Introduction

In the past few decades, advances in technology and understanding of the health sector have led to a significant decline in observed mortality due to critical illnesses, an observation that goes hand in hand with increased life expectancy. However, this also means that there is an increase in the number of patients who are admitted to the intensive care unit (ICU), and inevitably a growing number of people who are critical illness survivors. Within the last decade, the Society of Critical Care Medicine has focused on shedding light on the long-term effects of surviving a critical illness, an emerging phenomenon that is becoming a significant health issue. Post-intensive care syndrome (PICS) is an umbrella term used to refer to a collection of symptoms or impairments that are experienced by a patient as a result of treatment within the ICU and that persist or worsen after discharge from the ICU. Symptoms experienced by patients with PICS include physical, mental, behavioural and cognitive disorders. While patients are primarily affected by PICS, it was acknowledged that PICS can also develop in family members and caregivers of patients, as they too are significantly impacted by the burden of disease. This is referred to as PICS-family (PICS-F).^1,2

Admission to the ICU takes a heavy toll, physically and mentally, on both the patient and caregiver. And even with a positive outcome, instances of PICS are high. A study observing ICU survivors who were on mechanical ventilation for more than 48 hours found that at 2 months after discharge, 75% of patients required aftercare and support.³ Approximately 70% of all critical care survivors are thought to be at risk of developing PICS. Depending on factors like length of time in the ICU, disease severity and treatment received (e.g. mechanical ventilation, sedatives and analgesics administered), the effects of PICS can last anywhere from 6 months to 15 years.^2,4

Symptoms of PICS

PICS occurs as a consequence of treating a previous injury or disease, and as such, can be quite challenging to identify or diagnose. It is additionally challenging to accurately deduce the severity of PICS as there is currently no consensus as to how clinicians evaluate PICS.⁴ Nonetheless, it is generally accepted that patients with PICS will present with at least one symptom that can be classified as physical, psychological or cognitive in nature.

Physical impairments

Muscle weakness and disorders ICU-acquired weakness (ICUAW) is the most common kind of physical impairment observed with ICU survivors. The condition manifests as a result of prolonged stress from time and treatment in the ICU. These are inclusive of patient sedation, extended immobility, sepsis and use of a ventilator where a good proportion of these (40%) leads to muscle weakness or atrophy in patients.⁴ Muscle weakness tends to resolve with time and rehabilitation. However, this can be affected by the severity of muscle degeneration, which can hinder motor function and hence recovery can extend into years.

To minimise the risk of ICUAW, early identification and implementation is vital. Promoting motion in patients as soon as they are stable enough can help prevent muscle atrophy from prolonged immobility. Careful assessment to minimise patient exposure to sedatives can also help reduce the risk of developing PICS.²

Kidney Injury Patients who present to the ICU with damage or sustained injury to their kidney(s) can be at high risk of developing further complications. The most common is the progression from acute kidney injury to long term chronic kidney disease. Sustained kidney injury can also cause significant complications in other associated organs such as the lungs, brain or heart.⁵

Pulmonary dysfunction Patients treated for acute respiratory distress syndrome (ARDS), such as those admitted to the ICU from having contracted COVID-19, are likely to develop pulmonary dysfunction. Extended inflammation and regeneration of lung tissue can cause a degree of scarring. This scarring affects the structure and functional efficiency of the patient's lungs. Patients can experience breathing difficulties, breathlessness and a reduced capacity for exercise.

Immunosuppression and inflammation Due to the patient suffering from a critical illness on admission, their immune system is already in a highly active state. ICU survivors typically present with a significantly altered immune response to insult or injury. An absence of in mature immune cells responding to inflammation is instead taken up by immature immune cells, such as monocytes and neutrophils, which are less efficient at warding off pathogens. The presence of these cells in an individual often indicates a hospital acquired infection and poor clinical outcome.⁵

Cognitive impairment

Cognitive impairment in patients that have been admitted to the ICU can be a result of numerous causes. They can be rooted in the disease/condition that brought them into the ICU, the stresses that the patient experiences as a cause of treatment or a compounding effect of both. For healthcare workers, risk can be best mitigated at the point of care and as such consideration is to be given when administering treatments that can come under a fair degree of control. Examples include the administration of analgesics, blood pressure derangements and the use of a ventilator.⁴

Patients at a high risk of developing cognitive impairments as an ICU survivor are those that have preexisting conditions such as diabetes or vascular diseases. Patients who already suffer from a type of cognitive impairment are at risk of deteriorating further during their stay in ICU.^2,4 Patients typically present with speaking difficulty, problems with memory recall, focus and/or organisation. Some patients are able to recover cognitive abilities over time (cognitive dysfunction) whereas other patients are faced with a permanent or unchanged level of function (cognitive impairment). Both, however, fall under the umbrella of PICS.

Psychological impairment

Loss of physical strength and cognitive dysfunction has a significant impact on how a patient is able to carry out normal daily tasks, and inevitably becomes a hindrance to their quality of life. It is therefore not unexpected that in patients with one or both of these burdens, a subsequent psychological dysfunction can be triggered. The most commonly reported disorders are depression, anxiety and post-traumatic stress disorder (PTSD). The prevalence of these three disorders in critical illness survivors is in the range of 25 – 60%.⁴

Patients at high risk of developing a psychological disorder include pre-existing anxiety or depression. Distressing experiences in the ICU, medication, and physiological complications sustained by the body (increased hormonal regulation for example) also contribute to a patient's likelihood of developing a psychological disorder on discharge from the ICU.

Psychological impairments are also prone to be accompanied with physical manifestations such as loss of appetite, tiredness, sleep disturbance and sexual dysfunction. 

Prevention, diagnosis & assessment

Although there has been an increase in reports of PICS since its consensus a decade ago, there is still some way to go within the healthcare and research community before suitable guidance for diagnosing and assessing severity of PICS is agreed. In the meantime however, finding the exact prevalence and impact is seemingly difficult. Nonetheless, increased awareness and better practices in the clinic and on patient discharge can be attained to minimise risk.

Currently active measures to prevent PICS are considered the most effective option for improving patient outcomes. Early detection and standardised practices for ICU workers plays an important role in reducing PICS. In addition to taking detailed patient histories and measuring use of medications and sedatives, the ABCDE bundle is an approach that has been adopted by most ICU healthcare systems with good outcomes.⁶

The ABCDE bundle:

• Awakening – restricting the use of sedatives, inclusive of anxiolytic and antipsychotic agents
• Breathing – perform spontaneous breathing tests or exercise to check pulmonary output
• Care and continued communication both with the patient, families and within the core healthcare team
• Delirium – frequent and consistent monitoring, assessment, and management
• Early ambulation – encourage the patients to take on passive or active physical movement as soon as they are safe to do so

Tests used to screen and deduce the severity of PICS fall into four categories: Physical function, Subjective health (overall quality of life), Patient cognition and Mental health. While most patients are diagnosed with at least one symptom from these categories, an agreed consensus on which assessment tools are most effective for identifying PICS is yet to be reached. This unfortunately means that a reliable picture on the epidemiology cannot be performed with concrete certainty. The table below lists some of the tests used to determine PICS for each of the named categories.

Table 1 Tools used to assess Post Intensive Care Syndrome. Adapted from Vrettou, C. et al⁴

Summary

An undeniable correlation with PICS is the increased number of patients who survive chronic illness and are discharged from intensive care. In the last 10 years however, it has become apparent that simply surviving a critical illness is not where the story ends. While an increase in life expectancy facilitates the rise in PICS, environmental health emergencies, such as the COVID-19 pandemics, have further exacerbated an already growing healthcare issue.

For many patients and their loved ones, the time in critical care takes its toll, and for a good proportion of patients there may still be an extended period of recovery and rehabilitation to contend with after discharge from the ICU. This has a significant impact on the quality of life experience by all persons involved, as well as indirect implications on socio-economic infrastructure.

PICS - which includes physical, cognitive and psychological characteristics - requires a need for collaboration between healthcare teams to identify and minimise trauma in a timely manner for both the patient and their families. While further work needs to be done on improving the benchmark for diagnosis, severity and treatment approaches, it is evident that PICS has become well known in research literature since its naming consensus in 2012. And as research output continues to grow, there is every potential that questions may have their answers imminently.