Anesthestic Drugs Flashcards
Groups of anaest drugs
Induction agent
- Inhalation -> Volatile agent & Gas: Volatile agent: sevoflurane, desflurane, isoflurane, halothane, enflurane
Gas: nitrous oxide
- Intravenous drugs: propofol, ketamine, thiopentone
Local anest: lignocaine, bupivacaine, cocaine
Muscle relaxant: suxamethonium, rocuronium, atracurium
Analgesic: fentanyl, morphine, nsaid, paracetamol
Indication of volatile agent/gas
- children (uncooperative, needle phobia)
- no IV access
- airway compromised
Factors affecting uptake of anaes into the tissue
- solubility (blood to gas partition coefficient): high blood to gas partition coefficient, high uptake of gas into blood
- tissue blood flow: the greater the blood flow, the faster the uptake
What is minimum alveolar concentration (MAC) and acceptable range
Minimum gas concentration needed to anaesthetized 50% of patient
- high MAC, low potency
- acceptable range: around 0.8
Factors affecting MAC
Higher MAC needed in
- hyperthermia
- chronic opioid use (tolerance)
- chronic alcohol intake (tolerance)
- steroid usage
Lower MAC needed in
- neonate
- acute alcohol and opioid intake
- hypothermia
- pregnancy
- anemia/hypotension
- hypothyroidism
Common volatile agents
- nitrous oxide
- sevoflurane
- desflurane
- isoflurane
Nitrous oxide
- Indication
- S/E
- MAC
- describe/criteria
Indication: use as analgesic ONLY (ethonox in O&G), use as adjuvant to lower the MAC of volatile agent
S/E: respiratory depression, mild teratogen esp used in pregnancy during organogenesis, PONV
Describe/criteria:
- colourless, odourless, non explosive
- potent analgesic but weak anaesthetic
Sevoflurane
- indication
- s/e
- mac
- describe/criteria
Indication: for rapid induction and maintenance, and rapid recovery
Rapid S/E: mild effect on bp/hr, respiratory depression (decrease tidal volume, increase RR), bronchodilation
Mac: 2.0
Describe: sweet smell (can be used in paeds and adult)
Desflurane
- indication
- s/e
- mac
- describe/criteria
Indication: for maintenance (rapid onset and rapid recovery) & use in daycare surgery
S/e: same with sevoflurane for respiratory s/e, however on CVS has effect of tachycardia with rapid response to concentration
MAC: 6.0
Describe: has pungent smell (irritate the airway and can cause laryngospasm, coughing and secretions)
IV induction is divided into
- barbiturate: sodium thiopentone (STP)
- non barbiturate: propofol, ketamine, midazolam, etomidate
Criteria for ideal IV anaes agents
- rapid, smooth and safe
- limited CVS and respiratory effects
- should possess analgesic activity
- rapid return of consciousness
MOA of induction agents
All except ketamine potentiate GABA receptor
Ketamine: NMDA receptor
Propofol
- indication
- onset
- s/e
- CI
Indication (SIMS)
- sedation
- induction (+ TIVA)
- maintenance
- sedation in status epilepticus
Onset: fast onset (40-50sec)
S/e:
CVS: hypotension, brady (cardiovascular depressant)
Respi: resp depression, temporary apnea
Reduce PONV
CI: allergy to eggs, hypotension, known hypersensitivity to propofol
Thiopentone
- indication
- onset
- s/e
- CI
Pale yellow powder
Indication
- induction (potent anaest)
- tx status epilepticus
- induce coma (NOT used as maintenance agent)
Onset: 30-40s (short onset)
S/e:
CVS: hypotension with tachycardia
Respi: respiratory depression and bronchospasm
Anticonvulsant, anti analgesic (poor)
CI
- severe asthma & COPD (bronchoconstriction)
- porphyria, allergy to barbiturates
Ketamine
- indication
- onset
- s/e
- CI
Indication
- hypnotic
- analgesic (mass casualties, burn dressing)
- induction in pt risk of hypotension and bronchial asthma
- mx for severe bronchospasm and hypotensive pt
Onset: 1 min
S/e:
CVS: increase BP and HR
GIT: PONV
LA properties: emergence delirium, vivid dreams, hallucinations, increase catecholamine secretions
CI
- increase ICP
- hypertension
- glaucoma
- heart failure
Midazolam
- indication
- onset
- s/e
- CI
Indication
- premed sedation
- premed amnesia
- premed anxiolysis
*commonly use together with fentanyl as part of induction agent
Onset: 5 min (rapid onset)
S/e: resp depress, drowsiness, confusion, anterograde amnesia
CI: elderly/ ill patients with marked respiratory depression
Antidote: flumazenil
Etomidate (imidazole)
Indication:
Benefit:
S/e:
Indication: IV induction ONLY
Benefit: CVS stable (can be used in compromised CVS pt)
S/e: adrenal insufficiency
Types of muscle relaxant
Depolarizing agent: suxamethonium
Non depolarizing agent: atracurium, rocuronium
Suxamethonium/ succinylcholine
-MOA
-Onset & duration
-Reversal agent
-Indication
-S/e or complication
-Contraindication
MOA: bind to ACh receptor -> desensitized the receptor -> muscle relaxant effect
Onset: rapid onset (30-60sec) and short duration
Reversal agent: NO reversal agent. Hydrolyse by plasma cholinesterase
Indication: muscle relaxant in RSI, short procedures
S/E:
-muscle pain
- bradycardia
- hyperkalemia
- apnea
- malignant hyperthermia
- increase IOP, ICP, intragastric pressure
CI:
- known hypersensitivity/allergy
- positive history of malignant hyperthermia
- high risk of hyperkalemic response
- myotonia (muscular dystrophy)
Atracurium
-MOA
- Metabolism
-Onset & duration
-Reversal agent
-Indication
-S/e or complication
-Contraindication
MOA: compete with acetylcholine
Metabolism: spontaneous degradation by Hoffman elimination and ester hydrolysis
Onset: fast onset 3min and intermediate acting (20-35 min)
Reversal agent: neostigmine, sugamadex
Indication: muscle relaxant
S/e: hypotension, reflex tachycardia
CI: hypersensitivity, NMJ ds
Rocuronium
-Onset & duration
-Reversal agent
-Indication
-S/e or complication
-Contraindication
Onset: fast (1-2 min) and intermediate acting (20-35 min)
Reversal agent: same with atracurium
Indication: muscle relaxant, RSI (alternative for Suxa), tracheal intubation
S/e: large dose cause tachycardia. Minimal CVS effect and very low potential for histamine release
Contraindication: hypersensitivity, NMJ ds
S/e of neostigmine and given together with
Bradycardia
Cardiac arrest
PONV
Slow HR
Given together with anti cholinergic (atropine) or glycopyrulate
CI for sugamadex
Impaired renal fx cs excreted by kidney
CI in atropine
Worsen in CVS or hyperthyroid pt
