Evaluating temperature and duration in arterial tissue fusion to maximize bond strength

A novel discrete linkage-type electrode for radiofrequency-induced intestinal anastomosis

INTRODUCTION

For decades, radiofrequency (RF)-induced tissue fusion has garnered great attention due to its potential to replace sutures and staples for anastomosis of tissue reconstruction. However, the complexities of achieving high bonding strength and reducing excessive thermal damage present substantial limitations of existing fusion devices.

MATERIALS AND METHODS

This study proposed a discrete linkage-type electrode to carry out ex vivo RF-induced intestinal anastomosis experiments. The anastomotic strength was examined by burst pressure and shear strength test. The degree of thermal damage was monitored through an infrared thermal imager. And the anastomotic stoma fused by the electrode was further investigated through histopathological and ultrastructural observation.

RESULTS

The burst pressure and shear strength of anastomotic tissue can reach 62.2 ± 3.08 mmHg and 8.73 ± 1.11N, respectively, when the pressure, power and duration are 995 kPa, 160 W and 13 s, and the thermal damage can be controlled within limits. Histopathological and ultrastructural observation indicate that an intact and fully fused stomas with collagenic crosslink can be formed.

CONCLUSION

The discrete linkage-type electrode presents favorable efficiency and security in RF-induced tissue fusion, and these results are informative to the design of electrosurgical medical devices with controllable pressure and energy delivery.

Minimizing thermal damage using self-cooling jaws for radiofrequency intestinal tissue fusion

INTRODUCTION

Radiofrequency (RF)-induced tissue fusion shows great potential in sealing intestinal tissue without foreign materials. To improve the performance of RF-induced tissue fusion, a novel self-cooling jaw has been designed to minimize thermal damage during the fusion.

MATERIAL AND METHODS

The prototype of self-cooling jaws was developed and manufactured. A total number of 60 mucosa-to-mucosa fusions were conducted using ex-vivo porcine intestinal segments with the proposed design and conventional bipolar jaws. The effects of intestinal fusion were evaluated based on temperature curves, burst pressure, thermal damage, and histological appearances.

RESULTS

The self-cooling jaws showed significant decrease in temperature during the fusion process. An optimal burst pressure (5.7 ± 0.5 kPa) and thermal damage range (0.9 ± 0.1 mm) were observed when the applied RF power was 100 W. The thermal damage range of the prototype has almost decreased 36% in comparison with the conventional bipolar jaws (1.4 ± 0.1 mm). The histological observation revealed that a decrease of thermal damage was achieved through the application of self-cooling jaws.

CONCLUSIONS

The self-cooling jaws were proved to be effective for reducing the thermal damage during RF-induced tissue fusion, which could potentially promote the clinical application of tissue fusion techniques in the future.

Temperature Distribution of Vessel Tissue by High Frequency Electric Welding with Combination Optical Measure and Simulation

In clinical surgery, high frequency electric welding is routinely utilized to seal and fuse soft tissues. This procedure denatures collagen by electrothermal coupling, resulting in the formation of new molecular crosslinks. It is critical to understand the temperature distribution and collagen structure changes during welding in order to prevent thermal damage caused by heat generated during welding. In this study, a method combining optical measurement and simulation was presented to evaluate the temperature distribution of vascular tissue during welding, with a fitting degree larger than 97% between simulation findings and measured data. Integrating temperature distribution data, strength test data, and Raman spectrum data, it is discovered that optimal parameters exist in the welding process that may effectively prevent thermal damage while assuring welding strength.

Dynamic Impedance Monitoring for Large Diameter Vessel Sealing Using Bipolar Electrosurgery

Vessel sealing using bipolar electrosurgery is becoming a common practice in modern operating rooms. Despite all the advantages such as faster operation, less bleeding, and shorter postsurgery recovery time, side effects including sticking, charring, and rebleeding still occur, leading to increased surgery time and sometimes fatal complications. Tissue impedance during the electrosurgical process has been used to determine the electrical power of the process. However, little has been done to understand the dynamic tissue impedance and its effectiveness in monitoring the vessel sealing process. Moreover, the samples used in previous studies all had small diameters of 2–5 mm. In this study, an experimental setup was developed to perform vessel sealing tests using large-diameter blood vessel samples with mimicking blood flow. The tissue impedance during the heating process was obtained. Burst pressures after sealing were measured. A finite element simulation model was developed to understand the dynamic impedance behavior. It is seen that the tissue impedance increases rapidly in the beginning of the heating process and remains at a level that is several orders of magnitude higher than the initial value. This rapid impedance increase indicates protein denaturing, thus can be used to monitor the electrosurgical vessel sealing process. An impedance-based monitoring algorithm was developed, with which a burst pressure at least twice the normal human systolic blood pressure was achieved.

Evaluation of the performance of an endoscopic 3-mm electrothermal bipolar vessel sealing device intended for single use after multiple use-and-resterilization cycles

OBJECTIVE

To evaluate the performance of an endoscopic 3-mm electrothermal bipolar vessel sealing device (EBVS) intended for single use after multiple use-and-resterilization cycles.

STUDY DESIGN

Ex vivo study.

SAMPLE POPULATION

Eight 3-mm EBVS handpieces.

METHODS

Handpieces were subjected to a maximum of 15 cycles of testing, including simulated surgery, sealing and burst pressure testing of porcine carotid arteries, reprocessing, and hydrogen peroxide plasma resterilization. Failure was defined as two sequential vascular seal leakage events occurring at <250 mm Hg. Histological evaluation, maximum external temperature of the jaws, sealing time, tissue adherence, jaw surface characterization, and mechanical deterioration were studied. Failure rate was analyzed by using a Kaplan-Meier curve. Linear and ordinal logistic mixed models were used to analyze sealing time, handpiece jaw temperature, and adherence score.

RESULTS

Mean ± SD diameter of arteries was 3.22 ± 0.35 mm. Failure was observed starting at cycle 10 and going up to cycle 13 in 37.5% (3/8) of the handpieces. Tissue adherence increased after each cycle (P < .001). Maximum external temperature (79.8°C ± 13.9°C) and sealing time (1.8 ± 0.5 seconds) were not significantly different throughout cycles up to failure. A flatter surface and large scratches were observed microscopically throughout the jaw surface after repeated use and resterilization.

CONCLUSION

The 3-mm EBVS handpiece evaluated in this study can be considered safe to use for up to nine reuse-and-resterilization cycles.

CLINICAL SIGNIFICANCE

These data provide the basis for establishing preliminary guidelines for the reuse and hydrogen peroxide plasma resterilization of an endoscopic 3-mm EBVS handpiece.

Energy-Based Tissue Fusion for Sutureless Closure: Applications, Mechanisms, and Potential for Functional Recovery

As minimally invasive surgical techniques progress, the demand for efficient, reliable methods for vascular ligation and tissue closure becomes pronounced. The surgical advantages of energy-based vessel sealing exceed those of traditional, compression-based ligatures in procedures sensitive to duration, foreign bodies, and recovery time alike. Although the use of energy-based devices to seal or transect vasculature and connective tissue bundles is widespread, the breadth of heating strategies and energy dosimetry used across devices underscores an uncertainty as to the molecular nature of the sealing mechanism and induced tissue effect. Furthermore, energy-based techniques exhibit promise for the closure and functional repair of soft and connective tissues in the nervous, enteral, and dermal tissue domains. A constitutive theory of molecular bonding forces that arise in response to supraphysiological temperatures is required in order to optimize and progress the use of energy-based tissue fusion. While rapid tissue bonding has been suggested to arise from dehydration, dipole interactions, molecular cross-links, or the coagulation of cellular proteins, long-term functional tissue repair across fusion boundaries requires that the reaction to thermal damage be tailored to catalyze the onset of biological healing and remodeling. In this review, we compile and contrast findings from published thermal fusion research in an effort to encourage a molecular approach to characterization of the prevalent and promising energy-based tissue bond.

A Small Deformation Thermoporomechanics Finite Element Model and Its Application to Arterial Tissue Fusion

Understanding the impact of thermally and mechanically loading biological tissue to supraphysiological levels is becoming of increasing importance as complex multiphysical tissue-device interactions increase. The ability to conduct accurate, patient specific computer simulations would provide surgeons with valuable insight into the physical processes occurring within the tissue as it is heated or cooled. Several studies have modeled tissue as porous media, yet fully coupled thermoporomechanics (TPM) models are limited. Therefore, this study introduces a small deformation theory of modeling the TPM occurring within biological tissue. Next, the model is used to simulate the mass, momentum, and energy balance occurring within an artery wall when heated by a tissue fusion device and compared to experimental values. Though limited by its small strain assumption, the model predicted final tissue temperature and water content within one standard deviation of experimental data for seven of seven simulations. Additionally, the model showed the ability to predict the final displacement of the tissue to within 15% of experimental results. These results promote potential design of novel medical devices and more accurate simulations allowing for scientists and surgeons to quickly, yet accurately, assess the effects of surgical procedures as well as provide a first step toward a fully coupled large deformation TPM finite element (FE) model.

Risk management for surgical energy-driven devices used in the operating room

Complications related to energy sources in the operating room are not well-recognized or published, despite occasionally dramatic consequences for the patient and the responsible surgeon. The goal of this study was to evaluate the risks and consequences related to use of energy sources in the operating room.

PATIENTS AND METHODS

Between 2009 and 2015, 876 adverse events related to health care (AERHC) linked to energy sources in the operating room were declared in the French experience feedback data base "REX". We performed a descriptive analysis of these AERHC and analyzed the root causes of these events and of the indications for non-elective repeat operations, for each energy source.

RESULTS

Five different energy sources were used, producing 876 declared AERHC: monopolar electrocoagulation: 614 (70%) AERHC, advanced bipolar coagulation (thermofusion): 137 (16%) AERHC, ultrasonic devices: 69 (8%) AERHC, traditional bipolar electrocoagulation: 32 AERHC, and cold light: 24 AERHC. The adverse events reported were skin burns (27.5% of AERHC), insulation defects (16% of AERHC), visceral burns or perforation (30% of AERHC), fires (11% of AERHC), bleeding (7.5% of AERHC) and misuse or miscellaneous causes (8% of AERHC). For the five energy sources, the root causes were essentially misuse, imperfect training and/or cost-related reasons regarding equipment purchase or maintenance. One hundred and forty-six non-elective procedures (17% of AERHC) were performed for complications related to the use of energy sources in the operating room.

CONCLUSION

This study illustrates the risks related to the use of energy sources on the OR and their consequences. Most cases were related to persistent misunderstanding of appropriate usage within the medical and paramedical teams, but complications are also related to administrative decisions concerning the purchase and maintenance of these devices.

Predicting burst pressure of radiofrequency-induced colorectal anastomosis by bio-impedance measurement

The present study investigates the relationship between bio-impedance and burst pressure of colorectal anastomosis created by radiofrequency (RF)-induced tissue fusion. Colorectal anastomosis were created with ex vivo porcine colorectal segments, during which 5 levels of compression pressure were applied by a custom-made bipolar prototype, with 5 replicate experiments at each compression pressure. Instant anastomotic tensile strength was assessed by burst pressure. Bio-impedance of fused tissue was measured by Impedance Analyzer across frequency that 100 Hz to 3 MHz. Statistical analysis shows only a weak correlation between bio-impedance modulus and burst pressures at frequency of 445 kHz ([Formula: see text]  =  -0.426, P  =  0.099  >  0.05). In contrast, results demonstrated a highly significant negative correlation between reactance modulus and burst pressures ([Formula: see text]  =  -0.812, P  =  0.000  <  0.05). The decrease in mean reactance modulus with increasing burst pressures was highly significant (P  =  0.019  <  0.05). The observed strong negative correlation between reactance modulus and burst pressures at frequency of 445 kHz indicates that reactance is likely to be a good index for tensile strength of RF-induced colorectal anastomosis, and should be considered for inclusion in a feedback loops in devices design.

Strength and Persistence of Energy-Based Vessel Seals Rely on Tissue Water and Glycosaminoglycan Content

Vessel ligation using energy-based surgical devices is steadily replacing conventional closure methods during minimally invasive and open procedures. In exploring the molecular nature of thermally-induced tissue bonds, novel applications for surgical resection and repair may be revealed. This work presents an analysis of the influence of unbound water and hydrophilic glycosaminoglycans on the formation and resilience of vascular seals via: (a) changes in pre-fusion tissue hydration, (b) the enzymatic digestion of glycosaminoglycans (GAGs) prior to fusion and (c) the rehydration of vascular seals following fusion. An 11% increase in pre-fusion unbound water led to an 84% rise in vascular seal strength. The digestion of GAGs prior to fusion led to increases of up to 82% in seal strength, while the rehydration of native and GAG-digested vascular seals decreased strengths by 41 and 44%, respectively. The effects of increased unbound water content prior to fusion combined with the effects of seal rehydration after fusion suggest that the heat-induced displacement of tissue water is a major contributor to tissue adhesion during energy-based vessel sealing. The effects of pre-fusion GAG-digestion on seal integrity indicate that GAGs are inhibitory to the bond formation process during thermal ligation. GAG digestion may allow for increased water transport and protein interaction during the fusion process, leading to the formation of stronger bonds. These findings provide insight into the physiochemical nature of the fusion bond, its potential for optimization in vascular closure and its application to novel strategies for vascular resection and repair.

Bond Strength of Thermally Fused Vascular Tissue Varies With Apposition Force

Surgical tissue fusion devices ligate blood vessels using thermal energy and coaptation pressure, while the molecular mechanisms underlying tissue fusion remain unclear. This study characterizes the influence of apposition force during fusion on bond strength, tissue temperature, and seal morphology. Porcine splenic arteries were thermally fused at varying apposition forces (10-500 N). Maximum bond strengths were attained at 40 N of apposition force. Bonds formed between 10 and 50 N contained laminated medial layers; those formed above 50 N contained only adventitia. These findings suggest that commercial fusion devices operate at greater than optimal apposition forces, and that constituents of the tunica media may alter the adhesive mechanics of the fusion mechanism.

Sealing vessels up to 7 mm in diameter solely with ultrasonic technology

Introduction

Ultrasonic energy is a mainstay in the armamentarium of surgeons, providing multifunctionality, precision, and control when dissecting and sealing vessels up to 5 mm in diameter. Historically, the inability to seal vessels in the 5–7 mm range has been perceived as an inherent limitation of ultrasonic technology. The purpose of this study was to evaluate sealing of vessels up to 7 mm in diameter with an ultrasonic device that modulates energy delivery during the sealing period.

Methods

In ex vivo benchtop and in vivo acute and survival preclinical models, a new ultrasonic device, Harmonic ACE^®+7 Shears (Harmonic 7), was compared with advanced bipolar devices in sealing vessels 1–7 mm in diameter with respect of burst pressure, seal reliability, and seal durability. Lateral thermal damage and transection time were also evaluated.

Results

Ex vivo tests of Harmonic 7 demonstrated significantly greater median burst pressures than an advanced bipolar device both for vessels <5 mm in diameter (1,078 mmHg and 836 mmHg, respectively, P=0.046) and for those in the range of 5–7 mm (1,419 mmHg and 591 mmHg, P<0.001). In vivo tests in porcine and caprine models demonstrated similar rates of hemostasis between Harmonic 7 and advanced bipolar devices, with high success rates at initial transection and seal durability of 100% after a 30-day survival period.

Conclusion

Sealing 5–7 mm vessels is not a limitation of the type of energy used but of how energy is delivered to tissue. These studies document the ability of ultrasonic energy alone to reliably seal large vessels 5–7 mm in diameter, with significantly greater burst pressure observed in in vitro studies than those observed with an advanced bipolar technology when energy delivery is modulated during the sealing cycle. Furthermore, the seals created in 5–7 mm vessels are shown to be reliable and durable in in vivo preclinical studies.