The most likely cause of a serum potassium level of 4 mEq/L in a client taking hydrochlorothiazide (HCTZ) and furosemide (Lasix) for chronic renal insufficiency (CRI) is the combined effect of these diuretic medications.
Both HCTZ and furosemide are diuretics that increase the excretion of electrolytes, including potassium, through the urine. This can lead to a decrease in serum potassium levels, a condition known as hypokalemia.
In this case, the client is taking two diuretics, which can potentiate the potassium-wasting effect. It's important for healthcare providers to monitor the client's electrolyte levels regularly and consider potassium supplementation or adjusting the dosage of diuretics to maintain an appropriate potassium balance. Hypokalemia can lead to various health issues, including muscle weakness, cardiac arrhythmias, and other complications, so it's crucial to manage it appropriately in individuals with CRI.