SHA24/050003

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

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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

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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

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Invasive Haemodynamic Monitoring What do we need??

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Invasive Haemodynamic Monitoring ďƒ˜Intra-vascular catheter in situ ďƒ˜Fluid system coupled with a transducer-amplifier-monitor

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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

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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

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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

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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)

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Arterial Line Waveforms • A typical normal arterial blood pressure waveform contains rapid upstroke, clear dicrotic notch, and clear end diastole

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Waveform Assessment  Optimal reproduction  Clearly defined waveforms  All components of waveform clearly visible

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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

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Pulsus Alternans Possible Cause: Bigeminy - check patient’s ECG for PVCs every 2nd beat Left Ventricular dysfunction

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Flattened Waveform Possible Cause: Waveform damped or hypotension Check patient’s pulse & BP with NIBP

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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

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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

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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

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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

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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

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Heme’ and Other Gases Carboxyhemoglobin (COHb) and Methemoglobin (MetHb) “CANNOT CARRY OXYGEN”

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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

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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)

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Thank you.

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