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

The persistent inflammation, immunosuppression, and catabolism syndrome 10 years later

With the implementation of new intensive care unit (ICU) therapies in the 1970s, multiple organ failure (MOF) emerged as a fulminant inflammatory phenotype leading to early ICU death. Over the ensuing decades, with fundamental advances in care, this syndrome has evolved into a lingering phenotype of chronic critical illness (CCI) leading to indolent late post-hospital discharge death. In 2012, the University of Florida (UF) Sepsis Critical Illness Research Center (SCIRC) coined the term Persistent Inflammation, Immunosuppression, and Catabolism Syndrome (PICS) to provide a mechanistic framework to study CCI in surgical patients. This was followed by a decade of research into PICS-CCI in surgical ICU patients in order to define the epidemiology, dysregulated immunity, and long-term outcomes after sepsis. Other focused studies were performed in trauma ICU patients and emergency department sepsis patients. Early deaths were surprisingly low (4%); 63% experienced rapid recovery. Unfortunately, 33% progressed to CCI, of which 79% had a poor post-discharge disposition and 41% were dead within one year. These patients had biomarker evidence of PICS, and these biomarkers enhanced clinical prediction models for dismal one-year outcomes. Emergency myelopoiesis appears to play a central role in the observed persistent immune dysregulation that characterizes PICS-CCI. Older patients were especially vulnerable. Disturbingly, over half of the older CCI patients were dead within one year and older CCI survivors remained severely disabled. Although CCI is less frequent (20%) after major trauma, PICS appears to be a valid concept. This review will specifically detail the epidemiology of CCI, PICS biomarkers, effect of site of infection, acute kidney injury, effect on older patients, dysfunctional high-density lipoproteins, sarcopenia/cachexia, emergency myelopoiesis, dysregulated erythropoiesis, and potential therapeutic interventions.

A review of UF SCIRC’s research efforts characterizing CCI, PICS biomarkers, effect of site of infection, acute kidney injury, effects on older patients, dysfunctional high-density lipoproteins, sarcopenia/cachexia, emergency myelopoiesis, and dysregulated erythropoiesis.

Physicians' Knowledge of Abdominal Compartment Syndrome and Intra-Abdominal Hypertension in Saudi Arabia: An Online Cross-Sectional Survey Study

Objective

To determine physicians' knowledge of abdominal compartment syndrome and intra-abdominal hypertension in Saudi Arabia.

Methods

A cross-sectional online survey study was conducted on physicians in Saudi Arabia between March and August 2022. A previously developed questionnaire was adapted and used in this study. The survey instrument investigated the knowledge and management of intra-abdominal hypertension and abdominal compartment syndrome among physicians. Logistic regression was used to identify predictors of being knowledgeable about abdominal compartment syndrome and intra-abdominal hypertension.

Results

A total of 266 physicians participated in this study. Around one-fifth (21.8%) the study participants were ICU physicians and 25.0% reported that they practice internal medicine. Intra-abdominal hypertension (IAH) and the impact of increased intra-abdominal pressure (IAP) on organ function were terms that the majority of research participants (70.3%) reported they were familiar with. A similar percentage (73.7%) reported that they are familiar with abdominal compartment syndrome (ACS). Around 43.0% of the study participants reported that they do not know how to measure IAP. The most frequently reported (13.5%) intervention in the treatment of IAH and ACS was the use of inotropes or vasopressors. The study participants showed a weak level of knowledge of ACS and IAH with a median score of 3.00 (IQR: 5.00-2.00), which represents 27.3% of the maximum attainable score. Physicians working at hospitals with 20-50 ICU beds were 41.0% (odds ratio: 0.59 (CI: 0.37-0.96)) less likely to be knowledgeable about intra-abdominal hypertension and abdominal compartment syndrome (p≤0.05).

Conclusion

Physicians demonstrated a low level of IAP and ACS knowledge. To increase the safety of medical practices and enhance clinical outcomes for patients, awareness should be raised about the proper diagnosis and management of IAP and ACS. Future research should focus on developing effective educational strategies to improve physicians' understanding of IAP and ACS.

Opposite response of blood vessels in the retina to 6° head-down tilt and long-duration microgravity

The Spaceflight Associated Neuro-ocular Syndrome (SANS), associated with the headward fluid shifts incurred in microgravity during long-duration missions, remains a high-priority health and performance risk for human space exploration. To help characterize the pathophysiology of SANS, NASA's VESsel GENeration Analysis (VESGEN) software was used to map and quantify vascular adaptations in the retina before and after 70 days of bed rest at 6-degree Head-Down Tilt (HDT), a well-studied microgravity analog. Results were compared to the retinal vascular response of astronauts following 6-month missions to the International Space Station (ISS). By mixed effects modeling, the trends of vascular response were opposite. Vascular density decreased significantly in the 16 retinas of eight astronauts and in contrast, increased slightly in the ten retinas of five subjects after HDT (although with limited significance). The one astronaut retina diagnosed with SANS displayed the greatest vascular loss. Results suggest that microgravity is a major variable in the retinal mediation of fluid shifts that is not reproduced in this HDT bed rest model.

Decreased Vascular Patterning in the Retinas of Astronaut Crew Members as New Measure of Ocular Damage in Spaceflight-Associated Neuro-ocular Syndrome

Purpose

Ocular structural and functional changes, collectively termed spaceflight-associated neuro-ocular syndrome (SANS), have been described in astronauts undergoing long-duration missions in the microgravity environment of the International Space Station. We tested the hypothesis that retinal vascular remodeling, particularly by smaller vessels, mediates the chronic headward fluid shifts associated with SANS.

Methods

As a retrospective study, arterial and venous patterns extracted from 30° infrared Heidelberg Spectralis retinal images of eight crew members acquired before and after six-month missions were analyzed with NASA's recently released VESsel GENeration Analysis (VESGEN) software. Output parameters included the fractal dimension and overall vessel length density that was further classified into large and small vascular branching generations. Vascular results were compared with SANS-associated clinical ocular measures.

Results

Significant postflight decreases in Df, Lv, and in smaller but not larger vessels were quantified in 11 of 16 retinas for arteries and veins (P value for Df, Lv, and smaller vessels in all 16 retinas were ≤0.033). The greatest vascular decreases occurred in the only retina displaying clinical evidence of SANS by choroidal folds and optic disc edema. In the remaining 15 retinas, decreases in vascular density from Df and Lv ranged from minimal to high by a custom Subclinical Vascular Pathology Index.

Conclusions

Together with VESGEN, the Subclinical Vascular Pathology Index may represent a new, useful SANS biomarker for advancing the understanding of SANS etiology and developing successful countermeasures for long duration space exploration in microgravity, although further research is required to better characterize retinal microvascular adaptations.

Evaluation and Management of Abdominal Compartment Syndrome in the Emergency Department

BACKGROUND

Abdominal compartment syndrome is a potentially deadly condition that can be missed in the emergency department setting.

OBJECTIVE

The purpose of this narrative review article is to provide a summary of the background, pathophysiology, diagnosis, and management of abdominal compartment syndrome with a focus on emergency clinicians.

DISCUSSION

Abdominal compartment syndrome is caused by excessive pressure within the abdominal compartment due to diminished abdominal wall compliance, increased intraluminal contents, increased abdominal contents, or capillary leak/fluid resuscitation. History and physical examination are insufficient in isolation, and the gold standard is intra-abdominal pressure measurement. Abdominal compartment syndrome is defined as an intra-abdominal pressure >20 mm Hg with evidence of end-organ injury. Management involves increasing abdominal wall compliance (e.g., analgesia, sedation, and neuromuscular blocking agents), evacuating gastrointestinal contents (e.g., nasogastric tubes, rectal tubes, and prokinetic agents), avoiding excessive fluid resuscitation, draining intraperitoneal contents (e.g., percutaneous drain), and decompressive laparotomy in select cases. Patients are critically ill and often require admission to a critical care unit.

CONCLUSIONS

Abdominal compartment syndrome is an increasingly recognized condition with the potential for significant morbidity and mortality. It is important for clinicians to be aware of the current evidence regarding the diagnosis, management, and disposition of these patients.

Development of multiple organ dysfunction syndrome in older and young adult trauma patients

Objective

We sought out to determine the correlation between the injury severity score (ISS) and multiple organ dysfunction syndrome (MODS) between severely injured young adults (18-54 years) and elderly (>55 years) patients.

Materials and Methods

This was a cross-sectional observational study. We included all adult cases (>18 years) diagnosed with trauma defined by the International Classification of Diseases, Ninth Revision. For significance testing, Chi-square test and odds ratio were used. Severe injuries were defined by an ISS >15. The presence of MODS was based on the definitions proposed by society for critical care medicine.

Results

A total of 469 young and 173 elderly patients were included in the study. Among the 469 young adults, 193 had ISS >15, whereas out of the 173 elderly patients, 88 had an ISS >15. Severely injured young and elderly groups were more likely to develop MODS compared with those with an ISS <15 (P < 0.001 and P < 0.001, respectively). The elderly had a higher likelihood of developing MODS (P < 0.001; odds ratio: 5.17; 95% confidence interval: 2.74-9.80).

Conclusion

This study demonstrated a direct relationship between an ISS >15 and the development of MODS. We also observed a five-fold increase in the development of MODS among severely injured elderly patients.

Intra-Abdominal Hypertension is a Risk Factor for Increased VAP Incidence: A Prospective Cohort Study in the ICU of a Tertiary Hospital

BACKGROUND

Ventilator-associated pneumonia (VAP) might be increased in cases with intra-abdominal hypertension (IAH). However, despite animal experimentation and physiological studies on humans in favor of this hypothesis, there is no definitive clinical data that IAH is associated with VAP. We therefore aimed to study whether IAH is a risk factor for increased incidence of VAP in critical care patients. This 1-center prospective observational cohort study was conducted in the intensive care unit of the University Hospital of Larissa, Greece, during 2013 to 2015. Consecutive patients were recruited if they presented risk factors for IAH at admission and were evaluated systematically for IAH and VAP for a 28-day period.

RESULTS

Forty-five (36.6%) of 123 patients presented IAH and 45 (36.6%) presented VAP; 24 patients presented VAP following IAH. Cox regression analysis showed that VAP was independently associated with IAH (1.06 [1.01-1.11]; P = .053), while there was an indication for an independent association between VAP and abdominal surgery (1.62 [0.87-3.03]; P = .11] and chronic obstructive pulmonary disease (1.79 [0.96-3.37]; P = .06).

CONCLUSIONS

Intra-abdominal hypertension is an independent risk factor for increased VAP incidence in critically ill patients who present risk factors for IAH at admission to the ICU.

Persistent inflammation, immunosuppression, and catabolism and the development of chronic critical illness after surgery

As early as the 1990s, chronic critical illness, a distinct syndrome of persistent high-acuity illness requiring management in the ICU, was reported under a variety of descriptive terms including the "neuropathy of critical illness," "myopathy of critical illness," "ICU-acquired weakness," and most recently "post-intensive care unit syndrome." The widespread implementation of targeted shock resuscitation, improved organ support modalities, and evidence-based protocolized ICU care has resulted in significantly decreased in-hospital mortality within surgical ICUs, specifically by reducing early multiple organ failure deaths. However, a new phenotype of multiple organ failure has now emerged with persistent but manageable organ dysfunction, high resource utilization, and discharge to prolonged care facilities. This new multiple organ failure phenotype is now clinically associated with the rapidly increasing incidence of chronic critical illness in critically ill surgery patients. Although the underlying pathophysiology driving chronic critical illness remains incompletely described, the persistent inflammation, immunosuppression, and catabolism syndrome has been proposed as a mechanistic framework in which to explain the increased incidence of chronic critical illness in surgical ICUs. The purpose of this review is to provide a historic perspective of the epidemiologic evolution of multiple organ failure into persistent inflammation, immunosuppression, and catabolism syndrome; describe the mechanism that drives and sustains chronic critical illness, and review the long-term outcomes of surgical patients who develop chronic critical illness.

Persistent Inflammation, Immunosuppression and Catabolism Syndrome

Following advances in critical care, in-hospital multiple organ failure-related mortality is declining. Consequently, incidence of chronic critical illness is increasing. These patients linger in the intensive care unit, have high resource utilization, and poor long-term outcomes. Within this population, the authors propose that a substantial subset of patients have a new phenotype: persistent inflammation, immunosuppression, and catabolism syndrome. There is evidence that myelodysplasia with expansion of myeloid-derived suppressor cells, innate and adaptive immune suppression, and protein catabolism with malnutrition are major contributors. Optimal care of these patients will require novel multimodality interventions.

The role of NIGMS P50 sponsored team science in our understanding of multiple organ failure

The history of the National Institute of General Medical Sciences (NIGMS) Research Centers in Peri-operative Sciences (RCIPS) is the history of clinical, translational, and basic science research into the etiology and treatment of posttraumatic multiple organ failure (MOF). Born out of the activism of trauma and burn surgeons after the Viet Nam War, the P50 trauma research centers have been a nidus of research advances in the field and the training of future academic physician-scientists in the fields of trauma, burns, sepsis, and critical illness. For over 40 years, research conducted under the aegis of this funding program has led to numerous contributions at both the bedside and at the bench. In fact, it has been this requirement for team science with a clinician-scientist working closely with basic scientists from multiple disciplines that has led the RCIPS to its unrivaled success in the field. This review will briefly highlight some of the major accomplishments of the RCIPS program since its inception, how they have both led and evolved as the field moved steadily forward, and how they are responsible for much of our current understanding of the etiology and pathology of MOF. This review is not intended to be all encompassing nor a historical reference. Rather, it serves as recognition to the foresight and support of many past and present individuals at the NIGMS and at academic institutions who have understood the cost of critical illness and MOF to the individual and to society.

Intraabdominal Hypertension, Abdominal Compartment Syndrome, and the Open Abdomen

Abdominal compartment syndrome (ACS) is the end point of a process whereby massive interstitial swelling in the abdomen or rapid development of a space-filling lesion in the abdomen (such as ascites or a hematoma) leads to pathologically increased pressure. This results in so-called intraabdominal hypertension (IAH), causing decreased perfusion of the kidneys and abdominal viscera and possible difficulties with ventilation and maintenance of cardiac output. These effects contribute to a cascade of ischemia and multiple organ dysfunction with high mortality. A few primary disease processes traditionally requiring large-volume crystalloid resuscitation account for most cases of IAH and ACS. Once IAH is recognized, nonsurgical steps to decrease intraabdominal pressure (IAP) can be undertaken (diuresis/dialysis, evacuation of intraluminal bowel contents, and sedation), although the clinical benefit of such therapies remains largely conjectural. Surgical decompression with midline laparotomy is the standard ultimate treatment once ACS with organ dysfunction is established. There is minimal primary literature on the pathophysiological underpinnings of IAH and ACS and few prospective randomized trials evaluating their treatment or prevention; this concise review therefore provides only brief summaries of these topics. Many modern studies nominally dealing with IAH or ACS are simply epidemiologic surveys on their incidence, so this paper summarizes the incidence of IAH and ACS in a variety of disease states. Especially emphasized is the fact that modern critical care paradigms emphasize rational limitations to fluid resuscitation, which may have contributed to an apparent decrease in ACS among critically ill patients.

Postinjury Inflammation and Organ Dysfunction

The development of organ dysfunction (OD) is related to the intensity and balance between trauma-induced simultaneous, opposite inflammatory responses. Early proinflammation via innate immune system activation may cause early OD, whereas antiinflammation, via inhibition of the adaptive immune system and apoptosis, may induce immunoparalysis, impaired healing, infections, and late OD. Patients discharged with low-level OD may develop the persistent inflammation-immunosuppression catabolism syndrome. Although the incidence of multiple organ failure has decreased over time, it remains morbid, lethal, and resource intensive. However, single OD, especially acute lung injury, remains frequent. Treatment is limited, and prevention remains the mainstay strategy.

Persistent Inflammation, Immunosuppression, and Catabolism: Evolution of Multiple Organ Dysfunction

BACKGROUND

Multiple organ dysfunction (MOD) has plagued intensive care units (ICUs) for more than four decades, and its epidemiology has evolved because more patients are surviving previously lethal insults. Over the years, different predominant phenotypes of MOD have been described, all of which have consumed tremendous healthcare resources and have been associated with prolonged ICU stays and prohibitive mortality rates.

METHODS

Review of the English-language literature.

RESULTS

By the 1990s, it became widely accepted that MOD could ensue after both infectious and non-infectious insults by what appeared to be a similar auto-destructive systemic inflammatory response. A 1996 analysis recognized that MOD was a bimodal phenomenon. As a result of years of implementation efforts, fewer patients died of early fulminant sepsis, and those who developed MOD survived hospitalization. Unfortunately, a substantial portion of these patients enter a state of persistent inflammation, immunosuppression, and catabolism (PICS) marked by persistent loss of lean body mass with failure to rehabilitate, sepsis recidivism necessitating re-hospitalization, increasing functional dependence, and an indolent path to death.

CONCLUSION

Unfortunately, as our population ages and peri-operative care improves, PICS will become an insurmountable epidemic. We believe PICS is the next horizon in surgical critical care and have developed a program to study the pathogenesis and novel therapies for this vexing problem.

Novel markers predict death and organ failure following hemorrhagic shock

BACKGROUND

ADAMTS 13, sP-Selectin and HSP27 have been investigated as potential prognostic markers in patients with hemorrhagic shock.

METHODS

This study was part of a double-blind, randomized, parallel-group, controlled trial and included seventeen trauma patients presented to ED with severe hemorrhagic. The sera for testing were collected from these patients at the time of admission. Investigators and laboratory personnel performing testing were blinded to the patients' identity and clinical course.

RESULTS

The prognostic value of ADAMTS13, sP-Selectin, and HSP27 was compared to prognostic value of systolic blood pressure (SBP), base deficit estimation (BD), heart rate (HR), shock index (SI) and tissue oxygen saturation (StO2) by constructing the receiver operation characteristics (ROC). The area under the curve (AUC) of the ROC for HSP27 (0.92) was greater than for SBP (0.45), BD (0.89), HR (0.61), SI (0.45) and StO2 (0.46). AUC for sP-Selectin (0.86) and for ADAMTS13 antigen (0.74) were comparable with BD one, but greater than for the rest of currently used tests.

CONCLUSION

Serum concentrations of ADAMTS13, HSP27 and sP-Selectin measured during the admission, appear to be comparable to or better than SBP, BD, SI, HR and StO2 in predicting MODS and death after hemorrhage from trauma. These potential new markers deserve further investigation.

Early screening to identify patients at risk of developing intra-abdominal hypertension and abdominal compartment syndrome

BACKGROUND

To develop a screening tool to identify patients at risk of developing intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS) within 24 h of a patient's admission to intensive care unit (ICU).

METHODS

Prospective, observational study of 403 consecutively enrolled patients with an indwelling catheter, admitted to a mixed medical-surgical ICU in a tertiary referral, university hospital. Intra-abdominal pressure was measured at least twice daily and IAH and ACS defined as per consensus definitions.

RESULTS

Thirty-nine per cent of patients developed IAH and 2% developed ACS. Abdominal distension, hemoperitoneum/pneumoperitoneum/intra-peritoneal fluid collection, obesity, intravenous fluid received > 2.3 l, abbreviated Sequential Organ Failure Assessment score > 4 points and lactate > 1.4 mmol/l were identified as independent predictors of IAH upon admission to ICU. The presence of three or more of these risk factors at admission identified patients that would develop IAH with a sensitivity of 75% and a specificity of 76%, the development of grades II, III and IV IAH with a sensitivity of 91% and a specificity of 62%. Patients that developed IAH required a significantly longer duration of mechanical ventilation and ICU care. Patients that developed grades II-IV IAH had a significantly higher rate of ICU mortality.

CONCLUSION

IAH is a common clinical entity in the intensive care setting that is associated with morbidity and mortality. A screening tool, based on data readily available within a patient's first 24 h in ICU, was developed and effectively identified patients that required intra-abdominal pressure monitoring.

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: Incidence and prognostic factors influencing survival in Singapore

Aim of Study:

Abdominal compartment syndrome (ACS) is a distinct clinical entity in the critically ill-patient, which leads to end-organ dysfunction. However, data on the incidence of ACS is scarce, and this is also likely contributed by under-diagnosis of this clinical condition. This study reports all cases of ACS in a tertiary institution in Singapore over 10 years, and evaluates prognostic factors affecting survival.

Materials and Methods:

This retrospective clinical study included 17 patients with ACS, of which 13 underwent decompressive laparotomy, over a 10 years period. Univariate and multivariate analyses of prognostic factors predicting mortality was performed using Chi-square or Fisher-exact test as appropriate.

Results:

Mean arterial pressure was significantly improved postoperatively, and intra-abdominal pressure and positive end-expiratory pressure significantly decreased. Overall mortality was 47.1%. Advanced age of more than 65 years, gender, large volume resuscitation of more than 3.5 L over 24 h, three or more co-morbidities, requirement of inotropes, usage of mechanical ventilation, and the presence of concurrent lung and renal dysfunction were not adverse prognostic indicators of poorer outcome. The occurrence of multiple relook laparotomies was shown to be the only independent prognostic factor predicting a favorable outcome among these patients on univariate and multivariate analyses. The incidence of ACS accounts for only 0.1% of all Intensive Care Unit admissions during the study period of 10 years, likely due to under-diagnosis.

Conclusion:

We believe that a protocol for a focused measurement in high-risk groups will increase the diagnostic yield of this condition. Multiple laparotomies for abdominal decompression can lead to improved survival.

Clinical awareness of intra-abdominal hypertension and abdominal compartment syndrome in 2007

INTRODUCTION

There has been an exponentially increasing interest in intra-abdominal hypertension (IAH). The aim of this review is to evaluate the evolution in clinical awareness of this syndrome.

METHODS

A PubMed (U.S. National Library of Medicine) search and a ScienceDirect (Elsevier B.V.) search of recent literature were performed in order to assess clinical awareness of IAH and abdominal compartment syndrome (ACS).

RESULTS

In total, 489 articles and 8 clinical surveys have been identified. The results of the landmark papers and the surveys will be briefly discussed in this review.

CONCLUSION

Clinical awareness of ACS is steadily increasing. It is time to pay attention to ACS, but further, it is time to move forward with therapeutic bundles in a multi-centered, outcome trial on IAH/ACS therapy in order to elevate IAH/ACS management to an international standard of care.

Damage control surgery for abdominal emergencies

BACKGROUND

Damage control surgery is a management sequence initiated to reduce the risk of death in severely injured patients presenting with physiological derangement. Damage control principles have emerged as an approach in non-trauma abdominal emergencies in order to reduce mortality compared with primary definitive surgery.

METHODS

A PubMed/MEDLINE literature review was conducted of data available over the past decade (up to August 2013) to gain information on current understanding of damage control surgery for abdominal surgical emergencies. Future directions for research are discussed.

RESULTS

Damage control surgery facilitates a strategy for life-saving intervention for critically ill patients by abbreviated laparotomy with subsequent reoperation for delayed definitive repair after physiological resuscitation. The six-phase strategy (including damage control resuscitation in phase 0) is similar to that for severely injured patients, although non-trauma indications include shock from uncontrolled haemorrhage or sepsis. Minimal evidence exists to validate the benefit of damage control surgery in general surgical abdominal emergencies. The collective published experience over the past decade is limited to 16 studies including a total of 455 (range 3-99) patients, of which the majority are retrospective case series. However, the concept has widespread acceptance by emergency surgeons, and appears a logical extension from pathophysiological principles in trauma to haemorrhage and sepsis. The benefits of this strategy depend on careful patient selection. Damage control surgery has been performed for a wide range of indications, but most frequently for uncontrolled bleeding during elective surgery, haemorrhage from complicated gastroduodenal ulcer disease, generalized peritonitis, acute mesenteric ischaemia and other sources of intra-abdominal sepsis.

CONCLUSION

Damage control surgery is employed in a wide range of abdominal emergencies and is an increasingly recognized life-saving tactic in emergency surgery performed on physiologically deranged patients.

Resuscitation beyond the abdominal compartment syndrome

PURPOSE OF REVIEW

In the 1980s, we witnessed tremendous advances in trauma care including trauma system development, advanced trauma life support, damage control surgery and ICU resuscitation. As a result, patients who used to bleed to death in the operating room survived. However, many went on to develop multiple organ failure (MOF) and in the mid-1990s, an epidemic of abdominal compartment syndrome (ACS) that emerged in these MOF survivors stimulated fundamental changes in early management of patients arriving in shock with severe bleeding.

RECENT FINDINGS

In the early 2000s, a massive transfusion protocol (emphasizing aggressive use of fresh frozen plasma) coupled with hypotensive resuscitation and rapid hemorrhage control were implemented and refined at a busy level I trauma center in Houston, Texas, USA. These changes were associated with a 50% reduction in mortality in massive transfusion patients, and ACS virtually disappeared.

SUMMARY

ACS is a modifiable link in the MOF cascade to death after severe shock. However, as ACS disappears, MOF is still occurring. Although fewer patients are dying of MOF, it remains the leading cause of prolonged ICU stays and long-term disability. This experience underscores the importance of ongoing epidemiologic characterization of postinjury MOF.

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.

Early detection of subclinical organ dysfunction by microdialysis of the rectus abdominis muscle in a porcine model of critical intra-abdominal hypertension

The aim of this study was to evaluate microdialysis of the rectus abdominis muscle (RAM) for early detection of subclinical organ dysfunction in a porcine model of critical intra-abdominal hypertension (IAH). Microdialysis catheters for analyses of lactate, pyruvate, and glycerol levels were placed in cervical muscles (control), gastric and jejunal wall, liver, kidney, and RAM of 30 anesthetized mechanically ventilated pigs. Catheters for venous lactate and interleukin 6 samples were placed in the jugular, portal, and femoral vein. Intra-abdominal pressure (IAP) was increased to 20 mmHg (IAH20 group, n = 10) and 30 mmHg (IAH30, n = 10) for 6 h by controlled CO2 insufflation, whereas sham animals (n = 10) exhibited a physiological IAP. In contrast to 20 mmHg, an IAH of 30 mmHg induced pathophysiological alterations consistent with an abdominal compartment syndrome. Microdialysis showed significant increase in the lactate/pyruvate ratio in the RAM of the IAH20 group after 6 h. In the IAH30 group, the strongest increase in lactate/pyruvate ratio was detected in the RAM and less pronounced in the liver and gastric wall. Glycerol increased in the RAM only. After 6 h, there was a significant increase in venous interleukin 6 of the IAH30 group compared with baseline. Venous lactate was increased compared with baseline and shams in the femoral vein of the IAH30 group only. Intra-abdominal pressure-induced ischemic metabolic changes are detected more rapidly and pronounced by microdialysis of the RAM when compared with intra-abdominal organs. Thus, the RAM represents an important and easily accessible site for the early detection of subclinical organ dysfunction during critical IAH.

Incidence and prognosis of intra-abdominal hypertension in critically ill medical patients: a prospective epidemiological study

INTRODUCTION

The aim of this study was to determine the incidence of intra-abdominal hypertension (IAH) in patients with two or more categorized risk factors (CRF) for IAH, and their morbidity and mortality during their intensive care unit (ICU) stay.

METHODS

Prospective cohort study carried out at a medical ICU. A total of 151 medical patients were enrolled during a period of 3 months. After ICU whole staff training, we conducted daily screening of the four CRF for IAH based on the World Society of Abdominal Compartment Syndrome (WSACS) guidelines (namely, diminished abdominal wall compliance, increased intraluminal content, increased abdominal content, and capillary leak syndrome or fluid resuscitation). In those patients with risk factors of at least two different categories (≥2 CRF), intra-abdominal pressure (IAP) was measured every 8 h during ICU stay. Data included demographics, main diagnosis on admission, severity scores, cumulative fluid balance, daily mean IAP, resolution of IAH, days of ICU and hospital stay, and mortality.

RESULTS

Eighty-seven patients (57.6%) had ≥2 CRF for IAH, 59 (67.8%) out of whom developed IAH. Patients with ≥2 CRF had a significantly higher mortality rate (41.4 vs. 14.3%, p < 0.001). Patients with IAH had higher body mass index, severity scores, organ dysfunctions/failures, number of CRF for IAH, days of ICU/hospital stay and hospital mortality rate (45.8 vs. 32.1%, p = 0.22). Non-resolution of IAH was associated with a higher mortality rate (64.7 vs. 35.3%, p = 0.001). None of the cohort patients developed abdominal compartment syndrome. The multivariate analysis showed that IAH development (odds ratio (OR) 4.09; 95% confidence interval (CI) 0.83-20.12) was a non-independent risk factor for mortality, and its non-resolution (OR 13.15; 95% CI 22.13-81.92) was an independent risk factor for mortality.

CONCLUSIONS

Critically ill medical patients admitted to ICU with ≥2 CRF have high morbidity, mortality rate, and incidence of IAH, so IAP should be measured and monitored as recommended by the WSACS. Our study highlights the importance of implementing screening and assessment protocols for an early diagnosis of IAH.

Persistent inflammation and immunosuppression: a common syndrome and new horizon for surgical intensive care

Surgical intensive care unit (ICU) stay of longer than 10 days is often described by the experienced intensivist as a "complicated clinical course" and is frequently attributed to persistent immune dysfunction. "Systemic inflammatory response syndrome" (SIRS) followed by "compensatory anti-inflammatory response syndrome" (CARS) is a conceptual framework to explain the immunologic trajectory that ICU patients with severe sepsis, trauma, or emergency surgery for abdominal infection often traverse, but the causes, mechanisms, and reasons for persistent immune dysfunction remain unexplained. Often involving multiple-organ failure (MOF) and death, improvements in surgical intensive care have altered its incidence, phenotype, and frequency and have increased the number of patients who survive initial sepsis or surgical events and progress to a persistent inflammation, immunosuppression, and catabolism syndrome (PICS). Often observed, but rarely reversible, these patients may survive to transfer to a long-term care facility only to return to the ICU, but rarely to self-sufficiency. We propose that PICS is the dominant pathophysiology and phenotype that has replaced late MOF and prolongs surgical ICU stay, usually with poor outcome. This review details the evolving epidemiology of MOF, the clinical presentation of PICS, and our understanding of how persistent inflammation and immunosuppression define the pathobiology of prolonged intensive care. Therapy for PICS will involve innovative interventions for immune system rebalance and nutritional support to regain physical function and well-being.

Liver packing during elective surgery: an option that can be considered

BACKGROUND

Packing is a life-saving procedure in patients undergoing emergency surgery for blunt hepatic trauma, especially when massive blood transfusions, acidosis, or hypothermia have resulted in coagulation disorders. The purpose of this study was to apply this concept to the setting of elective liver surgery.

METHODS

Elective packing was performed in 7 patients who had sustained prolonged bleeding mainly related to partial outflow obstruction during the course of liver resection (n = 3) or transplantation (n = 4). At the time of packing, conventional methods of hemostasis had failed and surgery had lasted for 490 (range, 380-695) minutes, blood loss was 5,700 (range, 2,100-13,700) ml, and all patients had coagulation disorders (prothrombin time PT <30%, platelets <45 g/l), hypothermia (body temperature 35.4 °C), acidosis (median blood pH 7.24; serum lactate 6.5 mmol/l) and required catecholamine support.

RESULTS

Unpacking was performed after a median of 37 (range, 26-60) hours. At that time, all patients were normothermic, with platelet counts >45 g/l, PT >30%, and restored acid-base balance. Active bleeding had stopped, and secondary fascia closure was feasible. With a minimum follow-up of 6 months, all patients are alive without sequel.

CONCLUSIONS

Packing is a safe and efficient means to control venous bleeding when conventional methods of hemostasis have failed, knowing that commonly the reason for failure of conventional method of hemostasis is partial outflow obstruction.

Effect of damage control surgery on major abdominal vascular trauma

BACKGROUND

In 1982, we reported our experience with abdominal vascular trauma, highlighting the critical role of hypothermia, acidosis, and coagulopathy. Damage control surgery was subsequently introduced to address this "lethal triad." The purpose of the present study was to evaluate the outcomes from our most recent 6-year experience compared with a cohort from 30 years ago.

METHODS

Patients with major abdominal vascular injuries were examined, and the most recent 6-year period was compared with archived data from a similar 6-year period three decades ago.

RESULTS

The number of patients with major abdominal vascular injuries decreased from 123 patients in 1975 to 1980 to 64 patients in 2004 to 2009. The mean initial pH decreased from 7.21 to 6.96 (1975 to 1980 versus 2004 to 2009) for patients with overt coagulopathy. Despite increasingly protracted acidosis, mortality attributable to refractory coagulopathy decreased from 46% to 19% (1975 to 1980 versus 2004 to 2009, chi-square = 4.36, P = 0.04). No significant difference was found in mortality from exsanguinating injuries (43% versus 62%, 1975 to 1980 versus 2004 to 2009, chi-square = 1.96, P = 0.16). The prehospital transport times were unchanged (22 versus 20 min, 1975 to 1980 versus 2004 to 2009). Despite the administration of additional clotting factors and the advent of damage control surgery, the overall mortality remained largely unchanged (37% versus 33%, 1975 to 1980 versus 2004 to 2009, chi-square = 0.385, P = 0.53).

CONCLUSIONS

The adoption of damage control surgery, including the implementation of a massive transfusion protocol, was associated with a reduction in mortality for abdominal vascular injuries due to coagulopathy; however, patients have continued to die of exsanguination.

Strategies for modulating the inflammatory response after decompression from abdominal compartment syndrome

BACKGROUND

Management of the open abdomen is an increasingly common part of surgical practice. The purpose of this review is to examine the scientific background for the use of temporary abdominal closure (TAC) in the open abdomen as a way to modulate the local and systemic inflammatory response, with an emphasis on decompression after abdominal compartment syndrome (ACS).

METHODS

A review of the relevant English language literature was conducted. Priority was placed on articles published within the last 5 years.

RESULTS/CONCLUSION

Recent data from our group and others have begun to lay the foundation for the concept of TAC as a method to modulate the local and/or systemic inflammatory response in patients with an open abdomen resulting from ACS.

Decreased myosin phosphatase target subunit 1(MYPT1) phosphorylation via attenuated rho kinase and zipper-interacting kinase activities in edematous intestinal smooth muscle

BACKGROUND

Intestinal edema development after trauma resuscitation inhibits intestinal motility which results in ileus, preventing enteral feeding and compromising patient outcome. We have shown previously that decreased intestinal motility is associated with decreased smooth muscle myosin light chain (MLC) phosphorylation. The purpose of the present study was to investigate the mechanism of edema-induced decreases in MLC in a rodent model of intestinal edema.

METHODS

Intestinal edema was induced by a combination of resuscitation fluid administration and mesenteric venous hypertension. Sham operated animals served as controls. Contractile activity and alterations in the regulation of MLC including the regulation of MLC kinase (MLCK) and MLC phosphatase (MLCP) were measured.

KEY RESULTS

Contraction amplitude and basal tone were significantly decreased in edematous intestinal smooth muscle compared with non-edematous tissue. Calcium sensitivity was also decreased in edematous tissue compared with non-edematous intestinal smooth muscle. Although inhibition of MLCK decreased contractile activity significantly less in edematous tissue compared with non-edematous tissue, MLCK activity in tissue lysates was not significantly different. Phosphorylation of MYPT was significantly lower in edematous tissue compared with non-edematous tissue. In addition, activities of both rho kinase and zipper-interacting kinase were significantly lower in edematous tissue.

CONCLUSIONS & INFERENCES

We conclude from these data that interstitial intestinal edema inhibits MLC phosphorylation predominantly by decreasing inhibitory phosphorylation of the MLC targeting subunit (MYPT1) of MLC phosphatase via decreased ROCK and ZIPK activities, resulting in more MLC phosphatase activity.

Early Diagnosis and Evidence-Based Care of Surgical Sepsis

Sepsis continues to be a common and serious problem among surgical patients. It is a leading cause of both morbidity and mortality in the perioperative period. The early identification of sepsis and the early implementation of evidence-based care can improve outcomes. This focused review will identify ways to improve the early identification of sepsis and discuss the current evidence-based guidelines for the early management of sepsis, severe sepsis, and septic shock in the surgical patients.

Peritoneal negative pressure therapy prevents multiple organ injury in a chronic porcine sepsis and ischemia/reperfusion model

Sepsis and hemorrhage can result in injury to multiple organs and is associated with an extremely high rate of mortality. We hypothesized that peritoneal negative pressure therapy (NPT) would reduce systemic inflammation and organ damage. Pigs (n = 12) were anesthetized and surgically instrumented for hemodynamic monitoring. Through a laparotomy, the superior mesenteric artery was clamped for 30 min. Feces was mixed with blood to form a fecal clot that was placed into the peritoneum, and the abdomen was closed. All subjects were treated with standard isotonic fluid resuscitation, wide spectrum antibiotics, and mechanical ventilation, and were monitored for 48 h. Animals were separated into two groups 12 h (T12) after injury: for NPT (n = 6), an abdominal wound vacuum dressing was placed in the laparotomy, and negative pressure (-125 mmHg) was applied (T12 - T48), whereas passive drainage (n = 6) was identical to the NPT group except the abdomen was allowed to passively drain. Negative pressure therapy removed a significantly greater volume of ascites (860 ± 134 mL) than did passive drainage (88 ± 56 mL). Systemic inflammation (e.g. TNF-α, IL-1β, IL-6) was significantly reduced in the NPT group and was associated with significant improvement in intestine, lung, kidney, and liver histopathology. Our data suggest NPT efficacy is partially due to an attenuation of peritoneal inflammation by the removal of ascites. However, the exact mechanism needs further elucidation. The clinical implication of this study is that sepsis/trauma can result in an inflammatory ascites that may perpetuate organ injury; removal of the ascites can break the cycle and reduce organ damage.

Sodium hydrogen exchanger as a mediator of hydrostatic edema-induced intestinal contractile dysfunction

BACKGROUND

Resuscitation-induced intestinal edema is associated with early and profound mechanical changes in intestinal tissue. We hypothesize that the sodium hydrogen exchanger (NHE), a mechanoresponsive ion channel, is a mediator of edema-induced intestinal contractile dysfunction.

METHODS

An animal model of hydrostatic intestinal edema was used for all experiments. NHE isoforms 1-3 mRNA and protein were evaluated. Subsequently, the effects of NHE inhibition (with 5-(N-ethyl-N-isopropyl) amiloride [EIPA]) on wet-to-dry ratios, signal transduction and activator of transcription (STAT)-3, intestinal smooth muscle myosin light chain (MLC) phosphorylation, intestinal contractile activity, and intestinal transit were measured.

RESULTS

NHE1-3 mRNA and protein levels were increased significantly in the small intestinal mucosa with the induction of intestinal edema. The administration of EIPA, an NHE inhibitor, attenuated validated markers of intestinal contractile dysfunction induced by edema as measured by decreased STAT-3 activation, increased MLC phosphorylation, improved intestinal contractile activity, and enhanced intestinal transit.

CONCLUSION

The mechanoresponsive ion channel NHE may mediate edema-induced intestinal contractile dysfunction, possibly via a STAT-3 related mechanism.

A murine model for the study of edema induced intestinal contractile dysfunction

BACKGROUND

We have published extensively regarding the effects of edema on intestinal contractile function. However, we have found the need to expand our model to mice to take advantage of the much larger arsenal of research support, especially in terms of transgenic mouse availability and development. To that end, we have developed and validated a hydrostatic intestinal edema model in mice.

METHODS

Male C57 Black 6 mice were subjected to a combination of high volume crystalloid resuscitation and mesenteric venous hypertension in an effort to induce hydrostatic intestinal edema. Wet to dry ratios, myeloperoxidase activity, mucosal injury scoring, STAT-3 nuclear activation, phosphorylated STAT-3 levels, NF-κB nuclear activation, myosin light chain phosphorylation, intestinal contractile activity, and intestinal transit were measured to evaluate the effects of the model.

KEY RESULTS

High volume crystalloid resuscitation and mesenteric venous hypertension resulted in the development of significant intestinal edema without an increase in myeloperoxidase activity or mucosal injury. Edema development was associated with increases in STAT-3 and NF-κB nuclear activation as well as phosphorylated STAT-3. There was a decrease in myosin light chain phosphorylation, basal and maximally stimulated intestinal contractile activity, and intestinal transit.

CONCLUSION & INFERENCES

Hydrostatic edema in mice results in activation of a signal transduction profile that culminates in intestinal contractile dysfunction. This novel model allows for advanced studies into the pathogenesis of hydrostatic edema induced intestinal contractile dysfunction.

Gut barrier dysfunction in critically ill surgical patients with abdominal compartment syndrome

OBJECTIVES

This study investigated the effects of intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS) on gut barrier function in critically ill surgical patients.

METHODS

A prospective observational cohort study on patients with severe acute pancreatitis or abdominal sepsis admitted to an intensive care or high-dependency unit. Intra-abdominal pressure (IAP) and plasma levels of immunoglobulin G (IgG) and IgM antiendotoxin core antibodies (EndoCAb) and procalcitonin (ProCT) were measured serially.

RESULTS

Among 32 recruited patients, 24 (75%) and 8 patients (25%) developed IAH and ACS, respectively. The state of ACS was associated with significant reductions in plasma IgG EndoCAb (P = 0.015) and IgM EndoCAb (P = 0.016) and higher concentrations of plasma ProCT (P = 0.056) compared with absence of ACS. Resolution of IAH and ACS was associated with significant recovery of plasma IgG EndoCAb (P = 0.003 and P = 0.009, respectively) and IgM EndoCAb (P = 0.002 and P = 0.003, respectively) and reduction in plasma ProCT concentration (P = 0.049 and P = 0.019, respectively). Negative correlations were observed between IAP and plasma IgG EndoCAb (P = 0.003) and IgM EndoCAb (P = 0.002).

CONCLUSIONS

Intra-abdominal hypertension and ACS are associated with significantly higher endotoxin exposure and ProCT concentrations, suggestive of gut barrier dysfunction. Resolution of IAH and ACS is associated with evidence for recovery of gut barrier function.

Compartment syndromes from head to toe

Compartment syndrome is defined as the dysfunction of organs/tissues within the compartment due to limited blood supply caused by increased pressure within the compartment. The aim of this article is to introduce and discuss acute compartment syndromes that are essential for critical care physicians to recognize and manage. Various pathophysiological mechanisms (ischemia-reperfusion syndrome, direct trauma, localized bleeding) could lead to increased compartmental pressure and decreased blood flow through the intracompartmental capillaries. Although compartment syndromes are described in virtually all body regions, the etiology, diagnosis, treatment, and prevention are best characterized for three key body regions (extremity, abdominal, and thoracic compartment syndromes). Compartment syndromes can be classified as either primary (pathology/injury is within the compartment) or secondary (no primary pathology or injury within the compartment), and based on the etiology (e.g., trauma, burn, sepsis). A recently described phenomenon is the "multiple" compartment syndrome or "poly"-compartment syndrome, which is usually a complication of a severe shock and massive resuscitation. The prevention of compartment syndromes is based on preemptive open management of compartments (primary syndromes) in high-risk patients and/or careful fluid resuscitation (both primary and secondary syndromes) to limit interstitial swelling.

Management of liver trauma

BACKGROUND

Blunt and penetrating liver trauma is common and often presents major diagnostic and management problems.

METHODS

A literature review was undertaken to determine the current consensus on investigation and management strategies.

RESULTS

The liver is the most frequently injured organ following abdominal trauma. Immediate assessment with ultrasound has replaced diagnostic peritoneal lavage in the resuscitation room, but computerised tomography remains the gold standard investigation. Nonoperative management is preferred in stable patients but laparotomy is indicated in unstable patients. Damage control techniques such as perihepatic packing, hepatotomy plus direct suture, and resectional debridement are recommended. Major complex surgical procedures such as anatomical resection or atriocaval shunting are now thought to be redundant in the emergency setting. Packing is also recommended for the inexperienced surgeon to allow control and stabilisation prior to transfer to a tertiary centre. Interventional radiological techniques are becoming more widely used, particularly in patients who are being managed nonoperatively or have been stabilised by perihepatic packing.

CONCLUSIONS

Management of liver injuries has evolved significantly throughout the last two decades. In the absence of other abdominal injuries, operative management can usually be avoided. Patients with more complex injuries or subsequent complications should be transferred to a specialist centre to optimise final outcome.

Management of liver trauma

BACKGROUND

Blunt and penetrating liver trauma is common and often presents major diagnostic and management problems.

METHODS

A literature review was undertaken to determine the current consensus on investigation and management strategies.

RESULTS

The liver is the most frequently injured organ following abdominal trauma. Immediate assessment with ultrasound has replaced diagnostic peritoneal lavage in the resuscitation room, but computerised tomography remains the gold standard investigation. Nonoperative management is preferred in stable patients but laparotomy is indicated in unstable patients. Damage control techniques such as perihepatic packing, hepatotomy plus direct suture, and resectional debridement are recommended. Major complex surgical procedures such as anatomical resection or atriocaval shunting are now thought to be redundant in the emergency setting. Packing is also recommended for the inexperienced surgeon to allow control and stabilisation prior to transfer to a tertiary centre. Interventional radiological techniques are becoming more widely used, particularly in patients who are being managed nonoperatively or have been stabilised by perihepatic packing.

CONCLUSIONS

Management of liver injuries has evolved significantly throughout the last two decades. In the absence of other abdominal injuries, operative management can usually be avoided. Patients with more complex injuries or subsequent complications should be transferred to a specialist centre to optimise final outcome.

A novel mechanism for neutrophil priming in trauma: potential role of peritoneal fluid

BACKGROUND

We sought to determine the effect of peritoneal fluid from a novel animal model of abdominal compartment syndrome (ACS) on the proinflammatory status of polymorphonuclear leukocytes (PMNs) and monocytes. We hypothesize that peritoneal fluid is a potential priming and/or activating agent for PMNs/monocytes.

METHODS

ACS was induced in female Yorkshire swine, and peritoneal fluid was collected at the time of decompressive laparotomy. Naïve PMNs/monocytes were primed and/or activated with peritoneal fluid, phosphatidylcholine (PAF) plus peritoneal fluid, peritoneal fluid plus n-formyl-met-leu-phe (fMLP), and peritoneal fluid plus phorbol 12-myristate 13-acetate (PMA). Activation was determined by surface marker expression of integrins (CD11b an CD18) and selectins (CD62L). Additionally, proinflammatory cytokines in peritoneal fluid were analyzed.

RESULTS

Peritoneal fluid did not activate PMNs but increased CD11b expression on monocytes. When used as a primer for fMLP- or PMA-induced activation, peritoneal fluid significantly increased CD11b and CD18 expression on PMNs and monocytes. Peritoneal fluid collected at 6 and 12 h post decompressive laparotomy had similar effects. Interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) levels were increased in peritoneal fluid.

CONCLUSION

Peritoneal fluid represents a primer for PMNs/monocytes and seems to act through receptor-dependent and receptor-independent pathways. Strategies to reduce the amount of peritoneal fluid may decrease the locoregional and systemic inflammatory response by reducing priming and activation of neutrophils/monocytes.

A novel physiologic model for the study of abdominal compartment syndrome (ACS)

BACKGROUND

: Current abdominal compartment syndrome (ACS) models rely on intraperitoneal instillation of fluid, air, and other space-occupying substances. Although this allows for the study of the effects of increased abdominal pressure, it poorly mimics its pathogenesis. We have developed the first reported large animal model of ACS incorporating hemorrhagic shock/resuscitation.

METHODS

: Hemorrhagic shock was induced and maintained (1 hour) in 12 Yorkshire swine by bleeding to a mean arterial pressure (MAP) of 50 mm Hg. The collected blood plus two additional volumes of crystalloid was then reinfused. Mesenteric venous hypertension was induced by tightening a previously placed portal vein snare in a nonocclusive manner to mimic the effects of abdominal packing. Crystalloids were infused to maintain MAP. Hemodynamic measurements, abdominal pressure, peak inspiratory pressures, urine output, and blood chemistries were measured sequentially. Animals were studied for 36 hours after decompression.

RESULTS

: ACS (intra-abdominal pressure of > or =20 mm Hg with new organ dysfunction) developed in all animals. There were significant increases in peak inspiratory pressure, central venous pressure, and pulmonary artery pressure and decreases in MAP upon development of ACS. Urine output was significantly decreased before decompression. Mean blood lactate decreased and base excess increased significantly after decompression.

CONCLUSIONS

: We have created the first reported physiologic animal ACS model incorporating hemorrhagic shock/resuscitation and the effects of damage control surgery.

Evaluating the potential role of nitric oxide as a mediator of hydrostatic edema mediated intestinal contractile dysfunction

BACKGROUND

Administration of L-nil, a selective inhibitor of inducible nitric oxide synthase (iNOS), improves ileus in an animal model of resuscitation induced intestinal edema. The purpose of this study was to elucidate the iNOS/nitric oxide (NO) signal transduction pathway in intestinal edema.

MATERIALS AND METHODS

Male Sprague Dawley rats were divided into two groups; CONTROL and RESUS+VH (edema, 80 cc/kg normal saline (resuscitation) with mesenteric venous hypertension). iNOS mRNA and protein, iNOS activity, NO tissue levels, soluble guanylyl cyclase (sGC) expression, and cyclic guanosine monophosphate (cGMP) levels were measured. As a functional endpoint, we evaluated intestinal contractile strength and frequency in L-nil treated animals.

RESULTS

Edema was associated with increased iNOS mRNA and protein expression without subsequent increases in iNOS activity or tissue NO levels. There was no significant change in sGC expression or increase in cGMP induced by edema. Administration of L-nil did not decrease edema development or preserve contractile strength, but increased contractile frequency.

CONCLUSION

Hydrostatic intestinal edema is not associated with increased iNOS activity or tissue NO levels. Administration of L-nil in edema increases intestinal contractile frequency. This may represent a potential mechanism for the amelioration of ileus seen with the administration of L-nil.

Effects of preserved spontaneous breathing activity during mechanical ventilation in experimental intra-abdominal hypertension

PURPOSE

Ventilation problems are common in critically ill patients with intra-abdominal hypertension. The aim of this study was to investigate the effects of preserved spontaneous breathing during mechanical ventilation on hemodynamics, gas exchange, respiratory function and lung injury in experimental intra-abdominal hypertension.

METHODS

Twenty anesthetized pigs were intubated and ventilated for 24 h with biphasic positive airway pressure without (BIPAP(PC)) or with additional, unsynchronized spontaneous breathing (BIPAP(SB)). In 12 animals, intra-abdominal pressure was increased to 30 mmHg for two 9 h periods followed by a 3 h pressure relief each. Eight animals served as controls and were ventilated for 24 h. Hemodynamics, gas exchange and respiratory mechanics were measured and lung injury was determined histologically.

RESULTS

Intra-abdominal hypertension caused significant impairment of hemodynamics and respiratory mechanics in both modes. In the presence of intra-abdominal hypertension, BIPAP(SB) did not demonstrate superior respiratory mechanics and cardiovascular stability as compared to BIPAP(PC). Although the decrease of dynamic compliance and the increase of airway pressures were mitigated, BIPAP(SB) failed to lower pulmonary vascular resistance and caused increased dead space ventilation (p = 0.007). Blood pressures and cardiac output increased in BIPAP(SB), caused by an increase in heart rate (p < 0.001), but not in stroke volume (p = 0.06). BIPAP(SB) was associated with an increased breathing effort, decreased transpulmonary pressure during inspiration and lower lobe diffuse alveolar damage (p = 0.002).

CONCLUSIONS

In the presence of severe intra-abdominal hypertension, the addition of unsupported spontaneous breaths to BIPAP did not improve hemodynamic and respiratory function and caused greater histopathologic damage to the lungs.