I have a couple questions about BP. I get frustrated because as I look at more info from different sources, I become more confuses and I feel dumb.
First on orthostatic hypotension, I know BP falls because sometimes the vessels can't constrict. But in terms of dehydration, they are already constricted right? So because they can't constrict more when you stand, you lose BP?? also, why is BP higher when laying down exactly?
Second, on hypertension, P&P says that thickening and hardening of arteries causes hypertension, and on AOL it says hypertension causes those things. Which is it?? Also, it says that "The heart muscle thickens in order to pump blood against the higher pressure in the vessels. More blood is needed to do this, but narrowed blood vessels cannot supply that blood. " More blood is needed to do what? Also, how does hypertension exactly create risk for strock exactly? I mean how is high BP going to create a clot???
Thanks so much people! I read and read but never find answers to these questions!!!
Nov 14, '01
I will try to answer at least part of your question.
According to my Springhouse pathophysiology review, hyper tension is caused by:
1.changes in the arteriolar bed causing increased resistance
2. abnormally increased tone of vasomotor systems cause increased peripheral vascular resistance
3. increased blood volume caused by renal or hormonal dysfunction
4. increased arteriole thickening caused by genetic factors, leading to increased peripheral vascular resistance
5.abnormal renin release resulting in the formation of angiotensin II which constricts the arterioles and increases blood volume
Hypotension has various etiologies also. you can have a lack of/slow response of vasculature to consitrict, pooling of blood in periphery, or loss of volume which leads to reduced volume return.
Hope this helps.
Nov 14, '01
HTN can damage the inside wall of a vessel. A clot can form on this roughened, damaged area, which will cause a stroke if it breaks away and lodges in the brain.
Nov 14, '01
Strokes can also be cause by a bleed, or ruptured anyurism, excessive bp on a already thin walled vessel can cause it to rupture, thus a hemmorhagic cva, dman too many hard workd to spell, that can cause a cva also
Nov 15, '01
My primary focus used to be electrophysiology---sooo
Orthostatic hypotension can be caused by an autonomic nerves respose from changing positions too quickly, causing increased heart rate and dilation of the arteries---leading to hypotension.
"flight or fight"
The heart muscle thickens to provide more of a pump to move blood through the sclerotic vessels--against resistance. This is why the majority of people who have athrosclerotic heart disease also have hypertension. Think of it in terms of lifting weights, the more weight you lift(resistance) the bigger your muscles get(the heart).
Usually with dehydration, you have a high heart rate. The heart does not have time to adequately fill, and there is not enough volume to fill the chambers, which in turn circulating volume becomes less and the blood pressure drops, simply to lack of volume.
In conclusion to this lesson, checks can be made payable to...LOL
In the fourth triad of ACLS, all problems with blood pressure, the heart, cariopulmonary arrest etc.. can be catagorized into one of the following:
Good luck, if you have anymore questions, feel free to ask!
Just a side note, many patients (young women) have a condition called dysautonomia (aka: Postural Orthostatic Tachycardia Syndrome, or Shy-Drager Syndrome). This causes such profound changes in blood prssure and pulse that many of them need to go on medications (Norpace and effexor or Ritalin) and they must wear jobst stockings so they don't constantly pass out. This is an example of the autonomic nerve respose as indicated above.
Last edit by radnurse2001 on Nov 15, '01
Nov 15, '01
The process of arteriosclerosis and forming clots if slow. When BP is high it makes tiny pits in what was once a smooth lining. When this lining is pitted plaques can more easily attach instead of sliding along on its merry way. This is the case as to the importance of maintaining a low BP under 120 and < low 80's (even though definition says <90).
Often we may think bigger is better. In weight lifting we desire a bigger muscle. a good reccomendation is to work out hard and then rest. This creates a bigger healthy muscle. If we worked out continuously we would get the bigger muscle but also injury and exhaustion. The muscle would in turn be less effective if we needed to lift something heavy. With high blood pressure there is no rest for the heartand a larger less effective left ventricle muscle (hypertrophy) is created. Some medications (ace inhibitors- Lisopril and others) can make the left ventricle slightly larger without exhaustion as well as lowering BP and improving collateral blood vessels. This adds extra protection in the case of a later MI.
Nov 17, '01
Ok.. orthostatic HTN. Take a Ziploc bag. Put about 1/2 its volume of water in it. Set it upright. No water in the top, right? This is standing up. Blood is in the legs. Now lay it flat. Water is all through it. Blood is all over the body. When you are lying down, the blood can return to the heart to be pumped through the body, whereas if you are standing up, it just sits in your feet (simplistically put). That's why the BP is higher when you are lying down.
When you are talking about the heart hypertrophying, they mean that the heart itself needs more blood (bigger muscle, more metabolic need), but that the coronary arteries often can't keep up the supply.
Hope some of this helps..
Nov 18, '01
Thanks guys/gals for the responses to my questions. Very helpful. Actually I'm not needing to know pathophys inside and out at this point but I'm the type that wants to know it all right away. Thanks again!
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