Why do 80 per cent of intensive care patients suffer from delirium?

    5 May 2016

    Despite the usual hectic start to the week, the morning ward round is going frustratingly slowly. It’s being hampered by the presence of Frank, a dapper man in his seventies, dressed in chinos and a smart blue shirt. ‘It’s shameful, what you’re doing here,’ he tells us furiously. Frank isn’t an undercover journalist or someone from a clinical monitoring group. He’s a patient on the ward and he is acutely confused, convinced that we are some sort of police authority holding him against his wishes. A week ago he was his usual self, still running his small accountancy business. Then he developed a mild chest infection and his GP prescribed antibiotics. Two days later he was found wandering in a supermarket car park and brought to hospital. He remains lost, trapped somewhere far from reality.

    There’s no obvious cause for Frank’s persisting confusion. He has no other symptoms now, although he does have some mildly deranged blood tests typical of a resolving infection. But his brain scan is unremarkable and he is too physically well to fester in a hospital bed. The social care team is trying to arrange for him to go home with supervision (he lives alone) but meanwhile he remains with us. It’s easier to let him follow us around than try to persuade him, in his agitated state, to stay by his bed, surrounded by some very unwell patients. We take care to respect the confidentiality and dignity of other patients, but Frank is oblivious to them anyway, trapped in his own torment. He waits outside each bay or room then angrily berates us as we emerge, threatening legal action for keeping him against his will. Strangely, though, he seems to recognise that he is vulnerable and needs to be here — the main door is open and while the ward clerk and nurses keep a close eye to make sure he doesn’t leave, he goes no further than the front desk.

    Many of us have experienced feeling muddle-headed during an illness, but it is usually mild and settles after a few days. However, especially in older people, the confusional state we now call delirium can be very severe and may persist for weeks or even months. Sometimes it leaves a permanent drop in a person’s ability to function.

    Frank’s case is far from unusual. In every general hospital, one in three people arriving in the Emergency Assessment Unit has delirium. This rises to 80 per cent of patients in the intensive care unit or on a palliative care unit. And many of the things we do to people in hospital, from drug treatments and operations to simply moving them around often makes it worse. For example, 15 per cent of those admitted with a broken hip will already have delirium (possibly caused by their accident, although it might have been an undiagnosed delirium that lead to their fall). After the physiological onslaught of surgery to repair the hip, including doses of anaesthetic and powerful painkillers, at least half will be acutely confused. Confusion is a blanket term that doesn’t do justice to the subtle pattern of symptoms that usually defines delirium. A more clinical definition is a disturbance of consciousness that typically starts acutely, over one to two days, then follows a fluctuating course. The three core features are inattention, cognitive impairment (disordered thinking) and an abnormal sleeping and waking cycle. Inattention makes a person distractable, with a reduced ability to focus on a topic and a loss of awareness of their environment (Frank, for example, was remarkably oblivious to the ward around him). Cognitive impairment affects memory, orientation, language and comprehension, causing irrelevant, unfocused thought, and a loss of logic, rationality and executive function. As a result, the person may say and do senseless things. They may ramble or be unable to sustain a coherent conversation or follow commands, and this can interfere with treatments such as physiotherapy.

    A person’s behaviour often changes too. Between 5 and 25 per cent become, like Frank, hyperactive, agitated and aggressive. This can be very distressing for relatives, who see their calm, polite loved one behave so uncharacteristically. Some people become hyper-vigilant or hypersensitive to stimuli such as noise, which may develop into anxiety and paranoia, especially about the intentions of caregivers. Others follow a hypoactive pattern and become withdrawn, lethargic and sleepy, or may seem depressed. While a person can appear normal in the morning, they may become more confused as the day goes on, awake for much of the night, then drowsy the following day. Other features include visual hallucinations and vivid dreams. Symptoms may spill over into function, with loss of continence, falls and poor mobility.


    So what triggers delirium and how does this disturb the mind? Most people’s perception reflects the literary use of the word, which covers a myriad of ills, from the seething brains of Shakespeare’s lovers and madmen to dream-like states or the feverish madness of a dying man in Dickens’s The Stroller’s Tale. These reflect nicely the 1,001 events that can result in delirium — anything that disrupts the body’s internal milieu (even simple things like constipation or emotional stresses). Perhaps most important of all is the effect of chemicals, specifically medicines used with good intent which so often also disrupt brain function, and also caffeine or alcohol. But in at least one in five cases, no obvious cause can be identified.

    These triggers disturb the normal activity of cells in the central nervous system, although the exact -processes remain unclear. It’s difficult to study brain activity at a cellular level in a living person. Frank’s brain scan was normal, but most scans, such as CT and MRI, show only structural changes and provide little insight into the brain’s microscopic environment. Yet that is where current theories lie. Growing research evidence, from studies of blood and cerebrospinal fluid, points a finger at inflammation and physiological stress mechanisms. Other theories talk about nerve cells ageing, deficiencies or excesses of neurotransmitters (chemicals that transmit messages between nerve cells), neuroendocrine problems (the interaction between the nervous system and hormone systems) and ‘network disconnectivity’ (between different parts of the nervous system). Several factors probably interact in each patient to lead to biochemical derangement and delirium. People who already have fragile brain functioning are more vulnerable, so delirium is up to ten times more common in those with dementia, for example. Recent research shows that delirium strongly predicts future dementia, revealing a brain that has limited reserves to cope with challenges.

    Until we fully understand what’s going on, treatment is mostly aimed at trying to restore the patient’s physiology to normal and allow the brain to settle. This includes tackling disorientation, dehydration, low oxygen levels, acute illnesses, pain, effects of medication, poor nutrition and sleep disturbance.

    By the next morning, Frank was safely home with a team popping in to check on him. His delirium improved considerably once he was back in his familiar environment, helped by the sort of sleep you can get in your own bed but not on a ward. However, full recovery can take weeks or months and it will be essential to monitor him in the outpatients’ clinic. As many as 45 per cent of patients still have some delirium when discharged, and for one in five it’s still present at six months. Frank may also need support with daily activities — people may not get back to their usual level of functioning. There is no good evidence yet to show us how to prevent delirium, but it would seem logical that keeping healthy and treating illness promptly will play a key part.