Cystic Fibrosis, Tissue Rejection, Saline

[StilgarMD]

Some quick questions on topics I've found confusing.

1. Cystic Fibrosis causes Very thick, dehydrated secretions in the mucus of the lungs and nearly isotonic secretions in the sweat.

The former takes place because w/o CFTR, chloride can't leave the cell and balance out the charges created by the sodium. Since this loss makes the inside leaflet of the membrane more negative, sodium has a greater driving force to be sucked in to the cell via ENaC channels. Water follows sodium. Mucus is left thick.

the latter is caused by a lack of Chloride going into the cell. the CFTR channel's absence leads to chloride remaining the sweat, and keeping sodium there for electrical neutrality, leading to a very salty sweat, and potential for dehydration.

If this is an ATP operated channel, how does it facilitate movement in two directions, both in and out of the cell?

Edit: I apparently missed it on Wikipedia the 1st time I looked, but it seems the CFTR channel is more of an "ATP operated channel". It binds ATP and facilitates the flow of chloride down its gradient.

2. Why does hyperacute rejection have anything to do with blood types? Solid tissue matching is done via HLAs (Human MHCs) and I don't see how blood type difference can cause anything besides a transient hemolytic anemia of cells that came with the graft.

3. Is there a useful guide when to give Normal Saline vs other kinds? I find myself guessing on these questions.

Any insights would be appreciated.

Edit: Does anyone know where I can find a complete schematic of the Lysosomal storage disorders with the actual structures?

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[PaxRoma]

Some quick questions on topics I've found confusing.

3. Is there a useful guide when to give Normal Saline vs other kinds? I find myself guessing on these questions.

When in doubt, the safest 1st fluid to give is always normal saline
Dehydration -NS
Shock -NS
Extreme hypercalcemia -NS
and many, many other indications

 

[OnePunchBiopsy]

When in doubt, the safest 1st fluid to give is always normal saline
Dehydration -NS
Shock -NS
Extreme hypercalcemia -NS
and many, many other indications

If the patient is dehydrated and they are hypernatremic you give D5W. NS would make them worse. Unless they are diabetic, then you also have to give them insulin as well.

Goljan has a great section on fluid replacement.

 

[PaxRoma]

If the patient is dehydrated and they are hypernatremic you give D5W. NS would make them worse. Unless they are diabetic, then you also have to give them insulin as well.

Goljan has a great section on fluid replacement.

D5W is isotonic in packet but quickly become hypotonic once inside the body because glucose is rapidly metabolized by cellular processes.
Giving a hypotonic solution to a hypovolemic hypernatremic patient is dangerous for the following reason:
IV hypotonic solution -> drastic drop in serum Na+ concentration -> free water rapidly leaves the intravascular system and goes to organs such as the brain -> cerebral edema
Hypovolemic hypernatremic (i.e severe dehydration) patient need their hypernatremic state corrected SLOWLY by first given an isotonic solution like NS, once serum Na+ concentration has stabilized, a hypotonic solution maybe considered for better free water replacement.

 

[worldbeater]

Edit: Does anyone know where I can find a complete schematic of the Lysosomal storage disorders with the actual structures?

If you done the question on UWorld, you can look up "Q8524", it has the complete diagram in the explanation. It's obnoxious to memorize though, I just try to do it piecemeal by remembering the accumulations of the diseases I keep missing.