PRESENTATION
BROCHURE
Blood Pressure in Cats and Dogs. A Clinical Manual
Blood Pressure
in Cats and Dogs
A CLINICAL MANUAL
Enrique Ynaraja RamÃrez, PhD
Blood Pressure
Blood Pressure in Cats and Dogs. A Clinical Manual
Blood Pressure in Cats and Dogs. A Clinical Manual
in Cats and Dogs
A CLINICAL MANUAL
Enrique Ynaraja Ramírez, PhD
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AUTHOR: Enrique Ynaraja Ramírez. FORMAT: 17 × 24 cm. NUMBER OF PAGES: 128. NUMBER OF IMAGES: 105. BINDING: hardcover.
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€55
eBook included
A practical and simple manual on the methods and techniques to measure blood pressure in cats and dogs, how to interpret the results obtained, and the recommended treatments. It includes a brief review of the current official recommendations of the American College of Veterinary Internal Medicine (ACVIM), with clear rules and guidelines. This book also contains QR codes linked to videos on how to obtain precise blood pressure measurements.
Ermolaev Alexander/shutterstock.com
Blood Pressure in Cats and Dogs. A Clinical Manual
Presentation of the book Measuring blood pressure has been a routine procedure in human medicine for many years, since it offers valuable information on the interactions between the heart, kidney, blood vessels and autonomous nervous system. However, it has not yet become common practice in veterinary medicine, and protocols and techniques should thus be established to measure this parameter in a simple manner. This book explains the methods and techniques to measure blood pressure in small animal practice, with clear and precise information on how to use the equipment and cuffs, the areas where this parameter can be measured and the steps to follow. The images, diagrams and drawings help clarify the guidelines that should be followed to obtain accurate measurements. This book aims to be a practical and simple manual that explains the basic concepts of blood pressure monitoring without delving deeper into physiology or complex mechanisms and complicated systems, with an easy-to-read style and a visually attractive presentation. It also highlights the importance of maintaining blood pressure in a proper range and of knowing how to determine whether it is high (some possible causes are mentioned without a detailed review of their mechanisms) or below the normal value and how to treat both conditions. Finally, it includes a brief review of the current official recommendations of the American College of Veterinary Internal Medicine (ACVIM).
hkeita/shutterstock.com
Blood Pressure in Cats and Dogs. A Clinical Manual
The author Enrique Ynaraja Ramírez Dr Ynaraja holds a degree and PhD in Veterinary Medicine from the Complutense University of Madrid. He is an AVEPA (Spanish Small Animal Veterinary Association) certified specialist in small animal cardiology. He has spent time as a professor at two faculties of Veterinary Medicine – at the Complutense University of Madrid and at the CEU Cardinal Herrera University in Valencia. Dr Ynaraja is a founding member of CardioVet, a company that provides remote diagnostic services in veterinary cardiology to over 1,000 clinics in Spain, Portugal and Latin America, and currently works as a vet for Servicios Veterinarios Albeytar in La Vall d’Uixó, Castellón, Spain. He has published 140 articles in international journals from 18 countries, participated in over 500 courses and conferences held in 22 different countries and published 8 books and several online courses. Dr Ynaraja also actively collaborates with leading companies from the Spanish small animal veterinary sector to develop training courses and programmes, to disseminate information and to introduce and launch both pharmacological and nutritional products.
Blood Pressure in Cats and Dogs. A Clinical Manual
Blood Pressure
in Cats and Dogs
A CLINICAL MANUAL
Enrique Ynaraja RamĂrez, PhD
PY092808_Blood_pressure_cover.indd 3
27/6/18 14:24
Table of contents 1. Blood pressure Introduction
3. Blood pressure measurement techniques
Blood pressure measurement methods
Introduction
Normal values
What other methods are available?
Factors influencing blood pressure Blood pressure regulation mechanisms Immediate regulation: rapid control mechanisms Delayed regulation: mid-term control mechanisms Delayed regulation: long-term control mechanisms
2. Blood pressure measurement Introduction Blood pressure dynamics Anatomical locations for measuring blood pressure Measurements at the base of the tail Measurements on a forelimb Measurements on a hindlimb
Blood pressure measurement protocol for clinical practice
Doppler systems Oscillometric systems High-definition oscillometry (HDO) Plethysmography and photoplethysmography
Which parameters are measured?
4. Arterial hypertension Introduction Values obtained Diseases that cause hypertension in cats and dogs Hypertension and kidney disease Hypertension and obesity Hypertension and endocrine disorders
Target organ damage The central nervous system The heart The eyeballs The kidneys The blood vessels
5. Drug treatment of hypertension
6. Hypotension Introduction
Introduction
Causes of hypotension in cats and dogs
Courses of action to reduce blood pressure
Diseases and procedures that cause hypotension
Modification of cardiac output
Heart failure
Control over circulating volume
Diabetic coma or ketoacidosis
Vasodilation
Hypoadrenocorticism
Antihypertensive drugs Adrenergic receptor blockers Calcium channel blockers Angiotensin-converting enzyme inhibitors (ACEIs) Angiotensin II receptor antagonists (AIIRAs)
Hypothyroidism Direct alterations in blood vessels
7. Drug treatment of hypotension
Endothelin receptor antagonists
Introduction
Renin inhibitors
Courses of action to increase blood pressure
Direct vasodilators Centrally acting antihypertensives Catecholamine-depleting drugs Aldosterone antagonists
Drugs for treating hypotension Sympathomimetic drugs Phosphodiesterase inhibitors Other cardiac stimulants Fluid therapy solutions
References
Blood Pressure in Cats and Dogs. A Clinical Manual
An advantage of measurements at the base of the tail is the pneumatic cuff is more or less at the same height as the heart, which is a basic recommendation for obtaining accurate and reliable peripheral blood pressure readings. A lying position is ideal, not only for the patient who will be more comfortable and relaxed, but also because the base of the tail is at a similar height to the heart, as are all the other anatomical locations recommended for measurements.
As we have seen earlier, it is not a question of whether or not the base of the tail is a suitable location, but rather the vet needs to consider whether or not the base of the tail will produce reliable and repeatable measurements in this specific patient under the given clinical conditions.
Measurements on a forelimb On forelimbs, blood pressure is measured in the median artery, at the proximal portion of the carpus, and in the palmar digital artery, at the distal section of the carpus (Figs. 15 and 16). It basically involves placing the cuff around the forearm (above the carpus) or forepaw (beneath the carpus and above the first digit).
Figure 15. Cuff positioned to measure the arterial pressure in the median artery.
Figure 16. Cuff positioned to measure blood pressure in the palmar digital artery.
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Blood pressure measurement
2
Some authors also recommend placing the cuff around the upper arm, just above the elbow. It does represent a third possibility on the forelimb, but unfortunately this area is proportionally very thick and short, so it is hard to obtain a good fit with standard pneumatic cuffs. Furthermore, if the elbow is flexed, the flexion will reduce blood flow and decrease the pressure required by the cuff to obstruct blood flow completely. This effect distorts the measurement and can produce highly scattered and incoherent values. The forearm or the most distal portion of the forelimb, just above the digits, are more straightforward locations and produce more reliable readings (Figs. 17–23). However, it is not always easy to adjust the pneumatic cuff at very distal points in cats and small dogs, so the best option is to measure their blood pressure on the forearm (Figs. 24 and 25).
Figure 17. Measure the circumference of the forearm to determine the appropriate pneumatic cuff size for this patient.
Figure 18. Cuff size can be estimated by wrapping the width of the cuff around the girth of the carpus and checking that it encircles approximately 40 % of its circumference. This image shows the estimation being carried out on a cat under general anaesthesia.
Figure 19. Cuff size is not determined for a single patient, but rather for a specific area. This cat needs a larger cuff around the forearm than around the carpus.
Figure 20. Having selected the correct cuff size, it is placed in position and the patient given a few minutes to get used to it.
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Blood Pressure in Cats and Dogs. A Clinical Manual
Figure 21. The measurement equipment (a Vet20 semiautomatic oscillometric monitor) is then connected to the cuff once the patient has got used to it and seems calm.
Figure 22. Blood pressure can be measured simultaneously while administering intravenous fluids, but the same limb should not be used for both procedures (e.g. pressure should not be measured in the carpus if the patient has a catheter in the cephalic vein of the same limb).
Figure 23. In this example, the blood pressure can be measured in the opposite limb without any difficulties.
Figure 24. Cuff placed around the carpus to measure the pressure in a cat.
Figure 25. Here a different sized cuff is placed around the cat’s forearm.
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Blood pressure measurement
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Some authors prefer to raise the patient’s limb when measuring pressure over the forearm so that the cuff is at the same height as the heart. This is a practical option if the patient is calm, serene and allows their limb to be raised without bending the elbow, without strain and without stretching or relaxing it in order to counteract the lifting force applied by the vet (Figs. 26 and 27). Artefacts due to movements, tremors, tension in the limb, elbow flexion, etc., all have a greater effect on the measurement than just leaving the limb with the cuff discreetly below the height of the heart if the patient is calmer and more relaxed in this position.
Figure 26. If the patient is willing, it is better to raise the limb until the cuff is at approximately the same height as the heart as this will return more accurate results.
Figure 27. Even if the patient does not want to sit down, their limb can be raised while they remain standing in order to record more accurate measurements.
Video 8
Video 9
Measurement with a semiautomatic oscillometric monitor at the carpus of a seated dog
Measurement using a semiautomatic oscillometric monitor with the cuff placed around the raised forearm of a seated dog
Video 10
Video 11
Measurement with a semiautomatic oscillometric monitor at the forearm of a standing dog
Measurement with a semiautomatic oscillometric monitor at the forearm of a dog in lateral recumbency
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Blood Pressure in Cats and Dogs. A Clinical Manual
Target organ damage Regardless of the cause and mechanisms behind it, individuals with hypertension face potentially severe alterations. It should be diagnosed and pharmacologically controlled when necessary in order to limit any negative effects on the body. The effects of hypertension can primarily be observed in capillary blood flow; capillaries are the least robust and weakest part of the vascular system as their walls are both very fragile and porous. An increase in their internal hydrostatic pressure could lead to the extravasation of fluid into the interstitial space or capillary wall rupture with haemorrhaging. Some tissues and systems can withstand a hypertensive clinical picture better than others; the digestive and musculoskeletal systems do not usually present any damage until much later than other organs or systems. Rather alarming and dramatic bleeding can occur in some tissues, such as in the nasal mucosa, but this generally tends to have very few consequences, although it serves as a warning about the presence of hypertension which could have severe ramifications in other anatomical areas. Subconjunctival haemorrhage, which is also very conspicuous, may occur but it is usually insignificant in most cases. If the so-called target organs are affected by the hypertension (TOD, target organ damage), the consequences are more severe, often irreversible and sometimes even fatal (Fig. 2). The kidney, heart, central nervous system, arteries and eyeballs are all target organs damaged by hypertensive processes and can suffer alterations with grave consequences for the patient.
The risk is not the same in all cases and depends on the degree of hypertension, the underlying cause and the presence of any prior damage to these organs. Nevertheless, a risk score can be calculated in function of blood pressure values and used to help make therapeutic decisions in hypertensive patients; the greater the risk, the greater the need for management with antihypertensive treatment, which should be established as quickly as possible to limit said risks (Fig. 3). Table 1 shows the risk of TOD according to blood pressure values.
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Arterial hypertension
4
Central nervous system Eyeball
Heart
Renal glomerulus
Arterial hypertension
Arteries
Figure 2. Target organs primarily damaged by hypertension.
It is worth noting that an elevated degree of hypertension sustained over a certain period of time will always produce damage. All studies in hypertensive animals have reported different degrees of damage and various types of lesion, so it would be incorrect to adhere to the hypothesis that a patient can be hypertensive without suffering any consequences.
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Blood Pressure in Cats and Dogs. A Clinical Manual
SBP
DBP
Figure 3. Ranges of systolic (SBP) and diastolic (DBP) blood pressures associated with a lesser or greater risk of suffering target organ damage (data from Table 1).
TABLE 1. Risk of TOD based on blood pressure values. Category
Systolic
Diastolic
Risk (TOD)
I
<150
<95
Minimal
II
150–159
95–99
Low
III
160–180
100–120
Moderate
IV
>180
>120
High
The central nervous system Manifestations of hypertension in the central nervous system fall within what is known as hypertensive encephalopathy. Basically, brain damage occurs when the regulation system loses control and fails to maintain the cerebral blood pressure in a range of between 60 and 150 mmHg. If the blood pressure exceeds the maximum limits, it could trigger barotrauma, which may lead to cerebral oedema or haemorrhages. Contrastingly, when the blood pressure is below the minimum values, patients can show signs of cerebral hypoxia and ischaemia throughout the period of hypotension. The network of cerebral arteries and arterioles is regulated through local vasodilation and vasoconstriction so that it can always maintain a stable, controlled local blood pressure even though the systemic blood pressure suffers fluctuations. This capacity for local regulation is surpassed when the systemic blood pressure exceeds certain limits; the mechanism is unable to maintain normal cerebral blood pressures even though it responds with local vasodilation (in cases of hypertension) or vasoconstriction (for hypotension). 68
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