Porcine Model of Cerebral Ischemic Stroke Utilizing Intracortical Recordings for the Continuous Monitoring of the Ischemic Area.

PURPOSE: Our aim was to use intracortical recording to enable the tracking of ischemic infarct development over the first few critical hours of ischemia with a high time resolution in pigs. We employed electrophysiological measurements to obtain quick feedback on neural function, which might be useful for screening, e.g., for the optimal dosage and timing of agents prior to further pre-clinical evaluation. METHODS: Micro-electrode arrays containing 16 (animal 1) or 32 electrodes (animal 2-7) were implanted in the primary somatosensory cortex of seven female pigs, and continuous electrical stimulation was applied at 0.2 Hz to a cuff electrode implanted on the ulnar nerve. Ischemic stroke was induced after 30 min of baseline recording by injection of endothelin-1 onto the cortex adjacent to the micro-electrode array. Evoked responses were extracted over a moving window of 180 s and averaged across channels as a measure of cortical excitability. RESULTS: Across the animals, the cortical excitability was significantly reduced in all seven 30 min segments following endothelin-1 injection, as compared to the 30 min preceding this intervention. This difference was not explained by changes in the anesthesia, ventilation, end-tidal CO2, mean blood pressure, heart rate, blood oxygenation, or core temperature, which all remained stable throughout the experiment. CONCLUSIONS: The animal model may assist in maturing neuroprotective approaches by testing them in an accessible model of resemblance to human neural and cardiovascular physiology and body size. This would constitute an intermediate step for translating positive results from rodent studies into human application, by more efficiently enabling effective optimization prior to chronic pre-clinical studies in large animals.

Laser-Induced Porcine Model of Experimental Retinal Vein Occlusion: An Optimized Reproducible Approach.

Retinal vein occlusion (RVO) is a frequent visually disabling condition. The management of RVO continues to challenge clinicians. Macular edema secondary to RVO is often recurrent, and patients typically require intravitreal injections for several years. Understanding molecular mechanisms in RVO is a key element in improving the treatment of the condition. Studying the molecular mechanisms in RVO at the retinal level is possible using animal models of experimental RVO. Most studies of experimental RVO have been sporadic, using only a few animals per experiment. Here, we report on 10 years of experience of the use of argon laser-induced experimental RVO in 108 porcine eyes from 65 animals, including 65 eyes with experimental branch retinal vein occlusion (BRVO) and 43 eyes with experimental central retinal vein occlusion (CRVO). Reproducibility and methods for evaluating and controlling ischemia in experimental RVO are reviewed. Methods for studying protein changes in RVO are discussed in detail, including proteomic analysis, Western blotting, and immunohistochemistry. Experimental RVO has brought significant insights into molecular changes in RVO. Testing intravitreal interventions in experimental RVO may be a significant step in developing personalized therapeutic approaches for patients with RVO.

Optimal reperfusion strategy in acute high-risk pulmonary embolism requiring extracorporeal membrane oxygenation support: a systematic review and meta-analysis.

BACKGROUND: The optimal pulmonary revascularisation strategy in high-risk pulmonary embolism (PE) requiring implantation of extracorporeal membrane oxygenation (ECMO) remains controversial. METHODS: We conducted a systematic review and meta-analysis of evidence comparing mechanical embolectomy and other strategies, including systemic thrombolysis, catheter-directed thrombolysis or ECMO as stand-alone therapy, with regard to mortality and bleeding outcomes. RESULTS: We identified 835 studies, 17 of which were included, comprising 327 PE patients. Overall, 32.4% were treated with mechanical pulmonary reperfusion (of whom 85.9% had surgical embolectomy), while 67.6% received other strategies. The mortality rate was 22.6% in the mechanical reperfusion group and 42.8% in the "other strategies" group. The pooled odds ratio for mortality with mechanical reperfusion was 0.439 (95% CI 0.237-0.816) (p=0.009; I2=35.2%) versus other reperfusion strategies and 0.368 (95% CI 0.185-0.733) (p=0.004; I2=32.9%) for surgical embolectomy versus thrombolysis. The rate of bleeding in patients under ECMO was 22.2% in the mechanical reperfusion group and 19.1% in the "other strategies" group (OR 1.27, 95% CI 0.54-2.96; I2=7.7%). The meta-regression model did not identify any relationship between the covariates "more than one pulmonary reperfusion therapy", "ECMO implantation before pulmonary reperfusion therapy", "clinical presentation of PE" or "cancer-associated PE" and the associated outcomes. CONCLUSIONS: The results of the present meta-analysis and meta-regression suggest that mechanical reperfusion, notably by surgical embolectomy, may yield favourable results regardless of the timing of ECMO implantation in the reperfusion timeline, independent of thrombolysis administration or cardiac arrest presentation.

Biopsy-based optimization and calibration of a signal-intensity-ratio-based MRI method (1.5 Tesla) in a dextran-iron loaded mini-pig model, enabling estimation of very high liver iron concentrations.

OBJECTIVE: Magnetic resonance imaging (MRI)-based techniques for non-invasive assessing liver iron concentration (LIC) in patients with iron overload have a limited upper measuring range around 35 mg/g dry weight, caused by signal loss from accelerated T1-, T2-, T2* shortening with increasing LIC. Expansion of this range is necessary to allow evaluation of patients with very high LIC. AIM: To assess measuring range of a gradient-echo R2* method and a T1-weighted spin-echo (SE), signal intensity ratio (SIR)-based method (TE = 25 ms, TR = 560 ms), and to extend the upper measuring range of the SIR method by optimizing echo time (TE) and repetition time (TR) in iron-loaded minipigs. METHODS: Thirteen mini pigs were followed up during dextran-iron loading with repeated percutaneous liver biopsies for chemical LIC measurement and MRIs for parallel non-invasive estimation of LIC (81 examinations) using different TEs and TRs. RESULTS: SIR and R2* method had similar upper measuring range around 34 mg/g and similar method agreement. Using TE = 12 ms and TR = 1200 ms extended the upper measuring range to 115 mg/g and yielded good method of agreement. DISCUSSION: The wider measuring range is likely caused by lesser sensitivity of the SE sequence to iron, due to shorter TE, leading to later signal loss at high LIC, allowing evaluation of most severe hepatic iron overload. Validation in iron-loaded patients is necessary.

Metabolic changes during carbon monoxide poisoning: An experimental study.

Carbon monoxide (CO) is the leading cause of death by poisoning worldwide. The aim was to explore the effects of mild and severe poisoning on blood gas parameters and metabolites. Eleven pigs were exposed to CO intoxication and had blood collected before and during poisoning. Mild CO poisoning (carboxyhaemoglobin, COHb 35.2 ± 7.9%) was achieved at 32 ± 13 minutes, and severe poisoning (69.3 ± 10.2% COHb) at 64 ± 23 minutes from baseline (2.9 ± 0.5% COHb). Blood gas parameters and metabolites were measured on a blood gas analyser and nuclear magnetic resonance spectrometer, respectively. Unsupervised principal component, analysis of variance and Pearson's correlation tests were applied. A P-value ≤ .05 was considered statistically significant. Mild poisoning resulted in a 28.4% drop in oxyhaemoglobin (OHb) and 12-fold increase in COHb, while severe poisoning in a 65% drop in OHb and 24-fold increase in COHb. Among others, metabolites implicated in regulation of metabolic acidosis (lactate, P < .0001), energy balance (pyruvate, P < .0001; 3-hydroxybutyrc acid, P = .01), respiration (citrate, P = .007; succinate, P = .0003; fumarate, P < .0001), lipid metabolism (glycerol, P = .002; choline, P = .0002) and antioxidant-oxidant balance (glutathione, P = .03; hypoxanthine, P < .0001) were altered, especially during severe poisoning. Our study adds new insights into the deranged metabolism of CO poisoning and leads the way for further investigation.

In vivo calibration of the T2* cardiovascular magnetic resonance method at 1.5 T for estimation of cardiac iron in a minipig model of transfusional iron overload.

BACKGROUND: Non-invasive estimation of the cardiac iron concentration (CIC) by T2* cardiovascular magnetic resonance (CMR) has been validated repeatedly and is in widespread clinical use. However, calibration data are limited, and mostly from post-mortem studies. In the present study, we performed an in vivo calibration in a dextran-iron loaded minipig model. METHODS: R2* (= 1/T2*) was assessed in vivo by 1.5 T CMR in the cardiac septum. Chemical CIC was assessed by inductively coupled plasma-optical emission spectroscopy in endomyocardial catheter biopsies (EMBs) from cardiac septum taken during follow up of 11 minipigs on dextran-iron loading, and also in full-wall biopsies from cardiac septum, taken post-mortem in another 16  minipigs, after completed iron loading. RESULTS: A strong correlation could be demonstrated between chemical CIC in 55 EMBs and parallel cardiac T2* (Spearman rank correlation coefficient 0.72, P < 0.001). Regression analysis led to [CIC] = (R2* - 17.16)/41.12 for the calibration equation with CIC in mg/g dry weight and R2* in Hz. An even stronger correlation was found, when chemical CIC was measured by full-wall biopsies from cardiac septum, taken immediately after euthanasia, in connection with the last CMR session after finished iron loading (Spearman rank correlation coefficient 0.95 (P < 0.001). Regression analysis led to the calibration equation [CIC] = (R2* - 17.2)/31.8. CONCLUSIONS: Calibration of cardiac T2* by EMBs is possible in the minipig model but is less accurate than by full-wall biopsies. Likely explanations are sampling error, variable content of non-iron containing tissue and smaller biopsies, when using catheter biopsies. The results further validate the CMR T2* technique for estimation of cardiac iron in conditions with iron overload and add to the limited calibration data published earlier.

Terlipressin Increases Systemic and Lowers Pulmonary Arterial Pressure in Experimental Acute Pulmonary Embolism.

OBJECTIVES: We investigated whether the vasopressin-analog, terlipressin induces systemic vasoconstriction and pulmonary vasodilation in a porcine model of acute pulmonary embolism. DESIGN: Controlled, animal study. SETTING: Tertiary medical center research laboratory. SUBJECTS: Female pigs (n = 12, Cross of Land Race, Duroc, and Yorkshire ~ 60 kg). INTERVENTIONS: Acute pulmonary embolism was induced by administration of three large autologous emboli. Animals then received four increasing doses of either terlipressin (n = 6) or vehicle (n = 6). MEASUREMENTS AND MAIN RESULTS: Effects were evaluated in vivo at baseline, after pulmonary embolism and after each dose by invasive hemodynamic measures, transesophageal echocardiography, and blood analysis. Isolated pulmonary arteries were evaluated ex vivo in a myograph. Pulmonary embolism caused a four-fold increase in pulmonary vascular resistance (p < 0.0001) and a two-fold increase in mean pulmonary arterial pressure (p < 0.0001) compared with baseline. Terlipressin increased mean systemic blood pressure (28 ± 5 mm Hg; p < 0.0001) and systemic vascular resistance (1,320 ± 143 dynes; p < 0.0001) compared with vehicle. In the pulmonary circulation, terlipressin decreased mean pulmonary arterial pressure (-6.5 ± 1.8 mm Hg; p = 0.005) and tended to decrease pulmonary vascular resistance (-83 ± 33 dynes; p = 0.07). Terlipressin decreased cardiac output (-2.5 ± 0.5 L/min; p < 0.0001) and increased plasma lactate (2.7 ± 0.2 mmol/L; p < 0.0001), possibly indicating systemic hypoperfusion. A biomarker of cerebral ischemia, S100b, remained unchanged, suggesting preserved cerebral perfusion (0.17 ± 0.11 µg/L; p = 0.51). Ex vivo, terlipressin relaxed pulmonary and constricted mesenteric arteries. CONCLUSIONS: Terlipressin caused systemic vasoconstriction and pulmonary vasodilation in a porcine in vivo model of acute pulmonary embolism and vasorelaxation in isolated pulmonary arteries. Despite positive vascular effects, cardiac output declined and plasma lactate increased probably due to a predominantly systemic vasoconstrictor effect of terlipressin. These findings should warrant careful translation to the clinical setting and does not suggest routine use in acute pulmonary embolism.

Consequences of parenteral iron-dextran loading investigated in minipigs. A new model of transfusional iron overload.

Patients with blood transfusion-dependent anemias develop transfusional iron overload (TIO), which may cause cardiosiderosis. In patients with an ineffective erythropoiesis, such as thalassemia major, common transfusion regimes aim at suppression of erythropoiesis and of enteral iron loading. Recent data suggest that maintaining residual, ineffective erythropoiesis may protect from cardiosiderosis. We investigated the common consequences of TIO, including cardiosiderosis, in a minipig model of iron overload with normal erythropoiesis. TIO was mimicked by long-term, weekly iron-dextran injections. Iron-dextran loading for around one year induced very high liver iron concentrations, but extrahepatic iron loading, and iron-induced toxicities were mild and did not include fibrosis. Iron deposits were primarily in reticuloendothelial cells, and parenchymal cardiac iron loading was mild. Compared to non-thalassemic patients with TIO, comparable cardiosiderosis in minipigs required about 4-fold greater body iron loads. It is suggested that this resistance against extrahepatic iron loading and toxicity in minipigs may at least in part be explained by a protective effect of the normal erythropoiesis, and additionally by a larger total iron storage capacity of RES than in patients with TIO. Parenteral iron-dextran loading of minipigs is a promising and feasible large-animal model of iron overload, that may mimic TIO in non-thalassemic patients.

An impedance threshold device did not improve carotid blood flow in a porcine model of prolonged cardiac arrest.

BACKGROUND: An impedance threshold device (ITD) was developed to increase venous return to the heart and therefore increase cardiac output and organ blood flow during cardiopulmonary rescue (CPR). Basic CPR aims to maintain coronary and cerebral blood flow at the minimum level necessary for survival. The present study compared the effects of an ITD on cerebral blood flow assessed as blood flow in both carotid arteries to the blood flow of a control group during prolonged CPR. METHODS: Fourteen anaesthetized pigs were monitored during 60 min of CPR after induced ventricular fibrillation. The primary outcome was blood flow in both carotid arteries, and the secondary outcomes were blood pressure, acid-base parameters, plasma potassium, and plasma lactate. The pigs were randomized to mechanical compressions and ventilation with an ITD added to the ventilation or to a control group treated only with mechanical compressions and ventilation. The time course for the parameters was tested using analysis of variance. RESULTS: The cumulative carotid blood flow in the ITD group decreased from 64 to 42 ml/min, and it decreased from 69 to 51 ml/min in the control group during 60 min of CPR. The difference was not significant. The secondary outcome measures were also not significantly different. CONCLUSIONS: This study did not show any beneficial effect of an ITD on carotid blood flow.

Extracorporeal membrane oxygenation in life-threatening massive pulmonary embolism.

INTRODUCTION: In massive pulmonary embolism (PE) with circulatory collapse or with cardiac arrest, treatment can be difficult. Often, the diagnosis is unclear, and the time to treatment is crucial. Our institution has had an out-of-hospital team intended for the treatment of accidental hypothermia with extra corporeal membrane oxygenation (ECMO) since 2004. The team has occasionally been involved in patients suffering massive PE. METHODS: We were called to 38 patients with PE, but two were assessed as untreatable. Seventeen were treated with cardiopulmonary resuscitation followed by veno-arterial ECMO. Nineteen were prepared for ECMO with sheaths in the femoral vessels and were intensively observed during diagnosis and treatment. Five of these patients later progressed to ECMO due to cardiac arrest during treatment with thrombolytic medication. Most of the patients were treated with heparin and thrombolytic medication, but if the medications were contraindicated, they were treated with either surgical thrombectomy or only with heparin awaiting spontaneous thrombolysis. RESULTS: Of the 36 patients we intended to treat, 25 (69%) survived one month and 20 survived one year (56%). Of the 22 patients treated with ECMO, 11 survived one month (50%) and 10 survived one year (45%). DISCUSSION: The treatment could have been more uniform. It seems reasonable to build up a PE alert team with ECMO capability to take care of patients with massive PE. CONCLUSION: The treatment of thrombolytic medications in massive PE is risky, but if the patient is treated or prepared for ECMO, it can be lifesaving.

Long-Distance Transportation of Carbon Monoxide-Poisoned Patients on Extracorporeal Membrane Oxygenation Seems Possible: A Porcine Feasibility Study.

OBJECTIVE: Extracorporeal membrane oxygenation (ECMO) has been widely used to stabilize patients with impairment of cardiac/respiratory function, and ECMO has been used to stabilize cardiopulmonary insufficiency caused by carbon monoxide (CO) poisoning in a porcine model. Airborne transportation in fixed wing aircraft of patients suffering from CO poisoning is challenging because as the air pressure drops, the oxygen content falls correspondingly. The aim of this study was to show the feasibility of cannulating and establishing ECMO therapy during airborne transportation after severe CO poisoning in a porcine model. METHODS: An anesthetized pig was subjected to severe CO poisoning and loaded onto a Hercules aircraft. Cardiac arrest was induced at an altitude of 8,000 feet, after which cannulation and the establishment of venoarterial (VA) ECMO were performed. Vital signs were monitored, and arterial blood samples were analyzed while airborne. RESULTS: CO poisoning was induced with carboxyhemoglobin at 58% before takeoff. We successfully cannulated the animal in-flight during cardiac arrest and initiated VA ECMO. The animal regained spontaneous circulation and was successfully weaned from ECMO. During VA ECMO, PaO2 was maintained at high levels (420-615 mm Hg). CONCLUSION: It is possible to cannulate and initiate VA ECMO treatment as airborne en route therapy for cardiac arrest and severe CO intoxication in a porcine model.

Cerebral blood flow measured by positron emission tomography during normothermic cardiopulmonary bypass: an experimental porcine study.

BACKGROUND: Mean arterial blood pressure (MAP) and/or pump flow during normothermic cardiopulmonary bypass (CPB) are the most important factors of cerebral perfusion. The aim of this study was to explore the influence of CPB blood flow on cerebral blood flow (CBF) measured by dynamic positron emission tomography (PET) using 15O-labelled water with no pharmacological interventions to maintain the MAP. METHODS: Eight pigs (69-71 kg) were connected to normothermic CPB. After 60 minutes (min) with a CPB pump flow of 60 mL/kg/min, the pigs were changed to either 35 mL/kg/min or 47.5 mL/kg/min for 60 min and, thereafter, all the pigs returned to 60 mL/kg/min for another 60 min. The MAP was measured continuously and the CBF was measured by positron emission tomography (PET) during spontaneous circulation and at each CPB pump flow after 30 min of steady state. RESULTS: Two pigs were excluded due to complications. CBF increased from spontaneous circulation to a CPB pump flow of 60 mL/kg/min. A reduction in CPB pump flow to 47.5 mL/kg/min (n=3) resulted in only minor changes in CBF while a reduction to 35 mL/kg/min (n=3) caused a pronounced change (correlation coefficient (R2) 0.56). A return of CPB pump flow to 60 mL/kg/min was followed by an increase in CBF, except in the one pig with the lowest CBF during low flow (R2=0.44). CBF and MAP were not correlated (R2=0.20). CONCLUSION: In this experimental porcine study, a relationship was observed between pump flow and CBF under normothermic low-flow CPB. The effect of low pump flow on MAP showed substantial variations, with no correlation between CBF and MAP.

A Respiratory Marker Derived From Left Vagus Nerve Signals Recorded With Implantable Cuff Electrodes.

OBJECTIVE: Left vagus nerve (LVN) stimulation (LVNS) has been tested for lowering the blood pressure (BP) in patients with resistant hypertension (RH). Whereas, closed-loop LVNS (CL-LVNS) driven by a BP marker may be superior to open-loop LVNS, there are situations (e.g., exercising) when hypertension is normal. Therefore, an ideal anti-RH CL-LVNS system requires a variable to avoid stimulation in such conditions, for example, a respiratory marker ideally extracted from the LVN. As the LVN conducts respiratory signals, this study aimed to investigate if such signals can be recorded using implantable means and if a marker to monitor respiration could be derived from such recordings. MATERIALS AND METHODS: The experiments were performed in 14 anesthetized pigs. Five pigs were subjected to changes of the respiratory frequency and nine to changes of the respiratory volume. The LVN electroneurogram (VENG) was recorded using two cuff electrodes and the respiratory cycles (RC) using a pressure transducer. To separate the afferent and efferent VENGs, vagotomy was performed between the cuffs in the first group of pigs. The VENG was squared to derive respiration-related neural profiles (RnPs) and their correlation with the RCs was investigated in regard to timing and magnitude parameters derived from the two waveforms. RESULTS: The RnPs were morphologically similar with the RCs and the average RnPs represented accurate copies of the average RCs. Consequently, the lung inflation/deflation RC and RnP components had the same duration, the respiratory frequency changes affected in the same way both waveforms and the RnP amplitude increased linearly with the lung inflation in all tested pigs (R2 values between 0.85 and 0.99). CONCLUSIONS: The RnPs comprise information regarding the timing and magnitude of the respiratory parameters. As those LVN profiles were derived using implantable means, this study indicates that the RnPs could serve as respiratory markers in implantable systems.

Muscle Tissue Saturation Compared With Muscle Tissue Perfusion During Low Blood Flows: An Experimental Study.

OBJECTIVE: To investigate whether changes in muscle tissue perfusion measured with positron emission tomography would be reflected by parallel changes in muscle tissue oxygen saturation (StO2) measured using near-infrared spectroscopy during high and low blood flow levels achieved using cardiopulmonary bypass (CPB) in an animal model. DESIGN: A prospective, randomized study. SETTING: Research laboratory, single institution. PARTICIPANTS: Eight pigs (69-71 kg). INTERVENTIONS: In anesthetized pigs, normothermic CPB was established with a blood flow of 60 mL/kg/min for 1 hour. Thereafter, a low blood flow of either 47.5 or 35 mL/kg/min was applied for 1 hour followed by a blood flow of 60 mL/kg/min for an additional hour. Regional StO2 was measured continuously by placing a near-infrared spectroscopy electrode on the skin above the gracilis muscle of the noncannulated back leg. Muscle tissue perfusion was measured using positron emission tomography with 15O-labeled water during spontaneous circulation and the different CPB blood flows. Systemic oxygen consumption was estimated by measurement of venous saturation and lactate levels. MEASUREMENTS AND MAIN RESULTS: The results showed profound systemic ischemia during low CPB blood flow. StO2 remained high until muscle tissue perfusion decreased to about 50%, after which StO2 paralleled the linear decrease in muscle tissue perfusion. CONCLUSION: In an experimental CPB animal model, StO2 was stable until muscle tissue perfusion was reduced by about 50%, and at lower blood flow levels, there was almost a linear relationship between StO2 and muscle tissue perfusion.

Regional muscle tissue saturation is an indicator of global inadequate circulation during cardiopulmonary bypass: a randomized porcine study using muscle, intestinal and brain tissue metabolomics.

BACKGROUND: Muscle tissue saturation (StO2) measured with near-infrared spectroscopy has generally been considered a measurement of the tissue microcirculatory condition. However, we hypothesized that StO2 could be more regarded as a fast and reliable measure of global than of regional circulatory adequacy and tested this with muscle, intestinal and brain metabolomics at normal and two levels of low cardiopulmonary bypass blood flow rates in a porcine model. METHODS: Twelve 80 kg pigs were connected to normothermic cardiopulmonary bypass with a blood flow of 60 mL/kg/min for one hour, reduced randomly to 47.5 mL/kg/min (Group I) or 35 mL/kg/min (Group II) for one hour followed by one hour of 60 mL/kg/min in both groups. Regional StO2 was measured continuously above the musculus gracilis (non-cannulated leg). Metabolomics were obtained by brain tissue oxygen monitoring system (Licox) measurements of the brain and microdialysis perfusate from the muscle, intestinal mucosa and brain. A non-parametric statistical method was used. RESULTS: The systemic parameters showed profound systemic ischaemia during low CPB blood flow. StO2 did not change markedly in Group I, but in Group II, StO2 decreased immediately when blood flow was reduced and, furthermore, was not restored despite blood flow being normalized. Changes in the metabolomics from the muscle, colon and brain followed the changes in StO2. CONCLUSION: We found, in this experimental cardiopulmonary bypass model, that StO2 reacted rapidly when the systemic circulation became inadequate and, furthermore, reliably indicate insufficient global tissue perfusion even when the systemic circulation was restored after a period of systemic hypoperfusion.

Recover of peripheral nerve function after prolong hypothermic cardiac arrest in a porcine model with extra corporeal life support.

OBJECTIVES: Surviving long lasting cardiac arrest following accidental hypothermia has been reported after treatment with extra corporeal life support (ECLS), but there is a risk of neurologic injury. Most surviving hypothermia patients have a prolonged stay in the intensive care unit, where most patients experience polyneuropathy. Theoretically, accidental hypothermic cardiac arrest may in itself contribute to polyneuropathy. This study was designed to examine the impact of three hours of cardiac arrest at a core temperature of 20°C followed by reanimation of peripheral nerve function. METHODS: Seven pigs were cannulated for ECLS and cooled to a core temperature of 20°C followed by three hours of circulatory arrest where the extremities were packed with ice. After three hours, ECLS was started and rewarming was performed. During the process, neural testing of the ulnar nerve (a somatic nerve) and of the vagus nerve (an autonomic nerve) were performed and blood was drawn for analysis of p-potassium, serum-neuron-specific enolase, and S100b protein. RESULTS: The ulnar nerve was cooled from 34.9±1.6°C to 12.8±3.8°C and the vagus nerve from 36.2±1.2°C to 15.4±1.4°C. Physiologic function of both somatic and autonomic nerves were strongly affected by cooling, but recovered to almost normal levels during rewarming, even after three hours of hypothermic cardiac arrest. P-potassium rose from 3.9 (3.6-4.6)mmol/l to 8.1 (7.2-9.1)mmol/l after three hours of cardiac arrest, but normalized after recirculation. There was no rise in serum-neuron-specific enolase, but a slight rise in S100b protein during three hours of hypothermic cardiac arrest was observed. All pigs obtained return of spontaneous circulation (ROSC). CONCLUSIONS: Reanimation after three hours of hypothermic cardiac arrest using ECLS was possible with no or, if present, minor damage to the two nerves tested.

Effects of intracoronary melatonin on ischemia-reperfusion injury in ST-elevation myocardial infarction.

Acute coronary occlusion is effectively treated by primary percutaneous coronary intervention. However, myocardial ischemia-reperfusion injury is at the moment an unavoidable consequence of the procedure. Oxidative stress is central in the development of ischemia-reperfusion injury. Melatonin, an endogenous hormone, acts through antioxidant mechanisms and could potentially minimize the myocardial injury. The aim of the experimental study was to examine the cardioprotective effects of melatonin in a porcine closed-chest reperfused infarction model. A total of 20 landrace pigs were randomized to a dosage of 200 mg (0.4 mg/mL) melatonin or placebo (saline). The intervention was administered intracoronary and intravenous. Infarct size, area at risk and microvascular obstruction were determined ex vivo by cardiovascular magnetic resonance imaging. Myocardial salvage index was calculated. The plasma levels of high-sensitive troponin T were assessed repeatedly. The experimenters were blinded with regard to treatment regimen. Melatonin did not significantly increase myocardial salvage index compared with placebo [melatonin 21.8% (16.1; 24.8) vs. placebo 20.2% (16.9; 27.0), p = 1.00]. The extent of microvascular obstruction was similar between the groups [melatonin 3.8% (2.7; 7.1) vs. placebo 3.7% (1.3; 7.7), p = 0.96]. The area under the curve for high-sensitive troponin T release was insignificantly reduced by 32% in the melatonin group [AUC melatonin 12,343.9 (6,889.2; 20,147.4) ng h/L vs. AUC placebo 18,285.3 (5,180.4; 23,716.8) ng h/L, p = 0.82]. Combined intracoronary and intravenous treatment with melatonin did not reduce myocardial reperfusion injury. The lack of a positive effect could be due to an ineffective dose of melatonin, a type II error or the timing of administration.

No Effect of Rapamycin on Cardiac Adhesion Formation: A Drug-Loaded Bioresorbable Polylactone Patch in a Porcine Cardiac Surgical Model.

BACKGROUND: The fusing of the epicardium and sternum due to adhesion is a common problem during repeated cardiac surgery and carries with it an increased risk of bleeding. The use of barriers and patches has been tested to prevent the formation of adhesions, but the very presence of a patch can provoke adhesion formation. The objective of this study was, therefore, to investigate both biodegradable and bioresorbable polylactone patches [(polycaprolactone-poly(ethylene oxide)-polycaprolactone tri-block copolymer (PCE)]. The patches were also tested with a controlled release of rapamycin, which prevents cell migration and extracellular matrix deposition. The clinical effectiveness of rapamycin in pericardial patches has not previously been examined. MATERIALS AND METHODS: Three groups of 6 female Danish Landrace pigs underwent sternotomy and abrasion of the epicardium, before being randomized to either group 1--the control group (with no patch), group 2--PCE patch implanted between the sternum and epicardium, or group 3--PCE patch and slow-release 1.6-mg rapamycin. After a median time period of 26 days, the pigs were euthanized and their hearts removed en bloc with the sternum, for macroscopic, histological and pathological examination. RESULTS: Upon macroscopic examination, a significantly lower degree of adhesion in group 2, as compared to group 1 (p < 0.05), was found. Histological analysis of the tissues showed significantly more fibrosis, inflammation and foreign body granulomas (p < 0.05) in both group 2 and group 3, when compared to group 1. CONCLUSION: A PCE patch following sternotomy in animal subjects reduces postoperative macroscopic adhesions without reducing microscopic fibrosis or inflammation. Loading the patch with rapamycin was found not to increase the antifibrotic effect.

Proteins involved in focal adhesion signaling pathways are differentially regulated in experimental branch retinal vein occlusion.

Branch retinal vein occlusion (BRVO) is a common retinal vascular disease, but global protein changes following the condition remain largely unelucidated. To bring new insights into pathological processes and identify potential therapeutic targets, large-scale retinal protein changes following BRVO were studied by combining a porcine model of experimental BRVO with proteomic analysis by label-free liquid chromatography mass spectrometry. Among a total set of 1974 proteins, 52 significantly upregulated proteins and 10 significantly downregulated proteins were identified in retinas with BRVO after 15 days. Significantly upregulated proteins were involved in signaling pathways of focal adhesion via integrin and blood coagulation. Proteins involved in focal adhesion signaling included collagen α-2 chain, laminin subunit ß-2, laminin subunit γ-1, lipocalin-7, nidogen-2, osteopontin, integrin-ß, α-actinin-1, isoform 2 of α-actinin-1, talin-2 and filamin C. The identified proteins indicate that BRVO was associated with extracellular matrix remodeling processes. The present study identified focal adhesion signaling and ECM remodeling as important biological mechanisms to evaluate in the search for signaling pathways that promote neovascularisation and macular edema following BRVO.