A fetomaternal hemorrhage of 35 mL of fetal Rh-positive packed RBCs has been detected in an Rh-negative woman. How many vials of Rh immune globulin should be given?

To determine the correct dosage of Rh immune globulin for an Rh-negative woman following a detected fetomaternal hemorrhage of 35 mL of fetal Rh-positive packed red blood cells, we need to consider the standard protocol for administering this preventive treatment.

Rh immune globulin is given to Rh-negative women to prevent the development of Rh sensitization after exposures to Rh-positive blood. The typical dose of Rh immune globulin is sufficient to neutralize up to 15 mL of Rh-positive red blood cells. For each 15 mL, one vial of the immune globulin is recommended.

In this scenario, the amount of fetal Rh-positive blood is 35 mL. To calculate the number of vials required, the total volume of fetal blood is divided by the volume that one vial can cover. This is calculated as follows:

35 mL (detected fetomaternal hemorrhage) divided by 15 mL (volume one vial can neutralize) gives approximately 2.33. Since Rh immune globulin is administered in whole vials, you round up to ensure full coverage, necessitating the administration of 3 vials.

Thus, the appropriate response, based on the calculation and standard treatment guidelines, would be to