3. SURFACE ANAESTHESIA (TOPICAL)
● LA is applied on the mucous membrane of
the nose, mouth, eyes, throat, upper
respiratory tract, oesophagus, urethra,
ulcers, burns, fissures, etc.
● Surface anaesthetics are available as
solution, ointment, gel, cream, spray,
lozenges, etc.
● On addition of adrenaline doesn't prolong
the duration of surface anaesthesia because
of poor penetration.
● Drugs are Lignocaine (2 – 10%), Tetracaine
(2%) and Benzocaine.
● It is used to anaesthetize mucous membrane
of the eyes, nose, mouth, cornea, urinary
and upper respiratory tract, fissures, ulcers,
etc.
4. INFILTRATION ANAESTHESIA
● LA is injected directly into tissues to be operated-it blocks the sensory
nerve endings.
● LA is infiltrated into the skin, subcutaneous tissue or deeper structures,
including intra-abdominal organs.
● Addition of adrenaline to LA (1:200,000-250,000) prolongs the duration
of anaesthesia.
● Drugs are Lignocaine (0.5-1%), Procaine (0.5-1%), Bupivacaine
(0.125-0.25%) and Ropivacaine.
● It can be used for drainage of an abscess, excision of small swelling,
suturing of cut wounds episiotomy, etc.
NOTE:
Infiltration anaesthesia is
contraindicated, if there is
local infection and clotting
disorders.
5. CONDUCTION BLOCK ANAESTHESIA
The LA is injected around the neve trunks so that the area distal to
injection is anaesthetised and paralysed.
■ FIELD BLOCK
● LA is injected subcutaneously in a manner that
all the nerves coming to a particular field are
blocked.
● This principle is used in case of minor
procedures of scalp, anterior abdominal wall,
upper and lower extremities in which a smaller
dose produces large area of anaesthesia.
● Bupivacaine may be used for longer lasting
anaesthesia.
6. ■ NERVE BLOCK
● LA is injected very close to or around the
peripheral nerve or nerve plexuses.
● It produces larger areas of anaesthesia than
field block.
● Frequently performed nerve blocks are
lingual, intercostal, ulnar, sciatic, femoral,
branchial plexus, trigeminal, facial, phrenic,
etc.-used for tooth extraction, operation on
eye, limbs, abdominal wall, fracture setting,
trauma to ribs, neuralgia, persistent hiccup,
etc.
● Lidocaine is used in this technique as it has
intermediate duration of action.
7. SPINAL ANAESTHESIA
● LA is injected into the subarachnoid space to
anaesthetize spinal roots.
● Spinal anaesthesia is injected into the space between
L2-3 or L3-4 below the lower end of the spinal cord.
● Commonly used spinal LAs are Lignocaine, Tetracaine,
Bupivacaine, etc.
● Addition of adrenaline to spinal anaesthetic increases the
duration or intensity of block.
● Spinal anaesthesia can be used for surgical procedures
below the level of umbilicus, i.e. Lower limb surgery,
caesarean section, obstetric procedures, prostatectomy,
surgery on perineum, appendicectomy, etc.
8. EPIDURAL ANAESTHESIA
● LA is injected into epidural space where it acts
on spinal nerve roots.
● Lignocaine (2%) and Bupivacaine (0.5-0.75%)
are commonly used.
● Epidural anaesthesia is slower in onset than
spinal.
● It requires a much larger amount of drug.
● It is mainly used in Obstetric analgesic.
■ THORACIC
● Injection is made in the
midthoracic region.
● It is used generally for pain
relief following thoracic/
upper abdominal surgery.
9. ■ LUMBAR
● Relatively large volume of drug
is needed because epidural
space is wide.
● It produces anaesthesia of
lower abdomen.
■ CAUDAL
● Injection is given in the sacral
canal through the sacral hiatus.
● Produces anaesthesia of pelvic
and perineal region.
● Mostly used for vaginal
delivery, anorectal and
genitourinary operations.
● Lidocaine (1-2%) and
Bupivacaine (0.25-0.5%) are
popularly used.
10. BIER'S BLOCK
● LA is injected into the vein of
the limb whose blood flow is
occluded by a touniquet.
● It is mainly used in
anaesthetizing the upper limb.
● Lignocaine (0.5%) and
Prilocaine are commonly used.
NOTE:
● To anaesthetize
gastric mucosa-
Oxethazaine is used
in case of peptic
ulcer.
11. ADVANTAGES OF LOCAL ANAESTHESIA
● Safety (intraoperatively and postoperatively)
● Affordable.
● Ease of administration.
● Consciousness is not lost.
● The patient maintains his own airways.
● Aspiration of gastric contents unlikely.
● Reduction surgical stress.
● Recovery is smooth.
● Earlier discharge of outpatients.
● Postoperative analgesia.
12. CASE STUDY
A healthy full-term primigravida aged 26 years who has
gone into labour presents for delivery. There is no
c e p h a l o p e l v i c d i s p r o p o r t i o n o r a n y o t h e r
contraindication to normal delivery.
(a) Can some form of regional anaesthesia be used to
relieve her pain?
(b) If so, which type of regional anesthesia with which
drug would be most suitable for her?
13. CASE STUDY - Answer
(a) Labour pain as well as that due to stretching of the birth canal can
be largely relieved by spinal as well as epidural anaesthesia. It is
desirable, at the same time, not to produce motor block so that the
mother can actively participate in the process of labour. Since
motor fibres are less sensitive to local anaesthesia (LAs) than
sensory fibres, motor block of a lower level is usually produced
during spinal anaesthesia. Such separation is more pronounced
with epidural anaesthesia.
14. (b) Lidocaine and Bupivacaine are the two LAs commonly used for the
epidural anaesthesia. Out of these, bupivacaine is more suitable for this
purpose for the following reasons:
• It provides greater separation of sensory from motor block. Separation is
still larger when lower concentration (0.25% bupivacaine) is used.
• Because of higher lipid solubility, its tissue distribution is large and maternal
blood levels are lower. Less drugs likely to cross to the foetus, reducing
chances of neonatal depression.
It is longer acting.
Thus, epidural anaesthesia with 0.25% bupivacaine is most suitable for
this patient.
