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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 Abdominal Compartment Society (www.wsacs.org) previously created highly cited Consensus Definitions/Management Guidelines related to intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS). Implicit in this previous work, was a commitment to regularly reassess and update in relation to evolving research. Two years preceding the Fifth World Congress on Abdominal Compartment Syndrome, an International Guidelines committee began preparation. An oversight/steering committee formulated key clinical questions regarding IAH/ /ACS based on polling of the Executive to redundancy, structured according to the Patient, Intervention, Comparator, and Outcome (PICO) format. Scientific consultations were obtained from Methodological GRADE experts and a series of educational teleconferences were conducted to educate scientific review teams from among the wscacs. org membership. Each team conducted systematic or structured reviews to identify relevant studies and prepared evidence summaries and draft Grades of Recommendation Assessment, Development and Evaluation (GRADE) recommendations. The evidence and draft recommendations were presented and debated in person over four days. Updated consensus definitions and management statements were derived using a modified Delphi method. A writingcommittee subsequently compiled the results utilizing frequent Internet discussion and Delphi voting methods to compile a robust online Master Report and a concise peer-reviewed summarizing publication. A dedicated Paediatric Guidelines Subcommittee reviewed all recommendations and either accepted or revised them for appropriateness in children. Of the original 12 IAH/ACS definitions proposed in 2006, three (25%) were accepted unanimously, with four (33%) accepted by > 80%, and four (33%) accepted by > 50%, but required discussion to produce revised definitions. One (8%) was rejected by > 50%. In addition to previous 2006 definitions, the panel also defined the open abdomen, lateralization of the abdominal musculature, polycompartment syndrome, abdominal compliance, and suggested a refined open abdomen classification system. Recommendations were possible regarding intra-abdominal pressure (IAP) measurement, approach to sustained IAH, philosophy of protocolized IAP management and same-hospital-stay fascial closure, use of decompressive laparotomy, and negative pressure wound therapy. Consensus suggestions included use of non-invasive therapies for treating IAH/ACS, considering body position and IAP, damage control resuscitation, prophylactic open abdomen usage, and prudence in early biological mesh usage. No recommendations were made for the use of diuretics, albumin, renal replacement therapies, and utilizing abdominal perfusion pressure as a resuscitation-endpoint. Collaborating Methodological Guideline Development and Clinical Experts produced Consensus Definitions/Clinical Management statements encompassing the most contemporary evidence. Data summaries now exist for clinically relevant IAH/ACS questions, which will facilitate future scientific reanalysis.

Intra-abdominal hypertension (IAH) is an important contributor to early organ dysfunction among patients with trauma and sepsis. However, the impact of increased intra-abdominal pressure (IAP) among pediatric, pregnant, non-septic medical patients, and those with severe acute pancreatitis (SAP), obesity, and burns has been studied less extensively. The aim of this review is to outline the pathophysiologic implications and treatment options for IAH and abdominal compartment syndrome (ACS) for the above patient populations. We searched MEDLINE and PubMed to identify relevant studies. There is an increasing awareness of IAH in general medicine. The incidence of IAH and, to a lesser extent, ACS is high among patients with SAP. IAH should always be suspected and IAP measured routinely. In children, normal IAP in mechanically ventilated patients is approximately 7 ± 3 mm Hg. As an IAP of 10-15 mm Hg has been associated with organ damage in children, an IAP greater than 10 mm Hg should be considered IAH in these patients. Moreover, as ACS may occur in children at an IAP lower than 20 mm Hg, any elevation in IAP higher than 10 mm Hg associated with new organ dysfunction should be considered ACS in children until proven otherwise. Monitor IAP trends and be aware that specific interventions may need to be instituted at lower IAP than the current ACS definitions accommodate. Finally, IAH and ACS can occur both in abdominal trauma and extra-abdominal trauma patients. Early mechanical hemorrhage control and the avoidance of excessive fluid resuscitation are key elements in preventing IAH in trauma patients. IAH and ACS have been associated with many conditions beyond the general ICU patient. In adults and in children, the focus should be on the early recognition of IAH and the prevention of ACS. Patients at risk for IAH should be identified early during their treatment (with a low threshold to initiate IAP monitoring). Appropriate actions should be taken when IAP increases above 20 mm Hg, especially in patients developing difficulty with ventilation. Although on-operative measures should be instituted first, one should not hesitate to resort to surgical decompression if they fail.

Over the last few decades, increasing attention has been paid to understanding the pathophysiology, aetiology, prognosis, and treatment of elevated intra-abdominal pressure (IAP) in trauma, surgical, and medical patients. However, there is presently a relatively poor understanding of intra-abdominal volume (IAV) and the relationship between IAV and IAP (i.e. abdominal compliance). Consensus definitions on Cab were discussed during the 5th World Congress on Abdominal Compartment Syndrome and a writing committee was formed to develop this article. During the writing process, a systematic and structured Medline and PubMed search was conducted to identify relevant studies relating to the topic. According to the recently updated consensus definitions of the World Society on Abdominal Compartment Syndrome (WSACS), abdominal compliance (Cab) is defined as a measure of the ease of abdominal expansion, which is determined by the elasticity of the abdominal wall and diaphragm. It should be expressed as the change in IAV per change in IAP (mL [mm Hg]⁻¹). Importantly, Cab is measured differently than IAP and the abdominal wall (and its compliance) is only a part of the total abdominal pressure-volume (PV) relationship. During an increase in IAV, different phases are encountered: the reshaping, stretching, and pressurisation phases. The first part of this review article starts with a comprehensive list of the different definitions related to IAP (at baseline, during respiratory variations, at maximal IAV), IAV (at baseline, additional volume, abdominal workspace, maximal and unadapted volume), and abdominal compliance and elastance (i.e. the relationship between IAV and IAP). An historical background on the pathophysiology related to IAP, IAV and Cab follows this. Measurement of Cab is difficult at the bedside and can only be done in a case of change (removal or addition) in IAV. The Cab is one of the most neglected parameters in critically ill patients, although it plays a key role in understanding the deleterious effects of unadapted IAV on IAP and end-organ perfusion. The definitions presented herein will help to understand the key mechanisms in relation to Cab and clinical conditions and should be used for future clinical and basic science research. Specific measurement methods, guidelines and recommendations for clinical management of patients with low Cab are published in a separate review.

A compartment syndrome is defined as an increase in the compartmental pressure to such an extent that the viability of the tissues and organs within the compartment are threatened. The term describes a syndrome and not a disease, and as such there are many diseases and underlying pathophysiological processes that may lead to such a scenario. The aim of this review is to give a state-of-the-art overview on the current knowledge on different compartment syndromes and how they may interact. Suggested definitions are included. There are four major compartments in the human body: the head, chest, abdomen, and the extremities. Initially, the term multicompartment syndrome was suggested when more than one compartment was affected. But this led to confusion as the term multi- or multiple compartment syndromes is mostly used in relation to multiple limb trauma leading to compartment syndrome requiring fasciotomy. Only recently was the term 'polycompartment syndrome' coined to describe a condition where two or more anatomical compartments have elevated pressures. When more than one compartment is affected, an exponential detrimental effect on end-organ function to both immediate and distant organs can occur. Within each compartment, the disease leading towards a compartment syndrome can be primary or secondary. The compliance of each compartment is the key to determining the transmission of a given compartmental pressure from one compartment to another. The intra-abdominal pressure helps to explain the severe pathophysiological condition occurring in patients with cardiorenal, hepatopulmonary and hepatorenal syndromes. Initial treatment of a compartment syndrome should be focused on the primary compartment and is based on three principles: lowering of compartmental pressure, supporting organ perfusion, and optimisation and prevention of specific adverse events. Clinicians need to be aware of the existence of the polycompartment syndrome and the interactions of increased compartmental pressures between compartments.

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.