Opioids in induction

Why give an opioid at induction?

• Blunts the sympathetic response to laryngoscopy/intubation (tachycardia, hypertension).
• Reduces induction agent requirement (e.g., propofol) and can improve haemodynamic stability when used thoughtfully.
• Improves tolerance of airway instrumentation (mask ventilation, supraglottic airway, intubation).
• Provides early analgesia for surgical stimulus (especially if incision soon after induction).
• Helps prevent coughing/bucking on airway manipulation (useful for neurosurgery/eye surgery where coughing is undesirable).

Core concepts (simple definitions)

• Opioids are analgesic drugs acting mainly at mu receptors; they reduce pain and suppress airway reflexes but can depress breathing.
• Onset and peak effect depend on the drug and how fast you give it; timing matters as much as dose.
• Synergy: opioids + hypnotics (propofol/thiopentone) + sedatives can cause more hypotension and apnoea than expected.
• Context matters: the same opioid dose can be appropriate in a fit adult but unsafe in frail, elderly, hypovolaemic, or obstructed-airway patients.

Common opioids used around induction (practical overview)

• Fentanyl: common choice; relatively rapid onset; good for blunting intubation response; duration longer than remifentanil.
• Alfentanil: faster onset than fentanyl; useful when you want a short, sharp effect (e.g., brief airway stimulation).
• Remifentanil: very rapid onset/offset; excellent control with infusion/bolus; higher risk of bradycardia/hypotension and postoperative hyperalgesia if not managed well.
• Morphine: slower onset; not ideal as the sole opioid to blunt intubation response; better for longer-lasting analgesia once stable.
• Oxycodone/diamorphine: sometimes used for longer analgesia depending on local practice; slower onset than fentanyl/remifentanil for intubation blunting.

Timing and dosing (new-starter safe approach)

• Aim: opioid effect should be present at laryngoscopy (peak effect varies by drug).
• Give opioids in small increments, especially in elderly/frail patients; reassess BP/HR/ventilation after each increment.
• Avoid large rapid boluses unless you are ready to manage chest wall rigidity, apnoea, and hypotension.
• If you plan to use a potent opioid (especially remifentanil), consider reducing the induction agent dose and be ready with vasopressors.
• Document the opioid, dose, and time given; it helps you interpret haemodynamics and plan postoperative analgesia.

Choosing an opioid: quick clinical scenarios

• Stable adult, routine intubation: fentanyl in modest dose is common; balance with induction agent to avoid hypotension.
• Very short procedure / LMA with minimal stimulus: consider low-dose opioid or none; avoid unnecessary respiratory depression in recovery.
• High sympathetic response undesirable (e.g., intracranial pathology, severe coronary disease): consider a carefully titrated opioid plan (often fentanyl or remifentanil), with close BP/HR monitoring.
• Elderly/frail/hypovolaemic: use smaller doses, slower administration, and anticipate hypotension; treat causes (volume status) and use vasopressors early if needed.
• Obstructive sleep apnoea (OSA) or obesity: minimise opioid where possible; prioritise airway patency and consider multimodal analgesia.

Side effects to anticipate (and what to do)

• Apnoea/respiratory depression: support ventilation with bag-mask; ensure airway patency; consider reducing further sedatives/opioids.
• Hypotension: check depth of anaesthesia, volume status, and drug doses; treat with vasopressor (e.g., metaraminol/phenylephrine per local policy) and fluids if appropriate.
• Bradycardia: common with potent opioids (especially remifentanil) and vagal stimuli; treat with stopping/reducing opioid, anticholinergic (e.g., atropine/glycopyrrolate) if needed, and address hypoxia.
• Chest wall rigidity (rare, usually with rapid high-dose fentanyl/alfentanil/remifentanil): difficulty ventilating; manage with neuromuscular blockade, airway control, and avoid further rapid boluses.
• Nausea/vomiting: consider prophylaxis based on risk; opioids contribute.
• Itch/urinary retention: more common with longer-acting opioids; plan postoperative management.

Practical safety checklist (before you push the opioid)

• Confirm patient factors: age, frailty, OSA/obesity, COPD, renal/hepatic impairment, opioid tolerance, chronic pain meds.
• Check haemodynamics and volume status; anticipate hypotension if dehydrated or septic.
• Have airway plan and ventilation equipment ready (including suction and adjuncts).
• Have vasopressor drawn up and labelled; know local concentrations.
• Plan postoperative analgesia early: if you use remifentanil, ensure longer-acting analgesia is given before stopping it.

Special considerations

• Opioid tolerance (e.g., chronic opioids, opioid use disorder): may need higher doses for analgesia but still at risk of respiratory depression with sedatives; involve seniors early and plan multimodal analgesia.
• Renal impairment: fentanyl/alfentanil/remifentanil generally preferred over morphine due to active metabolites with morphine; still titrate carefully.
• Hepatic impairment: reduced clearance can prolong effect (especially fentanyl/alfentanil); titrate and monitor.
• Pregnancy/obstetrics: opioids cross placenta; timing and indication matter; follow local obstetric anaesthesia guidance and seek senior input.