Unique infrared thermographic profiles and altered hypothalamic neurochemistry associated with mortality in endotoxic shock.

Neonatal sepsis results in significant morbidity and mortality, but early detection is clinically challenging. In a neonatal rat model of endotoxic shock, we characterised unique infrared thermographic (IRT) profiles in skin temperature that could identify risk of later mortality. Ten-day old rats were placed in a thermally stable isolette and IRT images of cranial (TCR), scapula (TSC) and rump (TRU) skin temperature were obtained continuously for 8 h following an intraperitoneal injection of lipopolysaccharide (LPS) or saline. LPS resulted in ∼74 % mortality (designated as non-survivors, LPSNS) between 4.5 and 7.5 h post-injection. LPSNS and survivors of LPS (LPSS) rats displayed hypothermic tendencies with TCR, TSC and TRU decreasing at ∼80-100 min (T80-100) post-injection. Compared to LPSS rats, however, the hypothermia of LPSNS rats occurred slightly earlier (T80), was more severe, and failed to recover. The TCR, TSC and TRU of LPSS rats fully recovered by 4 h (T240) post-injection. In separate rats, hypothalamic microglia and extracellular matrix (ECM) expression at T240 post-injection were increased in putatively identified LPSNS rats (but not LPSS rats) and negatively correlated with IR temperatures. IRT could be a useful early identifier of infants at risk of death from endotoxic shock, which may be related to early failure of central nervous system (CNS) thermogenic mechanisms mediated by unique hypothalamic changes in inflammatory (microglia) and ECM neurochemistry.