To the Editor:
Pulse oximetry usually provides an accurate noninvasive estimate of arterial hemoglobin saturation, but errors can be produced by several confounding variables. Factors that can produce falsely low estimates of arterial hemoglobin saturation by pulse oximetry (SaO2) include the presence of methemoglobin (1) anemia combined with hypotension (2,3) motion (4), dark skin pigmentation including certain skin dyes (5), blue or green fingernail polish (6), and severe tricuspid regurgitation (7). We recently encountered a patient with docetaxel (Taxotere®)-induced nail bed changes that falsely depressed SaO2.
The patient was a 61-year-old woman who had received several courses of Taxotere for treatment of stage 4 breast cancer. We were contacted by nurses who were concerned that her measured SaO2 was 92–94% with the patient breathing room air. A Criticare® pulse oximeter with a Nellcor® probe was used. We noticed that the patient’s fingernails were a purplish color and were partially separated from the underlying tissues. These changes were consistent with existing reports of Taxotere-induced nail dystrophy (8,9,10). When the oximeter probe was attached to an unaffected toe, the oximeter read 97–99%, as did the probe when mounted sideways on a finger.
We have since seen erroneous SaO2 readings in another patient who had similar Taxotere-induced nail changes. Given the frequency with which Taxotere is used in treating both breast and lung cancers, it is important to be aware of the transcutaneous oximetric consequences of this therapy. Caution should therefore be exercised when using pulse oximetry to estimate arterial saturation in patients receiving Taxotere or related Taxol compounds.
Michael Paige, MD
Philip E. Bickler, MD, PhD
Professor of Anesthesia, Department of Anesthesia and Perioperative Care, University of California at San Francisco, San Francisco, CA
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