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A touch of anesthesia

A touch of anesthesia. Local anesthetics and other things. purpose. local anesthetics- mechanisms of action, pharmacology and toxicity conscious sedation- definition, drugs and dilemmas. Components of anesthesia. Anesthesia Amnesia Areflexia Autonomic areflexia Anxiolysis.

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A touch of anesthesia

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  1. A touch of anesthesia Local anesthetics and other things

  2. purpose • local anesthetics- mechanisms of action, pharmacology and toxicity • conscious sedation- definition, drugs and dilemmas

  3. Components of anesthesia • Anesthesia • Amnesia • Areflexia • Autonomic areflexia • Anxiolysis

  4. spectrum of sedation • minimal sedation • moderate sedation • deep sedation • general anesthesia

  5. benefit • sedation and analgesia allows patients to tolerate unpleasant procedures by relieving anxiety, discomfort and pain • children and uncooperative adults sedation analgesia may expedite procedures that may not necessarily painful but requires that the patient does not move

  6. minimal sedation • normal response to verbal stimulation • airway unaffected • spontaneous ventilation unaffected • cardiovascular function unaffected • cognitive and cordination may be impaired

  7. conscious sedation • drug induced depression of consciousness in which patients respond purposefully to verbal commands • no interventions are required to maintain the airway • spontaneous ventilation is maintained • cardiovascular function is maintained

  8. deep sedation • drug induced depression of consciousness during which patients can not be aroused easily but respond purposefully when stimulated repeatedly or painfully • ability to maintain respiration may be impaired • support of the airway may be needed • spontaneous respiration may be impaired • cardiovascular function is maintained

  9. general anesthesia • loss of consciousness patients are not rousable even to pain • the ability to maintain ventilation is often impaired • assistance is required in maintaining an airway and spontaneous ventilation • may be associated drug induced depression of neurological function • cardiac function may be impaired

  10. Induction • Maintenance • Emergence • Recovery • But a whole lot of other stuff too

  11. History • be familiar with the sedation oriented aspects of the patients History • abnormalities of major organs • adverse events with sedation or ANESTHESIA • DRUG ALLERGIES AND MEDICATIONS • NPO STATUS • TABACCO, ALCOHOL AND SUBSTANCE ABUSE

  12. PHYSICAL • AIRWAY AIRWAY AIRWAY

  13. NPO • 6 HOURS FOR light meals, FORMULA AND MILK • 4 HOURS FOR BREAST MILK • 2 HOURS FOR CLEAR FLUIDS

  14. VENTILATION • MAJOR MORBIDITY DRUG INDUCED RESPIRATORY DYSFUNCTION AND AIRWAY OBSTRUCTION • VENTILATION AND OXYGENATION ARE DIFFERENT • PULSO OXYMETRY IS NOT A SUBSTITUTE FOR VENTILATION MONITORING

  15. MODERATE/DEEP SEDATION • LEVEL OF CONSCIOUSNESS • OXYGENATION STATUS • HEMODYNAMICS

  16. EMERGENCY EQUIPMENT • PHARMACOLOGIC ANTAGONISTS • EQUIPMENT FOR ESTABLISHING AN AIRWAY • DEFIBRILLATOR • EMERGENCY DRUGS INCLUDING THOSE TO TREAT ANAPHYLAXIS

  17. DRUGS • SMALL INCREMENTAL DOSES • sufficient TIME ELAPSED TO ALLOW FOR THE EFFECT OF THE DRUG

  18. three step approach to sedation • environment (equipment, monitors, suction, personnel, resuscitation equipment) • procedure (diagnostic v therapeutic, duration of time, level of discomfort, position of the patient, special requirements) • patient (ability to tolerate sedation vs general anesthesia, ASA Grade and morbidity, Allergies, monitoring requirements)

  19. benzodiazapines • anxiolytic • amnesic • hypnotic • recovery of psychomotor and amnesic function may be significantly delayed

  20. midazolam • water soluble • non- irritant to the vein • short elimination half time( 1-4 hrs) • clearance unaffected by H2 antagonists • inactive metabolites resedation unlikely

  21. diazepam • Lipid soluble • pain on injection • thrombophlebitis common • long elimination half life (>20 hrs) • Active metabolites (desmethyl-diazepam, oxazepam)

  22. opioids • fentanyl, hydromorphone, morphine • equally effective analgesia with equal side effect profiles • used for a balanced effect • regional or local anesthesia techniques are n effective or inappropriate • awareness - lack amnestic properties

  23. morphine • acts presynaptically to decrease substance P • hyper-polarizes post synaptic neurons in the dorsal column • periaqueductal grey matter

  24. CNS effect of morphine • nausea and vomiting • muscle rigidity • cough reflex • urinary retention • histamine release • respiratory depression

  25. fentanyl

  26. remifentanyl

  27. specific groups • opioid tolerant groups • morbidly obese patients • OSA • elderly patients

  28. ketamine • Phencyclidine derivative • dissociative sedation • Analgesic • Induction of anesthesia especially in the setting of bronchospasm and hypotension • Antagonist at the calcium channel pore of the NMDA receptor and inhibitor of the NMDA receptor at phencyclidine binding site • Onset 30 seconds IV, IM 2-8 minutes

  29. ketamine • Stimulation of respiration • Bronchodilation • Sympathetic stimulation with an increase in circulating epinephrine and norepinehrine • Increased cerebral metabolic rate increased cerebral blood flow and increased metabolic rate • Post-operative nausea and vomiting

  30. Side effects of ketamine • Rashes • Pain on injection • Hallucinations • Emergence delerium and unpleasant dreams (less likely in children and the elderly)

  31. exerts its sympathomimetic activity by inhibiting the re-uptake of catacholamines • Severe heart disease • Hypertension • Porphyria

  32. ketamine • Duration • IV 5- 10 minutes • Intramuscular 10-20 minutes • Dose 1 - 2 mg/kg • Intramuscular 5- 10 mg/kg

  33. Propofol • Phenol derivative • White oil in water emulsion 0f 1% or 2% propofol in soybean oil • Induction, maintenance, sedation, intractable nausea vomiting, status epileticus • Potentates inhibitory neurotransmitters glycine, and gamma aminobutyric acid

  34. propofol • Onset 30 seconds • Duration 10 minutes for a single dose, but an infusion context sensitive half life increases with duration • Dose 1.5- 2.5 mg • 100 ug/kg minute

  35. Propofol • Pain on injection • Anaphylaxis • Not to be used for sedation in PICU as reported metabolic acidosis, myocardial failure and lipaemic serum

  36. context sensitive half life is short even after long infusions • easy titratable drug • low incidence of nausea and vomiting

  37. local anesthetics • the anatomy, the chemistry and everything else in between April 11 2007

  38. the anatomy • mixed nerves that contain both afferent and efferent fibers • each axon is surrounded by endoneurium -non neural glial cells • individual nerves are bundled into fascicles and and surrounded by perineurium -connective tissue • the entire peripheral nerve is wrapped in epineurium composed of dense connective tissue

  39. nerve fiber classification • size • conduction velocity • function • the more myelin and the bigger the nerve the faster the conduction velocity

  40. CnHn intermediate chain O N CnHn amide group Aromatic ring water soluble lipid soluble proton acceptor

  41. acidic alkaline influenced by PH of surroundings LA + H+ LA H + uncharged base lipid soluble NON-IONIZED Cation water soluble, IONIZED

  42. pK a the pH at which the ratio of ionized tonon-ionized molecules is 1:1 dissociatic constant

  43. lidocaine • pK of lidocaine is 7.7 and the acid solution has a pH of 6 ( hydrochloride salt) • lidocaine hydrochloride solution in a syringe 99% of the total is in the ionized form and 1% is in the non-ionized form. maintains its water solubility

  44. once injected .... • injected into the tissues, where the pH is 7.4 the ionized portion drops to 76% • 24% is now non-ionized or lipid soluble • able to diffuse passively down the concentration gradient across the nerve cell membrane

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