venipuncture (by either excessive vacuum of the blood draw or by a
collection needle that is of too fine a gauge); excessive tourniquet
time or fist clenching during phlebotomy (which presumably leads to
efflux of potassium from the muscle cells into the bloodstream); or
by a delay in the processing of the blood specimen."
"Pseudohyperkalemia Caused by Fist Clenching during Phlebotomy"
"Excessive tourniquet time, too tight tourniquet or fist clenching
during phlebotomy (which presumably leads to efflux of potassium from
the muscle cells into the bloodstream) are other important cause of
But I guess we should ask first "When have you calibrated pressure
gauge of the tourniquet?" (unless the nurse tend to lose temper...)