DESTA OLI WAKTASU https://www.facebook.com/abdii.biyyaa.5015/ MEDICAL LOCAL ANESTHESIA and ADJUVANTS.pptxCALL [phone]

THIS GIVES SOME CLUE ABOUT LOCAL ANESTHESIA TYPES AND ADVJUVANTS IN ANESTHESIA

1. REGIONAL ANESTHESIA-LOCAL ANESTHEISA DESTA OLI (BSC,BA,MSC LECTURER) AWHSC,DBU,ETHIOPIA 8/1/2024 1

2. OUTLINES OBJECTIVES INTRODUCTION PHARMACODYNAMICS/KINETICS TYPES OF LOCAL ANESTHETICS ADDITIVES TO LOCAL ANESTHETICS TREATMENT OF SYSTEMIC TOXICITY OF LOCAL ANESTHETICS REFERENCES 8/1/2024 2

3. OBJECTIVES By the end of this lesson, Students will be able to: Define LA Mention adjuvants of LA and anethesia implications Explain LAST Discuss Factors affecting the effectiveness of RA Manage LAST 8/1/2024 3

4. PRE-LECTURE QUIZ TRUE/FALSE Fentanyl is the only Adjuvant added to LA CHOICE W/c of the following is Odd? A.Lidocaine B. Bupivacaine C.Ropivacaine D.Cocaine .EXPLAIN/ESSAY 3.Define Local Anesthesia systematic toxicity and mention management principles 8/1/2024 4

5. BRAINSTORMING An 18-year-old woman in the active stage of labor requests an epidural anesthetic. Immediately following injection of 2 mL and 5 mL test doses of 1.5% lidocaine with 1:200,000 epinephrine through the epidural catheter, the patient complains of lip numbness and becomes very apprehensive. Her HR has increased from 85 to 105 beats/min. What is your presumptive diagnosis? What measures should be immediately undertaken? 8/1/2024 5

6. INTRODUCTION RA must be administered in an area where standard anesthetic monitors, supplemental oxygen, and resuscitative medications and equipment are immediately available The selection of a RA technique is a process that begins with a thorough Hx and PE. As with any medical procedure a risk–benefit analysis must be performed 8/1/2024 6

7. INTRODUCTION There are several kinds of regional anesthesia. Two of the most frequently used are SA and epidural anesthesia Another common type of regional anesthesia is a peripheral nerve block Often, both GA and RA are combined 8/1/2024 7

8. INTRODUCTION In a closed claims analysis, PNB were involved in 159 of the 6894 claims analyzed. PNB claims were for death (8%), permanent injuries (36%), and temporary injuries (56%). The brachial plexus was the most common location for nerve injury Cardiac arrest and epidural hematomas are two of the more common damaging events leading to severe injuries related to RA. 8/1/2024 8

9. INTRODUCTION Accidental IV injection and LA toxicity also contributed to claims for brain injury or death. Nerve injuries constitute the third most common source of anesthesia litigation . Perioperative nerve injuries may result from compression, stretch, ischemia, other traumatic events, and unknown causes. Improper positioning can lead to nerve compression, ischemia, and injury; however, not every nerve injury is the result of improper positioning 8/1/2024 9

10. INTRODUCTION Many peripheral nerve injuries do not become manifest until more than 48 h after anesthesia and surgery Suggesting some nerve damage may arise from events taking place after the patient leaves the OR 8/1/2024 10

11. Types of Local Anesthetics-Pharmacodynamics/Kinetics

12. Cont … Local and regional anesthesia and analgesia techniques depend on a group of drugs—local anesthetics—that transiently Inhibit some or all of sensory, motor, or autonomic nerve function when the drugs are applied near neural tissue. The decision about which LA to employ for a particular nerve block depends on the Desired onset,Duration , Relative blockade of sensory and motor fibers

13. Cont … LA drugs are classified as esters or amides Ester-Linked Local Anesthetics Ester-linked LAs are hydrolyzed at the ester linkage in plasma by pseudocholinesterase .

14. Cont … The rate of hydrolysis of all ester-linked LAs is markedly decreased in : Patients with atypical plasma pseudocholinesterase A prolonged epidural block in a patient with abnormal pseudocholinesterase has been reported. Hallmark of metabolism of ester-linked LAs is that their hydrolysis leads to the formation of para-aminobenzoic acid (PABA). PABA and its derivatives carry a small risk potential for allergic reactions.

15. Cont … Cocaine Cocaine occurs naturally in the leaves of the coca shrub and is an ester of benzoic acid. However, its toxicity and the potential for abuse have precluded wider clinical use of cocaine in modern practice. It has euphoric properties Other LAs do not block the uptake of norepinephrine and do not produce the sensitization to catecholamines , vasoconstriction, or mydriasis characteristics of cocaine. Currently, cocaine is used primarily to provide topical anesthesia

16. Cont … Procaine Procaine, an amino ester, was the first synthetic LA. Procaine is characterized by low potency, slow onset, and short duration of action. Mainly for infiltration anesthesia and perhaps diagnostic nerve blocks.

17. Cont … 2-Chloroprocaine An ester LA introduced in 1952, 2-chloroprocaine is a chlorinated derivative of procaine. Because of its rapid breakdown in plasma (<1 minute), it has a very low potential for systemic toxicity. This drug has largely replaced lidocaine for short-acting spinal anesthetics for procedures lasting less than 1 hour.

18. Cont … Tetracaine Tetracaine was introduced in 1932, and it is a long-acting amino ester. It is significantly more potent and has a longer duration of action than procaine or 2-chloroprocaine . Slowly metabolized than the other commonly used ester LAs, and it is considerably more toxic . Used in SA when a drug of long duration is needed, as well as in various topical anesthetic preparations. Because of its slow onset and potential for toxicity , tetracaine is used rarely for PNB Tetracaine in combination with local anesthetics, commonly lidocaine = “ supercaine .”

19. Cont … Amide-Linked Local Anesthetics As opposed to ester-linked drugs, amide-linked LAs are metabolized in the liver The hepatic blood flow and liver function determine the hepatic clearance of these anesthetics. Factors that decrease HBF or hepatic drug extraction result in an increased elimination half-life.

20. Cont … Lidocaine Lidocaine was introduced in 1948 and it remains one of the most versatile and widely used LAs . Lidocaine can be used in almost any peripheral nerve block in which a LA of intermediate duration A concentration of 1.5% / 2% with or without the addition of epinephrine is most commonly used More diluted concentrations are suitable in pain management, particularly for diagnostic blocks.

21. Cont … Mepivacaine Mepivacaine , introduced in 1957, is an intermediate duration amino amide LA. Its pharmacologic properties are similar to those of lidocaine . Although it was suggested that mepivacaine is more toxic to neonates Its onset of action is similar to that of lidocaine

22. Cont … Prilocaine Prilocaine is an intermediate-duration amino amide LA with a pharmacologic profile similar to lidocaine . The primary differences are a lack of vasodilatation and an increased volume of distribution, which reduces its CNS toxicity. Unique among amide LAs for its propensity to cause methemoglobinemia If necessary, it is treated by IV administration of methylene blue (1–2 mg/kg). Prilocaine is used infrequently in peripheral nerve blockade.

23. Cont … Etidocaine Etidocaine is a long-acting amino amide introduced in 1972. Its neuronal blocking properties are characterized by an onset of action similar to that of lidocaine and a duration of action comparable with that of bupivacaine. A major disadvantage of etidocaine is its profound motor blockade over a wide range of clinical concentrations, which often outlasts sensory blockade. For these reasons, etidocaine is not used for peripheral nerve blockade.

24. Cont … Bupivacaine Since its introduction in 1963, bupivacaine has been one of the most commonly used LAs in regional and infiltration anesthesia. Bupivacaine is a long-acting agent capable of producing prolonged anesthesia and analgesia It is substantially more cardiotoxic than lidocaine . Because of its toxicity profile, large doses of bupivacaine should be avoided.

25. Cont … Ropivacaine The cardiotoxicity of bupivacaine stimulated interest in developing a less toxic, long-lasting LA. Ropivacaine undergoes extensive hepatic metabolism after IV administration Ropivacaine is slightly less potent than bupivacaine in producing anesthesia when used in lower concentrations. Ropivacaine has become one of the most commonly used long acting LAs in peripheral nerve blockade .

26. Cont … Levobupivacaine Levobupivacaine contains a single enantiomer of bupivacaine hydrochloride, and is less cardiotoxic than bupivacaine. It is extensively metabolized with no unchanged drug detected in the urine or feces. Levobupivacaine is a suitable, less toxic alternative to bupivacaine.

27. Local anesthetics, their classification, chemical structure, and approximate time of introduction

28. ADDITIVES TO LOCAL ANESTHETICS Vasoconstrictors Addition of a vasoconstrictor to a LA delays vascular absorption, increasing the duration The net effect is prolongation of the blockade by as much as 50% and a decrease in the systemic absorption of LA. Epinephrine is the most commonly used vasoconstrictor in peripheral nerve blockade.

29. Cont … Epinephrine also serves as a marker of intravenous injection of local anesthetic. An increase in HR of 20 bpm or greater and/or an increase in SBP of 15 mmHg or greater after a dose of 15 mg of epinephrine is should raise a suspicion of IV injection

30. Cont … Opioids The injection of opioids into the epidural or subarachnoid space to manage acute or chronic pain is Based on the knowledge that opioid receptors are present in the substantia gelatinosa of the spinal cord. Thus combinations of a LA and an opiate are often successfully used in neuraxial blockade to both enhance the blockade and prolong analgesia. However, in peripheral nerves , similar receptors are absent or the effects of opiates are negligibly weak. For this reason, opiates do not have a significant clinical role in peripheral nerve blockade.

31. Cont … Clonidine Clonidine is a centrally acting selective partial α2-adrenergic agonist . Because of its ability to reduce sympathetic nervous system output from the CNS, clonidine acts as an antihypertensive drug . Preservative-free clonidine, administered into the epidural or subarachnoid space ( 150–450 μg ), Produces dose-dependent analgesia and, unlike opioids, does not produce depression of ventilation, pruritus, nausea, or vomiting . Clonidine produces analgesia by activating postsynaptic α2 receptors in the substantia gelatinosa of the spinal cord.

32. Choice of Local Anesthetic for Peripheral Nerve Blockade

33. MIXING OF LOCAL ANESTHETICS Mixing of LAs is often done for the faster onset and the longer duration Therefore, if long duration is desired, a long-acting drug alone will provide the best conditions. In addition, mixing LAs also carries a risk of a drug error.

34. Systemic Toxicity of Local Anesthetics In addition to interrupting peripheral nerve conduction, LAs interfere with the function of all organs in which the conduction or transmission of nerve impulses occurs. For instance, they have important effects on the CNS, the autonomic ganglia, the NMJ, and musculature. The risk is proportional to the concentration of LA achieved in the circulation

35. Cont … Plasma Concentration of Local Anesthetics The following factors determine the plasma concentration of LAs: The dose of the drug administered The rate of absorption of the drug Site injected, vasoactivity of the drug, use of vasoconstrictors Biotransformation and elimination of the drug from the circulation

36. Central Nervous System Toxicity Progression of local anesthetic toxicity.

37. Cardiovascular Toxicity The primary site of action of LAs in the cardiovascular system is the myocardium, Where they decrease electrical excitability, conduction rate, and the force of myocardial contraction. Most LAs also cause arteriolar dilatation, contributing to hypotension. Cardiovascular effects typically occur at higher systemic concentrations than those at which effects on the CNS are produced. However , note that it is possible for cardiovascular collapse and death to occur even in an absence of the warning signs and symptoms of CNS toxicity.

38. Suggested Emergency Drugs Required During Nerve Block Procedures

39. Cont …

40. TREATMENT OF LAST Three pillars of LAST treatment consist of Seizure management, Advanced cardiac life support ACLS administration of a 20% lipid emulsion. For hermodynamically stable patients with isolated seizure activity, intravenous benzodiazepines may be used.

41. Cont … Small doses of propofol are considered by some an acceptable alternative for seizure control but can worsen cardiac dysfunction that may develop with LAST. Supplemental oxygen is appropriate for any patient exhibiting signs of LAST, but for patients with apnea, hemodynamically unstable arrhythmias, or cardiac arrest, immediate, more aggressive airway management or circulatory support is required.

42. Factors affecting the effectiveness of RA The most important determinants are baricity of the local anesthetic solution, position of the patient during and immediately after injection, and drug dosage . Moreover , migration of the local anesthetic cephalad in CSF depends on its density relative to CSF ( baricity ). A hyperbaric solution of local anesthetic is denser (heavier) than CSF, whereas a hypobaric solution is less dense (lighter) than CSF.

43. Cont … The local anesthetic solutions can be made Hyperbaric by the addition of glucose or hypobaric by the addition of sterile water or fentanyl . A head-up position causes a hyperbaric solution to settle caudad and a hypobaric solution to ascend cephalad

44. Cont …

45. SUMMARY Knowledge of regional anatomy and an understanding of the planned surgical procedure are important for selection of the appropriate RA technique Anesthesists use LAs every day in various practice locations and for a wide variety of procedures. Every site where LAs are used in potentially toxic doses should be Equipped with basic resuscitation equipment and a 20% lipid emulsion. There is a greater likelihood for LAST in petite patients (small muscle mass), those at the extremes of age, and patients with preexisting heart disease

46. Cont … An intravascular marker such as 10–15 μg of epinephrine has reasonable sensitivity and positive predictive value and can be administered with a test dose. An increase in HR of 10 beats/minute or greater or an increase in SBP of 15 mm Hg or greater suggests an intravascular injection. Incremental injection of LAs (usually 3–5 mL) and frequent aspiration have been regularly recommended and, together with the use of the test dose, may have contributed to the decrease in the incidence of LAST seen with epidurals.

47. Cont … Baricity , in the context of SA, refers to The density of an LA solution relative to the density of CSF. It influences how the anesthetic spreads in the CSF and ultimately affects the level of anesthesia achieved.

48. Cont … No current monitoring method can prevent systemic toxicity. Cases have been reported despite Negative aspiration for blood, The use of recommended dosages The observation of local anesthetic spread in a tissue plane and not intravascularly . NOTE : Constant vigilance and preparation for Rx is essential during all regional anesthetic procedures

49. Cont … Local anesthetics potentiate NDMRB in laboratory experiments, but this likely has no clinical importance. Both succinylcholine and ester local anesthetics depend on pseudocholinesterase for metabolism. There is no evidence that this potential competition between ester local anesthetics and succinylcholine for the enzyme has any clinical importance. Dibucaine , an amide local anesthetic, inhibits pseudocholinesterase , and the extent of inhibition by dibucaine defines one form of genetically abnormal pseudocholinesterases

50. Cont … Resuscitation from bupivacaine-induced cardiac toxicity is often difficult and resistant to standard resuscitation drugs. Multiple clinical reports suggest that bolus administration of nutritional lipid emulsions at 1.5 mL/kg can resuscitate bupivacaine-intoxicated patients who do not respond to standard therapy

51. POST-LECTURE QUIZ TRUE/FALSE Fentanyl is the only Adjuvant added to LA CHOICE W/c of the following is Odd? A.Lidocaine B. Bupivacaine C.Ropivacaine D.Cocaine .EXPLAIN/ESSAY 3.Define Local Anesthesia systematic toxicity and mention management principles 8/1/2024 51

52. REFERENCES Hadzic’s Peripheral Nerve Blocks and Anatomy for Ultrasound-Guided Regional Anesthesia,second edition Morgan and mikhail's clinical anesthesiology Drasner K: Local anesthetic systemic toxicity. A historical perspective. Reg Anesth Pain Med 2010;35:162–166.