Analgesia and sedation in the ICU: targets and scales
- Concept
ICU patients need relief from pain and distress, but too much sedation keeps them longer on the ventilator; teams treat pain first and aim for calm and awake.
What it is
Critically ill patients feel pain from surgery, injuries, tubes, suctioning and turning, and many are anxious or agitated. Deep sedation, once routine, prolongs mechanical ventilation and ICU stay, adds delirium and may raise mortality. Modern practice is analgesia first (analgosedation): pain is assessed and treated, and a sedative is added only if needed, aiming for light sedation in which the patient is calm, easily roused and able to cooperate. Pain is measured by self-report when possible and by behavioural scales such as the Behavioral Pain Scale (BPS) or the Critical-Care Pain Observation Tool (CPOT) when the patient cannot speak; sedation is measured with the Richmond Agitation-Sedation Scale (RASS) or the Sedation-Agitation Scale. Drugs are chosen by mechanism and by the patient's organs: opioids act on mu receptors, propofol and benzodiazepines enhance GABA-A receptors, dexmedetomidine is an alpha-2 agonist, and ketamine blocks NMDA receptors. Daily interruption of sedation (the 'sedation vacation') or protocol-guided lightening shortens ventilation when paired with a spontaneous breathing trial.
Key points
- Indications for deep sedation: neuromuscular blockade, severe ARDS with ventilator asynchrony, raised intracranial pressure, status epilepticus and targeted temperature management.
- Opioids (mu agonists) treat pain and suppress cough and air hunger; morphine's active metabolites accumulate in kidney failure.
- Propofol (GABA-A) has a fast onset and offset; it causes hypotension, raises triglycerides and, rarely, a propofol infusion syndrome with acidosis and heart failure.
- Dexmedetomidine (alpha-2 agonist acting on the locus coeruleus) gives rousable sedation with little respiratory depression; it can cause bradycardia and hypotension.
- Ketamine (NMDA antagonist) spares opioids and keeps airway reflexes and blood pressure better; it can cause emergence reactions.
- Multimodal analgesia (paracetamol, ketamine, regional blocks, drugs for neuropathic pain) lowers opioid needs.
How it works
- Sedatives and opioids accumulate with prolonged infusion, especially in liver or kidney failure, so the effect outlasts what the infusion rate suggests.
- Deep sedation removes the patient's own breathing effort and cough, delays weaning and causes muscle weakness.
- Pain that is not treated causes stress hormone release, tachycardia, hypertension and agitation, which are often mistaken for a need for more sedation.
Step by step
- Score pain regularly with self-report or BPS/CPOT — what is not measured is not treated.
- Treat pain first with an opioid-based, multimodal plan — many agitated patients are in pain.
- Set a target RASS each day and record it — a shared target prevents oversedation.
- Add a sedative only if needed, preferring propofol or dexmedetomidine to benzodiazepines — this reduces delirium and ventilation time.
- Screen for safety and perform a daily awakening trial — it reveals oversedation and allows neurological assessment.
- Pair the awakening trial with a spontaneous breathing trial — the combination shortens ventilation.
- Reassess after each change and taper long infusions gradually — abrupt stopping can cause withdrawal.
Richmond Agitation-Sedation Scale (RASS)
| Score | Term | Description |
|---|---|---|
| +4 | Combative | Violent, immediate danger to staff |
| +3 | Very agitated | Pulls at tubes or catheters; aggressive |
| +2 | Agitated | Frequent purposeless movement; fights the ventilator |
| +1 | Restless | Anxious but movements not aggressive |
| 0 | Alert and calm | Awake, calm, attentive |
| −1 | Drowsy | Sustained eye opening and eye contact to voice |
| −2 | Light sedation | Brief eye contact to voice |
| −3 | Moderate sedation | Movement or eye opening to voice but no eye contact |
| −4 | Deep sedation | No response to voice; moves or opens eyes to physical stimulation |
| −5 | Unrousable | No response to voice or physical stimulation |
In practice
- Agitation is a symptom, not a diagnosis: look for pain, hypoxaemia, a full bladder, ventilator asynchrony, withdrawal and delirium before deepening sedation.
- Do not interrupt sedation in active seizures, alcohol withdrawal, on neuromuscular blockers, with raised intracranial pressure or myocardial ischaemia.
- A failed awakening trial (sustained agitation, pain, distress, desaturation or arrhythmia) means restarting sedation at a lower level than before and titrating to the target.
- Unexplained metabolic acidosis, rising triglycerides or rhabdomyolysis during long propofol use should raise suspicion of propofol infusion syndrome.
Next step
- Call a senior if the patient stays agitated despite treated pain and a reasonable sedative plan, or if deep sedation seems needed without a clear indication.
- Record pain and RASS scores at set intervals and with every change in sedation.
- After prolonged opioids or sedatives, plan a gradual taper and watch for withdrawal (agitation, tachycardia, sweating).
- Screen for delirium at least once per shift once the patient is rousable to voice.
- Explain the plan to the family; their presence often calms the patient and reduces the need for sedatives.
Test yourself
Think of the answer, then tap the question to see it.
What does 'analgesia first' mean in ICU sedation?
Pain is assessed and treated before sedatives are added, because pain often drives agitation and adequate analgesia reduces the need for sedation.
Which scales assess pain in a ventilated patient who cannot speak?
Behavioural scales such as the Behavioral Pain Scale (BPS) and the Critical-Care Pain Observation Tool (CPOT).
What is the receptor target of dexmedetomidine and what is its main advantage?
It is an alpha-2 adrenergic agonist; it gives rousable, cooperative sedation with little respiratory depression and less delirium than benzodiazepines.
Why must a patient on neuromuscular blockers be deeply sedated?
Neuromuscular blockers paralyse but give no sedation or analgesia, so without deep sedation the patient may be awake and in pain but unable to move.
Elsewhere in DurgiPedia
- Pain assessment scales: numeric, visual analogue, faces, behavioural (FLACC) and in dementia
- Pain assessment and pain scales
Connections
Educational content; it does not replace supervised training, your institution's protocols or the anaesthetist's or intensivist's decision. It contains no doses and no ventilator or infusion settings.
Sources: Sedation Vacation in the ICU (StatPearls (NCBI Bookshelf), 2025).
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Representative model, for educational purposes only.