KEY POINTS
Question: Are there racial-ethnic disparities in the use of peripheral nerve blocks (PNBs) for postoperative analgesia in patients having total mastectomy in the United States?Findings: In a cohort of 64,103 patients who underwent total mastectomy, non-Hispanic Asian, non-Hispanic Black, non-Hispanic patients of other races (American Indian, Alaskan Native, and Pacific Islander), and Hispanic patients had significantly reduced odds of receiving a PNB compared to non-Hispanic White patients.Meaning: There appears to be significant racial-ethnic disparity in the use of PNBs for postoperative analgesia in patients having total mastectomy in the United States, which highlights the need to better understand disparity causes and ensure equitable access to PNBs for all patients. Peripheral nerve blocks (PNBs) are used for postoperative analgesia in surgical patients and are associated with reduced opioid use and increased patient satisfaction.1–4 5 , 6 6 , 7 8–10 11–13
Mastectomy is one of the most common major surgical procedures performed for cancer in the United States. PNBs can be used for postoperative analgesia in mastectomy patients and have been shown in a randomized controlled trial to reduce postoperative opioid consumption and to lower postoperative pain scores.14
METHODS
Patients and Study Variables
The George Washington University institutional review board exempted the study and authorized a waiver of written informed consent. Patients who underwent total mastectomy were identified using the National Surgical Quality Improvement Program (NSQIP) participant use data files (PUFs) from 2015 to 2019. Patients who had the following current procedural terminology (CPT) codes for total mastectomy were included: 19303, 19305, 19306, and 19307. Patients who did not have general anesthesia listed as their primary anesthesia type and those who had partial mastectomy were excluded. Partial mastectomy patients were excluded because in the United States,<2% of patients having partial mastectomy receive a PNB.15
For all patients, we collected demographics, height, weight, BMI, medical comorbidities, estimated risk of morbidity, preoperative laboratory values, baseline functional status, and surgery details, including operation length and adjunctive breast reconstruction procedures (eg, rotational and free flaps). For the analysis, sex was categorized dichotomously as: (1) female, or (2) male or nonbinary. Male and nonbinary were grouped together because of their low frequency in the cohort.
Exposure
The NSQIP PUFs contain data on both race and ethnicity that are extracted from hospital medical records. Race is categorized as American Indian or Alaska Native, Asian, Black or African American, Native Hawaiian or Pacific Islander, other, unknown/not reported, or White. Ethnicity is categorized as Hispanic and non-Hispanic. For our analysis, we grouped patients into 5 race-ethnicity categories: non-Hispanic Asian, non-Hispanic Black, non-Hispanic patients of other races, non-Hispanic White, and Hispanic. Non-Hispanic White patients were selected as the reference group for analyses because they were hypothesized to have received PNBs more frequently than other race-ethnicity groups.
Primary Outcome
The primary outcome of the study was receipt of a PNB for postoperative analgesia. The NSQIP PUFs contain a data field for “additional anesthesia technique.” Any patient who had “regional” anesthesia listed for this field was considered to have received a PNB.
Secondary Outcomes
As a secondary outcome, we compared complications between patients who received a PNB and those who did not. We evaluated both individual complications and a composite outcome of major complications, which consisted of deep incisional surgical site infection, pneumonia, sepsis, pulmonary embolism, deep venous thrombosis, myocardial infarction, cerebrovascular accident, cardiac arrest, acute renal failure, and in-hospital mortality. We also collected length of hospital stay and hospital readmission data.
Statistical Analysis
Statistical analysis was performed using SAS 9.4 (SAS Corporation). Patients were stratified by whether they received a PNB for postoperative analgesia. Continuous patient variables were summarized as the mean ± standard deviation or median [25th, 75th] percentile, depending on normality. Normality was assessed using histograms, skewness, and the Shapiro-Wilk test. Categorical patient variables were summarized as the number and percentage of patients. Continuous variables were compared between groups using either Student t test or the Wilcoxon rank sum test. Categorical variables were compared between groups using the Pearson χ2 test.
To explore whether race-ethnicity was independently associated with receipt of a PNB for postoperative analgesia, we performed multivariable logistic regression with complete case analysis. In our regression model, we modeled receipt of a PNB as the dependent variable and race-ethnicity group as an independent variable. All demographics, comorbidities, preoperative laboratory values, and surgical details were considered for inclusion in the model as other independent variables, and final covariate selection was determined using the purposeful selection of covariates SAS macro, which creates a “main effects” model.16
A priori sample size calculation was not performed for the study. All eligible cases that were available in the NSQIP PUFs during the study period were included. The manuscript was checked against the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) checklist.
RESULTS
The Figure shows the study enrollment flow diagram. There were 64,103 patients who had total mastectomy and met study inclusion criteria. Among these, 4704 patients (7.3%) received a PNB for postoperative analgesia. Table 1 lists the characteristics of patients who did and did not receive a PNB. Patients who received a PNB were younger, more commonly women, were less likely to have diabetes and hypertension, and had less disseminated cancer (all P < .05). They also had longer median operative time (159 vs 136 minutes; P < .001). The percentage of patients in each race-ethnicity group who received a PNB differed significantly (P < .001) from that of patients who did not receive a PNB. Table 2 shows the incidence of individual postoperative complications and the composite outcome of any major postoperative complication in the 2 groups. There were no significant differences in any individual complication or hospital readmission between groups. The crude OR for any major complication in patients who received a PNB was 0.83 (95% confidence interval [CI], 0.65–1.08; P = .17), and the adjusted OR was 0.85 (95% CI, 0.65–1.10; P = .21). Median length of stay did not differ significantly between groups (1 day versus 1 day; P = .37).
Table 1. -
Patient Characteristics
Variable
Received PNB (n = 4704)
No PNB (n = 59,399)
P value
Age (y)
56 ± 14
58 ± 14
<.001
Female sexa
4619 (98.2)
57,998 (97.6)
.02
Race-ethnicity
Non-Hispanic Asian
133 (2.9)
3261 (5.5)
<.001
Non-Hispanic Black
217 (4.6)
5969 (10.0)
Non-Hispanic Otherb
311 (6.6)
3908 (6.6)
Non-Hispanic White
3497 (74.3)
37,200 (62.6)
Hispanic
546 (11.6)
9061 (15.3)
Height (cm)
162 ± 7
161 ± 8
.07
Weight (kg)
76 ± 19
76 ± 20
.86
Body mass index (kg/m2 )
29 ± 7
29 ± 7
.64
CPT code
19303
3574 (76.0)
44,145 (74.3)
.02
19305
82 (1.7)
1168 (2.0)
19306
4 (0.1)
132 (0.2)
19307
1044 (22.2)
13,954 (23.5)
ASA physical status
I
148 (3.2)
2804 (4.7)
<.001
II
2484 (52.8)
32,611 (54.9)
III
2005 (42.6)
22,835 (38.5)
IV
63 (1.4)
1072 (1.8)
V
0 (0)
2 (0.1)
Hematocrit (%)
39 ± 5
39 ± 5
.25
Platelet count × 109 /L
253 ± 71
253 ± 69
.69
Creatinine (mg/dL)
0.8 ± 0.5
0.8 ± 0.5
.32
INR
1.0 ± 0.3
1.0 ± 0.3
.87
Functional status before surgery
Independent
4633 (98.5)
58,342 (98.2)
.55
Partially dependent
45 (1.0)
702 (1.2)
Totally dependent
9 (0.2)
118 (0.2)
No data
7 (0.3)
237 (0.4)
Diabetes mellitus
Insulin-dependent
174 (3.7)
2395 (4.0)
<.001
Non–insulin-dependent
365 (7.8)
5558 (9.4)
None
4165 (88.5)
51,446 (86.6)
Hypertension requiring medication
1693 (36.0)
23,387 (39.4)
<.001
Congestive heart failure
14 (0.3)
212 (0.4)
.51
Active tobacco use
588 (12.5)
6801 (11.5)
.03
COPD
119 (2.5)
1657 (2.8)
.30
Ascites
1 (0.02)
12 (0.02)
.99
Dialysis
15 (0.3)
180 (0.3)
.85
Disseminated cancer
96 (2.0)
2028 (3.4)
<.001
Steroid use
126 (2.7)
1532 (2.6)
.68
Infected/open wound
26 (0.6)
463 (0.8)
.09
>10% weight loss in prior 6 mo
44 (0.9)
343 (0.6)
.002
Bleeding disorder
54 (1.2)
893 (1.5)
.05
Transfused in 72 h before surgery
5 (0.1)
66 (0.1)
.92
Estimated probability of morbidity
3.2 (2.4–4.2)
3.2 (2.4–4.3)
.13
Adjunctive reconstructive procedure
1313 (2.2)
95 (2.0)
.39
Total operative time (min)
159 (107–226)
136 (90–201)
<.001
Missing data were hematocrit (n = 11,777), platelet count (n = 12,501), creatinine (n = 13,402), INR (n = 49,993), age (n = 513), ASA physical status (n = 79), functional status before surgery (n = 10), and estimated probability of morbidity (n = 1).
Abbreviations: ASA, American Society of Anesthesiologists; COPD, chronic obstructive pulmonary disease; CPT, Current Procedural Terminology; INR, international normalized ratio; PNB, peripheral nerve block.
a There were 10 patients with nonbinary sex in the group who did not receive a PNB. They were grouped together with males for the tabulation in the table.
b Non-Hispanic Other includes American Indian or Alaska Native, Native Hawaiian or Pacific Islander, and unknown race.
Table 2. -
Postoperative Major Complications, Readmission, and Length of Stay
Variable
Received PNB (n = 4704)
No PNB (n = 59,399)
P value
Deep incisional SSI
26 (0.6)
389 (0.7)
.40
Pneumonia
6 (0.1)
71 (0.1)
.88
Sepsis
22 (0.5)
262 (0.4)
.79
Pulmonary embolism
7 (0.2)
111 (0.2)
.56
Deep vein thrombosis
8 (0.2)
139 (0.2)
.38
Myocardial infarction
0 (0.0)
39 (0.7)
.08
Cerebrovascular accident
2 (0.04)
33 (0.06)
.71
Cardiac arrest
2 (0.04)
22 (0.04)
.85
Acute renal failure
0 (0)
10 (0.0
.37
Inhospital mortality
0 (0)
10 (0.02)
.37
Any major complicationa
63 (1.3)
951 (1.6)
.16
Unplanned hospital readmission
193 (4.1)
2182 (3.7)
.13
Length of stay (d)
1 (1–2)
1 (1–2)
.37
Abbreviations: PNB‚ peripheral nerve block; SSI, surgical site infection.
a Composite major complication outcome includes all individual complications except unplanned hospital readmission.
Figure.: Flow diagram showing patient enrollment for the study. CPT indicates Current Procedural Terminology; PNB, peripheral nerve block.
Table 3. -
Multivariable Logistic Regression for Receiving a PNB
Variable
Odds ratio (95% CI)
P value
Race-ethnicity
Non-Hispanic White
Ref
<.001
Non-Hispanic Asian
0.41 (0.33–0.49)
<.001
Non-Hispanic Black
0.37 (0.32–0.44)
<.001
Non-Hispanic Othera
0.73 (0.64–0.84)
<.001
Hispanic
0.62 (0.56–0.69)
<.001
Age (per 1 y increase)
0.99 (0.99–0.99)
<.001
Estimated probability of morbidity (per 1% increase)
0.96 (0.93–0.98)
<.001
ASA physical status
<.001
IV or V
Ref
III
1.16 (0.87–1.55)
.32
II
0.82 (0.60–1.11)
.20
I
0.54 (0.38–0.79)
.001
Hypertension
0.97 (0.89–1.05)
.42
Preoperative hematocrit (per 1% increase)
1.00 (0.99–1.01)
.66
Diabetes mellitus
None
Ref
.06
Type I
0.86 (0.76–0.97)
.02
Type II
0.99 (0.83–1.18)
.92
Tobacco use
1.10 (0.99–1.22)
.08
Disseminated cancer
0.62 (0.50–0.76)
<.001
Operative time (per 5 min increase)
1.01 (1.01–1.01)
<.001
A total of 51,812 patients had complete data for variables in the regression model and were analyzed. C statistic for the model was 0.62.
Demographics, comorbidities, laboratory values, and surgical details were considered for inclusion as independent variables in the regression model. The model was fit using the purposeful selection of covariates SAS macro.
Abbreviations: ASA, American Society of Anesthesiologists; CI, confidence interval; PNB‚ peripheral nerve block.
a Non-Hispanic Other includes American Indian or Alaska Native, Native Hawaiian or Pacific Islander, and unknown race.
Table 3 shows the results of the multivariable logistic regression analysis. A total of 51,812 patients had complete data for variables in the regression model and were included in the regression analysis. Non-Hispanic Asian patients, non-Hispanic Black patients, non-Hispanic patients of other races, and Hispanic patients had significantly lower odds of receiving a PNB than non-Hispanic White patients. The odds of receiving a PNB were 59%, 63%, 27%, and 38% lower for the 4 groups, respectively, when compared to non-Hispanic White patients (OR, 0.41 [0.33–0.49], OR, 0.37 [0.32–0.44], OR, 0.73 [0.64–0.84], and OR, 0.62 [0.56–0.69], respectively).
DISCUSSION
In a 5-year retrospective cohort study of >60,000 patients who underwent total mastectomy, we found a low use (7.3%) of PNBs for postoperative analgesia. Furthermore, we found that the odds of receiving a PNB were significantly different for patients of different race-ethnicity, after controlling for potential confounders. The use of a PNB for postoperative analgesia was associated with a similar rate of major postoperative complications, hospital readmission, and length of hospital stay.
Patients undergoing total mastectomy are at high risk for moderate to severe postoperative pain and development of chronic neuropathic pain. In a prospective cohort study of 196 patients having mastectomy, 57% of patients experienced severe postoperative pain, and 22% had severe pain 1 month after surgery.17 18 14 , 19–22 23 15
Multiple studies have explored racial disparities in the use of PNBs and neuraxial blocks for postoperative analgesia, particularly in orthopedic surgical patients.6 , 11 , 13 6 24 25
Our analysis did not allow us to determine why non-Hispanic Asian patients, non-Hispanic Black patients, non-Hispanic patients of other races, and Hispanic patients were less likely to receive a PNB. There was no significant difference in estimated probability of morbidity between patients who received a PNB and those who did not. BMI, baseline functional status, and the percentage of patients having concurrent reconstructive procedures were also similar between groups. NSQIP PUFs do not contain hospital-level data, so it was not possible to control for hospital-level factors in our analysis. It is possible that some patients had reduced access to hospitals where PNBs were commonly performed. Alternatively, there may have been different opinions about PNBs, their risks, and the pressure to receive an invasive procedure among different race groups. These differences have previously been reported among Black women, with regard to neuraxial anesthesia for delivery.26 27 28
We did not find that performance of a PNB was associated with reduced odds of major complications after mastectomy. Previous studies have found varying results related to the impact of PNBs on major complications, but most were in orthopedic and vascular surgery patients.29–31 32
Our study should be interpreted within the context of several limitations. First, it is a retrospective cohort study, and the NSQIP PUFs only represent a fraction of US hospitals. Hence, our study findings may not be generalizable to other hospitals in the United States. Second, NSQIP PUFs do not contain hospital or insurance data, which impacted our ability to control for these factors. The discriminative capability of our model was poor, and this may have been in part because the hospital where surgery was performed had an important impact on whether a PNB was used. Third, the NSQIP PUFs did not reliably contain CPTs for the individual PNBs that were performed, so we could not determine whether specific PNBs were performed at different rates in patients of different races. Fourth, race-ethnicity data were extracted from hospital records by NSQIP personnel, and data may not have been self-reported to hospitals by patients. Fifth, there may have been systematic differences in the way that the additional anesthesia technique field was completed at each NSQIP hospital. NSQIP requires training for all surgical case reviewers (SCRs), and performs periodic audits to ensure interrater reliability. Nevertheless, anesthesia providers at different hospitals may have recorded PNBs in the medical record differently, and hence, these techniques may have been extracted by NSQIP SCRs at different rates. Sixth, some differences between patients with and without PNBs were statistically significant (eg, age), but the magnitude of the difference was small, and the difference may not be clinically significant. Finally, we did not have data on postoperative analgesia adequacy or opioid use.
In summary, in a retrospective cohort study of >60,000 patients who underwent total mastectomy, we found that the odds of receiving a PNB for postoperative analgesia differed significantly depending on patients’ race-ethnicity. Non-Hispanic Asian patients, non-Hispanic Black patients, non-Hispanic patients of other races, and Hispanic patients were significantly less likely to receive a PNB when compared to non-Hispanic White patients. These findings highlight the continued need to evaluate whether there is equitable access to PNBs in patients having total mastectomy. Additionally, further research is needed to better understand patients’ beliefs about PNBs and to determine what barriers prevent more widespread adoption of their use.
ACKNOWLEDGMENTS
The authors would like to thank the American College of Surgeons (ACS) and participating National Surgical Quality Improvement Program (NSQIP) centers for the data collection that allowed us to perform this study. The ACS NSQIP and the hospitals participating in the ACS NSQIP are the source of the data used herein; they have not verified and are not responsible for the statistical validity of the data analysis or the conclusions derived by the authors.
DISCLOSURES
Name: Michael A. Mazzeffi, MD, MPH, MSc.
Contribution: This author made substantial contributions to the conception, design, acquisition, analysis, and interpretation of study data; drafted and provided critical revisions to the manuscript; and is the author responsible for archiving the study files.
Name: Ryan Keneally, MD.
Contribution: This author made substantial contributions to the conception, design, and interpretation of study data; drafted and provided critical revisions to the manuscript; and approved the final manuscript.
Name: Christine Teal, MD.
Contribution: This author made substantial contributions to the conception, design, and interpretation of study data; drafted and provided critical revisions to the manuscript; and approved the final manuscript.
Name: Rundell Douglas, MPH.
Contribution: This author made substantial contributions to the conception, design, and interpretation of study data; drafted and provided critical revisions to the manuscript; and approved the final manuscript.
Name: Vanessa Starks, MD.
Contribution: This author made substantial contributions to the conception, design, and interpretation of study data; drafted and provided critical revisions to the manuscript; and approved the final manuscript.
Name: Jonathan Chow, MD.
Contribution: This author made substantial contributions to the conception, design, and interpretation of study data; drafted and provided critical revisions to the manuscript; and approved the final manuscript.
Name: Steven B. Porter, MD.
Contribution: This author made substantial contributions to the conception, design, acquisition and interpretation of study data; drafted and provided critical revisions to the manuscript; and approved the final manuscript.
This manuscript was handled by: Olubukola O. Nafiu, MD, FRCA, MS.
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