A change in K+ plasma concentration can cause a variety of clinical effects including cardiac, neuromuscular, and metabolic effects.
As hyperkalemia decreases the transmembrane K+ gradient, there are consequent effects to the cell membrane depolarization, slowing of ventricular conduction, and a decrease of the AP duration.
These changes result in cardiac arrhythmia which manifest in ECG findings as peaked T waves (result of resting membrane potential changes which lead to early excitatory reaction), widening of the QRS complex, loss of the P wave, and eventually ventricular fibrillation, which ultimately leads to asystole.
Impaired neuromuscular transmission is also present including paresthesias, weakness, paralysis, and absent or depressed deep tendon reflexes.
GI effects include nausea, vomiting, and diarrhea while metabolic pertuberations include negative ability to excrete acid load which may eventually cause hyperchloremic metabolic acidemia.