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PHARMACOLOGY > ANAESTHETIC AGENTS > Flashcards

ANAESTHETIC AGENTS Flashcards

1
Q

Give examples of Inhaled anaesthetic agents

A

Halothane
Enflurane
Desflurane
Xenon
Sevoflurane
Isoflurane
Nitrous Oxide

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2
Q

Why can the Inhalational be dangerous in clinical practice

A

Low safety margin / low therapeutic index

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3
Q

Most of them are volatile liquids except

A

Nitrous oxide and xenon ( gases )

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4
Q

What is the MOA of Inhaled anaesthetic agents at the Macroscopic level

A

Decrease transmission of noxious / pain afferent information from the spinal cords to cerebral cortex
* Norxious stimuli - dangerous stimuli sensed by nociceptors

2) Inhibit spinal efferent activity reducing movement response to pain

3) depress cerebral blood flow and glucose metabolism

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5
Q

Moa at the synaptic level

A

1) Influence presynaptic release of neurotransmitters
2) Inhibit excitatory neurotransmitters (nicotinic, serotonergic and glutaminergic)
3) Augment / increase the inhibitory neurotransmitters (GABA , Glycine)

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6
Q

Uptake of the Inhalational anaesthetic agents depends on

A

1) Alveolar concentration of the anaesthetic agents
2) Uptake from alveoli by pulmonary circulation

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7
Q

Give the 3 main factors affecting alveolar concentration

A

1) Inspired concentration
2) Alveolar ventilation
3) Functional residual capacity

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8
Q

Give 4 main factors affecting uptake of the Inhalational anaesthetic agents by pulmonary circulation

A

1) Solubility
2) Pulmonary alveolar blood flow ( CO)
3) Alveolar - venous partial pressure gradient
4) Second gas effect

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9
Q

Explain the effect of the inspired concentration and three factors that affect this

A

The greater the concentration the faster the induction

1) Higher fresh has flow
2) Lower breathin system
3) Lower circuit absorption

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10
Q

How does alveolar ventilation affect the alveolar conc of the Inhalational anaesthetic agents

A

Increased alveolar ventilation increases take up by the pulmonary blood flow and replaces its alveolar concentration

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11
Q

Explain FRC

A

A larger FRC dilutes inspired conc of gases thus slower onset of anaesthesia

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12
Q

What is the main factor that determines both the rate of induction and recovery

A

Solubility

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13
Q

The lower the blood - gas partition coefficient …

A

The faster the induction and recovery

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14
Q

What is the effect of the plasma proteins

A

Increases blood solubility by inc

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15
Q

How does cardiac output affect the pulmonary uptake and induction of anaesthesia

A

A high carduac output increases the uptake but slows induction to anaesthesia

A low cardiac output has reduced uptake but faster induction due to increases alveolar pressures

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16
Q

Define the Minimum alveolar concentration

A

Minimum alveolar concentration at 1atm pressure that prevents movement in response to a standard surgical midline incision in 50% test population

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17
Q

Give the effects of the Inhalational anaesthetic agents at the Respiratoy system

A

1) Depress ventilation
2) Increase PaCO2
3) Decrease sensitivity of respiratory centres to CO2
4) Bronchodilation due to reduced airway resistance

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18
Q

Give the effect at CVS

A

1) Reduce mean arterial pressure and CO
2) Reduced system vascular resistance leading to hypotension
3) Sevoflurane prolongs QT interval

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19
Q

Give effects of Inhaled anaesthetic agents at
1)CNS
2) Liver
3) Kidney

A

CNS
I) Decrease cerebral metabolic rate amd oxygen consumption
II) Causes cerebral vasodilation this increasing ICP
III) Decreases the cerebral perfusion pressure

LIVER - Reduces hepatic blood flow
KIDNEY - Nephrotoxicity from the metabolism of halogenated agents to inorganic flouride

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20
Q

Define what is CPP

A

Cerebral perfusion pressure is the net pressure gradient of MAP - ICP that drives oxygen delivery to brain tissues

21
Q

Halogenated anaesthetics can trigger what in skeletal muscle and what is the cause

A

Malignant hyperthermia in skeletal muscle caused by excessive release of Calcium from sarcoplasmic reticulum resulting in muscle contracture

22
Q

Give symptoms of malignant hyperthermia

A

Muscle rigidity
High fever
Fast heart rate
Rhabdomyolysis
Hyperkalemia
Rapid breathing

23
Q

Gibe a drugs used in the treatment of malignant hyperthermia

A

Dantrolene

24
Q

What is the pathophysiology of malignant hyperthermia

A

Malignant hyperthermia usually occurs in patients with a mutated RYR1 (ryanodine receptor on the sarcoplasmic reticulum) .

The inhaled anaesthetic agents usually trigger this receptor causing an excessive release of Calcium from sarcoplasmic reticulum and interference of calcium returning to storage.

This creates high intracellular calcium leads to high muscle contractility

25
Q

Give four main uses of IV induction drugs

A

1) Induce anaesthesia prior to maintenance anaesthesia
2) Sole drugs for short procedure
3) Maintain anaesthesia by IV infusion
4) Provide sedation

26
Q

Give for physical properties of an ideal IV induction agent

A

Water soluble
Stable to light
Non irritant
Cheap

27
Q

Give 4 pharmacokinetic properties of an ideal IV induction agent

A

1) Rapid onset (one arm - brain circulation)
2) Rapid redistribution
3) Rapid metabolism and clearance
4) No active metabolites

28
Q

Give four pharmacodynamic properties of IV induction agents

A

Wide therapeutic index
Minima CVS and Respiratory effects
No adverse effects
No hang over
Safe

29
Q

Give three Barbiturates

A

Sodium Thiopental
Thiamylal
Methohexital

30
Q

Give the
1) Duration it takes for unconsciousness in Thiopental
2) Duration of anaesthesia

A

10-30 seconds
5-8 minutes

31
Q

Thiopental doses are increased and reduced in

A

Increased in children
Reduced in elderly

32
Q

Dose reduction of Ythiopental is seen in premedication with which drugs

A

Benzodiazepines
Opiates
a2 agonists

33
Q

Give relative potency to Thiopental of
1) Thiamylal
2) Methohexital

A

Thiamylal is equipotent and Methohexital is 3x more potent

34
Q

Give the organs system effects of the Barbiturates in
1) CNS
2) CVS
3) Respiratory

A

CNS
1) Reduce cerebral metabolic rate
2) Reduce cerebral blood flow and ICP
3) Reduce intraocular pressure
4) Anticonvulsants

B) CVS
1) Hypotension due to decreased cardiac contractility and venodilation
2) Tachycardia- compensatory to low BP

C) RESPIRATORY
Respiratory depressant that causes wheezing in asthmatics

35
Q

Propofol is active metabolite of

A

Fospopofol

36
Q

What enzyme metabolizes fospropofol to propofol

A

Endothelial alkaline phosphatase

37
Q

Give four PK of Propofol

A

1) Highly protein bound
2) Has a large volume of distribution
3) Metabolized in liver by sulfation and glucunoridation
4) Excreted renally

38
Q

Propofol acts on which receptor

A

GABA-A receptor agonist

39
Q

Propofol is seen to decrease various things in the CNS , these are

A

1) Cerebral metabolic rate
2) Cerebral blood flow
3) Intraocular pressure
4) ICP
5) Reduced brains information integration capacity as seen on EEG

40
Q

Give the CVS effects of Propofol

A

Hypotension due to vasodilation and decreased myocardial contractility

41
Q

Give the respiratory effects of Propofol and how do es this effect differ from barbiturates

A

They cause respiratory depression but less bronchospasm and thus can be used in asthmatics

42
Q

What is the effect of propofol on
1) Nausea and Vomiting
2) Pregnancy

A

Antiematic
Safe in pregnancy

43
Q

What is PRIS with propofol and what are the symptoms

A

Propofol infusion syndrome is caused by infusion of high doses of propofol . Symptoms include
- Bradycardia followed by cardiac failure
- Rhabdomyolysis
- Metabolic acidosis
- Hyperkalemia
- Hyperlipidemia
- Liver enlargement
- Kidney failure

44
Q

Give three indications for use of Ketamine

A

Hypertensives
Asthmatics
Paediatrics

45
Q

In contrast to barbiturates and propofol , Ketamine has which effects in the CNS

A

Increased cerebral metabolic rate
Increased cerebral blood flow
Increased ICP
Increased intraocular pressure

46
Q

Ketamine can cause a nervous condition knowns as

A

Catalepsy - rigid body , slowing of body functions , salivation , lacrimation , pupillary dilation , increased muscle tone

47
Q

What are the CVS effects of Ketamine

A

Hypertension
Tachycardia
Increased cardiac output

48
Q

Ketamine is C/I in?

A

Myocardial infarction as it increases oxygen myocardial consumption

PHARMACOLOGY (17 decks)

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