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When possible, adult cattle should be fasted for 24–48 hours and water withheld for 24 hours before induction of anesthesia. Small ruminants, camelids, and swine should be fasted for 12–24 hours and water withheld for 8–12 hours before induction of anesthesia. Preanesthetic fasting may not completely prevent regurgitation, but it will decrease the amount of solid matter in the rumen content. Fasting also does not prevent bloating during anesthesia, but it reduces the rate of fermentation, thus reducing the amount of gas formation, the severity of bloating, and its effect on ventilation. In pigs, removal of alfalfa or other types of hay from their routine diet should be instituted 2–3 days prior to anesthesia to avoid prolonged gastric emptying time caused by this type of diet [11]. A shorter fasting period of 6–8 hours is sufficient for pigs undergoing most elective surgeries due to rapid intestinal transport times in the upper GI tract and less time required to empty the stomach [60]. Ruminants are born without a developed forestomach system and thus can be treated as monogastrics until 3 weeks of age [61]. Fasting of young ruminants less than 4 months old is not recommended because of the potential for hypoglycemia and prolonged recovery. Fasting may not be possible under emergency situations, and precautions should be taken to avoid aspiration of gastric fluid and ingesta. Prevention of regurgitation and aspiration of ruminal content can be achieved effectively by placing the animal in sternal recumbency and endotracheal intubation instituted immediately following induction. However, some practices may induce anesthesia with adult cattle already strapped to the table and in lateral recumbency. In this case, it is even more important to ensure animals are under an adequate plane of anesthesia to prevent stimulation of active regurgitation and allow immediate intubation. Regurgitation does not occur in pigs as commonly as in ruminants. However, vomiting can result from nonfasting prior to induction of anesthesia and following administration of xylazine. In general, removal of hay or alfalfa and withholding food for 12 hours and water for 6–8 hours the night before anesthesia should be sufficient for most elective surgeries [23].

In adult cattle, a 14‐gauge and 2‐ to 3‐in. needle is placed in the jugular vein for administration of IV anesthetics for induction of anesthesia and for maintenance of fluid therapy. A 14‐gauge, 5¼‐in. indwelling catheter can be used if postoperative IV medication or fluid therapy is needed. Cutdown of the skin at the catheterization site may be helpful to facilitate insertion of the catheter. A 16‐ or 18‐gauge catheter is appropriate for younger animals. The technique for IV catheterization in sheep and goats is similar to that used in calves. Venipuncture can be difficult in camelids because they have thick fiber coats and neck skin, and a less‐apparent jugular groove. The jugular vein lies deep to the sternomandibularis and brachiocephalicus muscles, ventral to the cervical vertebral transverse processes, and superficial to the carotid artery and vagosympathetic trunk within the carotid sheath for most of its length [62–66]. The jugular vein of camelids is not always visible even after occlusion of the vessels, particularly in adult males. The right internal jugular vein is the best choice for catheterization in these animals. A 14‐ or 16‐gauge indwelling catheter is appropriate for adult camelids, and an 18‐gauge catheter is suitable for younger animals. Catheters should be secured with suture or bandage. Skin cut down with a #15‐scalpel blade or a sharp 14‐gauge needle is helpful in passing the catheter into the vein [67]. An ear vein can be an alternative site for IV injection using a 25‐gauge needle or butterfly catheter to deliver a small volume of chemical restraint drugs in camelids. Also, camelids have four or five jugular valves that prevent flow of venous blood into the head when they lower the head during grazing. These valves may occlude the IV catheter and prevent backflow of the blood into the catheter, giving a false impression that the catheter may not be correctly placed in the vessel.

In swine, IV injection poses a greater challenge than in other species because pigs resist restraint and they have very few superficial veins accessible for IV injection or catheterization for administration of drugs or fluid therapy. In Vietnamese potbellied pigs, IV catheterization has been even more difficult because they have small ears with small vessels and their skin is usually dark colored. In large adult pigs with proper restraint, a central dorsal ear vein can be used for IV injection and/or catheterization. An 18‐ or 20‐gauge, 1‐ to 1½‐in. hypodermic needle or butterfly catheter can be used for large adult pigs. A 21‐ or 23‐gauge butterfly catheter will be suitable for smaller‐sized pigs with small ears. This author prefers a butterfly catheter because it has a shorter needle and tends to stay in the vessel better than hypodermic needles, especially when the animal struggles during injection. Shorter needles are easier to hold in place and decrease the chance of perivascular injection. IM injection of anesthetics or anesthetic combinations to pigs has been shown to produce short‐term anesthesia effectively. Always keep in mind that pigs have a thick subcutaneous layer of fat, and thus, to ensure the drug is deposited into the muscle, a longer needle (≥1½ in. for large, mature pigs; 1 in. for piglets) should be used [23].

Tracheal intubation is somewhat difficult in ruminants, camelids, and pigs. Blind intubation as in horses is less likely to be successful. For large ruminants, this author's preference is to use digital palpation to guide the endotracheal tube into the trachea immediately following induction of anesthesia with the animal in either sternal or lateral recumbency (Figure 1.4a). Another technique involves use of a stomach tube as a stylet with the aid of digital palpation to place the stomach tube in the trachea; the stomach tube then serves as a guide tube (Figure 1.4b). The endotracheal tube is threaded into the trachea and the stomach tube removed once the endotracheal tube is in place. Intubation should be performed immediately after induction. In calves, intubation is easier when placing the animal in sternal recumbency and an assistant pulls the mouth open by placing a loop of gauze around the upper jaw and a second loop around the lower jaw and tongue. An assistant should lift the head and keep the head and neck in a straight line to allow visualization of the epiglottis and the larynx. If the larynx cannot be visualized, the neck should be extended further. A long laryngoscope blade (250–350 mm) can be used to suppress the tongue base and epiglottis to enable visualization of the larynx. A guide tube or stylet (preferably a 10‐French, 22‐in.‐long polyethylene canine urethral catheter that is three times the length of the endotracheal tube) can be used (Figure 1.5). A cuffed endotracheal tube will prevent regurgitation and aspiration of ruminal contents, and the calf should be maintained in sternal recumbency until the cuff is inflated.

Figure 1.4 (a) Intubation in an adult bovid using digital palpation technique: A, trachea; B, epiglottis; C, endotracheal tube/guide tube; D, wedge. (b) Intubation in an adult bovid using a guide tube technique: A, trachea; B, epiglottis; C, guide tube; D, wedge.

Source: Illustration by Kim Crosslin.

Figure 1.5 Guide tube/stylet and laryngoscope used for endotracheal intubation for small ruminants, camelids, and pigs.

Intubation is more difficult in small ruminants and camelids as compared to large ruminants and other animal species because their mouths do not open widely, the intermandibular space is narrow, and the laryngeal opening is distant to the thick base of the tongue (Figure 1.6). In camelids, the presence of glottal folds adds to the difficulty in visualizing the epiglottis. The technique used for tracheal intubation of small ruminants and camelids is similar to the technique used in calves. It is easier when the animal is placed in sternal recumbency immediately after induction of anesthesia. Intubation is best accomplished with the help of a guide tube/stylet and long‐bladed laryngoscope (250–350 mm) as described for intubation in calves. Hyperextending the animal's neck helps visualization of the larynx (Figure 1.7). The method makes endotracheal intubation in small ruminants and camelids much easier to achieve than with other methods. A cuffed endotracheal tube should be used to provide an adequate seal between the tube and the tracheal mucous membrane to prevent aspiration of saliva and regurgitated ruminal contents. The animal should be maintained in sternal recumbency until the cuff is inflated. Blind intubation, similar to that used in horses, has been used for intubation in sheep and goats; however, it may require multiple attempts to successfully place the endotracheal tube in the trachea. Another technique, described as stick intubation, has been used effectively at Auburn University. With the animal in lateral recumbency, a small‐diameter rod made of wood or stainless steel can be used as a stylet to stiffen the endotracheal tube. One hand occludes the esophagus, and the other hand manipulates the endotracheal tube into the trachea (Figure 1.8). Care and gentle maneuvering should be used to prevent initiating laryngeal spasm and to minimize trauma to the oral mucous membrane.

Similar to small ruminants and camelids, pigs' mouths cannot be opened wide, the epiglottis is often entrapped behind the soft palate, and the small larynx slopes downward, creating a sharp angle to the tracheal opening (ventral floor fornix) (Figure 1.9). Laryngeal spasms are easily elicited by repeated attempts at tracheal intubation. Vomiting can also occur if attempting intubation while the pig is under a light plane of anesthesia, especially when the animal is not appropriately fasted prior to anesthesia. Spraying a small amount of local anesthetic to desensitize the larynx will reduce the potential for laryngeal spasm. In larger or adult pigs, tracheal intubation is easier to accomplish with the pigs placed in sternal recumbency. Using the same technique as in small ruminants and camelids, with the aid of laryngoscope and guide tube/stylet, the epiglottis and laryngeal aperture can be visualized. Be aware of the sharp angle between the larynx and tracheal opening; it is helpful to apply some pressure to the end of the endotracheal tube as it enters the larynx. This technique keeps the tip of the tube slightly elevated and enables the endotracheal tube to pass into the trachea. Another helpful tip for successful endotracheal intubation in pigs is to spin the tube 180° or in a screwlike fashion, advancing it in a dorsal direction while the tube passes through the arytenoid cartilages into the trachea [68].

Figure 1.6 Anatomic structures for endotracheal intubation in camelids.

Source: Illustration by Kim Crosslin.

Figure 1.7 Endotracheal intubation in anesthetized goats.

Figure 1.8 “Stick intubation” (blind intubation) in anesthetized goats.

Figure 1.9 Technique for endotracheal intubation in swine.

Source: Illustration by Kim Crosslin.

It is important to understand the anatomical and physiological differences of ruminants, camelids, and pigs as compared to other species. Veterinarians should incorporate this knowledge with proper preanesthetic preparations and appropriate perioperative management to ensure successful outcome of anesthesia in these animals.