Dehydration and Blood Pressure

[G1SG2]

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Hey, if a person is dehydrated, would you expect their blood pressure to increase or decrease? I figured it would decrease, due to the loss of fluid volume. However, won't the arteries constrict in an attempt to compensate for the loss of volume, and thus raise the BP? Thanks.

 

[StIGMA]

If your intravascular volume is depleted your blood pressure will decrease. Compensatory mechanisms (carotid baroreceptors, etc.) will kick in but will not result in blood pressure above your normal baseline (unless you replete the volume/add drugs, etc.).

 

[PiBond]

Hey, if a person is dehydrated, would you expect their blood pressure to increase or decrease? I figured it would decrease, due to the loss of fluid volume. However, won't the arteries constrict in an attempt to compensate for the loss of volume, and thus raise the BP? Thanks.

the person's blood pressure when dehydrated is generally decreased which thus increases plasma osmolarity. the body then uses vasopressin to act at the level of the kidneys to conserve water and thus get blood pressure back up

arteries constrict when there's a hemorrhage (for example) and you have an isotonic loss of blood volume. i'm not sure if they would constrict during dehydration

 

[AbbyNormal]

Personal experience anecdote:

last year following several days of N&V w/ diarrhea I saw a physician who did a tilt test to evaluate if I was dehydrated. My BP was slightly elevated sitting and standing but low normal when supine. He told me those values indicated I was dehydrated and I got a couple liters NS. So I suppose that means I was compensating at that point by vasoconstriction. At some point compensating fails and people will be hypotensive but I imagine there are many factors that would define when that point would be reached.

 

[G1SG2]

If your intravascular volume is depleted your blood pressure will decrease. Compensatory mechanisms (carotid baroreceptors, etc.) will kick in but will not result in blood pressure above your normal baseline (unless you replete the volume/add drugs, etc.).

the person's blood pressure when dehydrated is generally decreased which thus increases plasma osmolarity. the body then uses vasopressin to act at the level of the kidneys to conserve water and thus get blood pressure back up

arteries constrict when there's a hemorrhage (for example) and you have an isotonic loss of blood volume. i'm not sure if they would constrict during dehydration

Thanks for the response. So I guess the correct answer would be it decreases, but then increases later on (not above the baseline level)?

 

[G1SG2]

Personal experience anecdote:

last year following several days of N&V w/ diarrhea I saw a physician who did a tilt test to evaluate if I was dehydrated. My BP was slightly elevated sitting and standing but low normal when supine. He told me those values indicated I was dehydrated and I got a couple liters NS. So I suppose that means I was compensating at that point by vasoconstriction. At some point compensating fails and people will be hypotensive but I imagine there are many factors that would define when that point would be reached.

Yeah, I guess so, because then there are instances like hypovolemic shock where the blood pressure just drops (although that is a late sign).

 

[AbbyNormal]

Yeah, I guess so, because then there are instances like hypovolemic shock where the blood pressure just drops (although that is a late sign).

Well hypovolemia and shock are two different things. Hypovolemia is a fluid volume deficit in simple terms whether it is caused by N&V, diarrhea, or blood loss from trauma. Shock is inadequate tissue perfusion and hypovolemia is just one cause Just being hypovolemic doesn't mean that you are in shock. But if you stay hypovolemic for long enough you will end up in shock. Typically patients do compensate for hypovolemia initially with vasoconstriction and increased heart rate. They may be in the early stage of shock at that point. As you say hypotension is a late sign of hypovolemia and at that point there is no doubt that the patient is in shock. As you know (I hope) you treat the patient early with oxygen and the appropriate fluids and definitive care for the cause of hypovolemia rather than wait until shock is in later stages.

 

[G1SG2]

Well hypovolemia and shock are two different things. Hypovolemia is a fluid volume deficit in simple terms whether it is caused by N&V, diarrhea, or blood loss from trauma. Shock is inadequate tissue perfusion and hypovolemia is just one cause Just being hypovolemic doesn't mean that you are in shock. But if you stay hypovolemic for long enough you will end up in shock. Typically patients do compensate for hypovolemia initially with vasoconstriction and increased heart rate. They may be in the early stage of shock at that point. As you say hypotension is a late sign of hypovolemia and at that point there is no doubt that the patient is in shock. As you know (I hope) you treat the patient early with oxygen and the appropriate fluids and definitive care for the cause of hypovolemia rather than wait until shock is in later stages.

Right you are! I know, I'm an EMT 🙂 Was just pointing out a type of shock related to my original question.

 

[AbbyNormal]

Right you are! I know, I'm an EMT 🙂 Was just pointing out a type of shock related to my original question.

Awesome!!

I was an EMT too before I became a RN. I learned many things in my paramedic class that they never taught us in nursing school. EMS is exciting. You never know what your next call will be. One of our calls was a train versus train head on collision. Somebody screwed up big time there. I'd love to still do it but dragging people around killed my knees.

Are you wanting to do emergency medicine as a doc?

 

[howyoudoin]

It will initialy go up due to ADH or always digging holes and other things

 

[G1SG2]

Awesome!!

I was an EMT too before I became a RN. I learned many things in my paramedic class that they never taught us in nursing school. EMS is exciting. You never know what your next call will be. One of our calls was a train versus train head on collision. Somebody screwed up big time there. I'd love to still do it but dragging people around killed my knees.

Are you wanting to do emergency medicine as a doc?

Nice! Yeah, EMS is awesome, it taught me a lot. I actually don't want to do emergency medicine. More interested in internal medicine...just not as hectic as EM lol.

 

[ttperora]

I have checked int to the hospital a few times because of high blood pressure which leads to anxiety and nervousness.

I'm surprised the doctors never brought up the issue of dehydration as a propobale cause.
They just told me to relax and be less stressful.

So I cut down on alchohol, that didn't help for long
Then in the last 3 days, I have been drinking a lot of water and my anxiety and blood pressure has gone down.