Heparinized swine models for better surgical/endoscopic training

Establishment of a swine model of delayed bleeding after endoscopic procedure

Objectives

Although delayed bleeding after endoscopic procedures has become a problem, currently, there are no appropriate animal models to validate methods for preventing it. This study aimed to establish an animal model of delayed bleeding after endoscopic procedures of the gastrointestinal tract.

Methods

Activated coagulation time (ACT) was measured using blood samples drawn from a catheter inserted into the external jugular vein of swine (n = 7; age, 6 months; mean weight, 13.8 kg) under general anesthesia using the cut-down method. An upper gastrointestinal endoscope was inserted orally, and 12 mucosal defects were created in the stomach by endoscopic mucosal resection using a ligating device. Hemostasis was confirmed at this time point. The heparin group (n = 4) received 50 units/kg of unfractionated heparin via a catheter; after confirming that the ACT was ≥200 s 10 min later, continuous heparin administration (50 units/kg/h) was started. After 24 h, an endoscope was inserted under general anesthesia to evaluate the blood volume in the stomach and the degree of blood adherence at the site of the mucosal defect.

Results

Delayed bleeding was observed in three swine (75%) in the heparin-treated group, who had a maximum ACT of >220 s before the start of continuous heparin administration. In the non-treated group (n = 3), no prolonged ACT or delayed bleeding was observed at 24 h.

Conclusion

An animal model of delayed bleeding after an endoscopic procedure in the gastrointestinal tract was established using a single dose of heparin and continuous heparin administration after confirming an ACT of 220 s.

Novel device for blunt dissection in third space endoscopy: Preliminary animal study (with video)

Background and study aims

Blunt dissection is not commonly performed in flexible endoscopic procedures. We developed a novel blunt dissection device and evaluated its feasibility, safety, and potential effectiveness in third space endoscopy procedures.

Materials and methods

The device consists of a cotton swab and a flexible shaft. To evaluate its functionality, creation of 4-cm submucosal tunnels in live swine stomachs was attempted by either blunt dissection using our device or sharp dissection using a standard monopolar knife. Data on factors such as completion rate, operating time, adverse events, necessity of submucosal injection, and dissected submucosal thickness were collected.

Results

Eighteen submucosal tunnels were successfully created (sharp: 9, blunt: 9) by two experienced endoscopists and one novice endoscopist. Median operating time was significantly shorter in the blunt dissection group (239 vs. 429 s, P = 0.008). In the sharp dissection group, the experienced endoscopists did not cause any muscle layer injuries, but the novice endoscopist caused muscle layer injuries in all cases. In the blunt dissection group, neither experienced nor novice endoscopists caused muscle layer injuries. The blunt dissection group required significantly fewer submucosal injections (0 vs. 5, P < 0.001). Median dissected submucosal thickness was similar between the groups.

Conclusions

Blunt dissection using our device was feasible, safe, and potentially effective in third space endoscopy procedures by shortening operating time, reducing submucosal injections, and potentially minimizing muscle layer injury.

No Injury Observed in Kidneys Treated with Burst Wave Lithotripsy in Therapeutically Anticoagulated Pigs

Introduction: Current American Urological Association guidelines recommend that patients with acute obstructive kidney stone requiring continuous anticoagulation/antiplatelet therapy should not be treated by shockwave lithotripsy or percutaneous nephrolithotomy because of the risk of catastrophic renal hemorrhage possible with those techniques. Currently, ureteroscopy is the only recommended surgical treatment. We evaluated if burst wave lithotripsy (BWL) could be used in these cases by treating pigs with BWL while undergoing anticoagulation therapy. Materials and Methods: Six pigs (31-37 kg) were given 200 units/kg porcine heparin, and then the right kidney of each animal was treated with a dose of BWL (18,000 ultrasound pulses at 10 Hz, 20 cycles/pulse, peak positive pressure of 12 MPa) known to fracture kidney stones. The contralateral kidney served as a control. Therapeutic anticoagulation was confirmed by evaluating activated partial thromboplastin time (aPTT). Microhematuria was checked by urine test strips. Kidneys were subsequently evaluated for hemorrhagic injury via MRI. Results: aPTT was significantly elevated (>100 seconds) throughout the entire treatment period (p = <0.001) indicating therapeutic anticoagulation. Gross hematuria was not observed in any of the pigs. After BWL, microhematuria averaged 145.8 red blood cells (RBC)/μL in the BWL-treated kidney and 48 RBC/μL in the control kidneys, and there was no statistically significant difference noted in microhematuria rates between the two groups (p = 0.16). Hemorrhagic injury measured only 0.10 ± 0.02% of the tissue in the BWL-treated kidneys and 0.12 ± 0.04% in the control side, with a paired difference of -0.03 ± 0.05%, showing no significant difference (p = 0.58). Conclusions: A typical clinical dose of BWL causes no hemorrhagic injury to the kidney even during therapeutic anticoagulation therapy. This result suggests that BWL should be safe to use in patients with stone undergoing anticoagulation/antiplatelet therapy.

Intraoperative bleeding model for swine gastric endoscopic submucosal dissection via heparinization

Background and study aims: Live swine have a high degree of coagulation and aggregation and using them for training about how to manage intraoperative bleeding during endoscopic submucosal dissection (ESD) is unsatisfactory. This study aimed to identify the appropriate heparin dose in an intraoperative bleeding model and validate its applicability. Methods: First, we explored the dose of heparin required for a swine bleeding model in which the activated clotting time reached and maintained the upper limit of measurement (1500 s) after 10 minutes. Second, we compared intraoperative bleeding and hematoma frequency during ESD for 2-cm lesions between the heparinized bleeding model and control groups. Intraoperative bleeding was classified according to the Forrest classification. Results: The combination of a bolus (300 U/kg), continuous infusion (300 U/kg/h), and a bolus dose (150 U/kg) of heparin 10 minutes after the first infusion was identified as the dose for the bleeding model. Five ESDs were performed in each heparinized bleeding model and the control group. The median number of intraoperative bleeds was significantly higher in the heparinized model than in the control group (5 interquartile range [IQR] 4-7 vs. 3 [IQR 0-4, P = 0.028). All of the intraoperative bleeding events oozing (Forrest Ib) rather than spurting (Forrest Ia). The median number of hematomas was significantly higher in the heparinized model group than in the control group (3 [IQR 1-4] vs. 0 [IQR 0-1], P = 0.023). Conclusions: High doses of heparin significantly increased intraoperative bleeding and hematoma during swine ESD.

A Janus Gelatin Sponge with a Procoagulant Nanoparticle-Embedded Surface for Coagulopathic Hemostasis

Apart from the wide and safe application of natural polymer-based hemostatic materials/devices, it is still desirable to develop new types of hemostatic materials that can achieve both potent coagulopathic hemostasis and a facile preparation process. In this work, one Janus gelatin sponge (J-ZGS) is readily constructed for both coagulation-dependent and coagulopathic hemostasis by embedding zein nanoparticles on the surface of a self-prepared gelatin sponge (S-GS): zein nanoparticles were facilely prepared by an antisolvent method to achieve procoagulant blood-material interactions, while S-GS was prepared by freeze-drying a foaming gelatin solution. Due to the distinct secondary structure, the optimal zein nanoparticles possessed a higher in vitro hemostatic property than the pristine zein powder and other nanoparticles, the underlying mechanism of which was revealed as the superior RBC/platelet adhesion property in the presence/absence of plasma proteins. Compared with S-GS and a commercial gelatin sponge, J-ZGS achieved a significantly higher in vitro hemostatic property and similarly good blood compatibility/cytocompatibility. Moreover, in vivo artery-injury models confirmed the outstanding hemostatic performance of J-ZGS under both coagulation-dependent and coagulopathic conditions. Our work offers an appealing approach for developing potent hemostatic sponges from natural polymer-based nanoparticles that could be further extended to versatile hemostatic materials for coagulopathic hemostasis.

Development and evaluation of a titanium-based planar ultrasonic scalpel for precision surgery

This paper introduces a titanium-based planar ultrasonic microscalpel. The concept of silicon-based planar ultrasonic transducers has already been proven, but they are not yet suitable for clinical use due to material failure. The main objective of this work was to develop a smaller, lighter, and more cost-effective ultrasonic scalpel that could be used as an alternative or supplementary device to current surgical instruments. Various prototypes were fabricated and characterized, differing in bonding by three epoxy adhesives and two solder pastes as well as three variations in tip design. The instruments were designed to operate in the frequency range of commercial instruments and to generate a longitudinal displacement amplitude. The electro-mechanical characterization through impedance analysis and vibration measurements was complemented by an in vitro cutting trial and an acute in vivo animal experiment in comparison to commercial ultrasonic and electrosurgical devices. The operating frequency was around 40 kHz and 48 kHz depending on whether matched or unmatched operation was used. Unmatched operation turned out to be more suitable, achieving displacement amplitudes of 25.3 μm and associated velocity amplitudes of up to 7.9 m/s at an electrical power of 10.2 W. The cutting ability was demonstrated in vivo by successful dissection even under anticoagulation. The geometry of the instrument tip was found to have a major influence on cutting performance by affecting the resonance behaviour and tissue penetration.