Post-intensive care syndrome

ICU-acquired weakness (ICU-AW), sometimes called critical illness polyneuropathy, is the most common form of physical impairment, and is estimated to occur in 25 percent or more of ICU survivors.[5][6] It is thought to be an effect of long-term immobility and deep sedation that many critically ill patients experience while in the ICU.[4] In addition, severe infections and inflammation are significant risk factors for developing ICU-AW.[7]

ICU-AW often presents as difficulty performing activities of daily living (e.g. moving around the living environment, using the bathroom, ability to make meals or do laundry). Inability to effectively perform these tasks can be particularly distressing to patients. The deficits associated with ICU-AW have a direct and negative effect on a person’s independence. The natural course of ICU-AW is variable, but some patients recover within a year.[8]

Other physical impairments include joint contractures due to long periods of immobility while hospitalized. The elbow and ankle are the most commonly affected joints, followed by the hip and knee.[9] Some physical weakness may result from malnutrition during critical illness.[10] Though nutrition may be provided by tube-feeding or parenteral nutrition, the initiation of parenteral nutrition may be delayed, and interruptions in feeding often occur due to gastrointestinal intolerance or the performance of procedures that require an empty stomach.[10] In people who experience acute respiratory distress syndrome and are treated with mechanical ventilation, lung function is often compromised for months to years. The most commonly impaired lung function is diffusing capacity for carbon monoxide, as well as reduced lung volumes and spirometry.[11]

Cognitive impairments include deficits in memory, attention, mental processing speed, and problem solving. These impairments affect up to 80% of individuals who survive a critical illness.[12] Impairments in memory and executive function have the most profound effect in terms of prohibiting people from engaging in the tasks and behaviors needed to function effectively in daily life and carry out complex cognition.[13] The effect of cognitive dysfunction is significant – unemployment is not uncommon because of difficulties with tasks of executive function (e.g. completing regular tasks like balancing a checkbook, and remembering facts or events). Among individuals with PICS-associated cognitive impairments, most patients improve or completely resolve over the first year.

Major risk factors for cognitive impairment following ICU admission due to critical illness include delirium, prior cognitive deficit, sepsis, and acute respiratory distress syndrome (ARDS). It is currently believed that many factors can play a role in causing cognitive impairment following critical illness. Some possible mechanisms for include poor blood supply to the brain due to low blood pressure from sepsis, poor oxygen supply to the brain due to respiratory distress and impairment, inflammation of the brain, and disruption of the blood-brain barrier in the areas of the brain that are involved in executive function and memory[14][15][16]

Depression and anxiety are the two most common mental health disorders seen in individuals with PICS.[17][18] The range of possible mental health problems, however, is far wider. Dementia, post-traumatic stress disorder (PTSD), and persistent delusional behavior are also manifestations of the syndrome.[17] Although not completely understood, the anxiety and delusions seen in patients with PICS are likely linked to delusional memories that some individuals acquire during their stay in the ICU, rather than recall of factual memories.[19][20] It is thought that medically-induced sedation may contribute to the formation of delusional memories by raising the risk of delirium and hallucinations.

Risk factors are similar to those for cognitive impairment following critical illness, and include severe sepsis,[21] acute respiratory distress syndrome,[22] respiratory failure, trauma,[23] hypoglycemia,[24] and hypoxemia. Like ICU-acquired weakness, long-term immobility and deep sedation have been known to play an important part in the development of mental health problems seen in PICS.[4][19] Sleep pattern disturbance, a common problem in the ICU, is also a likely culprit. Age under 50 years, female gender, lower education level, pre-existing disability, alcohol abuse, pre-existing anxiety, depression, and PTSD are also risk factors for PICS-related mental health disorders.[25]

The natural history for mental health disorders following critical illness is not well known, likely due to lack of recognition that these psychiatric symptoms may be related to a remote ICU admission. With proper psychological and psychiatric help, mental illness related to PICS can be successfully managed, but research favors preventative strategies as the most effective management. While there are ongoing studies focused on determining the best way to treat and prevent psychiatric problems following critical illness, daily diaries, so-called “ICU diaries” seem to be the most promising. These ICU diaries appear to be effective in treating the delusional, false memories that some of these individuals develop.[26] Healthcare providers, especially clinical social workers who specialize in medical care, can be very helpful in advocating these practices and facilitating them for patients and families.

Although there are promising methods for treating PICS, prevention should be the primary focus. When strategies at primary prevention have failed, recognizing the syndrome and its long-term effects have been a significant step in effectively treating PICS.

Limiting deep sedation and immobility and bed-rest have had the largest impact in preventing the long-term functional deficits seen in PICS.[4] Attention to sleep hygiene while in the ICU also seems to be an important part of prevention. Early recognition and treatment of delirium appears to decrease the incidence of PICS. Early, aggressive physical and occupational therapy have had a positive effect.[31] In addition, a focused effort by the ICU health care team should reinforce the importance to family and patients regarding maintaining self-care including hygiene, adequate sleep and nutrition during and after the course of ICU stay.

Because PICS represents a range of disorders, no single treatment is likely to adequately address all the symptoms associated with the syndrome. Care can be sought from a variety of professionals, including primary care physicians, nurse practitioners, physical and occupational therapists, dietitians, clinical social workers trained in medical social work, psychiatrists and psychologists. In addition, there is a growing trend of dedicated follow-up clinics for ICU patients that show some promise for recognizing and triaging patients. They often offer support groups for patients and families affected by PICS and PICS-F.

Patients and caregivers should look for signs and symptoms associated with PICS or PICS-F including muscle weakness, fatigue, trouble with daily activities, memory or thinking problems, anxiety and depression, or nightmares and unwanted memories after leaving the ICU. If these symptoms are recognized, consulting a primary care doctor or other caregiver can help. Many other specialists can be enlisted to help patients recover including occupational or physical therapists, dietitians, medically trained clinical social workers, psychiatrists or psychologists, and speech therapists. Patients and families who have questions or concerns regarding PICS or PICS-F should refer to their local hospital and ICU for available resources.