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Al-Qurayshi Z, Randolph GW, Alshehri M, Kandil E. Analysis of Variations in the Use of Intraoperative Nerve Monitoring in Thyroid Surgery. JAMA Otolaryngol Head Neck Surg. 2016;142(6):584–589. doi:10.1001/jamaoto.2016.0412
Intraoperative nerve monitoring (IONM) is increasingly performed during thyroid surgery.
To examine the use of IONM and its association with patient demographic characteristics and surgeon volume.
Design, Setting, and Participants
A cross-sectional analysis used the State Inpatient Databases from January 1, 2010, to December 31, 2011, to assess patient demographic characteristics and surgeon volume. Available 30-day readmission data for all adult patients (aged ≥18 years) who underwent thyroidectomy in Florida, New York, and Washington were included. Follow-up was completed on December 31, 2011, and data were analyzed from March 11, 2015, to February 17, 2016.
Main Outcomes and Measures
Use of IONM and incidence of postoperative vocal cord paralysis.
A total of 17 268 patients undergoing thyroidectomy were included (20.3% men; 79.7% women; mean [SD] age, 53.0 [15.1] years), of whom 1433 patients (8.3%) had IONM. Patients who were significantly less likely to undergo IONM included black patients (185 [7.9%]; adjusted odds ratio [AOR], 0.79; 95% CI, 0.65-0.97) and those with Medicare (382 [8.4%]; AOR, 0.81; 95% CI, 0.69-0.94) or Medicaid (125 [5.5%]; AOR, 0.59; 95% CI, 0.48, 0.74) health coverage. Black patients had a higher prevalence of vocal cord paralysis compared with white patients (37 [1.6%] vs 138 [1.3%]; AOR, 1.64; 95% CI, 1.11-2.43) in a multivariate model that also controlled for IONM use. Low-volume surgeons were more likely to use IONM (1199 [9.2%] vs 234 [5.5%]; AOR, 1.76; 95% CI, 1.48-2.09). However, patients treated by low-volume surgeons had a higher risk for vocal cord paralysis compared with those treated by high-volume surgeons (187 [1.4%] vs 26 [0.6%]; AOR, 2.47; 95% CI, 1.61-3.80). The risk for vocal cord paralysis was not associated with the performance of IONM (AOR, 0.74; 95% CI, 0.48-1.16) or the type of thyroidectomy (AOR, 1.04; 95% CI, 0.75-1.44).
Conclusions and Relevance
Disparities in the use of IONM are based on demographic factors of the patients and surgeon volume. Intraoperative nerve monitoring appears to be used less in black patients or those with Medicare health coverage and is not associated with the risk for vocal cord paralysis.
The introduction of routine recurrent laryngeal nerve (RLN) identification has made thyroid surgery safer.1 Visualization of the RLN is currently considered the standard of care for prevention of nerve injury and the reduction of nerve palsy during thyroidectomy.2-6 The risk for permanent RLN injury is reported to be less than 1% in expert hands, but transient nerve palsy occurred in as many as 25% of cases in some reports.2,7-9
Intraoperative nerve monitoring (IONM) enhances identification of the RLN by providing a functional dynamic of evoked electromyography generated through nerve stimulation.3,10 Intraoperative nerve monitoring has been used as an adjunct to assist with identification of the RLN and to predict function after dissection. Although its use has increased and IONM has found its way to numerous guidelines, the exact role of IONM during thyroid surgery is still evolving.9,11 Some evidence supports the routine use of IONM in second operations, total thyroidectomy with neck dissection, and cases of malignant disease, where a trend for a lower rate of RLN palsy has been observed.9,11-13 The purpose of this study is to investigate the use patterns of IONM in relation to patient, hospital, and surgeon characteristics.
Question Does the use of intraoperative nerve monitoring (IONM) in thyroid surgery vary based on the patients’ demographic and economic factors and surgeon volume?
Findings In this cross-sectional analysis, black patients and those with Medicare coverage were less likely to undergo IONM, and low-volume surgeons were more likely to use IONM. A higher risk for vocal cord paralysis was significantly associated with black patients and low-volume surgeons but not with IONM use.
Meaning Demographic factors and surgeon experience play significant roles in the use of IONM; addressing these determinants and the development of educational outreach programs are warranted.
We performed a cross-sectional analysis using the State Inpatient Database for Florida, New York, and Washington from January 1, 2010, through December 31, 2011. The selection of these states was based on their year of availability and completeness of recorded variables. The State Inpatient Database is part of the Healthcare Cost and Utilization Project, sponsored by the Agency for Healthcare Research and Quality. The State Inpatient Database includes inpatient discharge records from community hospitals for a given state. The data include all patients, regardless of payer, which provides a unique view of inpatient care in a defined market or state over time. The State Inpatient Database is publicly available, and the deidentified data are exempt from approval of the institutional review board.14
We used the International Classification of Disease, 9th Revision (ICD-9) to define the study variables. The study population consisted of adult inpatients (aged ≥18 years) who underwent thyroidectomy (ICD-9 codes 06.2, 06.3, and 06.4). Thirty-day postoperative readmission data were included. The main study outcomes included the use of IONM (ICD-9 code 00.94), whereas secondary objectives included the association of IONM with 30-day postoperative vocal cord paralysis (present vs absent).
We considered patient demographic, socioeconomic, clinical, and hospital factors for this analysis. Patient demographics included age (<45, 45-65, and >65 years), sex, and race/ethnicity (white, black, Hispanic, and other). Socioeconomic factors included the main payer for health care services (Medicare, Medicaid, private insurance, or self-pay). Clinical factors included the thyroid diagnosis (Graves disease, benign disorder, and malignant neoplasm), thyroidectomy type (partial or unilateral and total), whether radical lymph node dissection was performed, overweight (body mass index [calculated as weight in kilograms divided by height in meters squared] ≥25), inpatient death, a modification of the Charlson Comorbidity Index score to assess patient comorbidities (low, 0-1; medium to low, 2-3; intermediate, 4-5; and high, ≥6),15 and surgeon volume (1-56 thyroidectomies per year [≤75th percentile or low] and ≥57 thyroidectomies per year [>75th percentile or high]). Hospital volume was defined as the number of thyroidectomies per year (1-289 [≤75th percentile or low] vs ≥290 [>75th percentile or high]).
Follow-up was completed on December 31, 2011, and data were analyzed from March 11, 2015, to February 17, 2016. We used univariate logistic regression models to examine the association between each of the independent factors and the outcomes of interest. Factors with a significant association were considered confounders and were included in multivariate logistic regression models. Multivariate logistic regression models were used for calculating the odds ratio (OR) and the 95% CI. Significance level was set as α = .05. All data analysis was performed using SAS for Windows (version 9.3; SAS Institute Inc).
A total of 17 268 discharge records were identified from 2010 to 2011 (20.3% men; 79.7% women) (Table 1). The mean (SD) age of the study population was 53.0 (15.1) years. Most of the sample was white (62.5%) and had private insurance (57.1%). Benign thyroid disorders formed more than half of the diagnoses (56.3%), whereas malignant neoplasms accounted for 40.5% of the study population; only 3.1% had Graves disease. Of the total study population, 1433 patients (8.3%) underwent IONM with their thyroidectomy. Through the 30-day postoperative period, vocal cord paralysis was reported in 213 cases (1.2%), and 39 patients (0.2%) died during their hospital stay. Hospital and clinical factors are described in Table 2.
White patients were more likely to undergo IONM (934 [8.9%]) compared with black patients (185 [7.9%]; adjusted OR [AOR], 0.79; 95% CI, 0.65-0.97) and ethnic or racial minority patients, including but not limited to Asian, Pacific Islander, and Native American (85 [4.3%]; AOR, 0.50; 95% CI, 0.39-0.64) (Table 3). Similarly, patients with private insurance were more likely to have IONM (874 [9.1%]) compared with patients with Medicare (382 [8.4%]; AOR, 0.81; 95% CI, 0.69-0.94) or Medicaid (125 [5.5%]; AOR, 0.59; 95% CI, 0.48-0.74) health coverage. With respect to surgeon volumes, low-volume surgeons were more likely to use IONM compared with high-volume surgeons (1199 [9.2%] vs 234 [5.5%]; AOR, 1.75; 95% CI, 1.48-2.09). Similarly, the prevalence of IONM use in low-volume hospitals was significantly higher than in high-volume centers (923 [8.3%] vs 198 [5.8%]; AOR, 1.35; 95% CI, 1.13-1.61). On the other hand, IONM was most likely to be performed in patients undergoing total thyroidectomy rather than unilateral thyroidectomy (467 [7.2%] vs 966 [9.0%]; AOR, 1.40; 95% CI, 1.23-1.61).
After controlling for other prognostic factors, patients who did not receive IONM had a lower rate of vocal cord paralysis compared with patients who did, although this difference was not statistically significant (189 [1.2%] vs 24 [1.7%]; AOR, 0.74; 95% CI, 0.48-1.16) (Table 4). Factors that showed significant association with vocal cord paralysis in the multivariate model included being older, black racial background, malignant disease, management by low-volume surgeons, and radical neck dissection.
In this study we found that patients who underwent IONM were more likely to be white than black or another ethnic or racial minority. In addition, patients with private insurance were more likely to undergo monitoring than patients with Medicaid coverage or self-pay. We also observed that high-volume surgeons and hospitals were the least likely to use IONM. Development of vocal cord paralysis after surgery was independently associated with age, race/ethnicity, thyroid diagnosis, surgeon volume, and whether a radical neck dissection was performed. Development of vocal cord paralysis was lower in patients who did not undergo IONM, although this difference was not statistically significant.
Recurrent laryngeal nerve injury is an uncommon but significant complication of thyroid surgery. The resulting vocal cord paralysis may result in significant physical, social, and occupational impairment. Approximately 75% of nerve injuries result from nerve traction.16,17
Two guideline studies from professional societies18-20 note that IONM has utility in neural identification, reduction of transient nerve paralysis rates, prognostication of nerve function, and avoidance of bilateral vocal cord paralysis. Intraoperative nerve monitoring is included in the American Academy of Otolaryngology–Head and Neck Surgery guidelines18 as an option during thyroid and parathyroid surgery and in particular during bilateral thyroid surgery, revision thyroid cancer surgery, or surgery involving a single functional RLN. Intraoperative nerve monitoring is also recommended by the American Head and Neck Society guidelines19 because it provides functional information about neural status during and at the conclusion of surgery and is believed to have special utility in thyroid cancer surgery with preoperative neural dysfunction. The 2015 American Thyroid Association guidelines for thyroid nodules and cancer20 note that IONM can be used to facilitate nerve identification and to confirm neural function.
In previous survey analyses,21-23 rates of IONM use have increased during the last decade. Intraoperative nerve monitoring is currently used in approximately 80% of thyroid surgical procedures performed by head and neck surgeons and by more than 50% of general surgeons in the United States and is used more commonly by higher-volume surgeons. In 2012, German researchers found that IONM can increase the surgical quality results of younger surgeons to a level consistent with that of their more experienced supervising surgeons.24 A recent survey of more than 40 thyroid or endocrine fellowship–trained surgeons25 suggests that after exposure to attending surgeons who use and do not use IONM, the fellowship-trained surgeons use IONM in nearly 100% of their own subsequent cases.25
Some studies found a decreased risk for vocal cord paralysis with use of IONM, but others have failed to demonstrate a significant association between the use of IONM and reduction in the risk for RLN palsy.5,7,9,11,26-28 Zheng et al29 performed a meta-analysis of 36 487 at-risk RLNs identified from 14 different studies and concluded that IONM decreases the risk for transient RLN palsy without affecting the rates of permanent injuries. Another meta-analysis30 described a similar finding.
Our study is limited by inclusion of inpatients only and the administrative nature of the database, which lacks clinical details such as factors related to the intraoperative environment or other specifics of management. Given our use of the administrative database, we are likely to some degree to underestimate the true rate of vocal cord paralysis; many of these cases may not be diagnosed during the initial inpatient admission, and many may be diagnosed, evaluated, and treated beyond our 30-day window. On the other hand, the strengths of the study include the large and generalizable study sample, the availability of a wide array of factors that were assessed for their confounding effect, and a 30-day follow-up for admissions.
We found disparities in the use of IONM based on the patients’ demographic factors and by hospital and surgeon volumes. Black patients and those with Medicare health coverage were less likely to have IONM used for their surgery, and black patients had a higher risk for vocal cord paralysis, even after adjustment for confounders, including the use of IONM. Another key finding is that the use of IONM during thyroid surgery was not associated with the risk for vocal cord paralysis. We believe further research is indicated to look at the determinants of this underuse of IONM technology in patients with certain race/ethnicity and medical insurance coverage.
Corresponding Author: Emad Kandil, MD, Department of Surgery, Tulane University School of Medicine, 1430 Tulane Ave, Mail Stop SL-22, New Orleans, LA 70112 (firstname.lastname@example.org).
Accepted for Publication: February 20, 2016.
Published Online: April 21, 2016. doi:10.1001/jamaoto.2016.0412.
Authors Contribution: Dr Kandil had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Study concept and design: Al-Qurayshi, Alshehri, Kandil.
Acquisition, analysis, or interpretation of data: All authors.
Drafting of the manuscript: Al-Qurayshi, Randolph, Alshehri.
Critical revision of the manuscript for important intellectual content: All authors.
Statistical analysis: Al-Qurayshi, Alshehri.
Study supervision: Randolph, Alshehri, Kandil.
Conflict of Interest Disclosures: None reported.
Previous Presentation: This paper was presented as an abstract at the 2015 Annual Meeting of American Head and Neck Society; April 23, 2015; Boston, Massachusetts.
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