PROCEDURE FOR ROOM TEMPERATURE CARDIAC OUTPUT
MEASUREMENTS IN CCTC USING CO-SET

  1. Hand Hygiene
  2. Prepare Monitor
  3. Connect Equipment and Review Setup
  4. Evaluate Proximal Port
  5. Confirm PA Waveform
  6. Prepare for Measurement
  1. Measure Cardiac Output
  2. Resume Therapy
  3. Obtain labwork
  4. Enter data in Critbase
  5. Document


Cardiac Output (CO) measurements are done in CCTC using the closed system CO-Set. Room temperature injectate (D5W 18-25 C) is the standard method.

Measurement of CO with a pulmonary artery catheter is done using the thermodilution technique:

  • A known volume of D5W at a temperature that is colder than blood temperature is injected into the right atrial port of the catheter
  • The temperature of this injectate solution is measured as it enters the catheter lumen
  • The blood temperature is measured at the tip of the catheter in the pulmonary artery
  • During cardiac output measurement, the temperature of the right atrial blood drops after the bolus. When this colder blood reaches the tip of the pulmonary artery catheter, the change in the blood temperature over time produces a cardiac output curve. The rise in the curve represents the falling temperature, while the decline in the curve is during temperature recovery
  • The computer program incorporates the volume of injectate (usually 10 ml), the injectate temperature and the model of catheter (lumen size and length) into the temperature change curve to produce a cardiac output value. The algorhithm also incorporates the specific gravity of the D5W solution, therefore, it is important that D5W is used.
  • Both Paceport and VIP catheters use the same computation constant. This is automatically adjusted based on injectate temperature.

Equipment Required

 

  1. Patient with a patent right heart catheter in good position (verified on x-ray by physician).               
  2. Cardiac output module (P4).
  3. Cardiac output cable with injectate and blood temperature measurement cables
  4. Closed-system CO Injectate Set with double barreled syringe and injectate thermistor
  5. 500 mL bag of D5W
  6. PPE - Non-sterile gloves
  7. Syringes and blood tubes for arterial and venous blood gases, lactate and hemoglobin as required.

PROCEDURE

RATIONALE FOR PROCEDURE

 1.

Hand Hygiene

Perform hand hygiene before and after contact with patient and patient equipment.

Wear non-sterile gloves as PPE during cardiac output measurement and blood sampling.

 1.

In accrodance with the MoHLTC 4 moments of hand hygiene and LHSC Infection Control Policies.

 2.

Prepare Monitor

  • Review monitoring mode that is displayed in right upper corner of monitor and confirm that it is "CCTC - Swan Ganz".
  • If a different mode is displayed, go to "Admit/Discharge", select "Mode" and choose "CCTC - Swan Ganz"
  • If CI does not display as a digit field, go to "Monitor Setup", "Digit Fields" and select CI.
  • Enter the patient's height and weight or BSA as it appears in Critbase and enter it into the patient demographic data (this will automatically convert CO measurements to CI)
  • Connect P4 module and use to measure PA pressures. Ensure cardiac output cables connected.

For information on Datex Modes

For information on printing from snapshots

P4 MODULE

Figure 1: P4 Module

 2.

The CCTC Swan Ganz mode automatically makes the following changes:

  • Enables P4 waveform display and makes the label "PA", scale "60", and color yellow
  • Displays "BTemp" in digit fields. BTempt is the Blood Temperature measured from the tip of the pulmonary artery catheter. Other temperature selections will not display blood temperatue.
  • Changes the snapshot waveforms to content from:
    • Wave 1 ECG 1
    • Wave 2 P4
    • Wave 3 ECG 2
    • Wave 4 P1
    • Wave 5 P2

Cardiac Output Cables

Figure 2: Cardiac Output Cables


 3.

Connect Equipment and Review Setup

  • Confirm D5W as injectate solution.
  • The syringe should be connected to the pulmonary artery bridge to allow injection in a straight line (maintenance infusion via proximal port stopcock at 90 degrees).
  • Ensure that cardiac output cable is connected to thermistor of pulmonary artery catheter (Note: there are only 3 pins within the pulmonary artery thermistor port. This is normal)
  • Ensure that injectate temperature clip is properly connected to syringe.

 

D5W

Figure 3: D5W Required

 3.

The algorhythm for cardiac output measurement assumes the specific gravity of D5W.          

Connection to the pulmonary artery is required to measure blood temperature and detect change in blood temperature during cardiac output.

The injectate clip must be connected to measure true injectate temp. The Datex module will automatically adjust the computation constant based on the measured injectate temperature.

Failure to measure the injectate temperature will produce a false cardiac output reading. The program will not provide an alert if this temperature is not correctly measured.  

 

Bridge

Figure 4: Bridge (blue to proximal injectate, yellow to pulmonary artery lumens)


 4.

Evaluate Proximal Injectate Port

Review proximal injectate infusions (blue port) and ensure there are no continuous infusions of vasoactive drugs prior to measuring cardiac outputs.

If continuous infusions are be administered through the proximal injecate port, DO NOT perform cardiac output measurements.

  1. Move the infusion to the introducer (preferred).
  2. If the introducer is not available, the VIP or Paceport lumens can be used.
  3. Wait 15 minutes before cardiac output measurement.
  4. If no other option for vasoactive drugs is available, use the proximal injectate port but do not perform cardiac output measurements.

Assess infusions via introducer and proximal infusion port (VIP) or Paceport. Very rapid infusions (> 100 ml/hr) or infusions of cold blood products can influence cardiac output measurements.

 4.

  1. During cardiac output measurement, administration of the D5W injection will administer a bolus of any fluid/medication within the proximal lumen. This could result in a bolus of 3-4 ml of vasoactive drug.
  2. During the period of cardiac output measurement, proximal injectate infusions are interrupted.
  3. At the completion of cardiac output measurement, a delay would occur after restarting the infusion before the patient would receive any medication. For example, an infusion running at 15 ml per hour would take ~15 minutes before the lumen would be reflushed and the drug would reach the patient.

All of these three issues would compromise th patient's hemodynamic status and render the cardiac output measurement invalid.

The introducer is the preferred port for administration of vasoactive drugs.  In the even that the pulmonary artery catheter requires sudden removal or partial withdrawal, the intoducer infusions remain unaffected. During catheter withdrawal, infusion running through any proximal port may end up infusing into the sleeve.

Using the proximal injectate port is a better option than running vasoactive agents via peripheral line.

 5.

Confirm PAP Waveform

Evaluate PA waveform and confirm pulmonary artery tracing.

Review previous or insertion waveforms if uncertain about patient's normal tracing.

A paper recording of PAP should be placed in the chart each shift to confirm placement and provide reference for subsequent shift.

 

 5.

 

Evaluation ensures that catheter is not already wedged (which places patient at risk of pulmonary infarction). Proper PA placement is necessary or accurate cardiac output measurements.

If you are unable to find a previous tracing in the chart:

  • Review snapshots. If monitor is in CCTC Swan Ganz mode, wave 2 will provide P4 (pulmonary artery) data.
  • To identify cardiac waveforms (RA, RV, PA and PWP) during insertion, go to central station and review full disclosure for hemodynamic waveforms.

6.

Prepare for Measurement

Re-level transducer and obtain hemodynamic profile including CVP and PWP (unless contraindicated).

Patient should be supine (head of bed can be elevated).

Post a paper recording (from snapshot) of the CVP and PWP tracings. Write on the snapshot "CVP" or "PWP" as both waveforms will print out as "PA" waveforms from P4 module.


Where to Inject

Figure 5:  Where to Connect to Bridge

 6.

 

Measurement of hemodynamic values is done before cardiac output for consistency. Transient rises in pressures can occur immediatelly following multiple injections, particularly in patients with severe cardiac dysfunction.

NOTE: CVP is measured by redirecting the stopcocks on the bridge. It will be measured through the P4 module and will appear as a "P4" wave. 

CVP and PWP waveforms can look very similar. Because they are not "labelled" by the monitor, you will need to correct the description manually.

You can differentiate CVP and PWP in the same patient by the timing. The a, c and v waves of the PWP will be right shifted (timing delay) when compared to the CVP.

7.

Measure Cardiac Output

  1. Select "CO/Wedge/SvO2" from menu option or press "Start CO" button on P4 module to enter cardiac output program
  2. Unclamp D5W line of CO Injectate Set
  3. Slowly draw exactly 10 ml into syringe and close clamp (if you pull the plunger too hard the barrel of syringe will actually come apart)
  4. Turn stopcock to maintenance IV to "off" and suspend infusion pump alarm.
  5. Press "Start CO" and wait until "Inject Now" is displayed.
  6. Before injecting, identify where the injectate temperature will display. It is important to watch this temperature duing the initial injection to ensure that the temperature drops.
  7. Wait until the patient inspires and then inject the entire 10 ml using a steady and continuous technique. This will result in the injectate volume reaching the heart as the patient begins to exhale.
  8. Repeat at least 3 times, or until you have 3 acceptable CO curves with results within +/- 10%.

 7.



The algorhithm assumes exactly 10 ml.

The double barrel syringe prevents premature warming of the injectate solution by the operator's hands.

The fall in the injectate temperature confirms that the injectate thermistor is correctly connected. A falsley low (often < 1.0) cardiac output may be due to a poor connection. There is no alert to notify you of this technique error.

When using room temperature solution, the greatest change occurs with the first injection when the luminal fluid is displaced for the first time.

Jerky injection technique will produce inaccurate readings as demonstrated by irregular cardiac output curves.

All injections should be delivered during the same phase of the cardiac output to avoid variable outputs due to breathing. The goal is end expiration when respiratory influence is most stable.

The timing of injection after the appearance of the "Inject Now" is not important. While older modules required injection within 4 seconds, current technology will wait for the change in the operator.

8.

Resume Therapy

When final CO injection is done, resume maintenance infusion by opening stopcock.

Turn stopcock to syringe to "off" (in case of accidental disconnection) and reclamp D5W line.

Confirm PA waveform.

 8.


Ensure therapy.

9.

Obtain Labwork

Blood gases should be measured within 5 minutes of cardiac output if used to calculate oxygen delivery or consumption.

 

Hb is measured to evaluate oxgen content (and delivery). Lactate should be measured as ordered to assess adequacy of cardiac output.

 9.

 

All values are requested in Cribase to calculate hemodynamic variables.

10.

Enter Data into Critbase

Enter hemodynamic values including temperature, CVP, all pressures and arterial/venous gases and hemoglobin into hemodynamic calculation program in Critbase.

Access data under Nursing tab and "new cardiac output. Values can be accessed at a later date and "edit" chosen to update lab values.

Before posting data into chart, review entered data and confirm transcription accuracy.

Hb must be entered in conventional units. A Hb of 100 is entered as 10.0 (move decimal to left).

Oxygen saturation (arterial and venous) must be entered as .95 for 95%.

 10.

 

Oxygen delivery is the total amount of oxygen being sent to the tissues. When it is inadequate, extraction increases as our second compensatory mechanism (SvO2 falls). When extraction fails to meet our needs, we enter our final compensation and lactate rises.

The numerical value of oxygen delivery is less important than the ratio fo oxygen delivery to oxygen consumption.

If oxygen delivery is < 4 times the oxygen consumption value, oxygen delivery is inadequate.



11.

Document

Place hemodynamic profile and hemodynamic waveforms in clinical record.  Include any vasoactive drugs, nitric oxide or other therapies aimed at improving hemodynamic variables.

Enter hemodynamic values in graphic record record. Enter venous blood gases that are drawn from the pulmonary artery catheter tip as "SVO2".

Prior to removal of a PA catheter it is useful to measure both a right atrial and pulmonary artery blood gas sample.

Review results with physician.

 11.

Data needs to be interpretted in light of the level of support.

SVO2 indicatest that these are "Mixed Venous Gases" from the pulmonary artery. These are different than an IJ or SC gas which only captures blood returning from the head and upper extremities.

SVO2 includes the oxygen that is remaining in the blood returning from the IVC, SVC and coronary sinus. This is a true "MIXED sample of venous blood" that is captured before reoxygenation in the lung.

Measuring RA and PA blood before catheter removal enables subsequent interpretation of the RA blood. These two sample are not usually identical and following removal of the pulmonary artery catheter it can be difficult to know how to interpret (e.g., has the patient actually changed or the different results reflect the different sampling location)

 

Developed: August 3, 2006, December 21, 2012
Last Update:March 23, 2010
Susan Williams RN BScN CNCC-C, CCTC
Brenda Morgan RN BScN MSc CNCC, CCTC

REFERENCES


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2. Lenart S, Polissar NL. Comparison of 2 methods for postpyloric placement of enteral feeding tubes. American Journal of Critical Care. 2003; 12:357-360.

3. Griffith DP, McNally AT, Battey CH, et al. Intravenous erythromycin facilitates bedside placement of post pyloric feeding tubes in critically ill adults: A double-blind, randomized placebo-controlled study. Critical Care Medicine. 2003; 31:39-44.

4. Booth, CM., Heyland, DK., Paterson, WG. (2002). Gastrointestinal promotility agents in critical care: A systematic review. Crit Care Med. 2002 Jul;30(7):1429-35.

5. Zaloga GP, Roberts PR. Bedside placement of enteral feeding tubes in the intensive care unit. Critical Care Medicine. 1998; 26:987-988.

6. Carroll GC. A Technique that improves the safety of feeding tube insertion. Critical Care Medicine. 2003; 31:1603-1604.

7. Thurlow PM. Techniques, materials and devices: Bedside enteral feeding tube placement in duodenum and jejunum. Journal of Parenteral Enteral Nutrition. 1986; 10:104-105.

8. Zaloga GP. Bedside method for placing small bowel feeding tubes in critically ill patients: A prospective study. Chest. 1991; 100:1643-1646.

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Last Updated December 21, 2012 | © 2007, LHSC, London Ontario Canada