The endoscope is a device placed into the nasal cavity to remove chronic sinus disease or tumor or create access into the skullbase for extensive tumor removal. Indocyanine Green (ICG) is a dye that is injected through an intravenous site and is used to light up vasculature and margins of a tumor during surgery. This helps avoid damage to important vasculature and obtain clear margins during surgery. This study aims to further assess the utility of ICG when operating within the nasal cavity or skullbase.

The investigators aim to evaluate the effectiveness and feasibility of using a fluorescent dye, Indocyanine Green (ICG), in endoscopic sinus, skullbase, sinus tumor resection, or posterior epistaxis surgery.

Adults 19 years or older, seen in the Principal Investigator and Sub investigator's offices presenting with either CRS, benign or malignant sinonasal, skull base tumors, or posterior epistaxis will be identified by the Principal Investigators and invited to participate in this prospective study. Patients will be recruited into the study in a consecutive manner. After providing consent, baseline characteristics will be collected. The investigators aim to recruit 10 patients in each study group respectively given the patients diagnosis.

Sinus tumor resection - Initially margins will be estimated with the naked eye. Then they will be compared to the margins that are fluorescing with the dye.

Skull base tumor resection - The investigators will use a part of the participant's septum for the reconstruction. The investigators will measure the time it takes for the flap to fluoresce and ensure that it is still lighting up at the end of the surgery. This means that it is still receiving a good supply and ensures longevity of the flap.

Sinus Surgery - During the participant's surgery, the investigator will come across important vessels that will be preserved. The investigator will see if the ICG is able to light up those vessels and if it does, then measure the time it takes to light up will be measured.

Posterior epistaxis - If a participant experiences a nose bleed that requires going into the operating room, the investigator will use ICG to locate the vessel that needs to be cauterized. The investigators will measure the time it takes for that vessel to light up.

The investigator will see the participants back on their day of surgery. During surgery, Indocyanine Green (ICG) will be injected through their intravenous line. The investigator will start with the smallest dose and increase to a dose that allows us to see the structures of interest such as vessels or tumor margins. The time it takes for a vessel or margins of a tumor to light up will be measured. Intra-operative data specific to each type of surgery being performed will be collected.

Dose-Escalation Protocol Intravenous injection

• 1.25mg (0.5mL)
• 2.5mg (1mL)
• 3.75mg (1.5mL)
• 5mg (2mL)
• 6.25mg (2.5mL) [at discretion of surgeon]
• 7.5mg (3mL) [at discretion of surgeon]

Intralesional injection

• 1.25mg (0.5mL)
• 2.5mg (1mL)
• 3.75mg (1.5mL)
• 5mg (2mL)
• 6.25mg (2.5mL) [at discretion of surgeon]
• 7.5mg (3mL) [at discretion of surgeon]

Descriptive statistics (count, absolute frequency, and 95% confidence interval) will be used to analyze the baseline characteristic data.

Inclusion Criteria:

• All patients undergoing skull base surgery with nasoseptal flap reconstruction.
• All patients undergoing endoscopic sinonasal surgery for benign and malignant tumor removal.
• All patients undergoing endoscopic sinus surgery for chronic rhinosinusitis (CRS) with or without polyposis.
• All patients undergoing surgical intervention for posterior epistaxis.

Exclusion Criteria:

• Patients less than 18 years of age
• Patients whom are currently pregnant
• Patients with allergies to sodium iodide or shellfish
• Patients with previous anaphylactic reaction to ICG