Physiologic Reserve Assessment and Application in Clinical and Research Settings in Liver Transplantation

Abstract

Physiologic reserve is an important prognostic indicator. Because of its complexity, no single test can measure an individual's physiologic reserve. Frailty is the phenotypic expression of decreased reserve and portends poor prognosis. Both subjective and objective tools have been used to measure one or more components of physiologic reserve. Most of these tools appear to predict pretransplant mortality, but only some predict posttransplant survival. Incorporation of these measures of physiologic reserve in the clinical and research settings including prediction models are reviewed, and the applicability to patient-related outcomes are discussed. Commonly used tools, in patients with cirrhosis, that have been associated with clinical outcomes were reviewed. The strength of subjective tools lies in low-cost, wide availability, and quick assessments at the bedside. A disadvantage of these tools is the manipulative capacity, restricting their value in allocation processes. The strength of objective tests lies in objective measurements and the ability to measure change. The disadvantages include complexity, increased cost, and limited accessibility. Heterogeneity in the definitions and tools used has prevented further advancement or a clear role in transplant assessment. Consistent use of objective tools, including the 6-minute walk test, gait speed, Liver Frailty Index, or Short Physical Performance Battery, are recommended in clinical and research settings.

Use of a mobile-assisted telehealth regimen to increase exercise (MATRIX) in transplant candidates – A home-based prehabilitation pilot and feasibility trial

“…Researchers in the field of hepatology have expanded the physical fitness toolbox to include frailty ( 18 , 19 ), cardiopulmonary endurance ( 20 , 21 ), and sarcopenia ( 22 , 23 ) metrics. It is now clear that investigating an LT candidate's physiologic reserve through any of these metrics yields pivotal prognostic information ( 6 , 24 ). Furthermore, the effect is carried over to the post-LT period where physical fitness affects not only survivorship but also recovery and health-related quality of life, each of which leads to significant health care utilization and cost ( 14 , 25 , 26 ).…”

The fundamentals of sex‐based disparity in liver transplantation: Understanding can lead to change

“…Sarcopenia is predictive of longer hospital stays and higher risk of bacterial infections after LT. [ 35 ] Post‐LT and de novo sarcopenia are associated with worse survival. [ 36 ] Pre‐LT sarcopenia tends to be more prevalent in men, but no studies have looked at how sarcopenia differs based on sex following LT. Frailty, by contrast, has been shown to be more common in women independent of age, MELD, or decompensation (ascites, hepatic encephalopathy) and is associated with poor outcomes before LT. [ 37 ] Further, frailty explained the sex‐based disparity in waitlist mortality by an additional 13%. [ 38 ] No studies have assessed sex‐based frailty outcomes after transplantation.…”

The sublingual microcirculation and frailty index in chronic kidney disease patients

“…The concept of physiological reserve quantifies the maximum additional work capacity a physiological system can produce under exposure to a stressor, in comparison to the basal work output needed to maintain homeostasis 25 . Frail patients use a greater proportion of their physiological capacity in maintaining homeostasis than nonfrail patients leaving them with limited reserve to respond to trivial insults, that can lead to decompensation 26,27 . At present, the underlying mechanisms responsible for the decline in physiological reserve, which are likely to be multifactorial, are poorly characterized at the cellular and tissue level.…”

“… 25 Frail patients use a greater proportion of their physiological capacity in maintaining homeostasis than nonfrail patients leaving them with limited reserve to respond to trivial insults, that can lead to decompensation. 26 , 27 At present, the underlying mechanisms responsible for the decline in physiological reserve, which are likely to be multifactorial, are poorly characterized at the cellular and tissue level.…”