| Complication | Description | Selected risk factors | Natural history |
| Patient outcomes | |||
| Pulmonary | Impairment in spirometry, lung volumes, and diffusion capacity | Diffusion capacity: duration of mechanical ventilation | Generally mild impairment with improvement during first year, but can persist five years or more |
| Neuromuscular/ICU-acquired weakness | Includes critical illness polyneuropathy and myopathy | Hyperglycemia | Polyneuropathy may recover more slowly than myopathy; can extend to five years |
| Systemic inflammatory response syndrome | |||
| Sepsis | |||
| Multiorgan dysfunction | |||
| Disuse atrophy | Immobility/bed rest | ||
| Physical function | Impairment in activities of daily living (ADL/IADL) and six-minute walk distance | Systemic corticosteroids | Some improvement in ADL within months, but impairments may be seen in ADL at one year and in IADL at two years |
| ICU-acquired illnesses | |||
| Slow resolution of lung injury | |||
| Age | Long-lasting impairment in six-minute walk distance versus population norms | ||
| Preexisting IADL impairment | |||
| Psychiatric | Depression | Traumatic/delusional memories of ICU, sedation, psychiatric symptoms at discharge, impairment of physical function | May decrease over first year |
| Posttraumatic stress disorder | Sedation, agitation, physical restraints, traumatic/delusional memories | Little improvement in first year | |
| Anxiety | Unemployment, duration of mechanical ventilation | May persist past first year | |
| Overall risk factors: female gender, younger age, less education, pre-ICU psychiatric symptoms, and personality | |||
| Cognitive | Impairments in memory, attention, executive function, mental processing speed, visuo-spatial ability | Lower pre-ICU intelligence | Significant improvement during first year, with residual deficits up to six years later |
| ICU delirium | |||
| Sedation | |||
| Hypoxia | |||
| Glucose dysregulation | |||
| Family outcomes | |||
| Psychiatric | Depression | Overall risk factors: female gender, younger age, less education, pre-ICU psychiatric symptoms, and personality, distance to hospital, restricted visiting | Depression and anxiety decrease over time, but are higher than population norms at six months |
| Posttraumatic stress disorder | Dissatisfaction with communication, ICU physician perceived as "uncaring," passive preference for decision-making, mismatch between involvement in decision-making and preference | Posttraumatic stress disorder and complicated grief can persist four years or more after death or discharge and may not decrease over time | |
| Anxiety | Severity of illness not associated with development of symptoms | ||
| Complicated grief | Complicated grief is worse when family does not have knowledge of patient's wishes | ||
| In pediatric ICU, paternal stress after discharge is associated with child stress in pediatric ICU | |||
