Hypothesis: There are differences between readings of peripheral blood oxygen saturation when the effect on saturation values of methylene blue is compared with that of isosulfan blue when used in sentinel lymph node biopsy in patients with breast cancer.
Design: Prospective randomized study.
Setting: University tertiary care center.
Patients: Thirty-two women undergoing surgery for breast cancer using sentinel lymph node biopsy.
Interventions: Sentinel lymph node biopsy using methylene blue (16 patients) and isosulfan blue (16 patients); there was also a control group of 6 surgical patients in whom dyes were not used.
Main outcome measures: Peripheral saturation of blood using pulse oximetry, oxygen saturation by blood-gas analysis, partial oxygen pressure by blood-gas analysis, and plasma dye levels, recorded before dye injection and 15, 30, and 60 minutes afterward.
Results: The 2 dyes interfered with the peripheral saturation reading, but only isosulfan blue showed significant differences. The differences in blood-gas analysis values between the 2 groups and with regard to the controls were not significant.
Conclusions: Methylene blue interferes less than isosulfan blue in the peripheral saturation reading. Desaturation is factitious in both cases, and does not correspond to alterations in blood-gas analysis values.