Critical Care Monitoring Nuts and Bolts

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Critical Care Monitoring Nuts and Bolts

• Mike McEvoy, PhD, REMT-P, RN, CCRN
• Albany Medical Center, Albany, New York, USA
• Cardiothoracic Surgical ICU

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Mike McEvoy, PhD, RN, CCRN, REMT-P www.mikemcevoy.
com
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Disclosures

• I serve on the speakers bureaus for Masimo Corp.
  and Medtronic Corp.
• I have no other financial relationships to
  disclose.
• I am the EMS editor for Fire Engineering
  magazine.
• I do not intend to discuss any unlabeled or
  unapproved uses of drugs or products.

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Jones Bartlett, 2010
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Goals for this talk

• Objectives of hemodynamic monitoring
• Blood pressure measurement
• Art lines in practice
• Preventing complications
• Troubleshooting
• Treatment parameters/goals
• Non-invasive monitoring
• New technologies

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Goal of hemodynamic monitoring

• Assess tissue perfusion
• Oxygenation and distribution (flow)
• Others?
• Respirations
• Hydration
• Labs
• Chemistries
• Hematology
• Toxicology
• Microbiology

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3 types of shock

• Distributive (septic)
• Volume (hypovolemic)
• Pump (cardiogenic)

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Are physical findings enough?

• HR
• LOC
• BP
• UO

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Apparently not

• 50 of physical assessments wrong
• Therapeutic interventions altered with invasive
  assessment 34 - 56 of the time
• 1980 Del Guercio - 1984 Connors
• 1984 Eisenberg - 1990 Bailey
• 1991 Steinberg - 1993 Coles
• 1994 Minoz - 1998 Staudinger
• 2002 Jacka

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Lung Sounds in HF

• If rales were present, all had a wedge pressure
  gt18, very specific
• Only 9 of 37 with a wedge pressure gt18 had rales,
  very insensitive
• Soclear lung fields tell you very little about
  fluid status in heart failure

Butman et al. J Amer Coll Cardiol. 10/93
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So we dove right in

• Swan Ganz Catheterization

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Connors et al 1996 JAMA

• 5734 adult ICU patients 1989-1994, 5 ICUs at 15
  tertiary med centers
• PA cath ? 30 day mortality, ? ICU LOS, ? costs
  of care

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Harvey et al PAC-Man 2005 Lancet - Game Over?
1014 patients at 65 UK institutions NO
DIFFERENCE between PA cath versus no PA cath
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Cochrane R R 2006 (Review and Reappraisal)
The PAC is a monitoring tool if it is used to
direct therapy and there is no improvement in
outcome, then the therapy does not help.
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Two Problems

• Define normal
• Whos behind the wheel?

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Blood Pressure
BP CO x SVR
Indirect Pressure Measurement
Direct Pressure Measurement
A diastolic pressure of 60 is necessary to
maintain coronary artery perfusion.
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Why do we measure BP?

• Because we can.

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Purpose of blood pressure
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Biventricular CV System
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Arterial Pressure Monitoring
Direct ? Pressure
Indirect ? Flow
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Flow Measurements Not Accurate

• Low blood flow states
• High SVR states
• Avg 33.1 mmHg difference cuff vs. a-line
• Cuff consistently underestimates pressure
• - Cohn, JM (JAMA 199972, 1967)

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Flow measurements

• Pulses
• Cuff
• NIBP
• Doppler
• All sense pulsatile flow

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What We Know about Flow(Indirect Measurement)

• Pulses
• Carotid SBP gt 60
• Femoral SBP gt 70
• Radial SBP gt 80
• Cuff
• Errors in measurement r/t size and heart level
• NIBP
• Calculates systolic and diastolic based on MAP
  and HR
• Doppler
• PEA
• Flow based measurements are NOT accurate in low
  flow states or with high SVR, e.g. shock

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Avoid assumptions !

• BP ? blood flow
• levophed
• Blood flow ? perfusion
• O2 or nutrient deficiency

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Arterial Pressure Monitoring

• Indications
• Patient in shock not rapidly responsive to
  therapy
• Insertion Sites
• Radial
• Brachial
• Axillary
• Femoral
• Dorsalis Pedis

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Arterial Pressure Monitoring

• Radial artery has the benefit of collateral
  circulation from the ulnar artery
• Allen Test used to evaluate the collateral flow
  prior to radial artery cannulation

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A-line Monitoring Set-up
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Invasive Monitoring Equipment

• Flush solution -- usually heparinized
• Continuous flush system (usually a pressure bag
  or pump)
• Pressure transducer and pressure tubing
• Invasive catheter
• Monitor

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Transducers

• Convert one form of energy to another
• Sense pressure
• Convert it to an electrical signal
• Electrical signal causes monitor reading

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Leveling, Referencing, Balancing

• Placing the air-fluid interface of the catheter
  system at the phlebostatic axis
• This negates the weight effect of the fluid in
  the catheter tubing (hydrostatic pressure)
• Setting the correct reference point is the
  single most important step in setting up a
  pressure monitoring system. Gardner, 1993

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Leveling the 1 Cause of Error in Pressure
Monitoring
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Phlebostatic Axis

• Located at the intersection of the 4th ICS and
  midway between the anterior and posterior
  surfaces of the chest
• Midaxillary line is NOT interchangeable with mid
  anteroposterior level in all persons Bartz, et
  al, 1988

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Phlebostatic Axis
As the patient moves from flat to upright, the
phlebostatic level rotates on the axis and
remains horizontal. This position confirmed by
CT by Paolella, et al, 1988.
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Phlebostatic Axis
The phlebostatic axis moves to midchest at the
4th ICS when patient is in the lateral position.
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Leveling

• 1.86 mmHg per inch

• Air fluid interface is the point in the system
  that is opened to air during zeroing
• Inaccuracies are produced if the air-fluid
  interface is above or below the phlebostatic axis
  1.86 mmHg/inch
• Phlebostatic axis determined by Windsor and Burch
  (1945) as correct reference for measurement of
  venous pressures

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Give 500 ml of LR for CVP lt 5

• Transducer leveled 2 inches too high
• 1.86 mmHg/inch x 2 underestimation of actual
  CVP by 3.72 mmHg (Ooops!)
• Recorded CVP 3
• 500 cc bolus of LR given
• Actual CVP 7 (before LR bolus)

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Zeroing

• Opening the system to air to establish
  atmospheric pressure as zero (0)
• This negates all pressure contributions from the
  atmosphere
• Allows only pressure values that exist within the
  heart or vessel to be measured

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When to Zero

• Before insertion
• After disconnecting transducer from pressure
  cable
• When values are in question
• Ahrens, T. et al. Frequency requirements for
  zeroing transducers in hemodynamic monitoring,
  Am J Crit Care, 19954466-471

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Arterial Pressure Waveform

• Systole
• Dicrotic notch
• Diastole

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Placement of Arterial Line
150 90 60
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MAP
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Art Line Placement

• The farther out, the higher the SBP
• Cuff has no correlation
• Pressure vs. Flow
• Mean Pressure always consistent

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If BP increases, does flow increase?

• Think of levophed
• NOPE

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Preventing Complications with Arterial Lines
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Troubleshooting Common Arterial Line Problems

• Damping of waveform
• Causes
• Flush bag empty or pressure lt patient pressure
• Catheter tip against vessel wall
• Clot at catheter tip
• Air bubbles in system
• Kinked catheter or tubing

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Troubleshooting Common Arterial Line Problems

• Damping of waveform
• Interventions
• Keep flush bag at 300 mmHg
• Reposition extremity, use splint if necessary
• Gently aspirate clot, then flush line
• Clear system of air bubbles (limit to 1 stopcock)
• Remove kinks in tubing, check site, consider
  suturing catheter to skin

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Troubleshooting Common Arterial Line Problems

• Abnormally high/low readings
• Causes
• Transducer not level
• Hypertension/hypotension
• System error
• Interventions
• Re-level system
• Assess pressure with alternate means
• Determine and optimize system dynamic response

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Two Problems

• Define normal
• Whos behind the wheel?

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What is normal?

• Blood Pressure
• Bland, ShoemakerJ Surg Obst 1978 -
• 74 of survivors achieved normal values
• 76 of NON-SURVIVORS achieved normal vital signs

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Is it the car or the driver?

• If you dont know how to interpret the data, a
  monitoring catheter can be a dangerous weapon.

• If you dont know how to drive, a car can be a
  dangerous weapon.

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What we really treat
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Critical Information

• Oxygenation
• Perfusion

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Evaluating Perfusion

• Tools we have

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Lactate (Lactic Acid)

• Hypoperfusion severity index
• NL lt 2, concerned when gt 4
• gt 15 often fatal
• More helpful as trend

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POC Lactate Testing

• Developed for athletes climbers
• Not FDA approved
• Currently underinvestigation in EMSand Fire
  service

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SvO2

• Reflects O2 reserve extraction
• lt 60 requires investigation
• ? Hct, CO, SaO2
• ? VO2
• The lower the level, the worse
• lt 40 typically fatal

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ScvO2

• O2 reserve extraction upper body
• Typically 5 13 gt SvO2 (avg 7.5)
• NL gt 70
• Sampled from CVC (oximetric CVL available)

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Gastric Mucosal CO2

• Recent data suggest PgCO2 may reflect perfusion
• CO2 clearance reflects perfusion
• A-g CO2 gap lt 10 is normal
• Pa CO2 - PgCO2 gap gt 10 is bad

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Sublingual CO2 PslCO2

• Very proximal gut
• NL 44 64 mmHg
• ? levels correlate with ? perfusion
• Studies halted August 2004

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Nellcor Capnoprobe

• US approval Jan 2003.
• Research study Children's Medical Center
  Dallas TX.
• 11 kids infected Burkholderia cepacia, 2 died.
• Traced to saline solution packaging of probes.
• 5,600 units _at_ 30 centers recalled

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Capnography

• CO2 clearance reflects perfusion!
• Available for intubated and non-intubated
  patients
• Developmentscoming IPI

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Decision to Call the Code

• 120 prehospital patients in nontraumatic cardiac
  arrest
• EtCO2 had 90 sensitivity in predicting ROSC
• Maximal level of lt10mmHg during the first 20
  minutes after intubation was never associated
  with ROSC

Source Canitneau J. P. 1996. End-tidal carbon
dioxide during cardiopulmonary resuscitation in
humans presenting mostly with asystole, Critical
Care Medicine 24 791-796
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End-tidal CO2 (EtCO2)

• Normal a-A gradient
• 2-5mmHg difference between the EtCO2 and PaCO2
  in a patient with healthy lungs
• Wider differences found
• In abnormal perfusion and ventilation
• Incomplete alveolar emptying
• Poor sampling

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Future Developments

• Perfusion assessment derived from exhaled CO
  coupled with bioimpedance data.

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Integrated Pulmonary Index
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IPI Values fuzzy logic
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Acoustic Resp Monitoring

• Likely release 2010
• Electrical sensor based
• Initially will report RR
• Future versions VT
• Telemetry based
• May replace capnography?

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Esophageal doppler (TED)

• Transducer probe inserted into distal esophagus
• Blood flow measured by doppler principle

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TTE (Trans Thoracic Echo)

• Also nurse or medic driven
• Chest wall instead of esophageal

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TED/TTE
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Bioimpedance (TEB)

• Thoracic electrical bioimpedance
• 4 electrodes sent current through thorax, analyze
  flow resistance
• With age, gender, height, weight calculate SV,
  ejection time, CO, thoracic fluid content,
  acceleration index, velocity index, etc.

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TEB (CardioDynamics BioZ)
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RELIANT Non Invasive Hemodynamic Monitor
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CAPTURES (14 ) PARAMETERSIn Real Time
CO Cardiac Output CI Cardiac Index SV
Stoke Volume SVV Stroke Volume Variance
SVI Stroke Volume Index HR Heart
Rate TPR Total Peripheral Resistance VET
Ventricular Ejection Time MAP Mean Arterial
Pressure NIBP Non Invasive Blood Pressure TFC
Thoracic Fluid Content TFCd Directional
Change in TFC/Time CP Cardiac Power CPI
Cardiac Power Index
SVR MAP-CVP / CO
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100 NoninvasiveMonitors Any Patient, Anywhere
Current of a known amplitude frequency is
applied on outer electrodes
Voltage signal captured on inner electrodes
Change in phase of the frequency is recorded and
the signal translated to flow (similar to Doppler
in concept)
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0
0
I
I
I
I
II
II
II
II
Volts
Amp.

Bioimpedance
Vo
Io
Bioreactance
Io
Vo
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PASSIVE LEG RAISE TEST (PLRT)
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Problem Enough Volume?

• Volume expansion 1st line of therapy.
• Only ½ of patients respond to fluids with
  increased CO.
• Need a reliable means to determine ability to
  respond to fluid.

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PLR??

• 150 300 ml volume
• Effects lt 30 sec.. Not more than 4 minutes
• Self-volume challenge
• Reversible

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Ocular Scanner

• EyeMarker Systems

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Retinal imaging

• Pattern recognition
• Botulism, neurotoxins
• Nerve Agents
• Carbon Monoxide
• Cyanide

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Hydration Status

• Saliva osmolality

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Perfusion Index

• Perfusion Index is an objective method for
  measuring a patients peripheral perfusion
• Perfusion Index is an early indicator of
  deterioration

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Perfusion Index
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What is a Normal PI ?

• 108 healthy, 37 critically ill adults (finger
  sensors)
• PI range 0.3 to 10, median 1.4
• ROC used to determine the cutoff value
• 1.4 PI best discriminated normal from abnormal

Lima, et al. CCM 2002
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Clinical Uses for PI

• Normals have been suggested to be
• gt1.4 adults, gt1.27 neonates
• Site selection (varies between patients and
  sites)
• Chorioamnionitis (placental membrane/amniotic
  fluid infection)
• Effectiveness of Servoflorane anesthesia
• Monitor onset/effectiveness of epidural
  anesthesia
• Predict illness severity scores (good
  correlation)
• Monitor/quantify peripheral perfusion
• Detect shock states
• PI trend may best reflect changes in condition

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Photoplethysmography
R IR
Absorption
Pleth Waveform
Photodetector
Time
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Pleth Waveform
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A-line versus Pulse Ox Pleth
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Definition of PVI

• Pleth Variability Index (PVI) is a measure of
  dynamic changes in PI that occur during the
  respiratory cycle
• PVI is a percentage from 1 to 100 1 no
  variability and 100 maximum variability

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Fluid Status/Volume Responsiveness

• High variability (high PVI) volume depletion
• 15 50 of patients are fluid non-responders
  low variability (low PI) suggests the patient is
  a non-responder
• The ventricle more sensitive to respiratory
  changes is more responsive to preload

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Pulse CO-Oximetry
Oxygenated Hb and reduced Hb absorb different
amounts of Red (RD) and Infrared (IR) Light
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Pulse CO-Oximetry

• Carboxyhemoglobin
• Methemoglobin
• Hemoglobin
• ? Glucose
• ? Cyanide
• ?

Oxygenated Hb and reduced Hb absorb different
amounts of Red (RD) and Infrared (IR) Light
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Summary

• Perfusion is the goal
• Perfusion oxygenation flow
• You cannot do it alone
• Less invasive is better
• Technology should make you a better clinician
  (only as good as u)

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Thanks for your attention!