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EFFECTS OF ISOSULFAN BLUE ON PULSE OXIMETRY MEASUREMENTS

Departments of Anesthesiology and Surgery, UT MD Anderson Cancer Center, 1515 Holcombe Blvd, Houston, TX 77030

INTRODUCTION

Isosulfan blue (IB) is used during cancer surgery to identify sentinel lymph nodes. Case reports and 1 small series 1 have shown that SpO₂ values may decrease after IB injection, due to interference with pulse oximetry measurements because of its absorbance peak of 646nm. This study examines the effects of IB on SpO₂ in a large number of patients having different types of surgery, so as to more fully characterize this phenomenon. This information will allow anesthesiologists to identify changes which normally occur, and focus on deviations from these as potentially representing true hypoxemia.

METHODS

After IRB approval, anesthetic records of 552 patients having sentinel lymph node biopsy with IB from January 1, 1996 to January 31, 2001 were reviewed. The SpO₂ and corresponding FiO₂ values were recorded at: 15 mins before IB injection (preIB); IB injection; every 15 mins after IB injection for 120 mins. Data were excluded if the FiO₂ differed from the preIB period. Data are shown as mean+1SD (median;range). Chi-square, t-tests and ANOVA were used for data analysis. P<0.05 was considered statistically significant.

RESULTS

Patients had the following surgery: melanoma - 315; breast cancer - 208; colon cancer - 10; penile cancer - 7; uterine cancer - 7; vulvar cancer - 5. Mean SpO₂ at each time after IB was significantly lower than preIB for all patients as a group, and for the breast and melanoma subgroups (p<0.05). Mean SpO₂ values were lower for breast than melanoma surgery at all times after IB (p<0.05). All means were 97.8%. SpO₂ fell below preIB at least once for 290 patients (53%). SpO₂ decreases began at 29.0 ± 23.3 mins (30;5-120) after IB injection. The lowest SpO₂ was 98.3 ± 1.73% (99;90-100) and maximum decrease in SpO₂ from preIB was 2.2+1.4% (2;1-8). Fifty-three patients (9.6%) had a moderate fall in SpO₂ ( 4% decrease from preIB). Melanoma and breast surgery subgroups are compared in Table.

SpO₂ values frequently fall after IB injection, but these changes are usually minor. Breast surgery had a higher incidence and greater extent of decreases than melanoma, which may be due to the greater volume of IB used.

REFERENCE

Anesthesiology 2000;93:1002–3.[Medline]

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