Postural hypotension Flashcards
How to take a lying and standing BP? Define Postural hypotension?
Lie for at least 5mins
Ask to stand - after one min of standing measure BP, again at 3mins - if BP dropped - measure again at 5mins
Postural hypotension = defined as a sustained reduction in systolic BP of at least 20mmHg, or diastolic BP of 10mmHg, that occurs within three minutes of standing.
Physiology of maintaining BP when standing?
When we stand – blood shifts from chest to below diaphragm –> reduced preload –> reduced BP
Normal:
gravity-induced reduction in blood pressure is detected by baroreceptors in the aortic arch and carotid sinus
- Baroreceptors induce baroreflexes including vasoconstriction and compensatory tachycardia
- increase in sympathetic outflow and a decrease in vagal nerve activity; thereby reducing parasympathetic stimulation to the heart
- baroreceptors also send signals to the arterioles and venules in the circulatory system to increase TPR
PPx of postural hypotension?
Postural hypotension occurs when either:
• Baroreflexes fail (autonomic failure)
• Volume depletion
• End-organ dysfunction
Causes of postural hypotension? Neurogenic and non-neurogenic
Neurogenic: insufficient release of noradrenaline from the sympathetic vasomotor neurons – limits vasoconstriction:
T2DM; PD
Also Small cell lung carcinoma, monoclonal gammopathies, light chain disease, or amyloid
Non-neurogenic: hypovolaemia, cardiac failure or venous pooling
Cardiac impairment (INC. MI, aortic stenosis)
Reduced intravascular volume (dehydration, adrenal insufficiency)
States that induce vasodilation (including fevers)
Medication: Diuretics, alpha blockers, anti hypertensives
Also: Insulin, levodopa, and tricyclic antidepressants can also cause vasodilation and postural hypotension in predisposed patients
Causes of Subacute onset of Postural hypotension that is rapidly progressing?
Small cell lung carcinoma, monoclonal gammopathies, light chain disease, or amyloid
Symptoms of Postural hypotension?
Dizziness, weakness, confusion, blurred vision, nausea, syncope
Why older people are more susceptible to postural hypotension?
more prone to hypovolaemia (increased natriuretic peptides, reduction in renin, angiotensin and aldosterone with age) as impaired ability to conserve water and sodium and reduced thirst response
decreased baroreflex sensitivity, with impaired a1-adrenergic vasoconstriction and affected heart rate responses
Chronic hypertension (common in older people) also results in reduced baroreflex sensitivity and left ventricular compliance
blunted response to the recruitment of the sympathetic nervous system in blood pressure control
more likely to be on medications that are associated with inducing postural hypotension, such as furosemide and terazosin
more likely to experience greater severity of the symptoms from postural hypotension, due to deconditioning from lack of exercise.
Exacerbating factors of postural hypotension?
Rising quickly after prolonged sitting or recumbency; Prolonged motionless standing;
Time of day (early morning after nocturnal diuresis);
Dehydration; Physical exertion; Alcohol intake; Carbohydrate-heavy meals;
Straining during micturition or defecation;
Fever
Mx of posutral hypotension aims?
- To raise standing blood pressure without also raising supine blood pressure
- To reduce orthostatic symptoms
- To increase the time the patient can stand
- To improve the ability of patients to perform activities of daily living
Non-pharma Mx of Posutral hypotention?
Non-pharma –
educate about condition
Emphasis avoidance of high-risk situations - rising quickly from sitting or supine positions, prolonged standing, hot environments and large meals
To reduce venous pooling: Compression stocking, abdominal binders, physical activity
Counter manoeuvres:
o exercises such as toe raising, leg elevation and leg crossing
o contraction of the muscles below the waist
Measures to expand blood volume:
o keeping the head of the bed elevated (reverse Trendelenburg) - increases plasma volume by decreasing overnight diuresis, with activation of the renin-angiotensin-aldosterone system.
o Increasing salt and water intake, including the use of regular boluses of water
Pharma Mx of postural Hypotension? CIs, SEs?
• Fludrocortisone: synthetic mineralocorticoid that expands plasma volume
o patients who have heart failure, ascites and chronic renal failure
o SEs: supine hypertension and severe hypokalaemia (Monitor potassium levels when commenced on fludrocortisone)
• Midodrine: short-acting vasopressor – useful in neurogenic postural hypotension
o Caution if severe heart failure, urinary retention and underlying hypertension
o SEs: supine hypertension, scalp paraesthesia and pilomotor reactions, such as goosebumps
• Pyridostigmine: acetylcholinesterase inhibitor
Complications of Postural hypotension?
Falls, reduced confidence of mobility, reduced ability to perform ADL independently,
