Synergy with Critical Care Assessment: Cellular Homeostasis, Oxygenation and Technology

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Synergy with Critical Care AssessmentCellular
Homeostasis, Oxygenation and Technology
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Our Next Step
ASSESS OXYGEN DELIVERY!
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Oxygen Delivery Objectives

• Discuss the role Oxygen Delivery plays in
  cellular homeostasis
• Identify discuss the main components of oxygen
  delivery and how we assess them
• Identify various technologies on the market used
  to measure oxygen delivery
• Case Study

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Oxygen Delivery (DO2)
Johnsons conceptual model of oxygenation,
Wagner, Johnson Kidd (2006)
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Failure of the Oxygen Delivery System SHOCK!

• momentary pause in the act of death
• John Collins Warren, 1800s
• a rude unhinging of the machinery of life
• Samuel Gross, 1872
• pushing back the edge of death Mikhail, 1999

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Optimal DO2 Aerobic Metabolism
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Suboptimal DO2 Anaerobic Metabolism
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Oxygen Delivery DO2

• Which tissues are most effected by ? DO2?
• Cardiomyocytes
• Neurons
• Kidney Liver (15-20 minutes)
• Less effected
• Skeletal muscle (60-90 minutes)
• Hair Nails? (Leach Treacher, 2002)
• Individual Organ DO2 measurement would be ideal
• Optimizing DO2 EARLY Better Outcomes

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Oxygen Delivery What are the components?
Oxygen Delivery DO2
Cardiac Output
CaO2
Stroke Volume
Heart Rate
PaO2
SaO2
Hgb
Preload
Afterload
Contractility
Synchrony
CVP PCWP
PVR SVR
EF
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Oxygen Delivery SIMPLIFIED

• Engine CO

Cargo Oxygen (4)
Cargo Cars Hemoglobin
Failure of any part of this train poor DO2.
What examples come to mind?
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Oxygen Delivery DO2

• DO2 is dependent on oxygen content (determines
  quality) in arterial blood (CaO2) CO
  (determines quantity)
• FICK Formula for DO2 DO2 CO X CaO2 X 10
• CaO2 (Hgb x 1.34 x SaO2) (PaO2 x .003)

Solubility coefficient for oxygen in plasma
ml of O2 that can be bound by 1 gm Hgb
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Oxygen Delivery DO2

• Simplified Formula
• D02 CO X (Hgb X 1.34 X Sa02) X 10
• (Notice that for practical purposes the PaO2 is
  removed?)
• Normal 700 1400 ml/min.
• How can we manipulate this? (Hint What are the
  three main components of the formula?)

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Oxygen Delivery Lets break it down!

• DO2
• CO X CaO2 X 10
• CaO2
• Normal 20 mL O2/dL
• PaO2
• SaO2
• Hgb
• CO
• HR
• Preload
• Afterload
• Contractility

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CaO2 ReviewPaO2

• 2 of Oxygen dissolved in plasma
• Reflects the tension (pressure) exerted by O2
  when dissolved in plasma
• Little value in a PaO2 gt 90mmHg due to oxyhgb
  dissociation curve.
• Did you know??? If PaO2 were
  our bodys only source of
  oxygen, we would need a C.O.
  of 120 l/minute to support life!

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CaO2 ReviewPaO2
Law Bukira (1999)
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CaO2 ReviewSO2

• Measurement of the amount of oxygen bound to Hgb
  98
• Hgb 4 iron-porphyrin groups (heme) attached to
  a protein (globin)
• Each heme molecule can carry one O2 molecule ( 4
  per Hgb)
• At rest, tissues only extract 25
• SpO2 How does it work? Red infrared light,
  absorbed by hgb and transmitted through
  photodetector. Amount type of light
  transmittted through tissue is converted to a
  digital value.

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CaO2 ReviewSpO2

• Several Technical Limitations very dependent
  upon good blood flow (pressors?), sickle cell
  crisis, temp, light
• Where is the best place for an SpO2?
• Clinical Alert SpO2 overestimates SaO2 (Sequin,
  et al, 2000)
• Once SaO2 falls lt80, accuracy for pulse ox ?s
• Need SpO2 gt96 to ensure SaO2 gt90
• Why is my ABG Sat different than my monitor sat??
  
• Besides OxyHgb, SpO2 also measures
  Carboxyhemoglobin
  Methemoglobin
• Masimo Radical 7 Co-oximeter

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CaO2 ReviewHGB

• Theoretically, increasing Hgb would increase DO2
• Hgb gt 10 g/dL increased blood viscosity can
  impair blood flow
• Increasing evidence of blood transfusions shows
  increased morbidity and mortality among open
  heart patients
• Will a transfusion immediately improve DO2?
• May take 18-24 hours to restore its 2,3 DPG An
  organic phosphate which alters affinity of Hgb
  for O2
• 1 Unit PRBCs 500
• Artificial Blood? (7.6 billion in U.S.) (Sarkar,
  S. 2008)

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DO2 CO X CaO2 X 10Cardiac Output

• The heart alone of all the viscera cannot
  withstand injury. This is to be expected because
  when the main source of strength is destroyed,
  there is no aid that can be brought to the other
  organs which depend on it. (Aristole 384BC
  322BC)

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DO2 CO X CaO2 X 10
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Oxygen Delivery

• Cardiac Output Our 1st Responder!
• Determined By
• Preload (CVP PAWP)
• Afterload (SVR PVR)
• Contractility (EF)
• Traditionally determined via PAC Thermodilution
  or CCO
• New Technologies
• Less Invasive
• Non-Invasive

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Cardiac Output/ Cardiac Index

• Cardiac Output Amount of blood ejected from
  heart in 1 minute.
• Normal 4-8L/Min
• Cardiac Index Amount of blood ejected from heart
  in 1 minute/ BSA
• Normal 2.5-4.5 L/Min

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Continuous Cardiac Output

• 10 cm Thermal filament lies b/t RA RV
• Heats .02 degrees C and cools Sending signals to
  thermister at tip of PAC
• Continuous Real Time
• Value updated q 3-6 minutes/ time averaged

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DO2CO Preload, Afterload, Contractility

• Filling Pressures
• AKA volume (indirectly)
• Right Ventricular End Diastolic Volume
• Left Ventricular End Diastolic Volume
• Starlings Law of the heart
• Effect of preload on CO.

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Starlings Law The Heart is a Demand Pump
Preload determines the force and efficiency of
systolic ejection. Factors influencing preload
1. Total blood volume. 2. Distribution of blood
volume (venous tone). 3. Atrial Kick.
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Preload Measurements

• CVP
• Normal 2-6 mm Hg
• What is patients goal?
• PAWP
• Normal 6-12
• Risks with wedging
• PAWP/ PAD Relationship
• PAD is generally to or within 4mm Hg higher
  than PAWP
• PAWP can NEVER physiol. be gt PAD!!!

• High Preload Causes
• Fluid Overload
• Heart failure
• Myocardial infarction
• Pericardial effusion or cardiac tamponade
• Low Preload Causes
• Absolute and Relative Hypovolemia
• Treatments
• Too Low?
• Fluids
• Blood if anemic
• Treat cause of fluid loss
• Too High?
• Diuretics
• Inotropes

What are we assuming here???
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Preload Measurements Is there more than CVP
Wedge??

• Pressure does not always volume
• Ventricular compliance is dynamic
• Volumetric parameters have been shown to reflect
  preload status more accurately (Cheatham, et al
  1998)

• RVEF PAC can offer
• SVO2
• Stroke volume 60 100ml
• End diastolic volume
• Normal RVEDV 100-160ml
• End systolic volume
• Normal RVESV 50-100ml
• RV ejection fraction
• 40 - 60
• Calculation of EF
• EF SV
• EDV

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DO2CO Preload, Afterload, Contractility

• Systemic vascular resistance
• SVR
• Resistance to ejection for left
  side of heart
• MAP- CVP/CO 80
• Normal 800-1200
• Pulmonary vascular resistance
• PVR
• Resistance to ejection from right side of heart
• Normal 50-250

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DO2CO Preload, Afterload, Contractility

• Defined as the ability to shorten and develop
  tension
• A calculated value
• Normal LVEF 60-70
• Calculated values estimate the work of the heart
  (i.e., LVSWI, EF)
• Echo, Nuclear Scan, RVEF PAC

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Got Contractility???
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Hemodynamic Monitoring Impedance for Accuracy

• Transducer
• HOB Elevation
• PAC Zone Placement
• Respiratory Variation
• Waveform Interpretation
• SCDS!

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Hemodynamic Monitoring Transducer 1Priority

• Does your transducer speak the same language as
  you? (translator)
• Level / Zero at 4th ICS, MAL
• For every inch the transducer is above/below the
  phlebostatic axis, the measurement is gt or lt2mmHg
  true value

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Hemodynamic Monitoring Square Wave Test

• How accurate is the system sensing pressure?
• Fast Flush square wave test
• Most frequent problem is empty flush bag or not
  pumped to 300mmHg

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Hemodynamic Monitoring Patient Position

• Measurements can be reliably measured with HOB _at_
  0 - 60 with patient supine (AACN 7 studies)
• Measurements should be avoided in any side lying
  position
• Allow 5 minutes b/t changes in position

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Hemodynamic Monitoring Respiratory
Influences

• Intrathoracic pressures changes are transmitted
  to the pulmonary vasculature and affect blood
  flow.
• Spontaneous Breathing Decreases intrathoracic
  pressure. Take reading at top (Peak for patient)
  just before inspiratory dip.
• Positive pressure ventilation Increases
  pressures. Take reading in valley of wave (Valley
  for vented) just before the upstroke.

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Hemodynamic Monitoring Appropriate Catheter
Placement
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Hemodynamic Monitoring Appropriate Catheter
Placement
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Hemodynamic Monitoring Appropriate Catheter
Placement

• Tip of catheter must be positioned below the
  level of the LA/ Lung Zone 3
• In zone 3 arterial and venous pressures will
  exceed alveolar pressures accurate PAWP

• Placement in zones 1 2 false high PAWP
• Lateral CXR is best way to confirm ( but is this
  realistic???)
• If PAWP gt PAD likely that catheter tip in zones 1
  or 2

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Hemodynamic Monitoring Impedance for Accuracy

• Killu, et al (2007)
• 43 patients w/ PACs and SCDs
• Findings CO measurements consistently lower
  while SCDs inflating
• Theory cooler blood from lower limbs sent to PA
  during inflation of SCDs causes a lower temp
  reading therefore lower CO reading

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Waveform Interpretation Review of Research

• 1. Digital display from monitor (most common
  least accurate)
• 2. Freeze framing respiratory pattern with wedge
  (cursor)
• 3. Graphic strip recording of ECG CVP/ Wedge
  Most accurate

• 3 Different Ways / One is most accurate!

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Hemodynamic Monitoring Impedance for Accuracy
Studies evaluating physician and nursing
knowledge of HD waveform interpretations are
TROUBLING!
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Hemodynamic Monitoring Impedance for Accuracy

• AACN (1998)
• These findings suggest that knowledge clinical
  competence in HD monitoring may be inadequate to
  ensure patient safety quality patient care
• Zellinger (1995)
• Found a 30 incidence of technical errors with
  PAWP readings. Errors were due to incorrect
  catheter transducer placement, incorrect
  zoning/ referencing, and pressure
  over/underdampening
• AACN, SCCM, ACCP, ATS (1997)
• Efforts must be taken to assure that this
  monitoring technology is being applied correctly
  and that effective QI programs r/t PAC are in
  place.

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And the beat goes on..

• Last several years of research and technology has
  been focused on the invention of less
  non-invasive hemodynamic monitoring capabilities.

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DO2 Technologies

• RVEF PAC Continuous end-diastolic volume
• measures RVED volumes and offers an improved
  assessment of preload recruitable CO
• provides continuous EF, SV, SVO2 (EF drops
  before any other clinical s/s)
• Technology Uses ECG in correlation w/
  beat-to-beat changes in temperature that occur
  b/t contractions of the heart.
• Limitations Uses with heart failure patients?
  (RVEF vs LVEF), Inaccurate with ectopy and high
  HR

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DO2 Technologies

• Esophageal Doppler Cardiac Output Monitoring
• NG tube type probe inserted into esophagus 40cm
  aligned to measure aortic blood flow
• Measures SV and HR adjusted CO, Flow Time and
  Peak Velocity
• Simple less invasive
• Usually requires patient sedation
• Cannot be used with esophageal varices

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Esophageal Doppler Cardiac Output Monitoring
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DO2 Technologies

• Capnography CO2 Measurement of Cardiac Output
• Completely non-invasive
• Rebreathing circuit attached to vent
• Assesses the change in exhaled CO2 during
  rebreathing and normal breathing (PetCO2)
• Uses modified Fick Equation
• Concept The amount of a substance taken up or
  produced by an organ is the product of the flow
  of blood through the organ
• Limitations need a controlled ventilated patient
  (OR), Only measures blood flow that participates
  in gas exchange (QS/QT)

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Capnography CO2 Measurement of Cardiac Output
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DO2 Technologies

• Gastric Tonometry
• Principle Gut is referred to as canary of the
  body. Responds to subtle perfusion deficits.
• Modified NG tube w/ gas permeable balloon at end
• CO2 diffuses from mucosal layer of stomach into
  balloon
• Gives values every 10 minutes
• Value gt45 hypoperfusion in tissue beds
• Limitations Tube feeds

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DO2 Technologies

• Bioimpedance Cardiography
• Non-invasive, Electrodes placed on jugulars,
  chest
• Uses a low-amplitude, high frequency alternating
  signal to calculate impedance of the flow of
  electricity through the chest.
• Derives parameters CO, CI, SV, SVR (calculated
  with pts MAP CVP)
• Limitations Pts must be very still, no ectopy,
  strong signals

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BioZ ICG Monitor
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DO2 Technologies

• Arterial Pressure-Based CO (APCO)
• Attaches to A-Line
• Takes age, sex, BSA into account
• Assesses pulse pressure (SBP DBP) variations to
  determine SV
• HR X SV CO
• Stroke Volume Variation (pulses paradoxus) gt
  10-15 fluid responsive pt
• Limitations Majority studies done on controlled
  MV patients, but newer data is out.

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DO2 Technologies Doppler

• Ultrasound device
• Measures blood flow across Aortic
  and Mitral Valves
• Beat-to-beat CO and SV measurements
• Simple to use/ portable
• Data available 2 - 6 minutes
• Need gt 100 patients to be proficient

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USCOM Doppler
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DO2 TechnologiesNICOM Noninvasive CO Monitor

• Uses chest Bioimpedance Bioreactance
  technology (an analysis of frequency related
  effects greater noise elimination)
• Measurements include CO, CI, SV, SVV, SVI,
  Thoracic Fluid Content, NIBP
• Advantages Studied on pts at rest as well as
  exercising

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Oxygen Delivery What if you dont have fancy
equipment?? Can be challenging.

• LOC
• Skin color
• Peripheral Edema (lbs?)
• Capillary refill (children maybe, elderly - no)
• Heart Rate BP (Late)
• Skin Temperature (Late)
• Urine Output (Late)
• Ultimately we must monitor oxygenation end points
  to determine if our delivery is sufficient!

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Time for a DO2 Case Study
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80 y/o male admitted to the ICU post-op CABG to
LAD, Circumflex and RCA. Currently the patient is
receiving sodium nitroprusside and nitroglycerin.
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250cc Albumin was administered to increase urine
output
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250cc Albumin was repeated
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Frank-Starling Curve for this patient with SV
EDV Data
EF 30 10pm
Stroke Volume
EF 24 9pm
EF31 8pm
EF 38 7pm
EDV
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Dobutamine 6 mcg/kg/min was started
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DO2 Questions to ask yourself

• Is the DO2 meeting the patient needs at this time
  (global as well as regional)?
• Is the DO2 occurring with adequate perfusion
  pressure?
• Is the patient able to use the oxygen being
  delivered?
• If you answer no, then what interventions are
  needed?

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Nursing Survivor???
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Even with an optimal DO2, your patient can still
be in trouble.
We can lead a horseto water, but
After lunch Oxygen Consumption