Name: a reproducible intensive care unit-oriented endotoxin model in rats
Uploaded: 2021-02-20T15:00:00
Description: Watch this Scientific Journal Video about A Reproducible Intensive Care Unit-Oriented Endotoxin Model in Rats at JoVE.com

The authors would like to thank Beatrice Beck-Schimmer (MD) and Erik Schadde (MD) for their critical examination and their valuable contribution for this manuscript.

All experiments presented in this protocol were approved by the Veterinary Authorities of the Canton Zurich, Switzerland (approval numbers 134/2014 and ZH088/19). Moreover, all steps performed in this experiment were in accordance with the Guidelines on Experiments with Animals by the Swiss Academy of Medial Sciences (SAMS) and Guidelines of the Federation of European Laboratory Animal Science Associations (FELASA).
1. Anesthesia induction and animal monitoring
<ol>
	<li>Keep male Wistar rat...

<ol>
	<li>Hotchkiss, R. S., Karl, I. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+pathophysiology+and+treatment+of+sepsis.">The pathophysiology and treatment of sepsis.</a> New England Journal of Medicine. 348 (2), 138-150 (2003).</li><li>Singer, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Third+International+Consensus+Definitions+for+Sepsis+and+Septic+Shock+(Sepsis-3).">The Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis-3).</a> Journal of the American Medical Association. 315 (8), 801-810 (2016).</li><li>Vincent, J. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Assessment+of+the+worldwide+burden+of+critical+illness:+the+intensive+care+over+nations+(ICON)+audit.">Assessment of the worldwide burden of critical illness: the intensive care over nations (ICON) audit.</a> Lancet Respiratory Medicine. 2 (5), 380-386 (2014).</li><li>Fleischmann, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Assessment+of+Global+Incidence+and+Mortality+of+Hospital-treated+Sepsis.+Current+Estimates+and+Limitations.">Assessment of Global Incidence and Mortality of Hospital-treated Sepsis. Current Estimates and Limitations.</a> American Journal of Respiratory and Critical Care Medicine. 193 (3), 259-272 (2016).</li><li>Kumar, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Duration+of+hypotension+before+initiation+of+effective+antimicrobial+therapy+is+the+critical+determinant+of+survival+in+human+septic+shock.">Duration of hypotension before initiation of effective antimicrobial therapy is the critical determinant of survival in human septic shock.</a> Critical Care Medicine. 34 (6), 1589-1596 (2006).</li><li>Gotts, J. E., Matthay, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sepsis:+pathophysiology+and+clinical+management.">Sepsis: pathophysiology and clinical management.</a> British Medical Journal. 353, (2016).</li><li>Akira, S., Takeda, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Toll-like+receptor+signalling.">Toll-like receptor signalling.</a> Nature Reviews Immunology. 4 (7), 499-511 (2004).</li><li>Urner, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Insight+into+the+beneficial+immunomodulatory+mechanism+of+the+sevoflurane+metabolite+hexafluoro-2-propanol+in+a+rat+model+of+endotoxaemia.">Insight into the beneficial immunomodulatory mechanism of the sevoflurane metabolite hexafluoro-2-propanol in a rat model of endotoxaemia.</a> Clinical and Experimental Immunology. 181 (3), 468-479 (2015).</li><li>Beck-Schimmer, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Which+Anesthesia+Regimen+Is+Best+to+Reduce+Morbidity+and+Mortality+in+Lung+Surgery?:+A+Multicenter+Randomized+Controlled+Trial.">Which Anesthesia Regimen Is Best to Reduce Morbidity and Mortality in Lung Surgery?: A Multicenter Randomized Controlled Trial.</a> Anesthesiology. 125 (2), 313-321 (2016).</li><li>Deitch, E. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Animal+models+of+sepsis+and+shock:+a+review+and+lessons+learned.">Animal models of sepsis and shock: a review and lessons learned.</a> Shock. 9 (1), 1-11 (1998).</li><li>Buras, J. A., Holzmann, B., Sitkovsky, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Animal+models+of+sepsis:+setting+the+stage.">Animal models of sepsis: setting the stage.</a> Nature Reviews Drug Discovery. 4 (10), 854-865 (2005).</li><li>Perretti, M., Duncan, G. S., Flower, R. J., Peers, S. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Serum+corticosterone,+interleukin-1+and+tumour+necrosis+factor+in+rat+experimental+endotoxaemia:+comparison+between+Lewis+and+Wistar+strains.">Serum corticosterone, interleukin-1 and tumour necrosis factor in rat experimental endotoxaemia: comparison between Lewis and Wistar strains.</a> British Journal of Pharmacology. 110 (2), 868-874 (1993).</li><li>Marechal, X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Endothelial+glycocalyx+damage+during+endotoxemia+coincides+with+microcirculatory+dysfunction+and+vascular+oxidative+stress.">Endothelial glycocalyx damage during endotoxemia coincides with microcirculatory dysfunction and vascular oxidative stress.</a> Shock. 29 (5), 572-576 (2008).</li><li>Thiemermann, C., Ruetten, H., Wu, C. C., Vane, J. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+multiple+organ+dysfunction+syndrome+caused+by+endotoxin+in+the+rat:+attenuation+of+liver+dysfunction+by+inhibitors+of+nitric+oxide+synthase.">The multiple organ dysfunction syndrome caused by endotoxin in the rat: attenuation of liver dysfunction by inhibitors of nitric oxide synthase.</a> British Journal of Pharmacology. 116 (7), 2845-2851 (1995).</li><li>Osuchowski, M. F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Minimum+quality+threshold+in+pre-clinical+sepsis+studies+(MQTiPSS):+an+international+expert+consensus+initiative+for+improvement+of+animal+modeling+in+sepsis.">Minimum quality threshold in pre-clinical sepsis studies (MQTiPSS): an international expert consensus initiative for improvement of animal modeling in sepsis.</a> Intensive Care Medicine Experimental. 6 (1), 26 (2018).</li><li>Fink, M. P., Heard, S. O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Laboratory+models+of+sepsis+and+septic+shock.">Laboratory models of sepsis and septic shock.</a> Journal of Surgical Research. 49 (2), 186-196 (1990).</li><li>Buras, J. A., Holzmann, B., Sitkovsky, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Animal+models+of+sepsis:+Setting+the+stage.">Animal models of sepsis: Setting the stage.</a> Nature Reviews Drug Discovery. 4 (10), 854-865 (2005).</li><li>Balls, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+principles+of+humane+experimental+technique:+timeless+insights+and+unheeded+warnings.">The principles of humane experimental technique: timeless insights and unheeded warnings.</a> Altex-Alternatives to Animal Experimentation. 27 (2), 144-148 (2010).</li></ol>

The protocol described here allows for a highly reproducible, yet simple to learn sepsis model, which can be adapted according the research question. Essential in vivo data referring to organ function such as heart rate, blood pressure, and peripheral arterial oxygen saturation may be collected continuously, and blood sampling may be performed repetitively throughout the experiment. In addition, modifications with regard to fluid replacement protocols and vasopressor support can be installed. Given the hemodynamic stabil...

Sepsis and its more severe form, septic shock, are syndromes on the ground of an infection, resulting in an overshooting inflammatory reaction with the release of cytokines, leading to physiological and biochemical changes with a suppressed immune defense and fatal results1,2. This unbalanced inflammatory reaction results in organ dysfunction and organ failure in various vital organs such as lung, kidney, and liver. With 37%3, sepsis is one of the most common reasons for a patient to be admitted to an intensive care unit (ICU). Mortality of sepsis currently ranges around 20-30%4. Early and effective antibiotic treatment is of utmost importance5. Fluid and vasopressor resuscitation need to be installed early, other than that, treatment is purely supportive6.
Sepsis is defined as a proven or suspected infection with bacteria, fungi, viruses, or parasites, which is accompanied by organ dysfunction. Septic shock criteria are met when a further cardiovascular collapse irresponsive to fluid treatment alone, and a lactate level of more than 2 millimole/liter is present2. Sepsis related organ failure may occur in any organ, but is very common in the cardiovascular system, the brain, the kidney, the liver, and the lung. Most patients suffering from sepsis require endotracheal intubation to secure the patient&#39;s airway, to protect from aspiration, and to apply positive end expiratory ventilation with a high fraction of inspired oxygen to prevent or overcome hypoxia. In order to tolerate a tracheal tube and mechanical ventilation, patients usually require sedation.
Endotoxins, such as lipopolysaccharides (LPS) as a component of the membrane of gram negative bacteria induce a strong inflammatory reaction via the toll-like receptor (TLR) 47. Activation of a defined pathway ensures a stable inflammatory reaction. Cytokines like cytokine induced neutrophil chemoattractant protein 1 (CINC-1), monocyte chemoattractant protein 1 (MCP-1), and interleukin 6 (IL-6) are known as prognostic factors for severity and outcome in this model8. Intravenous LPS application has been successfully used to study various aspects of sepsis in rats8,9.
Treatment of sepsis is still a challenge, particularly due to the lack of predictive animal models. If endotoxemia with activation of systemic inflammation is an adequate model for the development of pharmacological therapies is debatable. However, with the well-known LPS-induced TLR 4 pathway important knowledge can be gained.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>2-0 silk sutures</td>
			<td>Ethicon, Sommerville, NJ</td>
			<td>K833</td>
			<td>Standard surgical</td>
		</tr>
		<tr>
			<td>26 intravenous catheter</td>
			<td>Becton Dickinson, Franklin Lakes, NJ</td>
			<td>391349</td>
			<td>Standard anesthesia equipment</td>
		</tr>
		<tr>
			<td>6-0 LOOK black braided silk</td>
			<td>Surgical Specalities Corporation, Wyomissing, PA</td>
			<td>SP114</td>
			<td>Standard surgical</td>
		</tr>
		<tr>
			<td>Alaris Syringe Pump</td>
			<td>Bencton Dickinson</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Betadine</td>
			<td>Mundipharma, Basel, Switzerland</td>
			<td>7.68034E+12</td>
			<td>GTIN-number</td>
		</tr>
		<tr>
			<td>Curved fine tips microforceps</td>
			<td>World precision instruments (WPI), Sarasota, FL</td>
			<td>504513</td>
			<td>Facilitates vascular preparation</td>
		</tr>
		<tr>
			<td>Fine tips microforceps</td>
			<td>World precision instruments (WPI), Sarasota, FL</td>
			<td>501976</td>
			<td>Tips need to be polished regularly</td>
		</tr>
		<tr>
			<td>Infinity Delta XL Anesthesia monitoring</td>
			<td>Draeger, L&#252;beck, Germany</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Isoflurane, 250 mL bottles</td>
			<td>Attane, Piramal, Mumbai, India</td>
			<td>LDNI 22098</td>
			<td>Standard vet. equipment</td>
		</tr>
		<tr>
			<td>Ketamine (Ketalar)</td>
			<td>Pfitzer, New York, NY</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Lipopolysaccharide (LPS) from Escherichia coli, serotype 055:B5</td>
			<td>Sigma, Buchs, Switzerland</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Q-tips small</td>
			<td>Carl Roth GmbH, Karlsruhe, Germany</td>
			<td>EH11.1</td>
			<td>Standard surgical</td>
		</tr>
		<tr>
			<td>Ringerfundin</td>
			<td>Bbraun, Melsungen, Germany</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Tec-3 Isofluorane Vaporizer</td>
			<td>Ohmeda, GE-Healthcare, Chicago, IL</td>
			<td>not available anymore</td>
			<td>Standard vet. equipment</td>
		</tr>
		<tr>
			<td>Xylazine (Xylazin Streuli)</td>
			<td>Streuli AG, Uznach, Switzerland</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

a reproducible intensive care unit-oriented endotoxin model in rats

Sepsis and septic shock remain the leading cause of death in intensive care units. Despite significant improvements in sepsis management, mortality still ranges between 20 and 30%. Novel treatment approaches in order to reduce sepsis-related multiorgan failure and death are urgently needed. Robust animal models allow for one or multiple treatment approaches as well as for testing their effect on physiological and molecular parameters. In this article, a simple animal model is presented.
First, general anesthesia is induced in animals either with the use of volatile or by intraperitoneal anesthesia. After placement of an intravenous catheter (tail vein), tracheostomy, and insertion of an intraarterial catheter (tail artery), mechanical ventilation is started. Baseline values of mean arterial blood pressure, arterial blood oxygen saturation, and heart rate are recorded.
The injection of lipopolysaccharides (1 milligram/kilogram body weight) dissolved in phosphate-buffered saline induces a strong and reproducible inflammatory response via the toll-like receptor 4. Fluid corrections as well as the application of norepinephrine are performed based on well-established protocols.
The animal model presented in this article is easy to learn and strongly oriented towards clinical sepsis treatment in an intensive care unit with sedation, mechanical ventilation, continuous blood pressure monitoring, and repetitive blood sampling. Also, the model is reliable, allowing for reproducible data with a limited number of animals in accordance with the 3R (reduce, replace, refine) principles of animal research. While animal experiments in sepsis research cannot easily replaced, repetitive measurements allow for a reduction of animals and keeping septic animals anesthetized diminishes suffering.

The system presented allows for endotoxemia with hemodynamically stable animals as reported previously9. While the mean arterial pressure remains stable in animals with, and without LPS stimulation LPS treated animal develop characteristics of sepsis such as a negative base excess and a strong inflammatory reaction measured by plasma cytokines (6 hours after application) such as CINC-1 (867 ng/mL), MCP-1 (5027 ng/mL), and IL-6 (867 ng/mL)8, Figure 5</st...

Watch this Scientific Journal Video about A Reproducible Intensive Care Unit-Oriented Endotoxin Model in Rats at JoVE.com

A Reproducible Intensive Care Unit-Oriented Endotoxin Model in Rats

Here, we present a reproducible intensive care unit-oriented endotoxin model in rats.

Sepsis and septic shock remain the leading cause of death in intensive care units. Despite significant improvements in sepsis management, mortality still ...

This protocol is robust and reproducible model of endotoxemia in which physiological and molecular parameters can be assessed repeatedly. This approach may help to answer questions in sepsis research. While our model does not replace animal experiments, it refines sepsis models through continuous sedation and reduces the number of animals through repeated sampling.Beginners might struggle with the insertion of arterial and venous catheters, but only limited training is required to master these techniques. Visualization of the entire experimental setup facilitates researchers to set up, or adapt, their models to mimic more closely a situation on ICU. Begin by transferring the anesthetized animal to a heating mat.Keeping the body temperature between 36.5 and 37 degrees Celsius. Make sure that the animal is spontaneously breathing by providing oxygen with a nose cone. Confirm the level of anesthesia by the absence of the toe pinch reflex prior to the installation of tracheostomy and arterial and venous catheters.Use an ointment to protect the eyes. Prepare sterile surgical instruments and catheters along with pressure and oxygen saturation monitoring for sufficient oxygenation. Apply a tourniquet at the rat's proximal tail to facilitate venous access and disinfect the tail three times with alcohol.Introduce a 26-gauge intravenous catheter into one of the two lateral tail veins avoiding air injection. Untie the tourniquet after placing the intravenous catheter and fix the intravenous catheter in place with adhesive tape. Connect syringe pumps with three-way stopcocks to the intravenous access for continuous fluid and drug application.Begin the tracheostomy by shaving the animal's anterior neck area, and then disinfect the shaved skin three times with povidone iodine solution. Perform a two centimeter longitudinal incision using a scalpel blade number 10. Retract the skin with 2-0 silk sutures.Then bluntly prepared the larynx and the trachea to be opened with surgical scissors. Insert a sterile tracheal cannula into the trachea, being careful not to penetrate too deeply in order to avoid unilateral ventilation. Fix the cannula in place by using a 2-O silk suture and then connect the cannula to a ventilator for pressure or volume-controlled ventilation.Define fluid replacement protocols, vasoconstrictor application protocols, and abortion criteria before setting up the experiment. Disinfect the rat tail three times with povidone iodine solution and then cut the skin circle one centimeter longitudinally at the ventral side using a scalpel, taking care not to cut too deeply to avoid an injury of the tail artery. Use a surgical microscope to expose the artery carefully.Cut the fascia surrounding the artery with surgical micro scissors. Then ligate the distal part of the artery by performing proximal 6-0 silk suture, but do not tighten the silk. Introduce a 26-gauge catheter into the artery between the distal and proximal silk suture, and then tighten the proximal silk suture to fix the catheter in place.Connect the catheter to a pressure transducer to provide continuous arterial pressure measurement. Additionally, place a three-way stopcock between the catheter connected to the pressure transducer and the 26-gauge catheter for arterial blood sampling. After the animal has reached a steady state, induced sepsis by injecting LPS and collect blood samples.Replace fluid loss from the blood samples by Ringer's solution at a ratio of one to four, avoiding air injection at all times in order to prevent air embolism. The mean arterial pressure remains stable in animals with and without LPS stimulation. LPS-treated animals develop characteristics of sepsis, such as negative base excess.LPS-treated animals also developed a strong inflammatory reaction, which was measured by plasma cytokines, such as chemoattractant protein-1, monocyte chemoattractant protein-1, and interleukin-6. When attempting this protocol, remember to predefine fluid and vasopressor regimens as well as to define termination criteria in order to obtain solid and reproducible research data. This protocol can be adapted to other sepsis models.So a research question is answered with the most suitable approach and in accordance with the principles of reduce, refine, replace of animal welfare.

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Spectral Karyotyping to Study Chromosome Abnormalities in Humans and Mice with Polycystic Kidney Disease

Conventional method to identify and classify individual chromosomes depends on the unique banding pattern of each chromosome in a specific species being analyzed 1, 2. This classical banding technique, however, is not reliable in identifying complex chromosomal aberrations such as those associated with cancer. To overcome the limitations of the banding technique, Spectral Karyotyping (SKY) is introduced to provide much reliable information on chromosome abnormalities.
SKY is a multicolor fluorescence in-situ hybridization (FISH) technique to detect metaphase chromosomes with spectral microscope 3, 4. SKY has been proven to be a valuable tool for the cytogenetic analysis of a broad range of chromosome abnormalities associated with a large number of genetic diseases and malignancies 5, 6. SKY involves the use of multicolor fluorescently-labelled DNA probes prepared from the degenerate oligonucleotide primers by PCR. Thus, every chromosome has a unique spectral color after in-situ hybridization with probes, which are differentially labelled with a mixture of fluorescent dyes (Rhodamine, Texas Red, Cy5, FITC and Cy5.5). The probes used for SKY consist of up to 55 chromosome specific probes 7-10.
The procedure for SKY involves several steps (Figure 1). SKY requires the availability of cells with high mitotic index from normal or diseased tissue or blood. The chromosomes of a single cell from either a freshly isolated primary cell or a cell line are spread on a glass slide. This chromosome spread is labeled with a different combination of fluorescent dyes specific for each chromosome. For probe detection and image acquisition,the spectral imaging system consists of sagnac interferometer and a CCD camera. This allows measurement of the visible light spectrum emitted from the sample and to acquire a spectral image from individual chromosomes. HiSKY, the software used to analyze the results of the captured images, provides an easy identification of chromosome anomalies. The end result is a metaphase and a karyotype classification image, in which each pair of chromosomes has a distinct color (Figure 2). This allows easy identification of chromosome identities and translocations. For more details, please visit Applied Spectral Imaging website (<a href="http://www.spectral-imaging.com/" target="_blank">http://www.spectral-imaging.com/</a>).
SKY was recently used for an identification of chromosome segregation defects and chromosome abnormalities in humans and mice with Autosomal Dominant Polycystic Kidney Disease (ADPKD), a genetic disease characterized by dysfunction in primary cilia 11-13. Using this technique, we demonstrated the presence of abnormal chromosome segregation and chromosomal defects in ADPKD patients and mouse models 14. Further analyses using SKY not only allowed us to identify chromosomal number and identity, but also to accurately detect very complex chromosomal aberrations such as chromosome deletions and translocations (Figure 2).

Spectral Karyotyping (SKY) is an advanced cytogenetics technique to identify genomic and chromosomal aberrations. This technique takes advantage of chromosome painting probes, which allow classification of all chromosomes. SKY can also identify complex chromosome aberrations and segregation defects in mice and humans with various diseases, including polycystic kidney disease.

Conventional method to identify and classify individual chromosomes depends on the unique banding pattern of each chromosome in a specific species being ...

A Murine Closed-chest Model of Myocardial Ischemia and Reperfusion

Surgical trauma by thoracotomy in open-chest models of coronary ligation induces an immune response which modifies different mechanisms involved in ischemia and reperfusion. Immune response includes cytokine expression and release or secretion of endogenous ligands of innate immune receptors. Activation of innate immunity can potentially modulate infarct size. We have modified an existing murine closed-chest model using hanging weights which could be useful for studying myocardial pre- and postconditioning and the role of innate immunity in myocardial ischemia and reperfusion. This model allows animals to recover from surgical trauma before onset of myocardial ischemia.
Volatile anesthetics have been intensely studied and their preconditioning effect for the ischemic heart is well known. However, this protective effect precludes its use in open chest models of coronary artery ligation. Thus, another advantage could be the use of the well controllable volatile anesthetics for instrumentation in a chronic closed-chest model, since their preconditioning effect lasts up to 72 hours. Chronic heart diseases with intermittent ischemia and multiple hit models are other possible applications of this model.
For the chronic closed-chest model, intubated and ventilated mice undergo a lateral blunt thoracotomy via the 4th intercostal space. Following identification of the left anterior descending a ligature is passed underneath the vessel and both suture ends are threaded through an occluder. Then, both suture ends are passed through the chest wall, knotted to form a loop and left in the subcutaneous tissue. After chest closure and recovery for 5 days, mice are anesthetized again, chest skin is reopened and hanging weights are hooked up to the loop under ECG control.
At the end of the ischemia/reperfusion protocol, hearts can be stained with TTC for infarct size assessment or undergo perfusion fixation to allow morphometric studies in addition to histology and immunohistochemistry.

Surgical trauma induces an inflammatory response. Cytokines and endogenous ligands are known to modulate myocardial infarct size following ischemia and reperfusion. We present a modified closed-chest model of murine ischemia and reperfusion using hanging weights to minimize effects of thoracotomy.

Surgical trauma by thoracotomy in open-chest models of coronary ligation induces an immune response which modifies different mechanisms involved in ...

Lavage-induced Surfactant Depletion in Pigs As a Model of the Acute Respiratory Distress Syndrome (ARDS)

Various animal models of lung injury exist to study the complex pathomechanisms of human acute respiratory distress syndrome (ARDS) and evaluate future therapies. Severe lung injury with a reproducible deterioration of pulmonary gas exchange and hemodynamics can be induced in anesthetized pigs using repeated lung lavages with warmed 0.9% saline (50 ml/kg body weight). Including standard respiratory and hemodynamic monitoring with clinically applied devices in this model allows the evaluation of novel therapeutic strategies (drugs, modern ventilators, extracorporeal membrane oxygenators, ECMO), and bridges the gap between bench and bedside. Furthermore, induction of lung injury with lung lavages does not require the injection of pathogens/endotoxins that impact on measurements of pro- and anti-inflammatory cytokines. A disadvantage of the model is the high recruitability of atelectatic lung tissue. Standardization of the model helps to avoid pitfalls, to ensure comparability between experiments, and to reduce the number of animals needed.

Lavage-induced Surfactant Depletion in Pigs As a Model of the Acute Respiratory Distress Syndrome ARDS

Repeated pulmonary lavages in anesthetized pigs induce lung injury resembling major aspects of human acute respiratory distress syndrome (ARDS). For this purpose the lungs are repeatedly lavaged with 0.9% saline at 37 &#176;C. The goal of the protocol is a reproducible mitigation of gas exchange and hemodynamics for research in ARDS.

Various animal models of lung injury exist to study the complex pathomechanisms of human acute respiratory distress syndrome (ARDS) and evaluate future ...

A Model of Cardiac Remodeling Through Constriction of the Abdominal Aorta in Rats

Heart failure is one of the leading causes of death worldwide. It is a complex clinical syndromethat includes fatigue, dyspnea, exercise intolerance, and fluid retention. Changes in myocardial structure, electrical conduction, and energy metabolism develop with heart failure, leading to contractile dysfunction, increased risk of arrhythmias, and sudden death. Hypertensive heart disease is one of the key contributing factors of cardiac remodeling associated with heart failure. The most commonly-used animal model mimicking hypertensive heart disease is created via surgical interventions, such as by narrowing the aorta. Abdominal aortic constriction is a useful experimental technique to induce a pressure overload, which leads to heart failure. The surgery can be easily performed, without the need for chest opening or mechanical ventilation. Abdominal aortic constriction-induced cardiac pathology progresses gradually, making this model relevant to clinical hypertensive heart failure. Cardiac injury and remodeling can be observed 10 weeks after the surgery. The method described here provides a simple and effective approach to produce a hypertensive heart disease animal model that is suitable for studying disease mechanisms and for testing novel therapeutics.

A rat model of abdominal aortic constriction that induces cardiac hypertrophy and remodeling is described. An efficient, highly-reproducible, and minimally-invasive method is used to provide a simple yet useful platform for research in myocardial hypertrophy and dysfunction.

Heart failure is one of the leading causes of death worldwide. It is a complex clinical syndromethat includes fatigue, dyspnea, exercise intolerance, and ...

A Model to Simulate Clinically Relevant Hypoxia in Humans

In case of apnea, arterial partial pressure of oxygen (pO2) decreases, while partial pressure of carbon dioxide (pCO2) increases. To avoid damage to hypoxia sensitive organs such as the brain, compensatory circulatory mechanisms help to maintain an adequate oxygen supply. This is mainly achieved by increased cerebral blood flow. Intermittent hypoxia is a commonly seen phenomenon in patients with obstructive sleep apnea. Acute airway obstruction can also result in hypoxia and hypercapnia. Until now, no adequate model has been established to simulate these dynamics in humans. Previous investigations focusing on human hypoxia used inhaled hypoxic gas mixtures. However, the resulting hypoxia was combined with hyperventilation and is therefore more representative of high altitude environments than of apnea. Furthermore, the transferability of previously performed animal experiments to humans is limited and the pathophysiological background of apnea induced physiological changes is poorly understood. In this study, healthy human apneic divers were utilized to mimic clinically relevant hypoxia and hypercapnia during apnea. Additionally, pulse-oximetry and Near Infrared Spectroscopy (NIRS) were used to evaluate changes in cerebral and peripheral oxygen saturation before, during, and after apnea.

Hypoxia simulation in humans has usually been performed by inhaling hypoxic gas mixtures. For this study, apneic divers were used to simulate dynamic hypoxia in humans. Additionally, physiological changes in desaturation and re-saturation kinetics were evaluated with non-invasive tools such as Near-Infrared-Spectroscopy (NIRS) and peripheral oxygenation saturation (SpO2).

In case of apnea, arterial partial pressure of oxygen (pO2) decreases, while partial pressure of carbon dioxide (pCO2) increases. To avoid damage to ...

Use of a Central Venous Line for Fluids, Drugs and Nutrient Administration in a Mouse Model of Critical Illness

This protocol describes a centrally catheterized mouse model of prolonged critical illness. We combine the cecal ligation and puncture method to induce sepsis with the use of a central venous line for fluids, drugs and nutrient administration to mimic the human clinical setting. Critically ill patients require intensive medical support in order to survive. While the majority of patients will recover within a few days, about a quarter of the patients need prolonged intensive care and are at high risk of dying from non-resolving multiple organ failure. Furthermore, the prolonged phase of critical illness is hallmarked by profound muscle weakness, and endocrine and metabolic changes, of which the pathogenesis is currently incompletely understood. The most widely used animal model in critical care research is the cecal ligation and puncture model to induce sepsis. This is a very reproducible model, with acute inflammatory and hemodynamic changes similar to human sepsis, which is designed to study the acute phase of critical illness. However, this model is hallmarked by a high lethality, which is different from the clinical human situation, and is not developed to study the prolonged phase of critical illness. Therefore, we adapted the technique by placing a central venous catheter in the jugular vein allowing us to administer clinically relevant supportive care, to better mimic the human clinical situation of critical illness. This mouse model requires an extensive surgical procedure and daily intensive care of the animals, but it results in a relevant model of the acute and prolonged phase of critical illness.

This protocol describes a centrally catheterized mouse model of prolonged critical illness. We combine the cecal ligation and puncture method to induce sepsis with the use of a central venous line for fluids, drugs and nutrient administration to mimic the human clinical setting.

This protocol describes a centrally catheterized mouse model of prolonged critical illness. We combine the cecal ligation and puncture method to induce ...

Observational Study Protocol for Repeated Clinical Examination and Critical Care Ultrasonography Within the Simple Intensive Care Studies

Longitudinal evaluations of critically ill patients by combinations of clinical examination, biochemical analysis and critical care ultrasonography (CCUS) may detect adverse events of interventions such as fluid overload at an early stage. The Simple Intensive Care Studies (SICS) is a research line that focuses on the prognostic and diagnostic value of combinations of clinical variables.
The SICS-I specifically focused on the use of clinical variables obtained within 24 h of acute admission for prediction of cardiac output (CO) and mortality. Its sequel, SICS-II, focuses on repeated evaluations during ICU admission. The first clinical examination by trained researchers is performed within 3 h after admission consisting of physical examination and educated guessing. The second clinical examination is performed within 24 h after admission and includes physical examination and educated guessing, biochemical analysis and CCUS assessments of heart, lungs, inferior vena cava (IVC) and kidney. This evaluation is repeated at days 3 and 5 after admission. CCUS images are validated by an independent expert, and all data is registered in an online secured database. Follow-up at 90 days includes registration of complications and survival status according to patient&#39;s medical charts and the municipal person registry. The primary focus of SICS-II is the association between venous congestion and organ dysfunction.
The purpose of publishing this protocol is to provide details on the structure and methods of this on-going prospective observational cohort study allowing answering multiple research questions. The design of the data collection of combined clinical examination and CCUS assessments in critically ill patients are explicated. The SICS-II is open for other centers to participate and is open for other research questions that can be answered with our data.

Structured protocols are necessary to provide answers on research questions in critically ill patients. The Simple Intensive Care Studies (SICS) provides an infrastructure for repeated measurements in critically ill patients including clinical examination, biochemical analysis and ultrasonography. SICS projects have specific focus but the structure is flexible to other investigations.

Longitudinal evaluations of critically ill patients by combinations of clinical examination, biochemical analysis and critical care ultrasonography (CCUS) ...

A Protocol to Set Up Needle-Free Connector with Positive Displacement on Central Venous Catheter in Intensive Care Unit

Needle-free connectors were initially designed and promoted to avoid blood exposure for healthcare workers. Some recent data suggest that the latest generation of connectors (with positive displacement) may be of interest for reducing central venous line infections. We have been using needle-free connectors for several years in our intensive care unit and here we present a protocol for installing these connectors on central venous catheters. After insertion of the catheter and control of the permeability of the lines, the connectors must be purged with 0.9% NaCl before being connected. The connectors replace all disposable caps used on infusion stopcocks and manifolds. All the connectors are changed every 7 days as recommended by the manufacturer (except when there is macroscopic contamination, which requires an immediate change of the connector). Before each injection, the connector must be disinfected for at least 3 seconds with 70% isopropyl alcohol. The connectors must not be disconnected (unless changed), as the injection is done through the device. Setting up the connectors slightly increases the total time required to place the catheter and there is no formal evidence that these connectors reduce the incidence of infectious or thrombotic complications. However, these devices simplify the management of central venous lines and prevent the catheter circuit from &#34;opening&#34; once it has been sterilely installed.

We present a protocol to show the installation of a needle-free connector with positive displacement on a central venous catheter.

Needle-free connectors were initially designed and promoted to avoid blood exposure for healthcare workers. Some recent data suggest that the latest ...

Inducing Acute Lung Injury in Mice by Direct Intratracheal Lipopolysaccharide Instillation

Airway administration of lipopolysaccharide (LPS) is a common way to study pulmonary inflammation and acute lung injury (ALI) in small animal models. Various approaches have been described, such as the inhalation of aerosolized LPS as well as nasal or intratracheal instillation. The presented protocol describes a detailed step-by-step procedure to induce ALI in mice by direct intratracheal LPS instillation and perform FACS analysis of blood samples, bronchoalveolar lavage (BAL) fluid, and lung tissue. After intraperitoneal sedation, the trachea is exposed and LPS is administered via a 22 G venous catheter. A robust and reproducible inflammatory reaction with leukocyte invasion, upregulation of proinflammatory cytokines, and disruption of the alveolo-capillary barrier is induced within hours to days, depending on the LPS dosage used. Collection of blood samples, BAL fluid, and lung harvesting, as well as the processing for FACS analysis, are described in detail in the protocol. Although the use of the sterile LPS is not suitable to study pharmacologic interventions in infectious diseases, the described approach offers minimal invasiveness, simple handling, and good reproducibility to answer mechanistic immunological questions. Furthermore, dose titration as well as the use of alternative LPS preparations or mouse strains allow modulation of the clinical effects, which can exhibit different degrees of ALI severity or early vs. late onset of disease symptoms.

Presented here is a step-by-step procedure to induce acute lung injury in mice by direct intratracheal lipopolysaccharide instillation and to perform FACS analysis of blood samples, bronchoalveolar lavage fluid, and lung tissue. Minimal invasiveness, simple handling, good reproducibility, and titration of disease severity are advantages of this approach.

Airway administration of lipopolysaccharide (LPS) is a common way to study pulmonary inflammation and acute lung injury (ALI) in small animal models. ...

Halogenated Agent Delivery in Porcine Model of Acute Respiratory Distress Syndrome via an Intensive Care Unit Type Device

Acute respiratory distress syndrome (ARDS) is a common cause of hypoxemic respiratory failure and death in critically ill patients, and there is an urgent need to find effective therapies. Preclinical studies have shown that inhaled halogenated agents may have beneficial effects in animal models of ARDS. The development of new devices to administer halogenated agents using modern intensive care unit (ICU) ventilators has significantly simplified the dispensing of halogenated agents to ICU patients. Because previous experimental and clinical research suggested potential benefits of halogenated volatiles, such as sevoflurane or isoflurane, for lung alveolar epithelial injury and inflammation, two pathophysiologic landmarks of diffuse alveolar damage during ARDS, we designed an animal model to understand the mechanisms of the effects of halogenated agents on lung injury and repair. After general anesthesia, tracheal intubation, and the initiation of mechanical ventilation, ARDS was induced in piglets via the intratracheal instillation of hydrochloric acid. Then, the piglets were sedated with inhaled sevoflurane or isoflurane using an ICU-type device, and the animals were ventilated with lung-protective mechanical ventilation during a 4 h period. During the study period, blood and alveolar samples were collected to evaluate arterial oxygenation, the permeability of the alveolar-capillary membrane, alveolar fluid clearance, and lung inflammation. Mechanical ventilation parameters were also collected throughout the experiment. Although this model induced a marked decrease in arterial oxygenation with altered alveolar-capillary permeability, it is reproducible and is characterized by a rapid onset, good stability over time, and no fatal complications.
We have developed a piglet model of acid aspiration that reproduces most of the physiological, biological, and pathological features of clinical ARDS, and it will be helpful to further our understanding of the potential lung-protective effects of halogenated agents delivered through devices used for inhaled ICU sedation.

We describe a model of hydrochloric acid-induced acute respiratory distress syndrome (ARDS) in piglets receiving sedation with halogenated agents, isoflurane and sevoflurane, through a device used for inhaled intensive care sedation. This model can be used to investigate the biological mechanisms of halogenated agents on lung injury and repair.

Acute respiratory distress syndrome (ARDS) is a common cause of hypoxemic respiratory failure and death in critically ill patients, and there is an urgent ...