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Treatment of hyperkalemia

Hyperkalemia is a medical emergency.Treatment should be started as early as possible.
Approach to treatment is based on two main factors
1. Degree of hyperkalemia
2. Change in ECG

Aim of treatment 
1.Minimise the membrane depolarization over a few minutes with calcium gluconate
Calcium gluconate
Dose of calcium is 1g of 10% calcium gluconate or calcium chloride which is infused intravenously over 2-3 min; may require repeat dose if no improvement in ECG is seen by 5 minutes.
Onset and duration of action -Immediate onset of action, lasting 30-60 minutes.
Magnitude of [K+] decline-There is no decline in potassium.
Precautions - Calcium chloride should be administered preferably via a central vein to reduce the risk of extravasation and skin necrosis.

2. Shift the potassium into the cell over the next 30 to 60 minutes
This is achieved with following drugs which will shift the potassium into the cell.
a. Insulin
Dose of insulin-is 10unit to 20units of regular insulin IV (with one ampule of Dextrose 50 intravenous fluid if there is no significant hyperglycemia).
Onset and duration of action Onset of action is within 15 to 30 minutes it will last for 6-8 hour.
Magnitude of [K+] decline is 0.5 to 1.5 mEq/L.
Precaution - Watch for hypoglycemia or hyperglycemia (as dextrose is  given),they will affect the K+ lowering effect of insulin.
b. Albuterol
Dose is 10-20 mg ,it is given by nebulized inhalation over 15 minutes or can be given as a continuos nebulized treatment over 30 to 60 minutes OR 0.5 mg of albuterol in 100 mL of 5% dextrose infused intravenously over 15 minutes.
Onset and duration of action Onset is at 30 minutes,lasting for3-6 hour.
Magnitude of [K+] decline is .5 -1.5 mEq/L.
Precautions-Increased heart rate and variable effects on blood pressure can occur .
c. NaHCO3
Dose- 2-4 mEq/minute in drip (3 ampules NaHCO3 in sterile water or 5% dextrose infusion is given till the bicarbonate is normalized.
Onset and duration - Onset of action is at 4 hour, lasting > 6 hr.
Magnitude of [K+] decline -0.5-0.75 mEq/L.
NaHCO3 is not effective I there is concurrent inorganic metabolic acidosis;It can result in volume overload and lower ionized calcium.

3.Long term measures to reduce the serum potassium
aLoop +/− thiazide diuretics
Dose varry widely depending on GFR(glomerular filtration rate).
Onset start at 30-60 minutes, last for 4-6 hour (duration increased  in renal insufficiency).
Magnitude of [K+] decline is variable depending on the diuretic response.
Better to avoid in volume depleted states until euvolemia is restored.
b. Sodium polystyrene sulfonate
Dose is 25-50 g mixed in 100 mL 20% sorbitol per orally OR 50 g in 200 mL 30% sorbitol per rectum.
Onset of action is at 1-2 hour, lasting 4-6 hour.
Magnitude of [K+] decline is 0.5-1 mEq/L.
Use cautiosly in the postoperative patient because of risk of intestinal necrosis.
c. Hemodialysis
Response based on initial potassium value.
Immediate onset of action, lasting until dialysis completion.
Magnitude of [K+] decline - is variable, based on dialysis dose and dialysate [K+].
Rebound increase in potassium value after dialysis can occur.