Low-frequency ultrasound sonophoresis to increase the efficiency of topical steroids: a pilot randomized study of humans.

Topical steroids are efficient in vasoconstriction potential, which is linked to their anti-inflammatory activity. Low-frequency ultrasound (US) applied on the skin (sonophoresis) may enhance the transdermal transport of various steroids. We aimed to assess, in a simple, blinded, randomized controlled pilot study, the clinical efficiency of sonophoresis in increasing vasoconstriction by enhancing the transdermal penetration of topical steroids in human skin. The study took place in the Clinical Investigation Center of the University Hospital of Tours and involved healthy volunteers. Three circular zones were delimited on each of the subjects' forearms: zone 1 (right and left) received topical steroids with 1-h occlusion, zone 2 with 2-h occlusion, and zone 3 with massage. Forearms were randomized to first undergo US, using a 36 kHz probe, delivered in a pulsed mode (2s on/5s off), during 5 min, with a US intensity of 2.72 W/cm(2), or no US. We used betamethasone 17-valerate in cream form as the topical steroid. The primary outcome was difference between forearms in skin color (increased whiteness reflecting the intensity of vasoconstriction) measured by 2 scores: values obtained with a chromameter (the higher the value, the whiter the skin) and a clinical visual score. The measurements were taken by a dermatologist by blinded assessment. Fifteen subjects were included. Vasoconstriction was significantly higher with the topical steroid applied after US, especially in zone 2, than without US. Vasoconstriction was increased at 1, 2, 3, 4, and 6h (e.g., chromameter score 63.4 versus 65.2, p=0.017 at 4h) and disappeared at 24h. Moreover, 2-h occlusion gave higher vasoconstriction scores than did 1-h occlusion or massage alone, whether US was applied or not. The use of low-frequency US coupled with 2-h occlusion is a synergistic way to increase the efficiency of topical steroids by enhancing skin permeability.

Noninvasive creation of an atrial septal defect by histotripsy in a canine model.

BACKGROUND: The primary objective of this study was to develop an image-guided, noninvasive procedure to create or enlarge an atrial septal defect for the treatment of neonates with hypoplastic left heart syndrome and an intact or restrictive atrial septum. Histotripsy is an innovative ultrasonic technique that produces nonthermal, mechanical tissue fractionation through the use of high-intensity ultrasound pulses. This article reports the pilot in vivo study to create an atrial septal defect through the use of extracardiac application of histotripsy in an open-chest canine model. METHODS AND RESULTS: In 10 canines, the atrial septum was exposed to histotripsy by an ultrasound transducer positioned outside the heart. Ultrasound pulses of 6-microsecond duration at a peak negative pressure of 15 MPa and a pulse repetition frequency of 3.3 kHz were generated by a 1-MHz focused transducer. The procedure was guided and monitored by real-time ultrasound imaging. In 9 of 10 canines, an atrial septal defect was produced, and shunting across the atrial septum was visualized. Pathology of the hearts showed atrial septal defects with minimal damage to surrounding tissue. No damage was found on the epicardial surface of the heart or other structures. CONCLUSIONS: Under real-time ultrasound guidance, atrial septal defects were successfully created with extracardiac histotripsy in a live canine model. Although further studies in an intact animal model are needed, these results provide promise of histotripsy becoming a valuable clinical tool.

Thermal effects generated by high-intensity focused ultrasound beams at normal incidence to a bone surface.

Experiments and computations were performed to study factors affecting thermal safety when high-intensity focused ultrasound (HIFU) beams are normally incident (i.e., beam axis normal to the interface) upon a bone/soft-tissue interface. In particular, the temperature rise and thermal dose were determined as a function of separation between the beam focus and the interface. Under conditions representative of clinical HIFU procedures, it was found that the thermal dose at the bone surface can exceed the threshold for necrosis even when the beam focus is more than 4 cm from the bone. Experiments showed that reflection of the HIFU beam from the bone back into the transducer introduced temperature fluctuations of as much as +/-15% and may be an important consideration for safety analyses at sufficiently high acoustic power. The applicability of linear propagation models in predicting thermal dose near the interface was also addressed. Linear models, while underpredicting thermal dose at the focus, provided a conservative (slight overprediction) estimate of thermal dose at the bone surface. Finally, temperature rise due to absorption of shear waves generated by the HIFU beam in the bone was computed. Modeling shear-wave propagation in the thermal analysis showed that the predicted temperature rise off axis was as much as 30% higher when absorption of shear waves is included, indicating that enhanced heating due to shear-wave absorption is potentially important, even for normally incident HIFU beams.

Efficiency of low-frequency ultrasound sonophoresis in skin penetration of histamine: a randomized study in humans.

Low-frequency ultrasound (US) applied to skin (sonophoresis) has been investigated to enhance the transdermal transport of various drugs. Histamine is usually used in allergy investigations. We aimed to investigate, in a randomized study, the transdermal penetration of histamine with sonophoresis. Ten subjects were included. Their right forearm was divided into three zones, which were randomly assigned a treatment: no US, US(1) (I(1)=2.72 W/cm(2)), US(2) (I(2)=3.50 W/cm(2)). The primary outcome was area of induced papule, which revealed histamine penetration. Secondary outcomes were echographic measurement of papule (skin thickness) and pruritus. Measurements were taken immediately after US application and after 30 min, 2 h and 24 h. Arm zones without US application showed no papules induced by histamine; 9/10 subjects receiving US showed papules. Their mean size increased with increased intensity of US but not significantly. The skin thickness increased with US. Pruritus occurred in 7/10 cases after US and histamine. The adverse events were skin erythema, pain and tinnitus. Though this study included a few number of patients, it confirms that sonophoresis enhances skin penetration of histamine. This technology could be used at therapeutic levels: histamine could be used with sonophoresis as a positive control in allergy testing instead of prick tests, which involve skin disruption with a lancet.

Comparative analyses of cell disruption methods for mitochondrial isolation in high-throughput proteomics study.

One of the most crucial steps in mitochondrial isolation is disruption of intact cells to denude intracellular organelles, but the yield and purity of different disruption protocols have not been well addressed. In the present study, MDCK cells were disrupted by mechanical (sonication and homogenization), physical (repeated freeze/thaw cycles and hypoosmotic burst), and chemical (using Triton X-100, NP-40, or CHAPS) methods. Efficacy of cell disruption was evaluated by trypan blue staining and mitochondria were subsequently isolated by standardized differential centrifugation. The yield of isolation was also determined by measuring protein concentrations, whereas the purity was examined by Janus green B staining, Western blot analyses of markers for mitochondria (COX-4) and other subcellular organelles/locales (i.e., nucleus, cytoplasm, endoplasmic reticulum, and lysosome), transmission electron microscopy, two-dimensional electrophoresis, and Q-TOF MS and/or MS/MS analyses. Our data demonstrated that sonication is the method of choice for disruption of cells prior to mitochondrial isolation for proteome analysis.

The HAC Trial (Harmonic for Acute Cholecystitis) Study. Randomized, double-blind, controlled trial of Harmonic(H) versus Monopolar Diathermy (M) for laparoscopic cholecystectomy (LC) for acute cholecystitis (AC) in adults.

BACKGROUND: In the developmental stage of laparoscopic cholecystectomy (LC) it was considered 'unsafe' or 'technically difficult' to perform laparoscopic cholecystectomy for acute cholecystitis (AC). With increasing experience in laparoscopic surgery, a number of centers have reported on the use of laparoscopic cholecystectomy for acute cholecystitis, suggesting that it is technically feasible but at the expense of a high conversion rate, which can be up to 35 per cent and common bile duct lesions.The HARMONIC SCALPEL (H) is the leading ultrasonic cutting and coagulating surgical device, offering surgeons important benefits including: minimal lateral thermal tissue damage, minimal charring and desiccation.Harmonic Scalpel technology reduces the need for ligatures with simultaneous cutting and coagulation: moreover there is not electricity to or through the patient Harmonic Scalpel has a greater precision near vital structures and it produces minimal smoke with improved visibility in the surgical field.In retrospective series LC performed with H was demonstrated feasible and effective with minimal operating time and blood loss: it was reported also a low conversion rate (3.9%).However there are not prospective randomized controlled trials showing the advantages of H compared to MD (the commonly used electrical scalpel) in LC. METHODS/DESIGN: Aim of this RCT is to demonstrate that H can decrease the conversion rate compared to MD in LC for AC, without a significant increase of morbidity.The patients will be allocated in two groups: in the first group the patient will be submitted to early LC within 72 hours after the diagnosis with H while in the second group will be submitted to early LC within 72 hours with MD. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT00746850.

Thermocron iButton and iBBat temperature dataloggers emit ultrasound.

Thermocron iButton dataloggers are widely used to measure thermal microclimates experienced by wild animals. The iBBat is a smaller version of the datalogger, also commercially available, that is used to measure animal skin or core body temperatures when attached externally or surgically implanted. Field observations of bats roosting under a bridge suggested that bats avoided locations with iButtons. A heterodyne bat detector revealed that the dataloggers emitted ultrasound which was detectable from a distance of up to 30 cm. We therefore recorded and quantified the acoustic properties [carrier frequency (Hz) and root mean square sound pressure level (dB SPL)] of iButton and iBBat dataloggers. All units emitted a 32.9 kHz pure tone that was readily picked up with a time expansion bat detector at a distance of 1 cm, and most were detected at a distance of 15 cm. The maximum amplitude of iButton dataloggers was 46.5 dB SPL at 1.0 cm-a level within the range of auditory sensitivity for most small mammals. Wrapping iButtons in plastic insulation severely attenuated the amplitude of ultrasound. Although there was a statistically significant reduction in rates of warming and cooling with insulation, this effect was small and we suggest that insulation may be a viable solution to eliminate unwanted ultrasonic noise in instances when small delays in thermal response dynamics are not a concern. We recommend behavioural studies to assess if the electronic signals emitted by iButtons are disturbing to small mammals.

Skin-traction method prevents the collapse of the internal jugular vein caused by an ultrasound probe in real-time ultrasound-assisted guidance.

PURPOSE: Real-time ultrasound-assisted guidance for catheterization of the internal jugular vein (IJV) is known to be useful, especially for a small-sized vein, which is difficult to catheterize. However, one of the problems with real-time ultrasound-assisted guidance is that the ultrasound probe itself can collapse the vein. We have developed a novel "skintraction method (STM)", in which the puncture point of the skin over the IJV is stretched upwards with several pieces of surgical tape in the cephalad and caudal directions with the aim being to facilitate catheterization of the IJV. We examined whether this method increased the compressive force required to collapse the IJV. METHODS: In ten volunteers, the compressive force required to collapse the right IJV, and the cross-sectional area and anteroposterior and transverse diameters of the IJV were measured with ultrasound imaging in the supine position (SP) with or without the STM or in the Trendelenburg position of 10 degrees head-down (TP) without the STM. RESULTS: The compressive force to required to collapse the vein was increased significantly with the STM, while the crosssectional area and anteroposterior diameter of the vein in the SP with STM were similar to those in the TP without the STM. CONCLUSION: With the STM, not only the cross-sectional area but also the compressive force required to collapse the IJV increased. Thus, the STM may facilitate real-time ultrasoundassisted guidance for catheterization of the IJV by maintaining the cross-sectional area of the vein during the guidance.

The effect of ultrasonic treatmen on some functional properties of egg white

This work studied the effect of treatment with a high frequency ultrasound bath (40 kHz and a power of 80 W.) on the pH, foaming capacity and stability of the foam of the white of hens eggs (sample 1/120 hours post laying and sample 2/24 hours post laying). Exposure time was at varied intervals of 0, 5, 10 and 15 mins at 20°C. The samples were stored in refrigeration at 4°C for 3 days. The comparative study of the data was carried out using variance analysis(ANOVA) and surface response analysis (RSA); where it was found that the pH did not show any significant changes(P<0.05) due to the effect of the treatment and remained during storage. On the other hand, the results showed that treatment with ultrasound for ten minutes increased the foaming capacity by 15.84 and 13.07 percent in samples 1 and 2, respectively. However, the stability of the foam in both samples was seen to diminish by 13.89 and 8.50 percent.

En este trabajo se estudió el efecto del tratamiento con un baño de ultrasonido de alta frecuencia (40 kHz y una potencia de 80 W) durante 0; 5; 10 y 15 min. / 20°C, sobre el pH, capacidad espumante y estabilidad de la espuma de la clara de huevos de gallina (muestra 1/ 120 horas pos-postura y muestra 2/ 24 horas post-postura). Las muestras fueron almacenadas en refrigeración a 4°C durante 3 días. El estudio comparativo de los datos se realizó por análisis de varianza (ANOVA) y superficie de respuesta (RSA); donde se encontró que en el pH no presentó cambios significativos (P<0,05) por efecto del tratamiento y de igual manera se mantuvo durante el tiempo de almacenamiento. Por otro lado se observó que el tratamiento con ultrasonido durante 10 mins aumentó la capacidad espumante en un 15,84 y 13,07 por ciento en las muestras 1 y 2, respectivamente. Sin embargo, la estabilidad de la espuma de estas muestras se vio disminuida en un 13,89 y 8,50 por ciento.

Threshold estimation and superthreshold behavior of ultrasound-induced lung hemorrhage in rats: role of age dependency.

Age-dependent threshold and superthreshold behaviors of ultrasound-induced lung hemorrhage were investigated with one hundred ten 12.6 +/- 0.8-d-old rats, one hundred ten 22.9 +/- 0.8-d-old rats, and one hundred 57.7 +/- 3.9-d-old rats. Exposure conditions were: 2.8 MHz, 10-s exposure duration, 1-kHz pulse repetition frequency and 1.3-mus pulse duration. The in situ (at the pleural surface) peak rarefactional pressure (p(r(in situ))) ranged between 1.4 and 10.8 MPa for which there were either 9 or 10 acoustic pressure groups for each of the three rat ages (10 rats/exposure group). For each of the three rat ages there were also shams; there were no lesions in the shams. The p(r(in situ)) levels were randomized within each age group; rat age was not randomized. Individuals involved in animal handling, exposure and lesion scoring were blinded to the exposure condition. In addition, one hundred fifty-six 72-d-old rats were included from three completed studies (same experimental conditions) to provide a fourth age group for the analysis. Probit regression analysis was used to examine the dependence of the occurrence of lesions on p(r(in situ)) in the four age groups. Likewise, lesion depth and lesion root surface area were analyzed using Gaussian tobit regression analysis. Although p(r(in situ)) was a significant variable, no significant age dependence of the p(r(in situ)) effect was found. Furthermore, age had no significant effect on either the rate of occurrence or the depth of lesions. Given the occurrence of a lesion, a weak age dependence was found for the median surface area of the induced lesion (p-value = 0.037).

Induction of apoptosis in sonoporation and ultrasonic gene transfer.

The role of apoptosis in sonoporation and ultrasound-enhanced gene transfection of cell suspensions was examined in vitro. Suspensions of HL-60 and of CHO-K1 cells were exposed to 2.25-MHz continuous ultrasound for 1 min in a 60-rpm rotating-tube exposure system, with ultrasound contrast media added to ensure nucleation of cavitation. Cell necrosis was measured by trypan blue dye exclusion (using a hemacytometer) and by propidium iodide nuclear staining (using flow cytometry). Apoptosis was detected by the annexin V method with Alexa Fluor 350 as the fluorescent label, and confirmed by Hoechst 33342 nuclear staining. Sonoporation cell loading was assessed by uptake of large fluorescent-dextran molecules from the medium. Transfection was demonstrated by expression of green fluorescent protein (GFP) from plasmids transferred into the cells by the treatment. Cell scoring was performed by flow cytometry, with necrotic cell events excluded. For HL-60 cells at 0.4 MPa, cell loading and transfection was significantly increased relative to shams at 2, 6 and 24 h post exposure, peaking at 19.0 +/- 5.5% and 9.6 +/- 4.2% of non-necrotic cells, respectively, at 6 h. However, about one third of the treatment-positive cells were identified as apoptotic. The cell loading and gene transfer effects increased for increasing peak rarefactional pressure amplitude, reaching 24.4 +/- 7.7% and 12.7 +/- 5.1% of non-necrotic cells, respectively, for 0.6-MPa exposure. However, the lethal cellular injury caused by cavitation in the rotating tube system reduced the overall apparent efficacy of cell loading and gene transfer to 5.1 +/- 2.1% and 2.1 +/- 0.9%, respectively, after accounting for necrosis and apoptosis. Similar tests with CHO cells showed increased sonoporation but mostly cell death by necrosis, rather than apoptosis. The induction of apoptosis by cavitation treatments should be considered as a possible confounding factor, in addition to necrosis, in sonoporation and ultrasonic gene transfer research.

Description of radiation- and ultrasound-induced cell death by a stochastic process.

Cell survival is a stochastic process with the stochastic component being strongly dependent on the irradiation conditions. This process is described by a stochastic model which allows differentiation between the deterministic and stochastic components of survival. The proposed model is tested for four irradiation experiments (2 with ionizing radiation and 2 with ultrasound) and very good agreement with experimental results is demonstrated. It identifies the higher stochasticity of the cell survival for the temporally varying radiation fields and provides the possibility to compare the stochasticity of survival in different radiation fields.

High frequency ultrasound torturer.

The discernible aim of torture as everyone believes--and rightly so--is to destroy the personality of an individual in a way that would render his compliance in future. But to destroy a personality is easier said than done. It requires long sessions of detention and torture. The torturers risk themselves getting exposed. The Human Rights groups are active all around the world. Ultimately the personality may not be destroyed much to the chagrin of the torturers, and an unexpected resilient rebounding may take place. Therefore, with the repertoire of modern knowledge, the strategy may well change in the 21st century. Discreet methods may be employed to selectively destroy areas in brain by high dosage and high frequency ultrasound. It is completely a non-invasive technique that does not leave its fingerprint for painful, later denials of subornation. Nevertheless the personality will change--from rightful aggression to slavish submission. The aim of this article is to put forward the theoretical perspective and cofounded projection of the darker and menacing side of ultrasound technology so that future generation could be saved from sin of omission.

Pulpal temperature increase with high-speed handpiece, Er:YAG laser and ultrasound tips.

The aim of this study was to compare intrapulpal temperature increase produced by high-speed handpiece, Er:YAG laser and CVDentus ultrasound tips during cavity preparation. Thirty bovine mandibular incisors with an enamel/dentin thickness of 4 mm at buccal surface had their roots amputated and were allocated to the following groups (n=10): Group I- high-speed handpiece; Group II- noncontact Er:YAG laser (250 mJ/4 Hz); and Group III- CVDentus ultrasouns tips. All devices were used with water cooling. Class V cavities were prepared to a depth of 3.5 mm, measured with a periodontal probe. A type T thermocouple was placed inside the pulp chamber to determine the temperature increase (degrees C), which was recorded by a data acquisition system ADS 2000 IP (Lynx Technology) linked to a notebook computer. Data were analyzed statistically by one-way ANOVA and Tukey's test (p=0.05). The mean temperature rises were: 1.10 degrees C (+/-0.56) for Group I, 0.84 degrees C (+/-0.55) for Group II, and 3.00 degrees C (+/- 1.34) for Group III. There were no statistically significant differences (p>0.05) between Groups I and II, but both of them differed significantly from Group III (p<0.05). In conclusion, the use of Er:YAG laser and high-speed handpiece for cavity preparation resulted in similar temperature increase. Although ultrasound tips generated significantly higher intrapulpal temperature increase, it remained below the critical value of 5.5 degrees C and may be considered safe for use.

Transesophageal echocardiography-related complications.

PURPOSE: The use of transesophageal echocardiography has increased over the past several years. It is generally considered a safe diagnostic and monitoring tool. Whereas complications associated with echocardiographic examination rarely occur, such complications must be known to echocardiographers performing these examinations. The purpose of this review is to summarize potential complications associated with transesophageal echocardiography. SOURCES: A systematic search of the English and French literature was undertaken using PubMed from the National Library of Medicine. Relevant articles were obtained from a Medline search spanning the years 1975-2007, and their reference lists were used to retrieve additional articles. PRINCIPAL FINDINGS: Complications of transesophageal echocardiography are primarily related to the gastrointestinal, cardiovascular, and respiratory systems, and include infection, toxic drug reaction, local reaction through contamination of the probe, and ultrasound cavitation. Strategies to prevent these complications are reviewed. CONCLUSION: Whereas transesophageal echocardiography is associated with a low complication rate, the echocardiographer must be knowledgeable about the types of complications and their predisposing factors, and should be meticulous in preventing their occurrence.

Applications of ultrasonic skin permeation in transdermal drug delivery.

Transdermal ultrasound-mediated drug delivery has been studied as a method for needle-less, non-invasive drug administration. Potential obstacles include the stratum corneum, which is not sufficiently passively permeable to allow effective transfer of many medications into the bloodstream without active methods. A general review of the transdermal ultrasound drug delivery literature has shown that this technology offers promising potential for non-invasive drug administration. Included in this review are the reported acoustic parameters used for achieving delivery, along with the known intensities and exposure times. Ultrasound mechanisms are discussed as well as spatial field characteristics. Accurate and precise quantification of the acoustic field used in drug delivery experiments is essential to ensure safety versus efficacy and to avoid potentially harmful bioeffects.

Ultrasound targeted microbubble destruction for drug and gene delivery.

BACKGROUND: Gas-filled microbubbles have been used as ultrasound contrast agents for some decades. More recently, such microbubbles have evolved as experimental tools for organ- and tissue-specific drug and gene delivery. When sonified with ultrasound near their resonance frequency, microbubbles oscillate. With higher ultrasound energies, oscillation amplitudes increase, leading to microbubble destruction. This phenomenon can be used to deliver a substance into a target organ, if microbubbles are co-administered loaded with drugs or gene therapy vectors before i.v. injection. OBJECTIVE: This review focuses on different experimental applications of microbubbles as tools for drug and gene delivery. Different organ systems and different classes of bioactive substances that have been used in previous studies will be discussed. METHODS: All the available literature was reviewed to highlight the potential of this non-invasive, organ-specific delivery system. CONCLUSION: Ultrasound targeted microbubble destruction has been used in various organ systems and in tumours to successfully deliver drugs, proteins, gene therapy vectors and gene silencing constructs. Many proof of principle studies have demonstrated its potential as a non-invasive delivery tool. However, too few large animal studies and studies with therapeutic aims have been performed to see a clinical application of this technique in the near future. Nevertheless, there is great hope that preclinical large animal studies will confirm the successful results already obtained in small animals.

Proximal ureteral calculi: shock wave or ureterolithotripsy?

OBJECTIVE: To compare the success rates and efficiency of ureterolithotripsy (URL) and extracorporeal shock wave lithotripsy (SWL) for proximal ureteric stones. CASUISTRY AND METHODS: A prospective non-randomized study was performed between 1999 and 2004. Of a total of 235 patients, 121 underwent SWL and 114 had ureteroscopy with ultrasonic lithotripsy. There were no significant differences between the groups. The success rate, operative time, postoperative pain and complications were analyzed in each group. Patients were followed postoperatively for a minimum of 3 months (median 6 months). RESULTS: Treatment success rate was defined as the complete removal or as the radiographic absence of calculi at a 3-month follow-up. The URL success rate was 85.6% (98/114) and 89.5% (68/95) after one SWL session and (77/85) 90.6% after a second treatment. No differences were found in the results, overall complication rates and mean procedure time. However, the fluoroscopy time was longer in the URL group and pain was more frequent. CONCLUSIONS: Semirigid URL is as efficient as SWL in the treatment for proximal ureteral stone. However, SWL requires less fluoroscopic time and fewer pain relievers.

Consideraciones sobre embarazo ectópico: experiencia en el Instituto Autónomo Hospital Universitario de Los Andes: años 2000-2006 / Considerations on ectopic pregnancy: experience at the Hospital Universitario de Los Andes: years 2000-2006

Determinar factores de riesgo y modalidades diagnóstico-terapéuticas del Embarazo Ectópico (EE). Estudio descriptivo, analítico de 353 casos de EE. Período 2000-2006. Servicio de Gineco-obstetricia de IAHULA, Estado Mérida, Venezuela. 353 historias con diagnóstico de EE. Grupo predominante: 19-34 años (75,1 por ciento). Nuliparidad (25,5 por ciento). Antecedentes Gineco-obstétricos (27,2 por ciento); Anticonceptivos (45,3 por ciento); ITS (23, 2 por ciento); DIU (10,8 por ciento); Cirugía Ginecológica y/o Abdominal anterior (33,4 por ciento). ß-hCG positivas 94,3 por ciento; Culdocentesis positivas 78,16 por ciento. Hallazgo Ultrasonográfico: 88,33 por ciento, Hallazgo Quirúrgico: 310 casos; localización Tubarica (97,09 por ciento); Salpingectomía total: 84,1 por ciento. El EE es una emergencia obstétrica frecuente, pone en riesgo la vida de la paciente con patogénesis multifactorial.