The prescription within safe limits
Intravenous potassium chloride is a high-alert medication. It must be diluted and given by infusion pump, and through a peripheral line it commonly runs no faster than 10 mEq/h at a concentration of no more than about 40 mEq/L. The first option, 20 mEq in 500 mL over 2 hours by pump, gives 20 mEq ÷ 2 h = 10 mEq/h at 20 mEq ÷ 0.5 L = 40 mEq/L. Only the prescription of 20 mEq in 500 mL over 2 hours by infusion pump meets the rate, concentration, and equipment rules.
Checking each prescription
| Prescription | Rate | Concentration | Problem |
|---|
| 20 mEq in 500 mL over 2 h, pump | 10 mEq/h | 40 mEq/L | None; within limits |
| 20 mEq in 500 mL over 2 h, gravity | 10 mEq/h | 40 mEq/L | Gravity drip can speed up without warning |
| 20 mEq added to hanging 500 mL bag, pump | 10 mEq/h | Uneven | Never add potassium to a hanging bag |
| 20 mEq in 100 mL over 30 min, pump | 40 mEq/h | 200 mEq/L | Exceeds every peripheral limit |
Why each safety rule exists
Rapid potassium can cause fatal cardiac dysrhythmias and cardiac arrest. An infusion pump controls the rate exactly, while a gravity drip can suddenly run faster if the client moves or the roller clamp shifts. Adding potassium to a bag that is already hanging can leave the concentrated potassium pooled near the outlet, so the client may receive a bolus. High concentrations also irritate peripheral veins, causing pain and phlebitis. Watch out! Potassium is never given by IV push or bolus under any circumstance.
Why this client needs careful replacement
His potassium of 2.9 mEq/L is low, probably from the hydrochlorothiazide, which has been held. Hypokalemia explains his weakness, leg cramps, and palpitations. It is especially dangerous for him because he takes digoxin: low potassium increases the risk of digoxin toxicity and dysrhythmias. The nurse places him on cardiac monitoring, checks the IV site for pain and infiltration, monitors urine output before and during the infusion, and follows repeat potassium levels.
Exam takeaway
Peripheral IV potassium: diluted, by pump, no faster than about 10 mEq/h, at no more than about 40 mEq/L, never by push and never added to a hanging bag. Key point! Calculate both the hourly rate and the concentration; a prescription must pass both checks and the equipment rule.