[Randomized controlled trial on application of negative pressure materials of polyvinyl alcohol and polyurethane in full-thickness burn wounds after escharotomy].

Objective: To compare the effects and characteristic difference of negative pressure materials of polyvinyl alcohol and polyurethane in the treatment of full-thickness burn wounds after escharotomy. Methods: From January 2018 to December 2019, 60 patients with full-thickness burns who met the inclusion criteria and hospitalized in Xuzhou Renci Hospital were recruited in this prospective randomized controlled trial. According to the random number table, 60 cases were divided into polyvinyl alcohol group (n =30, 13 males and 17 females) and polyurethane group (n =30, 14 males and 16 females), aged (34±7) and (35±6) years respectively, with burn area of 4.20% (2.23%, 4.90%) total body surface area (TBSA) and 3.89% (2.18%, 4.76%)TBSA and escharectomy area of 2.70% (1.97%, 3.42%) TBSA and 2.87% (2.12%, 3.34%)TBSA, respectively. After patient's admission, debridement was immediately performed on the full-thickness burn wound, and the dressing was changed with iodophor once a day. Escharectomy was performed on post injury day 3. After thorough hemostasis and washing the wounds with normal saline, patients of the two groups chose corresponding foam materials and supporting facilities for continuous negative-pressure treatment for 1 week, with the negative pressure value setting at -19.9 kPa. Installation time of negative-pressure material was recorded. After a week of negative-pressure treatment, the maximum pulling force of removing foam material was recorded to evaluate the adhesional degree between foam materials and wounds. The amount of bleeding in the process of removing foam materials was recorded, hyperplasiaof granulation tissue was observed with hematoxylin eosin (HE) staining, and the expression of CD31 was detected by immunohistochemical staining and Western blotting to denote vascularization. The ratio of R1 to R0 of coefficient of restitution of foam material before and one week after negative-pressure treatment and drainage volume of wound exudate within a week of negative-pressure treatment were recorded to denote the drainage ability of foam material to wound exudate. One week after negative-pressure treatment, the bacterial colonization, residual foreign body, and eczema rate of skin edge were recorded. Data were statistically analyzed with chi-square test, independent-sample t test, and Mann-Whitney U test. Results: (1) Installation time of negative-pressure material of patients in polyurethane group was (14±3) min, which was significantly shorter than (18±3) min in polyvinyl alcohol group (t=2.788, P<0.01). (2) One week after negative-pressure treatment, the maximum pulling force of removing foam material of patients in polyvinyl alcohol group was (6.4±0.4) N, which was significantly lower than (16.7±0.8) N in polyurethane group (t=12.010, P<0.01). (3) One week after negative-pressure treatment, the volume of wound bleeding of patients in polyvinyl alcohol group was (20±3) mL in the process of removing foam material, which was significantly less than (59±3) mL in polyurethane group (t=50.200, P<0.01). (4) One week after negative-pressure treatment, HE staining showed that hyperplastic thickness of wound granulation tissue of patients in polyurethane group was (2.3±0.6) mm which was significantly higher than (1.6±0.4) mm in polyvinyl alcohol group ( t=6.667, P<0.01); immunohistochemical staining showed that the number of microvascular lumen in wound granulation tissue of patients in polyurethane group was significantly more than that in polyvinyl alcohol group; Western blotting showed that protein expression of CD31 in wound granulation tissue of patients in polyurethane group (1.00±0.05) was significantly higher than 0.42±0.03 of polyvinyl alcohol group (t=10.490, P<0.01). (5)The ratio of R1 to R0 of coefficient of restitution of foam material of patients in polyvinyl alcohol group was 0.39±0.19, which was significantly lower than 0.52±0.16 in polyurethane group (t=2.975, P<0.01). In patients of polyvinyl alcohol group, the drainage volume of wound exudate of foam material during one week after negative-pressure treatment was (1 258±444) mL, significantly less than (1 658±580) mL of polyurethane group (t=3.003, P<0.01). (6) One week after negative-pressure treatment, the number of residual foreign body in wounds of patients of polyurethane group was (14.14±0.37) particles, which was significantly more than (3.36±0.15) particles in polyvinyl alcohol group (t=26.200, P<0.01). The level of bacterial colonization of wounds and eczema rate of skin edge of patients between the two groups were close. Conclusions: Polyurethane foam material is easy to install and operate, relatively difficult to dry and shrink, and has strong ability to discharge wound exudation. Polyurethane foam material is better than polyvinyl alcohol foam material in promoting wound angiogenesis and tissue proliferation. Polyurethane foam material can be chosen firstly for the wounds with need of protecting deep tissues and important organs, as well as the wounds with obvious inflammatory edema and serious contamination. Polyvinyl alcohol foam material is less adherent to wounds, which is better than polyurethane foam material in the aspects of reducing wound bleeding and residual foreign body. Polyvinyl alcohol foam material can be firstly selected to fix and promote skin graft survival after skin grafting, wound bed preparation before skin grafting of burn with large area and deep wound cavity or sinus, etc. Both types of foam materials need to be improved in the aspects of bacterial colonization and prevention and treatment of skin eczema.