Situation: A 61-year-old woman with type 2 diabetes and hypertension takes losartan 100 mg and spironolactone 25 mg daily and recently began using a salt substitute. She comes to the emergency room with generalized weakness and tingling in her legs. Her serum potassium is 7.0 mEq/L (3.5–5.0 mEq/L) on a non-hemolyzed sample, serum creatinine 1.0 mg/dL (88 µmol/L), capillary blood glucose 142 mg/dL (7.9 mmol/L), and her 12-lead electrocardiogram (ECG) shows tall, peaked T waves. She is on a cardiac monitor. The physician orders the following: 1. Give 10 mL of 10% calcium gluconate intravenously over 10 minutes 2. Give sodium zirconium cyclosilicate 10 g orally 3. Check capillary blood glucose 1 hour after the insulin 4. Give regular insulin 10 units intravenously with 25 g of dextrose In what order should the nurse carry out these orders?

With ECG changes, the first step is to stabilize the heart with IV calcium gluconate, which works within minutes. Next, insulin with dextrose shifts potassium into the cells, and then a binder removes potassium from the body over hours. Because insulin can cause hypoglycemia, the glucose check follows the insulin at 1 hour.

Clinical context This patient has severe hyperkalemia with a serum potassium of 7.0 mEq/L and ECG changes. The tall, peaked T waves indicate that the elevated extracellular potassium is already altering cardiac repolarization, which places her at immediate risk for ventricular arrhythmias or cardiac arrest. Her kidney function is preserved (creatinine 1.0 mg/dL), so the potassium elevation is driven primarily by medication effects and the recent salt substitute use rather than impaired renal excretion. Losartan reduces aldosterone-mediated potassium secretion, spironolactone blocks the mineralocorticoid receptor, and many salt substitutes replace sodium chloride with potassium chloride. Together these factors explain why potassium accumulated to a dangerous level.

Why the sequence matters The correct order is calcium gluconate first, then insulin with dextrose, then the potassium binder, and finally the glucose check. Hyperkalemia treatment follows three distinct phases: membrane stabilization, intracellular shift, and elimination. Each intervention has a different onset and duration, so the nurse must sequence them according to the immediate threat.

Calcium gluconate does not lower serum potassium; it directly antagonizes the effect of potassium on the cardiac cell membrane. It restores the electrical gradient across myocardial cells within minutes, reducing the risk of lethal arrhythmias while other therapies take effect. This is the highest-priority action when ECG changes are present because the patient can deteriorate into ventricular fibrillation before potassium-lowering agents begin to work.

Step-by-step rationale

Order	Intervention	Mechanism and timing	Nursing priority
1	Calcium gluconate 10 mL of 10% IV over 10 minutes	Stabilizes myocardial cell membranes; onset within 1–3 minutes, duration 30–60 minutes	Give first because ECG changes are present; protects the heart immediately
2	Regular insulin 10 units IV with 25 g dextrose	Activates Na⁺/K⁺-ATPase, shifting potassium into cells; onset 10–20 minutes, peak 30–60 minutes	Give second to begin lowering serum potassium; dextrose prevents insulin-induced hypoglycemia
3	Sodium zirconium cyclosilicate 10 g orally	Binds potassium in the GI tract for fecal excretion; onset over 1–2 hours, peak effect at 4–6 hours	Give third because it removes potassium from the body but does not act quickly enough for the acute threat
4	Capillary blood glucose 1 hour after insulin	Detects hypoglycemia from IV insulin; insulin effect peaks around 30–60 minutes	Perform last, timed from insulin administration, not from arrival

Deeper look at each intervention

Calcium gluconate is the first-line membrane stabilizer in hyperkalemia with ECG changes. It works by raising the threshold potential of cardiac cells, making them less excitable and counteracting the depolarizing effect of excess extracellular potassium. The protective effect is temporary, so it must be followed by therapies that actually lower potassium. Watch out! Calcium should be given slowly over 10 minutes with continuous cardiac monitoring. Rapid infusion can cause bradycardia or hypotension. Also, calcium chloride contains three times more elemental calcium than calcium gluconate and is more irritating to peripheral veins, so gluconate is preferred when a peripheral line is used.

Insulin with dextrose is the primary intracellular shift therapy. Insulin stimulates the sodium-potassium ATPase pump on skeletal muscle and liver cells, driving potassium from the extracellular space into the intracellular compartment. The dextrose is given to prevent hypoglycemia because IV insulin acts rapidly. The glucose check is timed one hour after insulin administration because that is when the hypoglycemic effect of IV regular insulin is most pronounced. If the patient becomes hypoglycemic, additional dextrose may be needed, and blood glucose should be rechecked frequently for several hours.

Sodium zirconium cyclosilicate is a selective potassium binder that exchanges sodium and hydrogen ions for potassium in the gastrointestinal tract. Unlike older binders such as sodium polystyrene sulfonate, it has a faster onset and does not cause colonic necrosis. It is given orally and removes potassium from the total body pool over hours. It is not a rescue therapy for acute ECG changes but is essential for definitive correction and prevention of rebound hyperkalemia.

Key point! The sequence reflects the physiologic timeline: stabilize the membrane first, shift potassium second, eliminate potassium third, and monitor for treatment complications last. Reversing this order—for example, giving the binder before calcium—would leave the myocardium unprotected during the critical first minutes.

Why the other options are incorrect

Option 1 (4, 1, 2, 3) places insulin before calcium. This delays membrane stabilization while the patient remains vulnerable to arrhythmias. Insulin does not protect the heart from the immediate electrical effects of potassium.

Option 2 (1, 2, 4, 3) gives the binder after the glucose check. While calcium and insulin are correctly sequenced, delaying the binder means potassium elimination starts later. The glucose check is a monitoring task that can be performed after the binder is administered; it does not need to interrupt the treatment sequence.

Option 3 (2, 1, 4, 3) starts with the binder. This is the most dangerous error because the binder has the slowest onset and does nothing to stabilize the myocardium or shift potassium acutely. A patient with peaked T waves could develop ventricular tachycardia while waiting for the binder to work.

Clinical correlation with the patient’s medications

This case illustrates a classic drug–drug and drug–food interaction. Losartan, an angiotensin II receptor blocker, and spironolactone, an aldosterone antagonist, both reduce renal potassium excretion. When a potassium-based salt substitute is added, the total potassium load exceeds the kidneys’ ability to excrete it, even with normal renal function. Key point! Patients taking an ACE inhibitor, ARB, or aldosterone antagonist should be counseled to avoid potassium-containing salt substitutes and to have serum potassium monitored when these agents are combined.

Nursing responsibilities during treatment

Continuous cardiac monitoring is essential throughout the acute phase. The nurse should observe for resolution of peaked T waves, widening of the QRS complex, or development of bradyarrhythmias after calcium administration. Serum potassium should be rechecked 1–2 hours after insulin and again after the binder has had time to act. Blood glucose monitoring should continue for at least 4–6 hours after IV insulin because the hypoglycemic effect can persist beyond the one-hour mark. Intravenous calcium and insulin both require careful documentation of administration time because subsequent monitoring and repeat dosing depend on precise timing.