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

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

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

    2. Our Next Step:

    3. 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

    4. Oxygen Delivery (DO2)

    5. Failure of the Oxygen Delivery System = SHOCK! “momentary pause in the act of death” John Collins Warren, 1800’s “a rude unhinging of the machinery of life” Samuel Gross, 1872 “pushing back the edge of death” Mikhail, 1999

    6. Optimal DO2 = Aerobic Metabolism

    7. Suboptimal DO2 = Anaerobic Metabolism

    8. 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

    9. Oxygen Delivery: What are the components?

    10. Oxygen Delivery SIMPLIFIED = Engine = CO

    11. 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)

    12. 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?)

    13. Oxygen Delivery: Let’s break it down! DO2 = CO X CaO2 X 10 CaO2 = Normal = 20 mL O2/dL PaO2 SaO2 Hgb CO = HR Preload Afterload Contractility

    14. CaO2 Review: PaO2 2% of Oxygen dissolved in plasma Reflects the tension (pressure) exerted by O2 when dissolved in plasma Little value in a PaO2 > 90mmHg due to oxyhgb dissociation curve. Did you know??? If PaO2 were our body’s only source of oxygen, we would need a C.O. of 120 l/minute to support life!

    15. CaO2 Review: PaO2

    16. CaO2 Review: SO2 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.

    17. CaO2 Review: SpO2 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 <80%, accuracy for pulse ox ?’s Need SpO2 >96% to ensure SaO2 >=90% Why is my ABG Sat different than my monitor sat?? Besides OxyHgb, SpO2 also measures: Carboxyhemoglobin & Methemoglobin Masimo Radical 7 Co-oximeter

    18. CaO2 Review: HGB Theoretically, increasing Hgb would increase DO2 Hgb > =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 PRBC’s = ~ $500 Artificial Blood? ($7.6 billion in U.S.) (Sarkar, S. 2008)

    19. DO2 = CO X CaO2 X 10: Cardiac 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)

    20. DO2 = CO X CaO2 X 10:

    21. 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

    22. 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

    23. 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

    24. DO2 CO = Preload, Afterload, Contractility “Filling Pressures” AKA: “volume” (indirectly) Right Ventricular End Diastolic Volume Left Ventricular End Diastolic Volume Starling’s Law of the heart Effect of preload on CO…….

    25. Starling’s Law = “The Heart is a Demand Pump”

    26. Preload Measurements CVP Normal 2-6 mm Hg What is patient’s 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 > 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

    27. 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

    28. DO2 CO = 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

    29. DO2 CO = 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

    30. Got Contractility???

    31. Hemodynamic Monitoring: Impedance for Accuracy Transducer HOB Elevation PAC Zone Placement Respiratory Variation Waveform Interpretation SCD’S!

    32. 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 > or <2mmHg true value

    33. 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

    34. Hemodynamic Monitoring: Patient Position Measurements can be reliably measured with HOB @ 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

    35. 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.

    36. Hemodynamic Monitoring: Appropriate Catheter Placement

    37. Hemodynamic Monitoring: Appropriate Catheter Placement

    38. 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 > PAD likely that catheter tip in zones 1 or 2

    39. Hemodynamic Monitoring: Impedance for Accuracy Killu, et al (2007): 43 patients w/ PAC’s and SCD’s Findings: CO measurements consistently lower while SCD’s inflating Theory: cooler blood from lower limbs sent to PA during inflation of SCD’s causes a lower temp reading & therefore = lower CO reading

    40. Waveform Interpretation: Review of Research 3 Different Ways / One is most accurate! 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

    41. Hemodynamic Monitoring: Impedance for Accuracy

    42. 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.”

    43. 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.

    44. 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

    45. 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

    46. Esophageal Doppler Cardiac Output Monitoring:

    47. 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)

    48. Capnography: CO2 Measurement of Cardiac Output

    49. 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 >45 = hypoperfusion in tissue beds Limitations: Tube feeds

    50. 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

    51. BioZ ICG Monitor

    52. 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) > 10-15% = fluid responsive pt Limitations: Majority studies done on controlled MV patients, but newer data is out.

    53. 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 > 100 patients to be “proficient”

    54. USCOM Doppler

    55. DO2 Technologies: NICOM 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

    56. Oxygen Delivery: What if you don’t 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!

    57. Time for a DO2 Case Study…

    58. 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. What parameters are less than optimal? There was much concern about the patient’s low urine output. The PAWP of 14 was noted and the decision was made to administer fluids, hoping the urine output would improve. What parameters are less than optimal? There was much concern about the patient’s low urine output. The PAWP of 14 was noted and the decision was made to administer fluids, hoping the urine output would improve.

    59. 250cc Albumin was administered to increase urine output Note that the CO / CI and urine output is not significantly increased. The PAWP remained at 14 mmHg. The decision was made to administer more volume.Note that the CO / CI and urine output is not significantly increased. The PAWP remained at 14 mmHg. The decision was made to administer more volume.

    60. 250cc Albumin was repeated Following the additional volume administration, the urine output remained low and there were no significant changes in the hemodynamic parameters. There was a suggestion that an additional 250cc of Albumin be administered for the low urine output. Prior to additional volume administration, the RV parameters were plotted.Following the additional volume administration, the urine output remained low and there were no significant changes in the hemodynamic parameters. There was a suggestion that an additional 250cc of Albumin be administered for the low urine output. Prior to additional volume administration, the RV parameters were plotted.

    61. Frank-Starling Curve for this patient with SV & EDV Data Plotting this patients Frank-Starling Curve illustrates clearly what has happened. The improvement in stroke volume and decrease in end diastolic volume is indicative of the movement to a higher ventricular function.Plotting this patients Frank-Starling Curve illustrates clearly what has happened. The improvement in stroke volume and decrease in end diastolic volume is indicative of the movement to a higher ventricular function.

    62. Dobutamine 6 mcg/kg/min was started Following the initiation of inotropes, myocardial contractility was improved as evidenced by the increased CO/CI and RVEF. If the decreased RVEF had been assessed following the initial 250cc of Albumin, the clinicians might have considered initiating the inotrope sooner, resulting in improved myocardial performance, renal perfusion and urine output. Following the initiation of inotropes, myocardial contractility was improved as evidenced by the increased CO/CI and RVEF. If the decreased RVEF had been assessed following the initial 250cc of Albumin, the clinicians might have considered initiating the inotrope sooner, resulting in improved myocardial performance, renal perfusion and urine output.

    63. 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?

    64. Nursing Survivor???

    65. Even with an optimal DO2, your patient can still be in trouble….

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