Transcript Maintenance of anesthesia

Kelly Shinkaruk, MD FRCPC
HLT 123
October 17, 2009
1
Objectives
 What is anesthesia?
 Manual monitoring techniques
 Inspection
 Palpation
 Auscultation
 Evaluation and maintenance of anesthetic depth
using
 Non-invasive monitors
 Invasive monitors
 Nervous system monitors
 Adjusting medications to maintain anesthetic
2
Objectives
 What is anesthesia?
 Manual monitoring techniques
 Inspection
 Palpation
 Auscultation
 Evaluation and maintenance of anesthetic depth
using
 Non-invasive monitors
 Invasive monitors
 Nervous system monitors
 Adjusting medications to maintain anesthetic
3
What is anesthesia?
 “…drug induced reversible depression of the
central nervous system resulting in the loss of
response to and perception of all external stimuli.”
 Components of anesthesia
 Unconsciousness
 Amnesia
 Analgesia
 Immobility
 Attenuation of autonomic response to noxious
stimulation
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Components of General Anesthesia
Induction
Maintenance
Emergence
5
Components of General Anesthesia
Induction
Maintenance
Emergence
6
Goals of Maintenance
 Responsible for autonomic nervous system
 Maintenance throughout case of
 anesthesia
 amnesia
 analgesia
 paralysis (if indicated)
 In addition
 Minimize negative effects of anesthetic
 Fluid maintenance/balance/resuscitation
 Cardiac output and end organ perfusion
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Goals of Maintenance
 Why use monitors?
 Detect deficit or overdose of anesthetic agents and
resolve the aberrancy
 Early detection of adverse events
 Prevention of periop critical events
 Prior to advent of standard monitoring, anesthesia had
very high morbidity and mortality
 Now it’s very low 
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CAS Monitors
Required
•
•
•
•
Pulse oximeter
Blood pressure
Electrocardiography
Capnography, when
endotracheal tubes
or laryngeal masks
are inserted
• Agent-specific
anesthetic gas
monitor
Exclusively Available
• Apparatus to
measure temperature
• Peripheral nerve
stimulator
• Stethoscope
• Appropriate lighting
Immediately Available
• Spirometry
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CAS Monitors
 Use monitors to help narrow your differential
diagnosis
 No single monitor can make a diagnosis, must verify
one monitor with another!
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Depth of Anesthesia
 If monitored vitals change
 Consider differential diagnosis
 Simultaneously manage and diagnose
 ABCs, verify result with another monitor
 Inspect, palpate, auscultate
 Make adjustments to medications as appropriate!!!
11
Objectives
 What is anesthesia?
 Manual monitoring techniques
 Inspection
 Palpation
 Auscultation
 Evaluation and maintenance of anesthetic depth
using
 Non-invasive monitors
 Invasive monitors
 Nervous system monitors
 Adjusting medications to maintain anesthetic
12
Manual Monitoring Techniques
 “The only indispensable monitor is the presence, at all
times, of a physician or an anesthesia assistant, under
the immediate supervision of an anesthesiologist, with
appropriate training and experience.”

CAS guidelines 2008
 Provides valuable information about
 Depth of anesthesia
 Diagnosis of intraoperative complications
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Manual Monitoring Techniques
 Inspection (Adequate Lighting)
 Historically, sole monitor
 Initial information by observation
 Inspect for alterations







Diaphoresis
Spontaneous movement
Respiratory rate and pattern esp. when spontaneous
Abnormal retractions or indrawing
Cyanosis
JVP
Skin colour and/or rash
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Manual Monitoring Techniques
 Palpation
 Correlate information from inspection
 Physical contact with patient
 Palpate for



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Tracheal position
Subcutaneous emphysema
Pulsus paradoxus
Heart rate, rhythm, contour
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Manual Monitoring Techniques

Ausculation (Stethoscope!!!)
 Respiratory system



Endotracheal tube placement/malposition
Wheezes/crackles
stridor/decreased air entry
 Cardiovascular system


Murmurs/bruits
Changes in quality of heart sounds (S1, S2, decreased heart
sounds)
16
Objectives
 What is anesthesia?
 Manual monitoring techniques
 Inspection
 Palpation
 Auscultation
 Evaluation and maintenance of anesthetic depth
using
 Non-invasive monitors
 Invasive monitors
 Nervous system monitors
 Adjusting medications to maintain anesthetic
17
Non Invasive Monitors
Pulse
Oximetry
Blood
Pressure
Capnography
Expired
Agents/Gases
Non
Invasive
Monitors
Ventilatory
Pressures
ECG
Temperature
Monitoring
Respiratory
Function
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Non Invasive Monitors
 Pulse Oximetry
 Simple, noninvasive, continuous
 indirectly measures the oxygen
saturation of a patient's blood
 Detect and prevent hypoxemia
 Affected by

dyshemoglobins, vital dyes, nail
polish, ambient light, motion
artifact, background
noise/electrocautery
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Non Invasive Monitors
 Pulse Oximetry
 When sats fall, differential diagnosis

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Low FiO2 (relative or absolute)
Inadequate alveolar ventilation
V/Q mismatch
Excessive metabolic O2 demand
Low cardiac output
 Treatment?



100% O2
Increase ventilation rate/Vt or change vent mode
Recruitment maneuvers
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Non Invasive Monitors
 Blood Pressure (via cuff)
 Indicates adequacy of
circulation
 Minimum monitoring
interval - 5min
 Monitor location – upper
arm, leg, forearm
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Non Invasive Monitors
 Blood pressure
 Hypertension diagnosis?
○
○
○
Light anesthesia
Catecholamine release
 Laryngoscopy
 Surgical stimulation
 Emergence from anesthesia
Administration of vasopressors
 Treatment?
○
○
Deepen anesthetic
d/c vasopressors
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Non Invasive Monitors
 Blood Pressure
 Hypotension differential diagnosis?



Is extensive…
Hypovolemia
Relative overdose of anesthetic agents
 Treatment?
 Initially, go through ABCs, inspect for evidence of bleeding,
100%O2, turn down anesthetic
 Fluid bolus – NS/RL 500-1000mL
 Vasopressor – Phenylephrine 100mcg or Ephedrine 2-10mg
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Non Invasive Monitors
 Electrocardiogram
 Three or five leads
 Continuous measurement of
heart rate and rhythm
 Questionable indicator of
myocardial ischemia
 Signs of light anesthesia


tachycardia
Might notice changes in
rhythm
 Vasovagal episodes


Tell surgeon to STOP!!!
Atropine 0.4mg or Ephedrine
5-10mg
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Non Invasive Monitors
 Expired Agents/Gases
 The most important objective indicator of depth of
anesthesia


Monitors the concentration of gas (volatile, CO2, O2) being
expired from the patient
MAC (minimum alveolar concentration) = 50% of people will
not move with surgical stimulus
 Monitor end tidal concentration of agents
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Non Invasive Monitors
 Expired Agents/Gases
 MAC is affected by many things
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Intravenous medications – PPF, opioids, benzos
Pre-op medications – pregabalin, benzos
Age
Medical conditions/patient health
Hypo/hyperthermia
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Non Invasive Monitors
 Expired Agents/Gases
 If low and patient appears light

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
Increase flow rate
Increase percent of volatile delivered from vaporizer
Make sure to monitor MAC as can increase rapidly! (and cause
hypotension)
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Non Invasive Monitors
 Capnography
 Insp/exp CO2 concentration
 Vital monitor of physiology

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Confirm ETT placement
Recognize ETT
malposition/extubation/disconnection
Assess adequacy of ventilation/PaO2
Aids diagnosis of PE, partial A/W
obstruction, RAD/bronchospasm
Assess efficacy of CPR efforts
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Non Invasive Monitors
Increased
ETCO2
Decreased
ETCO2
Hyperthermia/Sepsis
MH
Hypothermia
Shivering
hypothyroidism
Hyperthyroidism
Hypoventilation
rebreathing
Hyperventilation
Hypoperfusion
Pulmonary embolism
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Non Invasive Monitors
 Capnography
 If increased ETCO2


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Check CO2 absorber!
Increase minute ventilation (RR or Vt)
?hypermetabolic process?
 If decreased ETCO2
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Sudden vs slow
Decrease ventilation
Verify other signs of hypoperfusion
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Non Invasive Monitors
 Respiratory Function
 Especially useful in spontaneously ventilating patient
 Light patient



Hyperventilation - increased RR/Vt and hypocapnia
Breath holding
Bronchospasm/laryngospasm
 Very deep patient
 Hypoventilation – decreased RR/Vt and hypercapnia
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Non Invasive Monitors
 Increase in respiratory rate
 Differential mainly light anesthetic and hypoventilation

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
Increase ventilation (RR or Vt)
Deepen anesthetic
Administer analgesic
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Non Invasive Monitors
 Ventilator Pressures
 Early indication of light anesthetic and other
problems! Always check:



Breathing circuit
ETT
Pulmonary compliance
 Alarms for increased pressure
 Coughing
 Insufficient muscle paralysis
 Bronchospasm
 Obstruction/pt biting ETT
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Non Invasive Monitors
 Ventilatory Pressure elevated
 Differential diagnosis

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

Manage and diagnose
Inspect patient and ETT – biting, blocked, disconnected (if
low pressure alarm)
Take off machine and verify compliance
Auscultate breath sounds – ETT malposition
 Treatment



Deepen anesthetic
Paralysis
Reposition/Suction/change ETT
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Non Invasive Monitors
 Temperature Monitoring
 Can be monitored via bladder, distal esophagus, ear
canal, trachea, nasopharynx, rectum
 Attempts made to maintain temperature as close to
normothermia as possible
 Situations requiring temp monitoring
○
○
○
○
Long cases
Anticipated fluctuations in temperature
Bair hugger
Malignant hyperthermia patients
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Invasive Monitors
Central
Venous
Pressure
Arterial
Line
Pulmonary
Artery
Catheter
Echo
Invasive
Monitors
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Invasive Monitors
 Arterial Line
 Continuous blood pressure measurement
 Placed in a peripheral artery
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Radial
Brachial
Dorsalis pedis
Rarely femoral
 Waveform gives information about intravascular status
 Help with diagnosis of cardiac tamponade,etc
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Invasive Monitors
 Arterial line
 Indications: induced hypotension, induced
hypothermia, major
cardiac/thoracic/vascular/neurosurgical procedures
 Always keep BP cuff in place for verification of arterial
BP
 Used for frequent blood sampling esp. ABGs
 Be aware that tracing can be damped/positional


Flattened waves might be artifactual
Verify with BP cuff
38
Invasive Monitors
 Central Venous Pressure (CVP)
 Estimates of right atrial/ventricular pressures
 Serial measurements more useful than single value
 monitor intravascular volume/fluid status

Renal failure patients
 Difficult IV access
 Anticipated need for vasopressor
infusion/TPN/Hemodialysis
 Massive transfusion
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Invasive Monitors
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Invasive Monitors
 Pulmonary Artery Catheter (PAC)
 Rarely indicated, TEE rapidly replacing
 Inflation in pulmonary artery reflects left atrial filling
pressure
 Can calculate cardiac output
 High risk of complications

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PA rupture
PVCs/Vtach
Hemo/pneumothorax
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Invasive Monitors
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Invasive Monitors
 Transesophageal Echo
 Echo probe placed in

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
esophagus during GA
Uses ultrasound technology
Assess cardiac
function/filling/valves
Replacing PAC technology
Requires special equipment
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Invasive Monitors
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Invasive Monitors
 Evaluation of
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Native valve disease
Prosthetic heart valve function/dysfunction
Cardiac masses
The ICU patient with hemodynamic instability
Congenital heart disease
Thromboembolic risk in patient with atrial fibrillation and inadequate
anticoagulation
 Detection of
 Aortic dissection
 Complications of endocarditis
 Potential etiologies of stroke
 Adjunct to
 Percutaneous cardiac procedures
 Cardiac surgical procedures
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Invasive Monitors

Heart valve repair

Most congenital heart surgery requiring
cardiopulmonary bypass

Endocarditis, particularly with extensive
disease or inadequate preoperative
evaluation of disease extent

Ascending aortic dissection repair when
aortic valve involvement unknown

Evaluation of life-threatening hemodynamic
disturbances when ventricular function is
unknown

Heart valve replacement

Removal of cardiac tumors

Increased risk of myocardial ischemia or
hemodynamic disturbances

Intracardiac thrombectomy or pulmonary
embolectomy

Suspected cardiac trauma or for detection of
foreign bodies

Cardiac aneurysm repair

Thoracic aortic dissection repair without
suspected aortic valve involvement

Pericardial window procedures

Evaluation of anastomotic sites during heart
and/or lung transplantation

Hypertrophic obstructive cardiomyopathy
repair

Monitoring placement and function of assist
devices
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Nervous System Monitors
EEG
BIS
Nervous System
Monitors
Evoked
Potentials
PNS
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Nervous System Monitors
 Electroencephalogram (EEG)
 Represents spontaneous electrical activity of the
cerebral cortex
 Measures amplitude and frequency of discharge
 Four frequencies: beta, alpha, theta, delta
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Nervous System Monitors
 Electroencephalogram (EEG)
 EEG may be used to detect intraop cerebral ischemia
 Deep anesthesia and cerebral ischemia decrease or
abolish normal alpha/beta; delta/theta predominate
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Nervous System Monitors
 Bispectral Index (BIS)
 A variable derived from the EEG
 Measure of the hypnotic effect of anesthetic
 Gives a value between 0 and 100


Decreasing numbers = deeper anesthetic
<60 appears to predict unconsciousness
 Used in trauma, crash OB, cardiac, unstable patient with
minimal reserve/anesthetic
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Nervous System Monitors
 Evoked Potentials
 Stimulation of neural structures to evoke responses to
monitor integrity of pathways


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

Brainstem Auditory Evoked Responses (BAER) – acoustic
neuroma/post fossa
Visual Evoked Potentials (VEP) – optic tract
Somatosensory Evoked Potentials (SSEP) – stimulate
peripheral nerves (median, ulnar, peroneal, posterior
tibial), spine surgery (scoliosis)
Motor Evoked Potentials (MEP)
Facial Nerve Stimulation – parotidectomy
 Affected by many anesthetic agents
51
Nervous System Monitors
 Peripheral Nerve Stimulator (PNS)
 Monitors the depth of neuromuscular blockade
and ease of reversibility
 Electrodes applied over peripheral nerve


Ulnar nerve most common
Facial nerve and common peroneal
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Nervous System Monitors
 Peripheral Nerve Stimulator (PNS)
 Nerve stimulated and muscle contraction
measured
 Train of Four most commonly measured
 Maintain one twitch during cases requiring
paralysis




Rocuronium most common
Cisatracurium occasionally
Pancuronium very rarely
Succinylcholine for RSI
 Block easily reversible if >1 twitch present
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Objectives
 What is anesthesia?
 Manual monitoring techniques
 Inspection
 Palpation
 Auscultation
 Evaluation and maintenance of anesthetic depth
using
 Non-invasive monitors
 Invasive monitors
 Nervous system monitors
 Adjusting medications to maintain anesthetic
54
Maintenance Medications
 IV agents
 Propofol – the old standby, Vitamin P



Light patient, administer 20-30mg bolus
May need to repeat
Be wary of decrease in BP
 Midazolam – amnestic


Most often for awake patients
Occasionally used for unstable patients on minimal
maintenance meds
55
Maintenance Medications
 Analgesics
 Fentanyl – fast onset, short acting




use when suspect patient light and experiencing pain
If increased stimulation anticipated (new incision) may give
bolus in advance
50mcg boluses
Higher doses if patient ventilated and stable
 Morphine/Hydromorphone – slower onset, longer
acting

Often titrated to resp rate end of case
56
Maintenance Medications
 Volatiles (sevo and des)
 Usually the main maintenance medication
 In light patient


Increase flow rates of O2/Air
Increase concentration delivered from vaporizer
 In patient suspected to be too deep

Increase flow rates but make sure to DECREASE vaporizer
concentration (turn off)
57
Maintenance Medications
 Muscle Relaxants
 NOT anesthetic agents!!!!
 Do not give muscle relaxants to light patients without
another medication

Just think about how you’d feel if you were awake and couldn’t
move or communicate!!!
 Very useful in conjunction with Propofol/Analgesics
 Rocuronium 10-20mg bolus
58
Maintenance Medications
 Fluids
 When patient has decreased BP, increased HR,
decreased urine output



Consider hypovolemia
Bolus fluids rapidly and assess response
May need a large bolus if patient significantly fluid avid
59
Maintenance Medications
 Emergency drugs
 Vasopressors




if patient unstable, need to stabilize while confirming
diagnosis
Phenylephrine 50-100mcg bolus, 40mcg/min infusion
Ephedrine 5-10mg bolus
Norepi/Epi/Vasopressin YIKES!
60
Maintenance Medications
 Other meds
 If patient has epidural, consider increasing or decreasing
infusion
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Questions???
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