Critical Care Monitoring Nuts and Bolts

1. Critical Care Monitoring Nuts and Bolts Mike McEvoy, PhD, REMT-P, RN, CCRN Albany Medical Center, Albany, New York, USA Cardiothoracic Surgical ICU

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

4. 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.

5. Jones & Bartlett, 2010

6. 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

7. Goal of hemodynamic monitoring • Assess tissue perfusion • Oxygenation and distribution (flow) • Others? • Respirations • Hydration • Labs: • Chemistries • Hematology • Toxicology • Microbiology

8. 3 types of shock: • Distributive (septic) • Volume (hypovolemic) • Pump (cardiogenic)

9. Are physical findings enough? • HR • LOC • BP • UO

10. 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

11. Lung Sounds in HF • If rales were present, all had a wedge pressure >18, very specific • Only 9 of 37 with a wedge pressure >18 had rales, very insensitive • So…clear lung fields tell you very little about fluid status in heart failure Butman et al. J Amer Coll Cardiol. 10/93

12. So we dove right in… Swan Ganz Catheterization

13. 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

14. Harvey et al: PAC-Man 2005 Lancet - Game Over? 1014 patients at 65 UK institutions: NO DIFFERENCE between PA cath versus no PA cath

16. 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.”

17. Two Problems: • Define “normal” • Who’s behind the wheel?

18. Blood Pressure BP = CO x SVR Indirect Pressure Measurement Direct Pressure Measurement ** A diastolic pressure of 60 is necessary to maintain coronary artery perfusion.

19. Why do we measure BP? • Because we can.

20. Purpose of blood pressure

21. Biventricular CV System

24. Arterial Pressure Monitoring Direct  Pressure Indirect  Flow

25. 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 199:972, 1967)

26. Flow measurements • Pulses • Cuff • NIBP • Doppler All sense pulsatile flow

27. What We Know about Flow(Indirect Measurement) • Pulses: • Carotid = SBP > 60 • Femoral = SBP > 70 • Radial = SBP > 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

28. Avoid assumptions ! • BP ≠ blood flow levophed… • Blood flow ≠ perfusion O2 or nutrient deficiency…

29. Arterial Pressure Monitoring • Indications • Patient in shock not rapidly responsive to therapy • Insertion Sites • Radial • Brachial • Axillary • Femoral • Dorsalis Pedis

30. 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

31. A-line Monitoring Set-up

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

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

34. 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

35. Leveling: the # 1 Cause of Error in Pressure Monitoring

36. 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

37. 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.

38. Phlebostatic Axis The phlebostatic axis moves to midchest at the 4th ICS when patient is in the lateral position.

39. 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

40. Give 500 ml of LR for CVP < 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)

41. 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

42. 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, 1995;4:466-471

43. ArterialPressureWaveform • Systole • Dicrotic notch • Diastole

45. Placement of Arterial Line 150 90 60

46. MAP

47. Art Line Placement: • The farther out, the higher the SBP • Cuff has no correlation • Pressure vs. Flow • Mean Pressure always consistent

48. If BP increases, does flow increase? • Think of levophed… NOPE

49. Preventing Complications with Arterial Lines

50. Troubleshooting Common Arterial Line Problems • Damping of waveform • Causes: • Flush bag empty or pressure < patient pressure • Catheter tip against vessel wall • Clot at catheter tip • Air bubbles in system • Kinked catheter or tubing