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

Summary

Here we present a protocol to experimentally assess plasma coagulation in liver tissue in vivo. In a porcine model, microcirculation is examined by laser Doppler, coagulation depth is measured histologically, temperature at coagulation site by infrared thermometer and thermographic camera, and duct sealing effect is documented by burst pressure experiments.

Abstract

Plasma coagulation as a form of electrocautery is used in liver surgery for decades to seal the large liver cut surface after major hepatectomy to prevent hemorrhages at a later stage. The exact effects of plasma coagulation on liver tissue are only poorly examined. In our porcine model, the coagulation effects can be examined close to the clinical application. A combined laser Doppler flowmeter and spectrophotometer documents microcirculation changes during coagulation at 8 mm tissue depth noninvasively, providing quantifiable information about hemostasis beyond the subjective clinical impression. The temperature at coagulation site is assessed with an infrared thermometer prior and post coagulation and with a thermographic camera during coagulation, a measurement of the gas beam temperature is not possible due to the upper threshold of the devices. The depth of coagulation is measured microscopically on hematoxylin/eosin stained sections after calibration with an object micrometer and gives an exact information about the power setting-coagulation depth-relation. The sealing effect is examined on the bile ducts as it is not possible for a plasma coagulator to seal larger blood vessels. Burst pressure experiments are carried out on explanted organs to rule out blood pressure related effects.

Introduction

Argon plasma coagulation (APC) is a widely used instrument in abdominal surgery for more than three decades^1,2. It is a standard technique for the achievement of secondary hemostasis after major hepatectomy by sealing the liver cut surface to prevent later hemorrhages³. Plasma coagulation is a specialized form of radiofrequency electrocautery, which delivers the electrical energy through an arc of ionized gas. Providing monopolar electrothermal hemostasis, this noncontact technique has the advantage of preventing the electrode to stick to the tissue⁴. The ionized....

Protocol

Rules governed by German legislation for animal studies as well as Principles of Laboratory Animal Care (National Institutes of Health publication ed. 8, 2011) were followed. Official permission is granted from the governmental animal care office (Landesamt für Natur, Umwelt und Verbraucherschutz Nordrhein-Westfalen, Recklinghausen, Germany).

1. Animals

1. Use female German landrace pigs (weighing 25-30 kg) housed in open cages.
2. Use 5 animals per group (argon and helium).
3. Allow the animals to acclimatize to the surroundings for at least one week before the experiments. Fast animals for 24 h prior to surgery....

Results

Microcirculation: Utilizing the diagnostic device for hemostasis following plasma coagulation can be demonstrated by microcirculation changes. Capillary blood flow (displayed as arbitrary units (AU)) decreases from a baseline value of 142.7 ± 76.08 AU to 57.78 ± 49.57 AU at 25 W device output power, to 48.5 ± 7.26 AU at 50 W and to 5.04 ± 1.31 AU at 100 W (Figure 4).

Tempera.......

Discussion

Rodent models for liver surgery are established for a long time¹⁶. Nevertheless, large animal models offer certain advantages: no microsurgical equipment is needed as standard operative equipment for humans can be applied, surgical techniques are comparable to clinical use and standard clinical evaluation methods can be transferred to the experiments. For example, standard clinical blood tests can be carried out without the need for special laboratory test methods (Figure 10

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Xylazine 20 mg/mL	Vetoquinol GmbH	Xylapan
Ketamine 100 mg/mL	Ceva GmbH	Ceva Ketamine Injection
Atropine 100 mg / 10 mL	Dr. Franz Köhler Chemie GmbH	Atropinsulfat Köhler 100mg Amp.
Propofol	Fresenius Kabi GmbH	Propofol 1% MCT Fresenius
Fentanyl	KG Rotexmedica GmbH	Fentanyl 0,5mg Rotexmedica
Isoflurane	Abbot GmbH	Forene 100% (V/V) 250 mL
Ringer's lactate solution	Baxter Deutschland GmbH		sodium 131mmol/l, potassium 5 mmol/l, calcium 2 mmol/l, cloride 111 mmol/l, lactate 29 mmol/l
Surgical disinfactant	Schülke & Mayr GmbH	Kodan Tinktur forte gefärbt 1l 104804
Motorized microscope	Nikon Instruments Europe	Eclipse TE2000-E
Microscope camera	Nikon Instruments Europe	Digitalsight DS-Qi1Mc
Imaging software	Nikon Instruments Europe	NIS elements Vers. 4.40
Plasma coagulator	Söring GmbH	CPC-1000
Argon gas	Linde AG	Argon 4.8
Helium gas	Linde AG	Helium 4.8
O2C	LEA Medizintechnik GmbH	O2C Version 1212	with LF-2 or LF-3 probe
Infrared thermometer	Voltcraft	VOLTCRAFT IR 260-8S
Thermographic camera	InfraTec GmbH	VarioCAM HD head 820
Thermographic analysis software	InfraTec GmbH	IRBIS 3
Mayer's Hematoxylin solution		Merck 1.09249
Eosin solution	VWR International GmbH	Merck 1.09844
Rollerpump Masterflex L/S easy Load	Cole-Parmer Instrument Company	model 7518-10
Perfusorpump	B. Braun Melsungen AG	Perfusor secura FT
Digital pressure meter	Greisinger electronic	GMH 3161
Perfusorsyringe, 50 mL	B. Braun Melsungen AG	REF 8728810 F
Perfusor line, Type IV Standard, PVC Luer lock	B. Braun Melsungen AG	REF 8722960
3-Way stopcock, Dicofix C35C	B. Braun Melsungen AG	REF 16494 C
Silk 2-0. 3 metric	Resorba	REF H5F
Vicryl 4-0 Sutupak	Ethicon	V1224H
NaCl 0.9 %	B. Braun Melsungen AG