1. Yuksel E, Duman D, Yeniay L,Ulukaya S SUBCUTANEOUS ISOSULFAN BLUE ADMINISTRATION MAY INTERFERE WITH PULSE OXIMETRY

2. Isosulfan blue frequently used for SLNB  Axillary lymph node status is the most important factor in estimating the survival, planning the adjuvant treatment and determining the prognosis of the patients with breast cancer.  Sentinel lymph node biopsy (SLNB) is a minimally invasive technique for staging of breast cancer.  Isosulfan blue stain is frequently used in SLNB and regarded as safe.

3. Isosulfan blue may interfere with pulse oximetry  Here we report a 67 years-old, 77 kg, ASA II female that underwent SLNB under general anesthesia and presenting an alarmingly low SpO2 reading on pulse oximeter after subcutaneous isosulfan blue injection.  The oximeter reading was inconsistent with the clinical picture and a normal SpO2 on arterial blood gas analysis confirmed that the false oximetry reading was due to the subcutaneously injected blue pigment.

4. Arterial gas analysis confirms normal SpO2  Ten minutes after subcutaneous injection of 10ml 1% isosulfan blue, SpO2 reading fell to 87% from 99% on pulse oximeter.  Quick checks confirmed that all anesthesia devices worked normally, airway pressure was not increased and endotracheal tube was placed accurately.  Arterial gas analysis showed pH: 7.54, PaCO2: 23.3 mmHg, PaO2: 281 mmHg, SpO2: %99, and MetHb: %2.7.  Biochemical analysis revealed a blood MetHb concentration of 2%.  2500 mg ascorbic acid in 500ml 5% Dextrose was given to the patient via intravenous route before the results of arterial blood gas were obtained.

5. False reading was caused by change in skin color  Despite the absence of respiratory and neurological distress, SpO2 value on pulse oximeter was increased only up to 85% after 2 hours with 5 L/min oxygen support via face mask in the surgery room as the patient was extubated.  At that time, the skin color in the upper part of the body has turned into blue, including face and arms. The color of plasma of the blood taken from the patient for biochemical analysis was blue. The color of urine coming throughout the urinary catheter placed in intensive care unit was also blue.  The patient was discharged fully recovered on the 3rd day after the procedure.

6. Conclusion  SLNB is a less invasive alternative to axillary dissection. However, false pulse oximeter reading due to pigment interference is a rare complication of this procedure. Arterial blood gas analysis should be used to confirm any fall in SpO2 reading during monitoring.