Assessment of Plasma Coagulation on Liver Tissue in a Large Animal Model In Vivo

This method can help answer key questions in the field of clinical liver surgery about the energy setting depth relation of argon and helium plasma coagulation and the plasma coagulation process itself. The main advantages of this technique are that the large animal model is similar to the clinical application and that no special equipment is needed. Infrared thermography can be used to monitor temperature distribution and temperature decay but also to monitor breathing rate and pies.

Furthermore, inflammation processes can be monitored by infrared thermography. Demonstrating the procedure will be Pascal Paschenda, a technician from our group. At least one hour before beginning the procedure, switch on the thermographic camera notebook and infrared thermometer.

When the equipment is ready, place an anesthetized 25 to 30 kilogram female German Landrace pig in the supine position on a standard surgical table and use a standard surgical swab to disinfect the surgical area three times with a standard surgical disinfectant. Then use a scalpel to make a wide midline laparotomy from the xiphoid process to the pubis and install surgical retractors to expose the liver tissue. To obtain baseline microcirculation measurements, switch on the laser doppler flow meter and spectrophotometer and use a flat probe to measure the flow and velocity.

Next, switch on the plasma coagulation device, open the appropriate carrier gas bottle, and adjust the gas flow to three liters per minute. Select the appropriate coagulation device output power and use a titanium mold with a square aperture of one by one square centimeter to standardize the coagulation zone. Then use a one centimeter probe distance to coagulate the region for five seconds.

To measure the post coagulation microcirculation, place the flat probe on each coagulation site to measure the flow and velocity of each site. To measure the temperature at each site, adjust the focus of the thermographic camera and set the frame over the first coagulation site so that the region of coagulation and the surrounding tissue affected by the heat transfer are located in the middle of the field of view. Record the coagulation process with the plasma coagulator on the liver surface with a thermographic camera over a two minute period.

Then analyze the image sequences with the appropriate thermography analysis software. To measure the burst pressure, first switch on the automatic pumps and pressure meter. Next, divide all of the ligamentous connections to the liver and divide the hepatic pedicle above the superior duodenal flexure, leaving long portions of portal vein and common bile duct intact.

Then divide the caval vein above and below the liver to allow retrieval of the organ. Using sharp scissors, resect half of the left medial liver lobe and plasma coagulate the cut surface. Isolate the portal vein, common hepatic artery, and bile duct in the hepatic pedicle.

Using overhold forceps, clamp the portal vein. Then use a monofil suture 4.0 to ligate the vessel. Clamp the common hepatic artery with a second pair of overhold forceps and ligate the artery with another monofil suture 4.0.

Insert a French 16 catheter into the common bile duct, ligating the duct with 2.0 silk suture. And connect the catheter to the automatic pumps. Install a three-way stopcock with a pressure meter and fill a profusion syringe with saline.

Start the automatic pumps with a delivery rate of 99 milliliters per hour. Then monitor the liver cut surface and pressure meter for leakage and record the burst pressure. In this representative experiment, the capillary blood flow decreased about 60%from baseline at 25 watts of device output power, 66%at 50 watts, and nearly 100%at 100 watts.

No change in temperature was observed during or after plasma coagulation. Plasma coagulation creates a superficial zone of necrosis that can be easily distinguished from the normal liver parenchyma. Following helium plasma coagulation, the coagulation depth increases significantly in direct correlation to the applied plasma device output power.

Note that burst pressure measurements carried out on the cut surface of the explanted left medial liver lobe demonstrate no difference after helium or argon plasma coagulation. Using these techniques, the last to quantify the local coagulatory effect and to estimate the bile duct sealing effect of plasma coagulation. These techniques can also be used to compare different means of bilio and hemostasis in a surgical setting similar to that in human patients.

Further, the hemo and biliostatic effects of plasma coagulation can be applied after major hepatectomies in the same model. After watching this video, you should have a good understanding of how to assess the major effects of argon and helium plasma coagulation in a large animal model.