4Generalanesthesia.pp general basic principles

General anesthesia basic principles, regional, local,

1. General anesthesia

2. It is a reversableblocking of
pain feeling in whole body or
in a part of it using
pharmacology or other
methods
Definition of anesthesia

3. Local-regional anesthesia,
patient is conscious or sedated
General-anesthesia interact with
whole body, function of central
nervous system is depressed:
–Intravenous
–Inhalation (volatile)
–Combined, balanced
Anesthesia-division

4. TIVA
Total Intra Venous Anaesthesia
VIMA
Volatile Induction and Maintain
Anaesthesia

5. Partsof general anesthesia
Hypnosis-pharmacological sleep,
reversable lack of consciousness
Analgesia-pain management
Areflexio-lack of reflexes
Relaxatio musculorum-muscle
relaxation, pharmacological reversable
neuromuscular blockade

6. Parts of general anesthesia must
be in balance between:
Hypnosis (anesthesia) Analgesia
Lack of reflexes (muscle relaxation)

7. Features of General anesthesia
1 Lack of consciousness
2 Pain management
3 Lack of reflexes
4 Neuromuscular blockade

8. Stagesof general
anesthesia
• Stadiumanalgesiae(analgesia and
sedationstage)
• Stadiumexcitationis(excitationstage)
• Stadiumanaesthesiaechirurgicae
(anesthesiafor surgery)
• Stadiumparalysisrespirationis
(intoxication, respiratoryarrest)

9. I. Analgesia stage
• Patient consciouss
• Spontaneus respiration
• Reflexes present
• Possible small surgery procedures like dressing change in burns
II. Excitation stage
• Possible uncontrolled movements, vomitings
• Increase in respiratory rate
III. Anesthesia for surgery
• It begins with lack of lid reflex
• 4 substages
• Airway opening necessary
• Possible surgery except for abdominal opening if no
relaxants are used
• Possible endotracheal intubation
IV. intoxication, overdosing
• Respiratory arrest
• If anesthesia not discontinued possible
cardiac arrest

10. Premedication
Main reasons for premedication:
Anxiolysislack of ofthreat
Sedation –calming down
Amnesia –lack lofmemories of
perioperative period
Methods of general anesthesia
OPEN OLD
SEMIOPEN USED MOSTLY IN PEDIATRIC ANESTESHIA
SEMICLOSED MOST COMMON
CLOSED MODERN ANESTESHIA

11. Methodsof general anesthesia
CIRCLE SYSTEM
*HIGH FLOW
FRESH GAS FLOW > 3 l/min.
*LOW FLOW
FGF ok. 1l/min.
*MINIMAL FLOW
FGF ok. 0,5 l/min.
Stages of general anesthesia
• Introduction to anesthesia (induction)
• Maintaining of anesthesia (conduction)
• Recovery from anesthesia

12. Anesthesiaagents
1. Inhalationanesthetics(volatile anesthetics) -
gases: N2O, xenon-Fluids(vaporisers)
2. Intravenousanesthetics-Barbiturans:
thiopental-Others : propofol, etomidat
3. Painkillers -Opioids: fentanyl, sufentanil,
alfentanil, remifentanil, morphine-Non Steroid
Anti InflamatoryDrugs: ketonal, paracetamol
4. Relaxants-Depolarising: succinilcholine-
Non depolarising: atracurium, cisatracurium,
vecuronium, rocuronium
5. adiuvants-benzodiazepins: midasolam,
diazepam

13. Volatile vs
intravenous
anesthesia

14. Mechanism of action of inhaled anesthetics
Reaction depends on concentration. This
depends on alveolar (first compartment), blood
and brain (central compartment) concentration ,
(third compartment-other tissue like muscles,
fataccumulationeffect):
–Minute ventilation
–Lung blood perfusion
–Solubility in tissues
MAC-minimal alveolar concentration
Concentration in which 50% of anesthetised patients do not
react on skin incision
Corelation with solubility in fat tissue
The lower MAC is the higher strenght of action is

15. Inhalation agents
Divisionof inhalationagents
1.Gases:
• N2O –old, weak, usedasadiuvant
• Xenon–latelyintroduced
2. Vapors(fluids):
• Halothan
• Enfluran
• Isofluran
• Sevofluran
• Desfluran

16. Features of ideal volatile
anesthetic
Not disturbing smell
Fast acting, titrable
Low solubility in blood-fast transport to
brain
Stable when stored, not reacting with other
chemicals
Non-flamable, non-explosive • Low
methabolismin body, fast elimination, no
accumulative effect
No depressing effect on circulatory and
respiratory systems

17. Nitrous oxide
• Old
• Weak
• Used as adiuvant
• Will be removed form medical use up to
2010
Halothan
• Used for many years with good effect
• First non-flamable volatile fluid anesthetic
• MAC high
• Depression of circulatory system
• May destroy liver
• Now-a-days used only in pediatric anesthesia

18. Isofluran
• Disturbing smell
• May interact with heart contractivity
• Increases relaxation of muscles
Desfluran
• Very disturbing smell-can not be used for
VIMA
• Is not methabolised
• Very fast acting
• May be used for one-day surgery
• Expensive, difficult to store (boiling temp.
about 20 C)
• Modern and widellyused

19. Sevofluran
• Not disturbing smell-may be used for
VIMA
• Low solubility in blood-fast acting
• Does not disturbs airway
• May depress circulatory system
• Methabolised to Compound A-may be
renal toxic (but not confirmed in humans)
• May be used in one-day surgery
• Modern, and more and more widely used
volatile anesthetic

20. Intravenous
anesthesia

21. TCI (target controlled infusion)
TCI is an infusion system which allows the
anaesthetistto select the target blood
concentration required for a particular effect
It allows to control depth of anaesthesiaby
adjusting the requested target concentration

22. Instead of setting ml/h or a dose rate
(mg/kg/h), the pump can be programmed
to target a required blood concentration.
Effect site concentration targeting is now
included for certain pharmacokinetic
models.
The pump will automatically calculate how
much is needed as induction and
maintenance to maintain that
concentration.

23. THIOPENTAL
Old, one of the first used intravenous
anesthetics
Depressing effect on circulatory system
May be used in patients with ASA 1

24. Ketamine
Only intravenous anesthetic which has
good analgesia effect
Does not depress circulatory nor respiratory
function
Used in children, and in emergency and
diseastermedicine
Gives night mare dreams in adult patients

25. Propofol
Very good anesthetic for induction and
maintainceof anesthesia with no
accumulation effect
Titrable
May be used in short procedures –
titrated do not effect circulatory and
respiratory system in important manner
Good for sedation, brain protecting effect
May be used in TCI

26. Opioids
fentanyl, alfentanil, sufentanil,
remifentanil
Maybe usedfor inductionand maintain
of anesthesiain repeatedbolusor
continuousinfusiontechnique
Sedative effect
In high dosesmaybe usedalone for so
calledopioidanesthesia-formerlyusedin
cardioanesthesia-verystablecirculatory
effect

27. Compications of use
Respiratory depression
Muscle rigidity in high doses
Post-Operative Nausea and
Vomitings
Accumulation effect after prolonged
administration (except for
remifentanil)

28. Remifentanil
T1/2 3-5 min
Methabolisedby non-specific tissue
esterases-methabolismis not
altered by renal or liver function
No accumulation effect after
prolonged

29. BENZODIAZEPINES
Used in anesthesia:
Diazepam
Midazolam
Used as adiuvants for premedication

30. MUSCLE
RELAXANTS

31. Division of relaxants depending on mechanism
of action
1.nondepolarising-
combine with receptor for Ach like antagonists-
they are fake mediators
do not cause muscle contractationbut block
access to receptors for Ach
2.depolarising-
they combine with receptors for Ach and cause
contractationof muscle but they stay
connected with receptor blocking access to it
for Ach.
They act like agonists.

32. Nondepolarisingagents
d-tubocurine–oldestdeliverateof
curarine –
alcuronium
-pancuronium–cheap and stillused–
pipercuronium–
vercuronium–
atracurium–
cisatracurium–
mivacurium
-rocuronium

33. Division of nondepolarisingrelaxants due to
Chemical structure:
AMINOSTEROIDS
Pankuronium( Pavulon)
Pipekuronium( Arduan)
Rapakuronium( Raplon)
Rokuronium( Esmeron)
Wekuronium( Norcuron)

34. Benzylizochinolons
Miwakurium( Mivacron)
Cisatrakurium( Nimbex)
Atrakurium(Trakurium)

35. Divisionof nondepolarisingrelaxants
due to time of action:
Short acting< 3 min: stillsearching
Midletime <60 min: mivacurium,
atracurium, cisatracurium, rocuronium,
vecuronium
Long acting> 60 min: pancuronium,
pipecuronium

36. Atracurium
Elimination non-enzymatic, independent of renal and liver
function, Hoffman elimination-hydrolisis
Releases histamine
Acts about 30 min
Cisatracurium
One of stereoisomers of atracurium,
Do not release histamine
Acts about 60 min

37. Rocuronium
Fast acting-time to 100% supresion60 sec.
Do not release histamine
Acts about 60 min
Is methabolisedin liver-disfunctionof liver may
alter elimination
Mivacurium
Releases histamine
Acts about 15-20 min –used for short
procedures
Methabolisedby plasma esterases

38. Reverse of neuromuscular blockade
Neostigmine, piridostigmine-blockersof
acetylocholinesterase
Must be giventoghetherwith atropine to avoid
bradycardiacausedby activationof perisympatic
system
Depolarisingagents
Only one: chlorsuccinilocholine–
It is methabolisedby pseudocholinesterase-
Causes many complications, has many
contraindications –
Indications: Rapid sequence induction: full
stomach, suspected difficult intubation because it
acts very fast < 30 seconds and short < 3 min

39. Complications of general
anesthesia
Respiratory: residual relaxants/opioids
action
Circulatory
Neurological: residual
anesthetics/opioids action
Post-Operative Nausea and Vomitings

40. Mortality connected with anesthesia
0,05 0,05 -4/10000 GA
2 2 -16 % of ofsurgical surgicalpatients
patients
80 % is iscaused causedby byhuman
humanmistakes
Major causes of deaths
Airway obstruction
Difficult and and unefficient intubation
Insufficient ventillation

41. Other causes of mortality and morbidity
Anoxia
Haemodynamic instability
Aspiration Aspiration
Toxity of drugs drugs
mostly inhalation agents
Anaphylaxia and and drug
interations