Postural Hypotention
Decrease in the blood pressure during standing position .also called orthstatic
hypotention .
Causes of Postural Hypotention
1-Failure of normal response of peripheral vascular resistence i.e in adequate
constriction of resistance blood vessel which is due to :
A-Disese of ANS,brian,peripheral N .
B-Use of vasodilator, prolong rest.
2-full in cardiac out put .This result from :
A-Decrease in venouse return due to increase
pooling of blood in the lower limbs.
B-Inadquate response of the heart (HR
,contractility).
C-Exceccive heat or prolonged orthostatic
response.
D-Faliure of capacitance vessel to constrict
adequately due to baroreflex defect or disease of
ANS.
F-Increase distesibilty of vein and valve which
causes varicose vein
.
3-Inadequately blood volume.
A-In assuming upright position ,the blood volume due to pooling of
blood, then the distensibility of capacitance blood vessel is increase
and lead to more pooling and result ibn decrease venous return and
cardiac out put .
B-loss of blood due haemorhage,loss of fluid due to diarrhea
,vomiting ,burun.
4-Inadequate baroreceptor reflex like in elderly.
5-Vasovagal attack
due to prolong standing ,truma,fear
(generalized parasympathetic activity).
Test of postural hypotension assessment
.
1-stading position .
2-Tilting test.
3-LBNP(LOWER BODY NEGATIVE
PRESSURE )
4-Neck suction (stimulation of
baroreceptor
).
5-Valsava manoeuvore:
forced expiratory effort against closed
glottis so that lead to increase in the intrathoracic to 100
mmHg.
There is 4 phases for V.M:
1-Immediate increase in the blood pressure due to increase in
the intrathoracic blood pressure and transient increase in
venous return from the lungs.
2-deacrese venous return which lead to decrease in the blood
pressure .
3-Further decrease in the blood pressure immediately follow
release of valsava due to decrease intra-abdominal and intra-
thoracic pressure .
4-overshoot of blood pressure in response to increase venous
return.
Notes: HR increase during valsalva and
decrese during overshoot.
Test of assessment of ANS.
1-Cold pressure test.
2-Stressful mental arithmetic .
3-reflex sweat test.
4-hyperventilation test.
5-exercise
6-I.V injection of atropine.