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This retrospective study assesses postoperative complications with simultaneous staphylectomy and unilateral arytenoid lateralization (SP + UAL) in dogs with laryngeal paralysis and concurrent elongation of the soft palate compared to dogs having a UAL alone. Medical records of dogs having a UAL performed from 2010 to 2013 were reviewed. Twenty-three dogs were diagnosed with a concurrent elongated soft palate and had a SP + UAL performed and 89 dogs were diagnosed with an appropriate soft palate and had only a UAL performed. A telephone questionnaire for long-term postoperative outcomes was completed. Survival probability was not statistically different between the 2 groups. Dogs in the SP + UAL group were more likely to be seen for respiratory distress after surgery (P = 0.05). There was no significant difference between the 2 groups in the number of dogs which developed postoperative aspiration pneumonia. The overall complication rate for both groups was high, with postoperative pneumonia being the most common complication.
Staphylectomie et latéralisation unilatérale de l’arythénoïde simultanées chez des chiens manifestant de la dyspnée : 23 cas (2010–2013). Cette étude rétrospective évalue les complications postopératoires associées à une staphylectomie et à une latéralisation unilatérale de l’arythénoïde (SP + LAU) simultanée chez des chiens atteints de paralysie laryngée et d’allongement concomitant du palais mou comparativement à des chiens atteints seulement de LAU. Les dossiers médicaux de chiens qui avaient subi une LAU de 2010 à 2013 ont été examinés. Vingt-trois chiens ont été diagnostiqués avec un palais mou allongé concomitant et ont subi une SP + LAU et 89 chiens ont été diagnostiqués avec un palais mou conforme et avaient subi seulement une LAU. Un questionnaire téléphonique pour les résultats postopératoires à long terme a été rempli. La probabilité de survie n’était pas statistiquement différente entre les deux groupes. Il était plus probable que les chiens du groupe SP + LAU soient examinés pour une détresse respiratoire après la chirurgie (P = 0,05). Il n’y avait pas de différence statistiquement significative entre les deux groupes quant au nombre de chiens qui ont développé une pneumonie de déglutition postopératoire. Le taux de complication global était élevé pour les deux groupes et la pneumonie postopératoire était la complication la plus fréquente.
(Traduit par Isabelle Vallières)
Laryngeal paralysis, which results in the inability to abduct the arytenoid cartilages during inspiration (1–4), can be a congenital condition in dogs, but is more commonly acquired (2,3). The most common form of acquired laryngeal paralysis is a generalized peripheral polyneuropathy recently labeled as geriatric onset laryngeal paralysis polyneuropathy (GOLPP) (2,4,5), which results in degeneration of laryngeal innervation and is a common cause of dyspnea in middle-aged to older large-breed dogs, with Labrador retrievers being over-represented (1,34,6). Clinical signs associated with laryngeal paralysis include inspiratory stridor, dyspnea, exercise intolerance, collapse, dysphonia, coughing, gagging, and hyperthermia (2–4,7). Dogs affected with GOLPP also have progressive pelvic limb weakness, muscle atrophy, and esophageal motility disorders (2,4,5).
Paradoxical movement (adduction during inspiration) of the arytenoid cartilages is seen in up to 45% of dogs with laryngeal paralysis (2). An increase in negative upper airway pressure has been documented with paradoxical movement of the arytenoid cartilages and has been suggested to lead to secondary elongation of the soft palate in brachycephalic breeds (2,8,9). However, there is no literature confirming that an increase in negative upper airway pressure leads to elongation of the soft palate in dogs. Nonetheless, there is a local reflex response with increased electromyographic activity of the soft palate and epiglottic musculature in the face of negative upper airway pressure in the dog (10,11). Soft palate muscle recruitment during negative upper airway pressure is thought to be helpful in preventing collapse of the upper airway and reducing negative pressure. This local reflex in the soft palate and epiglottic musculature is lost when the internal branches of the cranial laryngeal nerves are bilaterally transected (10,11). Degeneration of the cranial laryngeal nerves in dogs with GOLPP may lead to a reduced ability to decrease upper airway pressure because of an inability to augment the soft palate and epiglottis appropriately. A paretic soft palate, therefore, may be more prone to elongation due to increased negative airway pressure. Elongated soft palates may exacerbate upper airway obstruction, as seen in brachycephalic breeds (12–18). Therefore, respiratory signs in a dog with laryngeal paralysis and an elongated soft palate may benefit from correction of both disorders. A staphylectomy could reduce upper airway obstruction and help alleviate part of the cause for increased negative upper airway pressure in dogs afflicted with both an elongated soft palate and laryngeal paralysis.
Surgical management for laryngeal paralysis is palliative and is intended to increase the size of the glottis, thereby reducing upper airway resistance and negative pressure. Multiple surgical procedures have been developed and successfully applied to dogs suffering from laryngeal paralysis. Unilateral arytenoid lateralization (UAL) is considered the procedure of choice for laryngeal paralysis due to a reduced risk of laryngeal web formation, reduced rates of aspiration pneumonia, and a lower postoperative mortality rate (0% to 14%) compared to conventional partial or complete arytenoidectomy (1–4,19). Aspiration pneumonia is the most common serious complication following a UAL and occurs in 18% to 28% of dogs following the procedure (1,3,4,6). Many dogs continue to have clinical signs of coughing, choking, gagging, exercise intolerance, and weakness after a UAL because their disease is a progressive polyneuropathy. However, clinical signs in dogs with an elongated soft palate can be similar in appearance.
The length of the soft palate in an average mesaticephalic dog is 6 cm (20). The caudal border of the soft palate overlaps slightly with the tip of the epiglottis but generally extends no further than the mid to caudal aspect of the tonsillar crypt (20,21). An elongated soft palate overlies the epiglottis often by more than 1 cm and frequently has a pinched or pointed appearance from being drawn into the larynx on inspiration (21). The standard treatment for dogs with an elongated soft palate is partial resection so that the caudal border of the palate is level to the caudal pole of the tonsil (14,15,22,23). Excision with a scalpel or scissors followed by primary closure with apposition of the oropharyngeal and nasopharyngeal mucosa is the traditional method for removing the elongated portion of the soft palate (14,15,17). The most commonly reported complication following staphylectomy is dyspnea, attributable to pharyngeal edema and inflammation (15,16,22). Long-term complications in dogs that have undergone staphylectomy include aspiration pneumonia, nasal aspiration, and occasionally chronic rhinitis or sinusitis (15,22). Excessive resection of the soft palate may result in nasal regurgitation, rhinitis, and sinusitis (15,21).
Respiratory complications such as dyspnea and aspiration pneumonia overlap between the 2 procedures. No studies have evaluated whether a staphylectomy and UAL (SP + UAL) performed simultaneously in dogs result in an increased risk of developing postoperative respiratory complications. The first objective of this study was to determine if dogs undergoing simultaneous correction (SP + UAL) had a difference in survival time compared to those undergoing only a UAL. The second objective was to determine if there was an increased risk of postoperative respiratory complications in dogs having a SP + UAL compared with dogs having only a UAL. We hypothesized that there would be no difference in survival time or increase in postoperative respiratory complications in dogs undergoing the simultaneous procedure compared to those undergoing a UAL only.
Electronic medical records of all dogs that had a UAL procedure for laryngeal paralysis at the University of Minnesota Veterinary Medical Center between January 2010 and June 2013 were retrospectively reviewed. Standard of care had been provided to each animal. Cases were included in the study if they met the following criteria: were dogs presenting for dyspnea; were diagnosed with idiopathic, acquired laryngeal paralysis confirmed by laryngoscopy; had documentation in the medical record of the surgical procedure performed; and had completion of a telephone questionnaire or perioperative death at the time of follow-up. Breeds that are predisposed to brachycephalic airway syndrome were excluded because of their differences in upper respiratory anatomy from mesaticephalic dogs. Cases were divided into 2 groups: i) dogs that were diagnosed with laryngeal paralysis and concurrent elongated soft palate that had a SP + UAL, and ii) dogs that were diagnosed with laryngeal paralysis that had a UAL.
Information on signalment, age at time of the surgical procedure, and immediate post-operative complications was obtained from the medical record. Owners of the dogs included in the study were contacted by telephone to answer a questionnaire (Figure 1) on postoperative clinical signs and complications. Cause of death and postoperative survival times were recorded. Owners were asked if their dog suffered from any respiratory disease after the surgical procedure and if hospitalization or medical management was required. Specifically, a complication of aspiration pneumonia was documented if a dog was reported to be seen by a veterinarian and treated with antibiotics for suspected pneumonia.
In all dogs, a laryngoscopy following sedation was performed to confirm the diagnosis of laryngeal paralysis. Laryngeal examination was performed at the time of induction of anesthesia for the surgical procedure by the boarded surgeon responsible for the case. Propofol (Propoflo; Abbott Laboratories, Abbott Park, Illinois, USA) was used for sedation during the laryngeal examination. A diagnosis of laryngeal paralysis was made if there was minimal or absent abduction of the arytenoid cartilages. Paradoxical movement of the arytenoid cartilages was also used to confirm the diagnosis of laryngeal paralysis. If necessary, doxapram (Dopram; Zoetis, Tadworth, Surrey, UK) was administered to stimulate ventilation during the laryngeal examination. The soft palate was evaluated without placing traction on the tongue. A diagnosis of elongated soft palate was made if the caudal border of the soft palate extended 1 cm or more beyond the tip of the epiglottis.
Anesthetic protocol varied among the dogs in this study. Dogs were intubated and anesthesia was maintained with isoflurane or sevoflurane in oxygen. Isotonic crystalloid fluid was administered intravenously during the surgical procedure and adjusted by the anesthesiologist. Cefazolin (Ancef; Hospira, Lake Forest, Illinois, USA), 22 mg/kg body weight (BW), IV, was administered 20 min prior to the start of the surgical procedure and then given every 2 h for the duration of the surgery. The use of opioids was minimized during premedication and postoperative recovery. A board-certified surgeon was present at the time of all surgeries. Surgical procedures were performed by multiple board-certified surgeons and surgery residents.
Dogs that were diagnosed with an elongated soft palate in addition to laryngeal paralysis were placed in sternal recumbency first, with the upper jaw suspended by a metal frame placed behind the maxillary canine teeth and attached to the surgical table. The oropharynx was packed with gauze. The proposed level of palate resection, located at the caudal border of the palatine tonsils, was evaluated with minimal traction on the tongue or palate. The caudal edge of the palate was retracted rostrally. An incision was made at the level of the caudal border of the palatine tonsils. Resection was performed with scissors. A continuous suture pattern using 3-0 or 4-0 absorbable suture, depending on the size of the dog, was then used to appose the oral and nasal epithelial surfaces of the cut edge of the soft palate. The type of suture varied depending on surgeon preference but included either polyglactin 910 (Ethicon, Somerville, New Jersey, USA) or poliglecaprone 25 (Ethicon).
A UAL was performed in right lateral recumbency. A skin incision was made over the left side of the larynx just ventral to the jugular groove. The dorsal edge of the thyroid cartilage was rotated laterally to expose the thyropharyngeus muscle, which was incised transversely to increase exposure. After the muscular process of the arytenoid cartilage was palpated, the cricoarytenoideus dorsalis muscle inserting on the process was transected. Disarticulation of the cricoarytenoid articulation was performed, and 2 separate strands of either 0 or 2-0 polypropylene (Ethicon) were used to secure the muscular process of the arytenoid cartilage to the caudodorsal edge of the cricoid cartilage. An intraoperative laryngeal examination was performed to document left arytenoid abduction. Closure of the surgical site was routine.
To minimize sedation, postoperative use of opioids was avoided unless signs of pain, such as tachycardia and discomfort on palpation of the surgical site, were noted. Nonsteroidal anti-inflammatory drugs and local anesthetics were used to control postoperative pain. Endotracheal tubes were removed when the dog was able to swallow. Dogs were monitored closely for postoperative dyspnea and agitation. Low doses of acepromazine (PromAce; Boehringer Ingelheim Vetmedica; St. Joseph, Missouri, USA), 0.01 to 0.05 mg/kg BW, IV or SC, were administered as needed for sedation. If no immediate complications were noted the dogs were discharged the same day. Discharge instructions recommended feeding moist food for a period of time and transitioning the dog to dry food if tolerated. Use of a harness was recommended. Dogs were to be restricted from rigorous activity for 2 wk. Owners were instructed to seek veterinary attention immediately if there were signs that might indicate aspiration pneumonia such as an increase in respiratory rate, respiratory effort, decreased appetite, increasing cough, or lethargy.
All statistical analysis was performed using standard software (R Project for Statistical Computing, Vienna, Austria). A Kaplan-Meier survival curve was used to compare the survival probability of the dogs in the SP + UAL and UAL only groups. A log rank test was used to evaluate statistical significance between the 2 curves. A P-value ≤ 0.05 was considered significant. Logistic regression was used to compare, between the 2 groups, the number of individuals that had respiratory complications, aspiration pneumonia, respiratory distress, coughing, gagging, difficulty swallowing, changes in respiratory noise, and changes in the ability to perform activities. A likelihood ratio test was used to evaluate the statistical significance of the logistic regression; a P-value ≤ 0.05 was considered significant.
A total of 116 dogs had a UAL performed. Four dogs predisposed to brachycephalic airway syndrome were excluded; 3 pugs from the SP + UAL group and 1 pug from the UAL group. Twenty-three dogs were diagnosed with a concurrent elongated soft palate and had a simultaneous SP + UAL, and 89 dogs were diagnosed with an appropriate soft palate and had only a UAL. Signalment characteristics (age, gender, and breed) among surgical groups were similar (Table 1).
Follow-up data were available on 17 of the SP + UAL dogs and 46 of the UAL dogs. Two dogs from each group died or were euthanized within 48 h of surgery. One of these dogs in the SP + UAL group was euthanized because of pneumonia, and the other experienced cardiopulmonary arrest for unknown reasons. One of the 2 dogs from the UAL group was euthanized because, for unknown reasons, it was not recovering well after surgery and the other died of respiratory arrest. Two of the owners (12%) from the SP + UAL group reported that their dogs were euthanized later due to respiratory signs (2 and 3 y). Five of the owners (10%) from the UAL group reported that their dogs were euthanized later due to respiratory signs (2.4 to 18 mo). The median survival times after the surgical procedure for the SP + UAL and UAL groups were 14.4 mo (95% CI: 7.2, inf.) and 18.0 mo (95% CI: 12.0, inf.), respectively, as computed by the Kaplan-Meier survival curve. The log-rank test was not statistically significant between the 2 groups (Figure 2).
Fifteen and 44 owners from the SP + UAL and UAL groups, respectively, completed a telephone questionnaire. The median time to telephone questionnaire after surgery was 18 mo (range: 7.2 to 24 mo) and 18 mo (range: 6 to 36 mo) for the SP + UAL and UAL groups, respectively. Table 2 summarizes the differences in the incidence of various respiratory complications between the 2 groups. Statistically, more dogs in the SP + UAL group developed respiratory distress compared to the UAL group (P = 0.05), with the proportion developing postoperative respiratory distress being 29% and 9% in the SP + UAL group and UAL group, respectively. Four of the 5 dogs reported to be seen for respiratory distress in the SP + UAL group had a single episode, within 2 mo after surgery, that resolved with sedation. The fifth dog continued to have respiratory distress at times of excitement to the point of occasional collapse.
When owners rated their dog’s change in respiratory noise after surgery on a 0 to 5 scale (0 — worse than before surgery to 5 — very good improvement), no dogs were reported to have worse respiratory noise in the SP + UAL group. Two dogs had no improvement in respiratory noise in the SP + UAL group. Two dogs had worse respiratory noise in the UAL group and 8 had no improvement in respiratory noise in the UAL group. There was no significant difference in the proportion of dogs that had worse or no improvement (scores: 0,1) in respiratory noise between the 2 groups (P = 0.66). The median respiratory noise rating was 5 (range: 1 to 5) and 4.5 (range: 0 to 5) for the SP + UAL and UAL groups, respectively. Eleven dogs (73%) and 32 dogs (73%) were reported to have a good to very good improvement (scores: 4, 5) in respiratory noise after surgery (P = 0.96) in the SP + UAL and the UAL groups, respectively. When owners rated changes in their dog’s ability to perform activities or exercise within the first 2 mo after surgery (0 to 5 scale as stated above for respiratory noise), 8 dogs (53%) and 20 dogs (45%) were reported to have worse or no improvement (scores: 0, 1) in ability to perform activities in the SP + UAL and UAL groups, respectively (P = 0.94). Three dogs (20%) and 15 dogs (34%) had good to very good improvement (scores: 4, 5) in their ability to perform activities within the first 2 mo after surgery in the SP + UAL and UAL groups, respectively (P = 0.29).
The results suggest that a staphylectomy performed simultaneously with a UAL increases the risk of postoperative respiratory distress but does not change the overall survival probability of dogs when compared to those having a UAL alone. Therefore, we accept our hypothesis that there was no difference in survival time in dogs between the 2 procedures, but reject our hypothesis that there was no increase in postoperative respiratory complications in dogs undergoing the simultaneous procedure compared to those undergoing only a UAL. There were no statistically significant differences between groups for all other evaluated outcome measures.
Signalment characteristics were consistent with previously reported populations of dogs with laryngeal paralysis in both surgical groups (1,3–5,7). Respiratory complications were common in both groups. The most commonly reported respiratory complication in this study was aspiration pneumonia, which occurred in 29% and 35% of the cases in the SP + UAL and UAL groups, respectively. The postoperative aspiration pneumonia rate in this study was higher than the reported rates of 18% to 28% of cases undergoing a UAL, although the retrospective nature of this study limits any direct comparison (1,3–5). Owners were asked via a telephone questionnaire whether their dog had been diagnosed and treated for pneumonia after surgery. The gold standard diagnosis of pneumonia is based on clinical signs, thoracic radiographs, and a positive microbial culture of fluid collected by transtracheal wash, endotracheal lavage, or bronchoalveolar lavage (24). Some owners reported that their veterinarian did not take thoracic radiographs to confirm a diagnosis of pneumonia, but the dog’s clinical signs improved with antibiotic therapy. This may have led to an overall higher complication rate of aspiration pneumonia in both groups because a presumptive diagnosis of aspiration pneumonia appears to have been made in several cases.
The incidence of dogs having postoperative respiratory distress that required veterinary attention was statistically significant between the 2 groups; dogs in the SP + UAL group had a 29% predicted probability of developing respiratory distress compared to 9% of dogs in the UAL group. The most commonly reported complication after a staphylectomy is dyspnea attributed to postoperative swelling (15,16,22). Therefore, dogs undergoing the simultaneous procedure may be expected to have an increase in dyspnea in the short-term postoperative period. However, only 1 of the 5 SP + UAL dogs with respiratory distress had an onset of respiratory distress within 48 h of surgery. The remaining 4 dogs developed respiratory distress after surgical inflammation would have been expected to resolve. Possible causes for dyspnea not associated with surgical inflammation for these cases could be failure of the UAL, laryngeal collapse, eversion of the laryngeal saccules, inadequate soft palate resection or soft palate dysfunction, underlying lung disease from chronic respiratory distress, and pneumonia. Postoperative results from a larger sample size are needed to definitively assess the significance of this finding.
The number of dogs that coughed and gagged after the procedure was not statistically significant between the 2 groups. Many of the dogs in this study were reported to cough and gag prior to the procedure. Because of the nature of GOLPP, it is not surprising that many dogs continued to cough and gag after the procedure had been done. Persistent coughing was not reported to be associated with pneumonia in any of these cases; however, not all dogs had thoracic radiographs performed, and it is possible that low-grade or recurrent pneumonia was the cause of persistent coughing.
Four dogs (27%) and 3 dogs (7%) were reported to have difficult or exaggerated swallowing after the SP + UAL and UAL procedures, respectively. These numbers neared but did not achieve statistical significance. Humans report difficulty in swallowing with major soft palate defects and soft palate reconstruction (25). It is suspected that the lack of mobility in the soft palate reconstruction accounts for some of the difficulty in swallowing (25). Perhaps mobility of the soft palate is affected by scarring or by inappropriate length after resection. However, the difficult or exaggerated swallowing in both groups could be related to a progression of underlying polyneuropathy associated with GOLPP. Additionally, none of the dogs in this study had an increase in sneezing after surgery, despite previous reports of nasal aspiration and occasionally chronic rhinitis or sinusitis occurring in dogs that have an inappropriately short palate after partial staphylectomy (15,22).
The difference in postoperative respiratory noise was not statistically different between the 2 groups. The SP + UAL dogs did not have a significant improvement in respiratory noise compared to the UAL group. Perhaps the number of cases that had less than good to very good improvement in respiratory noise after surgery would increase if a staphylectomy were not performed in the dogs that were diagnosed with a concurrent elongated soft palate. A control group of dogs diagnosed with an elongated soft palate and laryngeal paralysis that had only a UAL performed without a simultaneous staphylectomy was not available at the time of this retrospective study. This control group would be helpful in determining if the simultaneous procedure improved respiratory noise in this subset of dogs.
Improvement in the ability of dogs to perform exercise or activities within the first 2 mo after the procedure was difficult to assess because of the suspected underlying progressive polyneuropathy. Additionally, comorbidities that could limit improvement in activity, such as arthritis, were not well-documented in all dogs. Owners were asked to recall how their dogs were within the first 2 mo after surgery to try to eliminate progression of underlying diseases influencing the outcome. Only 20% and 34% of cases were reported to have a good to very good improvement in their ability to perform activities within the first 2 mo after surgery in the SP + UAL and UAL group, respectively.
Limitations of this study include its retrospective nature and variability between clinicians and postoperative care, particularly the diagnosis and treatment of aspiration penumonia. Additionally, accurate measurement of soft palate length is difficult and likely varied among clinicians. This study also required owners to recall information about their dogs, which in itself has a large amount of bias. There was a small sample size and a limited number of cases from each group had follow-up information available (74% in the SP + UAL group and 50% in the UAL group) further decreasing the sample size. There was also no control group of dogs diagnosed with an elongated soft palate and laryngeal paralysis that had a UAL performed without concurrent staphylectomy. Lastly, the telephone questionnaire was not validated.
In conclusion, this study suggests that a staphylectomy performed simultaneously with a UAL does not decrease overall survival probability but might result in an increased incidence of postoperative respiratory distress. Dogs undergoing the simultaneous procedure were not more likely to develop aspiration pneumonia after surgery compared to dogs having only a UAL. Postoperative pneumonia was the most common major complication; it occurred in 29% of dogs that had a staphylectomy performed simultaneously.
The Statistical Consulting Center at the University of Minnesota and in particular Lindsey Dietz and Aaron Rendahl helped with the analysis of this study. CVJ
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