Complications in Equine Surgery. Группа авторов
and sedating horses with an alpha‐2 agonist, such as detomidine, to relax the esophagus [3]. It is important to note that smaller tube size may increase the risk of certain misplacements and sedation may impede the swallowing reflex. The risk of prolonged intubations in horses with persistent gastric reflux needs to be balanced against the risk of repeated, intermittent intubations.
Diagnosis
In most cases, mild pharyngeal trauma and bruising is subclinical and would only be recognized if the horse undergoes endoscopic inspection of the nasopharynx. Endoscopy was necessary to diagnose the pharyngeal trauma after horses developed clinical signs of ptyalism, dysphagia, bruxism, and coughing attributed to pharyngeal trauma [3]. Clinical signs of esophageal trauma have been reported to be indistinguishable from pharyngeal trauma [3]; however, other studies describe the concurrent presence of fever, cervical swelling, and cellulitis when esophageal perforation has occurred [8, 9]. In some perforation cases, the cellulitis and infection may travel caudoventral along the fascial planes towards the mediastinum.
Endoscopy is helpful in identifying esophageal ulcerations and perforations, although small perforations may be hidden within the esophageal folds in some cases [9]. In those situations, ancillary diagnostic tests, such as radiology and ultrasound, may be helpful to support the diagnosis and document the extent of cellulitis.
Treatment
Treatment of pharyngeal trauma and esophageal ulceration is antimicrobial therapy and anti‐inflammatory drugs to manage cellulitis, if present, and feeding of soft feeds or mashes if the horse is dysphagic. Sucralfate may aid in healing of esophageal ulcerations. Tracheostomy may be necessary if pharyngeal or peri‐esophageal swelling causes upper respiratory tract obstruction. Surgical debridement of esophageal perforations is recommended to establish ventral drainage and excise infected tissues. Broad spectrum antibiotic therapy is required because of the significant degree of contamination and extension of infection along fascial planes. Nutritional and fluid support is a major challenge in these cases, because of the esophageal defect and the need for it to heal. The risks and benefits of indwelling nasogastric tubes versus esophagostomy tubes need to be considered in each individual case [9].
Expected outcome
Prognosis for subclinical pharyngeal trauma and bruising is excellent, whereas prognosis for clinically evident pharyngeal trauma is guarded and depends on the ability to manage the cellulitis and avoid associated complications, such as antimicrobial associated colitis and laminitis [3, 7]. Prognosis for survival after esophageal ulceration is good, although stricture may occur with extensive or circumferential ulcerations. Prognosis for esophageal perforations is guarded, because there is often a delay in treatment, resulting in extensive cellulitis and tissue damage subsequent to the leakage of saliva and feed into the periesophageal tissues with subsequent abscessation, mediastinitis, and tissue necrosis [8, 9].
Fragmentation of Tube
Definition
Fragmentation of the tube refers to complete structural failure of the tube, resulting in discontinuity of the tube.
Risk factors
Repeated use of tubes
Retroflexion into oral cavity
Exposure to sunlight, chemical agents, or environmental extremes
Pathogenesis
Nasogastric tubes can fragment if they are brittle, have defects, or become retroflexed into the oral cavity. Nasogastric tubes can become brittle over time and with repeated use, especially if exposed to sunlight, chemical agents, or temperature extremes [10]. Tubes may also fragment if a horse chews on a tube which retroflexes into the oral cavity [6]. These fragments may remain within the esophagus or stomach.
Prevention
Nasogastric tubes should be frequently inspected to ensure that they are in good condition and without any defects or damage. Care should be taken to avoid oral retroflexion of nasogastric tubes and immediate correction, if it occurs. Awareness and prompt recognition of the problem may reduce the chance of complete transection of the tube. If the tube has been misdirected into the oral cavity, it should be removed and inspected for damage before continuing with nasogastric intubation.
Diagnosis
Once it is recognized that the tube is incomplete, it is essential to immediately locate the position of the fragmented segment of tube. This should include an oral examination, because some fragments may be retrieved orally [11]. If this is not successful, external palpation of the neck, endoscopic examination of the esophagus and stomach, and cervical and thoracic radiographs may locate the fragment [6, 11]. Multiple fragments may be present, so it is important that the entire tube is retrieved [10, 11].
Treatment
Treatment requires removal of the fragmented tube to prevent further gastrointestinal obstruction and trauma. The method of removal depends on the location of the tube, available equipment, and the success of each technique. Manual extraction from the oral cavity can be performed if the tube is located in the oral cavity and is facilitated by general anesthesia to allow safe and thorough manual exploration [11]. Homemade or commercially available snares can be used to endoscopically snare and retrieve tube fragments, either using standing sedation or general anesthesia [6, 10]. Surgical removal by esophagotomy or gastrotomy has been used in selected cases when other methods of retrieval were unsuccessful [6, 10].
Expected outcome
If nasogastric tube fragments are not removed, it is likely that they may cause future intestinal obstruction or injury and require emergency exploratory celiotomy (Figure 5.3).
Administration of Fluid into Lungs
Definition
Aspiration pneumonia in this circumstance is caused by administration of enterally administered fluids or medication into the lung.
Risk factors
Improper technique
Inadequate restraint
Incomplete passage into the stomach
Improper removal of the tube
Pathogenesis
Administration of fluid into the lungs can be a consequence of misplacement of a tube into the trachea or it may result from spillage from a properly placed nasogastric tube. The severity of the resulting pulmonary pathology depends on the type and volume of fluid that enters the lung. There are several mechanisms by which nasogastric procedures can result in aspiration pneumonia. First, the nasogastric tube may be misplaced into the trachea by improper technique, inadequate restraint, or by impaired swallowing reflexes in obtunded patients (Figure 5.1) [12]. Second, incomplete passage of the tube into the stomach or esophageal intubation may allow reflux of administered medication or fluid from the esophagus and into the trachea [12]. Third, rapid administration or administration of a large volume of fluid or medication into an already filled stomach can result in esophageal reflux and aspiration of that reflux into the lungs [12]. Fourth, failure to completely empty the tube, failure to kink or occlude the tube while removing, or rapid removal of the tube may allow any residual fluid or medication within the tube to spill into the nasopharynx where it can be aspirated [12].