RESEARCH Prospective validation of classification of intraoperative adverse BMJ: first published as 10.1136/bmj.m2917 on 25 August 2020. Downloaded from http://www.bmj.com/ on 29 January 2021 by guest. Protected by copyright. events (ClassIntra): international, multicentre cohort study Salome Dell-Kuster,1,2,3 Nuno V Gomes,1,3 Larsa Gawria,2,4 Soheila Aghlmandi,2 Maame Aduse-Poku,5 Ian Bissett,6 Catherine Blanc,7 Christian Brandt,8 Richard B ten Broek,4 Heinz R Bruppacher,9 Cillian Clancy,10 Paolo Delrio,11 Eloy Espin,12 Konstantinos Galanos-Demiris,13 I Ethem Gecim,14 Shahbaz Ghaffari,15 Olivier Gié,16 Barbara Goebel,17 Dieter Hahnloser,16 Friedrich Herbst,15 Ioannidis Orestis,13 Sonja Joller,18 Soojin Kang,5 Rocio Martín,12 Johannes Mayr,17 Sonja Meier,5 Jothi Murugesan,19 Deirdre Nally,10 Menekse Ozcelik,20 Ugo Pace,11 Michael Passeri,21 Simone Rabanser,22 Barbara Ranter,23 Daniela Rega,11 Paul F Ridgway,10 Camiel Rosman,4 Roger Schmid,24 Philippe Schumacher,8 Alejandro Solis-Pena,12 Laura Villarino,25 Dionisios Vrochides,21 Alexander Engel,19 Greg O’Grady,6 Benjamin Loveday,6 Luzius A Steiner,1,3 Harry Van Goor,4 Heiner C Bucher,2,3 Pierre-Alain Clavien,26 Philipp Kirchhoff,27 Rachel Rosenthal28 For numbered affiliations see Abstract endpoint was construct validity by investigating the end of the article. Objective risk adjusted association between the most severe Correspondence to: S Dell-Kuster To prospectively assess the construct and criterion intraoperative and postoperative complications, salome.dell-kuster@usb.ch (ORCID 0000-0001-7219-7138) validity of ClassIntra version 1.0, a newly developed measured in a multivariable hierarchical proportional Additional material is published classification for assessing intraoperative adverse odds model. For criterion validity, inter-rater reliability online only. To view please visit events. was evaluated in a survey of 10 fictitious case the journal online. scenarios describing intraoperative complications. Design Cite this as: BMJ2020;370:m2917 International, multicentre cohort study. Results http://dx.doi.org/10.1136/bmj.m2917 Setting Of 2520 patients enrolled, 610 (24%) experienced Accepted: 23 June 2020 at least one intraoperative adverse event and 838 18 secondary and tertiary centres from 12 countries in Europe, Oceania, and North America. (33%) at least one postoperative complication. Multivariable analysis showed a gradual increase in Participants risk for a more severe postoperative complication The cohort study included a representative sample of with increasing grade of ClassIntra: ClassIntra grade 2520 patients in hospital having any type of surgery, I versus grade 0, odds ratio 0.99 (95% confidence followed up until discharge. A follow-up to assess interval 0.69 to 1.42); grade II versus grade 0, 1.39 mortality at 30 days was performed in 2372 patients (0.97 to 2.00); grade III versus grade 0, 2.62 (1.31 (94%). A survey was sent to a representative sample to 5.26); and grade IV versus grade 0, 3.81 (1.19 of 163 surgeons and anaesthetists from participating to 12.2). ClassIntra showed high criterion validity centres. with an intraclass correlation coefficient of 0.76 Main outcome measures (95% confidence interval 0.59 to 0.91) in the survey Intraoperative complications were assessed (response rate 83%). according to ClassIntra. Postoperative complications Conclusions were assessed daily until discharge from hospital ClassIntra is the first prospectively validated with the Clavien-Dindo classification. The primary classification for assessing intraoperative adverse events in a standardised way, linking them to What is already known on this topic postoperative complications with the well established Clavien-Dindo classification. ClassIntra can be Intraoperative adverse events are a concern for patients, anaesthetists, and incorporated into routine practice in perioperative surgeons because of their association with adverse postoperative outcomes surgical safety checklists, or used as a monitoring In contrast with postoperative complications, prospectively validated systems for and outcome reporting tool for different surgical reporting intraoperative adverse events are lacking disciplines. Future studies should investigate whether Uniform definitions and transparent reporting of intraoperative adverse events the tool is useful to stratify patients to the appropriate are required for programmes to improve the safety of surgery and to compare postoperative care, to enhance the quality of surgical results from clinical research interventions, and to improve long term outcomes of surgical patients. What this study adds Trial registration ClassIntra is the first prospectively validated classification system with good ClinicalTrials.gov NCT03009929. reliability and practicability that includes intraoperative adverse events related to surgery and anaesthesia Introduction ClassIntra covers a major unmet need as it provides a standardised instrument to Over 310 million surgeries are conducted worldwide quantify and qualify intraoperative adverse events in clinical practice and clinical each year.1 One in six patients having elective surgery research for a range of surgical disciplines and for anaesthesia experiences at least one postoperative adverse the bmj | BMJ 2020;370:m2917 | doi: 10.1136/bmj.m2917 1 RESEARCH event.2 The growing annual surgical volume1 3 and confirmed the validity of the data from their centres. the increasing complexity of comorbid conditions in The results are reported according to STROBE BMJ: first published as 10.1136/bmj.m2917 on 25 August 2020. Downloaded from http://www.bmj.com/ on 29 January 2021 by guest. Protected by copyright. patients having surgery4 5 has caused a rise in adverse (strengthening the reporting of observational studies events related to surgery. Intraoperative adverse in epidemiology).19 events are associated with adverse outcomes,6-10 but in contrast with postoperative complications,11-13 a Patients and study procedures (prospective cohort prospectively validated instrument for standardised study) and transparent reporting of intraoperative adverse The centres prospectively included consecutive events is lacking. Uniform definitions of perioperative patients or a representative group of patients having outcomes, however, are required for programmes to any type of surgery from any surgical discipline. improve the safety of surgery, for benchmarking, and Excluded were day case surgeries, procedures not to adequately compare results from clinical research.14 taking place in the operating room, procedures with no In 2015, our group developed a CLASSification anaesthesia, and follow-up procedures. of Intraoperative Complications (ClassIntra version The surgical and anaesthesia team prospectively 1.0, formerly known as CLASSIC, supplementary recorded the severity grade and details of intraoperative table S1) in a Delphi process involving international, adverse events that occurred between skin incision interdisciplinary experts, which was retrospectively and skin closure, according to ClassIntra version 1.0 validated.15 This tool defines intraoperative adverse (table 1), during team sign-out20 at the end of surgery. events as any deviation from the ideal intraoperative Disagreement was resolved by consensus. All patients course between skin incision and skin closure, and were followed up until discharged from hospital and includes events related to surgery and anaesthesia. were assessed daily by the postoperative care team Similar to the widely used Clavien-Dindo classification to identify and grade postoperative complications for reporting postoperative complications (supplemen­ according to the Clavien-Dindo classification.11 tary table S2),11 we sought to develop a generic Because this was a pragmatic cohort study, performed classification, broadly applicable to all surgical during daily clinical practice, the postoperative disciplines, and including anaesthesia. To align team could not be blinded to the intraoperative with the validated Clavien-Dindo classification,16 17 adverse events, but was not aware of the ClassIntra CLASSIC was updated by including five severity grade. Postoperative complications after discharge, grades, maintaining the decision criterion on the need including mortality within 30 days, were assessed for treatment and severity of symptoms. during structured follow-up visits or telephone calls to The aim of this international, multicentre, pro­ patients or their relatives. spective cohort study was to investigate the validity Data describing the patients enrolled in the study and practicability of the updated classification in were anonymised before entry into a secure web based many different surgical disciplines. electronic database. The database had automated checks for plausibility, consistency, and completeness Methods of the data entries. Further consistency checks were Study oversight performed after recruitment was finished. This investigator initiated validation study of ClassIntra version 1.0 consisted of two parts. An international, ClassIntra multicentre, prospective cohort study was conducted ClassIntra version 1.0 was derived from CLASSIC,15 in 18 centres in 12 countries in patients having any which had four severity grades, but the same type of surgery requiring hospital admission for at definition depending on the intervention required to least one night. The objective was to assess construct treat the adverse event and the severity of symptoms validity. Because no gold standard exists for the (supplementary table S1). The only difference in severity of intraoperative adverse events, we assessed the updated ClassIntra is that grade II has been the relation between the ClassIntra grades and other divided into two grades. The additional grade (new indirect measures that we expected to be related.18 grade III) describes a moderate deviation from the In particular, we investigated the stepwise increasing ideal course, which requires moderate treatment effect of the severity grades of ClassIntra and relevant and results in severe symptoms. The rationale for postoperative outcomes, such as postoperative updating the classification was to align with the complications, length of hospital stay, and length number of grades in the Clavien-Dindo classification of surgery. The second part involved a survey of 10 to avoid misclassification in grading intraoperative fictitious case scenarios describing intraoperative or postoperative death (supplementary table S2).11 A adverse events. The survey was sent at the beginning retrospective (unpublished) pilot study showed high of the prospective cohort study to physicians from reliability for ClassIntra. the same international centres to grade severity. The We secured the rights to the ClassIntra classification aim was to assess criterion validity and reliability by filing a trademark with the Swiss Federal Institute by comparing severity ratings by physicians with of Intellectual Property. The trademark was extended benchmark ratings set by the core team. to relevant countries for our activities by inter­ Across all centres, collaborators were trained in national registration at the World Intellectual Property standardised data collection. Local study investigators Organisation. 2 doi: 10.1136/bmj.m2917 | BMJ 2020;370:m2917 | the bmj RESEARCH Outcomes Inter-rater reliability and practicability of ClassIntra The primary outcome was the association of the An online anonymous survey (SurveyMonkey, San BMJ: first published as 10.1136/bmj.m2917 on 25 August 2020. Downloaded from http://www.bmj.com/ on 29 January 2021 by guest. Protected by copyright. most severe intraoperative adverse events, according Mateo, CA, USA) of 10 fictitious case scenarios to ClassIntra, with the most severe postoperative (supplementary table S3) describing intraoperative complications, according to the Clavien-Dindo adverse events was sent to a representative sample classification.11 Secondary outcomes were the associa­ of physicians from the participating centres. The tion of the most severe intraoperative adverse events scenarios were designed to cover a range of severity with the sum of all postoperative complications, grades and medical specialties. The benchmark rating calculated by the comprehensive complication index,12 for each case scenario was determined by consensus postoperative length of hospital stay, length of surgery, of the core team. The physicians also rated the and 30 day mortality. Thirty day mortality was defined practicability of the instrument on a nine point scale, as death within 30 days of surgery, either in hospital or with end anchors of “very practical” and “not practical after discharge. at all.” All models for the primary and secondary outcomes were adjusted for confounders: American Society of Statistical analysis Anesthesiologists physical status,21 as a summary A multivariable hierarchical proportional odds model measure of perioperatively relevant comorbidities; was used to investigate the association between age; length of surgery; complexity of surgery, graded the most severe intraoperative and postoperative as one of five categories according to the British United adverse event considering clustering within study Provident Association (BUPA)22 23; urgency of the centres. The proportional odds assumption was procedure (planned or emergency); experience of the mainly assessed with the Brant test. Because of the surgical and anaesthesia team (for a definition, see the sparseness of the data for the higher severity grades statistical analysis plan in the supplementary file); and for intraoperative and postoperative adverse events, wound class.24 All confounders were defined according and breach of the proportionality assumption for the to biological plausibility and scientific rationale. Type five categories of the Clavien-Dindo system, a three of operation and complexity were recorded according category classification (Clavien-Dindo grade 0, grades to the BUPA classification.22 23 BUPA categorises I-II, and grades III-V) was used. The rationale for these all commonly performed surgical procedures into cut-offs was to distinguish an uneventful course from five complexity grades (minor, intermediate, major, a minor or major deviation, and was in line with cut- major plus, and complex major; supplementary table offs used in most publications combining categories.16 S15) and has been used previously for scientific The consistency of the coefficients was checked by purposes.25 26 performing an internal validation with bootstrapping Table 1 | ClassIntra version 1.0 classification of intraoperative adverse events. The classification defines intraoperative adverse events as any deviation from the ideal intraoperative course occurring between skin incision and skin closure. Any event related to surgery and anaesthesia during the index surgery must be considered and should be rated directly after surgery.* A requirement is that the indication for surgery and the interventions conform to current guidelines Grade Definition Examples Grade 0 No deviation from the ideal intraoperative course — • Bleeding: bleeding above average from small calibre vessel, self-limiting or definitively Any deviation from the ideal intraoperative course: manageable without additional treatment than routine coagulation Grade I • Without the need for any additional treatment or intervention • Injury: minimal serosal intestinal lesion, not requiring any additional treatment • Patient with no or mild symptoms • Cautery: small burn of the skin, no treatment necessary • Arrhythmia: arrhythmia (eg, extrasystoles) without relevance • Bleeding: bleeding from medium calibre artery or vein, ligation; use of tranexamic acid Any deviation from the ideal intraoperative course: • Injury: non-transmural intestinal lesion requiring suture(s) • With the need for any additional minor treatment or intervention Grade II • Cautery: moderate burn requiring non-invasive wound care • Patient with moderate symptoms, not life threatening, and not • Arrhythmia: arrhythmia requiring administration of antiarrhythmic drug, leading to permanent disability no haemodynamic effect • Bleeding: bleeding from large calibre artery or vein with transient haemodynamic instability, Any deviation from the ideal intraoperative course: ligation or suture; blood transfusion • With the need for any additional moderate treatment • Injury: transmural intestinal lesion requiring segmental resection Grade III or intervention • Cautery: severe burn requiring surgical debridement • Patient with severe symptoms, potentially life threatening or • Arrhythmia: arrhythmia requiring administration of antiarrhythmic drug, transient potentially leading to permanent disability haemodynamic effect • Bleeding: life threatening bleeding with splenectomy; massive blood transfusion; stay at Any deviation from the ideal intraoperative course: intensive care unit • With the need for any additional major and urgent treatment or • Injury: injury of central artery or vein requiring extended intestinal resection Grade IV intervention • Cautery: life threatening burn injury by cautery leading to • Patient with life threatening symptoms or leading to permanent fire requiring intensive care treatment disability • Arrhythmia: arrhythmia requiring electroconversion, defibrillation, or admission to intensive care Any deviation from the ideal intraoperative course with intraoper- Grade V — ative death of the patient *These events were not defined as intraoperative adverse events: sequelae, failures of cure, events related to the underlying disease, incorrect site or incorrect patient surgery, or errors in indication. the bmj | BMJ 2020;370:m2917 | doi: 10.1136/bmj.m2917 3 RESEARCH methods, with 100 replications of samples from 2520 were not publicly available for analysis by patients or patients. A model with a binary endpoint (any v no members of the public. Our protocol did not include BMJ: first published as 10.1136/bmj.m2917 on 25 August 2020. Downloaded from http://www.bmj.com/ on 29 January 2021 by guest. Protected by copyright. postoperative complication) was used as a sensitivity patient and public involvement in the planning or analysis. implementation of this research. No patients were The association of the most severe intraoperative asked to advise on interpretation or writing up of the adverse event and the weighted sum of all postoperative results. However, future research will evaluate the complications (comprehensive complication index)12 effect of intraoperative adverse events measured with was explored with a multivariable two level mixed effect ClassIntra on patient reported outcomes. regression model accounting for correlation between patients from the same study centre. Associations Results between the most severe intraoperative adverse event Patient and procedural characteristics and the secondary endpoints of postoperative length Of 2640 patients screened, 2520 were enrolled in of hospital stay and length of surgery were investigated 18 secondary and tertiary centres in North America, in a multivariable two level mixed effect log linear Europe, and Oceania, representing 12 countries. All regression model. The coefficients of the log linear patients were recruited between 14 February 2017 regression models were back transformed to improve and 27 July 2018. The median number of patients the interpretability of the results showing percentage enrolled per site was 130 (interquartile range 100- changes27 in hospital days or duration of surgery for 176). The main reason for exclusion was day surgery one unit increase in the corresponding covariate. (fig 1). Patients had a range of surgical procedures In the survey, the average agreement between from different surgical disciplines, except ophthalmic the ratings of the physicians and the core team was surgery (table 2), with 44% (n=1090) of surgeries calculated. Inter-rater reliability was assessed with the corresponding to the two highest complexity levels. intraclass correlation coefficient based on the mean Patient and procedural characteristics are described in absolute agreement, estimated in a two way random table 2 (examples of the most frequent types of surgical effects model.28 procedures are in supplementary table S15). Baseline The participating hospitals were a voluntary characteristics were similar in patients with and convenience sample. The planned sample size of without intraoperative adverse events. The American 2500 patients allowed for robust estimation in Society of Anesthesiologists’ physical status classes, the multivariable models, assuming at least one and the complexity of the surgical procedure, however, postoperative complication in 10% of the patients (that were higher in patients with an intraoperative adverse is, at least 250 events; for details, see the statistical event. analysis plan in the supplementary file). Analyses were performed with Stata 14 (StataCorp, Intraoperative adverse events according to College Station, TX). Further details on data manage­ ClassIntra ment and statistical analysis are in the statistical Of 2520 patients enrolled, 610 (24%) experienced analysis plan (supplementary file). 778 intraoperative adverse events (table 3). The most severe intraoperative adverse event per patient was Missing data grade I in 161 patients (6.4%), grade II in 309 (12%), When an undefined complexity grade in the BUPA grade III in 122 (4.8%), and grade IV in 18 patients classification system (in 4% of procedures) was found, (0.7%). No intraoperative deaths occurred (table 3). a grade corresponding to a similar procedure was used. This analysis was then compared with a complete Postoperative complications case analysis. If no information was available on During the postoperative course, 2509 complications the presence of the anaesthesia resident or nurse, or were seen in 838 patients (33%). Table 3 gives details whether they were in training or had graduated, we of the severity grades and number of postoperative assumed that these team members were not present or complications. were in training. There were no other missing values Multivariable analysis showed a gradual increase in for outcomes or covariates, except for data on 30 day the odds of a more severe postoperative complication mortality in patients lost to follow-up. with an increasing grade of the most severe intra­ operative adverse event (fig 2; supplementary table ClassIntra study group S5). Consistently, a stepwise increase in the sum The ClassIntra study group consisted of a of all postoperative complications (comprehensive multidisciplinary, international team of anaesthe­ complication index) with an increasing grade of tists, surgeons with a range of surgical specialties, ClassIntra was seen (supplementary table S6). epidemiologists, and statisticians with extensive expertise in perioperative care. More secondary outcomes Median postoperative length of hospital stay was 3 Patient and public involvement days (interquartile range 2-6) in all patients, and was This research was a multicentre collaboration doubled in patients with at least one intraoperative to evaluate a newly developed classification for adverse event (median 6 days; interquartile intraoperative adverse events. The data and software range 3-9 days) compared with patients with no 4 doi: 10.1136/bmj.m2917 | BMJ 2020;370:m2917 | the bmj RESEARCH 2640 Discussion Principal findings BMJ: first published as 10.1136/bmj.m2917 on 25 August 2020. Downloaded from http://www.bmj.com/ on 29 January 2021 by guest. Protected by copyright. Assessed for eligibility Representative sample of patients undergoing any type of surgery This international multicentre study showed that ClassIntra is a valid and standardised tool for assessing 120 intraoperative adverse events, with high construct Ineligible patients validity, given the increasing effects of severity 81 Day surgery grades on important patient outcomes. ClassIntra 19 Follow-up procedure also showed good criterion validity and practicability 13 Patient refused 7 No anaesthesia across different surgical disciplines. The association between severe intraoperative 2520 and postoperative complications, well established in Patients included abdominal surgery,6 8 was replicated in a heterogeneous Data available for analysis (primary and secondary endpoints) population of surgical patients from a range of surgical 2520 Postoperative complications disciplines. The association of intraoperative adverse 2520 Postoperative length of hospital stay events and postoperative length of hospital stay might 2520 Length of surgery have been mediated by postoperative complications (that is, more postoperative complications resulted in a 148 (6%) Lost to 30 day follow-up longer stay in hospital after operation). The association 38 Unreachable between intraoperative adverse events and length of 84 No resources for follow-up surgery was most likely related (that is, more adverse 1 Withdrawal events might have prolonged surgery, which in turn 25 Reason unknown could have led to more intraoperative adverse events). 2372 (94%) Strengths and limitations of the study Patients with 30 day follow-up Data available for analysis (secondary endpoint) ClassIntra is a comprehensive classification, with a 2372 30 day mortality patient centred perspective, because it records any event related to anaesthesia or surgery, and grades the Fig 1 | Flow diagram of patients in the validation study of ClassIntra outcomes according to those relevant to the patient, the symptoms caused by the event, and the measures taken to treat the event. ClassIntra was derived from intraoperative adverse events (3; 1-5 days) (table 3). CLASSIC, which was developed by an interdiscipli­ In the multivariable analysis, median postoperative nary, international group of anaesthetists, surgeons, length of hospital stay increased with each ClassIntra epidemiologists, and statisticians.15 ClassIntra aligns grade by 6.1% (95% confidence interval 2.8 to 9.3%; with the Clavien-Dindo classification of postoperative supplementary table S7). complications,11 allowing the reporting of intra­ The median length of surgery was 100 minutes operative and postoperative adverse events. (interquartile range 60-170) with a maximum length of Our robust study design, based on a large sample 760 minutes (table 3). The length of surgery was longer size involving a range of surgical disciplines, and in patients experiencing an intraoperative adverse on prospective multicentre data collection, implies event, with an increase of 16% in median length of good generalisability. Good generalisability always surgery with each grade increase in ClassIntra (95% introduces some heterogeneity, which was accounted confidence interval 13% to 18%; supplementary for by adjusting the analyses for the complexity of the table S8). Thirty day follow-up was available for 2372 surgical procedure and patient related factors. Whether (94%) patients (fig 1). Mortality at 30 days was 1.1% the results are mainly driven by the largest subgroup (n=26), with a higher incidence in patients with an of patients having an intra-abdominal procedure will intraoperative event (table 3 and table S9). be investigated in a secondary analysis comparing the results in several subgroups. The primary advantage Survey of a broad classification is that it increases uniformity The response rate to the survey was 83% (136/163 in reporting intraoperative adverse events and allows physicians). About a third of respondents were comparison of results between different centres and anaesthetists and two thirds were surgeons from times. In our study, details of each intraoperative various surgical disciplines with a range of years’ adverse event were collected. Our group is currently experience (supplementary table S4). Reliability investigating how the additional information can be among physicians showed an intraclass correlation used to support quality improvement in the future. We coefficient of 0.76 (95% confidence interval 0.59 therefore encourage adding details about the events to 0.91). Overall agreement with the ratings of the and intervention specific intraoperative outcomes of core team was 61% (interquartile range 42-71%; interest to the ClassIntra grade, whenever possible supplementary figure S1), with deviation usually within a framework of standardised core outcomes.29 explained by physicians rating one grade lower than To keep it practical and simple, the classification the core team. Physicians rated the practicability of uses generic definitions of the five severity grades; ClassIntra as 6 out of 9 (interquartile range 5-7). individual judgment is necessary for interpretation. the bmj | BMJ 2020;370:m2917 | doi: 10.1136/bmj.m2917 5 RESEARCH Table 2 | Patient and procedural characteristics for the whole study population and for subgroups with and with no intraoperative adverse events BMJ: first published as 10.1136/bmj.m2917 on 25 August 2020. Downloaded from http://www.bmj.com/ on 29 January 2021 by guest. Protected by copyright. All patients Patients with no intraoperative Patients with intraoperative Missing data (n=2520) adverse events (n=1910) adverse events (n=610) (No (%)) American Society of Anesthesiologists (ASA) physical status ASA I 503 (20) 431 (23) 72 (12) — ASA II 1118 (44) 852 (45) 266 (44) — ASA III 805 (32) 565 (30) 240 (39) — ASA IV 92 (3.7) 62 (3.3) 30 (4.9) — ASA V 2 (0.1) — 2 (0.3) — Age (median (IQR; range)) In adults (age ≥18; n=2340) 61 (46-72; 18-97) 60 (45-71; 18-97) 64 (49-74; 18-93) — In children (age <18; n=180) 9 (5-14; 0-17) 9 (5-14; 0-17) 8 (3-13; 0-16) — Sex Male 1382 (55) 1038 (54) 344 (56) — Female 1138 (45) 872 (46) 266 (44) — Body mass index in adults (median (IQR); n=2340) 26 (23-30) 26 (23-30) 26 (23-30) 14 (1) Weight in children (kg; median (IQR, range); n=180) 32 (19-53; 4-137) 33 (19-54; 4-137) 26 (17-37; 7.9-85) — Surgical discipline Gastrointestinal surgery 1437 (57) 1085 (57) 352 (58) — Orthopaedic surgery and traumatology 297 (12) 260 (14) 37 (6.1) — Vascular surgery 169 (6.7) 121 (6.3) 48 (7.9) — Urology 134 (5.3) 109 (5.7) 25 (4.1) — Ear, nose, throat, and maxillofacial surgery 122 (4.8) 99 (5.2) 23 (3.8) — Neurosurgery and spine surgery 96 (3.8) 53 (2.8) 43 (7.1) — Cardiac surgery 73 (2.9) 41 (2.2) 32 (5.3) — Paediatric surgery 54 (2.1) 48 (2.5) 6 (1.0) — Gynaecology 46 (1.8) 29 (1.5) 17 (2.8) — Obstetrics 44 (1.8) 31 (1.6) 13 (2.1) — Reconstructive and hand surgery 26 (1.0) 21 (1.1) 5 (0.8) — Thoracic surgery 22 (0.9) 13 (0.7) 9 (1.5) — Urgency of the procedure Planned 2153 (85) 1627 (85) 526 (86) — Emergency 367 (15) 283 (15) 84 (14) — Complexity of surgical procedure (original) Minor 105 (4.2) 94 (4.9) 11 (1.8) 98 (4) Intermediate 437 (17) 383 (20) 54 (8.9) Major 790 (31) 613 (32) 177 (29) Major plus 442 (18) 323 (17) 119 (20) Complex major operation 648 (26) 431 (23) 217 (36) Additional procedure 406 (16) 266 (14) 140 (23) Wound class Clean 1341 (53) 1033 (54) 308 (50) — Clean contaminated 1001 (40) 746 (39) 255 (42) — Contaminated 147 (5.8) 103 (5.4) 44 (7.2) — Dirty 31 (1.2) 28 (1.5) 3 (0.5) — Operating surgeon Senior consultant 1662 (66) 1239 (65) 423 (69) — Junior consultant 544 (22) 427 (22) 117 (19) — Resident 314 (12) 244 (13) 70 (11) — Assisting surgeon 2371 (94) 1781 (93) 590 (97) — Senior consultant 555/2371 (23) 385/1781 (22) 170/590 (29) — Junior consultant 578/2371 (24) 432/1781 (24) 146/590 (25) — Resident 1238/2371 (52) 964/1781 (54) 274/590 (46) — Anaesthesia consultant present 2311 (92) 1746 (91) 565 (93) — Senior consultant 1481/2311 (64) 1112/1746 (64) 369/565 (65) — Junior consultant 830/2311 (36) 634/1746 (36) 196/565 (35) — Anaesthesia resident present 1443 (57) 1017 (53) 426 (70) 1 (0.0) Anaesthesia nurse present 1866 (74) 1405 (74) 461 (76) 2 (0.1) Proportion who graduated 1699 (91) 1268 (90) 431 (93) 3 (0.2) Anaesthesia technique General anaesthesia 2035 (81) 1558 (82) 477 (78) — Regional anaesthesia 198 (7.9) 158 (8.3) 40 (6.6) — Combined techniques 265 (11) 176 (9.2) 89 (15) — Monitored anaesthesia care 22 (0.9) 18 (0.9) 4 (0.7) — Data are number (%) unless indicated otherwise. IQR=interquartile range. Similarly, defining an event as deviation from the ideal disagreement was mostly by one grade. We found the intraoperative course requires personal judgment. inter-rater reliability results reassuring, given that the Inter-rater reliability in the survey was strong and physicians had various backgrounds and were grading 6 doi: 10.1136/bmj.m2917 | BMJ 2020;370:m2917 | the bmj RESEARCH Table 3 | Outcomes for the whole study population and for subgroups with and with no intraoperative adverse events BMJ: first published as 10.1136/bmj.m2917 on 25 August 2020. Downloaded from http://www.bmj.com/ on 29 January 2021 by guest. Protected by copyright. All patients Patients with no intraoperative Patients with intraoperative Missing data (n=2520) adverse events (n=1910) adverse events (n=610) (No (%)) All iAE (several events per patient possible) 0 1910 (71) 1910 (100) — — I 198 (7.4) — 198 (25) — II 417 (16) — 417 (54) — III 142 (5.3) — 142 (18) — IV 21 (0.8) — 21 (3.0) — V — — — — Total No of iAE per patient 0 1910 (76) 1910 (100) — — 1 485 (19) — 485 (80) — 2 92 (3.7) — 92 (15) — 3 27 (1.1) — 27 (4.4) — 4 3 (0.1) — 3 (0.5) — 5 2 (0.1) — 2 (0.3) — 6 1 (0.0) — 1 (0.2) — Transfer after operation 677 (27) 403 (21) 274 (45) — Intermediate care unit 347/677 (51) 244/403 (61) 103/274 (38) — Intensive care unit 330/677 (49) 159/403 (39) 171/274 (62) — Unplanned 45/677 (6.7) 6/403 (1.5) 39/274 (14) — Length of surgery (minutes; median (IQR, range)) 100 (60-170, 4-760) 90 (55-147, 4-760) 151 (93-240, 12-673) — Most severe postoperative complication per patient 0 1682 (67) 1367 (72) 315 (52) — I 349 (14) 257 (13) 92 (15) — II 277 (11) 162 (8.5) 115 (19) — IIIa 72 (2.9) 45 (2.4) 27 (4.4) — IIIb 55 (2.2) 40 (2.1) 15 (2.5) — IVa 53 (2.1) 23 (1.2) 30 (4.9) — IVb 7 (0.3) 3 (0.2) 4 (0.7) — V 25 (1.0) 13 (0.7) 12 (2.0) — All postoperative complications (several events per patient possible) I 1106 (44) 747 (48) 359 (37) — II 983 (39) 557 (36) 426 (44) — IIIa 160 (6.4) 94 (6.1) 66 (6.8) — IIIb 105 (4.2) 72 (4.7) 33 (3.4) — IVa 110 (4.4) 51 (3.3) 59 (6.1) — IVb 20 (0.8) 9 (0.6) 11 (1.1) — V 25 (1.0) 13 (0.8) 12 (1.2) — Total No of postoperative complications per patient None 1682 (67) 1367 (72) 315 (52) — 1 412 (16) 288 (15) 124 (20) — 2-5 329 (13) 198 (10) 131 (21) — >5 97 (3.9) 57 (3.0) 40 (6.6) — Reoperation No 2421 (96) 1844 (97) 577 (95) — Any reoperation 99 (3.9) 66 (3.5) 33 (5.4) — Total No of reoperations 1 68 (69) 46 (70) 22 (67) — 2 16 (16) 11 (17) 5 (15) — 3 6 (6.1) 4 (6.1) 2 (6.1) — 4 8 (8.1) 5 (7.6) 3 (9.1) — 5 1 (1.0) ·· 1 (3.0) — Postoperative length of hospital stay (days; median (IQR, range)) 3 (2-6, 0-191) 3 (1-5, 0-106) 6 (3-9, 1-191) — Total length of hospital stay (days; median (IQR, range)) 4 (2-8, 1-193) 3 (2-7, 1-113) 7 (3-11, 1-193) — Stay during postoperative course 68 (2.7) 40 (2.1) 28 (4.6) — Intermediate care unit 18 (26) 15 (38) 3 (11) — Intensive care unit 50 (74) 25 (63) 25 (89) — 30 day mortality 26 (1.1) 13 (0.7) 13 (2.1) 148 (5.9) Data are number (%) unless stated otherwise. IQR=interquartile range; iAE= intraoperative adverse events. intraoperative adverse events in different surgical As clinicians become more familiar with ClassIntra, disciplines and in anaesthesia. In clinical practice and we believe the system will be easier to use, similar to in our prospective cohort study, joint assessment by the experience with the Clavien-Dindo classification surgeons and anaesthetists during sign-out20 should after its introduction into routine clinical practice. lower this variability and the risk of under-reporting Generally, different professional backgrounds, levels and downgrading of intraoperative adverse events. of experience, and cultural diversity among physicians the bmj | BMJ 2020;370:m2917 | doi: 10.1136/bmj.m2917 7 RESEARCH might have explained the practicability ratings of less refers to an intraoperative injury missed during surgery than five in 25% of the survey participants and ratings and requiring re-operation within seven days. Grade BMJ: first published as 10.1136/bmj.m2917 on 25 August 2020. Downloaded from http://www.bmj.com/ on 29 January 2021 by guest. Protected by copyright. greater than seven in another 25%. VI refers to intraoperative death. This classification Because our project was conducted as part of daily was based on a retrospective analysis of routinely clinical practice, having an independent person to collected data in selected patients with accidental record intraoperative and postoperative events would puncture or laceration. Although their classification not have been feasible, and blinding of those assessing approach differs considerably from ClassIntra, the postoperative outcomes would have been unethical. authors confirmed an association between major The direction of the potential bias is unclear, however, intraoperative and postoperative adverse events.8 Our as under-reporting and over-reporting could, theoreti­ study was based on prospective data in unselected cally, occur. Under-reporting and downgrading of patients from a range of surgical interventions and complications is a problem in healthcare settings and considered any event related to surgery or anaesthesia. should be handled with a positive, non-discriminative We did not include re-operation because of the learning culture. A classification for complications difficulty in determining if an intraoperative injury or should be sensitive enough to monitor and detect a postoperative complication was responsible for the rating variability caused by downgrading.30 31 re-operation. Our secondary endpoints included length of hospital A classification of surgical intraoperative adverse stay. We acknowledge that this outcome might be events for laparoscopic surgery was proposed, with affected by the variables included in the model (that is, five grades similar to ClassIntra, but excluded adverse the most severe intraoperative adverse event and the events related to anaesthesia.33 Others used readily confounding variables) and also by cultural norms, available information, such as quality indicators of logistical issues, and economic considerations. This the intraoperative period, to predict postoperative analysis should be viewed as supporting evidence as it outcome. Coulson and colleagues estimated the acute showed consistent stepwise increasing association in risk change in the probability of death before and alignment with all other postoperative endpoints. after operation based on two validated risk scores.34 35 The 10 point Apgar score for surgery was developed Findings in relation to other studies in patients having a colectomy and was evaluated Other classification systems for intraoperative in a broader surgical population.36 37 Prediction of adverse events have been published.32 Kaafarani and postoperative complications was based on estimated colleagues8 classified intraoperative adverse events blood loss, lowest mean arterial pressure, and heart into six grades. Grades I-IV depend on the intervention rate. Although both scores showed good predictive required to treat the intraoperative adverse events and ability, they provided only a surrogate marker for the deviation from the planned procedure. Grade V adverse intraoperative events. Factor Odds ratio (log scale) Odds ratio (95% CI) (95% CI) ClassIntra Grade I v 0 0.99 (0.69 to 1.42) Grade II v 0 1.39 (0.97 to 2.00) Grade III v 0 2.62 (1.31 to 5.26) Grade IV v 0 3.81 (1.19 to 12.2) Age (per decade increase) 1.04 (0.99 to 1.09) ASA class (ASA III-V v ASA I-II) 1.70 (1.40 to 2.06) Complexity of surgery Intermediate v minor 0.79 (0.52 to 1.19) Major v minor 0.85 (0.50 to 1.45) Major plus v minor 1.20 (0.74 to 1.94) Complex major v minor 1.27 (0.79 to 2.04) Length of surgery (per 10 minute increase) 1.05 (1.03 to 1.07) Urgency (emergency v planned) 1.57 (1.04 to 2.35) Wound class (non-clean v clean) 1.20 (0.99 to 1.46) Experience of surgical team 0.84 (0.69 to 1.03) Experience of anaesthesia team 0.88 (0.80 to 0.96) 0.5 1 2 5 10 Fig 2 | Multivariable hierarchical proportional odds model for the most severe postoperative complications according to the Clavien-Dindo classification (three categories for outcome: no postoperative complications, grades I-II, and grades III-V), adjusted for the most relevant confounders. ASA=American Society of Anesthesiologists’ physical status level 8 doi: 10.1136/bmj.m2917 | BMJ 2020;370:m2917 | the bmj RESEARCH Bothner and colleagues developed an incidents, hospital capacities, in view of the increase in events, and complications scale related to anaesthesia, postoperative length of stay with the increasing BMJ: first published as 10.1136/bmj.m2917 on 25 August 2020. Downloaded from http://www.bmj.com/ on 29 January 2021 by guest. Protected by copyright. based on a set of 63 events with five ascending severity severity of the ClassIntra grade. For day surgeries, grades depending on the effect on postoperative the risk of perioperative complications is minimal. care and outcome.38 The scale was implemented for Future research should investigate whether assessing quality assurance and covered the whole period of intraoperative complications is associated with early anaesthesia, from induction to discharge to the ward visits to the general practitioner or readmission. or to the intensive care unit. Their reported rate of 22% adverse events was relatively higher than our findings Conclusion where events related to anaesthesia and surgery were ClassIntra version 1.0 is a validated and standardised taken together, which could partly be explained by the tool to quantify and qualify intraoperative adverse restricted period covered in our study. events in clinical practice and research. It showed good reliability and practicability for all surgical Implications for clinicians or policy makers disciplines and for anaesthesia. We reproduced the Patient safety in the perioperative period has gained well established association between the severity considerable interest and successful interventions, grade for intraoperative adverse events and important such as the reduction in morbidity and mortality after postoperative outcomes. Hence ClassIntra is a useful introduction of a surgical safety checklist, have been tool for recording intraoperative adverse events and seen.20 ClassIntra covers a major unmet need, as the should be incorporated into the perioperative surgical first prospectively validated classification system safety checklist to highlight recurrent and potentially that is simple and generally applicable to all surgical avoidable complications. ClassIntra could improve the disciplines, to our knowledge. It takes a holistic technical aspects of intraoperative care and provide view by integrating any adverse event, regardless of clarity in audits of practice. origin. Also, because innovative surgical techniques are increasingly complex and implemented quickly, Author affiliations 1 preventing morbidity during the implementation Department of Anaesthesia, Prehospital Emergency Medicine and Pain Therapy, University Hospital Basel, Spitalstrasse 21, CH-4031 period is important.39 ClassIntra should be included in Basel, Switzerland routine practice to alert the postoperative care team to 2 Basel Institute for Clinical Epidemiology and Biostatistics, patients with intraoperative adverse events and at risk University Hospital and University of Basel, Basel, Switzerland of further postoperative complications. 3 Department of Clinical Research, University of Basel, Basel, Switzerland 4 Future research Department of Surgery, Radboud University Medical Centre, Nijmegen, Netherlands We acknowledge that our definition of intraoperative 5 Department of Anaesthesiology, Guy’s and St Thomas’ Hospital, adverse events included only the time between skin London, UK incision and closure. Induction of and emergence 6 Department of Surgery, University of Auckland, Auckland, New from anaesthesia were not covered, which can have Zealand risks for more adverse events. Assessing the construct 7 Department of Anaesthesiology, University Hospital Lausanne, validity of a new classification is an ongoing process, University of Lausanne, Lausanne, Switzerland 8 which requires confirmation by more convergent Department of Anaesthesiology, Bürgerspital Solothurn, Solothurn, Switzerland and discriminative validity assessments to increase 9 Department of Anaesthesiology, Schulthess Clinic, Zurich, credibility. In future research, we will evaluate the Switzerland properties of ClassIntra extending the assessment 10 Department of Surgery, Tallaght University Hospital, Dublin, period to include the periods related to anaesthesia Ireland 11 (that is, induction and emergence), focusing on patient Colorectal Surgical Oncology, Abdominal Oncology Department, Istituto Nazionale per lo Studio e la Cura dei Tumori, “Fondazione reported outcomes, thus expanding the hypothetical Giovanni Pascale” IRCCS, Naples, Italy construct for assessing validity. 12 Colorectal Surgery Unit, Hospital Valle de Hebron, Autonomous ClassIntra can be used in clinical research as a University of Barcelona, Barcelona, Spain defined core outcomes measure as it provides standard 13 Fourth Surgical Department, G Papanikolaou Hospital, Aristotle definitions, allowing accurate communication of University of Thessaloniki, Thessaloniki, Greece 14 research results and comparisons across research Department of Surgery, Ankara University Medical School, Ankara, Turkey studies.11 40 ClassIntra can help evaluate the origin 15 Department of Surgery, Hospital of St John of God Vienna, of the complications during the surgical procedure, Sigmund Freud University Vienna-Medical School, Vienna, Austria providing more granularity to the complication profile 16 Department of Visceral Surgery, University Hospital Lausanne, for each procedure or surgical unit. Also, ClassIntra University of Lausanne, Lausanne, Switzerland can be used in critical incidence reporting systems,41 17 Department of Surgery, University Children’s Hospital Basel, Basel, for measuring individual performance in educational Switzerland 18 settings and system performance for benchmarking Department of Anaesthesiology, University Children’s Hospital Basel, Basel, Switzerland by institutions, and for outcome research. Future 19 University of Sydney, Royal North Shore Hospital, Sydney, implementation studies should evaluate this tool Australia in daily clinical practice for risk stratification of 20 Department of Anaesthesiology, Ankara University Medical postoperative care or for planning resources and School, Ankara, Turkey the bmj | BMJ 2020;370:m2917 | doi: 10.1136/bmj.m2917 9 RESEARCH 21 Department of Surgery, Carolinas Medical Centre, Charlotte, NC, BL, HV, HCB, and RR interpreted the data. SD-K, NVG, RM, HCB, and USA RR wrote the manuscript. LG, SA, PFR, AE, GO, BL, HV, CR, P-AC, LAS, BMJ: first published as 10.1136/bmj.m2917 on 25 August 2020. Downloaded from http://www.bmj.com/ on 29 January 2021 by guest. Protected by copyright. 22 Department of Anaesthesiology, Cantonal Hospital Graubünden, and PK provided critical feedback on the manuscript. MA-P, IB, C Bl, Chur, Switzerland CBr, RTB, HRB, CC, PD, EE, KG-D, IEG, SG, OG, BG, DH, FH, OI, SJ, SK, 23 JMa, SM, JMu, DN, MO, UP, MP, SR, BR, DR, CR, RS, PS, AS-P, LV, and DV Department of Vascular Surgery, Medical University of Innsbruck, collected the data and provided critical feedback on the manuscript. Innsbruck, Austria 24 All authors revised the manuscript for important intellectual content, Department of Surgery, Bürgerspital Solothurn, Solothurn, approved the final version of the manuscript, and agreed to be Switzerland accountable for all aspects of the work. SD-K is the guarantor. The 25 Department of Anaesthesiology and Reanimation, Hospital Valle corresponding author attests that all listed authors meet authorship de Hebron, Autonomous University of Barcelona, Barcelona, Spain criteria and that no others meeting the criteria have been omitted. 26 Department of Surgery and Transplantation, University Hospital Funding: The research was supported by grants from the Zurich, Zurich, Switzerland Goldschmidt-Jacobson Foundation, University of Basel, Foundation 27 Department of General Surgery, University Hospital Basel, Basel, for Research and Education in Anaesthesiology, Switzerland, and Switzerland VSB fonds (Verenigde Spaar Bankenfonds), Netherlands. The funders 28 had no role in the study design, data collection, data analysis, data Medical Faculty, University of Basel, Basel, Switzerland interpretation, or writing of the report. The corresponding author had We thank Ramon Saccilotto who programmed and maintained full access to all data. the online database; Allison Dwileski for editorial assistance on Competing interests: All authors have completed the ICMJE uniform the manuscript; Christian Schindler for statistical advice; and all disclosure form at www.icmje.org/coi_disclosure.pdf and declare: of the centres in this investigator initiated study for their support. support from the Goldschmidt-Jacobson Foundation, University of In particular, we thank Esther Seeberger, Claudia Blaesi, Franziska Basel, Foundation for Research and Education in Anaesthesiology, Merz, Samuel Heim, and all participating surgical disciplines from Switzerland, and VSB fonds (Verenigde Spaar Bankenfonds) for the University Hospital Basel, Basel, Switzerland; Martin Taube, Kata submitted work; no financial relationships with any organisations that Papp, and Blanca Schuster, University Children’s Hospital Basel, might have an interest in the submitted work in the previous three Basel, Switzerland; Michael Winiker, University Hospital Lausanne, years; no other relationships or activities that could appear to have Lausanne, Switzerland; Victoria Koenig-Oberhuber and the influenced the submitted work. RR is an employee of F Hoffmann-La preoperative ambulatory unit team, Cantonal Hospital Graubünden, Roche (includes Stock-Settled Appreciation Rights). The study has no Chur, Switzerland; David Iannitti and Hiral Amin, Carolinas Medical connection to her employment by the company. RR continues to be Centre, Charlotte, NC, USA; Deniz Yalman, Ankara University Medical affiliated to the University of Basel. School, Ankara, Turkey; Christos Chatzakis, Savvas Symeonidis, Natalia Antigoni Savvala, Nikolaos Antoniou, Dimitrios Konstantaras, Lydia Ethical approval: The study was approved by the regional ethics Loutzidou, Loukiani Kitsikosta, Grigorios Gkasdaris, Stefanos Bitsianis, committee of Ethikkommission Nordwest- und Zentralschweiz Ioannis Mantzoros, Manousos George Pramateftakis, Efstathios (reference No Req-2016-00469) as Swiss lead ethics committee, and Kotidis, and Konstantinos Tsalis, medical school at Aristotle University by the local ethics committees of all international centres. Participants of Thessaloniki, Greece; the surgical trials unit team at University gave oral or written informed consent compliant with the relevant of Auckland, Auckland, New Zealand; Olivia Kirkland, Royal North legal requirements of each centre. Shore Hospital, Sydney, Australia; Astrid Chiari and René Schmutz, Data sharing: Anonymised patient level data are available for Department of Anaesthesiology, and Bernhard Dauser and Tudor investigators whose proposed use of the data has been approved by a Birsan, Department of Surgery, Hospital of St John of God Vienna, review committee identified for this purpose. Austria; and Kariem El-Boghdadly and Gill Arbane, Guy’s and St The lead author (the manuscript’s guarantor) affirms that the Thomas’ Hospital, London, UK. manuscript is an honest, accurate, and transparent account of the Part of the preliminary findings of this research were presented at study being reported; that no important aspects of the study have the following meetings: (11 November 2017) poster presentation been omitted; and that any discrepancies from the study as planned at the Congress of the Swiss Society for Anaesthesiology and (and, if relevant, registered) have been explained. Resuscitation (Interlaken, Switzerland); (2 November 2018) poster Dissemination to participants and related patient and public presentation at the Congress of the German Society of Gynaecology communities: To reach wide dissemination, the results of the study and Obstetrics (Berlin, Germany); (6 February 2019) QuickShot were presented at many international meetings. After publication, the presentation at the 14th Annual Academic Surgical Congress results will be disseminated to relevant medical societies and patient (Houston, TX, USA); (9 May 2019) short paper at the International organisations. The use of an (adapted) version of our web based Surgical Congress of the Associations of Surgeons of Great Britain database could easily be broadly implemented in other hospitals and Ireland (Telford, UK); (9 May 2019) oral presentation in the other than the study sites, which are interested to use ClassIntra general surgery section of the Royal Australasian College of Surgeons’ version 1.0 as a tool for internal quality control in daily clinical annual scientific congress (Bangkok, Thailand); (16 May 2019) practice and in research. oral presentation at the 106th Annual Meeting of the Swiss Society of Surgery (Bern, Switzerland), and abstract published as society Provenance and peer review: Not commissioned; externally peer abstract supplement (Br J Surg 2019;106(S4):9); (15 May 2019) oral reviewed. presentation at the XXIII National Meeting of the Spanish Association This is an Open Access article distributed in accordance with the of Coloproctology (Valladolid, Spain); (3 June 2019) oral presentation Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, at the European Anaesthesiology Congress Euroanaesthesia of the which permits others to distribute, remix, adapt, build upon this work European Society of Anaesthesiology (Vienna, Austria), and abstract non-commercially, and license their derivative works on different published as society abstract supplement (Eur J Anaesthesiol terms, provided the original work is properly cited and the use is non- 2019;36(S57):313); (26 June 2019) oral presentation at the Swiss commercial. See: http://creativecommons.org/licenses/by-nc/4.0/. Congress of Gynaecology (St Gallen, Switzerland); (15 August 2019) oral presentation at the World Congress of Surgery (Krakow, Poland); 1 Weiser TG, Haynes AB, Molina G, et al. Estimate of the global volume (26 September 2019) free paper presentation at the 14th scientific of surgery in 2012: an assessment supporting improved health and annual meeting of the European Society of Coloproctology outcomes. Lancet 2015;385(Suppl 2):S11. doi:10.1016/S0140- (Vienna, Austria); (7 November 2019) oral presentation at the 6736(15)60806-6 Congress of the Swiss Society for Anaesthesiology and Resuscitation 2 International Surgical Outcomes Study group. Global patient (Interlaken, Switzerland; prize for second best oral presentation); outcomes after elective surgery: prospective cohort study in 27 low-, and (8 November 2019) oral presentation at the National Surgery middle- and high-income countries. Br J Anaesth 2016;117:601-9. Congress of Spain (Santander, Spain). The authors were awarded the doi:10.1093/bja/aew316 first prize for Innovation Qualité by the Swiss Academy of Quality in 3 Weiser TG, Regenbogen SE, Thompson KD, et al. An estimation Medicine (SAQM) of the Swiss Medical Association. of the global volume of surgery: a modelling strategy based on available data. Lancet 2008;372:139-44. doi:10.1016/S0140- Contributors: SD-K and NVG contributed equally as first authors. PK 6736(08)60878-8 and RR contributed equally as last authors. SD-K, NVG, and RR did the 4 Bainbridge D, Martin J, Arango M, Cheng D, Evidence-based literature search. SD-K, NVG, PFR, HCB, P-AC, LAS, PK, and RR designed Peri-operative Clinical Outcomes Research (EPiCOR) Group. the study. S D-K, NVG, LG, RM, PFR, AE, GO, BL, HV, and PK collected Perioperative and anaesthetic-related mortality in developed the data. SD-K, LG, and SA analysed the data. 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