Hypothermia and thiopentone sodium: Individual and combined neuroprotective effects on cortical cultures exposed to prolonged hypoxic episodes

AbstractBecause there are many conflicting reports on cerebroprotective effects of hypothermia and barbiturates, we examined the degree of neuroprotection at defined temperatures (normothermia, 37°C; mild hypothermia, 32°C; deep hypothermia, 22°C; and profound hypothermia, 17°C) and various concentrations (low, 4 μM; moderate, 40 μM; and high, 400 μM) of thiopentone sodium (TPS), alone and in combination in cortical cultures exposed to prolonged hypoxia (24–48 hr). The survival rate of embryonic day (E)16 Wistar rat cortical neurons was evaluated on photomicrographs before and after experiments. During the 24‐hr hypoxic period, the survival rate of neurons was maximal with combinations of mild hypothermia with 40 μM (91.6 ± 0.7%) and 400 μM TPS (90.8 ± 0.7%) or deep hypothermia combined with all concentrations of TPS (4 μM, 90.6 ± 1.0%; 40 μM, 91.4 ± 0.8%; 400 μM, 91.8 ± 1.2%). During 48 hr hypoxia, the highest survival rate was seen with the combination of deep hypothermia and either 40 μM (90.9 ± 0.6%) or 400 μM (91.1 ± 1.4%) TPS. In the presence of profound hypothermia in combination with all concentrations of TPS, the survival rate was significantly reduced (P< 0.01) compared to combined application of either mild or deep hypothermia with TPS. In summary, maximal neuroprotection was attained with hypothermia and TPS in combination rather than applied individually, during prolonged hypoxic episodes (24– 48 hr). During a 24‐hr hypoxic period, both mild and deep hypothermia combined with a clinically relevant concentration of TPS (40 μM) offered the highest neuroprotection. Only deep hypothermia provided maximal neuroprotection when combined with 40 μM TPS, during 48‐hr hypoxia. Combination of profound hypothermia and TPS did not confer considerable neuroprotection during long lasting hypoxia. © 2002 Wiley‐Liss, Inc.