Complex sentence: Potassium replacement becomes of utmost importance in this setting because potassium is usually also lost in urine and hypokalemia promotes bicarbonate ion retention and prevents bicarbonate excretion, thus interfering with alkalinization of the urine.
Split into simpler sentences: Potassium replacement becomes of utmost importance in this setting because potassium is usually lost in urine. If blood levels of potassium are depleted below normal levels, then hypokalemia occurs, which promotes bicarbonate ion retention and prevents bicarbonate excretion, thus interfering with alkalinization of the urine.