Diabetic Ketoacidosis

[0dsmith88]

Hey im just looking for a little bit of help/ clarification.

Im know that one of the responses to hyperglycaemia in a diabetic is to produce ketone bodies for energy. Im also pretty sure that these ketone bodies are the eventual cause of acidosis in ketoacidosis im just not to sure how.

I kinda figured that as acetoacetate can decompose spontaneously to produce acetone that this also produces CO2-which lowers the pH of the blood-resulting in the acidosis.

Im not sure however if this is correct or if there are other causes of the acedosis.
Any help would be appreciated

[iain_261188]

acetoacetate and B-hydroxybutyrate are acid. so is lactate and free fatty acids. and CO2. plus kidney unable to filter hydrogen ions and ketones. i think.

[DevilishlyPure]

the ketones dissociate to produce H+ ions --> metabolic adicosis --> DKA
Basically because of the acidosis, the person starts vomiting and hyperventilating to get rid of some H+ ions, but with loss of fluid volume you get worsening of the electrolyte imbalance and dehydration. This impairs the ability of the kidney to excrete H+, and so the acidosis worsens

[iain_261188]

one might say it's a positive feedback loop, mightn't one?

[heed]

indeed - or a vicious, pear drop smelling circle :)

[andrewbaillie]

ah u obviously havent had les fixter as a facilitator. someone said they smelled like pear drops and he brought in a vial of whatever chemical they use in pear drops, so that we could smell the difference between that and acetone (they were very similar!)

[andrewbaillie]

oh and they get vomiting and abdo pain in DKA because the acidosis causes a transient ileus

[iain_261188]

apparently the acidosis also triggers the chemoreceptor trigger centre for vomitting. says clinical chemistry.

[heed]

i can just remember being told in first year the number of paediatric DKA patients that end up with a laparotomy scar because they are taken to have an acute abdomen and not DKA......

[Dehydrated Water]

just to be picky, the increased ketone body production isn't caused by the hyperglycaemia, but rather by the lack of insulin, as it normally inhibits both lipolysis and ketogenesis.

so increased lipolysis leads to increased FFA's which leads to increased Acetyl CoA to make the ketone bodies.

and as you know ketogenesis is a normal body process that normally only produces enough ketone bodies as required, and this is kept in check by insulin, so no insulin = too many ketone bodies = ketoacidosis

[Devlinator]

apparently the acidosis also triggers the chemoreceptor trigger centre for vomitting. says clinical chemistry.

sorry to be picky, but the CTZ and vomiting centre are different, the CTZ lies outwith the blood-brain barrier, and so is your brains filter for noxious substances (ie ketones, alcohol etc), and this feeds into the vomiting centre (inside the blood-brain barrier) which then co-ordinates the action of vomiting

[0dsmith88]

Cheers for all the help guys

[iain_261188]

sorry to be picky, but the CTZ and vomiting centre are different, the CTZ lies outwith the blood-brain barrier, and so is your brains filter for noxious substances (ie ketones, alcohol etc), and this feeds into the vomiting centre (inside the blood-brain barrier) which then co-ordinates the action of vomiting

question about this: Kumar and Clark says that vomitting centre is in the reticular formation, and the CTZ is in the floor of the 4th ventricle. wouldn't those both be classed as inside the BBB? ta

[heed]

In short, its both inside and outside. Anatomically i guess the CTZ is strictly inside the BBB on the floor of the forth ventricle (Area postrema) but in effect may as well be outside it as the BBB in this area is significantly more "porous" than elsewhere. Areas of the brain where the BBB is weaker are known as "circumventricular organs".

if youre asking this out of interest then cool beans - but if you are going into this much detail revising for MBChB1 then you are giving yourself waaaaay too much work......

[iain_261188]

nah i just happened to notice it in K&C. usually i'm on a need to know basis with the knowledge!

[Devlinator]

In short, its both inside and outside. Anatomically i guess the CTZ is strictly inside the BBB on the floor of the forth ventricle (Area postrema) but in effect may as well be outside it as the BBB in this area is significantly more "porous" than elsewhere. Areas of the brain where the BBB is weaker are known as "circumventricular organs".

if youre asking this out of interest then cool beans - but if you are going into this much detail revising for MBChB1 then you are giving yourself waaaaay too much work......

ok this is a bit more than you need to know, and i am going on what i have been told by consultant anaesthetists

[davidmed]

andrews always very through :rolleyes:

just dont tell me anymore stuff that i just didnt know i didnt know-if you know what i mean.......