Complications in Equine Surgery. Группа авторов

the suture material should be compatible with the tissue type being sutured and the anticipated post‐operative incisional tension [5, 9]. The suture should be as strong as the normal tissue through which it is placed [2, 3]. The rate of loss in tensile strength of the suture material and the gain in wound strength of the sutured tissues over time should coincide {2, 3]. Monofilament suture material has the advantages of low tissue drag and low tendency to foster infection [15]. There has been no beneficial effect in the use of antibiotic‐coated suture material in preventing suture‐related complications [16].

      Tension forces are converted to shear forces at the suture knot, thus making the knot the weakest point of the suture loop [9]. Secure square knots are important in preventing dehiscence and the appropriate number of throws for good knot security depends on the suture material characteristics and the nature of the suture pattern (interrupted vs. continuous) [3]. A surgeon's throw is only indicated when needed to appose the tissues, otherwise it is contraindicated, especially in deeper layers such as facial, subcutaneous, organs, joint capsule, paratenon, etc. [3] Unnecessary throws on a knot or the use of a surgeon's throw makes a bulkier knot and increases suture material within the tissues, thus increasing the risk of delayed wound healing, pressure necrosis, suture extrusion, and infection [3, 17].

Wound/incision location and the tissue layer being sutured will have important influence on the appropriate suture pattern indicated [3]. There is a wide variety of suture patterns (interrupted vs. continuous, inverting vs. everting, and tension sutures) and each have advantages and disadvantage which must be considered when determining an appropriate pattern for the given location, tension, and organ or tissue layer being sutured [3]. Interrupted sutures increase the amount of suture material in the wound/incision when buried and increase surgery time and cost [3]. Continuous patterns lack the ability to vary tension along the suture line and knot or suture failure can be catastrophic to the entire length of the apposed tissues [3]. Also, simple continuous and horizontal suture patterns can compromise the vascular supply to the wound/incision edge resulting in increased inflammation and edema formation [3, 11]. Depending on the wound/incision location, inversion, eversion, or edge‐to‐edge may be advantageous. Inversion is advantageous in preventing leakage in hollow viscera closure but also will reduce the luminal diameter of viscera, which can lead to complications which are discussed in the respective chapters. Slight eversion is recommended when there is a tendency for the skin edges to invert and the slight eversion results in positive cosmetic outcome [3]. A continuous intradermal pattern results in the best cosmetic outcome and does not require suture removal; however, there is a potential for suture fistula formation if improper technique was used and the epidermis was included in the closure.

      Incised wounds have limited tensile strength during the inflammatory phase of wound healing and apposition is primarily achieved by the suture [9]. Excessive tension placed on the suture line should be avoided, as the tissue’s ability to hold suture has more influence on the repair than the strength of the suture material itself [2, 3]. For wounds/incisions under tension it is discouraged to use a larger suture size; instead it is recommended to increase the number of sutures and use of appropriate tension relieving sutures in the suture line [2, 3]. Other options of tension relieving techniques, such as undermining, walking sutures, tension‐relieving incisions, mesh expansion, tissue flaps or plasties, can be used to prevent occurrence of dehiscence from tension [3, 6, 7]. Staggered suture removal in areas of tension is also recommended to prevent incisional dehiscence [6].

      Even the least reactive suture materials act as foreign material and decrease the ability of the wound to resist infection, thus suture number, suture size, and number of knots should be minimized [3, 9]. However, there is usually a variety of sutures that can be used with a favorable outcome in most situations, so surgeon preference can be considered in suture selection [9].

      Hematoma and seroma formation can be prevented by adequate intraoperative hemostasis, atraumatic surgical technique, and closure of dead space created [5]. Drains should be placed intraoperatively if seroma formation is anticipated [5]. As well adequate compression, bandaging should occur in indicated areas to prevent hematoma or seroma formation. Proper placement is essential and they should not be used as a substitute for proper wound cleansing, debridement, and lavaging [3]. Drains are not benign, so close monitoring and aseptic technique during bandage changes is important to prevent retrograde bacterial migration and excessive tissue irritation [3]. To prevent complications associated with drains, they should be removed as soon as possible, such as when there is a decrease in drainage or change from purulent or serosanguinous to serous and non‐odoriferous, and is typically at 2–4 days but varies depending on location and wound environment [3].

      Severely traumatized tissues or tissues suspected of blood supply loss should not be closed too soon and should be closely monitored until viability is ensured [5]. In some circumstances it is recommended to suture the tissues initially before viability is ensured, such as if it is over a joint or there is exposed cortical bone. An understanding and acceptance of tissue necrosis and future partial dehiscence in these circumstances may be of more benefit to overall healing and these expectations should be discussed in advance with the owner.

      Confinement should be used effectively to adequately immobilize excessive motion. Confinement and exercise may range from a cross tied patient to stall confinement to paddock turnout to pasture turnout, depending on the surgery and postoperative time frame. Horses should be introduced to exercise appropriately for the given surgical procedure performed and to allow for continued remodeling and strengthening of the incision.

      Incisional dressing and bandaging provide a barrier to environmental contamination but can also play a key role in decreasing motion of the surgical site. The location and surgical procedure performed will determine whether a light bandage, compression bandage, stent bandage, or no bandage is appropriate. In areas of high motion, such as over a joint, casting or splinting may be considered necessary for that specific case [7].

      Ensuring proper postoperative nutrition for the patient’s metabolic needs will help prevent a delay in wound healing due to protein and vitamin deficiencies [7, 18].

      Ensuring more focused or localized neoplastic treatment with radiation therapy and protection of adjacent healthy tissues is important in preventing unnecessary complications with wound healing [19, 20].

      General recommendations are difficult to make based on the current literature, but in wounds with suspected incomplete tumor resection, it has been thought to delay intra‐tumoral chemotherapy until wound healing has begun (7–14 days) to decrease the risk of dehiscence [5, 21].

       Diagnosis

      Dehiscence can occur from the immediate postoperative period up to several weeks after surgery. Dehiscence during the anesthetic recovery or soon after surgery can be a result of self‐induced trauma or inadequate steps to immobilize the region, confine the patient, or relieve tension on the suture line as appropriate. Most commonly, incisional dehiscence will occur 4–5 days postoperatively [5]. Clinical signs that may develop prior to dehiscence include serosanguineous discharge or in the case of an infection, a purulent odorous discharge. Tissue swelling, heat, and necrosis of the sutured tissue edges along with pain to palpation may also be evident prior to dehiscence. Dehiscence is diagnosed at the time where there is superficial or deep and partial or complete separation of the previously sutured wound or incision. Identifying any primary cause for the dehiscence before assuming it was a result of infection is important, since with incisional disruption and dehiscence there is often secondary infection present [5]. Clinical signs associated with incisional infections include incisional swelling, heat, pain, and drainage of a purulent nature [13]. If there is a suspected infection present, regardless of whether it was the primary cause or secondary to another cause, a deep swab should be obtained of the infected area after aseptic preparation [6]. The swab is then submitted for aerobic and anaerobic bacteriological culture and sensitivity testing. In some cases, a fungal culture is recommended. The degree of bacterial contamination will help determine the most appropriate wound management, thus qualitative and quantitative cultures can be beneficial [7]. If a foreign body and sequestra is the underlying cause of the dehiscence, it can be identified or