A 6.3-kg (13.9-lb) 4-hour-old female Huacaya alpaca cria, accompanied by its dam, was admitted to a veterinary medical teaching hospital because of respiratory distress and difficulty nursing since birth (day 0). On admission, the cria was bright, alert, and responsive; it was able to stand on its own, and had a suckle reflex. The cria was tachycardic (heart rate, 160 beats/min) and had open-mouth breathing (80 breaths/min); its rectal temperature was within the reference range at 37.5°C (99.5°F). The oral mucous membranes were cyanotic, and no airflow could be detected from either nostril during expiration. Introduction of a 5F flexible red rubber tube into the ventral meatus of each nostril revealed the lack of patency of either of the choanae. On the basis of these findings, a presumptive diagnosis of congenital complete bilateral choanal atresia was made. Evaluation of the head by CT was recommended to confirm the diagnosis and determine the type of choanal obstruction.
Supplemental oxygen delivery was initiated via face mask at a rate of 5 L/min. The patient was anesthetized and intubated orotracheally, and CT images of the nasal cavities and nasopharynx were acquired with 1.25-mm-thick slices in the transverse plane and reconstructed with imaging software.a Evaluation of the images revealed membranous obstruction of the nasal cavities bilaterally (3 mm thick on the left side and 5 mm thick on the right side) at the level of the choanae (Figure 1). These findings were consistent with a diagnosis of congenital complete bilateral membranous choanal atresia. The owner was informed that the prognosis was poor and that the condition could have a genetic component,1,2 but declined euthanasia and elected surgery. The cria was immediately taken to surgery.
A 5.2-mm fiberoptic bronchoscopeb was introduced into the oral cavity and retroflexed into the nasopharynx to allow visualization of the caudal aspect of the choanal membranes. The site to be perforated was located by placement of gentle pressure on the choanal membrane with a 10F red rubber tube passed through the right nostril. The stylet of a 14-gauge IV catheter was introduced through the red rubber tube and was used to perforate the choanal membrane at the intended site (Figure 2). A guidewire was introduced through the stylet, the stylet was removed, and a tissue dilatorc was passed in an over-the-wire manner to dilate the puncture in the choanal membrane. The tissue dilator was replaced with an 8-mm-diameter balloon dilatord (size selected on the basis of measurements on the CT images), which was insufflated to the maximum pressure (830 kPa [8.2 atm]) for a duration of 10 minutes. The balloon dilator and guidewire were then removed. The procedure was repeated on the left side. Patency of each choana was verified by instillation of saline (0.9% NaCl) solution through each nostril under endoscopic guidance. A temporary tube tracheostomy was performed in the proximal cervical region at the end of the procedure.
During anesthesia, lactated Ringer solution with supplemental glucose at a final concentration of 2.5% was administered (5 mL/kg/h [2.3 mL/lb/h]). Assessment of the patient's PCV and serum total solids concentration 3.5 hours after anesthetic induction revealed anemia (PCV, 22%; reference range, 25% to 37%) and hypoproteinemia (total solids concentration, 35 g/L; reference range, 45 to 55 g/L). Whole fresh blood from the dam (total volume, 46 mL) was administered IV because of active surgical bleeding and potential hemodilution. The cria's arterial blood pressure decreased substantially (from 73 to 50 mm Hg, as measured by direct blood pressure) during surgery, and colloid administration was needed. On the basis of the serum total solids concentration and the assumption that passive transfer was deficient because of the patient's inability to nurse, fresh frozen plasma administration was initiated during anesthesia (5 mL/kg/h [2.3 mL/lb/h] for a total of 37 mL) and continued after surgery to deliver a total volume of 160 mL (25.4 mL/kg [11.5 mL/lb]). The total crystalloid volume administered during anesthesia was 15 mL (2.4 mL/kg [1.1 mL/lb]). The tracheostomy tube was left in place for the postoperative period.
Perioperatively, the cria received ceftiofur sodium (2.2 mg/kg [1.0 mg/lb], IV, q 12 h) and 1 dose of flunixin meglumine (1.0 mg/kg [0.45 mg/lb], IV). Five hours after anesthetic recovery, the cria was found with signs of respiratory distress due to obstruction of the tracheostomy tube. Arterial blood gas measurements revealed severe hypoxemia (Pao2, 25 mm Hg; reference range, 80 to 100 mm Hg) and severe hypercapnia (Paco2, 64 mm Hg; reference range, 35 to 45 mm Hg) with a pH of 7.23. The tracheostomy tube was replaced, and signs of respiratory distress resolved. Thereafter, the tube was changed every 8 to 10 hours from days 0 to 3, and a mucolytic agent (acetylcysteine, 20 mg [0.1 mL of a 200-mg/mL solution]) was instilled every 4 hours into the tracheostomy tube. The cria was able to stand and nurse without assistance ≤ 8 hours after surgery.
On day 1, thoracic auscultation revealed increased lung sounds with intermittent wheezes. Thoracic radiographic examination revealed a bronchointerstitial pattern in the caudodorsal lung lobes. Results of a CBC revealed relative neutrophilia (9.77 × 109 cells/L [89%]; reference range, 34.9% to 63%) with a band neutrophil count of 0.11 × 109 band cells/L (reference range, 0 × 109 band cells/L to 0.36 × 109 band cells/L), 1+ toxic changes in neutrophils (evidenced by the presence of 1 or more Döhle bodies/cell, mild basophilic cytoplasm, or both; scale, 1+ [mild] to 3+ [severe]) indicating the presence of inflammation, and lymphopenia (0.55 × 109 cells/L [5%]; reference range, 18.3% to 41.9%).3 Aspiration pneumonia was suspected, and treatment with ceftiofur sodium was continued at the previously described dosage until the cria was discharged from the hospital.
On day 3, the tracheostomy site was temporarily occluded to allow patency of the choanae to be assessed. The cria became severely dyspneic with no airflow evident from either nostril, consistent with bilateral obstruction of the choanae. The owner declined euthanasia, and revision of the previous puncture sites was performed. With the cria under general anesthesia in sternal recumbency, the 5.2-mm flexible fiberoptic bronchoscope was introduced through the left nostril. The previous surgery site was observed, and a guidewire was passed through the initial puncture site into the nasopharynx. A 4-mm-internal-diameter silicone endotracheal tubee was threaded over the wire, pushed through the puncture site in the choanal membrane, and left in place to serve as a stent. The procedure was repeated on the right side. At the end of the procedure, each stent was cut close to the nostril opening and sutured in place. The tracheostomy tube was again left in place for the postoperative period.
The cria recovered uneventfully from anesthesia and was able to nurse without apparent disturbance from the stents. After removal of the tracheostomy tube on day 4, the cria failed to breathe through its nostrils and resumed open-mouth breathing. Endoscopic evaluation with a 2.85-mm-diameter flexible endoscopef revealed the presence of a small flap of granulation tissue obstructing the tracheal lumen immediately distal to the tracheostomy site, with the nasal stents remaining patent. Excessive granulation tissue in the trachea was removed with grasping forceps, which resolved the dyspnea. The tracheostomy site was allowed to heal by second intention.
On day 5, the nasal stents became occluded with mucus, and the cria resumed open-mouth breathing. Nebulizationg was performed, with a solution of acetylcysteine (20 mg [0.1 mL] diluted into 5 mL of distilled water) administered through a face mask to facilitate aspiration of mucus with a medical suction device. Thereafter, nebulization and cleaning of nasal stents by aspiration were necessary to maintain patency of the stents and were performed every 2 to 6 hours until stent removal. During hospitalization, the cria remained alert, nursed well, and gained 2 kg (4.4 lb) in 13 days.
On day 14, both nasal stents were removed, and the cria did not develop further signs of upper airway obstruction. No major complications occurred, except occasional accumulation of mucoid secretions in the nostrils, which resolved with serial intranasal instillation of 0.5 mL of physiologic saline solution.
The cria was discharged from the hospital on day 17; the owner was given instructions to continue nasal administration of physiologic saline solution as needed and to continue treatment with ceftiofur (2.2 mg/kg, SC, q 12 h) for 8 more days. Considering the potential genetic component of choanal atresia,1,2 it was suggested that the owner exclude this alpaca from the breeding population. At 5 months of age, follow-up by telephone with the owner revealed the cria was healthy, gaining weight normally, and breathing with a mild respiratory noise only. According to the owner, its subsequent growth was slower than that of herdmates of similar age during the first year of life; however, at 24 months of age, its weight was considered appropriate for an adult alpaca, and its body condition score was considered appropriate. At the time of last follow-up, the patient was 3 years old; the owner reported that the respiratory noise had gradually decreased over the first 2 years and was subsequently difficult to detect. The alpaca was kept in the herd for fiber production and had not been bred.
No source of funding was used for this clinical report.
Osirix imaging software, Pixmeo SARL, Bernex, Switzerland.
BF-160, Olympus Canada Inc, Richmond Hill, ON, Canada.
Multi-Lumen Central Venous Catheterization Set with Blue FlexTip Catheter, Catalog No. CS-14703, Arrow International, Reading, Penn.
Medi-Tech BMQ/8-4/5-8/75 , Boston Scientific-Meditech, Watertown, Mass.
COOK-SurgiVet, Dublin, Ohio.
11278 AUI/CE 0123, Karl Storz GmbH and Co KG, Tuttlingen, Germany.
MedPro Compressor Nebulizer System, AMG Medical Inc, Montreal, QC, Canada.
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