Induction and Maintenance Flashcards by Anna Zeng

What is the only agent listed as category A in pregnancy

Thiopentone

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What is the induction dose of thiopentone

3-5mg/kg
Similar rapid onset of action within circulation as propofol

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Effect of thiopentone on cardiovascular and respiratory system

CVS: Vasodilator and negative inotrope in high doses

RESP: Does not obtund airway reflexes to same degree as propofol
Will provoke coughing, laryngospasm as well as bronchospasm if sole agent for induction

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Cons of using thiopentone

Tissue damage can occur with extravasation (pH 11)
No antiemetic properties
Higher incidence of anaphylaxis than other induction agents
No analgesic properties

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What is the principle mode of action of ketamine?

Non competitive inhibition of NMDA receptors

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Dosing of ketamine for induction

IV induction of anaesthesia 1-2mg/kg, less if shocked

IM induction 5mg/kg

Knock-down IM dose 3mg/kg (an ampoule 200mg), to slow down the situation

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Induction dose variations of propofol

Healthy adult vs elderly vs paediatric vs shocked

Healthy adult patient 2mg/kg
Elderly patient 1mg/kg (smaller intravascular volume, reduced CO, increased sensitivity to propofol)
Paediatric patient 3-4mg/kg (relative larger intravascular volume, increased CO)
Shocked/hypovolaemic patient 20% normal dose (contracted intravascular volume and greater proportion CO directed to brain)

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Contents of propofol vial

Water
Propofol as 1% solution (10mg/ml)
Soya oil
Glycerol (maintain isotonicity)
Egg lecithin
Sodium oleate (emulsifying and stabilizing agents)

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Review graph of CSHTs for several anaesthetic drugs

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Define context sensitive half time (CSHT)

Time taken for the plasma concentration of a drug to fall by half after the cessation of an infusion designed to maintain a steady plasma concentration

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Draw structure of propofol

Phenol with two propyl groups stuck on 2 and 6 carbons of the benzene ring, 2,6-diisopropylphenol

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Principal action of propofol

Enhance the inhibitory function of GABA at GABA_A receptors in the brain
Decreasing rate of dissociation of GABA from receptor

GABA is main inhibitory neurotransmitter, binds and increases transmembrane chloride conductance and hyperpolarises the postsynaptic neuron

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How does ketamine affect the cardiovascular system

Increase HR and systemic/pulmonary blood pressure for 10-20mins by centrally mediated sympathetic drive

Has direct negative inotropic effect on heart that is outweighed by central sympathomimetic action

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How does ketamine affect cerebral haemodynamics

Increases cerebral metabolic rate of oxygen consumption (CMRO2), cerebral blood flow, ICP

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What is the MAC % of sevoflurane

2 (or 1.8)

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What is the MAC % of N2O

105

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What is the MAC % of desflurane

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What is the MAC % of isoflurane

1.15

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What is the blood gas coefficient

Ratio of amount of agent in the blood phase and gaseous phase at equilibrium. (The partial pressure of the agent in the two phases is the same)

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What is the blood gas coefficient

Ratio of amount of agent in the blood phase and gaseous phase at equilibrium. (The partial pressure of the agent in the two phases is the same)

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What patient parameters affect rate of wash-in of volatile gas

Alveolar ventilation, cardiac output and FRC

What is MAC defined as

Concentration of a volatile agent in 100% oxygen at equilibrium at atmospheric pressure that will prevent movement in response to noxious stimulus (surgical incision) in 50% of subjects

How does MAC requirement change with age and pregnancy

MAC requirement for neonates is decreased, then rises to peak value around 12 to 18 months of age and then steadily decreases by 6% per decade

Pregnancy decreases MAC by 30%

How much does cerebral blood flow increase proportional to PaCO2 rise?

CBF increases 4% per mmHg rise in PaCO2

What is the intubating dose of suxamethonium

1mg/kg

What is the intubating dose and onset time of suxamethonium

1mg/kg Onset - circulation ~30s/until fasciculations cease Lasts 3-9mins

What is the intubating dose and onset of rocuronium

0.6mg/kg - onset 90s Modified RSI 0.9mg/kg - onset 60s

What is the intubating dose of vecuronium

0.1mg/kg, onset 3min

What is the intubating dose, onset and duration of cisatracurium

0.15mg/kg (actual body weight) onset 4-5min duration 45min

What type of metabolism does Cisatracurium undergo?

Organ dependent elimitation Hofmann elimination (form of spontaneous chemical degradation) and to a lesser degree hydrolysis by plasma esterases Small proportion undergoes renal elimination

In what muscle and neuromuscular disorders is suxamethonium contraindicated

Muscular dystrophy (abnormal muscle membranes and have marked hyperkalaemic response) Myasthenia gravis (resistant to sux) Myotonic dystrophy (prolonged muscle contraction/sensitivity) Eaton-lambert Syndrome (prejunctional autoimmune disorder, sensitive)

Sux causes a transient increase in serum potassium by ….

0.5 to 1 mmol/L Due to efflux of potassium into ECF by depolarisation of the nicotinic receptors

What 3 conditions can predispose to a potentially lethal rise in potassium when sux is given

Burns Denervation - spinal cord injuries, motor neuron disease Immobility - catatonia of any cause, bed ridden patients

What dose of sux to give to break laryngospasm (not responsive to other manoevres)

10mg

What is the mechanism of action of neostigmine

Antagonises the action of acetylcholinesterase leading to an increased amount of Ach accumulating in the synaptic cleft and displacing NDMR from the nicotinic receptor

Dose of neostigmine

50mcg/kg Common dose given is 1 ampoule - 2.5mg

Dose of atropine or glycopyrrolate given with neostigmine

Atropine 20mcg/kg or an ampoule (1.2mg) Glycopyrrolate 2 ampoules (400mcg)

How does sugammadex work?

Creates diffusion gradient for rocuronium and vecuronium to diffuse out of neuromuscular junction and binds to these agents to form a complex

Dose of sugammadex

2mg/kg equates to 200mg ampoule for most

Variable patient response to codeine (tramadol and oxycodone) is due to what liver enzyme?

cytochrome P450 2D6 (CYP2D6) Low CYP2D6 activity → decreased analgesic response and vice versa

When not to use NSAIDs

Pregnancy (category C) Aspirin sensitive asthma Gastric ulceration Renal impairment (elderly, septic, CKD, critically ill, hypovolaemic, pre-eclamptic)

What is Apfel's crtieria

Max dose of lignocaine (with/without adrenaline)

3mg/kg plain 7mg/kg with adrenaline 1-2mg/kg/hr infusion rate

Max dose of bupivacaine

2mg/kg plain or with adrenaline 0.4mg/kg/hr infusion rate

Max dose of ropivacaine

3mg/kg plain or with adrenaline 0.4mg/kg/hr infusion rate

What is the effect site equilibration time for fentanyl

6 minutes

What is the dose required of fentanyl for intubation

2-4 mcg/kg

Surgical issues to consider at the start of a case?

Position Duration Expected blood loss Antibiotics DVT prophylaxis Special requests

What is the triad of anaesthesia

Hypnosis Analgesia Paralysis

Dose of alfentanil

10-20mcg/kg

Dose of morphine

Titrate, ~0.1mg/kg total