Cath Lab Digest

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  Prof. White notes that as with all antimicrobials, silver dressings must be used in an appropriate and structured manner for limited periods. A clinician should be able to give a sound reason why any dressing or technique is used, not used, continued, or discontinued in each specific lesion in each specific patient. Different types of wounds in different patients require different dressings and other measures during each stage of the wound healing process. After all, a venous leg ulcer in an elderly patient with cardiac failure and severe peripheral edema is very different from a 5% total body surface area (TBSA), superficial, partial-thickness burn in a healthy 20 year old and from a Stage II pressure ulcer in a paraplegic and from necrotizing fasciitis in any patient.

  In addition, dressings and materials cannot necessarily be compared, even although they may contain the same primary compound — eg, not all dressings containing silver release the same amount of Ag ions.^1-2 Varying silver concentrations and differing modes of silver ion delivery render direct dressing comparison inappropriate.³ Silver products such as silver sulfadiazine creams and silver nitrate solutions have side effects that can be both topical (eg, the formation of pseudo-eschar that makes judging the wound difficult4) or systemic (eg, methemoglobinemia development and/or electrolyte imbalance⁵). Such side effects are not linked to the silver per se but to the negative complex (NO3-, sulfadiazine) with which the silver forms a salt.

  Still, there is a general tendency to not consider pharmacological and physical differences among wounds when conclusions are drawn on a group of materials that seem superficially to be similar. Results of a trial⁶ of one specific type of silver dressing used in venous leg ulcers are sometimes used or quoted as “overall proof” that silver lacks efficacy in general and outcomes with one material in one indication often are used to justify (not) using a “similar” material, sometimes even for a entirely different indication.
  Moreover, healing differences may not always be the only important outcome in a trial. Everything else being equal, pain reduction might be a driver for using a specific (silver or other) material. Also, a dressing might be more expensive per se but it may help in reducing overall cost of care by reducing the number of dressing changes and subsequent nursing costs,⁷ making cost control an important outcome.

  Prophylactic use of a certain type of silver dressing may not be necessary for most ulcers, but in burn care topical agents (most commonly silver-containing materials) are virtually always used in burns exceeding 20% to 30% TBSA because patients with larger burns run a serious risk of wound infection and its sequalae, sepsis and death.⁸ Although prophylaxis is virtually impossible to study in a randomized, controlled trial (RTC), and, as such, does not appear in reviews such as Cochrane’s, silver creams and dressings are important in burns.^9-11

  As is the case with many other dressings and wound therapies, a large number of publications on silver-containing dressings is not based on true RTCs. Therefore, by some standards very little proof exists of the clinical efficacy of silver dressings and dressings in general, at least in the purely scientific sense of the word proof. However, one needs to realize that true level 1 RTCs¹² are virtually impossible to perform in wound care — the number of patients is too small and the number of variables so large that inclusion and exclusion criteria would lead to a level of stratification in which statistically relevant numbers per stratum are difficult to reach.