Critical Care and TraumaSection EditorJukka TakalaEvaluation of Bluetooth as a Replacement for Cables in Intensive Care and Surgery Mats K. E. B. Walling MD, MSc t, and Samson Wajntraub, MSc t From the Department of Anesthesiology and Intensive Care, Karolinska Hospital and the Division of Medical Engineering, Department of Medical Laboratory Science and Technology, Karolinska Institute, Stockholm, Sweden

In today’s intensive care and surgery, a great number of cables are attached to patients.  These cables can make the care and nursing of the patient difficult.  Replacing them with wireless communications technology would facilitate patient care.  Bluetooth is a modern radio technology developed specifically to replace cables between different pieces of communications equipment.  In this study we sought to Determine whether Bluetooth is a suitable replacement-for cables in intensive care and during surgery with respect  to electromagnetic compatibility. The following questions were addressed: Does Bluetooth interfere with medical equipment?  And does the medical equipment decrease the quality of the Bluetooth communication’.  A Bluetooth link, simulating a patient monitoring system, was constructed with two laptops.  The prototype was then used in laboratory and clinical tests according to American standards at the Karolinska Hospital in Stockholm.  The tests which included 44 different pieces of medical equipment, indicated that Bluetooth does not cause any interference.  The tests also showed that the hospital environment does not affect the  Bluetooth negatively. (Anesth Analg 2004,98:763-7)

Computerized ECG Interpretation Vmed Interpreter

“Computerized ECG interpretation programs are well established in the human field. The new Vmed ECG Interpreter now makes computerized interpretation a reality in veterinary medicine. The computer reading provides a second opinion and is especially helpful for inexperienced clinicians.  When the ECG Interpreter identifies an ECG as abnormal, the analysis software can then be used to further clarify the diagnosis. The Vmed system also makes it easy to store the Interpreter report on clinic computers and to email this report to a specialist if further confirmation is needed.”  Larry Tilley, DVM, DACVIM (Internal Medicine)

ECG in Clinical Practice, By Larry Tilley DVM, DACVIM (Internal Medicine) Vmed Diagnostics

Because of the new hand-held technology, recording an ECG is a simple task. By using the ECG, the quality of veterinary care is markedly improved. Arrhythmias and conduction disturbances can be quickly diagnosed and promptly treated. Hand-held units allow you to make a diagnosis quickly, and being portable you can easily perform the test in the exam room with the owner. If abnormalities are noted, the ECG can be printed and faxed for a telemedicine consult. You can easily pay for the ECG machine and generate additional income. A small screen ECG fee of $20-$25 can be charged since the tests is so easy to do. Considering how common heart disease is in dogs and cats, I would estimate that most veterinarian practices should be running at least one ECG daily.

No. The position of the animal is not critical for analyzing abnormalities in cardiac rhythm and AV nodal conduction. Right lateral recumbence has been established as a standard procedure for recording the ECG. This positioning is not critical on the majority of ECG’s that are done in veterinarian medicine. Right lateral recumbence is only critical for recording the ECG when the size of the complexes and “mean electrical axis” are used to determine heart chamber enlargement patterns and to assess for interventricular conduction disturbances. The ECG however is not the most sensitive or specific test for heart enlargement and should be used mainly for rhythm evaluation. The best way to determine heart enlargement in animals is with a chest X-ray or echocardiogram! This is why the hand-held ECG technology is so useful in veterinary medicine. The electrocardiogram can be recorded and an accurate rhythm diagnosis obtained with the animal standing or sitting, on the floor, table or in the cage.

With cats, you may find that the ECG complexes are very small and the unit may not display the heart rate. This is a common occurrence in cats and is seen with all equipment including hand-held technology. It is first important to check that the cause is not actual fluid in the chest cavity. Other factors that can cause this small signal are obesity or poor electrode contact. With the hand-held ECG technology, the unit can be positioned in a different direction on the chest wall and sometimes this can make the complexes larger based on how the electrodes are aligned on that particular case. In many cases the complexes are actually increased in size with hand-held technology because the electrodes are actually in close proximity to the heart. The hand-held technology is also capable of recording all of the leads using actual electrodes that are attached to the animal’s limbs. If the complexes are too small, all of the various leads should be recorded and in many cases, one of these leads will make it easier to see the complexes.

The majority of ECG’s are recorded at a paper speed of 25 or 50 mm/second. When the rate is rapid, as in cats, it often is desirable to record the ECG at a paper speed of 50. Even when the rate is not fast, it is often helpful to record a small portion at 50 mm/sec to make it easier to evaluate the complexes.

It is not uncommon with the hand-held recording to have complexes that have a negative polarity as the hand-held recording is actually recording in many cases a precordial chest lead, very similar to what is done when the fifth precordial chest lead of a ECG cable as positioned over the top of the heart on the left side. Precordial chest leads are quite useful as the complexes are often increased in size and are often easier to determine P-QRS complexes even though the complexes may be “upside down.” Remember, primary focus with the ECG is heart rate, analyzing any arrhythmias, and also conduction analysis. To determine if the heart is enlarged, the chest X-ray or the ultrasound study is the most accurate test.

Yes. One advantage of the hand-held units in large animal practice is the portability. They are small and battery operated, so you can easily bring them into a barn, field, or racetrack and obtain an ECG. This can be quite useful for a horse that quits in a race or during training and you suspect a transient arrhythmia. Immediately after a race or training period, the hand-held unit can be placed on the horse’s chest and the rhythm observed. Any abnormalities can be saved and printed for further analysis.

CVC Highlights: Essentials for interpreting ECGs in practice *  Larry P. Tilley, DVM, DACVIM (internal medicine), VetMed Consultants, Inc., 1704-B Llano St., Suite 279, Santa Fe, NM 87505.

Larry P. Tilley, DVM, DACVIM

Indications for electrocardiography include arrhythmias heard on auscultation, breathing problems, shock, fainting or seizures, cardiac murmurs, and systemic disease that affects the heart (e.g. tumors, kidney dysfunction, heartworm disease). Electrocardiography is also useful as part of the preoperative work-up in older animals, for monitoring patients during and after surgery, and for evaluating the effects of cardiac drugs. An electrocardiogram (ECG) is the only test that can accurately diagnose an arrhythmia or a conduction abnormality. And an ECG will help you decide when other diagnostic tests should be done, including blood pressure measurement, thoracic radiography, or even echocardiography.

Perform electrocardiography on a periodic basis in breeds prone to arrhythmias, especially if clinical signs are present. These breeds include boxers (myocarditis), Doberman pinschers (ventricular arrhythmias and possible cardiomyopathy), German shepherds (congenital ventricular arrhythmias), and miniature schnauzers (sick sinus syndrome and sinus arrest/block).

ECG analysis: A systematic approach

Most veterinarians can interpret their own patients’ ECGs by simply focusing on the heart rate and rhythm. The mean electrical axis and the size of the complexes can help identify heart chamber enlargement, but the best way to detect cardiac enlargement in animals is with a thoracic radiograph or an echocardiogram. It is recommended that practitioners have two electrocardiography machines: an oscilloscope and an electrocardiograph. An oscilloscope is necessary for monitoring patients during surgery, and an electrocardiograph is needed for clinical diagnostic testing. The electrocardiograph linked with a strip recorder or printer provides a permanent record. The ECG can be recorded with the patient in a standing position, or you can use a hand-held unit with the patient in any position. New wireless technology (e.g. Vmed PC Vet—Vmed Technology, Inc.) also allows an ECG to be done without wires connected directly from an animal to the electrocardiograph.  Before examining an ECG, read the tracing before it is cut and mounted; it is important to study long strips of one lead (usually lead II) for an accurate analysis of heart rate and rhythm. Lead II is typically used for the analysis of heart rate and rhythm and for measuring complexes and intervals. A systematic method for accurate electrocardiographic analysis of a rhythm strip (again, usually lead II) for arrhythmias includes the following steps:

Step 1. Generally inspect the rhythm strip

First, determine whether the rhythm is normal sinus or is characteristic of a cardiac arrhythmia. Next, assess whether the heart rate is rapid, slow, or normal. To easily calculate the heart rate (beats/min), count the number of beats (R-R intervals) between two sets of marks in the margin of the ECG paper (3 seconds at 50 mm/sec) and multiply by 20. ECG rulers are also available. This is all the measuring we need to do. Measuring the width and height of P-QRS-T complexes can also be done, but these measurements are not always accurate for a precise diagnosis of heart enlargement.

Step 2. Identify the P-waves

Determine whether the atrial activity is regular and the P-wave shape uniform.

Step 3. Recognize the QRS complexes

Evaluate the morphology, uniformity, and regularity of the QRS complexes.

Step 4. Evaluate the relationship between P-waves and QRS complexes

To assess atrioventricular (AV) conduction, measure the P-R interval, which is the time from the onset of the P wave to the onset of the QRS complex. In patients with normal sinus rhythm, P-R intervals are constant. By evaluating the relationship between the P wave and the QRS complex, you can identify the dominant rhythm. An abnormally long P-R interval may indicate an AV conduction delay or first-degree heart block. If a QRS complex doesn’t follow a P-wave, second-degree heart block is present. A decreased P-R interval may occur with accessory conduction around the AV node.

Step 5. Summarize the findings and classify the arrhythmia

What is the predominant rhythm? Is the arrhythmia an abnormality of impulse formation or impulse conduction or both? If either or both, what is the site of the abnormality? To classify arrhythmias, you need to know two things:
1. The site of origin of the abnormal beat (i.e. the sinoatrial node, the atrial conduction tissue, the AV node-His bundle junction, or the ventricular conduction tissue [bundle branches and Purkinje fibers]).
2. Deviations from the normal rate of automatically at that site (i.e. tachycardia, bradycardia, block, arrest).

Four types of arrhythmias can be identified on lead II by the following features:

1. Sinoatrial origin. Increased vagal tone results in sinus arrhythmia and sinus arrest. A lesion in the sinoatrial (SA) node can possibly result in SA block.
2. Atrial origin. These beats originate from somewhere in the atria other than the SA node. These atrial premature complexes look like a normally conducted beat except their timing is early. A big hint is that the P-wave of the atrial beat is superimposed on the T-wave of the beat before it. Atrial fibrillation (a rapid and irregular heart rate and no P-waves) usually indicates severe heart disease.
3. Junctional origin. These beats originate near the AV node and have a negative deflection P-wave, or no P-wave, with a normally conducted, short-duration QRS complex.
4. Ventricular origin. These beats originate somewhere in the ventricles. The QRS complexes are wide and bizarre-appearing and may have positive or negative polarity. Ventricular premature complexes and ventricular tachycardia are the result.

*Attendees selected this highlight from CVC lectures. The original paper was published in the proceedings of the 2005 Central Veterinary Conference.

Small Animal Blood Pressure Vmed Blood Pressure Solutions

Indirect Blood Pressure Determination in Cats using Doppler Ultrasonic and Oscillometric Methods

A Mollenhoff, I Nolte, S Kramer, Univ Leipzig, Fak Vet Med, Klin Kleintiere, Tierkliniken 23, D-04103 Leipzig, Germany. Tierarzliche Praxis Ausgabe Kleintiere Heimtiere, 2001, Vol 29, Iss 3 pp 191-197:

“Blood pressure measurements obtained using Doppler ultrasonic flow meter and an oscillometric device in 11 conscious cats were compared.  Systolic blood pressure was not significantly different from each other (p<0.05) within a range from 100 to 150 mmHg (Doppler) rsp. 101 to 154 mmHg (oscillometric device) using cuffs with a width 41.2% rsp 44.3% the limb circumference.  The oscillometric device failed when blood pressure was low, it required more time to obtain readings and measurements were less consistent compared to the Doppler technique.  The Doppler flow meter detected a pulse under all conditions and readings were hardly influenced by movement in contrast to the oscillometric device.”

Using the Doppler as a Surgical Monitoring Device Vmed Vet-Dop2

R. Randy Bassinger, DVM, ACVS, South Carolina Veterinary Referral Center, Columbia, SC

“Doppler flow technology presents several desirable characteristics over other monitoring devices as a surgical monitoring device.  The ability of the Doppler to measure blood flow in a peripheral artery and generate an audible sound with each pulse provides the surgeon with an ‘eyes free’ way to evaluate their patient’s cardiovascular performance while continuing to focus on their surgery.  If the peripheral Doppler sound is good, the systolic blood pressure is within an acceptable range, and with a sphygmomanometer above the Doppler transducer, the systolic pressure can be easily and economically measured and entered into the anesthetic record.  Although diastolic pressure cannot be measured this way, the reliability of Doppler blood pressure monitoring allows the anesthetist to spend less time fiddling with the monitor and more time monitoring the patient.  Heart rate can also be monitored audibly and recorded.  A particularly strong value of the Doppler is the ability of the anesthetist or surgeon to hear ventricular premature contractions (the most common arrhythmia under anesthesia) as a ‘dropped sound’ in and otherwise stable, rhythmic ‘whoosh, whoosh, whoosh’; often in plenty of time to look up at the ECG tracing and watch the VPC go by on the screen!  Supplemental ventilation of these patients will often resolve this common arrhythmia.  Because the Doppler is portable, it can be moved with the patient easily when moving to radiology or the recovery area.  Their low cost relative to other monitoring devices, reliability and toughness make them the best ‘bang for the buck’ surgical monitoring device in many people’s opinion.

Small Animal Blood Pressure Measurement

Larry P. Tilley, DVM, Diplomate, ACVIM (Internal Medicine) “Systemic Hypertension:  Diagnosis and Treatment”.  The 5 Minute Veterinary Consult, Larry P. Tilley and Francis W. K. Smith, Jr.  Williams and Wilkins
On a practical level, every veterinary practice should have a blood pressure unit, especially in feline medicine.  Numerous studies in the veterinary literature show that a large percentage of cats more than 12 years of age have hypertension, either secondary to chronic renal disease or from underlying thyroid disease. A blood pressure monitoring device is critical for practitioners who see a large number of geriatric feline patients. Blood pressure should be recorded for cats with left ventricular hypertrophy of an unknown cause, cats with renal disease, cats with acute visual problems, and other critically ill patients.  Diseases commonly associated with hypertension in both the dog and cat, include systemic hypertension and renal disease, hyperadrenocorticism, hyperthyroidism, essential of primary hypertension, and pheochromocytoma. Of these, Cushings disease (dogs) and renal disease are probably the most common. The majority of cats diagnosed as hypertensive are presented to veterinarians for the evaluation of ocular abnormalities such as dilated pupils, hyphema or presumed blindness.
Blood Pressure Guidelines
It is important to realize that “normals” are going to depend on technique and the status of the patient. tt is best to take 5 to 6 recordings and to eliminate the upper and lower values and average the remaining values. A systolic blood pressure is elevated in an unstressed, awake, dog or cat if it is consistently greater than 170 – 180 mmHg in the cat, or greater than 180 mmHg in the dog.

Measuring Blood Pressure

Though there is some variation in reported parameters in the literature, it is commonly accepted that a systolic pressure above 170 mmHg indicates clinically significant high blood pressure in cats. Because cats are prone to the so-called “white coat syndrome”, which is a stress response due to cortisol release as a result of handling, restraint, or just being in a clinic rather than in a familiar home environment, results of a single blood pressure check should not be considered accurate. Due to this variability associated with performing blood pressure measurements, it is recommended that seven measurements be taken, and that the highest and lowest values be discarded, with the remaining five averaged.   Other tips for accurate measurement include Using headphones to ensure that the sound does not stress the patient. This also allows you to hear the sound of the machine more effectively, increasing your accuracy.   Shave the area for the transducer very short, and apply adequate ultrasound gel so that good contact is ensured. If an assistant can hold the transducer in place, this will likely help because the artery tends to roll around under the skin, and minor adjustments in position often need to be made. Using tape is the alternative, but apply it so that it can be quickly removed and adjusted as needed.   Just the right amount of pressure on the transducer is essential. Too much and the flow will be reduced, too little and it will slip out of position. Make sure that if a limb is being used, that its position does not compromise blood flow to the extremity where the transducer is in place. Use a correctly sized cuff for the patient. Its width should be about 1.5-2 times the diameter of the antebrachium. Inflate the cuff slowly if the patient is awake to ensure they are not startled.

The Doppler Technique

1. Assemble the Doppler unit before addressing the cat. Plug in the headphones and place the ear pieces over your ears.
2. Position the cuff proximal to the hock, proximal to the elbow, or at the base of the tail, depending on which artery is to be used. Note: cuff size in width should be 40% of the circumference of the limb at the site of placement.  When the median tibial artery is used, a 2-to 4cm cuff is placed above the hock. The width of the cuff is critical when oscillometric technology is used, but it is not critical with Doppler technology. View cuff placement on a cat or a dog
3. Turn the unit on and set the volume in the high range. If the volume is too low, arterial sound may not be detected.
4. Apply a thin coat to coupling gel to the skin.
5. Apply coupling gel to the transducer.
6. Position the transducer over the artery. The median tibial artery is usually slightly medial to the midline. It is necessary to move the transducer until the “swishing” of the blood is heard in the artery. Hold it in place with your thumb. It may be necessary to apply firm pressure to assure proper contact between the transducer and the skin (too firm a pressure may occlude the artery).
7. Squeeze the bulb on the manometer until the pressure in the cuff exceeds that of the artery. At that point, the swishing of the blood in the artery will no longer be heard. Notice that filling the cuff too rapidly may frighten your patient.
8. Slowly reduce the pressure in the cuff by squeezing the manometer’s trigger. When the pressure in the cuff falls below the arterial pressure, the arterial swishing sound can again be heard. This should be noted and recorded.
9. Seven measurements should be taken. Discard the high and low readings and average the remaining five. This is considered the systolic blood pressure and is measured in mmHg.

Tips for using the Doppler

• Do not tape the transducer in place, as is recommended by some. The slightest movement of the cats foot or limb often moves the transducer enough that the arterial sounds are lost. Instead, hold the transducer in place with your thumb. If the artery is lost, slight movement of your thumb can relocate it.
• Use the maximal volume that is comfortable to your ears. Use the headphones. Although they are somewhat cumbersome, they minimize the stress of the procedure. The sounds of the external speaker frighten many cats, elevating their blood pressure. The headphones bypass the external speaker so the cat no longer hears the harsh sounds.
• The transducer is fragile (and expensive to replace). It may be damaged by dropping it or by striking it against something solid. Treat it with care.

• Use of ultrasound gel is essential. Do not use ECG paste or baby oil or alcohol. These products may cause deterioration of the resin surface of the transducer. Ultrasound gel is water soluble. Remove it from the transducer after each use. 4.  Comfortably extend the cat’s limb. If it is flexed, the blood flow through the artery may be abnormally restricted giving no readings or falsely low readings.

Hypertension defined 

• Cats systolic> 170-1 80 mm Hg; diastolic> 120 mm Hg

• Dogs systolic> 180 mm Hg; diastolic> 100 mm Hg
   Note the diastolic pressure can be detected in some cats by closely watching the dial of the manometer. It oscillates at the diastolic pressure level. However, a reproducible reading is not always    possible, especially in cats that are stressed due to catecholamine influence   (which makes the vessels more stiff than normal), cats that are cold, and very small patients. However, the important measurement in cats is the systolic blood pressure.

Treatment of Hypertension

The treatment for hypertension should focus on the underlying cause, if possible. Hyperthyroid cats that are hypertensive should be treated simultaneously for the hyperthyroidism and systemic hypertension. In cats with renal disease and systemic hypertension, medication is usually needed indefinitely to control the hypertension. The treatment of hypertension includes sodium restriction and specific medications. In the majority of cases, a low-sodium diet with a calcium channel blocker (amlodipine, for cats: 0.625 mg per cat every 24 hours). Angiotensin – converting enzyme inhibitors are sometimes also indicated if no response to a calcium channel blocker or, on some occasions, the two have to be given together. The blood pressure does need to be monitored on a periodic basis and to evaluate for any possible complications (especially retinopathy and glomerular disease). In the majority of patients, hypertension can be controlled with appropriate therapy.

The Doppler Stethoscope in Veterinary Medicine Vmed Doppler Stethoscope

Fredric L. Frye, BSc, DVM, MSc, CBiol, FiBiol

Ultrasonic Doppler Blood Flow Detection in Small Exotic Animal Medicine. Seminars in Avian and Exotic Pet Medicine, Vol. 3, No. 3, (July, 1994):  pp 133-139.

“Doppler ultrasound echocardiological examination is a useful means for evaluating the cardiovascular function in even the smallest reptiles and many, if not most, postmetamorphosed amphibians. The technique permits the resolution of the discrete sounds produced by atrial and ventricular myo0cardial contraction, atrioventricular and aortic valvular blood flow, intravenal caval filling and aortic ejection, and often the flow of blood within smaller individual arteries and veins.  The Doppler ultrasonic flow detector offers a relatively new, noninvasive, moderately priced, highly sensitive accurate and cost-effective alternative means for clinically evaluating intracardiac and intrvascular sounds even in very small patients.”