Pulmonary Hypertension

Cardiac ultrasound can be used to show the presence of pulmonary hypertension if there is a tricuspid insufficiency, pulmonary stenosis, or pulmonary insufficiency.  Continuous Wave Doppler is used to determine the velocity and pressure gradient of the valvular flow.  Pulsed Wave Doppler is not capable of measuring higher flow rates.  Pressure gradient indicates the difference between the pumping chamber (the right ventricle in this case) and the receiving chamber (either the right atrium in tricuspid insufficiency or the pulmonary artery in pulmonary stenosis).  A pressure gradient of 10-50 mm Hg is considered to mild pulmonary hypertension, 50-80 mm Hg is moderate, and greater than 80 mm Hg is severe.

Radiographs can also be used to show more severe pulmonary hypertension.  If the anterior pulmonary arteries are larger than the veins on the lateral views, pulmonary hypertension is present.  On the VD or DV views, the caudal pulmonary arteries will be larger than the veins.     

There seems to be some confusion about treatment of pulmonary hypertension.  Some recent lectures have unintentionally given the idea that all cases must be treated and that Viagra is the treatment.  First, show that pulmonary hypertension is present.  Then, identify and treat the cause of the hypertension.

If heartworm disease is present, treat the heartworm disease.  If pneumonia is present, treat the pneumonia, etc.

If pulmonary valve stenosis is present, mild cases (PG of 10-50 mm Hg) are not treated.  The patient will probably live a full life without symptoms or need for treatment.  In moderate to severe cases, ballon valvuloplasty can be done to partially relieve the stenosis.

Pulmonary hypertension is a secondary problem with mitral insufficiency or mitral stenosis because blood backs up to the lungs.  The right ventricle must pump against the increased resistance of the mitral insufficiency.  The presence of a tricuspid insufficiency allows us to use Continuous Wave Doppler to estimate the pressure of the right ventricle.  Normal pressure in the right ventricle is 20 mm Hg and a pressure of 30 mm Hg or higher is considered to represent pulmonary hypertension.  Usually, treatment of the mitral insufficiency will also treat the pulmonary hypertension.  

Viagra is usually only used in the last 30 days of the patient's life when end stage disease results in uncontrollable pleural effusion.  This can be seen in , end stage heart disease (severe mitral insufficiency, tricuspid insufficiency, pulmonary stenosis, pulmonary insufficiency, aortic stenosis, aortic insufficiency), pulmonary fibrosis, chronic fungal pneumonia, neoplasia, or other infiltrative diseases.

What Kind of Machine Should I Buy 3

Next, look for a machine that is user friendly. How can you tell if it will be easier to use? Look at the keyboard. Are the buttons, knobs, or toggles clearly labeled as to the function they control? With some machines, each button, knob, or toggle may have multiple functions. Ask to see the owner’s manual. If there is one booklet, the machine is probably user friendly. If there are 3 or 5 separate booklets, it is a very complicated machine. In my opinion, the complicated, “big box” ultrasound machine is capable of making multiple adjustments to give the absolute best quality image, but the operator must know and use all of the available button, knobs, and toggles to get that image. This type of machine may cost $80,000 to $350,000 or more and is a necessity for a radiologist or cardiologist. It is perfectly acceptable if this is the kind of machine you want. In my opinion, this is more ultrasound machine than a general practitioner needs. In my opinion, a general practitioner needs a machine that is user friendly and can be quickly learned and put to use in the practice. In my experience, when machines or procedures are difficult or tedious, most people will not use the machine or do the procedures. Take the time (2-3 days) to study the owner’s manual and learn how to use the machine you buy.

Fourth, what kind of training is available to you? An ultrasound machine is worthless if you do not know how to use it. Some ultrasound sales companies include training in the cost of the machine. It is not free. You are paying for it whether you use it or not. You will probably have to pay for your own travel and lodging to get to the training. You may consider separating the cost of training from the cast of the machine, especially if you are financing the cost of the machine. Some ultrasound companies offer training for a fee.

What Ultrasound Machine Should I Buy Part 2

After you have determined what your practice needs are, as you research ultrasound machines available, ask if the machine is capable of supporting the procedures you want and how many transducers you will need to do those procedures.  If you start with abdomens but eventually want to do hearts as well, does the machine have cardiac capability or can it be upgraded to cardiac functions when you are ready?  Sometimes you just need to buy a cardiac transducer when you are ready.  Sometimes you have to buy a new machine that can do hearts and abdomens.  Think about your future needs.  For shallow depths (like cat or exotic abdomens, equine tendons or repro) you need higher frequency transducers.  For deeper depths (like large dog or equine abdomens) you need lower frequency transducers.  For most procedures in the small animal abdomen, you want a micro-convex transducer.  For shallow structures (pancreas, intestines) a linear transducer could be helpful.  For cat hearts you need a higher frequency cardiac transducer.  For some large dogs and horses, you need a lower frequency cardiac transducer.  Colorflow Doppler is very useful in the abdomen, but it will increase the cost of the machine.  For cardiac studies, Colorflow and Spectral Doppler (both Pulsed Wave and Continuous Wave) are necessities and will increase your total cost.  I caution you not to buy a machine because it is cheap, but because it will do what you need.    For diagnostic purposes in any heart, you MUST HAVE COLORFLOW DOPPLER, PULSED WAVE DOPPLER, AND CONTINUOUS WAVE DOPPLER.  Will the machine allow you to easily download patient information and images?  Can it do video clips?  Can the hardware and software be upgraded?  How long is the warranty?  If it is an older model, how much longer will the manufacturer support repairs?    

Phantom

Someone just asked how to make a practice phantom since commercially available phantoms are rather expensive and have limited usage life.  When training, I use a jello mold filled with objects (mostly dried fruit) for developing scanning and fine needle biopsy skills.  It is a homemade phantom that is inexpensive and effective.

My Recipe: 

2 Large Packages Black Cherry Jello (the darkest color available to disguise the objects you add) + 2 packets of plain Knox gelatin (for firmness)
Disolve Jello and gelatin in 3 cups of hot water (not boiling)
Pour mixture into a 1 quart ziploc freezer bag.  Add 12 prunes.  Eliminate as much air as possible as you seal the bag.  Lay the bag flat in the refrigerator and allow the gelatin to set.  It will become quite firm.  Remove from the refrigerator, use ultrasound gel, and practice.

Sometimes I add small balloons filled with milk or water for cystocentesis practice.

Many people figured out how to use Jello to make phantoms.  I adapted my recipe from Knox Blox.  How many of you are old enough to remember those?  I think, more recently, they're called Jigglers.

What Kind of Machine Do I Buy?

What kind of ultrasound machine should I buy?

Many people visit our booth at veterinary convention exhibit halls to ask this question.  It is a very good question but will take some time to give a good answer.  I will divide this into four topics:

1.       List the ultrasound procedures you want to do

2.       Search for a machine that will support the applications you want to do

3.       Look for a machine that is user friendly

4.       Ask what kind of training is available 

Assess your wants and needs:   you need to decide what kind of ultrasound procedures you want to be able to perform BEFORE you start researching equipment.  If your practice is limited to small animals, do you want to limit yourself to abdominal ultrasound only, or would you like to expand to cardiac ultrasound some day?  Are you interested in exotic animals or reproduction studies?  If you are limited to large animal practice, do you want to do tendons, reproduction, cardiac, and abdominal studies?  If you are in a mixed animal practice, do you want to do everything?  Make a list of the types of procedures you want to be able to perform.  If you have multiple doctors in your practice, enlist them in the decision making process. 

 WHY?  The cost of your unit will depend upon the requirements you place on it. Your basic unit is hardware consisting of a computer processor (also known as the platform) attached to transducers (which gather the information that feeds the processor and a screen (which displays the images generated by the processor).  Most new ultrasound units display very good to excellent images.  Transducers, though versatile, tend to be task specific so it is important to know what tasks you want to perform.   The platforms depend upon software written to accomplish specific tasks:  creating an image, measurement and labeling packages, filing, retrieving data etc.  If your facility is computerized, you may also want to ask if the units you are considering are easily compatible with your current image storage system.

So, when looking for an ultrasound unit, it is very important for you to have a list of the types of procedures you want to perform, the types of patients you serve in your practice, and the kind of record storage you use in your clinic or hospital.

Learning to Perform Ultrasound Exams

My name is Dr. Craig McInnis.  I am a veterinary small animal practitioner, like you.  I just returned from NAVC in Florida.  Many people dropped by our booth with questions about ultrasound:  training, learning curve, ultrasound machines  etc.  Obviously learning and applying ultrasound in a general practice setting is increasing.  I've decided to start this blog to help field questions about learning ultrasound.

LEARNING ULTRASOUND

As a veterinary general practitioner, you read radiographs, but you are not a radiologist.  The same will be true of the ultrasound skills you develop.  You will do ultrasound to find lesions obvious to you.  After your ultrasound exam, if you feel you did not find the cause of the patient’s symptoms, you can consult with or refer to a more experienced sonographer.  This is the same thing you do with radiographs, surgeries, or internal medicine cases when you feel the patient needs more expertise than you have.

We DO NOT follow the traditional method of ultrasound training.  We have developed NEW and MUCH MORE EFFECTIVE methods of training that WILL help you learn much faster than I did.

A good beginning ultrasound training program should address three major areas

a.        It should teach the basic concept of using the transducer to move the ultrasound beam around the abdomen or the structures of the heart.  This is a process of developing manual skills to manipulate the transducer and visual skills of reading the ultrasound screen. 

b.      It should teach you to use the functions and controls of the ultrasound machine you will be using in your practice.  Every manufacturer uses different buttons, knobs, or toggles to control the qualities of the ultrasound beam and the image on the ultrasound screen.  You need to know how to establish a patient record, adjust depth, gain, and frequency, use cinematic loop, make measurements, and save and retrieve images.  Using all of the functions of your own ultrasound machine needs to become second nature; something you do not have to think about or search for.      

c.       It should teach a method of systematically finding and examining the organs of the abdomen or the structures of the heart.

Our intensive on site ultrasound training programs addresses all of these areas.  Even so, no one can remember everything from a training program.  For the abdomen, we have developed the Tips & Techniques and General Abdominal Scan DVDs to help you learn abdominal ultrasound.  You can review the DVDs as often as you need.  For the heart, we have developed the General Cardiac Exam.  The DVDs can also be used alone as a SELF STUDY training program.   

After learning the basic skills, you need to practice your skills A LOT.  Ideally, YOU should PERFORM ultrasound examinations under the supervision of an experienced sonographer for about 3-6 months.  This does not mean that you WATCH SOMEONE ELSE do exams.  YOU MUST PERFORM THE EXAMS.  This is when you practice and learn to recognize abnormalities.  Most of us can not afford the time or money to study and train in this way.

As an alternative, we have developed a series of DVDs to help you learn as much as possible on your own.  The individual organ DVDs help you learn to recognize abnormalities. 

Watching DVDs is not enough.  You must still practice your skills A LOT.  In the early stages of learning, most people feel that they are not competent enough to charge for their ultrasound skills.  This feeling is very common but counterproductive.  If you do not charge something, in your own mind, your services are worthless.  In the long run, you will not waste your time doing something that is worthless. 

It is much more productive to charge a lesser fee to help cover the cost of your time and your ultrasound machine.  I suggest calling your exam a FAST exam or an abdominal screen.  You should only offer to screen the abdomen for something that YOU will recognize, like free fluid or obvious masses.  For example, if a patient is presented for hematuria, you would be looking for signs of stones, infection, or a tumor in the kidneys or urinary bladder.  You will be providing a service for the patient and for the owner.  You will be gaining experience.  If you are not satisfied with your own results, you can refer to or consult with a specialist, just as you do now.  As you improve your own capabilities and experience, your fee can be increased. 

Even when you have experience and confidence, you will have clients who refuse a referral to a specialist or refuse to allow you to do a complete abdominal or cardiac scan.  Consider offering a targeted exam for a lesser fee.  If liver values are elevated, limit your ultrasound exam to the liver and gallbladder.  If urinary signs are present, limit your exam to the kidneys and urinary bladder.  This strategy will give another option to your client while making it possible for you to practice your skills and increase your income.  Both you and your client must realize that a targeted exam will miss lesions in other organs.

New discoveries continue to be made as technology advances.  Information we believe to be true today is often proven to be false tomorrow.  You should continue to supplement your studies with ultrasound books for your reference library and continuing education lectures. The study and application of ultrasound in your OWN practice will make YOU a BETTER VETERINARY PRACTITIONER.  Let’s get started!