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Iv anaesthetics final


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IV Anaesthesia (Pharmacology)

Published in: Health & Medicine

Iv anaesthetics final

  1. 1. Preanesthetic Medication
  2. 2. Intravenous Anesthetic Agents
  3. 3. Ideal IV anesthetics: 1-Drug compatibility (water solubility) and stability in solution. 2-lake pain on injection , veno irritation , and local tissue damage. 3-low potential to release histamine. 4-rabid and smooth onset of action without excitatory activity. 5-rabid metabolism to inactive metabolites. 6-a steep dose to minimize titratability and tissue accumulation. 7-lake of acute cardiovascular and respiratory depression. 8-decrease in cerebral metabolism and intracranial pressure. 9-rabid and smooth return to consciousness . 10-abcense of post operative nausea , vomiting, amnesia , psychoimetic reaction , dizziness , headache , and prolonged sedation.
  4. 4. Introduction • Used IV anesthetic drugs are: • 1. Propofol ,Fospropofol • 2.Thiopentone, Methohexital • 3.Ketamine • 4.Etomidate • 5.Benzodiazepines (Diazepam, midazolam, lorazepam) • 6.Dexmeditomidine
  5. 5. Pharmacokinetics: Anesthesia is produced by diffusion of drug from arterial blood across the blood brain barrier in to the brain which regulated by the following factors: -protein binding: unbound drug is free to cross BBB. -blood flow to the brain. -extracellular PH and Pka of the drug: nonionized. -solubility of the drug in lipid and water: high lipid solubility enhances transfer in to the brain. -speed of injection.
  6. 6. Barbiturates (Thiopental): • Available as sodium salts (yellowish powder) • Bitter taste + smell of garlic. • Solution of thiobarbiturates are stable for 2 weeks. • ph of solution of thiopental (2.5%) is 9. • Does not cause pain on injection. • Metabolized in liver to hydroxythiopental and carboxylic acid • Produce anesthesia in less than 30 sec after iv injection. • Induction dose: 3-5 mg/kg in adults 5-6 mg/kg in children 6-8 mg/kg in infants recovery after 10 min
  7. 7. • Produce decrease in CPF there by lowering ICP. • widely used to improve brain relaxation during neurosurgery and to improve cerebral infusion pressure after acute brain injury -It cause dose dependent anticonvulsant activity. -dose dependent respiratory depression. -it cause decrease in cardiac output and ABP. -early absence in eyelid reflex.
  8. 8. -tissue necrosis: median nerve damage may be occur after extravenous injection in the antecubital fossa if perivenous injection occurred the needle should be left in place and injection of hyaloronidase. -intra-arterial injection: pt usually complains of burning pain & in this case: -stop injection. -leave needle in artery. -administrate papaverine 20 mg. -heparin should be given iv and orally. -stellate ganglion or brachial plexus block may reduce arterial spasm.
  9. 9. Propofol: -(2,6-dispropylphenol). -Pain on injection 32-67% of patients. -t1/2 is 1-8 min (Barash 2009). -Eimination half time 2-24 min. -Metabolized in liver to sulfate and glucuronic acid which are eliminated by kidney. -Extra hepatic rout of elimination by lungs. -Anesthesia is induced in 20-40 sec after iv administration. -We can monitor the onset by loss of verbal contact. -Induction dose 1.5 – 2.5 mg/kg. -Children require bigger dose. -Euphoria effect.
  10. 10. -Decrease CPF and ICP. -Excitatory motor activity without EEG changes. -Dose and concentration dependent cardiovascular depression. -Dose dependent respiratory depression with apnea. -Antiemetic effects (10-20 mg to treat nausea and emesis in the early post operative period. -Antidopamenergic which lead to euphoria. -It decrease the pruritus produced by spinal opioids. -Agent of choice in malignant hyperthermia suspictable pt. -Propofol syndrome : after high dose infusion of propofol for long time – myocardial failure – metabolic acidosis – rabdomyolysis.
  11. 11. • no effect on bronchial muscle tone and laryngospasm is particularly uncommon . • regarded by most anesthetists as the drug of choice for induction of anesthesia when LMA (Laryngeal Mask Airway) is to be used.
  12. 12. Etomidate: -carboxylated imidazole. -ph 6.9 , pain on injection , venoirritation. -induction dose : 0.2-0.3 mg/kg. -involuntary myoclonic movement are common at induction. -metabolism in liver. -it decrease CPF and ICP. -inhibitory effect on adrenocortical synthetic function (5-8 h after single use) -inhibit platelet function. -minimal cardiorespiratory depression . -does not induce histamine release. -high incidence of post op nausea and emesis .
  13. 13. Absolute contraindication: -airway obstruction. -prophyria. -adrenal impairment. -long term infusion in ICU (increase infection and mortality).
  14. 14. Ketamine: -Arylcyclohexylamine. -water soluble compound. -potent anesthetics and analgesic properties +amnesia . -metabolized by liver to norkitamine which excreted by kidney. -elimination half life 2-4 h . -dose dependent CNS depression + stimulation of limbic s. -induction dose: 1-2 mg/kg IV. 4-8mg/kg IM. -duration of action: 10-20min –full orientation require more 60 – 90 min
  15. 15. -high incidence of psychomimetic reactions (namely , hallucination , nightmares , altered short term memory , and cognition). -ketamine increase CPF and ICP . -bronchodilatory activity - minimal respiratory depression. -increase oral secretion. -cardiovascular stimulation + increase peripheral resistant. -not recommended in severe coronary artery disease. -increase pulmonary artery pressure (contraindicated in poor right ventricular reserve.
  16. 16. Indications: -high risk pt: shocked patients. -pediatric anesthesia. -difficult locations: site of accidents. -developing countries: where anesthetic equipment and trained staff in short supply.
  17. 17. Benzodiazepines: -medazolam , lorazepam , diazepam and antagonist flumazenil. -metabolized in liver , excreted by kidney. -short acting: midazolam - flumazenil. -intermediate: diazepam. -long acting: lorazepam. -only midazolam can given by continuous infusion. -all benzodiazepines produce: anxiolytic, anterograde amnesia, sedative, hypnotic, anticonvulsant, and spinally mediated muscle relaxant properties.
  18. 18. -dose dependent respiratory depression. -it depress the swallowing reflex and depress upper airway reflex activity. -produce decrease in systemic vascular resistant and blood pressure in large doses. -specific antagonist :flumazenil
  19. 19. Dexmedetomidine: -alpha 2 adreno receptor agonist. -approved by FDA for the short term less than 24 h sedation of the mechanically ventilated pt in ICU. -unique type of sedation-analgesia with less respiratory depression + amnestic affect . -it produce hypotension and bradycardia more than diazepines. -infusion rate 0.2-0.6 mcg/kg/h. -improve post op pain control after major surgery. -slower onset and offset than propofol , sedation like midazolam. -high cost.
  21. 21. Side EffectsPROPOFOL THIOPENTONE KETAMINE ETOMIDATE BENZODIAZEPI NE Pain on injection ✔✔ ✔ ✗ ✔ ✗ Hypotension ✔✔ ✔ ✗ ✔ ✗ Bronchospasm ✗ ✔ ✗ ✗ ✗ Allergic rxn ✔ ✔ ✗ ✗ ✗ Emergence rxn ✗ ✗ ✔ ✗ ✗ Thrombophlebitis ✔ ✔✔ ✗ ✗ ✗ Hangover effect ✗ ✓ ✔ ✗ ✗ Tolerance and dependence ✔ ✔ ✔ − − Immunosuppress ion ✔ − − ✔ Neutrophil func. ê ê ✗ − ê
  22. 22. Thank you