Pharmacologic Wound Care
As the wound healing process has been better elucidated, the practice of wound care has evolved. However, the basic principles of good wound care have not changed significantly over time. The process begins with an assessment of the entire patient. Any underlying medical conditions that impair wound healing must be treated. These include systemic infection, hyperglycemia, inadequate nutritional status, poor circulation, a deficient immune system, and the absence of someone dedicated to caring for the wound. Once patient factors have been adequately addressed, attention should be turned to the wound itself. The majority of chronic wounds encountered in hospitalized patients can be categorized into four types of ulcers: pressure, diabetic, venous and ischemic.
In addition, chronically infected wounds can occur in the setting of underlying osteomyelitis or a foreign body (such as orthopedic hardware). With respect to local wound care, the principles are always the same: eradicate infection, debride necrotic tissue, remove any nonessential foreign material, maximize arterial inflow and venous outflow, and keep the wound moist and clean.Topical pharmacologic wound care can help achieve these goals to a certain extent. In broad terms, agents commonly used in local wound care can be grouped into three categories: antimicrobial agents, enzymatic agents and growth factors.
Topical antimicrobials are moderately effective in treating infected wounds. They provide the benefit of delivering a high therapeutic dose of the drug to a local area with minimal systemic side effects, particularly in wounds with relatively underperfused tissues. They are not, however, a substitute for systemic antimicrobial therapy when indicated (e.g., surrounding cellulites of the wound). The goal of topical antimicrobial therapy is to diminish the burden of bacteria to a level that is manageable by the host immune cells. In fact, sub-infection levels of bacteria have been shown to accelerate wound healing and granulation by promoting the infiltration of neutrophils, monocytes and increased collagen deposition. There are a variety of commercially available topical antimicrobials.
Silver sulfadiazine (Silvadene®) is used in superficial soft tissue infections. Its effectiveness against Pseudomonas makes it a favored choice in burn treatment. Two other commonly used antibiotic agents are Bacitracin® and Neosporin®. These petroleum-based ointments are useful more for superficial infections. In addition, they can be used on surgical incisions, particularly of the face, to minimize bacterial load and provide a moist wound environment to promote epithelialization.
The role of povidone-iodine (Betadine®) in topical wound care is somewhat controversial. Several animal studies demonstrate no adverse affect on wound tensile strength or reepithelialization rates. On the other hand, several human in vitro and in vivo studies have shown that Betadine inhibits fibroblast proliferation, kerotinocyte growth and migration, and hampers the phagocytic effect of monocytes and granulocytes. In addition, any admixture of blood, pus or fat has been proven to diminish the antimicrobial effect of Betadine. Given this data, many plastic surgeons do not use Betadine as a topical antimicrobial, although it is still commonly used in the operating room as a prepping agent. Other specialties that treat wounds still use Betadine due to the lack of convincing clinical trials and a long history of its use.
In addition to appropriate antimicrobial therapy, the wound must be properly debrided of any devitalized tissue. Necrotic tissue can serve as a culture medium for further bacterial proliferation, and its presence will impede the healing process. Sharp debridement is the simplest, most effective means of eliminating nonviable tissue. Enzymatic debriding agents are an adjunct to surgical debridement. As with antimicrobial agents, there is a spectrum of enzymatic agents that is commercially available.
Perhaps the realm with the greatest therapeutic potential in the pharmacologic treatment of wounds is the use of growth factors. A variety of growth factors and chemotactic agents have been discovered since the 1970s, and many have been probed for possible clinical applications. Platelet-derived growth factor (PDGF) is present in acute surgical wounds, however not in chronic, nonhealing wounds. In several randomized controlled trials, topical application of PDGF increased wound tensile strength and accelerated the healing process overall. Recombinant PDGF is currently the only cytokine approved for use in chronic wounds, specifically in neuropathic diabetic foot ulcers. It is available commercially as beclapermin (Regranex®); however the extremely high cost makes its use prohibitive in many centers.
Pearls and Pitfalls
1. Choosing a topical wound care agent must be done in conjunction with choosing the appropriate dressing.
2. If the wound is complicated by underlying osteomyelitis, topical antibiotics will not suffice in eradicating the infection.
3. Close observation is warranted when instituting a new therapy for the wound since many of these agents have side effects and can even induce an allergic reaction.
4. Enzymatic agents cannot penetrate thick eschar. Necrotic tissue should be sharply debrided before applying a topical enzymatic substance.
5. Some topical wound care agents, such as papain-containing enzymatic agents,
are painful when they come in contact with surrounding healthy skin.