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Module AE0001. Introduction to Anesthesiology D. John Doyle MD PhD FRCPC [email protected] 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

Module AE0001

Introduction to Anesthesiology

D. John Doyle MD PhD [email protected]

51 slides Rev 1.0


About anesthesiology

ABOUT ANESTHESIOLOGY

  • Goals of Anesthesia

  • General Anesthesia

  • Regional Anesthesia

  • Perioperative Problems


Anesthesiology involves

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


Anesthesia techniques for surgery

Anesthesia Techniques for Surgery

  • General Anesthesia

  • Spontaneous Breathing

  • Machine Ventilation

  • Cardiopulmonary Bypass

  • Regional Anesthesia

  • Epidural

  • Spinal

  • Plexus Block

  • Nerve Block


Anesthesia techniques for surgery1

Anesthesia Techniques for Surgery

  • Local Anesthesia (Infiltration)

  • Other Methods

    • Acupuncture

    • Hypnosis

    • Cold


What is general anesthesia

What is General Anesthesia?

  • Unconsciousness (no awareness)

  • Airway Management

  • Amnesia (no recall)

  • Analgesia (no pain)

  • Blunting of Reflexes

  • Physiological Homeostasis (stability)

  • Muscle Paralysis (sometimes)


General anesthesia

Assessment

Planning I: Monitors

Planning II: Drugs

Planning III: Fluids

Planning IV: Airway Management

Induction

Maintenance

Emergence

Postoperative

General Anesthesia


Goals and issues in general anesthesia

Goals and Issues in General Anesthesia

  • Unconsciousness

  • Amnesia

  • Analgesia

  • Oxygenation

  • Ventilation

  • Homeostasis

  • Airway Management

  • Reflex Management

  • Muscle Relaxation

  • Monitoring


Airway management choices

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


Airway equipment

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


Amnesia

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)


Analgesia

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


Reflexes

Reflexes

  • Gag reflex

  • Oculocardiac reflex

    NOTE:

    Epidural or spinal anaesthesia sympathectomy effects may blunt the tachycardia reflex response to hypovolemia


Homeostasis

Homeostasis

  • Fluid and electrolyte balance

  • Adequate

    • blood pressure

    • blood volume

    • hemoglobin concentration

    • urine output

    • temperature


Muscle relaxation

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


Muscle relaxants

Muscle Relaxants

  • Succinylcholine(very short effect; no reversal; occasional nasty side-effects)

  • Nondepolarizing Drugs(require reversal eg, neostigmine+atropine)

    • Curare

    • Pancuronuim

    • Vecuronium

    • Rocuronium etc.


Preoperative assessment

PreoperativeAssessment

  • ASA Physical Status

  • Allergies

  • Medications

  • Identify Anaesthetic Considerations

  • Review Need for Consultations

  • Estimate Potential for Blood Loss

  • Postop Ventilation?

  • Need for ICU bed?


Asa physical status

ASA Physical Status

  • ASA - 1 HEALTHY

  • ASA - 2 MILD DISEASE

  • ASA - 3 SYSTEMIC DISEASE

  • ASA - 4CONSTANT THREAT TO LIFE

  • ASA - 5MORIBUND

  • ASA -6BRAIN DEAD


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 …

Identify Anesthetic Considerations


Regional anesthesia

Regional Anesthesia

  • Epidural Anesthesia

  • Spinal Anesthesia

  • Brachial Plexus Blocks

  • Other blocks

    • intercostal blocks

    • femoral nerve block

    • ankle blocks


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

Pros and Cons of Regional Anesthesia


Complications of regional anesthesia

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


Perioperative problem solving start with the differential diagnosis

Tachycardia

Bradycardia

Hypertension

Hypotension

High Airway Pressures

Hypercarbia

Oliguria

Cyanosis

Restlessness

Hematuria

Hyperkalemia

Hypernatremia

Hypoxemia

Perioperative Problem Solving… Start with the Differential Diagnosis


Pneumothorax

Pneumothorax


Maximum dose of lidocaine xylocaine

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!)


Planning i monitors

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


Planning ii drugs

Planning II: Drugs

  • Induction

    • IV vs Inhalation

  • Maintenance

    • IV vs Inhalation

  • Muscle Relaxation

  • Narcotics

  • Hypnotics

  • Vasoactive / cardiac drugs

    etc.


Planning iii fluids

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


Planning iv airways

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


Planning v postoperative analgesia

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


Iv induction agents

IV Induction Agents

  • Thiopental

  • Propofol (Diprivan)

  • Etomidate

  • Ketamine

  • High-dose fentanyl (or other opiate)

  • High-dose midazolam


Potent inhaled anesthetics

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!


Opiates in the or

Opiates in the OR

  • Fentanyl (Sublimaze)

  • Sufentanil

  • Alfentanil

  • Remifentanil

  • Morphine

  • Meperidine (Demerol)

  • Hydromorphone (Dilaudid)


Anesthesiology operating room technology issues

Anesthesiology Operating Room Technology Issues

  • Anesthesia Machines

  • Airway Gas Monitors

  • Physiological Monitoring Equipment

  • IV and Inhalational Drug Delivery Technology

  • Medical Ergonomics

  • Safety Standards


About anesthesiology1

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


Clinical tools in anesthesiology

Clinical Tools in Anesthesiology

Drugs

  • intravenous

  • inhalational

  • epidural / spinal

  • oral / sublingual


Clinical tools in anesthesiology1

Clinical Tools in Anesthesiology

Airway Management Tools

  • Endotracheal tubes

  • Laryngoscopes

  • Oral and nasopharyngeal airways

  • Fiberoptic broncoscopes


Clinical tools in anesthesiology2

Clinical Tools in Anesthesiology

Monitors

  • Clinical observation

  • Noninvasive techniques

  • Invasive techniques


Anesthesia machines

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


Anaesthesia machines oxygen safety systems

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


Anaesthesia machines ventilator operations

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)


Respiratory monitoring

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


Breathing

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)


Respiratory assessment

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)


Respiratory assessment1

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


What is monitoring

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


Standard basic monitoring

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)


Patient monitoring management

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)


Low tech monitoring

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


Basic monitoring

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)


Special monitoring

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


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