Clinical application of the measurement of cord plasma lactate and pyruvate in the assessment of high-risk neonates

A Metabolomic Approach in Search of Neurobiomarkers of Perinatal Asphyxia: A Review of the Current Literature

Perinatal asphyxia and the possible sequelae of hypoxic-ischemic encephalopathy (HIE), are associated with high morbidity and mortality rates. The use of therapeutic hypothermia (TH) commencing within the first 6 h of life-currently the only treatment validated for the management of HIE-has been proven to reduce the mortality rate and disability seen at follow up at 18 months. Although there have been attempts to identify neurobiomarkers assessing the severity levels in HIE; none have been validated in clinical use to date, and the lack thereof limits the optimal treatment for these vulnerable infants. Metabolomics is a promising field of the "omics technologies" that may: identify neurobiomarkers, help improve diagnosis, identify patients prone to developing HIE, and potentially improve targeted neuroprotection interventions. This review focuses on the current evidence of metabolomics, a novel tool which may prove to be a useful in the diagnosis, management and treatment options for this multifactorial complex disease. Some of the most promising metabolites analyzed are the group of acylcarnitines: Hydroxybutyrylcarnitine (Malonylcarnitine) [C3-DC (C4-OH)], Tetradecanoylcarnitine [C14], L-Palmitoylcarnitine [C16], Hexadecenoylcarnitine [C16:1], Stearoylcarnitine [C18], and Oleoylcarnitine [C18:1]. A metabolomic "fingerprint" or "index," made up of 4 metabolites (succinate × glycerol/(β-hydroxybutyrate × O-phosphocholine)), seems promising in identifying neonates at risk of developing severe HIE.

Use of umbilical cord blood gas analysis in the assessment of the newborn

Analysis of paired arterial and venous specimens can give insights into the aetiology of acidosis in the newborn

The Timing of Neonatal Brain Damage

Although neonatal morbidity and mortality are less than in the past, the risk of pre-natal and neonatal brain damage has not been eliminated. In order to optimize pre-natal, perinatal and neonatal care, it is necessary to detect factors responsible for brain damage and obtain information about their timing. Knowledge of the timing of asphyxia, infections and circulatory abnormalities would enable obstetricians and neonatologists to improve prevention in pre-term and full-term neonates. Cardiotocography has been criticized as being too indirect a sign of fetal condition and as having various technical pitfalls, though its reliability seems to be improved by association with pulse oximetry, fetal blood pH and electrocardiography. Neuroimaging is particularly useful to determine the timing of hypoxic-ischemic brain damage. Cranial ultrasound has been used to determine the type and evolution of brain damage. Magnetic resonance has also been used to detect antenatal, perinatal and neonatal abnormalities and timing on the basis of standardized assessment of brain maturation. Advances in the interpretation of neonatal electroencephalograms have also made this technique useful for determining the timing of brain lesions. Nucleated red blood cell count in cord blood has been recognized as an important indication of the timing of pre-natal hypoxia, and even abnormal lymphocyte and thrombocyte counts may be used to establish pre-natal asphyxia. Cord blood pH and base excess are well-known markers of fetal hypoxia, but are best combined with heart rate and blood pressure. Other markers of fetal and neonatal hypoxia useful for determining the timing of brain damage are assays of lactate and markers of oxidative stress in cord blood and neonatal blood. Cytokines in blood and amniotic fluid may indicate chorioamnionitis or post-natal infections. The determination of activin and protein S100 has also been proposed. Obstetricians and neonatologists can therefore now rely on various methods for monitoring the risk of brain damage in the antenatal and post-natal periods.

Effect of delayed sampling on umbilical cord arterial and venous lactate and blood gases in clamped and unclamped vessels

BACKGROUND

Cord blood lactate at birth is a marker of antenatal hypoxia, and is comparable to pH as a prognostic tool.

OBJECTIVE

To determine, by a prospective observational study, the effect of delayed sampling from arteries and veins that were double clamped to isolate the blood from the placenta (clamped), and from vessels that were not isolated from the placenta (unclamped).

METHODS

Paired samples taken from clamped and unclamped vessels at 0, 20, 40, and 60 minutes were analysed for lactate, base excess, pH, and Pco(2). Data were analysed as the change from time 0 at 20, 40, and 60 minutes.

RESULTS

Thirty eight placentas of infants delivered by elective caesarean section were studied. Arterial samples were taken from 20 placentas, and venous samples from 18 placentas. Arterial and venous lactate was significantly higher than at time 0 by 20 minutes in both clamped and unclamped vessels. Changes in unclamped vessels were greater than in clamped vessels. The pH remained unchanged over 60 minutes in clamped vessels, but changed significantly in unclamped vessels. Base excess changed significantly in both clamped and unclamped vessels.

CONCLUSIONS

Cord blood samples taken after 20 minutes delay are unreliable for lactate measurement, even if the vessel has been doubly clamped to isolate the blood from the placenta. Current guidelines that state that blood can be sampled from a clamped cord for up to one hour after delivery should not apply to the interpretation of lactate or base excess. Delayed sampling from unclamped cords is very unreliable.

Effect of interleukin-10 on newborn piglet brain following hypoxia-ischemia and endotoxin-induced inflammation

OBJECTIVE

Previous animal studies indicated that interleukin (IL)-10 attenuates the inflammatory response to a challenge by inflammation and hypoxia-ischemia, but the effect of IL-10 administration after onset of inflammation has not been studied. We wanted to assess (1) whether IL-10 had a beneficial effect on brain metabolism and microcirculation in newborn piglets after an inflammatory, hypoxic and ischemic challenge, and (2) whether IL-10 had any harmful effects per se.

METHODS

Anesthetized piglets were randomized to control (n = 8), IL-10 (n = 10), endotoxin (ETX) (n = 10), or ETX and IL-10 (ETX/IL-10) (n = 10) groups. IL-10 was administered after pretreatment with saline in the IL-10 group or ETX in the ETX/IL-10 group. Then, cerebral hypoxia and ischemia was induced by bilateral clamping of the common carotid arteries and ventilation with 8% O(2) for 30 min, followed by 4 h of reoxygenation and reperfusion. Extracellular levels of lactate, pyruvate, and glycerol were measured with microdialysis in periventricular white matter and parasagittal subcortical tissue, and tissue oxygenation and microcirculation were measured with Doppler technique. We compared the areas under the concentration-time and flow-time curves and maximum concentrations between (1) the ETX/IL-10 and ETX groups, and (2) the control and IL-10 groups.

RESULTS

We found no differences between (1) the ETX/IL-10 and ETX groups, and also no differences between (2) the control and IL-10 groups.

CONCLUSION

We could not show that the treatment with IL-10 after onset of inflammation had neuroprotective effects in the newborn piglet brain. IL-10 did not attenuate metabolism in the absence of ETX-induced inflammation.