Validation study of Nexfin® continuous non-invasive blood pressure monitoring in critically ill adult patients.

BACKGROUND: Nexfin® (BMEYE, Amsterdam, The Netherlands) is a totally non-invasive blood pressure and cardiac output (CO) monitor based on finger arterial pulse contour analysis. METHODS: We performed an open observational study in a mix of medical-surgical-burns critically ill patients (N.=45) to validate Nexfin obtained blood pressures (MAPnex) against PiCCO (MAPfem) derived blood pressure measurements. MAPnex, MAPfem and corresponding systolic (SBP) and diastolic (DBP) blood pressures were measured continuously and registered with a 2 hour interval during the 8-hour study period. Statistical analysis was performed by Pearson regression, Bland and Altman, Concordance plot and Polar plot analysis. RESULTS: MAPnex shows excellent correlation with MAPfem (R² 0.88, mean bias ± LA -2.3±12.4 mmHg, 14.7% error) and may be used interchangeably with invasive monitoring. The excellent MAPnex -MAPfem correlation was preserved in subgroup analysis for patients with severe hypotension, high systemic vascular resistance, low CO, hypothermia and in patients supported by inotropic/vasopressive agents. MAPnex is able to follow changes in MAPfem during the same time interval (level of concordance 85.5%). Nexfin SBP and DBP show significant correlation with PiCCO but the criteria for interchangeability were not met. Finally, polar plot analysis showed that trending capabilities were excellent when changes in MAPnex (ΔMAPnex) were compared to ΔMAPfem (96.1% of changes were within the level of 10% limits of agreement). CONCLUSION: In this sample of critically ill patients we found a good correlation between MAPnex and invasive blood pressures obtained by PiCCO.

A systematic review and individual patient data meta-analysis on intra-abdominal hypertension in critically ill patients: the wake-up project. World initiative on Abdominal Hypertension Epidemiology, a Unifying Project (WAKE-Up!).

Intra-abdominal hypertension (IAH), defined as a pathologically increase in intraabdominal pressure, is commonly found in critically ill patients. While IAH has been associated with several abdominal as well as extra-abdominal conditions, few studies have examined the occurrence of IAH in relation to mortality. The aim of this paper was to evaluate the prognostic role of IAH and its risk factors at admission in critically ill patients across a wide range of settings and countries. An individual patient meta-analysis of all available data and a systematic review of published (in full or as abstract) medical databases and studies between 1996 and June 2012 were performed. The search was limited to "clinical trials" and "randomized controlled trials", "adults", using the terms "intra-abdominal pressure", "intraabdominal hypertension" combined with any of the terms "outcome" and "mortality". All together data on 2707 patients, representing 21 centers from 11 countries was obtained. Data on 1038 patients were not analysed because of the following exclusion criteria: no IAP value on admission (N.=712), absence of information on ICU outcome (N.=195), age <18 or >95 years (N.=131). Data from 1669 individual patients (19 centers from 9 countries) were analyzed in the meta-analysis. Presence of IAH was defined as a sustained increase in IAP equal to or above 12 mmHg. At admission the mean overall IAP was 9.9±5.0 mmHg, with 463 patients (27.7%) presenting IAH with a mean IAP of 16.3±3.4 mmHg. The only independent predictors for IAH were SOFA score and fluid balance on the day of admission. Five hundred thirteen patients (30.8%) died in intensive care. The independent predictors for intensive care mortality were IAH, SAPS II score, SOFA score and admission category. This systematic review and individual patient data meta-analysis shows that IAH is frequently present in critically ill patients and it is an independent predictor for mortality.

A Systematic Review And Individual Patient Data Meta-Analysis On Intraabdominal Hypertension In Critically Ill Patients: The Wake-Up Project World Initiative on Abdominal Hypertension Epidemiology, a Unifying Project (WAKE-Up!).

Background: Intraabdominal hypertension (IAH), defined as a pathologically increase in intraabdominal pressure, is commonly found in critically ill patients. While IAH has been associated with several abdominal as well as extra-abdominal conditions, few studies have examined the occurrence of IAH in relation to mortality. Objective: To evaluate the prognostic role of IAH and its risk factors at admission in critically ill patients across a wide range of settings and countries. Data sources: An individual patient meta-analysis of all available data and a systematic review of published (in full or as abstract) medical databases and studies between 1996 and June 2012 were performed. The search was limited to "clinical trials" and "randomized controlled trials", "adults", using the terms "intraabdominal pressure", "intraabdominal hypertension" combined with any of the terms "outcome" and "mortality". All together data on 2707 patients, representing 21 centers from 11 countries was obtained. Data on 1038 patients were not analysed because of the following exclusion criteria: no IAP value on admission (n=712), absence of information on ICU outcome (n=195), age <18 or > 95 years (n=131). Results: Data from 1669 individual patients (19 centers from 9 countries) were analyzed in the meta-analysis. Presence of IAH was defined as a sustained increase in IAP equal to or above 12 mmHg. At admission the mean overall IAP was 9.9±5.0 mmHg, with 463 patients (27.7%) presenting IAH with a mean IAP of 16.3±3.4 mmHg. The only independent predictors for IAH were SOFA score and fluid balance on the day of admission. Five hundred thirteen patients (30.8%) died in intensive care. The independent predictors for intensive care mortality were IAH, SAPS II score, SOFA score and admission category. Conclusions: This systematic review and individual patient data meta-analysis shows that IAH is frequently present in critically ill patients and it is an independent predictor for mortality.

Localised abdominal compartment syndrome: bladder-over-gastric pressure ratio (B/G ratio) as a clue to diagnosis.

INTRODUCTION: Intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS) have been identified as a cause of organ dysfunction and mortality in critically ill patients. The diagnosis of IAH/ACS depends on accurate intra-abdominal pressure (IAP) measurement, which is usually performed via the bladder or the stomach.The aim of this study was to describe cases where intragastric pressure (IGP) and intrabladder pressure (IBP) were measured simultaneously. PATIENTS AND METHODS: After review of medical records, four patients admitted to our ICU department where both IGP and IBP were measured, could be identified. IGP was measured using the Spiegelberg catheter and IBP was measured using the FoleyManometer LV. In all patients, the bladder-over-gastric pressure ratio (B/G ratio) was calculated. RESULTS: In two of four patients, IGP and IBP differed significantly. In one patient the B/G ratio was lower than 1 suggesting a diagnosis of epigastric ACS and in one patient B/G ratio was greater than 1 leading to a diagnosis of pelvic ACS. The latter patient was spared a decompressive laparotomy due to the additional IGP measurement and the subsequent diagnosis of localized ACS. CONCLUSION: The preferred methods for IAP measurement are via the bladder and via the stomach. In some patients, IGP and IBP may differ significantly and this may have clinical implications. Clinicians should be aware of the possibility of localized ACS. In order to identify risk factors and to recommend treatment for localized ACS, further study of simultaneous IGP and IBP measurements are needed.

Abdominal decompression for abdominal compartment syndrome in critically ill patients: a retrospective study.

BACKGROUND: The abdominal compartment syndrome (ACS) refers to organ dysfunction that may occur as a result of increased intra-abdominal pressure (IAP). Successful management may require abdominal decompression and temporary abdominal closure (TAC). The aim of this study was to analyze the characteristics of patients requiring abdominal decompression, to describe the methods used for TAC, and to study the outcome of these patients. METHODS: A series of critically ill patients who required abdominal decompression for ACS between January 2000 and March 2007 were reviewed retrospectively. Age, gender, severity of organ dysfunction before decompression and the cause of ACS as well as the type of abdominal closure system and length of ICU-stay were recorded. Definitive abdominal closure and in-hospital mortality were the main outcome parameters. RESULTS: Eighteen patients with primary ACS and 6 with secondary ACS required decompressive Laparotomy. Patients' ages ranged from 18 to 89 years (mean 50.7). The median preoperative IAP was 26 mmHg, and IAP decreased to 13 mmHg after decompressive laparotomy. Organ function, as quantified by the SOFA scoring system, improved significantly after the intervention. Eight patients had immediate primary fascial closure after the decompressive procedure and 16 patients required TAC. The majority of the survivors underwent planned ventral hernia repair at a later stage. The mean length of stay in the ICU was 23 (+/- 16) days. Overall, fifteen patients survived (63%). CONCLUSIONS: Decompressive Laparotomy was effective in reducing IAP and was associated with an improvement in organ function. In most of the patients, the abdomen could not be closed after decompression, and fascial repair was delayed.

Acute intestinal distress syndrome: the importance of intra-abdominal pressure.

This review article will focus primarily on the recent literature on abdominal compartment syndrome (ACS) as well as the definitions and recommendations published by the World Society for the Abdominal Compartment Syndrome (WSACS, www.wsacs.org). The risk factors for intra-abdominal hypertension (IAH) and the definitions regarding increased intra-abdominal pressure (IAP) will be listed, followed by a brief but comprehensive overview of the different mechanisms of end-organ dysfunction associated with IAH. Measurement techniques for IAP will be discussed, as well as recommendations for organ function support in patients with IAH. Finally, noninvasive medical management options for IAH, surgical treatment for ACS and management of the open abdomen will be briefly discussed.

Transvesical intra-abdominal pressure measurement using minimal instillation volumes: how low can we go?

OBJECTIVE: To determine the minimal instillation volume at which an intra-abdominal pressure (IAP) curve can be obtained and to compare this with the IAP measured at 20 ml instilled volume. DESIGN AND SETTING: Prospective cohort study in the Intensive Care Unit of Ghent University Hospital. PATIENTS: Twenty-five critically ill sedated and ventilated patients at risk for intra-abdominal hypertension (IAH). INTERVENTIONS: IAP was measured transvesically using a custom-designed IAP monitoring set. Measurement was started without any additional instillation of saline and was continued at 1-ml increments up to 10 ml. Finally, IAP was measured with 20 ml instillation volume. MEASUREMENTS AND RESULTS: After each instillation an "oscillation test" was performed. The minimal volume at which the oscillation test was positive was recorded. These values were compared to the IAP obtained using 20 ml saline (IAP20 ml). At 2 ml installed saline volume an oscillation curve could be obtained in all patients. Mean IAP2 ml) was 11.2+/-3.2 mmHg, IAP10 ml) 11.4+/-3.7 mmHg, and IAP20 ml) 11.7+/-3.2 mmHg. In four patients (16%) there was a clinically significant difference of 2 mmHg or more between IAP2 ml and IAP20 ml. The mean difference between IAP20 ml) and IAP2 ml was 0.60+/-0.91 mmHg (95% CI 0.22-0.98). CONCLUSIONS: In this sample of patients at risk for IAH 2 ml saline was sufficient for IAP signal transduction. Higher volumes for transvesical IAP measurement resulted in higher pressure readings in some patients.

Semicontinuous intra-abdominal pressure measurement using an intragastric Compliance catheter.

OBJECTIVE: To compare intra-abdominal pressure (IAP) measurements obtained from an intragastric Compliance catheter with the pressure measured directly in the abdominal cavity. DESIGN AND SETTING: Prospective cohort study in an operating room of the Ghent University Hospital PATIENTS: Seven patients undergoing elective laparoscopic cholecystectomy. INTERVENTIONS: IAP was obtained from both an intragastric catheter and directly from the peritoneal cavity at 1-minute intervals in patients undergoing elective cholecystectomy and compared using Bland-Altman analysis. MEASUREMENTS AND RESULTS: In 156 paired measurements obtained from 7 patients the mean difference between IAPgastric and IAPref was 0.12+/-0.70 mmHg (95% CI 0.01-0.23). CONCLUSIONS: IAP measured using an intragastric Compliance catheter reliably reflects the reference IAP in patients undergoing laparoscopic cholecystectomy.

Rational intraabdominal pressure monitoring: how to do it?

INTRODUCTION: Intraabdominal hypertension (IAH) is increasingly appreciated by intensivists as an important cause of organ dysfunction, even at pressure levels which were previously thought to be harmless. Therefore, the goal of this review is to describe the different methods commonly used in clinical practice for intraabdominal pressure (IAP) measurement, the advised methodology for each measurement method, and finally to give a rational approach for IAP monitoring in daily clinical practice. METHODS: A Medline search of the English literature was performed using the term "intra abdominal pressure" and "measurement". This resulted in 194 studies, which were then analysed based on the title and abstract. Only clinical studies in human subjects with IAP measurement or related issues as the subject of the study, were considered for inclusion in the study. Reviews, animal experiments and case reports were excluded, while one specific review on IAP measurement and 3 large animal studies (domestic swine > 40 kg) were included in the analysis. This left us with 19 studies, published between 1984 and 2006: 1 specific review, 2 studies in children, 13 in adults and 3 in domestic swine. The references from these studies were searched for relevant articles that may have been missed in the primary search. These articles served as the basis for the recommendations below. RESULTS: Clinical data regarding the validation of new IAP measurement methods or the reliability of established measurement techniques are scarce. The transvesical route, which has been studied most extensively, can be used as reliable route for intermittent IAP measurement, as long as instillation volumes below 25mL are used. Continuous IAP and APP monitoring can be done via a balloon-tipped catheter placed in the stomach or directly intraperitoneal. CONCLUSIONS: Rational IAP monitoring should be based on a site specific protocol, based on known risk factors, the monitoring equipment available and nursing staff experience, and should be linked directly to a local treatment protocol.

Consensus conference definitions and recommendations on intra-abdominal hypertension (IAH) and the abdominal compartment syndrome (ACS)--the long road to the final publications, how did we get there?

OBJECTIVE: There has been an exponentially increasing interest in intraabdominal hypertension (IAH) and the abdominal compartment syndrome (ACS) over the last decade, and different definitions have been suggested. Nevertheless, there has been an impetus from experts in the field to modify these definitions to reflect our current understanding of the pathophysiology of these syndromes. An international multidisciplinary group of interested doctors met with the goal of agreeing on a set of definitions that could be applied to patients with IAH and ACS. The goal of this consensus group was to provide a conceptual and practical framework to further define ACS, a progressive injurious process that falls under the generalized term 'IAH' and that includes IAH-associated organ dysfunction. DESIGN: In total, 21 North American, Australasian and European surgical, trauma and critical care specialists agreed to standardize the current definitions for IAH, ACS and related conditions in preparation for the second World Congress on Abdominal Compartment Syndrome (WCACS). The WCACS-meeting was endorsed by the European Society of Intensive Care Medicine (ESICM) and the World Society on Abdominal Compartment Syndrome (WSACS). METHODS: The consensus conference (Noosa, Australia; December 7, 2004) was attended by 21 specialists from Europe, Australasia and North America and approximately 70 other congress participants. In advance of the conference, a blueprint for the various definitions was suggested. After the conference the participants corresponded electronically with feedback. A writing committee was formed at the conference and developed the final manuscript based on executive summary documents generated by each participant. The final report of the 2004 International ACS Consensus Definitions Conference has recently been published. This article will describe the long road towards this final publication with the evolution of the different definitions and recommendations from the initial suggestions in 2004 to the further refinement and final publications in 2006 and 2007. It will try to explain how we got there and will also give the percentage of agreement with each proposed definition by the participants. RESULTS: New definitions were offered for some terms, while others were discarded and not kept in the final manuscript. Different cut-offs for defining IAH and ACS were given, as well as broad definitions of primary, secondary and recurrent IAH/ACS. A classification system was introduced taking into account the duration, origin, and etiology of IAH. The use of an organ severity scoring method, by means of the Sequential Organ Failure Assessment (SOFA) score when dealing with ACS patients was not recommended as an adjunctive tool to assess morbidity in the final publication. CONCLUSION: This document reflects a process whereby a group of experts and opinion leaders suggested definitions for IAH and ACS. This document should be used as a reference for the next consensus definitions conference in March 2007.

The influence of intraabdominal hypertension on the central nervous system: current insights and clinical recommendations, is it all in the head?

INTRODUCTION: Intra-abdominal hypertension (IAH) and abdominal compartment syndrome are a common occurrence in ICU patients. The deleterious effects of IAH on organ function are well known and increasingly appreciated in recent years, especially where renal and respiratory function are concerned. METHODS: This review will focus on the available literature from the last years.A Medline and PubMed search was performed in order to find an answer to the question "What is the impact of increased IAP on neurologic function in the critically ill?" RESULTS: The amount of data on the influence of IAH on the central nervous system is more scarce, but several animal and human studies have demonstrated a clear correlation between intra-abdominal pressure (IAP) and intracranial pressure (ICP). This correlation is probably due to transmission of the increased IAP to the thorax leading to increased intrathoracic, pleural pressure and central venous pressure, decreased venous return from the brain and increased ICP. This hypothesis is supported by the observation that the increase in ICP is abolished when a sternotomy and pleuropericardotomy are performed, and by the fact that abdominal decompression has produced good results in treating refractory intracranial hypertension (ICH) in patients with both IAH and ICH. CONCLUSIONS: A close relationship between IAP and ICP has been observed in several animal and human studies. The clinical impact of this association is dependent on the baseline ICP and the compensatory reserve of the patient. Some studies have reported good results in treating refractory ICH by abdominal decompression in patients with concomitant IAH. Monitoring of IAP and ICP in risk patients is essential.

Renal implications of increased intra-abdominal pressure: are the kidneys the canary for abdominal hypertension?

INTRODUCTION: Increased intra-abdominal pressure (IAP) or intra-abdominal hypertension (IAH) is a cause of organ dysfunction in critically ill patients and is independently associated with mortality. The kidneys seem to be especially vulnerable to IAH induced dysfunction and renal failure is one of the most consistently described organ dysfunctions associated with IAH. The aim of this paper is to review the historical background, awareness, definitions, pathophysiologic implications and treatment options for IAP induced renal failure. METHODS: This review will focus on the available literature on IAH-induced renal dysfunction. A Medline and PubMed search was performed in order to find an answer to the question "What is the impact of increased IAP on renal function in the critically ill?". The resulting references were included in the current review on the basis of relevance and scientific merit. RESULTS: Renal dysfunction in IAH is a multifactorial process. The mechanisms involved have not been clarified completely. However, decreased cardiac output, altered renal blood flow and hormonal changes have been implicated. Decompression seems to have a beneficial effect on renal dysfunction, although there are some conflicting data. This may be due to the fact that there is no consensus on indications for decompression, both in terms of IAP values and of timing. An overview of current literature is provided and some interesting leads for future research are suggested. CONCLUSION: IAH can cause renal dysfunction. Therefore, IAP measurements should be considered in our daily practice and preventive measures should be taken to avoid (deterioration of) renal failure in patients with IAH. Decompression may have a beneficial effect in patients with established IAH and renal failure.

Lymphatic drainage between thorax and abdomen: please take good care of this well-performing machinery...

INTRODUCTION: Patients with sepsis often receive large amounts of fluids and the presence of capillary leak, trauma or bleeding results in ongoing fluid resuscitation. This increases interstitial and intestinal edema and finally leads to intra-abdominal hypertension (IAH), which in turn impedes lymphatic drainage. Patients with IAH often develop secondary respiratory failure needing mechanical ventilation with high intrathoracic pressure or PEEP that might further alter lymphatic drainage. This review will try to convince the reader of the importance of the lymphatics in septic patients with IAH. METHODS: A Medline and PubMed literature search was performed using the terms "abdominal pressure", "lymphatic drainage" and "ascites formation". The references from these studies were searched for relevant articles that may have been missed in the primary search. These articles served as the basis for the recommendations below. RESULTS: Induction of sepsis with lesion of the capillary alveolar barrier results in an increased water gradient between the capillaries and the interstitium in the lungs. The drainage flow to the thoracic duct is initially increased in order to protect the Lung and maintain the pulmonary interstitium as dry as possible, however this results in increased intrathoracic pressure. Sepsis also increases the permeability of the capillaries in the splanchnic beds. In analogy to the lungs the lymphatic flow in the splanchnic areas increases together with the pressure inside as a physiological response in order to limit the increase in IAP. At a critical IAP level (around 20 cmH2O) the lymph flow starts to decrease and the splanchnic water content progressively increases. The lymph flow from the abdomen to the thorax is progressively decreased resulting in increased splanchnic water content and ascites formation. The presence of mechanical ventilation with high PEEP reduces the lymph drainage further which together with the increase in IAP decreases the lymphatic pressure gradient in the splanchnic regions, with a further increase in water content and IAP triggering a vicious cycle. CONCLUSION: Although often overlooked the role of lymphatic flow is complex but very important to determine not only the fluid balance in the lung but also in the peripheral organs. Different pathologies and treatments can markedly influence the pathophysiology of the lymphatics with dramatic effects on endorgan function.

ICU management of the patient with intra-abdominal hypertension: what to do, when and to whom?

INTRODUCTION: Intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS) are increasingly recognised to be a contributing cause of organ dysfunction and mortality in critically ill patients. The number of publications describing and researching this phenomenon is increasing exponentially but there are still very limited data about treatment and outcome. METHODS: This review will focus on the available literature from the last years. A Medline and PubMed search was performed using the search terms "abdominal compartment syndrome" and "treatment". RESULTS: This search yielded 437 references, most of which were not relevant to the subject of this paper. The remaining abstracts were screened and selected on the basis of relevance, methodology and number of cases. Full text articles of the selected abstracts were used to supplement the authors' expert opinion and experience. The abdomino-thoracic transmission of pressure has direct clinical consequences on the cardiovascular, respiratory and central nervous systems in terms of monitoring and management. These interactions are discussed and treatment recommendations are made. IAH-induced renal dysfunction is addressed as a separate issue. Finally, an overview of non-invasive measures to decrease IAP is given. CONCLUSION: This paper describes current insights on management of IAP induced organ dysfunction and lists the most widely used and published non-invasive techniques to decrease IAP with their limitations and pitfalls.

Current insights in intra-abdominal hypertension and abdominal compartment syndrome.

A compartment syndrome exists when increased pressure in a closed anatomic space threatens the viability of the tissue within the compartment. When this occurs in the abdominal cavity it threatens not only the function of the intra-abdominal organs, but it can have a devastating effect on distant organs as well. Recent animal and human data suggest that the adverse effects of elevated intra-abdominal pressure (IAP) can occur at lower levels than previously thought and even before the development of clinically overt abdominal compartment syndrome (ACS). The ACS is not a disease but truly a syndrome, a spectrum of symptoms and signs that can and mostly does have multiple causes. It is only recently that this condition received a heightened awareness. This article reflects the current state of knowledge on intra-abdominal pressure regarding etiology, epidemiology, diagnosis, IAP measurement, organ dysfunction, prevention and treatment.