classification.
Source: Based on Turk et al. [1], Eugster et al. [2], Nicholson et al. [3], Fitzpatrick and Solano [4], Beal et al. [5], Frey et al. [6], and Vasseur et al. [7].
| Clean | No infection No break in aseptic technique Nontraumatic |
| Clean‐contaminated | Controlled access to a hollow viscus Minor break in aseptic technique |
| Contaminated | Entry through nonseptic, yet inflamed tissues Spillage from a hollow viscus – localized, controlled Major break in aseptic technique Fresh, traumatic wounds (<4 h) |
| Dirty | Perforated hollow viscus Septic purulent discharge encountered Chronic, traumatic wounds (>4 h) |
Table 2.2 Halstead's principles.
| Gentle tissue handling Meticulous hemostasis Strict aseptic technique Preservation of blood supply Elimination of dead space Accurate apposition of tissues while minimizing tension |
2.2.2 ASA Status and Endocrinopathies
Preoperative ASA score (Table 2.3) has been correlated with risk for developing an SSI, such that the risk for SSI increases with each increment in ASA score [2]. As ASA scores take into consideration the overall health status of a patient, the higher the ASA score, the more systemically ill the patient. Animals with endocrinopathies have also been identified to be 8.2 times more likely to develop an SSI, likely due to alterations in immune function [3]. Logically, if an animal has a chronic illness, such as an unmanaged or poorly controlled endocrinopathy, postponement of elective orthopedic procedures until these illnesses are adequately addressed should be considered, when possible.
2.2.3 MRSP Carrier Status
As Staphylococcus spp. have been identified as one of the most common bacteria contributing to the development of SSIs following TPLO, and MRSP SSIs are increasing in frequency, monitoring for carriers of MRSP has been investigated [4, 13, 21,31–34]. In one study, 4.4% of animals were identified to be MRSP carriers preoperatively and carriers were 6.72 times more likely to develop an SSI. While screening for MRSP may help to determine those animals at higher risk for SSI, current screening tests are time‐consuming and not practical for routine implementation as this would result in delaying surgery [21]. Additionally, in human medicine, the goals of methicillin‐resistant Staphylococcus aureus (MRSA) screening are to allow for decolonization preoperatively [35–38]. In veterinary medicine, preoperative decolonization of MRSP is a challenge, due to not only the limited number of effective antimicrobials against MRSP, but also the inherent challenges of topical treatment of the sites most commonly colonized – the nasal passages, pharynx, and rectum [21].
Table 2.3 American society of anesthesiologists (ASA) scores.
Source: Based on Eugster et al. [2].
| ASA I | Normal, healthy patients |
| ASA II | Patients with mild systemic disease |
| ASA III | Patients with severe systemic disease |
| ASA IV | Patients with severe systemic disease that is life‐threatening |
| ASA V | Patients that will not survive 24 h without surgical intervention |
While decolonization may not be feasible, it is reasonable to alter perioperative antimicrobial prophylaxis in MRSP carriers undergoing higher risk procedures like TPLO. This may include measures such as adding a single dose of amikacin preoperatively to the typical (e.g., cefazolin) antimicrobial regime, assuming renal health has been evaluated.
2.2.4 Dermatitis, Clipping, and Skin Preparation
As mentioned, Staphylococcus spp. are amongst the most common bacteria causing SSIs. S. pseudintermedius is a commensal bacteria within the normal microbiome of dogs [39]. Assessment of the animal's skin for evidence of local or distant dermatitis is recommended, to reduce the risk of contamination of the surgical site (Figure 2.1). Despite this logical recommendation, 17.5% of all animals undergoing TPLO in one study had evidence of active local or distant dermatitis. Of those with local dermatitis, 16.7% developed an SSI and 10.2% with distant dermatitis developed an SSI [27]. As there was no significant difference identified between local and distant dermatitis resulting in SSI, the risk for SSI development should not be considered lower for animals with dermatitis not affecting the direct surgical site, as anecdotally thought, and postponement of elective orthopedic surgeries with local or distant dermatitis should be considered [27].
Identifying the underlying cause of the skin disease is paramount for improving the skin barrier and reducing the risk for SSI development. Depending on the type and severity of the dermatitis, cleansing with medicated shampoos, application of topical antimicrobials or antifungals and/or systemic antimicrobials or antifungals may be required. When managing bacterial dermatitis, local to or distant from the surgical site, culture and susceptibility testing is recommended to guide antimicrobial therapy and determine if MRSP is present. While awaiting these results, empirical treatment is recommended with cephalexin (22–30 mg/kg, PO q8h) or clindamycin (11 mg/kg, PO q12h). Antimicrobials should be continued for 1 week beyond resolution of clinical signs.
Ideally, the surgical site should be free of skin lesions prior to considering surgery. In circumstances where postponing surgery is not possible, topical treatment is recommended, along with the addition of amikacin to the routine perioperative antimicrobials. When lesions are located at sites other than the surgical site, topical treatment is recommended + systemic medications as determined by the extent of the disease process. Bathing these patients with a chlorhexidine shampoo the night prior to surgery can also be considered [40].
Before skin preparation can occur, hair is clipped from the proposed surgical field to facilitate direct skin preparation and the limb is suspended (Figure 2.2). Clipping should be performed following induction of general anesthesia and not sooner due to the increased risk for SSI development [41, 42]. This risk is likely associated with the greater potential for direct skin trauma that may occur when attempting to clip hair on a conscious patient. Any microtrauma caused by rough clipping or poorly maintained clipper blades may also play a role in increasing the risk for SSI development.
Skin preparation (Figure 2.3) begins with the removal of surface dirt and oils using a neutral, nonmedicated soap as antiseptic agents are not active in the presence of organic material. Antiseptic agents are subsequently applied to reduce the bacterial load present on the skin at the time of surgery. Antiseptic agents commonly used in veterinary medicine include povidone‐iodine and chlorhexidine gluconate (Figure 2.4). These antiseptic solutions are applied to the skin using a scrub technique or a paint or spray technique. Ultimately, contact time, meaning the time the antiseptic solution is in direct contact with the skin, is the most important aspect of skin
