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LOCAL ANESTHETICS,IV SEDATION AND PAIN MANAGEMENT MORAYA ALQAHTANI,MD Local Anesthetic history • • • • • • • • • Cocaine-1800 Niemann-1859 1884-1st use in clinical practice 1904-procaine 1925-dibucaine 1932-tetracaine 1942-Licocaine Mepivicaine,prilocaine,bupivicaine,etidocaine. ropivicaine neurophysiology Nerve structure pharmacokinetics • • • • Weak bases Lipid soluble Pka:8-9 at physiological pH Lipophilic portion-hydrophilic portion and intermediate link pharmacokinetics • • • • Degree of ionization. Both are involved in the blockage of the nerve They act by blocking Na channel Duration of esters are shorter pharmacokinetics • Vasoconstrictor activity at low doses • Vasodilatation at higher doses • Metabolism:Esters by plasma cholinesterase PAMA Amides metabolized in the liver pharmacokinetics • Vasoconstrictor activity at low doses • Vasodilatation at higher doses • Metabolism:Esters by plasma cholinesterase PAMA Amides metabolized in the liver pharmacokinetics • Clearance:amide mainly hepatic, • widely distributed compared to esters • More stable • Minimal allergic reaction Pharmacological factors • Lipid solubility • Absorption and distribution: • pharmacological factors • Physical factors:age,hepatic,renal,inflammation pharmacological factors *injection site *dosage *presence of epinephrine ,carbonation *protein binding *chemical properties Classification of LA Short acting Procaine 60-90 min Chloroprocaine 30-60 min Intermediate acting Mepivicaine Prilocaine 20-24 20-24 Long acting Lidocaine Tetracaine Bupivicaine 90-200 80-600 Etidocaine DRUG Maximum Plain(mg) Maximum Epinephrine(mg) Chloroprocaine 800 1000 Lidocaine 300 500 Mepivacaine 300 500 Prilocaine 500 600 Bupivacaine 175 225 Etidocaine 300 400 LA • Preparation: - topical :ointments,cream,lotion,spray -Injection • EMLA:Eutotic Mixture of Local Anesthetics 2.5% prilocaine 2.5% lidocaine TOXICITY Toxicity • Allergic reaction • Local toxicity • Systemic toxicity Allergic reaction • Rare condused with adverse effects • More with esters-PABA • Delayed type • No cross sensitivity • prevention: *proper Hx & PE *skin test- 20%-30% false positive Local toxicity • Direct trauma • Intraneuronal injection • Rare • preventable Systemic toxicity • CNS • CVS • Methemoglobinemia CVS • Conduction • Contractility • Peripheral effect • • • • CVS more resistant than CNS Bupivicaine more cardiac toxicity Ropivicaine less cardiac toxicity Lidocaine :anti arrhythmic drug CNS • • • • Concentration dependant Low concentration CNS:increases with hypoxia,acidosis ,pregnancy Adverse effect: drowsiness,light headiness slurred speech,restlessness, vertigo,tinnitus, muscle twitching, tremors,convulsion, coma, IV Sedation Practical consideration • Quite environment • Repeated cuff blood pressure measurement should be avoided • Monitors should be muted apart from alarm. Requirements of analgesia • 1.Continuous IV access. • 2.Continuous monitoring with both ECG and pulse oximeter. • 3.Both the practitioner and the assistant should have recently certified in CPR. • 4.Resuscitation equipments should be available (crash cart). • 5.Possibility to transfer for full critical care facilities e.g. Other hospital, ICU, OR. Steps to Sedoanalgesia • 1.Premedication with BDZ • 2.Adequate local or regional anesthesia • 3.IV sedation e.g. Midazolam • 4.Adjuvant analgesia with narcotics only if local/regional anesthetic is ineffective. IV Anesthetics • Neuroleptanesthesia • Neuroleptic drugs : Phenothiazines e.g. Chlorpromazine. • Butyrophenones e.g. Haloperidol, Droperidol. • Rarely used in anesthesia because of hypotension • droperidol –fentanyl (Innovar ) IV Anesthetics • Butyrophenones result in significant: • Sedation. • Tranquility. • Immobility • Antiemesis IV Anesthetics • Their side effects include: • An extrapyramidal syndrome with face and neck dyskinesia. • Oculogyric crises. • Torticollis. • Agitation • Hallucination IV Anesthetics • Droperidol (like other Butyrophenones) affect GABA receptors and alters the balance of dopamine and acetylcholine in certain brain sites. • Neuroleptanesthesia is contraindicated in patients receiving Mono Amine Oxidase Inhibitors, abusing drugs or alcohol and those with Parkinson’s disease. Benzodiazepines • Diazepam (valium) 1959 • Lorazepam (ativan) 1971 • Midazolam (versed) 1976 pharmacokinetics • Small molecule • Lipid soluble • Metabolized in the liver • Habitual use of alcohol • Lorazepam has higher affinity to receptors Benzodiazepines • • • • Action mediated through GABA Mainly on CNS ,minimal action on PNS Cells become hyperpolarized resistant to exitation Function is blood level dependant 20% :anxiolytic 30%-50% :sedation 60% :loss of consciousness • Tolerance Short acting Midazolam 6-11ml/kg/min Intermediate acting Lorazepam 0.8-1.8ml/kg/min Long acting Diazepam 0.2-0.5ml/kg/min Benzodiazepines • • • • • • Hypnotic Sedative Anxiolytic Amnestic Anticonvulsant:increases seizure threshold Muscle relaxant Benzodiazepines • Uses Sedation,Induction,maintainance • Contraindication: • Hypersensitivity, myasthenia gravis, COPD, acute narrow angle glaucoma. • Safety has not been established in children and pregnant females Benzodiazepines • Side effects *high safety margin *free allergic reaction *inactive non toxic metabolite *respiratory problem *venous irritation,thrombophlebitis *unpredictable interval of amnesia Rx: Flumazenil (Anexate) 0.2 mg IV over 15 sec. Then 0.1mg IV q60 sec. To effect (max. 1mg). Benzodiazepines • Dosage: midazolam: IM 0.07 mg/kg (5mg) 30 – 60 min.prior (50% of dose if >60 years) I.V. sedation: titrate with small doses (2mg initial followed by 1mg q2 min to effect) (max.dose 0.1mg/kg) (reduce dose by 30% if premedicated and by 50% if >60yo). • Diazepam (Valium ) : IM/PO premedication: 5-10 mg. 1 to 2 h prior (reduce dose by 50% if >60yo). • IV sedation: 5 - 10 mg IV q3h. (Reduce by 50% if >60yo). • Lorazepam (ativan): PO/SL premedication: 50mcg/kg (maximum 4mg) 1-2 hour prior (50% of dose if more than 60 yo) OPOIDS Classification • Natural • Semisynthetics • synthetics Natural opoids • Morphine • Codeine • Papaverine Semisynthetic • Heroin -dihydromorphone Synthetic opoids • Levorphenols: -Methadone -pentazocine • Phenypiperidine -meperidine -fentanyl opoids • Inhibit the action of opoid neurotransmitters • Analgesic effect differences: -access to the receptor -binding affinity -lipophility,ionization -distribution,clearance OPOIDS • In general most of them *respiratory depression *bradycardia except demerol *anti tussive *sleep *nausea,vomiting,constipation *hypersensitivity • Overdose :naloxone 0.4 mg IV q 2min opoids • Morphine: • Pharmacology: Onset of action 2 to 5 min. Duration of action 4-5 hrs. • Indication:Analgesia, induction of anesthesia. • Contraindication: • Hypersensitivity, MAO inhibitors within 14 days (hpertensive crises, tachyarrethmias). Dosage: 0.1-0.2 mg/kg IV/IM/SC q3h. opoids • Hydromorphone : -7-8 times stronger than morphine -rapid distribution -good in renal failure patient -dose:2-4 mg po Demerol • Pharmacology: Onset of action 2 to 5 min. via IV duration of action 2-4 hrs. • absorbed slowly • 7 to 10 times less potent than morphine • 60% bound to protien • Dosage:up to 1.8 mg/kg IM/SC/IV q2h. Fentanyl • Demorol family -100x morphine • High lipid solubility • Metabolized in the liver , excreted by bile or kidney • Poor hypnotic and sedative activity at low doses • No histamine release katamine • Cataleptic, analgesic, and dissociative anesthetic agent. • Onset of action 30 sec. For IV ,12-25 min for IM dosing. • Dosage:induction 2.0 mg/kg IV over 60 sec or 10 mg/kg IM (adults and children). • Maintenance of anesthesia: 50% of induction dose IV or IM, as anesthesia is lost. katamine • Contraindication:Hypersensitivity, pregnancy,uncontrolled HTN • Adverse effect:HR,BP,RR, pleasant dreams 5%, unpleasant dreams 2%, hallucinations 1%, confusion 3% (give BDZ with it to prevent bad trips). Other IV anesthetics propofol • • • • • Most resent 1977 High lipid solubility Alkylphenols Viscous milky white substance 1% of propofol *1%soy bean oil *2.25% glycerol *1.2% pure egg Propofol • • • • • Metabolized in the liver Iactive metabolite ,98% protein bound Hypnotic,analgesic,induction Titratable level of sedation Dose: sedation 10-50 micgm/kg/min induction 0.1-1 mg/kg over 3 min • Side effects:respiratory depression PAIN MANAGEMENT • Definition • Effect of pain -Neuroendocrine system -CVS -Resp -GIT -GUT -immunity NSAIDs • Limited use for acute PO pain • Mechanism of action • Prostaglandins -fever ,pain,vasodilatation Classification Mechanism of action pharmacokinetics • Rapidly absorped • Metabolized in the liver,inactive metabolites • High protein bound • Action dose dependent Side effects • Gastropathy • Hemostasis • nephrotoxocity Ketorolactromethaminne (Toradol) • Pyrolle acetic acid • High analgesic potency • 2mg of toradol = 1mg og morphine = 6-10mg of demerol • Dose 60mg IM followed by 30 mg IM q 6h • 50% in renal problem Toradol • Most sufficient for sever pain • 0.3% incidence of PU • Bleeding with long term use • Increases bleeding time Nausea and Vomiting • • • • • • • History of PO emesis Female Obesity Pain Type of surgery Anesthetic drugs Gastric distension Treatment • Prophylactic antiemetic droperidol 10 to 20 micgm/kg • Ondansetron 4 to 8 mg IV • Metoclopramide (10 to 20 mg IV) • Transdermal scopolamine