Electrolyte orders in the neuroscience intensive care unit: worth the value or waste?

To assess the value of the practice of obtaining frequent electrolyte measurements in patients with extended stay in a neuroscience intensive care unit (NICU).

We identified consecutive patients 18 years or older, admitted to the NICU between January 1 and July 31, 2009 with length of stay ≥ 5 days. We collected potassium, sodium, magnesium, ionized calcium, phosphorus laboratory measurements and hemoglobin levels, and recorded electrolyte replacement orders and red blood cell transfusions. Average laboratory costs were estimated.

93 patients were included in the study (54 men, mean age 54 years, range 18-85 years). Mean length of stay was 10.4 days (range 5-36 days). Sodium and potassium were the electrolytes most frequently measured (averages of 14.1 and 13.1 per patient, respectively). More than 75% of the results were within normal range for all electrolytes measured and critical values were extremely uncommon. The number of phlebotomies for electrolyte measurements was strongly associated with the degree of hemoglobin drop (P < 0.0001). Electrolyte panels were ordered much more often than individual electrolytes with average cost exceeding $2200 per patient. Replacing half of these electrolyte panels with single sodium or potassium orders would have resulted in savings greater than $100,000 in our population.

Electrolytes measurements are very frequent in the NICU, but results are most often normal and only exceptionally critical. The phlebotomies required for these tests significantly worsen hemoglobin levels. A more conservative use of electrolyte measurements can result in reduction of blood loss and substantial cost savings.