The document discusses the key aspects of general anesthesia, including: 1) An overview of general anesthesia, its goals of safety, amnesia, hypnosis, and analgesia. 2) Preoperative preparation such as evaluations, medications, and ensuring adequate hydration and intravenous access. 3) Induction of anesthesia through preoxygenation, intravenous or inhalational methods, and airway management including intubation. 4) Maintenance of anesthesia by maintaining homeostasis, monitoring depth to prevent awareness, and using various anesthetic methods and ventilation techniques. 5) Emergence from anesthesia and considerations for extubation such as ensuring the patient is awake, responsive, and has adequate pain

1. what do you see in the picture? An anesthesia machine A beautiful and smart anesthetist

2. Administration of General Anesthesia Xiao Ying （ 肖颖 ） The First Affiliated Hospital of Sun Yat-sen University Mar 2010

3. Overview What is general anesthesia? Preoperative preparation Induction: going off to sleep Maintenance: keeping pt asleep Emergence: waking up Transport

4. What is general anesthesia Primary goals Safety is top priority Amnesia: no memory of the event Hypnosis: unconcious Analgesia: free of pain Block certain autonomic reflexes Optimal surgical conditions: immobolity

5. What is general anesthesia Secondary goals Medical condition Surgical procedures Surgical settings

6. Examples for secondary goals Patients with CAD: Oxygen supply-demand balance Neurosugery: ICP control, brain relaxation and CPP maintenance Obstetrics: anesthetics and fetal depression, difficult airway Day surgery vs Inpatient: which kind of analgesic you should choose to minimize postoperative pain and decrease PONV?

7. Preoperative preparation Preoperative evaluations Airway examination Interim changes in pt’s condition Medications Laboratory data Consultant notes Last oral intake

8. Preoperative preparation Intravascular volume Dehydration: adequately hydrate the pt before induction Intravenous access Preoperative medications Anxiety Benzodiazepine: Midazolam Opioid: Morphine or Fentanyl Neutralize gastric acid and decrease gastric volume

9. Which kind of pt is at increased risk of aspiration of gastric content? Recent meal Trauma Bowel obstruction Pregnancy History of gastric surgery Increased intra-abdominal pressure History of active reflux

10. Monitoring Standard monitoring for GA ECG NBP Pulse oximetry Capnography Oxygen analyzer

12. Induction Let the pt go off to sleep Preoxygenation 8L~10L/min IV or Inhalational induction Airway management

13. Induction techniques Intravenous: the most common method Inhalation: for special pt (pt with difficult airway, pediatric pt) Intramuscular :rarely used,only used in uncooperative pts and young children

14. Airway management ASA Closed Claims Study( 美国麻醉学会已结案的诉讼） 35 % of claims are RESPIRATORY events 90 % resulted in brain damage or death 90% resulted from Difficulty in INTUBATION or EXTUBATION

15. Airway management Airway patency is critically important

16. Oral airway

18. Nasophryngeal airway

19. Laryngeal mask airway

20. Intubation

21. Maintenance Increasing depth of anesthesia stage Ⅰ Amnesia Loss of consciousness Stage Ⅱ Delirium Injurious responses to noxious stimuli Stage Ⅲ Surgical anesthesia Painful stimulation does not elicit somatic reflexes or deleterious autonomic responses Stage Ⅳ Overdosage Circulatory failure

22. Maintenance Maintain homeotasis Vital signs Acid-base balance Temperature Coagulation Volume status

23. Maintenance Lack of awareness and no memory of the event Incidence of awareness High risk surgical population High risk pt High risk anesthesia method

24. How to avoid awareness To recognize the high risk pt Monitor the depth of anesthesia Somatic and autonomic response are nonspecific and unreliable Bis monitor for high risk pt

25. Depth of anesthesia Intensity of surgical stimulation Response suggesting inadequate anesthetic depth: Somatic: movement, coughing, changes of respiratory pattern Autonomic: tachycardia, hypertension, mydriasis, sweating, tearing Unreliable and nonspecific Sympathetic activation may be caused by other reasons

26. Maintenance methods Volatile (Isoflurane, Desflurane or sevoflurane combined with nitrous oxide) Nitrous oxide-opioid relaxant technique IV anesthesia Combinations General anesthesia combined with regional anesthesia

27. Ventilation

28. Ventilation 1. Spontaneous or assisted ventilation 2. Controlled ventilation Tidal volume: 10-12ml/kg Respiratory rate: 8-10 breaths/min 3. Assessment of ventilation Capnography Pulse oximeter Airway pressure Reservoir breathing bag Ventilator bellow

29. Ventilation Peak inspiratory pressure High airway pressure >25~30cmH 2 O Breathing circuit problem ETT obstruction or movement Altered lung compliance Change in muscle relaxation Surgical compression

30. IV Fluids Intraoperative IV fluids requirements 1. Maintenance fluid requirements 2. Third space losses and insensible losses 3. Blood losses

31. IV Fluids 1. Crystalloid sollutions: maintenance fluid requirement, evaporative losses, and third space losses 2. Colloid sollutions: replace blood loss or restore intravascular volume 3. Blood transfusion

32. Intravascular volume assessment Trends of heart rate, blood pressure, and urine output Central venous pressure, pulmonary artery occlusion pressure, right and left end-diastolic volumes(using TEE) and cardiac output Hemotocrit, platelet count, fibrinogen concentration, prothrombin time, thromboplastin time

33. Emergence from GA Goals: awake Responsive Full muscle strength Adequate pain control

34. Extubation Awake extubation Indications Risk of aspiration Difficult airways Tracheal or maxillofacial surgery

35. Extubation Awake extubation Criteria Awake Hemodynamically stable Full muscle strength Able to follow simple verbal commands Breathing spontaneously with adequate ventilation

36. Extubation Awake extubation Special technique: removal of ETT over a flexible stylette Indication: patency of the airway is uncertain or reintubation may be difficult

37. Extubation Deep extubation Indications Severely asthmatic patients Middle-ear surgery Open-eye surgery Inguinal herniorrhaphy

38. Extubation Deep extubation Criteria Sufficient anesthetic depth to avoid response to airway stimulation Spontaneous breathing with adequate ventilation

39. Agitation Causes Pain Hypoxia Hypercarbia Airway obstruction Full bladder

40. Transport

41. Questions