Delayed protection by hypothermia. We measured the effect of delayed hypothermia using an lactate dehydrogenase (LDH) assay. The protective effect of hypothermia was progressively reduced as the time of hypothermia initiation was delayed 3, 6, and 12 hours (R(+3), R(+6), and R(+12)). However, hypothermia still offered significant protection when the initiation of hypothermia was delayed up to 12 hours. Values represent the mean ± S.E.M. of three different experiments. *P <0.05 compared to 4 hours of oxygen glucose deprivation (OGD) and 24 hours of reperfusion (R + 0) at 37°C; #P <0.05 compared to 4 hours of OGD and 24 hours of reperfusion at 33°C.