1. LOCAL ANAESTHETICS

2. Nernst Equation To calculate equilibrium for individual ions
Membrane potential = RT ln[X]out
FZ [X]in
R = Universal gas constant (8.31 J/K/mol)
T = Absolute temp
F = Faraday constant (coulombs per mole of charge)
Z = Valence
[61.5]
Na/K ATPase
Membrane relatively permeable to K+/impermeable to Na+

3. Membrane Potential IN OUT POTENTIAL (mV) Na 5 140 +60 K 150 -90 Cl 10
125
-70

4. Membrane Potential Resting Potential -70mV Gradients Electrical
Chemical
Ion
Electrical
Chemical Cl
Out In K Na

5. Goldman Constant Field Equation
Includes membrane permeabilities for each ion

6. Membrane potential [K] Potential 2 -115 Stabilised 4.5 -90 Normal 8
-78
Excitable
Nernst values
Small difference in K+ concentration, large effect on membrane
[Na]
Potential
110
+53
140
+60
165
+64

8. Local Anaesthetics
Binds open Na channels from the inside

9. LA - Structure Amides: lignocaine, bupivacaine, prilocaine
Esters: cocaine, procaine, amethocaine
Lipid-soluble hydrophobic aromatic group
charged hydrophilic amide group
bond between these two groups determines the class of the drug

10. Structure
Lignocaine
Bupivacaine

11. LA - Differences between esters and amides
Ester linkage is more easily broken than the amide
Ester less stable in solution, cannot be stored as long as amides
Metabolism of esters results in the production of para-aminobenzoate (PABA)
PABA associated with allergic reaction
For these reasons amides are now more commonly used than esters.

12. Physicochemical properties
Weak bases
Speed of onset
- pKa
Duration
- protein binding
Potency
- lipid solubility

13. pKa
Definition
Negative logarithm to the base 10 of the dissociation constant
Law of Mass Action
Henderson-Hasselbach equation
At pKa 50% ionised/unionised
At pH 7.4 all LAs are more ionised than unionised (as pKa greater than 7.4)
Unionised drug enters cell through the lipid cell membrane
Drug which is more unionised at physiological pH reaches target site faster
Lignocaine has a faster onset of action than bupivacaine

14. pKa Importance: lower pKa -> better absorption into nerve tissue
higher pKa -> more effective blockade within nerve
Inflamed/infected tissue
acidic environment
reduced unionised fraction
Increased blood supply – so faster washout

15. Physicochemical properties
Lignocaine
Bupivacaine
Relative Potency 1 4
Lipid solubility
150
1000
pKa
7.9
8.1
% unionised at pH7.4 25 15
% Protein bound 70 95

16. Lipid solubility Potency
Highly lipid soluble drugs readily cross membranes
Lipid partition coefficient
Prilocaine 0.9
Lignocaine 2.9
Bupivicaine 28

17. Duration of action Determined mainly by protein binding
Fraction available for metabolism

18. Metabolism and excretion
Esters (except cocaine)
rapid metabolism by plasma esterases
short half life
cocaine hydrolysed in the liver
ester metabolite excretion is renal
Amides
metabolised hepatically by amidases
slower, hence half-life longer
can accumulate

19. Metabolism and excretion
Prilocaine
metabolised most rapidly of amides– hepatic/renal
O-toluidine
high doses – methaemoglobinaemia
Methylene blue
Levobupivacaine
enantiomer of bupivacaine
similar onset / duration to bupivicaine
less cardio/cns toxicity
expressed as mg of base (not mg of hydrochloride salt)
so 13% more activity per given dose

20. EMLA 5% (2.5% lignocaine / 2.5% prilocaine)
2 compounds mixed to form substance with single set of characteristics
oil:water emulsion instead of crystalline
not on mucus membranes

21. Types of Neurone C Pain & temperature Post ganglionic autonomic B
Pre ganglionic autonomic - warm limb
A delta
Pain & temperature
Loss of pain sensation
A-gamma
Motor to muscle spindles - proprioception loss
A-beta
Touch and pressure loss
A-alpha
Motor paralysis

22. Conduction speed (m/s)
Neurones
size (μm)
myelin
Conduction speed (m/s)
A alpha
1-20 Y
70-120
A beta
50-70
A delta
30-50
A gamma
<30 B
1-3
<15 C
<1 N
<2

23. LA Toxicity Toxicity depends on amount of free drug in plasma
1. Dose given
2. Rate of injection
3. Site of injection
the greater the blood supply, the greater the systemic absorption
interpleural > intercostal > pudendal > caudal > epidural > brachial plexus > infiltration
absorption from injection site
direct intravascular injection

24. LA Toxicity
CNS
unintended epidural injection during posterior lumbar plexus block
LAs relatively small molecules
readily cross the blood-brain barrier
Lignocaine
3mg/kg ( +adr 7mgkg)
Bupivacaine
2mg/kg
Prilocaine
6mg/kg ( +adr 9mg/kg)

25. Cardiac SEs Class Ib, shorten AP
direct depressant effect on myocytes in dose-dependent fashion
myocardial contractility diminished at equivalent dose to achieve sodium channel block
example of frequency-dependent blockade
blockade of conducting system increases activity in re-entrant pathways
VT/VF resistant to treatment
highly lipid-soluble agents (bupivicaine) demonstrate different receptor binding patterns, so-called 'fast in, slow out'

26. Treatment ABC, amiodarone Prolonged resuscitation may be required
Consider cardiopulmonary bypass
Intralipid®
brand name nutritional supplement
emulsion of fats
Propofol/etomidate supplied in an emulsion of intralipid
20% Intralipid
1.5 mL/kg as an initial bolus, followed by
0.25 mL/kg/min for minutes
Bolus could be repeated 1-2 times for persistent asystole
Infusion rate could be increased if the BP declines

27. CNS SEs CNS excitation light-headedness, dizziness
circumoral paraesthesia
acute anxiety, disorientation
CNS Depression
drowsiness
siezures
loss of consciousness
respiratory hypoventilation / arrest

28. Treatment
ABC, oxygen
seizures increase oxygen demand from 200 ml/min to 800 ml/min
increased CO2 produces respiratory acidosis
exacerbates CNS toxicity
midazolam mg iv bolus
thiopentone 50mg
Prevention
Intravascular marker: epinephrine 1: or 1:
Incremental injection: careful aspiration after 5ml of LA
Monitoring: maintain verbal contact

29. Cardiac/CNS Ratio
ratio of blood level producing irreversible cardiovascular collapse to that level required to produce convulsions
bupivicaine 4
lignocaine 7
the lower the ratio, the more potentially hazardous
NO bupivicaine for ivra

30. Regional Anaesthesia of Lower Limbs

31. Basic Setup Patient position Monitoring ECG
Pulse oximeter (audible tone)
NIBP (5 min cycle)
Oxygen
IV access and fluid
Resuscitation Equipment
Airway kit
Assistant to operate nerve stimulator / inject LA

32. Basic Setup Skin disinfectant Skin LA Sterile gloves (scrub for LPB)
Landmarks
Sedation
Midazolam mg IV bolus
Fentanyl mcg IV bolus

33. Nerve Stimulator Peripheral nerve stimulator
Positive to patient (ECG electrode)
Negative to needle
Attach syringe to tubing extension
Set initial current to 2 mA, 2Hz
Endpoint
good twitch amplitude at < 0.5 mA
reduction of twitch response > 0.25 mA
N.A.P.T.A. (negative aspiration, positive twitch abolition) when 1ml injected

34. Landmarks Anterior Anterior superior iliac spine Pubic tubercle
Inguinal ligament (ASIS - PT)
Posterior superior iliac spine
Greater trochanter
Femoral crease
Posterior
Iliac crest / intercristal line
Posterior superior iliac spine (PSIS)
Greater trochanter (GT)
Sacral hiatus (SH)
Ischial tuberosity (IT)

35. Landmarks Distal Femoral condyles
Groove between biceps femoris (BF) and vastus lateralis (VL)
Tibial tuberosity
Fibular head
Ankle malleoli

37. Anatomy

40. Anatomy
A myotome is the group of muscles supplied by a nerve

41. An osteotome is that part of the bone whose periosteum is supplied by a nerve root

42. 1. Subcostal n.
2. ILIH
3. Genitofemoral
4. LFCN
5. Femoral n.
6. Obturator n.
7. Accessory Obturator
8. Inguinal ligament
9. ASIS
10. PT
11. Sympathetic chain

43. 1. Sympathetic chain
2. ILIH
3. Genitofemoral
4. LFCN
5. Iliac crest
6. Sciatic n.
7. Sciatic notch
8. Femoral n.

45. Femoral Nerve Block 3 in 1 Block
Landmark:
Mid-inguinal point = Fem art
1cm below inguinal ligament
1cm lateral to artery
Stimulation
patella twitch
sartorius too superficial/lateral
Distal pressure to get obturator (3 in 1)

49. LCNT Landmark ASIS 2 cm inferior, 2 cm medial Blunted needle
Perpendicular
Advance needle through skin
Discern a 'pop' or click as fascia penetrated
Fanwise distribution
10mls

50. Fascia Iliaca Block Landmarks ASIS Pubic tubercle
Connect & divide into thirds
Mark junction of lateral 1/3rd & medial 2/3rd
Insert blunt needle 1 cm inferior to mark
Perpendicular
Advance needle through skin
Discern 2 'pops' or clicks as fascia penetrated
fascia lata, fascia iliacus
30mls

52. Sciatic Nerve Block -Labat technique
Position
Lateral position (Sim's) with operative side uppermost
Landmarks
GT, PSIS
Connect & mark midpoint
From midpoint, draw perpendicular in caudad direction
Join this to line from GT, sacral hiatus

54. Sciatic - Labat Stimulation
Initially direct stimulation of gluteus maximus
Accept stimulation of tibial (plantar flexion)
Hamstrings
too medial
Electric shocks down half of penis / vagina
stimulation of pudendal nerve, toomedial
Common peroneal (dorsiflexion + eversion)
too lateral

55. Sciatic Nerve Block -Raj technique
Landmarks
Greater trochanter
Ischial tuberosity
Intermuscular groove
Insert needle midpoint between GT / IT
1 - 2 cm along longitudinal groove
Perpendicular in all planes
6 - 8 cm
Stimulation
Stimulation of tibial (plantar flexion + inversion)
Contraction of the hamstrings: may be direct stimulation
If no motor response re-insert needle 1cm caudal along PSIS/IT line

57. Lumbar Plexus Block Landmarks
Lateral position with operative side uppermost
Intercristal line (IC) / Tuffiers line = L4
PSIS, line parallel to horizontal
Aim to hit TP L4 and walk off above/below
8-12cm depth
Mainly injecting into psoas – watch dose
Stimulation
Patella twitch

58. Perpendicular in all planes

59. Location of TP and Nerve Posterior View

60. Lumbar Plexus Block Too medial = paravertebral = epidural injection
Hamstrings contraction
L4 component of lumbosacral trunk nerve
re-direct needle supero-laterally to initial pass
Iliopsoas contraction upper part of thigh
needle in psoas muscle
further advancement risks penetration through anterior surface of psoas & into adjacent structures

61. Ankle Block This block is often described as the blockade of 5 nerves
4 needle insertions, one of which will block 2 nerves
Anterior to medial malleolus: Saphenous nerve
1cm anterior to malleolus, 1cm proximal to inter-malleolus line (skin crease)
5ml LA
Posterior to medial malleolus: Tibial nerve
Posterior to posterior tibial artery
Contact bone and withdraw needle by 1mm

63. Ankle Block Anterior to lateral malleolus: Deep Peroneal
Insert needle between EHL and DP pulse; advance 1cm
5ml LA to block Deep peroneal nerve
Superficial Peroneal
Withdraw needle to skin, re-direct towards lat malleolus
Subcutaneous deposit 5ml LA along line to block Superficial peroneal nerve
Posterior to lateral malleolus: Sural nerve
Insert needle along line between lat malleolus & Achilles' tendon
Subcutaneous deposit 5ml LA along line

66. Knee PROCEDURE SUGGESTED PNB TKA LP Fem 3-in-1
Sciatic (Mansour / Labat)
ACL
Sciatic (Mansour / Labat / Raj)
AKA
BKA
IM Nail
Knee

67. Hip PROCEDURE SUGGESTED PNB THA LP Fem 3-in-1 Fracture NOF
LP Fem 3-in-1 Fascia iliaca
IM Nail
Sciatic (Mansour / Labat / Anterior)
Hip

68. Plan B GA
Total LA amount-rescue infiltration

69. Dr Wakelings Rule of Regional Anaesthesia
It doesn’t work

70. TIME TO COOK
“Failed” block often ends up with excellent post op analgesia
Technique
Blockade
Mean (mins)
Range
Labat
Sensory 9
3 - 20
Motor 16
3 - 75
Subgluteus 8
1 - 25 14

73. Contraindication to RA
Absolute contra-indications:
Patient refusal
Infection at proposed block site
Overt septicemia
Significant coagulopathy
LA allergy

74. Complications
Prospective survey > cases of regional anesthesia. Overall neurological complication rate 0.03% Estimated risk of complication
Per cases
PNB
Spinal
Neuropathy
1.9
5.9
Death
0.5
1.5

75. THE END