Change in whole blood lactate over time. Mean change in whole blood, venous lactate observed from time of initial measurement up to 30 minutes. Error bars represent 95% confidence interval, only upper bar shown for room temperature. * p < 0.05 comparing room temperature to wet ice, ** p < 0.05 comparing both room temperature to wet ice and room temperature to portable ice pack, respectively. Open triangles = wet ice (0°C); grey squares = portable ice pack (0°C); black triangles = room temperature (20°C).