Reference intervals and age and gender dependency for arterial blood gases and electrolytes in adults.

Background: Although results from blood gas analyzers are frequently used in clinical work surprisingly few and small studies have examined reference intervals for arterial blood gases and acid-base status. We have established reference values based on a large group of healthy people with a wide age distribution.

Methods: A group of medical students (n=182) aged 20-32 years old and a group of health professionals aged 21-76 years were used in this study. Arterial samples were analyzed on the blood gas analyzer ABL from Radiometer(TM). Age and gender dependency was examined for all analytes and reference intervals were calculated non-parametrically.

Results: Females had significantly higher pH and lower PaCO(2) (partial pressure of carbon dioxide in an arterial sample), base excess (BE, standard, extra cellular fluid), plasma standard and actual HCO(3), when compared to males (p<0.01). However, the differences were minor and common reference intervals were therefore also determined, generally at the same level as previously published. The lactate values were similar among the genders but with a high upper limit of 2.5 mmol/L. The non-smoker group of females and males had similar PaO(2) values (partial pressure of oxygen in an arterial sample). However, an age dependent effect was found and PaO(2) decreased by 0.29 kPa per decade (confidence interval of slope -0.11 to -0.47 kPa). Electrolytes and anion gap results depicted smaller differences from previous published reference intervals for sodium (136-141 mmol/L) and anion gap (10-16 mmol/L, with potassium included or 6-12 mmol/L without potassium).

Conclusions: Reference intervals for analytes on modern blood gas analyzers were established on a large group of healthy people. Gender and age dependency is generally without clinical importance, except for a lower PaCO(2) in women and a decreasing PaO(2) with higher age.