systemic effect of inhalational anesthetic : CNS

  1. CNS
    • dose dependent reduction in cerebral metabolic rate(CMR) and Cerebral oxygen consumption(CMO), isoflurane and Sevo can decrease upto 50%
    • all increases cerebral blood flow and hence ICT. order of vasodilation effect: halothane>desflurane=isoflurane>sevoflurane

    due to more favourable effects on cerebral hemodynamics, better preservation of autoregulation, equivalent reduction in CMR,  smoother recovery. Sevo is agent of choice in neuro surgery

    neurotoxicity and neuroprotection: in animal study,cognitive impairment in life if introduced at very young age. however human study inconclusive
  2. Liver
    • Direct hepatocellular damage seen with halothane(theory:iso and des)
    • all causes liver damage to some degree decreasing blood flow to liver
    • least direct damage seen with sevoflurane
    • max with halothane
  3. Renal system
    • All agent depress RFT by decreasing Renal blood flow.
    • direct renal toxicity d/t fluoride (fluorinated to decrease their flammability)
    • Vasopressin resistant polyuric renal failure 
    • renal threshold for fluoride toxicity 50 micro mole
  4. Hemapoetic system
    • N2O interacts with vitB12 
    • inhibits enzyme methionine synthetase and reduces production of thymidate and DNA 
    • causes megaloblastic anemia , aplastic anemia and homocystinuria
  5. spinal cord
    N2O inhibiting thymidylate production impair mylein production causing subacute degeneration of SC
  6. NM system
    • all are centrally acting muscle relaxant exceptN2O..
    • maximum relaxation seen with desflurane
  7. Teratogenicity
    seen in animal study not in human , N2O
  8. Inflammability of inhalational agent
    • current days agents : noninflammable 
    • in past : ether and cyclopropane
  9. Analgesia
    not good analgesic except N2O and xenon
  10. Reaction of inhalational agent with sodalime
    • Trielene : can produce dichloroacetyline (neurotoxic), phosgene gas(ARDS)
    • Sevoflurane: toxic compound c/a compound A
    • Desflurane: produce Carbonmonoxide with dessicated sodalime and barylime
    • Sevoflurane : hydrogen fluoride which burns respiratory mucosa
  11. Ozone destruction and Global warming
    • maximum caused by N2O,
    • solution is use of closed circuit and avoid N2O as much as possible
  12. Uterus
    uterine relaxants
  13. Amnesia
    except N2O all agents are good amnesic agent
Card Set
systemic effect of inhalational anesthetic : CNS