Effects of hemoglobin concentration and temperature on the in vitro release of cyanide from sodium nitroprusside

Purpose. This in vitro study was performed to determine whether changes in hemoglobin (Hb) concentration and temperature influenced the amount of cyanide (CN-) released from sodium nitroprusside (SNP). Methods. Canine whole blood with a Hb concentration of 8.5 to 18.9 g·dl (5.3 to 18.9 mM) was equilibrated with SNP at either 37°C or 25°C, and CN- levels in plasma and red blood cells (RBC) were measured using the microdiffusion method. Results. Changes in Hb concentration and temperature did not have any statistically significant effect on the CN- released from SNP in plasma. On the other hand, CN- levels in RBC decreased with increasing Hb concentrations. CN- levels in RBC were significantly lower at 25°C than at 37°C. Conclusion. Though the Hb concentration and temperature changed the amount of CN- released from SNP in RBC, the change observed was not clinically significant.