Introduction
The total ear canal ablation combined with lateral bulla osteotomy (TECA-LBO) procedure is generally considered to be the gold-standard surgical treatment for dogs and cats with auricular neoplasia, aural cholesteatoma, severe ear canal trauma, and end-stage, chronic otitis externa with concurrent otitis media that is deemed unresponsive to medical management.1–10 The procedure requires scrupulous surgical technique for complete removal of the ear canal and aural epithelium from the tympanic bulla, which can manifest as complications that could, but often do not, affect long-term treatment success.11–13
Medical management of any inflammation or infection of the ear canal (otitis externa) is often attempted prior to surgical invention, and this includes treatment of underlying or perpetuating causes, cleaning and drying the ear, and the use of appropriate topical medications that contain various combinations of antimicrobial, anti-inflammatory, and/or antifungal agents. Although the normal ear canal is inhabited by bacteria (eg, Staphylococcus and Streptococcus spp), antimicrobial choices are often directed at the bacteria that secondarily colonize the affected ear, including Corynebacterium spp, Escherichia coli, Pasteurella multocida, Proteus mirabilis, and Pseudomonas aeruginosa.1,11–14 Otitis media, characterized by inflammation of the tympanic cavity and membrane, occurs concurrently with otitis externa in 50% to 89% of affected dogs, and recommended treatment includes administration of targeted systemic antimicrobials for 6 to 8 weeks.2,3,7,15–17
When medical management fails, an appropriately executed TECA-LBO is a generally successful procedure, with improvement seen in 57% to 92% of patients.4,5,11,18,19 The TECA-LBO procedure is still considered an elective, salvage procedure because uncommon but serious complications are documented. Postoperative neurologic dysfunction secondary to TECA-LBO, characterized by facial nerve neuropraxia (3% to 58%4,6,9–11,18–25), vestibular disease (1% to 23%4,6,11,18–21,24–26), and Horner syndrome (7% to 67%6,9,23,25), can cause morbidity to dogs and cats. Recurrent infection suspected to be due to retained ear canal or middle ear epithelium and contaminated tissue at the time of closure has been reported, with wide variability between 5% to 82%.6,11,18,23,25–28 Although the overall trend in complication rates is decreasing based on a recent review,25 it is pertinent to assess additional perioperative factors that may contribute to both short- and long-term complications regarding infection-related complications and neurologic signs. Most available literature includes information pertaining to short-term postoperative incisional complications following TECA-LBO, with very little reported on long-term infection-related complications. This includes 2 recent studies in which the short-term (< 6 weeks) wound complication rates were 34% (27/79 ears) and 5.3% (7/133 ears).1,26 Additionally, the role of antimicrobial use and its long-term association with wound infections was not investigated in these studies, with 1 study26 noting that all but 1 patient received perioperative antimicrobials and no specifications regarding why the antimicrobial was chosen or administration duration. While the other study1 noted that all patients were discharged with empiric systemic antimicrobials followed by administration of definitive antimicrobials based on culture results for variable durations, no information was reported on statistical analysis of this factor or on long-term outcome regarding infection-related complications.
To the authors’ knowledge, there have been no large retrospective studies evaluating the correlations between the duration and choice of pre- and postoperative topical and systemic antimicrobials and short- and long-term postoperative complications, including infection-related signs, in dogs and cats undergoing TECA-LBO. The main objective of this study was to retrospectively evaluate a large cohort of dogs and cats undergoing TECA-LBO and to document any relationship between antimicrobial administration perioperatively and the occurrence of infection-related and neurologic complications. A secondary objective of the present study was to assess other additional patient and perioperative factors that could contribute to short- and long-term postoperative complications in dogs and cats undergoing TECA-LBO. The null hypothesis is that the duration and choice (empiric vs definitive) of pre- and postoperative antimicrobial administration will have no effect on short and long-term postoperative complications in dogs and cats undergoing TECA-LBO.
Materials and Methods
Case selection criteria
Medical records of dogs and cats that underwent TECA-LBO surgeries between January 2009 and January 2019 at the University of Tennessee Veterinary Teaching Hospital and the Veterinary Specialty Hospital were reviewed. All procedures were performed by either a Diplomate of the American College of Veterinary Surgeons or a surgical resident supervised by a Diplomate of the American College of Veterinary Surgeons. Exclusion criteria for the study consisted of dogs or cats with a history of TECA without LBO; no medical record information regarding patient presentation, surgery, or recovery; and patients without long term follow-up of ≥ 6 months. Patients that died or were euthanized secondary to surgery or surgical disease prior to 6 months were included in the study. All information pertaining to the hospital visits associated with the TECA-LBO surgery and at least 6 months postoperatively were collected from the available medical records, including communication with the clients and referring veterinarians.
Medical records review
Data collected included signalment, presenting complaint, clinical signs, neurologic status and examination findings at presentation, physical examination findings, location of otic disease (ie, right, left, bilateral), comorbidities, topical and systemic medication history prior to presentation, clinicopathologic findings, preoperative diagnostic imaging (CT), whether bilateral or unilateral (UL; including staged procedures) TECA-LBO was performed, intraoperative surgical findings, histopathologic and bacterial culture and sensitivity results, perioperative and postoperative antimicrobial administration, and perioperative and postoperative complications. Perioperative was defined as the time from 30 minutes prior to anesthetic induction to anesthetic recovery, intraoperative was defined as the time from the first skin incision until complete skin closure, and postoperative was defined as the time from anesthetic recovery up to 48 hours postoperatively. Postoperative antimicrobial use was classified as definitive when a corresponding culture and sensitivity was used to determine antimicrobial choice and empiric if there was no corresponding culture and sensitivity available to guide the correct antimicrobial choice. Endocrine comorbidities were recorded if the medical record documented the diagnosis of, or response to treatment for, the following conditions: hypothyroidism, hyperadrenocorticism, diabetes mellitus, and diabetes insipidus.
Biopsy samples collected at the time of surgery were divided into two broad categorizations following histopathologic examination: inflammatory disease (chronic otitis externa/media or inflammatory polyps) based on the predominant finding of inflammatory cells without evidence of neoplasia or neoplastic disease (benign or malignant).
Clinical signs, medications, and complications in the postoperative, short-term (48 hours to < 1 month), intermediate-term (1 month to ≤ 6 months), and long-term (> 6 months) follow-up periods were documented from the available medical records, and if this information was not available it was determined by a telephone conversation with the referring veterinarian and/or owner. The complications recorded included neurologic dysfunction and infection-related (involving or relating to the surgical site) signs. Neurologic dysfunction was classified as Horner syndrome, facial nerve paresis or paralysis, and signs consistent with vestibular dysfunction (nystagmus, head tilt, and ataxia) based on medical record documentation. Neurologic deficits were considered residual (permanent) if they were present within the short-term follow-up period and remained present at the long-term follow-up period. Transient (temporary) neurologic deficits were those that were present within the short-term postoperative period but absent for all subsequent visits or follow-up. Infection-related signs were classified as development of a draining tract, deep abscess, purulent discharge from the surgical incision, and dehiscence of the surgical site.
A revision procedure was defined as an additional surgical procedure following the initial TECA-LBO at or around the original surgical site. The need for a revision procedure was deemed necessary at the surgeon’s discretion due to the presence of infection-related signs at the TECA-LBO surgical site, persistence of infection-related signs despite conservative medical management, and/or recurrence of neoplastic disease or cholesteatoma.
Statistical analysis
Descriptive statistics were calculated. Normality tests were conducted on numeric variables using Shapiro-Wilke tests. Normally distributed data are presented as a mean ± SD, and nonnormally distributed data are expressed as median and range. Categorical data were expressed as frequencies and percentages. Logistic regression analysis was used to evaluate the effects of clinical indicators noted previously (signalment, clinical history, physical examination abnormalities, surgical and diagnostic imaging factors, anesthetic and surgical complications, histopathology and bacterial culture results, and antimicrobial use and duration at any time during the study) on the binary response outcome variables, including neurologic signs in the short-, intermediate-, or long-term follow-up period; infection-related signs at any time point postoperatively; death or euthanasia related to recurrence of disease; and need for a surgical revision procedure. All test P values were adjusted using a false discovery rate approach to control the false positive rate due to multiple testing. Statistical significance was identified at a value of P < 0.05. Analyses were conducted using commercially available software (SAS version 9.4 TS1M6 for Windows 64x; SAS Institute Inc).
Results
Animals
The medical records search from both hospitals identified 126 patients with the potential for study enrollment, 6 of these cases were not able to provide follow-up to the minimum of 6 months and were excluded. A total of 120 patients that included 149 ears were enrolled during the study period, including 107 (89.1%) dogs undergoing 135 TECA-LBOs and 13 (10.8%) cats undergoing 14 TECA-LBOs. Sixty-five of 120 (54.2%) medical records were reviewed from the university veterinary teaching hospital and 55 of 120 (45.8%) medical records were reviewed from the private practice veterinary referral center. The mean ± SD postoperative follow-up time was 985 ± 690 days.
Of the 120 patients, 61 (50.9%; 55 dogs and 6 cats) were castrated males, 51 (42.5%; 44 dogs and 7 cats) were spayed females, 7 (5.8%; 7 dogs) were intact males, and 1 (0.8%; 1 dog) was an intact female. Mean ± SD age of the patients that underwent surgery was 8 ± 3.3 years. Thirty-two dog breeds were represented including Cocker Spaniels (23/107 [21.4%]), mixed-breed dogs (13/107 [12.1%]), English Bulldogs (7/107 [6.5%]), Labrador Retrievers (6/107 [5.6%]), and 5 (4.7%) each of the following breeds: French Bulldog, Shar Pei, and Pug; 4 (3.7%) each of the following breeds: Golden Retriever, Shih Tzu, and Yorkshire Terrier; and 3 (2.8%) each of the following breeds: Lhasa Apso, Basset Hound, and German Shepherd Dog. An additional 21 dogs were recorded as 18 different breeds, with 13 representing small breed dogs and 6 representing large breed dogs. Of the 13 cats, 10 of 13 (76.9%) were domestic shorthairs, 2 of 13 (15.4%) were Maine Coon, and 1 (7.7%) was a Bengal. For clarity, the remainder of the results section will report findings as those noted in both dogs and cats unless specific species variations are explicitly stated. No variables associated with signalment were significantly associated with the outcome variables.
Initial presentation
The median weight of the dogs and cats in this study was 14 kg (range, 2.3 to 81 kg). For every additional kilogram increase in weight, the odds of postoperative infection-related recurrence increased by 3% (P = 0.04; OR = 1.03; CI = 1.00 to 1.06). The presenting complaints for the enrolled patients included chronic otitis (102/120 [85.0%]), evaluation of an aural mass noted previously via either an otoscopic examination or direct visualization (18/120 [15.0%]), and aural trauma (3/120 [2.5%]). Historical findings and nonneurologic clinical signs recorded in these patients included head shaking, scratching, and/or itching in 84 of 120 (70.0%), pain around the ears and/or head in 49 of 120 (40.8%), discharge from the ear canal and malodor in 14 of 120 (11.6%), discomfort when opening the mouth (temporomandibular joint pain) in 10 of 120 (8.3%), and aural hematoma in 3 of 120 (2.5%). Patients experiencing discomfort when opening the mouth were 7.4 times as likely to require a revision procedure compared to those who did not (P = 0.023; OR = 7.4; CI = 1.77 to 31.48).
Twenty-seven of 120 (22.5%) patients presented with neurologic signs including an ipsilateral head tilt in 19 of 120 (15.8%), ipsilateral facial nerve paralysis in 9 of 120 (7.5%), ipsilateral Horner syndrome in 7 of 120 (5.8%), incoordination/ataxia in 4 of 120 (3.3%), and nystagmus in 2 of 120 (1.6%). Patients without neurologic signs at presentation were 62% less likely to exhibit neurologic signs within the short-term follow-up period (P = 0.043; OR = 0.38; CI = 0.16 to 0.93); however, there was no significant difference with long-term (permanent) neurologic signs between patients who did and did not exhibit preoperative neurologic signs (P = 0.065). Median duration of preoperative clinical signs (including neurologic signs) in all patients was 52 weeks (range, 2 to 520 weeks).
Physical examination findings recorded included bilateral otic disease in 71 of 120 (59.2%); stenotic, thickened, and/or calcified ear canals in 70 of 120 (58.3%); UL otic disease in 49 of 120 (40.8%); obesity (defined as a body condition score of ≥ 6/9) in 45 of 120 (37.5%); and a visible, distinguishable aural mass in 32 of 120 (26.6%) patients. Patients with UL disease had a higher chance to exhibit postoperative neurologic signs with patients exhibiting bilateral disease being 78% less likely to exhibit neurologic signs postoperatively (P = 0.048; OR = 0.22; CI = 0.05 to 0.96).
Thirty-one of 120 (25.8%) patients were receiving systemic immunosuppressant therapy at the time of surgery including prednisolone in 15 of 31 (48.3%), oclacitinib (Apoquel) in 9 of 31 (29.0%), cyclosporine in 5 of 31 (16.1%), and azathioprine in 2 of 31 (6.5%). Eleven of 120 (9.2%) patients presented with concurrent endocrine comorbidities at the time of surgery including hypothyroidism in 6 of 120 (5.0%), hyperadrenocorticism in 4 of 120 (3.3%), diabetes mellitus in 1 of 120 (0.8%), and diabetes insipidus in 1 of 120 (0.8%). Patients without endocrine disease were 92% less likely to be euthanized due to recurrence of infection-related signs compared to those with endocrine disease (P = 0.035; OR = 0.08; CI = 0.01 to 0.670).
Sixty-one of 120 (50.8%) patients were presented with a history of preoperative systemic antimicrobial administration for a median duration of 1 week (range, 1 to 52 weeks). The most common antimicrobials administered to patients included amoxicillin-clavulanate potassium in 16 of 61 (26.2%), enrofloxacin in 15 of 61 (24.6%), cefpodoxime in 9 of 61 (14.7%), doxycycline in 6 of 61 (9.8%), cephalexin in 5 of 61 (8.2%), and marbofloxacin in 4 of 61 (6.6%) patients. Seventy-four of 120 (61.6%) patients were presented with a history of topical otic medication administration including a topical aminoglycoside (25/74 [33.8%]), topical steroid (20/74 [27.0%]), topical fluoroquinolone (13/74 [17.6%]), and topical cephalosporin (7/74 [9.5%]) with a median duration of 4 weeks (range, 4 to 192 weeks) prior to TECA-LBO. No data regarding preoperative use of topical or systemic antimicrobials were significantly associated with any of the outcome variables.
A summary of the preoperative bloodwork findings is listed (Table 1). For every 1-U increase in cholesterol, the odds of a patient being euthanized due to recurrence of disease increased by 1.5% (P = 0.048; OR = 1.015; CI = 1.000485 to 1.03). For every 1-U increase in alanine aminotransferase and aspartate aminotransferase, the odds of a patient needing another surgical intervention increased by 0.8% (P = 0.048; OR = 1.008; CI = 1.000239 to 1.02) and 3.3% (P = 0.049; OR = 1.033; CI = 1.000195 to 1.07), respectively.
Preoperative clinicopathologic test results for 107 dogs and 13 cats that underwent total ear canal ablation with lateral bulla osteotomy (TECA-LBO).
| Variable | Mean ± SD or median (range) | Reference range |
|---|---|---|
| CBC | ||
| Band neutrophil count | 0 (0–0.71) | 0.0–0.1 |
| (X 103 neutrophils/μL) | ||
| Hct (%) | 45 ± 0.5 | 40.5–59.9 |
| WBC count (X 103 WBCs/μL) | 11.6 (5.1–37.4) | 4.7–15.2 |
| Neutrophil count | 8.4 (3.3–27.0) | 2.41–10.88 |
| (X 103 neutrophils/μL) | ||
| Lymphocyte count | 1.8 (0.6–13.5) | 1.10–3.96 |
| (X 103 lymphocytes/μL) | ||
| Platelet count (X 103 platelets/μL) | 359.5 (145-914) | 147–423 |
| Serum biochemistry panel | ||
| Glucose (mg/dL) | 102 (63–232) | 82–132 |
| BUN (mg/dL) | 15 (5-47) | 9–26 |
| Creatinine (mg/dL) | 0.8 (2.8–0.4) | 0.3–1.1 |
| Alanine aminotransferase (U/L) | 36 (6–730) | 18–100 |
| Alkaline phosphatase (U/L) | 77.5 (9–4,499) | 13–240 |
| γ-Glutamyltransferase (U/L) | 3 (0–13) | 0–5 |
| Aspartate aminotransferase (U/L) | 24 (13–139) | 18–56 |
| Cholesterol (mg/dL) | 219 ± 6.2 | 130–354 |
| Albumin (g/dL) | 3.3 (0.8–4.3) | 3.2–4.3 |
| Globulin (g/dL) | 3.6 (2.2–6.5) | 1.9–3.1 |
| Total bilirubin (mg/dL) | 0.1 (0–0.8) | 0.1–0.6 |
| Potassium (mmol/L) | 4.3 ± 0.4 | 2.8–4.7 |
Normally distributed data are presented at mean ± SD; nonnormally distributed data are presented as median (range).
Seventy-nine of 120 (65.8%) patients had a skull CT scan performed prior to surgery for preoperative planning. For the patients who underwent preoperative imaging, final imaging reports were assessed and revealed lymphadenopathy in 48 of 79 (62.0%), otitis media in 43 of 79 (54.4%), osteomyelitis-lysis of the bone in 23 of 79 (29.1%), otitis interna in 11 of 79 (13.9%), and ear canal rupture in 7 of 79 (8.9%) patients. Patients without evidence of osteomyelitis or lysis of the bulla and otitis interna on CT were 70% (P = 0.04; OR = 0.30; CI = 0.11 to 0.87) and 78% (P = 0.04; OR = 0.22; CI = 0.06 to 0.84) less likely, respectively, to experience infection-related signs postoperatively.
Surgical data
Twenty-eight of 120 (23.3%) patients underwent bilateral single-session (BLSS) TECA-LBOs, and the other 92 of 120 (76.7%) patients underwent UL TECA-LBOs. Perioperative antimicrobials were administered in 118/120 (98.3%) patients, including cefazolin in 109 118 (92.4%), ampicillin-sulbactam in 12 of 118 (10.2%), and 2 of 118 (1.7%). Neither perioperative antimicrobial choice nor type of TECA-LBO surgery (BLSS or UL) was significantly associated with any outcome variable.
Intraoperative and anesthetic findings and complications were described, including hypotension in 43 of 120 (35.8%) patients, purulent material or abscessation within or around the ear canal or bulla in 32 of 120 (26.6%) patients, rupture of the ear canal in 19 of 120 (15.8%) patients, intraoperative hypothermia in 19 of 120 (15.8%) patients, and excessive hemorrhage in 13 of 120 (10.8%) patients. Patients without intraoperative hypothermia were 97% less likely to exhibit long-term neurologic signs as those with intraoperative hypothermia (P = 0.04; OR = 0.03; CI = 0 to 0.37).
Based on evaluation of the surgery reports, which were available for 120 of 120 (100%) patients, the aural epithelium was removed from the bullae via curettage, and bullae were flushed copiously with sterile saline in 100% of cases. In a few select cases, additional antiseptics were used including hypochlorous acid in 6 of 120 (5.0%) patients and betadine solution in 2 of 120 (1.7%) patients. Patients whose bullae were not flushed with hypochlorous acid were 94% less likely to exhibit long-term neurologic signs as those flushed with hypochlorous acid (P = 0.023; OR = 0.06; CI = 0.007 to 0.439). A passive (Penrose) drain or active suction (Jackson-Pratt) drain were placed into the surgical site in 16 of 149 (10.7%) ears and 13 of 149 (8.7%) ears, respectively. The suture material used for closure following the TECA-LBO procedures included poliglecaprone 25 in 146 of 149 (97.9%) ears, polydioxanone (PDS) in 40 of 149 (26.8%) ears, and nylon in 103 of 149 (69.1%) ears. Intralesional analgesia was administered at the time of surgery in 23 of 120 (19.2%) patients, including SC bupivacaine injection in 10 of 23 (43.5%), SC liposomal bupivacaine (Nocita) injection in 9 to 23 (39.1%), bupivacaine administered as a splash block in 3 to 23 (13.0%), and liposomal bupivacaine (Nocita) administered as a splash block in 1 to 23 (4.3%). Use of a surgical drain, suture type, and intralesional analgesia was not significantly associated with any of the outcome variables.
The overall median duration of surgery was 95 minutes (range, 45 to 305 minutes), and overall median duration of anesthesia was 170 minutes (range, 80 to 460 minutes). The median duration of UL TECA-LBO was 90 minutes (range, 45 to 295 minutes) with a median anesthetic duration of 155 minutes (range, 80 to 315 minutes), and the median duration of BLSS TECA-LBO was 150 minutes (range, 80 to 305 minutes) with a median anesthetic duration of 225 minutes (range, 90 to 460 minutes). The duration of anesthesia and surgery was not significantly associated with any outcome variables.
Biopsy specimens were obtained from 109 of 149 (73.1%) ears, all samples were evaluated by a board-certified veterinary pathologist, and 7 different histopathologic findings were noted. Chronic otitis was the most common histopathologic finding and was present in 80 of 109 (73.4%) samples submitted. Additional specimen results included ceruminous adenoma (8/109 [7.3%] samples), ceruminous gland adenocarcinoma (5/109 [4.5%]), inflammatory polyps (4/109 [3.6%]), squamous cell carcinoma (3/109 [2.7%]), cholesteatoma (2/109 [1.8%]), histiocytic sarcoma (1/109 [0.9%]), and soft tissue sarcoma (1/109 [0.8%]). All neoplasms were noted to be completely excised with clean margins on histopathologic examination. Patients with histopathology findings consistent with inflammatory disease were 3.68 times as likely to exhibit neurologic signs postoperatively within the short-term follow-up period as those without histopathology findings consistent with inflammatory disease (P = 0.025; OR = 3.68; CI = 1.39 to 9.70). Patients without cholesteatomas were 96.4% less likely to exhibit long-term neurologic signs as those diagnosed with cholesteatomas (P = 0.04; OR = 0.036; CI = 0.002 to 0.718).
Samples for aerobic and anaerobic cultures of the tympanic bulla were obtained from 111 of 120 (92.5%) patients with the remaining 9 of 120 (7.5%) patients having no cultures collected. If samples were collected from both ears during a BLSS TECA-LBO, the culture results were combined to account for a single culture per patient. Samples were collected prior to flushing the bulla in 69 of 111 (62.1%) patients, after flushing the bulla in 31 of 111 (27.9%) patients, and pre- and postflush samples were pooled in 11 of 111 (9.9%) patients. Growth of bacteria was appreciated in 95 of 111 (85.6%) of cultures with the growth of only one bacterial organism in 54 of 111 (48.6%) cultures, the growth of two or more bacterial organisms in 41 of 111 (36.9%) cultures, and no bacterial growth in 16 of 111 (14.4%) cultures. Gram-positive organisms were present in 78 of 111 (70.2%) cultures and gram-negative organisms were present in 37 of 111 (33.3%) cultures. Staphylococcus spp were the most common bacterial isolate, cultured from 55 of 111 (49.5%) cultures. Of the 37 of 111 cultures positive for Staphylococcus pseudintermedius, 5 of 37 (13.5%) were methicillin-resistant. The second most common bacteria isolated was Streptococcus cultured from 19 of 111 (17.1%) cultures, followed by Pseudomonas from 18 of 111 (16.2%) cultures, Enterococcus spp from 13 of 111 (11.7%) cultures, Escherichia coli from 11 of 111 (9.9%) cultures, and Corynebacterium from 8 of 111 (7.2%) cultures. Other bacterial isolates included Actinomyces spp, Proteus mirabilis, Acinetobacter baumannii, and Trueperella pyogenes. Patients without positive cultures for Staphylococcus pseudointermedius were 66% less likely to exhibit infection-related signs postoperatively as those with positive cultures (P = 0.035; OR = 0.34; CI = 0.14 to 0.82). Patients without gram-positive organisms were 73.4% less likely to exhibit infection-related signs postoperatively as those whose cultures grew gram positive organisms (P = 0.049; OR = 0.266; CI = 0.07 to 0.95). The number of organisms on culture and presence of methicillin resistance were not significantly associated with any outcome variables.
Postoperative data
Empirical antimicrobials were administered postoperatively in 92 of 120 (76.6%) patients, including 88 of 92 (95.6%) patients awaiting intraoperative cultures results and 4 of 92 (4.3%) without intraoperative cultures The most commonly administered postoperative empiric antimicrobials included amoxicillin-clavulanate in 45 of 92 (48.9%) patients, cephalexin in 22 of 92 (23.9%) patients, enrofloxacin in 7 of 92 (7.6%) patients, and marbofloxacin in 5 of 92 (5.4%) patients. Twenty-eight of 120 (23.3%) patients were not prescribed empirical antimicrobials postoperatively, including 19 of 28 (67%) patients with intraoperative cultures that revealed no bacterial growth in 10 of 19 (52%) and positive bacterial growth in 9 of 19 (48%), which resulted in administration of a definitive antimicrobial based on susceptibility. Nine of 28 (33%) patients without administration of empirical antimicrobials did not have intraoperative cultures submitted. The durations of antimicrobial administration are listed (Table 2). Intraoperative culture and susceptibility results based on the most commonly tested antimicrobials and the most cultured bacteria are summarized (Tables 3 and 4). Patients who were not administered empiric antimicrobials postoperatively were 2.83 times as likely to exhibit short-term neurologic signs as those started on empiric antimicrobials postoperatively (P = 0.035; OR = 2.83; CI = 1.2 to 6.70), while the later was 91.6% less likely to exhibit long-term neurologic signs as the former (P = 0.035; OR = 0.084; CI = 0.011 to 0.67), but this was not associated with any other outcome variable. If bacterial cultures were positive and the patients were started on definitive antimicrobials within the short-term follow-up period, these patients were found to be 85.8% less likely to exhibit infection-related signs postoperatively (P = 0.04; OR = 0.142; CI = 0.025 to 0.821) as patients who had positive cultures and were not started on definitive antimicrobials postoperatively. If bacterial cultures were positive and the patients were not started on definitive antimicrobials within the short-term follow-up period, these patients were 10.3 times as likely to require a revision surgery as those with positive cultures who were started on definitive antimicrobials (P = 0.025; OR = 10.3; CI = 1.8 to 57). With every additional month of systemic antimicrobials administered postoperatively, a patient was 9.88 times as likely to be euthanized due to recurrence of disease (P = 0.023; OR = 9.88; CI = 1.92 to 50.68) and 3.65 times as much likely to require a revision procedure (P = 0.035; OR = 3.65; CI = 1.27 to 10.45).
Duration of postoperative antimicrobial administration (median [range]) for the animals in Table 1.
| Variable | No. of patients | Duration of antimicrobial administration (range) |
|---|---|---|
| Empirical antimicrobial administration (n = 92) | ||
| No intraoperative culture | 4 (4.3%) | 7 d (5–30 d) |
| Bacterial resistance to antimicrobial choice; antimicrobial changed as appropriate based on culture | 27 (29.3%) | 15 d (0–90 d) |
| Bacterial resistance to antimicrobial choice; antimicrobial not changed based on culture | 22 (23.9%) | 7 d (6–30 d) |
| Empiric AM with culture susceptible to antimicrobial choice | 39 (42.4%) | 10 d (7–21 d) |
| No empirical antimicrobial administration (n = 28) | ||
| Positive intraoperative culture with administration of appropriate antimicrobials | 9 (25.0%) | 4 d (4–8 d) |
Mean duration of empirical antimicobial administration was 0.21 ± 0.4 weeks prior to documenting the duration following culture results. Note that 9 of 28 patients not administered empirical antimicrobials did not have intraoperative cultures submitted, and 10 of 28 with intraoperative cultures submitted had no bacterial growth.
A summary of intraoperative culture and susceptibility results for cases with only a single organism cultured (n = 54) based on the most commonly tested antimicrobials and cultured bacteria.
| Antimicrobial | No. of cases with antimicrobial tested | No. of cases with prior antimicrobial exposure | No. of cases susceptibility | No. of cases with resistance | Most-resistant bacteria to antimicrobial exposure (No. of antimicrobial isolates/total No. of isolates [%]) |
|---|---|---|---|---|---|
| Amikacin | 27 | 0 | 25 (92.6%) | 2 (7.4%) | Pseudomonas aeruginosa (1/2 [50%]) |
| Amoxicillin-clavulanate potassium | 51 | 8 (14.8%) | 30 (58.8%) | 21 (41.2%) | Staphylococcus pseudintermedius (7/21 [33.3%]) |
| Ampicillin | 44 | 0 | 16 (36.4%) | 28 (63.6%) | S pseudintermedius (15/28 [53.6%]) |
| Ceftazidime | 17 | 1 (1.8%) | 9 (52.9%) | 8 (47.1%) | P aeruginosa (3/8 [37.5%]) |
| Cephalothin | 42 | 1 (1.8%) | 23 (54.8%) | 19 (45.2%) | S pseudintermedius (5/19 [26.3%]) |
| Cefpodoxime | 23 | 4 (7.4%) | 11 (47.8%) | 12 (52.2%) | Corynebacterium spp (3/12 [25%]) |
| Chloramphenicol | 50 | 7 (12.9%) | 36 (72.0%) | 14 (28.0%) | S pseudintermedius (2/14 [14.3%]) |
| Ceftiofur | 19 | 0 | 10 (52.6%) | 9 (47.4%) | P aeruginosa (5/9 [55.6%]) |
| Clindamycin | 36 | 2 (3.7%) | 24 (66.7%) | 12 (33.3%) | S pseudintermedius (6/12 [50.0%]) |
| Enrofloxacin | 27 | 18 (33.3%) | 15 (55.6%) | 12 (44.4%) | P aeruginosa (7/12 [58.3%]) |
| Erythromycin | 39 | 0 | 28 (71.8%) | 11 (28.2%) | S pseudintermedius (6/11; 54.5%) |
| Gentamicin | 46 | 14 (25.9%) | 33 (71.7%) | 13 (28.3%) | S pseudintermedius (4/13 [30.8%]) |
| Marbofloxacin | 48 | 2 (3.7%) | 33 (68.8%) | 15 (31.2%) | S pseudintermedius (7/15 [46.7%]) |
| Oxacillin | 36 | 0 | 21 (58.3%) | 15 (41.7%) | S pseudintermedius( 5/15 [33.3%]) |
| Penicillin | 23 | 0 | 9 (39.1%) | 14 (60.9%) | S pseudintermedius (8/14 [57.1%]) |
| Tetracycline | 47 | 5 (9.2%) | 30 (63.8%) | 17 (36.2%) | S pseudintermedius (5/17 [29.4%]) |
| Trimethoprim-sulfonamide | 49 | 0% (0/54) | 31 (63.3%) | 18 (36.7%) | S pseudintermedius (6/18 [33.3%]) |
Prior antimicrobial exposure consisted of both systemic and topical treatments and included antibiotics in the same class. Note all percentage calculations are based on the number of cases with that antibiotic tested unless otherwise specified. Pseudomonas aeruginosa and Enterococcus spp have been excluded from the table because these bacteria have recognized intrinsic resistance.29
A summary of intraoperative culture and susceptibility results for cases with multiple organisms cultured (n = 41) based on the most commonly tested antimicrobials and cultured bacteria.
| Antimicrobial | No. of cases with antimicrobial tested | No. of cases with prior to antimicrobial exposure | No. of cases with complete susceptibility | No. of cases with with some resistance | No. of cases with with complete resistance | Most-resistant bacteria (No. of resistant isolates/total No. of isolates) |
|---|---|---|---|---|---|---|
| Amikacin | 36 | 0 | 23 (63.9%) | 13 (36.1%) | 0 | Pseudomonas aeruginosa (3/13 [23.1%]) |
| Amoxicillin-clavulanate potassium | 38 | 6 (14.6%) | 17 (44.7%) | 17 (44.7%) | 4 (10.5%) | Staphylococcus pseudintermedius (6/21 [28.6%]) |
| Ampicillin | 36 | 0 | 9 (25.0%) | 18 (50.0%) | 9 (25.0%) | Spseudintermedius (14/27 [51.9%]) |
| Ceftazidime | 26 | 0 | 9 (34.6%) | 16 (61.5%) | 1 (3.9%) | Corynebacterium spp (4/17 [23.5%]) |
| Eschericia coli (4/17 [23.5%]) | ||||||
| S pseudintermedius (4/17 [23.5%]) | ||||||
| Cephalothin | 36 | 2 (4.9%) | 9 (25.0%) | 20 (55.6%) | 7 (19.4%) | E coli (7/27 [25.9%]) |
| Cefpodoxime | 24 | 3 (7.3%) | 9 (37.5%) | 13 (54.2%) | 2 (8.3%) | Corynebacterium spp (3/15 [20%]) |
| S pseudintermedius (3/15 [20%]) | ||||||
| Chloramphenicol | 38 | 4 (9.8%) | 25 (65.8%) | 12 (31.6%) | 1 (2.6%) | S pseudintermedius (3/13 [23.1%]) |
| Ceftiofur | 32 | 0 | 6 (18.8%) | 22 (68.7%) | 4 (12.5%) | S pseudintermedius (10/26 [38.5%]) |
| Clindamycin | 33 | 1 (2.4%) | 12 (36.4%) | 17 (51.5%) | 4 (12.1%) | S pseudintermedius (7/21 [33.3%]) |
| Enrofloxacin | 36 | 14 (34.1%) | 15 (41.7%) | 14 (38.9%) | 7 (19.4%) | S pseudintermedius (11/21 [52.4%]) |
| Erythromycin | 34 | 0 | 12 (35.3%) | 19 (55.9%) | 3 (8.8%) | S pseudintermedius (9/22 [40.9%]) |
| Gentamicin | 38 | 14 (34.1%) | 30 (79.0%) | 7 (18.4%) | 1 (2.6%) | S pseudintermedius (2/8 [25%]) |
| Marbofloxacin | 38 | 2 (4.9%) | 21 (55.3%) | 10 (26.3%) | 7 (18.4%) | S pseudintermedius (8/17 [47.1%]) |
| Oxacillin | 34 | 0 | 6 (17.6%) | 21 (61.8%) | 7 (20.6%) | Eschericia coli (7/28 [25.0) |
| Enterococcus spp (7/28 [25.0%]) | ||||||
| Penicillin | 34 | 0 | 5 (14.7%) | 18 (52.9%) | 11 (32.4%) | S pseudintermedius (17/29 [58.6%]) |
| Tetracycline | 39 | 2 (4.9%) | 18 (46.2%) | 15 (38.4%) | 6 (15.4%) | S pseudintermedius (12/21 [57.1%]) |
| Trimethoprim-sulfamethoxazole | 38 | 0 | 19 (50.0%) | 18 (47.4%) | 1 (2.6%) | S pseudintermedius (8/19 [42.1%]) |
Prior antimicrobial exposure consisted of both systemic and topical treatments and included antibiotics in the same class. Note all percentage calculations are based on the number of cases with that antibiotic tested unless otherwise specified. Pseudomonas aeruginosa and Enterococcus spp have been excluded from the table because these bacteria have recognized intrinsic resistance.46
A summary of the infection-related and neurologic postoperative complications is listed (Table 5). A summary of complications between dogs and cats is listed (Table 6). Patients who exhibited no neurologic signs within 48 hours were only 5% as likely to exhibit neurologic signs within the short-term postoperative period (P = 0.008; OR = 0.05; CI = 0.02 to 0.16) and 7% as likely to exhibit neurologic signs within the intermediate-term postoperative period (P = 0.035; OR = 0.07; CI = 0.008 to 0.69) as those who exhibited neurologic signs within 48 hours postoperatively; however, postoperative neurologic signs were not significantly associated with long-term neurologic signs. In the short-term follow-up period, 13 patients had infection-related signs and 7 of these underwent a revision surgery of the initial TECA-LBO site. The invasiveness of all revision procedures varied widely from revision of the surgical incision to reexploration of the surrounding subcutaneous tissues and/or tympanic bulla, with or without drain placement. Patients without infection-related signs during the short-term follow-up period were 92.1% less likely to require a revision surgery compared to those who did exhibit infection-related signs within the short-term follow-up period (P = 0.008; OR = 0.079; CI = 0.019 to 0.332). The patients who did not need a revision procedure in the short-term follow-up were 95.5% less likely to be euthanized due to recurrence of disease compared to the patients who needed a revision procedure (P = 0.023; OR = 0.045; CI = 0.005 to 0.389).
Summary of the overall occurrence of both infection-related and neurologic complications and their dominance within the postoperative, short-, intermediate-, and long-term postoperative period in 120 patients following TECA-LBO. Neurologic signs were most common immediately following surgery and infection-related signs were predominant in the long-term follow-up period. Some patients experienced > 1 complication in each classification.
| Follow-up period | Total No. of cases with infection-related and neurologic complications | No. of cases with infection-related signs | No. of cases with neurologic signs |
|---|---|---|---|
| Postoperative (≤ 48 h) | 71/120 (58.3%) Description of signs |
2/71 (2.8%) Purulent incisional discharge (1) and incisional dehiscence (1) |
66/71 (92.9%) Ipsilateral facial nerve parlysis (56), vestibular signs (8), Horner syndrome (6), and bilateral facial nerve paralysis (5) |
| Short-term (> 48 h to 1 mo) | 59/120 (49.2%) Description of signs |
13/59 (22%) Purulent incisional discharge (7), incisional dehiscence (5), and abscess (3) |
47/59 (79.6%) Ipsilateral facial nerve paralysis (38), vestibular signs (7), Horner syndrome (7), and bilateral facial nerve paralysis (2) |
| Intermediate-term (1 to 6 mo) | 22/120 (18.3%) Description of signs |
11/22 (50%) Purulent incisional discharge (7), abscess (4) |
14/22 (63.6%) Ipsilateral facial nerve paralysis (13), vestibular signs (3), Horner syndrome (1), and bilateral facial nerve paralysis (1) |
| Long-term (> 6 mo) | 13/120 (10.8%) Description of signs |
9/13 (69.2%) Abscess (5), purulent incisional discharge (4), and pain on opening mouth (2) |
4/13 (30.8%) Ipsilateral facial nerve paralysis (3) and Horner syndrome (1) |
Summary of the incidence of neurologic and infection-related signs in dogs and cats, including those requiring a revision procedure and those that were euthanized.
| Variable | No. of dogs | No. of cats | Overall population affected |
|---|---|---|---|
| Transient neurologic complications | 42/107 (39.3%) | 5/13 (38.5%) | 47/120 (39.1%) |
| Permanent neurologic complications | 3/107 (2.8%) | 1/13 (7.7%) | 4/120 (3.3%) |
| Infection-related signs managed conservatively | 14/107 (13.7%) | 2/13 (15.4%) | 16/120 (13.3%) |
| Infection-related signs requiring revision surgery | 12/107 (11.2%) | 1/13 (7.7%) | 13/120 (10.8%) |
| 1 revision surgery for infection-related signs | 8/107 (7.5%) | 0/13 (0.0%) | 8/120 (6.6%) |
| ≥ 2 revision surgeries for infection-related signs | 4/107 (3.7%) | 1/13 (7.7%) | 5/120 (4.2%) |
| Euthanasia due to recurrence of disease | 3/107 (2.8%) | 1/13 (7.7%) | 4/120 (3.3%) |
Six of 11 (54.5%) patients with infection-related signs in the intermediate-term follow-up period underwent a revision surgery of their initial TECA-LBO site, including 3 patients that had undergone their first revision procedure within the short-term follow-up period. Five of 10 (50.0%) patients with long-term infection-related signs underwent a revision surgery of their initial TECA-LBO site, including 2 patients that had undergone their first revision procedure within the intermediate-term follow-up period.
Patients without infection-related signs at the intermediate-term follow up period were 90% less likely to require a revision surgery postoperatively as those exhibited infection-related signs (P = 0.035; OR = 0.10; CI = 0.01 to 0.67). Patients without infection-related signs at the time of their long-term follow-up were only 10.2% as likely to exhibit long-term neurologic signs as those with infection-related signs (P = 0.037; OR = 0.102; CI = 0.02 to 0.71) and 4.9% as likely to require a revision surgery (P = 0.008; OR = 0.049; CI = 0.01 to 0.26). However, patients with infection-related signs at the time of their long-term follow-up were 25.3 times as likely to be euthanized due to recurrence of disease as those without infection-related signs (P = 0.008; OR = 25.3; CI = 5.14 to 124.09). The patients exhibiting neurologic signs at the long-term follow-up were 4.75 times as likely to require a revision surgery as those without exhibiting neurologic signs (P = 0.048; OR = 4.75; CI = 1.058 to 21.327).
The mean duration of time between the initial TECA-LBO procedure and longest follow-up was 986 ± 693 days, between the initial TECA-LBO procedure and revision surgery (if indicated) was 265 ± 477 days, and between the revision surgery and follow-up was 530 ± 476 days.
Four of 120 (3.3%) patients were euthanized during the study period, all due to presence of infection-related signs following their initial TECA-LBO. Three of 4 patients were euthanized in the long-term follow-up period due to a first revision surgery being declined in the long-term period (n = 1), a revision surgery failure in the long-term period (1), and a third revision surgery being declined following recurrence after a revision surgery in both the short-term and intermediate-term periods (1). A single patient was euthanized in the intermediate-term period following a failed revision surgery in the short- and intermediate-term periods. The mean ± SD duration between the most recent revision procedure and euthanasia was 282 ± 104 days.
Discussion
To the authors’ knowledge, this is the largest retrospective analysis of complications related to TECA-LBOs in dogs and cats. Additionally, this study is the first to emphasize risk factors for infection-related signs postoperatively in the veterinary literature. A variety of significant factors were identified resulting in complicated or unsuccessful outcomes in this study. Infection-related signs postoperatively were related to bacteria type, evidence of significant disease on diagnostic imaging at the time of surgery, and failure to use the appropriate antimicrobial based on culture and sensitivity results, thus rejecting the null hypothesis. Additionally, risk factors were identified for postoperative complications including neurologic signs (infection of the site postoperatively, presence of neurologic signs prior to surgery, and deep inflammatory disease), the need for revision surgery (significant disease present at the time of surgery, appropriate antimicrobials based on culture and sensitivity were not administered, and postoperative complications related to infection and neurologic signs), and euthanasia related to the TECA-LBO surgery (systemic endocrine disease, infection-related complications, and need for revision surgery).
Potential complications during and following the TECA-LBO procedure are numerous and occasionally serious. Reported total complication rates immediately following TECA-LBO range from 21% to 82%,1,4–6,10,11,18–20,23–26,30,31 consistent with the findings of the current study in which 49.2% to 58.3% of patients exhibited complications following TECA-LBO in the first month. The overall incidence of late (≥ 6 months) complications following TECA-LBO reported in the literature are variable and range from 10.5% to 40%,1,11,18,20,24,25 and the results of this study are similar to some of the reports with a long-term complication rate of about 11%. It should be noted that higher long-term complications in previously reported studies include much lower case numbers or are over 20 years old.11,18,20,24 In the current study, neurologic signs predominated in the initial 48 hours and short-term postoperatively, representing approximately 93% and 80% of all complications, respectively. Infection-related signs were more prevalent in the intermediate- and long-term time frames, representing approximately 50% and 70% of all complications, respectively.
Patients presenting for TECA-LBO often have a long history of administration of topical antimicrobials due to the therapeutic concentrations reached in the ear canal exudates, and systemic antimicrobials, which are commonly used in cases of otitis media or severe otitis externa.12,15,17,32–35 More than half of the patients in the current study presented with a history of systemic and topical antimicrobial administration for variable durations. There are often discrepancies between the bacterial isolates and antimicrobial sensitivity patterns in the ear canal compared with those in the middle ear, so there are concerns for poorly targeting the correct bacteria when antimicrobials are chosen based on culture of the ear canal.12,13 Staphyloccocus pseudintermedius was the most common bacterial isolate in this study, and 14% of those cultures showed methicillin resistance, which is higher than a previously reported resistance rate of 4.8%.1 Patients that had S pseudintermedius and gram-positive cocci on culture samples were found were more likely to have infection-related signs postoperatively. Given the high rate of preoperative antimicrobial use and methicillin-resistant S pseudintermedius in this study, as well as the bacterial association with infection-related signs, it could be concluded that bacteria resistance from chronic antimicrobial administration may lead to infection-related complications and the potential need for an additional surgery.
While culture of the TECA-LBO site and tympanic bulla is controversial to some, it can be done to help guide postoperative antimicrobials in patients that have been exposed to a long history of antimicrobials.26,31,36 Given the somewhat sizeable body of evidence12,14,36,37 that suggests most TECA-LBO surgical sites are contaminated at the time of closure despite the surgeons’ best efforts, recommendations for postoperative antimicrobials are not unfounded. Results of recent study36 show no difference in the incidence of incisional infection immediately after surgery in dogs that received and did not receive antimicrobials perioperatively, but this study did not evaluate short and long-term complications. In the present study, 76.6% of patients were administered antimicrobials immediately after surgery for a duration ranging from 1 to 12 weeks. A variety of significant factors were identified as being significantly associated with antimicrobial administration in the current study, including higher risks of the following: neurologic signs when empirical antimicrobials were not administered within 24 hours postoperatively, infection-related signs and need for revision surgery with a failure to administer antimicrobials following a positive bacterial culture, and the need for revision surgery and euthanasia secondary to disease recurrence with longer durations of antimicrobial administration. Euthanasia was also associated with infection-related signs and the need for a revision surgery in this study. It should be noted that euthanasia related to the TECA-LBO was an infrequent occurrence (3% of the total population) and represented only 2 of 13 (15.4%) short-term infection-related complications that resulted in euthanasia and 2 of 10 (20%) long-term infection-related complications that resulted in euthanasia. In addition, euthanasia is mostly based on owner decision, in which euthanasia may be elected over the additional financial burden of chronic antimicrobial use and surgical intervention or the concern for a diminished quality of life or additional morbidity from another surgery. The importance of this information is reflected in the fact that failure to use antimicrobials in these cases has the potential to cause more morbidity and rarely mortality related to neurologic signs and recurrence of infection. Clinical decisions like intraoperative cultures and antimicrobial administration in this study were likely based on a variety of patient factors noted perioperatively that could have influenced the results presented. While it’s difficult to make statements that apply to every patient presented for TECA-LBO based on the clinician-dependent, retrospective findings in this study, in general, a patient with chronic, end-stage otitis externa may be more likely to suffer from recurrent infection following chronic antimicrobial exposure and deep infection of the bone or soft tissues, compared to a patient presenting with a shorter disease course as might be present with neoplasia. While the current study supports administration of systemic antimicrobials within the first postoperative month to prevent long-term complications when intraoperative cultures are positive for bacterial growth, each patient is different, and several factors may influence clinical decisions in regard to appropriate antimicrobial administration. A variety of microbes and antimicrobials were identified in this study with various microbes exhibiting relatively high percentages of susceptibility to specific antimicrobials (Tables 3 and 4), which should benefit the veterinary literature.
Computed tomography of the skull prior to TECA-LBO has become a commonplace diagnostic for presurgical assessment of patients with extensive local disease and disease extending beyond the ear canal or bulla and detecting the presence and severity of otitis media.16,34,38,39 A previous study documented a correlation between histopathologic severity of middle ear disease and increased opacity within the bulla, as well as bony proliferation of the bulla on CT,5 while another noted that CT diagnosis of otitis interna was based on significant destruction of the inner ear.39 Preoperative CT scans of the skull were performed in approximately 66% of the patients included in this study, and presence of otitis interna and osteomyelitis or lysis of the tympanic bulla were associated with infection-related complications. The association between bone lysis or osteomyelitis of the inner ear and bulla and infection-related complications could suggest a nidus of remaining infection leading to complications, and potential consideration for longer courses of antimicrobials to address inner ear and bone infection.
Histopathologic diagnoses consistent with an inflammatory disease process accounted for most of the samples in this study, while results consistent with a cholesteatoma were rare. Pain on opening the mouth is commonly reported in patients with cholesteatomas, reported in 20% to 55% of cases in previous reports, along with a high rate of recurrence (upwards of 50%) following TECA-LBO.22,40–42 The results of this study indicate that animals with a histopathologic diagnosis of inflammation or cholesteatoma were more likely to exhibit neurologic signs in the short-term and long-term periods, respectively. Additionally, animals that had pain on opening of the mouth were significantly more likely to undergo revision surgery, with infection-related complications approaching significance. Inflammation is always associated with development of a cholesteatoma,22 and given that further differentiation of histopathology results without the mention of cholesteatoma in the final diagnosis was beyond the scope of this study, cholesteatomas could have been underdiagnosed. Additionally, pain on opening the mouth could be a previously underreported sign of extensive disease associated with typical otitis externa and media.
Approximately 23% of the patients included in the current study presented with neurologic signs (including but not limited to facial nerve paralysis) prior to TECA-LBO, which is significantly higher than previous studies1,4,6,23 reporting an incidence from 6% to 15% in dogs and cats. In the animals of this study, the presence of neurologic signs at presentation was associated with short-term neurologic signs and the need for a revision surgery, suggesting that animals presenting with neurologic signs may be likely to have more extensive disease. Within 48 hours of surgery, the animals of this study showed an incidence within the entire population of facial nerve paralysis of about 50%, which is similar to previous reports4,6,9–11,18–24 that note postoperative facial nerve paralysis in 3% to 58%. Also, matching the literature, a majority of the neurologic signs in this study population were transient, with an incidence of only 3.3% of the entire population exhibiting permanent signs. Patients with neurologic signs postoperatively in this study were found to be more likely to exhibit infectious recurrence and require a revision procedure, which may be indicative of a more extensive dissection during surgery or reflect the severity of disease.
A recent study26 that evaluated BLSS and UL staged TECA-LBO procedures found that there were no significant differences in anesthetic or perioperative complications between the 2 procedure types. In the study presented here, patients initially examined with UL disease were significantly more likely to experience postoperative neurologic signs. This result may be due to more extensive disease in UL cases or due to local invasion of tissues from neoplasia, which is often UL in nature.
The use of hypochlorous acid for lavage of the tympanic bulla has not been previously described, although the findings of the current study advocate caution for its use in these specific circumstances. The subset of patients in which hypochlorous acid was used to lavage the bullae, although very small, was more likely to exhibit long-term neurologic signs. Hypochlorous acid and similar oxidizing agents have been demonstrated to adversely affect nervous tissue; nevertheless, it is difficult to discern whether its direct use for lavage of the bullae inadvertently caused local neurologic damage or its use was chosen based on the presence of severe disease, which predisposed to neurologic complications.43–45
In this study, there was much overlap in patients experiencing more than one of the outcome variables. For instance, long-term (permanent) neurologic signs postoperatively were more likely to occur in animals that also had infection-related signs at the long-term follow-up period and needed a revision surgery. Additionally, the need for a revision surgery and presence of long-term infection complications were associated with animals being euthanized for recurrence of infectious disease. Interestingly, this study also identified that animals with an endocrine-related comorbidity and elevated blood analytes (alanine aminotransferase, aspartate aminotransferase, and cholesterol), which may be consistent with endocrine disease, were also more likely to require a revision surgery and be euthanized due to recurrence of disease. Otitis externa and media are commonly associated with other dermatologic conditions, particularly allergic or immune-mediated skin diseases or systemic diseases like hypothyroidism and hyperadrenocorticism.11,34,46 Although only 10% of the population in this study were classified as having an endocrine disorder, the presence of a concurrent systemic illness could have made these patients less systemically healthy, poorer anesthetic candidates, and exhibit suboptimal signs at healing. It is also important to consider that these owners were more likely to elect euthanasia of the animal rather than place them through an additional recommended surgery.
This study has several limitations inherent with retrospectives studies, including incomplete medical records, owner recall bias, inability to control treatments administered, and variability in follow-up time. As much of the data as possible were obtained from the medical records to limit recall bias. A variety of board-certified surgeons and supervised surgical residents of various experience levels conducted the procedures and managed postoperative decision-making, and this could have influenced complication rates within and between groups; however, it was difficult to determine retrospectively the exact rolls of all participating surgeons retrospectively. All clients consented to have their patient undergo treatment based on the clinician’s preference. Ultimately, a randomized, controlled prospective study would need to be performed to determine the true effects of antimicrobial therapy on complication rates and outcomes of TECA-LBO surgeries, but given the findings of this study, there may be inherent ethical risks associated with such a study if it were to include withholding antimicrobial administration. Although this is the largest study to date evaluating TECA-LBO outcomes, certain subgroups such as cats and patients with cholesteatoma were underrepresented, which may have affected analysis of those populations. Given the vast number of variables assessed in the present study, it is possible that some of the significant findings described could be false-positive results. Future studies assessing new significant variables noted in the present study with a focused approach should be considered to either weaken or strengthen their significance for postoperative TECA-LBO patients.
The veterinary literature has limited information regarding the use of antimicrobials to prevent postoperative complications in patients undergoing TECA-LBO. This study provides additional valuable information to the literature on risk factors for occurrence of neurologic complications, but it also identified factors specific to previously underreported infection-related complications, including the need for revision surgery and death related to these complications. Although no association was found between the duration and choice of systemic antimicrobial administration, it is apparent that the use of antimicrobials postoperatively could play a role in the successful long-term outcome of TECA-LBO procedures. Additionally, the extensive data documented from antimicrobial use and bacterial resistance may help guide the clinician on empirical antimicrobial choices. This study will also provide clinicians with additional information for appropriate owner counseling on complications associated with the TECA-LBO procedure.
Acknowledgments
No external funding was used in this study. The authors declare that there were no conflicts of interest.
The authors thank Dr. Brian VanderVen for assistance with refining the microbiological data presented in the manuscript.
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