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Anesthesia Monitoring
David Roy Godden, MSN CRNA
Keck School of Medicine
Review need for monitoring
List the essential monitors for general anesthesia
Identify the most essential monitor in the OR.
Describe the indications contraindications for arterial line
Identify the techniques for arterial line placement.
List the complications of arterial line placement and
describe trouble shooting arterial line tracings
Be able to evaluate an arterial line tracing.
Know what the best monitor in the OR is!
• Describe the indications/contraindications for central line
• Identify the techniques for central line placement.
• List the complications of central line placement and
trouble shooting CVP waveform
• Be able to evaluate the CVP tracing.
• Discuss the BIS monitor and be able to discuss patient
awareness during anesthesia.
Why Monitoring
• Monitoring is an essential part of anesthesia care.
“Effective monitoring reduces the potential for poor
outcomes that may follow anesthesia by identifying
derangements before they result in serious or irreversible
injury” (Barish, 2006)
• Standard I for monitoring includes: 1) the presence of a
qualified provider to be present in the operating room at
all times to monitor the pt continuously and modify
anesthesia care based on clinical observations and
responses of the patient to treatments.
What to Monitor
• Standard II specifies: an oxygen analyzer with a low
concentration limit alarm; quantitative assessment of blood
oxygenation during anesthesia; continuously ensuring the
adequacy of ventilation by physical diagnostic techniques
during all anesthesia care. Quantitative monitoring of tidal
volume and capnography are encouraged in all pts
undergoing GA;
• Ensuring adequacy of circulation by by a) continuous
display of the ECG and b) blood pressure measurements at
least Q 5 minutes.
• Pulse quality via palpation is historically the method for
evaluating adequacy of circulation. Radial pulse =
MAP>60 or so while femoral pulse may be palpated at a
lower mean. Pre-cordial stethoscope anyone?
Monitoring cont
• Every patient that is endotracheal intubated or has an LMA placed
requires qualitative identification of carbon dioxide in the expired
• During GA capnography and end-tidal C02 analysis are encouraged!
Really encouraged not required?
• For Off site anesthesia care NC oxygen with capnography is
• So does every general anesthesia case require an airway? You would
think so. Wait till you get the CHLA.
• Mask Case with general anesthesia require what monitors?
• During all anesthetics the means for measuring a pt’s temperature
must be AVAILABLE. When changes in a pt’s temperature is
required or anticipated the continuous measurement and recording of
temperature should be done.
The Five Alarms
• During routine anesthesia care a minimum of 5 alarms
must be in use.
• Inspired oxygen and a low O2 limit alarm
• Airway pressure limit alarm
• Oximetry
• Blood pressure limit alarm
• Heart Rate limit alarms.
• Often too many alarms just cause confuse confusion.
When were you last in the ICU with alarms going off
• The Pulse Oxygen Tone must be monitored continuously!
Make sure that the volume of the tone is adequate for you!
What is the Best Monitor?
• I want you to think about all of the monitors that you
have available and try to decide which is the most useful
or most essential to provide safe anesthesia care.
• Is it the ECG or the Blood Pressure. What about
monitoring adequacy of ventilation with capnography?
• You must decide what is the most essential.
• What could you do without?
• Do you consider the pre-cordial stethoscope an essential
monitor? If so why? What info does the pre-cordial give
you about the patient?
Best Monitor
• Any biomedical engineer can design more monitors. The
list is potentially endless.
• However nothing replaces the presence of a Vigilant
anesthesia provider.
• You are the Best Monitor of a patients condition during
General Anesthesia.
• Through the use of visualization, palpation and
auscultation the anesthetist can monitor the adequacy of
circulation, ventilation and temperature. The use of
technology increases your ability to do this monitoring
quickly and efficiently but none of these advances replace
YOU. Be watchful. Pay attention. Look at the Patient.
• Use the pre-cordial stethoscope!
• So what's the best monitor?
Arterial Lines
• Indications for arterial line placement include:
– The need to continuously monitor a pts blood pressure
– In ASA class III or IV patient (relative indication) or
“sick” patients
– When frequent blood draws are anticipated
– When ABG evaluation in required
– Expected blood loss is high or the need to monitor Hct
with expected blood administration
– Vascular cases or cases when a hypotensive technique
is used
– If continuous vasoactive medications are required
Contraindications to Art Line
• Patient refusal? Discuss options with patient.
• Selection of cannulation site requires attention
• Choice of site by location. First use radial, then DP
(dorsalis pedis), then femoral, lastly brachial. Why?
• If there is infection at the site of entry then don’t go there
• Ischemia in an extremity with inadequate blood flow
• Large thrombus at chosen entry site
• What is the Allen’s test?
Radial Artery Cannulation
• The Allen’s Test do we routinely use it?
• In the past the patency of the ulnar artery circulation by
the performance of the Allen’s Test has been
recommended before cannulation
• The Allen’s Test is performed by compressing both radial
and ulnar arteries while the patient tightens his or her fist.
Releasing pressure on each respective artery determines
the dominant vessel supplying blood to the hand.
• The prognostic value of the Allen’s Test in assessing
adequacy of the collateral circulation has NOT been
Allen’s Test
• The arteries of the hand,
both the radial and ulnar,
have collateral circulation
• The predominant
circulation of the hand is
supplied by the ulnar
artery in most patients
Arteries of the Arm
• Note brachial artery
small collaterals
• Radial is larger and
more superficial
artery than Ulnar
NIBP vs. Arterial Cannulation
• NIBP (auscultatory /
• Pros
– Healthy patients
– Short case
• Cons
– Bladder cuff size
– Flow dependent
– Motion
– Interruption of IV
– Injury
– Cuff deflation rate
– Hydrostatic errors
• Arterial Cannulation
• Pros
– Continuous BP
– Sick patients
– Difficult cases
– ABG monitoring
• Cons
– Nerve dysfunction
– Thrombosis / Ischemia
– Hematoma formation
– Infection
– Hydrostatic errors
Art Line Placement Techniques
• Sterile prep and sterile towel. Wash hands vs. Surgical
scrub and the use of sterile gloves always
• Betadyne vs Chloroprep for skin preparation
• Dr. Sven-Ivar Seldinger (1921-1998) developed a
technique for arterial or venous cannulation
• IV method is very slick. Watch Kari Cole or Terrie Norris
they are great with this technique me I’m lame.
• Arrow Kit is in cart. This technique uses a very sharp
needle and soft cannula which is best for longer term use
Seldinger Technique
• Dr. Sven-Ivar Seldinger
• Use 20 ga needle/cannula
to transect artery
• Remove needle and then
• Draw cannula back slowly
till free flow of arterial
blood occurs
• Pass wire into artery down
• Thread cannula over the
• Easiest method.
Art Line Complications
Thrombus formation
Arterial laceration
Loss of distal perfusion to hand…ouch!
Nerve dysfunction from dissection
Errors in monitoring
Failed attempt. Always consider failure as a potential
Arterial Waveform Evaluation
• Tf – Foot
– Onset of ejection
– Systole
• T1 - First Shoulder
– Peak flow
• T2 - Second Shoulder
– Peak pressure
Ti – dichotic notch
End of ejection
Closure of aortic valve
Precedes the onset of
Tt – Pulse Duration
Arterial Waveform Shapes
• Rate of upstroke
– Indicates contractility
• Rate of downstroke
– Indicates peripheral vascular resistance
• Variations in size during respiration
– Suggest hypovolemia
• Mean arterial pressure
– Calculated by integrating the area under the
pressure curve
Arterial Line Tracing
• Dynamics of pulsatile
• Acceleration and
deceleration of blood
• Elasticity of the artery
• Modulated impedance
• Paradox (aorta􀃆distal
arteries) Mean arterial
pressure decreases
systolic pressure
• Systolic amplification is
particularly apparent in
noncompliant arteries
Patient Positioning
• Radial - Rotate shoulder by 20-30 degrees, palm upwards
and dorsiflex the wrist (a 500ml intravenous fluid bag
makes a useful rest) an assistant or adhesive tape can be
used to fix the wrist.
• Femoral - Abduct the leg by 30-40 degrees and externally
rotate the hip.
• Brachial - Fully extend the elbow but avoid
hyperextension, an assistant can help maintain elbow
• Dorsalis Pedis - plantar flex the foot.
Normal Arterial Waveform
Break Time
10 minutes or so
Central Line Indications
• Peripheral venous access is required for:
– Administration of fluids
– Administration of drugs
• Central venous access is required for:
– Parenteral nutrition
– Anticipated Inotropic medication infusion
– Anticipated large volume resuscitation
– Monitoring of central venous pressure (CVP)
– Cardiac pacing
– Difficult peripheral access
Central Line Contraindications
Patient refusal?
Severe Coagulopathy
Bundle Branch Blocks relative contraindication
Infection at site
Previous failed attempts at specific site
Unusual anatomy
Central Line Techniques
• Sterile techniques should be used for all central line
• Surgical scrub with Sterile gown and gloves
• Sterile prep of skin and surgical drapes.
• Local anesthetic should be used for central catheters in
awake patients
• Success may be improved by using ultrasound guidance
• Techniques of gaining access include:
Catheter over needle
Catheter through needle
Seldinger technique
Surgical cut-down is surgical technique as last resort.
Seldinger technique
• There are four steps to the Seldinger technique
• Venous puncture is performed with an introducer needle
• A soft tipped guide wire is passed through the needle and
the needle removed
• A dilator is passed over the guide wire
• Dilator is removed and catheter is passed over wire and
wire is removed
• Chest x-ray should be performed to check position of
Anatomy of Central Assess
• Internal jugular vein
Right sided access preferred. Why?
Apical pleura does not rise as high on right and avoids thoracic duct
Patient positioned head down
In the low approach triangle formed by two heads of sternomastoid and
clavicle identified
– Cannula aimed down and lateral towards ipsilateral nipple
• Subclavian vein
Usually approached from below clavicle
Patient positioned head down
Needle inserted below junction of medial 2/3 and lateral 1/3 of the clavicle
Needle aimed towards suprasternal notch
Passes immediately behind clavicle
Vein encountered after 4-5 cm
Normal CVP Waveform
Waveform Interpretation
• + a wave : This wave is due to the increased atrial
pressure during right atrial contraction. It correlates with
the P wave on an EKG.
• + c wave : This wave is caused by a slight elevation of the
tricuspid valve into the right atrium during early
ventricular contraction. It correlates with the end of the
QRS segment on an EKG.
• - x descent : This wave is probably caused by the
downward movement of the ventricle during systolic
contraction. It occurs before the T wave on an EKG.
Waveform Interpretation
• + v wave : This wave arises from the pressure
produced when the blood filling the right atrium
comes up against a closed tricuspid valve. It
occurs as the T wave is ending on an EKG.
• - y descent : This wave is produced by the
tricuspid valve opening in diastole with blood
flowing into the right ventricle. It occurs before
the P wave on an EKG.
Cannon “A” Waves
“A” Waveform Analysis
• Cannon Arterial Wave
• Cannon "a" waves are abnormalities in the a wave
that occur when right atrial contraction takes place
against a closed tricuspid valve
• Classically occurs in 3rd degree heart block or AV
• Unlike giant "a" waves, which are uniform in
height and are observed during each cardiac cycle,
cannon "a" waves are variable in height and occur
sporadically because of the variable relationship of
atrial contraction to ventricular systole.
Complications Central lines
• Early
– Hemorrhage
– Air embolus
– Pneumothorax
– Cardiac arrhythmias
– Pericardial tamponade
– Failed cannulation
• Late
– Venous thrombosis
– Infection
Infection Risks For Central Line
• 10% of central lines become colonized with bacteria
• 2% of patients in ICU develop catheter-related sepsis
• Usually due to coagulase-negative staphylococcus
• Occasionally due to Candida and Staph. aureus
• Infection can be prevented /lessened by aseptic
techniques and adequate care of lines
• Closed systems should be used at all times
• Dedicated lines should be used for parenteral nutrition
• Antimicrobial coating of lines may reduce the risk of
Break Time
10 minutes or so
BIS Monitoring
• Bispectral Monitoring by Aspect Medical
Systems is a non-invasive technology
• A BIS sensor is placed on your forehead and then
connected through a cable to a monitor.
• Together the sensor and monitor measures your
brain activity and then computes a number
between 0 and 100 which corresponds to your
level of consciousness.
• So What you say.
What is the BIS
• Through BIS technology, we may have a better
understanding of the human brain.
• The BIS technology measures the effects of drugs on the
brain; a previously unknown element of patient status.
• BIS technology is widely studied, and widely accepted,
and is supported by more than 2500 published studies.
More About the BIS
• The technology has been used on more than 15.2 million
patients around the world, and is utilized in more than
70% of the top-ranked US hospitals (according to a 2005
US News and World Report ranking).
• What's the Big Deal?
• It costs about 15 dollars per BIS strip. Is it worth it and
how does it help me?
Awareness Under Anesthesia
• Incidence and adverse outcomes of awareness with recall
in adults should be part of your post op assessment.
• Research demonstrates that awareness with recall occurs in
one to two patients per thousand receiving general
anesthesia. Historically in trauma and cardiac surgical
patients mostly.
• Prospective research shows that approximately 50% of
patients that experience awareness with recall suffer
psychological problems.
• The Joint Commission on Accreditation of Healthcare
Organizations (JCAHO) issued a Sentinel Event Alert on
preventing and managing the impact of anesthesia
Recent Article NEJM
• The New England Journal of Medicine published a study
that concludes that the Aspect Medical BIS Monitor is no
more effective than older products at preventing
anesthesia awareness.
• Really does it matter? I will say no because of all of the
other things the BIS monitor does.
Practice Guidelines
• The "Practice Advisory for Intraoperative Awareness and
Brain Function Monitoring" published in 2006 describes
using multiple monitoring modalities "clinical techniques,
conventional monitoring and brain function monitoring"
to assess anesthetic depth and reduce the likelihood of
intraoperative awareness. The Practice Advisory
consensus opinion was that "the decision to use a brain
function monitor should be made on a case-by-case basis
by the individual practitioner for selected patients."
Bottom Line with the BIS
• BIS can help clarify the distinction between brain and
spinal cord responses, enabling you to manage anesthetic
goals of hypnosis, analgesia and immobility
• Because BIS measures electrical activity in the brain, it
provides a direct correlation with depth of consciousness
• Responses to surgical stimulation are frequently indicators
of the need for additional analgesia. These responses are
often mediated at the spinal cord. What is MAC BAR?
• BIS enables you to assess consciousness and sedation
separately from cardiovascular reactivity
How it Works
• Raw EEG information is obtained via a sensor placed on
patient's forehead currently left or right brain monitoring.
• The BIS system processes the EEG information and
calculates a number between 0 and 100 that provides a
direct measure of the patient's level of consciousness
• A BIS value near 100 indicates the patient is fully awake.
I took a BIS reading off of a freshly pronounced body and
the BIS reading was 53!
• A BIS value of zero indicates the absence of brain activity
Drug Savings
• See References
• Less drug and less
overdosing of anesthesia.
• Sweet!
Faster Wake Ups
• BIS-monitored patients
wake up faster, are
extubated sooner, and are
more oriented upon
arrival to the PACU.
• Use of the BIS for wake
up is awesome!
PACU discharge time
• BIS-monitored patients
have been shown to be
eligible for PACU
discharge 16% sooner.
• I am on retainer at the
Aspect Medical Corp.
Just a little joke.
• Blitt CD, Hines HL. Monitoring in Anesthesia and
Critical Care Medicine. New York: Churchill
Livingstone, 1995.
• Costanzo, L. Board Review Series:
Physiology. Baltimore : Lipincott Williams and
Wilkins, 1998.
• Miller Anesthesia, 5th ed., Churchill Livingstone,
Inc, 2000.
• Mikhail M, Morgan GE, Murray MJ. Clinical
Anesthesiology, third edition. New York : McGraw Hill,
• Barish, P., et al. Clinical Anesthesia. Third ed.
• Lippencott, 1997. (626-629)
• Marino, D. The ICU Book. Second ed. New York:
LippincottWilliams & Wilkins, 1998. (143-153)
• Miller, R., et al. Anesthesia. Fourth ed, Vol.1. New York:
Churchill• Livingstone, 1994. (1166-1169)
• Morgan, G., et al. Clinical Anesthesiology. Third ed. San
Francisco:Lange, 2002. (91-97)
References Con’t
• New England Jounal Of Med, “Anesthesia Awareness and
the Bispectral Index” Volume 358:1097-1108
• Sandin R, Enlund G. Awareness during anesthesia: a
prospective case study. The Lancet 2000; Vol 355.
• Myles P, Williams D. Patient satisfaction after anaesthesia
and surgery: results of a prospective survey of 10,811
patients. British Journal of Anaesthesia 2000; 84 (1).
• Luginbuhl M, Schnider TW. Detection of awareness with
the Bispectral Index: two case reports. Anesthesiology
2002; 96 (1): 241-243.
More References
• Gan TJ, Glass PS, Windsor A, Payne F, Rosow C, Sebel
P, Manberg P, and the BIS Utility Study Group. Bispectral
Index monitoring allows faster emergence and improved
recovery from propofol, alfentanil, and nitrous oxide
anesthesia. Anesthesiology 1997; 87 (4): 808-815.
• Mayfield JB, Quigley JD. BIS monitoring reduces phase I
PACU admissions in an ambulatory surgical unit (ASU).
Anesthesiology 1999; 91 (3A): A28.
• Gan TJ, Glass PS, Windsor A, Payne F, Rosow C, Sebel
P, Manberg P, and the BIS Utility Study Group. Bispectral
Index monitoring allows faster emergence and improved
recovery from propofol, alfentanil, and nitrous oxide
anesthesia. Anesthesiology 1997; 87 (4): 808-815.