A potassium of 6.8 and the order that saves the heart
Three drugs are on the tray. Only one buys you time, and it doesn't lower potassium at all.
Potassium comes back at 6.8 with peaked T-waves on the monitor. What is the thing most likely to kill this patient, and how fast?
The heart. Potassium runs cardiac conduction, so I'm not waiting on paperwork, I want continuous cardiac monitoring and the crash cart within reach now. Peaked T-waves mean the membrane is already unstable.
You have calcium gluconate, insulin with dextrose, and a potassium binder on the tray. Which goes first?
Calcium. And here's the part people fail: it does not lower the potassium at all. It raises the threshold potential and stabilizes the myocardium so the heart doesn't fibrillate while the other drugs do the real work.
So once I've pushed calcium, the hyperkalemia is handled?
No, that's exactly the trap. The number on the lab is unchanged. Calcium buys minutes, not a cure. If I stop there, the patient still has a body full of potassium and will arrest when the calcium wears off.
Then what actually moves the potassium?
Two different verbs. Insulin with dextrose shifts it into cells, temporary, but fast. The binder or dialysis removes it from the body, that's what fixes the total load. Protect, shift, remove, in that order, every time.
Your patient is anuric from end-stage renal disease. Does the plan change?
The endpoint does. Shifting still buys time, but with no kidneys to excrete it, dialysis is the definitive move. A binder is slow and partial; dialysis is how you actually clear it when renal function is gone.
↑ answer it in your head first ↑
Traps
- ⚠ Giving calcium and assuming potassium is now lower. Calcium protects the heart; it does not shift or remove potassium.
- ⚠ Reaching for the binder first. It works, but far too slowly to matter in an emergency.
- ⚠ Forgetting that insulin needs dextrose, or you trade hyperkalemia for hypoglycemia.