‘Mixed depth’, ‘intermediate’, ‘indeterminate’ describe burn wounds that are difficult to assess accurately by even the most experienced burn surgeons. This is as true today as it was when Jackson (1953) acknowledged: “Initial white coagulation of the skin does not necessarily imply full-thickness skin loss, and this warning applies much more to the extended area of white necrosis on the surface of the burn after the zone of stasis has turned white. Those who excise the white areas of a burn at seven to ten days after burning, taking colour as their guide of complete skin destruction, will frequently excise skin that would heal naturally in two to three weeks with no scar”.
Sensitivity to pin-prick can be used to aid diagnosis but it is subjective and “One prick is valueless: about ten to the square inch are required, not only because the pain spots are localised but because areas of full thickness skin loss may be patchy in the burn” (Jackson, 1953). Use of laser Doppler enables the Burn Care Team to ‘see’ beyond the surface and assess blood flow that is not visible to the eye, and without pain.
Benefits of LDI-aided Assessment of Burn Severity
Conservatively Managed Burns: a significant percentage of burn wounds that are initially treated conservatively, based on clinical assessment alone, later require surgery (Engrav et al 1983). Introduction of LDI, as an aid to burn assessment, can reduce the delay of surgical treatment when conservative management is not the most appropriate choice. Delays and later reconstructions can be avoided with the aid of LDI imaging.
Early Excision: the benefits of early excision, especially in severe burns, are well known (Herndon et al 1989). LDI, in conjunction with clinical assessment, has been validated for accurate burn assessments (95%) as early as 48 hours post burn; this enables early and accurate planning of wound management, avoiding surgery when it is unnecessary.
Graft Area: accurate skin blood flow mapping of the burn wound with LDI enables the surgeon to limit excision to only the areas that require grafting. This leads to a reduction in donor site area and can also reduce dermal substitute requirements.
Dressings: early, accurate assessment of healing potential enables optimum choice of dressing with earlier healing and cost savings. Avoiding delays where surgery is needed and enabling preparation of cultured epithelial autograft where required (Kim et al, 2010); it can also reduce the number of dressing changes.
Patient Compliance: the need for surgery can be appreciated more readily when the graphical evidence of an LDI blood flow image is shown to the patient. Evidence of wound blood flow during healing may also help with compliance to advice regarding pressure therapy.
Length of Hospital Stay: early and accurate assessment of burns with LDI has been shown to reduce the average length of stay from 3.4 days, prior to regular use, to 2.1 days after and in patients treated surgically this reduction was from 15.1 days to 9.8 days (Petrie et al, 2004); in another study (Kim et al, 2010) time to surgical decision making was reduced by 2.7 days.
Rehabilitation: appropriate conservative management leads to faster wound healing and less scarring; appropriate early excision and grafting will lead to faster wound healing, less potential for infection and less scarring. Appropriate choice of management is aided by LDI and can enable faster and better rehabilitation.
Objective documentation: as the culture of medical litigation rises it becomes increasingly important to document wound status. This could help patients and insurance companies to settle injury claims more quickly and help surgeons to substantiate clinical opinion when providing evidence in medico-legal cases. It has also been reported as a useful tool when explaining diagnosis and treatment decisions to patients and their families, especially in paediatric cases.
Burns Research: comparison of different dressings and treatments requires an objective assessment of wound status before the treatments start. The improved accuracy with use of LDI enables more accurate comparisons to be made. LDI also plays a significant role in fundamental research and the study of microvascular mechanisms.
Engrav L.H, Heimbach D.M, Reus J.L, Harnar T.J, Marvin J.A. Early excision and grafting vs non-operative treatment of burns of indeterminant depth: A randomized prospective study. J Trauma, 1983, 23; 1001-1004.
Jackson D M, The diagnosis of the depth of burning. Br J of Surg, 1953, 40: 588-596.
Kim LH, Ward D, Lam L, Holland AJ. The Impact of Laser Doppler Imaging on Time to Grafting Decisions in
Pediatric Burns. J Burn Care Res. 2010, 31; 328-332.
Petrie N, Norbury W, Fogarty B, Philp B, Barrat J, Dziewulski P, The use of Laser Doppler Imaging to reduce operative intervention in the treatment of Paediatric Burns. 12th Congress of ISBI, Yokohama, Japan, 2004 (abs).