Plasma ET-1 and PGE₂ concentrations during the first 72 hours of hospitalization for sickle cell crisis and at time of asymptomatic follow-up. Although plasma ET-1 (A) and PGE₂ (B) levels appear to follow similar trends, neither varies significantly during the first 72 hours of hospitalization (P > .05). However, the mean peak crisis levels for each are elevated relative to those of the same patients when asymptomatic and are elevated relative to those of healthy age- and race-matched controls (Table 1). (ADM, admission time; 24H, 48H, and 72H indicate 24, 48, and 72 hours after admission, respectively; F/U, at time of postcrisis outpatient appointment). (⧫), Sickle cell; (▪), control.