Determination of optimal monopolar coagulation settings for upper GI bleeding in a pig model

Effective, safe and efficient porcine model of Forrest Ib bleeding gastric and colonic ulcers

BACKGROUND

Developing effective gastrointestinal (GI) bleeding animal models is necessary to advance endoscopic hemostasis methods and train endoscopists on their use. Our aim, therefore, was to develop an effective and safe porcine GI bleeding model in the stomach and colon of large and small-sized oozing-type ulcers.

METHODS

Gastric and colonic bleeding ulcers were created using either a hybrid endoscopic submucosal dissection (ESD) technique or a cap-assisted endoscopic mucosal resection (EMR-C) technique in 14 pigs. Prior to ulcer creation, animals were treated with either oral apixaban or intravenous (IV) unfractionated heparin anticoagulation in combination with clopidogrel and aspirin. The primary outcome was the technical success of inducing oozing-type Forrest Ib bleeding ulcers. Secondary outcomes included ulcer diameter, number, creation time and the number of complications associated with each technique.

RESULTS

Using hybrid ESD and IV heparin anticoagulation, bleeding was observed in 21/23 (91.3%) gastric ulcers and 6/7 (85.7%) colonic ulcers created. The mean diameter and ulcer creation time were 2.3 ± 0.3 cm and 5.3 ± 0.5 min, respectively, for gastric ulcers and 2.2 ± 0.4 cm and 4.06 ± 0.6 min, respectively, for colonic ulcers. Using EMR-C and IV heparin anticoagulation, bleeding was observed in 14/15 (93.3%) gastric ulcers and 6/6 (100%) colonic ulcers created. The mean diameter and ulcer creation time were 0.8 ± 0.2 cm and 2.1 ± 0.5 min, respectively, for gastric ulcers and 0.7 ± 0.2 cm and 1.7 ± 0.3 min, respectively, for colonic ulcers. None of the ulcers created in animals anticoagulated with apixaban developed bleeding. None of the 14 pigs developed any complications.

CONCLUSION

We have demonstrated the effectiveness and safety of a porcine GI bleeding model utilizing IV heparin anticoagulation and either hybrid ESD or EMR-C techniques to create oozing-type bleeding ulcers in the stomach and colon with customizable size.

Bigger Is Not Always Better: Effects of Electrocautery Setting on Tissue Injury in a Porcine Model

Introduction

Electrosurgery for dissection and hemostasis remains one of the foundational tools for the field of surgery as a whole. Monopolar cautery remains the most utilized modality for achieving the aforementioned goals. Given the prolonged history and pre-modern development of "Bovie" cautery, there remains a paucity of data regarding appropriate settings and intensity for various tissue types, procedures, or locales. As a result, utilized settings depend on precedent and personal preference. We aimed to determine the amount of secondary soft tissue injury by volume and depth beyond the electrocautery pen tip in the skin and subcutaneous tissue as well as skeletal muscle. 

Methods

Porcine samples were used for experimental testing using two testing types: 1) skin and subcutaneous tissue and 2) Skeletal muscle. Sample sizes were standardized at 1 cm3 cubes. For skin samples, tissue injury was created with either a scalpel or electrocautery pen on cut setting, and tested at intensities from 10 to 150 in increments of 10. Skeletal muscle samples were similarly tested using the electrocautery pen only in either a cut or coagulation setting. Samples were tested at incremental intensities from 10 to 120 for both settings. Electrocautery was tested for a period of five seconds with a continuous current. All samples were placed in formalin and underwent histologic staining with hematoxylin and eosin staining to be assessed for the extent of tissue injury in terms of depth, radius, and volume. The measurements were recorded in millimeters.

Results

For skin incision, there was a positive and significant correlation with respect to the radius (R=.73, p=0.006). When considering intensity with an interval of 10-70 there was a positive and significant correlation with respect to the radius, depth, and volume. The cold knife incision had no notable soft tissue injury beyond the depth of the incision. Regarding skeletal muscle, again, a significant and positive correlation between increasing monopolar settings was noted for both the coagulation and cut functions (R=.84, p=.0005; R=0.84, p=0.0006). A positive correlation was found between increasing cut intensity and volume of soft tissue injury (R=0.73, p=.008); this was not reflected in the coagulation setting. When limited to an intensity range of 10-60, a significant relationship was noted for depth, radius and volume (R=.95, p= <0.001; R=0.98, p= <.001; R=.92, p=.001).

Conclusion

In all samples, apart from the cold knife skin incision, additional soft tissue injury beyond the tip of the electrocautery pen was noted. Given our findings, recommendations include using the lowest setting required for the purposes of the given surgical case as well as minimizing electrocautery use for skin incisions given its association with a larger volume of tissue injury in comparison with a scalpel. Additionally, electrocautery should be used with care in, and around neurovascular structures as soft tissue injury did occur several millimeters beyond the tip of the electrocautery pen. Further study is needed to see if these patterns are similar in living animals as well as human tissue and whether they bear any clinical impact on surgical wound healing or other surgical complications.

Microperforation of the colon: animal model in rats to reproduce mucosal thermal damage

BACKGROUND

The aim of the present study was to develop a rat model of colonic microperforation secondary to thermal injury for future studies to assess new treatments.

METHODS

Twenty-four male Sprague-Dawley rats were used in this study. Hot biopsy forceps were used for all treatments. All lesions were created in proximal left colon using the soft coagulation setting. The power setting tested was 40 W, and the durations of monopolar soft coagulation application evaluated were 2, 3, and 4 s.

RESULTS

In the acute phase, 48 h after thermal injury, durations of cautery of 2 and 3 s resulted in transmural necrosis, whereas with 4 s microperforation was obtained. In the late phase, 7 d after the damage, only duration of cautery of 4 s showed deep cautery effects, with signs of peritonitis.

CONCLUSIONS

We determined optimal power settings and duration of therapy in a rat model for producing electrocautery that involves transmural necrosis with microperforation.