Table 1: Mean values and mean differences in electrolyte concentrations measured simultaneously by two analyzers for samples from acidic patients (pH < 7.40) or alkalemic patients (pH > 7.40).

pH < 7.40pH > 7.40

Na+ (mmol/L)
Blood gas analyzer135.7 ± 4.0131.5 ± 6.5
Central laboratory analyzer137.0 ± 3.6133.0 ± 6.7
Mean difference−1.27 ± 1.79−1.46 ± 1.590.74

K+ (mmol/L)
Blood gas analyzer3.6 ± 0.54.0 ± 0.5
Central laboratory analyzer3.9 ± 0.64.3 ± 0.5
Mean difference−0.25 ± 0.17−0.27 ± 0.200.68

Cl (mmol/L)
Blood gas analyzer105.5 ± 3.6101.2 ± 6.0
Central laboratory analyzer102.5 ± 3.4101.0 ± 6.0
Mean difference3.10 ± 4.230.62 ± 1.550.004

Values are means ± SD. Na+: sodium; K+: potassium; Cl: chloride.