Deterministic effects after fenestrated endovascular aortic aneurysm repair.

BACKGROUND Endovascular aortic aneurysm repairs (EVARs) with fenestrated (FEVAR) stent grafts are high radiation dose cases, yet no skin injuries were found retrospectively in our 61 cases with a mean peak skin dose (PSD) of 6.8 Gy. We hypothesize that skin injury is under-reported. This study examined deterministic effects in FEVARs after procedural changes implemented to detect skin injury. METHODS All FEVARs during a 6-month period with a radiation dose of 5 Gy reference air kerma (RAK; National Council on Radiation Protection and Measurements threshold for substantial radiation dose level [SRDL]) were included. Patients were questioned about skin erythema, epilation, and necrosis, with a physical examination of the back completed daily until discharge and then at 2 and 4 weeks and at 3 and 6 months. PSD distributions were calculated with custom software using input data from fluoroscopic machine logs. These calculations have been validated against Gafchromic (Ashland Inc, Covington, Ky) film measurements. Dose was summed for the subset of patients with multiple procedures ≤6 months of the SRDL event, consistent with the joint commission recommendations. RESULTS Twenty-two patients, 21 FEVARs and one embolization, reached an RAK of 5 Gy. The embolization procedure was excluded from review. The average RAK was 7.6 ± 2.0 Gy (range, 5.1-11.4 Gy), with a mean PSD of 4.8 ± 2.0 Gy (range, 2.3-10.4 Gy). Fifty-two percent of patients had multiple endovascular procedures ≤6 months of the SRDL event. The mean RAK for this subset was 10.0 ± 2.9 Gy (range, 5.5-15.1 Gy), with a mean PSD of 6.6 ± 1.9 Gy (range, 3.4-9.4 Gy). One patient died before the first postoperative visit. No radiation skin injuries were found. Putative risk factors for skin injury were evaluated and included smoking (32%), diabetes (14%), cytotoxic drugs (9%), and fair skin type (91%). No other risk factors were present (hyperthyroidism, collagen vascular disorders). CONCLUSIONS Deterministic skin injuries are uncommon after FEVAR, even at high RAK levels, regardless of cumulative dose effects. This study addresses the concern of missed injuries based on the retrospective clinical examination findings that were published in our previous work. Even with more comprehensive postoperative skin examinations and patient questioning, the fact that no skin injuries were found suggests that radiation-induced skin injuries are multifactorial and not solely dose dependent.