Hemostasia y tecnología. Energía. Desarrollo de las nuevas tecnologías

The hemostasis systems applied in surgery are based on endothermic heat production resulting from the interaction between energy and tissue.The most frequently used energy source is electrocoagulation, applied through two systems: monopolar and bipolar. More sophisticated electrocoagulation systems have progressively been developed such as the Argon beam, in which coagulation is superficial and does not injure the deep tissues, or LigaSure?, based on the use of a bipolar system with an inbuilt feedback system allowing vessels to be sealed without excessive heat and a consequent reduction of collateral lesions.Another system that has been developed in the last few years is the ultrasonic scalpel, based on the ability of the cell membrane proteins to denature as a result of ultrasonic vibration. This system avoids some of the risks involved in the use of electrical energy such as accidental burns due to stray electrical current or faulty insulation of an instrument. Moreover, the harmonic scalpel reaches a temperature of no more than 100° and the effect of lateral tissue destruction is much lower than with electrosurgery, although this reduction is negligible when compared with the electrosurgical methods developed in the last few years such as LigaSure.Another system that is also used is laser energy, consisting of a photon beam containing a specific wavelength; each photon moves in step with the others in both time and space. This system has not become widely used due to its high cost, the difficulty of controlling this type of energy, and the lack of objective advantages over conventional electrosurgery.     

Electrical resistance and current leakage of appliances for transurethral resection.

Urethral stricture following transurethral resection of the prostate (TUR-P) is closely related to the electrical resistance and current leakage of appliances. Electrical resistance and leakage were therefore investigated in 7 old bipolar loops, 3 new bipolar loops (1, 2 and 3) used for TUR-P, 2 new bipolar loops (4 and 5) for TUR-bladder tumor (TUR-Bt), and 4 new monopolar loops (6 through 9) for TUR-P. Two of the 7 old bipolar loops were found to be positive and 5 negative for current leakage. The 2 positive loops had resistances of 4.4 and 17 ohm . Before use, the electrical resistance of the 5 new bipolar loops (1 to 5) ranged from 0.5 to 0.6 ohm. The resistance of loop 1 was less than 5 ohm after the sixth use, and that of loop 3 was 2.8 ohm after the fifth use. By contrast, loop 2 exhibited resistance of 115 ohm after the third use. The average operation time for loops 1, 2 and 3 were 66, 64 and 62 minutes. Loop 4 showed resistance of 14 ohm after the third use, and loop 5 1 ohm even after the sixth use. Furthermore, none of the 5 loops showed current leakage. On the other hand, all 4 monopolar loops (6 through 9) exhibited current leakage after the first use, and showed relatively high electrical resistance. These findings demonstrate the necessity of timely replacement of bipolar loops and the exchange of monopolar loops after the first use.     

Laparoscopic partial nephrectomy in the pig: comparison of three hemostasis techniques

BACKGROUND AND PURPOSE: Control of intraoperative bleeding is the main technical difficulty encountered during laparoscopic partial nephrectomy. The objective of this study was to compare the efficacy and morbidity of three renal parenchymal hemostasis techniques: high-frequency bipolar electrical current, high-frequency unipolar spray electrical current, and ultrasound during laparoscopic partial nephrectomy performed in pigs without vascular control. MATERIALS AND METHODS: A standardized laparoscopic transperitoneal right lower-pole partial nephrectomy was performed in 27 pigs with a mean weight of 65 +/- 5 kg. The pigs were divided into three groups according to the technology used: Group 1 = bipolar electrical current, Group 2 = unipolar spray electrical current, and Group 3 = ultrasound. Intravenous urography was performed on the 28th day. The kidneys were then removed for histologic examination, and the pigs were sacrificed. The criteria evaluated were intraoperative and postoperative complications, blood loss, renal function, and thickness of the parenchymal lesions induced. The Kruskal-Wallis nonparametric test for comparison of medians was used for statistical analysis of the data (P < 0.05). Data from pigs that died before the end of the study were excluded from the analysis. RESULTS: All partial nephrectomies were performed laparoscopically, and all pigs were alive at the end of the operation. The postoperative complication rate was 11% (N = 3): two pigs died before the end of the study, one from hemorrhage on Day 6 (Group 2), and the other from prolonged reflex ileus with sacrifice of the pig on Day 7 (Group 3). One pig developed an asymptomatic urinoma (Group 2). Blood loss was significantly lower when ultrasound was used (P = 0.026). Global renal function was not significantly altered in the various groups. The median thickness of tissue necrosis and fibrosis detected in the scar zone was 6 mm (range 4-10 mm) and was similar in the three groups. CONCLUSION: Partial nephrectomy can be performed by laparoscopy without vascular control in the pig. Coagulation by ultrasound appears to present an advantage in terms of limitation of blood loss compared with coagulation by bipolar or unipolar spray electrical currents without presenting any benefit in terms of preservation of the renal parenchyma.     

Computerized Bipolar Diathermy with Scissors and Forceps in Cutaneous Surgery

BACKGROUND: Bipolar diathermy coagulates tissue as effectively as monopolar with less lateral tissue injury and no risk of interference with cardiac pacemakers or joint prostheses. OBJECTIVE: To test a novel computerized bipolar diathermy machine for combined cutting and coagulation in dermatologic surgery. METHODS: A divided cable was used to deliver current from a computerized bipolar diathermy unit to both scissors and forceps. The bipolar diathermy unit senses tissue contact with the instruments and starts automatically; a built-in microcomputer measures tissue impedance and automatically terminates the current when tissue coagulation is achieved. RESULTS: The equipment has been used successfully in more than 200 patients undergoing dermatologic surgery. The advantages were a reduced operating time and a more secure hemostasis. The microprocessor controlled bipolar diathermy unit minimized any tissue adherence to the instruments during use. CONCLUSION: We recommend the use of insulated scissors and computerized bipolar diathermy for safe and efficacious coagulation and cutting in dermatologic surgery.     

Comparison of bipolar and unipolar radiofrequency ablation in an in vivo experimental model.

OBJECTIVE: Linear atrial radiofrequency lesions have been used effectively for the treatment of atrial fibrillation. In most cases an endocardial approach has been suggested. A method for epicardial placement of lesions would reduce the complexity of these procedures. We compared lesions created in ovine hearts in vivo using irrigated bipolar or unipolar handheld radiofrequency ablation devices. METHODS: Radiofrequency lesions were produced around a left pulmonary vein, around the left atrial appendage and in the free wall of the right ventricle in ovine hearts. All lesions were created in the beating heart. A bipolar clamping device (n = 7) or a handheld unipolar device (n = 6) was used. Measurements of local electrograms and pacing thresholds were performed before and after ablation at each site to assess the electrical integrity of lesions. Tetrazolium and digital image analysis were used to assess lesion geometry. Results: In atrial tissue continuous transmural lesions were achieved more often with the bipolar than with the unipolar device (92.3 vs. 33.3%, P < 0.02). In atrial tissue the reduction in signal amplitude caused by the lesions was significantly larger with the bipolar than the unipolar device (87.6+/-9.4% vs. 60.6+/-23.7% reduction, P < 0.01). There was a significant relationship between loss of pacing capture and lesion transmurality (P < 0.05). The bipolar device created narrower lesions than the unipolar device (4.1+/-0.9 mm vs. 5.9+/-2.1 mm, P < 0.001). CONCLUSIONS: The bipolar clamping device produces narrower lesions which are more likely to be transmural and lead to electrical isolation of ablated tissue than those produced by the unipolar device. However, both devices failed to consistently produce transmural lesions using the epicardial beating heart technique studied, particularly in thicker tissues. High output pacing within the ablated tissue partially predicts lesion transmurality and be a guide to the need for further ablation. However, endocardial ablation or transmural bipolar ablation are likely to remain the techniques of choice for linear radiofrequency ablation in the atria until improved techniques are developed.     

Surgical diathermy

Surgical diathermy is a heating effect produced in the body by high-frequency electric current. It can be used to cut or coagulate tissue. The electrode systems used in surgical diathermy can be monopolar or bipolar; each has different characteristics and uses. The safety of surgical diathermy equipment is discussed in this article, as is its interference with other equipment. Finally, the hazards of diathermy smoke are also included.     

Deep brain stimulation in movement disorders: stereotactic coregistration of two-dimensional electrical field modeling and magnetic resonance imaging

OBJECT: Adjusting electrical parameters used in deep brain stimulation (DBS) for dystonia remains time consuming and is currently based on clinical observation alone. The goal of this study was to visualize electrical parameters around the electrode, to correlate these parameters with the anatomy of the globus pallidus internus (GPI), and to study the relationship between the volume of stimulated tissue and the electrical parameter settings. METHODS: The authors developed a computer-assisted methodological model for visualizing electrical parameters (the isopotential and the isoelectric field magnitude), with reference to the stereotactic target, for different stimulation settings (monopolar and bipolar) applied during DBS. Electrical field values were correlated with the anatomy of the GPI, which was determined by performing stereotactic magnetic resonance imaging in one reference patient. By using this method it is possible to compare potential and electrical field distributions for different stimulation modes. In monopolar and bipolar stimulation, the shape and distribution of the potential and electrical field are different and depend on the stimulation voltage. Distributions visualized for patient-specific parameters can be subsequently correlated with anatomical information. The application of this method to one patient demonstrated that the 0.2-V/ mm isofield line fits best with the lateral GPI borders at the level of the stimulated contacts. CONCLUSIONS: The electrical field is a crucial parameter because it is assumed to be responsible for triggering action potentials. Electrical field visualization allows the calculation of the stimulated volume for a given isoline. Its application to an entire series of patients may help determine a threshold for obtaining a therapeutic effect, which is currently unknown, and consequently may aid in optimizing parameter settings in individual patients.     

Histopathologic changes after bipolar resection of the prostate: depth of penetration of bipolar thermal injury

Abstract Background and Purpose: While the power needed to initiate bipolar vaporization is higher than conventional monopolar resection, the energy needed to maintain bipolar vaporization is significantly lower and may result in less thermal tissue injury. This may have implications for hemostasis, scarring, and perioperative morbidity. The objective of this study is to assess histopathologic changes in prostatic tissue after bipolar transurethral vaporization of the prostate. Patients and Methods: Male patients older than 40 years with a diagnosis of benign prostatic hyperplasia (BPH) who elected to undergo bipolar transurethral vaporization of the prostate were included in this study. Patients were excluded if they had a previous transurethral resection of the prostate (TURP) or prostate radiation therapy. An Olympus button vaporization electrode was used to vaporize prostate tissue. A loop electrode was then used to obtain a deep resection specimen. The vaporized and loop resection surfaces were inked and sent for pathologic analysis to determine the presence of gross histologic changes and the depth of penetration of the bipolar vaporization current. Results: A total of 12 men underwent bipolar TURP at standard settings of 290?W cutting and 145?W coagulation current. Mean patient age was 70±10.2 years (range 56-88 years). Mean surgical time was 48.7±20.2 minutes (range 30-89?min). Mean depth of thermal injury was 2.4±0.84?mm (range 0.3-3.5?mm). Histopathologic evaluation demonstrated thermal injury in all specimens, but no gross char was encountered. Conclusions: In bipolar systems, resection takes place at much lower peak voltages and temperatures compared with monopolar systems. Theoretically, this leads to less collateral thermal damage and tissue char. Our tissue study illustrates that the button vaporization electrode achieves a much larger depth of penetration than previous studies of bipolar TURP. This may be because thermal injury represents a gradual continuum of histologic changes.     

Light and electron microscopic studies of phrenic nerves after long-term electrical stimulation

Light and electron microscopic evaluation were carried out on canine phrenic nerves subjected to long-term electrical stimulation. A total of 34 stimulated and 19 control nerves were studied by light microscopy, and 10 stimulated and five control nerves were evaluated by electron microscopy. Except in a few cases in which a higher current was used, the current used for stimulation was between 1 and 2 mA. The pulse width was 150 microseconds. The typical charge per pulse was 0.22 microC and charge density per pulse 1.125 microC/sq cm of real area. The total number of days of electrical stimulation in individual phrenic nerves ranged from 4 to 374. No morphological changes in the phrenic nerve that could be attributed to the electrical stimulation were observed by light or electron microscopic study. There were, however, two phrenic nerves cuffed with bipolar electrodes which showed focal demyelination at the electrode level, but these changes were caused by factors other than the electrical stimulation. The results of the studies have direct clinical implications to long-term stimulation of phrenic nerves.     

Electrical stimulation with bone and wound healing

Electrical stimulation has been used to heal fractures and ulcers and reduce pain through modulation of local body processes. It has been recognized that mechanical forces and bioelectricity have an intimate relationship in influencing the production of bone. Science has developed techniques to affect change in the electrical charge of fractures to positively affect the healing process. Electrical stimulation, through invasive and noninvasive applications, has produced excellent results in the treatment of nonunions and ulcer care. A thorough review of the electrical properties of bone and soft tissue and the influence of electrical stimulation on healing is presented here.     

The effects of ultrasound and alternating current on the laser penetration in the tissue

The visible (VIS) and near-infrared (NIR) lasers are now widely used in therapeutic and other medical applications. Some of these applications require to deliver the laser energy deep toward the desired tissue target or organ. The aim of this in vitro study is to investigate practically whether the modulation of laser energy by employing the therapeutic ultrasound or electrical energies can increase the penetration depth of the laser light inside the tissue. Such modulation was implemented in this study by coupling the (c.w.) diode and Nd:YAG laser energies with the ultrasound or AC current simultaneously as they pass through preprepared ex vivo bovine muscular tissue strips. Two wavelengths of diode lasers were used, 637 and 808 nm beside the 1064-nm Nd:YAG laser. The results showed a noticeable decrease of these laser attenuation factors as they pass through the tissue strips in the presence of the ultrasound or AC energies. By using this coupling modulation, the capability of increasing the laser penetration depths inside the tissue was confirmed without having to increase their applied power.     

Electrically-induced osteogenesis in external fixation treatment

This animal model experiment is performed to evaluate how bipolar direct current of 20 microamp. affects osteogenesis once external fixation treatment is applied in different forms: stabilization, distraction, and compression. In all cases a secondary healing, typical of external fixation treatment, was found; but a more mineralized callus and an increase in osteoprogenitor cell proliferation and differentiation were obtained through the use of electrical stimulation especially in the compression group.     

Intraoperative protection of cranial nerves and perforating arteries by silicone rubber sheets. Technical note

The authors describe a technique whereby, during microneurosurgery, vital structures are covered or wrapped with small pieces of silicone rubber sheeting to protect them from intraoperative injury. In this way, perforating arteries located behind a large aneurysm can be covered to avoid their inclusion within the blades of the clip, and the cranial nerves coursing around or through a tumor can be wrapped to protect them from injury by a suction or forceps. By insulating nerves and arteries, this silicone rubber sheet has the added advantage of protecting them from injury due to electrical current of bipolar forceps. The silicone rubber sheet described here is smoother, thinner, and lighter than a cotton pattie.     

Irrigation-coupled bipolar cautery unit: A practical, economical, and simple version

Hemostasis is a fundamental principle of surgery for which electrocoagulation is universally used. Bipolar electrocautery has an advantage over monopolar electrocautery in terms of the precision of the extent of tissue coagulation and the lateral extent of thermal tissue injury. However, secondary to the thermal changes induced in the tissue due to electric current passage, there is charring of tissue, which adheres to the cautery tip. This, not only decreases its effectiveness, but also, by getting avulsed while removing the cautery tip from the surgical field, causes rebleeding and more trauma to the tissue. Irrigation of the surgical field during application of cautery reduces the charring effect, thereby improving the efficiency and efficacy. Irrigation-coupled electrocautery devices are available but are costly to acquire and maintain. We describe a simple and reliable version of an irrigation-coupled cautery device, which is of immense functional utility in our experience. It decreases the amount of charring of the tissue and its adherence to the bipolar forceps tips, thereby decreasing the frustrating loss of effectiveness and also increases the life of the bipolar forceps as cleaning needs to be less frequent. By virtue of its simplicity and cost-effectiveness, it can be used in almost all hospitals and situations.     

How safe is diathermy in patients with cochlear implants?

INTRODUCTION

Cochlear implants are surgically inserted electrical devices that enable severely or profoundly deaf individuals to interpret sounds from their environment and communicate more effectively. As a result of their electrical nature, they are susceptible to electromagnetic interference and can be damaged by excessive electrical energy. Surgical diathermy is one source of such potentially damaging energy. The British Cochlear Implant Group guidelines advise that monopolar diathermy should not be used in the head and neck region in patients with cochlear implants and that bipolar diathermy should not be used within 2cm of the implant (http://www.bcig.org.uk/site/public/current/safety.htm).

METHODS

A questionnaire was provided to 36 surgeons working in different specialties in the head and neck region, inquiring as to their knowledge of the safety considerations when using diathermy in cochlear implant patients. Thirty-five surgeons provided responses.

RESULTS

Overall, 77% of the respondents were unaware of the existence of published guidelines. Even when given an option to seek advice, 11% erroneously felt it was safe to use monopolar diathermy above the clavicles with a cochlear implant in situ and 49% felt that there was no restriction on the use of bipolar diathermy.

CONCLUSIONS

There is a significant deficit in the knowledge of safe operating practice in the rapidly expanding population of patients with cochlear implants which threatens patient safety. Through this publication we aim to increase awareness of these guidelines among members of the surgical community and this paper is intended to act as a point of reference to link through to the published safety guidelines.     

New bipolar resection device for transurethral resection of the prostate: first ex-vivo and in-vivo evaluation

BACKGROUND AND PURPOSE: Bipolar resection systems for transurethral resection of the prostate (TURP) offer some advantages over conventional monopolar devices. As both the active and the return electrode are placed on the tip of the resectoscope, current flow is locally limited, and negative effects caused by the current flow through the patient's body in the monopolar array can theoretically be reduced. Furthermore, bipolar resectoscopes use 0.9% sodium chloride solution as irrigation fluid, and therefore, the risk of TUR syndrome is theoretically eliminated. In this trial, we evaluated a new bipolar resectoscope in an ex-vivo model and in vivo and compared it with a standard monopolar resection device. MATERIALS AND METHODS: The modified model of the isolated blood perfused porcine kidney was used to determine cutting qualities, ablation rate, blood loss, and coagulation depth of the bipolar resection device compared with a monopolar resectoscope. A measurement system placed in the line between the generator and the patient was used to determine electric parameters when both resectoscopes were used in vivo. RESULTS: The ex-vivo evaluation showed worse cutting ability of the bipolar resection device compared with the monopolar resectoscope, with essential difficulties in starting a cut. The ablation rate was equal, as both resectoscopes had the same loop diameter. The bleeding rate was lower in bipolar (15.16+/-3.31 g/min) than monopolar (20.78+/-1.52 g/min) resection, whereas bipolar cutting resulted in marginally deeper coagulation zones (236.25+/-36.69 microm 216.0+/-42.25 microm). The in-vivo measurements made it clear that more power and more current is delivered to the patient during bipolar resection. The reason lies in a period at the beginning of each cut, when the patient's impedance is low and current flow high. CONCLUSION: Our results suggest that bipolar resection offers an alternative to conventional monopolar TURP. The advantage of a more localized energy field is at least in part compensated for by the higher generator output power during the procedure. Our ex-vivo results indicate a reduced bleeding rate compared with monopolar resection. Clinical studies have to be performed to prove the significance of our findings for patient treatment.     

Long-term local corticosteroid application does not influence nerve transmission or structure

The long-term effects of a locally applied depot form of a corticosteroid on the electrical properties and structure of nerves were investigated in an animal experimental model.
The conduction in electrically stimulated A-fibres of the plantar nerve was monitored by a bipolar volley recording of the sciatic nerve whereas the conduction in C-fibres of the plantar nerve was measured through a C-fibre evoked segmental flexion reflex in the anaesthetized rat. Droplets of either methylprednisolone acetate or vehicle were placed under direct observation on the plantar nerve. Saline was used as a control on the contralateral side. One to two weeks after the application both the A-fibre volley of the sciatic nerve and the C-fibre evoked reflex discharge of flexor motoneurons were recorded.
No difference was found between the nerves treated with corticosteroid, constituent vehicle or saline. Light and electron microscopic analysis of the nerves showed no changes in the nerve fibres or in the intraneural connective tissue in either the corticosteroid treated or the control nerves.
It is concluded that locally applied corticosteroids in limited amounts have no long-term effects on the electrical and structural properties of peripheral nerves.     

Radiofrequency ablation of the nerve to the corrugator muscle for elimination of glabellar furrowing

Glabellar furrows are caused by hyperdynamic activity of the corrugator supercilii muscles. A minimally invasive, percutaneous technique for eliminating glabellar furrows is described. An insulated, bipolar needle is inserted vertically through the eyebrow skin to entrap the corrugator nerve plexus. To confirm proper positioning, a stimulating current is delivered to the needle during observation of corrugator supercilii muscle response. Radiofrequency energy is then delivered to the needle, thereby ablating the intervening nerve tissue. This technique is in the early stage of optimization and is being evaluated in an ongoing Stanford University Human Subjects protocol, Stanford, Calif. The preliminary results are reported herein.     

Electrosurgery and energized dissection

This article outlines the biophysics of electrosurgery and tissue energy sources, including the basic concepts of both modalities. It explores the biophysics of electrodiathermy, including current density, waveforms and electrosurgical circuits. The principles of monopolar and bipolar diathermy are described with reference to the safety issues pertinent to implantable cardiac devices and other implants. Safe application of electrodiathermy in endoscopic and laparoscopic surgery is discussed, exploring potential risks such as direct and capacitance coupling. The principles behind tissue energizers, specifically advanced bipolar energy sources and ultrasonic devices, are also covered.     

The Vista system: a new bipolar resection device for endourological procedures: comparison with conventional resectoscope

OBJECTIVE: Conventional transurethral resection of the prostate (TURP) uses a monopolar electrocautery system in which the current passes from the active electrode through the patient's body towards the return plate and may cause distant negative effects. In this study a new developed resection device, the Vista system, using a bipolar electrocautery system and 0.9% sodium chloride solution for irrigation, was evaluated in an ex-vivo model. METHODS: The modified model of the isolated blood perfused kidney was used to determine cutting qualities, ablation rate, blood loss and coagulation depth of the bipolar resectoscope. After ablating the renal tissue of a perfused kidney in a surface area, blood loss was semiquantitatively determined. Afterwards samples were taken and processed for histological evaluation of the coagulation depth. We compared the new bipolar resection device against a conventional monopolar resectoscope. RESULTS: We found good cutting qualities of the bipolar resectoscope although it is more difficult to start a cut. The ablation rate is determined by the width of the electrode and is similar to the standard device (30 cm(2)/min). The bleeding is reduced with increasing output powers (26.13 +/- 6.15 g/min (level 5); 20.49 +/- 5,47 g/min (level 6); 13.16 +/- 5,47 g/min (level 7); 10.43 +/- 4.76 g/min (level 8) and lower compared to a conventional monopolar resectoscope (17.08 +/- 4.47 g/min). The coagulation depth increases with higher output powers but is reduced compared to the standard device (118 +/- 22 microm (level 5); 121 +/- 23 microm (level 6); 141 +/- 62 microm (level 7); 163 +/- 30 microm (level 8) versus 287 +/- 57 (monopolar resectoscope)). CONCLUSION: Our results with the bipolar resection device for TURP suggest that it may offer an alternative to conventional TURP. As active and the return electrode are placed on the resectoscope, high current densities are achieved locally and complications caused by distant negative effects of the current are theoretically reduced in vivo. Furthermore the risk of TUR syndrome is theoretically eliminated by using physiological sodium chloride solution for irrigation. To prove the clinical significance of our ex-vivo findings, clinical studies including large numbers of patients have to be performed.