??? ???? Inhalational Anesthesia

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??? ???? Inhalational Anesthesia

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???? (introduction) 1.??(concept)
2.??(characteristic)

• ????
• ???????

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???????????????? Uptake, distribution and
elimination of inhalational anesthetics

• 1??????Uptake and distribution
• ?????? central nerve system
• PA PB PBr ????
• dynamic equilibrium

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?????????

• ???? inspired concentration
• ????? minute volume
• ?/?????
• blood/gas partition coefficient
• ???????
• perfusion of pulmonary

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2.?? Elimination ??????????? Eliminated
mostly in an unchanged form via the lungs
?????????? a small proportion is metabolized
in liver and eliminated via kidney

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???????????? Clinical evaluation of
inhalational anesthetics

• 1.??? controllable
• ? ??/???????
• associated with blood/gas partition coefficient
• 2. ???? anesthetic potency
• ? ??/???????
• associated with oil/gas partition coefficient
• ? MAC(minimal alveolar concentration)

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MAC is minimal alveolar concentration of an
inhalational anesthetic at 1 atmosphere absolute
that prevents movements of 50 of the population
to a standard stimulus.

• 3. ???????
• Effects on Cardiovascular system
• ? ????
• depression of myocardial contractility

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????????????????

• Increased myocardial excitability
• Arrhythmias are common during halothane
• Increased circulating catecholamines

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????? Respiratory depression
dose-dependent depression of ventilation
?????? irritant to respiratory depression
????????? relaxation of bronchial
smooth muscle
4.?????? Effects on respiratory
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5.???????? Effects on neuromuscular junction

• ?????,??????????
• Skeletal muscle relaxation and potentiates
  non-depolarizing relaxants.
• ??????????
• Skeletal muscle relaxation of enflurane is
  the greatest in all inhalational anesthetic .
• ???????????????,????????
• Hatholane relaxes uterine muscle and may
  cause postpartum hemorrhage.

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6.?????EEG??? Effects on ICP and EEG

• ??????,???????
• increase ICP, and this action of isoflurane
  is the lowest in all volatiles.
• ???EEG,?????????EEG??
• Dose-dependent depression of EEG
  activity, at moderate to high concentration (more
  than 3), enflurane produces epileptiform
  paroxysmal spike activity.

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7.?????????? Properties of the ideal
inhalational anesthetic

• Pleasant odour, non-irritant to respiratory
  depression
• low blood/solubilityrapid induction and recover
  from anesthesia
• Neither flammable nor explosive
• Producing unconsciousness with analgesia and some
  degree of muscle relaxation
• Not be metabolized in the body, non-toxic, not
  provoke allergic reactions
• Minimal depression of cardiovascular and
  respiratory system and not interact with the
  other drugs used commonly during anesthesia, e.g.
  catecholamines.

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8.?????-???? anesthetic gasnitrous oxide
? ? ????,???????? low-toxicity, light
depression of cardiovascular system ???????
non-irritant to respiratory depression
???????? suitable for seriously ill
patient ? ?????? rapid induction and
recover from anesthesia
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???? announcements

• ??????????,????????????,??vitB12
• Affects vitamine B12 synthesis when the
  duration of nitrous oxide exceeds 8 hours.
• ???????,???????30,??,?????
• Diffusion hypoxia essential to administer a
  minimum FiO2 of 30
• ??????,???????????????
• Good analgesia, poor anesthesia, is used
  combination with enflurane or isoflurane

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?????????? Inhalational anesthesia outfit

• ?? Gases
• ??? Flow meters
• ??? Vaporizers
• ??? Breathing bag
• ????? Anesthetic breathing system
• ???? Breathing value
• ????????
• Canister or carbon dioxide absorber

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?????????? Methods of Inhalational
anesthesia ? ???(open circuits))???????
?????????

• ??
• ??????,?CO2????
• ??
• ???,???????????
• ??????????????????
• ??
• ?????,????
• ?????????????????,
• ????
• ?????????

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? ????(semi-open circuits) suitable for
spontaneous
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?? ???????????,?CO2???? ????????,????CO2lt1
?? ???????(??????2-3?), ????????CO2??
Fresh gas flow rate must be very high (at
least 2-3 times Alveolar minute volume to prevent
rebreathing) ????T???

• ????????????
• ????20Kg????,??????????
• ????????,?????????

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????? semi-closed circuits

• ??
• ???????,?????????,?
• ???CO2????
• ??
• ???????,????CO2??
• ??
• ???????,?????
• ????????????????

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????closed circuit or circle system is the only
true circuit as anesthetic gases are recycled.

• ??
• ?????,?????????,?CO2????,??? exhaled alveolar gas
  is rebreathed entirely
• ??
• ?CO2????
• ????????,?????????????
• ???????,??????????
• ????????????,??????
• ??
• ?????
• ??????CO2??,???????
• ????????

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???????? Inhalational anesthesia with Low flow
rate

• ??
• ????gt4L/min------???????
• ????lt2L/min------???????
• ??????????
• ??
• ??
• ?N2O???,?????lt30????
• ??????????
• ????????????????
• ????

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????????????? Induction, maintenance and
recovery of inhalational anesthesia

• ??
• ????
• ??????
• ???????????????????????
• ???????????
• ??
• ????????,????????
• ??
• ????????,?????
• ????,??????????

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??????????? Management during inhalational
anesthesia

• ??????preanesthetic preparation
• ? Preanesthetic visit to assess the risks of
  anesthesia and surgery and to plan the anesthetic
  management.
• ? Anesthetics, equipment for monitoring
  anesthetic machine and intravenous fluids should
  be prepared.
• ??????? monitoring depth of anesthesia
• ????????

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1.???? respiratory system
????-----???????
maintaining the airway

• ??
• ????????????
• ??
• ??????????????????
• ????????,??????
• ?TV?MV?SPO2?????----??????
• CO2??

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????Abnormal breathing ?????--????,??(??????????
) MV?, brachypnea, hypoxia ??????(airway
obstruction)???? (Dyspnoea),???(three
depressions sign) ?CO2??????HR??BP? ??????
(Upper respiratory tract obstruction )
??????? ??????( Lower respiratory tract
obstruction )
??(regurgitation)???? (secretion)??????(Br
onchospasm) ?????????????(distortion of
tracheal tube)?????(foreign body in
trachea)??????(malfunction of
anesthesia apparatus )
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2.????
?? ????,???? Cardiac sound and rhythm ?
Blood pressure, peripheral pulse, urine volume
MAP?CVP?PAWP?CO ECG???????????
arrhythmia and myocardial ischemia
HypovolemiaBP??P???????????CVP? Cardiac
failureBP??P???CVP??
?????????????? Deep Anesthesia BP??P?
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3.????????????

• ?????---????
• ???---???????
• ???????
• ????????????---????
• ????????????????---
• ????????
• ???????
• ???? ??????
• ???????????????
• ???? Intraoperative awareness

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???CO2?????

• ??????Initial signs of hypoxia
• BP??HR?????????(cyanosis)
• CO2??????Initial signs of carbon
• dioxide retention BP??HR???????????
• ?????CO2????
• ?????(respiration is irregular)?BP??HR?????????
  ?????