Intra-abdominal hypertension in the critically ill: it is time to pay attention

The relationship between positive end-expiratory pressure (PEEP) and intra-abdominal pressure (IAP) in mechanically ventilated patients: A prospective observational study

BACKGROUND

Positive end-expiratory pressure is a crucial mechanical breathing parameter. Intra-abdominal hypertension is well defined as a sustained increase in the intra-abdominal pressure ≥12 mmHg. There are still controversies about mechanical ventilation's effect and use of positive end-expiratory pressure on intra-abdominal pressure.

AIM

We aimed to delineate the relationship between positive end-expiratory pressure and intra-abdominal pressure in mechanically ventilated patients admitted to the intensive care units of a large tertiary hospital in Upper Egypt.

STUDY DESIGN

This study was a prospective observational study. The study was conducted at a university hospital from October 2023 to February 2024. The enrolled adult patients were allocated into two groups based on their positive end-expiratory pressure: group I, low pressure (<8 cm H2O) and group II, high pressure (8-10 cm H2O).

RESULTS

A total of 120 patients were enrolled, 60 patients in each group. The most commonly encountered diagnoses were pneumonia (32/120, 26.7%) and acute respiratory distress syndrome (ARDS) (31/120, 25.8%), respectively. There was a significant difference between the intra-abdominal pressure mean values of the two patient groups, 18.9 ± 3.3 versus 24.4 ± 5.9 mmHg in the group of low versus high pressure (correlation value of .454, p < .001), respectively. There were highly significant correlations between intra-abdominal pressure categories and the patient groups (correlation value of .495, p < .001). There were 24 (40%) versus 0 (0%) patients of high pressure versus low pressure within the category IV group of intra-abdominal hypertension (>25 mmHg).

CONCLUSIONS

We observed a significant relationship between positive end-expiratory pressure and intra-abdominal pressure in mechanically ventilated patients. The patient group with high pressure had higher mean values compared with the group with low pressure. The study highlights the importance of closely monitoring intra-abdominal pressure in mechanically ventilated patients who receive positive end-expiratory pressure. Further studies are warranted.

RELEVANCE TO CLINICAL PRACTICE

The relationship between positive end-expiratory pressure and intra-abdominal pressure is an essential issue in daily critical care nursing clinical practice. Considering the occurrence of multiple organ dysfunction as a result of a non-detected increase in intra-abdominal pressure, critical care nurses should pay attention to measuring this pressure to maintain intra-abdominal pressures that are safe for mechanically ventilated and critically ill intensive care unit patients, thereby preventing these undue effects.

The Need to Identify Novel Markers for Early Renal Injury in Cardiorenal Syndrome

The term "Cardiorenal Syndrome" (CRS) refers to the complex interplay between heart and kidney dysfunction. First described by Robert Bright in 1836, CRS was brought to its modern view by Ronco et al. in 2008, who defined it as one organ's primary dysfunction leading to secondary dysfunction in the other, a view that led to the distinction of five different types depending on the organ of primary dysfunction and the temporal pattern (acute vs. chronic). Their pathophysiology is intricate, involving various hemodynamic, neurohormonal, and inflammatory processes that result in damage to both organs. While traditional biomarkers have been utilized for diagnosing and prognosticating CRS, they are inadequate for the early detection of acute renal damage. Hence, there is a pressing need to discover new biomarkers to enhance clinical outcomes and treatment approaches.

Assessment of the Smartpill, a Wireless Sensor, as a Measurement Tool for Intra-Abdominal Pressure (IAP)

Background: The SmartPill, a multisensor ingestible capsule, is marketed for intestinal motility disorders. It includes a pressure sensor, which could be used to study intra-abdominal pressure (IAP) variations. However, the validation data are lacking for this use. Material and Methods: An experimental study was conducted on anesthetized pigs with stepwise variations of IAP (from 0 to 15 mmHg by 3 mmHg steps) generated by laparoscopic insufflation. A SmartPill, inserted by endoscopy, provided intragastric pressure data. These data were compensated to take into account the intrabdominal temperature. They were compared to the pressure recorded by intragastric (IG) and intraperitoneal (IP) wired sensors by statistical Spearman and Bland-Altmann analysis. Results: More than 4500 pressure values for each sensor were generated on two animals. The IG pressure values obtained with the SmartPill were correlated with the IG pressure values obtained with the wired sensor (respectively, Spearman ρ coefficients 0.90 ± 0.08 and 0.72 ± 0.25; bias of -28 ± -0.3 mmHg and -29.2 ± 0.5 mmHg for pigs 1 and 2). The intragastric SmartPill values were also correlated with the IAP measured intra-peritoneally (respectively, Spearman ρ coefficients 0.49 ± 0.18 and 0.57 ± 0.30; bias of -29 ± 1 mmHg and -31 ± 0.7 mmHg for pigs 1 and 2). Conclusions: The SmartPill is a wireless and painless sensor that appears to correctly monitor IAP variations.

Abdominal compartment syndrome: what radiologist needs to know

The intra-abdominal hypertension (IAH) and the abdominal compartment syndrome (ACS) are life-threatening conditions with a significant rate of mortality; therefore, early detection is paramount in their optimal management. IAH is diagnosed when the intra-abdominal pressure (IAP) is more than 12 mmHg. It can occur when the intra-abdominal volume increases (ileus, ascites, trauma, pancreatitis, etc.) and/or the abdominal wall compliance decreases. IAH can cause decreased venous flow, low cardiac output, renal impairment, and decreased respiratory compliance. Consequently, these complications can lead to multiple organ failure and induce the abdominal compartment syndrome (ACS) when IAP rises above 20 mmHg. The diagnosis is usually made with intravesical pressure measurement. However, this measurement was not always possible to obtain; therefore, alternative diagnostic techniques should be considered. In this setting, computed tomography (CT) may play a crucial role, allowing the detection and characterization of pathological conditions that may lead to IAH. This review is focused on the pathogenesis, clinical features, and radiological findings of ACS, because their presence allows radiologists to raise the suspicion of IAH/ACS in critically ill patients, guiding the most appropriate treatment.

Abdominal compartment syndrome in critically ill patients

Intra-abdominal hypertension can have severe consequences, including abdominal compartment syndrome, which can contribute to multi-organ failure. An increase in intra-abdominal hypertension is influenced by factors such as diminished abdominal wall compliance, increased intraluminal content, and certain systemic conditions. Regular measurement of intra-abdominal pressure is essential, and particular attention must be paid to patient positioning. Nonsurgical treatments, such as decompression of intraluminal content using a nasogastric tube, percutaneous drainage, and fluid balance optimization, play crucial roles. Additionally, point-of-care ultrasonography aids in the diagnosis and treatment of intra-abdominal hypertension. Emphasizing the importance of regular measurements, timely decompressive laparotomy is a definitive, but complex, treatment option. Balancing the urgency of surgical intervention against potential postoperative complications is challenging.

Is it feasible to measure intra-abdominal pressure using a balloon-tipped rectal catheter? Results of a validation study

The gold standard to measure intra-abdominal pressure (IAP) is intra-vesical measurement via the urinary bladder. However, this technique is restricted in ambulatory settings because of the risk of iatrogenic urinary tract infections. Rectal IAP measurements (IAP_rect) may overcome these limitations, but requires validation. This validation study compares the IAP_rect technique against gold standard intra-vesical IAP measurements (IAP_ves). IAP_rect using an air-filled balloon catheter and IAP_ves using Foley Manometer Low Volume were measured simultaneously in sedated and ventilated patients. Measurements were performed twice in different positions (supine and HOB 45° elevated head of bed) and with an external abdominal pressure belt. Sixteen patients were included. Seven were not eligible for analysis due to unreliable IAP_rect values. IAP_rect was significantly higher than IAP_ves for all body positions (p < 0.01) and the correlation between IAP_ves and IAP_rect was poor and not significant in each position (p ≥ 0.25, R² < 0.6, Lin's CCC < 0.8, bias - 8.1 mmHg and precision of 5.6 mmHg with large limits of agreement between - 19 to 2.9 mmHg, high percentage error 67.3%, and low concordance 86.2%). Repeatability of IAP_rect was not reliable (R = 0.539, p = 0.315). For both techniques, measurements with the external abdominal pressure belt were significantly higher compared to those without (p < 0.03). IAP_rect has important shortcomings making IAP estimation using a rectal catheter unfeasible because the numbers cannot be trusted nor validated.

Risk factors for abdominal compartment syndrome in trauma – A review

" Background and Aim: Abdominal compartment syndrome is a life-threatening complication that can occur in trauma patients and greatly increase their mortality. Although there is a better scientific understanding of the general phenomena involved in the pathogenesis of this complication, the particular risk factors and their implications in the trauma patient population are yet to be deciphered. Methods: The authors conducted research through 3 electronic databases (PubMed, Scopus, and ScienceDirect) using the following search formula: “(ACS OR abdominal compartment syndrome) AND (*trauma*) AND (risk factor)”. Subsequently, additional search formulas were used, including the risk factors taken into consideration (i.e. “shock”, “hypotension”, “acidosis”, “base deficit”, ”coagulopathy”, “retroperitoneal hematoma”, “HOB elevation”, “fluid resuscitation”, “damage control laparotomy”). Results: Throughout the 41 articles analyzed in this paper, 7 risk factors transcended and were further discussed: head of bed elevation/patient positioning, fluid resuscitation, the “lethal triad” of acidosis hypothermia and coagulopathy, Damage Control Laparotomy, shock/hypotension, retroperitoneal hematoma and demographics (age, gender, and race). Conclusions: To summarize, many potential risk factors were evaluated for the envisagement of the present paper, but the ones that prevailed the most were excessive fluid resuscitation, shock/hypotension, retroperitoneal hematomas, and the lethal triad. Consistent with other studies, no connection was found between age, gender, or race and the development of ACS. Further studies should focus more on the likely involvement of damage control laparotomy and patient positioning, as well as hypocalcemia, in the unfolding of ACS in trauma patients"

Mechanistic Insights in Cardiorenal Syndrome

Mechanistic Insights in Cardiorenal SyndromeLo and Rangaswami review the pathophysiology and management of cardiorenal syndrome, with a focus on decongestion, interpretation of kidney function, and implementation of guideline directed medical therapies.

Role of intra-abdominal pressure measurement in patients with acute abdomen requiring exploratory laparotomy

<b>Introduction:</b> Acute abdomen is one of the most common surgical emergencies faced by a surgeon. Monitoring Intra-Abdominal Pressure (IAP) in patients with acute abdomen referred for exploratory laparotomy may help guide the need for early intervention. </br></br> <b>Aim:</b> This study was performed to determine whether preoperative IAP had any significant association with organ failure as assessed using SOFA score. Furthermore, effect of IAP on patient outcome in terms of hospital stay, mortality was also evaluated. </br></br> <b>Materials and methods:</b> 60 patients above 18 years of age presenting with acute abdomen requiring exploratory laparotomy were included in this prospective observational study from November 2013 until March 2015. IAP and SOFA scores were calculated at the time of admission. The outcome of patients was assessed in terms of hospital stay, morbidity and mortality. The correlation between IAP and SOFA scores was also assessed to determine the risk of organ failure. The inferences were drawn with the use of SPSS v22.0 statistical software. ANOVA, Chi-square and Student's t-test were used in the analysis. </br></br> <b> Results:</b> There was a positive correlation between SOFA score and IAP; and this correlation was found to be statistically significant with Pearson's correlation coefficient being 0.6247 and significance levels being <0.0001. Both hospital stay and mortality positively correlated with the degree of IAP. </br></br> <b> Conclusions:</b> IAP should be routinely measured in patients with acute abdomen requiring exploratory laparotomy. Patients with preoperatively raised IAP should be referred for emergency surgery as soon as possible for better outcome.

Regular at-home abdominal paracentesis via Tenckhoff catheter in patients with refractory congestive heart failure

BACKGROUND

Peritoneal dialysis (PD) is increasingly used for the long-term management of refractory congestive heart failure (CHF). Patients with severe CHF and ascites were treated with regular at-home abdominal paracentesis via Tenckhoff catheter. We investigated the outcome of those patients, aiming to identify potential prognostic factors for longer survival.

METHODS

Patients with refractory CHF referred by cardiologists to the PD unit from years 2009 to 2019 and treated with regular at-home abdominal paracentesis via Tenckhoff catheter without peritoneal exchanges, were enrolled into this prospective observational study.

RESULTS

From the total of 69 refractory CHF patients treated with PD, 18 (26%) were managed with regular at-home abdominal paracentesis via Tenckhoff catheter and improved without the need for peritoneal exchanges for fluid removal (no peripheral oedema or pulmonary congestion) or for solutes removal. Median survival of severe CHF patients treated with abdominal paracentesis was 13.5 months (0-34 months). Long-term survivors demonstrated significant improvement in the New York Heart Association (NYHA) functional class, improvement in kidney function and decrease in serum C-reactive protein (CRP) and Brain natriuretic peptide (BNP) compared with their baseline status. A subgroup of patients with shorter survival were more likely to have evidence of liver cirrhosis and significantly lower serum sodium compared with patients with longer survival.

CONCLUSIONS

Refractory CHF patients with massive ascites could be successfully treated with regular at-home abdominal paracentesis via Tenckhoff catheter. This treatment provides a useful alternative to periodical percutaneous paracentesis on as-needed basis.

Intra-abdominal pressure during and after cardiac surgery: a single-centre prospective cohort study

PURPOSE

While intra-abdominal hypertension (IAH) has been associated with adverse outcomes in multiple settings, the epidemiology and clinical implications of IAH in the context of cardiac surgery are less known. In this study, we aimed to describe the prevalence of IAH in patients undergoing cardiac surgery and determine its association with patient characteristics and postoperative outcomes.

METHODS

We conducted a single-centre prospective cohort study in which intra-abdominal pressure was measured in the operating room after general anesthesia (T1), after the surgical procedure (T2), and two hours after intensive care unit (ICU) admission (T3) in a subset of patients. Intra-abdominal hypertension was defined as intra-abdominal pressure (IAP) ≥ 12 mm Hg. Postoperative outcomes included death, acute kidney injury (AKI), and length of stay in the ICU and hospital.

RESULTS

A total of 513 IAP measurements were obtained from 191 participants in the operating room and 131 participants in the ICU. Intra-abdominal hypertension was present in 105/191 (55%) at T1, 115/191 (60%) at T2, and 31/131 (24%) at T3. Intra-abdominal pressure was independently associated with body mass index, central venous pressure, and mean pulmonary artery pressure but was not associated with cumulative fluid balance. Intraoperative IAH was not associated with adverse outcomes including AKI.

CONCLUSIONS

Intra-abdominal hypertension is very common during cardiac surgery but its clinical implications are uncertain.

Respiratory Mechanics

Today's management of the ventilated patient still relies on the measurement of old parameters such as airway pressures and flow. Graphical presentations reveal the intricacies of patient-ventilator interactions in times of supporting the patient on the ventilator instead of fully ventilating the heavily sedated patient. This opens a new pathway for several bedside technologies based on basic physiologic knowledge; however, it may increase the complexity of measurements. The spread of the COVID-19 infection has confronted the anesthesiologist and intensivist with one of the most severe pulmonary pathologies of the last decades. Optimizing the patient at the bedside is an old and newly required skill for all physicians in the intensive care unit, supported by mobile technologies such as lung ultrasound and electrical impedance tomography. This review summarizes old knowledge and presents a brief insight into extended monitoring options.

Systematic Review of Diagnostic Sensors for Intra-Abdominal Pressure Monitoring

Intra-abdominal pressure (IAP) is defined as the steady-state pressure within the abdominal cavity. Elevated IAP has been implicated in many medical complications. This article reviews the current state-of-the-art in innovative sensors for the measurement of IAP. A systematic review was conducted on studies on the development and application of IAP sensors. Publications from 2010 to 2021 were identified by performing structured searches in databases, review articles, and major textbooks. Sixteen studies were eligible for the final systematic review. Of the 16 articles that describe the measurement of IAP, there were 5 in vitro studies (31.3%), 7 in vivo studies (43.7%), and 4 human trials (25.0%). In addition, with the advancement of wireless communication technology, an increasing number of wireless sensing systems have been developed. Among the studies in this review, five presented wireless sensing systems (31.3%) to monitor IAP. In this systematic review, we present recent developments in different types of intra-abdominal pressure sensors and discuss their inherent advantages due to their small size, remote monitoring, and multiplexing.

Computed tomography features predictive of intra-abdominal hypertension in acute necrotizing pancreatitis: A prospective study

BACKGROUND

Intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS) in acute pancreatitis (AP) are associated with development and worsening of organ failures and poor prognosis. Limited studies suggest that contrast-enhanced computed tomography (CECT) can predict the presence of IAH/ACS. We aimed to study clinical profile of patients with AP and IAH and identify predictive factors of IAH on CECT abdomen.

METHODS

Consecutive patients admitted with moderately severe and severe acute pancreatitis (SAP) were recruited. Clinical and radiological data were recorded prospectively. Intra-abdominal pressure was measured via a urinary catheter to document the presence of IAH/ACS. CECT abdomen was done within the first week of admission and various features that may predict the presence of IAH were studied.

RESULTS

Thirty-seven patients (24 SAP) (mean age: 39.78 ± 13.43 years and 67.6% males) with  AP were studied. The most common etiology was alcohol (37.7%). IAH developed in 54.05% of patients; patients with IAH had significantly higher bedside index of severity in AP (BISAP), Acute Physiologic Assessment and Chronic Health Evaluation II (APACHE II) score, persistent acute lung injury (ALI), persistent acute kidney injury (AKI), persistent cardiovascular failure (CVSF), intensive care unit (ICU) stay, and mortality. Among the CT predictors, patients with IAH more commonly had moderate-gross ascites (60% vs. 23.5%, p-value - 0.026), a pancreatic necrosis of > 50% (50% vs. 17.6%, p-value - 0.04), and a round belly sign (RBS) (50% vs. 5.9%, p-value 0.03). On multivariate analysis, only RBS was predictive of  IAH (odds ratio 12.6, 95% confidence interval 1.3-124.2, p-value 0.03). The sensitivity, specificity, positive predictive value, and negative predictive value for RBS were 50%, 94.12%, 90.9%, and 61.54%, respectively.

CONCLUSION

Presence of RBS, moderate-gross ascites, and pancreatic necrosis of > 50% on CECT can predict the presence of IAH in these groups of patients.

Acute Abdominal Compartment Syndrome complicating a chronic mesenteric ischemia revascularization

BACKGROUND

Abdominal Compartment Syndrome (ACS) is a pathological condition that results from an increase in pressure within the abdomen associated with organ failure. It can be acute or chronic, primary or secondary. ACS poses a serious diagnostic challenge for physicians as the clinical presentation is varied and can mimic other medical pathologies. To prevent a multi-organ failure and ultimately death due to this disease, the World Society of Abdominal Compartment Syndrome (WSACS) suggested clinical criteria and biology tests to facilitate an early diagnosis of acute ACS.

CASE PRESENTATION

We report a case of 61 year-old man diagnosed with chronic mesenteric ischemia that has been successfully treated by prosthetic bypass. The postoperative period was eventual, the patient presented complications corresponding essentially to a manifest acute ACS. The treatment consisted on abdominal decompression and resuscitation measures.

CONCLUSIONS

An early diagnosis of ACS disease for an appropriate therapeutic initiation is mandatory to prevent its complications and save the patient's life prognosis.

Diuretic Resistance in Heart Failure

Decompensated heart failure accounts for approximately 1 million hospitalizations in the United States annually, and this number is expected to increase significantly in the near future. Diuretics provide the initial management in most patients with fluid overload. However, the development of diuretic resistance remains a significant challenge in the treatment of heart failure. Due to the lack of a standard definition, the prevalence of this phenomenon remains difficult to determine, with some estimates suggesting that 25-30% of patients with heart failure have diuretic resistance. Certain characteristics, including low systolic blood pressures, renal impairment, and atherosclerotic disease, help predict the development of diuretic resistance. The underlying pathophysiology is likely multifactorial, with pharmacokinetic alterations, hormonal dysregulation, and the cardiorenal syndrome having significant roles. The therapeutic approach to this common problem typically involves increases in the diuretic dose and/or frequency, sequential nephron blockade, and mechanical fluid movement removal with ultrafiltration or peritoneal dialysis. Paracentesis is potentially useful in patients with intra-abdominal hypertension.

The relationship of abdominal perfusion pressure with mortality in critically ill pediatric patients

PURPOSE

To the best of our knowledge, in the literature, there is no data regarding clinical utility of the abdominal perfusion pressure (APP) in critically ill children. Thus, in the present study, we aimed to investigate the clinical utility of APP in predicting of survival in critically ill children with IAH.

DESIGN

A prospective cohort study of patients between 1 month to 18 years who had risk for intra-abdominal hypertension from June 2013 to January 2014.

SETTING

Pediatric intensive care unit (PICU) at a tertiary university hospital.

PATIENTS

Thirty-five (16 female) PICU patients who had risk for the development of IAH were included. Serial intraabdominal pressure (IAP) and mean arterial pressure (MAP) measurements were performed. Abdominal perfusion pressure was calculated using the formula (MAP-IAP).

MEASUREMENTS AND MAIN RESULTS

Overall mortality rate was 49% (n = 17). The mortality rate in patients with IAP mean ≥10 mmHg (n = 27, 77%) was 55% (n = 15), while 53% (n = 16) in patients with IAP max ≥10 mmHg (n = 30, 86%) and 47% (n = 7) in patients with IAP min ≥ 10 mmHg (n = 15, 43%). Overall mean APP was 58 ± 20 mmHg. Logistic regression analysis revealed that decrease in minAPP was associated with increased risk for mortality (Odds ratio for each 1 mmHg decrease in APP was 1.052 [CI 95%, 1.006-1.100], p < 0.05). ROC curve analysis revealed that, in predicting mortality, area under curve for minAPP was 0.765. The optimal cut-off point for APP was obtained as 53 mmHg with the 77.8% sensitivity and 70.6% specificity using the IU method.

CONCLUSIONS

Our findings showed that APP seems to be a useful tool in predicting mortality. Interventions to improve APP may be associated with better outcomes in critically ill PICU patients.

LEVEL OF EVIDENCE

Level II.

TYPE OF STUDY

Diagnostic.

Maternal Venous Hemodynamic Dysfunction in Proteinuric Gestational Hypertension: Evidence and Implications

This review summarizes current knowledge from experimental and clinical studies on renal function and venous hemodynamics in normal pregnancy, in gestational hypertension (GH) and in two types of preeclampsia: placental or early-onset preeclampsia (EPE) and maternal or late-onset (LPE) preeclampsia, presenting at <34 weeks and ≥34 weeks respectively. In addition, data from maternal venous Doppler studies are summarized, showing evidence for (1) the maternal circulation functioning closer to the upper limits of capacitance than in non-pregnant conditions, with intrinsic risks for volume overload, (2) abnormal venous Doppler measurements obtainable in preeclampsia, more pronounced in EPE than LPE, however not observed in GH, and (3) abnormal venous hemodynamic function installing gradually from first to third trimester within unique pathways of general circulatory deterioration in GH, EPE and LPE. These associations have important clinical implications in terms of screening, diagnosis, prevention and management of gestational hypertensive diseases. They invite for further hypothesis-driven research on the role of retrograde venous congestion in the etiology of preeclampsia-related organ dysfunctions and their absence in GH, and also challenge the generally accepted view of abnormal placentation as the primary cause of preeclampsia. The striking similarity between abnormal maternal venous Doppler flow patterns and those observed at the ductus venosus and other abdominal veins of the intra-uterine growth restricted fetus, also invites to explore the role of venous congestion in the intra-uterine programming of some adult diseases.

Thoracic complications of pancreatitis

Acute pancreatitis in its severe form may lead to systemic inflammatory response syndrome and multisystem organ dysfunction. Acute lung injury is an important cause of mortality in the setting of severe acute pancreatitis. Besides lung involvement, acute and chronic pancreatitis may also lead to the involvement of other thoracic compartments, including mediastinum, pleura, and vascular structures. These manifestations are an important cause of morbidity and may pose diagnostic and therapeutic challenges. These manifestations have not been discussed in detail in the available literature. In this review, we discuss the thoracic complications of pancreatitis, including lung, pleural, mediastinal, and vascular manifestations.

Liver function assessment by indocyanine green plasma disappearance rate in patients with intra-abdominal hypertension after "non-hepatic" abdominal surgery

BACKGROUND AND OBJECTIVE

Liver function assessment in patients with intra-abdominal hypertension (IAH) after major abdominal surgery is complex and often confounding. Elevated intra-abdominal pressure (IAP) often occurs after major abdominal surgery, and is associated with decreased abdominal blood flow and organ dysfunction, and it could cause abdominal compartment syndrome (ACS), which is a life-threatening condition. Plasma disappearance rate (PDR) of indocyanine green (ICG) and ICG retention rate after 15 min (R15) were used to evaluate liver function and as a prognostic parameter after major abdominal surgery.

METHODS

In this prospective/observational study, 51 patients were followed in the surgical intensive care unit after major abdominal surgery (operation of the small and large intestine, stomach, pancreas, spleen, or resection of the abdominal aorta), 29 had IAH. The PDR-ICG and R15 were analyzed 24 h after surgery concurrently with IAP, APP, bilirubin, AST, ALT, prothrombin time, albumin, cardiac index, arterial lactate, oxygen delivery, MAP (mean arterial pressure), APACHE II (acute physiology and chronic health evaluation), SOFA (sequential organ failure assessment), and SAPS II (simplified acute physiology score). IAH has been defined as a peak intra-abdominal pressure (IAP) value of ≥12 mmHg, at a minimum, as two standardized measurements obtained 1-6 h apart.

RESULTS

The PDR-ICG measured 24 h after surgery was not different among groups (20.95% [SD = 10.34] vs 25.40% [SD = 7.42]), p = .094. ICG R15 was significantly higher in patients with IAH, 11.10% [SD = 13.82] vs 8.30 [SD = 11.46], p < .05, respectively. The PDR/ICG value was significantly lower in non-survivors than survivors (16.82 [SD = 10.87] vs 24.35 [SD = 8.48], p < .05).

CONCLUSIONS

The results suggest that PDR/ICG and ICG R15 are useful dynamic tests for evaluation of complex liver function and survival prediction after major abdominal surgery in patients with IAH.

Open Abdomen in Trauma and Critical Care

The open abdomen technique and temporary abdominal closure after damage control surgery is fast becoming the standard of care for managing intra-abdominal bleeding and infectious or ischemic processes in critically ill patients. Expansion of this technique has evolved from damage control surgery in severely injured trauma patients to use in patients with abdominal compartment syndrome due to acute pancreatitis and other disorders. Subsequent therapies after use of the open abdomen technique and temporary abdominal closure are resuscitation in the intensive care unit and planned reoperation to manage the underlying cause of bleeding, infection, or ischemia. Determining the need for this potentially lifesaving intervention and managing the wound after the open abdomen has been created are all within the realm of critical care nurses. Case studies illustrate the implementation of the open abdomen technique and patient management strategies.

Management of the Open Abdomen

Management of the abdominal catastrophe requires a multidisciplinary approach. The plastic surgeon is a key member of the surgical team assisting in the creation of a durable, functional anatomic abdominal wall reconstruction. Plastic surgeons must be familiar with the concepts and pathophysiology related to the open abdomen, techniques for temporary abdominal closure, and when such techniques are appropriate to implement. In this article, the authors provide a review of the open abdomen concept, which practicing plastic surgeons and trainees may find helpful if faced with this clinical scenario.

Large-volume paracentesis effects plasma disappearance rate of indo-cyanine green in critically ill patients with decompensated liver cirrhosis and intraabdominal hypertension

BACKGROUND

Ascites is a major complication of decompensated liver cirrhosis. Intraabdominal hypertension and structural alterations of parenchyma involve decisive changes in hepatosplanchnic blood flow. Clearance of indo-cyanine green (ICG) is mainly dependent on hepatic perfusion and hepatocellular function. As a consequence, plasma disappearance rate of ICG (ICG-PDR) is rated as a useful dynamic parameter of liver function. This study primarily evaluates the impact of large-volume paracentesis (LVP) on ICG-PDR in critically ill patients with decompensated cirrhosis. Additionally, it describes influences on intraabdominal pressure (IAP), abdominal perfusion pressure (APP), hepatic blood flow, hemodynamic and respiratory function.

METHODS

We analyzed LVP in 22 patients with decompensated liver cirrhosis. ICG-PDR was assessed by using noninvasive LiMON technology (Pulsion® Medical Systems; Maquet Getinge Group), and hepatic blood flow was analyzed by color-coded duplex sonography.

RESULTS

Paracentesis of a median volume of 3450 mL ascites evoked significant increases of ICG-PDR from 3.6 (2.8-4.6) to 5.1 (3.9-6.2)%/min (p < 0.001). Concomitantly, we observed a raise in "ICG-Clearance" from 99 (73.5-124.5) to 104 (91-143.5) mL/min/m2 (p = 0.005), while circulating blood volume index was unchanged [2412 (1983-3025) before paracentesis vs. 2409 (1997-2805) mL/m2, p = 0.734]. Sonography revealed a significant impact of paracentesis on hepatic blood flow: Hepatic artery resistance index dropped from 0.74 (0.68-0.75) to 0.68 (0.65-0.71) (p < 0.001) and maximum flow velocity in hepatic vein increased from 24 (17-30) to 30 (22-36) cm/s (p < 0.001). Consistent with previous studies, paracentesis caused significant decreases in IAP from 19.0 (15.0-20.3) to 11.0 (8.8-12.3) mmHg (p < 0.001) and central venous pressure from 22.5 (17.8-29.0) to 17.5 (12.8-24.0) mmHg (p < 0.001) with inverse increases in APP from 63.0 (56.8-69.5) to 71.0 (65.5-78.5) mmHg (p < 0.001). Changes in ICG-PDR were concomitant with changes in IAP (r = - 0.602) and APP (r = 0.576). Moreover, we found a substantial improvement in respiratory function. By contrast, hemodynamic parameters assessed by transpulmonary thermodilution, serum bilirubin and international normalized ratio did not change after paracentesis.

CONCLUSION

Critically ill patients with decompensated cirrhosis and elevated IAP showed dramatically impaired ICG-PDR. Paracentesis evoked an improvement in ICG-PDR in parallel with a decreased IAP and an increased APP, while conventional parameters of liver function did not change. This effect on ICG-PDR is mainly referable to a relief of intraabdominal hypertension and changes in hepatosplanchnic blood flow.

Effect of retension sutures on abdominal pressure after abdominal surgery

PURPOSE

To evaluate the effect of retention sutures on abdominal pressure and postoperative prognosis in abdominal surgery patients.

METHODS

This prospective cohort study included patients who were admitted to Daping Hospital from May 15, 2014 to October 11, 2014. A total of 57 patients were enrolled, including 18 patients in the "U" type retention suture group, 17 patients in the intermittent retention suture group, and 22 patients in non-retention suture group. The demographic data, clinical data and risk factors for abdominal wound dehiscence were recorded. The bladder pressure (IVP) was monitored preoperatively, intraoperatively, and four days postoperatively. Additionally, the incidence of abdominal wound dehiscence and infection 14 days after the operation was recorded.

RESULTS

During the operation, the IVP decreased and then increased; it was at its lowest 1 h after the start of the operation (5.3 mmHg ± 3.2 mmHg) and peaked after tension-reducing (8.8 mmHg ± 4.0 mmHg). The IVP values in the "U" type retention suture group and intermittent retention suture group were higher than in the non-retention suture group 4 days after operation (p < 0.005). The Visual Analogue Scale (VAS) pain scores were 3.9 ± 2.2, 3.8 ± 2.0, and 3.0 ± 1.0 in the retention suture group, intermittent retention suture group and non-retention suture group, respectively. The VAS pain scores in the "U" type tension-reducing group and intermittent tension-reducing group were higher than in the non-tension-reducing group (p < 0.005).

CONCLUSION

Although retention sutures may reduce the incidence of postoperative wound dehiscence in abdominal surgery patients, they can increase the IVP and postoperative pain.

Association between kidney intracapsular pressure and ultrasound elastography

Background

Kidney congestion is a common pathophysiologic pathway of acute kidney injury (AKI) in sepsis and heart failure. There is no noninvasive tool to measure kidney intracapsular pressure (KIP) directly.

Methods

We evaluated the correlation of KIP with kidney elasticity measured by ultrasound surface wave elastography (USWE). We directly measured transcatheter KIP in three pigs at baseline and after bolus infusion of normal saline, norepinephrine, vasopressin, dopamine, and fenoldopam; infiltration of 2-L peritoneal dialysis solution in the intra-abdominal space; and venous, arterial, and ureteral clamping. KIP was compared with USWE wave speed.

Results

Only intra-abdominal installation of peritoneal dialysis fluid was associated with significant change in KIP (mean (95% CI) increase, 3.7 (3.2–4.2)] mmHg; P < .001). Although intraperitoneal pressure and KIP did not differ under any experimental condition, bladder pressure was consistently and significantly greater than KIP under all circumstances (mean (95% CI) bladder pressure vs. KIP, 3.8 (2.9–4.) mmHg; P < .001). USWE wave speed significantly correlated with KIP (adjusted coefficient of determination, 0.71; P < .001). Estimate (95% CI) USWE speed for KIP prediction stayed significant after adjustment for KIP hypertension (−0.8 (− 1.4 to − 0.2) m/s; P = .008) whereas systolic and diastolic blood pressures were not significant predictors of KIP.

Conclusions

In a pilot study of the swine model, we found ultrasound surface wave elastography speed is significantly correlated with transcatheter measurement of kidney intracapsular and intra-abdominal pressures, while bladder pressure overestimated kidney intracapsular pressure.

An experimental study on the impacts of inspiratory and expiratory muscles activities during mechanical ventilation in ARDS animal model

In spite of intensive investigations, the role of spontaneous breathing (SB) activity in ARDS has not been well defined yet and little has been known about the different contribution of inspiratory or expiratory muscles activities during mechanical ventilation in patients with ARDS. In present study, oleic acid-induced beagle dogs' ARDS models were employed and ventilated with the same level of mean airway pressure. Respiratory mechanics, lung volume, gas exchange and inflammatory cytokines were measured during mechanical ventilation, and lung injury was determined histologically. As a result, for the comparable ventilator setting, preserved inspiratory muscles activity groups resulted in higher end-expiratory lung volume (EELV) and oxygenation index. In addition, less lung damage scores and lower levels of system inflammatory cytokines were revealed after 8 h of ventilation. In comparison, preserved expiratory muscles activity groups resulted in lower EELV and oxygenation index. Moreover, higher lung injury scores and inflammatory cytokines levels were observed after 8 h of ventilation. Our findings suggest that the activity of inspiratory muscles has beneficial effects, whereas that of expiratory muscles exerts adverse effects during mechanical ventilation in ARDS animal model. Therefore, for mechanically ventilated patients with ARDS, the demands for deep sedation or paralysis might be replaced by the strategy of expiratory muscles paralysis through epidural anesthesia.

Intra-Abdominal Hypertension and Abdominal Compartment Syndrome after Abdominal Wall Reconstruction: Quaternary Syndromes?

Background and Aims:

Reconstruction with reconstitution of the container function of the abdominal compartment is increasingly being performed in patients with massive ventral hernia previously deemed inoperable. This situation places patients at great risk of severe intra-abdominal hypertension and abdominal compartment syndrome if organ failure ensues. Intra-abdominal hypertension and especially abdominal compartment syndrome may be devastating systemic complications with systematic and progressive organ failure and death. We thus reviewed the pathophysiology and reported clinical experiences with abnormalities of intra-abdominal pressure in the context of abdominal wall reconstruction.

Material and Methods:

Bibliographic databases (1950–2015), websites, textbooks, and the bibliographies of previously recovered articles for reports or data relating to intra-abdominal pressure, intra-abdominal hypertension, and the abdominal compartment syndrome in relation to ventral, incisional, or abdominal hernia repair or abdominal wall reconstruction.

Results:

Surgeons should thus consider and carefully measure intra-abdominal pressure and its resultant effects on respiratory parameters and function during abdominal wall reconstruction. The intra-abdominal pressure post-operatively will be a result of the new intra-peritoneal volume and the abdominal wall compliance. Strategies surgeons may utilize to ameliorate intra-abdominal pressure rise after abdominal wall reconstruction including temporizing paralysis of the musculature either temporarily or semi-permanently, pre-operative progressive pneumoperitoneum, permanently removing visceral contents, or surgically releasing the musculature to increase the abdominal container volume. In patients without complicating shock and inflammation, and in whom the abdominal wall anatomy has been so functionally adapted to maximize compliance, intra-abdominal hypertension may be transient and tolerable.

Conclusions:

Intra-abdominal hypertension/abdominal compartment syndrome in the specific setting of abdominal wall reconstruction without other complication may be considered as a quaternary situation considering the classification nomenclature of the Abdominal Compartment Society. Greater awareness of intra-abdominal pressure in abdominal wall reconstruction is required and ongoing study of these concerns is required.

Abdominal Muscle Activity during Mechanical Ventilation Increases Lung Injury in Severe Acute Respiratory Distress Syndrome

OBJECTIVE

It has proved that muscle paralysis was more protective for injured lung in severe acute respiratory distress syndrome (ARDS), but the precise mechanism is not clear. The purpose of this study was to test the hypothesis that abdominal muscle activity during mechanically ventilation increases lung injury in severe ARDS.

METHODS

Eighteen male Beagles were studied under mechanical ventilation with anesthesia. Severe ARDS was induced by repetitive oleic acid infusion. After lung injury, Beagles were randomly assigned into spontaneous breathing group (BIPAPSB) and abdominal muscle paralysis group (BIPAPAP). All groups were ventilated with BIPAP model for 8h, and the high pressure titrated to reached a tidal volume of 6ml/kg, the low pressure was set at 10 cmH2O, with I:E ratio 1:1, and respiratory rate adjusted to a PaCO2 of 35-60 mmHg. Six Beagles without ventilator support comprised the control group. Respiratory variables, end-expiratory volume (EELV) and gas exchange were assessed during mechanical ventilation. The levels of Interleukin (IL)-6, IL-8 in lung tissue and plasma were measured by qRT-PCR and ELISA respectively. Lung injury scores were determined at end of the experiment.

RESULTS

For the comparable ventilator setting, as compared with BIPAPSB group, the BIPAPAP group presented higher EELV (427±47 vs. 366±38 ml) and oxygenation index (293±36 vs. 226±31 mmHg), lower levels of IL-6(216.6±48.0 vs. 297.5±71.2 pg/ml) and IL-8(246.8±78.2 vs. 357.5±69.3 pg/ml) in plasma, and lower express levels of IL-6 mRNA (15.0±3.8 vs. 21.2±3.7) and IL-8 mRNA (18.9±6.8 vs. 29.5±7.9) in lung tissues. In addition, less lung histopathology injury were revealed in the BIPAPAP group (22.5±2.0 vs. 25.2±2.1).

CONCLUSION

Abdominal muscle activity during mechanically ventilation is one of the injurious factors in severe ARDS, so abdominal muscle paralysis might be an effective strategy to minimize ventilator-induce lung injury.

The effects of airway pressure release ventilation on respiratory mechanics in extrapulmonary lung injury

BACKGROUND

Lung injury is often studied without consideration for pathologic changes in the chest wall. In order to reduce the incidence of lung injury using preemptive mechanical ventilation, it is important to recognize the influence of altered chest wall mechanics on disease pathogenesis. In this study, we hypothesize that airway pressure release ventilation (APRV) may be able to reduce the chest wall elastance associated with an extrapulmonary lung injury model as compared with low tidal volume (LVt) ventilation.

METHODS

Female Yorkshire pigs were anesthetized and instrumented. Fecal peritonitis was established, and the superior mesenteric artery was clamped for 30 min to induce an ischemia/reperfusion injury. Immediately following injury, pigs were randomized into (1) LVt (n = 3), positive end-expiratory pressure (PEEP) 5 cmH2O, V t 6 cc kg(-1), FiO2 21 %, and guided by the ARDSnet protocol or (2) APRV (n = 3), P High 16-22 cmH2O, P Low 0 cmH2O, T High 4.5 s, T Low set to terminate the peak expiratory flow at 75 %, and FiO2 21 %. Pigs were monitored continuously for 48 h. Lung samples and bronchoalveolar lavage fluid were collected at necropsy.

RESULTS

LVt resulted in mild acute respiratory distress syndrome (ARDS) (PaO2/FiO2 = 226.2 ± 17.1 mmHg) whereas APRV prevented ARDS (PaO2/FiO2 = 465.7 ± 66.5 mmHg; p < 0.05). LVt had a reduced surfactant protein A concentration and increased histologic injury as compared with APRV. The plateau pressure in APRV (34.3 ± 0.9 cmH2O) was significantly greater than LVt (22.2 ± 2.0 cmH2O; p < 0.05) yet transpulmonary pressure between groups was similar (p > 0.05). This was because the pleural pressure was significantly lower in LVt (7.6 ± 0.5 cmH2O) as compared with APRV (17.4 ± 3.5 cmH2O; p < 0.05). Finally, the elastance of the lung, chest wall, and respiratory system were all significantly greater in LVt as compared with APRV (all p < 0.05).

CONCLUSIONS

APRV preserved surfactant and lung architecture and maintenance of oxygenation. Despite the greater plateau pressure and tidal volumes in the APRV group, the transpulmonary pressure was similar to that of LVt. Thus, the majority of the plateau pressure in the APRV group was distributed as pleural pressure in this extrapulmonary lung injury model. APRV maintained a normal lung elastance and an open, homogeneously ventilated lung without increasing lung stress.

Daily laxative therapy reduces organ dysfunction in mechanically ventilated patients: a phase II randomized controlled trial

INTRODUCTION

Constipation is a common problem in intensive care units. We assessed the efficacy and safety of laxative therapy aiming to promote daily defecation in reducing organ dysfunction in mechanically ventilated patients.

METHODS

We conducted a prospective, randomized, controlled, nonblinded phase II clinical trial at two general intensive care units. Patients expected to remain ventilated for over 3 days were randomly assigned to daily defecation or control groups. The intervention group received lactulose and enemas to produce 1-2 defecations per day. In the control group, absence of defecation was tolerated up to 5 days. Primary outcome was the change in Sequential Organ Failure Assessment (SOFA) score between the date of enrollment and intensive care unit discharge, death or day 14.

RESULTS

We included 88 patients. Patients in the treatment group had a higher number of defecations per day (1.3 ± 0.42 versus 0.7 ± 0.56, p < 0.0001) and lower percentage of days without defecation (33.1 ± 15.7% versus 62.3 ± 24.5%, p < 0.0001). Patients in the intervention group had a greater reduction in SOFA score (-4.0 (-6.0 to 0) versus -1.0 (-4.0 to 1.0), p = 0.036) with no difference in mortality rates or in survival time. Adverse events were more frequent in the treatment group (4.5 (3.0-8.0) versus 3.0 (1.0-5.7), p = 0.016), including more days with diarrhea (2.0 (1.0-4.0) versus 1.0 (0-2.0) days, p < 0.0001). Serious adverse events were rare and did not significantly differ between groups.

CONCLUSIONS

Laxative therapy improved daily defecation in ventilated patients and was associated with a greater reduction in SOFA score.

TRIAL REGISTRATION

Clinical Trials.gov NCT01607060, registered 24 May 2012.

Components separation technique is feasible for assisting delayed primary fascial closure of open abdomen

Background and aims:

The goal after open abdomen treatment is to reach primary fascial closure. Modern negative pressure wound therapy systems are sometimes inefficient for this purpose. This retrospective chart analysis describes the use of the ‘components separation’ method in facilitating primary fascial closure after open abdomen.

Material and methods:

A total of 16 consecutive critically ill surgical patients treated with components separation during open abdomen management were analyzed. No patients were excluded.

Results:

Primary fascial closure was achieved in 75% (12/16). Components separation was performed during ongoing open abdomen treatment in 7 patients and at the time of delayed primary fascial closure in 9 patients. Of the former, 3/7 (43%) patients reached primary fascial closure, whereas all 9 patients in the latter group had successful fascial closure without major complications (p = 0.019).

Conclusion:

Components separation is a useful method in contributing to successful primary fascial closure in patients treated for open abdomen. Best results were obtained when components separation was performed simultaneously with primary fascial closure at the end of the open abdomen treatment.

Pathophysiology and management of acute kidney injury in the setting of abdominal compartment syndrome

Abdominal compartment syndrome (ACS) is defined as an organ dysfunction caused by intra-abdominal hypertension (IAH). Up to 4.2% of the patients in intensive care unit may develop IAH with it being an independent predictor of mortality. However, overall, it still remains a relatively underdiagnosed condition, part in because physical examination alone is very unreliable. Acute kidney injury is one of the most consistently described organ dysfunctions with oliguria being one of the earliest clinical signs of IAH. We recommend that any patient with evidence of new onset oliguria in the setting of distended abdomen, unexplained respiratory failure, with or without hypotension should be suspected of having IAH/ACS. Intravesicular pressure measurement represents a safe, rapid, and cost-effective method of diagnosing IAH. We hereby review the pathophysiology, diagnosis, and management of ACS and its association with acute kidney injury.

Lymphatic drainage between thorax and abdomen: please take good care of this well-performing machinery…

INTRODUCTION

Patients with sepsis often receive large amounts of fluids and the presence of capillary leak, trauma or bleeding results in ongoing fluid resuscitation. This increases interstitial and intestinal edema and finally leads to intra-abdominal hypertension (IAH), which in turn impedes lymphatic drainage. Patients with IAH often develop secondary respiratory failure needing mechanical ventilation with high intrathoracic pressure or PEEP that might further alter lymphatic drainage. This review will try to convince the reader of the importance of the lymphatics in septic patients with IAH.

METHODS

A Medline and PubMed literature search was performed using the terms "abdominal pressure", "lymphatic drainage" and "ascites formation". The references from these studies were searched for relevant articles that may have been missed in the primary search. These articles served as the basis for the recommendations below.

RESULTS

Induction of sepsis with lesion of the capillary alveolar barrier results in an increased water gradient between the capillaries and the interstitium in the lungs. The drainage flow to the thoracic duct is initially increased in order to protect the lung and maintain the pulmonary interstitium as dry as possible, however this results in increased intrathoracic pressure. Sepsis also increases the permeability of the capillaries in the splanchnic beds. In analogy to the lungs the lymphatic flow in the splanchnic areas increases together with the pressure inside as a physiological response in order to limit the increase in IAP. At a critical IAP level (around 20 cmH2O) the lymph flow starts to decrease and the splanchnic water content progressively increases. The lymph flow from the abdomen to the thorax is progressively decreased resulting in increased splanchnic water content and ascites formation. The presence of mechanical ventilation with high PEEP reduces the lymph drainage further which together with the increase in IAP decreases the lymphatic pressure gradient in the splanchnic regions, with a further increase in water content and IAP triggering a vicious cycle.

CONCLUSION

Although often overlooked the role of lymphatic flow is complex but very important to determine not only the fluid balance in the lung but also in the peripheral organs. Different pathologies and treatments can markedly influence the pathophysiology of the lymphatics with dramatic effects on endorgan function.

Abdominal compartment syndrome and intraabdominal sepsis: two of the same kind?

BACKGROUND

Abdominal compartment syndrome and intra-abdominal hypertension are frequently associated with peritonitis. The aim of this study is to establish the relationship between intra-abdominal hypertension and intra-abdominal sepsis especially in critically ill patients.

METHODS

Relevant information was identified through a Medline search (1966-October 2006). The terms used were "intra-abdominal sepsis", "peritonitis", "abdominal compartment syndrome", "intra-abdominal hypertension" and "relaparotomy for sepsis". The search was limited to English- and French-language publications.

RESULTS

Only a few clinical trials exist on this specific topic. Further investigations are required to define the incidence of intra-abdominal hypertension in intra-abdominal sepsis, and the prognostic impact of this setting and finally the potential specific treatment. Abdominal compartment syndrome is more likely linked to the abdominal surgery than to peritonitis itself.

CONCLUSION

Intra-abdominal pressure monitoring can be valuable in critically ill patients with suspicion of persisting intra-abdominal sepsis after surgical peritonitis treatment.

Renal implications of increased intra-abdominal pressure: are the kidneys the canary for abdominal hypertension?

INTRODUCTION

Increased intra-abdominal pressure (IAP) or intra-abdominal hypertension (IAH) is a cause of organ dysfunction in critically ill patients and is independently associated with mortality. The kidneys seem to be especially vulnerable to IAH induced dysfunction and renal failure is one of the most consistently described organ dysfunctions associated with IAH. The aim of this paper is to review the historical background, awareness, definitions, pathophysiologic implications and treatment options for IAP induced renal failure.

METHODS

This review will focus on the available literature on IAH-induced renal dysfunction. A Medline and PubMed search was performed in order to find an answer to the question "What is the impact of increased IAP on renal function in the critically ill?". The resulting references were included in the current review on the basis of relevance and scientific merit.

RESULTS

Renal dysfunction in IAH is a multifactorial process. The mechanisms involved have not been clarified completely. However, decreased cardiac output, altered renal blood flow and hormonal changes have been implicated. Decompression seems to have a beneficial effect on renal dysfunction, although there are some conflicting data. This may be due to the fact that there is no consensus on indications for decompression, both in terms of IAP values and of timing. An overview of current literature is provided and some interesting leads for future research are suggested.

CONCLUSION

IAH can cause renal dysfunction. Therefore, IAP measurements should be considered in our daily practice and preventive measures should be taken to avoid (deterioration of) renal failure in patients with IAH. Decompression may have a beneficial effect in patients with established IAH and renal failure.

Defining gastrointestinal failure

INTRODUCTION

Gastrointestinal failure (GIF) has been postulated as the motor of multiple organ dysfunction syndrome (MODS) but is not commonly included among other organ failures in scoring systems identifying MODS.

MATERIALS AND METHODS

Relevant articles and published reviews were identified and analyzed through a PubMed search of English language literature on gastrointestinal problems.

RESULTS AND DISCUSSION

Wide variability in terms and definitions was observed. Data on the incidence of GIF and its impact on mortality in critically ill patients are controversial. Very few objectively measurable variables of GI function are available. Most of the definitions of GIF are diagnosis-, but not function-based. Diagnosis-based approach to GIF differs significantly from the function-based assessment of other organ failures and has not justified itself over time.

CONCLUSIONS

There is no consensus on definition of GIF and different medical specialties have different approaches. Development of a proper definition of GIF is warranted.

The role of intestinal mucosa injury induced by intra-abdominal hypertension in the development of abdominal compartment syndrome and multiple organ dysfunction syndrome

Introduction

Abdominal distension is common in critical illness. There is a growing recognition that intra-abdominal hypertension (IAH) may complicate nonsurgical critical illness as well as after abdominal surgery. However, the pathophysiological basis of the injury to the intestinal mucosal barrier and its influence on the onset of abdominal compartment syndrome (ACS) and multiorgan dysfunction syndrome (MODS) remain unclear. We measured intestinal microcirculatory blood flow (MBF) during periods of raised intra-abdominal pressure (IAP) and examined how this influenced intestinal permeability, systemic endotoxin release, and histopathological changes.

Methods

To test different grades of IAH to the injury of intestinal mucosa, 96 New Zealand white rabbits aged 5 to 6 months were exposed to increased IAP under nitrogen pneumoperitoneum of 15 mmHg or 25 mmHg for 2, 4 or 6 hours. MBF was measured using a laser Doppler probe placed against the jejunal mucosa through a small laparotomy. Fluorescein isothiocyanate (FITC)-conjugated dextran was administered by gavage. Intestinal injury and permeability were measured using assays for serum FITC-dextran and endotoxin, respectively, after each increase in IAP. Structural injury to the intestinal mucosa at different levels of IAH was confirmed by light and transmission electron microscopy.

Results

MBF reduced from baseline by 40% when IAP was 15 mmHg for 2 hours. This doubled to 81% when IAP was 25 mmHg for 6 hours. Each indicator of intestinal injury increased significantly, proportionately with IAP elevation and exposure time. Baseline serum FITC-dextran was 9.30 (± SD 6.00) μg/ml, rising to 46.89 (±13.43) μg/ml after 15 mmHg IAP for 4 hours (P <0.01), and 284.59 (± 45.18) μg/ml after 25 mmHg IAP for 6 hours (P <0.01). Endotoxin levels showed the same pattern. After prolonged exposure to increased IAP, microscopy showed erosion and necrosis of jejunal villi, mitochondria swelling and discontinuous intracellular tight junctions.

Conclusions

Intra-abdominal hypertension can significantly reduce MBF in the intestinal mucosa, increase intestinal permeability, result in endotoxemia, and lead to irreversible damage to the mitochondria and necrosis of the gut mucosa. The dysfunction of the intestinal mucosal barrier may be one of the important initial factors responsible for the onset of ACS and MODS.

Intra-abdominal high pressure induces intestinal barrier dysfunction in rats

AIM: To study the effect of different degrees of intra-abdominal high pressure on intestinal mucosal barrier dysfunction and to explore the possible mechanisms involved.

METHODS: Forty-five adult male SD rats were randomly divided into a normal control group, a 10 mmHg and a 20 mmHg group (n = 15 for each). Nitrogen pneumoperitoneum was induced to generate intra-abdominal high pressure in animal models. The two pneumoperitoneum groups were further divided into three subgroups (five rats in each subgroup) for testing when pneumoperitoneum was maintained for 1, 2 and 4 h, respectively. Twenty-four hours after the relief of pneumoperitoneum, a spectrophotometer was used to measure the concentration of blue dextran 2000 in different segments of the small intestine. Malondialdehyde (MDA), reduced glutathione (GSH) and superoxide dismutase (SOD) in intestinal tissue homogenates, as well as plasma diamine oxidase (DAO) and D-lactic acid were measured. Morphological changes in the intestinal tissue were observed by light microscopy and electron microscopy.

RESULTS: Compared to the control group, intestinal transit was significantly delayed, but intestinal SOD, GSH and MDA levels and plasma D-lactate level showed no significant changes in the two high intra-abdominal pressure groups (all P > 0.05). Plasma DAO level did not differ significantly between the 10 mmHg group and control group, but was significantly different between the 20 mmHg and control groups (1412.93 ± 1397.19 vs 542.41 ± 314.93, P < 0.05). Under the light microscope, postoperative intestinal mucosa showed no damage in the control group; however, mild (increase in small intestinal subepithelial gaps and villus capillary congestion) and severe (varying degrees of intestinal mucosal changes, small intestinal mucosal congestion and edema, expansion of small intestinal subepithelial gaps, and intestinal villus degeneration, necrosis or loss) pathological changes were observed in the 10 and 20 mmHg groups, respectively. Electron microscopy demonstrated that intestinal villus cells in the 10 mmHg group showed mild swelling of tight junctions, and the 20 mmHg group showed significant changes in the microvillus and mitochondrial structures.

CONCLUSION: High intra-abdominal pressure can delay intestinal transit, alter plasma DAO activity, cause significant damage to intestinal epithelial cells, and increase intestinal permeability.

Surveillance of intra-abdominal pressure and intestinal barrier function in a rat model of acute necrotizing pancreatitis and its potential early therapeutic window

OBJECTIVES

To monitor intra-abdominal pressure (IAP) and intestinal barrier function in a rat model of acute necrotizing pancreatitis (ANP) to elucidate a potential relevant therapeutic window.

METHODS

Sprague-Dawley rats were randomly divided into experimental or control groups. The ANP group (n = 40) was injected with 4.5% sodium taurocholate into the pancreatic duct to induce ANP. The controls received only abdominal opening surgery (sham-operated, SO; n = 40) or no treatment or surgery (baseline; 0 h, n = 20). The SO and ANP groups were then randomly subdivided into 3, 6, 12 and 24 h groups (n = 10 each). IAP was measured at each time point and the rats were sacrificed to measure the weight of accumulated ascites fluid and the amylase, endogenous creatinine (Cr), total bilirubin (TB), tumor necrosis factor- alpha (TNF-alpha), diamine oxidase (DAO), and D-lactate. Mortality and the development of pathological changes in the pancreas and intestines were also monitored.

RESULTS

IAP showed a continuous upward trend in the ANP group, with values 2 to 3 times higher than those in the SO group at the corresponding time points and the rising rate was peaking at 6 h. The levels of plasma amylase, TNF-alpha, Cr, TB, DAO, and D-lactate also gradually increased in the ANP group over time and were significantly higher than in the SO group at 3, 6, 12 and 24 h (all P<0.05). Moreover, the rising rate of TNF-alpha, DAO, and D-lactate also peaked at 6 h.

CONCLUSIONS

The ANP-induced changes in IAP, inflammatory factors and intestinal barrier that we observed in the rat model were especially obvious at 6 h post-induction, suggesting an early therapeutic window for the treatment of ANP in humans.