What is a potential complication of using isosulfan blue injection for sentinel node biopsy?

Isosulfan Blue Injection and Pulse Oximetry Interference

Isosulfan blue injection for sentinel node biopsy most commonly results in inaccurate pulse oximetry readings. 1

Mechanism and Clinical Presentation

• Isosulfan blue dye interferes with measurements of oxygen saturation in peripheral blood by pulse oximetry, causing falsely low readings that can be misinterpreted as hypoxemia 1
• The interference effect with pulse oximetry is maximal at approximately 30 minutes after injection and typically resolves within 4-6 hours 1, 2
• The magnitude of decrease in SpO2 readings can range from 2-11%, with a median decrease of about 5% 3

Evidence and Clinical Course

• In controlled studies, patients receiving intradermal isosulfan blue injection have a 4-fold increased rate of developing clinically significant declines in pulse oximeter readings compared to controls 4
• The latency period from injection to SpO2 decline averages 22.8 ± 12.7 minutes, with effects potentially lasting up to 195 minutes in some cases 4, 3
• Arterial blood gas analysis typically reveals normal arterial partial pressure of oxygen despite the decreased pulse oximeter readings, confirming this is an artifact rather than true hypoxemia 2

Clinical Management

• When pulse oximetry readings decrease after isosulfan blue injection, arterial blood gas analysis may be needed to verify actual oxygenation status 1
• For most otherwise healthy patients with normal pulmonary function, invasive monitoring is not necessary despite the changes in pulse oximeter readings 3
• Be aware that isosulfan blue may also cause falsely elevated readings of methemoglobin by arterial blood gas analyzers, potentially requiring cooximetry for accurate measurement 1

Other Potential Complications

• While pulse oximetry interference is the most common effect, clinicians should also be aware of:
  • Risk of hypersensitivity reactions including anaphylaxis (approximately 1% incidence), which can manifest as hypotension, urticaria, erythema, or severe cardiovascular collapse 5
  • Precipitation when mixed with local anesthetics like lidocaine in the same syringe (4-9% drug complex formation) 1

Clinical Pearls

• Monitor patients for at least 60 minutes after isosulfan blue administration, as both pulse oximetry changes and potential hypersensitivity reactions can occur during this timeframe 1
• Use separate syringes when administering local anesthetics and isosulfan blue to prevent precipitation 1
• The changes in pulse oximetry are predictable and follow a consistent pattern, which helps differentiate this phenomenon from true clinical deterioration 3