Reginol anasth. uday
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The document summarizes regional anesthesia techniques, focusing on epidural anesthesia. It defines regional anesthesia and describes the history of its development. It then discusses in detail the anatomy related to epidural anesthesia, factors that influence the spread and effects of an epidural block, different local anesthetics used, placement of epidural catheters, and the technique for performing an epidural block. Key aspects covered include the importance of injection site, dose, and volume in determining block level, and choices of local anesthetic affecting duration.
Reginol anasth. uday
- 1. Co-ordinator:- Dr. Chavi sethi (M.D)Co-ordinator:- Dr. Chavi sethi (M.D) Speaker:- Dr. Uday pratapSpeaker:- Dr. Uday pratap Co-ordinator:- Dr. Chavi sethi (M.D)Co-ordinator:- Dr. Chavi sethi (M.D) Speaker:- Dr. Uday pratapSpeaker:- Dr. Uday pratap
- 2. Regional anaesthesia Definition • Rendering a specific area of the body, e.g. foot, arm, lower extremities, insensate to stimulus of surgery or other instrumentation. • Koller - 1884 uses cocaine for topical anesthesia • Halsted - 1885 performs peripheral nerve block with local • Augest Bier - 1899 first spinal anesthesia. Regional blocks: • Epidural Anaesthesia • spinal Anaesthesia • Caudal Anaesthesia
- 3. indication When deciding between epidural and spinal anesthesia, a number of variables should be considered. • The procedure (or surgeon's typical time) of predictable length, thus minimizing the need to consider a continuous catheter technique • Conversely, is the surgeon's estimate so unpredictable that a combined spinal and epidural technique should be recommended • The surgical procedure so short that waiting for the epidural to take effect makes spinal anesthesia more practical • If the patient a candidate for prolonged postoperative analgesia, thus making a continuous epidural technique preferred • the procedure can be equally well handled with spinal or epidural anesthesia, thereby allowing consideration of patient variables affecting the incidence of headache (e.g., age and gender)? • There are concurrent patient diseases, such as hypertrophic cardiomyopathy, that may be of concern with either technique . • If the patient traveling a significant distance immediately after the procedure, thus making epidural blood patch therapy for a post–spinal puncture headache problematic.
- 4. Contraindications • patient refusal; • Patient's inability to maintain stillness during the needle puncture, which can expose the neural structures to an unacceptable risk of injury. • Raised intracranial pressure, which may theoretically predispose to brainstem herniation. • Relative contraindications • Intrinsic and idiopathic coagulopathy, such as that occurring with administration of warfarin (Coumadin) or heparin; • Skin or soft tissue infection at the proposed site of needle insertion; • Severe hypovolemia • Lack of anesthesiologist experience. • Preexisting neurologic disease (e.g., lower extremity peripheral neuropathy) is not usually based on medical criteria but rather on medico legal considerations.
- 5. Epidural Anaesthesia • Anatomy • The Epidural space surrounds the Dura Mater posterior, laterally and anteriorly • Nerve roots travel in this space as they exit the spinal cord laterally • They then exit the foramen and travel peripherally to become peripheral nerves carrying both afferent and efferent pathways • Review of Ligaments, Membranes & Spaces: (from skin in) 1) Supraspinous Ligament 2) Interspinous Ligament 3) Ligamentum Flavum 4) Epidural Space 5) Dura 6) Arachnoid 7) Sub-arachnoid space
- 7. Epidural Anesthesia • An Epidural block can be performed at the Lumbar, Thoracic, Cervical and Caudal level. • It can be used as a “Single Shot” or with a catheter that allows intermittent boluses or a Continuous Infusion • One advantage of an Epidural is that the muscle blockade can range from none to complete.
- 8. Cont… Advantages • Consequently, Epidural techniques have the advantage of better control of level (and also of sympathetic blockade) • Epidural techniques allow for the placement of a continuous catheter which is especially useful for: 1) Cases of unpredictable duration 2) Prolonged postoperative analgesia 3) Chronic pain control 4) Obstetric Analgesia & Anesthesia The variables are more numerous than those of spinal anesthesia KEY factor in spread and distribution of the block and Baricity plays a VERY small factor when dealing with Epidurals, whereas in a Spinal, baricity is a. 1- factors that affect the level of the Epidural block are: 1) Injection Site 2) Dose 3) Volume 4) Concentration 5) Position 6) Age
- 9. INJECTION SITE: • Unlike Spinal anesthesia, Epidural anesthesia produces a segmental block that spreads both caudally and cranially. • Based on that fact, then the INJECTION SITE is arguably THE most important determinant of the spread of an epidural block. • The injection site should be in the MIDDLE of the range of dermatomes that needs to be anesthetized and closest to the main nerve roots involved. • Caudal epidural blocks are largely restricted to sacral and LOW lumbar dermatomes. • Thoracic levels can be reached by the caudal approach only if large volumes (30cc) are given. • In Lumbar, local anesthetic injections of 10cc tend to spread caudad to include all the sacral dermatomes • In Lumbar, injections of 20cc volumes produce much better quality sacral blocks and can also extend cranially to include the mid thoracic levels.
- 10. Injection Site cont… • Thoracic injections tend to produce a symmetric segmental band of anesthesia with minimal lumbar spread. • When using a thoracic approach, it is prudent to decrease your volume about 30- 50% to prevent cranially spread • It is generally not feasible to produce surgical anesthesia in the low lumbar or sacral nerve distributions when using thoracic injection sites. • Thoracic injection sites are ideally suited for procedures of the chest and upper abdomen or for relief of post-op thoracotomy pain with a catheter being placed for continuous infusions.
- 11. Dose, Volume & Concentration • Within the range typically used for surgical anesthesia, drug CONCENTRATION is relatively unimportant in determining block spread • DOSE & VOLUME, however, are important variables in determining both spread and quality of the Epidural block obtained. • If drug CONCENTRATION is held constant, increasing the volume of LA (and thereby increasing the DOSE) results in significantly greater average spread. • DOSE = Volume x Concentration (i.e. 15cc x 2.5mg/cc = 37.5mg; 20cc x 2.5mg/cc = 50mg) • The CONCENTRATION of the LA generally affects the DENSITY of the block, NOT the spread. • So a small volume of a more concentrated LA will produce a very limited BUT very strong block. • But take the same DOSE and double the volume, the spread will increase BUT the strength of the block may not be as intense.
- 12. Cont….. • NOTE: The increase in block level IS NOT in directly proportion to the volume increase. Doubling the volume WILL NOT double the block spread. It is a NON- linear relationship and doubling the volume will only increase the level about 1/3- 1/2 the original number of segments. • The same relationship exists with DOSE; doubling the dose will usually only increase the level of block the same 1/3-1/2 of the original number of segments blocked. • Recommended amounts of LA differ as to which level is being injected: Cervical/Thoracic doses are 0.7 to 1cc per segment with an initial volume of 10cc Lumbar level doses are 1.25 – 1.5cc per segment with an initial volume of 15-20cc • This is due to the narrowing of the spinal canal as it progresses cranially.
- 13. Cont…. • Using a lower concentration anesthetic can sometimes give you a differential block • The lower concentration means the dose is lower and there is less LA to penetrate the nerve roots so the block acts more peripherally on the nerves, differentially blocking sensory and pain fibers over larger muscle fibers in the center of the nerves. • An example of this is used in Obstetrics: Bupivicaine 0.25%, 20cc, usually ONLY provides a sensory block but leaves the motor fibers intact so the patient can push when needed to. If Bupivicaine 0.5% is given with the same volume, then a sensory as well as motor block is obtained, paralyzing the muscles at the levels of the block so NO pushing is going to be possible.
- 14. Age • Most (but NOT all) studies that have examined the effect of age on Epidural blocks have demonstrated a greater spread in older patients. • This is thought to be related to a less compliant epidural space and Dura Mater Height and Weight • The correlation between patient Height or Weight and spread of epidural block is very weak at best and seems to have no clinical significance • The only instance where it may have an effect is in EXTREMELY TALL people (greater than 6’6”) or in EXTREMELY SHORT (less than 4’10”) or in MORBIDLY obese patients pregnancy • Some have shown a greater spread at TERM and early in pregnancy. • Other studies have shown no significant differences in level of spread between pregnant and non-pregnant patients. • All solutions should be injected in increments of 3-5cc every 3 minutes and titrated to the desired anesthetic level. • If a catheter has been placed and you are injecting through the catheter, then the catheter needs to be aspirated prior to every injection to show no CSF is present.
- 15. 2- factor affecting Onset of Blockade • The onset of an epidural block can usually be detected within 5 minutes in the dermatomes immediately surrounding the injection site • The time to PEAK effect differs somewhat among different LA’s • Shorter acting drugs usually reach their maximum spread in 15-20 minutes • Longer acting LA’s usually reach their maximum spread in 20-25 minutes • Increasing the DOSE of LA, SPEEDS the onset of both motor and sensory block 3- factor affecting Duration of the Epidural block depends on: 1) The LA itself 2) Dose given 3) Patient age 4) Use of Adrenergic Agonists • choice of LA is the most important factor in determining DURATION of the block • Chlorprocaine is shortest, Lidocaine & Mepivicaine are intermediate and Bupivicaine and Ropivicaine produce the longest lasting Epidural blocks
- 16. Comparative Onset Times and Analgesic Durations of Local Anesthetics Administered Epidurally in 20- to 30-mL Volumes Drug Conc. (%) Onset (min) Duration (min) Plain 1:200,000 Epinephrine 2-Chloroprocaine 3 10-15 45-60 60-90 Lidocaine 2 15 1hr 20min-2hrs 2hrs-3hrs Mepivacaine 2 15 90-140 140-200 Bupivacaine 0.5-0.75 20 2hrs 45min-3hrs 45min 3hrs-4hrs Etidocaine 1 15 120-200 150-225 Ropivacaine 0.75-1.0 15-20 2hrs20min - 3hrs 2hrs30min- 3hrs20min. Levobupivacaine 0.5-0.75 15-20 150-225 150-240
- 18. Duration of the Epidural block……. 1)-LA’s and Duration • In lower doses (concentrations) BUPIVICAINE seems to have a preferential sensory block with minimal motor effect. • That is why it is an ideal drug for Obstetric ANALGESIA during labor, eliminating pain while preserving muscle function. 2)DOSE: Increasing the DOSE of a LA results in increased duration AND density of the block 3)AGE: There are conflicting studies, but the majority seem to show a longer duration of action in the elderly population. The exact reason is unknown.
- 19. Conti….. 4)Adrenergic Agents • Epinephrine in a concentration of 5 micrograms/cc (1:200,000) is the most common adrenergic agent added to epidural LA’s • It has been shown to prolong the blocks of Lidocaine and Mepivicaine by as much as 80%. • Epinephrine has been shown NOT to significantly prolong the duration of anesthesia when added to concentrated solutions of Bupivicaine and Ropivicaine used for surgical anesthesia. • The mechanism proposed, although never proven, is that through vasoconstriction, it slows the systemic absorption and elimination of the LA.
- 20. Epidural Catheters • Placing a catheter into the epidural space allows for continuous infusion or intermittent bolus techniques. In addition to extending the duration of the block, it may allow a lower total dose of anesthetic to be used, and, therefore, decrease the hemodynamic insults if incremental initial dosing is used. • Epidural catheters are useful for intraoperative epidural anesthesia and/or postoperative analgesia. • Typically, a 19- or 20-gauge catheter is introduced through a 17- or 18-gauge epidural needle. When using a curved tipped needle, the bevel opening is directed either cephalad or caudad, and the catheter is advanced 2–6 cm into the epidural space. • The shorter the distance the catheter is advanced, the more likely it is to become dislodged. Conversely, the further the catheter is advanced, the greater the chance of a unilateral block, due to the catheter tip either exiting the epidural space via an intervertebral foramen or coursing into the anterolateral recesses of the epidural space. • After advancing the catheter the desired depth, the needle is removed, leaving the catheter in place. The catheter can be taped or otherwise secured along the back.
- 22. Epidural Needles • The standard epidural needle is typically 17–18 gauge, 3 or 3.5 inches long, and has a blunt bevel with a gentle curve of 15–30° at the tip. • Tuohy needle is most commonly used . The blunt, curved tip helps push 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. If a single-shot epidural technique is chosen, a Crawford needle is appropriate • Needle modifications include winged tips and introducer devices set into the hub designed for guiding catheter placement. • Epidural needle is usually 10 cm is long, tuohy needle with oblique bevel(huber point)
- 25. Epidural Technique The technique of epidural anesthesia relies on the same four P's as spinal anesthesia, with minor modifications. Patient preparation and positioning are similar to a Spinal Anesthetic • Either the sitting or lateral decubitus positions can be used • Emergency equipment and monitors should be attached. • The most commonly performed Epidural is a Lumbar Epidural, followed by a Caudal, then Thoracic and finally Cervical • Today most high thoracic and cervical epidurals are performed under flouroscopic guidance by pain specialists as it takes a greater level of skill to successfully perform those procedures • Angles of approach for the various levels are markedly different • The Lumbar region is at or greater than 90 degrees to the skin • The Thoracic is at a much more acute angle due to the anatomical arrangement of the Thoracic Spinous Processes • Finally the Cervical is at an angle in between the previous two
- 30. Cont… • The Lumbar region is by far the easiest due to: 1) The angle of the Spinous processes 2) The larger spaces BETWEEN adjacent spinous processes 3) Easily identifiable location by using easy to find landmarks (Iliac crests) • Width of epidural space is greatest at this level . • With a Spinal Anesthetic, the practitioner seeks CSF by piercing the Dura. • In an Epidural, the practitioner seeks to place the tip of the needle into the fat- filled space DEEP to the Ligamentum Flavum and SHALLOW to the Dura. • This is done by using a completely different needle and injection technique than with a Spinal anesthetic, • The blunted tip of 16, 17 or 18 gauge needle is also designed specially to AVOID puncture of the dura and if it comes in contact with the Dura, the lack of a sharp point will hopefully just inwardly push the dura without puncturing it.
- 31. Cont… • The procedure is begun by identifying your anatomical landmarks and locating planned interspace of insertion. • Then the patient is positioned either sitting, prone or lateral decubetus. • A sterile prep is performed with the planned insertion point. • Local anesthetic (usually Lido 1% plain) is injected at the planned insertion site and a skin wheal is raised with an injection of 1-2 cc of local with the 25 Gneedle. • some people change local needles and place the 22G needle on the local syringe, and in the center of the skin wheal, go deeper along the planned injection tract, injecting slowly as they penetrate deeper into the subcutaneous tissue. • The Epidural needle is place bevel up and introduced into the skin. • It is passed slowly through the Supraspinous ligament and seated in the Interspinous Ligament before the stylet is removed. • needle is seated in the Interspinous ligament . it should still be supported in the same position, not drop down .
- 32. Cont… • After the stylet is removed , the needle is slowly advanced using the “Loss of Resistance” technique. • LOR syringe is typically made of glass and is filled with either 3-4cc of air, normal saline, or a mixture of saline and air. • As the syringe/needle combo is advanced, pressure is applied to the plunger of the syringe by “Bouncing” or intermittently applying pressure to the plunger. • The pattern is “move-bounce-move-bounce-move-bounce” until LOR is obtained. • The syringe needle combo should only be moved 0.5-1cm at a time and then tested for resistance or LOR. • The syringe/needle combo is advanced by applying pressure to the NEEDLE and not the syringe. • As the needle passes through the Ligamentum Flavum, resistance increases and you may feel a distinct “pop” as you pass through it. • Once you pass through the LF, you will experience an immediate LOR and then the tip of the needle will be in the Epidural Space.
- 36. Cont… • Once the Epidural space is reached, pass your stylet through the needle to make sure there are no tissue plugs possibly blocking the flow of CSF with an inadvertent Dural puncture. • Once it is determined that your needle tip is in the Epidural space, begin first by injecting a “TEST” dose of 3cc of LA containing Epi (Lido 1.5% w/Epi) • If you are intravascular, you will see an increase in heart rate within 30 seconds • It is also important to question the patient after the injection of your test dose • The questions asked should be aimed at determining if you may have inadvertently obtained a dural puncture or are possible injecting directly into the vascular system • Besides the tachycardia, with an Intravascular injection, the patient may experience a “ringing” or “buzzing” in the ears, a metallic taste in the mouth or circumoral numbness • . If you happen to have dural puncture by accident, the test dose should produce numbness and/or weakness or a “pins and needles” sensation in the lower extremities • This can take up to three minutes to occur, so you need to wait at least three minutes before continuing your injection of LA
- 37. Cont… • At this point, techniques and opinions differ as to whether to pass a catheter and inject your total dose via the catheter or inject your total dose through the needle and then insert the catheter. • The catheter first crowd feels that it is better because you can slowly raise your level of anesthesia having better control and less incidence of sympathetic block • The problem with the cath first is that it is possible for the catheter NOT to go correctly into the epidural space. It may come out a nerve root or kink or coil up and then you will be performing a useless epidural. • The needle crowd believe that the injection of the LA opens up and distends the epidural space and makes it easier to pass the catheter into the correct location • Also, if the catheter fails, you will have a complete block for a period of time and that may be all the time you need to complete the surgery or procedure. • Regardless of which technique is used, as you pass the catheter, the patient should be warned that at that moment they may feel an “electric shock” or a feeling like they hit their “funny bone” • This is caused by the cath tip brushing up against a nerve root or as it is passed into the epidural space.
- 38. • As you pass the catheter, you may initially feel resistance at the tip of the needle • A slightly stronger push may be needed and then you will feel the resistance drop and the catheter will thread smoothly • It should be inserted between 3-5cm and no more (3-5 little black lines). • CAUTION • NEVER pull the catheter back through the needle once it has been inserted • It is possible to catch the catheter on the needle tip and shear or cut the tip off • Then it becomes a permanent new addition to the epidural space and will be there for the rest of the patient’s life!
- 39. Conclusion • Epidural anesthesia offers advantages, • Chief among them are the lower risk of PDPH, less hypotension, the ability to prolong or extend the block using an indwelling catheter, and options to use the same catheter for postoperative analgesia • Despite the advantages and disadvantages of BOTH techniques and even done with very experienced hands, BOTH blocks can have systemic, toxic reactions and complications.
- 40. Complications of Neuraxial Blocks • Complications Associated with Adverse or Exaggerated Physiological Responses • Spinal anesthesia ascending into the cervical levels causes severe hypotension, bradycardia, and respiratory insufficiency • Cardiac Arrest during Spinal Anesthesia • Urinary Retention • Complications Associated with Needle or Catheter Insertion • Inadequate Anesthesia or Analgesia • Intravascular Injection • Total Spinal Anesthesia • Subdural Injection • Backache • Postdural Puncture Headache • Neurological Injury • Spinal or Epidural Hematoma • Meningitis and Arachnoiditis • Sheering of an Epidural Catheter • Complications Associated with Drug Toxicity • Systemic ToxicityTransient • Neurological Symptoms • Lidocaine Neurotoxicity
- 41. Spinal Anesthesia • Anatomic Landmarks to perform a Spinal Anesthetic: Bilateral Iliac Crests Body of L4 Vertebra (which should correspond to the position of a line drawn between the tops of both Iliac crests) • An IMPORTANT point: • spinal anesthetic at L4-L5 or L5-S1 or L3-L4, injecting into the Cauda Equina and NOT any where near the actual Spinal Cord so there is no danger of damaging the spinal cord itself. • The Spinal Cord: 1) Extends to L1 and continues as the Filum Terminally ending at the first segment of the coccyx. 2) 31 (Thirty one) pairs of spinal nerves carry motor and sensory information: Cervical (8), Thoracic (12), Lumbar (5), Sacral (5) and Coccygeal (1)
- 42. Fiber Class Subclass Myelin Diameter (µm) Conduction Velocity (msec) Location Function y to Local Anesthetic Block A α + 6-22 30-120 Efferent to muscles Motor ++ β + 6-22 30-120 Afferent from skin and joints Tactile, propriocept ion ++ γ + 3-6 15-35 Efferent to muscle spindles Muscle tone ++++ δ + 1-4 5-25 Afferent sensory nerves Pain, cold temperatur e, touch +++ B + <3 3-15 Preganglion ic sympatheti c Various autonomic functions ++ C - 0.4-1.2 0.1-2.0 Afferent sensory nerves Various autonomic functions Pain, warm temperatur e, touch ++
- 44. Spinal Anesthesia • That is why as a nerve is anesthetized, the order of block is: Sympathetic/Parasympathetic – small fibers (C fibers, B fibers, preganglionic; afferent & efferent) Sensory – small ,middle and intermediate diameter fibers (C, A-delta and A-Beta; afferent & efferent) • Motor – large, thick diameter fibers (A alpha, efferent) (A beta, afferent & efferent) (A gamma, efferent) • The Peripheral nervous system is divided into the SOMATIC and AUTONOMIC • SOMATIC system contains: INCOMING (afferent) sensory neurons for pain, proprioception, pressure, touch, etc. OUTGOING (efferent) motor fibers to skeletal muscles for movement, both reflexive and purposeful. • AUTONOMIC nervous system is the other branch of the peripheral nervous system and is divided into two parts: SYMPATHETIC – (stimulating) PARASYMPATHETIC – (relaxing)
- 45. Differential Blockade of spinal anaesthesia • Spinal Anesthesia interrupts SENSORY, MOTOR AND SYMPATHETIC nervous system innervation • As the LA is injected, it blocks the small C fibers of the sympathetic system first and gradually diffuses into the interior of the nerve where the larger fibers are for sensory and then motor. • Sympathetic nervous system blockade typically exceeds somatic (sensory) blockade by two (2) dermatomes. • This actually may be a conservative estimate with Sympathetic blockade sometimes exceeding sensory blockade by as many as six (6) dermatomes • This explains why hypotension can accompany even low sensory block levels.
- 46. Cont… • The Motor level is usually 2 dermatomes BELOW your sensory level due to the position of the motor fibers in the middle of the nerves. It takes longer for diffusion to get the LA into the nerves and as the concentration of LA decreases as the level rises, the amount of LA available for diffusion decreases consequently providing a weaker motor block. • This can have serious implications if you end up with a T4 sensory level and the sympathectomy is at T2 or higher. • Cardiac Accelerator fibers of the sympathetic nervous system originate at T1-T4, so with a block at T4 you may loose their effect and bradycardia will result. • Usually treated with Atropine; in severe cases Epinephrine is necessary to stimulate the heart rate sufficiently to maintain adequate cardiac output
- 47. Drug used in spinal Anaesthesia Local Anesthetic Mixture Dose (mg) * Duration (min) To T10 To T4 Plain Epinephrine, 0.2 mg Lidocaine (5% in 7.5% dextrose) 50-60 75-100 1hr 1hr 15min.-1hr 40min. Tetracaine (0.5% in 5% dextrose) 6-8 10-16 70-90 100-150 Bupivacaine (0.75% in 8.5% dextrose) 8-10 12-20 1hr 30min- 2hrs 1hr 40min-2hrs 30mn Ropivacaine (0.5% in dextrose) 12-18 18-25 80-110 — Levobupivacaine 8-10 12-20 90-120 100-150
- 50. Cont… • Local Anesthetics • Mechanism of Action: Local anesthetics produce conduction blockade of neural impulses by preventing passage of sodium ions through ion selective sodium channels in nerve membranes They bond to the sodium channel itself and keep it in the active or open position.
- 52. Local Anesthetics and Vasoconstrictors • Remember, the lower the pKa, the lower the amount of ionization for any given pH • Consequently, the lower the pKa, the more rapid the speed of onset of the block because it is the NEUTRAL form that can diffuse across the cell membrane. • The more NEUTRAL form that is available, the more that diffuses and the faster the onset of the block. • Epinephrine or Phenylephrine are frequently added to LA’s to prolong their duration of action • Epinephrine dose is 0.1-0.2mg • Phenylephrine dose is 2-5mg • Can prolong spinal anesthesia by up to 50% by causing localized vasoconstriction and decreasing the amount of vascular absorption.
- 54. Factor affecting level of spinal anaestesia • Baricity • Three different mixtures of Local Anesthetics are possible: Hyperbaric Solutions Hypobaric Solutions Isobaric Solutions • CSF has a baricity (specific gravity) of 1.003-1.008 at normal body temperature • Position of Patient • The position of the patient during and shortly after injection of the LA is a primary determinate of how high your level goes. • Supine, head slightly down will push your level up to T4-5 • Supine level usually will give you a T6-7 level • Supine with head slightly up will usually give you a T10-11 level.
- 55. Cont… • Other contributing factors: Any condition that lowers the amount of CSF in the cord by increasing intraabdominal pressure and causing engorgement of the epidural veins, applying outside pressure on the spinal cord a) Pregnancy b) Ascites c) Large abdominal or pelvic tumors All of these conditions will push your level much higher than you anticipate Age related decreases in CSF volume may push your level higher than expected in the elderly • Preop Evaluation and Patient Selection • Pre-anesthesia Evaluation and careful examination of the back needs to be done to look for spinal deformities, scars or the presence of inflammation or infection
- 56. Spinal needles • Spinal needles fall into two main categories: those that cut the dura and those with a conical tip. • Dura cutting include the Quincke-Babcock needle, the traditional disposable spinal needle, and the latter contain the Whitacre and Sprotte needles is dura non cutting • If a continuous spinal technique is chosen, use of a Tuohy or other thin-walled needle can facilitate passage of the catheter. • The use of small needles reduces the incidence of post–spinal puncture headache, whereas the use of larger needles improves the tactile sense of needle placement. Multiple punctures probably increase the incidence of headaches. • If use of a smaller needle increases the number of punctures, the difference between small and large needles in producing headaches may be reduced. • There is also a decrease in the incidence of post–spinal puncture headache when a conical-tipped needle is used, even when needle sizes are comparable. • Spinal needle are available of sizes-18 to 29G
- 58. Spinal Anesthetic Techniques • There are three main approaches for a spinal anesthetic: Midline Approach Paramedian (Lateral) Approach Lumbosacral (Taylor) Midline Approach • positions the patient either the lateral decubitus, sitting, or prone positions, each with advantages in specific situations. • After the equipment, local anesthetics and the patient have been properly prepared, • The midline approach relies on the ability of patients and assistants to minimize lumbar lordosis and allow access to the subarachnoid space between adjacent spinous processes, usually at the L2-3, L3-4, or sometimes the L4-5 space. • The palpating fingers (usually the index and third fingers) should identify the interspinous area by locating the caudad extent of the more cephalad spine and the midline by rolling the fingers in a medial-to-lateral direction . • A subcutaneous skin wheal is developed over this space, and the introducer is
- 61. Midline Technique conti……. • The introducer is grasped with the palpating fingers and steadied while the other hand is used to hold the spinal needle like a dart, and the fifth finger is used as a tripod against the patient's back to prevent patient movement and unintentional insertion to a level deeper than intended. • The needle, with its bevel parallel to the midline, is advanced slowly to heighten the sense of tissue planes traversed and to prevent skewing of nerve roots until the characteristic change in resistance is noted as the needle passes through ligamentum flavum and dura. • The stylet is then removed, and CSF should appear at the needle hub. If it does not, the needle is rotated in 90-degree increments until CSF appears. If CSF does not appear in any quadrant, the needle should be advanced a few millimeters and rechecked in all four quadrants. • If CSF still has not appeared and the needle is at a depth appropriate for the patient, the needle and introducer should be withdrawn and the insertion steps should be repeated because the most common reason for lack of CSF return is that the needle is being inserted off the midline. • Another common error preventing subarachnoid placement is excessive cephalad angulation on initial insertion of the needle.
- 62. Midline Technique conti…… • After CSF is freely obtained, the dorsum of the nondominant hand steadies the spinal needle against the patient's back while the syringe containing the therapeutic dose is attached to the needle. • CSF is again freely aspirated into the syringe, and the anesthetic dose is injected at a rate of approximately 0.2 mL/sec. After completion of the injection, 0.2 mL of CSF is aspirated into the syringe and reinjected into the subarachnoid space to reconfirm location and clear the needle of the remaining local anesthetic. • The patient and operating table should then be placed in the position appropriate for the surgical procedure and drugs chosen. • The midline approach is the technique of first choice because it requires anatomic projection in only two planes and provides a relatively avascular plane. • Remember the local is heavier than the CSF so it will sink if you leave the patient sitting and then you will end up with a Saddle block and that won’t help you if the case is a knee or hip!!
- 63. Paramedian Approach • This approach is also called the LATERAL approach • The difference between the Lateral and the Midline is in its insertion site of the needle and the angle of approach. • The skin wheal is placed 1-2cm LATERAL to the chosen interspace. • The needle is directed medial and cephalad at an angle of 15-20 degrees pointing towards the midline. • Advance the needle slowly and steadily and then feel the “pop” as penetrate the dura. • From here the technique is the same as the Midline technique. • The Lateral Technique is better to use in a patient with limited flexion of the back. • It also bypasses calcified ligaments encountered in elderly patients.
- 65. Lumbosacral Approach • A variation on the paramedian approach is the lumbosacral approach described by Taylor know as Taylor approach. • This technique is carried out at the L5-S1 interspace, the largest interlaminar interspace of the vertebral column. • A 5-inch spinal needle is inserted in a cephalomedial direction through a skin wheal raised 1 cm medial and 1 cm caudad to the lowermost prominence of the posterior superior iliac spine. • If bone is encountered on initial needle insertion, the needle is walked off the sacrum into the subarachnoid space. After CSF is obtained, the steps are similar to those outlined previously . Clinical Usage of SA • The ideal uses for Spinal Anesthesia are for: 1) Patients with co-existing Asthma or COPD; long history of pulmonary disease or a heavy smoker 2) Patient fearful of GA 3) Obs patient for a C-section 4) Patient with a history of Thrombophlebitis or at an increased risk of developing Thrombophlebitis 5) Any patient with an obviously difficult airway and who is undergoing a procedure that can be done under spinal
- 66. Caudal Anesthesia • Caudal anesthesia involves needle or catheter penetration of the Sacrococcygeal Ligament covering the Sacral Hiatus. • The Hiatus is created by the unfused S4 and S5 lamina. • The Hiatus can be felt as a groove or notch above the coccyx and between two bony prominences, the Sacral Cornua. • The Posterior Superior Iliac Spines and the Sacral Hiatus form a triangle . • The patient is placed either prone or in lateral decubitus. • A Sterile prep is done similar to an epidural and the landmarks are again palpated. • A needle or catheter is inserted at a 45 degree angle to the skin until a “pop” is felt. • Then the angle of the needle is dropped down and advanced, aspirating for blood or CSF every 1-2cm.
- 70. Caudal Anesthesia conti… • Some clinicians recommend test dosing as with other techniques, while most simply rely on incremental dosing with frequent aspirations. • Repeated injections can be given or a catheter can be placed for boluses or a continuous infusion. • For adults undergoing anorectal procedures, caudal anesthesia can provide dense sacral sensory blockade with limited cephalad spread. • A dose of 15-20cc of 1.5-2.0% Lidocaine with or w/o epi is usually effective. • This technique should be avoided in patients with Pilonidal cysts because the needle may pass through the cyst track and introduce bacteria into the epidural space and lead to infection and abscess formation.
- 71. dosage prescription scheme of Armitage • Dosage prescription scheme of Armitage that was published many years ago still remains the most dependable. • With 0.5 mL/kg, all sacral dermatomes are blocked. • With 1.0 mL/kg, all sacral and lumbar dermatomes are blocked. • With 1.25 mL/kg, the upper limit of anesthesia is at least midthoracic. • However, when 1.25 mL/kg is injected there is a danger of excessive rostral spread (above T4). it is therefore preferable not to administer more than 1.0 mL/kg of local anesthetic.
- 73. adjuvents • epinephrine (0.2mg) • phenylephrine( 5mg) • Clonidine, an α2-agonist, prolongs the motor block • neostigmine • morphen
Editor's Notes
- #3: Definition of regional anesthesia is