Module AE0001

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Module AE0001

• Introduction to Anesthesiology
• D. John Doyle MD PhD FRCPCdoylej_at_ccf.org
• 51 slides Rev 1.0

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ABOUT ANESTHESIOLOGY

• Goals of Anesthesia
• General Anesthesia
• Regional Anesthesia
• Perioperative Problems

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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

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Anesthesia Techniques for Surgery

• General Anesthesia
• Spontaneous Breathing
• Machine Ventilation
• Cardiopulmonary Bypass
• Regional Anesthesia
• Epidural
• Spinal
• Plexus Block
• Nerve Block

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Anesthesia Techniques for Surgery

• Local Anesthesia (Infiltration)
• Other Methods
• Acupuncture
• Hypnosis
• Cold

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What is General Anesthesia?

• Unconsciousness (no awareness)
• Airway Management
• Amnesia (no recall)
• Analgesia (no pain)
• Blunting of Reflexes
• Physiological Homeostasis (stability)
• Muscle Paralysis (sometimes)

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General Anesthesia

• Assessment
• Planning I Monitors
• Planning II Drugs
• Planning III Fluids
• Planning IV Airway Management

• Induction
• Maintenance
• Emergence
• Postoperative

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Goals and Issues in General Anesthesia

• Unconsciousness
• Amnesia
• Analgesia
• Oxygenation
• Ventilation
• Homeostasis
• Airway Management
• Reflex Management
• Muscle Relaxation
• Monitoring

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Airway Management 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

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Airway Equipment

• 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

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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)

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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

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Reflexes

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

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Homeostasis

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

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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

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Muscle Relaxants

• Succinylcholine (very short effect no reversal
  occasional nasty side-effects)
• Nondepolarizing Drugs(require reversal eg,
  neostigmineatropine)
• Curare
• Pancuronuim
• Vecuronium
• Rocuronium etc.

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Preoperative Assessment

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

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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

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Identify Anesthetic Considerations

• Difficult Airway
• COPD
• Anemic
• Hypertensive
• Hypovolemic
• Elderly
• MH Susceptability

• Renal Failure
• Poor LVF
• Stridor
• Obesity
• TPN
• Small Bowel Obstruction
• and many other possibilities

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Regional Anesthesia

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

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Pros and Cons of Regional Anesthesia

• 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

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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

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Perioperative Problem Solving Start with the
Differential Diagnosis

• Tachycardia
• Bradycardia
• Hypertension
• Hypotension
• High Airway Pressures
• Hypercarbia

• Oliguria
• Cyanosis
• Restlessness
• Hematuria
• Hyperkalemia
• Hypernatremia
• Hypoxemia

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Pneumothorax
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Maximum Dose of Lidocaine (Xylocaine)

• TOXICITY Convulsions, CV Collapse
• 1 10 mg/ml 220 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!)

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Planning I Monitors

• ADVANCED
• CVP line
• PA line
• PA pressures
• CVP
• CO
• SVR
• TEE
• ICP
• Evoked Potentials

• BASIC
• EKG
• BP
• Temperature
• Oxygen FIO2
• Oxygen Line Pressure
• Airway Pressure
• Pulse Oximeter
• Capnogram
• Urine Output
• Nerve Stimulator

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Planning II Drugs

• Induction
• IV vs Inhalation
• Maintenance
• IV vs Inhalation
• Muscle Relaxation
• Narcotics
• Hypnotics
• Vasoactive / cardiac drugs
• etc.

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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

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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

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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

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IV Induction Agents

• Thiopental
• Propofol (Diprivan)
• Etomidate
• Ketamine
• High-dose fentanyl (or other opiate)
• High-dose midazolam

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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!

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Opiates in the OR

• Fentanyl (Sublimaze)
• Sufentanil
• Alfentanil
• Remifentanil
• Morphine
• Meperidine (Demerol)
• Hydromorphone (Dilaudid)

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Anesthesiology Operating Room Technology Issues

• Anesthesia Machines
• Airway Gas Monitors
• Physiological Monitoring Equipment
• IV and Inhalational Drug Delivery Technology
• Medical Ergonomics
• Safety Standards

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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

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Clinical Tools in Anesthesiology

• Drugs
• intravenous
• inhalational
• epidural / spinal
• oral / sublingual

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Clinical Tools in Anesthesiology

• Airway Management Tools
• Endotracheal tubes
• Laryngoscopes
• Oral and nasopharyngeal airways
• Fiberoptic broncoscopes

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Clinical Tools in Anesthesiology

• Monitors
• Clinical observation
• Noninvasive techniques
• Invasive techniques

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Anesthesia Machines

• Delivery of measured flows of gasesoxygen,
  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

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Anaesthesia MachinesOxygen Safety Systems

• Electronic oxygen controller forbids oxygen
  concentrations under 25
• Pulse oximeter provides good clinical oxygenation
  data (usually)
• Airway Gas Monitor warns 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 INDEX system

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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)

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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

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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)

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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)

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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

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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

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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)

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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)

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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 patients face
• colour OK?
• diaphoresis present?
• pupils

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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 lt 20 cm H2O)
• Auscultation (esophageal or precordial
  stethoscope)
• Visualization of some exposed portion of the
  patient (clinical signs)

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Special Monitoring

• Pulmonary artery lines (Swan Ganz)
• Intracranial pressure (ICP)monitoring
• Electrophysiological CNS monitoring
• Renal function monitoring (indices)
• Coagulation monitoring (eg ACT)
• Acid-base monitoring (ABGs)
• Monitoring depth of anaesthesia