Abdominal hypertension and liver dysfunction in intensive care unit patients: an "on-off" phenomenon?

Liver function assessment by indocyanine green plasma disappearance rate in patients with intra-abdominal hypertension after "non-hepatic" abdominal surgery

BACKGROUND AND OBJECTIVE

Liver function assessment in patients with intra-abdominal hypertension (IAH) after major abdominal surgery is complex and often confounding. Elevated intra-abdominal pressure (IAP) often occurs after major abdominal surgery, and is associated with decreased abdominal blood flow and organ dysfunction, and it could cause abdominal compartment syndrome (ACS), which is a life-threatening condition. Plasma disappearance rate (PDR) of indocyanine green (ICG) and ICG retention rate after 15 min (R15) were used to evaluate liver function and as a prognostic parameter after major abdominal surgery.

METHODS

In this prospective/observational study, 51 patients were followed in the surgical intensive care unit after major abdominal surgery (operation of the small and large intestine, stomach, pancreas, spleen, or resection of the abdominal aorta), 29 had IAH. The PDR-ICG and R15 were analyzed 24 h after surgery concurrently with IAP, APP, bilirubin, AST, ALT, prothrombin time, albumin, cardiac index, arterial lactate, oxygen delivery, MAP (mean arterial pressure), APACHE II (acute physiology and chronic health evaluation), SOFA (sequential organ failure assessment), and SAPS II (simplified acute physiology score). IAH has been defined as a peak intra-abdominal pressure (IAP) value of ≥12 mmHg, at a minimum, as two standardized measurements obtained 1-6 h apart.

RESULTS

The PDR-ICG measured 24 h after surgery was not different among groups (20.95% [SD = 10.34] vs 25.40% [SD = 7.42]), p = .094. ICG R15 was significantly higher in patients with IAH, 11.10% [SD = 13.82] vs 8.30 [SD = 11.46], p < .05, respectively. The PDR/ICG value was significantly lower in non-survivors than survivors (16.82 [SD = 10.87] vs 24.35 [SD = 8.48], p < .05).

CONCLUSIONS

The results suggest that PDR/ICG and ICG R15 are useful dynamic tests for evaluation of complex liver function and survival prediction after major abdominal surgery in patients with IAH.

Changes in Hepatic Blood Flow and Liver Function during Closed Abdominal Hyperthermic Intraperitoneal Chemotherapy following Cytoreduction Surgery

BACKGROUND

The increase in intra-abdominal pressure (IAP) during closed abdominal hyperthermic intraperitoneal chemotherapy (HIPEC) leads to major haemodynamic changes and potential organ dysfunction. We investigated these effects on hepatic blood flow (HBF) and liver function in patients undergoing HIPEC following cytoreductive surgery and fluid management guided by dynamic preload indices.

METHODS

In this prospective observational clinical study including 15 consecutive patients, we evaluated HBF by transesophageal echocardiography and liver function by determination of the indocyanine green plasma disappearance rate (ICG-PDR). Friedman's two-way analysis of variance by ranks and Wilcoxon signed-rank test were performed for statistical analysis.

RESULTS

During HIPEC, HBF was markedly reduced, resulting in the loss of any pulsatile Doppler flow signal in all but one patient. The ICG-PDR, expressed as median (interquartile 25-75), decreased from 23 (20-30) %/min to 18 (12.5-19) %/min (p < 0.001). Despite a generous crystalloid infusion rate (27 (22-35) ml/kg/h), cardiac index decreased during the increased IAP period, inferior vena cava diameter decreased, stroke volume variation and pulse pressure variation increased, lung compliance dropped, and there was an augmentation in plateau pressure. All changes were significant (p < 0.001) and reversed to baseline values post HIPEC.

CONCLUSION

Despite optimizing intravenous fluids during closed abdominal HIPEC, we observed a marked decrease in HBF and liver function. Both effects were transient and limited to the period of HIPEC but could influence the choice between closed or open abdominal cavity procedure for HIPEC and should be considered in similar clinical situations of increased IAP.

Biochemical Changes in Experimental Rat Model of Abdominal Compartment Syndrome

BACKGROUND

Increased intra-abdominal pressure (IAP) causes tissue ischemia, subsequent hypoxia, and impairment of normal tissue metabolism. Elevation of IAP above 20 mmHg leads to progression of abdominal compartment syndrome (ACS) that is associated with organ dysfunction or failure not previously manifested.

AIM

To evaluate the eff ects of diff erent grades and time of exposure to IAP on biochemical parameters and oxidative stress in organs aff ected by ischemia using previously developed rat model.

RESULTS

Three experimental groups exposed to diff erent IAP and time frames were tested for liver, kidney, and pancreas injury by measuring the activities of tissue specifi c enzymes in blood serum. Elevated activities of aspartate aminotransferase, pancreatic amylase, lipase, and higher concentrations of D-lactate, urea, and creatinine were found in some of the experimental groups compared to a control group of animals not subjected to increased IAP. Increased levels of biomarkers of oxidative stress as well as decrease in concentration of the major cellular antioxidant glutathione indicated the presence of oxidative injury as a result of elevated IAP.

CONCLUSIONS

The developed rat model is appropriate to study the mechanism and manifestation of tissue injury during diff erent grades of elevated IAP but also to test approaches aimed to attenuate the detrimental eff ects of ACS. This study also underlines the necessity of using not a single but a set of biochemical parameters in order to assess the severity of tissue injury during elevated IAP and progression to ACS.

Noosa, 2 years later… a critical analysis of recent literature

INTRODUCTION

Since the second World Congress on the Abdominal Compartment Syndrome (WCACS) in Noosa 2 years ago, interest and publications on intra-abdominal hypertension (IAH) and ACS have increased exponentially. This paper aimed to critically review recent publications and put this new data into the context of already acquired knowledge concerning IAH/ACS.

METHODS

A Medline and PubMed search was performed from January 2005 up to now using "intra-abdominal pressure (IAP)", "intra-abdominal hypertension (IAH)", "abdominal compartment syndrome (ACS)" and "decompressive laparotomy" as search items.

RESULTS

Although consensus definitions of IAH/ACS have been formulated recently, data on awareness are still disconcerting. Several groups refined current IAP measurement techniques and tested new direct IAP measurement devices for use in selected subpopulations. A series of recent publications identified specific patient subpopulations in IAH/ACS, like patients with burns or severe acute pancreatitis, with their specific pathophysiology and therapy. Although many studies already assessed the effect of elevated IAP on regional and micro-circulatory organ perfusion, a number of new publications attempted to unravel the link between elevated IAP and more "downstream" organ function or histology. Finally, therapy for IAH/ACS still reveals more questions than it answers. Global resuscitation does not necessarily equate with organ resuscitation. In fact, fluid-resuscitation may even induce IAH/ACS.

CONCLUSIONS

After publication of consensus guidelines on IAH/ACS, there is an urgent need for human intervention studies and, in parallel, clinically relevant animal models. Given moderately low incidence of ACS and the complex and interrelated pathologies of the critically ill patient with IAH/ACS, large animal models of pathology-induced IAH/ACS might create the opportunity to gain clinically relevant knowledge on the treatment of IAH/ACS.

Hepatic function and non-invasive hepatosplanchnic monitoring in patients with abdominal hypertension

A better understanding of intra-abdominal hypertension with relation to the liver is vital to the management of all forms of liver pathophysiology. Supporting good hepatic function within the critically ill patient is important not only in maintaining synthetic function, but also in avoiding the multi-organ complications of liver dysfunction. The resulting reduction in hepato-splanchnic blood flow (HSBF) observed with increasing intra-abdominal pressure has been clearly documented and seen to be exaggerated in animals with established liver disease. Unfortunately the tools required to measure this, remain difficult to apply routinely in the clinical setting and as such goal directed therapy to specifically improve the hepatosplanchnic circulation remains elusive. Given the documented effects of IAP on HSBF and the relatively high incidence of intra-abdominal hypertension and the abdominal compartment syndrome within "liver patients" as a whole, close attention to IAP and timely correction by appropriate medical or surgical means would appear to be essential.

Hypoperfusion, shock states, and abdominal compartment syndrome (ACS)

Cardiovascular dysfunction and failure are commonly encountered in patients with intra-abdominal hypertension or abdominal compartment syndrome. Accurate assessment and optimization of preload, afterload, and contractility are essential to restoring end-organ perfusion and maximizing patient survival. Application of a goal-directed resuscitation strategy, including abdominal decompression, when indicated, improves cardiac function, reverses end-organ failure, and minimizes intra-abdominal hypertension-related patient morbidity and mortality.

Ischemia-reperfusion injury in rats affects hydraulic conductivity in two phases that are temporally and mechanistically separate

Ischemia-reperfusion (IR) injury is a major insult to postcapillary venules. We hypothesized that IR increases postcapillary venular hydraulic conductivity and that IR-mediated changes in hydraulic conductivity result from temporally and mechanistically separate processes. A microcannulation technique was used to determine hydraulic conductivity (Lp) in rat mesenteric postcapillary venules serially throughout ischemia (45 min) and reperfusion (5 h) induced by superior mesenteric artery occlusion and release. Mesenteric IR resulted in a biphasic increase in Lp. White blood cell (WBC) adhesion slowly increased with maximal adhesion corresponding to the second peak (P < 0.005). After IR, tissue was harvested for RT-PCR analysis of ICAM-1, E-selectin, and P-selectin mRNA. Intercellular adhesion molecule-1 (ICAM-1) mRNA in the gut showed the most significant upregulation. Quantitative real-time PCR revealed that ICAM-1 mRNA was upregulated 60-fold in the gut. An ICAM-1 antibody was therefore used to determine the effect of WBC adhesion on Lp during IR. ICAM-1 inhibition attenuated Lp during the first peak and completely blocked the second peak (P < 0.005). When rats were fed a tungsten diet to inhibit xanthine oxidase and then underwent IR, Lp was dramatically attenuated during the first peak and mildly decreased the second peak (P < 0.005). Inhibition of xanthine oxidase by oxypurinol decreased Lp during IR by over 60% (P < 0.002). Tempol, a superoxide dismutase mimetic, decreased Lp during IR by over 30% (P < 0.01). We conclude that IR induces a biphasic increase in postcapillary hydraulic conductivity. Reactive oxygen species impact both the first transient peak and the sustained second peak. However, the second peak is also dependent on WBC-endothelial cell adhesion. These serial measurements of postcapillary hydraulic conductivity may lead the way for optimal timing of pharmaceutical therapies in IR injury.