Spinal anesthesia 1

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1. Central neural blockade Spinal Anaesthesia By: Seid Adem 1

2. Course out line Anatomy The spinal pack Technique The spread of the analgesic solution Drugs and doses Care of the patient under spinal anaesthesia Complications: Immediate Later Indications for spinal anaesthesia Contraindications Advantages 2

3. Spinal cord anatomy The spinal cord is the continuation of the brain and occupies the vertebral canal. It extends from the upper border of the first cervical vertebra (the atlas) to the upper border of the second lumbar vertebra In the foetus , the spinal cord occupies the whole of the vertebral canal. However, the vertebral canal grows faster than the spinal cord and at birth the cord terminates at L3 3

4. In the adult , the spinal cord occupies the upper two-thirds of the vertebral canal. It is 45cm long and ends in the conus medullaris, from the apex of which the filum terminale descends to the coccyx. Spinal puncture above L2 may result in cord damage. 4

5. Coverings of the spinal cord In the vertebral canal, the spinal cord is covered by three membranes: 1. The dura mater Is the tough, outer, protective membrane This layer is the direct extension of the cranial dura mater and extends as spinal dura mater from the foramen magnum to S2 5

6. 2 . The arachnoid mater Is a very thin and transparent layer closely adhering to the dura mater. The pia mater Is a vascular membrane closely adhering to the spinal cord. It invests the cord and sends septa into it 6

7. 7 Fig-the spinal cord and the meninges

8. Compartments related to spinal meninges These are the subarachnoid, subdural and epidural spaces. Subarachnoid space Found between the arachnoid and the pia mater Encompasses the CSF 8

9. In the subarachnoid space are The CSF Spinal nerves A trabecular network between the two membranes Blood vessels that supply the spinal cord Although the spinal cord ends at the lower border of L1 in adults, the subarachnoid space continues to S2. 9

10. Subdural space Is a potential one only; the arachnoid is in close contact with the dural sheath and is separated from it only by a thin film of serous fluid. The subdural space within the vertebral canal rarely enters the consciousness of the clinician, unless it is the accidental site of catheter placement during attempted epidural analgesia or anaesthesia. 10

11. Epidural space Is that part not occupied by the dura and its contents It extends from the foramen magnum to end by the fusion of its lining membranes at the sacrococcygeal membrane. It contains fat, nerve roots, blood vessels and lymphatic's. 11

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13. Spinal nerves There are 31 pairs of spinal nerves each arising by the fusion of the anterior and posterior nerve root. The anterior root is motor (i.e. it supplies the muscles). The posterior root is sensory. The nerve roots are blocked by the analgesic solution during spinal anaesthesia. The analgesic solutions block the finest fibers first. The sensory nerves, being of smaller diameter than the motor, are blocked first. 13

14. 14 Fig-the spinal cord in transverse section from a thoracic segment

15. Spinal segments The cord is divided into segments by the spinal nerves that leave it. Each segment gives off an anterior root and a posterior root. Each anterior root fuses with the corresponding posterior root at the intervertebral foramen. 15

16. Each spinal segment supplies specific region of skin and number of muscle perineum – S1-S4 Inguinal region – L1 Umbilicus – T10 Sub costal arch – T6-8 Nipple line – T3-T5 Second intercostal space – T2 Clavicle – C3-C4 16

17. Segmental level of spinal reflexes Epigastric –T7-T8 Abdominal –T9 & T12 Plantar –S1 & S2 Knee jerk –L2-L4 Ankle jerk –S1 & S2 Anal sphincter reflexes –S4-S5 17

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19. CSF The CSF occupies the potential space between pia and arachnoid mater Forms the volume of distribution for spinal anesthetic agents to the spinal cord structures. Formation - CSF is formed in the choroids plexus in the brain. 5o0ml/day and removed by arachinoid villi. 19

20. CSF baths spinal cord ,caudal equina and brain - contain 40-80 mg/dl glucose ,15-45mg/dl protein ,NA ,K ,Ca ,urea, bicarbonate , Cloride Uses –it maintains physiologically stable environment and buffering for CNS, biochemical function 20

21. SPINAL BLOCK 21

22. SA results from the delivery of anesthetic agents in to the CSF or in to the sub Arachinoid space. It is one of the simplest RA to perform and was 1 st described in human by august Bier in 1889. Indication ? SA is ideal for operation to lower extremities 22

23. Upper abdominal procedures with high spinal ,but today lumbar and thoracic epidural technique is advanced with heavy sedation or light GA Lower abdominal procedures e.g. appendectomy Gynecological procedures Dilation and curettage ,laparoscopy Cone biopsy ,tubal ligation ,ovarian Cystectomy Hysterectomy Obstetric surgery Cesarean section Vaginal delivery, VVF ,UVP 23

24. 5. Lower limb surgery Orthopedic ,vascular Amputations ,skin grafts 6) Urological procedures Trans urethral resections , orchidectomy Cystoscopy ,penile implant open prostatectomy 7) Perineal and rectal surgery Bartholins cyst Rectal fissures/fistulae 8) Hernioraphies 24

25. Contra indication Patient refusal –explanation Uncorrected hypovolemia Dehydration ,shock ,hypotension Diarrhea ,vomiting ,bleeding Infection at lumbar puncture site-local or systemic Coagulopathy -anti coagulated patient with heparin ,warfarin ,systemic coagulation problem. 25

26. Anatomic factors that makes CSF access very difficult or impossible kyphosis , lordosis ,scoliosis Certain neurological disorders which may be exacerbated by the pre operative stress or anesthesia and surgery. Elevated intracranial pressure ,progressive CNS disease Patient with fixed COP-heart block ,AV- block ,VHD Inadequate resuscitation drugs and equipment. Reluctant surgeon-unhappy to operate on awake patient or relatively unskilled surgeon 26

27. Severe HTN –it should be controlled before any anesthetic is given Long surgery Uncooperative patient Allergy to local anesthesia psychosis 27

28. Structures penetrated by the lumbar puncture needle Midline approach : • Skin • Subcutaneous tissue and fat • Supraspinous ligament • Interspinous ligament • Ligamentum flavum • Extradural space • Dura mater and arachnoid mater • Cerebrospinal fluid 28

29. Lateral approach: • Skin • Subcutaneous tissue • Ligamentum flavum • Extra dural space • Dura mater and arachnoid mater • Cerebrospinal fluid 29

30. Average depth penetrated by the spinal needle is 4 to 5 cm. This is greater in the obese patient. The spinal cord ends at the upper border of L2. Therefore make sure the lumbar puncture is done below this level, or else the cord may be damaged. In the elderly patient the supraspinous ligament may be calcified and the lateral approach may be easier. 30

31. THE SPINAL PACK This is a collection of items to be kept ready for spinal anaesthetics. The following list is an example of a basic spinal set but the contents may vary from hospital to hospital. 31

32. All sterile - 1 fenestrated drape or 4 towels. - 2 bundles of gauze swabs. - 2 gallipots and 1 kidney dish. - 1 spinal needle with stilette gauge 22 and/or 25G/27G, plus introducer (19 gauge needle). - 1 23G hypodermic needle (skin analgesia). - 1 18G hypodermic needle (for drawing up LA). - 1 swab holder. - 2 syringes: 5ml and 2ml. These must be glass if in a pack to be autoclaved. 32

33. TECHNIQUE OF SPINAL ANAESTHESIA Wash the patient's back (shave it if necessary). Check the blood pressure and leave the cuff on. Apply ECG and pulse oximetry monitoring, if available. Put in an indwelling needle or start an intravenous infusion if necessary. Make sure the following are available in the theatre before proceeding with the spinal anaesthesia: - Vasopressors (ephedrine or metaraminol) - Atropine - Oxygen - A gas machine or a means of ventilating the patient - Suction Select either the lateral or sitting position for the patient. 33

34. Lateral Position Place the patient on his side, right or left. The buttocks and the shoulders should be parallel to the edge of the table. The nurse stands in front of the patient and places one hand behind the patient's neck and the other hand behind the patient's knees. The back is arched to open up the intervertebral and the interlaminar spaces. 34

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37. Sitting position The patient sits on the table. He is instructed to arch his back like a cat or to "push out" his back. The feet are placed on a stool, arms folded across the chest and the head flexed. A nurse supports the patient. Positioning is frequently the most poorly managed part of the spinal technique 37

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39. With the patient in an appropriate position Scrub as for a surgical operation. Wear a sterile gown and gloves. Swab the patient. Use a fresh swab each time and discard it after use. Swab the lumbar spine from above downwards three times. Betadine solution or any other antiseptic that is used to prepare the site of surgery in theatre can be used. Open the pack. Draw up the drugs. 39

40. Drape the patient, preferably with a single "window" Sit on the stool so that the site of the lumbar puncture is at eye level. Choose the site of injection: - Feel for the highest point of the iliac crest. This passes through the body of the 4th lumbar vertebra or the interspace between 4th and 5th lumbar vertebrae. - Choose the widest space between 2 spines with the above point as a guide 40

41. THE SPREAD of the ANALGESIC SOLUTION The vertebral column if viewed from the side has a concavity in the thoracic region maximal at the 6th thoracic vertebra and a convexity in the lumbar region maximal at the third lumbar spine. At the usual site of injection most of the anaesthetic "rolls" down the lumbar curve 41

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43. This is of little use for abdominal surgery where the thoracic segments must be anaesthetized, so when the patient is placed on the back, a slight head down tilt is employed to help the distribution to the thoracic segments. In women there is a natural tilt, because the female pelvis is broad and the shoulders are narrow. 43

44. The spread of local anaesthetic in the subarachnoid space is affected by Patient characteristics    Age    Height    Weight    Gender    Intra-abdominal pressure    Anatomic configuration of the spinal column    Position 44

45. Technique of injection    Site of injection    Direction of injection (needle)    Direction of bevel    Use of barbotage    Rate of injection 45

46. Characteristics of the anesthetic solution    Density       Concentration Volume    Vasoconstrictors 46

47. DRUGS AND DOSAGES FOR FIT ADULTS Bupivacaine 0.5% plain (Marcaine) 2.5-3 ml may be used in the sitting or lateral position for lower limb and lower abdominal surgery Bupivacaine 0.5% hyperbaric Heavy or hyperbaric bupivacaine is a 0.5% solution mixed with 80mg/ml dextrose. This is the recommended choice for spinal anaesthesia predictable in onset and distribution of anaesthesia. 47

48. Dosage: Perineal surgery (saddle block) 1-1.5ml Prostatectomy, lower limb surgery 2.5ml Hysterectomy, appendicectomy 3 -3.5ml Lignocaine 5% heavy Perineal surgery (saddle block) 1-1.5ml Prostatectomy, lower limb surgery 2ml 48

49. CARE OF THE PATIENT UNDER SPINAL ANAESHESIA In the operating theatre Check the blood pressure every minute for the first 5 minutes and every 5 minutes thereafter. Record it on the anaesthetic chart. The treatment of hypotension is discussed later. Monitor the pulse rate every minute for the first 5 minutes and every 5 minutes thereafter. 49

50. Respiration: the depth and rate of breathing should be observed. The management of respiratory depression is discussed later Color or oximetry: Pallor or cyanosis require urgent attention. Observe the general condition of the patient carefully. Sweating, nervousness, nausea, dry retching, should be noted and appropriately treated. 50

51. In the recovery area and the ward Record blood pressure every 10-15 minutes for the first hour and half-hourly thereafter. Record pulse every 10-15 minutes for the first hour and half-hourly thereafter. Record SaO2 or observe colour every 10-15 minutes. Observe respiration rate and depth every10-15minutes. Level of consciousness Position : Patients are usually nursed lying flat for the first 6 –12 hours but may ambulate if a fine needle has been used. 51

52. Practical problems during SAB The spinal needle feels as if it is in the right position but no CSF appears. Wait at least 30 sec. then rotate needle 360⁰ and wait for some time Still no CSF attach 2ml empty syringe and injection of 0.5-1ml of air to ensure the needle is not blocked then use the syringe to aspirate whilst slowly withdrawing the spinal needle ,stop as soon as CSF appears in the syringe. 52

53. Blood flows from the spinal needle wait a short time . if the blood becomes pinkish and finally clear ,all is well. if blood only continues to drip then it is likely that the needle tip is in an epidural vein and it should be a little further to pierce the dura. The patient complains of sharp ,stabbing leg pain. The needle has hit a nerve root because it has deviated laterally. Withdraw the needle and redirect it more medially away from the affected site 53

54. Wherever the needle is directed it seems to strike bone Make sure the patient is still properly positioned ,lumbar flexion and needle still in the middle line If patient is elderly and can not bend very much and has heavily calcified intraspinous ligament, attempt paramedian approach 54

55. The patient complains of pain during needle insertion this suggests spinal needle is passing through either side of ligaments –redirect your needle away from the affected side of the pain to get back in to the midline or inject some LA The patient complains of pain during needle injection of the spinal solution –stop injection and change the position of the needle Assessing the block 55

56. COMPLICATIONS 56

57. COMPLICATIONS Immediate complications - Toxicity Causes of toxic reactions • The use of the drug in a dose greater than the safe maximum for that drug. • The accidental injection of the correct dose into a blood vessel. This will result in a very high blood concentration. • The use of the correct dose in a patient who is especially sensitive to the drug. 57

58. Symptoms, signs and emergency treatment of toxic reactions Central nervous system (CNS ) • Stimulation – tinnitus, numbness, nystagmus, restlessness, tremor, convulsions followed by • Depression – depressed conscious level, coma 58

59. Treatment Give oxygen Give sufficient diazepam or midazolam to control the convulsion . Thiopentone may also be used in a small dose (e.g. 50 mg ). If associated apnoea, give artificial ventilation with 100% oxygen following intubation with a dose of suxamethonium chloride. 59

60. Cardiovascular system (CVS) • Pulse – bradycardia, arrhythmias, cardiac arrest • Blood Pressure –hypotension, cardiovascular collapse Treatment: - Give IV fluids. - Give vasopressors and atropine, if necessary. - Give oxygen by mask. - Watch for and be ready to treat cardiac arrest. 60

61. Respiratory system • Respiratory depression, apnoea. Treatment - Clear airway - Give oxygen by mask - Assist or control ventilation 61

62. Allergic phenomena (rare) These may take the form of bronchospasm, urticaria , hypotension, etc. Reaction to vasoconstrictor drugs Pallor, tachycardia, palpitation, hypertension . 62

63. Generally Stop administering the drug Get senior help/assistance Concentrate on airway, breathing and circulation (ABC) Provide oxygen by a face mask If unconscious, perform tracheal intubation If intubated, commence ventilation to ensure that patient does not develop respiratory acidosis. (Acidosis worsens toxicity) Ensure adequate IV access and commence fluid resuscitation 63

64. If patient develops seizures, treat with diazepam or small doses of thiopentone or propofol If patient develops cardiac arrest, perform CPR. CPR may need to be performed for a long time and may require multiple trained assistants to take turns In a cardiac arrest, administer lipid emulsion ( Intralipid ® ), if available. Continue CPR throughout treatment with Intralipid 64

65. Lipid emulsion Give a bolus of 1.5 ml/kg IV over 1 minute, and Commence an infusion at 15 ml/kg/h If cardiac stability not achieved. Then, Repeat bolus injection twice at 5-minute intervals, and Increase the infusion rate to 30 ml/kg/h Continue CPR and the intralipid infusion until a stable circulation is established Maximum dose: 12 ml/kg (840ml) 65

66. For a 70 kg man:  Initial bolus:  100 ml of 20% Intralipid over 1 minute, and Commence an infusion at 1000 ml/hr. After 5 minutes:  repeat bolus of 100 ml. Maximum:  3 boluses in total and increase the infusion rate to 2000 ml/hr. 66

67. Cardiovascular system There may be a fall in blood pressure. This is usually seen in the first twenty minutes and could be explained by several mechanisms. Sympathetic blockade resulting in vasodilation The sympathetic nerves to the heart may be blocked. 67

68. Treatment of hypotension. In the event of a fall in blood pressure, exclude other causes e.g. blood loss, packs in the abdomen. If hypotension occurs: - Tilt the table head down. This must only be done if the spinal is 'fixed', otherwise the legs could be elevated, manually or by raising the lower half of the table 68

69. If blood pressure falls below 90mm Hg, increase IV fluids (Hartmann’s solution). Infuse 500ml rapidly. If blood pressure falls below 80mm Hg give ephedrine 5mg IV and repeat if necessary or aramine (Metaraminol) 0.25 - 0.5 mg IV in increments. Give oxygen by mask Give atropine IV if the hypotension is associated with a bradycardia Always exclude and treat aorto -caval compression in obstetric patients 69

70. Respiratory system . The breathing may become slow and shallow, perhaps as a result of the intercostal nerves being blocked by the spinal anaesthesia. The breathing may actually stop owing to paralysis of the respiratory centre after a total spinal. 70

71. Nausea and vomiting Due to a variety of causes. Always attempt to find out the cause. It may be associated with any of the following: • Hypotension • Hypoxia. • Traction on the nerve endings by the surgeon. • Morphine or pethidine given as pre-medication. • Nervousness, fear, 71

72. Treatment Treat the cause. -The main cause of nausea is hypotension. - Re-assurance. - Encourage deep breathing. - Metoclopramide ( Maxalon ) 10 mg IV or IM. - Ondansetron 4 mg. IV -Scopolamine 72

73. Broken needle A broken needle is a serious complication. Never apply force when inserting a needle into the subarachnoid space. If a needle does break leave the proximal part of the needle in place. Insert another needle along the tract. The patient must be X-rayed and the needle must be removed as soon as possible. 73

74. Total spinal Complete spinal block is caused by local anaesthetic interfering with the normal neuronal function in the cervical spinal cord and brain stem. This may occur accidentally. If a "total spinal" occurs, it means that either an excessive dose of local anaesthetic has been given or, because of faulty positioning 74

75. The results of a total spinal are: The blood pressure falls. If this is severe a cardiac arrest may result. Respirations become shallow and may even cease. The patient becomes cold and blue. 75

76. Treatment is supportive until the spinal wears off: - Ventilation with facemask or LMA. - Tracheal intubation and IPPV (with sedation). - Treat hypotension with fluid +/– vasopressor. Early recognition is vital as block progression may be mitigated (reverse trendelenberg /head raised) or serious cardio-respiratory compromise avoided. 76

77. FEATURE MANAGEMENT Bradycardia Vagolytics eg . atropine Hypotension Sympathomimetics eg . ephedrine, adrenaline Vasopressors eg . metaraminol , phenylephrine Fluid boluses Leg elevation Respiratory dysfunction Oxygenation Intubation and ventilation Loss of consciousness Secure airway , supportive measures 77

78. Shivering Post-anesthetic shivering is spontaneous, involuntary , rhythmic , oscillating, tremor-like muscle hyperactivity that increases metabolic heat production after general or regional anesthesia. The probable mechanisms could be decrease in core body temperature secondary to: sympathetic block; peripheral vasodilatation; Increased cutaneous blood flow, which leads to increased heat loss through skin; cold temperature of operation theatre; rapid infusion of cold IV fluids; and effect of cold anaesthetic drugs upon the thermo sensitive receptors in the spinal cord 78

79. Management Two approaches in the management of PAS: Non-pharmacological methods and minimising redistribution of heat; (ii) cutaneous warming during anaesthesia: Passive insulation/Active warming (iii) internal warming 79

80. Later complications PDPH Post-partum headache is the complaint of headache and neck or shoulder pain in the first 6 weeks Not all post headache is PDPH, and as anaesthetists are asked to review patients often, it is important to be aware of the differential diagnoses 80

81. PATHOGENESIS CSF leakage into the epidural space via a tear in the dura. CSF loss leads to a reduction in intracranial pressure and downward traction on pain-sensitive intracranial structures( veins , meninges and cranial nerves ) resulting in a headache that is classically worse in the upright position . The fall in intracranial pressure may also cause compensatory cerebro -vascular venodilation and this may contribute to the development of the headache 81

82. Differential diagnosis Infective: Meningitis, Encephalitis Pharmacological/Metabolic: D ehydration and Caffeine withdrawal Vascular: Migraine, Cerebral vein thrombosis , Cerebral infarction, Subdural haematoma & Subarachnoid haematoma 82

83. A history and examination should be performed taking account of the timing of the headache in relation to the neuraxial procedure, the nature of the headache as well as other symptoms and signs. In the case of a headache following a spinal procedure, PDPH is more likely following dural puncture with a larger gauge ‘ cutting’ tipped needle or after multiple attempts , increasing the chance of a CSF leak. 83

84. Classic features of the headache caused by dural puncture: Headache is often frontal-occipital. Most headaches do not develop immediately after dural puncture but 24-48 hours after the procedure with 90% of headaches presenting within 3 days. The headache is worse in the upright position and eases when supine. It is relieved by increasing abdominal pressure. Associated symptoms: neck stiffness, photophobia, tinnitus, visual disturbance and cranial nerve palsies 84

85. The incidence of spinal headaches is related to the size of the needle 85 Needle size Incidence of headaches 20G 22G 25G 26G 10–20% 8–15% 2–5% < 1%

86. Factors That May Increase the Incidence of Post–spinal Puncture Headache Age Younger more frequent Gender Females > males Needle size Larger > smaller Pregnancy More when pregnant Dural punctures (no.) More with multiple punctures 86

87. Prevention - Use a fine needle. - Make sure the fibres of the dura mater are divided and not cut by adjusting the bevel of the needle. - Avoid multiple punctures. - Nurse the patient flat for 6 hours post-operatively. - Avoid coughing and straining post-operatively. 87

88. Management Conservative Management: Most post-dural puncture headache will resolve spontaneously. Conservative management has traditionally involved bed rest and fluids though there is little evidence to support either of these measures. Simple analgesia should be instituted in all patients with PDPH; regular paracetamol and non-steroidal anti-inflammatory medications may control symptoms adequately 88

89. Caffeine: Caffeine was first reported as a treatment for PDPH in 1949. Caffeine is a central nervous system stimulant and is thought to influence PDPH by inducing cerebral vasoconstriction . Doses from 75 – 500 mg have been investigated and caffeine has been administered orally, intramuscularly and intravenously. Caffeine is associated with adverse events including cardiac arrhythmias and seizures 89

90. Epidural blood patch (EBP) after observation that patients blood spinal tap at lumbar puncture were less likely to develop PDPH. the first epidural blood patch was performed in 1960 by the American surgeon, Dr James Gormley. Just 2 ml of the patient’s blood was injected during the first epidural blood patch and the headache was relieved. 90

91. Epidural blood patching involves injection of autologous blood into the epidural space. It remains one of the few proven treatments of PDPH The resulting blood clot may have a “patch effect” on the dural tear while the volume of blood transfused into the epidural space raises intracranial pressure and reduces ongoing CSF leak. 91

92. EBP should be performed by two personnel, one an experienced anaesthetist, the other competent in taking a volume of blood from the arm. Both should employ full aseptic precautions. Contraindications to EBP include: - Sepsis, - Coagulopathy and - Patient refusal. 92

93. EBP is likely to be most effective if performed at least 24 hours after the onset of PDPH. Volumes of between 20-60mls of blood have been used. Optimal volume is unknown but current recommendations suggest 10 to 20ml should be injected 93

94. If the patient reports discomfort in the back during the procedure the injection should be stopped. The patient should lie flat for 1-2 hours after the procedure. There is no evidence that bed rest for longer than this time is beneficial. 94

95. Sepsis or infection This may take various forms. All of them are serious. • Extra dural abscess • Meningitis (inflammation of the coverings of the brain and spinal cord) • Encephalitis (inflammation of brain and spinal cord) • Radiculitis (inflammation of nerve roots) 95

96. Meningism This is an irritation of the meninges without actual infection. It presents like a meningitis and is diagnosed on a normal CSF tap. It is due to introduction of irritants into the subarachnoid space during the tap. 96

97. The advantage of spinal anesthesia over GA Minimal cost Patient satisfaction Reduced Respiratory disease- as long as high blocks are avoided Patent AW Muscle relaxation Minimal bleeding 97

98. Simple technique Splanchnic blood flow-increased blood flow to the gut ,so reduce incidence of anastomotic dehiscence Post op analgesia Prevent production of stress hormone-stress free Avoids risk of difficult intubation and its complication Increase feto -maternal bond 98

99. Decrease neonatal depression due to drugs DM-gut functions rapidly return to oral feeding and insulin Less post op. deep vein thrombosis and pulmonary embolism Decreased risk of air way obstruction or aspiration of gastric contents 99