Why is there a faint pulse with severe dehydration? Wouldn't it be thready & increased?

[757RN]

The nurse knows which of the following clinical manifestations indicate severe dehydration?

Select all that apply.

Cool limbs

Faint pulse

Obtunded LOC

Capillary refill time of 2 seconds

Extreme thirst

Bradycardia

Pain over lower back

Explanation

• Obtunded level of consciousness, faint pulse, extreme thirst and cool limbs indicate severe dehydration.

• Decreased urine output and capillary refill time of greater than 2 seconds are both indicative of mild dehydration.

• Dry mucous membranes and slow skin turgor indicate moderate dehydration.

• Bradycardia and back pain are not indicators of severe dehydration.

[Awesomocity0]

Thready is weak, which is the opposite of increased. Are you asking why it isn't increased and decreased at the same time? I think you may have gotten some terminology confused. Why it's weak, makes sense if you think about it. You have decreased volume. It's like if you lost 50lbs and put on the same dress. The fabric wouldn't be as snug around you.

[WookieeRN, BSN, MSN, RN]

Deficient volume means that there isn't enough fluid, this there is a drop in blood pressure and a faint pulse. If there was an excess of fluid, the pulse would be bounding because of the increase.

[Lev, MSN, RN, NP]

Thready and faint pulse are essentially the same thing. With dehydration, there may be some tachycardia to compensate initially. However, as the intravascular fluid deficit increases, the decreased blood volume means there is less pressure in the arteries and therefore a weak/faint/thready pulse.

[757RN]

Thank you Lev

I understand that HR increases initially, and then decreases overtime once dehydration becomes severe.

As for the pulse..I've read (in my NCLEX book..Saunders) that it increases with SEVERE dehydration.. But..this question above (from an iphone NCLEX app; NCLEX Mastery) states that the pulse is in fact faint with severe dehydration..contradicting one another.

So I guess what I'm trying to get at is..does pulse increase first (with mild dehydration) and THEN decrease (with severe dehydration)? Or does pulse remain decreased, no matter what the level of dehydration is (mild/moderate/severe)?

[FlyingScot, RN]

I think you're confusing pulse rate (sometimes referred to just as pulse) and pulse quality.