Rational intraabdominal pressure monitoring: how to do it?

The development, feasibility and credibility of intra-abdominal pressure measurement techniques: A scoping review

AIM

To provide a comprehensive overview on emerging direct and alternative methods for intra-abdominal pressure (IAP) measurement techniques.

METHODS

This was a scoping review study following Arksey and Malley's framework. The PubMed, EMBASE, Web of Science, EBSCO, Scopus and ProQuest databases were searched, and we only considered studies published from 2000 as we have extended the data from two previous reviews. Original studies that reported on the development, feasibility and credibility of IAP measurement techniques were included.

RESULTS

Forty-two of 9954 screened articles were included. IAP measurement techniques include three major categories: direct, indirect and less invasive measurement techniques. Agreement analyses were performed in most studies, and some explored the safety, time expenditure and reproducibility of IAP measurement techniques.

CONCLUSIONS

Clinical data assessing the validation of new IAP measurement techniques or the reliability of established measurement techniques remain lacking. Considering the cost and invasiveness, direct measurement is not recommended as a routine method for IAP measurement and should be preserved for critically ill patients where standard techniques are contraindicated or could be inaccurate. The measurement accuracy, reliability and sensitivity of the transrectal and transfemoral vein methods remain insufficient and cannot be recommended as surrogate IAP measures. Transvesical measurement is the most widely used method, which is the potentially most easy applicable technique and can be used as a reliable method for continuous and intermittent IAP measurement. Wireless transvaginal method facilitates the quantitative IAP measurement during exercise and activity, which laying the foundations for monitoring IAP outside of the clinic environment, but the accuracy of this technique in measuring absolute IAP cannot be determined at present. Less invasive technology will become a new trend to measure IAP and has substantial potential to replace traditional IAP measurement technologies, but further validation and standardization are still needed. Medical professionals should choose appropriate measurement tools based on the advantages and disadvantages of each IAP technique in combination with assessing specific clinical situations.

Monitoring and Management of Intra-abdominal Pressure in Critically Ill Children

BACKGROUND

Intra-abdominal hypertension is a comorbid condition in critically ill children, is an independent predictor of mortality, and has harmful effects on multiple organ systems through renal, pulmonary or hemodynamic damage. Intra-abdominal pressure monitoring is widely used in clinical practice because it is a safe, accurate, inexpensive, and rapid method for the clinical diagnosis of intra-abdominal hypertension.

OBJECTIVE

To improve pediatric critical care nurses' understanding of and ability to perform intra-abdominal pressure monitoring and provide a reference for standardizing intra-abdominal pressure monitoring in clinical practice.

METHODS

A literature review was performed using the following keywords: intra-abdominal pressure, bladder pressure, vesicular pressure, measurement, monitoring, critically ill children, pediatric intensive care, pediatric, and children. Four hundred fifty-four articles were initially identified and screened; 24 were included.

RESULTS

The monitoring and management of intra-abdominal pressure should include appropriate and clinically proven intra-abdominal pressure measurement techniques, appropriate patients, the proper frequency of measurement, and a repeatable intra-abdominal pressure measurement method.

CONCLUSIONS

Knowledge of intra-abdominal pressure monitoring in critically ill children enhances the ability of nurses in clinical practice to accurately measure intra-abdominal pressure to improve the timeliness and accuracy of clinical identification of intra-abdominal hypertension and guide decompression interventions.

Abdominal Compartment Syndrome in Acute Pancreatitis: A Narrative Review

Abdominal compartment syndrome (ACS) represents a severe complication of acute pancreatitis (AP), resulting from an acute and sustained increase in abdominal pressure >20 mmHg, in association with new organ dysfunction. The harmful effect of high intra-abdominal pressure on regional and global perfusion results in significant multiple organ failure and is associated with increased morbidity and mortality. There are several deleterious consequences of elevated intra-abdominal pressure on end-organ function, including respiratory, cardiovascular, gastrointestinal, neurologic, and renal effects. It is estimated that about 15% of patients with severe AP develop intra-abdominal hypertension or ACS, with a mortality rate around 50%. The treatment of abdominal compartment syndrome in acute pancreatitis begins with medical intervention and percutaneous drainage, where possible. Abdominal compartment syndrome unresponsive to conservatory treatment requires immediate surgical decompression, along with vacuum-assisted closure therapy techniques, followed by early abdominal fascia closure.

Preliminary study of reliability of transcutaneous sensors in measuring intraabdominal pressure

Early recognition of elevated intraabdominal pressure (IAP) in critically ill patients is essential, since it can result in abdominal compartment syndrome, which is a life-threatening condition. The measurement of intravesical pressure is currently considered the gold standard for IAP assessment. Alternative methods have been proposed, where IAP assessment is based on measuring abdominal wall tension, which reflects the pressure in the abdominal cavity. The aim of this study was to evaluate the feasibility of using patch-like transcutaneous sensors to estimate changes in IAP, which could facilitate the monitoring of IAP in clinical practice. This study was performed with 30 patients during early postoperative care. All patients still had an indwelling urinary catheter postoperatively. Four wearable sensors were attached to the outer surface of the abdominal region to detect the changes in abdominal wall tension. Additionally, surface EMG was used to monitor the activity of the abdominal muscles. The thickness of the subcutaneous tissue was measured with ultrasound. Patients performed 4 cycles of the Valsalva manoeuvre, with a resting period in between (the minimal resting period was 30 s, with a prolongation as necessary to ensure that the fluid level in the measuring system had equilibrated). The IAP was estimated with intravesical pressure measurements during all resting periods and all Valsalva manoeuvres, while the sensors continuously measured changes in abdominal wall tension. The association between the subcutaneous thickness and tension changes on the surface and the intraabdominal pressure was statistically significant, but a large part of the variability was explained by individual patient factors. As a consequence, the predictions of IAP using transcutaneous sensors were not biased, but they were quite variable. The specificity of detecting intraabdominal pressure of 20 mmHg and above is 88%, with an NPV of 96%, while its sensitivity and PPV are currently far lower. There are inherent limitations of the chosen preliminary study design that directly caused the low sensitivity of our method as well as the poor agreement with the gold standard method; in spite of that, we have shown that these sensors have the potential to be used to monitor intraabdominal pressure. We are planning a study that would more closely resemble the intended clinical use and expect it to show more consistent results with a far smaller error.

Elevated intra-abdominal pressure: A review of current knowledge

Elevated intra-abdominal pressure (IAP) is a known cause of increased morbidity and mortality among critically ill patients. Intra-abdominal hypertension (IAH) and abdominal compartment syndrome can lead to rapid deterioration of organ function and the development of multiple organ failure. Raised IAP affects every system and main organ in the human body. Even marginally sustained IAH results in malperfusion and may disrupt the process of recovery. Yet, despite being so common, this potentially lethal condition often goes unnoticed. In 2004, the World Society of the Abdominal Compartment Syndrome, an international multidisciplinary consensus group, was formed to provide unified definitions, improve understanding and promote research in this field. Simple, reliable and nearly costless standardized methods of non-invasive measurement and monitoring of bladder pressure allow early recognition of IAH and timely optimized management. The correct, structured approach to treatment can have a striking effect and fully restore homeostasis. In recent years, significant progress has been made in this area with the contribution of surgeons, internal medicine specialists and anesthesiologists. Our review focuses on recent advances in order to present the complex underlying pathophysiology and guidelines concerning diagnosis, monitoring and treatment of this life-threatening condition.

Urinary catheter monitoring of intra-abdominal pressure after major abdominal surgery, a cost-benefit analysis

OBJECTIVE

To estimate costs and benefits associated with measurement of intra-abdominal pressure (IAP).

METHODS

We built a cost-benefit analysis from the hospital facility perspective and time horizon limited to hospitalization for patients undergoing major abdominal surgery for the intervention of urinary catheter monitoring of IAP. We used real-world data estimating the likelihood of intra-abdominal hypertension (IAH), abdominal compartment syndrome (ACS), and acute kidney injury (AKI) requiring renal replacement therapy (RRT). Costs included catheter costs (estimated $200), costs of additional intensive care unit (ICU) days from IAH and ACS, and costs of CRRT. We took the preventability of IAH/ACS given early detection from a trial of non-surgical interventions in IAH. We evaluated uncertainty through probabilistic sensitivity analysis and the effect of individual model parameters on the primary outcome of cost savings through one-way sensitivity analysis.

RESULTS

In the base case, urinary catheter monitoring of IAP in the perioperative period of major abdominal surgery had 81% fewer cases of IAH of any grade, 64% fewer cases of AKI, and 96% fewer cases of ACS. Patients had 1.5 fewer ICU days attributable to IAH (intervention 1.6 days vs. control of 3.1 days) and a total average cost reduction of $10,468 (intervention $10,809, controls $21,277). In Monte Carlo simulation, 86% of 1,000 replications were cost-saving, for a mean cost savings of $10,349 (95% UCI $8,978, $11,720) attributable to real-time urinary catheter monitoring of intra-abdominal pressure. One-way factor analysis showed the pre-test probability of IAH had the largest effect on cost savings and the intervention was cost-neutral at a prevention rate as low as 2%.

CONCLUSIONS

In a cost-benefit model using real-world data, the potential average in-hospital cost savings for urinary catheter monitoring of IAP for early detection and prevention of IAH, ACS, and AKI far exceed the cost of the catheter.

Non-Invasive Intra-Abdominal Pressure Measurement by Means of Transient Radar Method: In Vitro Validation of a Novel Radar-Based Sensor

Intra-abdominal hypertension, defined as an intra-abdominal pressure (IAP) equal to or above 12 mmHg is one of the major risk-factors for increased morbidity (organ failure) and mortality in critically ill patients. Therefore, IAP monitoring is highly recommended in intensive care unit (ICU) patients to predict development of abdominal compartment syndrome and to provide a better care for patients hospitalized in the ICU. The IAP measurement through the bladder is the actual reference standard advocated by the abdominal compartment society; however, this measurement technique is cumbersome, non-continuous, and carries a potential risk for urinary tract infections and urethral injury. Using microwave reflectometry has been proposed as one of the most promising IAP measurement alternatives. In this study, a novel radar-based method known as transient radar method (TRM) has been used to monitor the IAP in an in vitro model with an advanced abdominal wall phantom. In the second part of the study, further regression analyses have been done to calibrate the TRM system and measure the absolute value of IAP. A correlation of -0.97 with a p-value of 0.0001 was found between the IAP and the reflection response of the abdominal wall phantom. Additionally, a quadratic relation with a bias of -0.06 mmHg was found between IAP obtained from the TRM technique and the IAP values recorded by a pressure gauge. This study showed a promising future for further developing the TRM technique to use it in clinical monitoring.

A New Device for Measuring Abdominal Wall Tension and Its Value in Screening Abdominal Infection

OBJECTIVE

This study is the largest clinical study of noninvasive Abdominal wall tension (AWT) measurement with a tensiometer to date. It also initially applies a polynomial regression equation to analyze the correlation between AWT measurement and intravesical pressure (IVP) measurement and remarkably finds interesting changes between different IVP intervals and AWT.

METHODS

Critically ill patients who were treated in the intensive care unit (ICU) of Daping Hospital, Army Medical University, from August 30, 2018, to June 30, 2020, and met the inclusion criteria were prospectively included in this study. The patients were divided into an intra-abdominal hypertension group and a non-intra-abdominal hypertension group and an abdominal infection group and no abdominal infection group. AWT and IVP were measured at 9 points on the abdominal wall on the first day after admission to the ICU. The correlations between AWTs and IVP were analyzed, and the role of AWT in the diagnosis of complications of abdominal infection and the prediction of adverse prognosis were analyzed.

RESULTS

A total of 127 patients were included. The average AWT and IVP were 2.77±0.38 N/mm and 12.31±7.01 mmHg, respectively, on the first day of admission. There was a positive correlation between AWT and IVP (correlation coefficient r = 0.706, p < 0.05). The polynomial regression model was AWT= -1.616×10-3 IVP2 +8.323×10-2 IVP+2.094. The cutoff value of the sensitivity and specificity of AWT for the diagnosis of abdominal infection was 2.57 N/mm. Furthermore, AWT = 2.57 N/mm had the best diagnostic efficiency, which was better than that of IAH and lactate.

CONCLUSION

There was a correlation between AWT and IVP. AWT measurement was helpful in the diagnosis of IAH and abdominal infection complications and can therefore serve as a new method for the clinical diagnosis of IVP and abdominal infection.

A concise overview of non-invasive intra-abdominal pressure measurement techniques: from bench to bedside

This review presents an overview of previously reported non-invasive intra-abdominal pressure (IAP) measurement techniques. Each section covers the basic physical principles and methodology of the various measurement techniques, the experimental results, and the advantages and disadvantages of each method. The most promising non-invasive methods for IAP measurement are microwave reflectometry and ultrasound assessment, in combination with an applied external force.

Early intra-abdominal hypertension: A reliable bedside prognostic marker for severe acute pancreatitis

BACKGROUND AND AIM

Severe acute pancreatitis (SAP) is commonly associated with intra-abdominal hypertension (IAH). This acute increase of intra-abdominal pressure (IAP) may be attributed to early organ dysfunction, leading to an increased morbidity and mortality. To assess the incidence of raised IAH and its correlation with other prognostic indicators and various outcomes in SAP.

METHODS AND RESULTS

This was a prospective observational study in patients of SAP between July 2009 and December 2010. All patients of SAP who were admitted to the hospital within 2 weeks of onset of pain were included in the study. A total of 35 patients with SAP were included in the study. Among these, 25 (71.4%) were males. All our patients had raised IAP; however, IAH was present in 51.4% (18/35). Patients with IAH were found to have a higher APACHE II score (88.9 vs 5.9%; P < 0.001), infectious complications (72.2 vs 5.9%; P < 0.001), circulatory failure (88.9 vs 0%; P < 0.001), and respiratory failure (100 vs 41.2%; P < 0.001). All the eight (22.8%) patients who succumbed to sepsis had IAH. Patients with IAH were found to have a significantly longer intensive care unit (ICU) stay (17.72 vs 12.29 days) and in-hospital stay (24.89 vs 12.29 days).

CONCLUSION

IAH is a good negative prognostic marker in SAP, seen in up to 51.4%. IAH was found to have a significant negative impact on the outcome in terms of increased mortality, morbidity, in-hospital stay, and ICU stay among the patients of SAP.

Intra-abdominal Hypertension and the Open Abdomen: Nursing Guidelines From the Abdominal Compartment Society

Intra-abdominal hypertension has been identified as an independent risk factor for death in critically ill patients. Known risk factors for intra-abdominal hypertension indicate that intra-abdominal pressures should be measured and monitored. The Abdominal Compartment Society has identified medical and surgical interventions to relieve intra-abdominal hypertension or to manage the open abdomen if abdominal compartment syndrome occurs. The purpose of this article is to describe assessments and interventions for managing intra-abdominal hypertension and open abdomen that are within the scope of practice for direct-care nurses. These guidelines provide direction to critical care nurses caring for these patients.

Autologous bionic tissue for inguinal hernia repair

The prosthetic mesh, which is widely used in tension-free hernioplasty, often result in avascular stiff fibrotic scar or mesh shrinkage, causing chronic pain and infection. Here, we developed an autologous bionic tissue (ABT), which was composed of autologous bone marrow-derived mesenchymal stem cells (MSCs), poly (lactic-co-glycolic acid) (PLGA) porous scaffolds, and extracellular matrix (ECM) produced by MSCs for inguinal hernioplasty. In ABT, MSCs produced a variety of ECM composites, such as structural proteins (insoluble collagen, elastin) that provided mechanical properties, macromolecules (hyaluronic acid, glycosaminoglycan) as water and cytokines reservoir, and cell-engaging proteins (fibronectin, laminin). The above ECM composites reached the highest level in 21 days. ECM degradation related cytokines (MMP-9 and its inhibitor TIMP-1) reached the highest level on the 14th day. ECM increased the mechanical properties, elasticity, and flexibility of PLGA. Compared with the PLGA, ABT greatly inhibited inflammatory factors and promoted anti-inflammatory factors (p < 0.05), and gradually reduced the M1/M2 ratio in vivo (p < 0.05). After implantation, the thickness of tissue regeneration (p < 0.05), the number of capillaries or mature vessels (p < 0.05), the mechanical properties of ABT (p < 0.05) were greater than PLGA. MSCs and ECM could reduce the inflammation caused by PLGA, and prevent PLGA from earlier degradation and facilitate host cellular infiltration, thus ABT could greatly promote tissue regeneration in hernia repairs.

Bench Validation of a Handcrafted Prototype Catheter for Intra-gastric Pressure Monitoring

BACKGROUND

Abdominal compartment syndrome is a sustained intra-abdominal pressure (IAP) >20 mm Hg associated with new organ dysfunction. In order to prevent its development and related complications, IAP monitoring should be performed in patients with risk factors. Although techniques for its monitoring have been developed, they are of high cost and not always available in low- and lower-middle-income countries. Therefore, we aim to develop and validate in a bench model a handcrafted catheter to be used as an alternative method to measure the intra-gastric pressure (IGP) as a surrogate of the IAP.

METHODS

We used an acrylic water container as a model of the abdomen and four handcrafted catheters made of a 16 Fr Levin tube with a globe finger tied with silk in the distal end, inflated with 1 cm of air. They were placed on the bottom of the container where the water pressure was directly measured as a gold standard. The agreement between the two measures was assessed with the Bland-Altman method.

RESULTS

We performed 120 simultaneous measures. The mean pressure difference was 0.218 (95% CI 0.074 to 0.363).

CONCLUSIONS

The handcrafted prototype catheter and the direct measure were highly correlated. The new catheter is a reliable and reproducible tool for pressure monitoring. However, before it can be used in the clinical setting for IAP monitoring, validation in human models in a real clinical setting needs to be performed.

Inpatient Evaluation of Intra-abdominal Pressure Completed With a Urinary Catheter as Compared With Ultrasonographic Vessel Measurements

Background:

The purpose of this study was to evaluate the diagnostic value of ultrasonography as compared with intra-abdominal pressure (IAP) measured with a urinary catheter.

Methods:

This was a cross-sectional study. The participants consisted of 146 patients hospitalized in the emergency wards of two hospitals in Isfahan (2017-2018). Following measurement of IAP through a urinary catheter, ultrasonographic measurement of the inferior vena cava (IVC) diameter, internal jugular vein diameter, common femoral vein (CFV) diameter, and ratio between the IVC and abdominal aortic diameters was completed. Correlation between these methods of measurements for IAP was investigated.

Results:

There was a significant positive correlation between intrabladder pressure and the right internal jugular vein (RIJV) and CFV ( P < .001, R > 0). There was also a reverse significant correlation between intrabladder pressure and RIJV, IVC, IVC:aorta diameter, systolic blood pressure, and tricuspid annular plane systolic excursion ( P < .001, r < 0). RIJV, CFV, and tricuspid annular plane systolic excursion were suitable predictors for the estimation of intrabladder pressure or IAP ( P < .05), but IVC, IVC:aorta, and systolic blood pressure were not suitable factors for estimating IAP ( P > .05).

Conclusion:

Ultrasonographic measurement is a noninvasive method for determining IAP.

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.

Reliability of intra-abdominal pressure measurements using the modified Kron technique

OBJECTIVES

Assessment of intra-abdominal pressure (IAP) and the likelihood of abdominal compartment syndrome using valid and reliable measures is an important tool in the assessment of critically ill patients. The current method of relying on a single IAP per measurement period to determine patient clinical status raises the question: is a single intermittent IAP measurement an accurate indicator of clinical status or should more than one measurement be taken per measurement period?

METHODS

This study sought to assess the reliability of IAP measurements. Measurements were taken using the modified Kron technique. A total of two transvesical intra-abdominal pressure measurements were undertaken per patient using a standardized protocol. Recordings were taken at intervals of 5 minutes.

RESULTS

The majority of participants (58%) were surgical patients. Thirty-two were males and the mean age was 58 years (SD: 16·7 years). The concordance correlation coefficient between the two measurements was 0·95. Both the scatter and Bland-Altman plots demonstrate that the comparisons of two measurements are highly reproducible.

CONCLUSION

The findings of this study suggest that conducting two IAP measurements on single patient produce comparable results; therefore, there appears to be no advantage in doing two IAP measurements on a single patient. The measurement of an IAP requires the implementation of a standardized protocol and competent and credentialed assessors trained in the procedure.

Abdominal compartment syndrome in children

Abdominal compartment syndrome is defined as sustained intra-abdominal pressure greater than 20 mm Hg (with or without abdominal perfusion pressure <60 mm Hg) associated with new organ failure or dysfunction. The syndrome is associated with 90% to 100% mortality if not recognized and treated in a timely manner. Nurses are responsible for accurately measuring intra-abdominal pressure in children with abdominal compartment syndrome and for alerting physicians about important changes. This article provides relevant definitions, outlines risk factors for abdominal compartment syndrome developing in children, and discusses an instructive case involving an adolescent with abdominal compartment syndrome. Techniques for measuring intra-abdominal pressure, normal ranges, and the importance of monitoring in the critical care setting for timely identification of intra-abdominal hypertension and abdominal compartment syndrome also are discussed.

Effect of mechanical ventilation on intra-abdominal pressure in critically ill patients without other risk factors for abdominal hypertension: an observational multicenter epidemiological study

BACKGROUND

Mechanical ventilation (MV) is considered a predisposing factor for increased intra-abdominal pressure (IAP), especially when positive end-expiratory pressure (PEEP) is applied or in the presence of auto-PEEP. So far, no prospective data exists on the effect of MV on IAP. The study aims to look on the effects of MV on IAP in a group of critically ill patients with no other risk factors for intra-abdominal hypertension (IAH).

METHODS

An observational multicenter study was conducted on a total of 100 patients divided into two groups: 50 patients without MV and 50 patients with MV. All patients were admitted to the intensive care units of the Medical and Surgical Research Centre, the Carlos J. Finlay Hospital, the Julio Trigo University Hospital, and the Calixto García Hospital, in Havana, Cuba between July 2000 and December 2004. The IAP was measured twice daily on admission using a standard transurethral technique. IAH was considered if IAP was greater than 12 mmHg. Correlations were made between IAP and body mass index (BMI), diagnostic category, gender, age, and ventilatory parameters.

RESULTS

The mean IAP in patients on MV was 6.7 ± 4.1 mmHg and significantly higher than in patients without MV (3.6 ± 2.4 mmHg, p < 0.0001). This difference was maintained regardless of gender, age, BMI, and diagnosis. The use of MV and BMI were independent predictors for IAH for the whole population, while male gender, assisted ventilation mode, and the use of PEEP were independent factors associated with IAH in patients on MV.

CONCLUSIONS

In this study, MV was identified as an independent predisposing factor for the development of IAH. Critically ill patients, which are on MV, present with higher IAP values on admission and should be monitored very closely, especially if PEEP is applied, even when they have no other apparent risk factors for IAH.

Effects of zero reference position on bladder pressure measurements: an observational study

BACKGROUND

Although the World Society for Abdominal Compartment Syndrome in its guidelines recommends midaxillary line (MAL) as zero reference level in intra-abdominal pressure (IAP) measurements in aiming at standardizing the technique, evidence supporting this suggestion is scarce. The aim of this study is to study if the zero reference position influences bladder pressure measurements as estimate for IAP.

METHODS

The IAP of 100 surgical patients was measured during the first 24 h of admission to the surgical intensive care unit of General Calixto Garcia Hospital in Havana (Cuba) following laparotomy. The period was January 2009 to January 2010. The IAP was measured twice with a six-hour interval using the transurethral technique with a priming volume of 25 ml. IAP was first measured with the zero reference level placed at MAL (IAPMAL), followed by a second measurement at the level of the symphysis pubis (SP) after 3 minutes (IAPSP). Correlations were made between IAP and body mass index (BMI), type of surgery, gender, and age.

RESULTS

Mean IAPMAL was 8.5 ± 2.8 mmHg vs. IAPSP 6.5 ± 2.8 mmHg (p < 0.0001). The bias between measurements was 2.0 ± 1.5, 95% confidence interval of 1.4 to 3.0, upper limit of 4.9, lower limit of -0.9, and a percentage error of 35.1%. IAPMAL was consistently higher than IAPSP regardless of the type of surgery. The BMI correlated with IAP values regardless of the zero reference level (R2 = 0.4 and 0.3 with IAPMAL and IAPSP respectively, p < 0.0001).

CONCLUSIONS

The zero reference level has an important impact on IAP measurement in surgical patients after laparotomy and can potentially lead to over or underestimation. Further anthropometric studies are needed with regard to the relative MAL and SP zero reference position in relation to the theoretical ideal reference level at midpoint of the abdomen. Until better evidence is available, MAL remains the recommended zero reference position due to its best anatomical localization at iliac crest.

A Novel Method (CiMON) for Continuous Intra-Abdominal Pressure Monitoring: Pilot Test in a Pig Model

Background. Intravesical pressure (IAP(ivp)) measurement is considered to be the gold standard for assessment of intra-abdominal pressure (IAP). This study evaluated a new minimally invasive IAP monitoring device (CiMON) against three other devices in a wide range of clinically relevant IAP and in different body positions in healthy pigs. Methods. The CiMON catheter (IAP(CiM)) and another balloon-tipped catheter (IAP(spie)) were positioned into the stomach. Fluid-filled catheters were used for direct intraperitoneal (IAP(dir)) and IAP(ivp) measurement. Both in supine and 25° head-of-bed positions, IAP was increased from baseline to 30 mmHg. At every IAP level, 4 IAP measurements were recorded simultaneously. Mean differences and the limits of agreement were calculated. Results. Bias between IAP(CiM) and IAP(spie) was nearly zero with very good agreement, both in supine and 25° position. In supine position, IAP(CiM) slightly overestimated IAP(ivp) and IAP(dir) by 1.5 and 2.1 mmHg with reasonable agreement. In 25° position, IAP(CiM) underestimated IAP(ivp) and IAP(dir) by 1.0 and 0.5 mmHg, again with reasonable agreement. Conclusions. Agreement between IAP(CiM) and IAP(spie) was very good, while good-to-moderate agreement exists between IAP(CiM) and IAP(dir) or IAP(ivp). Simplicity, continuous monitoring, and the combination with a feeding tube should lead to further clinical studies, evaluating this new CiMON device.

Does femoral venous pressure measurement correlate well with intrabladder pressure measurement? A multicenter observational trial

PURPOSE

To investigate if femoral venous pressure (FVP) measurement can be used as a surrogate measure for intra-abdominal pressure (IAP) via the bladder.

METHODS

This was a prospective, multicenter observational study. IAP and FVP were simultaneously measured in 149 patients. The effect of BMI on IAP was investigated.

RESULTS

The incidences of intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS) were 58 and 7% respectively. The mean APACHE II score was 22 ± 10, SAPS 2 score 42 ± 20, and SOFA score 9 ± 4. The mean IAP was 11.2 ± 4.5 mmHg versus 12.7 ± 4.7 mmHg for FVP. The bias and precision for all measurements were -1.5 and 3.6 mmHg respectively with the lower and upper limits of agreement being -8.6 and 5.7. When IAP was above 20 mmHg, the bias between IAP and FVP was 0.7 with a precision of 2.0 mmHg (lower and upper limits of agreement -3 and 4.6 respectively). Excluding those with ACS, according to the receiver operating curve analysis FVP = 11.5 mmHg predicted IAH with a sensitivity and specificity of 84.8 and 67.0% (AUC of 0.83 (95% CI 0.81-0.86) with P < 0.001). FVP = 14.5 mmHg predicted IAP above 20 mmHg with a sensitivity of 91.3% and specificity of 68.1% (AUC 0.85 (95% CI 0.79-0.91), P < 0.001). Finally, at study entry, the mean IAP in patients with a BMI less then 30 kg/m(2) was 10.6 ± 4.0 mmHg versus 13.8 ± 3.8 mmHg in patients with a BMI ≥ 30 kg/m(2) (P < 0.001).

CONCLUSIONS

FVP cannot be used as a surrogate measure of IAP unless IAP is above 20 mmHg.

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 hypertension in acute pancreatitis

The incidence of intra-abdominal hypertension (IAH) in patients with severe acute pancreatitis (SAP) is approximately 60-80%. It is usually an early phenomenon, partly related to the effects of the inflammatory process, causing retroperitoneal edema, fluid collections, ascites, and ileus, and partly iatrogenic, resulting from aggressive fluid resuscitation. It also can manifest at a later stage, often associated with local pancreatic complications. IAH is associated with impaired organ dysfunction, especially of the cardiovascular, respiratory, and renal systems. Using current definitions, the incidence of the clinical manifestation, abdominal compartment syndrome (ACS), has been reported as 27% in the largest study so far. Despite several intervention options, the mortality in patients developing ACS remains high: 50-75%. Prevention with judicious use of crystalloids is important, and nonsurgical interventions, such as nasogastric decompression, short-term use of neuromuscular blockers, removal of fluid by extracorporeal techniques, and percutaneous drainage of ascites should be instituted early. The indications for surgical decompression are still not clearly defined, but undoubtedly some patients benefit from it. It can be achieved with full-thickness laparostomy (midline or transverse subcostal) or through a subcutaneous linea alba fasciotomy. Despite the improvement in physiological variables and significant decrease in IAP, the effects of surgical decompression on organ function and outcome are less clear. Because of the significant morbidity associated with surgical decompression and the management of the ensuing open abdomen, more research is needed to define better the appropriate indications and techniques for surgical intervention.

Intra-abdominal pressure alterations after large pancreatic pseudocyst transcutaneous drainage

BACKGROUND

Acute pancreatitis leads to abdominal hypertension and compartment syndrome. Weeks after the episodes pancreatic fluids sometimes organize to pseudocysts, fluid collections by or in the gland. Aims of the present study were to evaluate the intra-abdominal pressure (IAP) induced by large pancreatic pseudocysts and to examine the effect of their transcutaneous drainage on IAP.

METHODS

Twenty seven patients with a pancreatic pseudocyst were included. Nine patients with pseudocysts greater than 1l (group A) had CT drainage and eighteen (volume less than 1l) were the control group. The measurements of group A were taken 6 hours before and every morning after the drainage, while for group B, two measurements were performed, one at the day of the initial CT and one 7 days after. Abdominal compliance (Cabd) was calculated. Data were analyzed using student's t-test.

RESULTS

Baseline IAP for group A was 9.3 mmHg (S.D. 1.7 mmHg), while the first post-drainage day (PDD) IAP was 5.1 mmHg (S.D. 0.7 mmHg). The second PDD IAP was 5.6 mmHg (S.D. 0.8 mmHg), the third 6.4 mmH (S.D. 1.2 mmHg)g, the fourth 6.9 mmHg (S.D. 1.6 mmHg), the fifth 7.9 mmHg (S.D. 1.5 mmHg), the sixth 8.2 mmHg (S.D. 1.4 mmHg), and the seventh 8.2 mmHg (S.D. 1.5 mmHg). Group B had baseline IAP 8.0 mmHg (S.D. 1.2 mmHg) and final 8.2 mmHg (S.D. 1.4 mmHg). Cabd after drainage was 185.6 ml/mmHg (SD 47.5 ml/mmHg). IAP values were reduced between the baseline and all the post-drainage measurements in group A. IAPs seem to stabilize after the 5th post-drainage day. Baseline IAP was higher in group A than in group B, while the two values, at day 7, were equivalent.

CONCLUSION

The drainage of large pancreatic pseudocyst reduces IAP. Moreover, the IAP seems to rise shortly after the drainage again, but in a way that it remains inferior to the initial value. More chronic changes to the IAP are related to abdominal cavity's properties and have to be further studied.

Recommendations for research from the International Conference of Experts on Intra-abdominal Hypertension and Abdominal Compartment Syndrome

OBJECTIVE

Intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS) have been increasingly recognized in the critically ill over the past decade, and the number of published studies has exploded in recent years. Interpretation of the results and comparison of these studies is difficult, because of incomplete and inconsistent reporting of data and statistics.

DESIGN

An international consensus group of multidisciplinary specialists convened at the third World Congress on Abdominal Compartment Syndrome to develop recommendations for research related to the diagnosis and management 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.

RESULTS

Three major types of studies were identified (measurement techniques, epidemiology, and interventions), each with different needs regarding methodology, reporting of data and statistical analysis.

CONCLUSIONS

These recommendations are proposed to guide clinical research in the field of IAH and ACS.

Intra-abdominal pressure measurements in lateral decubitus versus supine position

OBJECTIVE

Intra-abdominal pressure (IAP) has traditionally been measured in the supine position, however, measuring the pressure in lateral semi-recumbent position has not been studied.

DESIGN

A single centre prospective 1-day study.

PATIENTS

10 patients admitted for more then 24 hours who were mechanically ventilated and had an indwelling urinary catheter.

METHODS

Inclusion criteria included were age > 18 years, sedated to a RASS score of -5 and mechanically ventilated. The pressures were measured via the bladder with the mid-axillary line as zero reference point. When patients were nursed in lateral decubitus, pressures were measured and compared immediately to the supine position.

RESULTS

10 patients were included with a total of 60 measurements.The male/female ratio was 9:1 with a mean APACHE Pi score of 11.5 [95% CI 4.8-22.4], SAPS 2 of 31.5 [95% CI 8.9-35.8] and SOFA score of 4.0 [95% CI 1.8-7.2]. Four patients were medical and 6 were surgical. The mean IAP at different time intervals (morning, afternoon and evening) in lateral and supine position were 10.9 +/- 2.0 (in mmHg) vs 6.6 +/- 3.2 (SD with p < 0.001); 11.0 +/- 4.0 vs 5.4 +/- 2.2 (p < 0.0005) and 11.6 +/- 3.8 vs 7.8 +/- 3.0 (p< 0.001). Overall, the LSP did not change significantly (p= 0.76), but the SP did (p=0.006) with the afternoon reading being significantly lower than the evening measurement. However, the trend in the difference (LSP minus SP) was not significant (p=0.43).

CONCLUSION

There was a significant statistical difference in the pressures measured in LSP versus SP.The LSP position should not be used to measure IAP.

Direct intra-abdominal pressure monitoring via piezoresistive pressure measurement: a technical note

BACKGROUND

Piezoresistive pressure measurement technique (PRM) has previously been applied for direct IAP measurement in a porcine model using two different devices. Aim of this clinical study was to assess both devices regarding complications, reliability and agreement with IVP in patients undergoing elective abdominal surgery.

METHODS

A prospective cohort study was performed in 20 patients randomly scheduled to receive PRM either by a Coach-probe or an Accurate(++)-probe (both MIPM, Mammendorf, Germany). Probes were placed on the greater omentum and passed through the abdominal wall paralleling routine drainages. PRM was compared with IVP measurement by t-testing and by calculating mean difference as well as limits of agreement (LA).

RESULTS

There were no probe related complications. Due to technical limitations, data could be collected in 3/10 patients with Coach and in 7/10 patients with Accurate++. Analysis was carried out only for Accurate++. Mean values did not differ to mean IVP values. Mean difference to IVP was 0.1 +/- 2.8 mmHg (LA: -5.5 to 5.6 mmHg).

CONCLUSION

Direct IAP measurement was clinically uneventful. Although results of Accurate++ were comparable to IVP, the device might be too fragile for IAP measurements in the clinical setting. Local ethical committee trial registration: EK2024.

Gastrointestinal microcirculation and cardiopulmonary function during experimentally increased intra-abdominal pressure

OBJECTIVES

The aim of this study was to assess gastric, intestinal, and renal cortex microcirculation parallel with central hemodynamics and respiratory function during stepwise increase of intra-abdominal pressure (IAP).

DESIGN

Prospective, controlled animal study.

SETTING

Research laboratory, University Hospital.

SUBJECTS

Twenty-six anesthetized and mechanically ventilated pigs.

INTERVENTIONS

Following baseline registrations, CO2 peritoneum was inflated (n = 20) and IAP increased stepwise by 10 mm Hg at 10 mins intervals up to 50 mm Hg and subsequently exsufflated. Control animals (n = 6) were not insufflated with CO2.

MEASUREMENTS AND MAIN RESULTS

The microcirculation of gastric mucosa, small bowel mucosa, small bowel seromuscular layer, colon mucosa, colon seromuscular layer, and renal cortex were selectively studied at all pressure levels and after exsufflation using a four-channel laser Doppler flowmeter (Periflex 5000, Perimed). Central hemodynamic and respiratory function data were registered at each level and after exsufflation. Cardiac output decreased significantly at IAP levels above 10 mm Hg. The microcirculation of gastric mucosa, renal cortex and the seromuscular layer of small bowel and colon was significantly reduced with each increase of IAP. The microcirculation of the small bowel mucosa and colon mucosa was significantly less affected compared with the serosa (p < 0.01).

CONCLUSIONS

Our animal model of low and high IAP by intraperitoneal CO2-insufflation worked well for studies of microcirculation, hemodynamics, and pulmonary function. During stepwise increases of pressure there were marked effects on global hemodynamics, respiratory function, and microcirculation. The results indicate that intestinal mucosal flow, especially small bowel mucosal flow, although reduced, seems better preserved in response to intra-abdominal hypertension caused by CO2-insufflation than other intra-abdominal microvascular beds.

Can the abdominal perimeter be used as an accurate estimation of intra-abdominal pressure?

INTRODUCTION

Intra-abdominal pressure (IAP) is an important parameter and prognostic indicator of the patient's underlying physiologic status. Correct IAP measurement, therefore, is crucial. Most of the direct and indirect techniques are not free from risks and require some time and skills. This study looks at the possibility of using the abdominal perimeter (AP) as a quick estimation for IAP.

METHODS

In total, 237 paired measurements were performed in 26 intensive care unit patients. The IAP was measured according to the recommendations of the World Society on Abdominal Compartment Syndrome via an indwelling bladder catheter using a pressure transducer. The AP was defined as the abdominal circumference at its largest point using body marks as reference for consecutive measurements.

RESULTS

The male:female ratio was 1:1, age 69.8 +/- 15.2 yrs, Acute Physiology and Chronic Health Evaluation II score 26.5 +/- 9.2, and Simplified Acute Physiology Score II score 58 +/- 15.5. The number of measurements in each patient was 9.4 +/- 4.6. The IAP was 10.8 +/- 4.9 mm Hg, and the AP was 101 +/- 19.2 cm. There was a poor but statistically significant correlation between IAP and AP: AP = 1.8 x IAP + 81.6 (R2 = 0.21, p = 0.04), but the bias was considerable. The correlation was somewhat better between DeltaIAP (the difference between two consecutive IAP measurements) and DeltaAP (the difference between two consecutive AP measurements) in 210 paired measurements: DeltaAP = 0.4 x DeltaIAP + 0.1 (R2 = 0.24, p < 0.0001). The analysis according to Bland and Altman showed that DeltaIAP was almost identical to DeltaAP with a mean difference or bias of 0 +/- 3 (95% confidence interval: -0.4 to 0.4); however, the limits of agreement were large and thus reflect poor agreement.

CONCLUSIONS

In view of the poor correlation between IAP and AP, the latter cannot be used as a clinical estimate for IAP. The correlation between DeltaIAP and DeltaAP was somewhat better, meaning that DeltaAP can be used as an estimate of the evolution of IAP over time; however, for making a definite diagnosis of intra-abdominal hypertension or abdominal compartment syndrome, the exact value of IAP needs to be measured.

Validation of the urine column measurement as an estimation of the intra-abdominal pressure

OBJECTIVE

To evaluate the efficacy of the urine column (UC) measurement compared to the intra-vesicular pressure (IVP) measurement as an estimation of intra-abdominal pressure (IAP) in patients with IAP up to 30 mmHg.

METHODS

Fifteen patients undergoing a laparoscopic cholecystectomy were studied. All patients were catheterized. IVP measurements were performed using a pressure transducer connected to the culture aspiration port. UC measurements were done by holding up the tubing against a measuring rod. The symphysis pubis was used as the zero-reference. IAP was raised from 0 to 30 mmHg using increments of 5 mmHg, during which first the IVP and then UC measurement series were recorded end-expiratory. Fifty and 100 ml of saline were used as a priming volume.

RESULTS

The IVP and UC measurements showed a significant correlation with IAP. Comparing IVP and UC showed a correlation of 0.91 (p < 0.001) for 50 ml and 0.87 (p < 0.001) for 100 ml of saline as a priming volume. Using 50 ml of saline, UC was 0.68 mmHg higher than IVP (95% CI -7.21 to +5.85 mmHg). For 100 ml of saline, UC was 1.23 mmHg lower than IVP (95% CI -7.41 to +9.87 mmHg).

CONCLUSION

UC measurement shows significant correlation to IVP measurement as an estimation of the IAP. Further study needs to be done to conclude whether UC measurement is a reliable clinical alternative to IVP measurement.

Primary and secondary intra-abdominal hypertension--different impact on ICU outcome

OBJECTIVE

To investigate the differences in incidence, time course and outcome of primary versus secondary intra-abdominal hypertension (IAH), and to evaluate IAH as an independent risk factor of mortality in a presumable risk population of critically ill patients.

DESIGN

Prospective observational study.

SETTING

General intensive care unit of a university hospital.

PATIENTS

A total of 257 mechanically ventilated patients at presumable risk for the development of IAH were studied during their ICU stay and followed up for 90-day survival.

INTERVENTIONS

Repeated measurements of intra-abdominal pressure (IAP).

MEASUREMENTS AND RESULTS

IAP was measured intermittently, via bladder. IAH (sustained or repeated IAP > or = 12 mmHg) developed in 95 patients (37.0%). Primary IAH was observed in 60 and secondary IAH in 35 patients. Patients with secondary IAH demonstrated a significant increase of mean IAP during the first three days (mean DeltaIAP was 2.2 +/- 4.7 mmHg), whilst IAP decreased (mean DeltaIAP -1.1 +/- 3.7 mmHg) in the patients with primary IAH. The patients with IAH had a significantly higher ICU- (37.9 vs. 19.1%; P = 0.001), 28-day (48.4 vs. 27.8%, P = 0.001), and 90-day mortality (53.7 vs. 35.8%, P = 0.004) compared to the patients without the syndrome. Patients with secondary IAH had a significantly higher ICU mortality than patients with primary IAH (P = 0.032). Development of IAH was identified as an independent risk factor for death (OR 2.52; 95% CI 1.23-5.14).

CONCLUSIONS

Secondary IAH is less frequent, has a different time course and worse outcome than primary IAH. Development of IAH during ICU period is an independent risk factor for death.

Intra-abdominal hypertension: incidence and association with organ dysfunction during early septic shock

PURPOSE

The objective of this article is to study the cumulative incidence of intra-abdominal hypertension (IAH) in septic shock (SS) patients during the first 72 hours of intensive care unit (ICU) admission and to determine if the presence and severity of IAH are associated with sepsis morbidity and mortality.

MATERIALS AND METHODS

Eighty-one consecutive SS patients admitted to a surgical-medical ICU of an academic university hospital (January 2005 to January 2006) were included. Intra-abdominal pressure (IAP) and abdominal perfusion pressure (APP) were measured every 6 h (intermittently) for 72 h. Intra-abdominal pressure was registered as minimal, mean, and maximal values per day, during shock and throughout the study period. Intra-abdominal hypertension was diagnosed if IAP remained 12 mm Hg or higher on 2 consecutive measurements and stratified according to the most recent consensus definition (www.wsacs.org).

RESULTS

According to maximal and mean IAP values, 67 (82.7%) and 62 (76.5%) of the patients developed IAH during the study period, respectively. Mean IAP values remained stable throughout the study period. Surgical patients had a higher incidence of IAH than medical patients (93% vs 73%, P < .009). Maximal IAPs were normally distributed, with nonsurvivors exhibiting significantly higher IAP levels during shock (survivors, 17.2 +/- 5.3; nonsurvivors, 19.9 +/- 5.6 mm Hg; P < .04). Patients with IAH exhibited significantly lower values of APP and diuresis, higher values of lactate and creatinine, and higher maximal norepinephrine doses, and were more frequently mechanically ventilated (P < .05 for all). Increasing degrees of IAH and the development of the abdominal compartment syndrome were associated with lower APP and higher maximal serum creatinine levels (P < .03 for both).

CONCLUSIONS

Septic shock patients have a very high incidence of IAH, which seems to be associated with the severity of shock and could be related to the development of organ dysfunctions, particularly renal dysfunction. Intra-abdominal pressure should be routinely monitored during the course of SS.

The effect of different reference transducer positions on intra-abdominal pressure measurement: a multicenter analysis

OBJECTIVE

To investigate the effect of different reference transducer positions on intra-abdominal pressure (IAP) measurement. Three reference levels were studied: the symphysis pubis; the phlebostatic axis; and the midaxillary line at the level of the iliac crest.

DESIGN

Prospective cohort study.

SETTING

The intensive care units of participating hospitals

PATIENTS AND PARTICIPANTS

One hundred thirty-two critically ill patients at risk for intra-abdominal hypertension (IAH).

INTERVENTIONS

In each patient, three sets of IAP measurements were obtained in the supine position, using the different reference levels. The IAP measurements obtained at the different reference levels were compared using a paired t-test and Bland-Altman statistics were calculated.

MEASUREMENTS AND RESULTS

IAP(phlebostatic) (9.9 +/- 4.67 mmHg) and IAP(pubis) (8.4 +/- 4.60 mmHg) were significantly lower that IAP(midax) (12.2 +/- 4.66 mmHg; p < 0.0001 for both comparisons). The bias between the IAP(midax) and IAP(pubis) was 3.8 mmHg (95% CI 3.5-4.1) and 2.3 mmHg (95% CI 1.9-2.6) between the IAP(midax) and the IAP(phlebostatic). The precision was 3.03 and 3.40, respectively.

CONCLUSIONS

In the supine position, IAP(midax) is higher than both IAP(phlebostatic) and IAP(pubis), differences found to be clinically significant; therefore, the symphysis pubis or phlebostatic axis reference lines are not interchangeable with the midaxillary level.

Comparison of intermittent and continuous intra-abdominal pressure monitoring using an in vitro model

INTRODUCTION

Intra-abdominal pressure (IAP) is increasingly being considered as an important physiologic parameter to be measured in critically ill patients. Traditional methods of monitoring IAP rely on intermittent IAP (IIAP) measurements using indwelling bladder catheters. Recently, a method of continuous IAP (CIAP) monitoring has been developed using a three-way bladder catheter. This study evaluates the reliability of IIAP and CIAP measurement techniques using an in vitro model.

METHODS

An in vitro model of the abdomen was constructed using a 50 l container with a 100 ml infusion bag at the base to simulate a bladder. A three-way catheter tip was centered within the infusion bag filled with 50 ml saline. To simulate IAP the container was filled with water at 5 cm H(2)O increments from 10 to 25 cm H(2)O. Pressures were recorded by observers from a bedside monitor interfaced with a three-way Foley catheter using alternating intermittent and continuous techniques. Each subject was blinded to the known pressure values. Descriptive statistics and a generalised estimating equation (GEE) was used to describe the relationship of IIAP and CIAP to known pressures.

RESULTS

One hundred and thirty-two (132) observations were made by 20 subjects for both IIAP and CIAP estimates. In 45.5% of IIAP measures, the estimate was correct, and it was never more than 1 cm H(2)O different from the actual. Similarly, in 38.6% of CIAP measures, the estimate was correct, and was never more than 2 cm H(2)O from the actual. The GEE regression coefficients comparing known pressures with IIAP and CIAP were 1.007 and 0.976 respectively. The minimum and maximum pressure deviations never exceeded more than 1.3 cm H(2)O from the actual.

CONCLUSION

Intermittent IAP and CIAP are both reliable and reproducible methods to measure IAP in an in vitro model. There exists a direct and significant association between both measurements and the actual value. Neither measure was shown to be superior.

In vitro validation of a novel method for continuous intra-abdominal pressure monitoring

OBJECTIVE

Intra-abdominal pressure (IAP) measurement is important in daily clinical practice. Most measurement techniques vary in automaticity and reproducibility. This study tested a new fully automated continuous technique for IAP measurement, the CiMON.

METHODS

Three IAP measurement catheters (a Foley manometer and two balloon-tipped catheters) contained in a 50-ml infusion bag were placed on the bottom of a half open 3-l container. To simulate IAH the container was filled with water using 5 cmH2O increments (0-30 cmH2O). Pressure was estimated by observers using the Foley manometer (IAP(FM)) and simultaneously recorded using two IAP monitors: IAP(spie) with Spiegelberg and IAP(CiM) with CiMON. Observers were blinded to the reference levels. Fifteen observers (three intensivists, four residents, two medical students, and six nurses) conducted three pressure readings at each of the seven pressure levels with the FM technique, giving 315 readings. These were paired with the automated IAP(spie) and IAP(CiM) readings and the height of the H2O column.

RESULTS

The intra- and interobserver coefficients of variation (COVA) were low for all methods. There was no difference in the results between specialists, physicians in training, andnurses. Spearman's correlation coefficient (R2) values for all paired measurements were greater than 0.9, and Bland-Altman analysis comparing the reference H2O column, IAP(FM), and IAP(spie) to IAP(CiM) showed a very good agreement at all pressure levels (bias -0.1+/-0.6 cmH2O, 95%CI -0.2 to 0). There was a consistent, low underestimation of the reference H2O pressure by the Spiegelberg technique and a low overestimation at pressures below 20 cmH2O by both other techniques.

CONCLUSIONS

All three measurement techniques, IAP(FM), IAP(spie), and IAP(CiM) have good agreement with the applied hydrostatic pressure in this in vitro model of IAP measurement.