Abstract
The purposes of this study were to describe a modified surgical technique in which intraoperative extubation was performed to evaluate abduction of the arytenoid cartilage prior to tying the suture and to assess outcome and complication rates associated with this procedure. Medical records from 30 client-owned dogs with acquired idiopathic laryngeal paralysis were retrospectively reviewed. All clients were contacted by telephone to obtain follow-up information regarding their dog. Six of the 30 surgeries required additional dissection (primarily around the craniodorsal aspect of the cricoarytenoid joint) after the initial intraoperative laryngeal examination. The procedures in 29 of the 30 dogs were deemed a success by the owners. Three (10%) dogs developed postoperative aspiration pneumonia. One of these dogs required long-term antibiotic therapy. Twenty-nine dogs returned to normal activity, and none of the dogs had any exercise intolerance associated with respiratory difficulties. Three owners reported that their dogs were able to swim, and one dog hunted postoperatively. Results of this study suggest that intraoperative laryngeal examination may help limit postoperative complications by allowing for direct, intraoral visualization of the arytenoid cartilage. This enables a surgeon to modify the soft tissue dissection around the cricoarytenoid joint to ensure that adequate abduction is apparent.
Introduction
The purposes of the larynx are to regulate airflow and help prevent the aspiration of food or other foreign material. Degeneration of the recurrent laryngeal nerve leads to dysfunction of the larynx, resulting in impaired abduction of the arytenoid cartilage during inspiration.1–3 Clinical signs associated with this disease include exercise intolerance, gagging or coughing, change in bark, acute collapse, and death.1 Medium- to large-breed dogs older than 8 years of age are more likely to develop laryngeal paralysis than younger dogs.2,4–6 Although acquired laryngeal paralysis may be related to trauma, neoplasia, polyneuropathies, or hypothyroidism, idiopathic laryngeal paralysis is the most common diagnosis.4,6–8
Medical management with sedatives, oxygen, and steroids (if needed) can temporarily alleviate clinical signs in the acute phase, but surgery is considered to be the most effective means of treating and palliating the signs associated with laryngeal paralysis.1 Numerous surgical techniques have been described. These include unilateral arytenoid lateralization, bilateral arytenoid lateralization, castellated laryngofissure, partial laryngectomy, vocal fold resection, and reinnervation techniques.4,9–14 Currently, unilateral arytenoid lateralization is the most commonly performed procedure at our hospital.
The goal of the unilateral arytenoid lateralization technique is to abduct the arytenoid cartilage and maintain adequate airflow during inspiration.7,12,15 The primary reported postoperative complication associated with this procedure is aspiration pneumonia, although gagging, coughing, failure of the surgical repair, dyspnea, and acute death have also been described.4,7 Postoperative complication rates ranging from 10% to 58% have been reported in the literature.2,4,7,13,16,17 In addition, a low-tension suture was shown to be more effective at decreasing open-epiglottis laryngeal resistance and potentially limiting the risk of aspiration pneumonia when compared to a high-tension suture in vitro, although limited clinical studies have been performed.6 While recommendations have been made to extubate the dog intra- or postoperatively to evaluate the arytenoid cartilage, to our knowledge, no studies have been performed to evaluate outcomes in cases where this technique has been performed.7,15 Extubation prior to completion of the procedure would allow the surgeon to visually inspect the arytenoid and ensure adequate abduction in an attempt to reduce clinical signs associated with laryngeal paralysis.
The purposes of this study were 1) to describe a modified unilateral arytenoid lateralization technique in which intra-operative extubation was performed to evaluate abduction of the arytenoid cartilage prior to tying the suture (passed from the caudodorsal aspect of the cricoid cartilage to the muscular process of the arytenoid cartilage) and 2) to assess outcomes and complication rates associated with this procedure. The hypothesis was that an intraoperative laryngeal examination prior to tying of the suture would reduce the risk of complications following surgery. Ensuring adequate abduction could reduce postoperative laryngeal collapse, aspiration pneumonia, surgical failure, and poor anesthetic recovery.
Materials and Methods
Medical records of dogs presented to VCA Cheshire Animal Hospital between April 2006 and June 2008 that underwent unilateral arytenoid lateralization were reviewed. Dogs that had acquired uni- or bilateral laryngeal paralysis confirmed by a preoperative laryngeal examination were included in the study. All dogs had a complete blood count, serum biochemical profile, and thoracic radiography performed prior to surgery. Dogs with preexisting cardiac disease, radiographic evidence of megaesophagus or pneumonia, or other concurrent respiratory disease were excluded.
Information regarding breed, gender, age, body weight, duration of clinical signs, date of surgery, and presenting complaint were recorded. In addition, anesthetic drugs, peri-operative and postoperative medications, hospitalization time, complications, and follow-up time were noted. All owners were contacted via telephone at the time of follow-up, and complications were noted. A complication was defined as any problem associated with surgery that required hospitalization or affected quality of life as determined by the owners.
Laryngeal Examination and Anesthesia
Between April 2006 and June 2008, 30 dogs underwent unilateral arytenoid lateralization at our hospital. Bilateral laryngeal paralysis was documented via direct laryngeal examination in all dogs at the time of anesthesia induction. Hydromorphonea (0.1 mg/kg body weight intravenously [IV]) or buprenorphineb (0.015 mg/kg IV) was administered prior to induction. Dogs were induced with propofolc (3 to 6 mg/kg IV). Dexamethasone sodium succinated (0.1 mg/kg IV) and cefazoline (22 mg/kg IV) were administered at the time of induction. As soon as the dogs were induced, laryngoscopy was performed. Doxapram HClf (1 mg/kg IV) was administered to any dog in which minimal arytenoid movement (either normal or paradoxical) was noted. Dogs were intubated and maintained on isofluraneg and oxygen following laryngeal examination. Intravenous fluids were administered at a rate of 10 mL/kg per hour.
Surgical Procedure
An experienced surgeon (Weisman) certified with the American College of Veterinary Surgeons was present at the time of all surgeries. All dogs were positioned in right lateral recumbency. A left lateral approach to the larynx was made. The thyropharyngeus muscle was incised to expose the thyroid cartilage. The cricothyroid cartilage was disarticulated. The cricoarytenoid dorsalis muscle was transected, and the cricoarytenoid cartilage was disarticulated using a periosteal elevator. Blunt and sharp dissections were performed to further free the muscular process of the arytenoid cartilage until the rostral aspect of the cricoarytenoid joint was clearly visible. Two separate strands of 2-0 polypropylene sutureh were passed from the caudodorsal aspect of the cricoid cartilage to the muscular process of the arytenoid cartilage.
Following passage of the suture, each dog was extubated, and an intraoperative observer evaluated abduction of the arytenoid cartilage while tension was applied to the passed suture [Figures 1A, 1B⇓]. The same observer evaluated all 30 dogs included in this study. Subjectively, if adequate abduction was apparent, the sutures were tied to maintain abduction. The larynx was reevaluated after tying the suture and prior to reintubation. Satisfactory lateralization was defined as any degree of abduction of the left arytenoid, such that the lumen of the larynx was increased in diameter and the right arytenoid did not deviate axially when tension was applied to the suture (as compared to a nontensioned suture). If sufficient abduction was not apparent, the dog was reintubated, and additional blunt and sharp dissection was performed craniodorsal to the muscular process of the arytenoid cartilage. This was done to improve abduction of the left arytenoid cartilage and remove tension on the right side of the larynx, if present.
Photographs of an intraoperative laryngeal examination before (A) and after (B) the suture was tied to complete the unilateral arytenoid lateralization. Note the lateralization of the left arytenoid cartilage and increased diameter of the laryngeal lumen.
Extubation was repeated, and the larynx was reevaluated until adequate abduction was achieved. The suture was then tied. The thyropharyngeus muscle was sutured using 3-0 poliglecaprone 25 plusi in a simple continuous pattern. The remaining muscles and subcutaneous tissues were closed using 3-0 poliglecaprone 25 plusi in a simple continuous pattern. A subcuticular pattern of 3-0 poliglecaprone 25 plusi was placed, and 3-0 nylonj was placed in the skin.
Postoperative Care
Dogs were extubated postoperatively when swallowing was noted. All dogs were monitored overnight and were maintained on IV fluids postoperatively. Buprenorphine (0.3 mg/mL at a dose of 0.015 mg/kg q 6 to 8 hours) was administered IV during the immediate postoperative period. Dogs were handfed canned food made into small meatballs the night of surgery. Owners were instructed to hand-feed canned food for 2 weeks postoperatively and avoid dry food and treats for a total of 4 weeks postoperatively. In addition, owners were instructed to use a body harness instead of a neck lead to avoid putting pressure on the neck. Dogs were discharged on cephalexink (20 mg/kg per os [PO] q 8 hours) or cefpodoxime proxetill (10 mg/kg PO q 24 hours), as well as tramadol HClm (2 mg/kg PO q 12 hours).
Patient Follow-up
All clients were contacted by telephone, and standard questions were asked of the clients to determine if they felt the surgery was a success. In addition, attitude, activity, type of food fed, difficulty eating or drinking, and quality of life were all questioned.
Statistical Analysis
Mean, median, standard deviation (SD), and ranges (minimum, maximum) were calculated using Microsoft Excel.n
Results
Thirty dogs with acquired laryngeal paralysis were included in the study [see Table⇓]. Mean±SD age of the dogs was 11.1±1.2 years (median 11 years, range 8 to 14 years). Eighteen Labrador retrievers, six golden retrievers, one standard schnauzer, one American bulldog, one Brittany spaniel, one Gordon setter, one English springer spaniel, and one Labrador mixed-breed dog were included. Mean±SD body weight was 33.5±8.2 kg (median 32.5 kg, range 20 to 56.8 kg). Fifteen dogs were spayed females, three were intact males, and remaining dogs were neutered males (n=12).
Summary of Cases Included in Study Population
Clinical Findings
Duration of clinical signs prior to evaluation ranged from 1 day to 732 days (median 165 days, mean±SD 228.6±232.1 days) prior to presentation. Clinical signs (noted by owner) associated with laryngeal paralysis included inspiratory stridor (noted by owner and on examination; n=21), change in bark (n=6), exercise intolerance (n=4), and gagging (n=4). In addition, three dogs were presented for collapse, and two were presented for acute dyspnea. On presentation, two of the three dogs that collapsed were intubated. A temporary tracheostomy was performed by the referring veterinarian prior to referral on one of the dogs with acute dyspnea, and the second was intubated on presentation. The latter had three previous intraoral surgeries for laryngeal paralysis, all of which had failed.
Surgical Procedure
All dogs were extubated intraoperatively following placement of suture from the caudodorsal aspect of the cricoid cartilage to the muscular process of the arytenoid cartilage. Adequate abduction was evident in 24 dogs. Adequate abduction was defined as lateralization of the left arytenoid cartilage without narrowing of the lumen of the larynx or axial displacement of the right arytenoid cartilage.
In six (20%) dogs (case nos. 3, 7, 10, 12, 15, 23), adequate abduction was not apparent at the time of the first intraoperative evaluation. In four of the dogs (case nos. 3, 10, 12, 15), the right arytenoid cartilage deviated axially and narrowed the lumen of the larynx. In the remaining two dogs (case nos. 7 and 23), the entire lumen of the larynx narrowed. In each of these instances, minimal abduction of the left arytenoid cartilage was seen. Further dissection along the craniodorsal aspect of the cricoarytenoid joint was performed primarily at the craniodorsal aspect of the arytenoid cartilage, and sufficient abduction of the left arytenoid cartilage was evident on subsequent laryngeal examinations in five of these six cases. In the sixth dog (case no. 23), the sesamoid band was transected, and this allowed the left arytenoid cartilage to abduct without additional axial movement of the right arytenoid cartilage.
Hospitalization Time
Mean hospitalization time following surgery was 1.3±0.65 days (median 1 day, range 1 to 4 days). The dog that was hospitalized for 4 days developed radiographically confirmed aspiration pneumonia that was treated for 2 weeks. Follow-up radiographs did not reveal any residual disease.
Outcomes
All 30 dogs that underwent a left unilateral arytenoid lateralization procedure recovered from anesthesia without signs of respiratory distress. Subjectively, all dogs were more comfortable at the time of extubation than prior to surgery. No surgical failures or revisions (defined as any additional surgical procedure to improve respiratory function following the initial unilateral arytenoid lateralization) were reported at the time of follow-up.
Three (10%) dogs (case nos. 6, 10, 17) undergoing this procedure developed radiographically confirmed aspiration pneumonia. None of these three dogs required additional soft tissue dissection at the time of surgery following the initial intraoperative laryngeal examination. One (case no. 17) of these three dogs was diagnosed with aspiration pneumonia in the immediate postoperative period and remained hospitalized for treatment for 4 days following surgery. The second dog (case no. 10) developed pneumonia 6 weeks following surgery and required 2 days of hospitalization for therapy. This second dog recovered without additional complications. The third dog (case no. 6) developed pneumonia 3 months postoperatively. Initially, this third dog responded to outpatient therapy, but multiple recurrences of pneumonia were documented by endotracheal washes and aerobic bacterial cultures. Six months after the initial diagnosis, the dog was maintained on amoxicillin-clavulanic acid (13.75 mg/kg PO q 12 hours), which prevented any additional episodes.
One dog was found dead at home 2 days postoperatively. The owners reported that they were away from the house at the time of death, but that the dog had been confined to a small room. The owners did report that prior to its sudden demise, the dog was doing well and no warning led up to the dog’s death. The owners declined a necropsy, and the cause of death was not determined.
Follow-up
Mean±SD follow-up time for all dogs included in the study was 261±204.5 days (median 213 days, range 2 to 757 days). All clients were contacted by phone at the time of follow-up. Twenty-nine (97%) of the 30 owners deemed the surgery a success and stated that an improved quality of life was apparent. The owners of the dog that died 2 days postoperatively (case no. 15) did not view the surgery as a success. Three (10%) owners reported intermittent coughing when their dogs ate or drank, but they did not feel that it negatively affected the dogs’ quality of life. No other complications were reported. The dog (case no. 5) that had three intraoral surgeries prior to the unilateral arytenoid lateralization was reported to have a mild inspiratory stridor when excited. At the time of surgery, ventral webbing of the larynx was apparent (presumably due to the previous procedures); however, the owners elected not to have the tissue resected when queried about their dog’s condition at the time of follow-up.
Thirteen owners were feeding only dry food, 13 were feeding a mixture of wet and dry food, and three owners were feeding only wet food. One dog was fed dry food 4 weeks postoperatively, and its owner reported that the dog started coughing. The recommendation was given to feed canned food only, and the owners indicated the coughing resolved after instituting this change.
All owners indicated that their dogs returned to normal activity. Normal activity was defined as performing a typical daily routine (i.e., walks, playing, etc.) without increased respiratory difficulties or exercise intolerance. One dog returned to hunting, and three dogs were able to swim.
At the time of follow-up, nine of the 30 dogs had died. While one dog was acutely found dead 2 days postoperatively, none of the other dogs appeared to have died from issues associated with surgery, such as aspiration pneumonia, surgical failure, or poor anesthetic recovery [see Table⇑]. Mean±SD survival time for these nine dogs that died postoperatively was 306.7±226.2 days (median 285 days, range 2 to 591 days).
Discussion
Overall complication rates following unilateral arytenoid lateralization range from 10% to 58%.2,4,7,13,16,17 The purpose of this study was to evaluate the complication rate when an intraoperative laryngeal examination (subsequent to temporary extubation) was performed following placement of two strands of polypropyleneh suture. Compared to previous studies, this study appears to show that an intraoperative laryngeal examination may reduce the incidence of postoperative complications. The overall reported complication rate in this study was 10%.
Although intraoperative extubation may already be performed routinely by surgeons, to our knowledge, no previous studies have evaluated outcome associated with this practice. As in previous studies, the most common complication in this retrospective study was aspiration pneumonia; however, the 10% incidence reported here is lower than the recently reported 18% and 24% rates associated with this surgical procedure without intraoperative extubation and laryngeal examination.4,7 In the study by Hammel et al (2006), the larynx was evaluated at the completion of the surgery.7 While postoperative laryngeal evaluation is likely to help reduce the risk of postoperative complications, visualizing the lateralization intraoperatively is a dynamic process that allows for evaluation of the potential change in conformation of the larynx when tension is applied to the suture. This change in laryngeal conformation could be missed when observed postoperatively under static conditions. Although the risk of aspiration pneumonia is thought to be due to the inability of the arytenoids to properly protect the larynx postoperatively, other factors may play a role.4,18 Type of diet may play a role in the risk of pneumonia. Dry food and the subsequent crumbs and particles formed when chewing may have a higher likelihood of entering the airway than canned food. For this reason, all of our dogs are fed canned food for at least 4 weeks postoperatively.
In four of the six dogs that did not have adequate abduction based on intraoperative laryngeal examination, the right arytenoid cartilage deviated axially, and the lumen of the larynx narrowed. In the remaining two cases, the entire lumen narrowed. In each case, subjectively, the dissection of the cricoarytenoid joint appeared to be adequate. If left uncorrected, the collapse of the larynx could account for postoperative respiratory issues as well as an increased risk for aspiration pneumonia, respiratory distress, and acute death. Thus, intraoperative evaluation may have prevented potentially life-threatening complications. If complications were left undetected, the complication rate could have increased to nine (30%) out of 30 dogs (i.e., these six dogs plus the three dogs that developed aspiration pneumonia), which would be in line with previous reports.
To obtain adequate abduction following reintubation, dissection was concentrated along the craniodorsal aspect of the cricoarytenoid joint. In each case, sufficient dissection was apparent subjectively prior to extubation, but the laryngeal examination(s) did not confirm this. Additional dissection in this region was sufficient in only five of the six cases. The lack of sufficient abduction of the arytenoid cartilage may be secondary to mineralization of the cartilages and formation of scar tissue that prevents the left arytenoid from abducting properly, while placing tension on the contralateral cartilage and pulling it axially. By further dissecting the tissues around the cricoarytenoid joint, sufficient abduction of the left arytenoid cartilage was obtained. In one case, it was necessary to transect the sesamoid band to provide adequate abduction of the left arytenoid cartilage.
In this study, 97% of owners were satisfied with the results and felt that the surgery was a success. All dogs returned to normal activity, and no additional complications were reported. Three dogs returned to swimming following surgery, and no excessive coughing or gagging was noted during this activity. To our knowledge, this is the first study that has reported dogs swimming or hunting following unilateral arytenoid lateralization. Additional studies are required to determine further restrictions and potential safety issues associated with these activities.
At the time of follow-up, 21 of the 30 dogs were alive. Eight of the nine dogs that had died enjoyed a good quality of life following surgery, according to the owners. No ill effects were apparent from the surgery in the surviving dogs.
The limitations of this study include the retrospective nature and limited number of cases. In addition, no control group was used. Rather, comparisons were made to previous studies and historical controls. The mean and median follow-up times in these previous studies were 442 and 318 days and 888 and 840 days, respectively, which were longer than those reported in the current study.4,7 We do acknowledge that a longer follow-up time could increase the incidence of aspiration pneumonia; however, in one study, the mean and median times from surgery until clinical signs of aspiration pneumonia were 4.2 and 2 months, respectively.7 The mean follow-up time of 266 days for the present study is within this latter timeframe. In addition, follow-up data were obtained via telephone interview with the owners. Further measurements of outcome could be determined if a prospective study were performed. In a prospective study, for example, we could include serial chest radiographs, endotracheal washes, and blood work as parameters to monitor postoperatively.
Conclusion
The purpose of this study was to evaluate the complication rate associated with intraoperative extubation and evaluation of the arytenoid cartilage as tension was applied to the sutures prior to tying. The results indicate that adding this step may help limit postoperative complications by allowing for direct, intraoral visualization of the arytenoid cartilage. This enables a surgeon to modify the soft tissue dissection around the cricoarytenoid joint to ensure that adequate abduction is apparent.
Footnotes
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↵ a Hydromorphone Hydrochloride; Abbott Laboratories, Abbott Park, IL 60064
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↵ b Buprenorphine Hydrochloride; Abbott Laboratories, Abbott Park, IL 60064
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↵ c Propoflo; Abbott Laboratories, Abbott Park, IL 60064
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↵ d Dexamethasone Sodium Phosphate; Butler Pharmaceutical, New Paltz, NY 12561
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↵ e Cefazolin; Baxter, Deerfield, IL 60015
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↵ f Dopram V; Fort Dodge Animal Health, Fort Dodge, IA 50501
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↵ g Isoflo; Abbott Laboratories, Abbott Park, IL 60064
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↵ h Prolene; Ethicon, Johnson and Johnson Company, Somerville, NJ 08876
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↵ i Monocryl Plus; Ethicon, Johnson and Johnson Company, Somerville, NJ 08876
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↵ j Ethilon; Ethicon, Johnson and Johnson Company, Somerville, NJ 08876
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↵ k Keflex; Advancis Pharmaceutical Group, Germantown, MD 20874
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↵ l Simplicef; Pfizer, New York, NY 10017
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↵ m Tramadol; Caraco Pharmaceutical Laboratories, Detroit, MI 48202-3344
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↵ n MS Excel; Microsoft, Seattle, WA
