General anesthesia Methods

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General anesthesiaMethods
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Definition and goal

• Definition
• A state where the patient
• does not respond to painful stimuli
• does not recall these stimuli
• responses
• somatic
• vegetative control of anaesthesia
• emotional/behavioural
• Main goals
• total abolition of pain
• suppression of harmful reflexes
• relaxation of striated muscles (body cavity or
  extremities)

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Modes of general anaesthesia

• Main components
• analgesia-amnesia-unconsciousness(hypnosis)
  attenuation of unwanted (harmful) vegetatív
  reflexes immobility (muscle relaxation).
• Main types of anaesthesia
• mono-anaesthesia single agent (e.g.
  aether) in high doses
• overdosing of the agent to achieve certain
  special goals by side-effects of the drug (eg.
  muscle relaxation by high doses of aether)
• combined general anaesthesia all desired effects
  achieved with appropriate doses of specific
  agents ( balanced anaesthesia)
• side-effects avoided or diminished
• proper management of anaesthesia
• accommodation to individual needs
• accommodation to actual extent of variable
  intra-operative pain

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Stages of general anaesthesia with ether
according to Guedel

• I. Stadium analgesiae
• II. Stadium excitationis
• III. Stadium tolerantiae III/1-2-3-4.
• IV. Stadium asphyxiae
• Basics of classification
• consciousness
• ocular signs (pupilla)
• breathing pattern
• vegetative signs (pulse)
• muscle tone

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Stádium Conscious- ness Br. pupilla eyelid cornea secret. light gag vomit str. abd. smooth
I. 1. Anal- 2. gesia 3.
II. excitaton
III. 1.
Tole- 2.
rance 3.
4.
IV.As- phyxia

Reflexes
Muscle tone
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How can we get the anesthestics to the place of
their action?

• To the
• receptors and structions of the CNS
• peripheric receptors (e.g. neuromuscular
  junction)
• It is always the blood circulation the
  anesthetics are transported by
• Ways to the blood streem
• GI system (intestinal capillary-portal vene
  VCI- RA-RV-lungs LA LV arterial system)
• Mucous membranes (capillaries-venes-RA-RV-lungs
  LA LV arterial system)
• Injection into periferic tissues ? capillaries..
  (i.c., s.c., i.m. application)
• Intravenous injection
  (v.cava-RA-RV-lungs-LA-LV-arteries)
• Inhalation (lung capillaries-v.pulm.-LA-LV-arte
  ries)

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General anaesthesia

• Cannot be described by a simple and single
  process - at least two fundamental processes
• inhibition of painful stimuli
• and loss of consciousness
• Loss of consiousness is achieved by hypnotics
• Pain inhibition is achieved by analgetics
  (opioids)
• These two different effects are closely related,
  the relation is continuous
• very high dose of a hypnotic produces
  anti-nociception,
• very high dose of an analgetic (opioid) produces
  unconsciousness

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Preparation before anesthesia

• Before the patient arrives
• Preparation and check of the equipment
• (e.g. suction, monitors, infusion, intubation,
  airway maintenance equipment)
• Check up anesthesia machine, gas supply
• Preparation of medicaments
• After arrival of the patient
• Greeting of patient, documentation checkup,
  anesthesia sheet
• Monitors, registration of starting values
• Venous access

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Parts of general anesthesia

• Induction
• From the start of the induction agent to the
  point when the patient is ready for the operation
• Maintenance
• Maintenance of the necessary depth of anesthesia
  during operation and continuous control of the
  vital functions of the patient (values,
  tendencies, correction as necessary)
• End (arousal) and recovery
• On the operating table
• Delayed complete arousal later in the RR or ICU

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Drugs for general anaesthesia

• Drugs for preoperative preparation
• sedatives, analgesics, vegetative
  (parasympatholytic) drugs
• drugs for induction of anaesthesia
• short acting iv. anaesthetics, inhalation
  agent(s)
• maintenance of anaesthesia
• intravenous or/and volatile anaesthetics
• supplementary drugs
• analgesics, vegetative stabilizing drugs,
  additives, potentiating agents and other drugs
• drugs for awakening
• antagonists (opioids, benzodiazepines),
  antidote of muscle relaxants

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Which method of anaesthesia?

• Decision influenced by
• Patients demands
• Condition of the patient (hypertension, cardiac
  failure, )
• Circumstances of treatment (emergency or elective
  situations)
• Surgical aspects
• type of surgery (e.g. dental-, dento-alveolar-,
  maxillo-facial surgery)
• region of procedure (intraoral, extraoral)
• length of procedure
• special requirements (e.g. controlled hypotension
  needed)
• Personal experience of anaesthesiologist
• Available circumstances

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Intravenous anesthesia

• Bolus administration
• Continuous infusion (pump)

Advantages Drawbacks
Easy, quick administration Known dose Does not depend on breathing Combination of different agents possible No pollution Once given, the dose can not be reduced Elimination depends on organ function/enzymes Allergy - more often
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IV bolus administration

• effective concentration

concentration
First dose Second dose
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Methods

• Total IntraVenous Anesthesia (TIVA)
• Intravenous induction and maintenance (infusion
  pump)
• Ventilation oxygen air mixture
• IntraVenous Anesthesia (IVA) e.g. NLAII!
• Intravenous induction and mainetnance (continuous
  or bolus)
• Ventilation oxygen nitrous oxide
• Inhalation anesthesia
• Induction can be IV (adults), maintenance by
  inhalation
• VIMA Volatile Induction and Maintenance of
  Anaesthesia
• Balanced anesthesia
• Combination of intravenous and inhalational
  method (in a broader concept combination of more
  thasn one methods e.g. GA regional anesth.)

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Inhalation anesthesia

• Pro
• Easy continuous administration
• Easy modulation of blood concentration
• Elimination through the lungs
• Allergy rate low

• Contra
• Needs specific vaporizers
• Induction can be slow, unpleasant
• Pollution
• Price?

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Induction

• Venous access, documentation, monitoring
• Medical preparation
• Preoxigenation
• Hypnosis/narcosis
• (Muscle relaxation)
• Securing of the airways endotracheal intubation,
  laryngeal mask,
• Attachment of special equipment, (extra IV
  access?) invasive monitoring?
• (Bladder catheter, CVC)
• Positioning of the patient, stabilization
• Deepening of anesthesia, analgesia

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Induction II

• Medical preparation (coinduction)
• E.g. Fentanyl Midazolam (Earlier
  Fentanyl DHBP NLA)
• Intravenous induction (falling asleep)
• Bolus injection
• eg. Thiopenthal, Propofol, Ethomidate,(Ketamin)
  relaxant
• Continuous administration by infusion pump
• Inhalation induction
• Quick technique (single breath method a total
  vital capacity breath after filling up of
  the system)
• Continuous inhalation (children)

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Intravenous induction agents I.

• Intravenous barbiturates methohexital,
  thiopenthal, thiobutabarbital
• Only for single induction or short IV anesthesia!
  
• Quick action, redistribution, tendence to
  accumulation
• Velocity of the injection influences the action
• Negative inotropy vasodilation
• Reduced cerebral metabolism and oxygen
  consumption
• Tissue damage!
• Dose depends on the age, general state, previous
  medication (DHBP or Midazolam, Fentanyl reduce
  the dose)
• (1)-3-5 mg/kg diluted (1-2.5), according to
  the effect!
• Slow injection until the eyelid reflex
  disappeares!
• Contraindication porphyria, lack of good
  veins, ventilation
  difficulties, circulatory insufficiency

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Intravenous induction agents II.

• Ethomidate
• Only for induction (single dose) short action
• Dose 0.15-0.3 mg/kg of the 0.2 solution (10
  ml20 mg)
• Circulatory effects less than with other agents
  (for high risk cardiovascular patients).
  Spontaneous twiching possible
• Adrenal depression!
• Ketamine (S Ketamine)
• Dissociative anesthesia, hallucinogenic
  effects, analgesia
• Dose 1-2 mg/kg IV (3-4 mg/kg IM), for repetition
  or sedation 0.1-1 mg/kg
• Good for children, combinations - hypotensive
  patients
• Elevates the BP, intracranial pressure,
  intraocular pressure, blood concentrastions of
  catehcolamines! Reflex sensitivity elevated
• Propofol
• Other agents for IV induction or coinduction
• Midazolam
• Opioids
• .

• Clonidin

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Intravenous induction agents III.

• Anesthesia indction (and maintenance) with
  Propofol (Diprivan)
• Characteristic
• Quick and short action, easy control of
  anesthesia depth
• Reduces BP (cardiodepressive, vasodilatative)
• Venous irritation
• Bolus-administration
• Sleep dose 2 mg/kg (slowly), repeated dose
  0.5-1 mg/kg
• Continuous administration
• With infusion pump 4-12 mg/kg/hour
• TCI (Target Controlled Infusion)
  (target concentration 3-5 mg/ml)

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Typical coinduction method

• IV Midazolam (Dormicum) 0.1-(0.2) mg/kg
• IV Fentanyl 1-1.5 mg/kg
• Oxygen inhalation
• IV induction (Thiopenthal or Propofol or
  Ethomidate)
• Muscle relaxant (if mask ventilation easy)
• Endotracheal intubation
• Arteficial ventilation

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Inhalational anesthesia

• Inhalation anesthetics are gases (N2O) or vapors
• Halothan, Enfluran, Isofluran, Sevofluran,
  Desfluran
• Inhaled anesthestics get into the alveoli of the
  lung and according to the concentration gradient
  to the capillaries. The blood stream takes them
  through the left heart to the brain.

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Factors influencing the effect

• Concentration of the inhalation agent in the
  inhaled mixture
• Breathing minute ventillation, FRC
• Lungs diffusion, perfusion
• Solubility in blood, blood/gas coefficient
• Heart cardiac output
• Cerebral circulation
• Oil/water coefficient, boiling point

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Important values

• Blood/gas coefficient
• Halothan2.4 Isofluran 1.4 Sevofluran 0.6
  Desfluran 0.4
• MAC Minimal Alveolar Concentration
• Concentration of an inhalation anesthestic which
  prevents movements at surgical incision in 50 of
  the patients.
• 1 MAC isofluran 1.15 volume
• 1 MAC sevofluran 2 volume
• 1 MAC desfluran 7.3 volume

MAC reduced by premedication,
sedato-hypnotics, age, pregnancy, alcohol,
hypthermia, hyponatremia, N2O
co-administration
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Inhalation anesthesia

• Induction
• High starting flow, relatively high
  concentration filling up the system with the
  anesthetic
• Vital capacity rapid inhalation induction
  (VCRII)
• Maintenance
• Gradually reduced concentration, reduced gas flow
  (at low flow the inhaled concentration is
  entirely different from the concentration
  delivered by the vaporizer!)
• End of anesthesia
• Closing the vaporizer depending on the type of
  agent, flow and actual concentration.

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Indications for general anesthesia in dentistry

• Maxillofacial surgery
• Abscesses, other situations where local
  anesthesia is not effective
• Long, unpleasant dentoalveolar interventions
• Dental treatment patient comfort

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Goal of sedation for dental interventions

• Easier tolerance of unpleasant interventions
• Reduction of anxiety and connected risks and
  dangers
• Prevention of pain and unpleasant experiences
• Facilitate medical work

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Indication for sedation for dental interventions

• Very anxious patient
• Patients with elevated risk of a exaggerated
  sympathoadrenal reaction (hypertension, cardiac
  failure, hyperthyreosis, paroxysmal
  tachycardia, etc.)
• All problem patients (psychologic or medical
  risk)
• Imbecile, demented patients
• Not cooperative children

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Grades of sedation - the transition from one to
the other is contunuous!
Grade Consciousness CNS Airways Spontaneous breathing Cardiovasc.sytem Minimal monitoring
I. anxiolysis Clear, reactions OK Free OK OK inspection
II. conscious sedation Reacion t stimuli, lightly influenced Free Usually satisfactory Slightly affected NIBP, HR, Sat O2 - - also post-sedation
III. Deep sedation Consciousness partly lost, falls asleep, reaction only to strong stimuli Intervention often necessary Usually ? assisted ventillation necessary Usually influenced ? As above ECG
IV. General anesthesia Loss of consciousnessno reaction to painful stimuli Professionalairway management necessaryl! Assisted or controlled ventilation necessary Usually influenced Total anesthesio-logic equipment!!
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Methods of sedation

• Verbal, psychologic methods - straightforward
  behaviour suggesting security, empathy,
  information and asking for consent!
• Medical sedation
• Oral / rectal
• Intramuscular rarely, for children (Ketamine 3-6
  mg/kg)
• Intravenous
• Inhalation only N2O/O2
• - vaporised inhalational anesthetics

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Az oral (GI) sedation

• One hour before the intervention in adults
  (½ hour in children)
• Prolonged action (sedation grade I. )
• Drawbacks
• Not always practicable
• Diverse modes action in individual patients
• Inability ti drive afterwards (reaction-time ?!)
• Synergistic action with other drugs (alcohol!)
• Advantages
• Simple, no need for numerous personal,
• usually no circulatory depression,
• can be administered by the doctor resposible for
  the intervention
• Recommanded medication
• Midazolam (7,5-15 mg) - for children0,3-0,4
  mg/kg (in Panadol syrup)
• Alprazolam (0,25-0,5 mg), (Diazepam)
• Old patients are especially sensitive
  administer with care!

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Az inhalational sedation

• N2O/O2 for dental interventions
• Maximal concentration without the danger of
  hypoxia (60) causes superficial conscious
  sedation (grade II.)
• Special equipment necessary
• Requires an extra doctor, expert in airway
  management, mechanical ventilation and emergency
  techniques (anesthesiologist) , who is not
  involved in the dental intervention!

• Sedation with vaporized inhalation-anesthetics
  is already GA with the same objetive and
  subjective conditions

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Intravenous sedation

• Opioids -Antidot naloxone (0,l mg repeated
  if necessary.)
• For painful inteventions it is the first drug eg.
  fentanyl (1mg/kg), alfentanil, sufentanil,
  remifentanil, pethidin
• Danger respiratory depression, synergism -
  administration is the task of an
  anesthesiologist!
• Benzodiazepins - titrated administration,
  until we reach the intended grade of
  sedation
• Midazolam 0,03-0,05 mg/kg 0,1-(0,15)mg/kg
• Prepare for airway management mechanical
  ventilation!
• be careful in older patients reduce doses!
• Ketamine
• Propofol
• TCI sedation 2-2,5 mg/ml as a target
  concentration

Használatuk aneszteziológus orvosi feladat!
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Possible complication of sedation

• Apnoea, airway obstraction
• Vomiting, aspiration
• Circulatory depression, fall in BP
• Allergic reaction, anaphylaxis, anaphylactoid
• Be allways prepared for all possible
  complications!
• The intravenous and inhalational sedation
  requires the fulfillment of all subjective and
  objective conditions!!

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Suitability for sedation/anesthesia in the dental
practice

• Anesthesiologic evaluation (preadmission clinic!)
• History
• Physical examination
• Laboratory tests (?)
• Preoperatice carency NPO?
• Bladder emptying, necessary preparation

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Documentation

• Detailed petient information
• Signed informed consent
• Anesthesia sheet
• Post-sedation observation sheet
• Detailed operation instructions adapted to the
  function of the ward (competencies,
  responsibilities,etc.)

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Simplified discharge criteria

• Stable vital functions for more than 1 hour
• The patient
• Is well oriented in person, time, local
  conditions (mental state similar to the
  original)
• can drink alone
• can urinate (regional anesthesia!)
• takes up cloths, walks without help
• No
• PONV
• Serious pain (VAS lt30)
• bleeding
• Adult attendant
• Dentist and anesthesiologist agreed to discharge
• Home care arranged
• Written directions for the postoperative
  period (name and telephone of the contact
  persons!)

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Competency
Grade Doctor Nurse
I. anxiolysis doctor responsible for the intervention (dentist) Dental nurse
II. conscious sedation independent doctor with good knowledge in airway management and emergency medical methods (specialist anesthesist)!!! ?
III. Deep sedation Absolutly necessary the presence of a specialist anesthesist! The doctor, responsible for the intervention is not allowed to make anesthesia or deep sedation even if he/she is specialized in anesthesia as well! Necessary/ recommended
IV. General anesthesia Absolutly necessary the presence of a specialist anesthesist! The doctor, responsible for the intervention is not allowed to make anesthesia or deep sedation even if he/she is specialized in anesthesia as well! Necessary
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Objective conditions
Grade
I. anxiolysis
II. conscious sedation Easily accessible dental chair/operating table O2 (cylinders, reductor, connectors, tubes, masks) airway management equipment, tools of mechanical ventilation Necessary equipment for intravenous access Strong suction-set, BLS accessorries, emergency medication and equipment pulzoximeter, stetoscope, BP manometer
III. Deep sedation ECG, anesthesia machine, defibrillator, availability of quick medical help, ICU background, recovery room, supervising stuff
IV. General anesthesia ECG, anesthesia machine, defibrillator, availability of quick medical help, ICU background, recovery room, supervising stuff
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Have a nice relaxed (but not sedated) afternoon!
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Auditory Evoked Potential Waves ( AEP )

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General anaesthesia

• phases
• preparation
• induction
• maintenance
• emd of anesthesia (arousal)
• recovery
• pain relief!

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Old anesthesia methods

• Ether/chloroform drip method
• Intravenous barbiturates
• Gray method intubation anesthesia (!)
  thiopenthal induction, maintenance N2O/O2,
  opioid, muscle relaxants
• NLA type I. anesthesia haloperidol
  phenoperidin (N2O/O2)
• NLA II. anesthesia dehydrobenzperidol
  (DHBP)fentanyl (N2O/O2)
• DE CASTRO MUNDELEER

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Further modifications

• TypeII. neurolept anesthesia
• Induction DHBP 0,25-0,5 mg/kg Fentanyl
  2-3mg/kg N2O/O2
• Maintenance Fentanyl 1-1 mg/kg, N2O/O2,
  muscle relaxants if necessary
• Modified neurolept anesthesia
• Induction DHBP 0,05-0,1 mg/kg Fentanyl
  1mg/kg N2O/O2 Thiopenthal until the
  disapperance of the eyelid reflex
• Maintenance Fentanyl 1mg/kg N2O/O2, muscle
  relaxant
• Coinduction method
• Induction Midazolam 0,05 mg/kg, Fentanyl 1-2
  mg/kg Thiopenthal - until the disapperance of
  the eyelid reflex
• Maintenance Fentanyl, N2O/O2, muscle relaxant,
  with supplementation as necessary
  (balanced)

neurolept analgézia
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Neurolept anesthesia/analgesia

• Advantages
• Cooperable but emotionally indifferent patient
• mineralisation, antinociception
• Possibility of balanced maintenance
• Disadvantages
• DHBP is an a receptor blocking agent BP fall
  possible, prolonged action
• Control of anesthesia depth not easy, slow actions

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Induction by continuous infusion

• Oxigygen inhalation
• Propofol - TCI 5-6 mg/ml continuously reduced
• Remifentanil or Sufentanil or Fentanyl,
• (Fentanyl bolus 1-2 mg/kg)
• Remifentanil 5mg in 50 ml 1 mg/kg bolus 0.05-1
  mg/kg/min
• Fentanyl 500 mg (10 ml) diluted to 50 ml,
• 1-2 mg/kg bolus, 100-150 mg(5-7.5 ml)/hour
• Cumulation!
• After the patient is asleep, mask ventilation,
  than muscle relaxation
• Intubation

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Monitoring of anesthesia depth

• Changes in the ventilation type and frequency
• Autonomic nerve responses to stimuli
• Mechanical methods
• isolated upper arm
• Measurement of lower oesophagus contractions
• (Measurement of the concentration of anesthetics
  in the blood)
• Cerebral electric activity measurements
• Cerebral function monitor
• BIS monitoring
• PSI (physical state index)
• AEP

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Important values

• Blood/gas coefficient
• Halothan2.4 Isofluran 1.4 Sevofluran 0.6
  Desfluran 0.4
• MAC Minimal Alveolar Concentration
• Concentration of an inhalation anesthestic which
  prevents movements at surgical incision in 50 of
  the patients.
• 1 MAC isofluran 1.15 volume
• 1 MAC sevofluran 2 volume
• 1 MAC desfluran 7.3 volume

MAC reduced by premedication,
sedato-hypnotics, age, pregnancy, alcohol,
hypthermia, hyponatremia, N2O
co-administration
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Factors influencing the uptake of the
inhalational agent

• Inspiration concentration (parcial pressure)
• Alveolar ventillation
• Blood/gas coefficient bad solubility
  early saturation
• Tissue uptake, saturation
• A concentration difference between the end tidal
  (alveolar) and inhaled concentration FA/FI
  equilibrium after long continuous administration