Septic shock and chemotherapy-induced cytopenia: effects on microcirculation.

PURPOSE: Neutrophil and platelet activation and their interactions with endothelial cells are considered central features of sepsis-induced microcirculatory alterations. However, no study has evaluated the microvascular pattern of septic shock patients with chemotherapy-induced severe cytopenia. METHODS: Demographic and hemodynamic variables together with sublingual microcirculation recording [orthogonal polarization spectral imaging enhanced by sidestream dark-field technology (OPS-SDF) videomicroscopy] were collected in four groups of subjects: septic shock (SS, N = 9), septic shock in cytopenic patients (NSS, N = 8), cytopenia without infection (NEUTR, N = 7), and healthy controls (CTRL, N = 13). Except for controls, all measurements were repeated after complete resolution of septic shock and/or neutropenia. Video files were processed using appropriate software tool and semiquantitatively evaluated [total vascular density (TVD, mm/mm(2)), perfused vessel density (PVD, mm/mm(2)), proportion of perfused vessels (PPV, %), mean flow index (MFI), and flow heterogeneity index (FHI)]. RESULTS: Compared with controls, there were statistically significant microcirculatory alterations within all tested groups of patients (TVD: SS = 8.8, NSS = 8.8, NEUTR = 9.1 versus CTRL = 12.6, p < 0.001; PVD: SS = 6.3, NSS = 6.1, NEUTR = 6.9 versus CTRL = 12.5, p < 0.001; PPV: SS = 71.6, NSS = 68.9, NEUTR = 73.3 versus CTRL = 98.7, p < 0.001; MFI: SS = 2.1, NSS = 1.9, NEUTR = 2.1 versus CTRL = 3.0, p < 0.05; FHI: SS = 1.0, NSS = 0.9, NEUTR = 0.6 versus CTRL = 0.0, p < 0.001). No significant differences were detected between SS, NSS, and NEUTR groups at baseline. Incomplete restoration of microcirculatory perfusion was observed after septic shock and/or neutropenia resolution with a trend towards better recovery in MFI and FHI variables in NSS as compared with SS patients. CONCLUSIONS: Microvascular derangements in septic shock did not differ between noncytopenic and cytopenic patients. Our data might suggest that profound neutropenia and thrombocytopenia do not render microcirculation more resistant to sepsis-induced microvascular alterations. The role and mechanisms of microvascular alterations associated with chemotherapy-induced cytopenia warrant further investigation.

Hypothermic anticoagulation: testing individual responses to graded severe hypothermia with thromboelastography.

Selective incircuit blood cooling could be an effective anticoagulation strategy during hemodialysis. However, it is currently unknown what blood temperature would ensure sufficient anticoagulation. Similarly, no information exists about potential interindividual variability in response to graded hypothermia. Therefore, the aim of this study was to analyze effects of profound hypothermia on human coagulation. Furthermore, a mathematical relationship between blood temperatures and coagulation was sought to predict individual responses to blood cooling. It was designed as a laboratory study. Thromboelastography (TEG) measurements were taken at a temperature range of 38-12°C. To enable measurements below 20°C, the TEG device was placed into an air conditioned chamber allowing for setting of the temperatures over a wide range. The data were analyzed by regression analysis for pooled and individual measurements. Decreasing temperatures always led to a progressive reduction in blood coagulation by delaying the initiation of thrombus formation, as well as by decreasing the speed of its creation and growth. However, the response to cooling was not uniform and the interindividual variability exists. The relationship between blood temperature and coagulation is not linear but exponential (parameters R and K) and sigmoid (parameter α-angle). The lower the blood temperature, the more significant effect on blood coagulation decline. To predict an individual response of the coagulation system over a wide range of temperatures, a mathematical modeling can be used.

Searching for mechanisms that matter in early septic acute kidney injury: an experimental study.

INTRODUCTION: In almost half of all sepsis patients, acute kidney injury (AKI) develops. However, the pathobiologic differences between sepsis patients with and without AKI are only poorly understood. We used a unique opportunity to examine dynamic inflammatory, renal hemodynamic, and microvascular changes in two clinically relevant large-animal models of sepsis. Our aim was to assess variability in renal responses to sepsis and to identify both hemodynamic and nonhemodynamic mechanisms discriminating individuals with AKI from those in whom AKI did not develop. METHODS: Thirty-six pigs were anesthetized, mechanically ventilated, and instrumented. After a recovery period, progressive sepsis was induced either by peritonitis (n = 13) or by continuous intravenous infusion of live Pseudomonas aeruginosa (n = 15). Eight sham operated-on animals served as time-matched controls. All animals received standard intensive care unit (ICU) care, including goal-directed hemodynamic management. Before, and at 12, 18, and 22 hours of sepsis, systemic and renal (ultrasound flow probe) hemodynamics, renal cortex microcirculation (laser Doppler), inflammation (interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), oxidative stress (thiobarbituric acid reactive species (TBARS), nitrite/nitrate concentrations (NOx), and renal oxygen kinetics and energy metabolism were measured. RESULTS: In 14 (50%) pigs, AKI developed (62% in peritonitis, 40% in bacteria infusion model). Fecal peritonitis resulted in hyperdynamic circulation, whereas continuous bacteria infusion was associated with normodynamic hemodynamics. Despite insults of equal magnitude, comparable systemic hemodynamic response, and uniform supportive treatment, only those pigs with AKI exhibited a progressive increase in renal vascular resistance. This intrarenal vasoconstriction occurred predominantly in the live-bacteria infusion model. In contrast to AKI-free animals, the development of septic AKI was preceded by early and remarkable inflammatory response (TNF-α, IL-6) and oxidative stress (TBARS). CONCLUSIONS: The observed variability in susceptibility to septic AKI in our models replicates that of human disease. Early abnormal host response accompanied by subsequent uncoupling between systemic and renal vascular resistance appear to be major determinants in the early phase of porcine septic AKI. Nonuniform and model-related renal hemodynamic responses that are unpredictable from systemic changes should be taken into consideration when evaluating hemodynamic therapeutic interventions in septic AKI.

Sepsis and acute kidney injury are bidirectional.

Sepsis is the most common cause of acute kidney injury (AKI). There has been a growing body of evidence demonstrating the association between worsening of kidney function during sepsis and the risk of short- and long-term mortality. AKI in sepsis is associated with poor outcome and independently predicts increased mortality. Sepsis-associated AKI may therefore serve as a biomarker of adverse physiological events that portends worse outcome. Conversely, the important role of sepsis among intensive care unit patients with nonseptic AKI is increasingly being recognized. Indeed, sepsis represents a significant contributing factor to the overall mortality and incomplete recovery of kidney function in subjects who developed nonseptic AKI. Because AKI portends such an ominous prognosis in sepsis and vice versa, there has been a surge of interest in elucidating mechanisms underlying the complex and bidirectional nature of the interconnections between AKI, sepsis and multiorgan dysfunction. Accumulating data indicate that AKI can trigger several immune, metabolic and humoral pathways, thus potentially contributing to distant organ dysfunction and overall morbidity and mortality. The expanding population of patients with sepsis and AKI, and the associated excess mortality provide a strong basis for further research aimed at addressing more rigorously all potentially modifiable factors to reduce this burden to patients and health care systems. Better insights into bidirectional and synergistic pathways linking sepsis and AKI might open the window for new therapeutic approaches that interrupt this vicious circle. Here, we discuss the rationale for and the current understanding of the bidirectional relationship between AKI and sepsis.

Pharmacokinetic evaluation of voriconazole treatment in critically ill patients undergoing continuous venovenous hemofiltration.

INTRODUCTION: Voriconazole represents an essential part of antimicrobial therapy in critically ill patients. The aim of this study was to exclude a significant alteration in voriconazole pharmacokinetics in critically ill patients undergoing continuous venovenous hemofiltration (CVVH). METHODS: Six patients dependent on CVVH with evidence of an invasive mycotic infection treated with intravenous voriconazole at the standard dosing regimen were investigated. The total serum concentration of voriconazole in arterial blood and the concentration in ultrafiltrate were measured by reverse-phase high-performance liquid chromatography with ultraviolet detection. The authors profiled a 5-point pharmacokinetic concentration-time curve during the 12-hour standard maintenance dosing interval and derived the basic pharmacokinetic parameters. RESULTS: The serum voriconazole concentration did not decrease <1.0 mg/L at any time point, and the mean was 4.3 ± 2.6 mg/L and the median (range) 3.6 (9.0) mg/L. The sieving coefficient of the drug did not exceed 0.30 in any patient (0.22 ± 0.08). The mean serum AUC0-12, the mean total clearance, and the mean clearance via CVVH were 53.52 ± 29.97 mg·h/L [the median (range) of 57.74 (62.34) mg·h/L], 0.11 ± 0.07 L·h-1·kg-1, and 0.007 ± 0.003 L·h-1·kg-1, respectively. The clearance by the CVVH method ranged from 4% to 20% of the total drug clearance. The disposition of voriconazole was not compromised. The mean elimination half-life was 27.58 ± 35.82 hours [the median of 13.10 (92.21) hours], and the mean distribution volume value was 3.28 ± 3.10 L/kg [the median of 2.01 (8.10) L/kg]. Marked variability in serum concentrations, elimination half-life, distribution volume, and total clearance was seen. Half of the patients showed some drug accumulation. CONCLUSIONS: The clearance of voriconazole by CVVH is not clinically significant. In view of this finding, voriconazole dose adjustment in patients undergoing the standard method of CVVH is not required. However, the observed potential for an unpredictable voriconazole accumulation suggests the usefulness for monitoring its levels in critically ill patients.

Plasma and tissue levels of neuropeptide y in experimental septic shock: relation to hemodynamics, inflammation, oxidative stress, and hemofiltration.

Neuropeptide Y (NPY), a potent vasoconstrictor released from the sympathetic nerves, has been suggested to counterbalance sepsis-induced vasodilation. Thus, the changes in plasma and tissue NPY concentrations in relation to hemodynamic variables and inflammatory markers in a porcine model of moderate septic shock were investigated. Susceptibility of NPY to be removed by continuous hemofiltration in two settings has been also studied. Thirty-four domestic pigs were divided into five groups: (i) control group; (ii) control group with conventional hemofiltration; (iii) septic group; (iv) septic group with conventional hemofiltration; and (v) septic group with high-volume hemofiltration. Sepsis induced by fecal peritonitis continued for 22 h. Hemofiltration was applied for the last 10 h. Hemodynamic and inflammatory parameters (heart rate, mean arterial pressure, cardiac output, systemic vascular resistance, plasma concentrations of tumor necrosis factor-α, interleukin-6, and NPY) were measured before and at 12 and 22 h of peritonitis. NPY tissue levels were determined in the left ventricle and mesenteric and coronary arteries. Sepsis induced long-lasting increases in the systemic NPY levels without affecting its tissue concentrations. Continuous hemofiltration at any dose did not reduce sepsis-induced elevations in NPY plasma concentrations, nor did it affect the peptide tissue levels. The increases in NPY systemic levels were significantly correlated with changes in the systemic vascular resistance. The results support the hypothesis of NPY implication in the regulation of the vascular resistance under septic conditions and indicate that NPY clearance rate during hemofiltration does not exceed the capacity of perivascular nerves to release it.

The safety and efficacy of a new anticoagulation strategy using selective in-circuit blood cooling during haemofiltration--an experimental study.

BACKGROUND: Selective in-circuit blood cooling was recently shown to be an effective anticoagulation strategy during short-term haemofiltration. The aim of this study was to examine the safety of this novel method and circuit life. METHODS: Fourteen pigs were randomly assigned to receive continuous haemofiltration with anticoagulation achieved either by selective cooling of an extracorporeal circuit (ECC) (COOL; n = 8) or through systemic heparinization (HEPARIN; n = 6). Before (T0) as well as 1 (TP1) and 6 h (TP6) after starting the procedure the following parameters were assessed: animal status, variables reflecting haemostasis, oxidative stress, inflammation and function of blood elements. RESULTS: All animals remained haemodynamically stable with unchanged body core temperature and routine biochemistry. Regional ECC blood cooling did not alter clinically relevant markers of haemostasis, namely activated partial thromboplastin and prothrombin times, thrombin-antithrombin complexes, von Willebrand factor and plasminogen activator inhibitor-1. Platelet aggregability, serum levels of free haemoglobin, leukocyte count, oxidative burst and blastic transformation of T-lymphocytes were all found to be stable over the treatment period in both groups. ECC blood cooling affected neither plasma malondialdehyde concentrations (a surrogate marker of oxidative stress) nor plasma levels of cytokines (tumour necrosis factor-α, interleukin-6 and -10). While the patency of all circuits treated with systemic heparin was well maintained within the pre-selected period of 24 h, the median filter lifespan in the COOL group was 17 h. CONCLUSION: Utilizing clinically relevant markers, selective in-circuit blood cooling was demonstrated to be a safe and feasible means of achieving regional anticoagulation in healthy pigs. The long-term safety issues warrant further evaluation.

Reduced L-type calcium current in ventricular myocytes from pigs with hyperdynamic septic shock.

OBJECTIVE: To hypothesize that reduced L-type calcium current with consequent shortening of cardiac repolarization is present in a clinically relevant porcine model of hyperdynamic septic shock. Myocardial depression is a well-recognized manifestation of sepsis and septic shock. Reduction of L-type calcium current was demonstrated to contribute to the myocardial depression in endotoxemic rodents. DESIGN: Laboratory animal experiments. SETTING: Animal research laboratory at a university. SUBJECTS: Twenty-two domestic pigs of either gender. INTERVENTIONS: In anesthetized, mechanically ventilated, and instrumented pigs, sepsis was induced by bacteremia (central venous infusion of live Pseudomonas aeruginosa) and continued for 22 hrs. MEASUREMENTS AND MAIN RESULTS: Electrocardiogram was recorded before and 22 hrs after induction of bacteremia. RR, QT, and QTc intervals were significantly shortened by sepsis. In vitro, action potentials were recorded in right ventricular trabeculae. Action potential durations were shortened in septic preparations. Tumor necrosis factor-alpha did not influence action potential durations. L-type calcium current was measured in isolated ventricular myocytes. Peak L-type calcium current density was reduced in myocytes from septic animals (8.3 +/- 0.4 pA/pF vs. 11.2 +/- 0.6 pA/pF in control). The voltage dependence of both L-type calcium current activation and inactivation was shifted to more negative potentials in myocytes from septic animals. Action potential-clamp experiments revealed that the contribution of L-type calcium current to the septic action potential was significantly diminished. In cardiac myocytes incubated with tumor necrosis factor-alpha, L-type calcium current was not further affected. CONCLUSIONS: In a clinically relevant porcine model, hyperdynamic septic shock induced shortening of ventricular repolarization and reduction of L-type calcium current. The contribution of L-type calcium current to the action potential in septic ventricular myocytes was significantly diminished. Tumor necrosis factor-alpha probably did not contribute to this effect.

Differential effects of hemofiltration and of coupled plasma filtration adsorption on cardiac repolarization in pigs with hyperdynamic septic shock.

The aim was to investigate effects of continuous hemofiltration (CHF) and of coupled plasma filtration adsorption (CPFA) on electrophysiological properties of the septic heart. Sepsis was induced in anesthetized pigs by fecal peritonitis and continued for 22 h either without intervention (control sepsis) or with intervention (CHF or CPFA) applied for the last 10 h of this period. Electrocardiograms were recorded at baseline, before induction of peritonitis, and 22 h later, at the end of in vivo experiment. In vitro, action potentials were recorded in right ventricular trabeculae. RR, QT, and QTc (QT corrected for heart rate) intervals were shortened by sepsis. Action potential durations (APDs) were shortened by CHF, but not by CPFA, compared with control sepsis. Continuous hemofiltration prolonged APD. Coupled plasma filtration adsorption filtrate did not exert any effect on APD. Plasma separated during CPFA prolonged APD. Continuous hemofiltration shortened cardiac repolarization, and this effect was reversed by the hemofiltrate. In contrast, neither CPFA nor the CPFA filtrate influenced APD. The data indicate that some inflammatory mediators able to delay cardiac repolarization were removed from plasma to hemofiltrate by CHF but not by CPFA.

High versus standard-volume haemofiltration in hyperdynamic porcine peritonitis: effects beyond haemodynamics?

OBJECTIVE: The role of haemofiltration as an adjunctive treatment of sepsis remains a contentious issue. To address the role of dose and to explore the biological effects of haemofiltration we compared the effects of standard and high-volume haemofiltration (HVHF) in a peritonitis-induced model of porcine septic shock. DESIGN AND SETTING: Randomized, controlled experimental study. SUBJECTS: Twenty-one anesthetized and mechanically ventilated pigs. INTERVENTIONS: After 12 h of hyperdynamic peritonitis, animals were randomized to receive either supportive treatment (Control, n = 7) or standard haemofiltration (HF 35 ml/kg per h, n = 7) or HVHF (100 ml/kg per hour, n = 7). MEASUREMENTS AND RESULTS: Systemic and hepatosplanchnic haemodynamics, oxygen exchange, energy metabolism (lactate/pyruvate, ketone body ratios), ileal and renal cortex microcirculation and systemic inflammation (TNF-alpha, IL-6), nitrosative/oxidative stress (TBARS, nitrates, GSH/GSSG) and endothelial/coagulation dysfunction (von Willebrand factor, asymmetric dimethylarginine, platelet count) were assessed before, 12, 18, and 22 h of peritonitis. Although fewer haemofiltration-treated animals required noradrenaline support (86, 43 and 29% animals in the control, HF and HVHF groups, respectively), neither of haemofiltration doses reversed hyperdynamic circulation, lung dysfunction and ameliorated alterations in gut and kidney microvascular perfusion. Both HF and HVHF failed to attenuate sepsis-induced alterations in surrogate markers of cellular energetics, nitrosative/oxidative stress, endothelial injury or systemic inflammation. CONCLUSIONS: In this porcine model of septic shock early HVHF proved superior in preventing the development of septic hypotension. However, neither of haemofiltration doses was capable of reversing the progressive disturbances in microvascular, metabolic, endothelial and lung function, at least within the timeframe of the study and severity of the model.

Coupled plasma filtration adsorption in experimental peritonitis-induced septic shock.

The coupled plasma filtration adsorption (CPFA) was developed as an adsorptive hemopurification method aimed at nonselective removal of circulating soluble mediators potentially involved in the pathogenesis of sepsis. We hypothesized that this nonselective hemopurification could protect from detrimental consequences of long-term, volume-resuscitated porcine septic shock. In 16 anesthetized, mechanically ventilated, and instrumented pigs, the hyperdynamic septic shock secondary to peritonitis was induced by intraperitoneally inoculating feces and maintained for 22 h with fluid resuscitation and norepinephrine infusion as needed to maintain MAP above 65 mmHg. After 12 h of peritonitis, animals were randomized to receive either supportive treatment (control, n = 8) or CPFA treatment (CPFA, n = 8). Systemic, hepatosplanchnic, and renal hemodynamics; oxygen exchange; energy metabolism (lactate/pyruvate and ketone body ratios); ileal mucosal and renal cortex microcirculation; systemic inflammation (TNF-alpha, IL-6); nitrosative/oxidative stress (thiobarbituric acid reactive species, nitrates + nitrites); and endothelial/coagulation dysfunction (asymmetric dimethylarginine, von Willebrand factor, thrombin-antithrombin complexes, platelet count) were assessed before and 12, 18, and 22 h of peritonitis. Coupled plasma filtration adsorption neither delayed the development of hypotension nor reduced the dose of norepinephrine. The treatment failed to attenuate sepsis-induced alterations in microcirculation, surrogate markers of cellular energetics, endothelial injury, and systemic inflammation. Similarly, CPFA did not protect from lung and liver dysfunction and even aggravated sepsis-induced disturbances in coagulation and oxidative/nitrosative stress. In this porcine model of septic shock, the early treatment with CPFA was not capable of reversing the sepsis-induced disturbances in various biological pathways and organ systems. Both the efficacy and safety of this method require further rigorous experimental validation in clinically relevant models.

Regional cooling of the extracorporeal blood circuit: a novel anticoagulation approach for renal replacement therapy?

OBJECTIVE: To test the hypothesis that cooling of blood in the extracorporeal circuit of continuous veno-venous hemofiltration (CVVH) enables to realize the procedure without the need of anticoagulation. DESIGN: Experimental animal study. METHODS: We developed the device for selective cooling of extracorporeal circuit (20 degrees C) allowing blood rewarming (38 degrees C) just before returning into the body. Twelve anesthetized and ventilated pigs were randomized to receive either 6 h of CVVH with application of this device (COOL; n = 6) or without it (CONTR; n = 6). MEASUREMENTS: Before the procedure and in 15, 60, 180, 360 min after starting hemofiltration variables related to: (1) circuit patency [time to clotting (TC), number of alarm-triggered pump stopping (AS), venous and transmembranous circuit pressures (VP, TMP)], (2) coagulation status in the extracorporeal circuit [thrombin-antithrombin complexes (TAT(circ)), thromboelastography (TEG)] and (3) animal status (hemodynamics, hemolysis and biochemistry) were assessed. RESULTS: The patency of all circuits treated with selective cooling was well maintained within the observation period. By contrast, five of six sessions were prematurely clotted in the untreated group. As a result, the number of AS was significantly higher in the CONTR group. In-circuit thrombus generation in CONTR group was associated with a markedly increasing TAT(circ). TEG performed at 180 min of the procedure revealed a tendency to a prolonged initial clotting time and a significant decrease in clotting rate of in-circuit blood in the COOL group. No signs of repeated cooling/rewarming-induced hemolysis were observed in animals treated with "hypothermic circuit" CVVH. CONCLUSION: In this porcine model, regional extracorporeal blood cooling proved effective in preventing in-circuit clotting without the need to use any other anticoagulant.

Renal haemodynamic, microcirculatory, metabolic and histopathological responses to peritonitis-induced septic shock in pigs.

INTRODUCTION: Our understanding of septic acute kidney injury (AKI) remains incomplete. A fundamental step is the use of animal models designed to meet the criteria of human sepsis. Therefore, we dynamically assessed renal haemodynamic, microvascular and metabolic responses to, and ultrastructural sequelae of, sepsis in a porcine model of faecal peritonitis-induced progressive hyperdynamic sepsis. METHODS: In eight anaesthetised and mechanically ventilated pigs, faecal peritonitis was induced by inoculating autologous faeces. Six sham-operated animals served as time-matched controls. Noradrenaline was administered to maintain mean arterial pressure (MAP) greater than or equal to 65 mmHg. Before and at 12, 18 and 22 hours of peritonitis systemic haemodynamics, total renal (ultrasound Doppler) and cortex microvascular (laser Doppler) blood flow, oxygen transport and renal venous pressure, acid base balance and lactate/pyruvate ratios were measured. Postmortem histological analysis of kidney tissue was performed. RESULTS: All septic pigs developed hyperdynamic shock with AKI as evidenced by a 30% increase in plasma creatinine levels. Kidney blood flow remained well-preserved and renal vascular resistance did not change either. Renal perfusion pressure significantly decreased in the AKI group as a result of gradually increased renal venous pressure. In parallel with a significant decrease in renal cortex microvascular perfusion, progressive renal venous acidosis and an increase in lactate/pyruvate ratio developed, while renal oxygen consumption remained unchanged. Renal histology revealed only subtle changes without signs of acute tubular necrosis. CONCLUSION: The results of this experimental study argue against the concept of renal vasoconstriction and tubular necrosis as physiological and morphological substrates of early septic AKI. Renal venous congestion might be a hidden and clinically unrecognised contributor to the development of kidney dysfunction.

Continuous hemofiltration in pigs with hyperdynamic septic shock affects cardiac repolarization.

OBJECTIVE: Sepsis has been defined as the systemic host response to infection with an overwhelming systemic production of both proinflammatory and anti-inflammatory mediators. Continuous hemofiltration has been suggested as possible therapeutic option that may remove the inflammatory mediators. However, hemodialysis and hemofiltration were reported to influence cardiac electrophysiologic parameters and to increase the arrhythmogenic risk. We hypothesize that sepsis affects electrophysiologic properties of the pig heart and that the effects of sepsis are modified by hemofiltration. DESIGN: Laboratory animal experiments. SETTING: Animal research laboratory at university medical school. SUBJECTS: Forty domestic pigs of either gender. INTERVENTIONS: In anesthetized, mechanically ventilated, and instrumented pigs sepsis was induced by fecal peritonitis and continued for 22 hours. Conventional or high-volume hemofiltration was applied for the last 10 hours of this period. MEASUREMENTS AND MAIN RESULTS: Electrocardiogram was recorded before and 22 hours after induction of peritonitis. RR, QT, and QTc intervals were significantly shortened by sepsis. The plasma levels of interleukin-6 and tumor necrosis factor-alpha were increased in sepsis. High-volume hemofiltration blunted the sepsis-induced increase in tumor necrosis factor-alpha. Action potentials were recorded in isolated ventricular tissues obtained at the end of in vivo experiments. Action potential durations were significantly shortened in septic preparations at all stimulation cycle lengths tested. Both conventional and high-volume hemofiltrations lead to further shortening of action potential durations measured afterward in vitro. This action potential duration shortening was reversed by septic hemofiltrates obtained previously by conventional or high-volume hemofiltration. Tumor necrosis factor-alpha (500 ng/L) had no effect on action potential durations in vitro. CONCLUSIONS: In a clinically relevant porcine model of hyperdynamic septic shock, both sepsis and continuous hemofiltration shortened duration of cardiac repolarization. The continuous hemofiltration was not associated with an increased prevalence of ventricular arrhythmias. Tumor necrosis factor-alpha or interleukin-6 did not contribute to the observed changes in action potential durations.

Coagulation and endothelial dysfunction during longterm hyperdynamic porcine bacteremia--effects of selective inducible nitric oxide synthase inhibition.

Coagulation abnormalities have been implicated in the pathogenesis of sepsis and organ dysfunction. Nitric oxide (NO) is regarded as a critical mediator of many vascular pathologies, including sepsis. However, limited evidence is available to document a relationship between NO generated by inducible NO synthase (iNOS) and hemostatic abnormalities in sepsis. Therefore, we evaluated the effects of selective iNOS inhibition on markers of endothelial and coagulation homeostasis in a clinically relevant model of porcine bacteremia induced and maintained for 24 hours (h) with a continuous infusion of live P. aeruginosa. After 12 h of sepsis, animals received either vehicle (Control, n=7) or continuous infusion of selective iNOS inhibitor L-NIL (n=7). Before as well as 12, 18 and 24 h after starting P. aeruginosa following variables related to i) endothelial dysfunction (von Willebrand factor [vWf]; tissue plasminogen activator activity [t-PA]; ii) coagulation (thrombin-antithrombin complexes [TAT]; platelet count); iii) fibrinolysis (t-PA activity, activity of plasminogen activator inhibitor type 1 (PAI-1 act); and iv) oxidative/nitrosative stress (isoprostanes, nitrate/nitrite levels) were measured. L-NIL inhibited sepsis-induced increase in plasma nitrate/nitrite and isoprostanes concentrations, prevented hypotension and acidosis. L-NIL significantly attenuated sepsis-induced rise in plasma vWF and TAT. P. aeruginosa-induced drop in t-PA activity was blunted by iNOS inhibition, while increased PAI-1 and reduced platelet count were not reversed by the treatment. In conclusion, selective iNOS inhibition was associated with attenuation of sepsis-induced coagulation and endothelial dysfunction suggesting the interplay between mediators of vascular system and hemostatic balance. Reduction of oxidative stress probably contributes to the beneficial effects afforded by iNOS blockade.

Effects of combining inducible nitric oxide synthase inhibitor and radical scavenger during porcine bacteremia.

Complex interactions of nitric oxide and other free radicals have been implicated in the pathogenesis of sepsis and organ dysfunction. We hypothesized that simultaneous inducible nitric oxide synthase inhibition (L-N6-[1-iminoethyl]-lysine [L-NIL]) and neutralization of superoxide (O2-) (4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl [Tempol]) would protect from detrimental consequences of long-term, volume-resuscitated, hyperdynamic porcine bacteremia. In this prospective, randomized, controlled experimental study, 16 anesthetized, mechanically ventilated and instrumented pigs were exposed to 24 h of continuous infusion of live Pseudomonas aeruginosa. After 12 h of hyperdynamic sepsis, animals were randomized to receive either vehicle (control, n = 8) or combination of L-NIL and Tempol (n = 8). Systemic and hepatosplanchnic hemodynamics, oxygen exchange, metabolism, ileal mucosal microcirculation and tonometry, oxidative stress and coagulation parameters were assessed before, 12, 18, and 24 h of P. aeruginosa infusion. Combined treatment inhibited sepsis-induced increase in plasma nitrate/nitrite, 8-isoprostane, and thiobarbituric acid reactive species concentrations, prevented hypotension, and reversed hyperdynamic circulation. Despite lower intestinal macrocirculation, combined regimen attenuated the otherwise progressive deterioration in ileal mucosal microcirculation and prevented mucosal acidosis. Treatment substantially attenuated mesenteric and hepatic venous acidosis, preserved sepsis-induced impairment of hepatosplanchnic redox state, and prevented the development of renal dysfunction. Finally, coinfusion of L-NIL and Tempol largely attenuated the sepsis-induced rise in plasma von Willebrand factor and thrombin-antithrombin complexes. Thus, hemodynamic, microcirculatory, metabolic, renal, and coagulation data indicate that combining inducible inhibition with cell permeable O2(-) radical scavenger afforded significant protection in porcine sepsis, thus suggesting an important interactive role of O2(-) and nitric oxide in mediating organ dysfunction.

Effect of regional citrate anticoagulation on thrombogenicity and biocompatibility during CVVHDF.

This study was designed to assess the principal markers of thrombogenicity and biocompatibility during continuous veno-venous hemodiafiltration (CVVHDF) using regional citrate anticoagulation (RCA). In a prospective study, 11 procedures with a polysulfone membrane were performed in nine critically ill patients with acute renal failure and impaired hemostasis. Blood samples were taken before and during CVVHDF at diafilter outlet--before calcium-induced reversal of the effect of citrate--at 15, 60, 360, and 1440 minutes. In four patients, 10 CVVHDF sessions were performed with systemic heparin anticoagulation (HA) using a polyacrylonitrile membrane. During RCA, blood thrombocyte count, plasma thrombin-antithrombin III complexes, beta-thromboglobulin, and von Willebrand factor levels did not differ significantly from baseline. Plasma D dimer levels rose significantly at 360 minutes; however, the difference between diafilter inlet and outlet levels was nonsignificant. There was a significant increase in plasma C5a concentrations and a decline in blood leukocyte count in the early phase of CVVHDF. Just as in RCA, no increase in plasma thrombogenicity indices was observed during HA. However, clotting times in blood entering patients' circulation were significantly prolonged. Plasma C5a concentrations increased significantly at the beginning of CVVHDF. RCA can effectively inhibit the thrombogenic effect of the extracorporeal circuit in CVVHDF. The effect of HA may be similar, however, at the expense of systemic anticoagulation and risk of bleeding. RCA, performed in a way that overcomes thrombogenicity, does not completely eliminate complement activation and/or transient leukopenia during CVVHDF.

Effects of tempol, a free radical scavenger, on long-term hyperdynamic porcine bacteremia.

OBJECTIVES: Pretreatment with tempol, a membrane-permeable radical scavenger, has been shown to be protective in rodent models of endotoxic and Gram-positive shock. However, neither the pretreatment design nor hypodynamic endotoxic shock in rodents mimics the clinical scenario. Therefore, we investigated the effects of tempol in a posttreatment model of long-term, volume-resuscitated, hyperdynamic porcine bacteremia. DESIGN: Prospective, randomized, controlled experimental study. SETTING: University animal laboratory. SUBJECTS: Sixteen anesthetized, mechanically ventilated, and instrumented pigs. INTERVENTIONS: Sepsis was induced and maintained for 24 hrs with continuous infusion of live Pseudomonas aeruginosa. After 12 hrs of hyperdynamic sepsis, animals were randomized to receive either vehicle (control, n = 8) or continuous infusion of tempol (n = 8, 30 mg/kg/hr). MEASUREMENTS AND MAIN RESULTS: Systemic and hepatosplanchnic hemodynamics, oxygen exchange, metabolism, ileal mucosal microcirculation, and tonometry as well as oxidative stress and coagulation variables were assessed before and after 12, 18, and 24 hrs of P. aeruginosa infusion. Tempol significantly attenuated reduction in mean arterial pressure. Despite comparable mesenteric macrocirculation, tempol attenuated the otherwise progressive deterioration in ileal mucosal microcirculation and prevented mucosal acidosis. By contrast, treatment with tempol failed to influence the P. aeruginosa-induced derangements of hepatosplanchnic redox state, liver lactate clearance, and regional acidosis but prevented the development of renal dysfunction. In addition, tempol reduced nitrosative stress without significant effect on the gradual increase in plasma 8-isoprostanes. Finally, tempol attenuated sepsis-induced endothelial (von Willebrand factor) and hemostatic dysfunction (thrombin-antithrombin complexes, plasminogen activator inhibitor-type 1). CONCLUSIONS: The radical scavenger tempol partially prevented live bacteria from causing key features of hemodynamic and metabolic derangements in porcine hyperdynamic sepsis and beneficially affected surrogate markers of sepsis-induced endothelial and coagulation dysfunction. Incomplete reduction of oxidative stress because of dilutional effects and/or missed optimal therapeutic window for antioxidant treatment when used in posttreatment approach may account for the only partial protection by tempol in this model.

Lactate metabolism in acute uremia.

Lactate is a key metabolite that is produced by every cell and oxidized by most of them, provided that they do contain mitochondria. Its metabolism is connected to energetic homeostasis and the cellular redox state. It is well recognized as an indicator of severe outcome in severely ill patients, however, it is not a detrimental factor per se. Conversely, some recent data tend even to indicate a beneficial effect in several metabolic disorders. Although the liver has long been recognized as a key organ in lactate homeostasis, the kidney also plays a major role as a gluconeogenic organ significantly involved in the glucose-lactate cycle. In acute renal failure, sodium lactate is widely used as a buffer in replacement fluids because the anion (lactate - ) is metabolized and the cation (Na + ) remains, leading to decreased water dissociation and proton concentration. The metabolic disorders related to acute renal failure or associated with it, such as liver failure, may affect lactate metabolism, and therefore they are often regarded as limiting factors for the use of lactate-containing fluids in such patients. By investigating endogenous lactate production in severe septic patients with acute renal failure, we found that an acute exogenous load of lactate did not affect the basal endogenous lactate production and metabolism. This indicates that exogenous lactate is well metabolized even in patients suffering from acute renal failure and severe sepsis with a compromised hemodynamic status.