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

International cross-sectional survey on current and updated definitions of intra-abdominal hypertension and abdominal compartment syndrome

BACKGROUND

The Abdominal Compartment Society (WSACS) established consensus definitions and recommendations for the management of intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS) in 2006, and they were last updated in 2013. The WSACS conducted an international survey between 2022 and 2023 to seek the agreement of healthcare practitioners (HCPs) worldwide on current and new candidate statements that may be used for future guidelines.

METHODS

A self-administered, online cross-sectional survey was conducted under the auspices of the WSACS to assess the level of agreement among HCPs over current and new candidate statements. The survey, distributed electronically worldwide, collected agreement or disagreement with statements on the measurement of intra-abdominal pressure (IAP), pathophysiology, definitions, and management of IAH/ACS. Statistical analysis assessed agreement levels, expressed in percentages, on statements among respondents, and comparisons between groups were performed according to the respondent's education status, base specialty, duration of work experience, role (intensivist vs non-intensivist) and involvement in previous guidelines. Agreement was considered to be reached when 80% or more of the respondents agreed with a particular statement.

RESULTS

A total of 1042 respondents from 102 countries, predominantly physicians (73%), of whom 48% were intensivists, participated. Only 59% of HCPs were aware of the 2013 WSACS guidelines, and 41% incorporated them into practice. Despite agreement in most statements, significant variability existed. Notably, agreement was not reached on four new candidate statements: "normal intra-abdominal pressure (IAP) is 10 mmHg in critically ill adults" (77%), "clinical assessment and estimation of IAP is inaccurate" (65.2%), "intragastric can be an alternative to the intravesical route for IAP measurement" (70.4%), and "measurement of IAP should be repeated in the resting position after measurement in a supine position" (71.9%). The survey elucidated nuances in clinical practice and highlighted areas for further education and standardization.

CONCLUSION

More than ten years after the last published guidelines, this worldwide cross-sectional survey collected feedback and evaluated the level of agreement with current recommendations and new candidate statements. This will inform the consensus process for future guideline development.

Toward the "Perfect" Shunt: Historical Vignette, Current Efforts, and Future Directions

As a concept, drainage of excess fluid volume in the cranium has been around for more than 1000 years. Starting with the original decompression-trepanation of Abulcasis to modern programmable shunt systems, to other nonshunt-based treatments such as endoscopic third ventriculostomy and choroid plexus cauterization, we have come far as a field. However, there are still fundamental limitations that shunts have yet to overcome: namely posture-induced over- and underdrainage, the continual need for valve opening pressure especially in pediatric cases, and the failure to reinstall physiologic intracranial pressure dynamics. However, there are groups worldwide, in the clinic, in industry, and in academia, that are trying to ameliorate the current state of the technology within hydrocephalus treatment. This chapter aims to provide a historical overview of hydrocephalus, current challenges in shunt design, what members of the community have done and continue to do to address these challenges, and finally, a definition of the "perfect" shunt is provided and how the authors are working toward it.

Is it feasible to measure intra-abdominal pressure using a balloon-tipped rectal catheter? Results of a validation study

The gold standard to measure intra-abdominal pressure (IAP) is intra-vesical measurement via the urinary bladder. However, this technique is restricted in ambulatory settings because of the risk of iatrogenic urinary tract infections. Rectal IAP measurements (IAP_rect) may overcome these limitations, but requires validation. This validation study compares the IAP_rect technique against gold standard intra-vesical IAP measurements (IAP_ves). IAP_rect using an air-filled balloon catheter and IAP_ves using Foley Manometer Low Volume were measured simultaneously in sedated and ventilated patients. Measurements were performed twice in different positions (supine and HOB 45° elevated head of bed) and with an external abdominal pressure belt. Sixteen patients were included. Seven were not eligible for analysis due to unreliable IAP_rect values. IAP_rect was significantly higher than IAP_ves for all body positions (p < 0.01) and the correlation between IAP_ves and IAP_rect was poor and not significant in each position (p ≥ 0.25, R² < 0.6, Lin's CCC < 0.8, bias - 8.1 mmHg and precision of 5.6 mmHg with large limits of agreement between - 19 to 2.9 mmHg, high percentage error 67.3%, and low concordance 86.2%). Repeatability of IAP_rect was not reliable (R = 0.539, p = 0.315). For both techniques, measurements with the external abdominal pressure belt were significantly higher compared to those without (p < 0.03). IAP_rect has important shortcomings making IAP estimation using a rectal catheter unfeasible because the numbers cannot be trusted nor validated.

Intra-Abdominal Hypertension and Compartment Syndrome after Pediatric Liver Transplantation: Incidence, Risk Factors and Outcome

In pediatric liver transplantation (pLT), the risk for the manifestation and relevance of intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS) is high. This observational study aimed to evaluate the incidence, relevance and risk factors for IAH and ACS by monitoring the intra-abdominal pressure (IAP), macro- and microcirculation (near-infrared spectroscopy (NIRS)), clinical and laboratory status and outcomes of 27 patients (16 female) after pLT (median age at pLT 35 months). Of the patients, 85% developed an elevated IAP, most of them mild. However, 17% achieved IAH° 3, 13% achieved IAH° 4 and 63% developed ACS. A multiple linear regression analysis identified aortal hepatic artery anastomosis and cold ischemia time (CIT) as risk factors for increased IAP and longer CIT and staged abdominal wall closure for ACS. ACS patients had significantly longer mechanical ventilation (p = 0.004) and LOS-PICU (p = 0.003). No significant correlation between NIRS or biliary complications and IAH or ACS could be shown. IAH and ACS after pLT were frequent. NIRS or grade of IAH alone should not be used for monitoring. A longer CIT is an important risk factor for higher IAP and ACS. Therefore, approaches such as the ex vivo machine perfusion of donor organs, reducing CIT effects on them, have great potential. Our study provides important basics for studying such approaches.

Venous dynamics in anesthetized sheep govern postural-induced changes in cerebrospinal fluid pressure comparable to those in humans

Sheep are popular large animals in which to model human disorders and to study physiological processes such as cerebrospinal fluid dynamics. However, little is known about vascular compensatory mechanisms affecting cerebrospinal fluid pressures during acute postural changes in sheep. Six female white Alpine sheep were anesthetized to investigate the interactions of the vascular and cerebrospinal fluid system by acquiring measurements of intracranial pressure and central and jugular venous pressure during passive postural changes induced by a tilt table. The cross-sectional area of the common jugular vein and venous blood flow velocity was recorded. Anesthetized sheep showed bi-phasic effects of postural changes on intracranial pressure during tilting. A marked collapse of the jugular vein was observed during head-over-body tilting; this is in accordance with findings in humans. Active regulatory effects of the arterial system on maintaining cerebral perfusion pressure were observed independent of tilting direction. Conclusion: Anesthetized sheep show venous dynamics in response to posture-induced changes in intracranial pressure that are comparable with those in humans.

Systematic Review of Diagnostic Sensors for Intra-Abdominal Pressure Monitoring

Intra-abdominal pressure (IAP) is defined as the steady-state pressure within the abdominal cavity. Elevated IAP has been implicated in many medical complications. This article reviews the current state-of-the-art in innovative sensors for the measurement of IAP. A systematic review was conducted on studies on the development and application of IAP sensors. Publications from 2010 to 2021 were identified by performing structured searches in databases, review articles, and major textbooks. Sixteen studies were eligible for the final systematic review. Of the 16 articles that describe the measurement of IAP, there were 5 in vitro studies (31.3%), 7 in vivo studies (43.7%), and 4 human trials (25.0%). In addition, with the advancement of wireless communication technology, an increasing number of wireless sensing systems have been developed. Among the studies in this review, five presented wireless sensing systems (31.3%) to monitor IAP. In this systematic review, we present recent developments in different types of intra-abdominal pressure sensors and discuss their inherent advantages due to their small size, remote monitoring, and multiplexing.

The Correlation between Head of Bed Angle and Intra-Abdominal Pressure of Intubated Patients; a Pre-Post Clinical Trial

INTRODUCTION

The recommended position for measuring Intra-Abdominal Pressure (IAP) is the supine position. However, patients put in this position are prone to Ventilator-associated pneumonia. This study was done to evaluate the relationship between bed head angle and IAP measurements of intubated patients in the intensive care unit.

METHODS

In this clinical trial, seventy-six critically ill patients under mechanical ventilation were enrolled. IAP measurement was performed every 8 hours for 24 hours using the KORN method in three different degrees of the head of bed (HOB) elevation (0 ° , 15 ° , and 30 ° ). Bland-Altman analysis was performed to identify the bias and limits of agreement among the three HOBs. According to World Society of the Abdominal Compartment Syndrome (WSACS), we can consider two IAP techniques equivalent if a bias of <1 mmHg and limits of agreement of - 4 to +4 were found between them. Data were analyzed using SPSS statistical software (v. 19), and the significance level was considered as 0.05.

RESULTS

The prevalence of intra-abdominal hypertension was 18.42%. Mean ± standard deviation (SD) of IAP were 8.44 ± 4.02 mmHg for HOB angle 0°, 9.58 ± 4.52 for HOB angle 15 ° , and 11.10 ± 4.73 for HOB angle 30^o (p = 0.0001). The IAP measurement bias between HOB angle 0°and HOB angle 15° was 1.13 mmHg. This bias was 2.66 mmHg between HOB angle 0° and HOB angle 30°.

CONCLUSION

Elevation of HOB angle from 0 to 30 degree significantly increases IAP. It seems that the measurement of IAP at HOB angle 15° was more reliable than 30°.

Intra-abdominal hypertension, fluid balance, and adverse outcomes after orthotopic liver transplantation

BACKGROUND

Intra-abdominal hypertension (IAH) is frequently encountered in critically ill surgical patients. We aimed to evaluate the incidence of IAH after orthotopic liver transplant (OLT) and its impact on organ function, hospital length-of-stay (LOS), and death.

METHODS

This prospective, observational, cohort study evaluated consecutive adult patients admitted in the ICU after undergoing OLT. Intra-abdominal pressure (IAP) was measured every 4-6 h for 3 days. Worsening IAP was defined as a gradual increase in IAP over a period of time. Daily fluid balance was the daily sum of all intakes minus the output.

RESULTS

IAH was observed in 48% of the patients within the first 3 days after ICU admission, while ACS was diagnosed in 15%. Patients with IAH had a higher positive fluid balance at day 1 (1764 mL [812-2733 mL] vs. 1301 mL [241-1904 mL], p = 0.025). Worsening IAH was associated with fewer days free of organ dysfunction. IAH within 72 h after ICU admission was independently associated with a composite outcome of death or a longer ICU LOS (odds ratio 2.9; CI 95% 1.02-8.25, p = 0.043).

CONCLUSION

After OLT, nearly half of the patients presented IAH, that was associated with unfavorable outcomes.

Effect of intra-abdominal pressure on respiratory function in patients undergoing ventral hernia repair

AIM

To determine the influence of intra-abdominal pressure (IAP) on respiratory function after surgical repair of ventral hernia and to compare two different methods of IAP measurement during the perioperative period.

METHODS

Thirty adult patients after elective repair of ventral hernia were enrolled into this prospective study. IAP monitoring was performed via both a balloon-tipped nasogastric probe [intragastric pressure (IGP), CiMON, Pulsion Medical Systems, Munich, Germany] and a urinary catheter [intrabladder pressure (IBP), UnoMeterAbdo-Pressure Kit, UnoMedical, Denmark] on five consecutive stages: (1) after tracheal intubation (AI); (2) after ventral hernia repair; (3) at the end of surgery; (4) during spontaneous breathing trial through the endotracheal tube; and (5) at 1 h after tracheal extubation. The patients were in the complete supine position during all study stages.

RESULTS

The IAP (measured via both techniques) increased on average by 12% during surgery compared to AI (P < 0.02) and by 43% during spontaneous breathing through the endotracheal tube (P < 0.01). In parallel, the gradient between РаСО2 and EtCO2 [Р(а-et)CO2] rose significantly, reaching a maximum during the spontaneous breathing trial. The PаO2/FiO2 decreased by 30% one hour after tracheal extubation (P = 0.02). The dynamic compliance of respiratory system reduced intraoperatively by 15%-20% (P < 0.025). At all stages, we observed a significant correlation between IGP and IBP (r = 0.65-0.81, P < 0.01) with a mean bias varying from -0.19 mmHg (2SD 7.25 mmHg) to -1.06 mm Hg (2SD 8.04 mmHg) depending on the study stage. Taking all paired measurements together (n = 133), the median IGP was 8.0 (5.5-11.0) mmHg and the median IBP was 8.8 (5.8-13.1) mmHg. The overall r (2) value (n = 30) was 0.76 (P < 0.0001). Bland and Altman analysis showed an overall bias for the mean values per patient of 0.6 mmHg (2SD 4.2 mmHg) with percentage error of 45.6%. Looking at changes in IAP between the different study stages, we found an excellent concordance coefficient of 94.9% comparing ΔIBP and ΔIGP (n = 117).

CONCLUSION

During ventral hernia repair, the IAP rise is accompanied by changes in Р(а-et)CO2 and PаO2/FiO2-ratio. Estimation of IAP via IGP or IBP demonstrated excellent concordance.