Hepatorenal syndrome

An update of the role of renin angiotensin in cardiovascular homeostasis

The renin angiotensin system (RAS) is thought to be the body's main vasoconstrictor system, with physiological effects mediated via the interaction of angiotensin II with angiotensin I receptors (the "classic" RAS model). However, since the discovery of the heptapeptide angiotensin 1-7 and the development of the concept of the "alternate" RAS system, with its ability to reduce arterial blood pressure, our understanding of this physiologic system has changed dramatically. In this review, we focus on the newly discovered functions of the RAS, particularly the potential clinical significance of these developments, especially in the realm of new pharmacologic interventions for treating cardiovascular disease.

Kidney-Organ Interaction

The practice of critical care nephrology demands an intimate understanding of the interactions and “crosstalk” that occurs between the kidney and multiple organ systems, in particular the heart, lung, gut, and brain. Accumulating evidence suggests that acute injury and dysfunction to the kidney can incite and propagate cardiac, pulmonary, gastrointestinal, and neurologic injury and dysfunction through a host of mechanisms.

Update on new aspects of the renin-angiotensin system in liver disease: clinical implications and new therapeutic options

The RAS (renin-angiotensin system) is now recognized as an important regulator of liver fibrosis and portal pressure. Liver injury stimulates the hepatic expression of components of the RAS, such as ACE (angiotensin-converting enzyme) and the AT(1) receptor [AngII (angiotensin II) type 1 receptor], which play an active role in promoting inflammation and deposition of extracellular matrix. In addition, the more recently recognized structural homologue of ACE, ACE2, is also up-regulated. ACE2 catalyses the conversion of AngII into Ang-(1-7) [angiotensin-(1-7)], and there is accumulating evidence that this 'alternative axis' of the RAS has anti-fibrotic, vasodilatory and anti-proliferative effects, thus counterbalancing the effects of AngII in the liver. The RAS is also emerging as an important contributor to the pathophysiology of portal hypertension in cirrhosis. Although the intrahepatic circulation in cirrhosis is hypercontractile in response to AngII, resulting in increased hepatic resistance, the splanchnic vasculature is hyporesponsive, promoting the development of the hyperdynamic circulation that characterizes portal hypertension. Both liver fibrosis and portal hypertension represent important therapeutic challenges for the clinician, and there is accumulating evidence that RAS blockade may be beneficial in these circumstances. The present review outlines new aspects of the RAS and explores its role in the pathogenesis and treatment of liver fibrosis and portal hypertension.

Monitoring Hepatic and Renal Function

Liver disease represents a serious risk factor for patients requiring anesthesia and surgery. Even subclinical liver disease increases perioperative morbidity and mortality. Perioperative renal dysfunction and failure have similar implications. Thus, detection of early hepatic and renal dysfunction and monitoring of their progress is essential. This article discusses methods for monitoring hepatic and renal function in patients who have high risk for liver or renal injury in the perioperative period.

Review article: current management of renal dysfunction in the cirrhotic patient

The United Network for Organ Sharing database revealed that over the last 4-5 years, an average of 1800 patients were removed from the cadaveric waiting list annually because of patients' death and an additional 400-500 were removed from the list because of the severity of their illnesses. The pre-transplant evaluation process, therefore, requires careful and continued assessment of the patient's pulmonary, cardiac and renal function among others. This article describes a systematic approach to the evaluation and management of renal dysfunction complicating the course of advanced liver disease, the pathogenic mechanisms and current recommendations for the treatment of hepatorenal syndrome, and the indications for combined liver-kidney transplantation.

Preoperative and perioperative predictors of the need for renal replacement therapy after orthotopic liver transplantation

BACKGROUND

Acute renal failure developing after orthotopic liver transplantation (OLTx) requiring renal replacement heralds a poor prognosis. Our center has previously reported a 1-year survival of only 41.8%. We undertook this study to determine whether we could identify preoperative and perioperative factors that would predict which patients are at risk.

METHODS

OLTxs performed between January 1, 1996, and December 31, 2001, were included in our retrospective database review. Combined kidney-liver transplants or patients with preoperative renal replacement therapy (RRT) were excluded. A total of 724 OLTxs were studied, which were divided into group I: no RRT, n=637; group II: hemodialysis only post-OLTx, n=17; and group III: continuous RRT post-OLTx, n=70. Univariate and stepwise logistic multivariate analyses were performed.

RESULTS

Preoperative serum creatinine greater than 1.9 mg/dL (odds ratio [OR] 3.57), preoperative blood urea nitrogen greater than 27 mg/dL (OR 2.68), intensive care unit stay more than 3 days (OR 10.23), and Model for End-Stage Liver Disease score greater than 21 (OR 2.5) were significant. A clinical prediction model was constructed: probability of requiring dialysis posttransplant=(-2.4586+1.2726 [creatinine >1.9] + 0.9858 [blood urea nitrogen >27] + 0.4574 [Model for End-Stage Liver Disease score >21] + 1.1625 [intensive care unit days >3]). A clinical prediction rule for patients with a score greater than 0.12 was applied to OLTx recipients who underwent transplantation in 2002. A total of 15 of 20 patients who received RRT and 111 of 121 who did not were correctly classified with the model.

CONCLUSIONS

This model allowed us to identify patients at high risk for developing the need for RRT postoperatively. Strategies for these patients to prevent or ameliorate acute renal failure and reduce the need for RRT postoperatively are needed.

Reference distributions for alpha2-macroglobulin: a practical, simple and clinically relevant approach in a large cohort

In this 11th article in a series, reference values of serum levels alpha(2)-macroglobulin alpha(2)M) are examined. The study is based on a cohort of 40,420 Caucasian individuals from northern New England that were tested in our laboratory between 1994 and 2000. Measurements were standardized against Certified Reference Material (CRM 470)/Reference Preparation for Proteins in Human Serum (RPPHS) and the results analyzed using a previously described statistical approach. Individuals with unequivocal laboratory evidence of inflammation (C-reactive protein >10 mg/L) were excluded in one leg of the study and included in the other, confirming that alpha(2)M does not respond to acute phase drive in man. Nephrotic syndrome, diabetes mellitus, and chronic liver disease have significant effect on levels of alpha(2)M. Dramatic changes occur during life with males higher from birth to age 12, females thereafter have higher values until the ninth decade. When values were expressed as multiples of the age- and gender-specific median levels, the resulting distributions fitted a log-Gaussian distribution well over a broad range. When patient data are normalized in this manner, the distribution parameters can be used to assign a centile corresponding to an individual's measurement thus simplifying interpretation.