ANESTHESIA

1. ANESTHESIA Mong Lam, CRNA

2. Objectives • History • Basic concepts • Types of anesthesia • Anesthesia machine

3. CRNA: we never miss a beat!

4. History • Horace Wells and nitrous oxide • William Thomas Green Morton and ether • Ether Dome

5. History • Certified Registered Nurse Anesthetist (CRNA) • Anesthesiologist (MD) • Anesthesia model or practice setting

6. Anesthesia • Types of anesthesia • Concepts • Administration & Selection

7. Anesthesia • Definition: “Lack of Sensation” • Describes a process that is used to alleviate pain and suffering during a surgical procedure

8. Optimal Anesthesia • Achieved If All Of The Following Are Met: • Hypnosis • Anesthesia • Amnesia • Muscle Relaxation • Optimal Positioning of Patient • Homeostasis of Vital Functions

9. Hypnosis • Altered state of consciousness related to how the patient perceives his or her environment (surgical) and procedure (surgical) • Induce sleep • Can be light to fully unconscious

10. Anesthesia • Lack of sensation • Allows for “pain-free” surgery • Ranges from topical, local, regional and general (systemic) agents

11. Amnesia • Lack of recall of surgical events • Allows for more cooperative relaxed patient

12. Muscle Relaxation • Combined with inhalation (gases) agents to produce muscle relaxation to total paralysis • Allows for endotracheal intubation • Facilitates exposure of tissues and organs as muscles are in a relaxed state

13. Muscle Relaxation

14. Patient Positioning • Allows for surgical site exposure/access • Allows for monitoring of the surgical patient • Allows/provides physiological homeostasis

15. Homeostasis of Vital Functions • Maintenance of the patient’s physiological status until surgical intervention is complete • Most dangerous part of surgery is anesthesia • Are inducing a state close to death without crossing that line

16. Methods of Administration • Determining the Right Anesthetic • Patient’s age, weight, and build • Emotional, psychological and physical needs • Type of operation and duration of operation • Lab and X-ray findings • Pre-existing illnesses or diseases • Medications on • Allergies • History of drug or alcohol abuse • Time since last ingested food, particularly with emergencies

17. American Society of Anesthesiologists (ASA) • Based on the evaluation/assessment done preoperatively, the patient is assigned a Class # 1 through #6. This determines what kind of risk is involved for the patient for the surgical procedure about to be performed.

18. Class 1- Patient has no previous/current physical or mental medical history

19. Class 2- Mild to moderate disease present (controlled HTN, asthma, controlled diabetes, mildly obese, anemic, tobacco use) with no functional limitations

20. Class 3- severe disease present (controlled angina, has had a myocardial infarction, HTN that is not controlled, respiratory disease that is causing difficulties presently, greatly obese) with functional limitations

21. Class 4- severe disease (s) present that are life-threatening (unstable angina, CHF, respiratory disease that is debilitating, liver failure, kidney failure, myocardial infarction)

22. Class 5- Moribound patient who is not expected to survive with or without surgery

23. Class 6- Is brain dead/life support is being provided .This is an organ harvest or procurement.

24. (E) Emergency Modifier- an E is added to the Class # in cases of emergency surgery

25. Goal of Anesthesia • Patient safety • Optimal results

26. Anesthetic Agents • 3 types: 1. General • Focus on altering state of consciousness, awareness and pain perception 2. Nerve Conduction Blockade • Focus on preventing sensory nerve impulse transmission 3. MAC (monitored anesthesia care)

27. General Anesthesia • Combined to deliver “Balanced Anesthesia” • Inhalation agents • Intravenous agents • Less Common: • Intramuscular agents • Instillation

28. Components of General Anesthesia • Amnesia • Analgesia • Anesthesia • Muscle Relaxation • Together provide “Balanced Anesthesia”

29. Stages of General Anesthesia I. Amnesia stage is lightest stage that begins with administration of agent ends with loss of consciousness • Good stage for MAC II. Excitement or Delirium stage from loss of consciousness to loss of eyelid reflex and regular breathing • Patient movements are uninhibited • Might see vomiting, laryngospasm, hypertension, tachycardia • Rarely seen except in children due to drugs that are available now to carry patients straight to stage III III. Surgical anesthesia stage from regular breathing and loss of eyelid reflex to cessation of breathing • Patient unresponsive and hearing is last to go IV. Overdose stage dilated nonreactive pupils, cessation of breathing, hypotension can quickly lead to circulatory arrest if uncorrected • Autonomic response is totally blocked to all stimuli

30. Phases of Anesthesia • Preinduction begins with premed administered and ends when anesthesia induction begins in OR • Induction from consciousness to unconsciousness • Maintenance surgery takes place during this requires maintenance of physiological function by anesthetist • Emergence as surgery is completed (start to wake up), restoration of gag reflex, extubation • Recovery time during when patient returns to full consciousness begins in OR and carries into stay in PACU and beginning healing stages

31. Advantages verses Disadvantages • GA vs MAC • GA vs block • Types of surgery and length • Age and mental status

32. General Anesthesia • Inhalation Agents: • Nitrous Oxide (N²O) • Ethrane (Enflurane) • Forane (Isoflurane) • Halothane (Fluothane) • Sevoflurane (Sevoflurane) • Suprane (Desflurane)

33. General Anesthesia • Intravenous Agents: 1. Barbiturates • Short acting • Anesthesia • Not analgesic • Pentothal (thiopental) • Brevital (Methohexital)

34. General Anesthesia • Benzodiazepines • Sedative and amnesiac effects • Versed (Midazolam) • Valium (Diazepam) • Ativan (Lorazepam)

35. General Anesthesia • Individual Agent • Propofol (Diprivan) • Sedative/Hypnotic • Anesthetic • Amnesiac • No Analgesia • No Muscle Relaxation

36. General Anesthesia • Narcotics • Maintenance of general anesthesia • Anesthetic • Sublimaze (Fentanyl) • Alfenta (Alfentanil) • Sufenta (Sufentanil) • Morphine (Morphine Sulfate)

37. General Anesthesia • Muscle Relaxants (neuromuscular blocking agents) • To receive endotracheal intubation, patient must be paralyzed or have relaxed muscles • a. Depolarizing Agents: Initiate contractions called fasciculation example: Succinylcholine (Anectine) • b. Nondepolarizing Agents: Prevent contractions examples: Curare, Pavulon, Norcuron

38. Nerve Conduction Blockade • Includes: • Topical anesthesia • Local anesthesia • Regional anesthesia • Spinal (intrathecal) block • Epidural block • Caudal block • Nerve plexus block

39. Topical Anesthesia • Used on mucous membranes: upper aerodigestive tract, urethra, rectum, and skin • Cryoanesthesia reduces nerve conduction by localized freezing with a probe connected to a cryoprecipitate unit that uses nitrogen • Cryoanesthesia can also be performed with ice • Lidocaine jelly • Cocaine (topical only!) Most common use: sinus surgery

40. Local Anesthetics • Immediate surgical site anesthesia • Affects small circumscribed area • Can be injected or applied topically • Lidocaine (Xylocaine) • Bupivicaine (Marcaine, Sensorcaine) • Procaine (Novocain) • Tetracaine (Pontocaine) • Mepivacaine (Carbocaine) • Hyaluronidase (Wydase) facilitator/enhancer of above medications’ effects • Epinephrine (Adrenalin) additive to above for vasoconstrictive properties

41. Local Anesthesia with MAC • Combination of nerve conduction blockade on topical or local level with supplementation by the anesthesia provider with analgesics, sedative-hypnotics, or amnestics

42. Regional Anesthetics • Injected along a major nerve tract • Nerve Plexus Block or Field Block • Bier Block • Spinal • Epidural • Caudal Block

43. Nerve Plexus Block • Anesthetic injected into major nerve plexus or the base of a structure • Result is anesthesia of tissue innervated by that plexus • Used in dental and extremities • Examples: axillary, wrist, ankle, cervical plexus (CAE)

44. Bier Block • Anesthetic injected to an extremity into a vein below the level of a tourniquet • For arm/wrist/hand surgery that will last less than 1 hour • Blood exsanguinated from extremity with an esmark, tourniquet is inflated, anesthetic given • Tourniquet prevents anesthetic agent from circulating above it • Tourniquet will be released slowly to allow for gradual circulation of the agent to prevent cardiovascular or CNS effects

45. Bier Block

46. Spinal Block • Injected into CSF in the subarachnoid space between L-3 and L-5 vertebrae • For lower body procedures • Onset 3-5 minutes • Duration 1 ½ hours • Tetracaine most common agent used • Lidocaine and Procaine others used • Epinephrine can prolong effect • Never put patient in Trendelenburg position with spinal anesthesia

47. Spinal Block • Disadvantages: • Hypotension • Nausea and vomiting • One time dose means cannot adjust • Temporary or permanent paralysis

49. Spinal Block • Advantages: • Conscious patient • No respiratory irritation • Bowel contraction enhances abdominal visibility • Muscle relaxant effects allow easy abdominal wall retraction

50. Spinal Block