Spinal block
- 1. MODERATOR ---- Dr. Saba Ahad CConsultant department of anaesthesiology & critical care medicine Presented by: Dr. Mohsin Farooq
- 2. Spinal anesthesia is also called as spinal block or subarachnoid block (sab). SAB is a regional anesthesia involving injection of a local anesthetics into the subarachnoid space.
- 3. 3 HAVE A BASIC UNDERSTANDING OF • Anatomic structure of spine and vertebra •Anatomic structure of spinal cord •Blood supply of spinal cord •Features of neuraxial blockade •Indications/ contraindications •Patient evaluation and preparation •Techniques •Local anesthetics and factors effecting spread •complications
- 4. BRIEF HISTORY OF SPINAL ANAESTHESIA CSF DISCOVERED ---- by Domenico Catugno 1764 CSF CIRCULATION---- by F . Magendie 1825 FIRST SPINAL ANALGESIA--- by J Leonard Corning 1885 FIRST PLANNED SPINAL ANAESTHESIA--- by August Bier in 1891 The epidural space was first described by Corning in 1901, and Fidel Pages first used epidural anaesthesia in humans in 1921.
- 5. ANATOMY Spine consists of 33 vetrtebrae •cervical vertebrae (7) •thoracic vertebrae (12) •lumbar vertebrae (5) •sacral vertebrae (5) •coccygeal vertebrae (4 )
- 7. SPINAL CORD ADULTS– approx L1(30%T12;10%L3) CHILDREN--approx L3
- 8. ANATOMY The spinal cord usually ends at the level of L1 in adults (at T12 in 30% population and L3 in 10%) and L3 in children. Dural puncture above these levels is associated with a slight risk of damaging the spinal cord and is best avoided. Spinal cord give rise to 31 pairs of spinal nerves each composed of anterior motor & posterior sensory nerve roots. Spinal nerves that extend beyond the end of spinal cord to their exit site are called cauda equina Extension of pia mater, filum terminale penetrates dura and attaches terminal end of spinal cord to coccyx.
- 9. ARTERIAL SUPPLY OF SPINAL CORD Ant 2/3 of cord is supplied by single ant.spinal artery Post 1/3 by pair of post spinal arteries Additional :intercoastal arteries thoracolumbar,one of these is large called artery of adamkiewiecz (arteria redicualaris magna) its injury can lead to ant spinal artery syndrome
- 10. DERMATOMES A dermatome is an area of skin innervated by a single spinal nerve and corresponding cord segment. T4 – nipples T6 – xiphoid T10 – umblicus T12, L1 – inguinal ligament , crest of ileum S2-S4 – perineum
- 11. Dermatomal Levels of Spinal Anesthesia for Common Surgical Procedures Procedure Dermatomal Level Upper abdominal surgery( appendicectomy) LSCS T4 Intestinal, gynecologic, and urologic surgery T6 TURP, Vaginal delivery of a fetus, and hip surgery T10 Thigh surgery and lower leg amputations L1 Foot and ankle surgery L2 Perineal and anal surgery S2 to S5 (saddle block)
- 12. Spinous processes are palpable over the spine and help to define the midline Landmarks: • First palpable spinous process is C2 • Most prominent spinous process is C7 •Inferior tip of scapula T7 •Superior aspect of both iliac crest – body of L4& L3L4 space ( TUFFIER’S LINE) •Posterior superior iliac spine S2 •Sacral cornu S4S5
- 13. CONTRAINDICATIONS ABSOLUTE 1. Patients refusal. 2. Coagulopathy. 3. Infection at site of injection 4. Severe hypovolemia 5. Raised ICT 6. Allergy to drugs 7. Shock 8. severe AS or MS RELATIVE 1. Uncooperative pt 2. Preexisting neurological deficits(MS) 3. Demyelinating lesions 4. Severe spinal deformity 5. Infection at site remote from injection 6. Sepsis 7. left ventricular outflow obs
- 14. BEFOREHAND: Proper history, examination & informed written consent of patient. Remove your jewellery/watches/thorough scrubing, sterile gown and masks. I.V access/fluids bolus if needed Drapes and antiseptic solution should be ready Emergency drugs /equipment/check anesthesia machine. Ensuring that operating table tilts. Sedation if needed Monitoring NIBP/SPO2/ECG • EQUIPMENT FOR RESUSCITATION should be readily available.
- 15. POSITION LATERAL DECUBITUS: Most commonly used Patient lie on their side at the edge of couch with their knees flexed and pulled high against abdomen or chest and neck flexed.
- 16. SITTING: Patient should sit on the table with knees resting on the edge, legs hanging over the side and feet supported by a stool below Or Patients sit with their elbows resting on their thighs or bed side table or hugs a pillow with neck flexed. Commonly used : For saddle block anesthesia Obese patients, Pregnant patients, Patients with abnormal spinal curvatures
- 17. Jackknife (buie’s) position . This position is used for anorectal procedures using hypobaric anaesthetic solutions. Patient should be in prone position with OT table flexed under his flanks, just above the iliac crests .
- 18. 1.Midline approach 2.Paramedian approach 3.Lumbosacral or Taylors approach
- 19. PREPARATION: •Hands and lower forearms scrubbed for at least 3 minutes •Sterile gloves,gown and mask put on. •A large area of L-S spine should be painted using antiseptic solution( chlorhexidine acc. to ASoRA) •Excess antiseptics removed after waiting for some time for antiseptic to act •Selection of space –using tuffier’s line as landmark •Raise a skin wheal with 2ml of 2% lignocaine solution after negative aspiration for blood
- 20. MIDLINE APPROACH After selecting desired interspace {L3-L4;L4-L5) by palpating the depression between the spinous process of the vertebra above and below the level in midline infiltrate with local anesthetics should be kept parallel to the longitudinal axis of the spine to avoid pain on insertion. Insert needle in midline with slight cephalad angulation (10-15 degree). The subcutaneous tissue gives feeling of little resistance to the needle, after that needle will enter the supraspinous and interspinous ligaments.
- 21. As the needle meets the ligamentum flavam an increase in resistance is encountered and on piercing it, loss of resistance can be felt .The needle is advanced through the epidural space and penetrates the dura (2nd resistance loss “Pop”) and subarachnoid membrane. Once needle is correctly placed in space stabilize the spinal needle and attach the syringe by grasping the hub of spinal needle with thumb and index finger while propping the remaining fingers against the patient’s back to provide support (bromage grip) CSF is aspirated & LA injected <0.5ml/sec. After completing CSF is again aspirated to confirm needle tip remained in SAS while drug was deposited .
- 22. Layers traversed by the spinal needle (posterior to anterior) Skin Subcutaneous tissue Supraspinous ligament Interspinous ligament Ligamentum flavum Epidural space Duramater Sub dural space Arachnoidmater into the Subarachnoid space
- 23. Problems during SAB If no CSF then either -needle orifice is blocked by nerve root Or needle not in the space completely-- ---rotate needle 90 degree or advance 1-2 mm If bone encountered------- at shallow depth needle walking up…sup.spinous process> redirect caudad & if at greater depth needle walking down inf spinous process redirect cephalad. While redirecting -----withdraw tip into the subcutaneous tissue.
- 24. PARAMEDIAN APPROACH: Useful when there is inability to flex the spine or heavy calcified interspinous ligament, severe arthritis, kyphoscoliosis, prior spine surgery Needle is inserted 1cm lateral to the spinous process forming the lower border of desired interspace angling 45◦ cephalad with 10◦ medial angulation. The first resistance encountered is ligamentum flavum.
- 25. TAYLOR’S APPROACH (LUMBOSACRAL) Paramedian approach at L5-S1{Largest interlaminar space}. Needle is inserted 1cm medial & 1cm inferior to posterior superior iliac spine. Used when other approaches unfeasible and in cases of spine fusion, arthritic spine,
- 26. SPINAL NEEDLES: Three parts Hub Cannula Stylet Point of the cannula is beveled or pencil pointed Outer diameter determine the gauge. Sized 22-29G. Length: 3.5 to 4 inches
- 27. PENCIL POINT TIP(with side apertures) BEVEL POINT TIP ( with cutting edges) Whitacre, Eldor, Marx ,Sprotte QUIINKE, Greene,Atraucan Requires more force to insert, provide better tactile “feel” Requires less force to inset Do not deflect from intended path. Deflect from the path. Less chance of PDPH More chance of PDPH Spinal needles are Classified on the design of their tips :
- 28. Spinal needles Beveled tips with cutting edges Pencil tip with side apertures
- 29. Drug preparation Perineum, lower limbs (mg) dose Lower abdomen (mg)dose Upper abdomen (mg)dose Duration (min) procaine 10% solution 75 125 200 45 tetracaine 1% solution in 10% glucose 4-8 10-12 10-16 90-120 lidocaine 5% in 7.5% glucose 25-50 50-75 75-100 60-75 bupivacaine 0.75% in 8.25% dextrose 4-10 12-14 12-18 90-120 0.5% in 8% dextrose 7.5 to 12.5 12.5-17.5 17.5-25 90-120 ropivacaine 0.2-1% solution 8-12 12-16 16-18 90-120 Spinal anaesthetic agents
- 30. Adjuvants used Opioids Fentanyl – 12.5 mcg Sufentanyl – 2.5 – 5 mcg Diamorphine – 0.3 mg Morphine – 0.1 – 0.2 mg ADRENERGIC AGONIST Phenylephrine(2-5mg) Epinephrine (.2-.3mg) Clonidine (75-150mg)
- 31. SEQUENCE & ONSET OF BLOCK Onset of block within few minutes irrespective of LA. Time to reach peak block ht. differs with LA. (bupivacaine & tetracaine >20min.) Sequence of onset depends on conc. of LA achieved, duration of contact, size & myelination of nerve fibers. CLINICALLY OBSERVED SEQUENCE 1. Sympathetic nervous system fibers (B fibers: vasodilation, skin temp ↑) 2. Temperature & pain conduction (A delta& C fibers) 3. Proprioception & touch (Aγ & Aβ fibers) 4. Motor function (A alpha & β fibers)
- 32. DIFFERENTIAL NERVE BLOCK: Occurs with both neuraxial & peripheral nerve block ; Manifests as spatial separation in modalities blocked in central neuraxial block. Sympathetic block extends 2 or more dermatomes higher than sensory block , which in turn extends 2 dermatomes higher than motor block. In peripheral nerve block it is temporal phenomenon sympathetic occurring first followed by sensory than motor blockade.
- 33. TESTING THE LEVELS OF BLOCK Sympathetic block Dilatation of skin vessels Changes in the skin temperature Hypotension Sweating Sensory block Pin prick using sterile needle Loss of touch
- 34. Motor block Modified Bromage scale of onset of motor block
- 35. PHYSIOLOGICAL EFFECTS OF NEUROAXIAL BLOCK CARDIOVASCULAR EFFECTS: HYPOTENSION{30-40%} Due to blockade of sympathetic efferents(T5 –L1) ------ Venodilatation (↓preload) pooling of blood ↓ VR > ↓ CO Ateriolardilataion(↓afterload) ↓ PVR Risk factors: Age>40yrs ACE inhibitor/ARB Hypovolemia Obesity Concurrent GA
- 36. BRADYCARDIA (13%) Blockade of sympathetic cardioaccelerator fibers from T1-T4 segment. Risk factors : Block height Age <50 Beta blockers
- 37. Even with high thoracic levels, tidal volume is unchanged. A small decrease in vital capacity due to paralysis of abdominal muscles necessary for forced exhalation & not due to decrease in phrenic nerve or diaphragmatic function. Effective coughing & clearing of secretions may get affected with higher levels of block. • Rare respiratory arrest associated with spinal anaesthesia due to hypoperfusion of respiratory centers in brain stem. Patients with high block complain of dyspnoea despite normal MV due to inability to feel chest wall motion. Pulmonary effects:
- 38. Gastrointestinal function: Nausea and vomiting in upto 20% patients due to gastrointestinal hyperperistalsis caused by unopposed parasympathetic(vagal) activity. Vagal tone dominance results in small contracted gut with active peristalsis & can provide excellent operative conditions for some laproscopic procedures when used as an adjunct to GA. Hepatic blood flow will ↓ with decrease in mean arterial pressure.
- 39. Renal function: Renal function has a wide physiological reserve. ↓ in renal blood flow is of little physiological importance. Neuraxial blocks are a frequent cause of urinary retention as it effectively block sympathetic & parasympathetic control of bladder.
- 40. ENDOCRINE & METABOLIC Inhibits metabolic & endocrine changes associated with stress. Due to blockade of afferent sensory response from surgical site.
- 41. Drug Factors Patients Factors Procedure Factors Baricity of drug Age Needle position Drug dosage CSF volume Speed of injection Conc of drug injected Intraabdominal pressure(obesity,pregnancy Addition of vasoconstrictor Curvature of spine Patient position Fluid currents . Factors Affecting the Level of BLOCK height Spinal Anesthesia
- 42. Baricity Density of a solution in relation to density of CSF at 370C Density of CSF is 1.0003 to 1.0005 at 370C Hypobaric solutions : raise against gravity Isobaric solutions : tend to remain in the same sight where they are injected Hyperbaric solutions : tend to follow gravity ISOBARIC SOLUTIONS Densities between 0.9998 and 1.0008 • Solutions are mixed with physiological saline • Solutions with out added glucose • Bupivacaine, ropivacaine, levobupivacaine • Spread not influenced by position
- 43. . HYPOBARIC SOLUTIONS HYPERBARIC SOLUTIONS • Baricity less than 0.9998 at 370C • Prepared by diluting with distilled water • Solutions at 370c with baricity greater than 1.0008 • Made by addition of 5- 8% dextrose.
- 44. AGE Spinal space become smaller with age - distribution greater. OBESITY/ PREGNANCY • Increase intra-abdominal pressure • Decrease subarachnoid space SPINAL CURVATURE • Abnormal curvature have an effect on technical aspects Changes the contour of Subarachnoid space AMOUNT OF DRUG • Increase amount- increase Duration EFFECT OF TEMPERATURE • Decrease Temperature- increase Baricity
- 45. Problems withthe Block If after 10 minutes the patient still has full power in the legs and normal sensation, then the block has failed probably because the injection was not intrathecal. Try again. The block is one-sided or is not high enough on one side. lie the patient on the side that is inadequately blocked for a few minutes and adjust the table so that the patient is slightly "head down". SAB not high enough. tilt the patient head down while they are supine (lying on the back), so that the solution can run up the lumbar curvature. Flatten the lumbar curvature by raising the patient's knees. Block too high. The patient may complain of difficulty in breathing or of tingling in the arms or hands. Do not tilt the table "head up".
- 46. Continuous Spinal Anesthesia Inserting a catheter into the subarachnoid space increases the utility of spinal anesthesia by permitting continuous or repeated drug delivery in order to expand the level or duration of spinal block , dural puncture is done with an epidural needle. After that subarachnoid placement of the needle and ascertaining free flow of csf ,the catheter is threaded 2-3 cm in to the SAS .The catheter should never be pulled back in to the needle shaft because of the risk of shearing the catheter off into the subarachnonid space If the catheter needs to be removed both needle and catheter should be removed as a unit. 18 G epidural needle &20 G epidural catheter are used
- 47. Combined spinal-epidural anesthesia CSE is useful technique by which a spinal block and epidural catheter are placed simultaneously. Benefit: rapid onset,dense block This technique is done with special epidural needle having separate lumen to accommodate spinal needle, first a epidural needle is placed in epidural sace, and then spinal needle is introduced through epidural needle into SAS and desired drug is injected and spinal needle removed and then epidural catheter is placed into epidural space.
- 48. COMPLICATIONS/SIDE EFFECTS OF NEURAXIAL ANESTHESIA Hypotension Postdural Puncture Headache (25%) High Spinal Anesthesia Total spinal anaesthesia Cardiac arrest Neurological complications (peripheral neuropathy, TNS,CES) Arachnoiditis / Meningitis Spinal / Epidural Hematoma Formation Epidural Abscess Backache Hearing loss Urinary retension Pruritus shivering Systemic toxicity
- 49. HIGH NEURAL BLOCKADE AND TOTAL SPINAL ANAESTHESIA Can occur both with spinal and epidural Admins . Of an excessive dose, failure to reduce doses in selected pts (elderly, pregnant, obese, very short) or unusual sensitivity or spread of LA maybe responsible Presents with dyspnea, numbness in upper extremities, severe hypotension, bradycardia and respiratory insufficiency and even apnea Total spinal can occur following attempted epidural/caudal anesthesia if there is inadvertent intrathecal injection involving cranial neves. TREATMENT---vasopressors, atropine ,fluids, oxygen ,assisted ventilation and even intubation and mechanical ventilation may be needed
- 51. TRANSIENT NEUROLOGICAL SYMPTOMS AND CAUDA EQUINA SYNDROME TNS or transient radicular irritation refers to pain ,dysesthesia or both in the legs or buttocks after spinal anesthesia, resolving spontaneously within several days Most common with hyperbaric lidocaine and after surgery in lithotomy position CES characterized by bowel and bladder dysfunction together with evidence of multiple nerve root injury, assoc with use of continous spinal catheters and 5% lidocaine
- 52. NEURAXIAL BLOCKADE IN SETTING OF ANTICOAGULANTS AND ANTIPLATELET AGENTS---AMERICAN SOCIETY FOR REGIONAL ANESTHESIA RECOMMENDATIONS Pts taking NSAIDS or receiving SC unfractioned heparin for DVT prophylaxsis are not viewed as being at increased risk of spinal hematoma DISCONTINUE---ticlopidine 2 weeks, clopidogrel for 1 week ,abciximab 24 to 48 hrs, eptifibate and tirofiban 4 to 8 hrs before performing central neuraxial block. Pt who are fully anticoagulated or who are receiving thrombolytic or fibrinolytic theraphy should not receive central neuraxial block except in very unusual circumstances where other options are not viable. Patients receiving IV heparin, should be delayed for 1hour after CNB Delay atleast 10 -12 hrs after last dose of LMWH Post op t/t with LMWH delay 12hrs after compl of surgery Removal of epi ,spi catheters should take place 10—12hrs after last dose with subs dosing delay for atleast 2hrs.
- 53. Advantage of spinal over general anaesthesia Less chance of deep vein thrombosis Less chances of PONV Early ambulation Less bleeding Better post operative pain control Decreased stress response Less respiratory and cardiovascular complications
- 54. .