April 2020 HSC Section 4 - Plastic and Reconstructive Problems

Original Investigation Research

Indocyanine Green Angiography and Factors Associated With Perfusion of Paramedian Forehead Flaps

M anagement of structural defects of theheadandneck, particularlyof thenose, can frequently result inprob- lematic impairment of both function and cosmesis. A thorough understanding of the external nasal anatomy and its blood supply is crucial to achieve optimal nasal reconstruc- tion. Each defect is different in its size, location, and depth, requiring a unique reconstructive plan based on these fac- tors. Likewise, each patient presents with various character- istics (ie, age or tobacco use) or comorbidities (ie, diabetes or radiotherapy exposure) that may affect the optimal recon- structive plan. Therefore, it is crucial to evaluate all of these factors when planning a nasal reconstruction surgical proce- dure. Paramedian forehead flaps are commonly used to recon- struct large defects of the nose. 1 Forehead flaps are axial- pattern flaps suppliedby the supratrochlear bloodvessels; they have a reliable pedicle that can provide abundant skin cover- age of similar color, texture, and thickness to the nasal exte- rior of the face. The vascularity is also sufficient to simulta- neously vascularize associated grafts such as cartilage or chondromucosal grafts. 2 These flaps are generally used in a staged reconstruction procedure to provide sufficient time for neovascularizationof the flap independent of the pedicle. Neo- vascularization develops from the vascular bed and/or the pe- ripheral edges of the recipient site. 3,4 The time between the flap placement and pedicle division varies among surgeons, ranging from2 to6weeks. 4,5 Although several patient and ana- tomic defect characteristics may affect neovascularization, quantitative studies assessing forehead flap perfusion have been limited. 5-8 Various technologies to provide objective assessment of flap perfusion have been developed to provide a better understanding of flap hemodynamics. 9 Among these tech- nologies, indocyanine green (ICG) angiography using the SPY Elite Imaging System (LifeCell Corp Inc, Novadaq Tech- nologies Inc) is a frequently used, minimally invasive tech- nique to assess flap perfusion. Indocyanine green is a water- soluble dye that fluoresces maximally at 835 nm, which lies within the optical window of skin. The pharmacokinetics of ICG help for sequential monitoring of skin flap perfusion because of its short half-life of 2.5 to 4 minutes and its strict occupancy to the intravascular space. 10,11 It has been safely used to assess cardiac output, liver function, choroid perfu- sion, skin perfusion, and recently, bone perfusion after oste- otomy procedures. 11-17 The SPY Elite system uses an infrared-sensitive camera to detect intravascular-injected fluorescent dye. The system also contains software that pro- vides quantitative data of vascular perfusion and blood flow according to fluorescence dynamics. The SPY-Q software (LifeCell Corp Inc, Novadaq Technologies Inc) uses an algo- rithm to set the normal peripheral tissue perfusion at 100% and subsequently reports the perfusion percentage of the tissue in the flap under investigation. This technique has been previously used in smaller cohorts of patients to assess forehead flap perfusion. 5,6 Better understanding of factors affecting the neovascu- larization of pedicled flapsmay be associatedwith lower rates of vascular and functional complications. Understandingof the

effect of time between the stages of the procedures may also be associatedwith lower morbidity and increased tolerability of stagednasal reconstructive procedures. The objective of this studywas to evaluatewhether clinically important patient and procedural factors hypothesized to have an influence on flap perfusion are associatedwith intraoperative assessment of flap perfusion using ICG angiography in a large cohort of patients undergoing paramedian forehead flap reconstruction of na- sal defects. Methods A retrospective review of patients with nasal defects requir- ing paramedian forehead flap reconstruction between Janu- ary 1, 2010, and March 31, 2018, was conducted after approval from the Stanford University institutional review board, Stanford, California. Participant consent was waived by the Stanford University institutional review board because no protected health information shared in the study and the study was retrospective. Additional inclusion criteria included patients older than 18 years with available ICG angiography data from the SPY Elite Imaging System (LifeCell Corp Inc, Novadaq Technologies Inc) for both the first- and second-stage surgical procedures. Patients younger than 18 years who were pregnant, required recon- struction of other facial defects, or had an iodide hypersen- sitivity were excluded. Data from ICG angiography were reviewed, and patients with incomplete data or corrupted recording files were also excluded. One of the consider- ations during video recording was for the patients to avoid any movement for approximately 90 seconds during the dye inflow and outflow. This restraint of movement pro- vided consistent data for the software to automatically cal- culate fluorescence dynamics and avoided calculation errors. Perfusion data were collected from the recorded Digital Imaging and Communications in Medicine or Audio Video Interleaved files and were analyzed using the SPY-Q software. Key Points Question What patient or procedural factors are associated with the neovascularization of paramedian forehead flaps in staged nasal reconstruction surgical procedures as assessed by indocyanine green angiography? Findings In this cohort study of 71 participants, an increased number of days between the stages of the nasal reconstruction surgical procedures was independently and positively associated with the flap-to-cheek ingress (arterial inflow) ratio, whereas cartilage graft use was negatively associated with the flap-to-cheek outflow ratio. Meaning These findings suggest that indocyanine green angiography may help identify factors associated with flap perfusion, such as time between stages of surgery and cartilage graft use.

(Reprinted) JAMA Facial Plastic Surgery May/June 2019 Volume 21, Number 3

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