Post-intensive care syndrome: its pathophysiology, prevention, and future directions

Abstract

Expanding elderly populations are a major social challenge in advanced countries worldwide and have led to a rapid increase in the number of elderly patients in intensive care units (ICUs). Innovative advances in medical technology have enabled lifesaving of patients in ICUs, but there remain various problems to improve their long-term prognoses. Post-intensive care syndrome (PICS) refers to physical, cognition, and mental impairments that occur during ICU stay, after ICU discharge or hospital discharge, as well as the long-term prognosis of ICU patients. Its concept also applies to pediatric patients (PICS-p) and the mental status of their family (PICS-F). Intensive care unit-acquired weakness, a syndrome characterized by acute symmetrical limb muscle weakness after ICU admission, belongs to physical impairments in three domains of PICS. Prevention of PICS requires performance of the ABCDEFGH bundle, which incorporates the prevention of delirium, early rehabilitation, family intervention, and follow-up from the time of ICU admission to the time of discharge. Diary, nutrition, nursing care, and environmental management for healing are also important in the prevention of PICS. This review outlines the pathophysiology, prevention, and future directions of PICS.

Keywords: Cognitive impairment; ICU‐acquired weakness; PICS‐p; end‐of‐life; intensive care unit; mental impairment; physical impairment; post‐intensive care syndrome.

Figure 1

Conceptual framework of post‐intensive care syndrome (PICS). ICU, intensive care unit; PICS‐F, PICS – family.

Figure 2

Subclassification of the mechanisms of intensive care unit‐acquired weakness (ICU‐AW) into two main groups. The first group is ICU‐AW with electrophysiologic and histopathologic findings (critical illness polyneuropathy [CIP] and critical illness myopathy [CIM]); the other is ICU‐AW with normal diagnostic studies. CIM, abnormal reduction in the amplitude of compound muscle action potentials (CMAPs) and an increase in their duration, normal sensory nerve action potentials (SNAPs), reduced muscle excitability on direct stimulation, and myopathic motor unit potentials on needle electromyography; CINM, critical illness neuromyopathy, coexistence of CIP and CIM; CIP, reduction in the amplitude of CMAPs and SNAPs with normal or mildly reduced nerve conduction velocity; Muscle deconditioning, normal nerve conduction velocity and compound motor action potential, absence of spontaneous activity.

Figure 3

Three common cognitive impairments among older adults: delirium, dementia, and depression.

Figure 4

Proposed framework for post‐intensive care syndrome in pediatrics (PICS‐p). Compared to the concept of PICS for adult intensive care unit survivors, the unique features of PICS‐p include the importance of baseline status, system maturation and psychosocial development, stronger interdependence within the family, and recovery trajectories that can potentially impact a child's life for decades.

Figure 5

ABCDEFGH bundle for prevention of post‐intensive care syndrome.

Figure 6

Association between critical illness and intensive care unit‐acquired weakness (ICU‐AW)/post‐intensive care syndrome (PICS) and the importance of nutrition therapy and rehabilitation. Malnutrition and inactivity accelerate ICU‐AW/PICS, especially with skeletal muscle volume and strength/functional loss. Nutrition therapy and rehabilitation are essential factors and the basis for the prevention of PICS/ICU‐AW.