Levels of sedation: minimal, moderate, deep and general anaesthesia

In short: ANZCA's guideline on procedural sedation, PG09(G), describes a continuum. At minimal sedation you are calm and respond normally. At moderate sedation you are drowsy but respond purposefully to voice or touch. At deep sedation you are not easily roused. Under general anaesthesia you are unconscious and do not respond at all. The level can drift deeper than planned, which is why monitoring and a properly trained sedationist matter.

1. MinimalConscious and less anxious. You respond purposefully to speech or a light touch.
2. ModerateDrowsy. You still respond purposefully to speech and touch.
3. DeepNot easily roused. You may respond only to a painful stimulus.
4. General anaesthesiaUnconscious. No purposeful response to anything.

Deeper levels affect breathing and circulation more

Summarised from ANZCA PG09(G), section 3 and Appendix V. The bands are a continuum, not separate boxes.

The four levels, in ANZCA’s words

Each definition below is quoted from PG09(G), followed by what that level is usually like in a dental setting.

Minimal sedation

“A drug-induced state of diminished anxiety, during which patients are conscious” and “respond purposefully to verbal commands or light tactile stimulation.” ANZCA PG09(G), section 3

In the dental chair: you feel calmer but are fully aware of what is happening and can talk normally. An anti-anxiety tablet or happy gas is often used to reach this level. The Australian Dental Association’s policy on conscious sedation says a dentist with enough training and experience may provide minimal sedation.

Moderate sedation

“A drug-induced state of depressed consciousness during which patients retain the ability to respond purposefully to verbal commands and tactile stimulation.” ANZCA PG09(G), section 3

In the dental chair: you are relaxed and drowsy and may doze, but you wake enough to respond when someone asks you to turn your head or open wider. Your memory of the appointment may be patchy, although nobody can promise that it will be blank. This is the level people usually mean by “conscious sedation” or “twilight sedation”, and it is commonly given through a cannula (IV sedation). The guideline itself uses the word “moderate”.

In dentistry, moderate sedation can be provided by a dentist who holds an endorsement for conscious sedation from the Dental Board of Australia, or by a medical practitioner such as an anaesthetist. PG09(G) adds that when anaesthetic agents are used for sedation, “a separate sedationist with age-appropriate skills, competencies and experience is essential” (section 7.5).

Deep sedation

“A drug-induced state of depressed consciousness during which patients are not easily roused and may respond only to noxious stimulation.” ANZCA PG09(G), section 3

In the dental chair: you are unlikely to be aware of the treatment. Because you may not keep your airway clear or breathe adequately on your own, ANZCA’s patient information says deeper sedation is given by an anaesthetist, who is trained to manage its effects on breathing and the heart.

General anaesthesia

“A drug-induced state of unconsciousness characterised by absence of purposeful response to any stimulus, loss of protective airway reflexes, depression of ventilation and disturbance of circulatory reflexes.” ANZCA PG09(G), Appendix V (glossary)

In the dental chair, or more often in a day surgery or hospital: you are unconscious from start to finish. The anaesthetist protects your airway, usually with a breathing tube, and supports your breathing and circulation. The Australian Dental Association’s policy says a dentist must not treat a patient under general anaesthesia unless the anaesthetic is given by an appropriately qualified and registered practitioner.

Why the level can change during treatment

Sedation medicines do not stop neatly at a chosen level. PG09(G) describes “a continuum from minimal sedation through to deep sedation, which may inadvertently progress to general anaesthesia” (section 5.1), and warns that “inadvertent and unanticipated rapid progression from sedation to general anaesthesia may occur” (section 5.2.1).

People respond differently to the same dose, and the dental treatment itself changes from moment to moment: an injection or extraction can be stimulating, and quiet periods can let sedation deepen. In practical terms, this is why:

• your breathing, oxygen level, heart rate and blood pressure are monitored throughout
• the person giving the sedation must be able to recognise and manage a deeper level than the one planned
• you are asked to fast beforehand, because protective airway reflexes weaken as sedation deepens.

How your likely level is decided

PG09(G) says patients and carers “should be prepared for the procedure with information about their likely experience and expected degree of sedation” (section 9.3.1). The level suggested for you depends on:

• the length and type of dental treatment
• how anxious you are, and what has or has not worked before
• your general health, including your airway, weight, sleep apnoea and heart or lung conditions
• the setting, and the equipment and staff available there.

For people who are unwell or having complex procedures, PG09(G) states that “the sedationist should be an anaesthetist” (Appendix III).

Words you might hear

Questions to ask about your level

In an emergency, call 000. This information is general and does not replace advice from your treating practitioner.