Skip to main content

Strong ion acid–base abnormality and lactate:pyruvate ratio in children following cardiopulmonary bypass


To describe post-cardiopulmonary bypass (post-CPB) acid–base derangement in terms of the Fencl–Stewart strong ion approach and the lactate:pyruvate ratio (LPR).


A prospective observational study set in the PICU of a university hospital. Arterial blood gas, serum lactate, pyruvate, and electrolytes were measured on admission to the PICU following cardiac surgery with CPB. LPR, corrected chloride (cCl = 140 × Cl/Na), and unmeasured anions or cations (strong ion gap) were calculated using modified Fencl–Stewart equations. CPB time, percent predicted mortality (PIM I), PICU mortality, and duration of: ventilation; inotropic support; and PICU stay were recorded. Data are reported as the median (range), or n (%), and are analysed by Mann–Whitney and Fisher's Exact tests. Ninety-four children, median age 51 months (0.03–166), median weight 14 kg (2.1–50), were enrolled.


Surgery was performed for cyanotic heart disease in 41 children (44%) and acyanotic heart disease in 53 children (56%). Median CPB time was 80 min (17–232). One child died (PICU mortality 1%). Predicted mortality was 2% (SMR 0.50). The median pH was 7.38 (7.17–7.61). Of 69 children with standard bicarbonate < 22 mmol/l, the primary factor causing metabolic acidosis was elevated cCl in 32 patients (46%), lactate in three patients (4%), unmeasured anions in two patients (4%), and mixed in 32 patients (46%). The median base excess (BE) was -5.0 meq/l (-12.9 to -2.5), with chloride effect of -10.8 meq/l (-24 to +1.2), free water effect of -0.6 meq/l (-3.3 to +1.8), albumin effect of +3.5 meq/l (-0.6 to +6.8), and unmeasured cation effect of +3.7 meq/l (-10.7 to +17). The median cCl was 113 mmol/l (101–126). Hyperchloraemia (cCl >110 mmol/l) occurred in 66 children (70%) and was negatively associated with use of adrenaline by infusion (P = 0.005). Median lactate was 1.9 mmol/l (0.7–9.1) and hyperlactataemia (> 2 mmol/l) occurred in 41 children (44%). The median LPR was 18.8 (5.4–35) and LPR was raised (> 20) in 42 children (45%). Hyperlactataemia plus raised LPR was associated with use of adrenaline by infusion (P = 0.0009), CPB time (P = 0.04), percent predicted mortality (P = 0.05) and PICU stay (P = 0.03). Median albumin was 30 g/l (16–44) and hypoalbuminaemia (< 35 g/l) occurred in 81 children (86%). The median calculated strong ion gap was -3.8 mmol/l (-18.4 to +9.1) (i.e. unmeasured cation predominance).


In this group of children with low mortality post-CPB, hyperchloraemia was primarily responsible for metabolic acidosis, although both hyperlactataemia and raised LPR were common. Both hypoalbuminaemia and unmeasured cations limited the magnitude of the base deficit.

Author information

Authors and Affiliations


Rights and permissions

Reprints and Permissions

About this article

Cite this article

Hatherill, M., Salie, M., Waggie, Z. et al. Strong ion acid–base abnormality and lactate:pyruvate ratio in children following cardiopulmonary bypass. Crit Care 9 (Suppl 1), P415 (2005).

Download citation

  • Published:

  • DOI:


  • Cyanotic Heart Disease
  • Pyruvate Ratio
  • Unmeasured Anion
  • PICU Stay
  • Base Derangement