This is probably review as it is such a common occurrence for nephrologists as well as internists. Here's my protocol, along with useful dosing info (sometimes lacking in textbooks):
1. Get an EKG. Look to see if there are typical changes associated with hyperkalemia (e.g., peaked T waves, widening of QRS). This is important as some of the medications are generally only given if there is evidence of EKG change (e.g., calcium).
2. Calcium: probably the most important in terms of rapidly stabilizing the myocardium if there is evidence of EKG change. Either calcium chloride or calcium gluconate can be given. I usually give calcium chloride, 1gram given iv push over about 5 minutes. If you have time make sure the iv is a good one, as CaCl2 can be caustic if it leaks out of the vasculature.
3. Insulin/D50: This is also rapid and effective, though the effects are transient. I give 10 units of iv insulin along with 1 amp of D50 (which is 50ml of a 50% dextrose solution).
4. Kayexalate: the potassium-binding resin is most effective when the patient produces a bowel movement, and sometime multiple doses are necessary to achieve this. I typically start with 30gm of kayexalate and given additional rounds until the patient stools. It can be given per rectum if the patient is NPO or refuses to take it orally.
5. "Other Stuff": the first four things are the mainstay. Other stuff can also be tried, though I think is less effective. It's been taught to me by several "electrolyte gurus" that sodium bicarbonate is overrated in terms of its potassium-lowering properties, so I don't use it unless there is concomitant severe acidosis. Lasix and other loops can lower potassium, though usually if a patient is hyperkalemic it's because they're kidneys aren't working and lasix probably won't have much of an effect anyways. There's also the possibility of using albuterol--though you need a lot more than standard nebulizer dosing for asthma if you want it to work. Either stack multiple albuterol nebs together, or give 10mg inhaled x 1-2. It can also be as an iv injection (albuterol 2.5mg iv). I am told this is effective, but don't use it much--it can have a side effect of significant tachycardia.
6. If All Else Fails: there's always the dialysis machine!