When I met Sam, a 49-year-old man in A&E, he was perilously close to death due to a life-threatening tear in a major artery. He underwent emergency cardiothoracic surgery lasting 12 hours and was subsequently moved to the Intensive Care Unit (ICU).
Remarkably, Sam survived the operation and was discharged five weeks later. I saw him in clinic two months after our first encounter and asked how he was adjusting to life. He said he had physically recovered from his operation but was left distraught and exhausted: he could not sleep properly in hospital and since his discharge, woke up every hour. He stressed that while the medical care he received was exemplary, it came at the expense of something that is integral to our physical and mental health: sleep.
In the 18th century the astronomer Jean-Jacques d’Ortous de Mairan discovered that mimosa plants opened towards the sun during the day and closed at night. However, this process also occurred in the absence of light, which led to the concept of an innate biological clock. Each of our cells has a biological clock that is part of a “circadian rhythm”.
In 2017, Hall, Rosbash and Young were awarded the Nobel Prize for Physiology or Medicine for their work demonstrating how the inner biological clock, which is set to just over 24 hours in humans, governs the release of hormones, body temperature, metabolism and wakefulness. This allows us to be prepared for the different demands placed on our bodies during day and night.
We live in a cycle of sleep and wakefulness, the regulation of which occurs by an interplay between our biological clock and an internally regulated “sleep drive”. This is akin to an internal timer that influences our desire for sleep. With every waking hour, the sleep drive increases.
Specialised cells in the back of our eyes process light and tell the brain whether it is day or night. This in turn influences the sleep-wake cycle: exposure to light can delay sleep and make it difficult to return to sleep if you are awakened.
On the ICU there are few natural cues to demonstrate the shift from day to night. Light is usually artificial, and is either too bright at night or too dim during the day. The use of sedation in patients on ICU compounds the problems with sleep as it fluctuates their levels of consciousness and distorts reality. Noise levels far exceed the levels recommended by the World Health Organization and sleep is interrupted by staff performing procedures – one study reported an average of 43 interruptions per night.
There are several trials looking at ways to improve sleep in the critical care setting with the hope that this will reduce delirium and ultimately improve the health of patients.
Away from the clinical setting, modern life often disrupts the sleep-wake cycle: with jet-lag there is a mismatch between the actual clock and our internal body clock. Until we adjust, we are sleepy during the day and awake at night. Other causes include food and drink (eg caffeine and alcohol), medication, illness, stress and the environment in which we sleep.
The serious consequences of chronically disrupted sleep-wake cycles are well documented in night shift workers such as doctors and nurses. They suffer with drowsiness during the day (many have died in road traffic accidents while driving home from a night shift), a higher incidence of illnesses, more mood disorders and a lower life expectancy. However, sleep is not at the forefront of our minds when treating patients who are critically ill.
Sam recalled this time on ICU as being drowsy, surrounded by the constant bleeping of alarms, with an intense artificial light shining above his bed and frequent interruptions by staff during the night, all of which contributed to fragmented sleep, anxiety and delirium. He said of his experience, “Surgery and my time in ICU saved my life, but what I desperately needed to heal was a good night’s sleep.”
Nishat Siddiqi is a cardiologist based in South Wales
This article appears in the 06 Mar 2019 issue of the New Statesman, The next crash