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ANESTHESIA PHARMACOLOGY

ANESTHESIA PHARMACOLOGY. SFC HILL. OBJECTIVE.

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ANESTHESIA PHARMACOLOGY

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  1. ANESTHESIA PHARMACOLOGY SFC HILL

  2. OBJECTIVE As a Special Forces Medic given a patient requiring anesthesia, administer anesthesia utilizing your knowledge of anesthesia pharmacology and applying the five rights (right patient, right drug, right amount, right route, right time) in accordance with JSOMTC student manual of anesthesia.

  3. REASON As a Special Forces Medic the probability is high that you will be the only health care provider available to administer anesthesia.

  4. PROCEDURES • Review local/regional anesthesia pharmacology • Review anesthesia pharmacology adjuncts • Review intravenous anesthetics • Review intravenous anesthetics reversal agent

  5. Local/Regional Anesthetics

  6. Lidocaine • amide type anesthetic • the most commonly used local anesthetic • rapid onset and a duration of 60-75 minutes • extended when solutions with epinephrine are used for up to 2 hours • metabolized in the liver and excreted by the kidneys.

  7. INDICATIONS Lidocaine • used to produce local and regional anesthesia for surgical and diagnostic procedures

  8. DOSE AND ROUTES Lidocaine • Percutaneous infiltration: 0.5%, 1.0% • Regional infiltration: 0.5% • Peripheral nerve: 1.0%, 1.5%, 2.0% • Max dose 4 mg/kg or 7 mg/kg with epinephrine • Toxic IV dose: 250 mg

  9. ADVERSE REACTIONS, PRECAUTIONS, AND INTERACTIONS Lidocaine • contraindicated in patients with a known sensitivity to amide type anesthetics • All local anesthetics can produce CNS stimulation, depression, or both

  10. Chloroprocaine • ester type local anesthetic • onset of action is rapid (6-12 min.) and duration of anesthesia is up to 60 min. • rapidly metabolized in the plasma.

  11. INDICATIONS Chloroprocaine • production of local and regional anesthesia for surgical and diagnostic procedures

  12. DOSE AND ROUTES Chloroprocaine • Local infiltration: 2.0%, 3.0% for motor block • Peripheral nerve block: 1.0%, 2.0% • Maximum dose 11 mg/kg or 13 mg/kg with Epinephrine • Toxic IV dose: 450 mg

  13. ADVERSE REACTIONS, PRECAUTIONS, AND INTERACTIONS Chloroprocaine • contraindicated in patients with known hypersensitivity to drugs of the PABA ester group • All local anesthetics can produce CNS stimulation, depression, or both

  14. Procaine • ester type local anesthetic • slower onset of action than Lidocaine • duration of action is approximately one hour • primarily metabolized in the plasma

  15. INDICATIONS Procaine • used to produce local and regional anesthesia for surgical and diagnostic procedures

  16. DOSE AND ROUTES Procaine • Infiltration: 0.25%, 0.5% • Nerve block: 1.0%, 2.0% • Maximum dose 11 mg/kg or 13 mg/kg with Epinephrine • Toxic IV dose: 450 mg

  17. ADVERSE REACTIONS, PRECAUTIONS, AND INTERACTIONS Procaine • Contraindicated in patients with a known hyper-sensitivity to PABA ester type anesthetics • All local anesthetics can cause CNS stimulation, depression or both

  18. Bupivicaine • amide-type local anesthetic • onset of action is slower than lidocaine and anesthesia is long acting • metabolized in the liver and excreted by the kidneys • normally provides 2-4 hours of anesthesia • can be extended in some cases by using solution with epinephrine to 7 hours

  19. INDICATIONS Bupivicaine • production of local or regional anesthesia for surgical, diagnostic, or obstetrical procedures.

  20. DOSE AND ROUTES Bupivicaine • Local infiltration: 0.25% • Peripheral nerve block: 0.25%, 0.5% • Maximum dose 3 mg/kg or 4 mg/kg with Epinephrine • Toxic IV dose 80 mg

  21. ADVERSE REACTIONS, PRECAUTIONS, AND INTERACTIONS Bupivicaine • Contraindicated for use in pts with known hypersensitivity and in obstetrical paracervical blocks • All local anesthetics can produce CNS stimulation, depression or both

  22. Adjuncts to Anesthesia

  23. Atropine • anticholinergic drug that blocks the muscarinic receptor sites (mainly organs innervated by the Vagus nerve) • reduction in salivary and other airway secretions • inhibits Acetylcholine at the parasympathetic neuroeffector junction, blocking vagal effects on the SA node; this enhances conduction through the AV node and speeds heart rate

  24. Atropine • inhibits heat loss by suppressing perspiration • antisialogogue effects last up to 4 hours • increase in heart rate peaks in one hour.

  25. INDICATIONS Atropine • used preoperatively for diminishing secretions and blocking cardiac vagal reflexes

  26. DOSE AND ROUTES Atropine • 0.4-0.6 mg IM 45-60 prior to anesthesia

  27. ADVERSE REACTIONS, PRECAUTIONS, AND INTERACTIONS Atropine • may cause tachycardia • excessive dryness of the mouth and throat • dilation of the pupils • fever, flushing of the face, confusion, mania, and hallucinations • may increase intraocular pressure-contraindicating its use in narrow angle glaucoma

  28. ADVERSE REACTIONS, PRECAUTIONS, AND INTERACTIONS Atropine • contraindicated in obstructive uropathy, obstructive disease of the GI tract, myasthenia gravis, paralytic ileus, intestinal atony, unstable CV status in acute hemorrhage, and toxic megacolon • crosses the blood brain barrier and may cause confusion, post-op somnolence and delirium, particularly in children and elderly

  29. Promethazine • antihistamine, antiemetic, and sedative activity, all of which are useful in preanesthetic medication • weaker sedative than Diazepam • best premedication for Ketamine • competes (antagonist) for H1 receptor sites on effector cells • prevents but does not reverse histamine-mediated responses

  30. INDICATIONS Promethazine • is used for preoperative sedation and as an analgesic adjunct

  31. DOSE AND ROUTES Promethazine • 25-50 mg Deep IM, IV, or PO 30 min prior to anesthesia • If giving IV dilute with normal saline • Never give SC as this is an irritating solution. Injections should be deep IM

  32. ADVERSE REACTIONS, PRECAUTIONS, AND INTERACTIONS Promethazine • Contraindicated in pts. with increased intraocular pressure, intestinal obstruction, prostatic hypertrophy, bladder neck obstruction, epilepsy, bone marrow depression, coma, CNS depression, or stenosing peptic ulcers • Additive effects with other Phenothiazines and CNS depressants

  33. Intravenous Anesthetics

  34. Review the Components of General Anesthesia • Muscle Relaxation • Unconsciousness • Analgesia

  35. Intravenous Anesthetics Muscle Relaxation

  36. Diazepam • Benzodiazepine with sedative and amnesic properties • Depresses the CNS at the limbic and subcortical levels of the brain • Depresses the ventilatory response to PaCO2

  37. Diazepam • Mild muscle relaxation mediated at the spinal cord level; not at the neuromuscular junction • Highly alkaline pH • No analgesic properties

  38. INDICATIONS Diazepam • Basal sedation • Induction agent • Preanesthetic • Drug Of Choice for seizures

  39. DOSE AND ROUTES Diazepam • IV, IM, PO, and rectally • Pre-op sedation: 5 to 10 mg PO 1h before surgery • Induction of anesthesia: 0.1-0.2 mg/kg IV • Seizures: 5-10 mg IV q5min up to 30 mg • Basal sedation: Increments of 2.5 mg until pt. falls into light sleep (5-30 mg may be required)

  40. ADVERSE REACTIONS, PRECAUTIONS, AND INTERACTIONS Diazepam • Apnea, respiratory depression, post-op respiratory depression • contraindicated narrow angle glaucoma or patients < 6 m/o (in oral form) • incompatible with many drugs; when given IV with other medications, the IV line should be adequately flushed • should be injected < 5 mg/min to avoid respiratory arrest

  41. Midazolam • benzodiazepine that has a rapid onset with sedative and amnesic properties • depresses the CNS at the limbic and subcortical levels of the brain • depresses the ventilatory response to PaCO2

  42. Midazolam • no analgesic properties • mild muscle relaxation mediated at the spinal cord; not at the neuromuscular junction • water soluble--which allows for better absorption following IM injection

  43. INDICATIONS Midazolam • pre-op sedative • induction of anesthesia • Conscious sedation • commonly used for short diagnostic or endoscopic procedures

  44. DOSE AND ROUTES Midazolam • may be given IM, PO, or IV • Pre-op sedation: 0.07-0.08 mg/kg IM 1 hr prior • Induction of anesthesia: 0.050 - 0.350 mg/kg IV • Basal sedation: 0.035 mg/kg initially, then titrated slowly to a total dose of 0.1 mg/kg

  45. ADVERSE REACTIONS, PRECAUTIONS, AND INTERACTIONS Midazolam • Apnea, respiratory depression, post-op respiratory depression • Contraindicated in pts. with known hypersensitivity, and acute narrow angle glaucoma • Tends to reduce BP and peripheral vascular resistance more than Diazepam

  46. Reversal Agent • For Benzodiazepine

  47. Flumazenil • selective, competitive antagonist of benzodiazepines • relatively short duration of action between one and two hours • acts through competitive inhibition of GABA (benzodiazepine receptor in the CNS)

  48. INDICATIONS Flumazenil • Reversal of benzodiazepine sedation or overdose

  49. DOSE AND ROUTES Flumazenil • reversal of conscious sedation 0.2-1.0 mg IV q 20 min @ 0.2 mg/min • overdose 1.0 mg IV @ 0.5 mg/min • Maximum total safe total dose 3mg in an hour

  50. ADVERSE REACTIONS, PRECAUTIONS, AND INTERACTIONS Flumazenil • CNS excitation including seizures, nausea, dizziness, and agitation • May precipitate acute withdrawal

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