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ofSem i-O cclusiveon

1 Cellular Changesand Clive Osborn

ofAnatomyandCell Biology, United Medicaland Dental SchoolsofGuy'sand St.Thomas'sandSmitband Nepbew ResearchLtd.(SL, CO ), Harlow, Essex,U.K.

fujl-thickness ex-on porcine skin during the period from 5 d to 6

adecrease in the number of inflam-ells polymorphonuciear leukocytes and macro-to 60 d, whereas the number of proliferative

ells fibrohlasts and endothelial cells) increased from 55 and 7 d, that is, during the proliferative phase of

repair, and then progressively decreased as the prolifephase was succeeded by the remodeling phase. In cothe repair process in the hydrocolloid-dressed woundmore complex. The number of inflammatory cells remrelatively high throughout and there were consistently endothelial cells present throughout. Fibroblast nushowed an initial fall from 5 to 14 d but then starincrease in number from 21 to 60 d. This chronic inflatory reaction appeared to be in response to particulate mthat had been incorporated into the wound bed and hyplnis, and was still apparent 6 months after injury, whedrocolloid particles were detectable microscopically hypodermis.JIni;e5f Dermato/97:586-592 1991

t has been shown experimentally that wounds re-epithelial-ize more rapidly under moist conditions than under dry [ -5].Therateofdermal repair has also been showntoincreaseunder moist conditions[6].Dermal repair can be divided,for descriptive convenience,andmatrix formation andremod elling [7].of granulation tissue formation has also been termedtheofrepair [8], a conv entio n that lias been adoptedischaracterizedbycbangesincellularity as differ-ll types, mainly polymorpho nuciear leucocytes (PMN ), mo n-

dout ofthe woundbed [7].The changes in cellularity that occur during repaircanprovideonthe progress and quality of repair.Wehave the rate of dermal repair by means of differential cellin the tissue that developsin thewoundbed of full-indomestic pigs,andhave used thistocomp are the rate of dermal repair in moist and dry condi-has nowbeen extendedtocomparetherateofinwounds covered with semi-occlusive polyurethane and hydrocoUoid dressings. Both dressings providethe

e use of a hydrocoUoid dressing m igh t confer advantages over[9].

Manuscript received October 24, 1990; acceptedforpublication April8,Reprint requeststo :Dr. S.R. Youn g, Tissue Repair Researcb Uni t, Dep art-ofAnatomy, Guy's Hospital, London Bridge, LondonSEI9 R T ,En-

MATERIALS AND M E T H O D SOperat ing Procedure Seven large wh ite domestic piusedinthis study,one foreach time point (5,7, 10,14, 21168 d). Th e opera ting pro cedure is described in detail by Dys[6]. Briefly, six 25 X25 -m m full-thickness excised lesiomadein theskinofeach flankof the anesthetized pigs. Theextended throug h the full thicknessof the skin intothepanadipostts (hypodermis).Thesquare of isolated skin andpaadiposus was then dissected from the underlying musculaturing that no muscle was included with the tissue excisewounds were approximately 8 mmdeep.Wound Dressings: Immediately after surgery, the woundfilled wit h d ental rolls to absorb any free blood. After rem ovarolls,sixrandomly selected w ounds w ere covered w ith thocclusive adhesive polyurethane dressing Opsite (SOP) (SinNephew Medical Ltd) to ensure that the wound environmmained moist. The remaining six woundsoneach pig w ere withthehydro colloid dressing G ranuflex, also kno wn as D(HC) (Convatec Ltd).Granuflex is an adhesive hydrocolloid mass thatiscoatedfoam, and has a waterproof backing film that is impervious tture vapor. The dressings were, where appropriate, left in platotalof2 d post woundingand then removed.Seven pigs were treated in this way, so that 84 woundavailable for comparison, 42 covered with SOPdressings,withHCdressings.Maintena nce of Post-Opera tive Analgesia: Imm e d ia t e ly a f te r and while still anesthetised, each animal receivedanintraminjection of 60 mg of Pethidine (Roche Products Ltd., WGarden City, U.K.) to maintain analgesia postoperatively.

0022-202X /91 / 03 .50 C opyr igh t 1991by TbeSocietyforInvestigative Dermatolog y,Inc.

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. 97, NO. 3 SEPTEMBER 1991 REPAIR UNDER FILM AND HYDRO COLLOID DRESSINGS

Preparation for LightM icroscopy: At 5, 7, 10, 14, 21 , 60, and

d 1 cm from the wound margin, and the wound, together

flm, and stained with hematoxylin and eosin.

at te m pt was made to identify and count pericytes, other m esen-

it n e y U tests), t tests were considered inappropriate in view of

RESULTS By 5 d after injury,

instances, it appeared that the en tire dressing m atrix over the wsite had liquified. Some con traction w as visible in the SOP-drwounds, but none in the HC-dressed wounds. By 7 d after inthe HC-dressed wounds had started to show a slight contracbut not to the same extentasthe SOP-dressed w oun ds. By 14 dinjury, pink granulation tissue was visible in all wounds. By after injury, there was no visible macroscopic diiiference betany ofthe wounds. By 60 d after injury, there appeared to be scar tissue in the HC-dressed wounds, although this was not sured. By 168 d after injury, there was no apparent differenctween the wounds, al l showing minimal scarring.Light Microscopy All the results of the differential cell care shown in Table I and expressed graphically in Figs 1 aFigure 1 shows the n umb er of inflamm atory cells (neutrophilsmacrophages) in a count area of 50,460 /im^ of the woundFigure 2 shows the number of proliferative phase cells (fibroband endothelial cells) in the count area ofthe wound bed.Fii eD ays After hifur) : Th e majority of the cells in both the and HC -dressed w ound s were fibroblasts (Table I, Figs and 2the granulation tissue in the SOP-dressed wounds developed iwound beds appeared to be more vascularized than the granult issue ofth e HC-dressed w ounds (Figs 3-6 ). T he cel lular arrament in the SOP-dressed wounds appeared to be more orderly5) than in the HC-dre ssed w ound s (Fig 6). In the former, the mity ofthe fibroblasts from the central region ofthe granu lation tappeared to be arranged approximately parallel to the base ofwound, with many of the capillaries having developed appmately at right angles to them (Fig 5). This arrangement wasapparent in the HC-dressed wounds, where the presence of cavcontaining cellular and particulate debris appeared to have res

Table I. Differential Cell Co un t Me dian Values and Statistical Results

CellsDays Post

Injury571014216057101 4216057101 4216057101421605710142160

OPSITEMedian410100

1713573115 319615 013 811 41 0 9

8 ,11739418421716 514 612 811 5

(SOP) Dressing(range)(0-9)(1-2)(0-0)(0-3)(0-2)(0-0)

(10-37)(8-17)(4-9)(3-9)(2-5)(0-6)(139-156)(138-204)(126-164)(116-147)(99-125)(96-130)(5-19) 8-16)(6-11)(0-5)(6-13)(2-6)(163-203)(172-233)(138-175)(128-156)(114-143)(105-134)

N666654666654666654666654666654

Granuflex (HC) DressingMedian

57211194

33151930302017 213 613 212 914 916 9

76528322016 516 517 8207210

(range)(1-20)(2-10)(0-11)(2-46)(13-24)(2-22)(22-44) 12-17)14-39)(20-43)(14-46)(17-31)(138-204)(103-219)(116-152)(111-184)(130-218)(142-193)(1-17)(4-7)(3-9)(0-8)(2-11)(2-6)(196-248)(126-242)(133-184)(146-251)(187-258)(165-232)

N666655666655666655666655666655

Mann-Whitneyp Values0.8100.0080.0640.0130.0120.0160.0310.4710.0050.0050.0120.0200.0660.1280.1501.0000.0120.0200.4710.0050.1501.0000.3470.9030.0130.0930.8100.0200.0120.020

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