57.1Hyperkalemia

A 60-year-old diabetic male patient, hypertensive and on angiotensin-converting enzyme (ACE) inhibitors, was admitted with dizzy spells. On admission, his pulse was 60/min, BP was 110/70 mmHg, and sensorium was normal. His blood biochemistry showed urea 90 mg/dL, creatinine 2.0 mg/dL, Na 130 mEq/L, and K 6.5 mEq/L.

Table 57.3 ECG changes in hyperkalemia

Tall, peaked T waves with a shortened QT interval

Progressive lengthening of the PR interval and QRS duration

Disappearance of P waves

QRS widening and a sine wave pattern

Asystole and a flat ECG

Fig. 57.2 Hyperkalemia

Step 1: Initiate resuscitation

•Patients with severe hyperkalemia need an urgent intravenous access and continuous ECG monitoring.

•They can have sudden bradycardic arrest. ACLS protocol should be followed in these situations (See Chap. 19).

Step 2: Assess severity of hyperkalemia and urgency of correction

•Hyperkalemia should be urgently managed in the following circumstances:

–ECG changes (see Table 57.3 and Fig. 57.2)

–Muscle weakness or paralysis

–Rhabdomyolysis

–Crush injury

–Tumor lysis syndrome

–Serum potassium of more than 7.0 mEq/L

–Rapidly rising potassium above 5 mEq/L

Step 3: Rapidly correct severe hyperkalemia

•Intravenous calcium

–Give calcium gluconate or calcium chloride—10 mL of 10% solution over 2 min under continuous ECG monitoring.

–Intravenous calcium works within minutes, but effect is short-lasting (30–60 min).

–Calcium acts by directly antagonizing the membrane action of hyperkalemia and does not cause lowering of serum potassium.

–Calcium chloride contains three times elemental calcium compared to calcium gluconate (13.6 vs. 4.6 mEq in 10 mL of 10% solution) and is the preferred drug.

–Intravenous calcium can be repeated after 5 min, if ECG abnormalities persist.

–Concentrated calcium solution is tissue-irritant and should be given in a large peripheral vein or central vein.

–Calcium should not be given in a bicarbonate-containing solution to avoid precipitation of calcium carbonate.

–Calcium should be given cautiously as a slow infusion in patients on digitalis.

•Insulin with glucose

–Give 10 units of regular bolus insulin intravenously along with 50 mL of 50% dextrose.

–Monitor blood glucose every 30 min.

–In patients with baseline hyperglycemia above 250 mg/dL, only insulin can be given.

–The effect of insulin begins within 10 min and lasts for 4–6 h.

–Insulin and glucose lowers serum potassium by driving potassium inside the cells.

–It decreases serum potassium by 0.5–1.2 mEq/L.

–Beware of hypoglycemia in renal failure.

•Salbutamol (albuterol) nebulizer

–10 mg in 4 mL of saline to be nebulized over 10 min (four times the usual bronchodilator dose) is given.

–Its effect is seen within 90 min of nebulization.

–Serum potassium usually decreases by 0.5–1.2 mEq/L.

–It works by driving potassium inside the cell.

•Sodium bicarbonate

–It should be given cautiously in selected cases of hyperkalemia associated with severe metabolic acidosis.

–Usual dose is 25 mEq (25 ml of 8.4%) infused over 5 min.

Step 4: Assess the cause of hyperkalemia

•Detailed history and physical examination should be performed to look for features of diseases associated with hyperkalemia such as renal failure and adrenal disease.

•History of renal disease or potassium levels should be looked for to assess sudden deterioration of renal function.

•Drug history should be taken to exclude drugs such as angiotensin-receptor blockers, ACE inhibitors, nonsteroidal anti-inflammatory drugs, aldosterone antagonist, and potassium-containing syrup that can cause hyperkalemia specially in renally impaired patients.

Step 5: Send investigations

•Serum potassium should be monitored frequently.

•Blood urea, creatinine.

•Sodium, calcium, magnesium, phosphate.

•Arterial blood gases.

•Complete hemogram.

•Blood glucose.

•CPK.

•Lactate dehydrogenase.

Step 6: Stop the intake of potassium

•Start potassium-free diet.

•Avoid the use of drugs containing potassium.

•Avoid drugs that can cause hyperkalemia.

Step 7: Remove potassium

•Diuretics: A trial of loop diuretics in patients with preserved renal function and volume overload state may be made.

•Cation exchange resin: Sodium polystyrene sulfonate.

–In the gut, sodium polystyrene sulfonate takes up potassium (and calcium and magnesium to lesser degrees) and releases sodium (1 gm binds to 1 meq of potassium).

–It is usually given orally three times daily but may be given rectally.

–Oral dose is usually 20 g given with 100 mL of a 20% sorbitol solution to prevent constipation.

–A major concern with sodium polystyrene sulfonate in sorbitol is the development of intestinal necrosis, usually involving the colon and the ileum.

–The serum potassium falls by at least 0.4 mEq/L in the first 24 h.

•Dialysis

–It is indicated if hyperkalemia persists in spite of above measures or patients have any other indication of dialysis. Hemodialysis can remove 25–50 mEq of potassium per hour, with variability based on the initial serum potassium concentration, the type and surface area of the dialyzer used, the blood flow rate, the dialysate flow rate, the duration of dialysis, and the potassium concentration of the dialysate.

–Beware of rebound hyperkalemia after dialysis.