ICU & Anaesthetics
Critical care basics, sedation and perioperative medicine.
Use as a study guide only. These notes are part of a free open-access medical education (FOAMed) project and may contain errors or outdated information. Always verify against current guidelines (e.g. eTG, RACGP, local health district policies) and reputable sources before applying anything to patient care. See the full disclaimer.
Clinical pearls & learnings
Tips and tricks collected over the years — a living list that grows with every rotation. Use as a study guide only and check current guidelines before acting on anything.
Procedural sedation
Before you sedate — contraindications and risk
- Relative contraindications: right ventricular failure, obstructive sleep apnoea, Down syndrome (higher rate of difficult airway — macroglossia, midface hypoplasia, atlantoaxial instability), a previous difficult airway, and known drug allergies. Assess the airway formally (e.g. the LEMON approach: Look externally, Evaluate 3-3-2, Mallampati, Obstruction, Neck mobility).
- Risks to plan for: conversion to a general anaesthetic if sedation goes too deep, a difficult or prolonged bag-valve-mask ventilation, over- or under-sedation, ketamine emergence phenomena (dysphoria/hallucinations on recovery — reduced by co-administering a benzodiazepine and a quiet recovery space), and laryngospasm.
Common pitfalls
- Not allowing enough time for a drug to reach peak effect before giving more — fentanyl, for example, takes several minutes to peak; stacking doses too quickly risks oversedation.
- Not halving the dose in elderly or chronically unwell patients, who have markedly altered pharmacokinetics/dynamics.
- Stopping monitoring too early, before the patient meets safe discharge criteria.
- Not giving written post-sedation instructions — patients (and whoever is taking them home) need this in writing, not just verbally.
Anaesthetic considerations
Myasthenia gravis and general anaesthesia
Neuromuscular blockers in myasthenia — sensitivity runs in opposite directions
| Agent class | Effect in myasthenia | Consequence |
|---|---|---|
| Non-depolarising agents | Increased sensitivity | Risk of prolonged paralysis at standard doses |
| Depolarising agents (suxamethonium) | Relative resistance | Often needs a higher dose |
Muscle relaxants aren't strictly forbidden, but many anaesthetists minimise or avoid them where possible, use reduced doses with careful neuromuscular monitoring (train-of-four), and favour agents/techniques that allow the patient to breathe spontaneously sooner.
Local anaesthetic systemic toxicity (LAST)
Watch for perioral numbness/tingling and a metallic taste (early warning signs), progressing to seizures and then cardiovascular collapse/arrhythmias — though severe cardiac toxicity can occur without preceding CNS signs, especially with bupivacaine.
- Stop the injection, call for help, and secure the airway with 100% oxygen — avoid both hypoxia and acidosis, as either worsens LAST (this is why adequate ventilation matters, rather than deliberately over-breathing the patient).
- IV lipid emulsion (Intralipid) is the specific treatment — give early rather than as a last resort.
- Benzodiazepines for seizures; modified ACLS if arrest occurs (reduced adrenaline doses, avoid vasopressin, calcium channel blockers, beta-blockers and other local anaesthetics) — resuscitation may need to be prolonged, since lipid emulsion takes time to work.