Delirium – triggers and treatments

Delirium can affect up to 70 percent of patients in intensive care units (ICUs) and in other acute care settings; it is a condition that can have far-reaching consequences. In this series of interviews, Dr Cathrine McKenzie, Senior Pharmacist, Critical Care describes the causes, risk factors and treatments for this condition and explains how pharmacists can help.

Delirium can be described as “an acute brain dysfunction and that’s normally, typically, in response to a pathophysiological trigger, for example, exposure to a medicine or an acute infection or a change in a chronic condition”, explains Dr McKenzie. A diagnosis of delirium is important because it is the leading cause of cognitive decline in the acute care setting.

Risk factors for delirium include old age, severe infections, ischaemic heart disease, genetic predisposition and the anticholinergic burden of drug therapy.  “In the simplest terms, the higher the anticholinergic burden, the greater the risk of delirium, constipation, confusion, falls and, actually, if you expose yourself to these drugs for long periods of time you can actually develop dementia”, says Dr McKenzie.  The most well-known drugs are oxybutynin and solifenacin which are prescribed for management of urinary incontinence. “Polypharmacy in the elderly increases massively this anti-cholinergic burden”, she says.

The only group of drugs that has been shown to have any benefit is the alpha-2 agonists, clonidine and dexmedetomidine. Non-pharmacological treatments including early mobilisation, cognitive stimulation and re-establishment of the sleep-wake cycle are helpful.

Delirium is a major feature in severe covid-19 infection and about 25% of those affected will go on to develop cognitive decline.

One avenue of active research is into the use of intravenous thiamine for delirium.

Pharmacists in all sectors need to be aware of delirium because they all have something to contribute to the management and prevention of delirium. In ICU, “the more sedative an opioid we give to the patient the greater the risk of delirium later – so we should be there at the bedside every day ensuring that the doses are right for that patient and they are regularly reviewed”, says Dr McKenzie. In primary care it is important for pharmacists to monitor drug therapy to ensure that the anticholinergic burden does not escalate.

Pharmaceutical expertise is valuable in the intensive care setting and Dr McKenzie’s advice to young pharmacists thinking about a career in critical care pharmacy is “Don’t hesitate!”

Dr Cathrine A McKenzie, BsC PhD FRPharmS is Clinical Academic Research and Reader in Critical Care Therapeutics, Kings Health Partners, and Senior Pharmacist in Critical Care, University Hospital Southampton.  She is also Editor-in-chief,  Critical Illness www.medicinescomplete.com.

Read and watch the full series on our website or on YouTube.