Biochemical factors affecting newborn survival

Small animal neonates are vulnerable at birth and during the neonatal period. Three main conditions can hamper newborn survival: prolonged hypoxia during the birth process, hypoglycemia and failure of passive immune transfer. Promptly addressing the need for neonatal assistance is necessary to reduce high perinatal mortality rate. At birth, determining some blood gas factors, blood glucose concentration, serum cardiac troponin I concentrations and assessing the Day 2 IgG concentrations can be useful for clinicians. Although blood sampling is challenging in small animal neonates, use of very little blood volume on portable biochemical analyzers makes this testing feasible. In newborns, the events associated to delivery are responsible for a transient condition of hypoxia. However, if hypoxia progresses to asphyxia, metabolic acidemia (a life-threatening condition) can develop and ischemic myocardial damage occurs. Asphyxiated puppies were reported to show significantly differences in partial pressure O2, sO2, peripheral sO2 and cardiac troponin I (cTnI) in comparison to non-asphyxiated newborns [1]. Blood lactate is also a useful prognostic marker to assess the degree of acidosis and associated with death or neurological complications in puppies [2]. After birth and during the neonatal period, newborns can develop hypoglycemia, due to the hepatic immaturity, sepsis, or poor nursing leading to starvation. Some studies have indeed reported blood glucose thresholds associated with increased risk of neonatal death. Due to the nature of the canine and feline endotheliochorial placenta, passive immune transfer by colostrum is necessary for newborn immunity. Failure of immune transfer should be recognized as soon as possible for correct newborn management. The threshold for detecting the failure of passive immune transfer in newborn dogs was reported [3], while in kittens the exact threshold has not been yet determined. Although urine is easily collected from neonates by micturition, urinalysis is generally useful. However, hematuria was reported to be a negative prognostic factor. Another biological specimen useful for newborn assessment is fetal fluids. A study focusing on the composition of fetal fluids at birth, reported higher LDH, creatinine, UREA, GGT and, to a lesser extent, cholesterol and AST in fetal fluids of puppies that died within the first day after birth in comparison to those surviving. In conclusion, more extensive studies are needed to better elucidate the prognostic role of serum biochemistry in small animal neonates as well as to develop other suitable prognostic markers to improve neonatal survival.