Intraabdominal pressure and gastric intramucosal pH: is there an association?

Intestinal histopathological changes in a porcine model of pneumoperitoneum-induced intra-abdominal hypertension

BACKGROUND

Low splanchnic perfusion is an immediate effect of pneumoperitoneum-induced intra-abdominal hypertension (IAH). Anatomical structure results in the intestinal mucosa being the area most sensitive to hypoperfusion. The relationship between intestinal injury and clinical parameters of tissue perfusion [abdominal perfusion pressure (APP), gastric intramucosal pH (pH_i) and lactic acid (Lc)] has not been previously studied. This study aimed to monitorize intestinal pathogenesis through sequential ileal biopsies and to measure APP, pH_i, and Lc levels at different pneumoperitoneum-induced intra-abdominal pressures (20, 30, and 40 mmHg) to evaluate the potential relationships between them.

MATERIALS AND METHODS

Fifty pigs were divided into four groups; a control group (C) and three experimental groups with different pneumoperitoneum-induced levels [20 mmHg (G20), 30 mmHg (G30), and 40 mmHg (G40)], that were maintained for 3 and 5 h. APP, pH_i, and Lc were measured and ileal biopsies taken laparoscopically every 30 min. The mucosal damage was graded using the standardized Park's Score and animals were classified as injured (I+) or uninjured (I-).

RESULTS

Different histopathological lesions were observed in groups G20, G30, and G40 but no damage observed in group C. A 33.3% of animals in G20 and G30 were I+ after 3 h, while 93.3% were injured in G40. After 5 h, histopathological lesions were no longer seen in some animals in G20 and only 10% were I+. Conversely, in G30 I+ pigs increased to 80% while those in G40 remained at 93.3% I+. The I+ animals had significantly lower APP and pH_i than those I-. Lc was the clinical parameter that showed the earliest differences, with significantly higher figures in I+ animals.

CONCLUSIONS

The evolution of intestinal injuries from pneumoperitoneum-induced IAH depends on the degree of IAP. These damages may be associated with decreases in APP and pH_i, and increases in Lc.

Time-course evaluation of intestinal structural disorders in a porcine model of intra-abdominal hypertension by mechanical intestinal obstruction

BACKGROUND

A mechanical intestinal obstruction (MIO) can generate intraabdominal hypertension (IAH) that is life threatening. The intestines are very sensitive to IAH since the low splanchnic perfusion causes intestinal hypoxia, local acidosis and bacterial translocations. This may lead to acute intestinal distress syndrome (AIDS). The identification of intestinal injuries during IAH and its correlation with clinical parameters as the abdominal perfusion pressure (APP), the gastric intramucosal pH (pHi) and lactic acid (Lc) are still unknown. This study aimed to evaluate the sequence of intestinal histopathological findings in an MIO model and to analyze potential relationships with parameters currently used in clinical practice (APP, pHi and Lc).

MATERIAL AND METHODS

Twenty pigs were divided into three groups: a control group (n = 5) and two experimental groups with 20 mmHg (G1, n = 10) and 30 mmHg (G2, n = 5) of IAH by MIO. The pressures were maintained for 3 hours, except in 5 animals in G1 where it was maintained for 5 hours. The APP, pHi and LA were recorded and biopsies of the terminal ileum were taken every 30 minutes in all groups. The intestinal damage was graded according to the Park Score.

RESULTS

Intestinal injuries were found in 42.9% of pigs in the experimental groups. The lesions were independent of the level and duration of IAH. Although APP and pHi were slightly lower in injured animals (I +) of G1 and G2, there were no significant differences among those uninjured (I-). Lc was significantly increased in all I+ pigs from the onset of IAH.

CONCLUSION

The IAH by MIO causes intestinal lesions from the first 30 minutes with concurrent decreases in APP and pHi and increases in Lc. Lc could be the best clinical parameter related to intestinal damages with a clear difference between I + and I- animals.

Mechanical Intestinal Obstruction in a Porcine Model: Effects of Intra-Abdominal Hypertension. A Preliminary Study

Introduction

Mechanical intestinal obstruction is a disorder associated with intra-abdominal hypertension and abdominal compartment syndrome. As the large intestine intraluminal and intra-abdominal pressures are increased, so the patient’s risk for intestinal ischaemia. Previous studies have focused on hypoperfusion and bacterial translocation without considering the concomitant effect of intra-abdominal hypertension. The objective of this study was to design and evaluate a mechanical intestinal obstruction model in pigs similar to the human pathophysiology.

Materials and Methods

Fifteen pigs were divided into three groups: a control group (n = 5) and two groups of 5 pigs with intra-abdominal hypertension induced by mechanical intestinal obstruction. The intra-abdominal pressures of 20 mmHg were maintained for 2 and 5 hours respectively. Hemodynamic, respiratory and gastric intramucosal pH values, as well as blood tests were recorded every 30 min.

Results

Significant differences between the control and mechanical intestinal obstruction groups were noted. The mean arterial pressure, cardiac index, dynamic pulmonary compliance and abdominal perfusion pressure decreased. The systemic vascular resistance index, central venous pressure, pulse pressure variation, airway resistance and lactate increased within 2 hours from starting intra-abdominal hypertension (p<0.05). In addition, we observed increased values for the peak and plateau airway pressures, and low values of gastric intramucosal pH in the mechanical intestinal obstruction groups that were significant after 3 hours.

Conclusion

The mechanical intestinal obstruction model appears to adequately simulate the pathophysiology of intestinal obstruction that occurs in humans. Monitoring abdominal perfusion pressure, dynamic pulmonary compliance, gastric intramucosal pH and lactate values may provide insight in predicting the effects on endorgan function in patients with mechanical intestinal obstruction.

Postinjury abdominal compartment syndrome: from recognition to prevention

Postinjury abdominal compartment syndrome (ACS) is an example of a deadly clinical occurrence that was eliminated by strategic research and focused preventions. In the 1990s, the syndrome emerged with the widespread use of damage control surgery and aggressive crystalloid-based resuscitation. Patients who previously exsanguinated on the operating table made it to intensive care units, but then developed highly lethal hyperacute respiratory, renal, and cardiac failure due to increased abdominal pressure. Among many factors, delayed haemorrhage control and preload driven excessive use of crystalloid resuscitation were identified as modifiable predictors. The surrogate effect of preventive strategies, including the challenge of the 40-year-old standard of large volume crystalloid resuscitation for traumatic shock, greatly reduced cases of ACS. The discoveries were rapidly translated to civilian and military trauma surgical practices and fundamentally changed the way trauma patients are resuscitated today with substantially improved outcomes.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Hepatic function and non-invasive hepatosplanchnic monitoring in patients with abdominal hypertension

A better understanding of intra-abdominal hypertension with relation to the liver is vital to the management of all forms of liver pathophysiology. Supporting good hepatic function within the critically ill patient is important not only in maintaining synthetic function, but also in avoiding the multi-organ complications of liver dysfunction. The resulting reduction in hepato-splanchnic blood flow (HSBF) observed with increasing intra-abdominal pressure has been clearly documented and seen to be exaggerated in animals with established liver disease. Unfortunately the tools required to measure this, remain difficult to apply routinely in the clinical setting and as such goal directed therapy to specifically improve the hepatosplanchnic circulation remains elusive. Given the documented effects of IAP on HSBF and the relatively high incidence of intra-abdominal hypertension and the abdominal compartment syndrome within "liver patients" as a whole, close attention to IAP and timely correction by appropriate medical or surgical means would appear to be essential.

Tonometry as a predictor of inadequate splanchnic perfusion in an intra-abdominal hypertension animal model

BACKGROUND

The gastrointestinal system is the most sensitive to the presence of intra-abdominal hypertension. We aimed to assess the early prognostic value of gastric air tonometry as a predictor of inadequate splanchnic perfusion and determine its relation with abdominal perfusion pressure (APP).

METHODS

Twenty-five Large White swine were used for this study. A control group and two study groups were included, in which intra-abdominal pressure (IAP) was elevated with Co2 to 20 and 30 mmHg during 5 h. We measured the intramucosal gastric pH (pHim) and determined gastric luminal PCO2 (PgCO2) and PgCO2gap (gastric luminal CO2-arterial CO2) to evaluate gastric acidity. APP was indirectly obtained through IAP and mean arterial pressure. Additionally, histopathologic samples of small intestine were obtained and analyzed.

RESULTS

pHim showed a decrease in IAP groups, with statistical significance in the 30 mmHg group, 90 min after stabilization period (P < 0.01). Serum lactate showed delayed alteration when compared with pHim, with significant increase, 180 min after stabilization (P < 0.05). The values of PgCO2 and PCO2gap were increased in IAP groups, being statistically significant in the 30 mmHg group, 120 and 150 min, respectively, after stabilization. In increased IAP groups, there was a time progressive decrease of APP, with statistically significant differences observed between groups at 20 min (P < 0.001). The histopathology study revealed parenchymal injury of the intestine at 30 mmHg.

CONCLUSIONS

Tonometry is sensitive to the increase in IAP and relates to the reduction of APP generated by splanchnic hypoperfusion.

Intra-abdominal hypertension in the current era of modern trauma resuscitation

BACKGROUND

This study aimed to determine the incidence and outcome of post-traumatic (PT) intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS) after the advances in haemostatic resuscitation.

METHODS

This is a prospective cohort study from January 2009-December 2011 involving patients with PT haemorrhagic shock. Patients' demographics, fluid resuscitation (<24 h) and damage control laparotomy (DCL), morbidity and mortality were assessed. Patients were divided into group 1 (no DCL) and group 2 (DCL needed). Further, group 1 was subdivided into three subgroups (IA pressure (IAP) <12, 12-20 and >20 mmHg).

RESULTS

One hundred seventeen patients enrolled in the study (102 in group 1 and 15 in group 2) with a mean age of 35 ± 14, injury severity score (ISS) of 23 ± 10, base deficit of -8.7 ± 2.7 mmol/L, serum lactate of 4.6 ± 2.5 mg/dL and haemoglobin level of 8.8 ± 2. Patients received 7 ± 5 red blood cell units, 6 ± 4.7 fresh frozen plasma units and 8.3 ± 3 L of crystalloid per 24 h. There were significant difference between the two groups regarding crystalloid volume, blood transfusion, base deficit and intensive care unit length of stay. However, mortality was higher in group 2 (20% versus 6%). IAP ≥ 20 mmHg was reported in 16.7% patients, while 25.5% had IAP < 12 and 57.8% had IAP of 12-20 mmHg. Patients with IAP > 20 had worse metabolic acidosis and received more blood compared with other groups. One patient died because of ACS (0.9%). Overall multiorgan failure and mortality were 5 and 7.7%, respectively.

CONCLUSION

With current practice of minimal fluid resuscitation and liberal use of damage control strategies among trauma patients, the IAH was common transient phenomena but the incidence of ACS is remarkably low.

The effect of body position on compartmental intra-abdominal pressure following liver transplantation

BACKGROUND

Current assumptions rely on intra-abdominal pressure (IAP) being uniform across the abdominal cavity. The abdominal contents are, however, a heterogeneous mix of solid, liquid and gas, and pressure transmission may not be uniform. The current study examines the upper and lower IAP following liver transplantation.

METHODS

IAP was measured directly via intra-peritoneal catheters placed at the liver and outside the bladder. Compartmental pressure data were recorded at 10-min intervals for up to 72 h following surgery, and the effect of intermittent posture change on compartmental pressures was also studied. Pelvic intra-peritoneal pressure was compared to intra-bladder pressure measured via a FoleyManometer.

RESULTS

A significant variation in upper and lower IAP of 18% was observed with a range of differences of 0 to 16 mmHg. A sustained difference in inter-compartmental pressure of 4 mmHg or more was present for 23% of the study time. Head-up positioning at 30° provided a protective effect on upper intra-abdominal pressure, resulting in a significant reduction in all patients. There was excellent agreement between intra-bladder and pelvic pressure.

CONCLUSIONS

A clinically significant variation in inter-compartmental pressure exists following liver transplantation, which can be manipulated by changes to body position. The existence of regional pressure differences suggests that IAP monitoring at the bladder alone may under-diagnose intra-abdominal hypertension and abdominal compartment syndrome in these patients. The upper and lower abdomen may need to be considered as separate entities in certain conditions.

Incidence of gastric mucosal injury as measured by reactance in critically ill patients

Gastric reactance has been proposed as a measure of mucosal ischemic injury in the critically ill. The purpose of this study was to evaluate the incidence of gastric mucosal injury as measured by gastric reactance in different subgroups of critical patients. We studied 100 adult patients admitted to 7 different hospital intensive care units, requiring a nasogastric tube. Gastric impedance measurements were continuously obtained from each patient for 24 hours. Patients were managed based on conventional protocols by hospital staff, blinded to the changes in gastric impedance parameters. The low-frequency central reactance (X L) reflects tissue edema caused by prolonged ischemia. The previously reported threshold of X L ≥ 13 - jΩ was used to classify injured mucosa; 80% of all patients had mean X L above this threshold. No significant differences were found in the incidence of mucosal ischemia between medical versus surgical, hemodynamic versus respiratory or neurological patients. Significant lower urine output was found in patients with X L above threshold (P < .01); also, there was a significant effect of fluid balance in those patients (P < .05). More complicated patients had higher average reactance. This study shows that gastric ischemia as estimated by gastric reactance has a very high incidence in the critically ill, independently of the reason for admission. High reactance is related with higher morbidity in agreement with other reports using different methods of assessing splanchnic hypoperfusion in this patient population.

[Abdominal compartment syndrome and acute intestinal distress syndrome]

Seriously ill patients frequently present intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS) as complications, and the associated mortality is very high. This review offers an update on the most controversial aspects of these entities: factors favoring their appearance, the most common causes, prognosis, and methods of measuring intra-abdominal pressure (IAP), physiopathological consequences in relation to the different organs and systems, and the currently accepted treatment measures (medical and/or surgical). Simultaneously to the strictly physical mechanisms of injury, such as direct compression of intra-abdominal organs and vessels, the transmission of IAP to other compartments, and the drop in cardiac output, a series of immune-inflammatory mediators generated in the intestine itself may also intervene. Hypoperfusion, sustained ischemia and the ischemia-reperfusion phenomenon, would act upon the microbiota, intestinal epithelium and intestinal immune system, triggering a systemic inflammatory response and multiorgan dysfunction that appears in the final stages of ACS.

The abdominal compartment syndrome: review, experience report and description of an innovative biological mesh application

Intra abdominal hypertension (IAH) is defined as an intra-abdominal pressure (IAP) >12 mmHg. Abdominal compartment syndrome (ACS) is defined as an IAP above 20 mmHg with evidence of organ dysfunction/failure. The real incidence of the ACS is not clear, because there are few perspective studies. The origin of ACS can be divided into retroperitoneal, intraperitoneal, parietal and intestinal, and the diagnostic algorithm includes base and toxicological laboratory examinations, thorax X-ray, abdomen X-ray, abdomen TC, peritoneal washing, abdomen ultrasonography, diagnostic laparoscopy, and measurement of IAP. To allow a suitable decompression and avoid the damages to the abdominal organs, abdominal wall normally is not sutured primarily but secondarily and there are many methods of temporary closing: absorbable net, non-absorbable nets, 'Bogota bag', 'vacuum pack ice', gradual approximation of side cutaneous edges on the half-way line with permanence of an ample ventral hernia that could be subsequently repaired, and the use of 'skin expanders'. Since January 2000, until December 2008, eight patients were submitted to laparostomy, four of them for re-laparotomy, with mortality incidence of 37.5%. The defective size to fill was on the average 300 cm as reported by Bradley and Bradley (J Clin Invest 26:1010-1015, 1947). The abdominal wall reconstruction was performed using ample muscle edges derived from the slip in medial sense of the rectus muscle of the abdomen 'unmoored' through an incision 1 cm distant from semi-lunar line, and using absorbable prosthesis to cover the solution of continuity, thus allowing the closing of defects over 30 cm. We have found median post surgical hernia in one patient corrected in accordance with the time using polypropylene prosthesis. In one patient with parietal disaster and multiple traumatic splanchnic ruptures, we have used a pure pork-derived acellular collagen mesh (Permacol(®)) to close the wound, leaving enough space between fascia extremities, to solve the IAP. The employment of ample muscle edges represents the ideal solution in the reconstruction of the abdominal walls after laparotomic operations, offering a valid dynamic support preferable in comparison with the employment of alloplastic material. In consideration of the limits of this technique in the enormous parietal disaster-ACS treatment, we describe a new kind of innovative mesh application (Permacol(®)), most often used for parietal disaster or enormous incisional hernias, which can easily be preferred to dual mesh prosthesis, having a better biological profile and no capacity to produce intestinal adherences.

Understanding Intra-Abdominal Hypertension

Received November 10, 2009. Received Revised June 17, 2010. Submitted June 21, 2010. Intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS) are highly morbid conditions that are common and underrecognized in the intensive care unit. Intra-abdominal hypertension affects the critically ill patient population and is not solely limited to the trauma and surgical subgroups. The recognition of IAH and ACS as distinct clinical states has become more apparent. Extensive bench and clinical research has shed significant light into the definition, incidence, etiology, physiology, clinical manifestations, and treatment strategies. Although further research into this morbid condition is needed, improvement in recognition is a critical first step. This review aims to scrutinize the basic science and clinical literature available on this condition in a surgically focused, organ-system-based approach.

[Intraabdominal hypertension and abdominal compartment syndrome]

Although intraabdominal pressure (IAP) has been studied for more than 100 years, the concepts of intraabdominal hypertension (IAH) and abdominal compartmental syndrome (ACS) have only been developed as clinical entities of interest in intensive care in the last 5 years. At the first Congress on Abdominal Compartment Syndrome in December 2004, a series of definitions were established, which were published in 2006. IAH is defined as IAP ≥ 12 mmHg and is classified in four severity grades, the maximum grade being ACS, with the development of multiorgan failure. The incidence of IAH in patients in intensive care units is high, around 30% at admission and 64% in those with a length of stay of 7 days. The increase in IAP leads to reduced vascular flow to the splenic organs, increased intrathoracic pressure and decreased venous return, with a substantial reduction in cardiac output. If IAH persists, these physiopathologic episodes are followed by the development of multiorgan failure with renal, cardiocirculatory and respiratory failure and intestinal ischemia. Mortality from untreated ACS is higher than 60%. The only treatment for ACS is surgical decompression. In patients with moderate IAH, medical treatment should be optimized, based on the following measures: a) serial IAP monitoring; b) optimization of systemic perfusion and the function of the distinct systems in patients with high IAP; c) instauration of specific measures to decrease IAP; and d) early surgical decompression for refractory IAH. The application of the medical measures that can reduce IAP and early abdominal decompression in ACS improve survival in critically ill patients with IAH.

Increased serum adenosine and interleukin 10 levels as new laboratory markers of increased intra-abdominal pressure

BACKGROUND

Increased intra-abdominal pressure (IAP), intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS) are severe complications of surgical interventions with a high rate of mortality. The technique of IAP measurement is accurate, precise, reproducible and cost-effective. However, laboratory measures for monitoring of IAH have not been defined. We investigated the linkage between the serum levels of adenosine and interleukin 10 (IL-10) with IAP.

METHODS

The sera of 25 surgical patients with IAP <12 mmHg and of 45 surgical patients with IAP >12 mmHg were tested. Serum adenosine concentration was measured by HPLC. Serum IL-1β, IL-2, IL-4, IL-10, TNFα, IFNγ and IL-10 were determined by enzyme linked immunosorbent assay (ELISA). CRP was measured by nephelometry.

RESULTS

Significant correlations of IAP were found only with serum levels of adenosine and IL-10. In the sera of patients with IAP >12 mmHg, the levels of both adenosine (1.61 versus 0.06 µM, p < 0.01) and IL-10 (63.23 versus 27.27 pg/ml, p < 0.01) were significantly higher than those in patients with IAP <12 mmHg. Moreover, significant correlations were found between individual patient IAP-adenosine values (r = 0.766, p < 0.001), IAP-IL-10 values (r = 0.792, p < 0.001) and adenosine-IL-10 values (r = 0.888, p < 0.001). A direct linear correlation between IAP-adenosine and IAP-10 values was only observed with IAP >15 (Grade II-IV).

CONCLUSION

We report associations between IAP and the serum adenosine and IL-10 levels providing new tools for the laboratory monitoring of IAH as well as further understanding of the pathomechanisms contributing to ACS.

Intra-abdominal pressure and abdominal compartment syndrome in acute general surgery

BACKGROUND

Intra-abdominal pressure (IAP) is a harbinger of intra-abdominal mischief, and its measurement is cheap, simple to perform, and reproducible. Intra-abdominal hypertension (IAH), especially grades 3 and 4 (IAP > 18 mmHg), occurs in over a third of patients and is associated with an increase in intra-abdominal sepsis, bleeding, renal failure, and death.

PATIENTS AND METHODS

Increased IAP reading may provide an objective bedside stimulus for surgeons to expedite diagnostic and therapeutic work-up of critically ill patients. One of the greatest challenges surgeons and intensivists face worldwide is lack of recognition of the known association between IAH, ACS, and intra-abdominal sepsis. This lack of awareness of IAH and its progression to ACS may delay timely intervention and contribute to excessive patient resuscitation.

CONCLUSIONS

All patients entering the intensive care unit (ICU) after emergency general surgery or massive fluid resuscitation should have an IAP measurement performed every 6 h. Each ICU should have guidelines relating to techniques of IAP measurement and an algorithm for management of IAH.

Intra-abdominal hypertension: evolving concepts

This article focuses primarily on the recent literature on abdominal compartment syndrome (ACS) and the definitions and recommendations published by the World Society for the Abdominal Compartment Syndrome. The definitions regarding increased intra-abdominal pressure (IAP) are listed and are followed by an overview of the different mechanisms of organ dysfunction associated with intra-abdominal hypertension (IAH). Measurement techniques for IAP are discussed, as are recommendations for organ function support and options for treatment in patients who have IAH. ACS was first described in surgical patients who had abdominal trauma, bleeding, or infection; but recently, ACS has been described in patients who have other pathologies. This article intends to provide critical care physicians with a clear insight into the current state of knowledge regarding IAH and ACS.

Advances in intra-abdominal hypertension due to severe acute pancreatitis

Intra-abdominal hypertension due to severe acute pancreatitis (SAP) has attracted more and more attention of clinicians. It directly influences the treatment and prognosis of SAP and, moreover, becomes an important marker for judging the prognosis of SAP. The mechanism of intra-abdominal hypertension due to SAP is consistent with that of primary intra-abdominal hypertension. In this article, the definition, pathophysiology, and prognosis of intra-abdominal hypertension are reviewed.

Abdominal compartment syndrome

Compartment syndrome is a pathophysiological term, comprising a variety of tissues and organ alterations, due to a higher than normal pressure in an anatomically detached space (compartment). In the human body, areas denoted as compartments include the orbital globe, the sub and epidural space, the abdomen, pleura, pericardium, and others. Compartment syndrome was described initially in limbs. Abdominal compartment syndrome is defined as an intra-abdominal pressure above 20 mmHg with evidence of organ failure. Abdominal compartment syndrome develops when the intra-abdominal pressure rapidly reaches certain pathological values, within several hours (intra-abdominal hypertension is observed), and lasts for 6 or more hours. The key to recognizing abdominal compartment syndrome is the demonstration of elevated intra-abdominal pressure which is performed most often via the urinary bladder, and it is considered to be the "gold standard." Multiorgan failure includes damage to the cardiac, pulmonary, renal, neurological, gastrointestinal, abdominal wall, and ophthalmic systems. The gut is the most sensitive to intra-abdominal hypertension, and it develops evidence of end-organ damage before alterations are observed in other systems. The surgical decompression of the abdomen remains the treatment of choice of abdominal compartment syndrome; this usually improves the organ changes, and is followed by one of the temporary abdominal closure techniques in order to prevent secondary intra-abdominal hypertension.

Intraabdominal Hypertension in Patients with Septic Shock

Intraabdominal hypertension (IAH) develops frequently in patients with septic shock. Even a moderate increase in intraabdominal pressure (IAP) in this setting could be associated with high lactate levels. The authors conducted a prospective, observational, nonrandomized control trial in the surgical intensive care unit of an academic tertiary center. Twenty-seven patients with septic shock (septic shock group), and 19 patients undergoing abdominal surgery with more than two risk factors for IAH (postoperative control group) were admitted consecutively to the intensive care unit. IAP was measured every 6 hours during the first 48 hours. IAH was diagnosed with two consecutive measurements greater than 20 mm Hg. The main outcome measures were prevalence of IAH in septic shock and control groups; and comparative lactate levels, norepinephrine requirements and organ dysfunctions in patients with and without IAH in both groups. Fifty-one per cent of patients with septic shock and 31 per cent of control patients developed IAH. Patients with septic shock with and without IAH were comparable in peak norepinephrine dose, sequential organ failure assessment score, and mortality. However, peak lactate levels were significantly higher in patients with septic shock and IAH compared with those without IAH (3.5 mmol/L versus 1.9 mmol/L, P < 0.04). There was a significant positive temporal correlation between IAP and lactate levels in patients with septic shock with IAH. Peak levels of both occurred early and decreased progressively over time. Control patients with and without IAH exhibited comparable peak lactate levels. Intraabdominal hypertension is very common in septic shock and appears to be related to high lactate levels, which diminish as IAP decreases. Future studies should address the usefulness of IAP monitoring in patients with septic shock.

Microdialysis of the rectus abdominis muscle for early detection of impending abdominal compartment syndrome

OBJECTIVE

To investigate whether microdialysis is capable of assessing metabolic derangements during intra-abdominal hypertension (IAH), and whether monitoring of the rectus abdominis muscle (RAM) by microdialysis represents a reliable approach in the early detection of organ dysfunctions in abdominal compartment syndrome (ACS).

DESIGN

Prospective, randomized, controlled animal study.

SETTING

University animal research facility.

SUBJECTS

Fifteen isoflurane-anesthetized and mechanically ventilated Sprague-Dawley rats.

INTERVENTIONS

IAH of 20 mmHg was induced for 3 h and followed by decompression and reperfusion for another 3-h period (n = 10). Five sham-operated animals served as controls. Microdialysis was performed in the anterior gastric wall, liver, kidney, and RAM. The anterior cervical muscles served as distant reference. Glucose, lactate, pyruvate, and glycerol was analyzed throughout the 6-h experiment.

MEASUREMENTS AND MAIN RESULTS

Prolonged IAH induced significant cardiopulmonary dysfunction and persistent abdominal organ injury. Microdialysis revealed a significant increase of lactate/pyruvate and glycerol in kidney, intestine and liver, indicating ischemia, energy failure, and cell membrane damage. In addition, at 3 h IAH glucose was significantly decreased in all organs studied. The distant reference did not show any alteration of lactate/pyruvate, glycerol, and glucose over the entire 6-h observation period. In contrast to the other organs, microdialysis of the RAM showed an early and more pronounced increase of lactate, lactate/pyruvate and glycerol already at 1 h IAH. It is noteworthy that lactate, glycerol, and glucose did not completely recover upon decompression of IAH.

CONCLUSIONS

Our data suggest that continuous microdialysis in the RAM may represent a promising tool for early detecting IAH-induced metabolic derangements.

Intra-abdominal pressure measurement: validation of intragastric pressure as a measure of intra-abdominal pressure

BACKGROUND

The diagnosis of abdominal compartment syndrome depends upon the demonstration of an elevated intra-abdominal pressure (IAP). Direct measures of IAP are impractical in the critical care unit; intravesical pressure (IVP) and intragastric pressure (IGP) should represent acceptable surrogate measures. IVP is the preferred measure of IAP in critical care. We considered that IGP represents a practical alternative. The objective of this preliminary study was to observe the relationship between IGP and IAP.

METHODS

After Institutional Ethics Board approval, 29 patients having elective laparoscopic surgery were recruited. IAP was measured directly via the abdominal trochar. This was compared with IGP measured via a commercial balloon catheter placed into the stomach.

RESULTS

Measured IGP was always more positive than IAP; both showed linear correlation (r2>0.9). When IGP was calibrated against IAP, an estimated difference between the IGP and IAP of+/-2.5 mm Hg for 95% of the measurements was seen.

CONCLUSIONS

The study demonstrates the strength of the relationship between IGP and IAP in normal individuals. Application of IGP measurement in the critical care patient is necessary to demonstrate its suitability for continuous IAP assessment.

Direct measurement of intra-abdominal pressure with a solid microtranducer

OBJECTIVE

To describe a direct intra-abdominal pressure (IAP) measurement technique using a solid microsensor comparing its values with the ones simultaneously obtained by means of Kron's technique. Comparative study between two different methods to measure intra-abdominal pressure in a multidisciplinary intensive care unit of a university hospital.

METHODS

In 11 critical patients considered irreversibly ill, IAP was simultaneously measured via Kron's technique (IAPK) and by direct measure (IAPC) through an abdominal tap with a Codman microsensor, inserted through it. Several measurements were obtained at different PEEP levels (0, 10 and 20 cm of H20) and bed inclination (0 degrees , 40 degrees and 60 degrees ).

RESULTS

92 simultaneous measurements of IAPK and IAPC were made. The difference between both measurements (mean +/- SD) were: 0.286 +/- 0.938 mmHg. The correlation coefficient was r = 0.98. Bland-Altman plot showed a narrow distribution: 95% of the differences were between 1.87 mmHg of each averaged value. No complications with IAPC measurements were found.

CONCLUSIONS

Direct IAP measurement with a Codman microsensor allows continuous monitoring without urinary tract manipulation, is simple to use and to calibrate, minimally invasive and appropriate for patients at risk to develop abdominal compartmental syndrome. Due to its cost it should be reserved for selected critical patients where standard techniques are contraindicated or can be inaccurate.

Results from the International Conference of Experts on Intra-abdominal Hypertension and Abdominal Compartment Syndrome. II. Recommendations

OBJECTIVE

Intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS) have been increasingly recognized in the critically ill over the past decade. In the absence of consensus definitions and treatment guidelines the diagnosis and management of IAH and ACS remains variable from institution to institution.

DESIGN

An international consensus group of multidisciplinary critical care specialists convened at the second World Congress on Abdominal Compartment Syndrome to develop practice guidelines for the diagnosis, management, and prevention of IAH and ACS.

METHODS

Prior to the conference the authors developed a blueprint for consensus definitions and treatment guidelines which were refined both during and after the conference. The present article is the second installment of the final report from the 2004 International ACS Consensus Definitions Conference and is endorsed by the World Society of the Abdominal Compartment Syndrome.

RESULTS

The prevalence and etiological factors for IAH and ACS are reviewed. Evidence-based medicine treatment guidelines are presented to facilitate the diagnosis and management of IAH and ACS. Recommendations to guide future studies are proposed.

CONCLUSIONS

These definitions, guidelines, and recommendations, based upon current best evidence and expert opinion are proposed to assist clinicians in the management of IAH and ACS as well as serve as a reference for future clinical and basic science research.

Morphology, TNFα expression and apoptosis in the hearts of patients who died of abdominal compartment syndrome: An immunohistochemical study

Most of the existing reports on abdominal compartment syndrome (ACS) deal with pathophysiology, focusing on its clinical picture and course, and knowledge of the histopathological features of ACS is very poor. Since the heart, kidneys and lungs are the organs primarily targeted for injury in multi-organ failure, we investigated the expression of TNFalpha and apoptosis in tissue specimens of the heart. This retrospective study was conducted at the Department of Forensic Pathology, University of Foggia. A retrospective review of records extending over a period of 4 years, from 1 April 2001 to 31 March 2005, was carried out and all cases subjected to medico-legal autopsy during this period, whose detailed history and case records were available, were the subjects of our study. Over a 4-year period, on 848 cases subjected to medico-legal autopsy, three cases qualified for inclusion into the study. The immunohistochemical study revealed an intensive positive result for TNFalpha in heart specimens. The TUNEL assay was positive in heart specimens too. The presented study can contribute to elucidate the pathophysiology of fatal ACS and also define efficient markers for future therapeutic approaches suggesting anti-TNFalpha strategies may be useful in the management of ACS.

Renal arterial resistive index response to intraabdominal hypertension in a porcine model

OBJECTIVE

The abdominal compartment syndrome is a potentially life-threatening condition with frequent renal involvement. There are few if any means of inferring subclinical effects before organ dysfunction. Because intrarenal pressure correlates with renal sonographic indices in other renal diseases, the purpose of this study was to determine the relationship between increasing intraabdominal hypertension and renal vascular flow velocities in a porcine model using renal Doppler ultrasound.

DESIGN

Animal study.

SETTING

University research laboratory.

SUBJECTS

Eight anesthetized, mechanically ventilated, well-hydrated, 30-kg female Yorkshire pigs.

INTERVENTIONS

Intraabdominal hypertension was induced by instillation of warmed intraperitoneal saline through a midline laparoscopic port. Intraabdominal pressure (IAP) was continuously monitored directly from the peritoneum and indirectly from the bladder. IAP was varied from 0 to 50 mm Hg in increments of 5 mm Hg. At each IAP level, gray-scale, color, and spectral Doppler renal arcuate artery ultrasound was obtained and resistive index (RI) and peak airway pressure calculated.

MEASUREMENTS AND MAIN RESULTS

Excellent agreement between direct and indirect IAP was found (bias, 0.032 mm Hg; 95% limits, -5.5 to 5.6 mm Hg). A linear relationship between RI and indirect IAP was observed and was defined by the regression equation: RI = 0.553 + 0.0104 x bladder pressure. There was a trend toward different RIs between left and right kidneys (p = .052) at the same IAP. RI varied in a linear fashion at low peak airway pressure and demonstrated an inflection point with steeper subsequent slope after peak airway pressure of 30 cm H2O. RI values rapidly returned to near baseline after abdominal decompression.

CONCLUSIONS

In this model, the renal artery RI correlated strongly and linearly with the severity of intraabdominal hypertension, making renal Doppler ultrasound a potential noninvasive screening tool for the renal effects of intraabdominal hypertension. Further studies are warranted.

Intra-abdominal pressure in severe acute pancreatitis

BACKGROUND

Hospital mortality in patients with severe acute pancreatitis (SAP) remains high. Some of these patients develop increased intra-abdominal pressure (IAP) which may contribute to organ dysfunction. The aims of this study were to evaluate the frequency of increased IAP in patients with SAP and to assess the development of organ dysfunction and factors associated with high IAP.

METHODS

During 2001-2003 a total of 59 patients with severe acute pancreatitis were treated in the intensive care unit (ICU) of Helsinki University Hospital. IAP was measured by the intravesical route in 37 patients with SAP. Data from these patients were retrospectively reviewed.

RESULTS

Maximal IAP, APACHE II score, maximal SOFA score, maximal creatinine, age and maximal lactate were significantly higher in nonsurvivors. There was a significant correlation of the maximal IAP with the maximal SOFA, APACHE II, maximal creatinine, maximal lactate, base deficit and ICU length of stay. Patients were divided into quartiles according to the maximal IAP. Maximal IAP was 7-14, 15-18, 19-24 and 25-33 mmHg and the hospital mortality rate 10%, 12.5%, 22.2% and 50% in groups 1-4, respectively. A statistically significant difference was seen in the maximal SOFA, ICU length of stay, maximal creatinine and lactate values. The mean ICU-free days in groups 1-4 were 45.7, 38.8, 32.0 and 27.5 days, respectively. The difference between groups 1 and 4 was statistically significant.

CONCLUSION

In patients with SAP, increased IAP is associated with development of early organ failure reflected in increased mortality and fewer ICU-free days. Frequent measurement of IAP during intensive care is important in optimizing abdominal perfusion pressure and recognizing patients potentially benefitting from decompressive laparotomy.

La hipertensión intraabdominal y el síndrome compartimental abdominal: ¿qué debe saber y cómo debe tratarlos el cirujano?

Correct monitoring of medicosurgical critically-ill patients aids the early diagnosis and appropriate treatment of intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS). The abdominal cavity and the retroperitoneum act sealed compartments and any change in the volume of their contents can increase intraabdominal pressure (IAP). IAH is only one measure of elevated IAP, and ACS represents the end result of sustained IAH with the appearance of organ dysfunction. To diagnose IAH and ACS, measurement of IAP, abdominal perfusion pressure and intramucous gastric pH must be performed and the results correlated with signs of clinical deterioration in the patient. Medical therapeutic measures in ACS are limited and abdominal decompression is the established symptomatic treatment of this entity.

Results from the International Conference of Experts on Intra-abdominal Hypertension and Abdominal Compartment Syndrome. I. Definitions

OBJECTIVE

Intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS) have been increasingly recognized in the critically ill over the past decade. The variety of definitions proposed has led to confusion and difficulty in comparing one study to another.

DESIGN

An international consensus group of critical care specialists convened at the second World Congress on Abdominal Compartment Syndrome to standardize definitions for IAH and ACS based upon the current understanding of the pathophysiology surrounding these two syndromes.

METHODS

Prior to the conference the authors developed a blueprint for the various definitions, which was further refined both during and after the conference. The present article serves as the final report of the 2004 International ACS Consensus Definitions Conference and is endorsed by the World Society of Abdominal Compartment Syndrome (WSACS).

RESULTS

IAH is redefined as an intra-abdominal pressure (IAP) at or above 12 mmHg. ACS is redefined as an IAP above 20 mmHg with evidence of organ dysfunction/failure. ACS is further classified as either primary, secondary, or recurrent based upon the duration and cause of the IAH-induced organ failure. Standards for IAP monitoring are set forth to facilitate accuracy of IAP measurements from patient to patient.

CONCLUSIONS

State-of-the-art definitions for IAH and ACS are proposed based upon current medical evidence as well as expert opinion. The WSACS recommends that these definitions be used for future clinical and basic science research. Specific guidelines and recommendations for clinical management of patients with IAH/ACS are published in a separate review.

Measurement of compartment pressure of the rectus sheath during intra-abdominal hypertension in rats

OBJECTIVE

To investigate whether the compartment pressure of the rectus sheath (CPRS) reflects the intra-abdominal pressure (IAP) under various conditions of intra-abdominal hypertension (IAH).

DESIGN AND SETTING

Prospective experimental study with in vivo pressure measurements at the Institute for Clinical and Experimental Surgery, University of Saarland.

ANIMALS

Sprague-Dawley rats.

INTERVENTIONS

Stepwise increase and decrease in IAP with continuous measurement of the correspondent CPRS.

MEASUREMENTS AND RESULTS

Physiological IAP (2 mmHg) and CPRS (6 mmHg) showed a statistically significant difference. Stepwise elevation in IAP was associated with a simultaneous increase in CPRS. Accordingly, stepwise decompression of IAP resulted in a stepwise decrease in CPRS. Under both conditions Bland-Altman analysis comparing IAP to correspondent CPRS showed a very good agreement for IAP at or above 12 mmHg. In addition, closure of the overlaying subcutaneous tissue and skin did not affect CPRS or its correlation with IAP.

CONCLUSIONS

CPRS accurately reflects IAP for IAP of 12 mmHg or higher. Thus CPRS measurements may represent a novel approach for diagnosis and monitoring of IAH.

Abdominal Compartment Syndrome

BACKGROUND

Abdominal compartment syndrome (ACS) is a systemic syndrome involving derangement in cardiovascular haemodynamics, respiratory and renal functions as a result of sustained increase in intra-abdominal pressure (IAP) ending in multi-organ failure. It is a life threatening emergency and requires prompt action and treatment. For the last 20 years, there has been more awareness among surgeons and intensivists of ACS being a distinct disease entity but still widespread ignorance prevails. Presentation can be acute, chronic and acute on chronic. Initial diagnosis is clinical, confirmed by measurement of IAP. Treatment is abdominal decompression by laparostomy and delayed abdominal closure. Despite prompt treatment mortality remains high. Awareness among surgeons has increased because laparoscopy has resulted in determination of IAP as a readily measurable quantity and also they have been able to appreciate the benefit of abdominal decompression by performing repeated planned laparotomies for trauma.

METHODS

A medline, pubmed and Cochrane database search was performed and the articles found were cross referenced.

RESULTS AND CONCLUSION

Clinical diagnosis is not easy and serial urinary bladder pressure (UBP) monitoring leads to early diagnosis. Treatment is by laprostomy to decompress the abdomen followed by delayed abdominal closure.

Abdominal compartment syndrome

PURPOSE OF REVIEW

This review will set forth the new consensus definitions for intra-abdominal pressure, intra-abdominal hypertension, and the abdominal compartment syndrome from the World Congress on the Abdominal Compartment Syndrome in December 2004. The review will explore the challenges in diagnosis, pathophysiology, and recent concepts in the treatment of abdominal compartment syndrome.

RECENT FINDINGS

Intra-abdominal pressure greater than 12 mm Hg may exert adverse physiologic sequelae, progressing to intra-abdominal hypertension and full-blown abdominal compartment syndrome as intra-abdominal pressure increases. The first challenge is to recognize that abdominal compartment syndrome may be a potential problem in critically ill patients. Intra-abdominal pressure monitoring is essential for this. Continuous monitoring of intra-abdominal pressure and abdominal perfusion pressure adds real-time measurements and can be performed by way of the stomach or bladder. Intra-abdominal hypertension occurs in approximately 35% of patients in the intensive care unit, and abdominal compartment syndrome in approximately 5%.

SUMMARY

Massive resuscitation is increasingly recognized as a major contributor to abdominal compartment syndrome. Prophylactic decompression and temporary abdominal closure have important roles in preventing tertiary or recurrent abdominal compartment syndrome. Failure to recognize and treat intra-abdominal hypertension will result in increased risk of renal impairment, visceral and intestinal ischemia, respiratory failure and death.

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

PURPOSE OF THE REVIEW

There has been an exponentially increasing interest in intra-abdominal hypertension (IAH). Comparison of the published data however is difficult due to the lack of consensus definitions. This review will focus on the available literature from the last 2 years. A Medline and PubMed search was performed using 'intra-abdominal pressure' (IAP), 'intra-abdominal hypertension' (IAH), and 'abdominal compartment syndrome' (ACS) as search items. The aim was to find an answer to the question 'Isn't it time to pay attention to intra-abdominal pressure in the critically ill?'

RECENT FINDINGS

Although the number of studies published on this topic is steadily increasing and confirms the pathophysiologic implications of IAH on end-organ function within and outside the abdominal cavity it remains difficult to compare the literature data because the measurement methods and definitions used are not uniform. Provocative data have been published regarding the interactions between the abdominal and thoracic compartments especially in patients with capillary leak and fluid overload; most of this data raises even more questions than it gives answers and may therefore strengthen the nonbelievers who consider IAP, IAH and ACS as epiphenomena in critically ill patients. Unless the international scientific community does not come forward with clear-cut definitions we will keep comparing 'apples with oranges.'

SUMMARY

It is time to pay attention to intra-abdominal pressure in the critically ill. It is also time for standardized IAP measurement methods, good consensus definitions and randomized interventional studies.

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.

Abdominal compartment syndrome: the cause or effect of postinjury multiple organ failure

Abdominal compartment syndrome (ACS) has emerged to be a significant problem in patients who develop postinjury multiple organ failure (MOF). Current laboratory research suggests that ACS could be a second hit for the development of MOF. Recent studies demonstrate that ACS is an independent predictor of MOF and that the prevention of ACS decreases the incidence of MOF. The Trauma Research Centers at the University of Colorado and the University of Texas-Houston Medical School are focused on defining the role of the gut in postinjury MOF. Because ACS is a plausible modifiable risk factor, our interest has been to 1) describe the epidemiology of ACS, 2) build prediction models, 3) provide strategies for prevention and treatment of ACS, and 4) develop relevant laboratory models. This review summarizes our findings.

Prevalence of intra-abdominal hypertension in critically ill patients: a multicentre epidemiological study

OBJECTIVE

Although intra-abdominal hypertension (IAH) can cause dysfunction of several organs and raise mortality, little information is available on the incidence and risk factors for IAH in critically ill patients. This study assessed the prevalence of IAH and its risk factors in a mixed population of intensive care patients.

DESIGN

A multicentre, prospective 1-day point-prevalence epidemiological study conducted in 13 ICUs of six countries.

INTERVENTIONS

None.

PATIENTS

Ninety-seven patients admitted for more than 24 h to one of the ICUs during the 1-day study period.

METHODS

Intra-abdominal pressure (IAP) was measured four times (every 6 h) by the bladder pressure method. Data included the demographics, medical or surgical type of admission, SOFA score, etiological factors such as abdominal surgery, haemoperitoneum, abdominal infection, massive fluid resuscitation, and ileus and predisposing conditions such as hypothermia, acidosis, polytransfusion, coagulopathy, sepsis, liver dysfunction, pneumonia and bacteraemia.

RESULTS

We enrolled 97 patients, mean age 64+/-15 years, 57 (59%) medical and 40 (41%) surgical admission, SOFA score of 6.5+/-4.0. Mean IAP was 9.8+/-4.7 mmHg. The prevalence of IAH (defined as IAP 12 mmHg or more) was 50.5 and 8.2% had abdominal compartment syndrome (defined as IAP 20 mmHg or more). The only risk factor significantly associated with IAH was the body mass index, while massive fluid resuscitation, renal and coagulation impairment were at limit of significance.

CONCLUSION

Although we found a quite high prevalence of IAH, no risk factors were reliably associated with IAH; consequently, to get valid information about IAH, IAP needs to be measured.