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1.  Incidence and prognosis of intra-abdominal hypertension in critically ill medical patients: a prospective epidemiological study 
Annals of Intensive Care  2012;2(Suppl 1):S3.
Introduction
The aim of this study was to determine the incidence of intra-abdominal hypertension (IAH) in patients with two or more categorized risk factors (CRF) for IAH, and their morbidity and mortality during their intensive care unit (ICU) stay.
Methods
Prospective cohort study carried out at a medical ICU. A total of 151 medical patients were enrolled during a period of 3 months. After ICU whole staff training, we conducted daily screening of the four CRF for IAH based on the World Society of Abdominal Compartment Syndrome (WSACS) guidelines (namely, diminished abdominal wall compliance, increased intraluminal content, increased abdominal content, and capillary leak syndrome or fluid resuscitation). In those patients with risk factors of at least two different categories (≥2 CRF), intra-abdominal pressure (IAP) was measured every 8 h during ICU stay. Data included demographics, main diagnosis on admission, severity scores, cumulative fluid balance, daily mean IAP, resolution of IAH, days of ICU and hospital stay, and mortality.
Results
Eighty-seven patients (57.6%) had ≥2 CRF for IAH, 59 (67.8%) out of whom developed IAH. Patients with ≥2 CRF had a significantly higher mortality rate (41.4 vs. 14.3%, p < 0.001). Patients with IAH had higher body mass index, severity scores, organ dysfunctions/failures, number of CRF for IAH, days of ICU/hospital stay and hospital mortality rate (45.8 vs. 32.1%, p = 0.22). Non-resolution of IAH was associated with a higher mortality rate (64.7 vs. 35.3%, p = 0.001). None of the cohort patients developed abdominal compartment syndrome. The multivariate analysis showed that IAH development (odds ratio (OR) 4.09; 95% confidence interval (CI) 0.83-20.12) was a non-independent risk factor for mortality, and its non-resolution (OR 13.15; 95% CI 22.13-81.92) was an independent risk factor for mortality.
Conclusions
Critically ill medical patients admitted to ICU with ≥2 CRF have high morbidity, mortality rate, and incidence of IAH, so IAP should be measured and monitored as recommended by the WSACS. Our study highlights the importance of implementing screening and assessment protocols for an early diagnosis of IAH.
doi:10.1186/2110-5820-2-S1-S3
PMCID: PMC3390290  PMID: 22873419
intra-abdominal hypertension; abdominal compartment syndrome; intra-abdominal pressure; multiple organ failure; critically ill patients; intensive care.
2.  Intra-abdominal hypertension in patients with severe acute pancreatitis 
Critical Care  2005;9(4):R452-R457.
Introduction
Abdominal compartment syndrome has been described in patients with severe acute pancreatitis, but its clinical impact remains unclear. We therefore studied patient factors associated with the development of intra-abdominal hypertension (IAH), the incidence of organ failure associated with IAH, and the effect on outcome in patients with severe acute pancreatitis (SAP).
Methods
We studied all patients admitted to the intensive care unit (ICU) because of SAP in a 4 year period. The incidence of IAH (defined as intra-abdominal pressure ≥ 15 mmHg) was recorded. The occurrence of organ dysfunction during ICU stay was recorded, as was the length of stay in the ICU and outcome.
Results
The analysis included 44 patients, and IAP measurements were obtained from 27 patients. IAH was found in 21 patients (78%). The maximum IAP in these patients averaged 27 mmHg. APACHE II and Ranson scores on admission were higher in patients who developed IAH. The incidence of organ dysfunction was high in patients with IAH: respiratory failure 95%, cardiovascular failure 91%, and renal failure 86%. Mortality in the patients with IAH was not significantly higher compared to patients without IAH (38% versus 16%, p = 0.63), but patients with IAH stayed significantly longer in the ICU and in the hospital. Four patients underwent abdominal decompression because of abdominal compartment syndrome, three of whom died in the early postoperative course.
Conclusion
IAH is a frequent finding in patients admitted to the ICU because of SAP, and is associated with a high occurrence rate of organ dysfunction. Mortality is high in patients with IAH, and because the direct causal relationship between IAH and organ dysfunction is not proven in patients with SAP, surgical decompression should not routinely be performed.
doi:10.1186/cc3754
PMCID: PMC1269467  PMID: 16137360
3.  Intra-abdominal hypertension in cardiac surgery 
OBJECTIVES
The occurrence of intra-abdominal hypertension (IAH), as well as its promoting factors in cardiac surgery, has been poorly explored. The aim of the present study was to characterize intra-abdominal pressure (IAP) variations in patients undergoing cardiac surgical procedures, and to identify the risk factors for IAH in this setting.
METHODS
All consecutive adult patients requiring postoperative intensive care unit admission for >24 h were enrolled. Demographic data, pre-existing comorbidities, type and duration of surgery, cardiopulmonary bypass (CPB) use and duration, perioperative IAP, organ function and fluid balance were recorded. IAH was defined as a sustained increase in IAP >12 mmHg. Multivariate logistic regression and stepwise analyses identified the baseline and perioperative variables associated with IAH.
RESULTS
Of 69 patients, 22 (31.8%) developed IAH. In the logistic model, baseline IAP, high central venous pressure, vasoactive drugs administration, positive fluid balance, AKI, CPB, total sequential organ failure assessment score and age were all promoting factors for IAH (Hosmer–Lemeshow χ2 = 7.23; P = 0.843). Baseline IAP, high central venous pressure and positive fluid balance were independent risk factors for IAH in the stepwise analysis. The ROC curve analysis, obtained by plotting the occurrence of IAH vs the IAP baseline value, showed an AUC of 0.75 (SE 0.064; 99% CI 0.62–0.87; P < 0.0001). The best IAP cut-off value was at 8 mmHg (sensitivity 63% and specificity 76%). Considering on- and off-pump surgery groups, fluid balance and vasoactive drugs use were significantly higher in the on-pump group. Linear regression analysis showed a positive correlation (P = 0.0001) between IAP changes and fluid balance only in the on-pump group.
CONCLUSIONS
IAH develops in one-third of cardiac surgery patients and is strongly associated with higher baseline IAP values, higher central venous pressure, positive fluid balance, extracorporeal circulation, use of vasoactive drugs and AKI. Determinants of IAH should be accurately assessed before and after surgery, and patients presenting risk factors must be monitored properly during the perioperative period. In this context, the baseline value of IAP may be a valuable and early warning parameter for IAH occurrence.
doi:10.1093/icvts/ivt272
PMCID: PMC3781798  PMID: 23820668
Intra-abdominal pressure; Abdominal hypertension; Cardiac surgery; Cardiac surgical patients; Acute kidney injury
4.  Effect of mechanical ventilation on intra-abdominal pressure in critically ill patients without other risk factors for abdominal hypertension: an observational multicenter epidemiological study 
Annals of Intensive Care  2012;2(Suppl 1):S22.
Background
Mechanical ventilation (MV) is considered a predisposing factor for increased intra-abdominal pressure (IAP), especially when positive end-expiratory pressure (PEEP) is applied or in the presence of auto-PEEP. So far, no prospective data exists on the effect of MV on IAP. The study aims to look on the effects of MV on IAP in a group of critically ill patients with no other risk factors for intra-abdominal hypertension (IAH).
Methods
An observational multicenter study was conducted on a total of 100 patients divided into two groups: 50 patients without MV and 50 patients with MV. All patients were admitted to the intensive care units of the Medical and Surgical Research Centre, the Carlos J. Finlay Hospital, the Julio Trigo University Hospital, and the Calixto García Hospital, in Havana, Cuba between July 2000 and December 2004. The IAP was measured twice daily on admission using a standard transurethral technique. IAH was considered if IAP was greater than 12 mmHg. Correlations were made between IAP and body mass index (BMI), diagnostic category, gender, age, and ventilatory parameters.
Results
The mean IAP in patients on MV was 6.7 ± 4.1 mmHg and significantly higher than in patients without MV (3.6 ± 2.4 mmHg, p < 0.0001). This difference was maintained regardless of gender, age, BMI, and diagnosis. The use of MV and BMI were independent predictors for IAH for the whole population, while male gender, assisted ventilation mode, and the use of PEEP were independent factors associated with IAH in patients on MV.
Conclusions
In this study, MV was identified as an independent predisposing factor for the development of IAH. Critically ill patients, which are on MV, present with higher IAP values on admission and should be monitored very closely, especially if PEEP is applied, even when they have no other apparent risk factors for IAH.
doi:10.1186/2110-5820-2-S1-S22
PMCID: PMC3527157  PMID: 23281625
5.  Intra-abdominal pressure and abdominal perfusion pressure in cirrhotic patients with septic shock 
Annals of Intensive Care  2012;2(Suppl 1):S4.
Background
The importance of intra-abdominal pressure (IAP) and abdominal perfusion pressure (APP) in cirrhotic patients with septic shock is not well studied. We evaluated the relationship between IAP and APP and outcomes of cirrhotic septic patients, and assessed the ability of these measures compared to other common resuscitative endpoints to differentiate survivors from nonsurvivors.
Methods
This study was a post hoc analysis of a randomized double-blind placebo-controlled trial in which mean arterial pressure (MAP), central venous oxygen saturation (ScvO2) and IAP were measured every 6 h in 61 cirrhotic septic patients admitted to the intensive care unit. APP was calculated as MAP - IAP. Intra-abdominal hypertension (IAH) was defined as mean IAP ≥ 12 mmHg, and abdominal hypoperfusion as mean APP < 60 mmHg. Measured outcomes included ICU and hospital mortality, need for renal replacement therapy (RRT) and ventilator- and vasopressor-free days.
Results
IAH prevalence on the first ICU day was 82%, and incidence in the first 7 days was 97%. Compared to patients with normal IAP, IAH patients had significantly higher ICU mortality (74.0% vs. 27.3%, p = 0.005), required more RRT (78.0% vs. 45.5%, p = 0.06) and had lower ventilator- and vasopressor-free days. On a multivariate logistic regression analysis, IAH was an independent predictor of both ICU mortality (odds ratio (OR), 12.20; 95% confidence interval (CI), 1.92 to 77.31, p = 0.008) and need for RRT (OR, 6.78; 95% CI, 1.29 to 35.70, p = 0.02). Using receiver operating characteristic curves, IAP (area under the curve (AUC) = 0.74, p = 0.004), APP (AUC = 0.71, p = 0.01), Acute Physiology and Chronic Health Evaluation II score (AUC = 0.71, p = 0.02), but not MAP, differentiated survivors from nonsurvivors.
Conclusions
IAH is highly prevalent in cirrhotic patients with septic shock and is associated with increased ICU morbidity and mortality.
doi:10.1186/2110-5820-2-S1-S4
PMCID: PMC3390301  PMID: 22873420
liver cirrhosis; sepsis; compartment syndrome; septic shock; ascites; mortality.
6.  Abdominal compartment syndrome in patients with severe acute pancreatitis in early stage 
AIM: To study retrospectively the influence of intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS) in patients with early acute pancreatitis (AP) (during the first week after admission) on physiological functions, and the association of the presence of IAH/ACS and outcome.
METHODS: Patients (n = 74) with AP recruited in this study were divided into two groups according to intra-abdominal pressure (IAP) determined by indirect measurement using the transvesical route via Foley bladder catheter during the first week after admission. Patients (n = 44) with IAP ≥ 12 mmHg were assigned in IAH group, and the remaining patients (n = 30) with IAP < 12 mmHg in normal IAP group. For analysis of the influence of IAH/ACS on organ function and outcome, the physiological parameters and the occurrence of organ dysfunction during intensive care unit (ICU) stay were recorded, as were the incidences of pancreatic infection and in-hospital mortality.
RESULTS: IAH within the first week after admission was found in 44 patients (59.46%). Although the APACHE II scores on admission and the Ranson scores within 48 h after hospitalization were elevated in IAH patients in early stage, they did not show the statistically significant differences from patients with normal IAP within a week after admission (16.18 ± 3.90 vs 15.70 ± 4.25, P = 0.616; 3.70 ± 0.93 vs 3.47 ± 0.94, P = 0.285, respectively). ACS in early AP was recorded in 20 patients (27.03%). During any 24-h period of the first week after admission, the recorded mean IAP correlated significantly with the Marshall score calculated at the same time interval in IAH group (r = 0.635, P < 0.001). Although ACS patients had obvious amelioration in physiological variables within 24 h after decompression, the incidences of pancreatitic infection, septic shock, multiple organ dysfunction syndrome (MODS) and death in the patients with ACS were significantly higher than that in other patients without ACS (pancreatitic infection: 60.0% vs 7.4%, P < 0.001; septic shock: 70.0% vs 11.1%, P < 0.001; MODS: 90.0% vs 31.5%, P < 0.001; mortality: 75.0% vs 3.7%, P < 0.001).
CONCLUSION: IAH/ACS is a frequent finding in patients admitted to the ICU because of AP. Patients with IAP at approximately 10-12 mmHg and early signs of changes in physiologic variables should be seriously considered for urgent decompression to improve survival.
doi:10.3748/wjg.14.3541
PMCID: PMC2716618  PMID: 18567084
Acute pancreatitis; Abdominal compartment syndrome; Intra-abdominal pressure; Intra-abdominal hypertension; Organ dysfunction
7.  The Effect of Intra-Abdominal Hypertension Incorporating Severe Acute Pancreatitis in a Porcine Model 
PLoS ONE  2012;7(3):e33125.
Introduction
Abdominal compartment syndrome (ACS) and intra abdominal hypertension(IAH) are common clinical findings in patients with severe acute pancreatitis(SAP). It is thought that an increased intra abdominal pressure(IAP) is associated with poor prognosis in SAP patients. But the detailed effect of IAH/ACS on different organ system is not clear. The aim of this study was to assess the effect of SAP combined with IAH on hemodynamics, systemic oxygenation, and organ damage in a 12 h lasting porcine model.
Measurements and Methods
Following baseline registrations, a total of 30 animals were divided into 5 groups (6 animals in each group): SAP+IAP30 group, SAP+IAP20 group, SAP group, IAP30 group(sham-operated but without SAP) and sham-operated group. We used a N2 pneumoperitoneum to induce different levels of IAH and retrograde intra-ductal infusion of sodium taurocholate to induce SAP. The investigation period was 12 h. Hemodynamic parameters (CO, HR, MAP, CVP), urine output, oxygenation parameters(e.g., SvO2, PO2, PaCO2), peak inspiratory pressure, as well as serum parameters (e.g., ALT, amylase, lactate, creatinine) were recorded. Histological examination of liver, intestine, pancreas, and lung was performed.
Main Results
Cardiac output significantly decreased in the SAP+IAH animals compared with other groups. Furthermore, AST, creatinine, SUN and lactate showed similar increasing tendency paralleled with profoundly decrease in SvO2. The histopathological analyses also revealed higher grade injury of liver, intestine, pancreas and lung in the SAP+IAH groups. However, few differences were found between the two SAP+IAH groups with different levels of IAP.
Conclusions
Our newly developed porcine SAP+IAH model demonstrated that there were remarkable effects on global hemodynamics, oxygenation and organ function in response to sustained IAH of 12 h combined with SAP. Moreover, our model should be helpful to study the mechanisms of IAH/ACS-induced exacerbation and to optimize the treatment strategies for counteracting the development of organ dysfunction.
doi:10.1371/journal.pone.0033125
PMCID: PMC3293917  PMID: 22403734
8.  Effects of positive end-expiratory pressure on respiratory function and hemodynamics in patients with acute respiratory failure with and without intra-abdominal hypertension: a pilot study 
Critical Care  2009;13(5):R160.
Introduction
To investigate the effects of positive end-expiratory pressure (PEEP) on respiratory function and hemodynamics in patients with acute lung injury (ALI) or acute respiratory distress syndrome (ARDS) with normal intra-abdominal pressure (IAP < 12 mmHg) and with intra-abdominal hypertension (IAH, defined as IAP ≥ 12 mmHg) during lung protective ventilation and a decremental PEEP, a prospective, observational clinical pilot study was performed.
Methods
Twenty patients with ALI/ARDS with normal IAP or IAH treated in the surgical intensive care unit in a university hospital were studied. The mean IAP in patients with IAH and normal IAP was 16 ± 3 mmHg and 8 ± 3 mmHg, respectively (P < 0.001). At different PEEP levels (5, 10, 15, 20 cmH2O) we measured respiratory mechanics, partitioned into its lung and chest wall components, alveolar recruitment, gas-exchange, hemodynamics, extravascular lung water index (EVLWI) and intrathoracic blood volume index (ITBVI).
Results
We found that ALI/ARDS patients with IAH, as compared to those with normal IAP, were characterized by: a) no differences in gas-exchange, respiratory mechanics, partitioned into its lung and chest wall components, as well as hemodynamics and EVLWI/ITBVI; b) decreased elastance of the respiratory system and the lung, but no differences in alveolar recruitment and oxygenation or hemodynamics, when PEEP was increased at 10 and 15cmH2O; c) at higher levels of PEEP, EVLWI was lower in ALI/ARDS patients with IAH as compared with those with normal IAP.
Conclusions
IAH, within the limits of IAP measured in the present study, does not affect interpretation of respiratory mechanics, alveolar recruitment and hemodynamics.
doi:10.1186/cc8118
PMCID: PMC2784387  PMID: 19804634
9.  Intra-Abdominal Hypertension and Gastrointestinal Symptoms in Mechanically Ventilated Patients 
Background. We aimed to describe the incidence of intra-abdominal hypertension (IAH) and gastrointestinal (GI) symptoms and related outcome in mechanically ventilated (MV) patients. Methods. Intra-abdominal pressure (IAP) and gastric residual volumes were measured at least twice daily. IAH was defined as a mean daily value of IAP ≥ 12 mmHg. Results. 398 patients were monitored for all together 2987 days. GI symptom(s) occurred in 80.2% patients. 152 (38.2%) patients developed IAH. Majority (93.4%) of patients with IAH had GI symptoms. The more severe IAH was associated with the higher number of concomitant GI symptoms (P < .001). 142 (35.7%) patients developed both IAH and at least one GI symptom at any time in ICU, and in 77 patients they occurred simultaneously on the same day. This subgroup had the highest ICU mortality (21.8%). In contrast, the small group of patients presenting only IAH, but not GI symptoms (10 patients), had no lethal outcome. Three patients (4.4%) died without showing either IAH or GI symptoms. Conclusions. GI symptoms and IAH often, but not always, occur together. The patients having IAH solely without developing GI symptoms have rather good outcome.
doi:10.1155/2011/982507
PMCID: PMC3087429  PMID: 21547094
10.  Intestinal fatty acid binding protein as a marker for intra-abdominal pressure-related complications in patients admitted to the intensive care unit; study protocol for a prospective cohort study (I-Fabulous study) 
Background
Intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS) have detrimental effects on all organ systems and are associated with increased morbidity and mortality in critically ill patients admitted to an intensive care unit. Intra-bladder measurement of the intra-abdominal pressure (IAP) is currently the gold standard. However, IAH is not always indicative of intestinal ischemia, which is an early and rapidly developing complication. Sensitive biomarkers for intestinal ischemia are needed to be able to intervene before damage becomes irreversible. Gut wall integrity loss, including epithelial cell disruption and tight junctions breakdown, is an early event in intestinal damage. Intestinal Fatty Acid Binding Protein (I-FABP) is excreted in urine and blood specifically from damaged intestinal epithelial cells. Claudin-3 is a specific protein which is excreted in urine following disruption of intercellular tight junctions. This study aims to investigate if I-FABP and Claudin-3 can be used as a diagnostic tool for identifying patients at risk for IAP-related complications.
Methods/Design
In a multicenter, prospective cohort study 200 adult patients admitted to the intensive care unit with at least two risk factors for IAH as defined by the World Society of the Abdominal Compartment Syndrome (WSACS) will be included. Patients in whom an intra-bladder IAP measurement is contra-indicated or impossible and patients with inflammatory bowel diseases that may affect I-FABP levels will be excluded. The IAP will be measured using an intra-bladder technique. During the subsequent 72 hours, the IAP measurement will be repeated every six hours. At these time points, a urine and serum sample will be collected for measurement of I-FABP and Claudin-3 levels. Clinical outcome of patients during their stay at the intensive care unit will be monitored using the Sequential Organ Failure Assessment (SOFA) score.
Discussion
Successful completion of this trial will provide evidence on the eventual role of the biomarkers I-FABP and Claudin-3 in predicting the risk of IAP-associated adverse outcome. This may aid early (surgical) intervention.
Trial registration
The trial is registered at the Netherlands Trial Register (NTR4638).
Electronic supplementary material
The online version of this article (doi:10.1186/s13049-015-0088-0) contains supplementary material, which is available to authorized users.
doi:10.1186/s13049-015-0088-0
PMCID: PMC4324026  PMID: 25591785
Abdominal Compartment Syndrome; Biomarker; Critical care medicine; Intensive Care Unit; Intestinal integrity; Intra-abdominal hypertension; Intra-abdominal pressure; Risk factors
11.  Current recognition and management of intra-abdominal hypertension and abdominal compartment syndrome among tertiary Chinese intensive care physicians*  
This survey was designed to clarify the current understanding and clinical management of intra-abdominal hypertension (IAH)/abdominal compartment syndrome (ACS) among intensive care physicians in tertiary Chinese hospitals. A postal twenty-question questionnaire was sent to 141 physicians in different intensive care units (ICUs). A total of 108 (76.6%) questionnaires were returned. Among these, three quarters worked in combined medical-surgical ICUs and nearly 80% had primary training in internal or emergency medicine. Average ICU beds, annual admission, ICU length of stay, acute physiology and chronic health evaluation (APACHE) II score, and mortality were 18.2 beds, 764.5 cases, 8.3 d, 19.4, and 21.1%, respectively. Of the respondents, 30.6% never measured intra-abdominal pressure (IAP). Although the vast majority of the ICUs adopted the exclusively transvesicular method, the overwhelming majority (88.0%) only measured IAP when there was a clinical suspicion of IAH/ACS and only 29.3% measured either often or routinely. Moreover, 84.0% used the wrong priming saline volume while 88.0% zeroed at reference points which were not in consistence with the standard method for IAP monitoring recommended by the World Society of Abdominal Compartment Syndrome. ACS was suspected mainly when there was a distended abdomen (92%), worsening oliguria (80%), and increased ventilatory support requirement (68%). Common causes for IAH/ACS were “third-spacing from massive volume resuscitation in different settings” (88%), “intra-abdominal bleeding”, and “liver failure with ascites” (52% for both). Though 60% respondents would recommend surgical decompression when the IAP exceeded 25 mmHg, accompanied by signs of organ dysfunction, nearly three quarters of respondents preferred diuresis and dialysis. A total of 68% of respondents would recommend paracentesis in the treatment for ACS. In conclusion, urgent systematic education is absolutely necessary for most intensive care physicians in China to help to establish clear diagnostic criteria and appropriate management for these common, but life-threatening, diseases.
doi:10.1631/jzus.B1000185
PMCID: PMC3030961  PMID: 21265048
Questionnaire; Intra-abdominal pressure; Intra-abdominal hypertension; Decompression laparotomy; Abdominal compartment syndrome
12.  Recognition and management of abdominal compartment syndrome among German pediatric intensivists: results of a national survey 
Annals of Intensive Care  2012;2(Suppl 1):S8.
Introduction
Several decades ago, the beneficial effects of goal-directed therapy, which include decompressive laparotomy (DL) and open abdomen procedures in cases of intra-abdominal hypertension (IAH) in children, were proven in the context of closures of abdominal wall defects and large-for-size organ transplantations. Different neonatologic and pediatric disease patterns are also known to be capable of increasing intra-abdominal pressure (IAP). Nevertheless, a considerable knowledge transfer regarding such risk factors has hardly taken place. When left undetected and untreated, IAH threatens to evolve into abdominal compartment syndrome (ACS), which is accompanied by a mortality rate of up to 60% in children. Therefore, the present study looks at the recognition and knowledge of IAH/ACS among German pediatric intensivists.
Methods
In June 2010, a questionnaire was mailed to the heads of pediatric intensive care units of 205 German pediatric hospitals.
Results
The response rate was 62%. At least one case of IAH was reported by 36% of respondents; at least one case of ACS, by 25%. Compared with adolescents, younger critically ill children appeared to develop IAH/ACS more often. Routine measurements of IAP were said to be performed by 20% of respondents. Bladder pressure was used most frequently (96%) to assess IAP. Some respondents (17%) only measured IAP in cases of organ dysfunction and failure. In 2009, the year preceding this study, 21% of respondents claimed to have performed a DL. Surgical decompression was indicated if signs of organ dysfunction were present. This was also done in cases of at least grade III IAH (IAP > 15 mmHg) without organ impairment.
Conclusions
Although awareness among pediatricians appears to have been increasing over the last decade, definitions and guidelines regarding the diagnosis and management of IAH/ACS are not applied uniformly. This variability could express an ever present lack of awareness and solid prospective data.
doi:10.1186/2110-5820-2-S1-S8
PMCID: PMC3390295  PMID: 22873424
intra-abdominal pressure; intra-abdominal hypertension; abdominal compartment syndrome; children; intensive care unit; questionnaire; decompressive laparotomy.
13.  Early continuous veno-venous haemofiltration in the management of severe acute pancreatitis complicated with intra-abdominal hypertension: retrospective review of 10 years' experience 
Annals of Intensive Care  2012;2(Suppl 1):S21.
Background
Conservative treatment of patients with severe acute pancreatitis (SAP) may be associated with development of intra-abdominal hypertension (IAH), deterioration of visceral perfusion and increased risk of multiple organ dysfunction. Fluid balance is essential for maintenance of adequate organ perfusion and control of the third space. Timely application of continuous veno-venous haemofiltration (CVVH) may help in balancing fluid replacement and removal of cytokines from the blood and tissue compartments. The aim of the present study was to determine whether CVVH can be recommended as a constituent of conservative treatment in patients with SAP who suffer IAH.
Methods
A retrospective analysis of 10 years' experience with low-flow CVVH application in patients with SAP who develop IAH was. In all patients, measurement of the intra-abdominal pressure (IAP) was done indirectly through the urinary bladder. Sequential organ failure assessment (SOFA) score was calculated for severity assessment, and necrotizing forms were verified by contrast-enhanced computed tomography. Dynamics of IAP were analysed in parallel with signs of systemic inflammation, dynamics of C-reactive protein and cumulative fluid balance. All variables, complication rate and outcomes were analysed in the whole group and in patients with IAH (CVVH and no-CVVH groups).
Results
From the total of 130 patients, 75 were treated with application of CVVH and 55 without CVVH. Late hospitalization was associated with application of CVVH. Infection was observed in 28.5% of cases regardless of the type of treatment received, with a similar necessity for surgical intervention. IAH was observed in 68.5% of patients, and they had significantly higher SOFA scores compared to patients with normal IAP. CVVH treatment resulted in negative cumulative fluid balance starting from day 5 in patients with IAH, whereas without this treatment, fluid balance remained increasingly positive after a week. Finally, application of CVVH resulted in a lower infection rate and shorter hospital stay, 26.7% vs. 37.9%, and a median of 32 (interquartile range (IQR) = 60 to 12) days vs. 24 (IQR = 34 to 4) days, p = 0.05, comparing CVVH vs. no-CVVH group. Mortality rate reached 11.7% in the CVVH group and 13.8% in the no-CVVH group.
Conclusions
Early application of CVVH facilitates negative fluid balance and reduction of IAH in patients with SAP; it is not associated with increased infection or mortality rate and may reduce hospital stay.
doi:10.1186/2110-5820-2-S1-S21
PMCID: PMC3527156  PMID: 23281603
14.  Intra-Abdominal Pressure in the Early Phase of Severe Acute Pancreatitis: Canary in a Coal Mine? Results from a Rigorous Validation Protocol 
Gut and Liver  2013;7(6):731-738.
Background/Aims
Intra-abdominal hypertension (IAH) is being increasingly reported in patients with severe acute pancreatitis (SAP) with worsened outcomes. The present study was undertaken to evaluate intra-abdominal pressure (IAP) as a marker of severity in the entire spectrum of acute pancreatitis and to ascertain the relationship between IAP and development of complications in patients with SAP.
Methods
IAP was measured via the transvesical route by measurements performed at admission, once after controlling pain and then every 4 hours. Data were collected on the length of the hospital stay, the development of systemic inflammatory response syndrome (SIRS), multiorgan failure, the extent of necrosis, the presence of infection, pleural effusion, and mortality.
Results
In total, 40 patients were enrolled and followed up for 30 days. The development of IAH was exclusively associated with SAP with an APACHE II score ≥8 and/or persistent SIRS, identifying all patients who were going to develop abdominal compartment syndrome (ACS). The presence of ACS was associated with a significantly increased extent of pancreatic necrosis, multiple organ failure, and mortality. The mean admission IAP value did not differ significantly from the value obtained after pain control or the maximum IAP measured in the first 5 days.
Conclusions
IAH is reliable marker of severe disease, and patients who manifest organ failure, persistent SIRS, or an Acute Physiology and Chronic health Evaluation II score ≥8 should be offered IAP surveillance. Severe pancreatitis is not a homogenous entity.
doi:10.5009/gnl.2013.7.6.731
PMCID: PMC3848541  PMID: 24312716
Intra-abdominal hypertension; Pancreatitis
15.  Effects of intra-abdominal pressure on liver function assessed with the LiMON in critically ill patients 
Canadian Journal of Surgery  2011;54(3):161-166.
Background
Intra-abdominal pressure (IAP) and intra-abdominal hypertension (IAH) are associated with significant morbidity and mortality in critically ill patients. Our aim was to assess the effects of IAH on liver function using the noninvasive liver function monitoring system LiMON and to assess the prognostic value of IAP in critically ill patients.
Methods
We conducted a retrospective analysis of critically ill patients who were treated in the intensive care unit (ICU). The IAP and indocyanine green plasma disappearance rate (ICG-PDR) measurements were made within 24 hours after admission to the ICU and repeated 12 hours later. Intra-abdominal pressure was measured via a Foley bladder catheter, and ICG elimination tests were conducted concurrently using the LiMON.
Results
We included 30 critically ill patients (17 women and 13 men aged 28–89 yr) in our analysis. Statistical analysis showed that the baseline IAP values were significantly higher among nonsurvivors than survivors (19.38 [standard deviation; SD 2.08] v. 13.07 [SD 0.99]). The twelfth-hour IAP values were higher than baseline measurements among nonsurvivors (21.50 [SD 1.96]) and lower than baseline measurements among survivors (11.71 [SD 1.54]); the difference between groups was significant (p < 0.001). The baseline ICG-PDR values were significantly lower among nonsurvivors than survivors (10.86 [SD 3.35] v. 24.51 [SD 6.78]), and the twelfth-hour ICG-PDR values were decreased in all groups; the difference between groups was significant (p < 0.001).
Conclusion
Our results suggest that measurement of ICG-PDR with the LiMON is a good predictor of the effects of IAP on liver function and, thus, can be recommended for the evaluation of critically ill patients.
doi:10.1503/cjs.042709
PMCID: PMC3104306  PMID: 21443832
16.  Matching positive end-expiratory pressure to intra-abdominal pressure improves oxygenation in a porcine sick lung model of intra-abdominal hypertension 
Critical Care  2012;16(5):R208.
Introduction
Intra-abdominal hypertension (IAH) causes atelectasis, reduces lung volumes and increases respiratory system elastance. Positive end-expiratory pressure (PEEP) in the setting of IAH and healthy lungs improves lung volumes but not oxygenation. However, critically ill patients with IAH often suffer from acute lung injury (ALI). This study, therefore, examined the respiratory and cardiac effects of positive end-expiratory pressure in an animal model of IAH, with sick lungs.
Methods
Nine pigs were anesthetized and ventilated (48 +/- 6 kg). Lung injury was induced with oleic acid. Three levels of intra-abdominal pressure (baseline, 18, and 22 mmHg) were randomly generated. At each level of intra-abdominal pressure, three levels of PEEP were randomly applied: baseline (5 cmH2O), moderate (0.5 × intra-abdominal pressure), and high (1.0 × intra-abdominal pressure). We measured end-expiratory lung volumes, arterial oxygen levels, respiratory mechanics, and cardiac output 10 minutes after each new IAP and PEEP setting.
Results
At baseline PEEP, IAH (22 mmHg) decreased oxygen levels (-55%, P <0.001) and end-expiratory lung volumes (-45%, P = 0.007). At IAP of 22 mmHg, moderate and high PEEP increased oxygen levels (+60%, P = 0.04 and +162%, P <0.001) and end-expiratory lung volume (+44%, P = 0.02 and +279%, P <0.001) and high PEEP reduced cardiac output (-30%, P = 0.04). Shunt and dead-space fraction inversely correlated with oxygen levels and end-expiratory lung volumes. In the presence of IAH, lung, chest wall and respiratory system elastance increased. Subsequently, PEEP decreased respiratory system elastance by decreasing chest wall elastance.
Conclusions
In a porcine sick lung model of IAH, PEEP matched to intra-abdominal pressure led to increased lung volumes and oxygenation and decreased chest wall elastance shunt and dead-space fraction. High PEEP decreased cardiac output. The study shows that lung injury influences the effects of IAH and PEEP on oxygenation and respiratory mechanics. Our findings support the application of PEEP in the setting of acute lung injury and IAH.
doi:10.1186/cc11840
PMCID: PMC3682312  PMID: 23098278
17.  Management of intra-abdominal hypertension and abdominal compartment syndrome: a review 
Patients in the intensive care unit (ICU) are at risk of developing of intra abdominal hypertension (IAH) and abdominal compartment syndrome (ACS).
Aim: This review seeks to define IAH and ACS, identify the aetiology and presentation of IAH and ACS, identify IAP measurement techniques, identify current management and discuss the implications of IAH and ACS for nursing practice. A search of the electronic databases was supervised by a health librarian. The electronic data bases Cumulative Index of Nursing and Allied Health Literature (CINAHL); Medline, EMBASE, and the World Wide Web was undertaken from 1996- January 2011 using MeSH and key words which included but not limited to: abdominal compartment syndrome, intra -abdominal hypertension, intra-abdominal pressure in adult populations met the search criteria and were reviewed by three authors using a critical appraisal tool. Data derived from the retrieved material are discussed under the following themes: (1) etiology of intra-abdominal hypertension; (2) strategies for measuring intra-abdominal pressure (3) the manifestation of abdominal compartment syndrome; and (4) the importance of nursing assessment, observation and interventions. Intra-abdominal pressure (IAP) and abdominal compartment syndrome (ACS) have the potential to alter organ perfusion and compromise organ function.
doi:10.1186/1752-2897-8-2
PMCID: PMC3925290  PMID: 24499574
Intra-abdominal pressure; Intra-abdominal hypertension; Abdominal compartment syndrome; Abdominal perfusion pressure
18.  Vacuum-assisted closure device enhances recovery of critically ill patients following emergency surgical procedures 
Critical Care  2009;13(6):R194.
Introduction
Critically ill surgical patients frequently develop intra-abdominal hypertension (IAH) leading to abdominal compartment syndrome (ACS) with subsequent high mortality. We compared two temporary abdominal closure systems (Bogota bag and vacuum-assisted closure (VAC) device) in intra-abdominal pressure (IAP) control.
Methods
This prospective study with a historical control included 66 patients admitted to a medical and surgical intensive care unit (ICU) of a tertiary care referral center (Careggi Hospital, Florence, Italy) from January 2006 to April 2009. The control group included patients consecutively treated with the Bogota bag (Jan 2006-Oct 2007), whereas the prospective group was comprised of patients treated with a VAC. All patients underwent abdominal decompressive surgery. Groups were compared based upon their IAP, SOFA score, serial arterial lactates, the duration of having their abdomen open, the need for mechanical ventilation (MV) along with length of ICU and hospital stay and mortality. Data were collected from the time of abdominal decompression until the end of pressure monitoring.
Results
The Bogota and VAC groups were similar with regards to demography, admission diagnosis, severity of illness, and IAH grading. The VAC system was more effective in controlling IAP (P < 0.01) and normalizing serum lactates (P < 0.001) as compared to the Bogota bag during the first 24 hours after surgical decompression. There was no significant difference between the SOFA scores. When compared to the Bogota, the VAC group had a faster abdominal closure time (4.4 vs 6.6 days, P = 0.025), shorter duration of MV (7.1 vs 9.9 days, P = 0.039), decreased ICU length of stay (LOS) (13.3 vs 19.2 days, P = 0.024) and hospital LOS (28.5 vs 34.9 days; P = 0.019). Mortality rate did not differ significantly between the two groups.
Conclusions
Patients with abdominal compartment syndrome who were treated with VAC decompression had a faster abdominal closure rate and earlier discharge from the ICU as compared to similar patients treated with the Bogota bag.
doi:10.1186/cc8193
PMCID: PMC2811940  PMID: 19961614
19.  Risk factors for intra-abdominal hypertension and abdominal compartment syndrome among adult intensive care unit patients: a systematic review and meta-analysis 
Critical Care  2013;17(5):R249.
Introduction
Although intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS) are associated with substantial morbidity and mortality among critically ill adults, it remains unknown if prevention or treatment of these conditions improves patient outcomes. We sought to identify evidence-based risk factors for IAH and ACS in order to guide identification of the source population for future IAH/ACS treatment trials and to stratify patients into risk groups based on prognosis.
Methods
We searched electronic bibliographic databases (MEDLINE, EMBASE, PubMed, and the Cochrane Database from 1950 until January 21, 2013) and reference lists of included articles for observational studies reporting risk factors for IAH or ACS among adult ICU patients. Identified risk factors were summarized using formal narrative synthesis techniques alongside a random effects meta-analysis.
Results
Among 1,224 citations identified, 14 studies enrolling 2,500 patients were included. The 38 identified risk factors for IAH and 24 for ACS could be clustered into three themes and eight subthemes. Large volume crystalloid resuscitation, the respiratory status of the patient, and shock/hypotension were common risk factors for IAH and ACS that transcended across presenting patient populations. Risk factors with pooled evidence supporting an increased risk for IAH among mixed ICU patients included obesity (four studies; odds ratio (OR) 5.10; 95% confidence interval (CI), 1.92 to 13.58), sepsis (two studies; OR 2.38; 95% CI, 1.34 to 4.23), abdominal surgery (four studies; OR 1.93; 95% CI, 1.30 to 2.85), ileus (two studies; OR 2.05; 95% CI, 1.40 to 2.98), and large volume fluid resuscitation (two studies; OR 2.17; 95% CI, 1.30 to 3.63). Among trauma and surgical patients, large volume crystalloid resuscitation and markers of shock/hypotension and metabolic derangement/organ failure were risk factors for IAH and ACS while increased disease severity scores and elevated creatinine were risk factors for ACS in severe acute pancreatitis patients.
Conclusions
Although several IAH/ACS risk factors transcend across presenting patient diagnoses, some appear specific to the population under study. As our findings were somewhat limited by included study methodology, the risk factors reported in this study should be considered candidate risk factors until confirmed by a large prospective multi-centre observational study.
doi:10.1186/cc13075
PMCID: PMC4057241  PMID: 24144138
20.  Analyzing intra-abdominal pressures and outcomes in patients undergoing emergency laparotomy 
Background:
Studies have documented the impact of intra-abdominal hypertension (IAH) on virtually every organ. However, it still remains strangely underdiagnosed. The aims of the study were to assess, in patients undergoing emergency laparotomy, whether intra-abdominal pressure (IAP) is an independent predictor of morbidity and mortality, to evaluate the effects of IAH, and to identify hidden cases of abdominal compartment syndrome (ACS).
Materials and Methods:
The study comprised 197 patients undergoing emergency laparotomy. IAP was measured preoperatively and then postoperatively at 0, 6, and 24 hours. Duration of hospital stay, occurrence of burst abdomen, and mortality were noted as outcomes.
Results:
At admission, incidence of IAH was 80%. No significant association was found between IAP and occurrence of burst abdomen (P > 0.1). IAP was found to be a significant predictor of mortality in patients undergoing laparotomy (P < 0.001). Elevated IAP was found to affect all the organ systems adversely. The incidence of post-op ACS was 3.05% in the general population and 13.16% in trauma patients. The mortality rate for this subgroup was 100%.
Conclusions:
IAP is a significant predictor of mortality in patients undergoing laparotomy. IAH has detrimental effects on various organ systems. A more frequent monitoring with prompt decompression may be helpful in decreasing the mortality rate. Further studies are required to establish a screening protocol in patients undergoing laparotomy to detect and manage cases of IAH and ACS.
doi:10.4103/0974-2700.70747
PMCID: PMC2966562  PMID: 21063552
Abdominal compartment syndrome; intra-abdominal hypertension; intra-abdominal pressure
21.  Intra-abdominal hypertension and the abdominal compartment syndrome: updated consensus definitions and clinical practice guidelines from the World Society of the Abdominal Compartment Syndrome 
Intensive Care Medicine  2013;39(7):1190-1206.
Purpose
To update the World Society of the Abdominal Compartment Syndrome (WSACS) consensus definitions and management statements relating to intra-abdominal hypertension (IAH) and the abdominal compartment syndrome (ACS).
Methods
We conducted systematic or structured reviews to identify relevant studies relating to IAH or ACS. Updated consensus definitions and management statements were then derived using a modified Delphi method and the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) guidelines, respectively. Quality of evidence was graded from high (A) to very low (D) and management statements from strong RECOMMENDATIONS (desirable effects clearly outweigh potential undesirable ones) to weaker SUGGESTIONS (potential risks and benefits of the intervention are less clear).
Results
In addition to reviewing the consensus definitions proposed in 2006, the WSACS defined the open abdomen, lateralization of the abdominal musculature, polycompartment syndrome, and abdominal compliance, and proposed an open abdomen classification system. RECOMMENDATIONS included intra-abdominal pressure (IAP) measurement, avoidance of sustained IAH, protocolized IAP monitoring and management, decompressive laparotomy for overt ACS, and negative pressure wound therapy and efforts to achieve same-hospital-stay fascial closure among patients with an open abdomen. SUGGESTIONS included use of medical therapies and percutaneous catheter drainage for treatment of IAH/ACS, considering the association between body position and IAP, attempts to avoid a positive fluid balance after initial patient resuscitation, use of enhanced ratios of plasma to red blood cells and prophylactic open abdominal strategies, and avoidance of routine early biologic mesh use among patients with open abdominal wounds. NO RECOMMENDATIONS were possible regarding monitoring of abdominal perfusion pressure or the use of diuretics, renal replacement therapies, albumin, or acute component-parts separation.
Conclusion
Although IAH and ACS are common and frequently associated with poor outcomes, the overall quality of evidence available to guide development of RECOMMENDATIONS was generally low. Appropriately designed intervention trials are urgently needed for patients with IAH and ACS.
Electronic supplementary material
The online version of this article (doi:10.1007/s00134-013-2906-z) contains supplementary material, which is available to authorized users.
doi:10.1007/s00134-013-2906-z
PMCID: PMC3680657  PMID: 23673399
Intra-abdominal hypertension; Abdominal compartment syndrome; Critical care; Grading of Recommendations, Assessment, Development, and Evaluation; Evidence-based medicine; World Society of the Abdominal Compartment Syndrome
22.  A necessary evil? Intra-abdominal hypertension complicating burn patient resuscitation 
Objective
Severe burns are devastating injuries that result in considerable systemic inflammation and often require resuscitation with large volumes of fluid. The result of massive resuscitation is often raised intra-abdominal pressures leading to Intra-abdominal hypertension (IAH) and the secondary abdominal compartment syndrome. The objective of this study is to conduct (1) a 10 year retrospective study to investigate epidemiological factors contributing to burn injuries in Alberta, (2) to characterize fluid management and incidence of IAH and ACS and (3) to review fluid resuscitation with a goal to identify optimal strategies for fluid resuscitation.
Design
A comprehensive 10-year retrospective review of burn injuries from 1999.
Outcome Measures
Age, sex, date, mechanism of injury, location of incident, on scene vitals and GCS, type of transport to hospital and routing, ISS, presenting vitals and GCS, diagnoses, procedures, complications, hospital LOS, ICU LOS, and events surrounding the injury.
Results
One hundred and seventy five patients (79.4% M, 20.6% F) were identified as having traumatic burn injuries with a mean ISS score of 21.8 (±8.3). The mean age was 41.6 (±17.5) (range 14-94) years. Nearly half (49.7%) of patients suffered their injuries at home, 17.7% were related to industrial incidents and 14.3% were MVC related. One hundred and ten patients required ICU admission. ICU LOS 18.5 (±8.8) days. Hospital LOS 38.0 (±37.8) days. The mean extent of burn injury was 31.4 (±20.9) % TBSA. Nearly half of the patients suffered inhalational injuries (mild 12.5%, moderate 13.7%, severe 9.1%). Thirty-nine (22.2%) of patients died from their injuries. Routine IAP monitoring began in September, 2005 with 15 of 28 patients having at least two IAP measurements. The mean IAP was 16.5 (±5.7) cm H2O (range: 1-40) with an average of 58 (±97) IAP measurements per patient. Those patients with IAP monitoring had an average TBSA of 35.0 (±16.0)%, ISS of 47.5 (±7.5). The mean 48 hr fluid balance was 25.6 (±11.1)L exceeding predicted Parkland formula estimates by 86 (±32)%.
Conclusions
Further evaluation of IAP monitoring is needed to further characterize IAP and fluid resuscitation in patients with burn injuries.
doi:10.1186/1752-2897-8-12
PMCID: PMC4134468  PMID: 25132864
Abdominal compartment syndrome; Intra-abdominal hypertension; Burn; Fluid resuscitation; Critical care
23.  Effect of Acute, Slightly Increased Intra-Abdominal Pressure on Intestinal Permeability and Oxidative Stress in a Rat Model 
PLoS ONE  2014;9(10):e109350.
Introduction
Intra-abdominal hypertension (IAH) is known as a common, serious complication in critically ill patients. Bacterial translocation and permeability changes are considered the pathophysiological bases for IAH-induced enterogenic endotoxemia and subsequent multiorgan failure. Nevertheless, the effects of slightly elevated intra-abdominal pressures (IAPs) on the intestinal mucosa and the associated mechanisms remain unclear.
Methods
To investigate the acute effects of different nitrogen pneumoperitoneum grades on colonic mucosa, male Sprague-Dawley rats were assigned to six groups with different IAPs (0 [control], 4, 8, 12, 16, and 20 mmHg, n = 6/group). During 90 min of exposure, we dynamically monitored the heart rate and noninvasive hemodynamic parameters. After gradual decompression, arterial blood gas analyses were conducted. Thereafter, structural injuries to the colonic mucosa were identified using light microscopy. Colon permeability was determined using the expression of tight junction proteins, combined with fluorescein isothiocyanate dextran (FD-4) absorption. The pro-oxidant-antioxidant balance was determined based on the levels of malondialdehyde (MDA) and antioxidant enzymes.
Results
IAH significantly affected the histological scores of the colonic mucosa, tight junction protein expression, mucosal permeability, and pro-oxidant-antioxidant balance. Interestingly, elevations of IAP that were lower than the threshold for IAH also showed a similar, undesirable effect. In the 8 mmHg group, mild hyponatremia, hypocalcemia, and hypoxemia occurred, accompanied by reduced blood and abdominal perfusion pressures. Mild microscopic inflammatory infiltration and increased MDA levels were also detected. Moreover, an 8-mm Hg IAP markedly inhibited the expression of tight junction proteins, although no significant differences in FD-4 permeability were observed between the 0- and 8-mmHg groups.
Conclusions
Acute exposure to slightly elevated IAP may result in adverse effects on intestinal permeability and the pro-oxidant-antioxidant balance. Therefore, in patients with critical illnesses, IAP should be dynamically monitored and corrected, as soon as possible, to prevent intestinal mucosal injury and subsequent gut-derived sepsis.
doi:10.1371/journal.pone.0109350
PMCID: PMC4190173  PMID: 25295715
24.  The secondary abdominal compartment syndrome: not just another post-traumatic complication 
Canadian Journal of Surgery  2008;51(5):399-405.
The secondary abdominal compartment syndrome (ACS) is defined as the presence of organ dysfunction with concurrent intra-abdominal hypertension (IAH) in a scenario lacking primary intraperitoneal injury or intervention. This state appears to be related to visceral, abdominal wall and retroperitoneal edema and ascites induced by resuscitation. Despite a diverse range of associated causes such as pancreatitis, intra-abdominal sepsis, cardiac arrest, thermal injury and extraperitoneal trauma, this class of ACS is characterized by the presence of shock requiring aggressive fluid resuscitation. Secondary ACS is an extreme condition along a continuum of raised intra-abdominal pressure (IAP) that is pathoneumonic when associated with new overt organ failure. When IAP is above normal but is not associated with organ failure, IAH is diagnosed. Because these conditions are common among critically ill patients, the measurement of IAP is crucial. It is unclear whether preventing IAH reduces progression to ACS or influences outcomes. When overt ACS is confirmed, immediate surgical decompression of the patient's abdomen via a standard laparotomy is usually required. Because many disease processes resulting in critical illness require aggressive fluid resuscitation as a primary therapy, it is likely that secondary ACS is much more common than previously believed. Further study is needed.
PMCID: PMC2556543  PMID: 18841232
25.  Clinical review: Intra-abdominal hypertension: does it influence the physiology of prone ventilation? 
Critical Care  2010;14(4):232.
Prone ventilation (PV) is a ventilatory strategy that frequently improves oxygenation and lung mechanics in critical illness, yet does not consistently improve survival. While the exact physiologic mechanisms related to these benefits remain unproven, one major theoretical mechanism relates to reducing the abdominal encroachment upon the lungs. Concurrent to this experience is increasing recognition of the ubiquitous role of intra-abdominal hypertension (IAH) in critical illness, of the relationship between IAH and intra-abdominal volume or thus the compliance of the abdominal wall, and of the potential difference in the abdominal influences between the extrapulmonary and pulmonary forms of acute respiratory distress syndrome. The present paper reviews reported data concerning intra-abdominal pressure (IAP) in association with the use of PV to explore the potential influence of IAH. While early authors stressed the importance of gravitationally unloading the abdominal cavity to unencumber the lung bases, this admonition has not been consistently acknowledged when PV has been utilized. Basic data required to understand the role of IAP/IAH in the physiology of PV have generally not been collected and/or reported. No randomized controlled trials or meta-analyses considered IAH in design or outcome. While the act of proning itself has a variable reported effect on IAP, abundant clinical and laboratory data confirm that the thoracoabdominal cavities are intimately linked and that IAH is consistently transmitted across the diaphragm - although the transmission ratio is variable and is possibly related to the compliance of the abdominal wall. Any proning-related intervention that secondarily influences IAP/IAH is likely to greatly influence respiratory mechanics and outcomes. Further study of the role of IAP/IAH in the physiology and outcomes of PV in hypoxemic respiratory failure is thus required. Theories relating inter-relations between prone positioning and the abdominal condition are presented to aid in designing these studies.
doi:10.1186/cc9099
PMCID: PMC2945095  PMID: 20804560

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