Local Blocks Flashcards
MOA for local anaesthetics?
- Reversible block of voltage gated Na+
channels - No membrane depolarisation
- Sensory & Motor blockade
What different properties of Locals?
- Dissociation constant (pKA) -> Determines onset
- Lipid solubility determines potency (more lipid soluble more potent)
- Protein Binding (duration)
WHy do we use loco-regional anaesthesia?
- Reduced GA dose (also reduce AEs & quicker recovery)
- Improved peri-operative analgesia -> preemtive & multimodal ; prevention of central sensitization & chronic pain
COMPARE different locals
What different adjuncts can we use ?
- Adrenaline (vasoconstriction)
- ALpha2 (vasoC & more analgesia)
- Opioids (enhanced & prolonged analgesia
- Steroids (epidural)
- NaHCO2 (sodium bicarb) -> changes pH therefore onset/ duration
- Dexamethasone -> anti-inf
What adverse effects seen with increasing doses of lidocaine?
Suppotive tx for toxicity?
Intubation, 02
therapy, ventilation, benzodiazepines, propofol….
CPR (adrenaline, defibrillation, amiodarone…)
20% Lipid emulsion (intralipid)
T/F with bupivicaine cardiac & CNS signs with be seen at same time ?
True
What other adverse effects might we see?
- Nerve & local tissue injury
- Local haemorrhage
- Infections
- Allergic reactions
- Chondrotoxicity
How can we avoid these?
- Calculate the local anaesthetic volume before, staying below toxic dose!
- If multiple local anaesthetic used: keep individual dose below toxic dose
- Aspirate before injection, confirm absence of blood
- Aseptic techniques
- Beware of coagulopathies
What different ways can we PERFORM a loco-regional block?
- ANATOMICAL LANDMARKS (“BLIND APPROACH”)
- ELECTRICAL NERVE STIMULATION
- Insulated needles
- Peripheral nerve stimulator
- ULTRASOUND GUIDED
- Direct visualisation
Indications for infra-orbital or rostral maxillary blocks?
- Nose
- Upper lip
- Gengiva & teeth up to 2nd premolar
Landmarks for infra-orbital or rostral maxillary ?
- Infraorbital foramen
- 3
rd premolar tooth (maxilla)
Indications for Caudal (maxillary) block?
- Nose
- Upper lip
- Hard/soft palate
- Upper dental arch
- Maxilla
What different approaches & respective landmarks of maxillary nerve blocks?
Mental N block Indications & landmarks?
INDICATIONS: bone, teeth?, Lower lip/chin rostral to the block
LANDMARKS: Middle mental foramen (ventral to 2nd premolar)
Indications for Mandibular N Block (inferior alveolar) ?
bone, teeth, intra-oral tissues from the molars to the mandibular symphysis
Landmarks for mandibular block?
Mandibular foramen
(medial side of mandible)
What should we be careful about with mandibular N Block?
: risk of lingual nerve desensitization & self-trauma, do NOT block bilaterally (or use lido)
Indications for greater auricular & auricolo-temporal N.block?
Procedures of ear canal, pinna
Acute & chronic ear pain
Landmarks for GREATER AURICULAR & AURICOLO-TEMPORAL N. BLOCKS
- Zygomatic arch
- Vertical ear canal
- Vertebral Atlas transverse processes (wings)
Risk with Auricular block?
Risk of Facial nerve paralysis: EYE LUBE
What are all the thoracic limb blocks?
Cervical paravertebral nerve blck - blocks what?
From shoulder joint to entire limb: (C5),C6, C7, C8 & T1,(T2) nerves
What does brachial plexus block block?
from distal humerus/elbow (C6, C7,C8, T1)
Potential complications of Cervical paravertebral nerve block & brachial plexus block?
- Pneumothorax
- Phrenic nerve blockade (C5, C6, C7)
- Haemorrhage
What is RUMM?
(RADIAL-ULNAR-MEDIAN & MUSCULOCUTANEOUS N. BLOCK
Area blocked with RUMM?
- Area blocked: distal thoracic limb (carpus, manus & digits)
- Blind, nerve stim, US guided
How to block thorax?
Intercostal nerve block
Indications for Intercostal nerve block?
Thoracotomy
Rib fractures
Chest drainage insertion
Additional potential complications of intercostal nerve block?
- Pneumothorax
- Haemothorax
- Lung damage
What gets blocked by intercostal nerve block?
Block site + 3 spaces cranially & caudally
Describe Epidural block?
- Administration of drugs in the epidural space (space between vertebral canal and dura mater) * Usually at lumbo-sacral (L7-S1) or sacro-coccygeal space
Indications for epidural?
pelvis, pelvic limbs, tail, perineal and abdominal procedures, (thorax)
How to check epidural needle in right place?
- “Pop sensation”
- Loss of resistance
- Hanging drop * Running drip (Baraka method)
What can we use in epidural?
- Lidocaine/Bupivacaine/ Ropivacaine* +/- Preservative free morphine
Epidural contraindications?
- Infection/inflammation/ neoplasia @ injection site
- Coagulation disorders
- Hypotension/Hypovolemia (sepsis…) * Pre-existing neurological deficits
- Anatomical abnormalities? (RTA) * Obesity?
Adverse events of epidural?
- Motor blockade: pelvic limb ataxia * Vasodilation/Hypotension
- Respiratory depression
- Nerve damage
- Lack of hair growth * Pruritus (opioids) * Urinary retention (especially with
opioids)
What are the Hindlimb blocks?
Femoral nerve block?
Blind?, nerve stimulator, US guided
* Contraction quadriceps femoris
* Extension of stifle
Femoral N Block approach?
INGUINAL -> blind, nerve stim ,Us guided
When to use Femoral N Block? (what does it block)
- Contraction quadriceps femoris
- Extension of stifle
- Stifle not completely blocked (OBTURATOR n.)?
Landmarks for Sciatic B Block?
- Greater trochanter of femur * Ischiatic tuberosity
What does sciatic N block stop?
extension/flexion of the tarsus
When to use epidural vs unilateral block (femoral & sciatic ) ?
- Patient ability to walk
- Post-op care (Is the patient aggressive?, size of patient) * Does your patient have other comorbidities (i.e. osteoarthritis, patella luxation, recent surgery
on other leg) ? - Anaesthetist/surgeon Preference
- Schedule 3 procedure ( Femoral & Sciatic n. block)
Indications for intra-peritoneal lavage?
abdominal surgeries (e.g. ovario-hysterectomies)
How to do intra-peritoneal lavage ?
- Local anaesthetic instilled in the peritoneal cavity after incision or before closure of
the incision
Bupivacaine/ropivacaine
Describe an infiltration (incisional) block?
- Instillation of local anaesthetic around or directly into the incision or wound ‘field’ * Simple, safe, and inexpensive
