IV Induction Agents Flashcards
Thiopentone - class and properties
Ultra-short acting barbiturate
Yellow powder mixed with 20ml water to give 2.5% solution
Thiopentone - dosage
IVI: 3-6mg/kg (titration)
Onset: 30-40 seconds
Duration: 10-30 minutes
PR: 30-40mg/kg (kinders)
Onset: 8-10 minutes
Thiopentone - contraindications
- asthma
- porphyria
- not for TIVA (accumulation d/t enzyme saturation)
- barbiturate allergy
- history of paradoxic excitation
Thiopentone - metabolism
Redistribution: 2-7 minutes
Hepatic metabolism and renal excretion
Half life 3-8 hours
Thiopentone - physiological effects
CNS
- hypnosis and anesthesia without analgesia
- anticonvulsant
- ↓ ICP (decreased cranial blood flow)
- taste of onions/ garlic
- smooth and rapid recovery
CVS
- decreased SVR and myocardial depression (↓ BP)
- reflex increase in heart rate
Resp
- respiratory depression
- increased sensitivity to laryngospasm
- increased bronchial tone
Other
- decreased renal and hepatic blood flow
- histamine release
- ↓ IOP
- nausea and vomiting (low incidence)
- stimulate porphyrin production
- enzyme inducer
- minimal muscle relaxation
Thiopentone - complications
Perivenous injection - tissue necrosis (treat with hyaluronidase injection)
Intra-arterial injection - pain, vasoconstriction, thrombosis and necrosis (treated with intravascular local anesthetic and heparin)
Thrombophlebitis
Laryngospasm
Hypotension
Anaphylaxis
Propofol - class and properties
Non barbiturate short acting intravenous anaesthetic agent, alkyl phenol
Milky white emulsion (stabilised in fat emulsion). Comes in 20ml or 50ml vials, concentration 1% or 2%
Contains no antimicrobial preservative, therefore work aseptically and do not store once opened
Propofol - dosage
Induction: 1-2.5mg/kg
Onset: 90-100 seconds
Duration: 5-10 minutes
Infusion: 50-150μg/kg/hour
Propofol - contraindications
- obstetrics
- pediatrics (<3)
- egg or soy allergy
- hypertension or hypovolemia
- disorders of fat metabolism
Propofol - metabolism
Redistribution: 2-8 minutes
Hepatic Metabolism and renal excretion
Half life: 4-24 hours
Propofol - physiological effects
CNS
- hypnosis and anesthesia without analgesia
- ↓ ICP
- anticonvulsant
- quicker complete recovery
CVS
- decreased SVR and contractility (↓ BP)
- no change in heart rate - baroreceptor reflex inhibited
Respiratory
- respiratory depression (apnea)
- no histamine release
- depresses upper airway reflexes
Other
- decreased renal and hepatic blood flow
- ↓ IOP
- antiemetic
- antipruritic
Propofol - complications
Pain on local injection (prevented with 20mg lignocaine/ 200ml propofol) Hypotension Apnea Expensive Propofol Infusion Syndrome Excitatory phenomena
Etomidate - class and properties
Carboxylated imidazole
Clear liquid. 10ml amps, concentration 2mg/ml
Etomidate - dosage
Induction: 0.2-0.6mg/kg
Onset: 1 min
Duration: 3-5 min
Etomidate - contraindications
Not for infusion
Depressed adrenal function
Porphyria
Etomidate - metabolism
Redistribution: 3 min
Hepatic metabolism with renal excretion
Half-Life: 3-5 hours
Etomidate - physiological effects
CNS
- hypnotic
- anticonvulsant
- involuntary muscle movements during induction
- ↓ ICP
- rapid awakening with no hangover
CVS
- transient ↓ SVR causes hypotension
- generally stable wrt HR, contractility and CO
Other
- mild respiratory depression
- ↓ IOP
- postoperative nausea and vomiting (frequent)
- no histamine release
- depress 11B-hydroxylase
Etomidate - complications
Pain on local injection
Superficial thrombophlebitis
Excitatory phenomena (spontaneous movements, myoclonus, dystonia, tremors)
Transient adrenal suppression
Ketamine - class and properties
Non-barbiturate; phencyclidine derivative
10/50/100mg/ml vials
Ketamine - dosage
IV induction: 0.5-2mg/kg
Onset: 30-40 seconds
Duration: 10-15 minutes
IM induction: 4-6mg/kg
Onset: 2 minutes
TIVA: 30-90μg/kg/min
Analgesia: 0.1-0.25mg/kg IV
Ketamine - contraindications
Hypertension, IHD
↑ ICP
Psychiatric patients
Open eye injury
Ketamine - metabolism
Redistribution: 11-16 minutes
Hepatic metabolism and renal excretion
Half-Life: 2-3 hours
Ketamine - physiological effects
CNS
- hypnosis and anesthesia with analgesia amnd amnesia
- dissociative state
- hallucinations
- ↑ ICP
- tonic-clonic movements may occur
- anticonvulsant
CVS
- hypertension
- tachycardia
Respiratory
- potent bronchodilator
- apnea in high doses
- salivation (treat with anticholinergic)
Other
- nystagmus
- ↑ IOP
- nausea and vomiting (so-so)
Ketamine - complications
Hypertension
↑ ICP
Abnormal movements
Emergence delerium
Midazolam - class and properties
Short-acting imidazo-benzodiazepine
Clear solution concentration 0.1% and 0.5%
Midazolam - dosage
Induction: 0.1-0.4mg/kg IV
Onset: 2-3 min
Sedation: 0.01-0.1mg/kg IV
Midazolam - contraindications
Myasthenia gravis
Acute narrow angle glaucoma
Midazolam - metabolism
Hepatic metabolism and renal excretion
Half-life: 2-3 hours
Midazolam - physiological effects
CNS
- sedation
- anxiolysis
- hypnosis
- anticonvulsant
- muscle relaxant
- anterograde amnesia
- ↓ ICP
CVS
- slight hypotension
- slight tachycardia
Other
- apnea (increased risk with alcohol, and high dose)
- nausea and vomiting (meh)
Midazolam - complications
Excellent local tolerance
Prolonged awakening
Propofol infusion syndrome
Risk factors:
- poor oxygen delivery
- sepisi
- serious cerebral injury
- high dose (>4mg/kg/hour)
Features
- acute refractory bradycardia to asystole
- metabolic acidosis, hyperkalemia
- rhabdomyolysis, skeletal myopathy
- hepatomegaly
- lipaemia
- cardiomyopathy w/ acute cardiac failure
- hepatomegaly
Thiopentone - mechanism of action
- reduces dissociation of GABA from GABAA receptors
- direct activation of GABAA receptors
- acts on glutamate, adenosine, and nicotinic receptors
- inhibit calcium-dependent release of NT
Propofol - mechanism of action
- prolongation of GABA action on GABAA receptors
- inhibition of NMDA receptors
- raised dopamine in nucleus accumbens (pleasure)
- decrease serotonin in area postrema (antiemetic)
- depressed SC activity (antipruritic)
Etomidate - mechanism of action
Binds GABAA receptors and enhances affinity for GABA
Ketamine - mechanism of action
- competitive NMDA antagonist
- opioid receptor agonist
- activate descending monoaminergic pain pathways
- acts on muscarinic receptors
Midazolam - mechanism of action
Enhance chloride ion conduction through GABAA receptors
