The authors want to thank Dagmar Dirvonskis for her excellent technical support.

The experiments in this protocol were approved by the State and Institutional Animal Care Committee (Landesuntersuchungsamt Rheinland-Pfalz, Koblenz, Germany; Chairperson: Dr. Silvia Eisch-Wolf; reference number: 23 177-07/G 14-1-084; 02.02.2015). The experiments were conducted in accordance with the Animal Research&#160;Reporting of In Vivo Experiments (ARRIVE) guidelines. The study was planned and conducted between November 2015 and March 2016. After extended literature research, the pig model was chosen as a well-esta...

The protocol describes one method of inducing hemorrhagic shock via controlled arterial bleeding in pigs that is guided by systemic hemodynamics, as well as by cerebral microcirculatory impairment. Shock conditions were achieved by a calculated blood withdrawal of 25-35 mL kg-1 and confirmed by the mentioned composite of surrogate parameters indicating considerable cardio-circulatory failure. If untreated, this procedure was lethal within 2 h in 66% of the animals, which underlines the severity and reproducibi...

Massive blood loss is among the main causes of injury-related deaths1,2,3. The loss of circulatory fluid and oxygen carriers leads to hemodynamic failure and severe oxygen undersupply and can cause irreversible organ failure and death. The severity level of shock is influenced by additional factors like hypothermia, coagulopathy, and acidosis4. Particularly the brain, but also the kidneys lack compensation capacity due to high oxygen demand and the incapability of adequate anaerobic energy generation5,6. For therapeutic purposes, fast and immediate action is pivotal. In clinical practice, fluid resuscitation with a balanced electrolyte solution is the first option for treatment, followed by the administration of red blood cell concentrates and fresh frozen plasma. Thrombocyte concentrates, catecholamines, and the optimization of coagulation and the acid-base status support the therapy to regain normal physiological conditions after sustained trauma. This concept focuses on the restoration of hemodynamics and macrocirculation. Several studies, however, show that microcirculatory perfusion does not recover simultaneously with the macrocirculation. Especially, cerebral perfusion remains impaired and further oxygen undersupply may occur7,8.
The use of animal models allows scientists to establish novel or experimental strategies. The comparable anatomy, homology, and physiology of pigs and humans enable conclusions on specific pathological factors. Both species have a similar metabolic system and response to pharmacologic treatments. This is a great advantage in comparison to small animal&#160;models where differences in blood volume, hemodynamics, and overall physiology make it almost impossible to mimic a clinical scenario9. Furthermore, authorized medical equipment and consumables can be easily used in porcine models. Additionally, it is easily possible to obtain pigs from commercial suppliers, which allows a high diversity of genetics and phenotypes and is cost reducing10. The model of blood withdrawal via vessel cannulation is quite common11,12,13,14,15.
In this study, we extend the concept of hemorrhagic shock induction via arterial blood withdrawal with an exact titration of hemodynamic failure and cerebral oxygenation impairment. Hemorrhagic shock is achieved if the cardiac index and mean arterial pressure drops below 40% of the baseline value, which has been shown to cause considerable deterioration of the cerebral regional oxygenation saturation8. Pulse contour cardiac output (PiCCO) measurement is used for continuous hemodynamic monitoring. First, the system has to be calibrated by transpulmonary thermodilution, which enables the calculation of the cardiac index of the extravascular lung water content and the global end-diastolic volume. Subsequently, the continuous cardiac index is calculated by pulse contour analysis and also provides dynamic preload parameters like pulse pressure and stroke volume variation.
This technique is well established in clinical and experimental settings.Near-infrared spectroscopy (NIRS) is a clinically and experimentally established method to monitor changes in cerebral oxygen supply in real-time. Self-adherent sensors are attached to the left and right forehead and calculate the cerebral oxygenation non-invasively in the cerebral frontal cortex. Two wavelengths of infrared light (700 and 900 nm) are emitted and detected by the sensors after being reflected from the cortex tissue. To assess the cerebral oxygen content, contributions of arterial and venous blood are calculated in 1:3 relations and updated in 5 s intervals. The sensitivity in depth of 1-4 cm is exponential decreasing and influenced by the penetrated tissue (e.g., skin and bone), although the skull is translucent to infrared light. The technique facilitates quick therapeutic actions to prevent patients from adverse outcomes like delirium or hypoxic cerebral injury and serves as the target parameter in case of impaired cardiac output16,17. The combination of both techniques during experimental shock enables an exact titration of macrocirculation, as well as cerebral microcirculatory impairment, to study this life-threatening event.

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standardized hemorrhagic shock induction guided by cerebral oximetry and extended hemodynamic monitoring in pigs

Hemorrhagic shock ranks among the main reasons for severe injury-related death. The loss of circulatory volume and oxygen carriers can lead to an insufficient oxygen supply and irreversible organ failure. The brain exerts only limited compensation capacities and is particularly at high risk of severe hypoxic damage.This article demonstrates the reproducible induction of life-threatening hemorrhagic shock in a porcine model by means of calculated blood withdrawal. We titrate shock induction guided by near-infrared spectroscopy&#160;and extended hemodynamic monitoring to display systemic circulatory failure, as well as cerebral microcirculatory oxygen depletion. In comparison to similar models that primarily focus on predefined removal volumes for shock induction, this approach highlights a titration by means of the resulting failure of macro- and microcirculation.

After starting the shock induction, a short time of compensation can be registered. With ongoing blood removal, the aforementioned cardio-circulatory decompensation, as monitored by a significant decrease of crSO2, the cardiac index, the intrathoracic blood volume index, and the global end-diastolic volume index (Figure 2, Figure 3, and Figure 4), occurs. Furthermore, significant tachycard...

Watch this Scientific Journal Video about Standardized Hemorrhagic Shock Induction Guided by Cerebral Oximetry and Extended Hemodynamic Monitoring in Pigs at JoVE.com

Standardized Hemorrhagic Shock Induction Guided by Cerebral Oximetry and Extended Hemodynamic Monitoring in Pigs

Hemorrhagic shock is a severe complication in seriously injured patients, which leads to life-threatening oxygen undersupply. We present a standardized method to induce hemorrhagic shock via blood withdrawal in pigs that is guided by hemodynamics and microcirculatory cerebral oxygenation.

Hemorrhagic shock ranks among the main reasons for severe injury-related death. The loss of circulatory volume and oxygen carriers can lead to an ...

This standardized model of hemorrhagic shock induction guided by cerebral oxymetry and external hemodynamic monitoring can be used to simulate a realistic clinical scenario. The main advantage of this model is its simple and highly flexible design, which allow various levels of cardio cellulatory impairment to be easily selected. This techniques allows the evaluation of different therapy concepts of hemorrhagic shock such as fluid resuscitation, coagulation, and catecholamine therapy.This technique provides insight into the different pathophysiological aspects of hemorrhagic shock and hemodynamic effects on cerebral regional oxygenation, as assessed by near infrared spectroscopy. Visualization of hemorrhagic shock can be critical because the compensation mechanisms of the animals can disguise hemodynamic instability for long period of time. Before beginning covering the inguinal area, apply ultrasound gel to the ultrasound probe and cover the inguinal of an anesthetized approximately 28 kilogram two to three month old pig with a sterile fenestrated drape.Scan the right femoral vessels with ultrasound using the doppler technique to distinguish between the artery and the vein. Visualize the longitudinal axis of the right femoral artery and puncture the right femoral artery under ultrasound visualization with a Seldinger needle under permanent aspiration with a five milliliter syringe. Bright red, pulsating blood confirms correct positioning of the aspired needle position.After disconnecting the syring, insert the guide wire and retract the Seldinger needle. Visualize the right femoral vein before rotating the probe 90 degrees to switch to a longitudinal view of the vein. Next, puncture the right femoral vein under ultrasound visualization with the Seldinger needle under permanent aspiration with the five milliliter syringe.A high oxygen level is indicative of arterial blood and a low oxygen level is a sign of venous blood. After disconnecting the syringe, insert the guide wire and retract the Seldinger needle. Visualize both right vessels under ultrasound to control the correct wire position and push a two millimeter arterial introducer sheath over the guide wire into the right artery and the central venous line into the right femoral vein.Then aspirate all of the ports and flush the ports with saline solution. For a pulse contour cardiac output, or PiCCO measurement, insert the PiCCO catheter into the right arterial introducer sheath and connect the catheter with the arterial wire of the PiCCO system and the arterial transducer directly to the PiCCO port. Next connect the venous measuring unit of the PiCCO system with the right venous introducer sheath.Switch the three way stopcocks of both transducers open to the atmosphere to calibrate the systems to zero, according to the manufacturer's instructions. Turn on the PiCCO system and confirm that a new patient is being measured. To calibrate the continuous cardiac output measurement, click TD for thermo dilution and load four degree Celsius physiological saline solution into a 10 milliliter syringe.Click start and quickly and steadily inject 10 milliliters of the cold saline solution into the venous measuring unit. Then wait until the measurement is complete and the system requests a repetition before repeating the procedure two more times. For cerebral regional oxygenation monitoring, first stick two self adherent near infrared spectroscopy sensors to the forehead of the pig and connect the pre-amplifier to the monitor and the color coded sensor cable connectors to the pre-amplifier.Close the pre-amp locking mechanism and attach the sensors to the sensor cables. After switching on the monitor, click new patient, enter the study name, and click done. Check the incoming signal.When the signal is stable, click baseline menu and set baselines. If the baseline has already been entered, click yes and event mark to confirm the new baseline. Then use the arrow buttons on the keyboard under next event to select the three induction event followed by select event.For hemorrhagic shock induction, connect the left arterial introducer sheath with a three way stopcock and equip one port of the three way stopcock with a 50 milliliter syring and one with an empty infusion bottle. Measure and document the exact hemodynamic parameters and calculate 40%of the cardiac index and mean arterial pressure as hemodynamic targets. Select the 93 blood loss event in the near infrared spectroscopy system and aspirate 50 milliliters of blood into the syringe.Switch the tree way stopcock and push the blood into the empty bottle. Note the removed blood volume and monitor the arterial blood pressure, cardiac index, and the cerebral regional oxygenation saturation closely. Then, select the 97 hypotension event.Using hemorrhagic shock has challenging critical aspects and should performed with caution, as hemodynamic instability can lead to sudden death. With ongoing blood removal, cardio circulatory decompensation as monitored by a significant decrease in the cerebral regional oxygen saturation, cardiac index, intrathoracic blood volume index and global end diastolic volume index occur. Furthermore, significant tachycardia and a decrease in arterial blood pressure are common manifestations of hemorrhagic shock.The stoke volume variation increases significantly while extravascular lung water content and systemic vascular resistance are usually unaffected. After ending the blood withdrawal, the hemodynamic values and cerebral regional oxygenation saturation typically remain at a critically low level. The hemoglobin content and hematocrit do not directly decrease during hemorrhagic shock induction, but lactate levels rise and the central venous oxygen saturation decreases.Hemorrhagic shock is a serious complication in severely injured patients that can lead to life threatening oxygen under supply. A fast and effective therapy is required to avoid serious organ damage. This procedure can be expanded hemodynamic therapy concept like fluid resuscitation or catecholamine administration.To investigate different methods for optimizing treatment. This new model paves the way for the evaluation of new therapy concepts of hemorrhagic shock because it simulates a realistic scenario similar to clinical emergency situations. Working with human and animal blood can be hazardous.Always wear gloves, a face mask, and safety glasses to avoid infectious disease contamination.

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7.3K vues.  University Medical Center of the Johannes Gutenberg-University. Ce modèle normalisé d’induction hémorragique de choc guidé par oxymétrie cérébrale et surveillance hémodynamique externe peut être employé pour simuler un scénario clinique réaliste. Le principal avantage de ce modèle est sa conception simple et très flexible, qui permettent de sélectionner facilement différents niveaux d’affaiblissement cardio-cellulatoire. Ces techniques permettent l’évaluation de différents concepts thérapeutique du choc hémorragique tels que la r...