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General anesthesia

General anesthesia. Definition of anesthesia. It is a reversable blocking of pain feeling in whole body or in a part of it using pharmacology or other methods. Anesthesia - division.

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General anesthesia

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  1. General anesthesia

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

  3. Anesthesia- division 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

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

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

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

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

  8. Stages of general anesthesia • Stadiumanalgesiae (analgesia and sedation stage) • Stadiumexcitationis (excitation stage) • Stadiumanaesthesiaechirurgicae (anesthesia for 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 of threat • Sedation – calming down • Amnesia – lack lof memories of perioperative period Methods of general anesthesia • OPENOLD • SEMIOPENUSED MOSTLY IN PEDIATRIC ANESTESHIA • SEMICLOSED MOST COMMON • CLOSED MODERN ANESTESHIA

  11. Methods of 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. Anesthesia agents • 1. Inhalationanesthetics (volatile anesthetics) - gases : N2O, xenon - Fluids (vaporisers) • 2. Intravenousanesthetics - Barbiturans : thiopental - Others : propofol, etomidat • 3. Pain killers - 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, fataccumulation effect): – 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 • Division of inhalation agents • 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 methabolism in 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 widelly used

  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 anaesthetist to select the target blood concentration required for a particular effect • It allows to control depth of anaesthesia by 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 diseaster medicine Gives night mare dreams in adult patients

  25. Propofol Very good anesthetic for induction and maintaince of 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 • May be used for induction and maintain of anesthesia in repeatedbolus or continuousinfusiontechnique • Sedative effect • In high dosesmay be used alone for so calledopioidanesthesia- formerlyused in cardioanesthesia- verystablecirculatoryeffect

  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- methabolism is 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 contractation but block access to receptors for Ach • 2.depolarising- they combine with receptors for Ach and cause contractation of muscle but they stay connected with receptor blocking access to it for Ach. They act like agonists.

  32. Nondepolarising agents • d-tubocurine– oldestdeliverate of curarine – • alcuronium • -pancuronium – cheap and stillused– • pipercuronium – • vercuronium – • atracurium – • cisatracurium – • mivacurium • -rocuronium

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

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

  35. Division of 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% supresion 60 sec. • Do not release histamine • Acts about 60 min • Is methabolised in liver- disfunction of liver may alter elimination • Mivacurium • Releases histamine • Acts about 15-20 min – used for short procedures • Methabolisedby plasma esterases

  38. Reverse of neuromuscularblockade • Neostigmine, piridostigmine- blockers of acetylocholinesterase • Must be giventoghether with atropine to avoidbradycardiacaused by activation of perisympaticsystem • Depolarising agents • Only one: chlorsuccinilocholine– • It is methabolised by 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 of surgical surgical patients patients • 80 % is is caused caused by by human 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

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