RACE, INCOME, AND OPERATIVE TIMEJeffrey H. Silber, M.D., Ph.D.Paul R. Rosenbaum, Ph.D.

Xuemei Zhang, M.S.Orit Even-Shoshan, M.S.

The Center for Outcomes Research, The Children’s Hospital of Philadelphia

The Department of Pediatrics, Anesthesiology and Critical Care Medicine, PENN

The Department of Statistics, The Wharton School, PENN

The Leonard Davis Institute of Health Economics

Introduction

• Operative time is a common measure of surgical quality– Longer procedures are associated with higher

infection rates– Longer procedures are associated with

physicians-in-training

Measuring Operative Time

• Until now, studies analyzing operative time in the Medicare population have been limited to single (or very few) institutions.

• Operative time is usually defined as:– Surgical Time: Incision to closure– Anesthesia Time: Induction to Recovery Room

Measuring Operative Time in Medicare Patients

• In 1994, billing for Anesthetist and anesthesiologist services changed to a “by the minute” system

• Anesthetist bills (anesthesiologists, nurse anesthetists) from Medicare have never been utilized to examine procedure time on a large scale

• Race and Income have not been studied with respect to procedure time

Goals of this Talk• To examine the accuracy of using Anesthesia

Time Units from Medicare bills to estimate operative time

• To examine models that predict procedure length based on:– Patient comorbidities– Race– Income

• To explore the relationship between race and operative time at individual hospitals

• To discuss the implications of disparities in operative time

Data

• Medicare Claims on the 20 most common General Surgical procedures and the 20 most common Orthopedic procedures in Pennsylvania in 1995 and 1996, N = 77,638

• Chart Abstractions on a subset of 1931 Pennsylvania General Surgical and Orthopedic patients as part of the Surgical Outcomes Study

The Anesthesia Claim

• The Anesthesia Claim consists of two parts:– Base Units– Time Units

• Time units are in 15 minute intervals. The first digit of the time unit is a decimal tenths digit– For example: “25” for units = 15 x 25/10

minutes or 37.5 minutes

• We chose the single longest anesthesia bill associated with the same day as the principle procedure

Time Abstraction

• We defined four specific times for abstraction on 1931 charts in the SOS study:– Start induction– Start incision– Closure– To recovery room or ICU (if going directly to

ICU)

Bill Time - Chart Time. N = 1931 patients from the Surgical Outcomes Study

Shapiro-Wilk Test P < 0.0001

Chart Time as a Function of Claim Time, N = 1931

Variables Int. Slope P R2

Median Absolute Residual (minute)

P(Wald)

I: Unadjusted m-Estimation

-1.21 0.97 .0001 .89 5.49 N/A

II: Comorbidities, Procedures and Hospitals

2.47 0.98 .0001 .89 5.37 <.0001

The independent variable is anesthesia claim minutes, and the dependent variable is anesthesia chart minutes.

N = 1931, = 0.94.

Procedure N 25th %ile Median 75TH %ile

Abd-Perineal Rect Resect 422 210 260 320

Anterior Rectal Resection 685 165 251 255

Left Hemicolectomy 1307 155 195 242

Part Lg Bowel Excis Nec 507 150 191 251

Sigmoidectomy 2922 140 176 221

Lg Bowel Stoma Closure 326 116 164 221

Part Sm Bowel Resection 1253 120 155 209

Right Hemicolectomy 34350 120 155 195

Unilat Thyroid Lobectomy 370 120 135 176

Cholecystectomy-Open 3883 105 135 176

Peritoneal Adhesiolysis 1268 94 125 173

Estimated Anesthesia Time (Minutes) for Each General Surgical Principle Procedure

These times include principle procedures that were also accompanied with other secondary procedures billed on the same day.

Procedure N 25th %ile Median 75TH %ile

Abd-Perineal Rect Resect 84 206 240 285

Anterior Rectal Resection 222 146 176 218

Left Hemicolectomy 262 143 180 221

Part Lg Bowel Excis Nec 77 131 158 206

Sigmoidectomy 678 125 155 195

Lg Bowel Stoma Closure 159 101 125 180

Part Sm Bowel Resection 112 105 131 170

Right Hemicolectomy 940 110 135 170

Unilat Thyroid Lobectomy 286 108 135 167

Cholecystectomy-Open 978 90 116 146

Peritoneal Adhesiolysis 316 80 101 125

Estimated Anesthesia Time (minutes) for Each General Surgical Principle Procedure (when only one procedure performed)

These times only include principle procedures that did not have other secondary procedures billed on the same day.

Procedure N 25th %ile Median 75TH %ile

Lumbar/Lum-sac Fus Post 273 236 299 380

Other Cervical Fus Ant 152 182 240 343

Revise Hip Replacement 971 180 234 311

Spinal Canal Explor 3166 138 180 240

Revise Knee Replacement 1110 143 180 230

Excision Intervert Disc 2565 131 165 221

Total Hip Replacement 6215 140 165 197

Total Knee Replacement 12718 131 150 180

Open Red-Int Fix Hum 690 107 142 191

Partial Hip Replacement 4735 105 129 155

Shoulder Arthroplasty 909 105 124 158

Estimated Anesthesia Time (Minutes) for Each Orthopedic Principle Procedure

These times include principle procedures that were also accompanied with other secondary procedures billed on the same day.

Procedure N 25th %ile Median 75TH %ile

Lumbar/Lum-sac Fus Post 41 200 240 294

Other Cervical Fus Ant 30 155 195 245

Revise Hip Replacement 639 180 225 300

Spinal Canal Explor 1478 131 170 218

Revise Knee Replacement 792 140 179 227

Excision Intervert Disc 1529 122 155 196

Total Hip Replacement 4770 140 165 195

Total Knee Replacement 10551 131 150 180

Open Red-Int Fix Hum 459 101 131 170

Partial Hip Replacement 4102 105 125 150

Shoulder Arthroplasty 129 101 131 176

Estimated Anesthesia Time (minutes) for Each Orthopedic Principle Procedure (when only one procedure performed)

These times only include principle procedures that did not have other secondary procedures billed on the same day.

Estimating Anesthesia Time (Y = Mins. from bill)

Parameter Minutes P-value

Multiple procedures 18.3 .0001

Admit from ER .10 .90

Transfer In 6.6 .0003

Hx Coagulopathy 5.0 .0001

Hx Diabetes 2.5 .0001

Hx Paraplegia 4.7 .0004

Black Race Vs White 5.2 .0001

Severity Score 1 1.5 .04

Severity Score 2 .40 .59

Severity Score 3 & 4 2.2 .03

Severity Score 0 Ref N/A

N=77,638 patients, controlling for 39 (=n-1) surgical procedures and 182 (=n-1) hospitals and 34 patient covariates of which 8 are displayed above. The model was fit using m-estimation, rank R2 of 40%.

WL(n = 9,324)

BM(n = 513)

WM(n = 25,060)

BH(n = 547)

WH(n = 27,473)

BL (n = 2002) 29 (<.0001)

15 (<.0001) 30 (<.0001)

15 (<.0001)

27 (<.0001)

WL (n = 9,324) --- -14 <.0001)

1 (<.0001)

-14 (<.0001)

-2 (<.0001)

BM (n = 513)   --- 14 (<.0001)

0 (.8939)

12 (<.0001)

WM (n = 25,060)     --- -15 (<.0001) -3 (<.0001)

BH (n = 547)     --- 12 (<.0001)

Race, Income, and Procedure Time

WL(n = 9,324)

BM(n = 513)

WM(n = 25,060)

BH(n = 547)

WH(n = 27,473)

BL (n = 2002)BL adjusted by

183 hosp.

29 (<.0001) 9 (<.0001)

15 (<.0001)3 (0.159)

30 (<.0001) 7 (<.0001)

15 (<.0001) 8 (<.0001)

27 (<.0001) 8 (<.0001)

WL (n = 9,324)WL adjusted by

183 hosp.

--- -14 <.0001) -4 (.036)

1 (<.0001) 0 (.578)

-14 (<.0001) -5 (.486)

-2 (<.0001) 1 (.069)

BM (n = 513)BM adjusted by

183 hosp.

  --- 14 (<.0001) 4 (.036)

0 (.8939) 5 (.052)

12 (<.0001) 4 (.014)

WM (n = 25,060)WM adjusted by

183 hosp.

    --- -15 (<.0001)1 (.570)

-3 (<.0001) 1 (.126)

BH (n = 547)BH adjusted by

183 hosp.

    --- 12 (<.0001) 0 (.848)

Race, Income, and Procedure Time

HospitalNo.

BlackNo.

White Teaching TypeExcess Mins.

(b-w) P-Value

1 153 352 Major 3.3 .449

2 147 322 V Major 7.0 .115

3 130 326 V Major 0.8 .870

4 125 108 V Major 12.2 .039

5 118 1319 Major 14.3 .001

6 112 437 Major 12.1 .011

7 112 43 Major -4.6 .562

8 111 1006 Not Teaching 4.0 .366

9 109 71 V Major 6.9 .308

10 107 505 Major 9.3 .050

11 105 178 V Major 15.9 .004

12 100 1007 V Major -5.1 .274

Adjusted Differences Between Black and White Procedure Times in Pennsylvania Hospitals With the Largest Black Populations

The overall Wald test for equality was 0.029, suggesting there is variability in disparity across hospitals. General Surgical and Orthopedic Procedures

Policy Implications

Why might there be a disparity in operative time inside a hospital?

• Reasons consistent with fairness– Unobserved severity– Admission from ER– Emergency Surgery

• Reasons based on injustice– Different Surgeon/Physician-in-Training for

less empowered – Risk of Litigation– Racism (Conscious or Unconscious)

Why do we care about 15 minutes?

Identifying the Provider: Who is holding the retractor?

• In teaching hospitals it is not always clear from the chart or the claim who is performing surgery.

• Is the resident doing the dissection or holding the retractor?

• Differential times between the resident and the attending may help in identifying the two providers.

For a typical procedure like Colectomy, which was described in Khuri et al. (Annals Surgery 2001), we can estimate the relative speed of the resident and attending, assuming the hospital location does not influence this time.

VA Location

N Complexity

% of Cases by Residents

Hours of Surgery

Mean Time

Combined

Teaching 8,038 3.00 93.64 3.17 3.085

Non-Teach

1,201 2.95 1.42 2.54

From this table we can solve for the time a resident takes to perform the colectomy (TR) and the time an attending takes to perform the surgery (TA). We

have two equations and two unknowns:

(0.9346)TR + (0.0636)TA = 3.17

(0.0142)TR + (0.9808)TA = 2.52

Solving, we get TA = 2.523 and TR = 3.213 hours. This is very close to those in

table 8 above, as almost all the surgery in the teaching hospital was with residents and almost all the surgery in the non-teaching hospital was with attendings.

TB = TR * PB,R + TA * PB,A

TW = TR * PW,R + TA * PW,A

Or, since PB,R + PB,A = 1and PW,R + PW,A = 1, we can write:

TB = TR * PB,R + TA * (1 - PB,R ) and

TW = TR * PW,R + TA * (1 - PW,R ).

Hence, TB-TW = PB,R * [TR - TA] - PW,R*[TR - TA] and:

[TB - TW]/[TR-TA] = PB,R - PW,R Or:

[TB - TW]/ [PW,R][TR-TA] = [PB,R / PW,R]-1 and finally:

1+ {[TB - TW] / {[PW,R][TR-TA]}} = [PB,R / PW,R]

The Relative Risk of Getting a Resident in Black Versus White Patients

1B

B WRW WR R R A

T TP

P P T T

From Regression Data

From External Data or Matching Studies

Assuming:

TR-TA = 30 mins

TB – TW = 15 mins

Relative Risk of Obtaining a Resident if a Black Patient Versus

a White Patient

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Percent of Cases Performed by a Resident if Patient is White

Rel

ativ

e R

isk

for

Bla

cks

Advantages of using Procedure Time as a Measure of Disparity

• Bills available for literally all procedures performed in the OR for Medicare patients

• Procedure length is highly dependent on the surgeon, not patient compliance

• Procedure length is less dependent on the past history of the patient—insensitive to unobserved severity

• Time is not game-able, especially since it has not been used to measure disparity in the past

Conclusions

• Procedure time can be well estimated with Medicare claims data

• Procedure time is a function of race and income and the specific hospital, after adjustment for other patient factors

• There is a significant procedure length racial disparity inside of hospitals

• Mechanisms for this procedure length disparity need to be better understood

Acknowledgements

• This work was funded through a grant from the Leonard Davis Institute of Health Economics at PENN and supported in part from AHRQ Grant Number HS-09460

The End

Additional Slides for Potential Questions

Sometimes Sometimes

ALWAYS ALWAYS

TEACHING NON-TEACHING

N=96 SurgeonsN=480 Patients

N=480 Patients

N=480 Patients

N=480 Patients

Sometimes Sometimes

ALWAYS ALWAYS

TEACHING NON-TEACHING

P = 0.214

P = 0.002

P = 0.002

P = 0.393

P = 0.657

P = 0.0001

103 minutes

106 minutes

109 minutes

121 minutes