Sedation

This topic was the subject of a CRQ in March 2021 (69% pass rate); the examiners lamented a lack of knowledge on sedation scores.

Resources

Sedation is practiced in a wide variety of settings, by healthcare providers with a diverse range of education, training and experience
Administering sedative agents can blunt a patient's sensorium and compromise both cardiovascular and respiratory function
Significant morbidity and mortality can occur; ∽20% is accounted for by respiratory depression from either relative or absolute overdose; half of these are preventable with better monitoring

Benefits

Risks & side-effects

Grade of sedation	Minimal sedation (Anxiolysis)	Moderate sedation (Conscious sedation)	Deep sedation
Drugs	Small amount	More than minimal	Higher doses ≥1 drug used
State	Relaxed	Very relaxed	Mostly sleepy
Response	Talk normally	Talk normally Follow simple instructions	Unlikely to talk
Memory	Memory without detail	Partial memory	Unlikely to remember
Breathing	No effect	No effect	May be impaired

Depth of sedation may vary during a procedure, and should be assessed periodically
Methods include those used clinically and in research protocols

ASA Continuum of Sedation

Minimal sedation - anxiolysis, responds normally to verbal commands
Moderate sedation - analgesia, responds purposefully to verbal commands, either alone or accompanied by light tactile stimulation
Deep sedation - analgesia, responds purposefully but only to repeated or painful stimulus
General anaesthesia

Modified Observer's Assessment of Alertness/Sedation Scale (MOASS)

Modified Ramsay Sedation Scale

Awake and alert, minimal or no cognitive impairment
Awake but tranquil, purposeful responses to verbal commands at a conversational level
Appears asleep, purposeful response to verbal commands at a conversational level
Appears asleep, purposeful responses to commands but at a louder than conversational level, requiring light glabellar tap, or both
Asleep, sluggish purposeful responses only to loud verbal commands, strong glabellar tap, or both
Asleep, sluggish purposeful responses only to painful stimuli
Asleep, reflex withdrawal to painful stimuli only
Unresponsive to external stimuli, including pain

Processed EEG monitoring

Clinical assessment of the depth of sedation requires periodic stimulation, which may be difficult if access to the patient is limited and/or interfere with the procedure

Multiple studies correlate processed EEG indices with the above clinical sedation scores in a variety of settings
There is, however, a lack of discrimination of index value associated with each sedation state
The relationship between EEG and depth of sedation may also be confounded by concurrent use of analgesics

In general, there is no benefit over clinical methods in shorter procedures (bronchoscopy, colonoscopy)
For longer procedures e.g. ERCP, use of pEEG may be associated with:

All procedures should be compliant with National Safety Standards for Invasive Procedures (NatSSIPs) and the WHO Safe Surgery Checklist

Fasting

Typically not required to fast before minimal sedation
For moderate and deep sedation, standard starvation rules apply
Important to provide clear instructions for diabetic patients about timing of diabetic medication

Environment, equipment and monitoring

Anaesthetic equipment should be standardised where possible
Anaesthetic equipment should be checked in accordance with AAGBI checklist
Full resuscitation equipment should be available
Emergency drugs including reversal agents (sugammadex, naloxone, flumazenil) and for emergencies (dantrolene, intralipid)
Trolleys should be able to be tipped head-down and transferred to other areas within the hospital

RCoA recommend the same standards of monitoring are applied as for those patients receiving general anaesthesia

Staffing

All staffed trained and familiar with equipment
Suitably trained anaesthetic assistant
Recovery in post-anaesthetic care unit as for patients receiving general anaesthesia

Choice of drugs

E.g. if opioid/BZD are to be combined, give the opioid first and time allowed for it to have full effect, before titrating small amounts of BZD to effect

Painful procedures need to include an analgesic agent
Use of anaesthetic agents such as propofol and remifentanil reduces safety margins as they have narrow therapeutic windows
In one study, patient-controlled propofol TCI led to less propofol administration and greater safety than anaesthetist-led TCI (BJA, 2021)

On occasion, one might be asked to sedate an agitated individual
Said chemical sedation should only be employed for those who represent a risk to themselves or others, in whom non-pharmacological means have failed
This is a less controlled situation than the procedural sedation described above, and falls more under the remit of Emergency Medicine and Intensive Care colleagues
As such, good resources for further reading on this topic are: