instrumentation and monitoring techniques in femoral vascular access for hemodynamic assessment in a porcine model

Dosage-Dependent Induction of Endotoxemia in Pigs via LPS Infusion

Sepsis and septic shock rank among the leading causes of mortality in patients receiving intensive care treatment1,2,3. Sepsis arises when an infection triggers a dysregulated immune response resulting in multiorgan failure. It is characterized by life-threatening symptoms, including hemodynamic instability, respiratory distress, hepatic and renal failure, as well as cognitive impairment4,5. Septic shock represents a subset of sepsis with particularly severe symptoms that significantly increase mortality. These symptoms include persistent hypotension requiring vasopressor therapy and a serum lactate level exceeding 2 mmol&#8729;L-1&#160;4,5. Mortality rates in patients with septic shock have been estimated as high as 40%, even with hospital treatment1,3,5.
Gram-negative bacteria, such as Pseudomonas and Escherichia coli, often cause infections triggering this dysregulated immune response4. The underlying pathophysiological mechanisms are complex and not yet fully understood. One well-described aspect involves the activation of Toll-like receptors on immune cells by pathogen-associated molecular patterns (PAMPs), leading to the release of cytokines such as tumor necrosis factor-alpha (TNF&#945;) or Interleukin 1 (IL 1)4. One of these PAMPs is lipopolysaccharide (LPS), which constitutes a component of the cell membrane in gram-negative bacteria6. LPS has been employed in animal models to induce endotoxemia and endotoxemic shock7,8.
Animal models provide a controlled and standardized setting to develop and investigate novel treatment strategies. Due to its similar anatomy, immunological physiology, and comparable hemodynamic parameters, the pig model is particularly well-suited for studying the effects of endotoxemic shock9,10. Furthermore, standard medical equipment commonly used in human patients can be readily applied in pigs due to the similar size of their airways and blood vessels, facilitating instrumentation and hemodynamic monitoring.
With this protocol, we provide an experimental model for endotoxemic shock in pigs by intravenously infusing LPS derived from E. coli. To monitor the effects, we measured hemodynamic and pulmonary parameters, including arterial blood pressure, heart rate, peripheral oxygen saturation, pulmonary arterial pressure, and airway pressure. To evaluate the influence of endotoxemia on cerebral oxygen supply, we used near-infrared spectrometry (NIRS). With this method, the cerebral oxygen saturation can be evaluated via an adhesive electrode applied to the forehead11.

Author Spotlight: Induction of Experimental Endotoxemic Shock in Pigs for Studying Hemodynamic and Respiratory Failure

Lipopolysaccharide Infusion as a Porcine Endotoxemic Shock Model

With this protocol, we induce experimental endotoxemic shock in pigs. We were able to reliably cause symptoms of endotoxemia, such as hemodynamic instability and respiratory failure. Lipopolysaccharide is a toxic substance.When working with lipopolysaccharide, it is essential always to wear gloves, protective goggles, a mask, and a lab coat. This protocol provides an easy and reliable way to induce endotoxemia. Because of their similar anatomy and physiology, pigs are particularly well-suited for this kind of research as standard medical equipment may be used.Using this protocol, we will be able to study the effects of different ventilation strategies in respiratory failure and lung damage during endotoxemic shock.

Instrumentation and Monitoring Techniques in Femoral Vascular Access for Hemodynamic Assessment in a Porcine Model

To begin, place the anesthetized pig supine on a working platform. Apply an alcoholic disinfectant to the inguinal area and wipe it with a sterile swab. Then apply disinfectant and wait three minutes before placing a sterile fenestrated drape over the inguinal area.Using ultrasound, identify the femoral blood vessels and visualize them longitudinally. Next, puncture the femoral vein with a syringe attached to the needle and confirm venous puncture with slow-flowing, dark red blood. Insert the wire into the vein and remove the needle while leaving the wire in place.Then puncture the artery with a syringe attached to the needle for continuous aspiration. Confirm the arterial puncture with bright red, pulsating blood. Remove the syringe from the artery and insert the prepared wire.Then remove the needle while leaving the wire in place. Using ultrasound, visualize the femoral vessels to confirm the correct positioning of both wires. Next, use Seldinger's technique to insert the arterial introducer sheath into the femoral artery, and the venous introducer sheath into the femoral vein.To confirm proper positioning, draw the blood from the arterial and central venous lines for blood gas analysis. Next, flush the lines with saline to prevent clot formation. Secure the lines to the skin using surgical sutures to prevent dislocation.Connect the arterial and central venous lines to transducers for hemodynamic measurements. Insert a pulse contour cardiac output, or PICO catheter, into the arterial introducer sheath. Connect the catheter to the arterial pressure transducer and the temperature interface cable of the PICO monitor.While continuously measuring pressure, insert the Swan-Ganz catheter into the central venous inducer sheath. Inflate the balloon once the catheter is inserted approximately 30 centimeters, and upon the appearance of a central venous pressure curve. Slowly advance the catheter into the central venous introducer sheath while monitoring the pressure curve.Once the catheter enters the right ventricle, examine for a pulse curve with a high systolic and low diastolic value. To confirm the placement of the catheter in the pulmonary artery, advance the catheter further and look for a consistent systolic and an increased diastolic value. Fix the catheter in position and connect the injectate temperature sensor of the PICO system to the proximal lumen of the Swan-Ganz catheter.

Research

JoVE Journal

Medicine

Sepsis and septic shock are frequently encountered in patients treated in intensive care units (ICUs) and are among the leading causes of death in these ...