Brief introduction to the junior doctors whom newly enter the anaesthesia department.

1. DRUGS IN ANAESTHESIA
Dr Mohd Faeiz Pauzi
for
Introductory Course In Anaesthesia 2018

2. Contents
• Intravenous induction
• Inhalational agents
• Vasopressor agents

3. INTRAVENOUS INDUCTION

4. What are IV induction drug?
• When given IV in appropriate dose, cause a rapid loss
of conciousness.
• Occuring within “one arm-brain circulation time”.

5. History…
• 1932 – Wesse & Schrapff published their report into
the use of hexobarbitone, the first rapidly acting IV
drug.
• 1934 – sodium thiopental was introduced by Waters
& Lundy.
• Propofol discovered in 1977 and approved to use in
US in 1989.

6. Physical properties;
• Cheap and easy to make
• Long shelf life at room temperature
• Water soluble and so easy to store
• Painless on injection
• Safe if injected intra-arterially
• Rapid onset time
• Rapid offset time
• No excitation or emergence phenomena
• No accumulation following infusion
• No interaction with other drugs

7. Biological properties;
• Analgesic
• No effects on patient’s physiology, other than
rendering them unconsciousne
• No toxic effects

8. Classification
• Barbiturates
- Thiopental
- Thiamylal
- Methohexital
• Phenols
- Propofol
• Imidazoles
- Etomidate
• Phencyclidines
- Ketamine
• Benzodiazepines
- Midazolam

9. Propofol

10. • Presented as a 1% or 2% aqueous emulsion
containing soya oil, egg phosphatide and glycerol.
• It is isotonic to plasma, poorly water soluble, pH 7.0
– 8.5.
• Can cause pain to injection.

11. • Short acting, onset of action approx 30 s and
recovery usually rapid.
• Smooth induction follows a dose 2 -2.5 mg/kg.
• Should be titrated against the response of the
patient until the clinical signs show the onset of
anaesthesia. The best endpoint is loss of verbal
contact with the patient.

12. • Following IV bolus, there is rapid equilibrium between
plasma and the highly perfused tissue of the brain.
• Plasma levels decline rapidly as a result of distribution,
followed by more prolonged period of hepatic
metabolism and renal clearance.
• Initial redistribution half life between 2 – 4 min.
• Moderate hepatic or renal impairment does not alter the
pharmacokinetics of propofol.

13. • Propofol causes the most marked fall in blood pressure of
all induction drugs.
• Mainly due to systemic vasodilatation.
• The fall in BP is dose dependent and most marked in
elderly and shocked patients.
• This can be minimized by slow injection – avoiding
inadvertent overdose.

14. • All induction agents cause respiratory depression,
except ketamine.
• Most profound with propofol and period of apnoea
usually seen.
• Propofol markedly reduces airway and pharyngeal
reflexes  ideal for LMA

15. • Epileptiform movements (however it is not epileptogenic
and is used for treatment of status epilepticus).
• Infusion of propofol commonly used to provide sedation
for adults patients undergoing minor procedure and or
ICU. Most commonly used for TIVA.
• Not safe for infusion in children (> 75 mcg/kg/hr for > 24
hrs); propofol infusion syndrome – metabolic acidosis,
lipidaemia, cardiac arrhytmia and increased mortality.
• Green urine and hair, secondary to quinol metabolites.

16. Summary of Propofol
Advantages
• Pleasant sedation & recovery
• Rapid onset & easy titration to effect
• Suitable for both induction & maintanance
• Suppression of airway reflexes
• Anti-emetic effect
• Safe in porphyria
Diasadvantages
• Pain on injection
• Lipid emulsion carrier which support bacterial growth
• Vasodilation causes hypotension

17. Sodium thiopentone

18. • Thiopental / thiopentone is a barbiturate.
• Ampoules commonly contain 500 mg of sodium
thiopentone with 6% sodium carbonate in an inert
atmosphere of nitrogen.
• Reconstituted with 20 ml of water yields a 2.5% (25
mg/ml) with pH of 10.8.
• The alkaline solution is bacteriostatic and safe to keep for
48 hrs.

19. • Dose of 4-5 mg/kg of thiopentone produce a smooth onset of
hypnosis with good definitive endpoints within 30 sec of IV
injection.
• Recovery after single dose is rapid due to redistribution and there is
low incidence of restlessness and nausea and vomiting.
• 65 -85% protein bound in plasma. Metabolism is slow and occurs in
liver. Excretion of metabolites occurs mainly in the urine.
• Following repeated dose or infusions, metabolism follows zero
order kinetic  leading to an accumulation of the active drug and
delayed recovery.

20. • Directly depresses the contractile force of the heart,
reducing cardiac output and blood pressure.
• It also decreases venous tone, pooling of blood in
peripheral veins  hypotension (particularly in
hypovolaemic).
• Airway reflexes well preserved in comparison with
propofol  unsuitable for LMA (may cause coughing &
laryngospasm).
• Histamine release may precipitate bronchospasm.

21. • Reduces CBF, CMR & O2 demand.
• Potent anticonvulsant properties.
• “Barbiturate coma” – lowers ICP & may improve
neurological outcome.
• May precipitate porphyria (due to hepatic enzyme
induction insusceptible patient).

22. Summary of thiopentone
Advantages
• Very rapid onset of anaesthesia
• Potent anti-convulsant
• Tried & tested & chep
Disadvantages
• Unsuitable for maintanence
• Contraindicated in porphyria
• Antanalgesic

23. Etomidate
• Imidazole ester.
• Presented as lipid emulsion, concentration 2 mg/ml.
• Pain on injection is common.
• Induction dose 0.3 mg/kg.

24. • Induction can be accompanied by involuntary
movements which may be mistaken for generalized
seizure activity.
• Recovery is frequently unpleasant and accompanied by
nausea and vomiting.
• Rapidly metabolized by hepatic and plasma esterases to
yield inactive metabolites.
• Excretion predominantly urinary and the elimination half
life varies from 1-5 hrs.

25. • Causes the least CVS depression.
• Causes transient apnoea, cough, hiccup  not ideally for LMA.
• PONV common.
• Inhibits 11-B-hydroxylase (enzyme adrenal steroid production).
Single induction dose blocks the normal stress induced increase in
adrenal cortisol production for 4-8 hrs, up to 24 hrs in elderly and
debilitated patients.
• Continuous infusion for sedation in ICU has been shown to increase
mortality.

26. Summary of etomidate
Advantages
• Haemodynamic stability
• Reduction in CMRO2, CBF & ICP, with maintanence of CPP
• Very rapid onset of hypnosis & recovery.
Disadvantages
• Hyperosmolar propylene glycol carrier causes pain on
injection, thrombophlebitis & hemolysis.
• Profound but transient inhibition of steroidogenesis.
• Excitatory effects and myoclonus are common.
• PONV

27. Ketamine
• Derivative of phencyclidine.
• Its effects are mediated primarily by noncompetitive
antagonism at N-methyl-D-aspartate (NMDA)
receptor in brain & spinal cord
• Other mechanisms of action of ketamine may include
an interaction with opiod receptors; however
naloxone does not antagonize the analgesic effects of
ketamine in human.

28. • Dissociative anaesthesia – typified by catalepsy in which
the eyes may remain open with slow nystagmic gaze &
the corneal and light reflexes remain intact.
• Varying degrees of hypertonus and occasional purposeful
movements unrelated to painful stimuli can be seen,
even during adequate surgical anaesthesia.
• Psychic sensations including alterations in mood state,
floating sensations, vivid dreams and hallucinations are
common during emergence from ketamine anaesthesia.

29. • Induction: 0.5-1.5 mg/kg i.v, or 4-10 mg/kg i.m.
• Onset is slower than others (unconsciousness in 1-2 min
for IV use), and endpoint may difficult to judge with
patients staring into the distance for a short period of
time.
• Duration action approximately 5-10 min.
• Metabolized in liver, and conjugated metabolites
excreted in the urine.

30. • CVS: tachycardia, increased blood pressure, increased cardiac output 
useful in shocked, unwell patient.
• Minimal effect on respiratory drive, protective airway reflexes relatively
preserved  ideal to use in prehospital environment.
• However increased salivation (premedication with antimuscarinic e.g
glycopyrrolate).
• Bronchial smooth muscle relaxant  role in severe asthma.
• In the past, ketamine was thought to increase CBF & ICP, however
providing hypoventilation and hypercapnia are avoided, this does not
occur and there is some evidence that ketamine may have some cerebral
protective effect (via action on NMDA receptors).

31. Summary of ketamine
Advantages
• Dissociative anaesthesia and marked analgesia.
• Cardiorespiratory stability.
• Relative preservation of airway reflexes.
• Safe in patients with porphyria.
Disadvantages
• Unpleasant and troublesome psychomimetic emergence
reactions.
• Tachycardia & hypertension, undesirable with IHD.
• Contraindicated in raised ICP.

32. INHALATIONAL ANAESTHETIC (VOLATILE
AGENTS)

33. Ideal properties
Physical
• Non-flammable, non-explosive.
• Stable in light.
• Liquid and vaporizable at room temperature.
• Stable at room temperature, with long shelf life.
• Stable with soda lime, as well as plastics and metals.
• Environmentally friendly – no ozone depleteion.
• Cheap and easy to manufacture.

34. Ideal properties
• Biological
• Pleasant to inhale, non-irritant, induces
bronchodilatation.
• Low blood : gas solubility – i.e. faster onset.
• High oil : water solubility – i.e. high potency.
• Minimal effects on other system.
• No biotransformation – should be excreted ideally
via the lungs, unchanged.
• Non-toxic to operating theatre personnel.

35. In essence, the uptake and release of inhalational
agents depends on;
1) alveolar concentration of the inhalational agents
2) drug uptake from the lung

36. Alveolar concentration of the inhalational
agents
1) Inspired concentration agents
- Higher fresh gas flow, lower breathing system volume,
lower circuit absorption leads to higher inspired gas
concentration and faster induction and emergence from
anaesthesia.
2) Alveolar ventilation
3) Functional residual capacity
- A larger FRC dilutes the inspired concentration of gas
resulting lower alveolar partial pressure and therefore
slower onset of anaesthesia.

37. Drugs uptake from the lung
1) Solubility (blood : gas partition coefficient)
• higher blood gas partition coefficient (higher
solubility) leads to greater uptake by the pulmonary
circulation, but a slower increase in alveolar partial
pressure of the agent, therefore more prolonged
induction & recovery

38. 2) Cardiac output
• Low cardiac output state results in slow uptake of
anaesthetic agents and higher alveolar pressure
(higher FA/FI ratio), and therefore faster induction .
3) Alveolar-venous partial pressure gradient and tissue
uptake

39. 4) Effect of obesity and age
• Obese – prolonged emergence
• The rate of induction more rapid in infants and
children than adults.

40. Concentration and second gas effect
• - concentration effect occurs when N2O is used in
high concentration (disproportionate rise in alveolar
partial pressure of other gases).
• - the second gas effect refers to the effect that N2O
has on the speed of onset of anaesthesia of the
second gas (volatile)

41. MAC
• Minimum alveolar concentration, at equilibrium (15
min of inhalational), at sea level, in 100% O2 at
which 50% of the population will fail to respond to a
standard noxious stimulus.
• Stimulus refers to standard surgical skin incision, and
response refers to purposeful muscular movements.
• It is a measure of potency.

42. • MAC awake = 0.3-0.4 MAC, which eyes open on
verbal command during emergence from
anaesthesia.
• MAC intubation = 1.3 MAC, required to prevent
coughing and movement during endotracheal
intubation.
• MAC Bar = 1.5 MAC, prevent adrenergic response to
skin incision.

43. Factors affect MAC
Decreasing MAC Increasing MAC No influnce
- Increasing age
- Pregnancy
- Hypothermia
- Hypothyroidism
- Hyponatraemia
- Hyporension
- Hypoxia
- Metabolic acidosis
- Acute alcohol
- Narcotics
- Ketamine
- Benzodiazepines
- α2 agonists
- Lithium
- Young age (infants and
children)
- Hyperthermia
- Hypernatraeia
- Chronic alcohol use
- Increased
sympathoadrena
stimulation (MAO
inhibitors, acute
amphetamines,
ephedrine, cocaine)
- Duration of anaesthesia
- Sex
- Alkalosis
- Hypertension
- Anaemia
- Magnesium and
potassium level

44. Sevoflurane Desflurane Isoflurane
MAC (%) 2.0 6.0 1.1.5
CVS SVR ↓
HR ↓
MAP ↓
CO ↔
SVR ↓ (above 2.2
MAC)
HR ↑
MAP ↓
CO ↔
SVR ↓↓
HR ↑↑
MAP ↓
CO ↔
Respiratory Tidal volume ↓
RR ↑
Bronchodilation
Not irritant
Tidal volume ↓
RR ↑
Irritant ++
Tidal volume ↓
RR ↔
Bronchodilation
Irritant +
CNS CBF ↑ (>1 MAC)
CMRO2 ↓
No epileptiform
activity
CBF ↑ (>1 MAC)
CMRO2 ↓
No epileptiform
activity
CBF ↑ (>1 MAC)
CMRO2 ↓
No epileptiform
activity
Uterine tone ↓ ↓ ↓

45. BASIC RESUSCITATION DRUGS

46. Mechanism of
action
Dose / route Usage Special points
Adrenaline Sympathomimetics
(α and β-agonist)
IV 0.1 mg bolus
IV 1.0 mg bolus
IV 0.01-0.1
µg/kg/min infusion
(via ETT twice IV
dose)
Nebulizer 0.4 ml/kg
(max 5 ml)
Anaphylaxis
Cardiac arrest
Low CO states (as
inotropic drug)
Bronchospasm
Croup
Low doses gives the
β-effects and high
doses gives α-
effects
Atropine Anticholinergic IV 0.01-0.02 mg/kg Bradycardias Has tertiary
quaternary
structure which
crosses the blood
brain barrier and
may present with
central
anticholinergic
syndrome
(confusion,
amnesia, agitation)

47. Mechanism of
action
Dose / route Usage Special points
Ephedrine 1. Indirect action:
release of
noradrenaline
2. Direct action: α
and β-agonist
IV 3-6 mg bolus
Or 0.07 mg/kg
bolus
Hypotension (in
spinal / epidural)
Increases the BP by
invreasing the heart
rate and cardiac
contraction.
Tachyphylaxis.
Phenylephrine Sympathomimetics
(α1-agonist)
IV 25-100 mcg
bolus
Hypotension
(in obstetric RA)
Increases BP by
vasoconstriction
(have simultaneous
bradycardia).
Chosen for obstetric
RA due to the
better fetal acid-
base profile
compared to using
ephedrine (in large
doses).
Resembles
adrenaline but
more prolonged
effect and less
effect on the heart.

48. Take 5…

49. DRUGS IN ANAESTHESIA (PART 2)

50. • Local Anaesthesia
• Premedications Drugs
• Antiemetics for PONV

51. LOCAL ANAESTHESIA

52. What is local anaesthetics?
• A drug which reversibly prevents transmission of the
nerve impulse in the region to which it is applied,
without affecting consciousness.
• LA generally have lipid soluble hydrophobic aromatic
group and a charged, hydrophilic amide group. The
bond between these two groups determines the
class of the drug; amide or ester.

53. Amide Ester
- Lignocaine
- Bupivacaine
- Levobupivacaine
- Ropivacaine
- Prilocaine
- Etidocaine
(all containe an ‘i’ followed by ‘caine’
- Cocaine
- Amethocaine
- Procaine

54. - Act by blocking sodium channels.
- Weak bases with pKa > 7.4. means they are ionized at physiological pH (7.4)

55. 1) Potency
• More lipid-soluble, greater potency.
• e.g. bupivacaine is seven times more lipid soluble than lignocaine and therefore
more potent.
2) Duration
• More protein-bound, longer duration.
• e.g. bupivacaine is 95% protein-bound, longer than lignocaine which is 65%
• Addition of vasoconstrictors, such as adrenaline, also prolongs the duration of
action by reducing washout of the drug into the bloodstream.
3) Speed
• Lower pKa (close to pH 7.4), higher un-ionized fraction, means greater proportion
available to cross neuronal membrane and take effect more quickly.
• e.g. lignocaine pKa 7.9 is 25% unionized at pH 7.4, bupivacaine pKa 8.1, 15%
unionized, therefore lignocaine faster onset
• Bicarbonate may added to some epidural solution to raise pH of the solution, so LA
to be more unionized, resulting in faster onset
• Infected tissues and abscess reduced local pH, results in higher fraction LA
becoming ioised, thus reducing efficacy.

56. Rate of systemic vascular absorption of LA
• Important in terms of toxicity
Intercostal > Caudal > Epidural > Brachial plexus >
Femoral > Subcutaneous

57. Salient features
1) Lignocaine
• Amide
• Fast onset (pKa 7.9)
• Medium duration of action (70% protein bound). 1-2 hr
• Moderate vasodilatation.
• Max dose 3 mg/kg or 7 mg/kg with adrenaline.
2) Bupivacaine
• Amide
• Racemic mixture of R and S enantiomers.
• Long duration (95% protein bound). 4-8 hr.
• Max dose 2 mg/kg.
• Extremely cardiotoxic in overdose.
3) Levobupivacaine
• Amide.
• S enantiomer of bupivacaine.
• Long duration (95% protein bound).
• Max dose 2 mg/kg.

58. 4) Ropivacaine
• Amide.
• Long duration (94% protein bound). 4-8 hr.
• Less cardiotoxic than both bupivacaine and levobupivacaine.
• Max dose 3.5 mg/kg.
5) Cocaine
• Ester
• Short duration.
• Profound vasoconstriction – constituent of Moffat’s solution (topical).
• Side effects include hypertension, hallucinations, seizures and coronary ischaemia.
• Max dose 3 mg/kg.
6) EMLA
• - eutactuc mixture of LA: lignocaine 2.5% and prilocaine 2.5%

59. PREMEDICATION

60. • Definition – administration of drug before induction
of anaesthesia
• Consists of administration of drugs 1-2 hrs before the
induction of anaesthesia; orally, IM, IV

61. Goals
• Anxiolysis & sedation
• Analgesia
• Amnesia
• Increase in gastric fluid pH & decrease in gastric fluid volume
• Antisialogogue effect
• Decreased SNS reflex response
• Hemodynamic stability
• Decrease in anaesthetic requirement

62. Factors to be considered before premedication
• Patient’s physical status
• Age
• Level of anxiety and pain
• Type of surgery
• Timing of surgery
• History of drug allergy, nausea, vomiting

63. Anxiolysis & Sedation
• To minimize physical discomfort and pain.
• To control behavior particularly movements.
• To minimize psychological disturbances and distress.
• To maximize the potential for amnesia.
• To guard for patient’s safety.

64. 1) Benzodiazepines
• E.g. Midazolam, diazepam, lorazepam
2) Barbiturates
• E.g. phenobarbitone
3) Others
• E.g. promethazine

65. Midazolam
• Premedication: 0.07-0.1 mg/kg
• Sedative: 0.5-1.0 mg boluses
• Induction: 0.3 mg/kg
• Infusion: 0.05-0.2 mg/kg/hr
• Effects: Respiratory and CVS depression (especially
elderly and ill patients), dose have to be titrated
accordingly.
• Effects can be reversed by flumazenil.

66. Analgesia
Opioids;
• Pethidine 50-100mg im
• Morphine 8-12 mg im
• Fentanyl 50-100 mcg iv
NSAIDS
• Diclofenac
• Ketorolac

67. Aspiration Prophylaxis
Risk factors for aspiration;
• Extremes of ages
• Emergency cases
• Type of surgery
• Recent meal
• Trauma
• Pregnancy
• Pain and stress
• Depressed level of consciousness
• Morbid obesity
• Difficulty airway
• Poor motor control
• DM

68. Preventive measures
• Fasting
• Reduce gastric volume, increase gastric pH
- H2 receptor antagonist
- Proton pump inhibitor
- Antacid
• Increase gastric motility
- Prokinetic drugs

69. Antisiologogoue
• Decrease salivary gland and mucosal gland secretion.
• Glycopyrolate potent antisecretory
• Atropine
• Scopolamine

70. Continuation & Discontinuation of Drugs
Continuation Discontinuation
- Beta blocker
- Bronchodilators
- Anti-epileptics
- MAO-inhibitors
- Anti-coagulants
- Oral hypoglycaemic
- ACE inhibitors
- AT 2 antagonists

71. POST OPERATIVE NAUSEA VOMITING (PONV)

72. Risk factors for PONV
Patient related - Female gender (3x more common)
- History of PONV
- Non-smoker
- Children of > 3 years old (does not applied to adult)
- Low ASA status (I and II)
- History of migraine
- Preoperative anxiety
Anaesthesia related - Use of volatile / inhalational agents
- Use of N2O
- Use of intra and postoperative opioids
- Longer duration of GA (in surgery > 30 min)
- Use of GA vs RA
- Use of neostigmine
- Facemask ventilation
Surgical related - Paediatric strabismus surgery
- Open GIT surgery
- Laparoscopic surgery
- Middle ear surgery
- Opthalmic surgery
- Breast surgery
- Gynaecological surgery

73. 1) 5-HT3 antagonist:
• IV ondansetron 4 mg,
• IV granisetron 0.3-1.5 mg
2) Corticosteroid:
• IV dexamethasone 8 mg (adults) and 1-1.5 mg/kg (children)
3) Butyrophenones:
• IV droperidol 0.625 mg-1.25 mg
• IV/IM haloperidol 0.5-4 mg
4) Anticholinergic:
• Transdermal patch scopolamine 1.5 mg

74. 5) Dopamine antagonist (phenothiazines):
• IV metochlorpramide 25-50 mg
6) Opioid antagonist:
• Alvimopan 4 mg
7) NK1 receptor antagonist: aprepitant 40-80 mg
8) Others: IV propofol 10-20 mg (for refractory nausea),
gabapentin 600-800 mg

75. Thank you for your attention…
Enjoy your life in anaesthesia department