Optimal conditions for white cell reduction in red cells by filtration at the patient's bedside.

BACKGROUND: A quality control program of white cell (WBC) reduction in red cells at the bedside was implemented, based on postfiltration counting in a Nageotte chamber of the residual WBCs from samples taken from a segment of the transfusion set, after 1-in-10 sample dilution with Türks's solution. During a 1-year quality control program, 5.1 percent of counted units had apparent filtration failures, that is, WBC counts exceeding 5 x 10(6) per unit. The cause(s) for these apparent failures were investigated. STUDY DESIGN AND METHODS: In Study 1, residual WBCs from 150 buffy coat-free red cells filtered through one type of filter at 4 degrees C, 20 to 24 degrees C, or 27 degrees C in 5 to 10 minutes, 50 to 100 minutes, or 100 to 200 minutes were counted as described above. In Study 2, residual WBCs in samples collected from segments of the transfusion set and from the postfiltration bags were counted in parallel by a new, more sensitive counting method. In this method, 5 mL of filtered red cells was diluted with 20 mL of 3-percent paraformaldehyde and centrifuged, the pellet was resuspended to 500 microL with a lysis solution, and the WBCs were counted in a Nageotte chamber. In Study 3, residual WBCs were counted by the 3-percent paraformaldehyde method in samples from postfiltration bags of 1- to 2-day-old buffy coat-rich red cell units filtered through a second type of filter. Filtration was started within 30 minutes of the removal of the unit from the refrigerator, ambient temperature was 20 to 24 degrees C, and the median filtration time was 90 minutes per unit. RESULTS: Study 1: Median WBC counts per unit increased progressively from 51,000 at 4 degrees C to 934,000 at 27 degrees C, with intermediate values at 20 to 24 degrees C. In no unit did the WBC count exceed 5 x 10(6) if filtration at 20 to 24 degrees C was completed within 100 minutes, while counts in excess of 50 x 10(6) were found at 20 to 24 degrees C and at 27 degrees C with filtration times of 100 to 200 minutes, and 50 to 100 minutes, respectively. Study 2: The relation between segment and postfiltration bag WBC counts obtained by the 3-percent paraformaldehyde method was poor, with the latter being almost always lower than the former. Study 3: None of the 120 units filtered through the second type of filter at 20 to 24 degrees C in 50 to 100 minutes contained more than 3.2 x 10(6) WBCs; the median value was 147,000 WBCs per unit. CONCLUSION: On the basis of the results with the 3-percent paraformaldehyde method, which showed the unreliability of segment counts, a new policy was adopted for quality control of bedside WBC reduction, based on controlling the time of and temperature at transfusion. Bedside WBC reduction in 1- to 2-day-old red cells performed with the second type of filter at 20 to 24 degrees C in less than 100 minutes per unit allowed the preparation of units that meet the standard of fewer than 5 x 10(6) WBCs in all tested cases. Bedside WBC reduction with the second type of filter and under the controlled conditions reported seems effective.

CO binding to hemoglobin and myoglobin in equilibrium with a gas phase of low PO2 value.

The aim of this paper was to measure the binding of CO to myoglobin and hemoglobin at various PO2 values. For this purpose we have studied an "in vitro" system made up of solutions of hemoglobin and myoglobin equilibrated in two connected tonometers with the same gas phase of various PO2 and PCO. The results indicate that a significant proportion of CO is released by hemoglobin and binds myoglobin at low PO2 values (approximately 2-3 Torr), in qualitative agreement with the predictions of a previous computer simulation of the "in vivo" system.

The intermediate compounds between human hemoglobin and carbon monoxide at equilibrium and during approach to equilibrium.

The procedure of Perrella et al. (Perrella, M., Benazzi, L., Cremonesi, L., Vesely, S., Viggiano, G., and Rossi-Bernardi, L. (1983) J. Biol. Chem. 258, 4511-4517) for trapping the intermediate compounds between human hemoglobin and carbon monoxide was validated by quantitatively determining during the approach to equilibrium all the species present in a solution containing large amounts of intermediates. An accurate estimate of the intermediate compounds at 50% carbon monoxide saturation in 0.1 M KCl, pH 7, at 22 degrees C, allowed the calculation, according to Adair's scheme, of the four equilibrium constants. At 50% ligand saturation, the pool of intermediate species was about 12% of the total. A slightly greater concentration of tri-liganded than mono-liganded species was found. Carbon monoxide bound to beta chains in slightly greater excess with respect to alpha chains in both the mono- and tri-liganded species. The symmetrical bi-liganded intermediates, alpha 2 beta CO2 and alpha 2CO beta 2, were absent. The nature of the bi-liganded intermediate found to be present in detectable amounts by our technique has yet to be clarified: it could be either the asymmetrical species (alpha beta) (alpha CO beta CO) and (alpha beta CO) (alpha CO beta) or both of them. Such a finding on the functional heterogeneity among the four possible bi-liganded intermediates is consistent with hypotheses of the existence of more than two quaternary structures in the course of ligand binding to hemoglobin.