LOCAL ANESTHESIA: METHODS & THE MOST OFTEN USED LOCAL ANESTHETICS.

Question 1

types

Answer 1

Topical (surface)

Local infiltration

field block

Peripheral nerve block

Spinal / epidural.

Question 2

topical

Answer 2

direct application on skin, mucous membranes of the nose, mouth, throat, esophagus, GUT

eg lidocaine

Question 3

local infiltration

Answer 3

injection of anesthetics into various tissues without taking into consideration the network of cutaneous nerves

skin and deeper structures like intra-abdominal organs

increases time together with epinephrine

lidocaine and procaine

Question 4

field block

Answer 4

injection into area distal to the injection

scalp, anterior abdominal wall, lower extremities

Question 5

nerve block

Answer 5

injected into peripheral nerves or plexuses

injected around nerves and never directly into them

Question 6

spinal anesthesia

Answer 6

injected into csf
L2-L3
lidocaine

Question 7

epidural

Answer 7

injected into epidural space
continuous infusion or bolus
site of action is spinal nerve roots

Question 8

used in combination with

Answer 8

• May be combined with general anesthesia (intercostal nerve blocks after abdominal operation with Bupivacaine / Levobupivacaine).
• ± I.V sedation e.g. BZD (relaxation, anxiolytics, amnesia).
• Wound infiltration.

Question 9

choice of technique: local anesthesia

Answer 9

for calm & rational patients:
▪ Minor operation / minor but painful procedures.
▪ Unavailability of GA expertise.
▪ Patients are unfit for GA.
▪ Use of combined LA & vasoconstrictor for bloodless field & extended time of action.
▪ !! never in peripheries (end arteries = necrosis )!!

Question 10

choice of technique: Regional nerve block

Answer 10

▪ Minor surgery with wide field (femoral nerve block for varicose veins / pudendal block for forceps delivery).
▪ When it’s Undesirable to inject LA into operation site (abscess).
▪ To avoid tissue distortion from local infiltrate.
▪ Short lived & wide field ambulatory anesthesia for reduction of forearm fractures / hand surgery (Bier´s block I.V regional anesthesia).

Question 11

choice of technique: Epidural & spinal

Answer 11

▪ Lower limb surgery (amputation).
▪ Lower abdomen, groin, pelvic & perineal surgery (Normal Delivery, C section, inguinal hernia, prostatectomy).
▪ Epidural: ↓ motor block, onset 30-50 min, 3-5 hours duration (may have complications of dural puncture).
▪ Spinal: L3-L4, onset 2-3 min, 2-3 hours duration, common post dural puncture headache.

Question 12

choice of technique: I.V sedation / analgesia alone:

Answer 12

▪ Short – lived uncomfortable procedures (endoscopy).

Question 13

choice of technique: I.V sedation + LA

Answer 13

▪ Potentially unpleasant procedure despite LA (wisdom tooth extraction).

Question 14

choice of technique: regional analgesia + light GA

Answer 14

▪ Caudal epidural + GA for surgery in perianal area (transurethral prostatectomy, circumcision, peri / post operative analgesia).

Question 15

cocaine

Answer 15

▪ Not much used in medicine, vasoconstrictor properties (tampon - post nasal septum surgery).

Question 16

lidocaine

Answer 16

▪ Standard LA.
▪ Slow onset & slightly unpredictable effect.
▪ Without adrenaline: duration < 1h.
▪ Very rare allergic reaction.
▪ Wide range of concentrations available.
▪ Max dose 4mg/kg (with adrenaline up to 7mg/kg).

Question 17

Bupivacaine (Marcaine):

Answer 17

▪ ↑ Lipid solubility & protein binding → ↑duration.
▪ Low placental transfer.
▪ More sensory than motor block → Obstetrics!
▪ Slower onset.
▪ Max dose 2mg/kg.
▪ Addition of adrenalin does not increase safe dose.

Question 18

prilocaine

Answer 18

▪ Lowest toxicity potential – rapidly metabolized → safest when larger volume is required.
▪ Max dose 7mg/kg (vasoconstrictor - adrenaline not necessary).
▪ Rarely methemoglobinemia & hypoxia in large amounts.

Question 19

techniques

Answer 19

simple skin lesion excision ?????

ring block for digits:
1% Lidocaine, slowly infiltrate 2,5ml into each medial, dorsal, lateral & ventral side.

Question 20

advantages

Answer 20

1. Maintain airway.
2. ↓ Stress.
3. Post-operative analgesia.
4. ↓ Confusion.
5. Peristalsis not affected.
6. Thrombo Embolism prophylaxis.