Developing a Clinically Relevant Hemorrhagic Shock Model in Rats
March 22nd, 2024
Hemorrhagic shock kills 1.9 million people worldwide every year. Small animals are frequently used as hemorrhagic shock models but are associated with issues of standardization, reproducibility, and clinical significance, thus limiting their relevance. This article describes developing a new clinically relevant hemorrhagic shock model in rats.
Hemorrhagic shock is responsible for 2 million deaths worldwide every year. We are studying the pathophysiological mechanism of hemorrhagic shock with the aim of identifying new target and thus proposing innovative therapeutic strategies. Hemorrhagic shock is a difficult condition in its own right, hemodynamic alteration with metabolic damage and organ dysfunction.
The variety of experiments protocol make its study even more complex. In this study, we proposed to develop a reproductive, standardized, and clinically relevant rat model of hemorrhagic shock. We hope that this model of hemorrhagic shock can become one of the standard model for future study.
The use of a standard model would facilitate advance in the field, and at least because it would make it possible to compare results between differences in working on hemorrhagic shock. To begin, insert a lubricated rectal probe to control the temperature of the anesthetized rat during surgery. After locating the jugular region in the lower right neck region of the anesthetized rat above the clavicle, use DeBakey atraumatic forceps to gently grasp the skin and make a precise incision with fine sharp scissors or a scalpel.
Gently slash the tissue with standard pattern forceps. Locate and gently liberate the jugular vein from its muscular compartment. Place a 4-0 silk suture thread to securely ligate the distal side of the jugular vein.
Use the suture with the needle holders to tension the jugular vein. Place a 4-0 suture on the proximal side of the jugular vein and prepare a surgeon knot without tightening it. Using Vannas micro dissecting scissors, make a small incision in the jugular vein.
After carefully grasping the vein wall with small forceps, insert the PE50 catheter in the jugular vein. Slightly advance the catheter and to confirm its correct placement in the vein, draw a small amount of blood and re-inject it. Tighten the previously prepared knot to secure the catheter.
Apply a drop of lidocaine to the incised area. Cover the incision with a moist sterile gauze pad. Use DeBakey atraumatic forceps to grasp the skin of the Scarpa triangle on the left leg, and make an incision with fine sharp scissors or a scalpel.
Gently dilacerate tissue with standard pattern forceps. Locate the femoral triad and place one forceps under the triad. Then with a second standard pattern forceps, carefully separate the artery from the nerve and femoral vein.
Place a 4-0 suture the femoral artery distally and take the suture with the needle holders to put the femoral artery in tension. Now, place a 4-0 suture on the proximal side of the femoral artery and prepare a surgeon knot without closing it. After clamping the artery, use Vannas micro dissecting scissors to make a transverse incision in the femoral artery.
Grasp the artery wall with standard pattern forceps and cannulate the femoral artery with the catheter, holding it with forceps. Gently unclamp the artery and ensure that the blood is not flowing back into the catheter. If the signal is good, advance the catheter slightly into the artery and tighten the previously prepared surgeon knot.
Administer heparin into the rat and place a moistened sterile gauze pad over the incised area. After 10 minutes of stabilization, record the basal hemodynamic values for five minutes. To induce hemorrhagic shock, use a 1 mL syringe to draw 5 mL of blood from the femoral artery over five minutes.
Prepare a mix of 50%lactated Ringer's solution and 50%collected blood at room temperature. Place a 2 mL syringe filled with the mix at the end of the jugular vein cannula. For hemorrhagic shock maintenance, when mean arterial pressure exceeds 38 mmHg, withdraw 200 L of blood from the femoral artery.
If pressure drops below 32 mmHg, inject 200 microliters of the 50%blood, 50%lactated Ringer's mixture through the jugular vein. After sterile preparation of the tail with a gauze pad, use the tip of the needle to draw a blood drop from the end of the tail to measure peripheral blood lactate. Finally, resuscitate the rat with a lactated Ringer's solution using a 20 mL syringe through the jugular catheter with a syringe pump.
After hemorrhagic shock treatment, clamp the jugular vein of the anesthetized rat. Remove the catheter from the veins. Upon ligation, ensure that there is no blood leakage from the vessels.
Now, use a 5-0 sterile suture to close incised areas with subcutaneous and cutaneous stitches. Disinfect the surgical area with 10%povidone iodine solution. Using a 1 mL syringe fitted with a 26-gauge needle, subcutaneously inject buprenorphine.
Upon awakening, place the rat on the heating mat in its cage. After 16 hours of hemorrhagic shock induction, draw a blood drop from the end of the tail to measure blood lactate. Place the anesthetized rat on the surgical table and insert the rectal probe.
For carotid artery cannulation, use DeBakey atraumatic forceps to grasp the skin and make an incision in the middle of the neck with fine and sharp scissors, or a scalpel. With standard pattern forceps, gently dilacerate tissue. Separate the salivary glands and open the tracheal muscle to reveal the tracheal rings.
Isolate the left carotid artery from the nerve with standard pattern forceps and ligate it distally with a 4-0 silk thread. Now, place the suture thread on the proximal side of the artery and prepare a surgeon's knot without closing it. After clamping, use Vannas micro dissecting scissors to incise the carotid artery.
With standard operating forceps, gently grasp the artery wall to enlarge the opening and cannulate the artery with the catheter provided, holding it using forceps. Gently unclamp the artery and ensure that the blood is not flowing back into the catheter. After confirming the correct blood pressure signal, advance the catheter slightly into the artery and tighten the previously prepared surgeon knot.
Basal mean arterial pressure was similar between sham and hemorrhagic shock groups. 24 hours post-hemorrhagic shock induction, the mean arterial pressure significantly decreased in the hemorrhagic shock group due to a reduction in diastolic blood pressure. No changes were observed in systolic blood pressure, pulse pressure, and heart rate across groups.
While the shock index remained unchanged, the modified shock index exhibited a notable increase in the hemorrhagic shock group. Lactatemia, indicative of global metabolic impairment, showed a significant increase following hemorrhagic shock, further elevating after 16 hours of hemorrhagic shock. Temperature, and respiration rate, markers of systemic inflammatory response syndrome, remained unchanged between groups 16 hours after hemorrhagic shock induction.
Behavioral assessments demonstrated an increased behavioral score in the hemorrhagic shock group, suggesting altered postures and activities.
Overview
This article presents a new rat model for studying hemorrhagic shock, addressing the limitations of small animal models. The aim is to enhance standardization and clinical relevance in research.
Key Study Components
Area of Science
- Neuroscience
- Pathophysiology
- Animal Models
Background
- Hemorrhagic shock causes approximately 2 million deaths annually worldwide.
- Current small animal models face issues of standardization and clinical relevance.
- Understanding the mechanisms of hemorrhagic shock is crucial for developing therapeutic strategies.
- A standardized model could facilitate comparisons across studies.
Purpose of Study
- To develop a reproducible and clinically relevant rat model of hemorrhagic shock.
- To improve the understanding of hemorrhagic shock mechanisms.
- To establish a standard model for future research in this area.
Methods Used
- Insertion of a rectal probe for temperature control during surgery.
- Jugular and femoral artery cannulation for blood withdrawal and infusion.
- Induction of hemorrhagic shock through controlled blood withdrawal.
- Monitoring of hemodynamic parameters and blood lactate levels.
Main Results
- Establishment of a standardized surgical protocol for the rat model.
- Successful induction and maintenance of hemorrhagic shock.
- Comparison of hemodynamic values between sham and hemorrhagic shock groups.
- Potential for this model to serve as a standard for future studies.
Conclusions
- The developed rat model addresses key limitations of existing models.
- This model may enhance the understanding of hemorrhagic shock.
- Standardization will facilitate advancements in hemorrhagic shock research.
Frequently Asked Questions
Executive Industry Relevance
Standardized preclinical models are critical for de-risking therapeutic hypotheses in hemorrhagic shock, a complex and high-mortality indication. This rat model enables reproducible interrogation of pathophysiological mechanisms and quantitative assessment of candidate interventions. Its clinical relevance and reproducibility support robust target validation and portfolio triage in early-stage drug discovery.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Enables mechanistic de-risking by replicating human-relevant hemodynamic and metabolic responses.
- Supports functional target validation through quantitative measurement of organ damage and metabolic markers.
- Facilitates hypothesis-driven evaluation of new molecular targets in a standardized system.
Screening & Assay Development
- Provides a validated in vivo platform for assessing efficacy of candidate therapeutics under controlled shock conditions.
- Delivers reproducible endpoints such as lactate, behavioral scores, and hemodynamic parameters for quantitative screening.
- Enables assay standardization and cross-study comparability for compound evaluation.
Translational & Preclinical Research
- Aligns preclinical findings with clinically relevant endpoints, supporting translational biomarker development.
- Maintains continuity from discovery through preclinical validation by modeling patient care interventions.
- Reduces translational risk by mirroring human pathophysiology and therapeutic response.
Pipeline & Workflow Integration
This model bridges early discovery and preclinical validation, supporting lead identification and mechanistic studies in hemorrhagic shock research.
- Discovery Biology: Enables rigorous hypothesis testing and pathway clarification in a disease-relevant system.
- Screening: Provides reproducible, quantitative outputs for compound triage and prioritization.
- Analytics: Supports statistical comparison of intervention effects using standardized hemodynamic and metabolic readouts.
- Translational Research: Facilitates biomarker alignment and risk-adjusted advancement decisions.
- Enterprise Reuse: Establishes a reusable, standardized platform for ongoing therapeutic evaluation in hemorrhagic shock.
Operational & Enterprise Impact
- Scientific Value: Increases predictive confidence and reduces mechanistic ambiguity in target validation.
- Operational Value: Enhances reproducibility, standardization, and scalability across research teams.
- Strategic Value: Improves go/no-go decision quality and capital efficiency by reducing late-stage biological risk.
- Portfolio Impact: Enables risk-adjusted prioritization and advancement of candidate therapies.
Implementation Considerations
- Requires expertise in small animal surgery and hemodynamic monitoring.
- Demands access to instrumentation for blood pressure, lactate, and behavioral assessments.
- Necessitates protocol standardization for cross-team reproducibility.
- Adaptable to different rat strains or intervention types with protocol adjustments.
- Limitations include species-specific responses and the need for skilled personnel.
