Introduction

Laryngeal paralysis is a common disease process that occurs secondary to denervation atrophy of the recurrent laryngeal nerve resulting in dysfunction of the cricoarytenoid dorsalis muscle and failure of the arytenoid cartilages and vocal folds to abduct during inspiration.^1–3 Numerous surgical techniques have been described to treat this condition, with unilateral arytenoid lateralization being the most commonly performed.^1–3 Various complication rates for treatment of laryngeal paralysis have been reported in the literature, with a wide range of morbidity and mortality rates from 10% to 58% and 14% to 67%, respectively.^3–7 Treatment with unilateral arytenoid lateralization results in the lowest complication rate, with some studies reporting as little as 10%.⁸ The most common postoperative complications associated with unilateral arytenoid lateralization include aspiration pneumonia, which is reported to occur in 23.6%.⁷ In 1 study,⁷ the reported mortality rate in patients > 1 year postoperatively was 14.3% and secondary to aspiration pneumonia. Other complications can include coughing and recurrence of clinical signs from tearing of the suture or fracture of the arytenoid cartilage.² Complications such as coughing after eating or drinking have also been shown to occur in 89% of dogs.^4,9–11

Aspiration pneumonia is a lifelong potential complication of the procedure and has been reported to occur in 5% to 25%^3,7,12–15 of patients postoperatively, with 1 study¹³ reporting rates as high as 31.8% at 4-year follow-up periods. Because of the increased risk of aspiration pneumonia, numerous techniques have been evaluated in the immediate postoperative period to reduce the risk of vomiting and regurgitation. A prospective randomized multicenter clinical trial¹⁶ evaluated the effect of perioperative IV constant rate infusion of metoclopramide on the incidence of aspiration pneumonia. This study found no significant differences on the development of aspiration pneumonia between the control and treated groups. A retrospective study¹³ evaluating 232 patient undergoing unilateral arytenoid lateralization found that postoperative administration of an opioid was a significant risk factor for the development of aspiration pneumonia in the short term (< 14 days postoperatively).

Both human- and veterinary-based studies have shown that stress during hospitalization results in delayed wound healing, gastrointestinal diseases (gastric ulceration, vomiting, and nausea), and increased susceptibility to infections.^{10,11,17–19} In veterinary medicine, the following factors play a role in the high rate of stress seen in hospitalized patients: separation from primary caretaker, new environment and stimuli, increased noise levels, and confinement in cages.^20–26 One study²⁷ examined a less-invasive unilateral arytenoid lateralization and reported same-day discharge with no life-threatening adverse events. To the authors’ knowledge, no studies have directly compared inpatient versus outpatient treatment of dogs undergoing unilateral arytenoid lateralization. The objective of this study was to compare short-term outcome and complication rates between outpatient management and traditional inpatient management of dogs undergoing unilateral arytenoid lateralization. An additional objective was to determine whether outpatient management is a safe alternative to the traditional inpatient postoperative management with careful patient selection. The authors hypothesized that outpatient unilateral arytenoid lateralization would be a safe alternative to inpatient postoperative management and may be associated with less postoperative complications.

Materials and Methods

Results

One hundred five dogs met the initial criteria and were screened for study inclusion. Sixty-one cases were excluded due to lack of follow-up, incomplete medical records, or concurrent upper airway comorbidities. The remaining 44 dogs that underwent unilateral arytenoid lateralization were included in the study. Of the 44 patients included in the study, 35 (79.5%) were Labrador Retrievers, 2 (4.5%) were Golden Retrievers, 2 (4.5%) were Labradoodles, 1 (2.3%) was a Labrador Retriever mix, 1 (2.3%) was a Shepherd mix, 1 (2.3%) was a Doberman Pinscher, 1 (2.3%) was an American Staffordshire Terrier, and 1 (2.3%) was an American Pit Bull (Table 1). Mean and median body weights were 36.1 and 35.2 kg, respectively (range, 23 to 51 kg). Mean and median age was 11.9 and 12 years, respectively (range, 8 to 15 years). Twenty-three (52.3%) patients were male neutered, 19 (43.2%) were female spayed, 1 (2.3%) was female intact, and 1 (2.3%) was male intact. Of the 44 patients included in the study, 20 (45.4%) were hospitalized for 24 hours after surgery (inpatient group) and 24 (54.5%) were discharged the day of surgery (outpatient group). Of the surgical procedures performed, 12 (27.3%) were unilateral thyroarytenoid lateralizations, 32 (72.7%) were unilateral cricoarytenoid lateralizations, and there was no combination of unilateral thyroarytenoid and cricoarytenoid lateralization performed. Prokinetics were used in 26 patients with 10 (50%) of those being in the inpatient group and 16 (66.7%) being in the outpatient group. Antiemetic injections were used in 16 (80%) inpatients and 22 (91.7%) outpatients. Perioperative opioids were used in 10 (50%) inpatients versus 8 (33.3%) outpatients (P = .3588; Table 2). Dexmedetomidine was administered perioperatively in 4 (20%) inpatients and 2 (8.3%) outpatients (P = .3871). In the inpatient group, 11 (55%) had an anxiety score of 0, 3 (15%) had an anxiety score of 1, 4 (20%) had an anxiety score of 2, and 2 (10%) had an anxiety score of 3. In the outpatient group, anxiety scores were assigned on a scale of 0 to 3 and were found to be 19 (79.2%), 3 (12.5%), 1 (4.2%), and 1 (4.2%), respectively. In-hospital regurgitation was noted in 2 (10%) inpatients and none of the dogs in the outpatient group, and vomiting in hospital was noted in 1 (5%) inpatient and no outpatients. In the inpatient group, 4 (20%) dogs were represented to the emergency department for complications related to surgery within 2 weeks postoperatively compared to 2 (8.3%) dogs in the outpatient group (P = 0.3871). Radiographic evidence of aspiration pneumonia within the 2-week postoperative period was documented in 5 (25%) dogs in the inpatient group and 1 (4.2%) dog in the outpatient group (P = .0773). Three patients died within the 2-week postoperative period, resulting in a 6.8% mortality rate. Of those 3 patients, 2 were euthanized secondary to their disease process (5.0% of inpatients and 4.2% of outpatients) and 1 died on the way to the hospital after having an obstructive respiratory event (P = 1.00). The overall morbidity in the inpatient versus outpatient group was 5% versus 4.2%, respectively. The mortality rate for inpatients versus outpatients was 5.0% versus 8.3%, respectively. There was no significant difference in morbidity and mortality rates between groups (P = 1.00 and 1.00, respectively). The overall complication rate in this study was 22.7% with 35% of those being in the inpatient group and 12.5% being in the outpatient group. There was no significant difference in rate of complications between groups (P = .1466).

Discussion

The objectives of the present study were to compare complication rates and short-term outcome following elective unilateral arytenoid lateralization in dogs with laryngeal paralysis and determine whether there was a difference between outpatient procedures compared with inpatient procedures. Results of the present study suggest no statistically significant difference in mortality or morbidity during the postoperative period between the inpatient group (5%) and outpatient group (8.3%). Therefore, we accept our hypothesis that outpatient unilateral arytenoid lateralization is a safe alternative to overnight hospitalization following surgery.

Historically, the purpose of hospitalizing patients after unilateral cricoarytenoid lateralization was to administer prokinetic and antinausea therapy to try and reduce episodes of vomiting and regurgitation that may lead to development of aspiration pneumonia, as well as to monitor respiratory status. The effects of metoclopramide administration on the presence of postoperative aspiration pneumonia has been evaluated in several studies with mixed results. A retrospective study²⁸ including 43 client-owned dogs after unilateral arytenoid lateralization suggested that postoperative aspiration pneumonia may be reduced from 50% to 17% by metoclopramide administration in the immediate perioperative period. Another multicenter randomized clinical trial found no significant differences in the rate of development of aspiration pneumonia when a metoclopramide constant rate infusion was used.¹⁶ Given the minimal effects that prokinetic therapy had on the incidence of aspiration pneumonia, patients without a history of frequent regurgitation or vomiting likely wouldn’t benefit from hospitalization. Instead, it is possible that hospitalization may cause anxiety and distress, which would manifest as restlessness, panting, and vocalization. A catastrophic sequela of this would be strain on the surgical site and failure. Results of a large prospective observational study²⁹ found that 79% of dogs in a veterinary clinic had signs consistent with fear and anxiety. In the present study, the inpatient group had higher anxiety scores compared with those in the outpatient group. It is vital to keep patients calm after arytenoid lateralization procedures for a variety of reasons. The longer patients are hospitalized, the more likely they are to experience trigger stacking, necessitating fast-acting anxiolytics administered IV. Trigger stacking occurs when a patient experiences numerous stressors without time to return to baseline, which can be seen when measuring serum and salivary cortisol levels.^30,31 This can occur during short and long periods of time.^30,31 Trigger stacking often results in progressive anxiety and is associated with behaviors such as pacing, panting, barking, and whining. Excessive barking, panting, and whining could lead to increased stress on the arytenoid lateralization site and tearing of suture or breakage of arytenoid cartilages. In addition, the increased hyperventilation caused by anxiety could lead to excessive carbon dioxide loss and respiratory alkalosis. Lastly, hospitalization following surgery is associated with a higher cost compared to outpatient procedures. A 2019 paper³² in human medicine explored the perioperative costs and readmission rates in 73,724 individuals undergoing either ambulatory (outpatient) versus inpatient elective procedures (hernia repair, primary or total thyroidectomy, laparoscopic cholecystectomy, or laparoscopic appendectomy). Findings suggested that adjusted mean surgical costs were significantly lower for ambulatory versus inpatient cases for each procedure. Additionally, the odds of experiencing readmission within a 30-day period of the surgery was lower in ambulatory versus inpatients surgeries.³² Because there is no increased mortality with outpatient unilateral cricoarytenoid lateralization procedures, significant reductions in healthcare expenditures could allow for more owners to afford this procedure.

This study had several limitations secondary to its retrospective nature. Sixty-one cases were excluded because of incomplete medical records, loss of follow-up, and concurrent upper airway surgery. Additionally, patients were excluded if they presented as a transfer from the emergency department for respiratory distress. There was no standardized perioperative complication period, postoperative protocol, or grading for anxiety and pain management and lack of consistency in personnel observing and evaluating patients that were hospitalized. This could have led to under- or overreporting anxiety in the patients hospitalized following surgery. There was no standardized anesthetic, antiemetic, prokinetic, or gastroprotectant protocol among the surgeons in the study, which could have affected outcome of adverse events such as regurgitation, vomiting, and/or ileus. There were 5 patients (3 inpatients and 2 outpatients) that received hydromorphone IV as part of a premedication protocol. Due to its µ opioid receptor agonist properties, vomiting can occasionally be seen following administration. One study³³ found that the route of administration in dogs undergoing routine orthopedic surgery had no effect on the likelihood of vomiting. All patients that received hydromorphone in their anesthetic protocol were administered maropitant IV prior to reduce the chances of vomiting. Numerous studies have evaluated the efficacy of maropitant on inhibiting vomiting in patients receiving hydromorphone (both IV and IM).³⁴ These found that maropitant prevented vomiting, retching, and nausea when given prior to hydromorphone administration.³⁴ The surgeries performed in the current study were performed by 5 board-certified surgeons, and variations in surgeon experience and surgical technique may have also led to variation in outcome. Both cricoarytenoid and thyroarytenoid lateralization were performed in this study. Although studies have shown that each of these procedures affects the rima glottidis area differently, the clinical outcomes observed in dogs treated with either procedure have not been shown to differ.¹⁴ The decision to perform cricothyroid disarticulation was also left up to the surgeons’ discretion in this study, which also could have affected outcome as disarticulation has been shown to destabilize the larynx and affect glottic diameter.³⁵ Finally, one surgeon routinely used polyglyconate suture for arytenoid lateralization while the others used polypropylene. Although the former is absorbable, it retains a great amount of tensile strength after 4 weeks. Given the short-term follow-up period of 2 weeks used in this study, this likely shouldn’t have caused any clinical difference between groups. It is important to note that it is recommended to place a permanent suture (polypropylene) to reduce risk of failure of lateralization in the long term given the dynamic nature of the organ. Future prospective studies should be performed to look at inpatient versus outpatient unilateral cricoarytenoid lateralization and thyroarytenoid lateralization procedures. A prospective study would allow for standardized patient recordkeeping and protocols evaluating anxiety.

Results of the current study suggest no greater increase in mortality nor morbidity in patients discharged the same day as surgery. It is important to note that careful patient selection is vital to determining whether outpatient surgery is feasible.