A sentinel lymph node mapping with blue dye has been well accepted as a common procedure in breast cancer surgery. However, it is well known that blue dye absorbed into the circulation may interfere pulse oximetery reading. The aim of this study was to evaluate the change of pulse oximetery reading by isosulfan blue dye injection during sentinel lymph node mapping.

Thirteen breast cancer patients with normal preoperative cardiopulmonary functions were studied. Four ml of isosulfan blue dye was injected subdermally when the patient became stable after induction of general anesthesia. The pulse oximetery was monitored continuously. Multiple arterial blood gas analyses (ABGA) were performed before dye injection and 10, 30, 40 minutes after dye injection. The results of oxygen saturturation by oximetery (SpO₂) and the results of arterial oxygen tension (SaO₂) and arterial oxygen saturation (SaO₂) by ABGA were compared.

The value of both SaO₂ and PaO₂ measured by ABGA has not been altered by isosulfan dye injection. However SpO₂ decreased by isosulfan dye injection. SpO₂ decrease started 8.2±1.5 (2~20) minutes after dye injection and returned to preinjection level by 85.7±5.6 (60~126) minutes after injection. The lowest vaule of SpO₂ was 95.6±1.2% (93~97). Mean duration of SpO₂ decrease was 77.5±6.2 (40~117) minutes. The duration of SpO₂ decrease was longer in the aged patients, but it was not statistically significant (p=0.3). There was no siginificant difference in duration of SpO₂ decrease according to injection site, operation method, and body mass index (BMI).

Isosulfan dye injection using for sentinel lymph node mapping causes no change in true ABGA results but causes a mild reversible decrease in SpO₂, It is important to look for other causes when SpO₂ decrease is significant and persistent.