Anesthetic Care for Orthopedic Patients: Is There a Potential for Differences in Care?

DIFFERENCES in health care based on patient-specific factors represent a major problem for the healthcare system and society as a whole as they are unjust, unethical, and costly.¹  Much effort has been expended to study factors associated with and reasons for this phenomenon in many fields of medicine with the goal to reduce its prevalence and its associated negative medical and societal consequences.^2–5  Racial and ethnic differences in the treatment of pain have been well documented alongside differences in the use of neuraxial labor analgesia.^6,7  However, studies using large databases and those assessing differences in other fields of anesthesia practice where regional anesthesia is widely used and may be associated with improved outcomes remain sporadic.^8,9  Reasons for such lack of data are manifold but include the fact that, until relatively recently, population-based data needed for such analyses were unavailable. With the evolution of large national databases containing anesthesia-related information, such research is now possible and necessary to take first steps to establish if significant differences in care and the potential for differences related to patient and healthcare system factors do indeed exist.

The importance of such data has to be viewed in the context of recent publications suggesting that the type of anesthesia used for surgical procedures may significantly affect the risk for complications and negative economic outcomes.^10–12  Specifically, an increasing body of evidence suggests that neuraxial anesthesia may indeed lead to superior outcomes compared with general anesthesia.^10–12  This observation has been best documented in the ever increasing joint arthroplasty population, which is expected to reach 3.5 million per annum in the United States alone by the year 2030.¹³  Although patient subgroup differences in this population have been demonstrated regarding both the odds of undergoing an arthroplasty¹⁴  and the outcomes after the procedure,¹⁵  less is known about the factors affecting the process of anesthetic care that might mitigate particularly the latter.

Therefore, we utilized a large national database containing anesthesia-related information to study whether anesthesia practice (the use of neuraxial anesthesia and the use of peripheral nerve block) differs by patient factors including age, race, gender, and insurance type as well as healthcare system-related factors such as hospital size, location, and teaching status.

We hypothesized that significant differences in anesthetic care provided to members of different patient groups and in different healthcare settings exist. If identified, these data could be used to launch studies into the reasons for and consequences of potential differences in care.

Data used in this study were deidentified according to the Health Insurance Portability and Accountability Act,¹⁶  and therefore, this study was exempt from individual consent requirements by the Institutional Review Board of the Hospital for Special Surgery (New York, New York; #2012-050-CR2) and the Mount Sinai Medical Center (New York, New York; #14-00647).

The Premier Perspective database (Premier Inc., USA) containing hospital discharges from January 2006 to December 2013 was accessed for this retrospective analysis. It contains all diagnostic and procedural data from International Classification of Diseases, 9th revision, Clinical Modification codes, Current Procedural Terminology codes, and standardized billing items for approximately 20 to 25% of US hospitals. The number of hospitals in this dataset depends on the cohort requested and purchased; in this study, the dataset contained 540 hospitals. Although the Midwest, Northeast, and Northwest are also represented, the Southeastern United States is the most represented region. Our study goal was defined, and hypotheses were generated a priori.

All adult inpatients with an elective primary total hip or knee arthroplasty (THA/TKA), as indicated by International Classification of Diseases, 9th revision, Clinical Modification codes 81.51 and 81.54, respectively, were considered for this study. Excluded were those THA procedures undertaken for the treatment of fractures. Patients with missing information on gender (n = 69), discharge status (n = 498), or those who underwent multiple arthroplasties during a single admission (n = 212) were excluded. A flowchart depicting the study sample is provided in appendix 1.

Primary outcome variables were (1) use of neuraxial anesthesia and (2) use of a peripheral nerve block. These were determined from billing and procedural codes as reported by our study group.¹⁷  We combined spinal and epidural anesthesia into neuraxial because differential information was not reliably available. Moreover, we were interested in determining the choice to use regional anesthesia in a wider sense. In defining our outcome variables, the main assumption we make is that if there was no billing for neuraxial anesthesia or peripheral nerve block, then there indeed was no use of either of these techniques. As there are only few other large databases that contain this information on anesthesia type, it is difficult to test the validity of this assumption. However, one study using the National Anesthesia Clinical Outcomes Registry data of the Anesthesia Quality Institute (a database created specifically for this purpose) found a rate of neuraxial anesthesia of 31.3%, which is only moderately higher than the rate found in our dataset.¹⁸  For peripheral nerve blocks, there appears to be inadequate information in available population-based studies to compare our numbers to. In addition, we were not able to reliably distinguish single-shot techniques from catheter approaches.

The patient variables that were considered to be potentially important determinants in respect to care differences¹⁹  were age, gender, race, and insurance type. Race was categorized as white, black, Hispanic, and other. Insurance type was categorized as commercial, Medicaid, Medicare, uninsured, and other (e.g., other government payors). Healthcare-related variables included hospital location (rural, urban), hospital area (Midwest, Northeast, South, and West), hospital size (less than 300, 300 to 499, and more than or equal to 500 beds), and hospital teaching status. In addition, procedure-related variables were studied: type of procedure (THA, TKA), use of general anesthesia, use of anticoagulants (on the day of procedure: aspirin, warfarin, heparin, other, more than one medication, none), and year of procedure. To account for overall comorbidity burden, the updated Deyo adaptation of the Charlson comorbidities was used.²⁰ 

The use of neuraxial anesthesia and peripheral nerve block by study variables was described using mean and SD for continuous variables and percentages for categorical variables. Associations between groups were assessed using the chi-square test and the two-sample t test for categorical and continuous variables, respectively.

To measure the multivariable association between study variables and the use of neuraxial anesthesia and peripheral nerve block, two separate multilevel multivariable logistic regressions were specified. Each model included a random intercept term that varies at the level of each hospital and accounts for correlation of patients within hospitals. Only hospitals with more than 50 patients were included to assure a sufficient sample size per cluster. All patient-, healthcare-, and procedure-related variables (except for anticoagulant use as we do not know whether it was ordered before or after the decision for regional anesthesia) and individual Deyo–Charlson comorbidities (with significance threshold P < 0.15, see also appendix 2) were included in the main model for the outcomes of neuraxial anesthesia and peripheral nerve block.

To allow for a more specified description of potential differences in care by race and insurance status, the multivariable models were fitted with an interaction to assess differences in care between race groups within insurance categories. As has been suggested, an interaction may exist, and at least in theory sufficient insurance coverage may help reduce differences in care.²¹  In addition, as there might be interdependence in the choice for regional anesthesia (either neuraxial anesthesia or peripheral nerve block), we fitted an additional model with the outcome of receiving either one of these regional anesthetic techniques as an exploratory analysis to assess whether similar factors arise suggesting a potential for differences in care.

Given the large sample size, we present adjusted odds ratios (ORs), 95% CIs and P values together as a measure to allow the reader to interpret overall significance. For models containing interactions, Bonferroni-corrected ORs and P values are presented to account for multiple testing. Herein, we take into account the specific number of tests based on the interaction categories (race × insurance status or insurance status × race). The intraclass correlation, which explains the percentage of the total variance in the outcome accounted for by differences between hospitals, is also presented for each model.

All analyses were performed using SAS v9.3 statistical software (SAS Institute, Cary, USA); the GLIMMIX procedure was used for multilevel regression analyses. Code is available on request.

We identified a total of 1,062,152 elective hip and knee arthroplasty procedures performed in 540 hospitals. Of those, 22.2% (n = 236,083) received a neuraxial anesthetic and 17.9% (n = 189,732) received a peripheral nerve block.

Table 1 depicts the use of neuraxial anesthesia by study variables; its utilization decreased over the years (23.6% in 2006 vs. 19.6% in 2013); P < 0.0001. Interestingly, there were no differences in gender or Deyo–Charlson comorbidity index between groups.

Table 2 depicts the use of peripheral nerve blocks following the same setup of the previous table. Although there were (small) differences in gender and Deyo–Charlson comorbidity index between groups, hospital factors appeared to play a smaller role in this setting compared with neuraxial anesthesia. The use of peripheral nerve blocks increased from 2006 (13.3%) to 2013 (19.5%); P < 0.0001. Information on the use of neuraxial anesthesia and peripheral nerve blocks for THA and TKA patients separately can be found in appendices 3 to 6.

The multivariable multilevel regression analyses are shown in table 3 for the outcomes of neuraxial anesthesia and peripheral nerve block. These models do not include the “hospital area” variable because including this variable resulted in an unstable model. Age was associated with higher odds for receiving either neuraxial anesthesia (OR, 1.07; 95% CI, 1.07 to 1.08) or a peripheral nerve block (OR, 1.05; 95% CI, 1.04 to 1.06); both P < 0.0001. Lower adjusted odds for receiving neuraxial anesthesia were seen for black patients (OR, 0.88; 95% CI, 0.86 to 0.91) and those with noncommercial insurance, particularly Medicaid (OR, 0.78; 95% CI, 0.74 to 0.82) and those with no insurance (OR, 0.89; CI, 0.81 to 0.98). Hospital factors appeared to matter less in their associations with the use of neuraxial anesthesia. When comparing the odds for receiving peripheral nerve blocks (table 3; right half) with neuraxial anesthesia, the main difference included the lower odds for Hispanic patients (OR, 0.60; 95% CI, 0.56 to 0.65). The c-statistics of the models were high (0.94 for neuraxial anesthesia and 0.96 for peripheral nerve block), suggesting very good discrimination. Moreover, the intraclass correlation values suggested a substantial role of the hospital level effects in explaining variance in neuraxial anesthesia (0.75) and peripheral nerve block (0.86).

Results from the exploratory model with the outcome of receiving either one of the regional anesthetic techniques can be found in appendix 7. In summary, although similar patient factors arose suggesting a potential for differences in care, hospital factors appeared to matter less. In addition, we have added a sensitivity analysis by repeating the analyses depicted in table 3 with a restricted cohort of only those patients with a known type of anesthesia (n = 850,579) to test the validity of our assumption that patients who were not billed for neuraxial anesthesia or peripheral nerve blocks did not receive those. The sensitivity analyses (appendix 8) did not reveal any major differences compared with our main analyses.

Table 4 details the outcome of the same models while adding the insurance status × race interaction, which itself was significant for both models (both P < 0.005). Lower odds for neuraxial anesthesia were seen for black patients who were commercially insured and those on Medicare, whereas the lower odds for peripheral nerve blocks among Hispanic patients were seen for almost all insurance types.

In this study of population-based data derived from more than 500 US hospitals, we identified significant differences in the utilization of regional anesthetic techniques among patients of different demographics. In this regard, neuraxial anesthesia and peripheral nerve block were less likely to be used in black and Hispanic (vs. white) patients and those on Medicaid, Medicare, and no insurance (compared with commercially insured patients). Moreover, increasing age was associated with increased utilization of neuraxial anesthesia and peripheral nerve block. Compared with patient factors, hospital factors appeared to play a less important role in utilization of both regional anesthetic techniques. Sensitivity analyses taking into account missing information on anesthesia type generally validated our results.

These findings suggest (although do not prove) that differences in regional anesthetic care may exist among patients undergoing joint arthroplasty. Such differences in medical care have been described to be widely prevalent.²²  Unfortunately, despite some attention in the use of labor epidurals,^6,7,23  this topic has not been thoroughly examined for the practice of anesthesiology. This may be because this field has traditionally not been viewed as a priority in respect to influencing overall patient outcomes. However, this assumption, has been altered significantly in recent years with a number of researchers publishing investigations suggesting benefits of neuraxial anesthesia versus a general anesthetic approach in respect to major morbidity and mortality.^{8,10–12,24–26}  Such outcome differences have been especially well documented in orthopedic patients who are uniquely amenable to the use of regional anesthesia. Similar benefits have been reported for the use of a peripheral nerve block for improved pain control,^27,28  a major determinant of patient satisfaction, and the ability to rehabilitate.²⁹  Thus, potential differences in anesthetic care may indeed be more consequential than initially thought.

We identified race and insurance status to be significantly associated with the use of neuraxial anesthesia and peripheral nerve block. Hispanic and black patients and those on Medicare, Medicaid, and with no insurance were less likely to receive regional anesthetic interventions compared with commercially insured patients. These findings are in line with those reported in other medical fields, where significant socioeconomic and racial differences in care have long been pointed out.^2,3,22  Despite a general paucity in anesthesia-related studies, the few data available are in congruence with our findings. In a study of the use of neuraxial anesthesia for ambulatory hernia repair in the 1990s, our group found that black patients were less likely to receive epidural anesthesia (compared with white patients: OR, 0.36; 95% CI, 0.14 to 0.95).⁸  Although the mentioned study identified female gender to be associated with a reduced likelihood for neuraxial anesthesia use, we did not find such a difference in this analysis.

Advanced age was also found to be a major determinant of the use of neuraxial anesthesia and peripheral nerve block, a finding that has been reported by descriptive analyses.¹⁸  Although speculative, this may reflect anesthesiologists’ concern to avoid general anesthetics in older, more frail, individuals who are deemed at risk for pulmonary complications and delirium, which have been linked to the requirement for airway instrumentation and need for larger doses of opioids with general anesthesia.^22,30  Alternatively, avoiding rare, but potentially devastating side effects, such as postdural puncture headaches among younger individuals, who are known to be more prone to such adversities,³¹  may be another explanation. However, patient attitudes and preference might play an undervalued and underappreciated role in the choice of regional anesthetic techniques and may be partially responsible for the observed differences in regional anesthetic care. Although few studies have linked patient preferences to observed differences in care,³²  there is some evidence on the role of patient preferences differing by subgroup in the setting of anesthetic care. Younger age, for example, has been described as a patient-related factor for choosing general over other forms of anesthesia among individuals in hernia repair surgery.³³  In another study looking at patient perceptions of anesthesia in a variety of surgeries, it appeared that female patients were more likely to prefer general anesthesia.³⁴  Interestingly, one of the main drivers of these preferences was related to hearing and seeing the surgery and the fear of feeling pain. Furthermore, the more elaborate literature on care differences in obstetric analgesia offers some insights of differential preferences among patient subgroups; one study found Hispanic women to anticipate the use of neuraxial analgesia at a lower rate compared with other racial/ethnic groups.²³  Given that there is a paucity on data on patient preferences on regional anesthesia, more research in this field is needed, specifically research that focuses on potential differences in preference related to factors traditionally found to be related to care differences, e.g., race, insurance status, or even socioeconomic status.

The multilevel models additionally found a substantial role of unspecified hospital level effects in explaining variance in the use of neuraxial anesthesia and peripheral nerve blocks. The reasons for these findings have to remain speculative. It has been described that individual practice patterns are influenced by many factors such as practitioners’ choice (surgeon and anesthesiologists), which in turn may depend on the comfort and/or training of clinicians.^35,36  Further, the ability to deal with complications and/or the presence of compatible perioperative care, such as anticoagulation regimens, may be significant factors influencing practice.

Our study results have to be considered in the context of a number of limitations. Those related to the secondary analyses of large databases have been described in much detail and include lack of limited clinical detail, potential for coding bias, and lack of a complete list of confounders. Thus, information that may influence the choice of anesthesia such as contraindications, including physiologic derangements, anatomical abnormalities, and patient and physician wishes, cannot be considered here. The lack of information on these and other unknown factors influencing the choice of anesthesia may result in residual confounding affecting our current estimates. However, despite this limitation, the identified differences in care were based on the patient factors that are generally found in a wide range of other care settings including obstetric analgesia and treatment of pain in other environments.^6,7  In line with the lack of detailed clinical data, one important missing piece of information in the context of peripheral nerve block provision concerned our inability to accurately identify single-shot techniques from catheter approaches. More detailed clinical data and qualitative studies assessing (the relative importance of) factors influencing the choice for regional anesthetic techniques are needed to fully appraise decision-making in this context. Adding to the limitation of incomplete data, our dataset did not provide information on socioeconomic status, an important variable frequently identified in research that focuses on care differences.

As mentioned earlier, no causality can be inferred from the available data. Although our results do not answer the question of why, they do, however, provide the crucial first step, which is the establishment of the fact that differences in care appear to exist in the field of anesthesiology. To address and minimize the potential for differences in care, researchers and healthcare providers have to be willing to evaluate a large number possibly contributing factors. One important and arguably sensitive one is the potential for bias among healthcare providers. Such unconscious bias has been documented to exist,^37,38  but recognition is necessary for the design and implementation of strategies to reduce it.

Important next steps to further explore the potential for differences in care are validation of the current results using other data sources and a thorough assessment of factors that affect the decision-making process in the provision of regional anesthetic techniques. This would provide additional insight into what data are needed to appraise the observed differences in provision of anesthetic care.

Moreover, because neuraxial anesthesia and peripheral nerve blocks are frequently seen as “higher quality care,” investigations assessing differences in outcomes (e.g., perioperative outcomes such as thromboembolism, cardiac and pulmonary complications) should be prioritized and linked to studies on differences in the process of anesthetic care provision. When these two aspects can be reliably linked (i.e., differences in anesthetic practices lead to differences in patient outcome), ensuing evaluations should focus on ways to reduce this variation.

In conclusion, significant differences in the provision of regional anesthetic care exist. Factors such as insurance status, race, and age are determinants of anesthetic practice. Although reasons for these differences have to remain speculative, the fact that they appear to exist requires further and in-depth research, especially in the context of data suggesting that the choice of anesthesia type for orthopedic surgery significantly influences perioperative outcome.

This study was funded by the Anna Maria and Stephen Kellen Career Development Award (to Dr. Memtsoudis). The study sponsors had no role in the design and conduct of the study; in the collection, analysis, and interpretation of the data; or in the preparation, review, or approval of the manuscript. The views expressed in this article are those of the authors and do not necessarily represent the views of the sponsors or authors’ affiliated institutions.

The authors declare no competing interests.