When a premature baby is in the neonatal intensive care unit (NICU), reliable test results are critical to provide the most appropriate, safest, and fastest care. One such test, blood gas analysis, evaluates the amount of oxygen, carbon dioxide and electrolytes in the blood. Frequently, in this population, the results can be negatively impacted by hemolysis, which can occur during sample collection, compromising the accuracy of potassium measurement.
A frequent laboratory error, hemolysis, accounts for up to 70% of all unsuitable specimens.1 Suspected hemolysis in whole blood specimens can result in sample recollection, which, in the case of tiny, premature infants, may not be an option due to limited blood volume. It can also cause delays in treatment, inappropriate treatment, iatrogenic anemia, transfusion, pain, and other resulting complications.2
Understanding the need for improvement, Drs. Dennis J. Dietzen, Ronald Jackups, and Mark A. Zaydman set out to define the frequency and magnitude of error in whole blood potassium measurement in pediatric blood specimens. Below is an explanation of some of the important findings in their publication, “Clinical implications of inaccurate potassium determination in hemolyzed pediatric blood specimens,” as well as key insights into why hemolysis detection at the point of care is critical.2
A Summary of Dietzen Et Al
Dietzen et al collected and studied whole blood and plasma potassium data at St. Louis Children’s Hospital (SLCH) and Barnes-Jewish Hospital (BJH). This data, which spanned 34 months, focused on infants under two years of age. Using the plasma hemolysis or “H" index, the researchers were able to identify hemolysis. The team then assessed qualitative agreement between paired whole blood and plasmas measurements, separated by less than 2 hours. Their findings included:
- Hemolysis rates of 50%, the highest detected in the study, were in the neonatal nursery setting
- Of the 662 proximal whole blood and plasma paired results, 8% demonstrated elevated whole blood potassium with a normal plasma value (pseudohyperkalemia), while 4% saw normal whole blood potassium with low plasma potassium (pseudonormokalemia)
- The bias between whole blood and plasma potassium ranged from −1 to 4 mmol/L
Why Hemolysis Detection is Needed
Since current technology does not allow for real-time detection of hemolysis in whole blood, potassium results may be skewed, unbeknownst to a clinician. In the event that potassium concentrations are falsely elevated, a clinician may incorrectly determine the patient is hyperkalemic. If potassium levels are falsely normal, hypokalemia may go undetected. When potassium levels are too high or low, a patient may experience seizures, paralysis, and even cardiac arrest.2 Thus, it is critically important that hemolysis is detected, utilizing better, more effective methods.
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