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Intra-abdominal hypertension (IAH) is common and associated with morbidity and mortality in critically ill patients. IAH exists along a continuum that begins with a mild asymptomatic elevation of intra-abdominal pressure (IAP) and extends to life-threatening abdominal compartment syndrome (ACS). In 2013, evidence-based guidelines were published on the definitions, diagnosis, and treatment of IAH and ACS. Even using these guidelines, making bedside decisions regarding management of individual patients with IAH/ACS remains challenging due to the wide variety of conditions associated with IAH/ACS, the varying degrees of associated organ dysfunction, and the large number of available treatment options. Using a simplified treatment paradigm, we advocate that the optimal treatment strategy should not be based purely on the degree of IAP alone, but on three critical elements: the magnitude of IAP, the degree and dynamics of organ dysfunction (or thus the impact of increased IAP), and the etiology of increased IAP. In this chapter, we propose a conceptual framework of how to diagnose and manage patients with IAH/ACS, taking into account patient physiology, current scientific evidence, and experience. In this practical and clinical approach, both the necessity and urgency of intervention are discussed.

Although the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic is lasting for more than 1 year, the exposition risks of health-care providers are still unclear. Available evidence is conflicting. We investigated the prevalence of antibodies against SARS-CoV-2 in the staff of a large public hospital with multiple sites in the Antwerp region of Belgium. Risk factors for infection were identified by means of a questionnaire and human resource data. We performed hospital-wide serology tests in the weeks following the first epidemic wave (16 March to the end of May 2020) and combined the results with the answers from an individual questionnaire. Overall seroprevalence was 7.6%. We found higher seroprevalences in nurses [10.0%; 95% confidence interval (CI) 8.9-11.2] than in physicians 6.4% (95% CI 4.6-8.7), paramedical 6.0% (95% CI 4.3-8.0) and administrative staff (2.9%; 95% CI 1.8-4.5). Staff who indicated contact with a confirmed coronavirus disease 2019 (COVID-19) colleague had a higher seroprevalence (12.0%; 95% CI 10.7-13.4) than staff who did not (4.2%; 95% CI 3.5-5.0). The same findings were present for contacts in the private setting. Working in general COVID-19 wards, but not in emergency departments or intensive care units, was also a significant risk factor. Since our analysis points in the direction of active SARS-CoV-2 transmission within hospitals, we argue for implementing a stringent hospital-wide testing and contact-tracing policy with special attention to the health care workers employed in general COVID-19 departments. Additional studies are needed to establish the transmission dynamics. European Research Council (ERC) under the European UnionEuropean Research Council (ERC) [682540 TransMID]

Intra-abdominal hypertension (IAH) is an important contributor to early organ dysfunction in trauma and sepsis. However, relatively little is known about the impact of intra-abdominal pressure (IAP) in general internal medicine, pregnant patients, and those with obesity or burns. The aim of this paper is to review the pathophysiologic implications and treatment options for IAH in these specific situations. A MEDLINE and PubMed search was performed and the resulting body-of-evidence included in the current review on the basis of relevance and scientific merit. There is increasing awareness of the role of IAH in different clinical situations. Specifically, IAH will develop in most (if not all) severely burned patients, and may contribute to early mortality. One should avoid over-resuscitation of these patients with large volumes of fluids, especially crystalloids. Acute elevations in IAP have similar effects in obese patients compared to non-obese patients, but the threshold IAP associated with organ dysfunction may be higher. Chronic elevations in IAP may, in part, be responsible for the pathogenesis of obesity-related co-morbid conditions such as hypertension, pseudotumor cerebri, pulmonary dysfunction, gastroesophageal reflux disease, and abdominal wall hernias. At the bedside, measuring IAP and considering IAH in all critical maternal conditions is essential, especially in preeclampsia/eclampsia where some have hypothesized that IAH may have an additional role. IAH in pregnancy must take into account the precautions for aorto-caval compression and has been associated with ovarian hyperstimulation syndrome. Recently, IAP has been associated with the cardiorenal dilemma and hepatorenal syndrome, and this has led to the recognition of the polycompartment syndrome. In conclusion, IAH and ACS have been associated with several patient populations beyond the classical ICU, surgical, and trauma patients. In all at risk conditions the focus should be on the early recognition of IAH and prevention of ACS. Patients at risk for IAH should be identified early through measurements of IAP. Appropriate actions should be taken when IAP increases above 15 mm Hg, especially if pressures reach above 20 mm Hg with new onset organ failure. Although non-operative measures come first, surgical decompression must not be delayed if these fail. Percutaneous drainage of ascites is a simple and potentially effective tool to reduce IAP if organ dysfunction develops, especially in burn patients. Escharotomy may also dramatically reduce IAP in the case of abdominal burns.

In the future, medical management may play an increasingly important role in the prevention and management of intra-abdominal hypertension (IAH). A review of different databases was used (PubMed, MEDLINE and EMBASE) with the search terms 'Intra-abdominal Pressure' (IAP), 'IAH', ' Abdominal Compartment Syndrome' (ACS), 'medical management' and 'non-surgical management'. We also reviewed all papers with the search terms 'IAH', 'IAP' and 'ACS' over the last three years, only extracting those papers which showed a novel approach in the non-surgical management of IAH and ACS.IAH and ACS are associated with increased morbidity and mortality. Non-surgical management is an important treatment option in critically ill patients with raised IAP. There are five medical treatment options to be considered to reduce IAP: 1) improvement of abdominal wall compliance; 2) evacuation of intra-luminal contents; 3) evacuation of abdominal fluid collections; 4) optimisation of fluid administration; and 5) optimisation of systemic and regional perfusion. This paper will review the first three treatment arms of the WSACS algorithm: abdominal wall compliance; evacuation of intra-luminal contents and evacuation of abdominal fluid collections. Emerging medical treatments will be analysed and finally some alternative specific treatments will be assessed. Other treatment options with regard to optimising fluid administration and systemic and regional perfusion will be described elsewhere, and are beyond the scope of this review. Medical management of critically ill patients with raised IAP should be instigated early to prevent further organ dysfunction and to avoid progression to ACS. Many treatment options are available and are often part of routine daily management in the ICU (nasogastric, rectal tube, prokinetics, enema, sedation, body position). Some of the newer treatments are very promising options in specific patient populations with raised IAP. Future studies are warranted to confirm some of these findings.

Intra-abdominal hypertension (IAH) is an important contributor to early organ dysfunction in trauma and sepsis. However, relatively little is known about the impact of intra-abdominal pressure (IAP) in general internal medicine, pregnant patients, and those with obesity or burns. The aim of this paper is to review the pathophysiologic implications and treatment options for IAH in these specific situations. A MEDLINE and PubMed search was performed and the resulting body-of-evidence included in the current review on the basis of relevance and scientific merit. There is increasing awareness of the role of IAH in different clinical situations. Specifically, IAH will develop in most (if not all) severely burned patients, and may contribute to early mortality. One should avoid over-resuscitation of these patients with large volumes of fluids, especially crystalloids. Acute elevations in IAP have similar effects in obese patients compared to non-obese patients, but the threshold IAP associated with organ dysfunction may be higher. Chronic elevations in IAP may, in part, be responsible for the pathogenesis of obesity-related co-morbid conditions such as hypertension, pseudotumor cerebri, pulmonary dysfunction, gastroesophageal reflux disease, and abdominal wall hernias. At the bedside, measuring IAP and considering IAH in all critical maternal conditions is essential, especially in preeclampsia/eclampsia where some have hypothesized that IAH may have an additional role. IAH in pregnancy must take into account the precautions for aorto-caval compression and has been associated with ovarian hyperstimulation syndrome. Recently, IAP has been associated with the cardiorenal dilemma and hepatorenal syndrome, and this has led to the recognition of the polycompartment syndrome. In conclusion, IAH and ACS have been associated with several patient populations beyond the classical ICU, surgical, and trauma patients. In all at risk conditions the focus should be on the early recognition of IAH and prevention of ACS. Patients at risk for IAH should be identified early through measurements of IAP. Appropriate actions should be taken when IAP increases above 15 mm Hg, especially if pressures reach above 20 mm Hg with new onset organ failure. Although non-operative measures come first, surgical decompression must not be delayed if these fail. Percutaneous drainage of ascites is a simple and potentially effective tool to reduce IAP if organ dysfunction develops, especially in burn patients. Escharotomy may also dramatically reduce IAP in the case of abdominal burns.

The recent definitions on intra-abdominal pressure (IAP), intra-abdominal volume (IAV) and abdominal compliance (Cab) are a step forward in understanding these important concepts. They help our understanding of the pathophysiology, aetiology, prognosis, and treatment of patients with low Cab. However, there is still a relatively poor understanding of the different methods used to measure IAP, IAV and Cab and how certain conditions may affect the results. This review will give a concise overview of the different methods to assess and estimate Cab; it will list important conditions that may affect baseline values and suggest some therapeutic options. Abdominal compliance (Cab), defined as a measure of the ease of abdominal expansion, is measured differently than IAP. The compliance of the abdominal wall is only a part of the total abdominal pressure-volume (PV) relationship. Measurement or estimation of Cab is difficult at the bedside and can only be done in a case of change (removal or addition) in IAV. The different measurement techniques will be discussed in relation to decreases (ascites drainage, haematoma evacuation, gastric suctioning) or increases in IAV (gastric insufflation, laparoscopy with CO₂ pneumoperitoneum, peritoneal dialysis). More specific techniques using the interactions between the thoracic and abdominal compartment during positive pressure ventilation will also be discussed (low flow PV loop, respiratory IAP variations, respiratory abdominal variation test, mean IAP and abdominal pressure variation), together with the concept of the polycompartment model. The relation between IAV and IAP is linear at low IAV and becomes curvilinear and exponential at higher volumes. Specific conditions in relation to increased (previous pregnancy or laparoscopy, gynoid fat distribution, ellipse-shaped internal abdominal perimeter) or decreased Cab (obesity, fluid overload, android fat distribution, sphere-shaped internal abdominal perimeter) will be discussed as well as their impact on baseline IAV, IAP, reshaping capacity and abdominal workspace volume. Finally, we suggest possible treatment options in situations of unadapted IAV according to existing Cab, which results in high IAP. A large overlap exists between the treatment of patients with abdominal hypertension and those with low Cab. The Cab plays a key role in understanding the deleterious effects of unadapted IAV on IAP and end-organ perfusion and function. If we can identify patients with low Cab, we can anticipate and select the most appropriate surgical treatment to avoid complications such as IAH or ACS.

This review will describe the definitions on intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS). In order to understand these definitions the reader must be aware of the interactions between intra-abdominal pressure (IAP) and intra-abdominal volume (IAV), explaining why dramatic IAP increases can be observed in some patients related to anthropomorphic measurements, body positioning, use of positive pressure ventilation, or relatively small accumulations of fluid or blood. The adverse effects related to increased IAP have been named IAH for moderate cases and ACS for advanced cases. In order to improve clinical communication as well as evaluation of the scientific literature, the World Society for the Abdominal Compartment Syndrome (WSACS) has published its first guidelines and definitions in 2006. The definitions and guidelines have recently been revised according to evidence based medicine and the Grading of Recommendations Assessment, Development and Evaluation (GRADE) methodology. This review will be based on the revised guidelines. The standard method to measure IAP is via the bladder and as experience with IAP measurement has evolved considerably, a number of tips and potential pitfalls are listed.

BACKGROUND: Monitoring hepatic blood flow and function might be crucial in treating critically ill patients. Intra-abdominal hypertension is associated with decreased abdominal blood flow, organ dysfunction, and increased mortality. The plasma disappearance rate (PDR) of indocyanine green (ICG) is considered to be a compound marker for hepatosplanchnic perfusion and hepatocellular membrane transport and correlates well with survival in critically ill patients. However, correlation between PDRICG and intra-abdominal pressure (IAP) remains poorly understood. The aim of this retrospective study was to investigate the correlation between PDRICG and classic liver laboratory parameters, IAP and abdominal perfusion pressure (APP). The secondary goal was to evaluate IAP, APP, and PDRICG as prognostic factors for mortality. METHODS: A total of 182 paired IAP and PDRICG measurements were performed in 40 critically ill patients. The mean values per patient were used for comparison. The IAP was measured using either a balloon-tipped stomach catheter connected to an IAP monitor (Spiegelberg, Hamburg, Germany, or CiMON, Pulsion Medical Systems, Munich, Germany) or a bladder FoleyManometer (Holtech Medical, Charlottenlund, Denmark). PDRICG was measured at the bedside using the LiMON device (Pulsion Medical Systems, Munich, Germany). Primary endpoint was hospital mortality. RESULTS: There was no significant correlation between PDRICG and classic liver laboratory parameters, but PDRICG did correlate significantly with APP (R = 0.62) and was inversely correlated with IAP (R = -0.52). Changes in PDRICG were associated with significant concomitant changes in APP (R = 0.73) and opposite changes in IAP (R = 0.61). The IAP was significantly higher (14.6 ± 4.6 vs. 11.1 ± 5.3 mmHg, p = 0.03), and PDRICG (10 ± 8.3 vs. 15.9 ± 5.2%, p = 0.02) and APP (43.6 ± 9 vs. 57.9 ± 12.2 mmHg, p < 0.0001) were significantly lower in non-survivors. CONCLUSIONS: PDRICG is positively correlated to APP and inversely correlated to IAP. Changes in APP areassociated with significant concomitant changes in PDRICG, while changes in IAP are associated with opposite changes in PDRICG, suggesting that an increase in IAP may compromise hepatosplanchnic perfusion. Both PDRICG and IAP are correlated with outcome. Measurement of PDRICG may be a useful additional clinical tool to assess the negative effects of increased IAP on liver perfusion and function.

We read with interest the article byBecker et al. [1] looking at the cor-relation between directintraabdominal pressure (IAP) andpressures in the stomach obtained viaa balloon-tipped catheter in tenpatients with cirrhosis. We agree thatthe CiMON system needs to be clin-ically validated. However, we feel theauthors misinterpret their data statingthat the CiMON device cannot beregarded as a reliable substitute forstandard IAP measurement tech-niques, for the simple reason that nogold standard IAP technique wasused. The sample size is small, andthere are issues about themethodology.First, the statistical linear regres-sion analysis used suffers from anessential misconception. On average,approximately nine repeated sets ofmeasurements were collected fromten patients, giving a total of 90paired measurements. This meansthat there were two sources of varia-tion that have to be distinguished: thebetween-patients variation and thewithin-patients variation. This paperdeals mainly with the second kind ofvariation in view of the small samplesize and the (high) number ofrepeated measurements. However,instead of analysing the within-patients variation, the data weretreated as if they came from onepatient. Although it is not sure thatthis was the case, this kind of analysismay produce erroneous results [2, 3].Second, the major drawback isthat no clinically acceptable goldstandard method for IAP measure-ment like bladder pressure was used.We don’t agree with the statementthat the gold standard in experimen-tal studies is direct monitoring ofintraperitoneal pressure. This mayhold true for animal research; how-ever, this is not in accordance withthe latest recommendations for clin-ical research [4–6].Third, the population under studyis not homogeneous since somepatients were mechanically venti-lated, while others were not, and thedemographics were only brieflydescribed. The patient sample wasprobably more convenient than a realcohort sample, which is not a fair wayto validate a new measurementmethod [7]. The evolution ofabdominal wall compliance (Cab)could have been calculated as shownin Table 1 and Fig. 1.Finally, although the authors cor-rectly state some limitations of theirstudy, they try to explain the observeddifferences by alluding to the relativeposition of the probes. This suggeststhey do not consider the abdomen tobe primarily fluid in character, hencenot following the laws of Pascal. Isthis the case? Decramer [8] reportedindeed that gastric pressure swings indogs were not simply hydrostatic.This study found the abdomen notbehaving as a hydraulic system orliquid-filled container. However, theIAP differences observed in the dogsdisappeared when the abdominalcavity was filled with 2 l of saline.9] measuredpressures in the abdomen next to theventral abdominal wall and within thestomach of anaesthetised dogs, andconcluded there were three factorsaffecting IAP: gravity, uniform com-pression and shear deformation. In1996, Tzelepis [10] re-established theconcept that the abdomen behaves asa hydraulic system. Based on theavailable data, we hypothesise theimpact of the above-mentioned threefactors on the measurement of IAP isprobably not significant in the fullysedated mechanically ventilatedpatient with sepsis, capillary leak anda positive fluid balance, with orwithout neuromuscular blockingagents [11]. Therefore, in situationsof large amounts of intraperitonealfluid (as was the case in the presentstudy), the abdomen does probablybehave as a hydraulic container, and

Surveillance for intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS) should be implemented in every intensive care unit (ICU), because it has been demonstrated that surveillance is effective. Several criteria that have led to the conclusion that IAH/ACS monitoring is of value: First, IAH is a frequent problem in critically ill patients that directly affects function of all organ systems to some degree, and that is associated with considerable mortality. Furthermore, simple tools for intra-abdominal pressure (IAP) monitoring are available, and it can be safely applied without the need for advanced tools. Finally, both ACS and IAH can be treated with either medical or surgical interventions. Treatment for IAH/ACS should be selected on the basis of the severity of symptoms and the cause of IAH. IAP monitoring should also be incorporated in the daily ICU management of the patient.