Hemodynamic Made Easy
Hemodynamic Monitoring Martina Douglas RN, CCRN, BSc, MSc 1
Objectives Definition Discuss •Non-invasive Vs. invasive monitoring •Principles •Arterial pressure waveform assessment •Central venous pressure waveform assessment •Pulse Oxymetry 2
Hemodynamic Monitoring Definition ďƒ˜ The monitoring of the movement of blood ďƒ˜ Changes in blood pressure and volume
3
Non-invasive Monitoring • • • •
Level of consciousness Colour Pulses Peripheral perfusion – Colour, temperature, capillary refill, limb equality, demarcation line
• Blood pressure • Urine output 4
Invasive Hemodynamic Monitoring ďƒ˜ Accurate and continuous measurement of peripheral or central vascular pressures in critically ill patients
5
Principles ďƒ˜ Pulsatile pressures transmitted through fluidfilled connecting tubing to pressure-sensitive transducer ďƒ˜ Pressure-induced motion converted into electrical signals displayed as real-time waveforms on cardiac monitor
6
Invasive Haemodynamic Monitoring What do we need??
7
Invasive Haemodynamic Monitoring ďƒ˜Intra-vascular catheter in situ ďƒ˜Fluid system coupled with a transducer-amplifier-monitor
8
Recording Accuracy- Leveling ďƒ˜ Pressure transducer and tip of in-situ catheter are aligned to same vertical level ďƒ˜ Phlebostatic axis- reference point for monitoring circulatory pressures
9
Recording Accuracy- Zeroing Eliminates effects of atmospheric pressure on measured hemodynamic values Gives transducer-monitoring system a neutral pressure point of 0 mmHg to begin measurements 15 mmHg transducer drift (from zero point) may occur in 3 hours 10
Transducer/Monitor Calibration A known pressure is applied to the transducer–monitor system to verify accurate display of that pressure signal Amplifier/Monitor – checked by Bio-Engineering Dept. Transducer - industry tested and standardized to a fixed pressure sensitivity
11
Advantages Continous displayed values and waveforms Essential assessment tools to evaluate patient condition and immediate response to treatment (volume, inotropes) Allows early detection, identification of lifethreatening condition NIBP increasingly less accurate with hypotension 12
Disadvantages • Intravascular catheter related complication • • • • •
Infection Embolization Bleeding Vessel and tissue damage Arrhythmias
• Inaccuracy in measurement easily introduced and undetected if nursing staff not well trained
13
Arterial Pressure Measurement
Numerical values S/D/M MAP used for assessment & decision making because: ďƒ˜ same in all parts of the cardiovascular system in supine patient ďƒ˜ not overly affected by motion artifact or poor damping in system ďƒ˜ does not vary significantly even in vessels further from aortic arch (compared to changes in systolic & diastolic readings)
14
Arterial Line Waveforms • A typical normal arterial blood pressure waveform contains rapid upstroke, clear dicrotic notch, and clear end diastole
15
Waveform Assessment Optimal reproduction Clearly defined waveforms All components of waveform clearly visible
16
Waveform Assessment Fast flush (square wave) assessment Sharp vertical upstroke Small overshoot Followed by straight vertical downstroke 1 or 2 oscillations (ringing) before quick return to baseline 17
Waveform Assessment Underdamping / Ringing (exaggerated response) Numerous oscillations (> 3) above and below the baseline after the fast flush
Usually caused by: Small air bubbles Excess length of tubing used 18
Waveform Assessment Overdamping (blunted response) Slurred upstroke and downstroke No oscillations above or below baseline after the fast flush
Usually caused by: Air in line Blood in line Kinks in tubing
19
Pulsus Alternans Possible Cause: Bigeminy - check patient’s ECG for PVCs every 2nd beat Left Ventricular dysfunction
20
Flattened Waveform Possible Cause: Waveform damped or hypotension Check patient’s pulse & BP with NIBP
21
Flattened Waveform Check blood pressure with NIBP
If the pressure is very low or unobtainable, suspect hypotension If NIBP significantly higher than arterial line, suspect damping Troubleshoot problem by flushing the line 22
Pulsus Paradoxus Possible Cause: Ventilation / PEEP Pericardial Tamponade Hypervolemia
23
Pulsus Paradoxus Check systolic blood pressure regularly ďƒ˜ The difference between the highest and the lowest systolic pressure should be less than 10 mm Hg ďƒ˜ If the difference is greater than 10 mm Hg, suspect pulsus paradoxus caused, for example, by pericardial tamponade
24
Fling Possible Cause: Catheter tip movement in artery Air in the system Stabilize catheter by taping and splinting Reposition the catheter - physician Aspirate and flush system 25
Slow Upstroke Possible Cause: aortic stenosis Notify doctor, check heart sounds
26
CVP Measurement
The pressure within the SVC or RA CVP approximates RAP, reflection of RV preload A guide to fluid balance in critically ill patients Estimate the circulating blood volume 27
CVP Measurement Assists in monitoring circulatory failure Rapid infusion via CVC may alter CVP value CVP always obtained at end expiration CVP should not be interpreted alone but in conjunction with other systemic measurements 28
CVP Waveform CVP waveform reflects changes in the RA pressures during cardiac cycle
29
CVP Waveforms ‘A’ wave: RA contraction – P wave on ECG ‘C’ wave: Closure of tricuspid valve (TV) – QRS complex on ECG ‘X’ descent: RA relaxation ‘V’ wave: Filling of RA and bulging of TV into RA – T wave ending on ECG ‘Y’ descent: atrial emptying as blood enter ventricle 30
Pulse Oximetry Light source emits two light wavelengths • Red • Infrared
Light sources pass through underlying, pulsating arterioles to a photo detector Saturated Hb (carrying O2 ie. oxyhemoglobin) absorbs more infrared light Desaturated Hb (not carrying O2) absorbs more red light Oxymeter determines % of oxyhemoglobin against % of total Hb 31
Heme’ and Other Gases Heme molecule of Hb can Transport gases other than oxygen Be altered by other gases or other agents e.g. nitric oxide / lidocaine / sulfa drugs 32
Heme’ and Other Gases Heme carrying oxygen creates oxyhemoglobin (O2Hb) Heme carrying carbon monoxide creates carboxyhemoglobin (COHb) Heme that changes its shape creates methemoglobin (MetHb) 33
Heme’ and Other Gases Elevated COHb levels – Carbon monoxide poisoning Elevated MetHb levels – nitrates (GTN), anesthetics – lidocaine, benzocaine
34
Heme’ and Other Gases Carboxyhemoglobin (COHb) and Methemoglobin (MetHb) “CANNOT CARRY OXYGEN”
35
Pulse Oximetry Estimates functional haemoglobin oxygen saturation SpO2 may not be the same as SaO2 Sources of error – poor signal detection • • • •
Hypoperfusion – vasoconstriction Movement – shivering or diathermy Incorrect sensor application – too tight Sensor on same limb as NIBP (weak pulse during cuff inflation) 36
Pulse Oximetry Falsely Lowered SpO2 some nail polishes very dark skin infrared heating lamps IV administered dyes (methylene blue) lipid infusions hemodilution, severe anemia (Hct < 10%) 37
Pulse Oximetry Falsely raised SpO2 ď&#x192;&#x2DC;elevated COHb or MetHb ď&#x192;&#x2DC;intense surgical or fluorescent lights NB: Monitor SaO2 or SvO2 via ABG machine in patients with known carbon monoxide poisoning or methemoglobinemia
38
SpO2 (Functional) Measured with a saturation probe The saturation probe cannot identify COHb or MetHB in comparison to O2Hb COHb and MetHB (abnormal Hb’s) are included into O2Hb measurement e.g. 70% COHb but SpO2 still measured 90% on the monitor 39
SaO2 (Fractional) Shows other types of Hb such as COHb and MetHb Measured by an ABG machine All forms of Hb included in the calculation Fractional SaO2 compares the percentages of oxyhemoglobin (O2Hb) to carboxyhemoglobin (COHb) and methemoglobin (MetHb) 40
SaO2 (Fractional)
41
Thank you.
42