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Introduction to ED Airway Drugs

The following doses on Intubation Drugs in ED are to serve as a guide only and clinical experience is needed for exact dose titration

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Thiopentone

|Type of Drug |Barbiturate – ultra-short acting |

|Indication |Induction of General Anaesthesia |

|Mode of Action |Inhibits GABA receptors in CNS. Causes hypnotic & sedative effects & has anticonvulsant properties. |

| |No analgesic properties. |

|Dose |2-5mg/kg as IV bolus NB: in ED RSI – lower dose range 0.5-3mg/kg is SAFER |

|Ampoule |500mg powder, made up with 20mL water. |

| |Standard dilution = 25mg/mL |

|Pharmocokinetics notes |Time to effect one arm-brain-circulation time. Fast onset action due to high cerebral blood flow and highly |

| |lipid soluble. |

| |Duration of action 5-15mins. Off-set of action due to re-distribution to other tissues (muscle, then fat), |

| |metabolism by liver. |

|EFFECTS by Systems: |

|CVS |Negative inotropy |

| |↓ cardiac output by 20% |

| |↓ SVR |

| |Resulting ↓ BP |

| |HR can ↑ as compensation |

|Resp |Potent respiratory depressant |

| |Can cause bronchospasm |

|CNS |↓ CBF |

| |↓ ICP |

| |Anticonvulsant activity |

|Other |Post-op nausea & vomiting prominent. |

|Special Points |Tissue necrosis if extravasation occurs. |

| |Can precipitate with neuromuscular blockers – ensure flushed well between administration . |

| |Section 29 drug. |

| |Is traditional drug for RSI & is still drug of choice for RSI in AED. In theatres – trend to use propofol |

| |instead for RSI. |

PROPOFOL

|Type of Drug |Phenol derivative (not expected to remember!) |

|Indication |Induction of General Anaesthetic. |

| |Agent for procedural sedation. |

| |Sedation post intubation |

|Mode of Action |Unclear mode |

|Dose |0.5-2.5mg/kg as IV bolus for induction |

| |For sedation post intubation – infusion of 10mL/hr (ie: 100mg/hr) upwards, “standard” dose|

| |is 20mL/hr |

|Ampoule |200mg in 20mL ampoule in white oil-in-water emulsion. |

| |Concentration = 10mg/mL |

|Pharmocokinetics notes |LOC occurs in approx. 30secs. |

| |Highly protein bound. Waking in 10 minutes. |

| |Metabolism by liver. |

|EFFECTS by Systems: |

|CVS |↓CO |

| |↓BP |

| |↓ SVP |

| |No change in HR |

|Resp |Dose –dependent reduction in ventilation. |

| |Apnoea after bolus induction. |

|CNS |Smooth induction. |

| |Smooth awakening without CNS effects |

|Other |Antiemetic properties |

| |Involuntary movements can occur but are not epileptiform on EEGs |

|Special Points |Painful to injection |

| |No analgesic properties. |

| |Contains purified egg lecithin (yolk component) & soya bean oil. (within anaesthesia |

| |literature – no evidence so far to avoid in pts with egg or soy allergies) |

Etomidate

|Type of Drug |Carboxylated imidazole derivative (not expected to remember!) |

|Indication |Induction of general anaesthesia |

|Mode of Action |Acts on GABA receptors |

|Dose |0.2-0.3mg/kg as IV bolus |

|Ampoule |20mg in 10mL ampoule – in lipid emulsion. |

| |Concentration = 2mg/mL |

|Pharmocokinetics notes |Acts in 10-60 secs, duration of action 6-8 mins |

| |Non-cumulative on repeated dosing as rapidly metabolised by plasma & hepatic esterases |

|EFFECTS by Systems: |

|CVS |Relative cardiovascular stability |

|Resp |Dose –related ↓ RR & Vt |

| |Transient apnoea . coughing / hiccupping can occur |

|CNS |↓ CBF, ICP & cerebral metabolic rate. |

| |Involuntary muscle movements, tremors, hypertonia can occur. |

| |Epileptiform EEGs can occur in 20% pts |

|Other |Potent inhibitor of steroidogenesis – ie: ↓ cortisol & aldosterone for 24hrs post single |

| |dose. |

| |Best to avoid in septic patients |

|Special Points |Pain on injection. |

| |Section 29 drug. |

Ketamine

|Type of Drug |Phencyclidine derivative |

|Indication |Induction of anaesthesia |

| |Procedural sedation |

|Mode of Action |Non-competetive antagonist as NMDA receptor. |

| |May modulate opioid & muscarinic receptors |

|Dose |1-2mg IV bolus over 60seconds |

| |(other routes not discussed here) |

|Ampoule |200mg/2mL ampule. Dilute to 20mL saline |

| |Concentration = 10mg/mL |

|Pharmocokinetics notes |Onset action 30secs, duration 5-10 mins |

|EFFECTS by Systems: | |

|CVS |↑ HR |

| |↑ BP |

| |↑ CO |

| |↑ sympathetic tone |

|Resp |Sli ↑ RR |

| |Airway reflexes preserved |

| |Bronchodilation is a feature |

|CNS |Dissociative anaesthesia |

| |Amnesia |

| |↑ CBR |

| |↑ cerebral metabolic rate |

| |Emergence delirium, unpleasant dreams & hallucinations - reduced by quiet awakening |

|Other |Post-op nausea & vomiting common |

| |↑ salivation |

|Special Points |In Controlled Drug cupboard. |

| |Increased muscle tone means it’s not as good for reduction of major joint dislocations |

Suxamethonium

|Type of Drug |Depolarising neuromuscular blocker |

|Indication |Rapid & profound paralysis to facilitate intubation |

|Mode of Action |Prolonged depolarisation of skeletal muscles by attachment to post-synaptic membrane. |

| |Depolarised NMJ cannot respond to new acetylcholine |

|Dose |1mg/kg |

|Ampoule |100mg in 2mL plastic ampoule with red writing. Use undiluted. |

| |Kept refrigerated. |

|Pharmocokinetics notes |Onset action 30seconds as evidenced by generalised muscular contractions & fasiculations. |

| |Duration 3-5minutes. |

| |Metabolised by plasma cholinesterases. |

|EFFECTS by Systems: |

|CVS |Bradycardia if repeated doses |

|Resp |Apnoea |

|CNS |↑ ICP |

| |↑ intraocular pressure |

|Other |↑ K levels by 0.4mmol/L |

| |↑ intragastric pressure |

| |↓ lower oesophageal sphincter tone |

|Special Points |Atypical plasma cholinesterases can cause a prolonged blockade of 1-3 hrs. |

| |Potent trigger of malignant hyperthermia. |

| |Hyperkalaemic response is exaggerated ( with potential VF arrest) in |

| |Burns (after 24-48hrs, & can last up to 1-2 yrs) |

| |Denervated skeletal muscles leading to atrophy (eg: post spinal cord injury) from 96 hrs |

| |post denervation |

| |Muscular dystrophy |

| |Severe skeletal muscular trauma |

Rocuronium

|Type of Drug |Non-depolarising neuro-muscular blocker |

|Indication |Paralysis for intubation and control of ventilation. |

| |Used for RSI when suxamethonium is contraindicated |

|Mode of Action |Competitive antagonist of acetylcholine at the post-synaptic membrane of neuromuscular junction. |

|Dose |0.6mg/kg is standard intubating dose - intubate after 60- 90 secs |

| |1mg/kg – intubation in 45 secs ( similar to suxamethonium) |

|Ampoule |Ampoule of 5mL, concentration = 10mg/mL |

|Pharmocokinetics notes |Excreted by hepatic route. |

| | |

| |Duration of action depends on dose used |

| |30-40mins for standard dose |

| |up to 1 hour for higher dose. |

|EFFECTS by Systems: |

|CVS |Nil |

|Resp |Apnoea |

|CNS |Nil |

|Other | |

|Special Points |Use of Rocuronium as a paralysing agent mandates that the pt is easy to ventilate prior to paralysis, |

| |and airway assessment indicates an easy intubation. NEVER use if any doubt exists ! |

| | |

| |There is a reversal agent (Sugammadex) that provides rapid reversal of Rocuronium– but at the profound |

| |blockage stage post RSI, onset of action can still be up to 6-7 minutes - long enough that hypoxic |

| |brain injury would occur if you can’t oxygenate. It is NOT available in AED. |

| | |

| |Precipitates with thiopentone. |

| |Safe in patients with malignant hyperthermia. |

Metaraminol

|Type of Drug |Synthetic sympathomimetic |

|Indication |Management of hypotension |

|Mode of Action |Direct * & Indirect # sympathomimetic agonist. |

| |Acts predominantly at alpha adrenoreceptors |

|Dose |0.5mg – 1mg boluses , titrating to effect |

|Ampoule |10mg/mL ampoule. Dilute into 20mL syringe with saline |

| |Concentration = 0.5mg/mL |

|Pharmocokinetics notes |Onset 1-2mins. |

| |Maximum effect at 10mins |

|EFFECTS by Systems: |

|CVS |↑ SBP |

| |↑ DBP |

| |Reflex ↓ HR occurs |

| |Positive inotropy |

|Resp | |

|CNS |↓ CBF |

|Other | |

|Special Points | |

| | |

|Direct * |Binds at receptor to activate it directly |

|Indirect# |Binds at postganglionic sympathetic nerve endings to cause release of neurotransmitter |

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