General anesthesia
Methods
Definition and goal
Definition:

A state where the patient
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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)
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)
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side-effects avoided or diminished
proper management of anaesthesia
accommodation to individual needs
accommodation to actual extent of variable intra-operative pain
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:
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consciousness
ocular signs (pupilla)
breathing pattern
vegetative signs (pulse)
muscle tone
Consciousness
Stádium
Reflexes
Br.
pupilla
I.
1.
Anal- 2.
gesia 3.
II.
excitaton
III.
1.
Tole-
2.
rance
3.
4.
IV.Asphyxia
eyelid cornea secret. light gag
vomit
Muscle tone
str. abd.
smooth
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:
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GI system (intestinal capillary-portal vene – VCI- RA-RVlungs – 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-arteries)
General anaesthesia

Cannot be described by a simple and single process at least two fundamental processes:
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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:
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very high dose of a hypnotic produces anti-nociception,
very high dose of an analgetic (opioid) produces
unconsciousness
Preparation before anesthesia
Before the patient arrives
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Preparation and check of the equipment
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(e.g. suction, monitors, infusion, intubation, airway
maintenance equipment)
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Check up: anesthesia machine, gas supply
Preparation of medicaments
After arrival of the patient
 Greeting of patient, documentation checkup,
anesthesia sheet
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Monitors, registration of starting values
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Venous access
Parts of general anesthesia
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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)
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End (arousal) and recovery
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On the operating table
Delayed– complete arousal later
ICU
in the RR or
Drugs for general anaesthesia
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Drugs for preoperative preparation
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drugs for induction of anaesthesia
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intravenous or/and volatile anaesthetics
+ supplementary drugs
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short acting iv. anaesthetics, inhalation agent(s)
maintenance of anaesthesia
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sedatives, analgesics, vegetative (parasympatholytic) drugs
analgesics, vegetative stabilizing drugs, additives,
potentiating agents and other drugs
drugs for

awakening
antagonists: (opioids, benzodiazepines), antidote of muscle
relaxants
Which method of anaesthesia?
Decision influenced by:
 Patient’s demands
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Surgical aspects
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Condition of the patient (hypertension, cardiac failure, …)
Circumstances of treatment (emergency or elective situations)
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
Intravenous anesthesia
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Bolus administration
Continuous infusion (pump)
Advantages
•Easy, quick
administration
•Known dose
•Does not depend on
breathing
•Combination of different
agents possible
•No pollution
Drawbacks
•Once given, the dose can not be
reduced
•Elimination depends on organ
function/enzymes
•Allergy - more often
concentration
IV bolus administration
effective concentration
First dose
Second dose
Methods
• Total IntraVenous Anesthesia (TIVA)

Intravenous induction and maintenance (infusion pump)
Ventilation: oxygen – air mixture

e.g. NLAII!
Intravenous induction and mainetnance (continuous or bolus)
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Ventilation: oxygen – nitrous oxide
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• IntraVenous Anesthesia (IVA) –
• Inhalation anesthesia
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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.)
Inhalation anesthesia

Pro
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Contra
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Easy continuous
administration
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Needs specific
vaporizers
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Easy modulation of blood
concentration
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Induction can be slow,
unpleasant
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Elimination through the
lungs
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Pollution
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Price?
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Allergy rate low
Induction
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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
Induction II
 Medical preparation (coinduction)
 E.g. Fentanyl
+ Midazolam
(Earlier: Fentanyl + DHBP – NLA)
 Intravenous induction – („falling asleep”)
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Bolus injection
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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)
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
Intravenous induction agents II.
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Ethomidate
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Only for induction (single dose) – short action
Dose: 0.15-0.3 mg/kg of the 0.2% solution (10 ml=20 mg)
Circulatory effects less than with other agents (for high risk cardiovascular
patients). Spontaneous twiching possible
Adrenal depression!
Ketamine (S+ Ketamine)
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„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
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Propofol
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Other agents for IV induction or coinduction:
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Midazolam
Opioids
….
Clonidin
Intravenous induction agents III.
Anesthesia indction (and maintenance) with
Propofol (Diprivan)
Characteristic:
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Quick and short action, easy control of anesthesia depth
Reduces BP (cardiodepressive, vasodilatative)
Venous irritation
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Bolus-administration:
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Sleep dose: 2 mg/kg (slowly), repeated dose: 0.5-1 mg/kg
Continuous administration
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With infusion pump 4-12 mg/kg/hour
TCI („Target Controlled Infusion”)
(target concentration 3-5 mg/ml)
–
Typical coinduction method
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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
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.
Factors influencing the effect
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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
Important values

Blood/gas coefficient:
Halothan:2.4 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.
MAC reduced: by
1 MAC isofluran = 1.15 volume%
premedication, sedato-hypnotics,
age, pregnancy, alcohol,
1 MAC sevofluran= 2 volume%
hypthermia, hyponatremia,
N2O co-administration
1 MAC desfluran = 7.3 volume%
Inhalation anesthesia
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Induction:
High starting flow, relatively high concentration
filling up the system with the anesthetic
„Vital capacity rapid inhalation induction” (VCRII)
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Maintenance:
Gradually reduced concentration, reduced gas flow (at low
flow the inhaled concentration is entirely different from the
concentration delivered by the vaporizer!)
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End of anesthesia:
Closing the vaporizer depending on the type of agent, flow
and actual concentration.
Indications for general anesthesia in
dentistry
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Maxillofacial surgery
Abscesses, other situations
where local anesthesia is not effective
Long, unpleasant dentoalveolar interventions
Dental treatment : patient comfort
Goal of sedation for dental interventions
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Easier tolerance of unpleasant
interventions
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Reduction of anxiety and connected
risks and dangers
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Prevention of pain and unpleasant
experiences
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Facilitate medical work
Indication for sedation for dental
interventions
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Very anxious patient
Patients with elevated risk of a exaggerated
sympathoadrenal reaction (hypertension, cardiac failure,
hyperthyreosis, paroxysmal tachycardia, etc.)
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All problem patients (psychologic or medical risk)
Imbecile, demented patients
Not cooperative children
Grades of sedation - the transition from one to the other is contunuous!
Grade
Consciousness
CNS
I.
anxiolysis
Clear,
reactions OK
II.
„conscious
sedation”
Reacion t
stimuli,
lightly
influenced
III. Deep
sedation
Consciousness
partly lost,
falls asleep,
reaction only
to strong
stimuli
IV. General Loss of
anesthesia
consciousness
no reaction
to painful
stimuli
Airways
Free
Free
Intervention
often
necessary
Professional
airway
management
necessaryl!
Spontaneous
breathing
Cardiovasc.
sytem
OK
OK
Usually
satisfactory
Slightly
affected
Usually ↓
Usually
influenced
↓
assisted
ventillation
necessary
Assisted or
controlled
ventilation
necessary
Usually
influenced
Minimal
monitoring
inspection
NIBP, HR,
Sat O2 - also postsedation
As above +
ECG
Total
anesthesiologic
equipment!!
Methods of sedation
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Verbal, psychologic methods straightforward behaviour suggesting security, empathy,
information and asking for consent!
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Medical sedation
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Oral / rectal
Intramuscular –rarely, for children (Ketamine 3-6 mg/kg)
Intravenous
Inhalation
– only N2O/O2
- + vaporised inhalational anesthetics
Az oral (GI) sedation
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One hour before the intervention in adults
(½ hour in children)
Prolonged action (sedation grade I. )
Drawbacks:
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Advantages:
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Not always practicable
Diverse modes action in individual patients
Inability ti drive afterwards (reaction-time ↑!)
Synergistic action with other drugs (alcohol!)
Simple, no need for numerous personal,
usually no circulatory depression,
can be administered by the doctor resposible for the intervention
Recommanded medication:
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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!
Az inhalational sedation
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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
Intravenous sedation
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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!
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Benzodiazepins - titrated administration,
until we reach the intended grade of sedation
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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!
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Ketamine Használatuk aneszteziológus orvosi feladat!
Propofol
TCI sedation: 2-2,5 mg/ml as a target concentration
Possible complication of
sedation
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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!!
Suitability for sedation/anesthesia in the
dental practice
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Anesthesiologic evaluation (preadmission
clinic!)
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History
Physical examination
Laboratory tests (?)
Preoperatice carency – NPO?
Bladder emptying, necessary preparation
Documentation
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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.)
Simplified discharge criteria
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Stable vital functions for more than 1 hour
The patient
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No
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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
PONV
Serious pain (VAS <30)
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!)
Competency
Grade
I. anxiolysis
II. „conscious sedation”
III. Deep
sedation
IV. General anesthesia
Doctor
Nurse
doctor responsible
for the intervention
(dentist)
Dental nurse
+ independent doctor
with good knowledge in
airway management and
emergency medical
methods (specialist
anesthesist)!!!
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
Necessary
Objective conditions
Grade
I. anxiolysis
II. „conscious
sedation”
III. Deep
sedation
IV. General
anesthesia
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
+
+ ECG, anesthesia machine, defibrillator,
availability of quick medical help,
ICU
background, recovery room, supervising stuff
Have a nice relaxed (but not sedated)
afternoon!
General anaesthesia

phases:
 preparation
 induction
 maintenance
 emd of anesthesia (arousal)
 recovery
pain relief!
Old anesthesia methods
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Ether/chloroform… drip
Intravenous barbiturates
method
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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
Further modifications
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TypeII. neurolept anesthesia
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Modified neurolept anesthesia
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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
Induction:
neurolept analgézia
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
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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 anesthesia/analgesia
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Advantages:
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Cooperable but emotionally indifferent patient
„ mineralisation”, antinociception
Possibility of balanced maintenance
Disadvantages:
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DHBP is an a receptor blocking agent – BP fall
possible, prolonged action
Control of anesthesia depth not easy, slow actions
Induction by continuous infusion

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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
Monitoring of anesthesia depth
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Changes in the ventilation type and frequency
Autonomic nerve responses to stimuli
Mechanical methods
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„isolated upper arm”
Measurement of lower oesophagus contractions
(Measurement of the concentration of anesthetics in
the blood)
Cerebral electric activity measurements
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Cerebral function monitor
BIS monitoring
PSI (physical state index)
AEP
Important values

Blood/gas coefficient:
Halothan:2.4 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.
MAC reduced: by
1 MAC isofluran = 1.15 volume%
premedication, sedato-hypnotics,
age, pregnancy, alcohol,
1 MAC sevofluran= 2 volume%
hypthermia, hyponatremia,
N2O co-administration
1 MAC desfluran = 7.3 volume%
Factors influencing the uptake of the
inhalational agent

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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