Physiology of Blood Pressure - Regulation

This presentation gives you a brief, understandable, captivating and presentable idea on the physiology of blood pressure regulation both on hypertension and hypotension cases.

1. Blood Pressure - Regulation S.D.Hadassah 1 st yr MDS, Public health Dentistry

2. CONTENTS INTRODUCTION FACTORS EFFECTING BLOOD PRESSURE REGULATION OF BLOOD PRESSURE MEASUREMENT OF BLOOD PRESSURE SHORT-TREM REGULATION INTERMEDIATE REGULATION

3. LONG-TERM REGULATION HORMONAL REGULATION LOCAL REGULATION APPLIED PHYSIOLOGY DENTAL IMPLICATIONS PUBLIC HEALTH SIGNIFICANCE CONCLUSION REFERENCES

4. INTRODUCTION In healthy people, each heartbeat forms a pressure wave that travels down the arterial system. Systemic circulation provides oxygenated blood to all organs in the body. It is essential that this blood supply is maintained at all times. The brain regulates the BP with various mechanisms. BP is one of the vital signs.

5. BLOOD PRESSURE Blood pressure is the hydrostatic pressure exerted by the blood on the blood vessel wall on it can also be defined as the lateral pressure exerted by a column of blood against the arterial wall. Measured in mmHg and expresses in terms of systolic pressure over diastolic pressure. Generally, the term blood pressure refers to arterial blood pressure (ABP). ABP is expressed in four different terms.

6. Systolic blood pressure (SBP) is the maximum pressure within the large arteries during systole. Average value is 120 mmHg (110mmHg – 140mmHg), indicates the extent of work done by heart. Diastolic blood pressure (DBP) is the minimum pressure within the large arteries during diastole. Average value is 70 mmHg (60 mmHg – 80 mmHg) measures the total peripheral vascular resistance.

7. Pulse Pressure (PP) is the difference between SBP and DBP. Normal PP is 40 mmHg (120-80 = 40). Mean Arterial Blood Pressure(MAP) is the average pressure existing in the arteries. The diastolic pressure plus one third of PP . Normal mean arterial pressure is 93 mmHg (80+13 = 93) MAP = DP + 1/3 rd of PP.

8. 2020 ACC/AHA HYPERTENSION GUIDELINES Normal BP ranges: Normal - <120 systolic & <80 mmHg diastolic. Elevated – 120-129 systolic and <80 mmHg diastolic. Hypertension BP ranges: Stage 1 hypertension – 130-139 systolic and 80-89 diastolic. Stage 2 hypertension - >140 systolic and >90 mmHg diastolic. Hypertensive crisis - >180 systolic and > 120 mmHg diastolic.

9. FACTORS EFFECTING BLOOD PRESSURE

10. FACTORS MAINTAINING ARTERIAL BLOOD PRESSURE Also called local factors, mechanical factors or determinants of blood pressure. Two types: Central factors – Cardiac output & Heart rate. Peripheral factors – Peripheral resistance, Blood volume, Venous return, Elasticity of blood vessels, Velocity of blood flow, Diameter of blood vessels & Viscosity of blood.

11. Arterial blood pressure Factors Directly proportional Cardiac output Heart rate Peripheral resistance Blood volume Venous return Velocity of blood flow Viscosity of blood Indirectly proportional Elasticity of blood vessel Diameter of blood vessel

12. MEASUREMENT OF ARTERIAL BLOOD PRESSURE Measured by two methods: Direct method: measured particularly in critically ill patients. Indirect method: Apparatus used to measure blood pressure in human beings is called sphygmomanometer, stethoscope is also necessary to measure blood pressure. Brachial artery is usually chosen because of convenience.

13. Blood pressure can be measured by three methods. Palpatory method Auscultatory method Oscillatory method Palpatory method: While feeling the pulse on the radial artery, pressure is increased in the cuff by inflating air into it, with the help of a hand pump. Pressure in the cuff is slowly reduced and pulse appears at nearly 120 mmHg called as systolic pressure.

14. Auscultatory method: Most accurate method to determine arterial blood pressure. After determining the systolic pressure in palpatory method, the pressure in the cuff is raised by about 20 mm Hg above that level, so that the brachial artery is occluded due to compression. Series of sounds heard through the stethoscope are called Korotkoff sounds. Oscillometry method: At the level of systolic pressure as the pressure gradually reduces causes some oscillations at the top of mercury columns. It denotes the systolic pressure.

15. NEED FOR BLOOD PRESSURE REGULATION

16. REGULATION OF BLOOD PRESSURE Body has four such regulatory mechanisms to maintain the blood pressure within normal limits. Nervous mechanism or short term regulatory mechanism. Baroreceptor/ Sinoaortic mechanism. Chemoreceptor mechanism Vasomotor center mechanism

17. Intermediate term mechanism. Stress relaxation Fluid shift mechanism Renin angiotensin mechanism Renal mechanism or long term mechanism. Renin-Angiotensin-Aldosterone mechanism.

18. NERVOUS MECHANISM OR SHORT TERM REGULATORY MECHANISM. Rapid among all the mechanisms involved in the regulation of arterial blood pressure. Although nervous mechanism is quick in action, it operates only for a short period and then it adapts to the new pressure. Baroreceptor mechanism: Baroreceptors are stretch receptors located in the walls of heart and blood vessels.

19. When BP increases, BR present in the carotid sinus (bifurcation of carotid artery) and arch of aorta are stimulated. Inhibits the vasomotor center (VMC) and stimulates Vagal nucleus. lX & X cranial nerves called buffer nerves, are involved in regulating the blood pressure. Changing of posture - lying down, sitting or standing reduces arterial BP and blood flow to the upper parts of the body. Discharge of impulse decreases from baroreceptors - triggers spontaneous discharge from VMC, restoring the BP with increase in HR and peripheral resistance.

20. Chemoreceptor mechanism: Decrease in BP <60 mmHg reduces the blood flow to the chemoreceptors present in the carotid body and arch of aorta. Reduced oxygen supply stimulates the chemoreceptor. In turn the VMC is stimulated increasing the heart rate and peripheral resistance by vasoconstriction. Thereby increase in BP.

21. Vasomotor center mechanism: Reduced blood flow to VMC causes its ischemia. Stimulates VMC causing increase in heart rate and peripheral resistance. And with the same process the net effect would be increase in BP.

22. INTERMEDIATE TERM REGULATION It takes few minutes to few hours. Stress relaxation: When the pressure in the blood vessels become too high, they become stretched and keep on stretching more and more for minutes or hours. This extensive stretch makes the pressure in the walls fall towards normal. The continuing stretch response of the vessels can serve as an intermediate-term pressure “buffer.”

23. Fluid shift mechanism: Increased BP increases hydrostatic pressure. This pushes fluid out of the blood vessel into interstitial space. Loss of fluid from blood vessel reduces BV. Reduced venous return and hence decrease in BP.

24. Renin angiotensin mechanism: Reduced BP decreases blood flow to kidney. Causes juxta glomerular apparatus of kidney to produce Renin. Renin acts on plasma substrate the angiotensinogen to form angiotensin 1. Angiotensin l converted to angiotensin ll by angiotensin converting enzyme present in lungs. Causes vasoconstriction and BP becomes normal. ACE inhibitors prevent this conversion, as angiotensin ll causes peripheral vasoconstriction and decreases peripheral resistance in hypertensive patients.

25. LONG TERM REGULATION Renin-Angiotensin-Aldosterone mechanism: Angiotensin ll produced during intermediate term regulation stimulates adrenal cortex to produce aldosterone as a delayed effect. Aldosterone increases sodium reabsorption. Causes water retention and increases fluid volume within the vessels. In turn increases venous return to heart and also the blood pressure.

26. Angiotensin ll stimulates hypothalamus & posteriors pituitary to release anti diuretic hormone (ADH). ADH along with Aldosterone helps in water retention. Mechanism activates thirst, enhancing fluid intake. Retention of salt and water increases systemic arterial pressure. In turn will increase hydrostatic pressure facilitating formation of larger volume of filtrate. Increased salt and water promoting formation of a larger volume of filtrate rich in salt is termed Pressure Natriuresis and diuresis.

27. HORMONAL MECHANISM

28. LOCAL MECHANISM In addition to nervous, renal, hormonal mechanisms, some local substances also regulate the blood pressure by vasoconstriction and vasodilation. Local vasoconstrictors: Derived from vascular endothelium. Called as endothelium-derived constricting factors (EDCF). Common EDCF are endothelins (ET) –nET1, ET2, ET3.

29. Endothelins are produced by stretching blood vessels, these activate phospholipase, in turn activates prostacyclin and thromboxane A2. These two substances cause constriction of blood vessels and increase the blood pressure. Local vasodilators: Two types – metabolic & endothelial origin. Vasodilators of metabolic origin are CO2, lactate, hydrogen ions and adenosine.

30. Vasodilators of endothelial origin are Nitric oxide synthesized from arginine. Deficiency leads to constant vasoconstriction and hypertension.

31. APPLIED PHYSIOLOGY Hypotension Hypertension

32. HYPOTENSION Low blood pressure is generally considered a blood pressure reading lower than 90 mmHg of systolic pressure or 60 mmHg of diastolic pressure. BP below 100/60 mmHg in females and less than 110/70 mmHg in men.

33. Pregnancy hypotension: A pregnant women’s BP can be lower in the 1 st 24 weeks. Caused as the blood vessels expand to let the blood flow into the uterus. Postural hypotension: A drop in systolic blood pressure (BP) of at least 20 mm Hg or diastolic BP of at least 10 mm Hg within 3 minutes of standing when compared with normal blood pressure from the sitting or supine position. Postprandial hypotension: A drop in blood pressure occurs 1 to 2 hours after eating. Mostly seen in older individuals. Types :

34. Causes: Diseases – severe hemorrhage, heart diseases, Addison’s disease. Drugs: anti hypertensive drugs, diuretics, vasodilators. Treatment: If the cerebral, renal and cardiac perfusion is maintained, hypotension itself doesn’t need any vigorous direct treatment. Sympathomimetic agents used in emergency are – nor epinephrine, phenylephrine.

35. HYPERTENSION It is the persistent high blood pressure. Clinically when systolic pressure remains elevated above 140 mmHg and diastolic pressure remains elevated above 90 mmHg it is considered as hypertension. Types Primary hypertension - Benign hypertension - Malignant hypertension

36. Secondary hypertension - Cardiovascular hypertension - Endocrine hypertension - Renal hypertension - Neurological hypertension - Hypertension during pregnancy

37. PRIMARY HYPERTENSION Elevated blood pressure in the absence of any underlying diseases. It is increases because of increased peripheral resistance which occurs due to some unknown cause. About 90-95 % of all people who have hypertension are said to have primary hypertension also widely known as essential hypertension. In most patients, excess weight gain and sedentary lifestyle appear to play a major role in causing hypertension.

38. Benign hypertension: Benign hypertension is a term used to describe uncomplicated hypertension usually of long duration and mild to moderate severity. Historical terms that are considered misleading as hypertension is never benign and consequently they have fallen out of use. Causes: A combination of genetics, diet, lifestyle, and age. Lifestyle factors include smoking, drinking too much alcohol, stress, being overweight, eating too much salt, and not getting enough exercise.

39. Malignant hypertension: ( Typically above 180/120 mmHg). Malignant hypertension is an emergency medical condition and requires quick treatment.  The prevalence of malignant hypertension is low — about 1-2 cases in 100,000. Cause: High blood pressure is the main cause of malignant hypertension. Missing blood pressure medications can also cause it. Collagen vascular disease, kidney disease, spinal cord injuries, tumor of adrenal gland. Use of certain medications, including birth control pills and MAOIs. Use of illegal drugs such as cocaine.

40. This is a life threatening condition, because high blood pressure can damage essential organs or cause complications such as an aortic dissection or tear or bleeding in the brain.  When your blood pressure suddenly rises above 180/120 and you have symptoms from this sudden increase in blood pressure. These include: chest pain, headache , shortness of breath. Dizziness & visual changes.

41. Malignant hypertension can cause brain swelling which leads to dangerous condition called hypertensive encephalopathy. Symptoms include: Blindness Disturbance in mental status Coma Confusion Severe worsened Headache Nausea and vomiting Seizures

42. Diagnosis: Based on blood pressure readings and signs of acute organ damage. Recheck the BP and listen to heart and lung sounds for abnormal sounds. Examine eyes to check for damage to the blood vessels of the retina and swelling of the optic nerve. Blood and urine tests may include to check blood sugar level, sodium, potassium and abnormal hormonal levels. ECG and echocardiogram to check hearts function and blood flow. Chest x-ray.

43. Treatment: Goal of the treatment is to carefully lower blood pressure within a matter of minutes, as it is a medical emergency. BP medicines through an IV, once blood pressure is at safe level, the medications maybe switched to oral forms. If not, can develop kidney failure, need to do kidney dialysis. Complications: If untreated- death. Aortic dissection, coma, pulmonary edema, heart attack, heart failure, stroke and sudden kidney failure.

44. SECONDARY HYPERTENSION Secondary hypertension is when there’s an identifiable— and potentially reversible cause of your hypertension. Only about 5-10 % of hypertension is the secondary type. It’s more prevalent in younger people. Causes: N arrowing of the arteries that supply blood to your kidneys. Adrenal gland disease S ide effects of some medications, including birth control pills, diet aids, stimulants, antidepressants, and some over-the-counter medications H ormone abnormalities, obstructive sleep apnea.

45. RENAL VASCULAR HYPERTENSION Caused by kidneys hormonal response to narrowing of the arteries supplying the kidneys. Due to low local blood flow the kidneys release hormones to maintain a higher amount of sodium and water retention which in turn causes blood pressure to rise. Forms secondary hypertension. Signs & symptoms: high blood pressure at early age, kidney dysfunction.

46. Factors contribute: Diabetes, high cholesterol, older age. Diagnosis: blood test, urine test, serology, lipid profile, urinalysis. Treatment: Surgical revascularization medical therapy for atherosclerosis, balloon angioplasty. Percutaneous surgical revascularization, nephrectomy or auto transplantation. Inpatient care is necessary for the management of hypertensive urgencies, quick intervention is required to prevent further damage to the kidneys.

47. PREGNANCY HYPERTENSION Up to 11% develop hypertension of pregnancy. There are 3 complications during pregnancy. Pre-Eclampsia: A disorder of pregnancy characterized by the onset of high blood pressure and often a significant amount of protein in the urine. HELLP syndrome: Characterized by hemolysis, elevated liver enzymes and low platelet count. Eclampsia: onset of seizures (convulsions) in a woman with pre – Eclampsia.

48. CHRONIC HYPERTENSION The high blood pressure caused due to impaired renal fluid excretion. Diastolic blood pressure is greater than about 90 mm HG and systolic pressure is greater than 135 mmHg. In severe hypertension, the mean arterial pressure can rise to 150-170 mmHg, with diastolic pressure as high as 130 mm HG and systolic pressure as high as 250 mm HG. In these cases a persons life expectancy will be reduced.

49. NEUOGENIC HYPERTENSION Excessive secretion of norepinephrine and epinephrine which promotes vasoconstriction. Resulting from chronic high activity of the sympathoadrenal system and adrenal gland. Stress hormones (adrenaline, noradrenaline) which increase blood output from heart and constrict the arteries.

50. ISOLATED SYSTOLIC HYPERTENSION Isolated Systolic Hypertension (ISH) is defined as systolic blood pressure above 140 mm Hg and diastolic blood pressure under 90 mm Hg. An estimated 15% of people of 60 years or older have isolated systolic hypertension. Caused by underlying conditions like – artery stiffness, hyperthyroidism and diabetes. ISH can lead to serious health conditions such as – stroke, heart disease, chronic kidney disease.

51. Rx - NONPHARMACOLOGICAL APPROACHES: Reducing salt intake (to less than 5g daily) Eating more fruit and vegetables Being physically active on a regular basis. Avoiding use of tobacco & reducing alcohol consumption. Limiting the intake of foods high in saturated fats. Eliminating/reducing trans fats in diet. WHO suggests a follow up every 3–6 months for patients whose blood pressure is under control. *https://iris.who.int/bitstream/handle/10665/344424/9789240033986-eng.pdf

52. 1st line agents in pharmacotherapy: 1. thiazide and thiazide-like agents 2. angiotensin-converting enzyme inhibitors ( ACEis )/angiotensin-receptor blockers (ARBs) 3. long-acting dihydropyridine calcium channel blockers (CCBs). Antihypertensive medications used in combination therapy with the following three drug classes: Diuretics (thiazide or thiazide-like) Angiotensin-converting enzyme inhibitors (ACE)/angiotensin-receptor blockers (ARBs). Long-acting dihydropyridine calcium channel blockers (CCBs). *https://iris.who.int/bitstream/handle/10665/344424/9789240033986-eng.pdf

53. DENTAL IMPLICATIONS General hypertensive patient considerations: Evaluate vital signs, including heart rate (pulse) and blood pressure at every dental visit. Mostly dental patients experience acute high blood pressure related to a physiologic response to pain and anxiety.

54. Symptoms include headache, vision changes, shortness of breath, chest pain need immediate referral to emergency care. Use anxiety reduction protocol. For mild and moderate hypertensive patients. Avoid rapid posture changes in patient taking vasodilator drug. Delay the optional dental treatment until hypertension controlled in severe cases. Consider referral to oral and maxillofacial surgeon for emergent problems.

55. Premedication – anxiolytic night before or immediately before scheduled appointment Appointment scheduled in the morning. Minimization of office waiting time. Psychosedation during treatment. Adequate pain control during treatment. Short duration appointments. Anti-anxiety protocol

56. Dental treatment considerations for adult patients with hypertension: Dental practitioners are advised to reduce or avoid vasoconstrictor-containing formulations in individuals with cardiovascular compromise. Using slow injection technique, and aspirating carefully and repeatedly are common recommendations to prevent rapid systemic absorption of epinephrine and other vasoconstrictors. Postural hypotension, also known as orthostatic hypotension, is the second-leading cause of transient loss of consciousness in dental settings.

57. Oral Effects Of Hypertensive Medications Most classes of antihypertensive mediations can cause dry mouth (xerostomia). In addition, in 2% to 83% of patients being treated with a calcium- channel blocker, gingival hyperplasia has been reported; eg ; Nifedipine. Gingival hyperplasia induced by calcium-channel blocker therapy may be treated surgically.

58. PUBLIC HEATH SIGNIFICANCE An estimated 1.28 billion adults aged 30–79 years worldwide have hypertension, most (two-thirds) living in low- and middle-income countries An estimated 46% of adults with hypertension are unaware that they have the condition. Less than half of adults (42%) with hypertension are diagnosed and treated. Approximately 1 in 5 adults (21%) with hypertension have it under control. Hypertension is a major cause of premature death worldwide. *https://www.who.int/news-room/fact-sheets/detail/hypertension/?gad_source=1&gclid=Cj0KCQjw8J6wBhDXARIsAPo7QA-XDVYa5Ym7vBW7HHgTudCBZ-NaK_3V1M5_r71hZ2GGPFYNH2tHKsQaAsc8EALw_wcB

59. According to National Family Health Services-5 (2019-2021) INDIA VARIABLES PREVALENCE Males 56.41 Females 47.20 Adolescents (15-19) 40.53 Young (20-39) 47.14  Middle-aged (≥40 to 49) 52.84 Underweight 60.37 normal weight 62.61 Overweight/Obese 58.64 * Basu S, Malik M, Anand T, Singh A. Hypertension control cascade and regional performance in India: A repeated cross-sectional analysis (2015-2021) Cureus . 2023;15:e35449. doi : 10.7759/cureus.35449. 

60. Global Burden Disease (GBD) study estimated that Hypertension led to 1.6 million deaths and 33.9 million disability-adjusted life years in 2015. Intensive public health effort is required to increase the awareness, treatment and control. Sustainable Development Goals highlight the importance of high rates of hypertension control for achieving target of 1/3 rd reduction in NCDs mortality by 2030. It is estimated that better hypertension control can prevent 400-500,000 premature deaths in India. One of the global targets for noncommunicable diseases is to reduce the prevalence of hypertension by 33% between 2010 and 2030.

61. CONCLUSION Blood pressure in the body is regulated through different mechanism which helps the body to maintain normal physiological functions. Mild to severe variation in it, can alter normal physiological function and even damage of organs which can even lead to death. Thus it is important to have regular checkups to maintain the normal blood pressure.

62. REFERENCES K Sembulingam , Sembulingam P, Essentials of medical physiology.6th ed. New Delhi: Jaypee Brothers Medical publishers; 2012. Park K. Park’s textbook of Preventive and Social Medicine. 25 th ed. India: Bhanot Publishers; 2017. Malamed SF. Medical emergencies in the dental office. 7 th ed. St. Louis: Mosby; 2015. Hall JE, Hall ME. Guyton and Hall textbook of medical physiology. 14 th ed. Philadelphia: Elsevier; 2021.

63. Editor Medshop . It Took Thousands of Years of Theory Plus 200 Years of Med Tech to Build the Sphygmomanometer [Internet]. Medshop Australia; 2017 [cited 2021May23]. Available from: https://www.medshop.com.au/blogs/news/it-took-thousands-of-years-of-theory-plus-200-years-of-medtech-to-build-the-sphygmomanometer Unger T, Borghi C, Charchar F, Khan NA, Poulter NR, Prabhakaran D, et al. 2020 International Society of Hypertension Global Hypertension Practice Guidelines. Hypertension. 2020;75(6):1334-57. Raven PB, Chapleau MW. Blood pressure regulation XI: overview and future research directions. European Journal of Applied Physiology. 2014;114(3):579-86.

64.  Jacob JJ, Chopra S, Baby C. Neuro-endocrine regulation of blood pressure. Indian Journal of Endocrinology and Metabolism. 2011;15(8):281. Rahimi K, Emdin CA, MacMahon S. The Epidemology of Blood Pressure and its Worldwide Management, Circulation Research. 2015; 116(6):925-36. Gupta R, Xavier D. Hypertension: The most important non communicable disease risk factor in India. Indian Heart Journal. 2018;70(4):565-72.