Temporal order of events (each event can take minutes to hours)
Bioimpedance: Paid about $40; PAC: about $100; EDM: about $250 Pulse contour: reimbursed for a line only, not SV optimization
Typically, the optimal signal is obtained when the probe is placed in the esophagus, level with or just below the heart.
Here are typical normal ranges for selected parameters: Flow Time corrected or FTc is typically between 330 and 360 milliseconds Peak Velocity or PV varies with age. At age 20 it is 120 cm/sec, falling to 100 by age 50 and to 80 by age 70. Mean Acceleration or MA varies with contractility and varies from patient to patient Stroke Distance or SD varies from patient to patient
The Art & Science ofHemodynamic Monitoring Tom Ahrens DNS RN CCNS FAAN Research Scientist Barnes-Jewish Hospital email@example.com 1
Science works within an established paradigm: a set of rules that govern the definition of terms, thecollection of data and the boundaries of inquiry. But over time, anomalies appear inside the paradigm,data that can’t be explained, questions that can’t be answered using the tools of the existing model. As new methods and tools are introduced that explore outside the boundaries of the existing view, the old paradigm collapses Thomas Kuhn The Structure of Scientific Revolutions 2
Can’t I look at my patient and tell if they are OK?NO! Physical Assessment is often inaccurate, slow to change and difficult to interpret 3
Are Physical Signs Early or Late Indicators of Clinical Status? LV dysfunction BP Hypovolemia HR Sepsis LOC Urine output
References – Inaccuracies of Physical Assessment• Connors AF Jr, Dawson NV, Shaw PK, Montenegro HD, Nara AR, Martin L. Hemodynamic status in critically ill patients with and without acute heart disease. Chest. 1990 Nov;98(5):1200-6.• Dawson NV, Connors AF Jr, Speroff T, Kemka A, Shaw P, Arkes HR. Hemodynamic assessment in managing the critically ill: is physician confidence warranted? Med Decis Making. 1993 Jul-Sep;13(3):258-66.• Eisenberg PR, Jaffe AS, Schuster DP. Clinical evaluation compared to pulmonary artery catheterization in the hemodynamic assessment of critically ill patients. Crit Care Med. 1984 Jul;12(7):549-53.• Iregui MG, Prentice D, Sherman G, Schallom L, Sona C, Kollef MH. Physicians estimates of cardiac index and intravascular volume based on clinical assessment versus transesophageal Doppler measurements obtained by critical care nurses. Am J Crit Care. 2003 Jul;12(4):336-42.• Neath SX, Lazio L, Guss DA. Utility of impedance cardiography to improve physician estimation of hemodynamic parameters in the emergency department. Congest Heart Fail. 2005 Jan-Feb;11(1):17-20.• Staudinger T, Locker GJ, Laczika K, et al. Diagnostic validity of pulmonary artery catheterization for residents at an intensive care unit. J Trauma. 1998 May;44(5):902- 6. 5
Does CVP and PAOP tell us about blood volume and flow? • CVP and PAOP should never be used in isolation – Inconsistent in revealing information about volume and flow • Flow and pressure do not always correlate – Marik et al. Based on the results of our systematic review, we believe that CVP should no longer be routinely measured in the ICU, operating room, or emergency department.Marik P, Baram M, Vahid B. Does central venous pressure predict fluid responsiveness?A Systematic Review ofthe Literature and the Tale of Seven Mares. Chest 2008;134;172-178 6
BP Measurement - Useful or Misleading?• Is BP is measured because it can be measured• If BP increases, does blood flow increase? – think of use of levophed• Blalock 1943, says: “It is well known by those interested in this subject that the blood volume and cardiac output are usually diminished in traumatic shock before the arterial blood pressure declines significantly” Blalock A, (1943) Surgery 14: 487-508 7
Blood Pressure and Blood Flow Do they equal each other? 8
BP = CO x SVR• CO = Stroke volume x heart rate – decrease in SV causes increase in heart rate – decrease in CO causes increase in SVR• Compensatory changes keep the BP close to normal initially in shock states• BP does not change until late due to these compensatory responses 9
Temporal order of events (each event can take minutes to hours)• Stroke volume falls • Heart rate compensates to keep cardiac output normal – Many reasons for heart rate to increase• Cardiac output falls • Heart rate compensation fails • Vasoconstriction (increase in SVR), BP remains unchanged• Increased oxygen extraction of hemoglobin • Peripheral initially (StO2) • Central later (ScvO2) 10• Blood pressure, urine output change
Moving toward Blood Flow Measurement Stroke Volume as an End point Stroke volume normal values Stroke volume variation 11
Evidence (10 RCTs) of Using SV as• Endpoint Chytra I, Pradl R, Bosman R, Pelnar P, Kasal, Zidkova A. Esophageal Doppler-guided fluid management decreases blood lactate levels in multiple-trauma patients: a randomized controlled trial. Critical Care 2007 Feb 22;11(1):1-9.• Conway DH, Mayall R, Abdul-Latif MS, Gilligan S, Tackaberry C. Randomized controlled trial investigating the influence of intravenous fluid titration using esophageal Doppler monitoring during bowel surgery. Anesthesia 2002 Sept;57(9):845-849.• Gan TJ, Soppitt A, Maroof M, El-Moalem H, Robertson K, Moretti E, Dwane P, Glass PS. Goal-directed intra-operative fluid administration reduces length of hospital stay after major surgery. Anesthesiology 2002;97:820-826.• Mark JB, Steinbrook RA, Gugino LD, et al. Continuous noninvasive monitoring of cardiac output with esophageal Doppler during cardiac surgery. Anesth Anlg 1986;61:1013-1020.• McKendry M, McGloin H, Saberi D, Caudwell L, Brady AR, Singer M. Randomized controlled trial assessing the impact of a nurse delivered, flow monitored protocol for optimization of circulatory status after cardiac surgery. BMJ 2004;329(7460):258 (31 July), doi:10.1136/bmj.38156.767118.7C.• Mythen MG, Webb AR. Peri-operative plasma volume expansion reduces the incidence of gut mucosal hypoperfusion during cardiac surgery. Archives of Surgery 1995;130:423-429.• Sinclair S, James S, Singer M. Intraoperative intravascular volume optimization and length of hospital stay after repair of proximal femoral fracture: randomized controlled trial. BMJ 1997 October 11;315:909-912.• Valtier B, Cholley BP, Belot JP, Coussay JE, Mateo J, Payen DM. Noninvasive monitoring of cardiac output in critically ill patients using transesophageal Doppler. Am J Respir Crit Care Med. 1998;158:77-83.• Venn R, Steele A, Richardson P, Poloniecki J, Grounds M, Newman P. Randomized controlled trial to investigate influence of the fluid challenge on duration of hospital stay and perioperative morbidity in patients with hip fractures. British Journal of Anesthesia 2002;88:65-71.• Wakeling HG, McFall MR, Jenkins CS, Woods WGA, Miles WFA, Barclay GR, Fleming SC. Intraoperative esophageal Doppler guided fluid management shortens postoperative hospital stay after major bowel surgery. Br J Anaesth. 2005 Nov;95(5):634- 12 42.
IX. CMS Conclusion – May 2007• CMS was asked to reconsider our current national coverage determination (NCD) on ultrasound diagnostic procedures. CMS has determined that there is sufficient evidence to conclude that esophageal Doppler monitoring of cardiac output for ventilated patients in the ICU and operative patients with a need for intra- operative fluid optimization is reasonable and necessary under Section 1862(a)(1)(A) of the Social Security Act and therefore, we are removing the past non-coverage of cardiac output Doppler monitoring.• CMS will amend the NCD Ultrasound Diagnostic Procedures at section 220.5 of the NCD manual by adding “Monitoring of cardiac output (Esophageal Doppler) for ventilated patients in the ICU and operative patients with a need for intra-operative fluid optimization” to Category I, and deleting “Monitoring of cardiac output (Doppler)” from Category 13
SV Optimization for Fld AdministrationIf SV/SI or FTc is low Give 200 ml of colloid Or 500 ml of crystalloid Is the heart Pumping enough Blood? YES NO (SI increased < 10%) (SI increased > 10%) Stop giving fluids Monitor SI as indicated If SV/SI decreased >10% 14
SV Optimization for Ht Failure If SV/SI or PV is low Give preload reducer, afterload reducer or inotrope Is the heart Pumping enough Blood? YES NO (SI increased < 10%) (SI increased > 10%) Stop treatment Monitor SI as indicated If SV/SI decreased >10% 15
Moving TowardBlood Flow Measurement SV as an End point SV normal values SV variation 16
Why are we Not measuring SV?Is it because we don’t have a way to measure SV? 17
Methods of Measuring SV Uses Ease of use Accuracy Professional Reimbursemen tDoppler - USCOM Anywhere Good Good -Doppler (EDM) OR, ICU Excellent Excellent $$$ECON OR, ICU Good Fair -Bioimpedance Anywhere Good Fair $Pulse contour OR, ICU Difficult Fair -(FloTrac, LiddCo,PICCO)NICO OR, ICU Difficult Fair -PAC OR, ICU Difficult Good $$Bioreactance OR, ICU Good Good $ 18
Common Measures of Blood Flow• Cheap (<$5/pt) • $175/pt – physician • $10/pt (initial cost is capital• Research shows that is reimbursed >$100-$400/pt purchase) frequently inaccurate and • Accurate • Accurate slow to reflect patient • 10 RCT’s showing use can • Can be used on almost changes reduce LOS (save hospital anyone• No evidence it changes 4X cost of the device) • OR, ICU, ED, floors, RRT, patient outcome • Used on sedated patients paramedics, MD office• Easy to use only • Uses same principle as the • OR, ICU, PAR above RCT’s showing • Gives continuous readings • No MD reimbursement • Easy to use • Gives intermittent readings Pulse Contour Esophageal Doppler Non invasive Doppler
Use of Blood Flow Techniques• All methods have strengths and limitations• Many acute and critical care patients can have these techniques used• All can be used within limitations• Use oxygenation end points to validate information regarding blood flow 20
Which Technique is Best? Arguable – but the one with the mostevidence is clear – esophageal doppler 21
Placement• S: Is the sound on?• H: Is the HR correlating?• A: Are the arrows displaying the beginning and the end of systole?• G: Is the green triangle not notched?Prentice D, Sona C. Esophageal doppler for hemodynamic measurement 28Crit Care Nurs Clin North Am. 2006 Jun;18(2):189-93,
Normal Ranges• SV: How much blood is pumped with each beat Normal: 50-120 ml/beat• SI: How much referenced against body size Normal: 25-50 ml/m2• SD: The distance that blood flows in a specific time period (This is the most accurate). Normal: > 10; Hypovolemia: <10*Normals are just reference points. The real test is whether or not they change if fluid is given. 32
Esophageal Doppler Variables Normal Ranges FTc: Flow Time corrected 330 - 360 milliseconds The time of systolic flow corrected to heart rate. 20 yrs: 90 - 120 cm/sec PV: Peak Velocity 50 yrs: 60 - 90 cm/sec The velocity of the blood measured at the peak of 70 yrs: 50 - 80 cm/sec systole.NOTE: Normal Ranges should not be confused with a Physiological Target. 33
• After induction, FTc of 323ms, (low) indicated possible hypovolemia.• SV of 77 ml was reasonable; however, HR of 60 gives a cardiac index (CI) of 2.3 l/m/m2.• 200ml of colloid was given.• SV increased >10%, suggesting more colloids be given to optimize the intravascular volume.
• After 2nd bolus, SV increased by 14 ml (19%) and FTc also increased.• CI increased from 2.3 to 2.7 l/min/m2• Indicated more fluid could be given to optimize SV.• More colloid given in accordance with the SV optimization algorithm until SV increases were less than 10%.
Treatment GuidelinesDetermine success of fluid or inotropic therapy byThe response in stroke volume/index and SvO2 Stroke Volume ∆ 0% ∆ < 10% ∆ > 10% End-Diastolic Volume 36
Acceptance of Non Invasive Technology Who is being harmed by our current practices? We must have a sense of urgency 37