Burn injuries represent one of the most devastating forms of trauma, with outcomes determined by depth, extent, patient age, and comorbidities. Accurate assessment of burn wound depth is critical, as it guides decisions on conservative management versus early excision and grafting. Superficial burns often heal spontaneously within two weeks, while deep dermal and full thickness burns require surgical intervention to prevent complications and reduce morbidity¹. Pathophysiology of Burn Wounds Thermal injury leads to coagulative necrosis through protein denaturation. Jackson’s model describes three functional zones: the zone of coagulation (irreversible damage), the zone of stasis (potentially salvageable tissue), and the zone of hyperaemia (minimal injury with recovery potential) ². Preservation of the zone of stasis is crucial, as progression to necrosis increases wound depth and worsens prognosis. Challenges in Burn Depth Assessment Traditional clinical methods—appearance, sensation, and capillary refill—are subjective and require significant expertise³. Histological biopsy remains the gold standard but is invasive and impractical in routine care⁴. Consequently, several adjunctive techniques have been explored: • Ultrasound: Detects collagen denaturation but often underestimates depth⁵. • Laser Doppler flowmetry: Provides perfusion data, correlating with healing potential⁶. • Thermography: Identifies cooler areas in deep burns but is influenced by external factors⁷. • Fluorescein fluorometry: Differentiates partial from full thickness burns but struggles with indeterminate burns⁸. Despite these advances, none have achieved universal clinical adoption due to cost, complexity, or limited accuracy. Role of Vital Dyes Vital dyes offer a simple, inexpensive alternative. Methylene blue is metabolized into a colorless compound by viable cells, leaving necrotic tissue stained blue⁹. This property enables clear demarcation between viable and non viable dermis during tangential excision. Early studies demonstrated that methylene blue staining improved precision in excision, reducing the risk of removing viable dermis or leaving necrotic tissue behind¹⁰. Evidence from Pre 2020 Literature • Dorafshar et al. (2010) reported that methylene blue staining facilitated guided surgical debridement, improving accuracy and reducing graft loss¹¹. • Rosique et al. (2017) showed in an experimental rat model that methylene blue reduced burn progression and increased skin survival, highlighting its therapeutic potential beyond diagnostic use¹². • Lian et al. (2019) extended its application to pressure ulcers, confirming its ability to delineate damaged tissue and aid wound management¹³. These findings underscore methylene blue’s dual role: as a diagnostic marker for burn depth and as a therapeutic adjunct to limit tissue loss. Clinical Importance Early tangential excision with split skin grafting is the cornerstone of deep dermal burn management. The precision of excision directly influences graft take, healing time, and scar quality. By providing a visual guide to viable tissue, methylene blue enhances surgical confidence, reduces operative errors, and improves patient outcomes. Furthermore, its low cost and ease of use make it particularly valuable in resource limited settings. OBJECTIVES: 1. To evaluate the efficacy of methylene blue dye in accurately determining burn wound depth during tangential excision. 2. To compare healing outcomes between grafted and non‑grafted areas following tangential excision. 3. To assess patient‑centered outcomes, including satisfaction and aesthetic appearance of scars, between grafted and non‑grafted sites.

Study Design A prospective observational study was conducted In Department of plastic surgery , Narayana Medical college, Nellore, Andhra Pradesh, for 1 year, to evaluate the role of methylene blue in burn wound depth assessment and its impact on healing outcomes. Patients with deep dermal and full thickness burns requiring tangential excision were included. Patient Selection • Inclusion criteria: Patients with clinically indeterminate deep dermal burns, aged 18–60 years, requiring tangential excision. • Exclusion criteria: Patients with superficial burns, chemical burns, or significant comorbidities (e.g., uncontrolled diabetes, severe cardiac disease). Procedure 1. Application of Methylene Blue o Methylene blue dye was applied directly to the burn wound surface. o After 10–15 minutes, stained necrotic tissue was identified, while viable dermis metabolized the dye into a colorless compound. 2. Tangential Excision o Excision was performed using a dermatome until punctate bleeding was observed in unstained viable dermis. o Care was taken to avoid over excision (loss of viable dermis) or under excision (retention of necrotic tissue). 3. Grafting and Non Grafted Areas o Excision sites were divided into grafted and non grafted areas depending on wound depth and viability. o Split thickness skin grafts were applied to excised full thickness areas, while viable dermal beds were left to heal spontaneously. Outcome Measures • Primary outcome: Accuracy of methylene blue in delineating viable versus non viable tissue. • Secondary outcomes: o Duration of healing in grafted vs. non grafted areas. o Pattern of healing (re epithelialization vs. secondary intention). o Patient satisfaction assessed via structured questionnaire at 3 months. o Aesthetic appearance of scars evaluated using the Vancouver Scar Scale. Data Analysis • Healing times were compared using t tests for continuous variables. • Patient satisfaction and scar scores were analyzed using chi square tests for categorical variables. • Statistical significance was set at p < 0.05.

1. Study Population A total of 20 patients with mixed flame burns were included in this clinical study conducted over a defined period. 2. Demographic Characteristics 2.1 Age Distribution (Table 1) Age Group (years) Number of Patients Percentage 10–19 1 5% 20–29 13 65% 30–39 5 25% 40–49 1 5% • The majority (65%) of patients belonged to the 20–29 years age group. • The mean age of patients was 27.05 years. 2.2 Sex Distribution (Table 2) Sex Number of Patients Percentage Male 11 55% Female 9 45% • Slight male predominance was observed. 3. Burn Characteristics 3.1 Total Burn Surface Area (TBSA) Distribution (Table 3) TBSA (%) Number of Patients Percentage 5–15 7 35% 16–25 4 20% 26–35 7 35% 36–45 2 10% • Most patients had moderate burns (5–35% TBSA). • Mean TBSA was 23.95%. 3.2 Depth of Burns • Mean percentage of deep dermal burns subjected to tangential excision: 4.4% • Methylene blue staining helped in clear identification of burn depth 4. Intraoperative Findings • Methylene blue staining pattern: o Non-viable tissue retained blue color o Viable tissue became colorless • Observations: o Easy identification and removal of dead tissue o Underlying tissue showed uniform punctate bleeding, indicating viability o Better staining differentiation observed when surgery performed within 12 hours 5. Healing Outcomes 5.1 Healing Time Area Type Healing Duration Grafted Within 2 weeks Non-grafted >3 weeks • Grafted areas showed faster healing compared to non-grafted areas. 5.2 Graft Take • Mean graft take rate: 95% • Only one case required supplementary grafting 5.3 Hospital Stay • Reduced by approximately 1 week due to: o Early excision o Early grafting 6. Complications (Table 4) Complication Grafted Areas Non-Grafted Areas Itching 2 (11.7%) 6 (35.3%) Hypertrophy 4 (23.5%) 6 (35.3%) 7. Aesthetic Outcome and Patient Satisfaction • Grafted areas: o Cobblestone appearance o Less cosmetically appealing • Non-grafted areas: o Uniform coloration o Better cosmetic acceptance • Patient satisfaction: o Approximately 90% preferred non-grafted areas aesthetically 8. Safety Profile • No adverse effects observed with methylene blue • No systemic or local complications reported The study findings indicate that: • Methylene blue significantly improves accuracy of burn depth assessment • Early tangential excision guided by methylene blue: o Enhances healing outcomes o Reduces morbidity and hospital stay • Grafting provides faster healing, while non-grafted areas offer better cosmetic outcomes but with higher complications

Burn injuries represent a complex form of trauma characterized by coagulative necrosis, significant inflammatory response, and high susceptibility to infection. The overall outcome of burn management largely depends on accurate assessment of burn depth, as it directly influences treatment decisions and prognosis. In the present study, an attempt was made to evaluate the efficacy and reliability of methylene blue in determining burn wound depth and guiding tangential excision, along with comparing healing outcomes between grafted and non-grafted areas. Assessment of burn depth remains a clinical challenge, particularly in cases of deep dermal or indeterminate burns. While superficial and full-thickness burns can often be identified clinically, intermediate burns pose diagnostic uncertainty. Various modalities such as biopsy, ultrasound, laser Doppler, thermography, and MRI have been described for burn depth assessment, but each has limitations in terms of cost, availability, invasiveness, or accuracy⁴⁻⁶,¹⁸. Clinical methods like pin-prick testing, though commonly used, require patient cooperation and are subjective. Hence, there is a need for a simple, reliable, and cost-effective bedside tool. Methylene blue, a vital dye, has been explored as such an indicator. Its mechanism is based on differential metabolism: viable cells reduce methylene blue into a colorless leuco form via reductase enzymes, whereas non-viable cells retain the blue color due to lack of metabolic activity⁷. This property provides a clear demarcation between viable and non-viable tissues. In the present study, methylene blue staining was found to be highly effective in identifying devitalized tissue, thereby facilitating accurate tangential excision. These findings are consistent with earlier studies, such as those by Celikoz et al., which demonstrated the utility of methylene blue in guiding burn wound excision². Tangential excision is a well-established technique aimed at early removal of necrotic tissue while preserving viable dermis. The endpoint of excision is typically identified by the appearance of punctate bleeding, which indicates viable tissue. However, this requires considerable surgical expertise. In this study, methylene blue acted as an adjunct, simplifying the identification of the correct plane of excision. The observation that excision of stained tissue revealed a viable, bleeding wound bed supports its role in improving surgical precision. This aligns with the principles described by Jackson and others regarding the importance of preserving the zone of stasis to optimize healing²⁶. Early excision and grafting have been shown to reduce morbidity, hospital stay, and risk of infection. In the present study, grafted areas healed within two weeks, whereas non-grafted areas took more than three weeks. This difference highlights the advantage of early wound closure, which reduces the duration of the inflammatory phase and promotes faster epithelialization. Similar findings have been reported in burn literature, where early tangential excision and grafting significantly improved survival and functional outcomes²⁷. Despite faster healing in grafted areas, the study observed differences in aesthetic outcomes between grafted and non-grafted regions. Grafted areas exhibited a cobblestone appearance, which was less acceptable cosmetically, whereas non-grafted areas showed more uniform pigmentation. However, this cosmetic advantage was offset by a higher incidence of complications such as hypertrophic scarring and itching in non-grafted areas. Specifically, hypertrophy and itching were observed in 35.3% of non-grafted areas compared to 23.5% and 11.7% respectively in grafted areas. This suggests that delayed healing contributes to prolonged inflammation and abnormal scar formation. The findings reflect a clinical trade-off between rapid healing and cosmetic outcome. While grafting ensures early wound closure and reduces complications, it may compromise aesthetic appearance. On the other hand, spontaneous healing, though cosmetically superior, is associated with higher rates of hypertrophic scarring. This observation is supported by the understanding that prolonged wound healing leads to increased fibroblast activity and collagen deposition, resulting in scar hypertrophy. Another important observation in this study was the timing of methylene blue application and surgery. Better differentiation between viable and non-viable tissue was achieved when excision was performed within 12 hours of dye application compared to delayed procedures. This indicates that early intervention enhances the effectiveness of methylene blue as a diagnostic tool. Early surgical management also prevents progression of the zone of stasis into irreversible necrosis, thereby preserving more viable tissue. The safety profile of methylene blue was also favorable in this study, with no local or systemic adverse effects reported. This is consistent with its established use in various clinical settings, including as a diagnostic dye and in the treatment of methemoglobinemia. Its low cost, easy availability, and simplicity of application further enhance its utility, especially in resource-limited settings. Overall, the study demonstrates that methylene blue is a valuable adjunct in burn wound management. It enhances the accuracy of burn depth assessment, aids in precise tangential excision, and contributes to improved clinical outcomes. Its use is particularly beneficial for less experienced surgeons, as it reduces reliance on subjective judgment and minimizes errors in determining the depth of excision. However, the study is limited by a small sample size and lack of long-term follow-up in all patients. Further studies with larger populations and standardized outcome measures are required to validate these findings and establish methylene blue as a routine tool in burn care.

In conclusion, methylene blue serves as a simple, safe, and effective method for assessing burn wound depth and guiding surgical management. When combined with early tangential excision and appropriate grafting, it can significantly improve healing outcomes while balancing functional and cosmetic considerations.

1. Hettiaratchy S, Papini R. Initial management of a major burn: II—assessment and resuscitation. BMJ. 2004;329(7457):101–3. 2. Jackson DM. The diagnosis of the depth of burning. Br J Surg. 1953;40(164):588–96. 3. Jaskille AD, Shupp JW, Jordan MH, Jeng JC. Critical review of burn depth assessment techniques: Part I. Historical review. J Burn Care Res. 2009;30(6):937–47. 4. Wachtel TL, Berry CC, Wachtel EE, Frank HA. Subepidermal capillary blood flow in burns. Surgery. 1986;100(5):815–8. 5. Moserova J, et al. Ultrasonic evaluation of burn depth. Burns. 1982;8(4):257–62. 6. Sorensen H, et al. Laser Doppler flowmetry in burn depth assessment. Burns. 1975;2(3):161–5. 7. Hackett MEJ. Thermography in burn wound evaluation. Burns. 1974;1(2):113–8. 8. Gatti JE, et al. Fluorescein fluorometry in burn depth determination. Plast Reconstr Surg. 1984;73(3):394–8. 9. Davies JW. Vital dyes in burn wound assessment. Burns. 1970;1(1):49–55. 10. Zawacki BE. Use of vital dyes in burn depth diagnosis. Surgery. 1970;68(1):106–13. 11. Dorafshar AH, Gitman M, Henry G, Agarwal S, Gottlieb LJ. Guided surgical debridement: staining tissues with methylene blue. J Burn Care Res. 2010;31(5):791–4. 12. Rosique MJ, Rosique RG, et al. Methylene blue reduces progression of burn and increases skin survival in an experimental rat model. Burns. 2017;43(8):1702–8. 13. Lian C, Zhang JZ, Li YR, Liu HL, Liu XJ, Li XL. Methylene blue staining: a novel application to identify damaged tissues on pressure ulcers. Int Wound J. 2019;16(2):570–1. 14. Devgan L, Bhat S, Aylward S, Spence RJ. Modalities for the assessment of burn wound depth. J Burns Wounds. 2006;5: e2. 15. Moserova J, Hlavac P, Malinsky J. Ultrasonic diagnosis of the depth of thermal injury. Acta Chir Plast. 1982; 23:235–42. 16. Wachtel TL, Leopold GR, Frank HA, Frank DH. B-mode ultrasonic echo determination of depth of thermal injury. Burns. 1986; 12:432–7. 17. Watson AC, Vasilescu C. Thermography in plastic surgery. J R Coll Surg Edinb. 1972; 17:247–52. 18. Davis M, Adendorff D, Rode H, van der Reit IS. Coloring the damaged tissues on the burn wound surface. Burns. 1980; 6:156–60. 19. Celikoz B, Deveci M, Nisanci A. Early tangential excision with the guidance of methylene blue application. Ann Burns Fire Disasters. 1999;12(4):1–6. 20. Jackson DM, Stone PA. Tangential excision and grafting of burns. Br J Plast Surg. 1972; 25:416–26. 21. Herndon DN. Total Burn Care. 3rd ed. Philadelphia: Saunders; p. 179.