Blood Pressure Measurement (2011)

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Blood Pressure Measurement (2011)

  1. 1. Dr Liesl Brown Department of Pharmacy University of Limpopo (Medunsa Campus)Module 2.2: Cardiovascular Pharmacy (2011)
  2. 2. Aim How to measure blood pressure using different sphygmomanometers: Aeroid (mercurial and non mercurial) and Anaeroid (automatic)
  3. 3. ObjectivesAfter this practical experience, you will be able to providethe answers to the following questions:• WHAT is the importance of monitoring blood pressure?• HOW do we measure blood pressure?• HOW do we measure pulse rate?• WHAT accounts for the variability in blood pressure measurements?• WHAT is considered to be normal and what high blood pressure?• WHO should have their blood pressure checked?• HOW do your measure blood pressure using a sphygmomanometer?• WHAT are Korotkoff sounds?• DOES cuff size matter?• WHAT is ‘white coat’ hypertension?• WHICH drugs are available for the treatment of hypertension?
  4. 4. The structure of blood vessels (Revision) TransparenciesThe structure of blood vessels (Davies et al, 2001, p 502)
  5. 5. Changes in blood pressure as blood flows through the circulatory system (Revision) TransparenciesChanges in blood pressure (Davies et al, 2001, p 501)
  6. 6. Pressure-volume relationships in arteries and veins (Revision)  TransparenciesPressure-volume relationships in arteries and veins (Davies et al, 2001, p 504)
  7. 7. The relationship between heart rate and systolic blood pressure (Revision) Transparencies
  8. 8. Control of blood pressure (BP) (Revision)• Short term control: Baroreceptor reaction to pressure differences• Long-term control: • Arterial baroreceptor discharge returns to normal, within days of chronic incr. of BP • Kidneys – control plasma by retaining/losing water and salt ( BP)
  9. 9. The endocrinological control of blood pressure (Revision) Transparencies
  10. 10. Control of arteriolar diameter (Revision)(a) Neural control: (c) Endothelial and blood-based control • Sympathetic • Endothelial derived factors noradrenergic • Sympathetic cholinergic • Prostaglandins • Thromboxane • Parasympathitic • Leucotrines cholinergic(b) Hormonal control • Platelet-activating factor • Catecholamines • Histamine • Bradykinin • ADH • 5-hydroxytryptamine (5-HT) • Angiotensin-aldosterone • Aterial natriuretic peptide (d) Metabolic influences • Functional hyperaemia • Reactive hyperaemia
  11. 11. Blood pressure aka systemic arterial blood pressure Definition:Blood pressure is the pressure which the circulating blood exertsagainst the walls of the blood vessels in the course of circulation, and isa good indication of the capacity of the blood vessels and of cardiacfunction (Griesel, p62)• Measured in millimetres-mercury (mmHg)
  12. 12. Blood pressure• Resistance = pressure (Ohm’s law) flowWhere:resistance = total peripheral resistanceflow = cardiac outputpressure = arterial blood pressureThus:arterial blood pressure =cardiac output x total peripheral resistance An illustration of arterial pressure waves• Arterial wave = systolic pressure (its peak) and diastole pressure (its lowest point)• Pulse pressure = systolic pressure minus diastolic pressure
  13. 13. Types of blood pressure 1. Normal BP• Up to 140/90 mmHg with an average of  120/80 mmHg [ 100 to 140 mmHg systolic / 60 to 90 mmHg] in an average adult (WHO)• Increases gradually with age – systolic more than diastolic 2. Hypertension• Mild: 140/90 mmHg to 160/95 mmHg (WHO)• Moderate to serious hypertension: 160/95 mmHg• In special cases: Diabetics -  140/90 mmHg Pregnant women -  140/90 mmHg Isolated systolic hypertension – systolic > 160 mmHg / diastolic < 90 mmHg 3. Hypotension•  < 120/80 mmHg
  14. 14. -Hypertension (HT)Definition:Hypertension is defined as a sustained increase inthe systolic and/or diastolic arterial pressureabove the normal (Griesel, p63)
  15. 15. Classification of hypertension• Primary (essential, idiopathic) hypertension• Secondary hypertension• Other types of hypertension: • Malignant hypertension (MH) Definition: MH is a sudden, acute condition which develops in primary hypertensive patients • Pre-eclampsia (Pregnancy associated hypertension) (PE) Definition: PE is a condition characterised by hypertension with a degree of renal limitation which suddenly develops during the second half of pregnancy?
  16. 16. --Causes of hypertension• Complication of renal disease/failure• Causes: • Secretion of abnormal large amounts of renin + in ability to excrete adequate amounts of salt & H2O • E.g. during early renal failure: the kidney experiences ischaemia and secretes renin  angioTS I conversion to angioTS II resulting in vasoconstriction + aldosterone (salt + H2O retaining)
  17. 17. -Hypotension (low blood pressure)Definition:Hypotension is defined as a decrease in systolic and diastolic arterial pressure below the normal
  18. 18. -Chronic low blood pressureSufferers presents with: • Tiredness • Lack of energy • Periods of vertigo
  19. 19. -Orthostatic hypotensionDefinition:BP that falls > 20 mmHg on standing froma sitting or recumbent position• Seen more in the elderly• Causes: • Reduction of compliance of arteries is a normal part of aging • inadequate heart rate response owing to a decline in autonomic control • Certain HT drugs (give drugs at night)
  20. 20. -Syncope (fainting)Caused by a sudden lowering of blood pressure with resultant cerebral anoxia and loss of consciousness • Causes: • E.g. When a person stands for a long period of time – blood accumulates in the lower limbs leading to the draining of blood from the brain • Neurogenic factors (e.g. sudden pain, bad news) • Can turn into a shock condition, esp. when if accompanied by other causes e.g. trauma, serious infection
  21. 21. -ShockCondition of acute circulatory failure which characteristic hypotension and decrease in µ- circulation leading to hypoxia of the vital organs• Factors leading to shock: • Heart pump failure • Blood volume decrease • Peripheral circulatory failure due as a result of vasodilatation so that the blood accumulates in non-essential areas
  22. 22. Arterial pressure measurement• Direct measurement: • most precise measure • direct connection to major artery to a transductor via a catheter• Indirect measurement: • Method developed by Riva-Rocci • Use a sphygmanometer • Auscultatory method (hear) • Palpatory method (feel)
  23. 23. -The ausculatatory method• Involves listening to Korotkoff sounds using a stethoscope placed over the brachial artery in antecubital fossa of the elbow• When: • Pressure (exerted by the cuff ) much bigger that the pressure of the systolic pressure there is no blood flow, hence no sound • Pressure much lower that the systolic pressure this leads to blood forcing its way under the cuff for short periods at the beginning of the systole when the pressure is highest • Blood flow sound are turbulent, and move in a high velocity . This causes the sharp tapping (1st Korotkoff sound) that can be heard (systolic pressure) • Pressure in cuff falls lower and lower the sound (lub-dup) becomes louder, then diminishes (you hear the change in sound from a tapping to a muffeld sound and then thereafter to silence (this is the diastolic pressure / 5th Korotkoff sound)
  24. 24.  Transparencies
  25. 25. -The palpatory method• Taking the radial pulse while inflating the cuff• The systolic pressure is the pressure where the cuff pressure cuts off the pulse, hence no pulse can be felt• Limitations: • Cannot measure diastolic pressure• Advantage: • Provides a wise instrument in a patient suspected of HT (silent period with Korotkoff sounds)
  26. 26. How to measure systemic arterial• Let the patient be seated or lie down (document this) blood pressure• Using the left arm of the patient, determine the radial pulse• Wrap the cuff around the left arm, above elbow at the level of the heart• Inflate the cuff, keeping track of the radial pulse• When the radial pulse cannot be felt anymore, you have an estimate of what the systolic BP is• Place the stethoscope in your ears• Deflate the cuff and pump the cuff 20 mmHg higher than the systolic blood pressure• Slowly deflate the cuff again• Listen to the beginning of the throbbing sound (systolic blood pressure) and the end of the throbbing sound (diastolic pressure)• Repeat the procedure three times and determine a mean BP• Readings are influenced if: • The cuff is too small ( leads to the pressure not adequately transmitted to artery) • Cuff is not wrapped around the arm
  27. 27. Correct determination of arterial blood pressure• Points of importance during BP measurements: • The patient • Instruments • The person taking the reading • Environmental factors • Interpretation
  28. 28. Significance of blood pressure readings• BP varies over a 24 hour period• Influenced by factors such as: • Physical activity • Emotional status of patient • Pain • Temperature of the environment • Use of tobacco • Use of caffeine • Certain drugs • Physiological factors e.g. gender build posture emotions physical exertion age (BP increases with age)
  29. 29. An illustration of blood pressure differences with age Transparencies
  30. 30. The effect of sleep on blood pressure• While sleeping there is a decrease in sympathetic tone leading to a fall in BP• Arterial CO2 tension also rises + together with cyclic BP changes this leads to an increase cerebral blood flow
  31. 31. • Antiadrenergic agents: • Agents acting on the • Centerally acting: arteriolar smooth • Resperpine muscle: • Methyl dopa • Diazoxide • Clonidine • Hydralazine • Minoxidil • Peripherally acting: • Na-nitroprusside • -adrenoceptor blocking agents •Prazosin • Calcium channel •Doxazosin blockers: •Urapidil • Verapamil •Indoramin • Nifedipine •Urapidil • Amlopidine • Diltiazem • Felodipine •  + -adrenoceptor • Istradipine blocking agents: • Labetalol • Lacidipine • Carvedilol • Nimodipine
  32. 32. • Diuretics: • Low ceiling diuretics • Hydrochlorothiazide • Cyclopenthiazide • Chlortalidone • Indapamide • Metolazone• Agents acting on renin- • angiotensin system: High ceiling diuretics • ACE-I • Furosemide • Captopril • Bumetanide • Benzapril • Piretanide • Cilazapril • Ramipril • K+-sparing diuretics • Trandolapril • Spironolactone • ACE-I and diuretic combos • Amiloride • Captopril/diuretic • Triamterene • Enalapril/diuretic • Lisinopril/diuretic • Quinapril/diuretic
  33. 33. Drugs that affect blood pressureDrugs that increase BP/affect antihypertensive therapy:• Sympathomimetics in cold and flu medication e.g. ephedrine, phenylephedrine, phenylpropanolamine• Most appetite suppressants• NSAIDs• MOA-I should it be used with foods that contain tyramine / dopamine e.g. cheese and wine• Methylphenidate (Ritalin®)• Oral contraceptives• Carbenoxolone• Corticosteroids• Antihypertensive medication – should they be withdrawn suddenly
  34. 34. Drugs that affect blood pressureDrugs that tend to decrease BP or to potentiate therapy for hypertension:• Cardiac antidysrhythmic drugs e.g. amiodarone, bretylium• BDZs e.g. diazepam• Bromocryptine• Droperidol• Levo-dopa• Meprobamate• Phenothiazines• Phenothiazines• TCAs e.g. imipramine
  35. 35. Part V: Practical Exercise: Measuring blood pressure using different types of sphygmomanometers

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