Martin Matejovic

Glucose metabolism and catecholamines.

Until now, catecholamines were the drugs of choice to treat hypotension during shock states. Catecholamines, however, also have marked metabolic effects, particularly on glucose metabolism, and the degree of this metabolic response is directly related to the &bgr;2-adrenoceptor activity of the individual compound used. Under physiologic conditions, infusing catecholamine is associated with enhanced rates of aerobic glycolysis (resulting in adenosine triphosphate production), glucose release (both from glycogenolysis and gluconeogenesis), and inhibition of insulin-mediated glycogenesis. Consequently, hyperglycemia and hyperlactatemia are the hallmarks of this metabolic response. Under pathophysiologic conditions, the metabolic effects of cate-cholamines are less predictable because of changes in receptor affinity and density and in drug kinetics and the metabolic capacity of the major gluconeogenic organs, both resulting from the disease per se and the ongoing treatment. It is also well-established that shock states are characterized by a hypermetabolic condition with insulin resistance and increased oxygen demands, which coincide with both compromised tissue microcirculatory perfusion and mitochondrial dysfunction. This, in turn, causes impaired glucose utilization and may lead to inadequate glucose supply and, ultimately, metabolic failure. Based on the landmark studies on intensive insulin use, a crucial role is currently attributed to glucose homeostasis. This article reviews the effects of the various catecholamines on glucose utilization, both under physiologic conditions, as well as during shock states. Because, to date (to our knowledge), no patient data are available, results from relevant animal experiments are discussed. In addition, potential strategies are outlined to influence the catecholamine-induced effects on glucose homeostasis.

Nitric Oxide Synthase Inhibition in Sepsis? Lessons Learned from Large-animal Studies

Nitric Oxide (NO) plays a controversial role in the pathophysiology of sepsis and septic shock. Its vasodilatory effects are well known, but it also has pro- and antiinflammatory properties, assumes crucial importance in antimicrobial host defense, may act as an oxidant as well as an antioxidant, and is said to be a “vital poison” for the immune and inflammatory network. Large amounts of NO and peroxynitrite are responsible for hypotension, vasoplegia, cellular suffocation, apoptosis, lactic acidosis, and ultimately multiorgan failure. Therefore, NO synthase (NOS) inhibitors were developed to reverse the deleterious effects of NO. Studies using these compounds have not met with uniform success however, and a trial using the nonselective NOS inhibitor NG-methyl-l-arginine hydrochloride was terminated prematurely because of increased mortality in the treatment arm despite improved shock resolution. Thus, the issue of NOS inhibition in sepsis remains a matter of debate. Several publications have emphasized the differences concerning clinical applicability of data obtained from unresuscitated, hypodynamic rodent models using a pretreatment approach versus resuscitated, hyperdynamic models in high-order species using posttreatment approaches. Therefore, the present review focuses on clinically relevant large-animal studies of endotoxin or living bacteria-induced, hyperdynamic models of sepsis that integrate standard day-to-day care resuscitative measures.

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

IntroductionOur 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.MethodsIn 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.ResultsAll 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.ConclusionThe 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.

Effects of ventilation with 100% oxygen during early hyperdynamic porcine fecal peritonitis.

Objective: Early goal-directed therapy aims at balancing tissue oxygen delivery and demand. Hyperoxia (i.e., pure oxygen breathing) has not been studied in this context, since sepsis increases oxygen radical production, which is believed to be directly related to the oxygen tension. On the other hand, oxygen breathing improved survival in various shock models. Therefore, we hypothesized that hyperoxia may be beneficial during early septic shock. Design: Laboratory animal experiments. Setting: Animal research laboratory at university medical school. Subjects: Twenty domestic pigs of either gender. Interventions: After induction of fecal peritonitis, anesthetized and instrumented pigs were ventilated with either 100% oxygen or supplemental oxygen as needed to maintain arterial hemoglobin oxygen saturation ≥90%. Normotensive and hyperdynamic hemodynamics were achieved using hydroxyethyl starch and norepinephrine infusion. Measurements and Main Results: Before and at 12, 18, and 24 hrs of peritonitis, we measured lung compliance; systemic, pulmonary, and hepatosplanchnic hemodynamics; gas exchange; acid-base status; blood isoprostanes; nitrates; DNA strand breaks; and organ function. Gluconeogenesis and glucose oxidation were calculated from blood isotope and expiratory 13CO2 enrichments during continuous intravenous 1,2,3,4,5,6-13C6-glucose. Apoptosis in lung and liver was assessed postmortem (TUNEL staining). Hyperoxia did not affect lung mechanics or gas exchange but redistributed cardiac output to the hepatosplanchnic region, attenuated regional venous metabolic acidosis, increased glucose oxidation, improved renal function, and markedly reduced the apoptotic death rate in liver and lung. Conclusions: During early hyperdynamic porcine septic shock, 100% oxygen improved organ function and attenuated tissue apoptosis without affecting lung function and oxidative or nitrosative stress. Therefore, it might be considered as an additional measure in the first phase of early goal-directed therapy.

Selective inducible nitric oxide synthase inhibition during long-term hyperdynamic porcine bacteremia.

We have recently demonstrated that selective inducible nitric oxide (NO) synthase (iNOS) inhibition with 1400W attenuated the hemodynamic and metabolic alterations affiliated with hyperdynamic porcine endotoxemia. In contrast to endotoxemia, limited evidence is available to document a relationship between NO and organ dysfunction in large animal bacteremic models. Therefore, using the same experimental setup, we investigated the role of selective iNOS blockade in porcine bacteremia induced and maintained for 24 h with a continuous infusion of live Pseudomonas aeruginosa. After 12 h of sepsis, animals received either vehicle (Control, n = 8) or continuous infusion of selective iNOS inhibitor, L-N6-(1-iminoethyl)-lysine (L-NIL; n = 8). Measurements were performed before, and 12, 18, and 24 h after P. aeruginosa infusion. L-NIL inhibited sepsis-induced increase in plasma nitrate/nitrite concentrations and prevented hypotension without affecting cardiac output. Despite comparable hepatosplanchnic macrocirculation, L-NIL blunted the progressive deterioration in ileal mucosal microcirculation and prevented mucosal acidosis. L-NIL largely attenuated mesenteric and hepatic venous acidosis, significantly improved P. aeruginosa-induced impairment of hepatosplanchnic redox state, and mitigated the decline in liver lactate clearance. Furthermore, the administration of L-NIL reduced the hepatocellular injury and prevented the development of renal dysfunction. Finally, treatment with L-NIL significantly attenuated the formation of 8-isoprostane concentrations, a direct marker of lipid peroxidation. Thus, selective iNOS inhibition with L-NIL prevented live bacteria from causing key features of metabolic derangements in porcine hyperdynamic sepsis. Underlying mechanisms probably include reduced oxidative stress with improved microcirculatory perfusion and restoration of cellular respiration.

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

IntroductionIn 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.MethodsThirty-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.ResultsIn 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).ConclusionsThe 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.

Hyperoxia may be beneficial

The current practice of mechanical ventilation comprises the use of the least inspiratory O2 fraction associated with an arterial O2 tension of 55 to 80 mm Hg or an arterial hemoglobin O2 saturation of 88% to 95%. Early goal-directed therapy for septic shock, however, attempts to balance O2 delivery and demand by optimizing cardiac function and hemoglobin concentration, without making use of hyperoxia. Clearly, it has been well-established for more than a century that long-term exposure to pure O2 results in pulmonary and, under hyperbaric conditions, central nervous O2 toxicity. Nevertheless, several arguments support the use of ventilation with 100% O2 as a supportive measure during the first 12 to 24 hrs of septic shock. In contrast to patients without lung disease undergoing anesthesia, ventilation with 100% O2 does not worsen intrapulmonary shunt under conditions of hyperinflammation, particularly when low tidal volume–high positive end-expiratory pressure ventilation is used. In healthy volunteers and experimental animals, exposure to hyperoxia may cause pulmonary inflammation, enhanced oxidative stress, and tissue apoptosis. This, however, requires long-term exposure or injurious tidal volumes. In contrast, within the timeframe of a perioperative administration, direct O2 toxicity only plays a negligible role. Pure O2 ventilation induces peripheral vasoconstriction and thus may counteract shock-induced hypotension and reduce vasopressor requirements. Furthermore, in experimental animals, a redistribution of cardiac output toward the kidney and the hepato-splanchnic organs was observed. Hyperoxia not only reverses the anesthesia-related impairment of the host defense but also is an antibiotic. In fact, perioperative hyperoxia significantly reduced wound infections, and this effect was directly related to the tissue O2 tension. Therefore, we advocate mechanical ventilation with 100% O2 during the first 12 to 24 hrs of septic shock. However, controlled clinical trials are mandatory to test the safety and efficacy of this approach.

Specific adsorption of some complement activation proteins to polysulfone dialysis membranes during hemodialysis

Dialyser bioincompatibility is an important factor contributing to complications of hemodialysis with well known systemic consequences. Here we studied the local processes that occur on dialysis membranes by eluting proteins adsorbed to the polysulfone dialyser membranes of 5 patients after 3 consecutive routine maintenance hemodialysis sessions. At the end of each procedure, a plasma sample was also collected. These eluates and their accompanying plasma samples were separated by 2-dimensional gel electrophoresis; all proteins that were present in all patients were analyzed by tandem mass spectrometry; and a ratio of the relative spot intensity of the eluate to plasma was calculated. Of 153 proteins detected, 84 were found in all patients, 57 of which were successfully identified by mass spectrometry as 38 components of 23 unique proteins. In 10 spots the relative eluate intensity differed significantly from that in the plasma, implying preferential adsorption. These proteins included ficolin-2, clusterin, complement C3c fragment, and apolipoprotein A1. Our finding of a selective binding of ficolin-2 to polysulfone membranes suggests a possible role of the lectin complement pathway in blood-dialyser interactions.

Hemodynamic, metabolic, and organ function effects of pure oxygen ventilation during established fecal peritonitis-induced septic shock.

Objective:To test the hypothesis whether pure oxygen ventilation is equally safe and beneficial in fully developed fecal peritonitis-induced septic shock as hyperoxia initiated at the induction of sepsis. Design:Prospective, randomized, controlled, experimental study with repeated measures. Setting:Animal research laboratory at a university medical school. Subjects:Twenty anesthetized, mechanically ventilated, and instrumented pigs. Interventions:Twelve hours after induction of fecal peritonitis by inoculation of autologous feces, swine, which were resuscitated with hydroxyethyl starch and norepinephrine to maintain mean arterial pressure at baseline values, were ventilated randomly with an Fio2 required to keep Sao2 >90% (controls: n = 10) or Fio2 1.0 (hyperoxia, n = 10) during the next 12 hrs. Measurements and Main Results:Despite similar hemodynamic support (hydroxyethyl starch and norepinephrine doses), systemic and regional macrocirculatory and oxygen transport parameters, hyperoxia attenuated pulmonary hypertension, improved gut microcirculation (ileal mucosal laser Doppler flowmetry) and portal venous acidosis, prevented the deterioration in creatinine clearance (controls 61 (44;112), hyperoxia: 96 (88;110) mL·min−1, p = .074), and attenuated the increase in blood tumor necrosis factor-&agr; concentrations (p = .045 and p = .112 vs. controls at 18 hrs and 24 hrs, respectively). Lung and liver histology (hematoxyline eosine staining) were comparable in the two groups, but hyperoxia reduced apoptosis (Tunel test) in the liver (4 (3;8) vs. 2 (1;5) apoptotic cells/field, p = .069) and the lung (36 (31;46) vs. 15 (13;17) apoptotic cells/field, p < .001). Parameters of lung function, tissue antioxidant activity, blood oxidative and nitrosative stress (nitrate + nitrite, 8-isoprostane levels; deoxyribonucleic acid (DNA) damage measured using the comet assay) were not further affected during hyperoxia. Conclusions:When compared with the previous report on hyperoxia initiated simultaneously with induction of sepsis, i.e., using a pretreatment approach, pure oxygen ventilation started when porcine fecal peritonitis-induced septic shock was fully developed proved to be equally safe with respect to lung function and oxidative stress, but exerted only moderate beneficial effects.

Successful reversal of resistent hypodynamic septic shock with levosimendan.

Myocardial depression is a well-recognized feature of septic shock. End-stage hypodynamic septic shock characterized by a severely low cardiac output state invariably carries a poor prognosis. We report, for the first time, successful treatment of a fatal form of catecholamine resistent hypodynamic septic shock using a novel inotropic calcium-sensitizing drug, levosimendan. This compound was originally developed for the treatment of decompensated heart failure (1), and there are no data available regarding the effects of levosimendan in human hypodynamic septic shock. A 37-year-old woman was admitted to our intensive care unit (ICU) because of septic shock caused by methicillin-sensitive Staphylococcus aureus. The patient had multiple sclerosis lasting for 9years and her customary therapy consisted of methylprednison (16mgday ) and azathioprin (75mgday ). She was mechanically ventilated and received aggressive fluid resuscitation using both crystalloids and colloids targeting the central venous pressure (CVP) between 12 and 14mmHg. Despite volume resuscitation, noradrenaline (0.4mgkg min ) was required to maintain mean arterial pressure (MAP) above 70mmHg. Vancomycin (1.5 g), ceftazidime (2g every 8h) and fluconazol (0.2g every 12h) were infused intravenously (at that time, the results of blood cultures were not known) and stress doses of hydrocortizon were administered (50mg i.v. every 6h). During the next 12h, the patient’s condition progressively deteriorated. She required substantial, increasing doses of noradrenaline (1.3mgkg min ), her body temperature rose (39 C), and oligo-anuria developed. Repeated laboratory assessment revealed a progressive rise in arterial lactate (5.2mmol l ) and worsening of metabolic acidosis (pH7.25). A pulmonary artery catheter was inserted, showing a reduced cardiac index (CI) of 2.4 lmin m 2 despite sufficient cardiac filling pressures (CVP 19mmHg, pulmonary artery occlusion pressure 17mmHg). Mixed venous oxygen saturation was 54%. As an additional fluid challenge did not improved CI, an infusion of dobutamine was started(5mgkg min ) and the dose was increased incrementally (maximum dose 24mgkg min ). In a couple of hours the state rapidly progressed into cold shock with no capillary refill and mottled cool extremities. CI was 0.6 lmin m 2 and a bedside echocardiography showed markedly depressed cardiac contractility (left ventricular ejection fraction of approximately 15%). Despite massive doses of combined catecholamine support (noradrenaline 2.3mgkg 1 min , adrenaline 3.1mgkg min , dobutamine 24mgkg min ), MAP kept falling further (46mmHg). In a desperate attempt to reverse this fatal catecholamine-resistent hypodynamic shock, a decision was made to start an intravenous levosimendan infusion (initial loading dose 12mgkg 1 over 10min, followed by a continuous infusion of 0.2mgkg min 1 for 24h) as a last resort therapy. In approximately 30min of levosimendan infusion, we observed a sustained gradual increase in CI reaching the maximum of 3.6 lmin m . The improved CI resulted in the restoration of effective perfusion pressure (MAP 75mmHg) and recovery of urine output. This impressive effect of levosimendan allowed complete and rapid weaning from adrenaline and a significant dose reduction of noradrenaline (0.6mgkg min ) as well as dobutamine (8.1mgkg 1 min ). Repeated echocardiography, performed 5 h after the start of levosimendan, showed a dramatic improvement in myocardial contractility (left ventricular ejection fraction 60%). Subsequently, the typical multiple organ failure requiring long-term ICU care developed. She was discharged from the ICU on the 52nd day, recovering from severe critical-illness polyneuropathy and myopathy. In summary, in this immunocompromized patient, the novel calcium-sensitizing inotropic drug levosimendan was an essential, life-saving therapeutic component in an otherwise fatal course of hypodynamic septic shock. So far, only one studyhas addressed the effects of levosimedan in experimental septic shock (2), but, to our knowledge, there are no human data available. This significant observation should encourage further studies evaluating the role of levosimendan in septic shock associatedwith profoundmyocardial depression.