S-100a₀ protein in blood and urine during open-heart surgery

Concentrations of S100a₀ protein and CK-MB were measured by enzyme immunoassay in serial samples of arterial and coronary-sinus blood and urine taken from 26 patients who were undergoing mitral valve surgery. The mean concentration of arterial S100a₀ in plasma was 0.32 (SD 0.28) ng/mL at the beginning of anesthesia, increased sharply after reperfusion, peaking [14.4 (SD 6.63) ng/mL] after 45 min of reperfusion, then decreased rapidly. The concentration of creatine kinase (CK) isoenzyme MB in arterial blood plasma was greatest 3 h after reperfusion [107 (SD 54.5) ng/mL]. S100a₀ concentrations in urine increased dramatically after reperfusion [16.300 (SD 12.000) ng/h vs 44 (SD 32) ng/h], while CK-MB increased slightly [135 (SD 75) ng/h vs 19 (SD 12) ng/h]. These results suggest that S100a₀ in cardiac muscle is released into the bloodstream during open-heart surgery and is discharged into the urine more rapidly than is CK-MB. Determination of S100a₀ in plasma or urine thus may be useful for estimating damage to heart muscle during open-heart surgery.