Epidural Anaesthesia.pptx

Epidural Anesthesia

1. Epidural Anaesthesia Presenter- Dr Tess Jose Resident Anaesthesia Moderator – Dr Giles George

2. Anatomy of spine and para axial region The vertebral column consists of 33 vertebrae (7 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 4 coccygeal segments ) The vertebral column is straight when viewed dorsally or ventrally. When viewed from the side, the cervical and lumbar regions are concave posteriorly ( lordosis ), and the thoracic and sacral regions are concave anteriorly (kyphosis) 

3. Structure of Vertebrae

4. THE SPINAL CORD The spinal canal contains the spinal cord with its coverings (the meninges), fatty tissue, and a venous plexus The meninges are composed of three layers: the pia mater, the arachnoid mater, and the dura mater. The pia mater is adherent to the spinal cord, whereas the arachnoid mater is usually adherent to the thicker and denser dura mater. Cerebrospinal fluid (CSF) is contained between the pia and arachnoid maters in the subarachnoid space. The spinal subdural space is generally a poorly demarcated, potential space that exists between the dura and arachnoid membranes.

5. The spinal cord normally extends from the foramen magnum to the level of L1 in adults .In children, the spinal cord ends at L3 and moves upwith age because the spinal cord normally ends at L1, lower nerve roots course some distance before exiting the intervertebral foramina. These lower spinal nerves form the cauda equina (“horse’s tail”; ) Therefore, performing a lumbar (subarachnoid) puncture below L1 in an adult (L3 in a child) usually avoids potential needle trauma to the spinal cord;

6. Surface Anatomy Spinous processes are usually palpable and help to define the midline. The spinous processes of the cervical and lumbar spine are nearly horizontal, whereas those in the thoracic spine slant in a caudal direction and can overlap significantly . Therefore, when performing a lumbar or cervical epidural block (with maximum spinal flexion), the needle is directed with only a slight cephalad angle, whereas for a thoracic block, the needle must be angled significantly more cephalad. A line drawn between the highest points of both iliac crests ( Tuffier ’s line) usually crosses either the body of L4 or the L4–L5 interspace. In slender persons, the sacrum is easily palpable, and the sacral hiatus is felt as a depression just above or between the gluteal clefts and above the coccyx, defining the point of entry for caudal blocks.

7. History 1885-Corning' first performed peridural anesthesia with cocaine for relief of pain in an extremity. It was apparently accidental. 1895-Cathelin first used epidural anesthesia in sacral region. This is now called caudal analgesia. 1910-Läwen investigated the anatomy of the spinal and epidural areas, he found that injections into the sacral canal did not reach the subarachnoid space. 1921-F. Pages (Madrid) performed extradural anes thesia in his surgical practice. 1939-Dogliotti wrote a book on regional anes thesia and thoroughly discussed epidural anesthesia. 1949-Curbelo first performed continuous peridural anesthesia by means of a ureteral catheter 1951-Crawford used peridural anesthesia for thoracic surgery.

8. Definition Epidural anesthesia (peridural or extradural) is anesthesia obtained by blocking spinal nerves in the epidural space as the nerves emerge from the dura and then pass into the intervertebral foramina. The anesthetic solution is deposited outside the dura and therefore differs from spinal or subdural anesthesia, where the solution is deposited in the subarachnoid space. A segmental block is produced chiefly of spinal sensory and sympathetic nerve fibers . Motor Fibers may be partially blocked.

9. Deposition of anesthetic solutions may be accom- plished at the thoracic, lumbar, or caudal area. 1. Thoracic epidural block is achieved by introducing a needle between thoracic spines into the epidural space and instilling an amount of solution that will spread sufficiently to block the desired segments. This is called thoracic segmental epidural anaesthesia

10. 2. Lumbar epidural block , often called spinal epi- dural block, is achieved by introducing a needle between lumbar spines into the epidural space and instilling varying volumes of solution de- pending on the extent of anesthesia desired. Thus, for perineal or extremity surgery, 15 mL of 2% lidocaine are injected; for lower abdominal surgery, 20 mL of solution are used, and for upper abdominal surgery, 30 mt of solution. Extensive anesthesia thus depends on diffusion of large volumes of anesthetic solution.

11. Caudal epidural block , or caudal anesthesia, is accomplished by introducing a needle through the sacrococcygeal ligament into the caudal canal. Varying volumes of anesthetic solution are instilled depending on extent of anesthesia de- sired The sacrum is a triangular-shaped bone formed by the fusion of the sacral vertebrae. Nonfusion of the fifth sacral vertebral arch creates the structure known as the sacral hiatus, which is covered by the sacrococcygeal ligament (an extension of the ligamentum flavum) and bordered by bony prominences known as the sacral cornua. The sacral hiatus is the point of access into the sacral epidural space. It is usually identified as a groove above the coccyx

12. Cervical epidural block :the ligamentum flavum is discontinuous at midline in the cervical region in a large percentage of patients, contributing to a false LOR. Also, it is important to bear in mind that the ligamentum flavum is thinner at this level (1.5–3 mm) than at the lumbar and thoracic levels. In the cervical region, the C7–T1 interspace is widest and easiest to access. In addition, the depth from the skin to the epidural space is larger at this interspace, and the distance from the epidural space to the dural sac is greater than at other cervical levels.

13. Indication

14. Physiology LA or other solutions injected into epidural space ( steroids or narcotics ) spread anatomically. Horizontally spread via intervertebral foramen to paravertebral space. Vertically spread preferentially in cephalad direction. Because epidural anaesthesia is DIFFUSION dependent,relatively LARGE volumes of LA needed to acheive block that expands several dermatomes. The block ONLY goes as high or low deprnding on volume. It is a DIFFERENTIAL block.It depends on concentration. A drug at lower concentration will produce only sensory block while at higher concentration can produce motor block.

15. STRUCTURE OF EPIDURAL SPACE The epidural space is a potential space between perioteum lining vertebralcanal and spinal dura matter. Anatomically, the connective tissue is present in significant amounts ventrally, forming strong con- nections between the dura mater and the anterior longitudinal ligaments in the vertebral canal. Of great interest is the extent of fibrous connections in the posterior part of the epidural space.

16. Epidural space - boundaries Cranially by foramen magnum Caudally by sacrococcygeal ligament. Anterioly by posterior longitudinal ligament Laterally by vertebral pedicles &intervertebral foramina Posterioly by ligamentamum flavum.

17. Epidural space - contents It contains connective tissue fat aerolar tissue spinal nerve roots lymphatics a few blood vessels.

18. Epidural fat It is principally present in posterior and lateral space. It has effects on pharmacology of drugs injected intrathecally. There is a linear relationship between opioid's lipid solubility and its terminal elimination halftime in the epidural space. Increased lipid solubility leads to sequestration of drugs in fat, thereby reducing bioavailability of drug.

19. Lymphatics The lymphatics of the epidural space are concentrated in the region of the dural roots where they remove foreign materials including microorganisms from the subarachnoid and epidural spaces.

20. Blood vessels Epidural veins -Prominent in lateral portion of epidural space Drain to azygos vein and connect to pelvic veins, providing an alternative route from pelvis to right heart. Therefore, they become distended when inferior vena cava is obstructed Also connect to cerebral venous sinuses by way of basivertebral veins

21. Size of epidural space The distance across the semi or half moon circular epidural space varies. In the anterior region it is almost nonexistent while it canbe measured in posterior region, the average values are; Upper thoracic: 2.5mm-3mm Cervical: Imm-1.5mm Lower thoracic: 4mm-5mm Lumbar: 5mm-6mm

22. How to reach? To reach epidural space in midline these structures have to be penetrated: Skin subcutaneous tissues Supraspinous ligaments Interspinous ligaments Ligamentum flavum

23. The first three tissues offer little resistance to the advancing needle, but when the ligamentum flavum is reached, the resistance increases. As the needle passes through this tissue, there is a sudden disappearance of resistance. In performing peridural anės- thesia, it is essential that this point be recognized lest further advancement result in subarachnoid penetration.

24. Clinical corelation Ligamentum flavum has varying degrees of thickness at different spinal levels .Hence it provide risk of dural puncture or determine whether injection was into the epidural space . Presence of dorsomedian connection the difficulty and the effort needed to advance a catheter freely into the epidural space because of the need to "stab" through the midline connective tissue. The impingement of a catheter in connective tissue bands may also cause it to coil within the epidural space.

25. EPIDURAL SPACE IN CHILDREN In children under six years of age, the epidural space has spongy, gelatinous lobules and distinct spaces. This is in contrast to the densely packed fat globules and fibrous strands characteristic of the mature epidural space. Because of this difference, there is a more rapid longitudinal spread of drugs within the juvenile epidural space.

26. POSITION OF PATIENT The lateral position is widely used, especially in the pregnant patient. In clinical practice, retaining the lateral position after injection of the anesthetic solution can be used to obtain a more reliable and intense anesthesia on the dependent side, if this is appropriate for surgery on that side. To provide a relatively major block of the dependent side, the patient should be left in the lateral position for approximately 1 5 minutes

27. The sitting position is indicated in obese patients for technical ease of introducing the epidural needle. It is also desirable when perineal anesthesia is desired, since blockade of the sacral nerves is morecomplete and reliable. For upper thoracic and cervical region block, the sitting position also provides greater ease of inser- tion of the needle into the epidural space,

28. Epidural needles Typically 17-18 gauge 9cm to hub Tuohy needle most commonly used Blunt bevel with a gentle curve of 15-30° at the tip Pushes away the dura after passing through the ligamentum flavum instead of penetrating it Straight needles without a curved tip ( Crawford needles) may have a higher incidence of dural puncture but facilitate passage of an epidural catheter. Needle modifications include winged tips and introducer devices set into the hub designed for guiding catheter placement.

29. Epidural catheter Made of nylon or pvc Radioopaque Tip is atraumatic , rounded having lateral holes and closed end. Connector with Luer -lock cap Catheter length: 90–100 cm with markings at 5 cm, 6 cm, 7 cm, 8 cm, 9 cm, 10 cm, 15 cm, 20 cm from the tip Catheter size—16 G, 18 G, 19 G, 20 G available. Bigger the gauge thinner the catheter, it can pass through any size epidural needle. However a 16 G catheter will not pass through a 18G epidural needle. Catheter diameter: 0.9 mm (18G), 1.1 mm (16 G). Color coded: Dark blue (18G), light blue (16 G ). Filter : 0.22 hydrophilic made of micron mesh

30. Loss of resistance (LOR) syringe: Made of glass or plastic, has a low-resistance plunger to identify the epidural space by the LOR technique. The LOR using saline for catheter placement is the commonly used technique. Catheter distance from tip to the epidural space is 3–4 cm. The catheter should be advanced only 3–5 cm into the epidural space . Continuous epidural analgesia is given in chronic pain, acute postoperative pain, cancer pain with the help of infusion devices and patient-controlled analgesia (PCA) pumps.16 Epidural catheters are used for labor analgesia

31. Clinical Factors in Epidural Spread 1. Spread increases with age . After 20 years of age, the dose requirements decrease considerably. This is explained by the fact that escape from the epidural space is less due to intervertebral foramina being more fixed and epidural vessels less penetrable. 2. Spread is greater in pregnant females . Dosage should be decreased by one-third the dose in non-pregnant women. 3. In arteriosclerosis and occlusive arterial disease, the spread is also greater than in normals , thus, a smaller dose should be used . In early diabetes when widespread angiopathy (arterioles and cap- illaries ) is present, dose-requirement is reduced and more so, later in the course of the disease as occlusion becomes increasingly apparent. 4. Spread is decreased in dehydration , shock and cachexia, 5. Extent of anesthesia is greater with more con- centrated solutions. 6. A greater dose is required in taller individuals.

32. DETECTION OF EPIDURAL SPACE NEGATIVE PRESSURE TECHNIQUES 1. Hanging Drop Sign.(Gutierrez's sign) A small drop of sterile distilled water is placed on the hub of the needle after it has been introduced to the level of resis tance indicating the beginning of the ligamentum flavum. When the needle is advanced through the yellow fibrous tissue, this drop will be "sucked into" the epidural space. This is called the "sign of the drop."

33. Capillary Tube Method ." A Visual Technique). Odom devised a small capillary tube filled with sterile saline in which one or two bubbles of air were placed. These acted as a meniscus. As soon as the needle entered the epidural space, the saline was sucked in, and the air bubbles could be seen,An air bubble can be placed in a syringe filled with saline, and when the attached needle enters the epidural space, the bubble will double in size.

34. 3. Odum's Manometer Technique . A small "U-shaped glass tube about 3 to 4 inches high is used as water manometer. After the needle has been in troduced into the intraspinous ligaments, th sterile glass manometer is attached to the needle . As it is advanced through the ligamentum fla vum and enters the epidural space, there is a immediate movement of the liquid, signifying negative pressure.

35. DISAPPEARANCE OF RESISTANCE TECHNIQUES 1. syringe technique Sudden loss of resistance on plunger of syringe on reaching epidural space.

36. Spring-Loaded Syringe Although the syringe is heavy, when the peri- dural space is entered, the syringe automatically unloads itself by virtue of the diminished resis tance in the space.

37. Balloon Technique A small light balloon mounted on a glass adapter is attached to the epidural needle when this needle has reached the yellow ligament. The balloon is just inflated with 2 or 3 mL of air. When so fully inflated the pressure within the balloon is approximately 50 mm Hg. As the needle is advanced and penetrates into the epidural space, the balloon will collapse.

38. Brooks' Device . An Odom's indicator or capillary tube can be sealed at one end and a glass bubble created there. This is filled with water or saline, and a few bubbles. of air placed in the tube part. It is attached to the epidural needle when the needle reaches the ligamentum flavum. At this point, the bulb is the barrel. heated to create a slight positive pressure . When the needle penetrates to the epidural space the positive pressure of the heated water advances, the meniscal bubble toward the epidural space.

39. Vertical Tube of Dawkins : In this method, a slight positive pressure is created by a short vertical column of water in a tube less than 10 cm high connected at right angles to the hub of the epidural needle. A bubble of air also may be placed in the water. The force of gravity on the column of water produces the pressure. When the epidural space is entered, the level of the column of water drops indicating a disappearance of resistance.

40. Ultrasonography Ultrasound technology is being used increasingly to aid in the identification of the epidural space. Studies suggest that the use of ultrasonography to identify the anticipated depth to space, particularly in obese parturients

41. Clinical Observation ( Bonniot's Phenomenon On entering the epidural space with a bare needle (no stylet or syringe attached), an audible hiss may be noticed, signifying that air is sucked into the epidural space. This is not a predictable and dependable sign. However, Mostert has reported a reverse phenomenon. When a syringe filled with a 5- to 10-mL mixture of equal parts air and saline is injected rapidly into the epidural space, and the syringe is quickly reversed, there will occur an outward reflux of froth.

42. A midline approach is commonly chosen for lumbar and low thoracic approaches. After local anesthetic infiltration of the skin, the nondominant hand can be rested on the back of the patient, with the thumb and index finger holding the needle hub or wing. The angle of approach should be only slightly cephalad in the lumbar and low-thoracic regions, whereas in the midthoracic region, the approach should be more cephalad because of the significant downward angulation of the spinous processes . In a controlled fashion, the needle should be advanced with the stylet in place through the supraspinous ligament and into the interspinous ligament, at which point the stylet can be removed and the syringe attached. STEPS

43. Like spinal it can be given in sitting and lateral position. Usually epidural space is encountered at 4-5 cm from skin and has negative pressure in 80% individuals. Most commonly used method to locate epidural space is by loss of resistance lechnique . Once the needle pierces the ligamemum flavum there is sudden loss of resistance and the syringe filled with air or saline will be felt literally sucked in epidural space. Once the needle is confirmed in epidural space, a test dose of 2-3 ml of hyperbaric lignocaine with adrenaline (except for obstetric patient where epinephrine should not be used) is given and if in 5 minutes there is no evidence of either spinal block ( inabili ty to move foot) or intravascular injection ( tachycardia by adrenaline ), further doses can be given. Epidural catheter is passed through the needle 3-4 cm or catheter should be in epidural space. A microfilter is attached to catheter to prevent contamination. Onset of effect takes place in 15-20 M inutes .

44. Site of Action of Drug Anterior and posterior nerve roots (main site of action). Mixed spinal nerves. Drug diffuses through dura and arachnoid and inhibits descending pathways in spinal cord

45. Drugs used for Epidural Anesthesia Local Anesthetics Usually 2-3 mL of local anesthetic is required for blocking 1 segment; therefore normally 15 to 20 mL of drug is required. Lignocaine (with or without adrenaline): 1-2% concenrration is used. Bupivacaine 0.625- 0.5%, Ropivacaine 0.11.0% and Levobupivacaine 0. 125-0. 75% depending whether used for sensory or motor b lock. Ropiuacaine because of if high safety profile is most preferred. Other drugs like prilocaine, chloroprocaine or mepivacaine are seldom used now a day. However, a new preservative free preparation of chloroprocaine has been recently launched for central neuraxial blocks

46. Opioids Morphine: 4-6 mg (diluted in 10 mL saline). Onset within 30 minutes. Effect lasts for 12- 16 hours. Depodur is an extended-release liposomal form ulation of morphine which can provide analgesia for 48 hours. Fentanyl: 100 mcg {diluted in IO mL saline). Onset within 10 minutes. Effect lasts for 2-3 hours.

47. Fentanyl (2-4 mcg/mL) + bupivacaine (0.125%) or ropivacaine (0.2%) (ropivacaine preferred) as continuous infusion given by syringe pump through epidural catheter is the most commonly used combination for postoperative analgesia and painless labor. Site of action of opioids after epidural administration : Opioids after diffusion through meninges reaches the spinal cord where they bind to opioid receptors present in substanria gelatinosa of dorsal horn cells.

48. advantages of epidural opioids over local anesthetics: Only sensory block is produced while with local anesthetics there are chances of motor blockade if high concentration is used. The effect of single dose (especially morphine) lasts long (12-16 hrs) obviating the need for frequent injections. No sympathetic block

49. Disadvantages : Respiratory depression: Respiratory depression is more profound with less lipid soluble opioids like morphine than with more lipid soluble (fentanyl, alfentanil, sufemanil). The less lipid soluble agents because of prolonged stay in CSF mixes with CSF to reaches brain to inhibit respiratory medullary centers producing delayed respiratory depression after 6- 12 hours. Urinary retention. Pruritus. Nausea and vomiting. Sedation.

50. Factors Affecting the Spread (Level) of Block Volume of the drug: It is the most important factor. Age: Old requiring less dose because volume of epidural space is less. Gravity (Patient's position): Does not affect level too much as in case of spinal. Intra-abdominal tumors, pregnancy: Less dose is required. Level of injection. Length of vertebral column: Taller individuals require higher dose. Concentration of local anesthetic: High the concentration, higher is the spread

51. Factor Effecting Onset and Duration of Block Dose and concentration : Higher dose or higher concentration facilitates onset pKa : It is the pH at which a local anesthetic is 50% ionized and 50% nonionized. Since local anesthetics are weak bases, agents with pKa closer to physiologic pH vvill have more drugs in nonionized form which can diffuse through axonal membrane enhancing the onset. That is why lignocaine with lower pKa of 7.8 has fast onset as compared to bupivacaine with higher pKa of8.l. Addition of sodabicarbona/e : As local anesthetics are bases, adding soda bicarbonate will prevent ionization making more drug to be available in nonionized form to cross the axonal membrane. On the other hand in ischemic tissue (like abscess) acidic pHwilll ionize the drug, delaying the onset of action Type of nerve fiber: A fibers are blocked earlier than B which are blocked earlier than C Frequency of nerve stimulation : Since activated channels are blocked more easily, a stimulated nerve will be blocked earlier as compared to nonstimulated nerve. This kind of block by local anesLherics is called as use-dependent block.

52. Addition of vasoconstrictors : Vasoconstrictors by decreas ing the systemic absorption increases the duration of action. The most commonly used vasoconstrictor is adrenaline in a concentration of 1 in 2,00,000 (l in 2 lakhs). Adrenaline when added to Lignocaine increases the duration of both sensory and motor blockade while with bupivacaine only sensory block is prolonged. Other vasoconstrictors which can be used are phenylephrine (I in 20,000), noradrenaline and felypressin.

53. Advantages of Epidural over Spinal Less hypotension : As the onset of action of epidural is slow body gets sufficient time to compensate for hypotension making epidural a better choice than spinal for cardiac compromised patients. No postspinal headache however headache can occur if dura is punctured accidentally. By giving top up doses through catheter can change level of block and duration of anesthesia.

54. Disadvantages Over Spinal Inadequate (patchy) block/block failure rate is high: Epidural space has fibrous bands and other tissues leading to unequal distribution of drug producing patchy block/failed block. y. higher chances of total spinal : Total spinal is one of the mos t feared complication of epidural. It occurs, if accidently dura is punctured during drug injection and whole volume (10-20 mL) of drug is injected in subarachnoid space. As plain bupivacaine and lignocaine are slightly hypobaric th is volume will reach cranium producing total spinal manifested as marked hypotension,

55. 3 . bradycardia , apnea, dilated pupils and unconsciousness . Prevention – Always confirm the position of needle or catheter by giving a test dose with lignocaine with adrenaline Never inject as a bolus, always give drug in increments of 3-5 mL confirm negative aspiration of CSF before injecting next increment of the drug. Treatment Intubate and IPPV with 100% oxygen. Vasopressors

56. 4.Accidental dural puncture: If dura is punctured with epidural needle, there are two alternatives: - Give hyperbaric local anesthetic through this needle, i.e., convert it to spinal. - Remove the needle and give epidural in higher space.

57. 5 . More chances of epidural hematoma and intravascular injection: As the needle or catheter is near to epidural venous plexus chances of bleeding, hematoma formation and intravascular injection are more. The possibility of hematoma formation can be 10 fold higher than spinal. As the veins are denser laterally the epidura l should be given in midline. To prevent intravascular injection inject the drug only after confirming negative aspiration of blood.

58. . Higher chances of infectious complications: the maximum safe time for which an epidural catheter can be kept however majority of the clinicians recommended a maximum period of 4 days. Higher incidence of neuropathies: Studies have shown higher incidence of radiculopathies with epidural as compared to spinal.

59. Higher incidence of local anesthetic toxicity: Higher volumes used in epidural increases the chances of local anesthetic toxicity. Catheter related complications like broken catheter. If the catheter gets broken in epidural space and is not infected, it can be left in situ (a retained catheter is no more reactive than a suture) and reassure the patient however if it gets broken in subcutaneous tissue then it should be removed.

60. lntraocular hemorrhage: Rapid injection of drug can raise intraocular pressure causing subhyaloid bleeding. Compare to spinal epidural sets are more expensive . Technically epidural is more difficult as compared to spinal.

61. Contraindications for Central Neuraxial Blocks Absolute Raised intracranial tension: Medullary coning can cause death if spinal is given to patients with raised ICT. Patient refusal. Severe hypovolemia and hypotension. Patients on anticoagulants : Patients on anticoagulants can bleed significantly cause epidural hematoma and paraplegia .

62. Patients on new anticoagulants CNB should be delayed for 48 hours after fondaparinux, 72 hours after rivaroxaban (Xarelto} and 5 days after dabigatran (Pradaxa). They can be given safely 6 hours after CNB or epidural catheter removal. Patients on antiplalelels : Patients on aspirin and NSAIDs can be safely given central neuraxial blocks while for other antiplatelets CNB should be delayed for 7 days after clopidogrel, dipyridamol, and prasugrel, 14 days after eticlopidine, 2 days after abciximab and 8 hours after ep tifibatide. Antiplatelets can be restarted 6 hours after CNB or epidural catheter removal.

63. Bleeding disorders/coagulopathy. Infection at local site. Severe fixed cardiac output lesions (aortic and mitral stenosis, constrictive pericarditis, coarctation of aorta): These patients can not compensate for decrease in cardiac output and cannot tolerate fluid overload, therefore should not receive CNB.

64. Relative Mild to moderate fixed cardiac output lesions: Mild to moderate cases can be given central Neuraxial block if necessary. Mild to moderate hypotension and hypovolemia. Uncontrolled hypertension(may develop sudden hypotension after spinal.) Severe ischemic heart disease especially history of recent MI. Thrombocytopenia: Patients with platelet count more than 80,000/ cubic mm can be safely given central neuraxial blocks. Platelet count between 50,000- 80,000/ cubic mm is a relative contraindication while count less than 50000 becomes an absolute contraindication. Heart blocks and patient on Bblockers: Severe bradycardia can occur. Spinal deformity and previous spinal surgery

65. Psychiatric and uncooperative patients History of headache: (are more vulnerable PDPH) GIT perforation:Theoretically parasympathetic over activity increases the peristalsis and can open the seal. Myelopathy and peripheral neuropathies: exaggerates an existing neuropathy Nerve blocks should be avoided in these patients for medicolegal reasons.

66. CNS disorders: - Multiple sclerosis: Due to increased sensitivity of local anesthetics patients of multiple sclerosis exhibit a prolonged block however, the evidence proving the exacerbation of multiple sclerosis symptoms by central neuraxial blocks is lacking. - Spinal stenosis: These patients may be at increased risk of neurologic complications after neuraxial blocks. Resistant surgeon Chronic backache Septicemia and bacteremia

67. Thank you.

68. Reference Oxford regional anaesthesia a pocket guide. Collins Millers anaesthesia 9 th edition. nysora