Blood Cell Count and the Presence or Absence of Infection in Venous Ulcers Treated With Platelet-Rich Plasma

Beatriz Guitton Renaud Baptista de Oliveira, DN, RN; Joyce Beatriz de Abreu Castro, MSN, RN; Bruna Maiara Ferreira Barreto Pires, RN, PhD; Márcia de Assunção Ferreira, DN, RN; Jane Marcy Neffá Pinto, PhD, MD; Lenise Arneiro Teixeira, DSC, BF

Disclosures

Wounds. 2021;33(5):113-118. 

In This Article

Discussion

Upon tissue injury, an inflammatory process immediately begins. Initially, there is acute inflammation, which consists of the body's reaction to harmful agents such as microorganisms and damaged cells and entails the triggering of vascular responses, leukocyte migration/activation, and systemic reactions.[17] When the acute inflammatory response does not resolve in a timely manner, typically due to persistence of the noxious agent or interference with the normal healing process, a transition to the chronic inflammatory response occurs.[18] Chronic inflammation is also referred to as slow long-term inflammation, lasting for prolonged periods of several months to years.[18]

The proliferation of microorganisms will trigger a response that involves the entire body, with clinical manifestations such as heat, erythema, edema, purulent exudate, and pain and/or systemic signs, including fever and leukocytosis, although such signs are often absent. In cases involving infected chronic wounds, including venous ulcers, the infection is usually localized to the wound; therefore, there are no systemic signs. In such cases, evaluations need to be targeted to local clinical characteristics.[3–5]

Blood changes (qualitative and quantitative) occur secondary to local or systemic pathological processes. Hemograms can be used to assess peripheral blood and reflect a patient's status at the moment of sample collection. Analyses of changes in leukocytes refer to production, release, and transit of these cells through the peripheral blood toward the target tissue.[17] However, an increased level of leukocytes in the blood does not necessarily indicate the presence of infection; therefore, the clinical signs and symptoms that a patient presents should be considered when interpreting test results.[17] In this sense, a hemogram should be used as a complementary datapoint to clinical evaluation that may aid evaluation of the intensity of a pathological process. Notably, good characterization of a wound is the first step in decision-making regarding the type and continuation of treatment.

Platelet-rich plasma presents itself as an intervention that allows the local application of growth factors in the wound, which stimulate the production of collagen and extracellular matrix through small amounts of plasma; PRP is a promising alternative in cases where conventional treatments were not successful.[19] The conventional treatments considered in this study were wound irrigation with saline followed by the application of a nonadherent dressing to provide a moist healing environment and use of compression therapy.[12]

Growth factors are members of a large group of polypeptides secreted by various regulatory molecules in the body. They act as mediators in cell maturation and are responsible for tissue damage repair processes.[20] Among the growth factors released by the platelets contained in plasma, transforming growth factor beta, vascular endothelial growth factor, growth factor of fibroblasts, platelet-derived growth factor, and epidermal growth factor can aid in tissue repair.

Growth factors can favor the repair of the injuries and enable the quickest return to functionality, possibly by stimulating neovascularization, which improves the blood supply and provides necessary nutrients for tissue regeneration.[21,22] The promising impact of application of platelet-derived growth factors to chronic wounds has been indicated in the literature,[23] which at the present time remains limited.

In the present study, the use of autologous PRP improved the signs of infection. It is believed that WBCs and innate immune defense peptides present in PRP may act as agents that decrease the proliferation of microorganisms.[13] Thus, by reducing the microbial load in wounds, PRP treatment may reduce wound colonization and infection, favoring the process of physiological tissue repair. According to Silva et al,[24] purulent exudate differed from the exudate produced from debridement.

It is noteworthy that studies have identified PRP as a protective factor against wound infection; in particular, in vitro experiments have demonstrated antimicrobial effects of PRP on methicillin-resistant Staphylococcus aureus, methicillin-sensitive S aureus,[25,26]Escherichia coli, Enterobacter cloacae, Bacillus cereus, and Bacillus subtilis.[13] Thus, for wounds colonized by these microorganisms, microbial load could be reduced via the topical application of PRP.

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