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Knapp et al. Plast Aesthet Res 2020;7:7 I http://dx.doi.org/10.20517/2347-9264.2019.69 Page 7 of 14

via nitric oxide vasodilation with arginine supplementation [12,13,82-84] . Omega-3 fatty acids/fish oils dampen
the metabolic response to stress, decrease inflammation, regulate bowel motility via vagal efferents, and
stimulate the resolution of the inflammatory response by the endogenous production of SPMs [12,13,82,85,86] .
Several large meta-analyses in the past decade have added support to the use of perioperative metabolic
manipulation. This concept has been shown to be beneficial not in the perioperative period but also
when given only preoperatively with essentially preparing the host for the metabolic insult of surgery.
The overall conclusions from these studies are that immune-enhancing formulations (more so than other
nutritional regimens) lead to decreased overall infections, a reduction in hospital LOS, a decrease in overall
[91]
complication rate [87-90] , and one study even reporting a decrease in mortality .

Another area of metabolic manipulation that has been explored is preoperative carbohydrate loading,
which has shown usefulness mostly in reducing perioperative hyperglycemia/insulin resistance [92,93] . In a
standard protocol, patients consume a 300-mL isotonic clear beverage with 50 g of complex carbohydrate
three hours prior to surgery to decrease insulin resistance in the perioperative period. The original
carbohydrate loading studies administered the isotonic formulations the night prior to surgery and the
morning of surgery with the concept of maximally loading the myocardium, liver, and muscle with
glycogen. Subsequent studies have shown that the carbohydrate loading the night before surgery is not
[94]
necessary . Reported outcomes with this regimen include: no increased risk of aspiration, decreased
postoperative insulin resistance, maintenance of muscle strength, decreased patient anxiety, and possibly
decreased LOS but no major difference in major clinical significant outcomes such as reduced infections
or length of stay [95-97] . While the European Society for Clinical Nutrition and Metabolism consensus
guidelines for surgical nutrition endorses carbohydrate loading [98,99] , further studies are needed to better
elucidate quantity and optimal timing of intervention.

Skin preparation, antibiotics, and the microbiome
The literature suggests that acute changes in the host microbiome may alter metabolism on a systemic
level. A majority of surgeons and hospitals instruct patients to shower with chlorhexidine gluconate soap
the night prior to and the morning of surgery. A Cochrane Database review in 2015 summarizing seven
studies and over 10,000 patients showed that, while they reported a decrease in skin bacterial colonization,
there was no reduction of surgical-site infections with use of chlorhexidine compared to other agents [100] .
Furthermore, a study using prospectively collected data in VHR patients actually suggested the use of pre-
[101]
hospital chlorhexidine scrub increases the risk of infection . While preoperative bathing can certainly
reduce bacteria counts on the skin, it does not clearly translate into positive impacts on surgical outcomes.
It may disrupt normal skin flora and therefore remove the competitive inhibition that usually prevents
pathogenic bacteria from proliferating. These antibacterial soaps destroy not only pathogenic bacteria but
[102]
also commensal strains . However, more research is necessary before making any definitive changes to
standard of care. Our program has eliminated the night before surgery chlorhexidine showers as we believe
that the elimination of normal skin flora for long periods before surgery allows potential pathogens to
colonize.

The data on the choice of skin preparation in the operating room are more conclusive and stem from two
[103]
major trials. A prospective trial by Swenson et al. with over 3200 patients demonstrated that iodine
skin preparation was superior to chlorhexidine preparations. Then, a prospective randomized trial was
[104]
[105]
published reporting that chlorhexidine was superior to iodine . Swenson and Sawyer then reanalyzed
the data from both studies and concluded that the decreased infection rate was related to the alcohol in
preparations. Duraprep and Cloraprep had similar infection risk, whereas the iodine preparation without
alcohol was associated with higher surgical site infections (SSI) rates.

Staphylococcus aureus is the most common culprit in postoperative surgical infections and the rate of
chronic colonization in the patient population is rising. Several studies have been conducted to investigate