In the United States, nearly 27% of hospital admissions involve the use of intensive care unit (ICU) services.1 Due to advancements in acute care, survival rates have increased among patients admitted to the ICU. However, these individuals are at high risk for mortality and readmission following discharge, along with numerous long-term challenges that are collectively referred to as post-intensive care syndrome (PICS).
“PICS refers to problems that have either emerged or worsened since an individual’s critical illness — problems in domains such as cognitive functioning, mental health functioning, and/or physical functioning,” James C. Jackson, PsyD, research associate professor of medicine in the division of allergy, pulmonary, and critical care medicine at Vanderbilt University Medical Center in Nashville, Tennessee, told Pulmonology Advisor. These issues are associated with reduced quality of life and difficulties with occupational and social functioning, which can have an effect on long-term outcomes.1
A large percentage of ICU survivors report somatic complaints that negatively affect their quality of life and activities of daily living. In a 2015 study by researchers in The Netherlands, > 80% of ICU survivors reported such symptoms, most commonly fatigue (74.4%), muscle weakness (48.8%), dyspnea (34.9%), pain (38.4%), and weight loss (33.3%).2
ICU-acquired weakness ranging from “generalized deconditioning to ICU polyneuromyopathy” has been linked with greater post-discharge mortality and long-term difficulty performing activities of daily living.1 In a study published in 2003, patients treated in the ICU for acute respiratory distress syndrome (ARDS) demonstrated worse performance in the 6-minute walk distance test and had reduced quality of life as assessed by the Short Form-36 (SF-36) for up to 5 years following discharge.1 Considering the large number of survivors with ARDS in the United States alone —>100,000 — the overall effect of these types of impairments is evident.3
Prolonged pulmonary dysfunction is another deficit that commonly affects ICU survivors, especially patients with acute lung injury. In a 2013 study, one-quarter of survivors with acute lung injury showed decreased total lung capacity, forced vital capacity, and diffusing capacity for carbon monoxide at 180 days after diagnosis, and these values correlated with abnormal findings on chest computed tomography scans.5 “Of note, these relationships were found to be independent of any neuromuscular dysfunction,” according to a 2019 review.1
Elevated rates of various psychiatric disorders have been noted in ICU survivors. In the 2015 study described above, ICU survivors who attended the hospital’s post-ICU aftercare clinic >6 weeks after discharge had clinically significant depression and/or anxiety (45.4% of patients) as assessed by the Hospital Anxiety and Depression Scale (HADS), and 43.3% of patients screened positive for posttraumatic stress disorder (PTSD) on the Impact of Event Scale-Revised (IES-R) questionnaire.2 A greater number of psychiatric symptoms was observed in women vs men.
ICU survivors may experience long-term cognitive deficits including impaired executive function, memory, and attention. One study identified neurocognitive dysfunction in 33% of ICU survivors 6 months following discharge.1 The actual prevalence may be higher, as hospital follow-up does not typically include evaluation of cognitive function and mild cognitive dysfunction may go unrecognized. “These unrecognized deficits, in addition to the above-mentioned psychological and physical deficits, can lead to increased patient morbidity, including economic hardship on patients and their family members,” wrote the authors of the recent review.1
Several national and professional societies have identified long-term outcomes in critical care survivors as a priority for improvements in research and clinical practice.3 Evidence in this area is currently lacking, as results have been largely inconsistent for a range of interventions targeting PICS-related outcomes. A limited number of clinical trials have found benefits associated with interventions “focused on functional mobility, conducted by nurses, physical therapists and/or occupational therapists and started within days of ICU admission.”3 In addition, experience from programs for patients with heart failure “suggests the possibility that very early case management interventions may help improve intermediate-term outcomes, including mortality and hospital readmission.”
To learn more about PICS, Pulmonology Advisor interviewed Dr Jackson and the following experts: Mark E. Mikkelsen, MD, MSCE, FCCM, chief of the section of medical critical care and medical director of the medical intensive care unit at Penn Presbyterian Medical Center in Philadelphia, Pennsylvania, and associate professor of medicine at the Hospital of the University of Pennsylvania, also in Philadelphia; and Jennifer Stevenson Jutte, PhD, MPH, a rehabilitation psychologist in private practice who conducted research on PICS while she was on the faculty at the University of Washington in Seattle.
Pulmonology Advisor: According to the available evidence, what is known thus far about PICS?
Dr Jackson: Findings from dozens of investigations suggest that problems in the domains of physical, cognitive, and mental health functioning are incredibly widespread. More than one-third of individuals consistently report cognitive and psychological problems after intensive care, and physical debility, which is often reflected by extreme weakness, is even more common.5
Some individuals suffer from isolated cognitive difficulties, for example, or they experience a condition like PTSD in the absence of other challenges. Alternatively, in a significant portion of cases, patients report limitations in all 3 of these broad domains. We continue to learn about the risk factors and contributors to these problems. Delirium is a key risk factor of concern, as is mechanical ventilation, and there are certainly others. The presence of preexisting deficits — whether frailty or psychological conditions — also puts people at risk.
Our understanding of the natural history of PICS is growing. Our clinical experience is that approximately one-third of individuals with deficits after being in the ICU get better — that is, they move in the direction of baseline — and approximately one-third remain as they are after discharge. The other one-third may get worse; these are often, but by no means always, individuals with progressive conditions that seem to be uncovered and exacerbated by the dire effects of being critically ill.