The Importance of Hydration in Wound Healing

What happens when the skin is injured?

When the integrity of the skin is compromised, the mechanisms responsible for maintaining the proper level of hydration in the given tissue are jeopardized. The ability to maintain the interstitial fluid pressure necessary to control fluid passage from the bloodstream and its removal by the lymphatic system is reduced. Inflammation-induced vessel dilation increases fluid leakage from the bloodstream into surrounding tissues, and most of this fluid is absorbed into the components of the extracellular matrix (ECM).

When the skin is injured, hemostasis is ensured by covering the defect with a fibrin network, forming a scab. Inflammatory cells migrate to the injury site, triggering signaling cascades that lead to cell proliferation and ECM deposition. Collagen synthesis initiates the formation of new tissue matrix, and granulation tissue with a dense network of newly forming blood vessels begins to form. Then, tissue remodeling and reepithelialization occur, restoring the skin barrier at the injury site. 

Moist wound healing

In pilot studies conducted in the 1960s, it was shown that wounds exposed to air and left to dry healed more slowly and with worse final appearance compared to wounds maintained in a moist environment. Tissue biopsies showed that 'dry' wounds experienced delayed reepithelialization.

The concerns that wound occlusion and maintaining a moist environment would lead to an increase in bacterial counts and infections were not confirmed. On the contrary, wounds treated with dressings that support moist healing exhibited lower levels of infections despite bacterial colonization.

Hyperhydration of tissues and healing

When maintaining a wound in a moist environment, it is necessary to avoid maceration of the skin around the wound. It appears that the harmful effects of maceration are not due to excessive hydration, but to the presence of biologically active substances in the fluid. Rinse solutions are successfully used to support healing in many different types of wounds (acute injuries, infected wounds, diabetic ulcers). Healing in a moist environment is also supported by the healing of fetal injuries in utero without scar formation and the rapid healing of tissues in the oral cavity.

Tissue damage caused by exudate

The finding that tissue hyperhydration can be as beneficial for wound healing as a moist environment may seem somewhat surprising. An excessive amount of exudate in prolonged contact with the skin is usually associated with difficult healing and exacerbation of problems such as maceration.

Studies have shown that exudate from chronic ulcers is fundamentally different from fluid produced by fresh acute wounds. Chronic exudate contains large amounts of proteolytic enzymes, such as matrix metalloproteinases and neutrophil elastase, and also pro-inflammatory cytokines. The presence of these irritating components leads to damage to both the wound bed and its surroundings.

Conclusion

Maintaining optimal hydration balance is a key feature of modern wound dressings. The most advantageous dressings appear to be those with improved ability to regulate fluid amounts and absorb corrosive components contained in chronic wound exudate while simultaneously providing optimal hydration levels and preventing wound drying.

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Source: Ousey, K., Cutting K. F., Rogers A. A., Rippon M. G. The importance of hydration in wound healing: reinvigorating the clinical perspective. J Wound Care 2016; 25 (3): 122, 124–130, doi: 10.12968/jowc.2016.25.3.122.