Alterations in Blood Pressure
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what is arterial blood Pressure?
- it is reduced by the force of the Lt ventricular contraction overcoming the resistance of the aorta to open the aortic valve.
- It is the pressure maintained in the arterial system throughout the cardiac cycle.
- It is the pressure difference b/t the Lt and Rt sides of the heart that produce the gradient allowing systemic movement of blood.
What is Blood Pressure?
It is the measurement of force applied to the arterial wall.
What determines the systemic blood (arterial) pressure?
- Cardiac output and the resistance to the ejection of blood from the heart.
- Cardiac output.
- Stroke volume.
- Preload, and afterload.
- Systemic vascular resistance.
What is Cardiac output?
- Cardiac output is the product of 2 variables: stroke Volume (SV) and HR.
- It the the amount of blood leaving the heart, measured in L/min.
What is Stroke Volume (SV)?
It is the specific volume of blood leaving the heart with each contraction, which itself is determined by the vole of blood in the heart before systole (en-diastolic volume) and contractibility of the myocardium.
What is Cardiac preload (end-diastolic volume)?
It is determined by the amount of blood returned to the heart b/t contractions.
What is Systemic Vascular Resitance (SVR)? how is it determined?
- It is the resistance to ejection into the arterial circulation.
- It is determined by the radius of arteries and the degree of vessel compliance.
What is cardiac afterload? how can be altered?
- It is synonymous of SVR (the resistance to ejection into the arterial circulation)
- It is altered by constriction or relaxation (dilation) of the smooth muscle.
What are the components of blood pressure measurements?
- Systolic blood pressure (It is the pressure of the aorta after a ventricular contraction, peak)
- Diastolic blood pressure (It is when the pressure in the aorta falls to an average minimum value)
- SV, which is the primary factor influencing systolic pressure.
- SVR, which is the major factor determining of diastolic pressure.
- Mean arterial pressure (MAP) is the calculated average pressure within the circulatory system throughout the cardiac cycle.
- Pulse pressure = systolic - diastolic.
what is direct measurement of blood pressure?
- Requires intra-arterial catheter to transduce arterial fluid pulsations into electrical signals (waveforms)
- Catheter commonly placed in radial artery.
- Most accurate method of measuring blood pressure.
What is indirect measurement of blood pressure?
- It is the one we know.
- Commonly measured indirectly via the brachial artery using stethoscope and sphygmomanometer or automated oscillometric system.
- Requires carful technique to ensure accuracy.
What can causes short-term regulation of systemic blood pressure?
- Changes in the BP are mediated through activation of the sympathetic nervous system (SNS)
- Results in release of neurotransmitters (epi and norepi) which are vasoconstrictors.
- Parasympathetic nervous system (PNS) Slows HR.
what can cause long-term regulation of systemic blood pressure?
- It is regulated by neural, hormonal, renal systems (most important).
- An increase in the extracellular luis volume = increased in CO and SVR = elevated BP.
- Increased serum sodium level = increased osmolality (concentration of a solution) = increased ADH secretion.
- Renin-angiotensin-aldosterone system (RAAS) important regulator of BP.
- Connected to fluid volume.
What is HTN? what are the 2 types?
- It is defined as a sustained BP that is greater than normal.
- It is not a single disease, but a syndrome with multiple causes.
- 2 types: Primary and secondary.
What is Primary HTN?
- It is often called essential HTN
- Idiopathic: the cause is unknown
- 90% of all cases.
- Rare prior to the age of 10.
- Major risk factor for CardioVascular (CV) disease
- "silent killer" bc damage to internal organs could have occurred before dx.
what are the most common mechanism/causes of primary HTN?
- Neural: excessive SNS.
- Renal: Excessive volume leads to high tissue perfusion and compensatory tissue resistance.
- Humoral: Excessive RAAS, excessive insulin, too little natriuretic peptide.
- Vascular: insufficient dilators and/or excessive constrictors.
What is Secondary HTN? what are the most common causes?
- It is when the cause of HTN is known, only 10% of all cases.
- Causes: Contraceptive use,Renal disease ,Renal artery stenosis ,Cushing syndrome,Pheochromocytoma ,Pregnancy-induced hypertension, Polycythemia
What are the pathophysiology of HTN (essential)?
- Kidney: regulates vascular volume through salt and water elimination and effect of RAAS on blood vessel tone.
- It is a result in vasoconstriction or narrowed peripheral blood vessels.
- Increased workload and more and more pressure (afterload)
- LVH (left ventricular hypertrophy.
What are some primary HTN treatments? non-pharmacological and pharmacological?
- Life style modification: weight loss, exercise, alcohol moderation, decreased sodium intake.
- Drug therapy: medications that will affect the HR, SVR, and/or stroke volume.
What are the treatments of secondary HTN?
- The main thing is to treat the cause.
- may be related to: renal artery stenosis, pheochromocytoma, pregnancy, obesity/obstrictive sleep apnea, hyperalsosteronism: most common cause.
Clinical manifestations of HTN?
- Maybe asymptomatic.
- Headache is common. (wake up with a headache, in the back of the head, and it gets better as the day goes by)
- Visual disturbances
- Renal insufficiency.
What are the most common complication of HTN?
- Kidney failure.
What are the common causes of Orthostatic (postural) hypotension?
- Problem with vasomotor or baroreceptor response.
- Adverse effect of drug therapy (diuretics particulllary.
- Arterial stiffness
- volume depletion.
- Secondary disease process.
- vasovagal reaction.
- cardiac dysrhythmias.
What are orthostatic (postural) hypotension treatment?
- Slow positional changes.
- Avoid hot environments
- Avoid large or carbohydrate- heavy meals.
- squatting/bending when episode begins, forward or crossing legs may reduce effect.
- Increase salt and fluid intake if not contraindicated.
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