The pathophysiological impact of intra-abdominal hypertension in pigs.

BACKGROUND: Intra-abdominal hypertension and abdominal compartment syndrome are common with clinically significant consequences. We investigated the pathophysiological effects of raised IAP as part of a more extensive exploratory animal study. The study design included both pneumoperitoneum and mechanical intestinal obstruction models. METHODS: Forty-nine female swine were divided into six groups: a control group (Cr; n = 5), three pneumoperitoneum groups with IAPs of 20mmHg (Pn20; n = 10), 30mmHg (Pn30; n = 10), 40mmHg (Pn40; n = 10), and two mechanical intestinal occlusion groups with IAPs of 20mmHg (MIO20; n = 9) and 30mmHg (MIO30; n = 5). RESULTS: There were significant changes (p<0.05) noted in all organ systems, most notably systolic blood pressure (SBP) (p<0.001), cardiac index (CI) (p = 0.003), stroke volume index (SVI) (p<0.001), mean pulmonary airway pressure (MPP) (p<0.001), compliance (p<0.001), pO2 (p = 0.003), bicarbonate (p = 0.041), hemoglobin (p = 0.012), lipase (p = 0.041), total bilirubin (p = 0.041), gastric pH (p<0.001), calculated glomerular filtration rate (GFR) (p<0.001), and urine output (p<0.001). SVV increased progressively as the IAP increased with no obvious changes in intravascular volume status. There were no significant differences between the models regarding their impact on cardiovascular, respiratory, renal and gastrointestinal systems. However, significant differences were noted between the two models at 30mmHg, with MIO30 showing worse metabolic and hematological parameters, and Pn30 and Pn40 showing a more rapid rise in creatinine. CONCLUSIONS: This study identified and quantified the impact of intra-abdominal hypertension at different pressures on several organ systems and highlighted the significance of even short-lived elevations. Two models of intra-abdominal pressure were used, with a mechanical obstruction model showing more rapid changes in metabolic and haematological changes. These may represent different underlying cellular and vascular pathophysiological processes, but this remains unclear.

Intracisternal BioGlue injection in the fetal lamb: a novel model for creation of obstructive congenital hydrocephalus without additional chemically induced neuroinflammation.

OBJECTIVE: The authors hypothesized that new agents such as BioGlue would be as efficacious as kaolin in the induction of hydrocephalus in fetal sheep. METHODS: This study was performed in 34 fetal lambs randomly divided into 2 studies. In the first study, fetuses received kaolin, BioGlue (2.0 mL), or Onyx injected into the cisterna magna, or no injection (control group) between E85 and E90. In the second study, fetuses received 2.0-mL or 2.5-mL injections of BioGlue into the cisterna magna between E85 and E90. Fetuses were monitored using ultrasound to assess lateral ventricle size and progression of hydrocephalus. The fetuses were delivered (E120-E125) and euthanized for histological analysis. Selected brain sections were stained for ionized calcium binding adaptor 1 (Iba1) and glial fibrillary acidic protein (GFAP) to assess the presence and activation of microglia and astroglia, respectively. Statistical comparisons were performed with Student's t-test for 2 determinations and ANOVA 1-way and 2-way repeated measures for multiple determinations. RESULTS: At 30 days after injection, the lateral ventricles were larger in all 3 groups that had undergone injection than in controls (mean diameter in controls 3.76 ± 0.05 mm, n = 5). However, dilatation was greater in the fetuses injected with 2 mL of BioGlue (11.34 ± 4.76 mm, n = 11) than in those injected with kaolin (6.4 ± 0.98 mm, n = 7) or Onyx (5.7 ± 0.31 mm, n = 6) (ANOVA, *p ≤ 0.0001). Fetuses injected with 2.0 mL or 2.5 mL of BioGlue showed the same ventricle dilatation but it appeared earlier (at 10 days postinjection) in those injected with 2.5 mL. The critical threshold of ventricle dilatation was 0.1 for all the groups, and only the BioGlue 2.0 mL and BioGlue 2.5 mL groups exceeded this critical value (at 30 days and 18 days after injection, respectively) (ANOVA, *p ≤ 0.0001). Moderate to severe hydrocephalus with corpus callosum disruption was observed in all experimental groups. All experimental groups showed ventriculomegaly with significant microgliosis and astrogliosis in the subventricular zone around the lateral ventricles. Only kaolin resulted in significant microgliosis in the fourth ventricle area (ANOVA, *p ≤ 0.005). CONCLUSIONS: The results of these studies demonstrate that BioGlue is more effective than Onyx or kaolin for inducing hydrocephalus in the fetal lamb and results in a volume-related response by obstructive space-occupancy without local neuroinflammatory reaction. This novel use of BioGlue generates a model with potential for new insights into hydrocephalus pathology and the development of therapeutics in obstructive hydrocephalus. In addition, this model allows for the study of acute and chronic obstructive hydrocephalus by using different BioGlue volumes for intracisternal injection.

Intestinal histopathological changes in a porcine model of pneumoperitoneum-induced intra-abdominal hypertension.

BACKGROUND: Low splanchnic perfusion is an immediate effect of pneumoperitoneum-induced intra-abdominal hypertension (IAH). Anatomical structure results in the intestinal mucosa being the area most sensitive to hypoperfusion. The relationship between intestinal injury and clinical parameters of tissue perfusion [abdominal perfusion pressure (APP), gastric intramucosal pH (pHi) and lactic acid (Lc)] has not been previously studied. This study aimed to monitorize intestinal pathogenesis through sequential ileal biopsies and to measure APP, pHi, and Lc levels at different pneumoperitoneum-induced intra-abdominal pressures (20, 30, and 40 mmHg) to evaluate the potential relationships between them. MATERIALS AND METHODS: Fifty pigs were divided into four groups; a control group (C) and three experimental groups with different pneumoperitoneum-induced levels [20 mmHg (G20), 30 mmHg (G30), and 40 mmHg (G40)], that were maintained for 3 and 5 h. APP, pHi, and Lc were measured and ileal biopsies taken laparoscopically every 30 min. The mucosal damage was graded using the standardized Park's Score and animals were classified as injured (I+) or uninjured (I-). RESULTS: Different histopathological lesions were observed in groups G20, G30, and G40 but no damage observed in group C. A 33.3% of animals in G20 and G30 were I+ after 3 h, while 93.3% were injured in G40. After 5 h, histopathological lesions were no longer seen in some animals in G20 and only 10% were I+. Conversely, in G30 I+ pigs increased to 80% while those in G40 remained at 93.3% I+. The I+ animals had significantly lower APP and pHi than those I-. Lc was the clinical parameter that showed the earliest differences, with significantly higher figures in I+ animals. CONCLUSIONS: The evolution of intestinal injuries from pneumoperitoneum-induced IAH depends on the degree of IAP. These damages may be associated with decreases in APP and pHi, and increases in Lc.

[Evaluation of competencies in urology. Esscolap® basic, as aproximation to urologists skills improvement.] / Evaluación de competencias en Urología. Esscolap® basic, como aproximación a la mejora de las capacidades de los urólogos.

Urology needs models of competencies assessment, although there is a wide range of tools not yet integrated into the official training programs. CONTEXT: At present, there is no universal framework for measuring surgeons' level of competence. Urology training programs should provide and consider knowledge, pyschomotor/cognitive skills, and simulator, cadaver or animal models-based training. Validity is a complex concept that refers to the capacity of the evaluation tool, so it is necessary to demonstrate several types of validation to assure the capacity of a method, reinforced with different reliability tests and calculation of internal consistency between evaluators. OBJECTIVE: Based on a structured dossier of surgical skills, classified by groups, the ESSCOLAP® Basic system was proposed with 5 simulator tasks to evaluate basic laparoscopic skills. Once validated in the JUMISC (Spain), the tool was proposed to extend its scope and implementation in other locations. RESULTS: Our system has not yet demonstrated a full validity in the real clinical setting because a predictive validity needs to be demonstrated on the basis of clinical data. It also suffers from a certain range of subjectivity, thus implying clear and defined criteria for any situation. Factors like the number of evaluators and tasks to assess will influence the reliability tests that measure the degree of agreement between evaluators, so that a higher number of evaluated cases would imply a greater reliability of our system. Finally, we assume that the incorporation of this type of tools implies an added cost, charged to the public and private responsible institutions, which will only be considered cost-effective when it is demonstrated its real and positive traceability in health outcomes. CONCLUSIONS: ESSCOLAP® Basic, of quick and simple implementation capacity, has been validated and calibrated for the evaluation of basic technical skills in laparoscopy.

Time-course evaluation of intestinal structural disorders in a porcine model of intra-abdominal hypertension by mechanical intestinal obstruction.

BACKGROUND: A mechanical intestinal obstruction (MIO) can generate intraabdominal hypertension (IAH) that is life threatening. The intestines are very sensitive to IAH since the low splanchnic perfusion causes intestinal hypoxia, local acidosis and bacterial translocations. This may lead to acute intestinal distress syndrome (AIDS). The identification of intestinal injuries during IAH and its correlation with clinical parameters as the abdominal perfusion pressure (APP), the gastric intramucosal pH (pHi) and lactic acid (Lc) are still unknown. This study aimed to evaluate the sequence of intestinal histopathological findings in an MIO model and to analyze potential relationships with parameters currently used in clinical practice (APP, pHi and Lc). MATERIAL AND METHODS: Twenty pigs were divided into three groups: a control group (n = 5) and two experimental groups with 20 mmHg (G1, n = 10) and 30 mmHg (G2, n = 5) of IAH by MIO. The pressures were maintained for 3 hours, except in 5 animals in G1 where it was maintained for 5 hours. The APP, pHi and LA were recorded and biopsies of the terminal ileum were taken every 30 minutes in all groups. The intestinal damage was graded according to the Park Score. RESULTS: Intestinal injuries were found in 42.9% of pigs in the experimental groups. The lesions were independent of the level and duration of IAH. Although APP and pHi were slightly lower in injured animals (I +) of G1 and G2, there were no significant differences among those uninjured (I-). Lc was significantly increased in all I+ pigs from the onset of IAH. CONCLUSION: The IAH by MIO causes intestinal lesions from the first 30 minutes with concurrent decreases in APP and pHi and increases in Lc. Lc could be the best clinical parameter related to intestinal damages with a clear difference between I + and I- animals.

Intervertebral disc degeneration: an experimental and numerical study using a rabbit model.

Animal models have been extensively used for the study of degenerative diseases and evaluation of new therapies to stop or even reverse the disease progression. The aim of this study is to reproduce lumbar intervertebral disc degeneration in a rabbit model by performing a percutaneous annular puncture at L4L5 level. The effect of this damage on the spine behaviour was analysed combining three different techniques: imaging processing, mechanical testing and computational modelling. Twenty New Zealand white rabbits were divided into control and experimental groups and followed up during 6 months. Intervertebral disc height, as well as nucleus area and signal intensity, decreased with degeneration while storage and loss moduli increased. Both changes may be related to the loss of water and tissue fibrosis. Similar but slighter changes were reported for adjacent discs. A finite element model was built based on MRI and mechanical testing findings to add new biomechanical information that cannot be obtained experimentally. Four stages were computationally simulated representing the different experimental phases. The numerical simulations showed that compressive stresses in the damaged and adjacent discs were modified with the progression of degeneration. Although extrapolation to humans should be carefully made, the use of numerical animal models combined with an experimental one could give a new insight of the overall mechanical behaviour of the spine.

[Intra-abdominal hypertension: effects on the splanchnic circulation. Preliminary study in a model of ascites]. / Hipertensión intraabdominal: consecuencias sobre la circulación esplácnica. Estudio preliminar en un modelo de ascitis.

INTRODUCTION: Intra-abdominal hypertension is defined as a rise in intra-abdominal pressure leading to progressive dysfunction of the abdominal organs. OBJECTIVE: To evaluate the effects of intra-abdominal hypertension on the splanchnic circulation in a porcine animal model with a view to determining the diagnostic method of choice. MATERIAL AND METHODS: A total of 10 swine were divided into 2 groups: a control group and a group with an ascites pressure of 20mmHg. Transvesical and transperitoneal intra-abdominal pressures were registered, and the correlation between the measurements obtained was determined. Concentrations of lactic acid, alanine aminotransferase, glucose and gastric mucosal pH were also obtained. We registered the mean arterial and abdominal perfusion pressures, and the correlation of the latter with gastric mucosal pH and lactic acid concentrations. The parameters were registered for a total of 3hours. RESULTS: We observed a high correlation between transvesical and transperitoneal measurements of intra-abdominal pressure (R(2)=0.98). In the 20mmHg pressure group, lactic acid concentrations increased significantly at 180min (p<0.011). Gastric mucosal pH differed significantly between the 2 groups from the beginning of the study (p=0.004) and significantly decreased from 120min onward. Mean arterial and abdominal perfusion pressures gradually decreased during the trial, with early significant changes in the abdominal perfusion pressure (p=0.001), and a good correlation with the remaining study parameters. There were no significant changes in hepatic indicators. CONCLUSIONS: We believe the transvesical approach to be the technique of choice to determine intra-abdominal pressure. Abdominal perfusion pressure is a sensitive marker of intra-abdominal hypertension, and gastric mucosal pH is the first parameter to be affected.

Tonometry as a predictor of inadequate splanchnic perfusion in an intra-abdominal hypertension animal model.

BACKGROUND: The gastrointestinal system is the most sensitive to the presence of intra-abdominal hypertension. We aimed to assess the early prognostic value of gastric air tonometry as a predictor of inadequate splanchnic perfusion and determine its relation with abdominal perfusion pressure (APP). METHODS: Twenty-five Large White swine were used for this study. A control group and two study groups were included, in which intra-abdominal pressure (IAP) was elevated with Co2 to 20 and 30 mmHg during 5 h. We measured the intramucosal gastric pH (pHim) and determined gastric luminal PCO2 (PgCO2) and PgCO2gap (gastric luminal CO2-arterial CO2) to evaluate gastric acidity. APP was indirectly obtained through IAP and mean arterial pressure. Additionally, histopathologic samples of small intestine were obtained and analyzed. RESULTS: pHim showed a decrease in IAP groups, with statistical significance in the 30 mmHg group, 90 min after stabilization period (P < 0.01). Serum lactate showed delayed alteration when compared with pHim, with significant increase, 180 min after stabilization (P < 0.05). The values of PgCO2 and PCO2gap were increased in IAP groups, being statistically significant in the 30 mmHg group, 120 and 150 min, respectively, after stabilization. In increased IAP groups, there was a time progressive decrease of APP, with statistically significant differences observed between groups at 20 min (P < 0.001). The histopathology study revealed parenchymal injury of the intestine at 30 mmHg. CONCLUSIONS: Tonometry is sensitive to the increase in IAP and relates to the reduction of APP generated by splanchnic hypoperfusion.