Evaluation of lateral thermal damage and reepithelialization of incisional wounds created by CO2-laser, monopolar electrosurgery, and radiosurgery: a pilot study on porcine oral mucosa

Novel Strategies for Orofacial Soft Tissue Regeneration

Significance: Orofacial structures are indispensable for speech and eating, and impairment disrupts whole-body health through malnutrition and poor quality of life. However, due to the unique and highly specialized cell populations, tissue architecture, and healing microenvironments, regeneration in this region is challenging and inadequately addressed to date. Recent Advances: With increasing understanding of the nuanced physiology and cellular responses of orofacial soft tissue, novel scaffolds, seeded cells, and bioactive molecules were developed in the past 5 years to specifically target orofacial soft tissue regeneration, particularly for tissues primarily found within the orofacial region such as oral mucosa, taste buds, salivary glands, and masseter muscles. Critical Issues: Due to the tightly packed and complex anatomy, orofacial soft tissue injury commonly implicates multiple tissue types, and thus functional unit reconstruction in the orofacial region is more important than single tissue regeneration. Future Directions: This article reviews the up-to-date knowledge in this highly translational topic, which provides insights into novel biologically inspired and engineered strategies for regenerating orofacial component tissues and functional units.

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.

Terminal Deoxynucleotidyl Transferase-Mediated Deoxyuridine Triphosphate Nick End Labeling (TUNEL) Assay to Characterize Histopathologic Changes Following Thermal Injury

Background

Despite the wide application of lasers and radiofrequency (RF) surgery in dermatology, it is difficult to find studies showing the extent of damage dependent on cell death.

Objective

We evaluated histopathologic changes following in vivo thermal damage generated by CO₂ laser, 1,444 nm long-pulsed neodymium:yttrium-aluminum-garnet (LP Nd:YAG) laser and RF emitting electrosurgical unit.

Methods

Thermal damage was induced by the above instruments on ventral skin of rat. Specimens were stained with hematoxylin and eosin, along with a terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling (TUNEL) assay, to highlight the degree of irreversible cellular injury.

Results

The volume of vaporization was largest with the CO₂ laser. Area of cell death area identified by TUNEL assay, when arranged from widest to narrowest, was 1,444 nm LP Nd:YAG laser, CO₂ laser, and RF emitting electrosurgical unit.

Conclusion

This histopathologic evaluation of the acute characterization of injury across devices may be advantageous for attaining better treatment outcomes.

In vitro histological evaluation of the surgical margins made by different laser wavelengths in tongue tissues

BACKGROUND

Lasers have become standard tools for the surgical treatment of oral lesions. The purpose of this study is to determine the surgical margins and histologically evaluate the tissue thermal effects induced by different types of surgical instruments.

MATERIAL AND METHODS

Cuts were made in pork tongues' mucosa with different lasers (Er:YAG at 2W with and without air / water spray and at 4W with and without air / water spray; CO2 at 3.5W and 7W in pulsed mode and at 7W in continuous mode; the diode laser at 3.5W and boost 3.5W in pulsed mode; Nd:YAG at 6W, 40Hz and electroscalpel at 5W and conventional scalpel as control. Macroscopic and microscopic morphological changes were evaluated.

RESULTS

The results of this study showed that the surgical instruments that caused greater tissue damage extension were: the Nd:YAG laser (670.68μm), the diode 3.5W and boost PW (626.82μm), the CO2 7W CW (571.18μm), the CO2 at 7W PW (485.45μm), the diode 3.5W PW (456.15μm), the electroscalpel (409.57μm) and lastly the CO2 laser 3.5W PW (306.19μm) and Er:YAG (74.66μm) laser, regardless of power, mode or air / water spray used. An association between the Tissue Damage Extension and the Degree of Carbonization (r = 0.789; P = 0.01), and an association between the Tissue Damage Extension and Regularity of the Incision were found (r = -, 299; P = 0.01).

CONCLUSIONS

The results of this study suggest that lasers can be used in soft tissues biopsies of the oral cavity, enabling a correct histopathological analysis, as long as the biological effects of each laser type are considered. The Er:YAG laser revealed its potential for biopsies of the oral mucosa ensuring a successful histological evaluation and the CO2 laser at 3,5W in pulsed mode presented itself as the best choice for surgeries with hemostasis. Key words:CO2 laser, diode laser, Er:YAG laser, laser surgery, Nd:YAG laser, oral mucosa, thermal effect.

Comparison of ferromagnetic induction and bipolar electrosurgery and suction in corticotomies in pig cerebrum

INTRODUCTION

The effects of newer energy-based surgical dissection and coagulation modalities on cerebral tissue have not been investigated. Several instruments have been developed to address the limitations of traditional electrosurgical instruments in the nervous system. We compared the effects of standard bipolar electrocautery and suction (BPS) with those of a new ferromagnetic induction (FMI) device in corticotomies of pig cerebral tissue as assessed by magnetic resonance imaging (MRI) and histological analysis.

METHODS

Three adult pigs underwent bilateral corticotomies (3 cm long×1 cm deep) using both FMI and BPS. The acute cerebral tissue edema created by each method was measured on coronal volumetric T2-weighted MRI sequences immediately after surgery. A lateral thermal "damage index" was calculated by dividing the width of the visible T2 tissue edema by the measured depth. The radiographic damage indices with each method were compared statistically. Histological analysis of each incision was conducted to compare the extent of tissue damage.

RESULTS

MRI showed that the mean radiographic damage index of each corticotomy was significantly lower with the FMI (0.30 ± 0.02 (0.28-0.32)) than with the BPS method (0.54 ± 0.11 (0.42-0.64)) (p = 0.02). Histological analysis suggested a correlation with the radiographic findings as the FMI tissue samples demonstrated less adjacent tissue damage than BPS.

CONCLUSIONS

FMI appeared to cause less adjacent tissue damage than the BPS method in pig cerebral tissue based on quantitative radiographic and qualitative histological analysis. Future studies are needed to investigate the clinical implications of energy-based surgical dissection on cerebral tissue.

Electrosurgery: part I. Basics and principles

The term electrosurgery (also called radiofrequency surgery) refers to the passage of high-frequency alternating electrical current through the tissue in order to achieve a specific surgical effect. Although the mechanism behind electrosurgery is not completely understood, heat production and thermal tissue damage is responsible for at least the majority--if not all--of the tissue effects in electrosurgery. Adjacent to the active electrode, tissue resistance to the passage of current converts electrical energy to heat. The only variable that determines the final tissue effects of a current is the depth and the rate at which heat is produced. Electrocoagulation occurs when tissue is heated below the boiling point and undergoes thermal denaturation. An additional slow increase in temperature leads to vaporization of the water content in the coagulated tissue and tissue drying, a process called desiccation. A sudden increase in tissue temperature above the boiling point causes rapid explosive vaporization of the water content in the tissue adjacent to the electrode, which leads to tissue fragmentation and cutting.

Electrosurgery: part II. Technology, applications, and safety of electrosurgical devices

Electrosurgical currents can be delivered to tissue in monopolar or bipolar and monoterminal or biterminal modes, with the primary difference between these modes being their safety profiles. A monopolar electrosurgical circuit includes an active electrode and a dispersive (return) electrode, while there are 2 active electrodes in bipolar mode. In monoterminal mode, there is an active electrode, but there is no dispersive electrode connected to the patient's body and instead the earth acts as the return electrode. Biterminal mode uses a dispersive electrode connected to the patient's body, has a higher maximum power, and can be safer than monoterminal mode in certain situations. Electrosurgical units have different technologies for controlling the output power and for providing safety. A thorough understanding of these technologies helps with a better selection of the appropriate surgical generator and modes.