INTRA-ARTERIAL BLOOD PRESSURE MONITORING

Comprehensive presentation on intra arterial blood pressure with a good insight into the the basic physics and brief look into the risks and complications.

1. INVASIVE ARTERIAL PRESSURE MONITORING Dr. T. Vikram Kumar Naidu MD(Anaesthesia), (DM) (Cardiac anaesthesia) (UNMICRC)

2. SUBTITLES Introduction Indications Basic priciples Percutaneous radial artery cannulation Complications Components Levelling and zeroing Normal arterial pressure waveforms Arterial blood pressure gradients Abnormal arterial pressure waveforms Waveform analysis for prediction of intravascular volume responsivenesss 05-06-2016 2 Dr. Vikram Naidu

3. INTRODUCTION Intra-arterial blood pressure (IBP) measurement is often considered to be the gold standard of blood pressure measurement . Despite its increased risk, cost, and need for technical expertise for placement and management, its utility in providing crucial and timely information outweighs its risks in many cases 05-06-2016 3 Dr. Vikram Naidu

4. Indications for Arterial Cannulation Continuous, real-time blood pressure monitoring Planned pharmacologic or mechanical cardiovascular manipulation Repeated blood sampling Failure of indirect arterial blood pressure measurement, e.g . burns or obesity Supplementary diagnostic information from the arterial waveform 05-06-2016 4 Dr. Vikram Naidu

5. BASIC PRICIPLES The pressure waveform of the arterial pulse is transmitted via the column of fluid, to a pressure transducer where it is converted into an electrical signal . This electrical signal is then processed, amplified and converted into a visual display by a microprocessor. 05-06-2016 5 Dr. Vikram Naidu

6. Percutaneous Radial Artery Cannulation The radial artery is the most common site for invasive blood pressure monitoring because it is technically easy to cannulate and complications are uncommon Modified Allen’s test 05-06-2016 6 Dr. Vikram Naidu

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8. “ Transfixation ” technique 05-06-2016 8 Dr. Vikram Naidu

9. ULTRASOUND IMAGING 05-06-2016 9 Dr. Vikram Naidu

10. Alternative Arterial Pressure Monitoring Sites Ulnar Brachial Axillary Femoral – seldinger technique D orsalis pedis 05-06-2016 10 Dr. Vikram Naidu

11. Complications of Direct Arterial Pressure Monitoring Hemorrhage Misinterpretation of data Distal ischemia Pseudoaneurysm Arteriovenous fistula Arterial embolization Infection Peripheral neuropathy 05-06-2016 11 Dr. Vikram Naidu

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15. PHYSICAL PRINCIPLES A wave is a disturbance that travels through a medium, transferring energy but not matter. One of the simplest waveforms is the sine wave 05-06-2016 15 Dr. Vikram Naidu

16. Fourier Analysis The arterial waveform is clearly not a simple sine wave, but it can be broken down into a series of many component sine waves The process of analysing a complex waveform in terms of its constituent sine waves is called Fourier Analysis . 05-06-2016 16 Dr. Vikram Naidu

17. Properties Natural frequency Damping coefficient 05-06-2016 17 Dr. Vikram Naidu

18. The natural frequency of a system determines how rapidly the system oscillates after a stimulus T he damping coefficient reflects frictional forces acting on the system and determines how rapidly it returns to rest after a stimulus 05-06-2016 18 Dr. Vikram Naidu

19. Natural Frequency It is important that the IBP system has a very high natural frequency – at least eight times the fundamental frequency of the arterial waveform (the pulse rate ). Therefore , for a system to remain accurate at heart rates of up to 180bpm, its natural frequency must be at least: (180bpm x 8) / 60secs = 24Hz. 05-06-2016 19 Dr. Vikram Naidu

20. Natural Frequency The natural frequency of a system may be increased by : Reducing the length of the cannula or tubing Reducing the compliance of the cannula or diaphragm Reducing the density of the fluid used in the tubing Increasing the diameter of the cannula or tubing Commercially available systems -200Hz 05-06-2016 20 Dr. Vikram Naidu

21. Damping Anything that reduces energy in an oscillating system will reduce the amplitude of the oscillations. This is termed damping. Some degree of damping is required in all systems ( critical damping ), but if excessive ( overdamping ) or insufficient ( underdamping ) the output will be adversely effected . 05-06-2016 21 Dr. Vikram Naidu

22. Underdamped arterial pressure waveform Overdamped arterial pressure waveform 05-06-2016 22 Dr. Vikram Naidu

23. Factors that cause overdamping include : Friction in the fluid pathway Three way taps Bubbles and clots Vasospasm Narrow, long or compliant tubing Kinks in the cannula or tubing 05-06-2016 23 Dr. Vikram Naidu

24. FAST-FLUSH TEST Provides a convenient bedside method for determining dynamic response of the system Natural frequency is inversely proportional to the time between adjacent oscillation peaks The damping coefficient can be calculated mathematically, but it is usually determined graphically from the amplitude ratio 05-06-2016 24 Dr. Vikram Naidu

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26. COMPONENTS OF AN IBP MEASURING SYSTEM 05-06-2016 26 Dr. Vikram Naidu

27. COMPONENTS OF AN IABP MEASURING SYSTEM Intra-arterial cannula 05-06-2016 27 Dr. Vikram Naidu

28. COMPONENTS OF AN IABP MEASURING SYSTEM Intra-arterial cannula Fluid filled tubing 05-06-2016 28 Dr. Vikram Naidu

29. COMPONENTS OF AN IABP MEASURING SYSTEM Intra-arterial cannula Fluid filled tubing Transducer 05-06-2016 29 Dr. Vikram Naidu

30. COMPONENTS OF AN IBP MEASURING SYSTEM Intra-arterial cannula Fluid filled tubing Transducer Infusion/flushing system 05-06-2016 30 Dr. Vikram Naidu

31. COMPONENTS OF AN IBP MEASURING SYSTEM Intra-arterial cannula Fluid filled tubing Transducer Infusion/flushing system Signal processor, amplifier and display 05-06-2016 31 Dr. Vikram Naidu

32. Levelling and zeroing Zeroing : For a pressure transducer to read accurately, atmospheric pressure must be discounted from the pressure measurement. This is done by exposing the transducer to atmospheric pressure and calibrating the pressure reading to zero. T he level of the transducer is not important . 05-06-2016 32 Dr. Vikram Naidu

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34. Levelling : The pressure transducer must be set at the appropriate level in relation to the patient in order to measure blood pressure correctly. This is usually taken to be level with the patient’s heart, at the 4th intercostal space, in the mid-axillary line . A transducer too low over reads, a transducer too high under reads. 05-06-2016 34 Dr. Vikram Naidu

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36. Normal Arterial Pressure Waveforms The systolic waveform components consist of a steep pressure upstroke, peak, and ensuing decline, and immediately follow the ECG R wave. The downslope of the arterial pressure waveform is interrupted by the dicrotic notch , continues its decline during diastole after the ECG T wave, and reaches its nadir at end-diastole 05-06-2016 36 Dr. Vikram Naidu

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38. As the pressure wave travels from the central aorta to the periphery , the arterial upstroke becomes steeper, the systolic peak increases, the dicrotic notch appears later, the diastolic wave becomes more prominent, and end-diastolic pressure decreases . 05-06-2016 38 Dr. Vikram Naidu

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40. Arterial Blood Pressure Gradients The nature of the operative procedure is important when choosing the appropriate site Ex: Coarctation of aorta Thoracic and abdominal aortic surgeries Cardiopulmonary bypass 05-06-2016 40 Dr. Vikram Naidu

41. Cardiopulmonary bypass : The mean radial artery pressure decreases on initiation of bypass and remains less than mean femoral artery pressure throughout the bypass period. P ersists in the first few minutes following separation from bypass , often by more than 20 mm Hg. 05-06-2016 41 Dr. Vikram Naidu

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43. Abnormal Arterial Pressure Waveforms Morphologic features of individual arterial pressure waveforms can provide important diagnostic information 05-06-2016 43 Dr. Vikram Naidu

44. 05-06-2016 44 Condition Characteristics Aortic stenosis Pulsus parvus (narrow pulse pressure) Pulsus tardus (delayed upstroke) Aortic regurgitation Bisferiens pulse (double peak) Wide pulse pressure Hypertrophic cardiomyopathy Spike and dome (mid-systolic obstruction) Systolic left ventricular failure Pulsus alternans (alternating pulse pressure amplitude) Cardiac tamponade Pulsus paradoxus (exaggerated decrease in systolic blood pressure during spontaneous inspiration) Dr. Vikram Naidu

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46. Waveform analysis for prediction of intravascular volume responsiveness Variations in arterial blood pressure observed during positive pressure ventilation, as well as a variety of derived indices, are the most widely studied of these dynamic indicators . They result from changes in intrathoracic pressure and lung volume that occur during the respiratory cycle. 05-06-2016 46 Dr. Vikram Naidu

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48. REFERENCES Miller's 8th edition Physical principles of intra-arterial blood pressure measurement anaesthesia Kaplan's cardiac anesthesia the echo era 6edition 05-06-2016 48 Dr. Vikram Naidu

49. Thank you