PFO EVALUATION WITH Power M-Mode TCD

Power M-Mode (PM)-TCD machine is used to monitor the anterior circulation of the brain through the temporal bones or by interrogating the cervical internal carotid arteries.  A right or left upper extremity vein (the antecubital site is optimal and preferred) is accessed using a 21, 22 or 23 gauge butterfly infusion set or an IV catheter set.  Three syringes are prepared with 9cc’s of saline and 1 cc of air.  Intravenous injections are made using agitated saline during normal respiration and with a 10-second 40 mmHg calibrated Valsalva strain and a 10-second non-calibrated Valsalva strain.  Injections may be confirmed by Doppler monitoring the pulmonary artery or by echocardiography of the right atrium.* 

PROTOCOL 

1.  Check to ensure you have the following for the Power M-Mode TCD machine.

• Hand held probe
• Two Ball probes
• Two cables
• Head frame with pads
• Ultrasound gel

2.   Check to ensure you have the following for the intravenous injections. 

• One unit of 30 ml bacteriostatic sodium chloride 0.9% solution (aka saline).
• Four 10 cc syringes
• One needle for drawing solution into the syringes
• Alcohol swabs (2-3)
• One of the following:  butterfly infusion set or IV catheter with 6-inch extension set
• One 3-way stopcock with rotating male luer lock adaptor
• Surgical tape and/or 3M Tegaderm
• Cotton ball
• Gloves
• Valsalva meter
• Tubing
• Pulmonary Artery Monitoring Device or transthoracic echo monitoring*

*To avoid false negatives and to time the Valsalva, we monitor the pulmonary artery with a Doppler probe (2-5 MHz) placed along the left mid-sternum border.  Here we detect the “bubble cloud” that produces a loud noise when it impacts the right side of the heart.

 

3.    Turn on pm-TCD machine and enter patient data.

4.    Place head frame on patient, being sure the frame is snug, but not painful for the patient.

5.    Plug in hand held probe.  Find the best temporal window and mark and/or note location of the window and attach ball probe to the head frame so that the probe aligns in the area the windows was found.

6.    Plug cable that is connected to the ball probe into one of the two ports on the pm-TCD (note:  use the top port for the left probe and the lower port for the right probe).

7.    Annotate/label the vessel on the pm-TCD accordingly.

8.    Optimize signal and then tighten probe to the head frame.  Lock the desired angle of the probe by tightening the lever. Proceed to the contralateral side and repeat steps # 5, 6 and 7.

 

Intravenous injection preparation and procedure using butterfly infusion set: 

1.   Determine which arm and vein will be used for venous access (antecubital access is preferred).       

2.    Prep the arm by applying a tourniquet and prep site of venous entry with an alcohol swab.              

3.    Open the butterfly needle package, straighten out the tubing of the set and attach the three-way stopcock to the end of the tubing. 

4.    Attach one of the prepared saline syringes to one of the two available ports on the stopcock.  (Saline syringe should be on the port that aligns with the tubing). 

5.     If gloves are not already on, put gloves on now.

6.     Advise the patient you are ready to proceed with the “stick” just before you do so.

7.     Insert needle into the vein.

8.     Remove tourniquet.

9.   Attach the second (1 cc of air) syringe to the stopcock.

 

Intravenous injection preparation and procedure using an IV catheter

1.   Determine which arm and vein will be used for venous access (antecubital access is preferred).

2.    Prep the arm by applying a tourniquet and prep site of venous entry with an alcohol swab.                 

3.    Open 6” tubing extension kit

4.     Open the stopcock package and attach stopcock to the tubing.

5.    Open the IV catheter needle.

6.     If gloves are not already on, put gloves on now.

7.     Advise the patient you are ready to proceed with the “stick” just before you do so.

8.     Insert needle in the vein.   Advance canula and remove the needle by pulling the needle out while advancing the canula.

9.     Remove tourniquet.

10.   Remove needle and dispose of in a Sharps Container.

11.   Quickly attach the 6” tubing extension set to the IV.

12.    With the stopcock lever in the off position connect the saline syringe and the 1 cc of air syringe to the stopcock.

 

BUBBLE STUDY

Intravenous injection at rest and with normal respiration – first injection

1. Place CW probe slightly left to the left of the mid chest to monitor the pulmonary artery to confirm arrival and timing of micro bubbles after the injection.
2. Press “Record” and then “Save” on the pm-TCD.
3. Draw a small amount (~.5 cc) of blood (if possible) from the vein into the syringe with the saline solution and then proceed to agitate the saline solution to create micro bubbles for the injection.
4. After approximately 10 agitations, rapidly inject the solution into the access site.  Announce when you start the injection and press “Save” on the pm-TCD.  Note the number of cardiac cycles/seconds it takes for the bubbles to reach the pulmonary artery (this information will be used for the timing of the Valsalva strain(s) during the calibrated and non-calibrated injections.
5. Observe the pm-TCD screen for micro embolic tracks (bubbles) for a period of one minute post injection.

 

VALSALVA STRAIN INJECTIONS

The patient will be instructed when to perform the Valsalva maneuver based on the number of cardiac cycles determined from pulmonary artery monitoring or visualization of the bubble bolus in the right atrium utilizing echocardiography during the first injection.  A brief explanation of how to perform both the calibrated and non-calibrated Valsalva maneuver should precede the second and third injections.  For the second injection the patient will be advised to take a deep breath, bare down and blow on the tubing connected to a syphgmometer for a count of 10 seconds.  For the non-calibrated Valsalva, advise the patient to hold their breath while bearing down for a count of 10-seconds.

 

Intravenous injection – 40 mmHg calibrated Valsalva strain

1. Connect tubing to the syphgmometer.
2. Hand tubing to patient and discuss what they will need to do in order to adequately perform the Valsalva maneuver portion of the exam.
3. Repeat steps #2, 3 and 4 (from the “at rest” injection description above); advise the patient to begin the Valsalva maneuver at the appropriate time post iniation of the injection and to then blow into the tubing.  Press “Save” when the patient starts to bare down and blows on the tubing. 
4. After 10-seconds advise the patient to breathe normally and to remain still and quiet.  Press “Save” on the pm-TCD at this time.
5. Observe the pm-TCD screen for micro embolic tracks (bubbles) for a period of one minute post injection.

 

Intravenous injection – non-calibrated Valsalva strain

6. Repeat steps #2, 3 and 4 (from the “at rest” injection description above); advise the patient to begin the Valsalva maneuver at the appropriate time (i.e. the number of cardiac cycles/seconds) after the iniation of the injection and to hold their breath for a count of 10 seconds.  Press “Save” when the patient starts to bare down. 
7. After 10-seconds advise the patient to breathe normally and to remain still and quiet.  Press “Save” on the pm-TCD at this time.
8.  Observe the pm-TCD screen for micro embolic tracks (bubbles) for a period of one minute post injection.