Intra-abdominal hypertension and abdominal compartment syndrome

BACKGROUND: The effects of increased intra-abdominal pressure in various organ systems have been noted over the past century. The concept of abdominal compartment syndrome has gained more attention in both trauma and general surgery in the last decade. This article reviews the current understanding and management of intra-abdominal hypertension and abdominal compartment syndrome. METHODS: Relevant information was gathered from a Medline search of the English literature, previous review and original articles, references cited in papers, and by checking the latest issues of appropriate journals. RESULTS AND CONCLUSION: Akin to compartment syndrome in extremities, the pathophysiological effects of increased intra-abdominal pressure developed well before any clinical evidence of compartment syndrome. These effects include cardiovascular, pulmonary, renal and intracranial derangement, reduction of intestinal and hepatic blood flow, and reduction of abdominal wall compliance. Although abdominal compartment syndrome is more commonly noted in patients with abdominal trauma, it is now evident that non-trauma surgical patients could also develop the condition. Early initiation of treatment for intra-abdominal hypertension is currently advocated in view of the possibility of subclinical progress to the full-blown abdominal compartment syndrome.     

Intra-abdominal hypertension and the abdominal compartment syndrome

The pressure within the abdominal cavity is normally little more than atmospheric pressure. However, even small increases in intra-abdominal pressure can have adverse effects on renal function, cardiac output, hepatic blood flow, respiratory mechanics, splanchnic perfusion and intracranial pressure. Although intra-abdominal pressure can be measured directly, this is invasive and bedside measurement of intra-abdominal pressure is usually achieved via the urinary bladder. This cheap, easy approach has been shown to produce results that correlate closely with directly measured abdominal pressures. Significant increases in intra-abdominal pressure are seen in a wide variety of conditions commonly encountered in the intensive care unit, such as ruptured aortic aneurysm, abdominal trauma and acute pancreatitis. Abdominal compartment syndrome describes the combination of increased intra-abdominal pressure and end-organ dysfunction. This syndrome has a high mortality, most deaths resulting from sepsis and multi-organ failure. Detection of abdominal compartment syndrome requires close surveillance of intra-abdominal pressure in patients thought to be at risk of developing intra-abdominal hypertension. The only available treatment for established abdominal compartment syndrome is decompressive laparotomy. Prevention of abdominal compartment syndrome after laparotomy by adoption of an open abdomen approach may be preferable in the patient at significant risk of developing intra-abdominal hypertension, but this has not been demonstrated in any large trials. Most surgeons prefer to adopt a 'wait and see' policy, only intervening when clinical deterioration is associated with a significant increase in intra-abdominal pressure.     

Intra-abdominal hypertension and the abdominal compartment syndrome

BACKGROUND: Abdominal compartment syndrome (ACS) occurs when intra-abdominal pressure is abnormally high in association with organ dysfunction. It tends to have a poor outcome, even when treated promptly by abdominal decompression. METHODS: A search of the Medline database was performed to identify articles related to intra-abdominal hypertension and ACS. RESULTS: Currently there is no agreed definition or management of ACS. However, it is suggested that intra-abdominal pressure should be measured in patients at risk, with values above 20 mmHg being considered abnormal in most. Abdominal decompression should be considered in patients with rising pressure and organ dysfunction, indicated by increased airway pressure, reduced cardiac output and oliguria. Organ dysfunction often occurs at an intra-abdominal pressure greater than 35 mmHg and may start to develop between 26 and 35 mmHg. The mean survival rate of patients affected by compartment syndrome is 53 per cent. CONCLUSION: The optimal time for intervention is not known, but outcome is often poor, even after decompression. Most of the available information relates to victims of trauma rather than general surgical patients.     

Intra-abdominal hypertension and abdominal compartment syndrome in burn patients

BACKGROUND: Intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS) are known to occur in patients after major abdominal surgery. The incidence of IAH and ACS in the burn population is not known. METHODS: We prospectively recorded the intra-abdominal pressures of major burn patients admitted to our burn center from February 1999 to September 1999. A bladder pressure greater than 25 mm Hg was diagnosed as IAH. ACS was diagnosed when pulmonary compliance decreased in association with persistent IAH and was treated with abdominal decompression. RESULTS: Ten patients were placed on the protocol; of these, seven developed IAH. Five responded to conservative treatment. Two patients with 80% body surface area burns developed ACS and required decompression. CONCLUSIONS: IAH occurs commonly in major burn patients, and ACS is seen regularly in patients with more than 70% body surface area burns. We recommend bladder pressure measurements after infusion of more than 0.25 L/kg during the acute resuscitation phase and for peak inspiratory pressures greater than 40 cm H2O. Whereas ACS warrants surgical decompression of the abdominal cavity, IAH usually responds to conservative therapy.     

Intra-abdominal hypertension and abdominal compartment syndrome: the journey forward

Intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS) are recognized causes of significant morbidity and mortality among a wide variety of critically ill patient populations. Our understanding of IAH and ACS as causes of organ failure and patient death has increased significantly over the past two decades since their "rediscovery" as clinically important disease processes. The development of consensus definitions and recommendations for the diagnosis and management of IAH/ACS, patient care algorithms, an international clinical research working group, and other educational tools have advanced efforts to improve patient outcome. Nonoperative management strategies to reduce elevated intra-abdominal pressure (IAP) and early surgical intervention for refractory IAH/ACS have been demonstrated to significantly improve patient survival. It is only through such a comprehensive, goal-directed approach that patient outcome will continue to improve. Despite the significant advances that have been made, the journey toward conquering IAH/ACS as a cause of patient death after injury and/or illness has only just begun. It is remarkable to consider that two decades ago, IAH, the detrimental physiological effects of elevated IAP and ACS, the development of IAH-induced organ dysfunction and failure were essentially unrecognized as causes of morbidity and mortality among critically ill adult and pediatric patients. It is not because these disease processes have been recently discovered. The pathophysiological impact of elevated IAP on cardiac, pulmonary, and renal function was well defined over 150 years ago. It has only been within the past 15 years that physicians and nurses worldwide rediscovered this long-forgotten pathophysiological knowledge and began to actively reconsider these two disease processes in their patient's daily differential diagnosis. Originally considered diseases affecting solely the traumatically injured, IAH and ACS are now recognized to occur in both medical and surgical patients of any age and to result from a wide range of injuries and disease processes. Tremendous progress has been made in recent years with regard to our understanding of the diagnosis and management of IAH and ACS. Within this special supplement of The American Surgeon, you will find a series of "state-of-the-art" reviews authored by a number of the world's experts on IAH/ACS as well as abstracts of research that will be presented at the Fifth World Congress on the Abdominal Compartment Syndrome (Lake Buena Vista, Florida, August 10-13, 2011). This commentary will review where we were, where we are today, and where we are going with respect to the future of IAH and ACS.     

Intra-abdominal hypertension and abdominal compartment syndrome in the medical patient

Critically ill medical patients are at significant risk for developing intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS). Although surgical IAH/ACS is commonly acute and dramatic in onset, medical IAH/ACS is more slow and insidious in its development but no less deadly. The presence of pre-existing comorbid illnesses among medical patients imparts morbidity and mortality rates that are significantly greater than those of their surgical counterparts. A variety of effective medical management strategies for reducing elevated intra-abdominal pressure (IAP), coupled with early abdominal decompression when necessary, has been demonstrated to significantly improve patient survival from IAH/ACS. Serial IAP measurements, increased collaboration between surgeon and nonsurgeon, institution of medical management strategies, and early abdominal decompression for refractory IAH/ACS will lead to decreased rates of organ failure and improved survival for medical patients who develop IAH/ACS.     

Intra-abdominal hypertension and abdominal compartment syndrome in nontrauma surgical patients

Intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS) are commonly encountered in nontrauma surgical patients. Depending on the etiology of the patient's surgical illness (ruptured abdominal aortic aneurysm, acute pancreatitis, burns, etc.), both the incidence and mortality of IAH/ACS may be quite high. Recent advances in both the diagnosis and resuscitation of these surgical patients have resulted in significantly improved survival over that seen in years past. Intra-abdominal pressure measurements should be performed in any surgical patient who demonstrates risk factors for IAH/ACS.     

Intra abdominal hypertension and the abdominal compartment syndrome

The patho-physiological significance of raised intra-abdominal pressure, known as Intra Abdominal Hypertension, with subsequent organ dysfunction and failure, known as Abdominal Compartment Syndrome, has recently been demonstrated to occur relatively frequently in mixed populations of critically ill patients. Clinical diagnosis is unreliable, so routine measurement of intra abdominal pressure should be undertaken, particularly in specific groups of patients known to be at high risk. Whilst definitive therapy requires surgical abdominal decompression, less invasive therapies have been investigated and, if initiated early, may help to minimise progression of the condition. Clearly defined indications for surgical intervention remain elusive however and require prospective investigation. This review summarises the patho-physiology of the syndrome, its diagnosis and surveillance, and current management strategies, both medical and surgical.     

Resuscitation in intra-abdominal hypertension and abdominal compartment syndrome

Resuscitation and the development of abdominal compartment syndrome (ACS) are closely associated and frequently overlapping critical care topics. Elevated intra-abdominal pressure (IAP) can cause major deterioration of cardiac function by affecting preload, contractility, and afterload. Pathologically elevated IAPs are often compounded by the presence of shock leading to imminent organ failure. Excessive or overzealous resuscitation in an attempt to restore perfusion and correct these organ dysfunctions and failures can worsen elevated IAP and increase the risk of ACS. The aim of this review is to discuss these multilevel interactions between resuscitation and ACS identifying appropriate resuscitative strategies for the patient with elevated IAP.     

Intra-abdominal compartment syndrome as a complication of ruptured abdominal aortic aneurysm repair

In four patients with ruptured abdominal aortic aneurysms increased intra-abdominal pressure developed after repair. It was manifested by increased ventilatory pressure, increased central venous pressure, and decreased urinary output associated with massive abdominal distension not due to bleeding. This set of findings constitutes an intra-abdominal compartment syndrome caused by massive interstitial and retroperitoneal swelling. The purpose of this report is to establish criteria for this syndrome and suggest a method of treatment. The syndrome developed within 24 hours; in one patient within 5 hours postoperatively. All four patients received more than 25 liters of fluid resuscitation (electrolyte and blood) during and within 16 hours after operation and had massive abdominal distension. Decompressive laparotomies were performed in the Intensive Care Unit with placement of Marlex (Bard Corp., Billerica, MA) mesh. In two additional patients, at the completion of the aneurysmectomy the abdominal incision was left open with interposition Marlex mesh. Opening the abdominal incision was associated with dramatic improvements in central venous pressure, urinary output, ventilatory pressure, arterial carbon dioxide tension, and oxygenation. The authors conclude that some patients with ruptured abdominal aortic aneurysm do not tolerate the closure of the abdominal wall, as manifested by increased ventilatory pressures, decreased oxygenation, and decreased urinary output. Opening the abdominal wound or delayed closure may reverse the oliguria and improve oxygenation. Recognition and treatment of this condition by opening the abdominal wound or delayed closure may affect outcome in some cases.     

Acute intra-abdominal hypertension and "abdominal compartment syndrome"

The acute intra-abdominal hypertension causes profound physiologic abnormalities, both within and outside the abdomen. Just as in compartment syndrome in the extremities, gut mucosal ischemia begins long before clinical signs are evident, explaining the name of "abdominal compartment syndrome" given to the acute, markedly increased intra-abdominal pressure. The abdominal compartment syndrome was initially described in patients with severe abdominal injuries and massive transfusions and crystalloid infusions, caused by the closure of fascia or skin under tension, the use of bulky abdominal packs to control diffuse bleeding, the massive bowel distension and edema, and the continued bleeding into the abdominal cavity. Intra-abdominal pressure can be monitored by measuring the urinary bladder pressure with a manometer, connected to the transurethral Foley catheter, with the symphysis pubis as the zero point. A persistent elevation of the intra-abdominal pressure beyond 20-25 cmH2O, with significant respiratory, hemodynamic and renal dysfunction is an indication for abdominal decompression, before the manifestations of abdominal compartment syndrome became clinically evident. The mortality in patients with abdominal compartment syndrome is over 40%, even when adequately treated.     

Surgical management of intra-abdominal hypertension and abdominal compartment syndrome

The initial management of intra-abdominal hypertension (IAH) is medical measures to reduce intra-abdominal pressure (IAP). These, in combination with percutaneous drainage of peritoneal free fluid, may serve to reduce IAH. If these measures fail, surgical decompression of the abdomen by laparotomy is necessary to control the IAP, search for and treat inciting factors, and reduce the hypertension. The abdomen is usually left open with temporary abdominal closure techniques. Surgical decompression of IAH associated with acute pancreatitis or secondary abdominal compartment syndrome has other surgical options besides a complete celiotomy. Attention to detail in surgical technique and postoperative care is essential for optimal outcome.     

Recognition and management of intra-abdominal hypertension and the abdominal compartment syndrome

Intra-abdominal pressure can be elevated by a variety of surgical and medical causes. Abnormally high intra-abdominal pressures can lead to multi-system organ dysfunction due to a combination of direct pressure effects and the release of endo-toxins which can be life threatening.     

Renal dysfunction associated with intra-abdominal hypertension and the abdominal compartment syndrome

Once considered mostly a postsurgical condition, intra-abdominal hypertension (IAH) and the abdominal compartment syndrome (ACS) are now thought to increase morbidity and mortality in many patients receiving medical or surgical intensive care. Animal data and human observational studies indicate that oliguria and acute kidney injury are early and frequent consequences of IAH/ACS and can be present at relatively low levels of intra-abdominal pressure (IAP). Among medical patients at particular risk are those with septic shock and severe acute pancreatitis, but the adverse effects of IAH may also be seen in cardiorenal and hepatorenal syndromes. Factors predisposing to IAH/ACS include sepsis, large volume fluid resuscitation, polytransfusion, mechanical ventilation with high intrathoracic pressure, and acidosis, among others. Transduction of bladder pressure is the gold standard for measuring intra-abdominal pressure, and several nonsurgical methods can help reduce IAP. The role of renal replacement therapy for volume management is not well defined but may be beneficial in some cases. IAH/ACS is an important possible cause of acute renal failure in critically ill patients and screening may benefit those at increased risk.     

Definitions and pathophysiological implications of intra-abdominal hypertension and abdominal compartment syndrome

For any syndrome or disease process, uniform definitions are essential to facilitate effective clinical communication as well as evaluation of the scientific literature and standardization of research. The following consensus definitions for intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS) have been proposed by the World Society of the Abdominal Compartment Syndrome and are now widely accepted around the world. The use of these definitions, and their subsequent revisions as new evidence becomes published, will further improve communication and future research in this area. This review briefly addresses the present definitions as well as the pathophysiological effects of IAH/ACS on end-organ function.