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Module AE0001

Module AE0001. Introduction to Anesthesiology D. John Doyle MD PhD FRCPC doylej@ccf.org 51 slides Rev 1.0. ABOUT ANESTHESIOLOGY. Goals of Anesthesia General Anesthesia Regional Anesthesia Perioperative Problems. Anesthesiology Involves . Drugs and fluids Lines and catheters

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Module AE0001

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  1. Module AE0001 Introduction to Anesthesiology D. John Doyle MD PhD FRCPCdoylej@ccf.org 51 slides Rev 1.0

  2. ABOUT ANESTHESIOLOGY • Goals of Anesthesia • General Anesthesia • Regional Anesthesia • Perioperative Problems

  3. Anesthesiology Involves ... • Drugs and fluids • Lines and catheters • Monitors and equipment • Clinical knowledge and judgment • Technical and psychomotor skills • Team building and interpersonal relations • Crisis management and problem prevention • Dealing with patients and their fears

  4. Anesthesia Techniques for Surgery • General Anesthesia • Spontaneous Breathing • Machine Ventilation • Cardiopulmonary Bypass • Regional Anesthesia • Epidural • Spinal • Plexus Block • Nerve Block

  5. Anesthesia Techniques for Surgery • Local Anesthesia (Infiltration) • Other Methods • Acupuncture • Hypnosis • Cold

  6. What is General Anesthesia? • Unconsciousness (no awareness) • Airway Management • Amnesia (no recall) • Analgesia (no pain) • Blunting of Reflexes • Physiological Homeostasis (stability) • Muscle Paralysis (sometimes)

  7. Assessment Planning I: Monitors Planning II: Drugs Planning III: Fluids Planning IV: Airway Management Induction Maintenance Emergence Postoperative General Anesthesia

  8. Goals and Issues in General Anesthesia • Unconsciousness • Amnesia • Analgesia • Oxygenation • Ventilation • Homeostasis • Airway Management • Reflex Management • Muscle Relaxation • Monitoring

  9. AirwayManagement Choices • Intubation vs. LMA vs. “nothing special” • Positive pressure ventilation vs. spontaneous breathing • Intubation awake vs. asleep • Conservative vs. surgical airway • Muscle relaxant vs. none

  10. AirwayEquipment • Single Lumen Tracheal Tubes • Regular • RAE • Armored • Nasal • Double Lumen Tubes • Laryngeal Mask Airway • Oropharyngeal Airways • Fiberoptic Intubation Cart • Difficult Intubation Kit • Surgical Airway Kit

  11. Amnesia • Generally sought, but not always desirable • Lorazepam (Ativan) 2-4 mg sublingually 60 - 90 min preop • Midazolam (Versed) 1 mg IV increments • Scopolamine (old but still effective)

  12. Analgesia • Analgesia = no pain • Anesthesiologists generally accept the notion of “unconscious pain” • Pain manifests under general anaesthesia as increased sympathetic tone with tachycardia, hypertension, diaphoresis etc. • Pain Rx: fentanyl, morphine, epidural analgesia

  13. Reflexes • Gag reflex • Oculocardiac reflex NOTE: Epidural or spinal anaesthesia sympathectomy effects may blunt the tachycardia reflex response to hypovolemia

  14. Homeostasis • Fluid and electrolyte balance • Adequate • blood pressure • blood volume • hemoglobin concentration • urine output • temperature

  15. Muscle Relaxation • For intubation • Where inadvertent patient movement might be disastrous • For abdominal muscle relaxation • To facilitate positive pressure ventilation • Special purposes • ECT therapy • tetanus / lock jaw

  16. Muscle Relaxants • Succinylcholine(very short effect; no reversal; occasional nasty side-effects) • Nondepolarizing Drugs(require reversal eg, neostigmine+atropine) • Curare • Pancuronuim • Vecuronium • Rocuronium etc.

  17. PreoperativeAssessment • ASA Physical Status • Allergies • Medications • Identify Anaesthetic Considerations • Review Need for Consultations • Estimate Potential for Blood Loss • Postop Ventilation? • Need for ICU bed?

  18. ASA Physical Status • ASA - 1 HEALTHY • ASA - 2 MILD DISEASE • ASA - 3 SYSTEMIC DISEASE • ASA - 4 CONSTANT THREAT TO LIFE • ASA - 5 MORIBUND • ASA -6 BRAIN DEAD

  19. Difficult Airway COPD Anemic Hypertensive Hypovolemic Elderly MH Susceptability Renal Failure Poor LVF Stridor Obesity TPN Small Bowel Obstruction and many other possibilities … Identify Anesthetic Considerations

  20. Regional Anesthesia • Epidural Anesthesia • Spinal Anesthesia • Brachial Plexus Blocks • Other blocks • intercostal blocks • femoral nerve block • ankle blocks

  21. Pros no airway problem inexpensive postop analgesia easy cerebral monitoring (by talking to patient) Cons takes time takes skills high failure rate uses needles nerve injury potential Pros and Cons of Regional Anesthesia

  22. Complications of Regional Anesthesia • Local anesthetic toxicity (CNS, CVS) • Nerve injury / irritation / radiculopathy • Hematoma • Infection • Technique failure • For epidurals • high or total spinals • wet taps and headaches • For spinals • headaches • hypotension

  23. Tachycardia Bradycardia Hypertension Hypotension High Airway Pressures Hypercarbia Oliguria Cyanosis Restlessness Hematuria Hyperkalemia Hypernatremia Hypoxemia Perioperative Problem Solving… Start with the Differential Diagnosis

  24. Pneumothorax

  25. Maximum Dose of Lidocaine (Xylocaine) • TOXICITY: Convulsions, CV Collapse • 1% = 10 mg/ml 2%=20 mg/ml • Toxic dose of lidocaine • 5 mg/kg plain • 7 mg/kg with added epinephrine • EXAMPLE: 25 ml of 2% = 500 mg(This is over 10 mg/kg if patient weighs only 100 lbs!)

  26. BASIC EKG BP Temperature Oxygen FIO2 Oxygen Line Pressure Airway Pressure Pulse Oximeter Capnogram Urine Output Nerve Stimulator ADVANCED CVP line PA line PA pressures CVP CO SVR TEE ICP Evoked Potentials Planning I: Monitors

  27. Planning II: Drugs • Induction • IV vs Inhalation • Maintenance • IV vs Inhalation • Muscle Relaxation • Narcotics • Hypnotics • Vasoactive / cardiac drugs etc.

  28. Planning III: Fluids • Maintenance fluid requirements • Preoperative fluid deficit (from being NPO overnight) • Third space losses • Blood loss replacement • Issues • When to give colloid • When to give blood products • How to manage oliguria

  29. Planning IV: Airways • General Anesthesia vs. Regional Anesthesia • Spontaneous Ventilation vs. Positive Pressure Ventilation • Awake Intubation? • Tracheostomy under local? • Airway Equipment • Oropharyngeal airway • Nasopharyngeal airway • Laryngeal Mask Airway (LMA) • Endotracheal tube

  30. Planning V: Postoperative Analgesia • IM morphine e.g. 10 mg IM q3h prn • IV morphine e.g. 2-4 mg IV q10 min prn • PCA • Epidural Analgesia • Oral Analgesics

  31. IV Induction Agents • Thiopental • Propofol (Diprivan) • Etomidate • Ketamine • High-dose fentanyl (or other opiate) • High-dose midazolam

  32. Potent Inhaled Anesthetics • Ether (flammable) • Halothane (20% metabolized) • Enflurane (2% metabolized) • Isoflurane (0.2% metabolized) • Sevoflurane (newer, expensive, good for inhalation inductions) • Desflurane (newer, expensive, not good for inhalation inductions) • Even Xenon makes a passable agent!

  33. Opiates in the OR • Fentanyl (Sublimaze) • Sufentanil • Alfentanil • Remifentanil • Morphine • Meperidine (Demerol) • Hydromorphone (Dilaudid)

  34. Anesthesiology Operating Room Technology Issues • Anesthesia Machines • Airway Gas Monitors • Physiological Monitoring Equipment • IV and Inhalational Drug Delivery Technology • Medical Ergonomics • Safety Standards

  35. About Anesthesiology • MD degree, then 4-5 years more training • Written and oral board exams • Work in OR, ICU, pain service, even palliative care • Experts in resuscitation / reanimation • Bring patients “to the brink of death” several times a day • Among most technically inclined MDs

  36. Clinical Tools in Anesthesiology Drugs • intravenous • inhalational • epidural / spinal • oral / sublingual

  37. Clinical Tools in Anesthesiology Airway Management Tools • Endotracheal tubes • Laryngoscopes • Oral and nasopharyngeal airways • Fiberoptic broncoscopes

  38. Clinical Tools in Anesthesiology Monitors • Clinical observation • Noninvasive techniques • Invasive techniques

  39. Anesthesia Machines • Delivery of measured flows of gases:oxygen, nitrous oxide, anesthetic gas • Percent oxygen adjustable 25 to 100% • Ventilator with adjustable rate and volume • Lots of dials and gauges • Lots of safety features • Can be expensive and requires maintenance

  40. Anaesthesia Machines:Oxygen Safety Systems • Electronic oxygen controllerforbids oxygen concentrations under 25% • Pulse oximeterprovides good clinical oxygenation data (usually) • Airway Gas Monitorwarns about hypoxic gas mixtures or about rebreathing of CO2 • Gauges display tank pressure, oxygen flow, percent oxygen being delivered • Oxygen tanks are green in US (white elsewhere) and hook to yoke via PIN INDEXsystem

  41. Anaesthesia Machines: Ventilator Operations ANESTHESIA VENTILATOR PARAMETERS • Respiratory Rate (frequency) • Volume of each breath (tidal volume) • Ratio of expiration to inspiration (eg, 2 to 1) • Baseline lung distension (PEEP) • Percent (fraction) oxygen (FIO2)

  42. Respiratory Monitoring • Clinical: wheezing, crackles, equal air entry, color, respiratory, pattern (rate, rhythm, depth) • Airway pressure • Spirometry (measured tidal volume) • Capnography (CO2 concentration vs. time) • Oxygraphy(O2 concentration vs. time) • Pulse oximetry • OTHER : ETT cuff pressure, NIF, VC

  43. BREATHING • Spontaneous Breathing • Specify percent (fraction) oxygen (FIO2) • Clinically monitor airway, breathing characteristics, and respiration rate • Machine Ventilation • Respiratory Rate (frequency) • Volume of each breath (tidal volume) • Baseline lung distension (PEEP) • Percent (fraction) oxygen (FIO2)

  44. Respiratory Assessment Clinical Assessment of Breathing • Visual inspection: breathing pattern, rate, depth, signs of airway obstruction • Trend charting of respiratory rate (increases in respiratory rate may herald pulmonary edema; decreases in respiratory rate may herald apnea)

  45. Respiratory Assessment Lab Respiratory Monitoring Methods • Pulse Oximeter (art oxygen saturation ) • Capnograph (expired CO2 conc signal) • Oxygram (expired O2 concentration sig) • Arterial Blood Gas Analysis • arterial oxygen tension • arterial carbon dioxide tension • arterial pH

  46. What is Monitoring? • Keeping an “eye on the patient” • Patient defense strategy / algorithm • High-tech electronics • Old fashioned viligence • Preparing for future events • Keeping “quality” in the system, including monitoring care providers

  47. Standard Basic Monitoring • Clinical means such as inspection, ascultation, attention to movement, etc • Blood pressure (usually by automatic cuff) • Electrocardiogram(rate, rhythm, ST segment ) • Pulse Oximeter(arterial oxygen saturation) • Capnogram (carbon dioxide conc signal at the airway) • Anesthetic Agent Concentration Monitor • Temperature(hypothermia is often undesirable) • Neuromuscular Blockade (if needed) • Tidal Volume (where available)

  48. Patient Monitoring / Management Involves: • things you measure (physiological measurement) • things you observe (clinical observation) • planning to avoid trouble(eg. induction planning) • inferring diagnoses (eg. big QT interval and hypotension following massive transfusion: your best guess is hypocalcemia) • planning to get out of trouble (eg. differential diagnosis and response algorithm formulation)

  49. Low Tech Monitoring • BP cuff • Finger on the pulse and forehead • Monaural stethoscope • Eye on the rebreathing bag (SV) • Watching for desired or undesired movements • Looking at the patient’s face • colour OK? • diaphoresis present? • pupils

  50. Basic Monitoring • Cardiac: Blood Pressure, Heart Rate, ECG • ECG: Rate, ST Segment (ischemia), Rhythm • Respiratory: AW Pressure, Capnogram, Pulse Oximeter • Temperature [pharyngeal, axillary, PA (SGC)] • Urine output (if catheter placed) • Nerve stimulator [face, forearm](if NMB used) • ETT cuff pressure (keep < 20 cm H2O) • Auscultation (esophageal or precordial stethoscope) • Visualization of some exposed portion of the patient (clinical signs)

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