SEDATED INSOMNIA IN THE ICU

Here’s an interesting article from Anesthesiology Clinics. A review of current understanding of sleep and sedation in ICU patients. I can’t say it’s a subject I know a lot about. But it is clear to me that there are some aspects worth considering.

Sleep in the ICU
Sleep and sedation are not equivalent.

Normal sleep is influenced by circardian rhythmicity and cyclic progression through the sleep stages. In the ICU and with sedation this rythmicity is lost. Sleep becomes fragmented with all the stuff that is constantly going on in an ICU. Cannulations, catheterisations, suctioning, recruiting and so on.

That’s a no-brainer.  Less obvious and less known is how our sedatives mess with the sleep stages.

Sleep and sedatives
With sedation the patient is more often suspended in one of the light sleep stages (Non–REM stages I and II) with only a small percentage of time spent in the deeper stages (slow wave sleep, formerly known as Non-rem Stages III and IV, and REM-sleep).

All the sedatives that are relevant seem to do this. They significantly increase the proportion of sleep in stages Non-REM I and II while depriving the patient of SWS and REM-sleep.

Depriving a person of the deeper sleep stages or fragmenting the sleep is known to produce deprivation of the same magnitude as total sleep deprivation, ie. all that lost REM-sleep needs to be regained.

The take home message
Sleep and sedation are not equivalent and when the patient comes of sedation he might ‘wake up’ severely deprived of deeper sleep stages. The patient will have to regain this sleep deficit. This partly explains the sometimes severe sleep disturbances ICU-patients have after coming off sedation. It could also explain some drawn out cases where weaning and waking the patient up takes a surprisingly long time.

And how does it fit with modern ICU tactics where the patient is taken off sedation for a period of time every 24h? This has proven to shorten the time weaning takes and shortens the time it takes to get the patient off sedation.

Obviously this practice results in smaller doses of sedatives accumulating, but could this practice also have some beneficial effect on the patients circadian rhythm and progressing throught the sleep stages?

Anyway, link to the article below. A good primer and overview on a subject most of us anaesthetists never give much thought.

Sedation and Sleep Disturbances in the ICU
Anesthesiology Clinics, Volume 29, Issue 4, Pages 675-685
Gerald L. Weinhouse, Paula L. Watson

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