Radiolabeled red cell viability. I. Comparison of 51Cr, 99mTc, and 111In for measuring the viability of autologous stored red cells.

The simultaneous determination of autologous 99mTc red cell (RBC) and 51Cr RBC viability at 24 hours was measured in 19 normal volunteers whose RBCs had been stored in additive media (Nutracel) for 42 or 49 days. The ratio of the 51Cr:99mTc value was 1.23. In this experiment we also calculated 51Cr RBC viability by both the single-isotope method (extrapolation) and the double-isotope method (using 125I human serum albumin for an independent plasma volume) in the same volunteers. The corresponding viability values were not significantly different. The simultaneous determination of autologous 111In-oxine RBC and 51Cr RBC viability at 24 hours was measured in 19 other normal volunteers whose RBCs had been stored in citrate-phosphate-dextrose-adenine (CPDA-1) for 1 or 15 days. The ratio of the 51Cr:111In value was 1.1. Use of these 24-hour viability ratios as conversion factors permits direct comparison of 99mTc or 111In RBC viability with a 51Cr standard, and therefore expands the application of these newer RBC radiolabels.

Radiolabeled red cell viability. II. 99mTc and 111In for measuring the viability of heterologous red cells in vivo.

The authors developed a double in vivo crossmatch method using 2 to 3 ml of potential donor blood labeled with either 400 microCi of 99mTc or 30 microCi of 111In-oxine. Data are presented for 19 crossmatches on nine patients, using one blood specimen labeled with 99mTc or two specimens, one labeled with 99mTc and the other with 111In. Normal values are given for standardization purposes. This method appears to have advantages over earlier in vivo crossmatch techniques using 51Cr-labeled RBCs. These advantages include the rapidity with which the in vivo crossmatch may be repeated, the ready availability of 99mTc and 111In-oxine, and the lower radiation absorbed doses with the shorter-lived radionuclides.

pH changes caused by bacterial growth in contaminated platelet concentrates.

While platelet concentrates are stored at room temperature, lactic and other acids are produced and the pH decreases as the buffering capacity of the plasma is exhausted. Platelet viability will be compromised if the pH decreases to pH 6.0 and below. Similarly, a pH decrease can be produced also by bacterial contamination if the organisms produce acid as an end product. Thus the determination of pH could serve as a sensitive indicator of bacterial contamination. This hypothesis was tested by us by inoculating known organisms into platelet concentrations. It was found that the pH may decrease, may remain unchanged, or, in a few cases, even increase. Visual signs of contamination could be observed but not consistently enough to be entirely dependable. Therefore, this method does not appear to detect bacterial contamination reliably in platelet concentrates.