Ventilations and HR - Peds

[DieselBolus17]

hi all, tried doing a quick Google search but nothing specific is coming up. What is the reason/pathophysiology ventilation increases heart rate in children?

Thanks in advance.

 

[WildlandEMT89]

Is this a homework question?
All of your post kinda have that homework question vibe to them.

 

[Flying]

CO2 + H2O <> H2CO3 <> HCO3(-) + H(+)

Assuming a shift from normal state.

Hyperventilation blows off CO2 by repeatedly refreshing the air mixture at alveoli.
Reduced blood CO2 causes a shift in blood equilibrium, causing more free H+ to be taken up by buffer system. Result is more alkaline blood.
Reduced H+ environment will make free calcium in blood have a higher affinity for albumin protein floating around, resulting in more bound calcium and less free calcium.

Calcium has a negative chronotropic (reduces time/rate, so reduced heart rate) effect on the heart. So a lack of Ca will result in a positive chronotropic shift (guess what that will do).

 

[Brandon O]

Interesting, never heard that theory. But calcium, if anything, is a positive chronotrope.

 

[Flying]

Oh shoot, better read up again.

 

[DieselBolus17]

Not a HW question. I'm out of school lol. Just random stuff that pops into my head that I can't remember the answers to.

 

[Flying]

More conventional thinking:
Lowered CO2 in brain stem/medulla results in reduced sympathetic stimulation of vasomotor center, reducing vasoconstriction.
Apparently CO2 has an independent vasodilatory effect, so a lowered pCO2 will reduce vasodilation as well?

I'm assuming the effect of the vasomotor center is much larger, given how sensitive it is, causing an overall dilation of the blood vessels and respective compensation by circulatory system until the chemical equilibrium of the blood is made closer to normal by the kidneys (assuming you've stopped ventilating/hyperventilating at this point).

 

[Brandon O]

Maybe dial it back a bit.

The Occam's Razor answer: does ventilation increase heartrate in children? I'm not entirely sure what you mean.

 

[Carlos Danger]

Maybe dial it back a bit.

The Occam's Razor answer: does ventilation increase heartrate in children? I'm not entirely sure what you mean.

I was about to ask the same thing.

 

[Seirende]

Like when a kid is bradycardic due to respiratory failure and that is reversed, reversing the bradycardia?

 

[Underoath87]

In the case of pediatric/neonatal resuscitation, it is because hypoxemia causes their hearts to slow and eventually stop. I'd suppose it is just a physiological mechanism to reduce oxygen consumption (maybe related to the mammalian diving reflex), but I've yet to hear of a detailed explanation or term for it.

So focus your efforts on determining why hypoxemia causes bradycardia, rather than ventilations increasing HR.

 

[chaz90]

In the case of pediatric/neonatal resuscitation, it is because hypoxemia causes their hearts to slow and eventually stop. I'd suppose it is just a physiological mechanism to reduce oxygen consumption (maybe related to the mammalian diving reflex), but I've yet to hear of a detailed explanation or term for it.

So focus your efforts on determining why hypoxemia causes bradycardia, rather than ventilations increasing HR.

Hypoxia leading to bradycardia isn't some great physiologic mystery. It's obviously not just present in pediatric patients either.

Oxygen is an essential component of the electron transport chain in aerobic cellular respiration. It is the final reducing component that accepts the electrons that have been used in creation of ATP. If there is no oxygen available (or less than usual), cellular respiration slows as the ion pumps are unable to repolarize the cellular membrane and create a proper action potential. Less oxygen leads to slower action potential regeneration, leading to a prolongation of Phase III, leading to bradycardia.

 

[Seirende]

Oxygen is an essential component of the electron transport chain in aerobic cellular respiration. It is the final reducing component that accepts the electrons that have been used in creation of ATP. If there is no oxygen available (or less than usual), cellular respiration slows as the ion pumps are unable to repolarize the cellular membrane and create a proper action potential. Less oxygen leads to slower action potential regeneration, leading to a prolongation of Phase III, leading to bradycardia.

I will understand this... Someday, I WILL understand this. [/dramaticmoment]

 

[Underoath87]

Oxygen is an essential component of the electron transport chain in aerobic cellular respiration. It is the final reducing component that accepts the electrons that have been used in creation of ATP. If there is no oxygen available (or less than usual), cellular respiration slows as the ion pumps are unable to repolarize the cellular membrane and create a proper action potential. Less oxygen leads to slower action potential regeneration, leading to a prolongation of Phase III, leading to bradycardia.

Well there's your answer, OP.