Why Do the Mechanistic Actions of Albumin Not Translate Into Tangible Clinical Benefits?

Introduction to the concept of effective albumin concentration

PURPOSE

The purpose of this article is to discuss how the structural and presumably functional integrity of albumin, as described by the concept of effective albumin concentration (eAlb), has potentially important clinical implications beyond the total albumin concentration (tAlb) routinely reported by clinical laboratories.

SUMMARY

Albumin has several functions beyond its oncotic effects, including molecule binding, substance transport, detoxification actions, and serving as an antioxidant. However, there are conformational changes that occur during or following the manufacture of albumin and during its administration to patients with various disease states, such as decompensated liver disease, that often impair these functions. Such impairments are not reflected in tAlb values reported by clinical laboratories and might explain the disconnect often seen between albumin's proposed beneficial mechanistic functions and its less-than-predicted clinical effectiveness as noted in published studies. The concept of eAlb has been introduced to describe albumin with structural and functional integrity. Limited studies have found associations between eAlb values and patient prognostic indicators, but the techniques used to decide these effective concentrations to date are complicated and require specialized equipment and experienced researchers for proper interpretation.

CONCLUSION

Estimation of eAlb may provide valuable information on the functional ability of albumin beyond the tAlb reported by clinical laboratories, but more research is needed to decide how this information is best used in the clinical setting.

Hepatorenal Syndrome With Acute Kidney Injury: Diagnosis and Medical Management

OBJECTIVES

To review the current definitions and diagnostic criteria for acute kidney injury (AKI) and type 1 hepatorenal syndrome (HRS) now termed HRS-AKI and discuss the challenges in deciding the most appropriate medication regimens to treat patients with HRS-AKI.

DATA SOURCES

PubMed (inception to April 2023) with bibliographies of retrieved articles searched for additional articles; organizational websites for clinical practice guidelines (CPGs).

STUDY SELECTION AND DATA EXTRACTION

Randomized controlled trials (RCTs) evaluating albumin and vasoconstrictors for HRS-AKI.

DATA SYNTHESIS

A major change in the most recent revision of definitions and diagnostic criteria for HRS-AKI is the elimination of the set cutoff serum creatinine values for AKI. This change should be considered when comparing studies of HRS-AKI over time. Albumin has been administered to both vasoconstrictor treatment and placebo groups in all recent RCTs; however, there has never been a large RCT evaluating a no-albumin group. Most prospective trials comparing a midodrine/octreotide combination or norepinephrine to placebo or terlipressin have enrolled less than 100 patients limiting any conclusions regarding clinically important outcomes. Terlipressin with albumin has shown mixed results for complete HRS-AKI reversal with no reductions in crude mortality but adverse effect concerns involving ischemic and pulmonary events.

RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE

Type 1 hepatorenal syndrome with acute kidney injury is a potentially life-threatening syndrome with diagnostic and treatment challenges. Albumin plus a vasoconstrictor has become the routine HRS-AKI treatment even though there has not been a large RCT evaluating a no-albumin group. Terlipressin is the vasoconstrictor of choice for HRS-AKI in current CPGs, but it has adverse effect concerns and, until recently, was not available in the United States.

CONCLUSIONS

In conjunction with changes in the definitions and diagnostic criteria for HRS-AKI, debate continues regarding the optimal therapy for HRS-AKI, particularly considering recent trials demonstrating ischemic and pulmonary adverse events with terlipressin used in combination with albumin.