On evaluation of organ damage in perinatal asphyxia : an experimental and clinical study

Leakage of intracellular enzymes such as alanine aminotransferase (ALT), aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) signalling multi organ dysfunction (MOD) is seen together with hypoxic ischemic encephalopathy (HIE) after perinatal asphyxia. Hypothermia (HT) can attenuate HIE following perinatal asphyxia and hypoxia-ischemia (HI) but the neuroprotective efficacy falls dramatically the longer the delay in initiating HT. However, the knowledge was scarce regarding protective or adverse effects of HT in organs beyond the brain. Also, the relative effectiveness of the two clinically used modes of cooling; selective head cooling (SHC) and whole body cooling (WBC) had not been studied.

In this thesis we studied (1) the time course of LDH, ALT and AST serum activity during the first week of life after asphyxia and (2) if these enzymes predicts HIE in newborn term infants with asphyxia and intra partum signs of fetal distress. (3) In a newborn pig model of global HI, we investigated whether plasma values of these enzymes differ between newborn pigs with liver injures after a severe global HI insult and pigs with normal livers. (4) In the newborn pig model of global HI we studied whether 24h HT initiated 3h after global HI is brain- and/or organ-protective using pathology, neurology and biochemical markers.

RESULTS: (1) Two different temporal serum-ALT or AST pattern were seen in 26 newborn asphyxiated infants during the first week post partum. One pattern were characterized by increasing values during first days of life while the other pattern showed a peak enzyme activity seen in the first sample at less than 12 hours after birth followed by a decrease. (2) In asphyxiated infants with differing degree of HIE (n=44) and in infants where there had been signs of fetal distress during birth (n=202) a cut off level of 1049 U/L for LDH was the most suitable predictor of mild, moderate and severe HIE with a sensitivity of 100% and specificity of 97%. The cut off levels for ALT and AST were 16 and 59 U/L respectively giving a sensitivity of 100% and 93% and a specificity of 83% and 93% respectively. (3) No differences in area under the curve (AUC) for AST, ALT and LDH values were seen between newborn pigs with liver injures (n=12) after a severe global HI insult and pigs with normal livers (n=7) during 72h after a HI insult. However, in pigs with liver injuries a transient significant increase in LDH at the end of the HI insult (928 U/L (567-1031)) was seen compared to the baseline value (679 U/L (548-866), p=0.010). (4) No differences in injury to the brain or organs in pigs subjected to global HI followed by NT (n=16) or 24h of SHC (n=17) or WBC (n=17), initiated 3h after the insult were seen. The post-insult decline in lactate was temperature independent. However HT animals normalized their plasma-calcium, magnesium and potassium significantly faster than NT. There were no differences in adverse effects across groups.

CONCLUSIONS: There is a potential usefulness of intracellular enzymes as predictors of HIE in newborn infants with perinatal asphyxia. In the newborn pig subjected to global HI only LDH increases in pigs with pathological changes in the liver and normal values of ALT and AST do not exclude hepatic injury. Delayed SHC or WBC, initiated 3h after HI; do not reduce pathology in the brain nor in organs in newborn pigs after global HI.

List of scientific papers

I. Karlsson M, Blennow M, Nemeth A, Winbladh B (2006). Dynamics of hepatic enzyme activity following birth asphyxia. Acta Paediatr. 95(11): 1405-11
https://pubmed.ncbi.nlm.nih.gov/17062468

II. Karlsson M, Tooley JR, Satas S, Hobbs CE, Chakkarapani E, Stone J, Porter H, Thoresen M (2008). Delayed hypothermia as selective head cooling or whole body cooling does not protect brain or body in newborn pig subjected to hypoxia-ischemia. Pediatr Res. Mar 26: Epub ahead of print
https://pubmed.ncbi.nlm.nih.gov/18391848

III. Karlsson M, Satas S, Stone J, Porter H, Thoresen M (2008). Liver enzymes cannot be used to predict liver damage after global hypoxia-ischemia in a neonatal pig model. [Submitted]

IV. Karlsson M, Wiberg-Itzel E, Chakkarapani E, Blennow M, Winbladh B, Thoresen M (2008). Lactate dehydrogenase predicts hypoxic ischemic encephalopathy in newborn infants. [Submitted]