Basic Concept Of General Anesthesia 2

Basic Concept of General Anesthesia

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Review Anesthesia It indicates that medicine or other methods is used to make patient lose sense completely or partly, and finally to make them feel no pain during operation.

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Review General anesthesia I t is an anesthetic method that narcotic acts on central nervous system and restrains its function.

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Review Local anesthesia I t is an anesthetic method that narcotic only acts on peripheral nervous system and retrains some or one nerve’s functional password to make one part of the body losing sense of pain.

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Review Airway examination Mallampati classification 1. Class 1: able to visualize the soft palate, fauces, uvula, anterior and posterior tonsillar pillars. 2. Class 2: able to visualize the soft palate, fauces, and uvula. The anterior and posterior tonsillar pillars are hidden by the tongue. 3. Class 3: only the soft palate and base of uvula are visible. 4. Class 4: only the soft palate can be seen (no uvula seen). 5

Review Assessment of physical status A normal healthy patient A patient with mild systemic disease A patient with severe systemic disease A patient with severe systemic disease that is a constant threat to life Ⅴ A moribund patient who is not expected to survive without the operation Ⅵ A declared brain-dead patient whose organs are being removed for donor purposes For emergent operations, add the letter ‘E’ after the classification Ⅰ Ⅱ Ⅲ Ⅳ

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Basic Concept of General Anesthesia

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Definition of General Anesthesia General anesthesia is an altered physiologic state characterized by reversible loss of consciousness, analgesia of the entire body, amnesia and some degree of muscle relaxation.

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Anesthesia – denotes a lose of sensibility Surgical Anesthesia – is a controlled degree of CNS depression with the following component • Analgesia – lack of pain • Amnesia – lack of memory • Inhibition from reflexes such as bradycardia and laryngospasm • Skeletal muscle relaxation • (altered state consciousness) state of unconsciousness.

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Depth of Surgical Anesthesia – can be divided into a series of four sequential stages:

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Depth of Surgical Anesthesia Stage I: Analgesia Loss of pain sensation results from interference. With sensory transmission in the spinothalamic tract. The patient is conscious and conversational. A reduced awareness of pain occurs as stage II is approached.

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Depth of Surgical Anesthesia Stage II: Excitement The patient experience delirium and violent combative behaviour. There is a rise and irregularity in blood pressure. The respiratory rate may be increase

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Depth of Surgical Anesthesia Stage III: Surgical anesthesia Regular respiration and relaxation of the skeletal muscle occur in this stage. Eye reflexes decreases progressively, until the eye movements cease and the pupil is fixed. Surgery may proceed during this stage.

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Depth of Surgical Anesthesia Stage IV: Medullary paralysis Severe depression of the resp. center & vasomotor center. Death can rapidly ensure.

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KINETICS OF ANESTHESIA 2. Induction 2. Maintenance 3. Recovery

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Two Kinds of General Anesthetics D.Inhalational E.Intravenous

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Induction and Recovery from Anesthesia Induction – is the period of time from onset of administration of the anesthetic to the development of effective surgical anesthesia in the patient. It depends on how fast the anesthetic reaches the brain.

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Recovery – is the time form discontinuation of adm. of anesthetic until consciousness is regained .It depends on how fast the anesthetic is removed from the brain.

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Maintenance of Anesthesia – maintenance is the time during which the patient is surgically anesthetized, anesthesia is usually maintained by the administration of gases or volatile anesthetics since these agents offer good minute to minute control over the depth of anesthesia.

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Inhalational Gen Anesthetics 1. N2O (Nitrous oxide) – laughing gas 2. Halothane 3. Enflurane 4. Isoflurane 5. Methyoxyflurane 6. Diethyl ether Newer Inhalational General Anesthetics 1. Desflurane 2. Seroflurane

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Mechanism of Action of Inhalational General Anesthetics These agents decrease the firing rate of nerve cells by decreasing the rise of the action potential. They inhibit the rapid increase in membrane premeability to sodium ion.

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Intravenous General Anesthetics : are often use for the rapid induction of anesthesia

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A.Barbiturates – Ultra-short Acting: 1. Thiopental 2. Thiamylal 3. Methohexital Acts less than one (1) minute, B.P due to myocardial depression. Depresses the resp center in a dose dependent manner may cause laryngospasm – not an analgesic.

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B. Ketamine (Ketalar) – Dissociative anesthesia – a short – acting non barbiturate – induces a dissociative state in which the patient appears to be awake consist of Amnesia. Analgesia and often catatonia (rigidity). There is disorientation, hallucinations and changes in perception.

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Combination Anesthetics – lighter stage of anesthesia is produce using 2 or more drugs.

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A.Balanced Anesthesia : Full loss of consciousness and pain – induced reflexes with muscle relaxation using: a. Ultra – short acting barbiturate b. Opioid analgesic (Meperidine, Morphine, Fentanyl or Sufentamil) c. Muscle relaxation d. Nitrous Oxide + Oxygen

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B. Neuroleptanesthesia – is induced by the combined actions of a narcotic analgesic (Fentanyl) and a neuroleptic agent (Droperidol), together with N2O & Oxygen. Consciousness is not lost, there is tranquility and reduce motor activity. Useful in pnt wherein cooperation is needed (diagnostic procedures) but may cause resp. depression.

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Pre-Anesthetic Medications : - Administered prior to anesthesia to reduce pain, relieve anxiety decrease excess salivation and to combat nausea.

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A. Anxiolytic drugs – provides sedation, relieve anxietyBenzodiazepam - diazepam, Lorazepam and Midazolam B. Narcotic Analgesic - reduces pain – Morphine Fentanyl C.Neuroleptics - promethazine, trimeprazine or chlorpromazine; use to sedate and for its anti-emetic properties. D.Anticholinergic - Atropine and Scopolamine decreases bronchial and salivary secretions, and promote bronchodilatation.

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Properties Anesthetics (Learn by yourself)

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Rapid-sequence Intravenous Induction s e d a t i v e s , h y p n o t i c s I n t r a v e n o u s a n e s t h e t i c s

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Rapid-sequence Intravenous Induction -- Disadvantage

and Complications

Regurgitation and Vomitting Cardiovascular depression Respiratory depression Histamine release Pain on injection Hiccup and muscle movements

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Inhalational Induction-- Indications young children myasthenia gravies upper airway obstruction, e.g. Epiglottises lower airway obstruction with foreign body bronchopleural fistula or empyema no accessible veins

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Inhalational Induction -- Methods Initially, nitrous oxide 70% in oxygen is used and anesthesia is deepened by gradual introduction of increments of a volatile agent, e.g. Halothane 1-3%, Enflurane 1.5-2.5%, Isoflurane 1-2% .

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Inhalational Induction-- characteristics Spontaneous ventilation is to be maintained. The face mask is applied firmly as consciousness is lost and the airway is supported manually.  Insertion of an oropharyngeal airway , a laryngeal mask airway or a tracheal tube may be considered when anesthesia has been established.

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Inhalational Induction --Disadvantage and Complications Slow induction of anesthesia Airway obstruction , bronchospasm Laryngeal spasm , hiccups Environmental pollution

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Induction with spontaneous ventilation -- Indications

Airway obstruction Anticipant difficult intubation

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Induction With Spontaneous Ventilation -- Characteristics Maintaining spontaneous ventilation throughout the procedure Sufficient surface anesthesia

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Other induction methods Intramuscular injection of ketamine Take midazolam orally Administration of fentanyl via mucosa

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Maintenance of general anesthesia Sedation Analgesia muscle relaxation

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Maintenance of general anesthesia Inhalational agents Intravenous anesthetics Opioids Muscle relaxants

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Recovery Antagonizing residual neuromuscular blockade Extubation Airway supporting Recovery position is benefit to avoid airway obstruction

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Prevention and treatment of serious complications during general anesthesia

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Introduction Complications of anesthesia involve three aspects ： A. Patient's condition B. Diathesis of anesthetist C. Influence and fault of anesthetics 、 anesthetic apparatus and correlated instrument 45

Serious Complications during General Anesthesia Respiratory tract obstruction Respiratory depression Hypotension and Hypertension Myocardial ischemia Hyperthermia and Hypothermia Awareness and Delay of Awake Cough 、 Singultus 、 Postoperative vomiting 、 Postoperative pulmonary infection Malignant hyperthermia

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Respiratory Obstruction  Glossocoma ： A ． Etiology ： B ． Liability factor ： ◆Justo major of corpus linguae ◆ Short and stout ◆ Short neck ◆ Lymphadenosis of throat posterior wall ◆ Hypertrophy of tonsils

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Respiratory Obstruction C ． Clinical features ： D ． Management ： ◆ Side lying 、 ◆ Head hypsokinesis 、 ◆ Lift submaxilla 、 ◆ Oropharyngeal parichnos ◆ Nasopharyngeal parichnos

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Respiratory Obstruction Airway obstruction by secretion 、 purulent sputum 、 blood and foreign object A ． Etiology ： ◆ Inhalation of stimulant anesthetic ， ◆ Bronchiectasis 、 pulmonary abscess 、 pulmonary tuberculous cavity

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Respiratory Obstruction ◆ Operation

of cavum nasopharyngeum 、 oral cavity 、 Harelip ◆ Desquamation of tooth or artifcial teeth B ． Management ： ◆ Sufficient belladonna premedication ◆ Intubation ◆ Suck respiratory tract ◆ Pull out dentium vacillatia or artifcal teeth 51

Respiratory Obstruction Regurgitation and Aspiration A ． Etiology ： Anticholinergic agent Morphine General anaesthetics Muscle relaxant B ． Clinical features ： ◆ Bronchospasm ◆ Tachypnea and dyspnea ◆ Moist rales ◆ Sever hypoxia 52

Respiratory Obstruction C ． Management ： ◆ Fasting ： Adult ： 8h before anesthesia Children ： milk and solid diet <6m 4h 6~36 m 6h > 36 m 8h

liquid 2h 3h 3h

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Respiratory Obstruction ◆ Preoperative

administration of an H2receptor antagonist （ cimetidine or ranitidine ） to decrease further secretion of additional acid. ◆ Application of gastric decompression by a wide-bore nasogastric tube; Preparing for suction ◆ Full stomach/high level ileus ： awake intubation ◆ Rapid - sequence induction and intubation without positive - pressure ventilation before intubation. 54

Respiratory Obstruction ◆ Application

of cricoid compression to control regurgitation of gastric contents ◆ Extubation when the patient is fully awake ◆ Aspiration ： Head down position ， suck vomitus Bronchial antispasmodic and antibiotics Respiration support Lavage of trachea using 0.9%NaCl 55

Respiratory Obstruction Malposition of catheter 、 Obstruction of lumina 、 Anaeshetic machine failure A. Etiology ： Catheter twist Block by sputum Corrugated tube twist Malfunction of respiration valve B. Management ： Examine position of catheter Respiratory sound Breathing circuit Respiration valve 56

Respiratory Obstruction Trachea Compression A. Etiology ： tumor of neck or mediastinum hematoma 、 edema calidum B. Management ： Inflame affection of pharyngo-oral cavity 、 Larynx tumor 、 Allergia laryngeal edema A. Etiology ： peritonsillar abscess 、 Larynx tumor 、 pharynx posterior wall abscess B. Management ：

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Respiratory Obstruction Laryngospasm and Bronchospasm Laryngospasm ： A. Etiology ： pharyngeal vagus nerve excitability↑ B. Evoked reasons ： ◆hypoxemia

、 hypercapnia 、 secretion 、 intubation oropharynx parichnos 、 laryngoscope ◆light anesthesia 58 C. Clinical features

Respiratory Obstruction E. Prevention ： avoid light anesthesia 、 hypoxia 、 carbon dioxide accumulation Bronchospasm ： A. Etiology ： ◆ Tracheal intubation 、 aspiration 、 suck sputum ◆ Operation stimulate ◆ Thiopental Sodium 、 Morphine

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Respiratory depression Central Respiratory depression A ． Etiology ： anesthetics 、 hyperventilation narcotic analgesics 、 inflate lung unduly B ． Management ： ◆ Anesthetics → reduce depth of 　　 　　 　　　 　　 　　　 　　 　　 　　 　 anesthesia ◆ Narcotic analgesics → Naloxone ◆ Hyperventilation 、 inflate lung

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Respiratory depression Peripheral Respiratory depression A. Etiology ： muscle relaxant hypopotassemia general anaesthesia + 　　　 　　　 　 epidural block B. Management ： ◆ Muscle relaxant → Neostigmine 　 　　　 　　　 　　 　　　 　 Bromide ◆ Hypopotassemia → supply potassium 　　　 in time ◆ Spinal nerve block → wait the block

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Respiratory depression Respiration Management A. Effective ventilation B. Select of ventilation mode ： ◆ Assistor respiration ◆ Controlled respiration

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Hypotention and Hypertension Hypotension(P380) A ． Hypotension ： > 20% or ↓80mmHg B ． Etiology ： ◆ anesthesia aspects ◆ operation aspects ◆ patient aspects

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Hypotention and Hypertension C ． Prevention ： ◆ Insufficient body fluid → sufficiently supply ◆ Severe anemia ◆ Severe mitral valve stenosis ◆ Myocardial ischemia → maintain blood pressure

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Hypotention and Hypertension ◆ Myocardial

infarction ◆ Congestive heart failure ◆ Ⅲ°BBB 、 sick sinus syndrome → pacemaker ◆ Hypopotassemia ◆ Atrial fibrilation → 80~120 bpm ◆ Using long-term corticosteroid

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Hypotention and Hypertension D ． Management ： ◆ Reduce depth of anesthesia ◆ Transfusion ， Ephedrine ◆ Severe coronary heart disease → support cardiac pump function ◆ Drag internal organs →stop operative procedure ◆ Adrenal insufficiency →large dose of dexamethasone ◆ Cardiac arrest→cardiac resuscitation 66

Hypotention and Hypertension Hypertension A ． Hypertension ： B ． Etiology ： ◆ Anesthesia aspects ◆ Operation aspects ◆ Patient aspects

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Hypotention and Hypertension C. Prevention ： ◆ Sufficient premedication ◆ hyperthyroidism ◆ Intubation → enhance anesthesia surface anaesthesia α or β-receptor blocker ◆ Avoid hypoxia and carbon dioxide accumulation

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Hypotention and Hypertension ◆ Craniocerebral

operations→droperidol ◆ Operation stress → compound with epidural block D ． Management ： ◆ Increase depth of anesthesia ◆ α or β-Receptor blocker 、 vascular smooth muscle relaxant ◆ ↑Ventilatory capacity 、↑ FiO2

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Myocardiac Ischemia Correlative physiological knowledge A. Oxygen consumption of myocardium ： ◆ HR ◆ myocardial contractility ◆ intraventricular pressure B. Coronary Perfusion Pressure = AOP – IMP AOP- aortic pressure IMP- intramyocardial pressure

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Myocardiac Ischemia Diagnostic method ： ECG A. Cardiac conduction abnormality B. Arrhythmia C. Q wave ， R wave progressive step down D. S-T↓> l mm or ↑> 2 mm E. T wave is low 、 bidirection or inversion

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Myocardiac Ischemia Etiology A. Tension 、 fear 、 pain B. Hypotension or hypertension C. Myocardial contractility suppression and vessel distension by anesthetic D. Hypoxia E. Tachyrhythmia or Arrhythmia

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Myocardiac Ischemia Management A. Maintain the balance of Oxygen supply　　 demand B. Delay selective operation C. Monitor ： ECG 、 MAP 、 CVP 、 CO 、 SVR 、 Urine volume D. β-receptor blocker or calcium channel 　　 blocker E. Analgesia using morphine F. General anaesthesia + epidural block 73

Hyperthermia and hypothermia Heat Production and Elimination A ． Heat Production ： B ． Heat Elimination ： ◆ Radiation ： > 60% ◆ Conduction ： 3% ◆ Convection ： 12% ◆ Evaporation ： 25%

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Hyperthermia and hypothermia Normal Thermoregulation ： A. Thermoregulatory control system ： ◆ Cold-response thresholds ： 36.5℃,vasoconstriction ◆ Warm-response thresholds ： 37℃,sweat B. Thermoregulation during General Anesthesia ： ◆ warm-response thresholds ：↑ 1℃ to 38℃ ◆ cold-response thresholds ：↓ 2℃ to 34.5℃

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Hyperthermia and hypothermia Hypothermia ： core temperature < 36℃ A ． Evoked reasons ： ◆Cold operating rooms ◆Indoor vent(high theatre flow rates) ◆ Administration of cold intravenous fluids ◆ Evaporation from surgical incisions ◆ General anesthetic

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Hyperthermia and hypothermia B ． Influence of hypothermia ： ◆ Drug metabolism is markedly ↓ ↓ duration of action of anesthetics ↑ ◆ Coagulation is impaired ◆ Blood vicidity↑ ◆ Oxygen dissociation curve shift to left ◆ Shivering → oxygen capacity↑↑ C ． Prevention ： measures depend on the cause 77

Hyperthermia and hypothermia Hyperthermia ： A ． Evoked reasons ： ◆ Room temperature > 28℃ ◆Sepsis ◆Excessive catecholamine secretion ◆ large dosage of atropine ◆ Response to transfusions ◆ Malignant hyperthermia

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Hyperthermia and hypothermia B ． Influence of Hyperthermia ◆ Basal metabolic rate↑ ◆ Metabolic acidosis 、 hyperkalemia hyperglycosemia ◆ > 40℃→convulsion C ． Prevention

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Awareness and Delay of Awake Awareness A. Etiology Low concentrations of volatile agents B. Anesthetic technique ◆ N2O-O2- Muscle relaxant ◆ Fentanyl - Diazepam ◆ Thiopental or Thiopental - Ketamine

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Awareness ◆ N2O-

Fentanyl ◆ Etomidate - Fentanyl ◆ Procaine combined anesthesia C. Management ： ◆ Avoid light anaesthesia ◆ Monitor brain stem auditory evoked potential （ BSAEP ）

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Delay of Awake Delay of Awake ： > 30min A. Etiology ： ◆ Influence of Anaesthetic ： Premedication Inhalation Anaesthetic Narcotic Analgesic Muscle Relaxant

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Delay of Awake ◆

Respiratory depression ： Narcotic Analgesic and Muscle Relaxant Hypocapnia Hypercarbia Kaliopenia Overdose of Transfusion Complications of operation Severe metabolic acidosis

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Delay of Awake ◆ Severe

Complications ： massive bleeding serious cardiac arrhythmias acute myocardial infarction rupture of intracranial aneurysm cerebral hemorrhage cerebral embolism ◆ Long time of hypotension and hypothermia ◆ Cerebral vessels affection before operation

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Delay of Awake B. Management ： ◆ Aspect of Anaesthetic technique ◆ corresponding management ◆ dehydration ： encephaledema intracranial hypertension ◆ hypothermia - warm ◆ long-term hypotension ◆ primary cerebral disease

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Postoperative vomiting A. Etiology ： ◆ role of anaesthetics inhalation anesthetic ： ether > methoxyflurane >enflurane > isoflurane > N2O > sevoflurane

intravenous anesthetic ◆ category of operation ◆ conditions of patients

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Postoperative vomiting B. Harmful effects of vomiting ： ◆ pain 、 wound dehiscence ： ◆ vomit aspiration or asphyxiation ◆ Water-Electrolyte unbalance and Acid-Base unbalance C. Management

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Postoperative pulmonary infection Etiology ： A. Aerosolizer pollution B. Intubation 、 incision of trachea 、 endotracheal anesthesia C. Aspiration D. Surgery E. Abuse medication

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Postoperative pulmonary infection Clinical manifestation A. Sings and symptoms B. Examination of bacteriology ◆ Smear of sputum and bacterial culture ◆ Hemoculture C. Chest X-ray

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Postoperative pulmonary infection Diagnostic criteria A. Fever 、 rales ， X-ray B. Pathogenic bacteria C. Hemoculture ： positive D. Secretion of lower respiratory tract E. Secretion of respiratory tract 、 serum 、 and other body fluid

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Postoperative pulmonary infection Treatment ： A. antibiotics B. immunotherapy

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Malignant Hyperthermia Malignant hyperthermia （ MH ） : an eerie and erratic metabolic mayhem, is a clinical syndrome that in its classic form occurs during anesthesia with a potent volatile agent such as halothane and the depolarizing muscle relaxant succinylcholine, producing rapidly increasing temperature （ by as much as 1 ℃/5 min ） and extreme acidosis. incidence was 1:1.6~10×104 ， mortality rate was 73% 92

Malignant Hyperthermia Evoked reasons ： halothane 、 ethoxyflurane enflurane 、 scoline 、 chloropromazine lidocaine 、 bupivacaine Clinical Syndromes ： A. Temperature increases : exceed 43℃ B. Whole-body rigidity occurs

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Malignant Hyperthermia C. Myocardial function is severely altered D. Increased serum levels of CK myoglobinuria E. Contractile response F. PaCO2 may exceed 100 mm Hg, and pHa may be less than 7.00

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Malignant Hyperthermia Lab ❏ hyper CO2, hypoxia (early) ❏ metabolic acidosis ❏ respiratory acidosis ❏ hyperkalemia ❏ myoglobinemia/myoglobinuria ❏ increased creatine kinase (CK)

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Malignant Hyperthermia Complications ❏ death/coma ❏ disseminated intravascular coagulation (DIC) ❏ muscle necrosis/weakness ❏ myoglobinuric renal failure ❏ electrolyte abnormalities (i.e. iatrogenic hypokalemia)

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Malignant Hyperthermia Prevention ❏ suspect possible MH in patients presenting with a family history of problems/death with anesthetic ❏ dantrolene prophylaxis no longer routine ❏ avoid all triggers ❏ central body temp and ET CO2 monitoring ❏ use regional anesthesia if possible ❏ use equipment “clean” of trigger agents

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Malignant Hyperthermia Treatment: A. Discontinue all anesthetic agents and hyperventilate with 100% oxygen. B. Control fever by iced fluids, surface cooling, cooling of body cavities with sterile iced fluids, and a heat exchanger with a pump oxygenator C. Administer bicarbonate （ 2 to 4 mEq/kg ）

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Malignant Hyperthermia D. Repeat administration of dantrolene ： 2mg/kg ， 5~l0 min repeat E. Treatment of hyperkalemia :10u insulin F. Monitor urinary output : mannitol 0.5g/kg frusemide lmg/kg G. Corticosteroids H. ICU: monitor and treat for 48h

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