REGIONAL ANAESTESIA

DR I NoethDepartment AnaesthesiologySteve Biko Academic Hospital

REGIONAL ANAESTESIAKEYPOINTS:Spinal, epidural and caudal blocks are known as the neuraxial blocksPrincipal site of action of neuraxial blocks is the spinal nerve roots Sensory, motor and to some degree sympathetic block is achieved with neuraxial techniquesLevel is below L1/2 in adults and L3 in childrenNb definite contra- indications to neuraxial techniquesANATOMY

AnatomySpine is composed of vertebral bones and cartilaginous intervertebral discs7cervical, 12 thoracic, 5 lumbar vertebraeThe 5 sacral vertebrae is fused and there is small rudimentary coccygeal vertebraVertebral structure: body anteriorly, connected via 2 pedicles to transverse processes that in turn is connected posteriorly to the spinous process via 2 lamina. Each vertebral has 4 small synovial joints connecting it to the vertebra above and below it allowing movement of the spinal columnANATOMY

ANATOMYLamina of S5 and S4 normally doesnt fuse, leaving small caudal opening to the spinal canal called the sacral meatusEach vertebral body is separated by an intervertebral discSpinal column has double-C shape: convex anteriorly in the cervical and lumbar areasLigament provide (together with muscles) structural support and help maintain unique shape.Vertebral body and discs are connected and supported by ant and post longitudinal ligaments and dorsally the ligamentum flavum, interspinous and supraspinous ligaments provide additional stability

ANATOMY

ANATOMY

ANATOMYSpinal canal contains spinal cord, its coverings (meninges) fatty tissue and an venous plexusMeninges: 3 layers: pia mater closely adhered to spinal cord arachnoid losely adherent to thicker and denser dural materCSF containe between arachnoid and pia materSpinal subdural space potential space between dura and arachnoidEpidural space between dura mater and ligamentum flavum

ANATOMYSpinal cord extends from the foramem magnum to L1 in adults and L3 in childrenAnt and post nerve roots join each other forming spinal nerves exiting through intervertebral foramina on each levelFrom L1 down lower spinal nerves travel some distance before exiting through intervertebral foramina, forming the cauda equinaSafe level for neuraxial techniques below L1 in adult and L3 in children to avoid direct cord damage ANATOMY

Mechanism of action Principle site of action of neuraxial techniques is nerve rootBlocking post nerve roots interrupts somatic and visceral sensationBlocking anterior nerve root prevent motor and autonomic outflowDifferential blockade: sympathetic blockade 2 levels above sensory block which in turn is 2 levels above motor blockAUTONOMIC BLOCKSympathetic plexus from T1 to L1Blocking anything from T5 downwards result in decreased vasomotor tone, pooling of blood in lower limbs and decrease in blood pressure... Normally with compensatory tachycardiaBlocking T1-T4 blocks cardiac accelaratory fibres leading to bradycardia and decreased cardiac contractilityDeleterious CVS effects must be countered by volume loading pt with 10-20ml/kg IVI fluid and early administration of vasopressorsBradycardia should be treated with atropineAUTONOMIC BLOCKGIT- Sympathetic block leads to vagal predominance leading to small contracted gut with active peristalsis. Hepatic bloodflow reduction mirrors drop in BPUrinary Tract lumbar and sacral level blocks block both sympathetic and parasympathetic bladder control leading to urinary retention till block wears offNeuraxial techniques partially or totally block the neuro-endocrine stress response induced by surgeryCONTRAINDICATIONS TO NEURAXIAL TECHNIQUESAbsolute:Infection at site of injectionPatient refusalCoagulopathy or bleeding diathesisSevere mitral or aortic stenosisSevere hypovolemiaIncreased intracranial pressureCONTRAINDICATIONS contdRELATIVESepsisPreexisting neurological deficitsSevere spinal deformityUncooperative patientStenotic valve lesionsCONTRAINDICATIONS contdCONTROVERSIALPrior back surgery at site of injectionInability to communicate with patientComplicated surgery major bloodloss expectedPatients with coagulopathy Excepted preoperative valuesINR - < 1,5 ( 80 000Bleeding time - 12 ( > 15 in experienced hands)Strategies for discontinuation of anticoagulation in peri-op periodMinimum delay pre-op or prior to placement or removal of epidural catheterMimimum delay post op or after removal of neuraxial cathetersUFH4h1hLMWH prophylaxis12h4hLMWH treatment24h6-8hAspirin 0h0hWarfarin3-5daysImmediatelyBut controversialFondaparinux36 hours but epidural catheter not recommendedEpidural not recommendedDosing not recommended ropivacaineOther regional techniquesA nerve can be block anywhere along its courseRegional techniques avoid some of the complications associated with neuraxial techniquesContra- indications: Uncooperative patientBleeding diathesisInfectionPeripheral neuropathyRegional techniques

Regional techniques

Regional techniquesNormally done with nerve stimulator to identify correct nerves to be blocked

Regional techniques: Biers blockIntravenous regional techniqueNormally of the forearmShort procedures (45-60min)Jelco/ IV access established on dorsum of handDouble pneumatic tourniquet is placed on upper armThe extremity is elevated and exsanguinated by tightly wrapped Eschmark bandages Upper tourniquet is inflated0.5% lignocaine injected 25ml for forearm, 50ml for whole armBiers BlockAnaesthesia normally established in 5-10minPt often complain of tourniquet pain after 20-30minWhen this occurs the lower tourniquet is inflated and the proximal one deflated.THE END