Establishment and efficacy evaluation of a rabbit lower limb partial-thickness scald model

Objective To establish a rabbit lower limb partial-thickness scald model and evaluate its efficacy. Methods This study was a repeated measures designed and group designed experimental study. Forty healthy male New Zealand rabbits aged 6 to 8 months were selected and divided into scald group (30 rabbits) and normal control group (10 rabbits) according to the random number table method. After depilation and anesthesia, rabbits in the scald group were subjected to a lower limb partial-thickness scald model by immersing their right lower limb in 70 ℃ hot water for 12 s using a bucket-type constant temperature water bath pot and a self-made rabbit scald fixation bracket, followed by fluid resuscitation within 6 h post-injury. The rabbits in normal control group were subjected to hair removal and anesthesia as scald group at the same time point except for scald and fluid resuscitation. Ten rabbits were randomly selected from scald group, and the wound tissue morphology was observed after hematoxylin-eosin staining before injury and at 6 and 24 h after injury, respectively. Another 10 rabbits were randomly selected from scald group for observation of skin blood perfusion volume in right lower limb using laser Doppler flowmetry before injury and at 0 (immediately), 1, 3, 6, 12, 24, and 48 h after injury, respectively. The remaining 10 rabbits in scald group were measured for subcutaneous and deep muscle temperatures in right lower limb using non-contact infrared temperature sensors and contact temperature sensors before injury and at 10 s, 20 s, 40 s, 2 min, 10 min, 20 min, 40 min, 1 h, 2 h, 3 h, 4 h, 5 h, and 6 h after injury, respectively. The 10 rabbits for blood perfusion volume observation in scald group were measured for right lower limb circumference before injury and at 1, 2, 3, 4, 5, 6, 24, 48, and 72 h after injury, respectively, and wound healing time of dorsal foot, plantar foot, and crural regions were recorded. Ten rabbits from normal control group and 10 rabbits after temperature measurement from scald group were taken to detect the serum levels of interleukin-1β (IL-1β), IL-6, tumor necrosis factor-α (TNF-α), superoxide dismutase (SOD), and malondialdehyde by enzyme-linked immunosorbent assay at 24 h after injury. Results Before injury, epidermis and skin appendages of the right lower limb of rabbits in scald group were intact. At 6 h after injury, epidermal continuity was interrupted, partial skin appendages disappeared, interstitial spaces increased, and edema increased. At 24 h after injury, skin appendages atrophied and disappeared, tissue edema increased significantly, and inflammatory cell infiltration increased in superficial dermis. The skin blood perfusion volume of right lower limb of rabbits in scald group before injury and at 0, 1, 3, 6, 12, 24, and 48 h after injury was (1.00±0.26), (1.03±0.29), (1.04±0.29), (1.19±0.37), (1.30±0.50), (1.36±0.99), (1.39±0.22), and (0.72±0.21) perfusion units, respectively (main effect of time factor, F=12.55, P<0.05). The subcutaneous temperature in right lower limb of rabbits in scald group before injury and at 10 s, 20 s, 2 min, 10 min, 20 min, 40 min, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h after injury was significantly lower than that at 40 s after injury (P<0.05). The deep muscle temperature in right lower limb of rabbits in scald group before injury and at 10 s, 20 s, 40 s, 2 min, 20 min, 40 min, 1 h, 2 h, 3 h, 4 h, 5 h, and 6 h after injury was significantly lower than that at 10 min after injury (P<0.05). The right lower limb circumference in rabbits in scald group at 24 h after injury was significantly larger than that before injury and at 1, 2, 3, 4, 5, 6, 48, and 72 h after injury (with P values all <0.05). The wound healing time of plantar foot of rabbits in scald group was significantly shorter than that of dorsal foot and crural region (with P values both <0.05). Compared with those in normal control group, serum levels of IL-1β, IL-6, TNF-α, and malondialdehyde in rabbits in scald group were significantly increased (with t values of 21.92, 7.48, 12.58, and 117.34, respectively, P<0.05), while serum level of SOD was significantly decreased at 24 h after injury (t=6.63, P<0.05). Conclusions The rabbit lower limb partial-thickness scald model established in this study can safely and stably simulate the pathophysiological process and clinical characteristics of human limb scald, thus is a better model for studying partial-thickness scald of human limbs.