Regional anesthesia

regional anaesthesia - spinal , epidural, and caudal anaesthesia. procedure and complications

1. DR. SUHAS. U DEPARTMENT OF SURGERY APOLLO HOSPITAL , MYSORE A PRESENTATION ON REGIONAL ANESTHESIA BY

2. Regional Anesthesia

3. Objectives Anatomy of spinal canal Identify anatomic landmarks for proper placement of a spinal needle Define appropriate steps for placement of spinal, epidural, or caudal needle Distinguish level of anesthesia after administration of regional State factors affecting level and duration of spinal vs. epidural block Explain potential complications and corresponding treatments associated with administration of regional anesthetics

4. Spinal Anatomy 33 Vertebrae 7 Cervical 12 Thoracic 5 Lumbar 5 Sacral 4 Coccygeal

5. Spinal Cord GENERAL CONSIDERATIONS Adult Begins: Foramen Magnum Ends: L1 Newborn Begins: Foramen Magnum Ends: L3 Terminal End: Conus Medullaris Filum Terminale : Anchors in sacral region Cauda Equina : Nerve group of lower dural sac

6. Sagittal Sections (ANATOMY CONTD) Supraspinous Ligament Outer most layer Interspinous Ligament Middle layer Ligamentum Flavum Inner most layer Space that surrounds the spinal meninges Potential space(epidural) Widest at Level L2 (5-6mm) Narrowest at Level C5 (1-1.5mm)

7. Spinal Meninges Dura Mater Outer most layer Fibrous Arachnoid Middle layer Non-vascular Pia Inner most layer Highly vascular Sub Arachnoid Space Lies between the arachnoid and piamater .

8. Spinal Technique Preparation & Monitoring ECG NBP Pulse Oximeter Patient Positioning Lateral decubitous Sitting Prone (hypobaric technique)

9. Spinal APPROACHES Midline Approach Skin Subcutaneous tissue Supraspinous ligament Interspinous ligament Ligamentum flavum Epidural space Dura mater Arachnoid mater Paramedian or Lateral Approach Same as midline excluding supraspinous & interspinous ligaments

10. Technique Palpate the spinous process Cervical and lumbar are horizontal Thoracic – slant in caudal Slight angled in lumbar Identification of the spine level C7- most prominent cervical spine T7-inferior angle of scapula L4- line joining iliac crest S2- PSIS Loss of resistance and flow of CSF

11. Mechanism of Action Un-ionized local anesthetic diffuses into nerve axon & the ionized form binds the receptors of the Na channel in the inactivated state.

12. Metabolism & Toxicity Metabolism Ester locals are metabolized by plasma psuedocholinesterase Amide locals are metabolized by the liver Toxicity Determined by blood concentration of local anesthetics

13. Sequence of Loss of Nerve Function with Local Anesthetics (LA) 1 . Sympathetic (vasomotor): dilation of skin and blood vessels including arteries and veins 2. Temperature discrimination & pain recognition 3. Touch and pressure sense 4. Proprioception (awareness of body position) 5. Motor function Sympathetic block is 2-6 dermatomes higher than sensory block Motor block is 2 dermatomes lower than sensory block

14. Factors Effecting Distribution Site of injection Shape of spinal column Patient height Angulation of needle Volume of CSF Characteristics of local anesthetic Density Specific gravity Baricity Dose Volume Patient position (during & after)

15. Local Anesthetics & Baricity Hyperbaric Typically prepared by mixing local with dextrose Flow is to most dependent area due to gravity Hypobaric Prepared by mixing local with sterile water Flow is to highest part of CSF column Isobaric Neutral flow that can be manipulated by positioning Very predictable spread Increased dose has more effect on duration than dermatomal spread

16. Most commonly used local anesthetic : Bupivacaine 0.5% and 0.25% Lignocaine 2% (transient neurological symptoms) Adjoints like opioids and adrenaline

17. Indications & Advantages Anatomic distortions of upper airway Lower abdominaL surgeries Obstetrical surgery (T4 Level) Decreased post-operative pain Con traindications Absolute : Refusal Infection Coagulopathy Severe hypovolemia Increased intracranial pressure Severe aortic or mitral stenosis Relative: Doctor’s judgment

18. SYSTEMIC EFFECTS Cardiovascular Effects Blockade of Sympathetic Preganglionic Neurons Send signals to both arteries and veins Predominant action is venodilation Reduces: Venous return Stroke volume Cardiac output Blood pressure

19. T1-T4 Blockade Causes unopposed vagal stimulation Bradycardia Associated with decrease venous return & cardioaccelerator fibers blockade Decreased venous return to right atrium causes decreased stretch receptor response Treatment Best way to treat is physiologic not pharmacologic Primary Treatment Increase the cardiac preload Large IV fluid bolus within 30 minutes prior to spinal placement, minimum 1 liter of crystalloids Secondary Treatment Pharmacologic Ephedrine is more effective than Phenylephrine

20. Respiratory System Healthy Patients Appropriate spinal blockade has little effect on ventilation High Spinal Decrease functional residual capacity (FRC) Paralysis of abdominal muscles Intercostal muscle paralysis interferes with coughing and clearing secretions Apnea is due to hypoperfusion of respiratory center

21. Different settings Oral coagulants – INR / prothrombin time Antiplatelet drugs- Ticlopidine (14days), clopidogrel (7days) , Abciximab (48hrs), Eptifibatide (8hrs) Unfractionated Heparin Minidose s.c heparin – not a contraindication Need for systemic heparin intraop - block to be given 1Hr before Increased aPTT - avoid regional

22. COMPLICATIONS AND SURGICAL RELAVENCE Exaggerated physiological response Associated with needle placement Associated with catheter placement Associated with medication toxicity

23. Exaggerated Physiological Response Include High neural blockade Cardiac arrest Urinary retention High Neural Blockade Causes Excessive doses of local anesthetic are administered Failure to reduce dose in patients susceptible to excessive spread (i.e. the elderly, pregnant, obese, or short patients) Unusual sensitivity Unusual excessive spread

24. High Neural Blockade – SYMPTOMS AND MANAGEMENT Dyspnea Numbness and tingling of the upper extremities (i.e. fingers) Nausea generally preceedes hypotension due to hypoperfusion of the chemoreceptor trigger zone Mild to moderate hypotension TREATMENT Change position with hyperbaric technique(i.e. reverse Trendelenberg ) Stop the administration of local anesthetics with an epidural technique Supplemental oxygen Liberal use of IV fluids Treat hypotension with ephedrine or phenylephrine Treat bradycardia

25. Urinary Retention Due to blockade of S2-S4 Leads to a decrease in bladder tone and inhibition of normal voiding reflex Neuraxial opioids may contribute to urinary retention More common in elderly men and those with a history of benign prostatic hypertrophy Urinary catheterizes should be provided for patients undergoing moderate to lengthy procedures Postoperative assessment is important to detect urinary retention Prolonged urinary retention may be a sign of serious neurological injury

26. Complications Associated with Needle Placement or Catheter Insertion Inadequate anesthesia or analgesia Inadvertent intravascular injection Total spinal Subdural injection Backache Postdural puncture headache Neurological injury Spinal or epidural hematoma Meningitis and arachnoiditis Epidural abscess Sheering off the tip of the epidural catheter

27. Inadequate Analgesia or Anesthesia- May be associated with anatomical factors with epidural more than spinal. Inadvertent Intravascular Injection Toxicity will affect the central nervous system and cardiovascular system SYMPTOMS : Hypotension, Arrhythmias , Cardiovascular collapse , Seizures, Unconsciousness. Local Anesthetic Toxicity Treatment i.V intralipoid solution

28. SUBDURAL INJECTION Most commonly associated with epidural analgesia Larger doses of local anesthetics associated with epidural anesthesia may result in a total spinal . BACK ACHE Back ache may be a sign of serious complications such as epidural/spinal hematoma, abscess

29. Postdural Puncture Headache Headache occurs due to leakage of CSF through the dura Decrease in intracranial pressure occurs due to the leak Upright position in the patient leads to traction on the dura , tentorium, and blood vessels resulting in pain. Traction on the 6 th cranial nerve can result in diplopia and tinnitus Headache may be bilateral, frontal, retroorbital and/or occipital with or without radiation to the neck Described as “throbbing” or constant May be associated with nausea and/or photophobia Onset is generally 12-72 hours; rarely is the onset immediate If untreated it may last for weeks Increased post dural puncture headache in younger patients, in female patients, and in pregnant patients

30. Postdural Puncture Headache- Associations Increased incidence related to needle size, needle type The larger the needle the higher the incidence Cutting point needles have a higher incidence of post dural puncture headache than pencil points When using cutting point needles orientate the bevel “sideways” so it will be parallel with the fibers. This will act to “spread” the fibers as opposed to cutting them A wet tap with a 17 g. epidural needle will yield a 50% incidence of pdph

31. PDPH TREATMENT Supine position - will reduce symptoms, no evidence that bed rest will reduce the duration of post dural puncture headache. Theoretically it should decrease the amount of CSF leak and allow replacement of lost CSF. Hydration - theoretically helps to encourage the production of CSF . Caffeine - theoretically helps to decrease symptoms by vasoconstriction of the cerebral vessels. May decrease symptoms but does not necessarily decrease the number of patients that will require an epidural blood patch. IV caffeine can be administered in a dose of 500 mg Oral caffeine can be encouraged. Analgesics - will decrease the severity of symptoms and include acetaminophen and NSAIDS Stool softners and soft diet may help decrease Valsalva straining which may increase leakage of CSF

32. PDPH - Epidural Blood Patch Generally offered 12-24 hours after the initiation of conservative treatment Check coagulation status Ensure no anticoagulants have been administered (i.e. DVT prophylaxis) Ensure that the patient is not bacteremic Should be administered one space below the dural puncture site Blood patch works by mass effect and stops the leakage of CSF or alternatively by coagulating and “plugging” the hole Place 15-20 ml of blood into the epidural space Increased risk of meningitis or infection has to be explained to the patient. PDPH is 90% effective and not absolutely curative.

33. Other Less encountered complications Neurological Injury Spinal/Epidural Hematoma Meningitis Arachnoiditis Epidural Abscess Transient Neurological Symptoms Cauda Equina Syndrome Allergic Reactions

34. EPIDURAL ANESTHESIA

35. The epidural space is a potential space and is normally filled with blood vessels, lymphatic vessels, fatty tissue and spinal nerve roots . Epidural catheters in the epidural space do not pose a mechanical threat to the spinal cord. Single bolus , or the catheter is left in place for ideally 2 to 5 days with a continuous infusion, depending on the surgery.

36. There are two types of medications commonly administered via the epidural route for surgical patients: 1. Opioid - usually, Fentanyl or Hydromorphone , 2. Local Anesthetics (LA) - usually Bupivicaine or Ropivicaine These are usually administered as combined (1 local anaesthetic and 1 opioid solution) for continuous epidural infusions. The dose of spinal analgesia is only 1/10th of the dose used in the epidural space.

37. CONTRAINDICATIONS FOR EPIDURAL ANESTHESIA Absolute Sensitivity to local anaesthetic Concurrent or recent anticoagulation Patient refusal Uncorrected hypovolemia Relative ( used with caution): Coagulation disorders Sepsis (local or generalized ) Increased intracranial pressure Unstable spinal fractures Morbid obesity (difficulty with line placement)

38. Lumbar and Thoracic Epidurals LUMBAR More likely to cause urinary retention More likely to cause lower extremity weakness/ motor block THORACIC Less likely to cause a lower extremity motor block Less likely to cause urinary retention: o Epidural T10 level or higher: question the need for an indwelling urinary catheter. o Evidence shows that the risk for developing a UTI is much higher for patients who have a urinary catheter in for the duration of the epidural infusion compared to those who have the urinary catheter removed on Postoperative Day 1.

39. DISCONTINUING EPIDURAL THERAPY If patient has received anticoagulation while an epidural is insitu , DO NOT REMOVE epidural catheter. Removal must be carefully coordinated and often includes holding a dose and/or administering Vitamin K and ensuring PTT/INR are within normal limits prior to removal. If recent PTT/INR available ensure INR equal to or below 1.2 and PTT less than 40. If elevated, DO NOT REMOVE CATHETER . Remove epidural catheter 2 hours prior to next dose of unfractionated subcutaneous heparin .

40. If patient on once a day LMWH such as Dalteparin or Enoxaparin , removal must be 12 hours after last dose(2 hours prior to the next dose of Dalteparin or Enoxaparin ). Assess black tip of catheter is smooth and round Apply band aid to site for 24 hours. COMPLICATIONS ARE SIMILAR TO SPINAL ANESTHESIA AS MENTIONED EARLIER

41. Caudal Anaesthesia Pediatric patients Anorectal surgery in adults Sacral portion of epidural space Needle penetration of the sacrococcygeal ligament covering sacral hiatus In children usually combined with GA

42. Procedure Lateral or prone position Both hips flexed and sacral hiatus palpated Needle advocated at 45 degree cephalad Pop felt – sacrococcygeal ligament pierced Angle is then flattened and advanced Bupivacaine with epinephrine with opiods

43. Uses Infants and children Surgery of perianal and rectal region Inguinal and femoral hernia Cystoscopy and urethral surgery Haemorrhoidectomy Evaluation of perianal , pelvic, perineal and lower extremity pain For PAIN MANAGEMENT

44. Difficulties and problems Calcification of sacrococcygeal ligament Inadvertant intrathecal Total spinal and intravascular anaesthesia Avoided in patients with pilonidal cyst

45. BIBLIOGRAPHY MILLER TEXT BOOK OF ANESTHESIA – 8 TH EDITION OXFORD HANDBOOK OF ANESTHESIOLOGY CLINICAL ANESTHESIA – MORGAN AND MIKHAIL BRITISH JOURNAL OF ANESTHESIOLOGY INTERNET