CVP.pptx

Central venous pressure and IABP

1. WHAT IS CVP? The central venous pressure is the pressure measured in the central veins close to the heart. It indicates mean atrial pressure and is frequently used as an estimate of right ventricular preload. CVP reflect the amount of blood returning to the heart and the ability of the heart to pump blood into arterial system It is the pressure measured at junction of right atrium and SVC. It reflect the driving force for filling of the right atrium and ventricle. Normal CVP in awake, spontaneously breathing patient : 1-7 mmHg(or 5-10 cmH2O) Mechanical ventilation: 3-5 cmH2O higher

2. FACTOR AFFECTING CENTRAL VENOUS PRESSURE: FACTOR INCREASING CVP FACTOR DECREASING CVP Raised intrathoracic pressure Circulatory overload Venoconstriction Impaired cardiac function SVC obstruction IPPV Reduced intrathoracic pressure Hypovolemia Venodilation

3. CVP MONITORING In CVP monitoring, we insert a catheter through a vein and advances it until its tip lies in or near the right atrium Because no major valves lies at the junction of the vena cava and right atrium, pressure at end diastole reflects back to the catheter. When connected to manometer, the catheter measures CVP an index of right ventricular function. CVP monitoring helps to assess cardiac function, to evaluate venous return to the heart, and to indirectly gauge how well the heart is pumping.

4. METHODS TO MEASURE CVP Indirect method: Inspection of jugular venous pulsation in the neck. Direct method fluid filled manometer connected to central venous catheter. Calibrated transducer.

5. Inspection of jugular venous pulsation in the neck: No valve between right atrium and internal jugular vein Degree of distension and venous wave form reflects information about cardiac function.

6. 2. Fluid filled manometer connected to central venous catheter CVP is measured using a column of water in a marked manometer. CVP is height of the column in cm of H2O when column is at the level of right atrium ADVANTADE: simplicity to measure DISADVANTAGE: 1) inability to analyze the CVP waveform 2) relative slow response of water column to change in intrathoracic pressure

7. METHOD: With the CV line in place, position the patient flat. Align the base of the manometer with the determined zero reference point by using leveling device. Because CVP reflect right atrium pressure, you must align the right atrium with the zero mark on manometer To find right atrium locate the fourth intercostal space at the midaxillary line. Mark the appropriate place on patients chest so that all subsequent recordings will be made using same location. Attach water manometer to pint stand or place it to the next to patient’s chest. Make sure the zero reference point is level with right atrium.

8. A 3 way tap is used to connect the manometer to in IV drip set on one side and via extension tubing filled with IV fluid to patient on other side Check that the CVP catheter tubing is not kinked or blocked, and IV fluid can easily flushed in and blood can easily aspirated from CVP line. The 3 way tap is then turned so that it is open to the fluid bag and manometer but closed to the patient, allowing manometer column to fill with fluid. Once manometer has filled adequately the 3 way tap is turned again- this time so it is open to patient and manometer, but close to the fluid bag.

9. The fluid level within the manometer column will fall to the level of the CVP, the value of which can be read on manometer scale which is marked in CM of water therefor giving value of CVP in cmH2O. The fluid level will continue to rise and fall slightly with respiration and average reading should be recorded.

10. 3. Calibrated transducer Automated, electronic pressure monitor. Pressure wave form displayed on an oscilloscope or paper. ADVANTAGE: 1)more accurate 2)direct observation of waveform

11. METHOD : The transducer is fixed at the level of right atrium and connected to patient’s CVP catheter via fluid filled extension tubing. The transducer than ‘zeroed, to atmospheric pressure by turning its 3 way tap so that it is open to the transducer and to room air but closed to patient. The 3 way tap is then turned so that it is now closed to room air and open between patient and transducer. A continue CVP reading measured in mmHg

12. CVP WAVEFORM

13. CVP waveform Waveform component Phase of cardiac cycle Mechanical event a wave End diastole Atrial contraction c wave Early systole Isovolumetric ventricular contraction, tricuspid bulge in right atrium v wave Late systole Systolic filling of atrium x decent Mid systole Atrial relaxation Y decent Early diastole Early ventricular filling

14. COMLICATION Haemorrhage Pneumothorax Air embolism Arteriovenous fistula Adjacent organ puncture Thrombosis Thrombo embolism Skin infection and necrosis sepsis

15. INTRA ARTERIAL BLOOD PRESSURE MONITORING 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.

16. INDICATION Continuous, real time BP monitoring Planned pharmacological or mechanical cardiovascular manipulation Repeated blood sampling Failure of indirect arterial bp monitoring Supplementary diagnostic information from the arterial waveform

17. BASIC PRINCIPLE The pressure waveform of the arterial pulse is transmitted via the column of fluid, to a pressure transducer where it is converted into electrical signal. The electrical signal is then processed, amplified and converted into a visual display by a microprocessor.

18. ARTERIAL PRESSURE MONITORING SITE radial artery – most commonly used Ulnar artery Brachial artery Axillary artery Femoral artery Dorsalis pedis artery

19. COMPLICATION Hemorrhage Distal ischemia Pseudoaneurysm Arteriovenous fistula Infection Peripheral neuropathy

20. COMPONENT OF AN IBP SYSTEM: Intra arterial cannula Fluid filled tubing Transducer Infusion/flushing system Signal processor, amplifier and display

21. PHYSICAL PRINCIPLES A wave is disturbance that travel through a medium, transferring energy but not matter. One of the simplest waveforms is the sine wave. Fourier analysis: The arterial waveform is clearly not simple sine wave but it can be broken down into a series of many component sine waves. The process of analyzing a complex waveform in terms of its constituent sine waves is called Fourier analysis. Property: Natural frequency Damping coefficient

22. NATURAL FREQUENCY The natural frequency of a system determines how rapid the system oscillates after a stimulus. It is important that IBP system has a very high natural frequency at least eight timed the fundamental frequency of arterial waveform(pulse rate). Therefore, for a system to remain accurate at heart rate of up to 180bpm, its natural frequency must be at least: (180bpm *8)/60sec=24Hz

23. The natural frequency of a system may be increased by Reducing the length and compliance of tubing Reducing the density of the fluid used in tubing Increase the diameter of tubing Commercially available system -200Hz

24. DAMPING: Anything that reduces energy in an oscillating system will reduce the amplitude of oscillation. This is termed damping. Some degree of damping required in for all system(critical damping), But if excessive(overdamping) or insufficient(underdamping) the output will be adversely affected. The damping coefficient reflects forces acting on the system and determines how rapidly it returns to rest after a stimulation.

25. FAST FLUSH TEST Provide a convenient bedside method for determining dynamic response of 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 amplitude ratio