The plasma scalpel is an electrosurgical device that uses pulsed radiofrequency to generate a plasma-mediated discharge along the exposed rim of an insulated blade. It is neither a laser nor a scalpel or radiofrequency device. Plasma, from the physical point of view, is believed to be the fourth state of aggregation of matter, between the liquid and the gaseous states, a sort of liquefied gas according to physicists. This plasma rim provides a cutting edge for precise tissue dissection with simultaneous hemostasis and lesser thermal damage by the blade at physiological body temperatures [1
is a newly developed technology that makes it possible to generate plasma energy directly from the air, therefore, without using other inert gases (Argon or Helium) [4
]. The ionization process of the air is achieved through an electronic process. Initially neutral, the air is ionized by passing a strong high-frequency and high-voltage electromagnetic pulse through an electronic process. In this way, the insulating power of the air is eliminated, thus transforming it into an ideal conductor of energy. The generated plasma is visible in the form of a glow [4
is a plasma scalpel that uses Airplasma®
technology for a thermo-clotting-electro-plasma- device (Figure 1
). According to the manufacturer, this device offers the following features: combined cutting, ablation, and coagulation function, reduces invasiveness due to the absence of return plates, necrotized area almost wholly absent or limited, operating temperature ≤50 °C, no need for protection for the operator and patient, and no use of inert gases.
Despite the increasing popularity and widespread use of the plasma scalpel, there is a paucity of data on morphological changes in injured tissues [7
]. The aim of the present study was to compare the effects of the cold-blade, electrosurgical, and air plasma units on the skin morphology, using both light microscopy and scanning electron microscopy (SEM), also considering the type and spread (invasivity) of damage on the cut skin.
2. Materials and Methods
The study was performed on client-owned dogs presented to the veterinary teaching hospital, Department of Emergencies and Organ Transplantation of the University of Bari, Italy. Informed written consent was obtained for each patient before the inclusion in the study. All devices used in this study are approved for use in veterinary medicine in the United Europe.
The study included four female dogs, two mixed-breed and two Cocker Spaniel dogs, with an average age of 6.3 years and an average weight of 9.5 kg, diagnosed with mammary cancer and undergoing a total unilateral mastectomy. Premedication included acepromazine 0.002 mg/kg and morphine 0.3 mg/kg IM Anesthetic induction was performed with propofol 4–5 mg/kg IV. After endotracheal intubation, isoflurane in O2 was used for anesthetic maintenance. All patients were monitored during the recovery phase and received antibiotic, anti-inflammatory, and analgesic therapy.
As a plasma scalpel, the Onemytis®
device is constituted by a central unit equipped with intensity adjustment commands from 0 to 100, a sterilizable autoclave handpiece, a needle tip, and a delivery pedal (Figure 1
Based on the manufacturer’s indications and a previously reported study [7
was used with a medium–high intensity (about 70% of the maximum deliverable power) on skin tissue.
A scalpel blade number 22 was used for the skin and subcutaneous dieresis (cold blade). An electric scalpel, model SURTRON 160 in coagulation mode and power of 60, was employed as the electrosurgical unit.
2.2. Surgical Technique
Patients were placed in dorsal recumbency, and the sterile field was prepared. An elliptical incision of the skin and subcutaneous tissues was performed along the mammary chain with at least 3-cm margins of healthy tissue on each side.
The dieresis was performed with the cold blade for the thoracic with the electric scalpel for the abdominal, and with the plasma scalpel for the inguinal mammary chain. Once the exeresis of the surgical incision was completed, the three different portions were then prepared by isolating three normal skin and subcutaneous samples not affected by the neoplasia.
2.3. Histology Processing
Skin fragments of 1 cm2 were harvested and fixed in 4% (v/v) phosphate-buffered paraformaldehyde, pH 7.4, for 24 hours at 4 °C. After embedding in paraffin wax, serial sections (7-μm thick) were cut and stained with hematoxylin-eosin (Abcam, Cambridge, UK).
2.4. Scanning Electron Microscopy
Formalin-fixed skin fragments, after rinsing in phosphate buffer, were post-fixed in 1% OsO4 for 2 h at 4 °C, rinsed, dehydrated in an ethanol series, and then critical point dried using CO2. Specimens were mounted on stubs, coated with gold–palladium in a sputter coater, and examined using a Quanta 250 (FEI Company, Milan, Italy) scanning electron microscope (SEM).
2.5. Histomorphometric Analysis
To evaluate the presence, entity, and invasivity (width) of the thermal injury, stained sections at distances of 7, 77, 119, 300, 600, 700, 800, 900, and 1000 μm from the surgical incision were photographed with a 4´ lens using a light microscope (Eclipse Ni-U; Nikon, Tokyo, Japan) and analyzed with the image-analyzing program NIS Elements BR (Version 4.30) (Nikon, Tokyo, Japan).
For each slice, carbonization, coagulation, necrosis of the epithelium, detachment of the epidermis from the basement membrane, loss of cellular detail, cell fusion were considered to be alterations of the epidermis, whereas cellular hypereosinophilia, arrangement of bundles of collagen fibers, interstitial edema, hyperemia, lymphangiectasia were considered for the dermis. The following scores were assigned: 0 = normal; 1 = slight alteration; 2 = moderate alteration; 3 = severe alteration.
The sum of the scores relative to the portions of the epidermis (Epidermal Score, ES), derma (Dermal Score, DS), and total (Total Score, TS) was then evaluated.
2.6. Statistical Analysis
Statistical analysis was performed using Medcalc software 14 (MedCalc Software bv, Ostend, Belgium). Semi-quantitative values were evaluated through the non-parametric Kruskal–Wallis test, and the mean and standard error are indicated. The significance was set at p < 0.05.
Plasma electrocoagulation allows effective cutting and coagulation without altering tissue healing, representing a significant innovation when compared with traditional techniques in surgery [7
This study compared the effects of the cold blade, electrosurgical scalpel, and Onemytis®
plasma scalpel on normal skin, evaluating the histological aspects of thermal damage on the epidermis and dermis. Similar to previous findings, the plasma scalpel was superior to the electrosurgical unit in reducing tissue injury. Indeed, [7
]. The histological examination of the skin biopsies showed an absence of necrosis of the epidermis and dermis with the use of the cold blade, moderate necrosis with the use of the Onemytis®
device, and severe necrosis with the use of the electrosurgical unit, as confirmed by the literature [7
]. The thermal damage of skin tissues occurs from 0 to 600 μm adjacent to the surgical incision using the plasma scalpel, with a cellular resentment of damage up to 700 μm from the cutting edge. It is of considerable importance that the absence of carbonization and drying of the tissues leads to better and faster healing of the tissues than with electrosurgery. Tissue necrosis and the lateral thermal damage associated with the ischemia caused by the electrosurgical system may slow down tissue healing [7
The technology on which Onemytis®
is based is the transformation of the air into an energy conductor thanks to the generation of high-voltage pulses through a high-frequency sinusoidal oscillator. In this way, the device can also operate without direct contact, using the air column interposed between the handpiece and the tip as an energy conductor, and not exceeding an average dissipation temperature of 50 °C [14
]. In addition, the plasma scalpel confines its effect on the target tissue or vessel without carbonization, and with minimal thermal diffusion to adjacent tissues to reduce tissue damage.
The histological comparison concerning the lateral depth of the thermal damage induced by two devices, the plasma scalpel and the electrosurgical unit, showed a statistically significant difference between these two devices. In this study, we did not evaluate the deepness of the damage provided by the device. However, it has been reported that the plasma scalpel provides better control of surgical depth incision, limiting accidental damage to deep layers. [7
Our current study confirms that high operating temperatures for deep thermal coagulation are not essential for tissue hemostasis as used with electrosurgery. For example, the plasma scalpel uses lower temperatures and showed reduced thermal damage to adjacent tissues.
A major limitation of this study is the lack of wound healing assessment. This was not feasible due to the nature of our client-owned canine population recruited for the study. However, some studies on pig skin have demonstrated that the histologic scoring for injury and wound strength was equivalent between the plasma scalpel and cold blade incisions after the 6th week [8
]. The latter device promoted better healing both in canine species and rats [4
]. Moreover, it has been demonstrated that the use of a plasma scalpel on human skin produces better cosmetic outcomes compared with electrosurgery, because of the reduced duty cycle that allows for efficient cooling of the plasma blade. [1
This study aimed to assess the histological effects of thermal injury and coagulative necrosis produced by a plasma scalpel compared with other techniques. Hemostasis was not considered, and it should be considered another limitation of the study. Other studies confirmed that the plasma scalpel produces proper bleeding control in animals and humans [7
]. In particular, Loh et al. demonstrated that the plasma scalpel significantly reduces bleeding compared with the scalpel and is comparable to traditional electrosurgical devices [8
]. It has been supposed that the coagulative necrosis was able to control the bleeding by a combination of the denaturation of proteins and molecules, tissue shrinkage, and vessel sealing due to the fusion of blood vessel collagen and elastic fibers. Another possible mechanism of hemostasis produced by the plasma scalpel may be a nonthermal vasoconstrictive and thrombotic effect [15
]. In our study, the plasma scalpel produced coagulative necrosis effects with less width tissue damage resulting in a more precise tissue dissection. This could be due to lower blade temperature than electrosurgery, but further studies are warranted to compare these techniques in terms of hemostasis. We demonstrated that the plasma scalpel provides an efficient skin surgical incision comparable to that of the cold-blade scalpel. These results make Onemytis®
a potential device in various surgical fields where electrosurgery is not used extensively for fear of tissue damage.
plasma scalpel has already been used in human and veterinary medicine with several publications [7
], and the results of our study suggest that Onemytis®
provides useful advantages over conventional electrosurgery.