HOW-TO SESSION: FIELD SURGERY - SOFT TISSUE AND WOUND MANAGEMENT


ternal hemorrhage should involve supportive care in the form of IV fluids and possibly aminocaproic acid (100 mg/kg, IV). Referral should be considered if internal bleeding is suspected, hemorrhage is pro- longed, its source cannot be identified, or signs of hypovolemic shock develop.


5. Eventration/Evisceration


Although a rare complication of castration, eventra- tion of the small intestine through the inguinal rings is oftentimes fatal. A breed predilection for in- creased risk may occur with Standardbreds, Draft Horses, and possibly Saddlebreds and Tennessee Walking horses. Recently, a large online survey was conducted of equine practitioners with regard to eventration following castration, which agreed with an earlier study that the overall incidence of this complication is low (0.2%).6 The survey also sug- gested that castrations performed standing and the use of emasculators vs twisting the cord until break- age were less likely to lead to eventration.7 When eventration occurs, initial therapy should be aimed at protecting the bowel from further damage. The bowel should be thoroughly lavaged with sterile iso- tonic fluids and held in place in the scrotal incision with large sutures or towel clamps. If more intes- tine has passed through the incision than can be held within the scrotal remnant, a sling may be fashioned with a small towel sutured to either side of the scrotal skin. Alternatively, the horse may be re-anesthetized and the external inguinal ring enlarged to allow the bowel to be replaced within the abdomen. Replacing the bowel into the abdomen once a horse has been re-anesthetized is generally not possible due to edema that forms in the intesti- nal wall and mesentery once eventration has oc- curred. The internal inguinal ring is not readily accessible; however, with one hand acting as a re- tractor to protect the intestine against further dam- age, a pair of surgical scissors or a curved bistoury may be guided into the cranial end of the external inguinal ring and the ring may be extended several centimeters. This greatly facilitates replacement of the intestine into the abdomen but also requires primary closure of the external inguinal ring with heavy-duty absorbable suture.5 The author prefers to use #2 polyglactin 910a threaded through a her- nia/kidney needle with the two ends tied together. Once the blunt point of the needle is guided across the cranial aspect of the external inguinal ring, the needle can be pulled through the loop of suture so no knot is needed and subsequent bites are facilitated by holding the suture in traction. Further bowel prolapsing through the canal during transportation to a referral hospital is unlikely with the eternal inguinal ring sutured closed and further damage to the intestine should be halted. If one is unfamiliar with suturing the external inguinal ring a thorough knowledge of the anatomy is helpful and an assis- tant, if available, will greatly facilitate the proce- dure. The horse should be sent for an exploratory


laparotomy as soon as possible because the intestine cannot be adequately evaluated for viability in the field. Broad-spectrum antibiotic therapy and NSAIDs are instituted prior to shipping. It is the author’s opinion that the further one is from a sur- gical facility, the more one should consider re-anes- thetizing the horse and attempt to replace the bowel into the abdomen with closure of the external ingui- nal ring if an effort to save the horse is going to be made.


6. Other Considerations


Duration of surgery may be related to an increased complication rate so having all instruments open and set out prior to anesthesia can save valuable time. Less additional anesthesia may be needed if Lidocaine is used to directly infuse the testicle and possibly the spermatic cord in order to maintain a deeper plane of anesthesia.6 Injury to the penile shaft has been reported dur-


ing routine castration. A quick review of the rele- vant anatomy and double checking that the correct structures are present prior to emasculation should reduce the chances of inadvertently damaging any unrelated tissue.5 There are reports that use of the Henderson


equine castration tool results in fewer complications and may decrease surgical time by twisting the cord until breakage rather than emasculation.8 Use of the Henderson castration tool has become relatively common although this author has limited experi- ence with its use. Some thought should be given to anesthetic com- plications during even short field procedures. Fa- cial nerve paralysis can result from direct pressure to the facial nerve from the buckle on a halter so the halter should be removed until the horse is ready to be stood up. Pulling the down leg forward will de- crease the likelihood of radial nerve paralysis. Care should be taken to find the safest place to perform castration in the field with regard to steril- ity and safety from fixed objects when standing. Covering the patient’s eyes and keeping the environ- ment quiet will help maintain horses in recumbency until they are ready to stand. If a horse is to stum- ble and fall as they stand, they generally fall for- ward so an assistant applying steady traction to their tail as they stand, and then quickly relieving the tension once they are up, frequently provides for a better recovery. Once the horse is standing, the tail should be released, and the assistant can care- fully put a hand on the cheek piece of the halter and one on their shoulder until they are steady on their feet.


7. Conclusion


While complications associated with castration can- not be eliminated, proper preoperative planning, good surgical technique, and early recognition and treatment will improve outcome. Having every- thing needed to address complications as they arise


AAEP PROCEEDINGS  Vol. 65  2019 175


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