Mats Eriksson

Propofol (Diprivan-EDTA) counteracts oxidative injury and deterioration of the arterial oxygen tension during experimental septic shock.

PURPOSE Human septic shock can be replicated in the endotoxaemic pig. Endotoxaemia causes a multitude of events, including reduced PaO(2) and increased lipid peroxidation. This study was designed to evaluate the possible effects of a commonly used anaesthetic drug with known antioxidant properties (propofol) during porcine endotoxaemia. METHODS Ten pigs were anaesthetised and given a 6 h E. coli endotoxin infusion. The animals received, randomly, a supplementary continuous infusion of propofol emulsion (containing 0.005% EDTA) or the corresponding volume of vehicle (controls). Pathophysiologic responses were determined. Non-enzymatic (by measuring plasma 8-iso-PGF(2 alpha) and enzymatic (by measuring plasma 15-keto-dihydro-PGF(2 alpha)) lipid peroxidations were evaluated. Plasma levels of the endogenous antioxidants alpha- and gamma-tocopherols, were also analysed. RESULTS Endotoxaemia increased plasma levels of 8-iso-PGF(2 alpha) (1st-4th h) and 15-keto-dihydro-PGF(2 alpha) (1st-4th h) significantly more in controls than in the propofol+endotoxin group. PaO(2) was significantly less affected by endotoxin in the propofol treated animals (2nd-4th h). Mean arterial pressure (4th-6th h) and systemic vascular resistance (6th h) were reduced significantly more by endotoxin among the propofol-treated animals. Vitamin E (alpha-tocopherol) increased in all animals, significantly more in the propofol+endotoxin group (1/2-6th h) than in the control group. CONCLUSIONS Propofol reduced endotoxin-induced free radical mediated and cyclooxygenase catalysed lipid peroxidation significantly. The implication is that propofol counteracts endotoxin-induced deterioration of PaO(2).

Lipid peroxidation induced by an early inflammatory response in endotoxaemia

Background: Endotoxaemic challenge promptly causes lipid peroxidation. Porcine endotoxaemia can be used to replicate severe human septic shock. This model was used to evaluate non‐enzymatic [8‐Iso‐prostaglandin F2α (8‐Iso‐PGF2α)] and enzymatic [15‐keto‐13,14‐dihydro‐prostaglandin F2α (15‐K‐DH‐PGF2α)] lipid peroxidation, respectively, in relation to survival. The aim of this study was to correlate, if possible, pathophysiologic events during endotoxaemia to the levels of these arachidonic acid metabolites.

Endotoxin neutralization and anti-inflammatory effects of tobramycin and ceftazidime in porcine endotoxin shock

IntroductionAntibiotics used for treatment of severe bacterial infections have been shown to exert effects on the inflammatory response in addition to their antibacterial effects. The aim of the present study was to investigate whether the biological effects of endotoxin in a porcine model could be neutralized by tobramycin, and whether tobramycin or ceftazidime was able to modulate the inflammatory response.MethodThirteen piglets were subjected to endotoxin infusion at an initial rate of 4 μg/kg per hour, which was reduced to 1 μg/kg per hour after 30 min. Before endotoxin infusion, the animals received saline (n = 4), ceftazidime (n = 5), or tobramycin (n = 4) at clinically relevant doses. Physiological parameters were measured and blood samples were taken hourly for 6 hours for analysis of tumour necrosis factor-α, IL-6 and endotoxin concentrations.ResultsAll of the animals exhibited physiological signs of severe sepsis without major differences between the groups. Plasma endotoxin concentration was stable after 1 hour. There were no differences in endotoxin concentration or initial tumour necrosis factor-α and IL-6 concentrations between the groups. At 6 hours the IL-6 concentration was significantly lower in the ceftazidime group than in the saline group (P < 0.05), and in both the ceftazidime and the tobramycin groups there were significantly greater reductions from peak values (P < 0.05).ConclusionThere was no neutralization of the biological effects of endotoxin in this porcine model. However, our data indicate a possible anti-inflammatory effect exerted by both ceftazidime and tobramycin, which manifested as a significantly greater reduction in IL-6 in comparison with the untreated group.

Effects of mechanical ventilation on platelet microparticles in bronchoalveolar lavage fluid

INTRODUCTION Mechanical ventilation (MV) is considered to contribute to lung injury. Platelet membrane-derived microparticles (PMPs) are procoagulant and participate in the inflammatory process. The bronchoalveolar space could, besides plasma, be a site of origin of these microparticles. We evaluated the presence of these PMPs and two prostaglandin-derived metabolites in bronchoalveolar lavage fluid (BALF) regarding their possible relation to MV. MATERIALS AND METHODS Before and after 1 h of MV, PMPs and prostaglandin metabolites were analyzed, in BALF from 14 anesthetized pigs, by flow cytometry and RIA, respectively. Tracheal mucus from five humans was analyzed for PMPs at extubation after surgery. RESULTS Activated PMPs and prostaglandin metabolites were present in all BALF samples. The time needed to count 5000 cellular events was prolonged six-fold after 1 h of mechanical ventilation (p<0.001). The relative content of PMPs was constant in all samples. The PMPs were thrombogenic, i.e. they were fibrinogen, p-selectin and von Willebrand factor positive. Lavage did not per se affect the period necessary to count 5000 cellular events. PMPs in human tracheal mucus were in the same range as in the pig after 1 h of MV aiming at a PaCO(2) between 5.0 and 5.5 kPa. CONCLUSIONS Activated PMPs are present in the pulmonary air-liquid interface. The prolongation of the time needed to count 5000 cellular events in BALF after MV indicates activation and adherence. Adherent microparticles bind neutrophils, which may aggravate pathological processes leading to pulmonary dysfunction. Evaluation of PMPs in BALF may be useful in evaluating strategies for lung-protective ventilator treatment.

Inflammatory, coagulatory and circulatory responses to logarithmic increases in the endotoxin dose in the anaesthetised pig

Although porcine intravenous endotoxin shock models are widely employed in experimental sepsis, endotoxin dose-effect studies are scarce. Our primary aim was to establish the dose response to increasing endotoxin doses in inflammatory, coagulatory and haemodynamic effect variables, as well as to determine the optimal time point for assessment in a pig model. A secondary aim was to study pathophysiological covariations between the different responses. Twenty anaesthetised piglets received endotoxin intravenously in doses of 0.063 (n = 3), 0.25 (n = 3), 1.0 ( n = 3), 4.0 (n = 3), 8 (n = 3) and 16 µg/kg/h (n = 2). In addition, non-endotoxin piglets constituted a control group (n = 3). Physiological variables were registered and blood samples analysed for TNF-α, IL-6, leukocyte, platelet and haemoglobin concentrations hourly for 6 h. Increases in the endotoxin dose induced significant log—log cytokine responses as well as log—linear leukocyte and platelet responses. Significant log—linear responses were observed for circulatory parameters, plasma leakage, hypoperfusion and pulmonary compliance. Significant covariations in the responses were noted. In conclusion, there were log—log or log—linear responses to endotoxin suggesting a greater effect of a given dose at lower pre-existing endotoxin concentrations and lower doses of ≤ 1 µg/kg/h may be of advantage in experiments designed to study potential anti-endotoxin effects of experimental drugs or measures.

Mental stress impairs endothelial vasodilatory function by a beta-adrenergic mechanism

Mental stress has been shown to impair endothelium-dependent vasodilation (EDV) in the human forearm. The aim of this study was to investigate if this response could be blunted by local infusions of beta-blockade (propranolol), alpha-blockade (phentolamine), or neurogenic blockade. Thirty-one young healthy volunteers underwent forearm blood flow (FBF) measurements, using venous occlusion plethysmography, during local intra-arterial infusions of metacholine (MCh; inducing EDV) and sodium nitroprussid (SNP; inducing endothelial-independent vasodilation [EIDV]), respectively. These measurements were repeated during a 5-min mental arithmetic stress test without (n = 8) or with concomitant local infusion of propranolol (n = 7) or phentolamine (n = 8) in the forearm or during axillary plexus blockade (n = 8). An index of endothelial vasodilatory function (EFI) was calculated as the EDV to EIDV ratio. Mental stress impaired EDV significantly (p < .05), and as a result, EFI was significantly reduced (p = .02). This effect on EFI could be blocked by propranolol and neurogenic blockade but not by phentolamine (p < .05). Thus, impairment of endothelial vasodilatory function induced by mental stress could be blocked by beta-adrenergic, but not alpha-adrenergic, receptor blockade.

Early endotoxin-mediated haemostatic and inflammatory responses in the clopidogrel-treated pig

We have previously shown that the thrombin inhibiting agent melagatran markedly prolongs aPTT and counteracts creatinine increase in endotoxemic pigs. Against this background the effects of the platelet-inhibiting agent, clopidogrel on basic haemostatic, inflammatory and physiological variables were evaluated during porcine endotoxemia. Clopidogrel (10 mg/kg) or saline was randomly injected i.v. 30 min before start of a 6-h continuous infusion of endotoxin in 12 anaesthetised pigs. Another three pigs were given clopidogrel but not endotoxin. Clopidogrel did not affect physiological variables, formation of activated platelet microparticles, PK, aPTT, platelet count, plasma fibrinogen, TNF-α, or IL-6 during porcine endotoxemia. Although renal function, as evaluated by creatinine clearance (CLcr) deteriorated significantly (P = 0.01) in the saline–endotoxin, but not in the clopidogrel–endotoxin group, there was no significant difference between the saline–endotoxin and the clopidogrel–endotoxin groups. Renal biopsies were marked with a FITC-labelled chicken anti-fibrinogen antibody detecting fibrinogen and platelet bound fibrinogen, as a marker of porcine platelet activation, and examined by light microscopy. Evaluation of these immunohistochemical slides did not indicate that clopidogrel, significantly reduced the amount of intrarenal fibrin or fibrinogen depositions. Besides a trend to preserve renal function, clopidogrel did not affect haemodynamics or the coagulatory and inflammatory responses in porcine endotoxemia.

F2-isoprostane, inflammation, cardiac function and oxygenation in the endotoxaemic pig

Prostaglandins are profoundly involved in endotoxaemic shock. Twenty pigs were given endotoxin at various doses (0.063-16 microg kg(-1) h(-1)). Three non-endotoxaemic pigs served as controls. Two eicosanoids were measured in plasma (8-iso-PGF(2alpha), a free radical-mediated lipid peroxidation product, and 15-keto-dihydro-PGF(2alpha) a major metabolite of COX activity) and evaluated against the pathophysiological responses that occur during endotoxaemic shock. Endotoxin mediates an increase in both 8-iso-PGF(2alpha) and 15-keto-dihydro-PGF(2alpha). An increase in the endotoxin dose induced significant log-linear responses in 8-iso-PGF(2alpha) and 15-keto-dihydro-PGF(2alpha). Oxidative injury correlated to the TNF-alpha, IL-6, reductions in cardiac performance and to oxygen delivery and utilisation. COX-mediated inflammatory responses correlated to TNF-alpha, IL-6 and to reductions in arterial oxygen tension. Thus, oxidative injury and COX-mediated inflammation play a central role in the manifestation of endotoxaemic shock. Furthermore, formation of these eicosanoids on endotoxin-mediated alterations in pulmonary hypertension, oxygen delivery and oxygen utilisation seems to be independent of the administered endotoxin dose.

Angiotensin Converting Enzyme Dependent and Non-dependent Effects of a Fibrinogen-derived Pentapeptide on Microvascular Permeability in Rat Skin

A permeability-increasing pentapeptide, termed peptide 6A, derived from plasmin-degraded human fibrinogen and known to potentiate the increase in microvascular permeability caused by bradykinin was investigated concerning its angiotensin converting enzyme (A.C.E.) related effects. When applied to a rat skin model together with a specific inhibitor of this enzyme, peptide 6A showed a potentiated effect after 30 min. but not after 5 min. The same was also true for bradykinin. These findings suggest that the degradation rate of these peptides is decreased with resulting prolongation of the period of leakage, when the action of A.C.E. is opposed. It is deduced that peptide 6A may act as a partial antagonist of this enzyme in the rat skin model. Addition of peptide 6A to a mixture of bradykinin together with inhibitors of the enzymes degrading bradykinin before application to the rat skin, significantly augmented the extravasation of 125I-albumin. These findings are consistent with data indicating that peptide 6A is a prostacyclin-releaser able to induce vasodilation. This effect of peptide 6A on the microcirculation seems to be separate from its angiotensin converting enzyme-related effects.

Ropivacaine May Have Advantages Compared to Bupivacaine in Porcine Endotoxemic Shock

Patients that undergo major abdominal surgery often receive epidural postoperative analgesia. Septic complications are frequently seen in this cohort. In a porcine model of endotoxemic shock, resembling human gram-negative septic shock, we evaluated the effects of two widely used local anaesthetics, bupivacaine and ropivacaine given intravenously. In the endotoxin-ropivacaine group mixed venous saturation and platelet count were higher as compared to endotoxemic controls. Mean arterial blood pressure and platelet count were higher in ropivacaine-endotoxin pigs than in bupivacaine-endotoxin ones. Bupivacaine augmented endotoxin-mediated decrease in left ventricular stroke work index. Ropivacaine displays pathophysiological advantages compared to bupivacaine in septic shock, which may be explained by improved tissue perfusion by ropivacaine.