Principles of conscious sedation

Conscious sedation is indicated when nonpharmacological interventions, local or regional anaesthesia and oral analgesics are inadequate for the procedure, and a level of sedation is required. Conscious sedation should achieve analgesia and a depressed conscious state, but the patient can respond purposefully to commands.

Overview of procedural sedation and analgesia levels  lists the interventions commonly used to achieve conscious sedation. Factors influencing the choice of drug used for procedural sedation and analgesia  lists factors influencing drug choice, and Commonly used drugs for procedural sedation and analgesia  outlines the properties of commonly used drugs for procedural sedation and analgesia.

Do not use midazolam or an opioid alone for conscious sedation—midazolam does not have analgesic properties and opioids are prone to causing opioid-induced ventilatory impairment at the doses required for conscious sedation.

In some patients, an inhaled analgesic alone (eg nitrous oxide or methoxyflurane) may provide both adequate analgesia and conscious sedation. More often, conscious sedation is achieved using a combination of drugs with sedating and analgesic properties. For example, midazolam (which has sedating, anxiolytic and amnestic effects, but does not provide analgesia) is often combined with an opioid (which has analgesic effects). If additional effect is needed, inhaled nitrous oxide can be added to an opioid and/or midazolam. Due to its rapid onset of effect, nitrous oxide is initiated immediately prior to the procedure.

If combination therapy is used, drugs should be initiated sequentially—the effect of each drug should be established before another is started. Adverse effects (eg respiratory depression, cardiovascular depression, deep sedation) are more likely if multiple drugs are used. For drug regimens using nitrous oxide, midazolam or an opioid for conscious sedation in adults, see here. For drug regimens using methoxyflurane, nitrous oxide, midazolam or an opioid for conscious sedation in children, see here.

Alternatively, conscious sedation can be achieved with ketamine or propofol. Propofol does not provide analgesia and should not be used for procedures that will cause moderate or severe pain. Ketamine and propofol have a significant risk of causing deep sedation and they must only be administered by anaesthetists or other appropriately trained and credentialed medical practitioners. Their use is limited to settings with appropriate local protocols, staffing, monitoring and resuscitation equipment; see Requirements for procedural sedation and analgesia. These requirements are similar to those for deep sedation. For drug regimens using ketamine or propofol for conscious sedation in adults, see here. For drug regimens using ketamine or propofol for conscious sedation in children, see here.

It is easy to inadvertently proceed from conscious to deep sedation. Staff involved in delivering or monitoring conscious sedation must be able to assess the level of sedation achieved, manage deep sedation if it were to occur, and have resuscitation skills relevant to the patient’s age and condition; see Requirements for procedural sedation and analgesia. To reduce the risk of achieving deeper sedation than intended (ie deep sedation), drugs must be cautiously titrated to effect.

If conscious sedation proves to be inadequate to perform the procedure, deep sedation may be required. However, it must only be used if the requirements for monitoring, staffing, and equipment and facilities for deep sedation are met.