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Anaethetics 2 > Intravenous Anaesthetic Agents > Flashcards

Intravenous Anaesthetic Agents Flashcards

1
Q

Name the slower-acting agents

A

Benzodiazepines
Neuroleptic anaesthetics
Large dose opioids

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2
Q

Advantages of intravenous induction?

A

Rapid onset
Smooth induction, with rapid transfer through stage 2
Pleasant for the patient
Pollution free

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3
Q

Disadvantages of intravenous induction

A

Venepuncture required
Overdose easy
No removal of drug via lungs (once in its in) recovering requires redistribution, metabolism and excretion
Sudden loss of normal protective mechanism and often apnoea

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4
Q

Name the Rapidly-acting induction agents

A

Propofol
Thiopentone
Etomidate
Ketamine

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5
Q

Mechanism of action if intravenous induction agents?

A

Modulates y-aminobutyric acid (GABA), neuronal transmission, interfering with transmembrane electrical activity.

Ketamine is a opioid receptor agonist and antagonises the NMDA receptor

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6
Q

What does TIVA stand for?

A

Total intravenous anaesthetia

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7
Q

What’s does TIVA entail?

A

No inhalation all agents are used during induction or maintenance of GA

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8
Q

What does patient still require even with TIVA?

A

Mixture of air/ N2O and oxygen to be delivered via the breathing circuit.

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9
Q

What two agents can be used for TIVA?

A

Propofol and ketamine

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10
Q

How is TIVA administered?

A

With a syringe at a steady, set rate, to avoid overdose or awareness

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11
Q

At what flow rate is TIVA syringe pumps made?

A

Very low flow rates

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12
Q

What do most TIVA’s contain?

A

A library of frequently used drugs and their usual concentrations

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13
Q

What is the simple regime of Propofol TIVA? What is is called?

A 
Initial bolus of 1mg kg-1 follows by an
Infusion of 10mg kg hr for 10mins
                   8mg kg hr for 10mins
                   6mg kg hr thereafter 
The 10-8-6 regimen
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14
Q

What is the TIVA Propofol regime in kids?

A

15-13-11mg kg hr

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15
Q

What is the target plasma concentration (Cp)?

A

3ug ml

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16
Q

What is TCI?

A

Target controlled infusion, an method of delivering TIVA

17
Q

What does a TCI do?

A

It’s uses a microprocessor controller syringe pump to automatically and variably control the rate of infusion of a drug to attain a defined target level in the plasma or effect site

18
Q

Physical properties of Propofol?

A

Insoluble in water. Current pre 1% (10mg ml).

Fat emulsion may act as culture medium therefore must be used in 6 hours after opening available in 20ml, 50ml, 100ml

Also 2% (20mg ml) for infusions

Highly lipophilic engraving ability to cross blood brain barrier

Pain on injection (30-40%)

19
Q

Uses of Propofol?

A

Induction, maintenance or sedation (ICU sedation, regional A, cardioversion)

20
Q

Pharmacodynamics of Propofol

A

Induction: 1.5-2.5mg kg adults, 2.5-3mg kg in kids

Maintenance: TIVA (6-12mg kg hr) reduce in combination with N2O and or opioid
Plasma concentration for TCI: induction 4-8ugml and maintenance 3-6ugml

Sedation: 1.5-3mg kg hr and Cp 0.1- 2.5ug ml

21
Q

Physical properties of sodium thiopentone

A

Yellow, amorphous powder, can be dissolved in water or normal saline. It is a barbiturate. Aqueous solution is strongly alkaline pH 10,5, must not be mixed with low pH solutions such as glucose containing fluids–> will cause precipitation of free barbituric acid (also when mixed with mm relaxants (weak bases with higher pH)

22
Q

What is the preferred strength of sodium thiopentone?

A

2,5% (mix 500mg amp with 20ml= 25mg ml) stable for 24-48hrs

23
Q

Pharmacodynamics of sodium thiopentone?

A

3-5mg kg in adults and kids 5-6mg mg

24
Q

Is thiopentone used for maintenance and why?

A

No, because of long elimination half-life with accumulation

25
Q

What happens with intravasculature injection of thiopentone?

A

Precipitation of solid crystals blocking arterioles and capillaries. Causes intense spasm and thrombosis.

Early signs: white hand with cyanosed fingers, skin discoloration and slow onset anesthesia

Late sign: ulcers, blisters, oedema and gangrene

26
Q

Treatment of inter-arterial injection of thiopentone?

A

1- prevention
2- 2,5% solution with test dose
3- treat spasm- leave cannula in artery and inject:
Papaverine 40-80mg in 10-20ml saline
Procaine 10-20ml of 0,5% solution
Phenoxybenzamine 0,5mg
4- brachial plexus or stellar ganglion block: sympathetic block for vasodilation
5- treat thrombosis with heparin bolus 5 000iu
6- analgesia

27
Q

Contraindications to thiopentone?

A

Absolute: porphyria, known allergy

Relative: CVS (HF, hypovol, fixed CO, asthma

28
Q

Etomidate physical properties?

A

Imidazole
In 10ml ampoules with 2mg ml dissolved in water with 35% propylene glycol. pH= 8,1z Can be diluted with 10ml saline or water to make a 1mg ml solution

Pain on injection in 25-50%

29
Q

How do you reduce the pain on injection of Etomidate?

A

Fast injection
Use of large vein
Addition of 10-20mg of lignocaine

30
Q

What is the induction dose of Etomidate?

A

0,2-0,3mg kg

31
Q

Physical properties of ketamine?

A 
Acidic solution
Can use as IV, IM, oral
Available as 1% (10mgml), 10% (100mgml) 
Stable in solution and log shelf life
Non-irritant
32
Q

Why do you get protracted emergence in ketamine induction?

A

50-60% still remains in body on active form after surgical anaesthesia terminated.

Main metabolite is norketamine, with weak hypnotic properties

33
Q

Pharmacodynamics of ketamine?

A

Induction:
IV: 1-2mg kg (onset 30-60secs, last 5-15mins)
IM: 5-10mg kg onset 3-8min lasts 10-30mins

Maintenance:
IV: 0,5mg kg, as incremental boluses or 1-4mg kg hr by infusion

Analgesia:
IV: 0,2-0,4mg kg
IM: 2-4mg kg

Infusion of 0,2-0,3mg kg hr

34
Q

Indications for Ketamine?

A

Poor risk surgical patients
Pediatric surgery
Debridement, painful dressings and skin-grafts in patients suffering from burns
Short procedures
Analgesia
Anaesthesia in sub-optimal conditions (trauma, rural)
Treat status asthmaticus

35
Q

Contraindications of ketamine?

A 
CVS disorders- hypertension, IHD, AA, heart failure
Raised ICP, cerebral aneurysm 
Open eye surgery, increased intraoccular pressure
Psychiatric patients 
Epileptics
Thyrotoxicosis
Oral cavity or airway surgery
Early pregnancy 
Tricyclic antidepressants
36
Q

Why can you give midazolam as an infusion?

A

It has a high clearance, and a short elimination half-life, therefore shorter duration of action and accumulation is less likely to occur

37
Q

Indications for Flumazenil?

A

Termination of GA induced and maintained on benzo
Reversal of benzo sedation in short diagnosis and therapeutic procedure
Reversal of benzo OD
Diagnosis of unconsciousness of unknown origin

Anaethetics 2 (10 decks)

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