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REGIONAL ANAESTESIA

REGIONAL ANAESTESIA. DR I Noeth Department Anaesthesiology Steve Biko Academic Hospital. KEYPOINTS:. Spinal, epidural and caudal blocks are known as the neuraxial blocks Principal site of action of neuraxial blocks is the spinal nerve roots

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REGIONAL ANAESTESIA

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  1. REGIONAL ANAESTESIA DR I Noeth Department Anaesthesiology Steve Biko Academic Hospital

  2. KEYPOINTS: • Spinal, epidural and caudal blocks are known as the neuraxial blocks • Principal site of action of neuraxial blocks is the spinal nerve roots • Sensory, motor and to some degree sympathetic block is achieved with neuraxial techniques • Level is below L1/2 in adults and L3 in children • Nb definite contra- indications to neuraxial techniques

  3. ANATOMY

  4. Anatomy • Spine is composed of vertebral bones and cartilaginous intervertebral discs • 7cervical, 12 thoracic, 5 lumbar vertebrae • The 5 sacral vertebrae is fused and there is small rudimentary coccygeal vertebra • Vertebral 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 column

  5. ANATOMY

  6. ANATOMY • Lamina of S5 and S4 normally doesn’t fuse, leaving small caudal opening to the spinal canal called the sacral meatus • Each vertebral body is separated by an intervertebral disc • Spinal column has double-C shape: convex anteriorly in the cervical and lumbar areas • Ligament 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 ligamentumflavum, interspinous and supraspinous ligaments provide additional stability

  7. ANATOMY

  8. ANATOMY

  9. ANATOMY • Spinal canal contains spinal cord, it’s coverings (meninges) fatty tissue and an venous plexus • Meninges: 3 layers: pia mater – closely adhered to spinal cord arachnoidlosely adherent to thicker and denser dural mater • CSF containe between arachnoid and pia mater • Spinal subdural space – potential space between dura and arachnoid • Epidural space – between dura mater and ligamentumflavum

  10. ANATOMY • Spinal cord extends from the foramem magnum to L1 in adults and L3 in children • Ant and post nerve roots join each other forming spinal nerves exiting through intervertebral foramina on each level • From L1 down lower spinal nerves travel some distance before exiting through intervertebral foramina, forming the caudaequina • Safe level for neuraxial techniques – below L1 in adult and L3 in children to avoid direct cord damage

  11. ANATOMY

  12. Mechanism of action • Principle site of action of neuraxial techniques is nerve root • Blocking post nerve roots interrupts somatic and visceral sensation • Blocking anterior nerve root prevent motor and autonomic outflow • Differential blockade: sympathetic blockade 2 levels above sensory block which in turn is 2 levels above motor block

  13. AUTONOMIC BLOCK • Sympathetic plexus from T1 to L1 • Blocking anything from T5 downwards result in decreased vasomotor tone, pooling of blood in lower limbs and decrease in blood pressure... Normally with compensatory tachycardia • Blocking T1-T4 blocks cardiac accelaratory fibres leading to bradycardia and decreased cardiac contractility • Deleterious CVS effects must be countered by volume loading pt with 10-20ml/kg IVI fluid and early administration of vasopressors • Bradycardia should be treated with atropine

  14. AUTONOMIC BLOCK • GIT- Sympathetic block leads to vagal predominance leading to small contracted gut with active peristalsis. Hepatic bloodflow reduction mirrors drop in BP • Urinary Tract – lumbar and sacral level blocks block both sympathetic and parasympathetic bladder control leading to urinary retention till block wears off • Neuraxial techniques partially or totally block the neuro-endocrine stress response induced by surgery

  15. CONTRAINDICATIONS TO NEURAXIAL TECHNIQUES • Absolute: • Infection at site of injection • Patient refusal • Coagulopathy or bleeding diathesis • Severe mitral or aortic stenosis • Severe hypovolemia • Increased intracranial pressure

  16. CONTRAINDICATIONS cont’d • RELATIVE • Sepsis • Preexisting neurological deficits • Severe spinal deformity • Uncooperative patient • Stenotic valve lesions

  17. CONTRAINDICATIONS cont’d • CONTROVERSIAL • Prior back surgery at site of injection • Inability to communicate with patient • Complicated surgery – major bloodloss expected

  18. Patients with coagulopathy – Excepted preoperative values • INR - < 1,5 ( <1.75 if experienced anaestetist) • PTT – upper limit of normal ( < 35s) • Platelet count - >80 000 • Bleeding time - <10 min • Ureum - > 12 ( > 15 in experienced hands)

  19. Strategies for discontinuation of anticoagulation in peri-op period

  20. NEURAXIAL TECHNIQUES –anatomic approach

  21. NEURAXIAL TECHNIQUESanatomic approach • Identify spinous processes • Spinous processes almost horizontal in cervical and lumbar area where in thoracic area they slant in caudal direction and can overlap • Direct needle slightly cephalad angle for cervical and lumbar blocks, and significantly cephalad for thoracic blocks

  22. PATIENT POSITIONING

  23. SPINAL ANAESTHESIA • Sterile technique with handwashing, sterile gowning of doctor, then cleaning block field with alcohol and water solution, wiping it off, then draping with surgical drapes • Midline or paramedian approach used • Injection area localized with local anaesthetic • Spinal needle advanced through skin • Further advanced until two “pops” are felt. 1st is penetration of liagmentumflavum and 2nd penetration of dura-arachnoid membrane.

  24. SPINAL ANAESTHESIA • Remove stylet • Successful dural puncture confirmed by free flow of CSF • Persistent parasthesia or pain on injection –indicate direct nerve root contact. Needle should be withdrawn and redirected. • Needle bevel should be turned to side, this ensure that nerve fibres are seperated and not cut on dural puncture

  25. SPINAL ANAESTHESIA

  26. SPINAL ANAESTHESIA

  27. SPINAL ANAESTHESIA factors influencing level of block • Baricity of solution hyperbaric solutions is denser than CSF, therefore spreading downward with gravity, wherease hypobaric is less dense and will spread more cephalad. • Positioning of patient Head down position – hyperbaric solution spreads cephalad Head up – hyperbaric solution spreads caudad Lateral position – Hyperbaric solution will have greater spread on dependent side

  28. SPINAL ANAESTHESIA factors influencing level of block • Drug dosage • Site of injection • Age ( decreased volume of CSF – higher level for same dosage) • Drug volume • Intra- abdominal pressure and pregnancy • Patient height

  29. SPINAL ANAESTHESIA different agents used

  30. EPIDURALS • Single shot or indwelling catheter techniques • Boluses or constant infusion • Wider scope of out of theatre use , for example labour epidurals • Motor block can range from absent to complete • Slower in onset ( 10-20min) and less dense block than spinals

  31. EPIDURALS • Tuohy needle most commonly used • The blunt curved tip push away the dura after passing through the ligamentumflavum instead of penetrating it.

  32. EPIDURALS

  33. EPIDURALS • Epidural catheters is useful for intraop and post op pain control • Midline of paramedian approach can be used • Passes from skin through to space between dura and ligamentumflavum • 2 techniques for identifying whether needle/catheter tip in epidural space: the “loss of resistance technque” and the “hanging drop” technique

  34. EPIDURALS • Loss of resistance technique is preferred • The needle is advanced through subcut. tissue with stylet in place for about 2 centimetres • Stylet removed and needle connected to a syringe • According to physician preference the syringe can be filled with air or saline • The needle is slowly advanced millimetre by millimetre with rapidly repeated attempts at injection

  35. EPIDURALS • As the tip enters epidural space there is a sudden loss of resistance and injection is easy. • The hanging drop technique requires that the hub of the needle be filled with saline so that a drop hangs from its outside opening. • As the tip enters the epidural space a negative pressure is created that sucks the drop of fluid into the needle.

  36. EPIDURALS

  37. EPIDURALS • The quantity of local anaesthetic is large compared to that used in spinal and will result in significant toxicity if injected intrathecally or intravascularly • Test dose designed to detect intrathecal or intravasc injection • Lignocaine 40mg and 15ug of Adrenaline • In case of intrathecal injection lignocaine will result in immediate spinal anaesthesia • The adrenalin will cause tachycardia and increase in BP on intravasc injection

  38. EPIDURAL AGENTS

  39. CAUDAL ANAESTHESIA • Form of epidural anaesthesia • Commonly use in pediatric population • Involves needle/catheter penetration of sacrococcygeal ligament covering the sacral hiatus • Calcification of this ligament in adults makes caudals difficult or impossible in adults

  40. CAUDAL ANAESTHESIA

  41. COMPLICATIONS OF NEURAXIAL TECHNIQUES • ADVERSE OR EXAGGERATED PHYSIOLOGICAL RESPONSES • Urinary retention • High block • Cardiac arrest • Anterior spinal artery syndrome • Horner’s syndrome

  42. COMPLICATIONS cont’d • COMPLICATIONS RELATED TO NEEDLE/CATHETER PLACEMENT • Trauma – backache - postdural puncture headache - diplopia - tinnitus • Neural injury – nerve root damage - spinal cord damage - caudaequina syndrome • Bleeding – spinal or epidural haematoma

  43. COMPLICATIONS cont’d • Misplacement –no/inadequate anaesthesia - subdural block - inadvertent spinal block - inadvertent intravasc injection • Catheter shearing/retention • Inflammation – arachnoiditis • Infection – meningitis or epidural abscess

  44. COMPLICATIONS cont’d • RELATED TO DRUG TOXICITY • Systemic local anaesthetic toxicity • Transient neurological symptoms • Caudaequina syndrome

  45. INCIDENCE OF SERIOUS COMPLICATIONS

  46. COMPLICATIONS cont’d • CARDIAC ARREST - 1:1500 spinals - preceded by bradicardia and decreased preload - occures in young healthe patients - pt’s with high basal vagal tone at risk

  47. COMPLICATIONS cont’d • HIGH NEURAL BLOCK - pt often complain of dyspnoea or inability to cough - numbness or weakness in upper extremities - nausea with or without vomiting precedes hypotension - unconsciousness, apnea and hypotension are referred to as high or total spinals Pt should be reassured, given O2 supplementation and bradycardia and hypotension treated. Once unconsciousness or apnoea occurs pt should be intubated and ventilated

  48. COMPLICATIONS cont’d • POST DURAL PUNCTURE HEADACHE • Typically bilateral, frontal or retro orbital and extends into the neck • Throbbing or constant • Associated with photophobia and nausea • Hallmark = associated with position • Pain aggrevates by sitting or standing, improves by lying down • Onset normally 12-72 h after puncture, but may even be seen immediately after puncture

  49. Post puncture headaches • Untreated pain may last for weeks • Believed to be caused by CSF leakage from dural defect • Loss of CSF cause traction on structures supporting the brain, particularly the dura • Increased traction on bloodvessels also contribute to pain • Blood vessel dilation to compensate for central volume loss may also contribute to pain

  50. Post puncture headaches • Incidence strongly related to needle type, needle size and pt population • Cutting point needles higher incidence than pencil points • Factors that increase risk: young pt, female and pregnancy • Conservative Rx: bedrest, hydration, analgesics and caffeine • Epidural bloodpatch is very effective. It involves injecting 10-20ml of the patients blood into epidural space at the level or 1 level below previous puncture

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