Hospitals are doing more to help the growing number of patients who receive treatment for serious illness in the intensive-care unit—only to find their release is the start of a whole new set of problems.

With medical advances, even the sickest patients now often survive potentially life-threatening conditions after a stay in intensive care. Many experience aftereffects, not only of the illness but also of the very medical care that may have saved their lives.

Doctors call it "post-intensive care syndrome" and say it is becoming more common. In the ICU, patients may be heavily sedated and hooked up to a ventilator, keeping them immobile, breathing and free of pain. But they can develop a temporary brain injury known as "ICU delirium," that is linked to later problems with memory and thinking. As many as 80% of ICU survivors have some form of cognitive or brain dysfunction, according to the Society of Critical Care Medicine, and some never recover. Many experience post-traumatic stress symptoms, depression, fatigue and prolonged muscle weakness.

More than five million patients are admitted to an intensive care unit each year for conditions such as respiratory failure and heart failure, and for monitoring after invasive surgery.

Especially at risk of developing post-ICU syndrome are patients who have sepsis. Often referred to as "blood poisoning," sepsis is the body's toxic response to infection and the most common life-threatening illness leading to ICU admission world-wide. It can arise from a seemingly benign cut or scrape, or set in as a complication of pneumonia, urinary tract infection or burst appendix.