The past several decades have resulted in improved care of critically ill patients and dramatically decreasing mortality rates, resulting in a large and expanding population of intensive care unit (ICU) survivors.(1) Although many survivors are discharged home after treatment, their lives and daily functioning are often dramatically altered compared to their functional abilities before critical illness. Many individuals do not return to work, require admission to a care facility or physical rehabilitation, and endure adverse long-term effects of critical illness. As Conti et al point out, studies should not only assess short-term outcomes such as mortality, but should also assess patient-centered outcomes such as quality of life after the patients return home and resume (or try to resume) their normal activities.(2)
Signs of Post-Intensive Care Syndrome
A large and growing body of work by outstanding investigators indicates that a majority of critical illness survivors have substantial morbidities that are often moderate to severe in intensity and can persist from months to years after hospital discharge. These morbidities, collectively called post-intensive care syndrome (PICS),(3) consist of new or worsening impairments in physical, cognitive and mental health that adversely impact daily functioning, a return to work and quality of life (QOL). While the prevalence of patients who have these morbidities is variable, the rates are high, ranging from 15% to more than 50% of patients. The prevalence not only varies by the type of PICS morbidity, but limited data suggest that the etiology of critical illness (e.g., acute lung injury, sepsis) affects outcome, with sicker patients having worse outcomes. Reduced QOL is reported in patients admitted to surgical ICUs, with morbidities following critical illness varying by the time they were measured. For example, cognitive impairments are reported in almost all patients at hospital discharge, but their prevalence declines over the first several months (approximately 25% to 45% of patients in the one to six years after critical illness) and appears to plateau during the first year following hospital discharge.
The trajectories of outcome following critical illness are also variable; some patients recover their pre-ICU level of function, but many have severe and persistent impairments, including individuals who improve somewhat and those whose impairments are stable but do not improve over time. It is unclear if the trajectories vary by type of morbidity (physical, cognitive or mental health) or if other factors, such as aging, cause additional decline in function over time. Furthermore, critical illness results in “accelerated aging” that negatively modifies the individual’s outcome trajectory.
Impact on QOL
QOL is one of the many commonly used measures to assess important health-related outcomes. It has been applied in a variety of disease states, including critical illness, where the illness or its treatment may lead to significant morbidities. A large and increasing number of investigations have shown reduced QOL following critical illness in a variety of populations, including those with acute respiratory distress syndrome (ARDS) or sepsis and individuals who require mechanical ventilation. Investigations into critically ill populations suggest that QOL varies by domain and may be related to differences in premorbid functional status, burden of comorbid illness, and the nature, severity, and duration of the illness. While pre-existing morbidity likely adversely impacts QOL, young, relatively healthy individuals (mean age of 45 years) have fewer comorbid medical diseases and good functional status (working before their illness), with persistent reduction in QOL assessed five years after developing ARDS.(4) Unlike the mental health domains, the physical domains improved during the first few months after critical illness.
A longitudinal study in survivors of severe sepsis who were followed at several time points, including five years after hospital discharge, found that QOL physical domains remained significantly lower than normal population scores, whereas mental health domains were only slightly below normative population scores.(5) A systematic review of 21 studies and over 7,000 survivors of ARDS found substantially reduced QOL scores following ICU discharge compared to matched, normative control data.(6) In this population, physical domains declined moderately and mental health domains revealed mild to moderate decreases after ICU discharge. This systematic review confirmed previous findings from small cohort studies showing improvement in physical domain, at least to some degree after critical illness, whereas there was little change in mental health over time.
A number of factors likely contribute to impaired QOL after critical illness, including personal factors (e.g., older age, prior health status, preexisting disease and psychiatric disorders), critical illness factors (e.g., delirium, hypoxia, hypotension, glucose dysregulation, illness severity, immobility, inflammation, loss of muscle and sedative use), and post-ICU factors (impairments in physical, cognitive, and mental health [see Table 1]). These various factors are not independent and likely interact. While many factors contribute to the development of PICS and the reduced QOL, some personal factors (e.g., older age, prior health status,) and critical illness factors (e.g., hypoxia) are difficult – if not impossible – to alter. A recent review of studies that assessed QOL in elderly critically ill populations found that these patients had worse QOL in most domains (especially physical function), compared to age-matched population data.(2) Although this finding may not be surprising, it highlights the fact that older age may be a risk factor for worse QOL after critical illness. Such ICU factors as delirium, sedative use and glucose dysregulation are potentially modifiable while the individuals are in the ICU and may prevent or improve PICS morbidities and thereby improve QOL.
Post-ICU morbidities are also associated with reduced QOL. Not surprisingly, physical morbidities, including muscle weakness, critical illness polyneuropathy and pulmonary function abnormalities, are associated with reduced QOL.(7) Delirium and ICU-acquired weakness are associated with PICS and reduced QOL in critically ill populations.(8) A study of older ICU survivors found that the inability to perform activities of daily living (e.g., bathing, dressing, grooming, walking across a room) at one month after ICU discharge was associated with reduced QOL on both physical and mental health components.(9) However, the relationship between impaired activities of daily living and QOL resolved by 12 months.
In addition to physical morbidities, impaired cognitive function, depression, anxiety and post-traumatic stress disorder (PTSD) are associated with reduced QOL.(10) Several studies have shown that ICU survivors with cognitive sequelae have worse QOL than survivors without such sequelae. Depression is also associated with reduced QOL on the mental health domains at one-month follow-up. Given that multiple studies find the prevalence of depression in ICU survivors as high as 50%, its potential adverse impact on QOL is enormous. QOL is also negatively impacted by anxiety and PTSD. A systematic review found the median point prevalence of PTSD symptoms was 22% in populations of general critically ill patients.(11)
Together, these data indicate that ICU survivors’ QOL is adversely influenced by personal, critical illness and post-ICU factors. This raises questions regarding what interventions can prevent or improve PICS and QOL (see Table 2). Research in this area is in its infancy, but the prevention or reduction of delirium in survivors of critical illness has the potential to improve PICS and QOL. A study in which survivors of critical illness were randomized to receive a rehabilitation handbook with self-help exercises or to usual care found that the intervention group had improved physical function, depression and QOL.(12) The use of an ICU diary has been shown to reduce the prevalence of PTSD, but QOL was not measured in these studies. Data from several other studies suggest that the right sedative regimen and daily spontaneous awakening and breathing trials can reduce delirium. Because delirium is associated with PICS and reduced QOL, decreasing it and its adverse long-term consequences is one intervention with the potential to improve outcomes.
ICU interventions, such as physical activity (or early mobility), have been shown to improve physical function, shorten ICU and hospital stays, reduce hospital readmission rates, and decrease delirium.(13-15) Physical activity is associated with improved cognitive function, depression, anxiety and – not surprisingly – physical function in many disease states.(16) While it remains to be studied, physical rehabilitation within the ICU may improve PICS and concomitantly improve QOL for survivors of critical illness. A recent small randomized study in survivors that used a combined intervention of physical and cognitive rehabilitation showed improved executive function and better functional outcome in the intervention group compared to the group who received usual care.(17) This study did not assess QOL, but extrapolation from existing data suggests better cognitive and physical function results in better QOL.
Physical, cognitive and mental health morbidities and their associated impairments in functional abilities and QOL are common and can last anywhere from months to years following critical illness. While descriptive information regarding the adverse effects of critical illness on physical, cognitive and mental health, and quality of life is well documented, studies are needed that assess mechanisms of injury and risk factors for developing PICS morbidities and their relationship to QOL after critical illness. Likewise, ICU interventions that can prevent or ameliorate post-ICU morbidities must be identified and assessed, as must interventions to ameliorate or provide compensatory strategies for post-ICU morbidities. Such interventions, if successful, have profound implications for improving daily functioning and QOL for survivors of critical illness.
- Iwashyna TJ, Cooke CR, Wunsch H, Kahn JM. Population burden of long-term survivorship after severe sepsis in older Americans. J Am Geriatr Soc. 2012;60(6):1070-1077.
- Conti M, Merlani P, Ricou B. Prognosis and quality of life of elderly patients after intensive care. Swiss Med Wkly. 2012;142:w13671.
- Needham DM, Davidson J, Cohen H, et al. Improving long-term outcomes after discharge from intensive care unit: report from a stakeholders' conference. Crit Care Med. 2012;40(2):502-509.
- Herridge MS, Tansey CM, Matte A, et al. Functional disability 5 years after acute respiratory distress syndrome. N Engl J Med. 2011;364(14):1293-1304.
- Cuthbertson BH, Roughton S, Jenkinson D, et al. Quality of life in the five years after intensive care: a cohort study. Crit Care. 2010;14(1):R6.
- Dowdy DW, Eid MP, Sedrakyan A, et al. Quality of life in adult survivors of critical illness: a systematic review of the literature. Intensive Care Med. 2005;31(5):611-620.
- Desai SV, Law TJ, Needham DM. Long-term complications of critical care. Crit Care Med. 2011;39(2):371-379.
- Banerjee A, Girard TD, Pandharipande P. The complex interplay between delirium, sedation, and early mobility during critical illness: applications in the trauma unit. Curr Opin Anaesthesiol. 2011;24(2):195-201.
- Vest MT, Murphy TE, Araujo KL, Pisani MA. Disability in activities of daily living, depression, and quality of life among older medical ICU survivors: a prospective cohort study. Health Qual Life Outcomes. 2011;9:9.
- Jackson JC, Mitchell N, Hopkins RO. Cognitive functioning, mental health, and quality of life in ICU survivors: an overview. Crit Care Clin. 2009;25(3):615-628.
- Davydow DS, Gifford JM, Desai SV, et al. Posttraumatic stress disorder in general intensive care unit survivors: a systematic review. Gen Hosp Psychiatry. 2008;30(5):421-434.
- Jones C, Skirrow P, Griffiths RD, et al. Rehabilitation after critical illness: a randomized, controlled trial. Crit Care Med. 2003;31(10):2456-2461.
- Schweickert WD, Pohlman MC, Pohlman AS, et al. Early physical and occupational therapy in mechanically ventilated, critically ill patients: a randomised controlled trial. Lancet. 2009;373(9678):1874-1882.
- Needham DM, Korupolu R, Zanni JM, et al. Early physical medicine and rehabilitation for patients with acute respiratory failure: a quality improvement project. Arch Phys Med Rehabil. 2010;91(4):536-542.
- Morris PE, Griffin L, Berry M, et al. Receiving early mobility during an intensive care unit admission is a predictor of improved outcomes in acute respiratory failure. Am J Med Sci. 2011;341(5):373-377.
- Hopkins RO, Suchyta MR, Farrer TJ, et al. Improving post-intensive care unit neuropsychiatric outcomes: understanding cognitive effects of physical activity. Am J Respir Crit Care Med. 2012;186(12):1220-1228.
- Jackson JC, Ely EW, Morey MC, et al. Cognitive and physical rehabilitation of intensive care unit survivors: results of the RETURN randomized controlled pilot investigation. Crit Care Med. 2012;40:1088-1097.