Local Environment of Chronic Wounds Under Synthetic Dressings

Abstract

Local wound environment under oxygen-permeable and oxygen-nonpermeable dressings in patients with chronic ulcers was investigated. The oxygen tensions under both these dressings were very low or zero. Wound fluid was more acidic under the nonpermeable hydrocolloid dressing than under the oxygen-permeable polyurethane dressing. Bacterial growth studied in vitro was retarded at the more acidic pH similar to that found under the hydrocolloid dressing. Viable and functioning neutrophils were found under both the polyurethane and hydrocolloid dressings, with a greater percentage of viable cells under the polyurethane film. Our data suggest that these synthetic dressings create hypoxic conditions in which wound healing occurs whether or not the dressing is permeable to oxygen. Furthermore the local wound environment can be modified by use of synthetic dressings.

Treating the chronic wound: A practical approach to the care of nonhealing wounds and wound care dressings

“…52 Not only do these dressings speed re-epithelialization; they also stimulate collagen synthesis and create a hypoxic environment at the wound bed that promotes angiogenesis. [53][54][55] An added benefit of moisture-retentive dressings is that many patients experience pain relief with their use. [56][57][58][59] Despite initial fears that occlusive dressings would promote wound infection, it has now been shown that they actually decrease infection rates compared to nonocclusive dressings.…”

pH-Wert des Milieus chronischer Wunden

“…Im Sekret chronischer Wunden wird unter nicht permeablen Verbänden ein saureres Wundmilieu gefunden als bei der Verwendung eines permeablen Wundverbandes. In weiterführenden In-vitro-Untersuchungen konnten allerdings keine Unterschiede bezüglich des Bakterienwachstums in den beiden untersuchten Wundsekreten festgestellt werden,sodass hier die Akkumulation von anaerob generierten Stoffwechselprodukten als ein kausaler Faktor diskutiert wurde [24].Die meisten humanpathogenen Keime werden in ihrem Wachstum in einem pHWert Bereich <6,0 und insbesondere zwischen pH 4 und 5 gehemmt, wohingegen deren pH-Optimum mit 6,2-7,8 angegeben wird [14,21,23]. So konnte bei Patienten mit Hemiplegie oder Diabetes mellitus gezeigt werden, dass nach Senkung des pH-Wertes der intakten Haut durch topische Verwendung von sauren Externa die Bakteriendichte deutlich reduziert wird [12].Ein Grund könnte die veränder-te Aktivität,die beispielsweise für Enzyme von Staphylokokken in unterschiedlichen pH-Wert-Bereichen beschrieben wurde sein.So sind die meisten Staphylokokkenenzyme in alkalischen Milieus weniger aktiv, wohingegen in sauren Milieus vermehrt Proteasen ausbildet werden [6].Für das Staphylokokkenenterotoxin C2 (SEC2) konnte aktuell gezeigt werden, dass sich die 3-dimensionale Struktur abhängig vom dem umgebendem pH-Milieu än-dert und somit eine differenzierte Aktivität resultieren könnte [11].Die Modifikation des pH-Wertes im Milieu chronischer Wunden könnte somit über eine gezielte Reduktion der bakteriellen Kolonisation einen relevanten Faktor in der verzöger-ten Abheilung chronischer Wunden beeinflussen.…”

Biodegradable Films in Trauma and Orthopedic Surgery

“…It could be shown that this resulted in reduction of bacterial growth as well as enhanced proliferation of epithelial cells [85]. High local lactate concentration can stimulate local collagen synthesis, increased plasma lactate levels were not found in clinical studies [74].…”

“…Further investigations proved that by use of these materials as a cell culture carrier there was a positive influence on cell growth [92][93][94]. A substantial reason for this observation might be the acid change of the pH value of the film surface by hydrolysis as well as the high lactate concentration, since low pH values, besides the reduction of germ growth [85], also promote epithelisation [86,95,96].…”

“…Many advantages of the occlusive and semi-occlusive wound dressings regarding application, patient comfort (mobility and pain reduction) and wound healing over wound treatment with textiles, fat gauze or strongly adhesive products were pointed out in detail in the last 30 years [58,61,64,85,[96][97][98]. The necessary changes with non-degradable dressings lead to repeated trauma to the wound ground, in large surface wounds sometimes to substantial blood loss, and are extremely painful for the patient.…”