General anesthesia.ppt

1、General anesthesia,Ma Ling Department of Anesthesiology Shengjing Hospital, China Medical University Tel:What is general anesthesia?,A. pain relief (analgesia) B. blocking memory of the procedure (amnesia) C. producing unconsciousness D. inhibiting normal body reflexes to make surgery s

2、afe and easier to perform E. relaxing the muscles of the body,Definition,General anesthesia is anesthetics-induced reversible suppression on CNS, and has the following manifestations: producing unconsciousness pain relief (analgesia) blocking memory of the procedure (amnesia) inhibiting normal body

3、reflexes to make surgery safe and easier to perform relaxing the muscles of the body,Induction period,Maintenance period,Recovery period,Lost consciousness,awake,IV,quickly,IV+Inhale,Exhale,Course of General Anesthesia,Route of Action,blood,Central nervous system,Anesthesia,Intravenous anesthetics,A

4、lveolar,Inhalation anesthetics,Inhalation anesthetics,Through airway Maintenance (most); induction (some) Most are halogenated hydrocarbons Mechanism: interact with the brain cell membrane, details are not clear,How to compare anesthetic potency?,MAC (minimum alveolar concentration) 最低肺泡有效浓度 The con

5、centration (at 1atm) required to prevent movement in 50% of subjects following a surgical stimulus Oil-gas partition coefficient Anesthetic potency MAC MAC is also an index for depth of anesthesia,Inhalational anesthesia,Lower MAC higher potency,Elder hypotension hypothermia hypothyroidism concurren

6、t use of opioids,Infant pyrexia drug abuser,MAC,MAC,How to determine its controllability?,Blood-gas partition coefficient (solubility) The lower the blood-gas partition coefficient the easier for the partial pressure in alveolar, blood and brain to get equilibrium the easier to control its concentra

7、tion in brain,Physicochemical property,(1) oil-gas partition coefficient anesthetic potency MAC (2) blood-gas partition coefficient controllability,reverse,reverse,reverse,Which has the best anesthetic potency?Which takes effect fastest?,FA: alveolar concentration of anestheticFI: inspired concentra

8、tion of anesthetic,FA /FI shows the increasing rate of anesthetic in alveolar,Factors determine FA dose dependent inhibition Muscle relaxation Induction and maintenance, unavailable in USA Patient with epilepsy history should be avoided (seizure activity on EEG),Isoflurane, 异氟烷,Properties ：clear col

9、ourless volatile anesthesia, pungent odor MAC 1.15 B/G 1.4 Metabolism 0.2 % Cardiovascular: mild depression of myocardial contractility systemic vascular resistanceBP coronary steal little sensitization of myocardium to Catecholamine Respiratory: dose dependent inhibition Muscle relaxation Maintanen

10、ce,Sevoflurane, 七氟烷,Properties ：clear colourless volatile anesthetic; pleasant smell MAC 2% B/G 0.65 (rapid induction in children) Metabolism 2% Cardiovascular: similar to isoflurane Respiratory: dosedependent inhibition, no irritate to airway Muscle relaxation: similar to isoflurane Both Induction

11、and maintenance Decomposition in soda lime and when temperature rises,Desflurane, 地氟烷,Properties: clear colorless volatile anesthesia MAC 6.0-7.25% B/G 0.42 (very rapid onset) Metabolism 0.02% Cardiovascular: similar to isoflurane but no coronary steal Respiratory: no pungent odor but irritant Muscl

12、e relaxation: stronger than isoflurane Induction and maintenance Nausea and vomiting Special vaporizer, expensive,Halothane, 氟烷,Properties: clear colorless volatile anesthesia; pleasant smell MAC 0.75 B/G 2.4 Metabolism 20 % Cardiovascular: Myocardial contractility reduced Systemic vascular resistan

13、ceBP Increase sensitization of myocardium to catecholamine Respiratory: non-irritant; pleasant smell; dilate bronchial; inhibition Muscle relaxation Induction and maintenance Halothane associated hepatitis: seldom in use now, unavailable in China,Questions,What are the MACs of different anesthetics?

14、 What determines the anesthetic potency? Which anesthetics is the best choice in induction of anesthesia in children? Which halogenated anesthetic takes effect fastest?,Intravenous anesthetics,Ideal Intravenous anesthetic,Water-soluble, no pain on injection Rapid onset, rapid recovery, little accumu

15、lation, little depression on respiratory-cardiovascular system. No nausea and vomiting, no interact with muscle relaxant, no release of histamine.,Intravenous anesthetics,Thiopentone,Sedation maintenance: TCI/TIVA Supplement to local anesthesia Sedation in ICU Side effect :cardiovascular& respirator

16、y suppression, excitatory phenomenon, pain on injection,Sodium hydroxybutyrate, 羟丁酸钠,Site: Cortex(皮层)、hippocampus(海马)、limbic system(边缘系统) Normal physical sleeping Circulation：BP slightly increase、HR reduce Respiration: TV increase、frequency slow Indication：Induction and maintenance basal anesthesia+

17、ketamine (poor analgesia effect) Dosage: 50-100mg/kg Onset ：5-10min, duration：45-60min,Questions,Which drug has dissociated anesthesia? Which drug can depress steroid synthesis? Which intravenous anesthetic can increase intracranial pressure? What is the induction dosage of propofol?,Muscle relaxant

18、s(肌肉松弛药),Skeletal muscle relaxants No anesthetic effect Cannot make patient lost consciousness Cannot produce amnesia Suitable condition for surgery Avoid hazardous of deep anesthesia No analgesia,Mechanism: interfere with the normal action of acetylcholine (ACH) at the motor end plate, block the re

19、ceptors on the postsynaptic muscle membrane,Presynaptic membrane,Postsynaptic membrane,synaptic gap ACH,Depolarization Muscle contraction,ACH,ACH,ACH,ACH,ACH,胆碱酯酶水解ACH,repolarization,Impulse,Classification,Depolarizing muscle relaxants suxamethonium (Succinylcholine, scoline) Nondepolarizing muscle

20、relaxants Pancuronium Vecuronium Atracurium Tubocurarine,Depolarizing muscle relaxantSuxamethonium (琥珀胆碱),similar to acetylcholine (ACH)，binding to receptor, depolarizing contraction (fasciculation) cant be hydrolyzed by cholinesterase，NO responses to further action，flaccid-muscle relaxant Indicatio

21、n tracheal intubate 1-2mg/kg peak at 1min, 4-5min, recover at 10min Side effects: muscle pains intraocular, intragastric, intracranial pressure hyperkalaemia Malignant hyperthermia,Nondepolarizing muscle relaxant,tubocurarine(筒箭毒碱)： binding to receptor , but non-depolarizing compete for the receptor

22、s antagonist by inhibitor of cholinesterase （neostigmine新斯的明） 。,Muscle relaxants,agents intubating dose onset action duration (mg/kg) (min) (min) Scoline 1-2 0.5 3-8 琥珀胆碱 Tubocurarine 0.6 4-6 30-40 筒箭毒碱 Pancuronium 0.1 3-6 30-6 泮库溴胺 Atracurium 0.6 3-5 15-35 阿曲库胺 Vecuronium 0.1 2-3 25-30 维库溴胺,Muscle

23、relaxants,肌松药 advantage side effect metabolisam histamine release Scoline rapid fasciculation,K+ cholinesterase （-） pressure Tubocurarine asthma kidney 、bile （+） Pancuronium HR liver kidney bile （） Atracurium Hoffmann Hoffmann血浆胆碱酯酶 （+） Vecuronium liver kidney bile （-） Cis-atracurium Hoffmann Hoffmann血浆胆碱酯酶,Atracurium and cisatracurium,Dose intubation 0.5-0.6mg/kg maintenance 0.15-0.2mg/kg Time intubation 90-1