Research

JAMA Surgery | Original Investigation

Familiarity of the Surgeon-Anesthesiologist Dyad

and Major Morbidity After High-Risk Elective Surgery
Julie Hallet, MD, MSc; Angela Jerath, MD, MSc; Pablo Perez d’Empaire, MD; François Carrier, MD, MSc;
Alexis F. Turgeon, MD, MSc; Daniel I. McIsaac, MD, MPH; Chris Idestrup, MD, MSc; Gianni Lorello, MD, MSc;
Alana Flexman, MD; Biniam Kidane, MD, MSc; Wing C. Chan, MPH; Anna Gombay, BA, Hons;
Natalie Coburn, MD, MPH; Antoine Eskander, MD, ScM; Rinku Sutradhar, PhD

Invited Commentary
IMPORTANCE The surgeon-anesthesiologist teamwork is a core component of performance in Multimedia
the operating room, which can influence patient outcomes.
Supplemental content
OBJECTIVE To examine the association between surgeon-anesthesiologist dyad familiarity (as
dyad volume, the number of procedures done together) with 90-day postoperative major
morbidity for high-risk elective surgery.

DESIGN, SETTING, AND PARTICIPANTS This population-based retrospective cohort study used
administrative health care data from Ontario, Canada. Participants included high-risk elective
operations (cardiac, low- and high- risk gastrointestinal [GI], genitourinary, gynecology
oncology, neurosurgery, orthopedic, spine, vascular, and head and neck) from 2009 through
2019. Data were analyzed from January 2009 to March 2020.

EXPOSURE Dyad familiarity, as the annual volume of procedures done by the

surgeon-anesthesiologist dyad in 4 years prior to index surgery.

MAIN OUTCOMES AND MEASURES 90-day major morbidity (any Clavien-Dindo grade 3 to 5).
The association between exposure and outcome was examined using multivariable logistic
regression, stratified by type of procedure.

RESULTS Among 711 006 index procedures, the median dyad volume and rate of 90-day
major morbidity varied by type of procedure. There was higher median volume and dyad
consistency for cardiac, orthopedic, and lung surgery. For other procedures, the median dyad
volume was low (3 or less procedures per dyad per year). An independent association was
observed between dyad volume and 90-day major morbidity for high-risk GI surgery (odds
ratio [OR], 0.92; 95% CI, 0.88-0.96), low-risk GI surgery (OR, 0.96; 95% CI, 0.95-0.98),
gynecology oncology surgery (OR, 0.97; 95% CI, 0.94-0.99), and spine surgery (OR, 0.97;
95% CI, 0.96-0.99), after adjusting for hospital setting, hospital, surgeon and
anesthesiologist volume, and patient age, sex, and comorbidity burden. The adjusted
associations were not significant for other types of procedures.

CONCLUSIONS AND RELEVANCE In this study, increasing familiarity of the surgeon-

anesthesiologist dyad was associated with improved postoperative outcomes for patients
undergoing low- and high-risk GI surgery, gynecology oncology surgery, and spine surgery.
For each additional time that a unique surgeon-anesthesiologist dyad worked together, the
odds of 90-day major morbidity decreased by 4% for low-risk GI surgery, 8% for high-risk GI
surgery, 3% for gynecology oncology surgery, and 3% for spine surgery. Additional research is
needed to determine the most effective care structures that harness the benefits of
surgeon-anesthesiologist familiarity to potentially improve patient outcomes.

Author Affiliations: Author

affiliations are listed at the end of this
article.
Corresponding Author: Julie H.
Hallet, MD, MSc, Sunnybrook Health
Sciences Centre, 2075 Bayview Ave,
JAMA Surg. doi:10.1001/jamasurg.2025.1386 Toronto, ON M4N 3M5, Canada
Published online May 28, 2025. (julie.hallet@sunnybrook.ca).

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 Research Original Investigation Familiarity of the Surgeon-Anesthesiologist Dyad and Major Morbidity After High-Risk Elective Surgery

T
he operating room is a fast-paced and complex envi-
ronment where team dynamics have the potential to in- Key Points
fluence patient outcomes.1-7 Among the many interac-
Question Is familiarity of the surgeon-anesthesiologist dyad
tions that take place, the relationship between the surgeon and associated with 90-day major morbidity after high-risk elective
anesthesiologist is a core component of functioning.1,2,8,9 surgery?
Recently, our team reported how familiarity between surgeon-
Findings In this study, increasing familiarity of the
anesthesiologist dyads is associated with postoperative out-
surgeon-anesthesiologist dyad was associated with improved
comes after hepatopancreatobiliary and esophageal opera- postoperative outcomes for low- and high-risk gastrointestinal
tions. We observed that greater familiarity between a surgeon (GI), gynecology oncology, and spine surgery. For each additional
and anesthesiologist—measured by the number of times they time that a unique surgeon-anesthesiologist dyad worked
had worked together—was associated with a reduction in the together, the odds of 90-day major morbidity decreased by 4% for
odds of major morbidity within 90 days of surgery.9 These find- low-risk GI surgery, 8% for high-risk GI surgery, 3% for gynecology
oncology surgery, and 3% for spine surgery.
ings suggest that organizing perioperative care in a way that
promotes more frequent collaboration between specific sur- Meaning These results demonstrate that increasing the familiarity
geon-anesthesiologist pairs could improve outcomes for pa- of surgeon-anesthesiologist dyads represents an opportunity to
tients undergoing these procedures. However, it remains un- improve patient outcomes for GI, gynecology oncology, and spine
surgery.
clear whether these results apply to other high-risk operations.
Effective teamwork is recognized as a key determinant of
success in various high-pressure environments, including avia- Data Sources
tion, sports, and prehospital emergency care, where team per- Datasets were linked using unique encoded identifiers and
formance improves when team members frequently work analyzed at ICES. All datasets used are detailed in eTable 1 in
together.10-12 This improvement is often attributed to en- Supplement 1. The Ontario Cancer Registry is a provincial
hanced coordination, shared mental models, and a better database comprised of all patients with a cancer diagnosis.30,31
understanding of how to respond to challenges under Additional data were obtained from the Registered Persons
pressure, together.13-18 Although these principles could logi- Database, the Canadian Institute of Health Information
cally extend to the operating room, data in this domain are Discharge Abstract Database, the National Ambulatory Care
limited.7,9,19-24 Given that postoperative morbidity is a signifi- Reporting System, the cancer Activity Level Reporting, the
cant factor in long-term disability, health care costs, and pa- Ontario Health Insurance Plan Claims Database, and the ICES
tient recovery, understanding how surgeon-anesthesiologist Physicians Database.32
familiarity impacts patient outcomes in broader contexts is
essential.25-28 Perioperative team organization, including the Study Population
scheduling of specific surgeon-anesthesiologist dyads, repre- Ontario’s 14.5 million residents receive health services through
sents a modifiable factor that could be leveraged to improve a universal public single-payer health system.33 All patients 18
patient outcomes. years or older who underwent high-risk elective surgical pro-
We conducted a population-based retrospective cohort cedures (eTable 2 in Supplement 1) with a postoperative inpa-
study to examine the association between the familiarity of the tient stay over 24 hours from January 2009 to December 2019
surgeon-anesthesiologist dyad (defined as the dyad’s clinical were identified. Those procedures were chosen because they
volume) and postoperative outcomes after high-risk elective are commonly performed, associated with higher morbidity
surgery. risk, and more sensitive to differences in the experience of
the surgeon-anesthesiologist dyad. All procedures were per-
formed at public institutions covered under the Canada Health
Act. We excluded patients with an invalid identification num-
Methods ber, a duplicate surgery record (primary record could not be
Study Design identified reliably), if the primary anesthesiologist or sur-
We conducted a population-based retrospective cohort study geon could not be identified, or if the surgery occurred at a hos-
using administrative health care data in Ontario, Canada, pital performing fewer than 50 procedures over the entire study
housed at ICES (formerly known as the Institute of Clinical period. If a patient had more than 1 procedure of interest
Evaluative Sciences). ICES is a prescribed entity under Ontar- performed, unique procedures more than 90 days apart were
io’s Personal Health Information Protection Act (PHIPA). Proj- included.
ects that use data collected by ICES under section 45 of PHIPA,
and use no other data, are exempt from research ethics board Exposure
review. The use of the data in this project is authorized under To assess the familiarity between health care professionals, we
section 45 and approved by ICES’ Privacy and Legal Office. Re- captured the dyad’s volume: the annual volume of cases done
porting followed the Reporting of Studies Conducted Using Ob- by a unique surgeon-anesthesiologist dyad prior to index sur-
servational Routinely-Collected Health Data (RECORD) exten- gery, as previously reported by our group.34,35 The dyad vol-
sion of the Strengthening the Reporting of Observational ume was defined as the average annual number of proce-
Studies in Epidemiology (STROBE) reporting guidelines dures of interest (within the same group of procedures, such
statement.29 as cardiac or genitourinary) done by that same dyad in the 4

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 Familiarity of the Surgeon-Anesthesiologist Dyad and Major Morbidity After High-Risk Elective Surgery Original Investigation Research

Table 1. Characteristics of Included Patients Stratified by Type of Procedure

Surgery type, No. (%)

Gynecologic
Cardiac High-risk GI Low-risk GI Genitourinary oncologic
Characteristic (n = 14 328) (n = 13 728) (n = 84 709) (n = 51 584) (n = 16 629)
Age, y, median (IQR) 74 (65-82) 64 (56-72) 66 (55-75) 64 (57-69) 62 (55-70)
Sex
Female 5439 (38.0) 5894 (42.9) 40 422 (47.7) 9438 (18.3) 16 629 (100)
Male 8889 (62.0) 7834 (57.1) 44 287 (52.3) 42 146 (81.7) NA
High comorbidity burden
Elixhauser index ≥4 2865 (20.0) 3349 (24.4) 11 156 (13.2) 6125 (11.9) 823 (4.9)
pFI >0.21 3629 (25.3) 1535 (11.2) 7377 (8.7) 2517 (4.9) 755 (4.5)
Rural residence 1515 (10.6) 1320 (9.6) 9409 (11.1) 5293 (10.3) 1623 (9.8)
Material deprivation,
quintiles
1 (Least deprived) 3287 (22.9) 2937 (21.4) 16 724 (19.7) 11 712 (22.7) 3305 (19.9)
2 3051 (21.3) 2730 (19.9) 17 255 (20.4) 10 976 (21.3) 3370 (20.3)
3 2748 (19.2) 2681 (19.5) 17 007 (20.1) 10 352 (20.1) 3307 (19.9)
4 2662 (18.6) 2702 (19.7) 16 923 (20.0) 9597 (18.6) 3365 (20.2)
5 (Most deprived) 2472 (17.3) 2594 (18.9) 16 198 (19.1) 8597 (16.7) 3190 (19.2)
Hospital annual volume, 1267 157 281 113 367
procedures, y, median (IQR) (1058-1560) (88-219) (166-443) (61-198) (250-493)
Hospital setting
Community 2405 (16.8) 3901 (28.4) 56 023 (66.1) 26 815 (52.0) 7590 (45.6) Abbreviations: GI, gastrointestinal;
NA, not applicable; pFI, preoperative
Teaching 11 923 (83.2) 9827 (71.6) 28 686 (33.9) 24 769 (48.0) 9039 (54.4)
frailty index.

years prior to index surgery. This approach accounts for dy- diagnoses) summed as a continuous variable, as well as dichoto-
namic changes of the surgeon and anesthesiologist volumes mized using a cutoff of 4 or higher for high burden.44 We cre-
over time.36,37 The 4-year window ensured that longitudinal ated groups of specialty-based procedures based on the surgi-
familiarity was taken into account; this number of proce- cal specialty and morbidity risk profile: cardiac, high-risk
dures was annualized to create the final dyad annual volume gastrointestinal (GI) (esophageal, hepatobiliary, and pancre-
reported as number of procedures per dyad per year. The dyad atic), low-risk GI (gastric, enteric, colorectal), genitourinary, gy-
volume focused on procedures of interest acknowledging that necology oncology, neurosurgery, orthopedic, spine, vascular,
separate groups of surgeons, and sometimes anesthesiolo- thoracic, and head and neck (eTable 2 in Supplement 1). We also
gists, perform each group of procedure. captured surgeon, anesthesiologist, and hospital annual vol-
ume of procedures of interest (computed as for dyad volume),
Outcome as well as hospital setting (academic vs community).
The primary outcome was 90-day major morbidity (eTable 3
in Supplement 1). Major morbidity was defined as any Clavien- Statistical Analysis
Dindo grade 3 to 5 postoperative complications, which in- Because distinct groups of physicians perform the different
cludes mortality as a grade 5 complication.38 The 90-day win- types of procedures and because there was variability in the
dow was chosen as it provides a better representation of the risk of the included procedures, all analyses were stratified by
morbidity burden of surgery.39-41 Patients were followed-up procedure group. Descriptive statistics were calculated for each
until date of death, date of last clinical contact with the health group; categorical variables were reported as frequencies with
care system, or end of study date on March 31, 2020, allowing proportions and continuous variables as median with IQR.
for the opportunity of 90 days follow-up for all patients. We first explored the linear and nonlinear associations be-
tween dyad volume (primary exposure) and the outcome. Lo-
Covariates gistic regression was implemented to examine the outcome,
Patient, physician, and hospital characteristics were captured. where dyad volume was incorporated and assessed in numer-
Clinical and demographic characteristics were measured at the ous ways: as a continuous linear variable, as a continuous poly-
time of surgery. Patient age, sex, and rural residence, defined ac- nomial variable (with a quadratic term, and with a quadratic
cording to the Rurality Index of Ontario, were captured.42 So- and cubic term), and as a continuous spline.45 Log-likelihood
cioeconomic status was assessed with material deprivation quin- values and assessment of figures plotting the estimated out-
tile, a multidimensional ecologic measure assessing come probability against dyad volume were used to deter-
socioeconomic status that incorporates socioeconomic factors, mine the final functional form of dyad volume. We also ex-
such as education and income.43 The patient’s comorbidity bur- amined the spline-based fitted curve to identify any inflection
den was measured using the Elixhauser comorbidity index with point that may determine a clinically meaningful dichotomi-
the number of comorbidities (excluding cancer and metastases zation of dyad volume.46

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 Research Original Investigation Familiarity of the Surgeon-Anesthesiologist Dyad and Major Morbidity After High-Risk Elective Surgery

Table 2. Characteristics of Included Patients Stratified by Type of Procedure

Surgery type, No. (%)

Head and neck Neuro Orthopedic Spine Lung Vascular
Characteristic (n = 3253) (n = 13 140) (n = 414 313) (n = 49 738) (n = 25 803) (n = 23 781)
Age, y, median (IQR) 64 (56-73) 57 (47-66) 68 (61-75) 61 (50-70) 67 (58-73) 69 (62-76)
Sex
Female 1128 (34.7) 7430 (56.5) 245 907 (59.4) 23 391 (47.0) 13 405 (52.0) 6816 (28.7)
Male 2125 (65.3) 5710 (43.5) 168 406 (40.6) 26 347 (53.0) 12 398 (48.0) 16 965 (71.3)
High comorbidity burden
Elixhauser index ≥4 687 (21.1) 2227 (16.9) 28 024 (6.8) 2996 (6.0) 4547 (17.6) 3789 (15.9)
pFI >0.21 295 (9.1) 782 (6.0) 11 721 (2.8) 1522 (3.1) 2316 (9.0) 4663 (19.6)
Rural residence 305 (9.4) 1264 (9.6) 51 750 (12.5) 6673 (13.4) 3496 (13.5) 3304 (13.9)
Material deprivation, quintiles
1 (Least deprived) 592 (18.2) 2886 (22.0) 89 439 (21.6) 9794 (19.7) 4851 (18.8) 3654 (15.4)
2 614 (18.9) 2677 (20.4) 87 256 (21.1) 10 036 (20.2) 4975 (19.3) 4135 (17.4)
3 625 (19.2) 2476 (18.8) 83 663 (20.2) 9769 (19.6) 5224 (20.2) 4759 (20.0)
4 651 (20.0) 2592 (19.7) 79 985 (19.3) 10 005 (20.1) 5320 (20.6) 5181 (21.8)
5 (Most deprived) 750 (23.1) 2413 (18.4) 70 799 (17.1) 9695 (19.5) 5239 (20.3) 5834 (24.5)
Hospital annual volume, 70 (40-148) 250 (109-338) 727 (443-1094) 557 (312-774) 210 (112-288) 177 (94-256)
procedures, y, median (IQR)
Hospital setting
Community 126 (3.9) 1977 (15.0) 282 727 (68.2) 18 245 (36.7) 13 697 (53.1) 12 598 (53.0)
Teaching 3127 (96.1) 11 163 (85.0) 131 586 (31.8) 31 493 (63.3) 12 106 (46.9) 11 183 (47.0)

Abbreviations: GI, gastrointestinal; pFI, preoperative frailty index.

Informed by the relationships explored above, we de- Statistical tests were 2-sided and P value less than .05 con-
scribed the association between dyad volume and the pri- sidered statistically significant. All analyses were conducted
mary outcome using the exposure as a continuous variable with using SAS Enterprise Guide version 7.1 (SAS Institute).
both linear and quadratic terms (per increment of 1 proce-
dure per dyad per year). We then implemented multivariable
logistic regression models to adjust for potential confound-
ers. Collinearity was assessed, defined as variance inflation fac-
Results
tor of 2.5 or higher.47 To build a parsimonious model, a di- A total of 711 006 index procedures were included (eFigure 2
rected acyclic graph was built to illustrate the interconnected in Supplement 1). Of those, 102 972 patients had 2 procedures
associations between the exposure, outcomes, and mea- (17.9%) and 15 266 had 3 or more procedures (2.7%), most of
sured covariates (eFigure 1 in Supplement 1).48,49,51 The fol- which were for orthopedic surgery. The characteristics of in-
lowing covariates were adjusted for in each model: patient age, dex procedures are detailed in Table 1 and Table 2. The index
sex (except for gynecology oncology), and comorbidity bur- procedures were performed at 95 unique hospitals.
den, hospital annual volume, surgeon and anesthesiologist an- The number of unique surgeon-anesthesiologist dyads car-
nual volumes, hospital setting, and year of surgery. We exam- ing for patients varied depending on the type of procedures
ined the correlation coefficient within models; this was near (Table 3). The ratio of procedures to number of unique dyads
0 and, thus, we did not further account for clustering in the was highest for cardiac, orthopedic, and lung surgery, indi-
models. We also presented changes in adjusted odds ratio (OR) cating higher dyad volumes and dyad consistency for those
for each subsequential increment in dyad volume (1 vs 0; 2 vs types of procedures. The distribution of dyad volume varied
1; 3 vs 2; 4 vs 5; and so forth). depending on the type of procedure (eFigure 3 in Supple-
We conducted a sensitivity analysis to examine the asso- ment 1); most distributions were right skewed. The median
ciation between dyad volume and 30-day major morbidity. Re- dyad volume was 3 or less procedures per dyad per year for
sults from the regression models were reported as ORs with most types of procedures, except for cardiac surgery (median
95% CI. of 9 procedures per dyad per year) and orthopedic surgery (me-
We looked at missing data for key variables. There were dian of 8 procedures per dyad per year) that presented higher
no missing data on the exposure or outcomes used for the medians, despite persistent right-skewness (Table 3).
analysis. For covariates, data were missing in 0.2% for rural The occurrence of 90-day major morbidity also varied de-
residence and 0.8% for material deprivation. These were not pending on the type of procedure: 9343 for cardiac surgery
included in multivariable models and, therefore, complete case (65.2%), 5505 for high-risk GI surgery (40.1%), 20 450 for low-
analyses were conducted. risk GI surgery (24.1%), 7779 for genitourinary surgery (15.1%),

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 Familiarity of the Surgeon-Anesthesiologist Dyad and Major Morbidity After High-Risk Elective Surgery Original Investigation Research

Table 3. Characteristics of Surgeon-Anesthesiologist Dyads, Stratified by Type of Procedure

Surgery type
Gyneco- Head
Low- Genito- logic and Ortho-
Cardiac High-hrisk risk GI urinary oncologic neck Neuro pedic Spine Lung Vascular
(n = GI (n = (n = (n = (n = (n = (n = (n = (n = (n =
Characteristic 14 328) (n = 13 728) 84 709) 51 584) 16 629) 3253) 13 140) 414 313) 49 738) 25 803) 23 781)
Surgeon- 9 (5-19) 1 (0-2) 1 (1-3) 2 (1-3) 2 (1-3) 1 (0-2) 1 (0-2) 8 (4-13) 3 (1-5) 3 (1-4) 2 (1-4)
anesthesiologist dyad
volume,
procedures/dyad/y,
median (IQR)
No. of unique 1147 3256 15 415 7447 6965 1125 3200 12 893 5406 2277 3287
surgeon-
anesthesiologist dyads
Procedure dyads ratio 12.5 4.2 5.5 6.9 2.4 2.9 4.1 32.1 9.2 11.3 7.2

Abbreviation: GI, gastrointestinal.

1924 for gynecologic oncologic surgery (11.6%), 1284 for head The associations between dyad volume and outcome per-
and neck surgery (39.5%), 4690 for neurosurgery (35.7%), sisted when examining 30-day major morbidity (eTable 6 in
31 504 for orthopedic surgery (7.6%), 4732 for spine surgery the Supplement). There was an independent adjusted asso-
(9.7%), 6071 for lung surgery (23.5%), and 8794 for vascular ciation between dyad volume and 30-day major morbidity for
surgery (37.0%). The unadjusted and adjusted ORs for the as- high-risk GI surgery (OR, 0.90; 95% CI, 0.86-0.94) and low-
sociation between dyad volume and 90-day major morbidity risk GI surgery (OR, 0.96; 95% CI, 0.94-0.97). The direction of
are depicted in Figure 1 and detailed in eTable 4 in Supple- the association also persisted for gynecology oncologic sur-
ment 1. There was evidence of a linear association between gery (OR, 0.99; 95% CI, 0.95-1.02) and spine surgery (OR, 0.99;
dyad volume and 90-day major morbidity for all types of pro- 95% CI, 0.97-1.01).
cedures , except for lung surgery. Nonlinear association were
also identified when adding a quadratic term for high-risk GI
surgery, low-risk GI surgery, and genitourinary surgery
(eFigure 4 in Supplement 1). Restricted cubic splines did not
Discussion
consistently identify meaningful inflection points. In this population-based study, we observed an association be-
Given the presence of a nonlinear association but lack of tween care by a more familiar surgeon-anesthesiologist dyad
meaningful inflection points, the dyad volume was treated as and lower 90-day major morbidity for GI surgery, gynecology
continuous variable with a linear and quadratic term. Unad- oncology surgery, and spine surgery. For each additional pro-
justed and adjusted ORs for each type of procedure are pre- cedure performed by the same surgeon-anesthesiologist dyad,
sented in Figure 1; eTable 4 in Supplement 1. The association there was an associated reduction in the odds of 90-day ma-
of each increment of 1 procedure per year with 90-day major jor morbidity by 4% for low-risk GI surgery, 8% for high-risk
morbidity was assessed. Unadjusted ORs were statistically sig- GI surgery, 3% for gynecology oncology surgery, and 3% for
nificant for high-risk GI surgery, low-risk GI surgery, and geni- spine surgery, after adjusting for potential confounders. This
tourinary surgery, but not for other procedures. After adjust- association did not show any clear dyad volume threshold point
ing for hospital setting, hospital, surgeon and anesthesiologist where the relationship changed. These findings indicate that
volume, and patient age, sex, and comorbidity burden, an in- for each additional procedure performed by a specific surgeon-
dependent association was observed between dyad volume anesthesiologist dyad, there is a corresponding decrease in the
and 90-day major morbidity for high-risk GI surgery (OR, 0.92; likelihood of experiencing 90-day major morbidity. Each pro-
95% CI, 0.88-0.96), low-risk GI surgery (OR, 0.96; 95% CI, 0.95- cedure done together matters.
0.98), gynecologic oncologic surgery (OR, 0.97; 95% CI, 0.94- Existing literature on team dynamics in the operating room
0.99), and spine surgery (OR, 0.97; 95% CI, 0.96-0.99). The ad- has focused on different components of the team and relied
justed associations were not significant for other types of on single-center designs. Higher familiarity of the surgeon and
procedures. The detailed multivariable models are presented surgical trainee has been associated with more efficient pro-
in eTable 5 in Supplement 1. cedures, with reduced clamp time in vascular surgery, and
Using the quadratic term, the changes in adjusted OR for shorter operative time in orthopedic surgery.22,23 Familiarity
each subsequential increment in dyad volume were ob- between the surgeon and scrub nurse has been associated with
served (for example, 1 vs 0; 2 vs 1; 3 vs 2; 4 vs 5), which are pre- smoother workflows and fewer disruptions in neurosurgery.7
sented in Figure 2 and eFigure 4 in the Supplement. For pro- Patient outcomes were not assessed in those studies. A single-
cedures with an independent association between dyad volume center study20 in vascular surgery also examined familiarity
and 90-day major morbidity, the ORs reduction was more pro- of the entire operating room team, using a complex familiar-
nounced immediately as the dyad volume started to increase ity score across all team members, and observed that higher
(high-risk GI and low-risk GI surgery) or remained stable (gy- levels of familiarity were associated with reduced operative
necologic oncologic, and spine surgery). time, shorter length of stay, and fewer complications. The cur-

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 Research Original Investigation Familiarity of the Surgeon-Anesthesiologist Dyad and Major Morbidity After High-Risk Elective Surgery

Figure 1. Unadjusted and Adjusted Associations Between Surgeon-Anesthesiologist Dyad Volume and 90-Day
Postoperative Major Morbidity, Stratified by Type of Procedure

OR of 90-d major Decreased odds with each Increased odds with

Surgery type morbidity (95% CI) additional procedure/y each additional procedure/y
Cardiac
Unadjusted 0.99 (0.98-1.01)
Adjusted 0.99 (0.98-1.00)
High-risk GI
Unadjusted 0.90 (0.86-0.94)
Adjusted 0.92 (0.88-0.96)
Low-risk GI
Unadjusted 0.94 (0.92-0.96)
Adjusted 0.96 (0.95-0.98)
Genitourinary
Unadjusted 0.95 (0.93-0.96)
Adjusted 1.01 (0.99-1.02)
Gynecologic oncologic
Unadjusted 0.98 (0.95-1.00)
Adjusted 0.97 (0.94-0.99)
Head and neck
Unadjusted 1.07 (0.96-1.20)
Adjusted 1.03 (0.94-1.14)
Neurosurgery
Unadjusted 0.98 (0.97-1.00)
Adjusted 0.99 (0.97-1.01)
Orthopedic Odds ratios (ORs) (unadjusted, and
Unadjusted 0.98 (0.97-1.00) adjusted for patient age, sex, and
Adjusted 1.00 (0.99-1.00) comorbidity burden, hospital annual
Spine volume, surgeon and anesthesiologist
annual volumes, hospital setting, and
Unadjusted 1.00 (0.98-1.02) year of surgery) are presented with
Adjusted 0.97 (0.96-0.99)
95% CIs. ORs represent the change in
Lung odds of 90-day postoperative major
Unadjusted 1.02 (0.99-1.05) morbidity for each increment of 1
Adjusted 1.01 (0.99-1.03) procedure per dyad per year An OR
Vascular below 1 indicates reduced odds of
Unadjusted 0.92 (0.90-0.95) 90-day postoperative major
Adjusted 0.98 (0.96-1.00) morbidity. The dotted line represents
the null value of the OR. Complete
0.80 0.90 1.00 1.10 1.20 models for adjusted ORs are available
OR of 90-d major morbidity (95% CI) in eTable 5 in Supplement 1. GI
indicates gastrointestinal.

rent study brings novel information by focusing specifically dynamics may further be impacted by the sociodemograph-
on the surgeon-anesthesiologist dyad, using a simple prag- ics of anesthesiologists and surgeons within unique dyads; ex-
matic measure of familiarity that is actionable and can be moni- ploring how the association between dyad familiarity may be
tored in practice, and analyzing multicenter data represent- modified by the dyad sociodemographics fell beyond the scope
ing an entire health system. The results outline differences in of the current study but would be a worthy area for future in-
the relationships between dyad volume and postoperative out- vestigations.
comes depending on the type of procedure. The associations between surgeon-anesthesiologist dyad
Team familiarity in the operating room may improve pa- volume and 90-day major morbidity differed across proce-
tient outcomes through enhanced teamwork and trust.19 Non- dures. This may point to different structures of care and dif-
technical skills are recognized as essential for maintaining the ferent baseline risks and management. First, no significant as-
flow of procedures and ensuring positive outcomes in the op- sociation was observed for procedures where the median dyad
erating room, and are facilitated within stable and familiar volume was high (cardiac, lung, and orthopedic surgery). Struc-
teams.50-53 Familiarity created transactive memory systems, tures of care for these procedures are unique within our sys-
whereby close relationships lead to a shared understanding of tem, with higher dyad volume and familiarity overall. Car-
each other’s tasks, goals, resources, and environment.54-57 This diac surgery is only performed by a small group of specialized
results in increased cooperation, cohesiveness, trust, sup- anesthesiologists in designated centers, lung surgery is re-
port, and assistance, all of which are correlated with im- gionalized with requirements for specific anesthesiology train-
proved perceptions of work effectiveness and satisfaction.21 ing for designated centers of excellence, and most elective or-
More familiar teams are more likely to adhere to best prac- thopedic surgery is performed in specialized centers dedicated
tices and care processes, respond effectively to unexpected to hip and knee surgery where smaller anesthesiology teams
events, and offer (and accept) support when needed.54-57 These work. Second, for procedures like genitourinary surgery, neu-

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 Familiarity of the Surgeon-Anesthesiologist Dyad and Major Morbidity After High-Risk Elective Surgery Original Investigation Research

Figure 2. Association Between Surgeon-Anesthesiologist Dyad Volume and 90-Day Postoperative Major Morbidity by Dyad Volume

A Cardiac surgery B Orthopedic surgery

1.10 1.10

1.05 1.05
Adjusted OR

Adjusted OR
1.00 1.00

0.95 0.95

0.90 0.90

0.85 0.85
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Incremental surgeon-anesthesiologist dyad volume Incremental surgeon-anesthesiologist dyad volume

C High-risk GI surgery D Low-risk GI surgery

1.10 1.10

1.05 1.05
Adjusted OR

1.00 Adjusted OR 1.00

0.95 0.95

0.90 0.90

0.85 0.85
1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 10
Incremental surgeon-anesthesiologist dyad volume Incremental surgeon-anesthesiologist dyad volume

E Gynecologic oncologic surgery F Spine surgery

1.10 1.10

1.05 1.05
Adjusted OR

Adjusted OR

1.00 1.00

0.95 0.95

0.90 0.90

0.85 0.85
1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 10
Incremental surgeon-anesthesiologist dyad volume Incremental surgeon-anesthesiologist dyad volume

Odds ratios (ORs) (adjusted for patient age, sex, and comorbidity burden, postoperative major morbidity. The dotted line represents the null value of the
hospital annual volume, surgeon and anesthesiologist annual volumes, hospital OR. Each x-axis value represents a comparison between that value and the
setting, and year of surgery) with 95% CIs error bars presented for the increment below, ie, 1 vs 0, 2 vs 1, 3 vs 2, and so on. Data for other types of
association between surgeon-anesthesiologist dyad volume and 90-day procedures can be found in eFigure 3 in Supplement 1. GI indicates
postoperative major morbidity. The OR was determined for each increment of gastrointestinal.
dyad volume. An OR below 1 indicates a reduction in the risk of 90-day

rosurgery, or vascular surgery, it is possible that either the dyad definitely conclude that no relationship exists between sur-
volumes in the cohort were too small and skewed toward low geon-anesthesiologist dyad familiarity and patient out-
numbers with little spread to be able to detect a difference. The comes. For procedures for which high dyad volume had been
number of events was high in those groups and confidence in- achieved and no association was observed (cardiac, orthope-
tervals narrow, such that we do not believe the lack of signifi- dic, lung), we can conclude that when high dyad familiarity
cance was related to lack of statistical power. For those pro- (or dyad volume) already exists, no association was observed
cedures (genitourinary, neurosurgery, vascular), we cannot with further increases in dyad volume.

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 Research Original Investigation Familiarity of the Surgeon-Anesthesiologist Dyad and Major Morbidity After High-Risk Elective Surgery

The results regarding low- and high-risk GI surgery, gyne- sitive to detecting differences based on team characteristics,
cology oncology surgery, and spine surgery can inform team and there is more opportunity to intervene on team sched-
models and care organization for high-risk elective surgery that ules in elective settings than in emergency operations. We rec-
leverage surgeon-anesthesiologist familiarity to optimize post- ognize that there was heterogeneity in procedure risk across
operative patient outcomes. Dedicated or specialized anes- the procedures included in the study, which is one of the rea-
thesiology teams could contribute to increasing dyad vol- son the analyses were stratified by type of procedures. We also
ume. However, one may foresee unintended consequences, acknowledge that team expertise and familiarity also likely
such as reducing the volume of other operations for anesthe- matter in the emergency setting; this would require separate
siologists in specialized teams, resulting in challenges main- studies to ascertain. Lastly, our findings are based on the dyad
taining expertise for general practice necessary to cover all op- volumes existing within our cohort, and it is possible that in
erating room activities. Novel models of care fostering other systems with different baseline volumes or distribu-
increased surgeon-anesthesiologist dyad familiarity need to tion of volumes, the magnitude of the observed effect esti-
take this into account. It is also important to note that famil- mates could differ. However, we believe that the direction of
iarity cannot be replicated through protocols and processes of the association would remain consistent across different con-
care. Both familiarity and optimized processes of care are texts.
needed.21,54-61

Limitations
This study has limitations that ought to be considered when
Conclusions
interpreting the results. First, the routinely collected health In this study, increasing the familiarity of the surgeon-
administrative data used were not collected specifically to ad- anesthesiologist dyad was associated with improved postop-
dress the research question. This introduces risk of misclas- erative outcomes for patients undergoing low and high-risk GI
sification for some variables and limits the availability of de- surgery, gynecology oncology surgery, and spine surgery. For
tails on factors that may have impacted the dyad volume- each additional time that a unique surgeon-anesthesiologist
outcome association, such as organizational culture or dyad worked together, the odds of 90-day major morbidity de-
institutional protocols. Additionally, unmeasured confound- creased by 4% for low-risk GI surgery, 8% for high-risk GI sur-
ing cannot be avoided. Second, we focused on the relation- gery, 3% for gynecology oncology surgery, and 3% for spine sur-
ship between surgeon-anesthesiologist dyads, which did not gery. Increasing the familiarity of surgeon-anesthesiologist
capture the contributions of other key team members, such dyads, or the number of procedures they do together, repre-
as nurses, trainees, or anesthesiology assistants. While famil- sents an opportunity to improve patient outcomes for GI,
iarity among those team members certainly also matters, the gynecology oncology, and spine surgery. Additional research
importance of dyadic relationships within teams is well is needed to determine the most effective care structures that
described.58 Third, we limited our analysis to high-risk and harness the benefits of surgeon-anesthesiologist familiarity to
elective operations, as these types of procedures are more sen- improve patient outcomes.

ARTICLE INFORMATION Medicine, Division of Critical Care Medicine, Providence Health Care, Vancouver, British
Accepted for Publication: March 23, 2025. Université Laval, Québec City, Québec, Canada Columbia, Canada (Flexman).
(Turgeon); CHU de Québec–Université Laval Author Contributions: Ms Chan had full access to
Published Online: May 28, 2025. Research Centre, Population Health and Optimal
doi:10.1001/jamasurg.2025.1386 all of the data in the study and takes responsibility
Health Practices Research Unit, Trauma– for the integrity of the data and the accuracy of the
Author Affiliations: Department of Surgery, Emergency–Critical Care Medicine, Université Laval, data analysis.
University of Toronto, Toronto, Ontario, Canada Québec City, Québec, Canada (Turgeon); Concept and design: Hallet, Perez d'Empaire,
(Hallet, Coburn); Division of Surgical Oncology, Departments of Anesthesiology & Pain Medicine, Turgeon, McIsaac, Idestrup, Lorello, Flexman,
Odette Cancer Centre, Sunnybrook Health Sciences University of Ottawa and The Ottawa Hospital, Coburn, Eskander, Sutradhar.
Centre, Toronto, Ontario, Canada (Hallet, Coburn, Ottawa, Ontario, Canada (McIsaac); Department of Acquisition, analysis, or interpretation of data:
Eskander); Clinical Evaluative Sciences, Sunnybrook Anesthesiology and The Wilson Centre, University Hallet, Jerath, Carrier, Turgeon, Lorello, Flexman,
Research Institute, Toronto, Ontario, Canada Health Network, Toronto Western Hospital, Kidane, Chan, Gombay, Eskander, Sutradhar.
(Jerath, Gombay, Coburn, Eskander); ICES, Toronto, Toronto, Ontario, Canada (Lorello); Women’s Drafting of the manuscript: Hallet, Perez d'Empaire,
Ontario, Canada (Jerath, Chan, Coburn, Eskander, College Research Institute, Women’s College McIsaac, Sutradhar.
Sutradhar); Department of Anesthesiology, Hospital, Toronto, Ontario, Canada (Lorello); Critical review of the manuscript for important
Sunnybrook Health Sciences Centre, Toronto, Department of Anesthesiology, Pharmacology and intellectual content: All authors.
Ontario, Canada (Jerath, d’Empaire, Idestrup); Therapeutics, University of British Columbia, Statistical analysis: Hallet, Chan, Sutradhar.
Department of Anesthesiology and Pain Medicine, Vancouver, British Columbia, Canada (Flexman); Obtained funding: Hallet, Perez d'Empaire,
University of Toronto, Toronto, Ontario, Canada Section of Thoracic Surgery, Departments of Turgeon.
(Jerath, d’Empaire, Idestrup, Lorello); Carrefour Surgery and of Community Health Sciences, Administrative, technical, or material support:
de l’innovation et santé des populations, Centre University of Manitoba, Winnipeg, Manitoba, Hallet, Jerath, Perez d'Empaire, Lorello, Kidane,
de recherche du CHUM, and Department of Canada (Kidane); Department of Otolaryngology– Gombay, Eskander.
Anesthesiology and Division of Critical Care, Centre Head & Neck Surgery, University of Toronto, Supervision: Hallet, McIsaac, Kidane, Coburn,
Hospitalier de l’Université de Montréal, Montréal, Toronto, Ontario, Canada (Eskander); Division of Sutradhar.
Québec, Canada (Carrier); Department of Biostatistics, Dalla Lana School of Public Health,
Anesthesiology and Pain Medicine, Université de University of Toronto, Ontario, Canada (Sutradhar); Conflict of Interest Disclosures: Dr Flexman
Montréal, Montréal, Québec, Canada (Carrier); Department of Anesthesiology, St Paul’s Hospital/ reported grants from Michael Smith Health
Department of Anesthesiology and Critical Care Research BC during the conduct of the study;

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 Familiarity of the Surgeon-Anesthesiologist Dyad and Major Morbidity After High-Risk Elective Surgery Original Investigation Research

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