Canadian Practical Nurse Registration Examination (CPNRE) Practice Exam

In cases of hyperkalemia, which refers to elevated levels of potassium in the blood, the primary effect on cardiac function is related to the impairment of depolarization of heart cells. High potassium levels can lead to a decreased resting membrane potential, making it more challenging for the cardiac cells to depolarize successfully. This often results in slower conduction of electrical impulses through the heart, which is typically reflected in a slow heart rate. The heart may struggle to generate impulses at a faster rate due to the altered ion concentrations affecting the excitability of the cardiac myocytes.

While hyperkalemia can indeed lead to irregular heart rhythms and other changes in heart rate, the most characteristic effect regarding impaired cardiac depolarization is a slowdown in the heart rate. Understanding this mechanism is crucial for identifying and managing the cardiovascular consequences of hyperkalemia in clinical practice.