In reviewing the electrolytes of a patient, the nurse notes the serum potassium level has increased from 4.3 mEq/L to 5.9 mEq/L. Which assessment does the nurse initiate first to prevent further harm?

An increased serum potassium level, also known as hyperkalemia, can have adverse effects on the electrical conduction of the heart, potentially leading to life-threatening cardiac dysrhythmias. Therefore, it is crucial to assess the patient's pulse rate and rhythm promptly to identify any abnormal cardiac activity. Assessing the oxygen saturation (oxygen stats), respiratory rate and depth, and deep tendon reflexes are also important assessments, but they are not the priority in this case. Hyperkalemia primarily affects cardiac function, and prompt identification of any potential cardiac rhythm disturbances is essential to prevent further harm.