0.2
0.4
0.7 0.6
0.8
0.9
1.1
1.0
1.3 1.2
Hemodynamic Monitoring
(sec) 1.4
35 40 45 50 55 60
Technique
How often should it be done?
SvO2 Indicates adequacy of tissue oxygenation, the primary reason many patients receive hemodynamic monitoring
60-70%
The SvO2 helps identify which blood pressue and cardiac output are acceptable for each patient.
Level the transducer to the phlebostatic axis
Place any stopcock at the phlebostatic axis. Patient should be supine. Elevation can be from flat to 45 degrees
Only if the patient has moved from the original position. Relevel if reading has unexplainably changed.
Stroke Index (SI) How much blood is pumped with each beat referenced against body size.
25-45 ml/m2
Used in conjunction with cardiac pressures to diagnose and evaluate treatment.
Zero the Transducer/amplifier
Must zero on initial setup. Rezero if readings have unexplainably changed.
Cardiac Index How much blood is pumped during one minute reference against body size. It is a product of stroke index and heart rate
2.5-4.0 L/m/m2
Not as early an indicator of a hemodynamic problem as stroke index due to the compensating role of heart rate when stroke index is low.
With the stopcock off to the patient and open to air, cap removed and leveled at the phlebostatic axis, activate the monitor’s zero function. Close transducer to air and open to patient and then recap stopcock.
Perform a square wave test. The square wave test checks the accuracy of the tubing/ catheter system.
Activate the fast flush device and release. Interpret the response. See illustration below
Prior to obtaining readings
Pulmonary artery pressure (PAP)
About 25/10 mmHg
5 6
70
4 7
100 90 80
3
Hemodynamic Monitoring
2 8
Heart rate at 25 mm/sec (Measure two cardiac cycles from the reference arrow)
1 9
400 300
200 150
Steps
Pulmonary artery occlusive pressure (PAOP or wedge)
About 8-12 mmHg
When the stroke index is low, the PAOP helps differentiate left ventricular dysfunction (PAOP>12mmHg) and hypovolemia (PAOP< 8mmHg).
Central venous pressure (CVP) Right atrial pressure. A reflection of right ventricular end diastolic pressure. The CVP is an estimation of preload.
About 2-6 mmHg
When stroke index is low, the CVP helps differentiate right ventricular dysfunction (CVP> 6 mmHg) and hypovolemia (CVP is normal or < 2 mmHg.
Blood Pressure Reflects pressure in systemic arterial system.
Varies with site, size, age and sex.
A common less invasive form of estimating blood flow. With hemodynamic monitoring available (SvO2, SI, CI), blood pressure is less useful.
Systemic Vascular Resistance (SVR)
900-1300 dynes/sec/ cm5
Often used to assess the response of arterial dilators.
10
A supplement to CRITICAL CARE NURSE®
Printed in the USA, July 1999
Useful in assessing response to therapies for pulmonary hypertension. Normally not a primary parameter in assessing hemodynamics.
It is better way of verifying the arterial line accuracy than the blood pressure cuff comparison.
Performing Square Wave Test Characteristics
Illustration
How to correct? Clinical Result
Optimal Dampening 1) Should have a small overshoot, followed by a small overshoot (about 1/3 the distance of the undershoot) 2) Should have 1-2 blocks between oscillations
No necessary correction
Under Dampening 1) Either extra oscillations are present or 2) Prolonged distance (more than 2 blocks between bounces.
1)
Over Dampening 1) Obstruction in line prevents oscillation 2) Note slurring on downstroke.
Find source of problem. 1) Air in line 2) Blood in line 3) Kink in tubing/catheter
2)
Waveforms are accurately reproduced
Remove excess tubing. Insert dampening device Systole is artificially depressed, diastole may be higher than actual. Use mean values if unable to correct.
Page 1
Importance
8:03 AM
Normal Value
11/1/00
MM
REF 5968-6249E
Determining the Accuracy of Hemodynamic Values
Parameter
PR, QRS, and QT interval
30
REF
0.5
0.3
hemo_mont.qxd
0.1
Waveform
Pre C wave
Find the c wave on the downstroke of the a wave (usually near the end of the QRS complex)
Theoretically the most sound method. Use this method if possible
Right Ventricular 1) Rapid upstroke to waveform systole. Systole found after the QRS but before the T-wave. 2) Terminal diastolic rise-diastole found near the end of the QRS complex Pulmonary 1) Rapid upstroke to Artery waveform systole. Systole found after the QRS but before the T-wave. 2) Progressive diastolic runoff-diastole found near the end of the QRS complex. 3) A dicrotic notch (closure of the pulmonic valve) is sometimes visible during the progressive diastolic runoff.
Types of Artifact
How to Read
Patient initiated includes spontaneous breathing and patient initiated ventilator breaths
1) Locate where the baseline drops 2) Read the last clear wave before the drop occurs
Mechanical Ventilation
1) Locate where the baseline moved upward 2) Read the last clear wave before the baseline elevates.
Example
Page 2
Often the easiest to use since the c waves are not always visible. Use this method if c wave is not present.
Example
8:03 AM
Find the a wave in the PR interval. Locate top and bottom of a-c wave. Average the two values.
Characteristics
11/1/00
Indications
Average of the a-c waves
Avoiding Respiratory Artifact
How to read a Right Ventricular & PA waveform
Technique
How to read a PAOP waveform Avoiding Abnormal Waveforms
Z point
Draw a line down from the end of the QRS complex. Where the line hits the baseline, is the CVP reading.
Method
Technique
Indications
Average of the a-c waves
Find the a wave after the QRS complex. Locate top and bottom of a-c wave. Average the two values.
Often the easiest to use since the c waves are not always visible. Use this method if c wave is not present
Z point
Draw a line down from about .08 to .12 seconds after the QRS complex. Where the line hits the baseline, is the PAOP reading.
Use this method when no clear a or c wave present (e.g. atrial fibrillation and paced rhythms)
Use this method when no clear a or c wave present. (e.g. atrial fibrillation and paced rhythms)
Clinical Situation
How to Read
Large V wave Common with CHF
Locate the pre c point or the mean of the a-c wave before the large V wave.
Large or absent a Use the Z point method. wave
hemo_mont.qxd
How to read a CVP waveform Method
Example