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 • 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
TIVA Total Intra Venous Anaesthesia
VIMA Volatile Induction and Maintain Anaesthesia
Parts of general anesthesia • 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 must be in balance Hypnosis Analgesia (anesthesia) Lack of reflexes (muscle relaxation)
� General anesthesia Lack of Lack of consciousness consciousness 1 1 features Pain management management Pain Lack of Lack of reflexes reflexes 2 2 Neuromuscular Neuromuscular blockade blockade 3 4 4
Stages of general anesthesia • Stadium analgesiae (analgesia and sedation stage) • Stadium excitationis (excitation stage) • Stadium anaesthesiae chirurgicae (anesthesia for surgery) • Stadium paralysis respirationis (intoxication, respiratory arrest)
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
Estimation of of the the risk risk of of anesthesia anesthesia ( (American American Estimation Society of of Anesthesiologists Anesthesiologists scale scale) ) Society � � ASA 1 ASA 1: : healthy healthy patient patient. . � ASA 2: : patient patient with with stable stable, , treated treated illness illness like like arterial arterial � ASA 2 hypertension, , diabetes melitus, , asthma bronchiale, , hypertension diabetes melitus asthma bronchiale obesity obesity � ASA 3: : patient with systemic illness decreasing � ASA 3 patient with systemic illness decreasing suffitiency like like heart heart ilness ilness, , late late infarct infarct suffitiency � ASA 4: : patient patient with with serious serious illness illness influencing influencing his his state state � ASA 4 like renal insuficiency, , unstable hypertension, , like renal insuficiency unstable hypertension circulatory insuficiency insuficiency circulatory � � ASA 5 ASA 5: : patient patient in in life life treatening treatening illness illness � ASA 6: : brain brain death death- - potential potential organ donor organ donor � ASA 6
Premedication Premedication Main reasons reasons for for premedication premedication: : Main � Anxiolysis Anxiolysis- - lack lack of of threat threat � � Sedation Sedation – – calming calming down down � � Amnesia Amnesia – – lack lack of of memories memories of of � perioperative period period perioperative
• Methods of general anesthesia OPEN SEMIOPEN SEMICLOSED CLOSED
• METHODS OF GENERAL ANESTHESIA OPEN- old SEMIOPEN – used mostly in pediatric anesthesia SEMICLOSED- most common CLOSED- modern anesthesia
• Methods of general anesthesia CIRCLE SYSTEM CIRCLE SYSTEM *HIGH HIGH- -FLOW FLOW FRESH GAS FLOW 3 l/min. *LOW LOW- -FLOW FLOW FGF ok. 1l/min. *MINIMAL MINIMAL- -FLOW FLOW FGF ok. 0,5 l/min.
Stages of general anesthesia • Introduction to anesthesia (induction) • Maintaining of anesthesia (conduction) • Recovery from anesthesia
Anesthesia agents 1. Inhalation anesthetics (volatile anesthetics) - gases : N 2 O, xenon - Fluids (vaporisers) 2. Intravenous anesthetics - Barbiturans : thiopental - Others : propofol, etomidat 3. Pain killers - Opioids: fentanyl, sufentanil, alfentanil, remifentanil, morphine - Non Steroid Anti Inflamatory Drugs: ketonal, paracetamol 4. Relaxants - Depolarising : succinilcholine - Non depolarising : atracurium, cisatracurium, vecuronium, rocuronium 5. adiuvants -benzodiazepins: midasolam, diazepam
Volatile vs intravenous anesthesia
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, fat- accumulation 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
Inhalation agents
Division of inhalation agents 1. Gases: • N 2 O – old, weak, used as adiuvant • Xenon – lately introduced 2. Vapors (fluids): • Halothan • Enfluran • Isofluran • Sevofluran • Desfluran
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
Nitrous oxide, laughing gas • Old • Weak • Used as adiuvant • Will be removed form medical use up to 2010- destroyes ozone lawyer
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
Isofluran • Disturbing smell • May interact with heart contractivity • Increases relaxation of muscles
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
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
Intravenous anesthesia
TCI Target Controlled Infusion
Defining TCI When applied to anaesthesia • TCI is an infusion system which allows the anaesthetist to select the target blood concentration required for a particular effect … … and then to control depth of anaesthesia by adjusting the requested target concentration
What is TCI? • 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.
Intravenous anesthetics
Thiopental • Old, one of the first used intravenous anesthetics • Depressing effect on circulatory system • May be used in patients with ASA 1
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
Etomidat • Has no depressing effect on circulatory system- may be used in patients with circulatory insufficiency • May give musle contractions • Depressing effect on epirenals function • Can not be given in repeated bolus nor continuous infusion
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
Pain killers
Opioids • fentanyl, alfentanil, sufentanil, remifentanil • May be used for induction and maintain of anesthesia in repeated bolus or continuous infusion technique • Sedative effect • In high doses may be used alone for so called opioid anesthesia- formerly used in cardioanesthesia- very stable circulatory effect
Compications of use • Respiratory depression !!!! • Muscle rigidity in high doses • Post-Operative Nausea and Vomitings • Accumulation effect after prolonged administration (except for remifentanil)
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