[Intra-abdominal hypertension: effects on the splanchnic circulation. Preliminary study in a model of ascites]

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 (pH_i) and lactic acid (Lc)] has not been previously studied. This study aimed to monitorize intestinal pathogenesis through sequential ileal biopsies and to measure APP, pH_i, 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, pH_i, 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 pH_i 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 pH_i, and increases in Lc.

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.

Mechanical Intestinal Obstruction in a Porcine Model: Effects of Intra-Abdominal Hypertension. A Preliminary Study

INTRODUCTION

Mechanical intestinal obstruction is a disorder associated with intra-abdominal hypertension and abdominal compartment syndrome. As the large intestine intraluminal and intra-abdominal pressures are increased, so the patient's risk for intestinal ischaemia. Previous studies have focused on hypoperfusion and bacterial translocation without considering the concomitant effect of intra-abdominal hypertension. The objective of this study was to design and evaluate a mechanical intestinal obstruction model in pigs similar to the human pathophysiology.

MATERIALS AND METHODS

Fifteen pigs were divided into three groups: a control group (n = 5) and two groups of 5 pigs with intra-abdominal hypertension induced by mechanical intestinal obstruction. The intra-abdominal pressures of 20 mmHg were maintained for 2 and 5 hours respectively. Hemodynamic, respiratory and gastric intramucosal pH values, as well as blood tests were recorded every 30 min.

RESULTS

Significant differences between the control and mechanical intestinal obstruction groups were noted. The mean arterial pressure, cardiac index, dynamic pulmonary compliance and abdominal perfusion pressure decreased. The systemic vascular resistance index, central venous pressure, pulse pressure variation, airway resistance and lactate increased within 2 hours from starting intra-abdominal hypertension (p<0.05). In addition, we observed increased values for the peak and plateau airway pressures, and low values of gastric intramucosal pH in the mechanical intestinal obstruction groups that were significant after 3 hours.

CONCLUSION

The mechanical intestinal obstruction model appears to adequately simulate the pathophysiology of intestinal obstruction that occurs in humans. Monitoring abdominal perfusion pressure, dynamic pulmonary compliance, gastric intramucosal pH and lactate values may provide insight in predicting the effects on endorgan function in patients with mechanical intestinal obstruction.

Gastric tonometry guided therapy in critical care patients: a systematic review and meta-analysis

Introduction

The value of gastric intramucosal pH (pHi) can be calculated from the tonometrically measured partial pressure of carbon dioxide (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {P}_{C{O}_2} $$\end{document}PCO2) in the stomach and the arterial bicarbonate content. Low pHi and increase of the difference between gastric mucosal and arterial \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {P}_{C{O}_2} $$\end{document}PCO2 (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {P}_{C{O}_2} $$\end{document}PCO2 gap) reflect splanchnic hypoperfusion and are good indicators of poor prognosis. Some randomized controlled trials (RCTs) were performed based on the theory that normalizing the low pHi or \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {P}_{C{O}_2} $$\end{document}PCO2 gap could improve the outcomes of critical care patients. However, the conclusions of these RCTs were divergent. Therefore, we performed a systematic review and meta-analysis to assess the effects of this goal directed therapy on patient outcome in Intensive Care Units (ICUs).

Methods

We searched PubMed, EMBASE, the Cochrane Library and ClinicalTrials.gov for randomized controlled trials comparing gastric tonometry guided therapy with control groups. Baseline characteristics of each included RCT were extracted and displayed in a table. We calculated pooled odds ratios (ORs) with 95% confidence intervals (CIs) for dichotomous outcomes. Another measure of effect (risk difference, RD) was used to reassess the effects of gastric tonometry on total mortality. We performed sensitivity analysis for total mortality. Continuous outcomes were presented as standardised mean differences (SMDs) together with 95% CIs.

Results

The gastric tonometry guided therapy significantly reduced total mortality (OR, 0.732; 95% CI, 0.536 to 0.999, P = 0.049; I² = 0%; RD, −0.056; 95% CI, −0.109 to −0.003, P = 0.038; I² = 0%) when compared with control groups. However, after excluding the patients with normal pHi on admission, the beneficial effects of this therapy did not exist (OR, 0.736; 95% CI 0.506 to 1.071, P = 0.109; I² = 0%). ICU length of stay, hospital length of stay and days intubated were not significantly improved by this therapy.

Conclusions

In critical care patients, gastric tonometry guided therapy can reduce total mortality. Patients with normal pHi on admission contributed to the ultimate result of this outcome; it may indicate that these patients may be more sensitive to this therapy.