Cardiovascular Monitoring

1. Cardiovascular Monitoring Albert Woo, MD

2. Arterial Blood Pressure Monitoring • Arterial BP is the most important determinant of LV afterload and therefore workload of the heart • 2 Categories: indirect Riva-Rocci cuff devices vs direct cannulation and pressure transduction • Direct measurement is gold standard, but results can be spurious due to techniques

3. Indirect Measurement of BP / Manual Intermittent technique • Common sources of error: inappropriate cuf size and rapid cuff deflation. Width of BP cuff should be 20% > arm diameter. Cuff should be applied snugly. Pneumnatic bladder should span > half the circumference of arm and be centered over an artery. • * Use of cuffs that are too narrow tend to result in overestimation of BP. Too large a cuff generally work well with little error.

4. Automated Intermittent Techniques • Advantage: frequent, regular measurement and free operator to perform other clinical duties. • Based on oscillometry. Peak amplitude of pulsation measures MAP, SBP & DBP values are derived from formulas that examine rate of change of pulsations. • Complications: pain, petechiae, echymoses, limb edema, venous stasis, & thrombophlebitis, peripheral neuropathy, and compartment syndrome.

5. Direct Measurement of BP • Indications: Continuous, real-time BP monitoring. Planned pharmacologic or mechanical cardiovascular manipulation. Repeated blood sampling. Failure of indirect arterial BP measurement. Supplementary diagnostic information from arterial waveform. • Allen test: predictive value has been questioned. • Radial artery most commonly used. Alternative sites: ulnar, brachial (although no collateral, trials proved to be safe), dorsalis pedis, posterior tibial, superificial tempora, axillary, femoral. • Complications: distal ischemia, psudeoaneurysm, av fistula, hemorrhage, arterial emoblization, infection, peripheral neuropathy, misinterpretation, misuse of equipment.

6. Transducer Setup • Zero, calibration, & leveling. • Zero-ing: to atmospheric pressure. (pt position does not affect zeroing) • Calibration: No longer necessary because of accurate disposable transducers • Levelling: reference to a specific position on the pt’s body. • Supine pt: common practice of aligning pressure transducers at midchest position in the midaxillary line. • More accurate pressure monitoring at 5 cm below sternal border in the 4th intercostal space.

7. A-line facts • A catheter in the distal arteries will show a higher SBP, lower DBP, higher pulse pressure, and same MAP than pressure measured at the aorta. • Air bubble in the tubing will cause underdamping of the system, leading to the same MAP, lower SBP, and higher DBP.

8. PA Cath / Swan Ganz • Most common insertion site is RIJ, most direct route to right heart chambers. • Standard catheter has 4 lumens. • Distal port at tip for PAP monitoring • Proximal 30cm from tip for CVP monitoring and med/fluid administration • A lumen to inflate the ballon • Wire leading to a thermistor to measure PAP Temp • The one we use at BMC has an extra VIP (Venous Infusion Port)

9. PA Cath Picture

10. Indications: • ASA task force: selected surgical pt undergoing procedures associated with a high risk of complications from hemodynamic changes or in those with advanced cardiopulonary diseases who would be at increased risk for adverse perioperative events because of their preoperative medical condition. Furthermore, the characteristics of the practice setting should be considred, including the proficiency and experience of clinicians who would be using perioperative PAC monitoring.

11. Before Placing the PA Cath • Level the transducer at the level of the heart. You should see a pressure of 0 mmHg. • Raising the catheter tip 30 cm vertically should give you a pressure of 22 mmHg on the PA tracing.

12. Distances (rough estimates) • RIJ: • Right Atrium: 20-25 cm • Right Ventricle: 30-35 cm • PA: 40-45 cm • Wedge 45-55 • If LIJ or R Ext Jugular, add 5-10 cm • If Femoral: add 15 cm • If Antecubital: add 30-35 cm • Common problems: coiling in the right atrium or right ventricle – deflate balloon, withdrawn to 20 and refloat

13. PA tracings

14. Maneuvers • Head down will aid floatation past the tricuspid valve • Right tilt and head up will aid flotation out of the RV and reduce frequency of ventricular arrythmias. • Most cath float to right PA, right lateral decub position if left PA is targeted selectively

15. Complications: • Catheterization: arrythmias, v. fibb, RBBB, complete heart block • Catheter residence: mechanical, knobs, thromboemoblism, Pulmonary infarct (particularly when balloon is kept up), infection, endocarditis, endocardial damage, valve injury, PA rupture (50% mortality), PA psuedoaneurysm • Misinterpretation of data • Misuse of equipment

16. Precautions • Critical AS pt undergoing valve replacement. • V fib risk is greatest in pt with MI, particularly RV ischemia. • Prophylactic lidocaine has not shown to be beneficial • RBBB occurs in up to 5% of pts during a PA cath placement. Although clinically insignificant, pt with a preexisting LBBB may result in a complete heart block. Consider backup pacing options.

17. Hemodynamic Variables • Cardiac output, mvO2, PA and wedge pressures. • PAWP provides an accurate indirect measurement of both Pulmonary venous pressure and left atrial pressure / left ventricular filling pressure. • PA Cath tip must be wedged in lung zone 3 (where Pa>Pv>PA) to provide an accurate measure of Pv or LA pressure.

18. Interpreting Values • CVP to estimate LV Preload, beware of confounding factors • Predicting LVEDP with PAWP (Z-point) • Underestimation • Diastolic dysfx, AR, PR, RBBB, PostPneumonectomy • Overestimation • PEEP, PA HTN, Pulm veno-occlusive Ds, MS, MR, VSD, Tachycardia

19. Other facts • PA cath balloon should not be inflated with saline because it increases incidence of PA rupture.

20. Cardiac Output Monitoring / Thermodilution Method • Stewart-Hamilton Equation • Temperature is measured at the tip of the PA catheter, another thermistor at the injection port. • Taking the average of a series of 3 is suggested by some authors.

21. Normal Hemodynamic Values

22. Sources of Error in Thermodilution Cardiac Output Monitoring. • Intracardiac or extracardiac shunts • Tripcupis or pulmonic valve regurg • Inadequate delivery of thermal indicator • Central venous injection site w/I catheter introducer sheath • Warming of iced injectate • Thermistor malfunction from fibrin or clot • PA blood temp flutuations • After cardiopulmonary bypass • Rapid IV fluid administration • Resp cycle influences

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