Monitoring parenteral nutrition in hospitalized patients: issues related to spurious bloodwork

Monitoring hospitalized patients receiving parenteral nutrition requires regular bloodwork. However, blood specimens, if not drawn appropriately, may be contaminated by parenteral nutrition, leading to spurious results and unnecessary medical interventions. The objective was to determine, in a large academic center, the frequency of spurious bloodwork, unnecessary medical interventions, and contributing factors.

This was a 1-year prospective cohort study monitoring hospitalized patients receiving parenteral nutrition and their bloodwork. Sudden unexplained changes in serum levels of glucose, potassium, and sodium were identified. Subsequent medical interventions were tracked. Factors affecting blood collection, such as technique, shifts, nursing units, nursing, and patient demography, were assessed and compared with those of a control group.

Out of 201 patients, 34 had 63 incidents of spurious bloodwork. This led to 23 medical interventions. The most frequent problem was the failure to clamp the parenteral nutrition infusion prior to blood collection or too short a time between clamping and drawing. There was an increased occurrence of spurious bloodwork drawn by nurses with < 10 years of experience due to failure in following blood collection policy. Cost of spurious bloodwork and subsequent interventions for 63 incidents was approximately $3480 (CAD) per year. This excluded physician time.

Spurious bloodwork was due to parenteral nutrition contamination by incorrect blood draw techniques. This led to a policy amendment to incorporate a "wait time" between stopping the parenteral nutrition infusion and drawing blood and to an institution-wide nursing reeducation.