Intra-abdominal hypertension in obese patients undergoing coronary surgery: A prospective observational study

Optimization of kidney function in cardiac surgery patients with intra-abdominal hypertension: expert opinion

Cardiac surgery-associated acute kidney injury (CSA-AKI) affects up to 42% of cardiac surgery patients. CSA-AKI is multifactorial, with low abdominal perfusion pressure often overlooked. Abdominal perfusion pressure is calculated as mean arterial pressure minus intra-abdominal pressure (IAP). IAH decreases cardiac output and compresses the renal vasculature and renal parenchyma. Recent studies have highlighted the frequent occurrence of IAH in cardiac surgery patients and have linked the role of low perfusion pressure to the occurrence of AKI. This review and expert opinion illustrate current evidence on the pathophysiology, diagnosis, and therapy of IAH and ACS in the context of AKI.

Individualised flow-controlled ventilation reduces applied mechanical power and improves ventilation efficiency in a porcine intra-abdominal hypertension model

BACKGROUND

Aim of this study was to evaluate feasibility and effects of individualised flow-controlled ventilation (FCV), based on compliance guided pressure settings, compared to standard of pressure-controlled ventilation (PCV) in a porcine intra-abdominal hypertension (IAH) model. The primary aim of this study was to investigate oxygenation. Secondary aims were to assess respiratory and metabolic variables and lung tissue aeration.

METHODS

Pigs were randomly assigned to FCV (n = 9) and PCV (n = 9). IAH was induced by insufflation of air into the abdomen to induce IAH grades ranging from 0 to 3. At each IAH grade FCV was undertaken using compliance guided pressure settings, or PCV (n = 9) was undertaken with the positive end-expiratory pressure titrated for maximum compliance and the peak pressure set to achieve a tidal volume of 7 ml/kg. Gas exchange, ventilator settings and derived formulas were recorded at two timepoints for each grade of IAH. Lung aeration was assessed by a computed tomography scan at IAH grade 3.

RESULTS

All 18 pigs (median weight 54 kg [IQR 51-67]) completed the observation period of 4 h. Oxygenation was comparable at each IAH grade, but a significantly lower minute volume was required to secure normocapnia in FCV at all IAH grades (7.6 vs. 14.4, MD - 6.8 (95% CI - 8.5 to - 5.2) l/min; p < 0.001). There was also a significant reduction of applied mechanical power being most evident at IAH grade 3 (25.9 vs. 57.6, MD - 31.7 (95% CI - 39.7 to - 23.7) J/min; p < 0.001). Analysis of Hounsfield unit distribution of the computed tomography scans revealed a significant reduction in non- (5 vs. 8, MD - 3 (95% CI - 6 to 0) %; p = 0.032) and poorly-aerated lung tissue (7 vs. 15, MD - 6 (95% CI - 13 to - 3) %, p = 0.002) for FCV. Concomitantly, normally-aerated lung tissue was significantly increased (84 vs. 76, MD 8 (95% CI 2 to 15) %; p = 0.011).

CONCLUSIONS

Individualised FCV showed similar oxygenation but required a significantly lower minute volume for CO2-removal, which led to a remarkable reduction of applied mechanical power. Additionally, there was a shift from non- and poorly-aerated lung tissue to normally-aerated lung tissue in FCV compared to PCV.

Postoperative intra-abdominal hypertension predicts worse hospital outcomes in children after cardiac surgery: a pilot study†

OBJECTIVES

Our goal was to determine the incidence and characteristics of postoperative intra-abdominal hypertension (IAH) in paediatric patients undergoing open-heart surgery.

METHODS

This single-centre study included consecutive children (aged <16 years) who underwent open-heart surgery between July 2020 and February 2021. Patients who entered the study were followed until in-hospital death or hospital discharge. The study consisted of 2 parts. Part I was a prospective observational cohort study that was designed to discover the association between exposures and IAH. Postoperative intra-abdominal pressure was measured immediately after admission to the intensive care unit and every 6 h thereafter. Part II was a cross-sectional study to compare the hospital-related adverse outcomes between the IAH and the no-IAH cohorts.

RESULTS

Postoperatively, 24.7% (38/154) of the patients exhibited IAH, whereas 3.9% (6/154) developed abdominal compartment syndrome. The majority (29/38, 76.3%) of IAH cases occurred within the first 24 h in the intensive care unit. Multivariable analysis showed that the Society of Thoracic Surgeons-European Association for Cardio-Thoracic Surgery score [odds ratio (OR) = 1.86, 95% confidence interval (CI) 1.23-2.83, P = 0.004], right-sided heart lesion (OR = 5.60, 95% CI 2.34-13.43, P < 0.001), redo sternotomy (OR = 4.35, 95% CI 1.64-11.57, P = 0.003), high baseline intra-abdominal pressure (OR = 1.43, 95% CI 1.11-1.83, P = 0.005), prolonged cardiopulmonary bypass duration (OR = 1.01, 95% CI 1.00-1.01, P = 0.005) and deep hypothermic circulatory arrest (OR = 5.14, 95% CI 1.15-22.98, P = 0.032) were independent predictors of IAH occurrence. IAH was associated with greater inotropic support (P < 0.001), more gastrointestinal complications (P = 0.001), sepsis (P = 0.003), multiple organ dysfunction syndrome (P < 0.001) and prolonged intensive care unit stay (z = -4.916, P < 0.001) and hospitalization (z = -4.710, P < 0.001). The occurrence of a composite outcome (P = 0.009) was significantly increased in patients with IAH.

CONCLUSIONS

IAH is common in children undergoing cardiac surgery and is associated with worse hospital outcomes. Several factors may be associated with the development of IAH, including basic cardiac physiology and perioperative factors.

TRIAL INFORMATION

This study was registered in the Chinese Clinical Trial Registry (Trial number: ChiCTR2000034322)URL site: https://www.chictr.org.cn/hvshowproject.html?id=41363&v=1.4.

Abdominal compartment syndrome: an often overlooked cause of acute kidney injury

Abdominal compartment syndrome (ACS) is defined as any organ dysfunction caused by intra-abdominal hypertension (IAH), referred as intra-abdominal pressure (IAP) ≥ 12 mm Hg according to the World Society of Abdominal Compartment Syndrome. Abdominal compartment syndrome develops in most cases when IAP rises above 20 mmHg. Abdominal compartment syndrome, while being a treatable and even preventable condition if detected early in the stage of intra-abdominal hypertension, is associated with high rates of morbidity and mortality if diagnosis is delayed: therefore, early detection is essential. Acute kidney injury (AKI) is a common comorbidity, affecting approximately one in every five hospitalized patients, with a higher incidence in surgical patients. AKI in response to intra-abdominal hypertension develops as a result of a decline in cardiac output and compression of the renal vasculature and renal parenchyma. In spite of the high incidence of intra-abdominal hypertension, especially in surgical patients, its potential role in the pathophysiology of AKI has been investigated in very few clinical studies and is commonly overlooked in clinical practice despite being potentially treatable and reversible. Aim of the present review is to illustrate the current evidence on the pathophysiology, diagnosis and therapy of intra-abdominal hypertension and abdominal compartment syndrome in the context of AKI.

Impact of intra-abdominal pressure on early kidney transplant outcomes

Increased intra-abdominal pressure (IAP) is common among post-surgical patients and may cause organ dysfunction. However, its impact after kidney transplantation on early postoperative complications and graft recovery remains unclear. We designed a prospective, observational cohort study to describe the prevalence and determinants of IAP, as well as its effect on delayed graft function, postoperative complications, and graft recovery. IAP was measured in 205 kidney transplant recipients every 8 h during the first 72 h after surgery using the urinary bladder technique. Intra-abdominal hypertension was defined as IAP ≥ 12 mmHg. Patients were followed for 6 months or until graft failure/death. Mean IAP was 12 ± 3.3 mmHg within the first 24 h. 78% of subjects presented with intra-abdominal hypertension during the first 72 h. Increased IAP was associated with higher renal resistive index [r = 0.213; P = 0.003] and lower urine output [r =  - 0.237; P < 0.001]. 72 h mean IAP was an independent risk factor for delayed graft function [OR: 1.31; 95% CI: 1.13-1.51], postoperative complications [OR: 1.17; 95% CI: 1.03-1.33], and absence of graft function recovery [HR for graft function recovery: 0.94; 95% CI: 0.88-0.99]. Increased IAP was highly prevalent after transplantation and was independently associated with delayed graft function, postoperative complications, and absence of graft function recovery. Routine IAP monitoring should be considered post-transplantation to facilitate early recognition of relevant complications.

Gut Microbiota Was Involved in the Process of Liver Injury During Intra-Abdominal Hypertension

Background: Intestinal damage caused by intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS) can lead to the ectopic gut microbiota, which can contribute to liver injury via portal veins. Therefore, it is speculated that gut microbiota disorder caused by IAH/ACS may result in liver injury. The relationship between gut microbiota and IAH/ACS-related liver injury was investigated in this study.

Methods: A model of IAH was established in rats, and 16S rRNA sequencing was analyzed for gut microbiota in the feces of rats. The elimination of gut microbiota was completed by antibiotics gavage, and fecal microbiota transplantation (FMT) was used to change the composition of gut microbiota in rats.

Results: In addition to the traditional cause of liver blood vessel compression, liver injury caused by IAH was also associated with gut microbiota dysbiosis. Gut microbiota clearance can relieve liver injury caused by IAH, while FMT from IAH-intervened rats can aggravate IAH-related liver injury.

Conclusion: The gut microbiota was one of the most important factors contributing to the IAH-related liver injury, and the JNK/p38 signaling pathway was activated in this process.

Intra-abdominal pressure during and after cardiac surgery: a single-centre prospective cohort study

PURPOSE

While intra-abdominal hypertension (IAH) has been associated with adverse outcomes in multiple settings, the epidemiology and clinical implications of IAH in the context of cardiac surgery are less known. In this study, we aimed to describe the prevalence of IAH in patients undergoing cardiac surgery and determine its association with patient characteristics and postoperative outcomes.

METHODS

We conducted a single-centre prospective cohort study in which intra-abdominal pressure was measured in the operating room after general anesthesia (T1), after the surgical procedure (T2), and two hours after intensive care unit (ICU) admission (T3) in a subset of patients. Intra-abdominal hypertension was defined as intra-abdominal pressure (IAP) ≥ 12 mm Hg. Postoperative outcomes included death, acute kidney injury (AKI), and length of stay in the ICU and hospital.

RESULTS

A total of 513 IAP measurements were obtained from 191 participants in the operating room and 131 participants in the ICU. Intra-abdominal hypertension was present in 105/191 (55%) at T1, 115/191 (60%) at T2, and 31/131 (24%) at T3. Intra-abdominal pressure was independently associated with body mass index, central venous pressure, and mean pulmonary artery pressure but was not associated with cumulative fluid balance. Intraoperative IAH was not associated with adverse outcomes including AKI.

CONCLUSIONS

Intra-abdominal hypertension is very common during cardiac surgery but its clinical implications are uncertain.

Intra-abdominal hypertension and abdominal compartment syndrome: a current review

PURPOSE OF REVIEW

Intra-abdominal hypertension (IAH) and its deleterious effects are present in at least one-third of ICU patients. Increased recognition of IAH has led to significant reduction in the incidence of abdominal compartment syndrome (ACS). Many questions remain regarding what therapeutic interventions truly reduce morbidity and mortality associated with IAH/ACS. Recent research sheds new light on the effects of IAH in individual organ systems and unique disease states. This paper will review recent research in IAH/ACS recognition, treatment, and management.

RECENT FINDINGS

Recent research on IAH/ACS includes an improved understanding of the prevalence of IAH/ACS and confirmation of its independent association with organ failure. Specifically, new research adds clarity to the effects of IAH/ACS on individual organ systems and specific disease states. These results combine to improve the clinical ability to diagnose, monitor, and treat IAH/ACS.

SUMMARY

There is significant research on the broad impact of IAH/ACS in the ICU setting. Focus on IAH/ACS has gone beyond the purview of intensivists and surgeons to include outstanding work by specialists in multiple sub-specialties. These advances have generated improvements in current treatment algorithms. We review recent IAH/ACS literature and have categorized the most pertinent results into organ system-specific contributions.