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Association between blood lactate and acid-base status and mortality in ventilated babies
1Newcastle Neonatal Service, Special Care Baby Unit, Royal Victoria Infirmary, Newcastle upon Tyne.
Insights
Acid-base parameters like pH and base excess do not reliably indicate blood lactate levels in sick, ventilated neonates. Serial blood lactate measurements are crucial for early warning and prognosis in these infants.
Area of Science:
- Neonatal Medicine
- Critical Care
- Biochemistry
Background:
- Acid-base balance is critical in neonates.
- Blood lactate is a marker of tissue hypoperfusion.
- Reliable indicators for lactate levels are needed in sick neonates.
Purpose of the Study:
- To determine the relationship between acid-base parameters and blood lactate.
- To assess the prognostic value of these parameters in neonates.
Main Methods:
- Serial measurements of arterial acid-base status and blood lactate.
- Study included 75 mechanically ventilated neonates.
- Data analyzed for correlations and prognostic significance.
Main Results:
- No significant correlation found between blood lactate and pH or base excess.
- Base excess was an insensitive indicator of hyperlactatemia.
- Raised lactate concentrations were associated with increased mortality.
Conclusions:
- pH and base excess are not reliable surrogates for blood lactate.
- Independent measurement of blood lactate is essential.
- Serial lactate measurements offer valuable prognostic information in neonates.
Aim:
To investigate the relation between common acid-base parameters and blood lactate concentrations and their prognostic importance in sick, ventilated neonates.
Methods:
Two hundred and seventy eight serial simultaneous measurements of arterial acid-base status and blood lactate concentrations were carried out in 75 mechanically ventilated neonates with indwelling arterial catheters (gestational age and birthweight, median (range) -29 (23-40) weeks, and 1340 (550-4080) g, respectively).
Results:
There were no correlations between arterial blood lactate and pH and base excess within subjects (r = 0.07 and r = -0.06, respectively) and only weakly positive but clinically irrelevant positive correlations between subjects (r = 0.28 and r = 0.27) in this group. Even in those infants who had not received any bicarbonate before their initial measurements (n = 48), there were no correlations between initial blood lactate concentrations and pH (r = 0.27), base excess (r = 0.17), or serum bicarbonate concentrations (r = -0.18). There was no relation between peak lactate concentration (PLC) and base excess (r = 0.16), and only a weak correlation between peak lactate concentration (PLC) and pH (r = 0.28). Negative base excess was an insensitive indicator of raised lactate concentrations. Only two out of 33 (6%) instances of hyperlactataemia (lactate > 2.5 mmol/l) would have been identified with a base excess < -10 mmol/l as a cutoff. Lower cutoff values of base excess or pH performed no better. Raised lactate concentrations were associated with increased mortality at all levels. While six of 53 (11%) infants with a PLC < 2.5 mmol/l died, this proportion increased to four of 15 (27%) with a PLC between 2.5-5.0 mmol/l, and four of seven (57%) with a PLC > 5.0 mmol/l. Infants showing little rise or a substantial fall in blood lactate fared better than those with persistently raised values. A clinically important increase in blood lactate preceded the development of clinical markers of deterioration and complications in six infants.
Conclusions:
Contrary to popular belief, pH or base excess cannot be used as proxy measures for blood lactate concentration, and independent measurement of the latter are needed. Blood lactate concentrations may provide an early warning signal and important prognostic information in ill, ventilated neonates. In this regard, serial measurements of blood lactate are more useful than a single value.