Regional anaesthesia Flashcards
Neuraxial blockade placement - spinal v epidural
Spinal:
- below L1 (in adult, lower in child) to avoid spinal cord
- insert guide needle through skin
- advance thru SC tissue, supraspinous lig, interspinour lig
- “pop” on passing thru lig flavum, remove stylet and CSF returns
- apply syringe and aspirate, look for “swirl”
- administer medication
- position for gravity-dependent spread
Epidural:
- insert epidural needle through skin
- advance thru SC tissue, supraspinous lig, interspinour lig
- apply glass syringe with saline and bubble
- advance slowly and push gently until saline is easily injected
- advance catheter through needle
- attach syringe to catheter and aspirate
- “test dose” (epinephrine + LA)
- ?tachycardia =intravascular ?rapid numbness/weakness = intrathecal
- secure and administer
Neuraxial anaesthesia - indications, contraindications
Indications
- surgical anaesthesia maintianing consciousness e.g. obstetrics
- post-operative pain managements
- labour analgesia
- chronic pain management
Contraindications
- patient refusal/inability to cooperate
- raised ICP (herniation risk)
- site infection
- inadequate volume status
- coagulopathy (inherited or acquired)
Peripheral nerve blocks - location & indication
Cervical plexus - carotid endarterectomy
Stellate ganglion - complex regional pain syn (upper extremity)
Upper extremity
- brachial plexus - shoulder, arm, wrist, hand
- distal nerves (median, radial, ulnar) - forearm, hand
- digital nerves - fingers (no epunephrine!)
Intercostals - rib #, chest tubes
Coeliac plexus - chronic abdo pain e.g. pancreatic Ca
Lumbar plexus - lower extremity procedures
Lower extremity
- femoral, obturator, lateral femoral cutaneous - thigh and knee
- sciatic and saphenous - lower leg, calf, ankle, foot
- ankle - foot
Bier block
Intravenous regional anaesthesia
- large volume, low conc LA (e.g. 0.5% lidocaine WITHOUT epinephrine)
- exsanguinate extremity; apply tourniquet; infuse LA distally
- short procedures <1hr (due to tourniquet pain)
- after 20-30 minutes tourniquet can be safely removed without toxic effects
Neuraxial blocks - indications (2)
- where there are no contraindications
- where the advantages and disadvantages outweigh other techniques
Neuraxial blocks - contraindications
communication
- patient refusal
- unable to consent
patient factors
- coagulation disorder - inherited or acquired
– aim INR <1.5, PT <1.5, Platelets approx 100, last VTE >12h ago, aspirin is ok, NB can cause spinal haematoma
- fixed cardiac output disorder e.g. AS, HOCM – need good DBP for coronary flow and needs good preload
- increased ICP
unwell patient
- hypovolaemia due to decreased sympathetic tone
- sepsis - local infection or systemic (can cause epidural abscess)
Spinal - types of operation
- below L1/L2
- “single shot” to cover:
- lower abdomen, especially abdominal wall
- pelvis/pelvic organs
- perineum
- lower limbs
Spinal - advantages
- rapid onset
- dense (not patchy), reliable block
- can be awake/avoids GA
- pain-free recovery
- long-acting analgesia
- better surgical field/reduced blood loss
- decreased DVT risk
- decreased need for airway manipulation in risky patients
- avoids respiratory depression NB can cause intercostal paralysis causing subjective DIB
- decreased graft occlusion
Spinal/Epidural - disadvantages
- hypotension (sympathetic blockade causes peripheral vasodilation – may need vasoconstrictor cover)
- postdural puncture headache – <0.5% incidence with single pass using low-gauge atraumatic needle
- finite duration - 2-4hrs
- leg weakness, urinary retention, itching (edpecially with intrathecal opiois)
- high block (even lower BP, subjective DIB)
- shivering
- N/V (from low BP or opioids)
- nerve damage (mostly transient – <8/10K in spinal, <1/10K in epidural)
- paralysis 2ry to abscess/haematoma, <1/100K
- epidural abscess/haematoma
- total spinal – epidural medication moved into subarachnoid space
- meningitis
Disadvantages of epidural compared to spinal
- slow onset
- less dense/predictable block (therefore often combiend with GA)
- PDPH in 1% (70% if 16G needle breaches dura)
- leg weakness
- block may have lower limit
Causal epidurals
sacro-coccygeal membrane at base of coccyx
- no PDPH
- no subarachnois infiltration
Spinal - procedure
- LA infiltration
- introducer
- spinal needle insertion, remove obturator
- attach syringe, aspirate and observe swirl, inject LA
- remove both needle and introducer
Neuraxial block - complications
during - inability to site - pain - vasovagal after - hypotension - bradycardia (esp if high -- T2-T4) - high spinal - total spinal
Epidural - procedure
Does not breach dura so can be above L2
- insert epidural needle
- remove obturator
- attach saline syringe
- “loss of resistance” technique
- advance catheter
- withdraw needle, keeping catheter in place
Siphon test
Aspiration test
Test dose with bacterial filter
Neuraxial block complications
Trivial
- motor block
- urinary retention
- N/V
- itch
- shiver
- high block
- low BP (vasodilation, bradycardia)
- DIB (subjective)
- UL weakness
