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JoVE Journal Bioengineering

Bioengineering

Noninvasive and Invasive Renal Hypoxia Monitoring in a Porcine Model of Hemorrhagic Shock

Published: October 28, 2022 doi: 10.3791/64461
1, 2,3, 1,4, 4,5
1Department of Biomedical Engineering, University of Utah, 2Department of Emergency Medicine, University of Utah, 3Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, 4Department of Anesthesiology, University of Utah, 5Geriatric Research, Education, and Clinical Centre, VAMC

Abstract

Up to 50% of patients with trauma develop acute kidney injury (AKI), in part due to poor renal perfusion after severe blood loss. AKI is currently diagnosed based on a change in serum creatinine concentration from baseline or prolonged periods of decreased urine output. Unfortunately, baseline serum creatinine concentration data is unavailable in most patients with trauma, and current estimation methods are inaccurate. In addition, serum creatinine concentration may not change until 24-48 h after the injury. Lastly, oliguria must persist for a minimum of 6 h to diagnose AKI, making it impractical for early diagnosis. AKI diagnostic approaches available today are not useful for predicting risk during the resuscitation of patients with trauma. Studies suggest that urinary partial pressure of oxygen (PuO2) may be useful for assessing renal hypoxia. A monitor that connects the urinary catheter and the urine collection bag was developed to measure PuO2 noninvasively. The device incorporates an optical oxygen sensor that estimates PuO2 based on luminescence quenching principles. In addition, the device measures urinary flow and temperature, the latter to adjust for confounding effects of temperature changes. Urinary flow is measured to compensate for the effects of oxygen ingress during periods of low urine flow. This article describes a porcine model of hemorrhagic shock to study the relationship between noninvasive PuO2, renal hypoxia, and AKI development. A key element of the model is the ultrasound-guided surgical placement in the renal medulla of an oxygen probe, which is based on an unsheathed optical microfiber. PuO2 will also be measured in the bladder and compared to the kidney and noninvasive PuO2 measurements. This model can be used to test PuO2 as an early marker of AKI and assess PuO2 as a resuscitative endpoint after hemorrhage that is indicative of end-organ rather than systemic oxygenation.

Introduction

Acute kidney injury (AKI) affects up to 50% of patients with trauma admitted to the intensive care unit1. Patients who develop AKI tend to have longer hospital and intensive care unit lengths of stay and a threefold greater risk of mortality2,3,4. Currently, AKI is most commonly defined by the Kidney Disease Improving Global Outcomes (KDIGO) guidelines, which are based on changes in serum creatinine concentration from baseline or periods of prolonged oliguria5. Baseline creatinine concentration data are unavailable in most patients with trauma, and estimation equations are unreliable and have not been validated in patients with trauma6. In addition, serum creatinine concentration may not change until at least 24 h after the injury, precluding early identification and intervention7. While research suggests that urine output is an earlier indicator of AKI than serum creatinine concentration, the KDIGO criteria require a minimum of 6 h of oliguria, which precludes interventions targeting injury prevention8. The optimal hourly urine output threshold and appropriate duration of oliguria for defining AKI are also debated, which limit its effectiveness as an early marker of the disease9,10. Thus, current diagnostic measures for AKI are not useful in trauma settings, lead to delayed diagnosis of AKI, and do not provide real-time information regarding a patient's risk status for developing AKI.

While the development of AKI in a trauma setting is complex and likely associated with several causes such as poor renal perfusion due to hypovolemia, reduced renal blood flow due to vasoconstriction, trauma-related inflammation, or ischemia-reperfusion injury, renal hypoxia is a common factor among most forms of AKI11,12. In particular, the medulla region of the kidney is highly susceptible to an imbalance between oxygen demand and supply in the trauma setting due to reduced oxygen delivery and high metabolic activity associated with sodium reabsorption. Thus, if it were possible to measure renal medulla oxygenation, it may be possible to monitor a patient's risk status for developing AKI. While this is not clinically feasible, urinary partial pressure of oxygen (PuO2) at the outlet of the kidney strongly correlates with medullary tissue oxygenation13,14. Other studies have shown that it is possible to measure bladder PuO2 and that it changes in response to stimuli that alter medullary oxygen and renal pelvis PuO2 levels, such as a decrease in renal blood flow15,16,17. These studies suggest that PuO2 may indicate end-organ perfusion and could be useful for monitoring the impact of interventions in trauma settings on renal function.

To monitor PuO2 noninvasively, a noninvasive PuO2 monitor was developed that can easily connect to the end of a urinary catheter outside the body. The noninvasive PuO2 monitor consists of three main components: a temperature sensor, a luminescence quenching oxygen sensor, and a thermal-based flow sensor. Since each oxygen sensor is optically based and relies on the Stern-Volmer relationship to quantify the relationship between luminescence and oxygen concentration, a temperature sensor is necessary to offset any potential confounding effects of changes in temperature. The flow sensor is important to quantify urine output and to determine the direction and magnitude of urine flow. All three components are connected by a combination of male, female, and t-shaped luer lock connectors and poly-vinyl chloride (PVC) flexible tubing. The end with the conical connector connects to the outlet of the urinary catheter, and the end with tubing over the conical connector connects slides over the connector on the urine collection bag.

Despite measuring distally to the bladder, a recent study showed that low urinary PuO2 during cardiac surgery is associated with an increased risk of developing AKI18,19. Similarly, current animal models have primarily focused on the early detection of AKI during cardiac surgery and sepsis14,20,21,22. Thus, questions remain about the use of this novel device in settings of trauma. The aim of this research is to establish PuO2 as an early marker of AKI and investigate its use as a resuscitative endpoint in patients with trauma. This manuscript describes a porcine model of hemorrhagic shock that includes the placement of the noninvasive PuO2 monitor, a bladder PuO2 sensor, and a tissue oxygen sensor in the renal medulla. Data from the noninvasive monitor will be compared to bladder PuO2 and invasive tissue oxygen measurements. The noninvasive monitor also includes a flow sensor which will be useful for understanding the relationship between urine flow rate and oxygen ingress, which reduces the ability to infer renal medullar tissue oxygenation from noninvasive PuO2 as urine traverses the urinary tract. Additionally, data from the three oxygen sensors will be compared to systemic vital signs, such as mean arterial pressure. The central hypothesis is that noninvasive PuO2 data will strongly correlate with invasive medullary oxygen content and will reflect medullary hypoxia during resuscitation. Noninvasive PuO2 monitoring has the potential to improve trauma-related outcomes by identifying AKI earlier and serving as a novel resuscitative endpoint after hemorrhage that is indicative of end-organ rather than systemic oxygenation.

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Protocol

The Institutional Animal Care and Use Committee of the University of Utah approved all experimental protocols described here. Prior to the experiment, a total of 12 castrated male or non-pregnant female Yorkshire swine weighing 50-75 kg and between 6-8 months old were acclimated in their enclosures for at least 7 days. During this period, all care is directed by a veterinarian and in accordance with the Guide for the Care and Use of Laboratory Animals and the Animal Welfare Act Regulations and Standards. The animals are fasted overnight prior to induction of anesthesia but are allowed free access to water.

1. Sensor assembly

  1. Cut a 6 cm piece of 3/8 in thermoplastic elastomer (TPE) tubing, 25 mm pieces of 1/8 in and 3/16 in PVC tubing, and 31 mm pieces of 1/8 in and 3/16 in PVC tubing.
  2. Drill a hole in the top of the non-vented cap to fit the exposed tip of the temperature probe; start with a 3/32 in drill bit, then use a 1/8 in drill bit.
  3. Use a 5/32 in drill bit to drill out the top part of the T-connector to fit the oxygen sensor.
  4. Slide the shorter piece of the 1/8 in PVC tubing over the inlet side of the flow sensor. Slide the longer 1/8 in piece of PVC tubing over the outlet side (as designated by the arrow on the flow sensor itself) of the flow sensor. Slide the shorter and longer 3/16 in pieces of PVC tubing over the corresponding lengths of the 1/8 in PVC tubing. Insert the barbed end of the male luer lock connector into the open end of the 1/8 in PVC tubing.
    NOTE: If necessary, use a heat gun to heat the tubing prior to sliding over barbed fittings. It is also possible to use isopropyl alcohol to lubricate the barbed end to make it easier to slide the tubing over the barbed connector.
  5. Mix the biocompatible glue.
  6. Expose the tip of the temperature probe by removing any protective sheathing or tubing. Fill the inside of the tubing of the thermistor with biocompatible glue but do not cover the exposed tip.
  7. Assemble the parts as shown in Figure 1. Use the glue to secure each luer lock connection, when inserting the thermistor in the non-vented cap, and prior to sliding the 3/8 in TPE tubing over the barbed end.
  8. Prior to sterilization, ensure the blue cap on the oxygen stick is not twisted too tightly, or it will be difficult to undo after sterilization.
    NOTE: An image of an assembled device is shown in Figure 1 for reference. For this experiment, the fiber optic cable was connected to an electro-optical module that contains software that is designed to work with the specific oxygen sensors used in the device. Any luminescence quenching-based oxygen sensor and compatible data collection device will work. In addition, a custom module and a printed circuit board were designed to connect the flow sensor and temperature probe. Custom software was used to collect and display data in real-time.

2. Experimental procedure

  1. Induction of anesthesia and monitoring.
    1. Sedate the animal with a combined intramuscular injection of Ketamine (2.2 mg/kg) and Xylazine (2.2 mg/kg).
    2. Depending on the size of the animal, place an appropriately sized (most likely between 7 mm and 8 mm) cuffed endotracheal tube with the assistance of a laryngoscope.
    3. Apply eye lubricant to both eyes.
    4. Following induction, mechanically ventilate the animal with the maintenance of anesthesia with 1.5%-3.0% gaseous isoflurane mixed in oxygen. Set the fraction of inspired oxygen between 40%-100%, the positive end-expiratory pressure to 4 cm H2O, the tidal volume to 6-8 mL/kg, and adjust the respiratory rate and tidal volume to maintain end-tidal CO2 of 35-45 mmHg.
    5. Monitor and confirm the proper depth of anesthesia by assessing jaw tone, palpebral reflex approximately every 15 min, and absence of spontaneous movement throughout the experiment. Additionally, monitor clinical parameters of tissue perfusion (mucous membrane color, capillary refill time, heart rate), pulse oximetry, end-tidal CO2, core body temperature, and electrocardiogram.
    6. Position the animal in dorsal recumbency on a warming blanket and secure each leg to the table.
    7. The protocol is a non-survival procedure with euthanasia of the animal at the end of the experiment, as described in section 5.
  2. Prepare the animal for the experiment.
    1. Prepare all puncture sites (which are listed in steps 2.2.3-2.2.7) by scrubbing the skin with three alternating scrubs of chlorhexidine followed by alcohol. After the third scrub, apply chlorhexidine and allow to dry completely, then drape the surgical site in a sterile fashion.
    2. Locally infiltrate all puncture and incision sites with 2% lidocaine for local pain relief.
    3. Using ultrasound guidance and the Seldinger technique, place a 9 Fr catheter in the right external jugular vein for medication infusion and central venous pressure monitoring and a 7 Fr catheter in the right femoral vein for resuscitation.
    4. Under ultrasound guidance, place a 7 Fr sheath in the right brachial artery.
    5. Under ultrasound guidance, place a 7 Fr sheath in the right femoral artery.
    6. Under ultrasound guidance, place a 7 Fr sheath in the left femoral artery.
    7. Under ultrasound guidance, place a 5 Fr sheath in the right or left carotid artery.
    8. Monitor the pressure distal to the balloon of the resuscitative endovascular occlusion of the aorta (REBOA) catheter via the left femoral artery sheath.
      1. Connect a disposable pressure transducer to the arterial catheter that is distal to the REBOA balloon.
    9. Monitor the pressure proximal to the balloon of the REBOA catheter via the carotid artery sheath.
      1. Connect a disposable pressure transducer to the arterial catheter that is proximal to the REBOA balloon.
    10. Perform a midline laparotomy by making an incision along the midline of the abdomen, starting at the inferior part of the sternum and ending at the pubis.
    11. With the abdomen open, identify the bladder and perform a cystotomy, or make a small incision, to insert the tip of a 20 Fr urinary catheter in the bladder. Close the cystotomy with the urinary catheter in place using a purse string suture. After the catheter is in place, secure it to the skin with sutures.
    12. Prior to connecting the outlet of the catheter to the urinary collection bag, insert the cone-shaped end of the noninvasive PuO2 monitor into the outlet of the catheter.
    13. Place the open tubing at the end of the novel PuO2 monitor over the cone-shaped connector on the tubing that is connected to the urine collection bag.
    14. Remove the spleen.
      1. Locate the spleen. Identify the hilum of the spleen or the site where the splenic artery and vein enter the spleen. Clamp and transect each vessel.
      2. After transection, ligate each vessel using modified Miller knots using 2-0 sutures.
  3. Place the instrument to measure bladder PuO2 and tissue oxygenation.
    1. Measure PuO2 in the bladder.
      1. Remove all air from the bladder by slowly squeezing the bladder while ensuring urine does not leak out.
      2. Place the tip of the luminescence quenching-based PuO2 sensor in the bladder via a cystotomy, similar to the catheter.
      3. Connect the fiber optic cable from the bladder sensor to the data collection device.
      4. Create a new file on the data collection and note the time difference between the stand-alone collection device and other devices used in the experiment.
        1. For the data collection device used in this study: push the back arrow to reach the main menu.
        2. Go to measurement settings and click on Ok. Use the arrows to highlight the measurement browser box and push Ok.
        3. Push the right arrow to create a new file. Type in the name of the new file and select Done.
        4. Highlight the new file name and select Ok. Navigate to the measurement screen and click on Ok to start recording.
    2. Measure medullary renal tissue oxygenation.
      1. Identify the location of the kidney internally.
      2. Make a flank incision large enough to expose the kidney (approx. 2-3 in) on the side of the pig at approximately the same location where the kidney was identified.
      3. With the tips of a retractor together, introduce the retractor into the incision and then spread the tips of the retractor to expose the kidney.
      4. Use a micro-manipulator or similar tool to hold the oxygen probe steady. If possible, attach this tool to the end of an articulating arm.
      5. Attach the other end of the articulating arm to the surgical table so that the other end that will hold the oxygen probe is near the opened incision. If the tool that is used to hold the oxygen probe is not connected to an articulating arm, position the tool so the oxygen sensor is near the opened incision and is stable.
      6. Unlock all articulating joints of the arm. Using ultrasound, place the tip of the oxygen probe in the medulla region of the kidney. Lock all articulating joints on the arm.
      7. After confirming placement of the tip of the sensor in the medulla with ultrasound, use the micromanipulator to retract the needle housing the luminescence-based oxygen sensor. Connect the other end of the sensor to the data collection device connected to the computer running the data collection software. Start recording.
        1. Go to the Measurements tab. Click on the New button.
        2. Click on the name of the data collection device in the column on the far left. Click on the name of the new file and click the Assign To button at the top of the screen.
        3. In the Live View tab, press Start to begin recording. Note the time on the computer relative to other data collection devices.
      8. Wait for 10 min before beginning the experimental protocol after preparing the instrumentation and animal. This will be considered a baseline period.
  4. Experimental protocol
    1. Prior to starting the experimental procedure, ensure the mean arterial pressure (MAP) is ≥65 mmHg. If MAP is below the threshold, give up to two 5 mL/kg boluses of isotonic crystalloid solution. If MAP remains below 65 mmHg, infuse norepinephrine (0.02 µg/kg/min) until target MAP is achieved.
    2. Induce hemorrhagic shock.
      1. Remove 25% (estimated as 60 mL/kg) of the animal's estimated blood volume through the right brachial artery sheath over 30 min into gently agitated citrated blood collection bags. Mark the beginning of blood removal as t = 0 min.
      2. Store the removed blood in a warm water bath at 37 °C.
      3. Then perform randomization to assign animals to either the REBOA with whole blood or REBOA with crystalloids group (n = 6 for each group).
    3. Place the REBOA catheter.
      1. Insert a 7 Fr REBOA catheter in the right femoral artery sheath. Place the balloon of the catheter immediately superior to the diaphragm and confirm the location using fluoroscopy.
      2. At t = 30 min, inflate the REBOA balloon and completely occlude the aorta for 45 min.
    4. Initiate resuscitation and administer critical care.
      1. At t = 70 min, transfuse each animal with their shed blood over 15 min.
      2. Infuse intravenous calcium over 10 min to prevent citrate-induced hypocalcemia.
      3. At t = 75 min, deflate the REBOA balloon over 10 min.
      4. Until t = 360 min, resuscitate the animal with fluids and norepinephrine to maintain a MAP > 65 mmHg.
  5. End of experiment and euthanasia
    1. Collect any remaining blood or urine samples.
    2. Euthanize the animal by injecting a combination of Pentobarbital Sodium (390 mg) and Phenytoin Sodium (50 mg) (1 mL/10 lbs).

3. Data processing

  1. Time-sync all data files.
    1. Based on the times that were noted on each device relative to each other and the start of the experiment, align all data files such that t = 0 indicates the start of the experiment.
  2. Remove any data points associated with error flags from the flow sensor.
    NOTE: The error types are High Flow Rate and Air-in-Line. The High Flow Rate error indicates the flow rate exceeded the sensor's output limit. The Air-in-Line error flag is raised when the sensor detects air in the flow channel.
  3. Discard the data associated with the negative flow.
    1. Once flow becomes negative, track the volume that flows past the sensor in the backward direction.
    2. After the flow becomes positive, track the volume and compare it to the volume of negative flow to only include measurements from recently voided urine.

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Representative Results

Figure 1 shows an image of the noninvasive PuO2 monitor described in this manuscript. Figure 2 shows a plot of MAP and noninvasive PuO2 measurements in a single subject during an experiment similar to the described porcine hemorrhage model. At the start of the experiment, as hemorrhage was initiated, there was a drop in MAP and PuO2. Following the initial decline in PuO2 it gradually increased until after the REBOA balloon was deflated. The gradual increase corresponded with a period of drastically reduced urine output due to hemorrhage-induced hypovolemia followed by aortic occlusion. During the period of low urine output, PuO2 data were not reliable because of oxygen exchange with surrounding tissue and air as urine traveled from the outlet of the kidney to the noninvasive measurement site. This must be considered when interpreting or analyzing data collected by following this protocol. During the critical care phase, there was a significant drop-off in PuO2, which corresponded with an increase in urine output. The increase in urine output limited the impact of the oxygen exchange with surrounding tissue, and PuO2 data were determined to be valid. Noninvasive PuO2 data collected during periods of the experiment can be compared to other data, such as MAP. In this subject, MAP appears to remain constant during the critical care period and PuO2 reaches a maximum at around 180 min followed by a decrease until 240 min, which is followed by a gradual increase until the end of the experiment.

Figure 1
Figure 1: An image of the noninvasive PuO2 monitor. The device connects between the catheter and the collection bag. The device contains a temperature probe, a luminescence-based oxygen sensor and associated fiber optic cable, and a thermal-based flow sensor. Please click here to view a larger version of this figure.

Figure 2
Figure 2: Noninvasive PuO2 and MAP measured during the described hemorrhagic shock porcine model. All data were sampled at 1 Hz. HEM = Hemorrhage, MAP = mean arterial pressure. Please click here to view a larger version of this figure.

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Discussion

AKI is a common complication in patients with trauma, and currently, there is no validated bedside monitor for kidney tissue oxygenation, which could enable earlier AKI detection and guide potential interventions. This manuscript describes the use and instrumentation of a porcine hemorrhagic shock model to establish noninvasive PuO2 as an early indicator of AKI and a novel resuscitation endpoint in trauma settings.

One of the distinct advantages of this porcine model is the ability to compare oxygen measurements at three different locations, including directly in the medulla. While it is possible to measure bladder and noninvasive PuO2 in humans, it is not possible to measure oxygen content directly in the medulla. Prior animal models studying the application of PuO2 monitoring in sepsis and cardiac surgery have typically relied on noninvasive or bladder oxygen measurements, with only a handful of studies also measuring medullary tissue oxygen content simultaneously23. Also, many of the previous studies have been performed in smaller animals such as mice or rabbits, which limits the translational impact. The use of swine is advantageous because the animals are large enough to allow monitoring and critical care similar to what critically ill patients undergo. It is important to note that the oxygen sensor is placed in the medulla under ultrasound guidance, as this region is highly susceptible to hypoxia compared to the cortex. In addition, the noninvasive monitor contains a urinary flow sensor. This is important as one of the confounding factors of measuring PuO2 distal to the renal pelvis is oxygen ingress along the urinary tract24. The impact of ingress of oxygen was seen in the data presented from the prior experiment. During periods of aortic occlusion and corresponding low urine flow, PuO2 was artificially elevated compared to the critical care phase, when urine output was increased. Using the urine flow rate data, it is possible to compare only valid noninvasive PuO2 data to bladder PuO2 and medullary tissue oxygen levels, as well as determine a flow rate threshold below which noninvasive PuO2 data no longer represents renal oxygenation.

In addition to comparing oxygen data at different measurement sites, this model will help compare which resuscitation products are most effective for improving renal oxygen delivery, renal tissue oxygenation, and indicators of global perfusion such as MAP. The current iteration of the model will compare whole blood and crystalloids. Current guidelines suggest using crystalloids as the first line of treatment in hypotensive bleeding trauma patients25. Others have shown that fluid resuscitation with crystalloids did not restore renal tissue oxygenation, while blood transfusion did26. However, the optimal transfusion endpoint is unclear, and resources may be limited in some trauma settings (rural, remote, or armed conflict environments). Based on the data from this study, the noninvasive PuO2 monitor may serve as a novel endpoint for determining an appropriate transfusion threshold in patients with trauma. After validating the noninvasive PuO2 monitor in this study, future iterations of this model may explore the use of other resuscitation fluids, such as hypertonic solutions and the use of synthetic colloids.

Similar to comparing different resuscitation products, data from this model can be used to compare global perfusion measurements to regional oxygenation and the relationship between systemic and regional oxygenation and outcomes. The current guidelines for trauma care recommend maintaining a MAP of 60-65 mmHg25. Studies have not found a conclusive optimal target MAP during hemorrhagic shock to preserve renal function27. The results from the prior experiment suggest that MAP may only be one factor that influences PuO2. While MAP was constant during the critical care phase, PuO2 was varied, which means there are likely other factors that influence PuO2. Thus, a method to monitor kidney oxygenation, such as noninvasive PuO2 monitoring, may be useful for guiding interventions compared to measures of global perfusion such as MAP. Noninvasive PuO2 monitoring has the potential to preserve renal function by reducing tissue hypoxia and minimizing organ dysfunction.

One of the key limitations of the noninvasive monitor used in this model is that no urine is produced during the hemorrhage or aortic occlusion phases. This limits comparisons between noninvasive PuO2, bladder PuO2 and medullary oxygenation to the resuscitation phase, where data collected from similar experiments show that urine flow is sufficient during this period. A second limitation of this model is that REBOA is used in both treatment groups. Based on current clinical practice, REBOA is typically only used in non-compressible torso hemorrhage scenarios28. Thus, future studies should investigate the use of noninvasive PuO2 monitoring with conventional hemorrhage control and resuscitation methods.

This model will help validate noninvasive PuO2 monitoring as a tool for early detection of AKI and assessing the response to resuscitation methods. This is important because this novel monitor can potentially reduce early and delayed morbidity and mortality related to trauma. This methods paper provides a step-by-step description of how to implement the model.

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Disclosures

N. Silverton, K. Kuck, and L. Lofgren are inventors of a patent and patent application surrounding the noninvasive monitor used in this study. This prototype is under development for commercial consideration by N. Silverton and K. Kuck, but as of yet, no commercial activity has occurred. The other authors declare no competing interests. The interpretation and reporting of these data are the responsibility of the authors alone.

Acknowledgments

The work in this grant is funded by the University of Utah Clinical and Translational Science Institute through the Translational and Clinical Studies Pilot Program and the Department of Defense office of the Congressionally Directed Medical Research Programs (PR192745).

Materials

Name Company Catalog Number Comments
1/8" PVC tubing Qosina SKU: T4307 Part of noninvasive PuO2 monitor
3/16" PVC tubing Qosina SKU: T4310 Part of noninvasive PuO2 monitor
3/32" (1), 1/8" (1), 5/32" (1) drill bit Dewalt N/A For building noninvasive PuO2 monitor
3/8" TPE tubing  Qosina SKU: T2204 Part of noninvasive PuO2 monitor
Biocompatible Glue Masterbond EP30MED Part of noninvasive PuO2 monitor
Bladder oxygen measurement device Presens Fibox 4 Stand-alone fiber optic oxygen meter
Bladder PuO2 sensor Presens DP-PSt3 Oxygen dipping probe
Chlorhexidine 4% scrub Vetone N/A For scrubbing insertion or puncture sites
Conical connector with female luer lock Qosina SKU: 51500 Part of noninvasive PuO2 monitor
Cuffed endotracheal tube Vetone 600508 For sedating the subject and providing respiratory support
Euthanasia solution (pentobarbital sodium|pheyntoin sodium) Vetone 11168 For euthanasia after completion of experiment
General purpose temperature probe, 400 series thermistor Novamed 10-1610-040 Part of noninvasive PuO2 monitor
Hemmtop Magic Arm 11 inch Amazon B08JTZRKYN Holding invasive oxygen sensor in place
HotDog veterinary warming system HotDog V106 For controlling subject temperature during experiment
Invasive tissue oxygen measurement device Presens Oxy-1 ST  Compact oxygen transmitter
Invasive tissue oxygen sensor Presens PM-PSt7 Profiling oxygen microsensor
Isoflurane Vetone 501017 To maintain sedation throughout the experiment
Isotonic crystalloid solution HenrySchein 1537930 or 1534612 Used during resuscitation in the critical care period
Liquid flow sensor Sensirion LD20-2600B Part of noninvasive PuO2 monitor
Male luer lock to barb connector Qosina SKU: 11549 Part of noninvasive PuO2 monitor
Male to male luer connector Qosina SKU: 20024 Part of noninvasive PuO2 monitor
Noninvasive oxygen measurement device Presens EOM-O2-mini Electro optical module transmitter for contactless oxygen measurements
Non-vented male luer lock cap Qosina SKU: 65418 Part of noninvasive PuO2 monitor
Norepinephrine HenrySchein AIN00610 Infusion during resuscitation
O2 sensor stick Presens SST-PSt3-YOP Part of noninvasive PuO2 monitor
PowerLab data acquisition platform AD Instruments N/A For data collection
REBOA catheter Certus Critical Care N/A Used in experimental protocol
Super Sheath arterial catheters (5 Fr, 7 Fr, 9 Fr) Boston Scientific C1894 For intravascular access
Suture Ethicon C013D For securing catheter to skin and closing incisions
T connector, all female luer locks Qosina SKU: 88214 Part of noninvasive PuO2 monitor

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References

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Lofgren, L. R., Hoareau, G. L., Kuck, K., Silverton, N. A. Noninvasive and Invasive Renal Hypoxia Monitoring in a Porcine Model of Hemorrhagic Shock. J. Vis. Exp. (188), e64461, doi:10.3791/64461 (2022).… More

Lofgren, L. R., Hoareau, G. L., Kuck, K., Silverton, N. A. Noninvasive and Invasive Renal Hypoxia Monitoring in a Porcine Model of Hemorrhagic Shock. J. Vis. Exp. (188), e64461, doi:10.3791/64461 (2022).

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