoxin-induced decrease in cardiac output and abolished the increase in systemic and renal vascular resistance, while renal plasma flow was maintained. Better perfusion in other organs as well was indicated by a more gradual increase in arterial lactate concentration and less intestinal damage. By contrast, GFR decreased considerably during endotoxemia, irrespective of laparotomy. This change in GFR could be reliably assessed using creatinine clearance. The ratio of creatinine-to-inulin clearance averaged between .5 and .75. Renal ATP content did not change and the endotoxin-induced increase in the number of granulocytes lodged in glomeruli was not affected by laparotomy. In conclusion, our study indicates that laparotomy significantly influences the vascular effects caused by endotoxin. Laparotomy also revealed an effect of endotoxin on GFR, independent of renal blood flow.

Gram-negative shock in rats depends on the presence of capsulated bacteria and is modified by laparotomy

To develop a hyperdynamic sepsis model in rats, four Escherichia coli strains were used, which differed in the presence or absence of a capsule or K antigen (K1 and K-, respectively) and/or in O serogroup (O9 and O18). Of the two clinical isolates, O9K- did not survive in rat serum, whereas O18K1 and two isogenic laboratory strains (O18K1 and O18K-) were able to resist serum bacteriolysis. Pentobarbital-anesthetized rats (n = 21) received an intravenous bolus of 10(9) bacteria. In contrast to the two noncapsulated strains, both capsulated strains induced hyperdynamic shock; arterial lactate rose from a mean value of .91 to 3.09 mmol.L-1, systemic vascular resistance dropped from 1.15 to .78 mmHg.min.mL-1, and cardiac output transiently increased from 98 to 115 mL.min-1; renal plasma flow remained at 3-4 mL.min-1, whereas glomerular filtration rate decreased from 1.3 to .7 mL.min-1. Laparotomy, which is often performed to study kidney function, completely abolished the hyperdynamic condition, while glomerular filtration rate was still decreased. We conclude that in rats, in contrast to humans, capsulated bacteria are required to induce a hyperdynamic septic shock; the hyperdynamic characteristics of the shock do not occur in animals subjected to a laparotomy.

Effects of endotoxin on tone and pressure-responsiveness of preglomerular juxtamedullary vessels

Endotoxin might affect renal vasoreactivity, but in vivo this is difficult to assess (systemic influences). Therefore, we used the in vitro blood-perfused juxtamedullary nephron preparation to study early changes in preglomerular vascular reactivity induced by exposure to endotoxin. Pressure-evoked vasomotor responses were determined videometrically by measuring steady-state inside vessel diameters at a perfusion pressure of 60 or 120 mmHg. Intraluminal application of endotoxin (primary contact with endothelium) for 120 min elicited an early (within 30 min) and sustained approximately 25% vasoconstriction from arcuate artery to the distal portions of the afferent arterioles; autoregulatory responses, indicated by pressure-induced vasoconstriction, were unchanged. When topically applied, endotoxin (primary contact with smooth muscle cells) had no vasomotor effects. Significant constrictions, and increases in autoregulatory responses were obtained when the preparation was taken from kidneys from endotoxin-treated rats. Endotoxin had no effect on efferent arteriolar dimensions. Such preferential preglomerular early vasoconstriction is consistent with the early increase in renal resistance and parallel decrease in renal blood flow and glomerular filtration observed during endotoxin shock in vivo. Our results support the concept of local, endothelium-mediated effects of endotoxin on renal vessels.

The fall of cardiac output in endotoxemic rats cannot explain all changes in organ blood flow: a comparison between endotoxin and low venous return shock

During endotoxin shock mean arterial pressure (MAP) and cardiac output (CO) fall, and the latter is redistributed. To evaluate whether these changes are solely caused by the low output, or are also based on endotoxin itself, we compared regional hemodynamic changes during endotoxemia with those in a nonendotoxemic state of decreased CO in anesthetized rats. In group E (n = 10) endotoxin Escherichia coli O127:B8 (8 mg.kg-1) was infused from t = 0 till t = 60 min. In group B (n = 10) the same decrease of CO and MAP was obtained as in group E by inflating a balloon in the inferior caval vein, distal to the renal veins, from t = 0 till t = 60 min. We measured MAP, CO (thermodilution), central venous pressure, heart rate, organ blood flow, and redistribution of CO (microspheres), arterial lactate and glucose, and hematocrit. MAP and CO decreased (p < .05) in both groups (by 30 and 50%, respectively at t = 60). Heart rate, hematocrit, arterial lactate, and arterial glucose were significantly higher (p < .05) in group E (by 17, 12, 180, and 55%, respectively). Blood flow to most organs had similarly decreased in both groups. The decreased intestinal blood flow lead to macroscopic damage only in group E. Blood flows (absolute or as percentage of CO) to heart, hepatic artery, and diaphragm, however, had significantly increased in group E while blood flows to skin, skeletal muscle, and stomach had decreased more in group E. Except for the heart these differences could be explained by increased work load (detoxification: liver; hyperventilation: diaphragm, muscle) and thus to a more pronounced redistribution at the expense of skin and muscle blood flow. Regional hemodynamic changes during endotoxemia thus could largely be attributed to decrease of CO and redistribution of the circulating blood volume. In the heart, endotoxin seemed to exert effects independent of the hypodynamic state. This was also true for the intestinal damage and the rise in hematocrit and arterial lactate.

Abdominal compressions increase vital organ perfusion during CPR in dogs: relation with efficacy of thoracic compressions

STUDY OBJECTIVE

Abdominal compressions can be interposed between the thoracic compressions of standard CPR (SCPR). The resulting interposed abdominal compression CPR (IAC-CPR) may increase blood pressures and patient survival, particularly if applied as a primary technique after in-hospital cardiac arrest. We used a predominant cardiac compression canine model to study the effects of IAC-CPR on blood pressures and total and vital organ perfusion as a function of time after cardiac arrest and efficacy of SCPR.

DESIGN

In a crossover design, we measured blood pressures and total and regional blood flow (radioactive microspheres) during 6-minute episodes of mechanical SCPR and IAC-CPR, both early (4 to 16 minutes) and late (18 to 30 minutes) after induction of ventricular fibrillation in eight dogs (weight, 25 to 33 kg) under neuroleptanalgesia/anesthesia.

RESULTS

During IAC-CPR, the ascending aortic-right atrial pressure gradient increased (P < .05), and retrograde pressure pulses contributed to the rise of ascending aortic pressure. Within 2 minutes after the start of IAC-CPR, end-tidal CO2 fraction increased by 0.6 +/- 0.4 vol% (P < .05), suggesting enhanced venous return. IAC-CPR enhanced (P < .05) total forward blood flow (574 +/- 406 versus 394 +/- 266 mL/minute during SCPR for the early phase) and vital organ perfusion (including myocardium), in both early and late phases. The IAC-CPR-induced augmentation of blood flow was greater if perfusion was relatively high during SCPR.

CONCLUSION

Compared with predominant cardiac compressions alone (SCPR), the addition of interposed abdominal compressions (IAC-CPR) improves total and vital organ oxygen delivery through enhanced venous return and perfusion pressures.

Protective role of NO in the regional hemodynamic changes during acute endotoxemia in rats

The role of NO during the first hour of endotoxemia is still controversial. To evaluate whether NO is protective or detrimental to the regulation of systemic blood pressure, cardiac output (CO), and organ perfusion in rats during acute endotoxemia, we have studied the effects of inhibition of NO synthesis. Thirty minutes after 0.1 mg NG-nitro-L-arginine (L-NNA; group L, n = 7, partial inhibition), 1 mg L-NNA (group H, n = 6, complete inhibition), or saline (group E, n = 7) intravenous infusion, anesthetized volume-loaded rats were infused with endotoxin Escherichia coli O127:B8 (8 mg.kg-1 x h-1) from time (t) = 0 to 60 min. Organ blood flow was measured with radioactive microspheres. In group H, at time 0, CO was lower than in group E (by -29%; P < 0.05), and systemic vascular resistance (SVR) was higher than in groups E and L (by 72 and 51%, respectively; P < 0.05). Perfusion of the pancreas, stomach, intestines, and kidney was lower (P < 0.05) and corresponding organ vascular resistance (OVR) higher (P < 0.05) in group H than in groups E and L (except kidney in group L). At t = 60 min, in groups H and L, CO was lower (by -45 and -26%, respectively; P < 0.05) and SVR was higher (by 112 and 54%, respectively; P < 0.05) than in group E. In group L only blood flow to the heart, pancreas, intestines, and kidney was significantly lower than in group E, and corresponding OVR was higher.(ABSTRACT TRUNCATED AT 250 WORDS)

Systemic and regional hemodynamic changes during endotoxin or platelet activating factor (PAF)-induced shock in rats

To evaluate the role of platelet activating factor (PAF) during endotoxin shock, we compared its effects with those of endotoxin. We measured arterial pressure (MAP), heart rate (HR), cardiac output (CO; thermodilution), arterial lactate (Calact), organ blood flow (radioactive microspheres), and organ vascular resistance in four groups of anesthetized (pentobarbital) male Wistar rats (n = 7 per group), infused from t = 0 to t = 60 min with saline (group C: time matched control), endotoxin Escherichia coli O127:B8, 8 mg.kg-1 (group E), a "low PAF dose" (1 microgram.kg-1) to cause the same decrease in MAP as in group E (group PL), or a "high PAF dose" (3 micrograms.kg-1) to cause the same decrease in CO as in group E (group PH). At t = 60 min, MAP had decreased by 33% in E and PL, and by 55% in PH group. CO had decreased by 41% in the E and PH group. Calact had increased in the E and PH group by 300 and 200%, respectively. In the E, PL and PH group, coronary vascular resistance decreased. In the splanchnic organs, endotoxin caused a decrease in blood flow due to vasoconstriction, whereas PAF (both concentrations) caused vasodilation (except for spleen). Renal vascular resistance decreased (P < 0.05) in the PL group. In all groups, vascular resistance had increased (P < 0.05) in skin, and not changed in skeletal muscle (P < 0.05). Thus, hemodynamic changes after PAF infusion were partially similar to those after endotoxin infusion (coronary vasodilation and vasoconstriction in spleen and skin).(ABSTRACT TRUNCATED AT 250 WORDS)

Organ blood flow and distribution of cardiac output in dopexamine- or dobutamine-treated endotoxemic rats

Endotoxemia causes a decrease of blood flow to most organs. If this could be prevented, chances of survival might improve. In endotoxemic rats, we studied the effect of a therapeutic infusion of dopexamine (dopaminergic, beta 2-adrenergic) on blood flow and percentage of the cardiac output distributed to heart, brain, hepatic artery, stomach, intestines, spleen, pancreas, kidneys, adrenals, diaphragm, skeletal muscle, and skin. Dopexamine action was compared with that of dobutamine (beta 1-adrenergic). Endotoxin shock was induced in 28 rats with infusion of 8 mg/kg Escherichia coli O127:B8 endotoxin from 0 to 60 minutes; the rats were then divided into 3 groups, which received from 60 to 135 minutes of an infusion of saline (ES; n = 10), dopexamine hydrochloride (DX, 3 x 10(-8) mol/kg.min; n = 10) or dobutamine (DB, 10(-7) mol/kg.min; n = 8). A fourth group served as time-matched controls (C, saline from 0 to 135 minutes; n = 8). In the untreated endotexemic rats, cardiac output decreased and organ blood flow decreased except in the diaphragm, heart, and brain; the percentage of the cardiac output to those organs increased. Dopexamine and dobutamine similarly improved cardiac output in endotoxemic rats. All organs benefitted to the same extent from the increased cardiac output. Therapeutic infusion of dopexamine during endotoxemia did not favor flow to any particular organ; redistribution of cardiac output changed little after administration of dopexamine, and its effects were not significantly different from those of dobutamine.

Development of renal failure in endotoxemic rats: can it be explained by early changes in renal energy metabolism?

Endotoxin shock not only causes renal failure, endotoxemia also leads to metabolic impairment, resulting in energy shortage and loss of cellular integrity; therefore, we tested the hypothesis that early changes in renal metabolism contribute to the development of acute renal failure during endotoxin shock. Endotoxin (Escherichia coli 127B8; 8 mg/kg from t = 0 to 60 min) was infused in three groups of 8 rats, in which renal biopsies were taken at t = 30, 50 and 90 min, respectively; a fourth group (n = 8) served as control. In the biopsies, glucose, lactate, ATP, ADP, AMP and creatine phosphate concentrations were determined. Renal plasma flow (RPF) and glomerular filtration rate (GFR) were measured from the clearances of 131I-hippurate and 125I-thalamate, respectively. We also assayed urine flow (V; catheter in the bladder), cardiac output (CO), blood pressure (MAP), heart rate (HR) and arterial lactate, glucose and creatinine concentrations. During the first 30 min of endotoxemia, we found no systemic hemodynamic or biochemical changes. From t = 30 to t = 90, CO and MAP decreased to 59 and 70%, respectively, while HR and serum levels rose to 110 and 800%, respectively (p < 0.05), indicating progression of shock. Renal function clearly deteriorated from t = 30; at t = 90 RPF, GFR and V had decreased by 86, 84 and 86%, respectively, plasma creatinine being 193% of the baseline value (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Metabolic vasodilatation with glucose-insulin-potassium does not change the heterogeneous distribution of coronary blood flow in the dog

OBJECTIVE

The heterogeneous distribution of coronary blood flow could represent regional differences in demand, or mismatching of regional O2 supply to demand, caused by regionally exhausted vasodilatation (anatomical/mechanical factors) or by regional arteriovenous diffusional O2 shunting. Regional coronary blood flow and global myocardial oxygenation and metabolism were measured during metabolic vasodilatation with glucose-insulin-potassium (GIK).

METHODS

Variables were studied before and 30 and 60 min after start of a 30 min infusion of GIK (50% glucose, 4 ml.kg-1, 8 mM KCl, and 3 U insulin.kg-1). Regional blood flows were measured by radioactive microsphere technique and cardiac output by thermodilution. Experimental subjects were six anaesthetised mongrel dogs, weighing 20-27 kg.

RESULTS

GIK increased plasma osmolarity and lactate, decreased haemoglobin, and increased cardiac output by 67(29)% and systemic O2 supply by 32(13)%, at unchanged arterial and central venous pressures and heart rate. Coronary blood flow rose by 97(50)% and left ventricular O2 supply by 56(41)%. Although regional blood flows in small tissue samples of about 1 g in the left ventricle ranged from a factor 0.31 to 1.73 of mean flow, GIK did not change flow heterogeneity and regional flows significantly correlated in time. Left ventricular O2 uptake rose by 42(40)%, while venous PO2 increased and O2 extraction decreased. Global lactate uptake increased at unchanged extraction. Changes were reversed after GIK.

CONCLUSIONS

GIK transiently increases myocardial O2 uptake following a raised cardiac output, caused by a hyperosmolarity induced rise in cardiac contractility rather than by haemodilution. Although myocardial O2 supply is distributed heterogeneously, the fractional rise with GIK is almost equal among regions. At constant lactate extraction, increased venous PO2 and decreased O2 extraction do not indicate overperfusion in some regions at the cost of underperfusion in others, are probably caused by a small, direct vasodilating effect of hyperosmolarity, and argue against diffusional O2 shunting. As for global O2 supply to demand, the increase in regional O2 supply is probably well adapted to regionally increased demand during GIK, so that the heterogeneous distribution of O2 supply can be explained by regional differences in demand and not by regionally exhausted vasodilatation or O2 shunting.

Maldistribution of heterogeneous coronary blood flow during canine endotoxin shock

STUDY OBJECTIVE - The aim was to investigate whether heterogeneous coronary blood flow is maldistributed during endotoxin shock. DESIGN - Variables were studied before (t = 0) and at t = 90 and t = 120 min after bolus injection of saline (n = 6) or endotoxin (n = 6). SUBJECTS - 12 anaesthetised mongrel dogs, weight 20-27 kg, were used. MEASUREMENTS AND MAIN RESULTS - We studied myocardial blood flows in small tissue sections (of about 1 g in left and 2 g in right ventricle) with radioactive microspheres, together with haemodynamic variables and global myocardial metabolism. At t = 0 min in controls, regional flows per 100 g were heterogeneous and ranged from a factor 0.2 to 2.7 and 0.6 to 1.6 of mean flow per 100 g to the left and right ventricle respectively; heterogeneity was unchanged at t = 90 and t = 120 min. Between t = 0, t = 90, and t = 120 min regional flows correlated: r = 0.78(SD 0.14), n = 18, for left ventricle, and r = 0.70(0.17) for right ventricle. In the endotoxin group, cardiac output and mean arterial pressure decreased by 44(7) and 48(11)% respectively, and lactate increased by 3.2(0.6) mmol.litre-1 at t = 120 min. Global left ventricle blood flow and delivery and metabolism of O2 were unchanged; lactate extraction and external work fell. The ratio between global right ventricular O2 delivery and external work also rose. Regional blood flows ranged from a factor 0.2 to 2.7 and 0.1 to 1.8 of mean flow to left and right ventricles respectively; heterogeneity did not differ from controls and did not change with time. Flow correlations with time were reduced: 0.45(0.24) for left ventricle and 0.45(0.26) for right ventricle (both n = 18, p less than 0.005 v controls). The left ventricular endocardial to epicardial flow ratio fell; flow was redistributed to both layers. CONCLUSIONS - Heterogeneous blood flow is redistributed throughout the heart during canine endotoxin shock so that, at unchanged global blood flow and flow heterogeneity, flow decreases in some but increases in other areas. Flow maldistribution may be associated with focal ischaemia, which may be masked by a rise in O2 uptake for a given workload (contractile inefficiency) in overperfused areas, and may thereby contribute to a fall in global myocardial external work for a given O2 delivery.

Whole body plasma extravasation in saline and Haemaccel loaded rats: effects of endotoxemia

Endotoxin causes only a limited increase in plasma leakage in rats. This may be due to a concomitant fall in venous pressure. We therefore studied effects of increases in this pressure on plasma loss. After a 60 min. endotoxin (20 mg/kg. hr E coli 0127-B8) or saline (control) infusion anesthetized rats were volume loaded (3 ml/10 min. 100 g for 10 min.) at t = 120 min. with saline (shock group n = 8; control group n = 8) or Haemaccel (shock group n = 6; control group n = 8). At t = 180 min. the experiments ended. We measured mean arterial and central venous pressure, heart rate, arterial lactate, blood volume (51Cr-labeled red cells), hematocrit (conductivity cell), macromolecular extravasation (125I-HSA) and fluid retention (calculated from change in plasma volume). Whole body transcapillary filtration coefficient (Kf) and interstitial compliance (Ci) were obtained from saline retention curves. During volume loading central venous pressure increased, then fell again. At the end of saline loading (t = 130) 50 and 60% of infused volume remained intravascularly in control and endotoxin treated rats, respectively; at the end of Haemaccel infusion retention was 110 and 120%, respectively. Fifty minutes later (t = 180) it was 25 and 30% after saline loading and 50 and 60% after Haemaccel loading in control and endotoxin treated rats, respectively. Between control and endotoxin group filtration coefficients (Kf; .094 vs .111 ml/min.mmHg.100 g, respectively) and compliances (Ci; 1.90 vs 1.58 ml/mmHg.100 g, respectively) were not significantly different. No increase in leakage of 125I-HSA was found in either group. Increased venous pressure thus did not reveal an increase in macromolecular permeability in endotoxin treated rats.

Blood flow and plasma extravasation in skeletal muscle during endotoxemia. A study in rats

Apparently skeletal muscle is little affected during endotoxemia. We therefore studied in anesthetized rats the effects of endotoxin on blood flow and extravasation of plasma in skeletal muscle of different regions (thorax, abdomen, foreleg, hind limb) and whether or not extravasation, if present, is related to hypoperfusion. Endotoxemia was induced by infusion of E. coli endotoxin (10 mg/kg) from t = 0 to t = 60 min (E-group: n = 8); control rats received saline (C-group: n = 8). One femoral artery (C:n = 6, E: n = 6) was ligated to cause muscle hypoperfusion in that limb. Experiments ended at t = 120 min. Cardiac output and blood flow were measured at t = 0 and 120 (radioactive microspheres); extravasation was measured with a double isotope technique: 125I-HSA as plasma and 51Cr-labeled red cells as intravascular marker (injected at t = -50 and t = -40 min, respectively). Cardiac output decreased and lactate levels increased markedly during endotoxemia, but muscle blood flow was not affected: percentage of cardiac output to muscles increased in all regions (by 50-100%, p less than 0.05). Femoral artery ligation caused a 33% decreased in muscle blood flow at t = 0; at t = 120 the reduction was 88% in the E-, but only 15% in the C-group. Extravasation of 125I-HSA (from t = 0 to t = 120, as percentage of the total integrated plasma supply over 2-hr) increased during endotoxemia for abdominal, thoracic and foreleg muscles by 178, 148 and 133%, respectively (p less than 0.05). In the non-ligated hind limb endotoxin had no significant effect on extravasation; hypoperfusion alone caused a 300% increase (p less than 0.05%) and the combined effect was a 400% increase (p less than 0.05) in extravasation. Our results show that during endotoxemia muscle blood flow hardly decreases, and that plasma extravasation is only substantial when muscle blood flow is also severely impaired.

Effects of endotoxemia on systemic plasma loss and hematocrit in rats

Endotoxemia in rats increases plasma extravasation but does not result in continuously rising hematocrit. These contradictory observations led us to design a study in anesthetized rats (C, control rats, n = 10; E, endotoxin rats, n = 10) in which we continuously measured in blood hematocrit (conductivity cell) and changes in concentration of 125I-HSA (human serum albumin) and 51Cr-labeled red cell (51Cr-RBC; multichannel analyzer) in an extracorporeal circuit. In two additional series of experiments we measured in blood samples changes in protein concentration (series II, C: n = 7, E: n = 7) and uptake of intraperitoneally injected 125I-HSA and 51Cr-RBC (reflecting lymph flow rate; series III, C: n = 6, E: n = 7). Endotoxemia was induced by infusion (iv, 0.2 ml/100 g.hr) of Escherichia coli endotoxin (20 mg/kg) from t = 0 to t = 60 min; controls received saline. Experiments ended at t = 120 (series I and II) or 150 min (series III). The endotoxemia resulted in a marked rise of serum lactate (by ca 500% at t = 120); heart rate increased and central venous pressure decreased (by ca 20 and -95% at t = 120, respectively). All rats showed characteristic changes in hematocrit during endotoxemia: an increase from t = 20 to t = 45 (by ca 9%) followed by a decrease to preshock values or less at t = 120. The 51Cr activity per microliter blood cells did not change, indicating that there was no red cell mobilization. Protein concentration and 125I-HSA activity also showed a temporary increase during endotoxemia, but 125I-HSA activity per gram protein was decreased. Peritoneal uptake of 125I-HSA and 51Cr-RBC was significantly increased during endotoxemia (by 200%). We conclude that fluid extravasation during endotoxemia is temporary, mainly concerns plasma water, and is compensated by mechanisms like reabsorption and increased lymph flow, resulting in restoration of plasma volume.

Regional lactate production in early canine endotoxin shock

High serum lactate may not reflect the severity of endotoxin shock: the lactate load could even be formed immediately after the endotoxin challenge. During the first 30 min after endotoxin injection (Escherichia coli; 1.5 mg/kg iv) into anesthetized dogs (4 mg.kg-1.h-1 etomidate, n = 19) we studied arterial lactate concentration; contributions of portal and splanchnic (n = 6), renal and pulmonary (n = 7), and femoral (n = 6) vascular beds to the early lactate rise; and regional O2 extraction and blood flow (microspheres). In control dogs (n = 5, no endotoxin), we found no significant hemodynamic and biochemical changes. Endotoxin caused an immediate decrease in blood pressure, cardiac output, and organ perfusion, followed by recovery after approximately 5 min to approximately 75% of preshock values at t = 30 min (except for renal blood flow, which remained low). Arterial lactate concentration started to increase almost immediately after endotoxin and increased rapidly until t = 15 min (to 300%) and then leveled off, but in spite of the hemodynamic recovery it remained elevated. A major part of the early increase in lactate concentration can be explained by splanchnic lactate production. The total splanchnic bed released more lactate than the portal bed, indicating that the liver produces lactate. We conclude that the lactate concentration later in canine endotoxin shock depends on events that occur during early shock in which the liver may play a crucial role.

Changes in regional plasma extravasation in rats following endotoxin infusion

Regional differences in plasma extravasation during endotoxin shock in rats and a possible relationship with changes in regional blood flow were studied with radioactive isotopes (125I-HSA, 51Cr-labeled red blood cells, microspheres) in anesthetized rats (pentobarbital). Shock was induced by intravenous infusion of endotoxin (Eschericia coli; 10 mg X kg-1) for 60 min (starting at t = 0); at t = 120 min, the experiments were terminated. These rats (n = 8) were compared with time-matched control rats (n = 8). A third group (rats killed 7.5 min after injection of 125I-HSA, i.e., no extravasation; n = 8) served as baseline. The amount of plasma extravasated in 2 hr of endotoxin shock was significantly increased over control values in skin (by 67%), colon (88%), skeletal muscle (105%), stomach (230%), pancreas (300%), and diaphragm (1300%). Losses of 125I-HSA into intestinal lumen and peritoneal cavity had also increased over control values by 146 and 380%, respectively. Blood flow was compromised in most organs except heart and diaphragm. Extravasation when normalized for total plasma supply was correlated with total blood supply; the more the blood supply decreased, the higher the normalized extravasation. In the diaphragm, however, blood supply and plasma leakage increased together. Decreased blood supply and plasma extravasation may be related but they could also be simultaneously occurring independent phenomena with a common origin.

Myocardial metabolic and morphometric changes during canine endotoxin shock before and after glucose-insulin-potassium

Glucose-insulin-potassium (GIK) improves myocardial function during endotoxin shock but the mechanism of this action is not clear. We have studied in open chest dogs the effects of GIK (n = 9) on haemodynamics, myocardial biochemistry (repeated drill biopsies; glucose-6-phosphate, G-6-P; fructose-6-phosphate, F-6-P; adenosine triphosphate, ATP; creatinine phosphate, CP; glycogen) and myocardial histomorphometry. The animals were anaesthetised (etomidate 4 mg X kg-1 X h-1) and artificially ventilated (N2O:O2 = 2:1). After endotoxin (1.5 mg X kg-1) cardiac output (CO) and mean arterial pressure (MAP) fell rapidly, with a temporary recovery followed by gradual circulatory collapse. Coronary blood flow (cbf; radioactive microspheres) decreased, but this was not significant. G-6-P tended to fall, as did ATP levels while CP levels were unaltered. Histomorphometrical analysis showed myocardial cell swelling with compression of capillaries and decreased interstitial volume. GIK infusion (50% glucose, 2 g X kg-1bw, 8 mmol KCl and 3 U insulin kg-1bw) increased CO and coronary blood flow. Glycogen and G-6-P levels did not change, while F-6-P tended to increase. ATP levels were not influenced by ATP/CP ratio decreased. Myocardial cell swelling markedly decreased; average capillary cross-sectional area, as an index of capillary compression, returned to control value. In two dogs, which died before the end of the experiment, myocardial oedema, with disturbed capillary volume and reduced interstitial volume was unaltered after GIK. The initial effects of GIK are most likely due to restoration of myocardial perfusion. Improved perfusion, and the influence of elevated serum osmolality and insulin levels on excitation-contraction coupling may help to improve myocardial function.

Skeletal muscle perfusion and metabolism during canine endotoxin shock

Conflicting data exist in literature about the effects of endotoxin on skeletal muscle perfusion and metabolism during canine endotoxin shock. In 12 dogs we therefore studied (six control and six endotoxin treated, 1.5 mg X kg-1) under etomidate (4 mg X kg-1 X h-1) anaesthesia muscle blood flow (radioactive microspheres) in fore limb, thorax, diaphragm and hind limb (five different muscles) and skin blood flow before (t = 0) and 90 and 120 min after endotoxin. We also measured blood flow in the femoral artery and vein (electromagnetic flow transducers) and the arteriovenous differences of oxygen, lactate, glucose and FFA over the femoral vascular bed (at t = 0, 30, 90 and 120 min). Endotoxin administration caused a fall of flow in the femoral artery and vein (by 65 and 63%, respectively at t = 15). After t = 60 flow in the femoral artery and vein increased slowly but the flows were still below the preshock values at t = 20 (by 33 and 50%, respectively). Skeletal muscle and skin flow did not decrease or even increased after endotoxin but decreased in the control group. Percentage of cardiac output distributed to brachial, intercostal and hind limb muscle and skin increased after endotoxin (by 163, 167, 111 and 120%, respectively at t = 20). The five muscles of the hind limb did not respond differently to endotoxin. In spite of diminished arterial inflow, skeletal muscle perfusion was thus maintained in the hind limb, probably due to closing of shunts and redistribution of blood away from bone. Oxygen extraction but also lactate release by the femoral bed had increased during endotoxin shock. After endotoxin femoral glucose extraction was only elevated at t = 30 when arterial glucose concentration had also increased. The femoral bed produced free fatty acids (FFA) but during endotoxin shock the arteriovenous concentration difference of FFA decreased. Our data suggest that skeletal muscle flow nor oxygen consumption and glucose metabolism is affected during 2 h of canine endotoxin shock. Lactate production, however, tended to increase.

Distribution of cardiac output, oxygen consumption and lactate production in canine endotoxin shock

Endotoxin causes shock accompanied by compensatory changes such as redistribution of cardiac output and increased oxygen extraction. We studied these effects in anaesthetised dogs (etomidate: 4 mg X kg-1 X h-1, n = 14) randomly assigned to a control (n = 6) and a shock group (endotoxin 1.5 mg X kg-1; n = 8). We measured left ventricular pressure, LVEDP and LVdP/dt (Millar microtip), mean systemic, central venous and pulmonary artery pressure (Statham P23Db), cardiac output (thermodilution), organ flow (microspheres, 15 micron, 5 labels), bloodgases (PO2, PCO2), pH and lactate. All measurements were performed before and at 60, 90, 120 and 150 min after endotoxin or saline. Sixty minutes after endotoxin mean systemic pressure, LVdP/dt and cardiac output had decreased (by 60, 50 and 35%), while heart rate had increased (by 30%). Arterial PO2 was lower after endotoxin (-29%), haematocrit and mixed venous PCO2 were higher (+16 and +38%) and arterial pH had decreased from 7.34 to 7.14. After endotoxin perfusion of heart and adrenals did not change but muscle perfusion increased (by 33% at t = 90). Endotoxin caused vasoconstriction in spleen and kidneys: the percentage of cardiac output to these organs thus decreased (by 50 and 69%). Sixty minutes after endotoxin we found vasodilatation in the hepatic arterial, pancreatic, and gastrointestinal beds. Later the percentage of cardiac output to these beds decreased. Systemic arterio-venous shunting fell (from 6.5 to 0.7%). Systemic and splanchnic oxygen extraction increased (by 66 and 71% at t = 60): oxygen consumption hardly changed; 60 min after endotoxin it tended to decrease. During shock serum lactate rose (by 167% at t = 60) before oxygen consumption fell. Myocardial oxygen consumption did not alter during shock but the tension time index decreased.