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<p>07:35 93% Colic. 40 de 82 manipulating the large viscera of the horse. The sensitivity and are Escherichia a gram-negative tacultative anaerobe, and the specificity of laparoscopy as a diagnostic technique are greater gram-positive Streptococcus and Staphylococcus spp.4 Gram-negative 526 SECTION V ALIMENTARY SYSTEM bacteria including E. coli are typically sensitive to gentamicin, level of the xiphoid to the inquinal region and extended out to a bactericidal aminoglycoside, and it is therefore considered to the rib cage before the skin is aseptically prepared for surgery. be a suitable first-choice Aminoglycosides are concentration-dependent antimicrobials and therefore the effectiveness of gentamicin is dependent on the peak concentration Surgical Approaches to the Abdomen A dose of 6.6 mg/kg IV is typically recommended to The most frequently utilized surgical approach to the abdomen achieve a peak plasma concentration greater than 25 of the horse with acute colic is the ventral midline celiotomy, or more than 8 to 10 times the minimum inhibitory concentration laparotomy. An incision is made through the skin and subcutane- (MIC) of E. coli. ous tissues starting at the level of the umbilicus and extending Gram-positive bacteria including the Streptococcus and Staphy- cranially for approximately 30 to 40 cm. Hemorrhage is controlled lococcus spp. are generally sensitive to penicillin, a bactericidal using hemostatic forceps or electrocautery to allow visualization with an MIC of at or below 0.5 The effectiveness of the linea alba. At the level of the umbilicus, the linea alba is of penicillin depends on achieving and maintaining a tissue approximately 10 mm thick and easily A small, 2- to concentration greater than the MIC for a prolonged period of 3-cm-long incision is made through the linea alba at or very Pharmacokinetic studies demonstrate that a penicillin close to the umbilicus, taking care not to incise any distended dose of 22,000 IU/kg administered by either the intravenous or The small incision in the linea alba is extended cranially intramuscular route will result in a serum concentration above using an instrument such as thumb forceps or the surgeon's MIC for both Streptococcus and Staphylococcus spp. Intravenous fingers to shield the viscera. As the incision extends cranially the administration results in higher peak serum concentrations, but linea alba becomes thinner and care should be taken to continue because of the short half-life (30-40 min) repeated intraoperative the incision in the dense, white, fibrous tissue on The administration after 4 hours may be warranted to ensure the incision should be extended approximately 30 to 40 cm to allow serum concentration remains above the Intramuscular complete exploration of the abdomen by palpation and exteri- administration of penicillin results in a significantly lower peak oristation of viscera without restriction or excessive tension serum concentration but greater half-life (20 hours), eliminating increasing the risk of iatrogenic damage to the viscera. The the need for repeated intraoperative Intravenous falciform ligament may be identified and the peritoneum is administration of antimicrobials is usually recommended in bluntly perforated by the surgeon's fingers to gain access to the human surgical prophylaxis guidelines, but the availability of peritoneal cavity. A ventral midline celiotomy allows the surgeon IV penicillin formulations and cost can be limiting factors in to exteriorize approximately 75% of the gastrointestinal tract, equine practice. The actions of penicillin and gentamicin are with the exception of the stomach, duodenum, distal ileum, synergistic, and they are therefore frequently administered together dorsal body and base of the cecum, distal right dorsal colon, for both prophylaxis and In an effort to prevent the transverse colon, and terminal descending colon (Figure development of antimicrobial resistance, enrofloxacin and the In cases where a significantly distentended fluid or food-filled third- and fourth-generation cephalosporins such as ceftiofur viscera is encountered or access to the stomach is required, the and cefquinome should not be administered for the purposes incision can be extended cranially as necessary. of surgical prophylaxis.4 Closure of the linea alba in the adult horse is performed with Although there is limited information on the effect of timing large absorbable suture material in a simple continuous pattern of antimicrobial administration on the effectiveness of prophylaxis placing bites between 1.2 and 1.5 cm from the wound margin. in the horse, evidence from human surgery suggests that admin- Common choices of suture material include polyglactin 910 (USP istration should occur within 60 minutes of clean-contaminated size No. 6, metric size No. 8) and polydioxanone (USP size No. surgery. All colic surgery is potentially 7, metric size No. 9). Dissection of the subcutaneous tissues therefore preoperative administration of antimicrobials is recom- to ease placement of sutures in the linea alba is not recom- mended. Early (>120 min) or late (<30 min) administration mended as it is associated with an increased risk of incisional prior to surgery reduces the effectiveness of prophylaxis in complications, most likely because of the increased deadspace. Since antimicrobials are frequently administered prior to the Clinically, dehiscence of the body wall in the perioperative period induction of anaesthesia, effort should be made to limit the is To reduce the risk of incisional infection, the linea time for surgical preparation to 1 hour and account for this time alba should be lavaged with sterile isotonic fluids before closure when considering repeat dosing of drugs with a short of the subcutaneous tissues. Absorbable suture material, typically If antimicrobials are administered under general anesthesia, the USP size 2/0 (metric size 3.5), in a simple continuous pattern potential adverse effects such a decrease in blood pressure should is typically used to close the subcutaneous tissues. The skin is be anticipated and managed as necessary. closed with either nonabsorbable monofilament suture material, If the colic patient has not already received an NSAID, flunixin absorbable suture material, or skin staples; however, there is meglumine (0.25-1.1 mg/kg IV) should be administered pre- some evidence that skin staples are associated with an increased operatively to treat surgical pain and endotoxemia. risk of incisional Modifications of the standard Before surgery, a nasogastric tube should be placed to allow wound closure have been a study found that a 2-layer stomach decompression during surgery as necessary. The horse's closure of linea alba and combined subcutaneous and subcuticular mouth should be rinsed to prevent aspiration of feed material tissues had a decreased risk of incisional drainage when compared during intubation. Any bedding or other material in the horse's with a standard 3-layer However, a study comparing a hair coat should be removed with a dry brush to reduce con- standard 3-layer closure to a 2-layer closure without a subcutane- tamination of the operating room. Following induction of ous layer found no difference in wound The anaesthisia the horse is positioned and secured in dorsal skin can be sutured in an interrupted or continuous pattern; recumbency. An indwelling urinary catheter should be placed and one author prefers to use USP size 2/0 (metric size 3.5) and in male horses the penis should then be secured within the polypropylene in a Ford interlocking pattern (JFM). Finally, a prepuce by suturing it closed. The hair coat is clipped from the wound stent or incise drape is applied to protect the wound CHAPTER 33 COLIC 527 skin and muscle layers. A skin incision is then made centered between the tuber coxae and last rib, just proximal to the palpable 1. Exteriorized dorsal edge of the internal abdominal oblique muscle. The external 2. Visualized but not abdominal oblique muscle is then sharply divided vertically, exteriorized whereas the internal abdominal oblique and transverse abdominal 3. Palpated but not muscles are bluntly divided parallel to their fiber directions, visualized usually with the surgeon's hand or a pair of Mayo scissors. The peritoneum is bluntly perforated by a short thrust with the fingers or scissors. The incision is closed by apposing the muscle layers with absorbable suture material in a simple continuous pattern before closing the skin with either staples or nonabsorbable suture material in a simple interrupted or continuous When performing surgery on a stallion with an inguinal hernia, an inguinal approach is used in conjunction with a ventral midline incision The inguinal approach allows access to the incarcerated intestine while the ventral midline approach allows complete exploration and decompression of stenotic and poststenotic intestine A skin incision is made the superficial inguinal ring and blunt dissection of the soft tissues is performed to expose the parietal tunic, which is sharply incised to reveal the</p>