This document discusses the anatomy and techniques related to central neuroaxial blockade. It covers the anatomy of the vertebral column, spinal cord, meninges, epidural space and its contents. It describes the physiological effects of spinal and epidural anesthesia. Some key points include: - Spinal anesthesia involves injection of local anesthetic into the subarachnoid space - Factors like drug used, volume, patient position can affect the level and duration of the block - Potential complications include hypotension, nausea, urinary retention - Epidural anesthesia is commonly used for postoperative pain control and labor pain.

1. SMG® 1
Central Neuroaxial Blockade
Dr Sachin Gaikwad

2. SMG® 2
Applied Anatomy
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Vertebral column consist of 33 vertebra
●
7 cervical , 12 thoracic , 5 lumbar , 5 fused
sacral and 4 fused coccygeal vertebra.

3. SMG® 3

4. SMG® 4
Vertebral column curves
4 curves
● Kypotic curves-
Thoracic and
sacral
● Lordotic curves-
lumbar and cervical

5. SMG® 5
Vertebral canal boundaries

6. SMG® 6

7. SMG® 7
Surface landmarks

8. SMG® 8
Epidural Space ( Extradural or Peridural
space)
●
It lies outside duramater.
●
Extends from foramen magnum to sacral hiatus.
●
It is triangular in shape with apex dorsomedial

9. SMG® 9
Contents of epidural space
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Anterior and posterior nerve root
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Epidural veins
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Spinal arteries
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Lymphatics
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Fat

10. SMG® 10
Epidural Veins
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Venous plexus of Batson
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Valveless veins connecting pelvic veins to cranial veins
directly
●
Accidental injection of air or LA can directly ascend to
cranium
●
These veins directly drains into IVC so whenever there
is obstruction to vena caval flow as in pregnancy
,abdominal tumours these veins are engorged reducing
the size of epidural space and less dose is required.

11. SMG® 11
Anatomy of Spinal Cord
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Extend from medulla oblongata to lower border of L1 in adults.
●
In infants and neonates it ends at the lower border of L3
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Adult level is achieved by 2 yr of age
●
So in infancy spinal anaesthesia is given at L4-L5 space.
●
Below L1 vertebral canal is occupied by lumbar,sacral and
coccygeal nerve roots in oblique and downward direction
forming cauda equina (horse tail).
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Divides into 31 pairs of spinal nerves
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8 cervical ,12 thoracic,5 lumbar,5 sacral and 1 coccygeal.
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Each spinal nerve has anterior and posterior root.

12. SMG® 12
Important dermatological segment
levels
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T4 – Nipples
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T6 - Xiphisternum
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T10 – Umbilicus
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L1- Inguinal ligament
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S1 to S4 - Perineum

13. SMG® 13
Segmental levels of Spinal reflexes
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T7,8 – Epigastric
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T9-T12- Abdominal
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L1,2- cremasteric
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L2,3,4- Knee jerk
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S1,2 – Ankle jerk
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S4,5- Anal sphincter
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S1,2- Planter

14. SMG® 14
Meninges
●
Inside to outside by piamater ,arachnoid and
duramater.
●
Duramater extends up to S2 in adults and up to
S4 in infants while piamater extends as filum
terminale up to coccyx.

15. SMG® 15
Cerebrospinal Fluid
●
CSF is present between pia and arachnoid mater ie subarachnoid
space that is why spinal anaesthesia is also called as subarachnoid
block.
●
Secreted by choroid plexus of 3rd
, 4th
and lateral ventricles and is
absorbed into venous sinuses via arachnoid villi
●
500 ml in 24 hours.
●
Volume of CSF at one time is 140ml , half of which is present in
cramium and half in spinal canal.
●
Sp.gravity = 1.003 to 1.009 ( avg 1.004)
●
.pH – 7.35
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CSF pressure – 100- 150 mm of H2O

16. SMG® 16
Advantage over GA
●
Cheap
●
Less risk of pulmonary aspiration
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Respiratory complications are obviated like bronco-spasm,post
op atelectasis
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Systemic effect of GA drugs not seen
●
Consequences failed intubation avoided
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Disturbances of body chemistry are avoided
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Bleeding is less because of low mean arterial pressure
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Decreased incidence of thromboembolism due to increased
vascularity of lower limbs.

17. SMG® 17
Physiological alteration of central
Neuroaxial blocks
Cardiovascular System
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Most prominent effect is hypo tension
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Venodilation because of sympathetic block
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Dilatation of post arteriolar capillaries
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Decreased cardiac output
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Decreased venous return
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Bradycardia
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Decreased catecholamine release due paralysis of nerve supply of
adrenal glands
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Supine hypotension syndrome- compression of IVC and aorta by
pregnant uterus,abdominal tumours.

18. SMG® 18
Bradycardia is due to
●
Bainbridge reflex – decreased arterial
pressure because of decreased venous return.
●
Direct inhibition of cardioacceletor fibres T1 to
T4.

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Nervous system
●
Sequence of blockage of nerve fibres
Autonomic-> Sensory -> Motor
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Recovery in reverse order
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Autonomic level is 2 segment higher than sensory
which is 2 segment higher than motor
This is called as differential blockage .
●
Autonomic level is tested by temp.,sensory by pin
prick and motor by toe movement.

20. SMG® 20
Respiratory system
●
Tidal volume , minute volume, arterial oxygen
tension are well maintained
●
Apnea may occur due to severe hypotension
causing medullary ischemia. Other causes are
High spinal (C3,C4,C5),Total spinal,Accidental
injection of LA in systemic circulation

21. SMG® 21
Gastrointestinal system
●
Contracted gut with relaxed sphincters due to
sympathetic block with parasympathetic over
activity
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Nausea
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Vomiting
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Liver – no impairment

22. SMG® 22
Excretory system and reproductive
system
●
Renal function not impaired unless MAP falls
below critical pressure of Kidney for auto-
regulation ( 55 mm of Hg)
●
Urinary retention due blockage of sacral
parasympathetic fibres (S2,3,4)
●
Engorgement of penis

23. SMG® 23
Endocrine system
●
Stress response to surgery is inhibited
●
Hypoglycaemia due to augmented response to
insulin
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Increased in ADH is supressed during surgery

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Thermoregulation
●
Vasodilatation causes hit loss which is
compensated by vasoconstriction above the
block and shivering

25. SMG® 25
Spinal Anaesthesia
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Subarachnoid block
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Intrathecal block

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Indications
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Orthopaedic surgery of lower limb and pelvis
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General surgery – all pelvic and perineal surgeries ,
hernia,hydrocele, appendix,testicular surgeries.
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Gynaecological and obs –
hysterectomy,myomectomy, C section,
tubectomy,tuboplasty,ovarian surgeries,cervical
surgeries
●
Urology- bladder and ureteric stone,prostate

27. SMG® 27
Procedure
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Position – lateral ,sitting, prone
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Approach – mid-line, paramedian, lumbosacral
(Taylor)
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Under AAP spinal needle is inserted in Sub
arachnoid space and after confirmation of free
and clear flow CSF LA is injected.
●
LA mainly act on spinal nerves and dorsal
ganglion.

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31. SMG® 31

32. In the horizontal supine position ,hyperbaric local anesthetic
solutions injected at the height of the lumbar lordosis (circle) flow
down the lumbar lordosis to pool in the sacrum and in the thoracic
kyphosis. Pooling in the thoracic kyphosis is thought to explain the
fact that hyperbaric solutions produce blocks with an average
height of T4-6.

33. SMG® 33
Drugs used for SA
1) Xylocain – 5% made hyperbaric by addition of 7.5%
dextrose.
2)Bupivacaine – 0.5% made hyperbaric by addition of
8% dextrose.
3)Tetracaine - 1% made hyperbaric by addition of 5%
dextrose.
4)Procaine - 10% made hyperbaric by addition of 5 %
dextrose.
5)Opioid-

34. SMG® 34
Drug Concentration Specific gravity
Lignocaine 5% in 7.5% in D 1.0333
Bupivacaine o.5% in 8% in D 1.0273
Tetracaine 1% in 5% in D 1.0203
Procaine 10 % in 5% in D 1.0203

35. SMG® 35
Spinal Needles
●
Dura cutting and dura separating
●

36. SMG® 36
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Dura cutting- Quincke- bobcock ,Greene
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Dura separating – these are pencil tip
point end. Whitre ,sporte and pitkin
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Incident of Post spinal puncture headache
and cost

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38. SMG® 38
Factors affecting the height of the block
1)Volume of drug- greater volume higher level
2) Baricity – it is the ration of sp. Gravity of an agent at body temperature to sp. Gravity of
CSF at same temperature.
Hyperbaric technique- common ,outcome is govern by position of patient
Hypobaric technique- less common,agent used is tetracaine 0.3% which is made
hypobaric by addition of sterile water. Useful in colorectal surgery and applied in prone
position where head is lower than buttocks ( Jack Knife position.
Isobaric technique- commonly used bupivacaine 0.5% plain.settled at the same level of
injection
3) Position of patient- very important factor eg if Trendelenburg position is given then same
volume will produce a much higher block
4)Intra Abdominal pressure – in ascities,pregnancy,abdo tumours decreases volume of
subdural space and increases CSF pressure producing higher blocks

39. SMG® 39
5)Spinal curvature- by affeccting contour of sub
arachnoid space can affect the level of block
4) Patient factors –
Age -in old age due to reduced spinal and epidural
space chances of higher block
Obesity – affects block due to increase in intra abdo
pressure
Height- taller patient have long spine so require
more drug and vice versa.

40. SMG® 40
Factores affecting duration of block
1.Dose
2.Increased concentration of agent
3.Pharmacological profile of drug like protien
binding ,metabolism
4.Type of drug used .Bupivacaine vs lignocaine
5.Addetives- Adrenaline,opiod.

41. SMG® 41
Complications of SAB

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1 Hypotension
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Most common complication
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Mild hypotenison do occure in all patients but in 1/3rd patient BP
may fall < 90 systolic
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Treatment-
I. Prophylactic- preloading with 1 to 1.5 L of crystalloid
II.Curative-
(a)Head low position to increase venous return up to 15 %
(b)Fluids- colloids are better than crystalloids
(c)Vasopressors – ephedrine,mephenteramine,methoxamine( sympatho memetic
actin
(d)I notropes- Dopamine ,dobutamine improve cardiac output
(e)Oxygen inhalation – prevent hypoxia of brain

43. SMG® 43
2 Bradycardia
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Treatment – IV atropine

44. SMG® 44
3. Respiratory paralysis
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Apnea – it usually because of hypotension so
treat hypotension .if high or total spinal then
give IPPV
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Slight respiratory difficulty is treated with
oxygenation and reassurance

45. SMG® 45
4. Nausea and vomitting
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Because of central hypoxia due to hypotension
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Treatment – treat hypotension,oxygenation,
antiemetics

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5. Difficulty in phonation
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Due to high spinal block involving cervical level
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Treatment – IPPV

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6.Restlessness,anxiety,apprehension
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Ruleout hypoxia then reassure and sedate

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7 LA toxicity
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Due to intra vascular injection
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Treat symptomatically

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8.Cardiac arrest
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May be due to total / High spinal,severe
hypotension,LA toxicity/ anaphylaxis
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Start CPCR

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9 .High spinal /Total spinal
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If involving lower inter costal then patient will
complain of dysnea, give oxygenation and
reassurance
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If high to block cardioaccelerator fibres then
sever bradycardia & hypotension
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If too high to involve cervical fiber then IPPV
may required

51. SMG® 51
10. Miscellaneous
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Pain during injection
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Bloody tap
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Broken needle

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Post OP complications
1) Urinary retention – due to blockage of S2,S3 S4
.Catheterisation may require
2)Post spinal headache-Post dural puncture headache
3)Meningitis- chemical ,infective
4)Cauda equina syndrome- due direct injury to nerve fibres by
needle or LA agent. Mostly seen with continuous spinal with
small bore catheter.
5)Paraplegia- epidural hematoma, abscess
6)Spinal cord ischemia -severe prolong hypotension, use of
vasocontrictors

53. SMG® 53
7)Local toxicity of LA like chloro procaine can
injure spinal cord and can cause paraplegia
8)Anterior spinal artery syndrome- Epidural
haematoma,abscess, epidermoid tumour can
lead to compression of anterior spinal artery
causing anterior spinal artery syndrome
manifested by motor deficit without involving
posterior column.

54. SMG® 54
Contraindications
Absolute
1) Raised intra cranial pressure
2)Patient refusal
3)Severe hypo volumic shock
4)Patient on anti coagulant
5)Thrombolytic / fibrinolytic therapy
6)Bleeding disorders / coagulopathies
7)Septicemia and bacteremia
8)Infection at local site

55. SMG® 55
Relative
1) Fixed cardiac output lesions( AS , MS)
2)Mild to moderate hypo volemia or hypotension
3)Uncontrolled hyper tension
4) H/o recent MI,severe ischemic heart disease
5)Heart blocks and patient on beta blockers
6)Patients on aspirin
7)Patients on low dose heparin
8)Spinal deformity
9)Previous spinal surgery

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10) History of headache
2) GIT perforation
3)Neuropathies
4)CNS disorders

57. SMG® 57
Spinal anaesthesia in children
●
Should be given in low space L4-L5
●
Preloading is not require as children less than 8
years are virtually free of heamodynamic side
effects
●
Use of narcotics is contra indicated
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Chances of systemic toxicity is high

58. SMG® 58
EPIDURAL ANAESTHESIA

59. SMG® 59
Indications
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All surgeries under spinal block can be performed
under epidural block.
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Mainly used for controlling post op pain
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Painless labour
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To control chronic pain
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To control pain due to cancer
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Acute occlusive vascular conditions
●
Blood patch for post spinal headache

60. SMG® 60
Epidural needle
●
Most common is Tuophy’s needle
●
It is blunt bevel with curve of 15 to 30 degree at
tip.
This curve is called as Huber Tip.
●
Weiss – is winged
●
Crawford – straight blunt bevel with no curve

61. SMG® 61

62. SMG® 62
Technique
Like in spinal it can be given in sitting or lateral.
Usually epidural space is encountered 4 to 5
cm from skin and it has negative pressure .

63. SMG® 63
Methods to locate epidural space
●
Loss of resistance technique – after piercing
ligamentum flavum there is loss of resistance.
●
Hanging drop technique ( Guttierrez’s sign)-
drop of saline in hub sucked in due to negative
pressure .
●
MacIntosh extradural space indicator
●
Movement of bubble on Odom’s indicator

64. SMG® 64
Confirmation
●
Test dose of 1ml of hyperbaric lignocaine with
adrenaline is given if in 5 min there is no
evidence of either spinal block or intravascular
injection further dose can be given

65. SMG® 65
Then
epidural catheter is passed through the needle
and 3 to 4 cm of catheter should be in epidural
space. Microfilter is attached to prevent
contamination
●
Onset of action – 15 to 20 min
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Successful block is assessed by absence of
knee jerk and pain by pin prick

66. SMG® 66
Site of action of drug
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Mainly Anterior and posterior nerve roots
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Mixed spinal nerve
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Drug diffuses through dura and arachnoid and
inhibits descending pathways in spinal cord

67. SMG® 67
Drugs used
NO Drugs concentration
1 Lignocaine 1-2 %
2 Bupivacaine 0.25- 0.5 %
3 Chloroprocaine 2-3 %
4 Mepivacaine 1-2 %
5 Prilocaine 2-3 %
LA

68. SMG® 68
●
Opioids
Morphine- 4 to 6 mg
Fentanyl- 100 mcg ( diluted in 10ml NS) onset
within 10 min last for 2 to 3 hours
●
Fentanyl + bupivacaine – for post op analgesia
and painless labour.

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Advantage of opioid
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Only sensory block
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Long lasting effect
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No sympathetic block

70. SMG® 70
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Disadvantage
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Respiratory depression
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Urinary retention
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Pruritus
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Nausea and vomiting
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Sedation

71. SMG® 71
Factors affecting level
●
Volume of drug
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Age
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Gravity
●
Intra abdominal tumours, pregnancy
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Speed of injection
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Level of injection
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Length of vertebral column
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Conc of LA

72. SMG® 72
Complications
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Inadequate block
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Hypotension
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Apnea
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Total Spinal
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Dural puncture
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Subdural block
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Intravascular injection
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LA toxicity
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Horners syndrome
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Epidural heamatoma
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Epidural abscess
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Anterior spinal artery syndrome
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Direct injury to cord
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Brocken catheter
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Meningitis

73. SMG® 73
Advantage of epidural anaesthesia
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Less hypotension
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No post spinal headache
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Level of block can be changed
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Any duration of surgery can be performed

74. SMG® 74
Comparison
Spinal Epidural
1 cost Cheaper Expensive
2 onset of action Early Delayed
3 Technically Easier Difficult
4 Duration of action Less Prolonged
5 Quality of block Excellent May be patchy
6 Change of level Not possible after fixation Can be possible
7 Block failure rate Less High
8 Post dural puncture
headache
Seen Not seen
9 epidural Heamatoma less High incidence
10 Total spinal rare High
11 intravascular inj rare High chance
12 drug toxicity less high
13 Catheter complications Not seen present

75. SMG® 75
Thank you