Oh! These are such good questions. I've been looking at the components of the various IV solutions this past week. To get my CRNI (Certified RN Intravenous) some years ago, fluids and electrolytes was, and still is, a BIG part of that examination process. Please excuse me for do a little bit of re-writing of your questions.
Scenario A
A patient has an order for IV fluids of 0.9 NS with 20 meq of KCL. The potassium level was 4.4. Would you give these IV fluids?
Yes. But I think you also have to look at the other factors going on with the patient beside just his potassium level before making a decision not to give this IV fluid. Normal potassium levels are between 3.5 and 5.0 mEq/liter. A 4.4 is about right in the middle of that, so this would be considered a normal potassium level. Potassium is normally lost through urine. 20mEq of potassium in a liter of fluid is a conservative replacement. 0.9 Normal Saline is an isotonic solution that is primarily used to replace fluid to the body and give back some of the sodium and chloride that the body has lost. It contains 154 mEq of sodium and 154 mEq of chloride. The body looses unusual amounts of potassium with diuretics, digitalis intoxication, vomiting, diarrhea, diabetic acidosis, and metabolic acidosis. It is normal for 40mEq of potassium to be added to a liter of an IV solution, so 20mEq is not much. It is more of a maintenance dose. What is important is that it is diluted down. Intravenous potassium should never be infused any faster than 10mEq per hour. And, that serum electrolytes are being monitored by the doctor on a regular basis.
Scenario B
Patient unable to take po meds. Lasix IV not given due to not being able to administer potassium orally. Potassium level 4.5. Would you have held the Lasix?
No. The Lasix is being given for a reason and that reason needs to be included in any decision to hold it. Lasix (furosemide) is a loop diuretic that takes a lot of potassium out of the body with the fluid. It acts by inhibiting the reabsorption of water and electrolytes. In other words, it encourages them to pass through the kidneys and on into the urine. This results in water loss, which is the intended goal. Potassium is excreted through the kidneys. Lasix therapy can also result in complications such as excess sodium loss (hyponatremia) and excess potassium loss (hypokalemia).
Again, a potassium level of 4.5 is right in the middle of normal levels. Lasix is normally given to reduce edema often due to an underlying congestive heart failure. Depending on what the patient's underlying disease process is, withholding the Lasix might be more harmful and make his disease process worse. A potassium level can easily be determined in a matter of minutes and compensated for intravenously. In fact, any patient on Lasix should be having regular serum potassium assessments being made.
I just want to make one final point. When you have any patient on IV fluids, you should be monitoring their labwork, particularly their serum electrolytes. Know the normal levels and know the clinical signs and symptoms of hypo- or hyper- states of each.
Would you like to comment?
As far as the second scenario, I wouldn't hold the lasix, their K was normal. And it's in their IVF, and in a liter bag they can ceratainly go higher on the mEq of KCL (I'm assuming you can't give mini bags of KCl on your unit?). I think your decisions were fine! 
