HEMODYNAMICS

© 2018 Mark Tuttle

INDICATIONS FOR RIGHT HEART CATHETERIZATION  ⇒ No evidence-based, validated indication exists for the use of a pulmonary artery catheter. However, many of the studies that failed to find a benefit with PA catheters are not generalizable to the patients in which we perform them. ● Heart failure​ ​(AHA 2013)1​ ○ Respiratory distress/↓ perfusion + clinical exam inconclusive re: congestion (Class I) ○ Persistent symptoms despite standard therapies (Class IIa), and: ■ Uncertain fluid status, perfusion, SVR, PVR ■ Renal function worsening with therapy ■ Requiring vasoactive agents, or ■ May need mechanical support or transplantation ⇒ ESCAPE trial​2​: No effect on mortality vs usual care. ​Caveat​: not all patients required inotropes. ⇒ SUPPORT study​3​: Increased mortality in ICU patients with RHC. ​Caveat​: Observational study. ● One of the sites was Beth Israel Hospital   NORMAL VALUES  RA  RV  PA  PCWP  CO  CI  SVR  PVR  5 Normal 0-5 15-30/1-12 15-30/6-12 6-12 4-7 L/min 2.6-4.2 800-1200 dyn·s·cm​ 40-150 dyn·s·cm​5 For ease, use “Rule of 5s” to remember: RA 5, RV 25/5, PA 25/10, PCWP 10.   Hemodynamic values from healthy subjects​4  PAs  PAd  PAm  PCWP  HR  CO  CI  PVR  SVR​5  20.8±3.3 8.8±3.0 14.0±3.3 8.0±2.9 76±14 7.3±2.3 L/in 4.1±1.3 74±30 dyn·s·cm​5 1170±270 dyn·s·cm​5   CARDIAC OUTPUT  ● Fick’s Principle: ​Fick’s principle states that the total uptake or release of a substance by an organ is the product of the blood flow to the organ and the arteriovenous concentration difference of the substance. V O2 125 ml/min/m2 ×BSA ○ Fick Equation C O = CaO −CvO = (SpO −SmvO ) × Hgb × 1.36 × 10 2

2

2

2

■ Body surface area​6​= (weight[kg]* 0.425 x height[cm] 0.725) x 0.007184 ■ O​2​ consumption can also be estimated by 3ml O​2​/kg ○ Pitfalls​5​: ■ Oxygen consumption is usually assumed and not measured (but it can be measured with a mask) and can vary significantly in critically ill patients ■ Invalid if inappropriate sampling (high right atrium, low right atrium, distal PA in partial wedge) ■ High-output states with narrow AV O2 difference ● Thermodilution​: Integral (area under the curve) of temperature vs. time. Higher CO causes more rapid temp change. ○ Low CO: large AUC. High CO: small AUC ○ Cold saline injected into proximal port and measured at the tip in the PA ■ Better to use cold saline rather than room temperature since it improves signal:noise ratio ○ Compared to estimated Fick, thermodilution better predicts mortality​7 ○ Pitfalls​5​: ■ Tricuspid regurgitation (indicator abnormally recirculated) ■ Intracardiac shunt (indicator abnormally recirculated) ■ Low output states (may overestimate CO since saline warmed by chamber walls rather than blood) ● Error up to 35% when cardiac output < 2.5 L/minute ■ Atrial fibrillation (incomplete mixing of indicator with atrial stasis) ■ Simultaneous administration of IV fluids RESISTANCE ● Calculations involve physiology analogous to Ohm’s Law (V=IR). The potential energy (voltage, or pressure difference in a hemodynamic circuit) is equal to current (or blood flow [cardiac output]) multiplied by resistance. ○ In this case ΔP = CO x Resistance; rearranging to Resistance = ΔP/CO ○ For pulmonary vascular resistance, PVR = (PA​mean​-PCWP)/CO. Multiply by 80 for dyn·s·cm​5​.

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HEMODYNAMICS ○

© 2018 Mark Tuttle

For systemic vascular resistance, SVR = (MAP-CVP)/CO. Multiply by 80 for dyn·s·cm​5​.

  RIGHT ATRIAL PRESSURE TRACING  ● a wave​: atrial contraction; follows P wave by ~80ms on RA trace (during PR interval) and ~240ms on PCWP trace (after QRS). ○ Absent in atrial fibrillation ● c wave​: ​may occur ​as displacement of AV valves into atria during early ventricular contraction. ● x descent​: atrial relaxation and downward motion of AV junction (tricuspid valve). ● v wave​: passive atrial filling in ventricular systole when MV and TV are closed; near end of the T wave. ● y descent​: rapid atrial emptying following opening of the MV and TV.

DETECTION OF INTRACARDIAC SHUNT Left-to-right Shunt Detection of left-to-right Shunt by Oximetry​5  Level of Shunt  Atrial (SVC/IVC to RA)  ● Mean step-up of SpO​2​ to distal chamber samples: ≥ 7% ● Minimal Q​p​:Q​s​ required for detection: 1.5-1.9

Ventricular (RA to RV)  ● Mean step-up of SpO​2​ to distal chamber samples: ≥ 5% ● Minimal Q​p​:Q​s​ required for detection: 1.3-1.5

Possible Causes  ● Atrial septal defect ● Partial anomalous PV return ● Ruptured sinus of Valsalva ● VSD with TR ● Coronary fistula to RA ● VSD ● PDA with PR ● Primum ASD ● Coronary fistula to RV ● PDA ● Aorta-pulmonic window ● Aberrant coronary artery origin ● All of the above

Great Vessel (RV to PA)  ● Mean step-up of SpO​2​ to distal chamber samples: ≥ 5% ● Minimal Q​p​:Q​s​ required for detection: ≥ 1.3 Any Level (SVC to PA)  ● Mean step-up of SpO​2​ to distal chamber samples: ≥ 7% ● Minimal Q​p​:Q​s​ required for detection: ≥ 1.5 ● Based on original experiments from BWH by Dexter and colleagues​8 SOURCES 1.

2.

3. 4. 5. 6.

Yancy CW, Jessup M, Bozkurt B, Butler J, Casey DE Jr, Drazner MH, Fonarow GC, Geraci SA, Horwich T, Januzzi JL, Others: WRITING COMMITTEE MEMBERS; American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines. 2013 ACCF/AHA guideline for the management of heart failure: a report of the American College of Cardiology Foundation/American Heart Association Task Force on practice guidelines. Circulation 2013; 128:e240–e327. Binanay C, Califf RM, Hasselblad V, O’Connor CM, Shah MR, Sopko G, Stevenson LW, Francis GS, Leier CV, Miller LW, ESCAPE Investigators and ESCAPE Study Coordinators: Evaluation study of congestive heart failure and pulmonary artery catheterization effectiveness: the ESCAPE trial. JAMA 2005; 294:1625–1633. Connors AF Jr, Speroff T, Dawson NV, et al.: The effectiveness of right heart catheterization in the initial care of critically ill patients. SUPPORT Investigators. JAMA 1996; 276:889–897. Kovacs G, Berghold A, Scheidl S, Olschewski H: Pulmonary arterial pressure during rest and exercise in healthy subjects: a systematic review. Eur Respir J 2009; 34:888–894. Moscucci M: Grossman & Baim’s Cardiac Catheterization, Angiography, and Intervention. Lippincott Williams & Wilkins, 2013,. Du BOIS D, Du BOIS EF: CLINICAL CALORIMETRY: TENTH PAPER A FORMULA TO ESTIMATE THE APPROXIMATE

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HEMODYNAMICS 7.

8.

© 2018 Mark Tuttle

SURFACE AREA IF HEIGHT AND WEIGHT BE KNOWN. Arch Intern Med American Medical Association, 1916; XVII:863–871. Opotowsky AR, Hess E, Maron BA, et al.: Thermodilution vs Estimated Fick Cardiac Output Measurement in Clinical Practice: An Analysis of Mortality From the Veterans Affairs Clinical Assessment, Reporting, and Tracking (VA CART) Program and Vanderbilt University. JAMA Cardiol 2017; 2:1090–1099. Dexter L, Haynes FW: Studies of congenital heart disease; the pressure and oxygen content of blood in the right auricle, right ventricle, and pulmonary artery in control patients, with observations on the oxygen saturation and source of pulmonary capillary blood. J Clin Invest 1947; 26:554–560.

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HEMODYNAMICS MarkTuttleMD.com

​Caveat​: not all patients required inotropes. ⇒ SUPPORT study​3​: Increased mortality in ICU patients with RHC. ​Caveat​: Observational study. ○ One of ...

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