Hyperkalemia: hypertonic solution?

You're correct that you want the potassium to move into the cell. But you're rationale about the hypertonicity of the D50 is incorrect. It doesn't matter that the D50 in the bag is hypertonic. (As an aside, remember that while D50 is hypertonic in the bag, once administered, the dextrose is quickly used up and your left with the tonicity of the base solution.) You give D50 because you're also going to give insulin. The insulin helps the glucose in the D50 move into the cell, and takes the potassium along with it. You may also be giving D50 because you're likely to have some hypoglycemia from the insulin.

The idea of trating hyperkalemia (remember, that's high K+ in the blood) is to move it out of the blood and back on the other side of the cell membranes where most of the body's K+ belongs.

The way to do that is glucose and insulin.

Now don't forget this important point: this question is about treating hyperkalemia using added dextrose and insulin. The same thing happens when you have a hyperglycemic patient and you give him insulin-- the insulin and (his own) glucose will drive his serum K+ into his cells. This will make him hypokalemic and at risk for cardiac arrhythmia....so remember to check his K+ early and often, and be ready for an IV potassium replacement rx.

No extra charge, lol.

Ah....I think I understand now. The rationale to use D50w has less to do with its hypertonicity but more to do with the amount of glucose in d50w that will bind to potassium and drive it back into the cell via insulin's help, and to prevent hypoglycemia that might occur from the use of insulin. So with that reasoning...D5W is too low to use with insulin right?

I hope my understanding is correct.

Thank you so much, Double-Helix and AliNinjaCat!! :)

So with that reasoning...D5W is too low to use with insulin right?

I hope my understanding is correct.

Yes, D5W is not enough dextrose to counteract the insulin. At my hospital, we usually give 10 units of regular insulin IV (not subcutaneous), "one amp" of D50 (which is actually a 50mL bottle that we draw up in a giant syringe), a stat albuterol breathing treatment, and sometimes an amp of bicarb (which is also not an ampule...it's either a Bristojet or a 50mL bottle).

I always check the blood sugar prior to adminstration...if it's already, say, 150 and the patient is a diabetic, chances are their blood sugar will be 180 30 to 45 minutes after administration. On the other hand, if their blood sugar is 85 pre-administration and they are NOT a diabetic, their blood sugar might be (and has been!) 46 after 30 to 45 minutes. In which case, per our policy, they get another amp of D50. If they're a renal failure patient, their blood sugar could be 300 before administration and then 32 after administration (yep, it's happened...without the kidneys clearing the insulin from the system, it just keeps hanging around).

The tonicity of D50 probably has very little effect...it turns into 50mL of sterile water pretty quickly in the body. However, if a patient is acidotic (which can lead to hyperkalemia), it is possible that they are septic or in DKA. Fluid replacement *is* an important part of treatment if that's the case, though I usually see isotonic solutions.

Other causes of hyperkalemia: Anything that breaks a lot of cell membranes. Think blood reaction, where you lyse a lot of RBCs; crush injury, where you crush a lot of muscle cells (also look out for myoglobinemia; that'll gum up your functioning renal units pretty fair too); and iatrogenic causes, like somebody gave too much KCL IV, or POTASSIUM penicillin or other med.

The treatment of hyperkalemia can be 4 fold:

1.) Calcium Gluconate or Calcium Chloride

This is given to prevent cardiac arrhythmias that may be caused by the high serum potassium. This should be given first, and will be considered a cardio-protective measure. Calcium will not reduce the serum potassium levels, but will prevent potential arrhythmias. The following measures should also be given immediately after the Calcium is administered.

2.) Insulin Regular + D50W

D50W alone will not do anything to lower the serum potassium level. The Dextrose is given to counteract the hypoglycemia caused by the insulin. Insulin Regular is given because it increases the permeability of many cells to potassium. Insulin activated sodium-potassium ATPase channels in many cells, which will cause a influx of potassium ions from the plasma into the cells.

3.) Kayexelate or Sodium polystyrene

Kayexelate is given as a potassium binder, and it will bind to potassium to form potassium polysyrene sulfonate and will be excreted in the feces.

4.) Sodium bicarbonate

Sodium bicarbonate will raise the pH level in the plasma to help facilitate the influx of potassium into the cells via the sodium-potassium ATPase channel.