Impact of the COVID-19 Pandemic on a Cancer Fast-Track Programme.

INTRODUCTION: The COVID-19 pandemic has disrupted many aspects of clinical practice in oncology, particularly regarding early cancer diagnosis, sparking public health concerns that possible delays could increase the proportion of patients diagnosed at advanced stages. In 2009, a cancer fast-track program (CFP) was implemented at the Clinico-Malvarrosa Health Department in Valencia, Spain with the aim of shortening waiting times between suspected cancer symptoms, diagnosis and therapy initiation. OBJECTIVES: The study aimed to explore the effects of the COVID-19 pandemic on our cancer diagnosis fast-track program. METHODS: The program workflow (patients included and time periods) was analysed from the beginning of the state of alarm on March 16th, 2020 until March 15th, 2021. Data was compared with data from the same period of time from the year before (2019). RESULTS: During the pandemic year, 975 suspected cancer cases were submitted to the CFP. The number of submissions only decreased during times of highest COVID-19 incidence and stricter lockdown, and overall, referrals were slightly higher than in the previous 2 years. Cancer diagnosis was confirmed in 197 (24.1%) cases, among which 33% were urological, 23% breast, 16% gastrointestinal and 9% lung cancer. The median time from referral to specialist appointment was 13 days and diagnosis was reached at a median of 18 days. In confirmed cancer cases, treatment was started at around 30 days from time of diagnosis. In total, 61% of cancer disease was detected at early stage, 20% at locally advanced stage, and 19% at advanced stage, displaying time frames and case proportions similar to pre-pandemic years. CONCLUSIONS: Our program has been able to maintain normal flow and efficacy despite the challenges of the current pandemic, and has proven a reliable tool to help primary care physicians referring suspected cancer patients.

Clinical usefulness of serum angiotensin converting enzyme in silicosis.

INTRODUCTION: Silicosis is an irreversible and incurable disease. Preventive measures to eliminate exposure are the only effective way to reduce morbidity and mortality. In such situations, having a biomarker for early diagnosis or to predict evolution would be very useful in order to improve control of the disease. The elevation of serum angiotensin-converting enzyme (sACE) in silicosis has been described in previous studies, although its relationship with severity and prognosis is not clear. AIMS: To determine the levels of sACE in a cohort of patients with exposure to silica dust with and without silicosis, and to assess their impact on the prognosis of the aforementioned patients. METHOD: Prospective observational study on patients treated in a silicosis clinic from 2009 to 2018. sACE levels and pulmonary function tests were performed. Radiological progression was assessed in patients who had already had 2 X-rays of the thorax and / or two CT scans with at least a 1-year interval, from the time of inclusion in the study. RESULTS: A total of 413 cases of silicosis were confirmed, as well as 73 with exposure to silica dust but without silicosis. The mean sACE level for healthy subjects was 27.5±7.3U/L, for exposed patients without silicosis it was 49.6±24.2U/L, for simple silicosis it was 57.8±31,3U/L and for complicated silicosis it was 74.5±38.6U/L. Patients with a higher sACE generally progressed radiologically during follow-up (73.3±38.0 vs. 60.4±33.7; p<.001) and so the category of silicosis changed (73,9±38.1 vs. 62.5±34.6; p<.021). CONCLUSIONS: sACE was elevated in patients with silicosis, and the greater its severity, the higher it was, which is associated with disease progression measured radiologically or as a category change of silicosis.

Ten-year assessment of a cancer fast-track programme to connect primary care with oncology: reducing time from initial symptoms to diagnosis and treatment initiation.

BACKGROUND: Cancer is the second leading cause of mortality worldwide. Integrating different levels of care by implementing screening programmes, extending diagnostic tools and applying therapeutic advances may increase survival. We implemented a cancer fast-track programme (CFP) to shorten the time between suspected cancer symptoms, diagnosis and therapy initiation. PATIENTS AND METHODS: Descriptive data were collected from the 10 years since the CFP was implemented (2009-2019) at the Clinico-Malvarrosa Health Department in Valencia, Spain. General practitioners (GPs), an oncology coordinator and 11 specialists designed guidelines for GP patient referral to the CFP, including criteria for breast, digestive, gynaecological, lung, urological, dermatological, head and neck, and soft tissue cancers. Patients with enlarged lymph nodes and constitutional symptoms were also considered. On identifying patients with suspected cancer, GPs sent a case proposal to the oncology coordinator. If criteria were met, an appointment was quickly made with the patient. We analysed the timeline of each stage of the process. RESULTS: A total of 4493 suspected cancer cases were submitted to the CFP, of whom 4019 were seen by the corresponding specialist. Cancer was confirmed in 1098 (27.3%) patients: breast cancer in 33%, urological cancers in 22%, gastrointestinal cancer in 19% and lung cancer in 15%. The median time from submission to cancer testing was 11 days, and diagnosis was reached in a median of 19 days. Treatment was started at a median of 34 days from diagnosis. CONCLUSIONS: The findings of this study show that the interval from GP patient referral to specialist testing, cancer diagnosis and start of therapy can be reduced. Implementation of the CFP enabled most patients to begin curative intended treatment, and required only minimal resources in our setting.

End-of-life practices in patients with devastating brain injury in Spain: implications for organ donation. / Prácticas clínicas al final de la vida en pacientes con daño cerebral catastrófico en España: implicaciones para la donación de órganos.

OBJECTIVE: To describe end-of-life care practices relevant to organ donation in patients with devastating brain injury in Spain. DESIGN: A multicenter prospective study of a retrospective cohort. PERIOD: 1 November 2014 to 30 April 2015. SETTING: Sixty-eight hospitals authorized for organ procurement. PATIENTS: Patients dying from devastating brain injury (possible donors). Age: 1 month-85 years. PRIMARY ENDPOINTS: Type of care, donation after brain death, donation after circulatory death, intubation/ventilation, referral to the donor coordinator. RESULTS: A total of 1,970 possible donors were identified, of which half received active treatment in an Intensive Care Unit (ICU) until brain death (27%), cardiac arrest (5%) or the withdrawal of life-sustaining therapy (19%). Of the rest, 10% were admitted to the ICU to facilitate organ donation, while 39% were not admitted to the ICU. Of those patients who evolved to a brain death condition (n=695), most transitioned to actual donation (n=446; 64%). Of those who died following the withdrawal of life-sustaining therapy (n=537), 45 (8%) were converted into actual donation after circulatory death donors. The lack of a dedicated donation after circulatory death program was the main reason for non-donation. Thirty-seven percent of the possible donors were not intubated/ventilated at death, mainly because the professional in charge did not consider donation alter discarding therapeutic intubation. Thirty-six percent of the possible donors were never referred to the donor coordinator. CONCLUSIONS: Although deceased donation is optimized in Spain, there are still opportunities for improvement in the identification of possible donors outside the ICU and in the consideration of donation after circulatory death in patients who die following the withdrawal of life-sustaining therapy.

Intensive care practices in brain death diagnosis and organ donation.

We conducted a multicentre study of 1844 patients from 42 Spanish intensive care units, and analysed the clinical characteristics of brain death, the use of ancillary testing, and the clinical decisions taken after the diagnosis of brain death. The main cause of brain death was intracerebral haemorrhage (769/1844, 42%), followed by traumatic brain injury (343/1844, 19%) and subarachnoid haemorrhage (257/1844, 14%). The diagnosis of brain death was made rapidly (50% in the first 24 h). Of those patients who went on to die, the Glasgow Coma Scale on admission was ≤ 8/15 in 1146/1261 (91%) of patients with intracerebral haemorrhage, traumatic brain injury or anoxic encephalopathy; the Hunt and Hess Scale was 4-5 in 207/251 (83%) of patients following subarachnoid haemorrhage; and the National Institutes of Health Stroke Scale was ≥ 15 in 114/129 (89%) of patients with strokes. Brain death was diagnosed exclusively by clinical examination in 92/1844 (5%) of cases. Electroencephalography was the most frequently used ancillary test (1303/1752, 70.7%), followed by transcranial Doppler (652/1752, 37%). Organ donation took place in 70% of patients (1291/1844), with medical unsuitability (267/553, 48%) and family refusal (244/553, 13%) the main reasons for loss of potential donors. All life-sustaining measures were withdrawn in 413/553 of non-donors (75%).

Implementation and assessment of a fast-track programme to improve communication between primary and specialized care in patients with suspected cancer: how to shorten time between initial symptoms of cancer, diagnosis and initiation of treatment.

PURPOSE: This study aims to asses a cancer fast-track programme (CFP) to shorten the time since a patient with suspicion of cancer is referred by the primary care (PC) physician to the specialized medical team. METHODS: Guidelines for main suspected tumours were designed to help PC physicians to detect and rapidly refer cases to the CFP oncology coordinator, who sent them to the appropriate department to accelerate diagnosis, staging and therapy. All patients analysed in this report were referred from June 2009 to July 2012. RESULTS: A total of 897 suspected cancer cases were submitted and finally 705 were studied. In 205 (29 %) a cancer diagnosis was confirmed within 23 days (median). Therapy was initiated within 46 days after referral (median). Early diagnoses with a potential curative approach were made in 166 (82 %). CONCLUSIONS: This CFP decreased the waiting time for cancer diagnosis, by improving communication between PC physician and specialized care teams. Most patients included in this program could get therapy with curative intent.

Effectiveness of a protocolized system to alert pulmonologists of lung cancer radiological suspicion.

PURPOSE: When lung cancer (LC) is suspected in chest radiography, an adequate interpretation and management by experts would improve the selection, the access to rapid diagnostic units, the diagnostic effectiveness and prevent the loss of patients with suspected LC. To ensure this, we planned a system for alerting pulmonologists by radiologists to radiological suspicion of LC. METHODS: This system consists of an alert from radiologists to pulmonologists through a specific email. The pulmonologists alerted has to contact the study doctor petitioner who must refer the patient for study to the Lung Cancer Rapid Diagnostic Unit (LCRDU). We have prospectively analyzed all patients studied in a 2-year period including clinical variables, time invested in the different diagnostic steps and the degree of collaboration and satisfaction among the involved professionals. RESULTS: Of 118 alerts received, 84 (71 %) were studied in our LCRDU. The median of days until petitioner contact, patient consulted at LCRDU and to obtain a diagnosis was 1 (IQR 0-1.5), 2 (IQR 1-5) and 13 (IQR 7.5-30), respectively. In 45 cases (53 %), the suspicion of malignancy was confirmed (LC 84.4 % and metastasic 10.1 %). After staging was complete, 33 % of non-small cell lung cancer was potentially resectable (clinical TNM stage I-II). The level of satisfaction was high so that only one of the petitioner's studies chose other diagnostic pathways. CONCLUSION: This strategy for radiological suspicion of LC ensures the communication between general practitioners, radiologists and pulmonologist improving the LC diagnostic effectiveness. This system can be easily implemented in health care systems.

Usefulness of procalcitonin clearance as a prognostic biomarker in septic shock. A prospective pilot study.

OBJECTIVE: To evaluate procalcitonin clearance as a prognostic biomarker in septic shock. DESIGN: Prospective, observational pilot study. SETTING: Intensive care unit. PATIENTS: Patients admitted to the ICU due to septic shock and multiorgan dysfunction. INTERVENTIONS: Serum concentrations of procalcitonin were determined within 12h of onset of septic shock and multiorgan dysfunction (coinciding with admission to the ICU), and the following extractions were obtained after 24, 48 and 72h in patients who survived. DATA COLLECTED: Demographic data, Acute Physiology and Chronic Health Evaluation II score, and Sequential Organ Failure Assessment score, data on the primary focus of infection, and patient outcome (ICU mortality). RESULTS: Procalcitonin clearance was higher in survivors than in non-survivors, with significant differences at 24h (73.9 [56.4-83.8]% vs 22.7 [-331-58.4], p<0.05) and 48h (81.6 [71.6-91.3]% vs -7.29 [-108.2-82.3], p<0.05). The area under the ROC curve was 0.74 (95%CI, 0.54-0.95, p<0.05) for procalcitonin clearance at 24h, and 0.86 (95%CI, 0.69-1.0, p<0.05) at 48h. CONCLUSIONS: ICU mortality was associated to sustained high procalcitonin levels, suggesting that procalcitonin clearance at 48h may be a valuable prognostic biomarker.

Psychological care: social and family support for patients awaiting a liver transplant.

INTRODUCTION: In patients awaiting a transplant, the help received from friends and/or family members is considered to be an important factor in the transplantation process. Our objective was to determine the level of social/family support for patients on the liver transplant waiting list and to determine the relationship between clinical psychopathology and the level of social/family support. MATERIALS AND METHODS: The study population consisted of 70 patients on the liver transplant waiting list. We used the following instruments: (1) Medical Outcomes Study-Social Support Survey (MOS) Questionnaire. For size of the social network, four support dimensions and a global support index for emotional support, material/instrumental support, leisure/free time activities, and love/care; (2) Family Apgar Questionnaire for personal perception of family function; (3) SA-45 questionnaire of psychopathologic symptoms for somatizations, obsessive-compulsivity, interpersonal sensitivity, depression, anxiety, hostility, phobic anxiety, paranoid ideation, and psychoticism. RESULTS: The MOS showed that the mean size of the social network of these patients was 12 people. In these patients, social/family support was nonfunctional in 20% of the cases. By dimensions, the patients had the following percentage of nonfunctional support: 24% in emotional support; 10% material/instrumental support; 23% social relations of leisure/free-time activities; and 11% compassionate love/care support. The patients with nonfunctional support had the following associated psychopathologic symptoms (SA-45): depression (79% vs 39%; P = .008), anxiety (86% vs 46%; P = .008), hostility (43% vs 12%; P = .009), and psychoticism (14% vs 2%; P = .039) compared to functional patients. The Family Apgar showed that 27% of patients perceived a family dysfunction. These patients had greater interpersonal sensitivity-type emotional symptoms (32% vs 8%; P = .012), depression (79% vs 35%; P = .001), anxiety (79% vs 45%; P = .011), and hostility (42% vs 10%; P = .002) compared to normally functioning patients. CONCLUSIONS: Nearly a quarter of patients on the liver transplant waiting list have social/family support that is nonfunctional, which leads to greater emotional psychopathologic symptoms that would need to be treated.

Psychological characteristics of patients on the liver transplantation waiting list with depressive symptoms.

INTRODUCTION: Untreated psychiatric morbidity can worsen the quality of life in the posttransplantation stage. Therefore, it is important to detect and treat alterations associated with depression in transplantation patients from the beginning of the process. The objective of this study was to determine the psychological characteristics of patients on the liver transplantation waiting list with emotionally depressed symptoms. MATERIAL AND METHODS: We evaluated 70 patients on the liver transplantation waiting list for psychopathological symptoms of depression using the Symptom Assessment-45 Questionnaire (González and Cuevas) using chi-squared tests, Student t tests, and logistic regression analysis. RESULTS: Forty-seven percent of the patients on the liver transplantation waiting list showed relevant depressive-type psychopathological symptoms. The presence of the following factors were associated with the emotionally depressed characteristics of these patients: psychiatric mental disorders (P = .015); no partner (P = .009); and alcohol abuse (P = .050). Other related factors included the following: obsessive-compulsive-type emotional alterations (P = .001); interpersonal sensitivity (P < .001); anxiety (P < .001); hostility (P = .017); phobic anxiety (P = .017); and paranoid ideation (P = .029). With regard to coping strategies, these patients used defenselessness (P < .001) and anxious preoccupation (P = .016). With regard to the social-family setting, emotionally depressed patients had nonfunctional family and/or social support, according to the global MOS (Medical Outcomes Study-Social Support Survey) index (P = .008) and the total Apgar Family Score (P < .001). CONCLUSIONS: Almost half of the patients on the liver transplantation waiting list showed emotionally depressed-type symptoms. Other emotional-type alterations were related to this psychological profile: coping strategies of defenselessness and anxious preoccupation as well as nonfunctional social and/or family support.

Importance of introduction of a psychological care unit in a liver transplantation unit.

BACKGROUND: Psychological changes in terminally ill patients with liver disease are underestimated. Therefore, a psychological care unit was introduced in the liver transplantation unit in a transplantation hospital in Spain. OBJECTIVES: To describe the establishment of the psychological care unit in a liver transplantation unit and to review its operation, and to evaluate and diagnose psychological changes in patients on the waiting list for liver transplantation. MATERIALS AND METHODS: Variables evaluated included consultations, interviews, level of care provided, appointments postponed, difficulties, and cost-effectiveness. Psychopathologic symptoms were evaluated using the Symptom Assessment-45 questionnaire (Derogatis, 1975), examining 9 psychopathologic dimensions. RESULTS: Thirty-eight patients were given an appointment, and 28 were interviewed. Twelve postponed the appointment. The level of support provided to patients on the waiting list was 70%. The hospital structure was used to develop the care unit, which is why it was only necessary to employ 1 professional psychologist. Of patients assessed, 54% exhibited relevant clinical symptoms of depression, and 47 demonstrated anxiety. Patients with symptoms of depression reported "loss of interest"; those with anxiety reported feeling "worried and tense." Of these patients, an increased presence of symptoms was associated with various emotional problems such as hostility (33%), somatization (60%), obsession/compulsion (73%), interpersonal sensitivity (40%), phobic anxiety (20%), paranoid ideation (20%), and psychosis (6%). CONCLUSIONS: Patients on the waiting list for liver transplantation demonstrate increased clinical symptoms of depression and anxiety. Therefore, it is of great importance to introduce a psychological care unit to detect and treat these conditions. Introduction of the liver transplant unit program has improved multidisciplinary care and is cost-effective.

[Implementation of a protocol of management of chronic kidney disease between Nephrology and Primary Health Care. Preliminary results]. / Resultados preliminares de la implantación de un protocolo conjunto de manejo de la enfermedad renal crónica entre atención primaria y nefrología.

During the last years there has been an important advance in the knowledge of chronic kidney disease (CKD). In order to adapt our clinical practice to these new data, a protocol of management of CKD between Nephrology and Primary Health Care has been developed. The protocol includes several items like cardiac and renal protection strategies, diagnosis and treatment of complications, use of drugs and clear derivation criteria. Implementation of the protocol has been only partial and has implied, for the Renal Unit, an increase in the number of patients,specially the oldest ones, but a clear improve in the quality of the information too,and a first positive step in the right way to face the challenge of CKD. In view of analysed data we propose some modifications for the protocol.

[Use of rechargeable stimulators in 2 cases of cauda equina syndrome]. / Utilización de sistemas de estimulación recargables. A propósito de dos casos de síndrome de cola de caballo.

The first of the 2 cases of cauda equina syndrome we report occurred following phenolization of sacral roots after a series of operations for Hirsprung disease. The second occurred after trauma from a bullet that hit the spine. Fecal and urinary incontinence and neuropathic pain in the lower extremities were present in both cases. After various treatments failed, both patients were given dual spinal stimulation for integrated treatment of both incontinence and neuropathic pain. We applied a novel approach, connecting both stimulators to a single rechargeable generator, reducing medium- and long-term costs. Fewer generator replacements (every 2-3 years with the standard approach) and fewer generator implantations (2 each time with the usual system) are required when rechargeable generators are used. Patient quality of life is thus improved. The overall cost of the implants is reduced from their second year of use.

Durability of a cardiac valve leaflet made of calf pericardium: fatigue and energy consumption.

We studied the mechanical behavior of membranes of calf pericardium, similar to those employed in prosthetic valve leaflets, when subjected to tensile fatigue. The objective was to assess its durability, as a fundamental property of cardiac bioprosthesis, and analyze the energy consumption. For this purpose, the authors built a hydraulic simulator to subject a spherical valve leaflet made of calf pericardium to cyclic stress mimicking cardiac function. A total of 522 assays were performed in 40 samples, subjected to cyclic pressures greater than 6 atm, and 482 subjected to pressures ranging between 2 and 6 atm. The mathematical expression that establishes the relationship between the pressure exerted and the frequency was obtained. If we assume that the function is continuous, this equation provides the range of fatigue tolerated for a given number of cycles. Using the optimal values (the five highest values per series), the expression was found to be y = 9.95x(-0 1214) (R(2) = 0.955), where x represents the frequency in cycles per second and y the pressure in atmospheres. In addition, we established the mathematical relationship between the energy consumed and the frequency, which was a function of the pressure exerted, regardless of the region or zone from which the samples had been obtained. The methods of manual and morphology-based selection employed produced widely dispersed results. When a mechanical criterion was included, the similarity in the energy consumed during fatigue testing markedly improved the correlation, with a coefficient of determination between paired samples of R(2) = 0.7477. A mechanical criterion, such as energy consumption, can help to improve sample selection and produce more consistent results. Finally, we obtained the mathematical expression that relates the energy consumed to the pressure exerted and the number of cycles per second to which the valve leaflet was subjected. This procedure enables us to establish the limit to the energy that a biomaterial can consume over a period of time during which it is subjected to a working pressure and, thus, calculate more precisely its durability.

Resistance and stability of a new method for bonding biological materials using sutures and biological adhesives.

The valve leaflets of cardiac bioprostheses are secured and shaped by sutures which, given their high degree of resistance and poor elasticity, have been implicated in the generation of stresses within the leaflets, contributing to the failure of the bioprostheses. Bioadhesives are bonding materials that have begun to be utilized in surgery, although there is a lack of experience in their use with inert tissues or bioprostheses. Tensile testing is performed until rupture in samples of calf pericardium, a biomaterial employed in the manufacture of bioprosthetic heart valve leaflets. One hundred and thirty-two trials are carried out in three types of samples: intact or control tissue (n = 12); samples transected and glued in an overlapping manner with a cyanoacrylate (n = 60); and samples transected, sewn with a commercially available suture material and reinforced at the suture holes with the same cyanoacrylate (n = 60). Seven days after their preparation, 12 samples from each group, including the controls, are subjected to tensile testing until rupture and the findings are compared. In the stability study, groups of 12 each of the remaining 48 glued and 48 sutured and glued samples underwent tensile testing until rupture on days 30, 60, 90, and 120, after their preparation. The results show that bonding with the adhesive provided a resistance ranging between 1.04 and 1.87 kg, probably insufficient for use in valve leaflets, but also afforded a high degree of elasticity. After 120 days, both the glued and the sutured and glued series show excellent elastic behavior, with no rigidity or hardening of the pericardium. These samples present reversible elongation, or strain, when they surpass their elastic limit at rupture. This finding may be due to a load concentration that is damaging to the pericardium, to the behavior of the tissue as an amorphous material, or perhaps to both circumstances. These results need to be confirmed in future studies as they may be of value in the design and manufacture of cardiac bioprostheses.

Comparative study of the mechanical behaviour of a cyanoacrylate and a bioadhesive.

We compared the mechanical resistance of 18 samples of calf pericardium bonded with a 100 mm2 overlap, by two types of glues: a cyanoacrylate (Loctite 4011) and a bioadhesive (BioGlue). Comparative tensile testing was also carried out in 40 paired samples, 20 bonded with the cyanoacrylate and 20 unbonded controls. The findings at rupture showed a greater resistance of the calf pericardium glued with cyanoacrylate, with a mean tensile strength of 0.15 MPa vs. 0.04 MPa for the biological glue (p= 0.000). They also demonstrated a loss of resistance of the samples bonded with cyanoacrylate when compared with that of the unbonded other halves of the pairs: 0.20 MPa and 0.27 MPa vs. 19.47 MPa and 24.44 MPa (p < 0.001). The method of selection by means of paired samples made it possible to establish the equations that relate the stress and strain, or deformation, with excellent coefficients of determination (R2). These equations demonstrate the marked elastic behaviour of the bonded samples. Moreover, these findings show the cyanoacrylate to be superior to the biological glue, leading to the examination of the compatibility, inalterability over time and mechanical behaviour of the cyanoacrylate in sutured samples, as well as the study of the anisotropy of the biomaterial when bonded with a bioadhesive.

Resistance to tensile stress of a bioadhesive utilized for medical purposes: Loctite 4011.

Sutures are the materials presently employed to secure and give shape to the valve leaflets of cardiac bioprostheses. Their high resistance and low degree of elasticity in comparison with the calf pericardium of which the leaflets are made generates internal stresses that contribute to the failure of the bioprostheses. Biological adhesives are bonding materials that have begun to be utilized in surgery, although there is a lack of experience in their use with inert tissues or bioprostheses. We report our study of Loctite 4011, a biological glue composed of a cyanoacrylate that has been employed for medical purposes, in which samples of pericardium bonded with this adhesive were subjected to uniaxial tensile stress. The samples were glued in such a way as to leave an overlap of 1 cm2 between the surfaces of the tissue. The series included 83 samples: 12 tested 24 h after bonding, 17 after 45 days, 17 after 90 days, 19 after 106 days and 18 after 152 days. The samples subjected to deferred trials were preserved using three types of chemical substances: glutaraldehyde, glycerol or saline plus antibiotics. The mean resistance to rupture of the series tested 24 h after gluing was 0.15 MPa (1.47 machine kg). This resistance remained nearly unchanged, regardless of the preservation solution employed, for at least 152 days, the time at which the study ended. The stress-strain curves demonstrated a high degree of elasticity throughout the 152 days, a finding that was not influenced by the preservation solution. This adhesive showed a considerable resistance to tensile stress, although probably insufficient to replace sutures. However, it maintained a surprisingly high degree of elasticity in the samples. Perhaps the time has come to combine these two elements, sutures and adhesives, to improve the elasticity of the structure without a loss of resistance, and increase the durability of bioprostheses.

Comparison of the mechanical behaviors of biological tissues subjected to uniaxial tensile testing: pig, calf and ostrich pericardium sutured with Gore-Tex.

The purpose of this study was to compare the mechanical behavior of calf pericardium, pig pericardium and ostrich pericardium when subjected to tensile testing. Tensile stress was applied to 108 tissue samples, 36 of each type of tissue, until rupture. Groups of three adjacent strips measuring 12 x 2 cm(2) were cut longitudinally. Each group consisted of an unsutured center sample, or control, and the two contiguous samples, that on the right sutured with Gore-Tex at a 90 degrees angle with respect to the longitudinal axis and that on the left sewn with the same suture material at 45 degrees angle. The sutured samples showed a statistically significant loss of resistance (p<0.001) when compared with the corresponding unsutured tissue. The mean stresses at rupture for sutured ostrich pericardium were 21.81 and 20.81 MPa in the samples sewn at 45 degrees and 90 degrees, respectively, higher than those corresponding to unsutured calf and pig pericardium, 14.0 and 11.49 MPa, respectively, at rupture. The analysis of the stress/strain curve shows a smaller difference between sutured and unsutured ostrich pericardium than those observed in the other two biomaterials. These results demonstrate that, in addition to its greater resistance, ostrich pericardium also presents a less pronounced interaction with the suture material. Its capacity to absorb the shearing stress produced by the suture is greater. This report also confirms that the method of selection using paired samples ensures their homogeneity and makes it possible to predict the behavior of a sample by determining that of the other half of the pair.