title: Toward a standard approach to measurement and reporting of perioperative mortality rate as a global indicator for surgery.
abstract: BACKGROUND
  The proportion of patients who die during or after surgery, otherwise known as the perioperative mortality rate (POMR), is a credible indicator of the safety and quality of operative care. Its accuracy and usefulness as a metric, however, particularly one that enables valid comparisons over time or between jurisdictions, has been limited by lack of a standardized approach to measurement and calculation, poor understanding of when in relation to surgery it is best measured, and whether risk-adjustment is needed. Our aim was to evaluate the value of POMR as a global surgery metric by addressing these issues using 4, large, mixed, surgical datasets that represent high-, middle-, and low-income countries.
  
  
  METHODS
  We obtained data from the New Zealand National Minimum Dataset, the Geelong Hospital patient management system in Australia, and purpose-built surgical databases in Pietermaritzburg, South Africa, and Port Moresby, Papua New Guinea. For each site, we calculated the POMR overall as well as for nonemergency and emergency admissions. We assessed the effect of admission episodes and procedures as the denominator and the difference between in-hospital POMR and POMR, including postdischarge deaths up to 30 days. To determine the need for risk-adjustment for age and admission urgency, we used univariate and multivariate logistic regression to assess the effect on relative POMR for each site.
  
  
  RESULTS
  A total of 1,362,635 patient admissions involving 1,514,242 procedures were included. More than 60% of admissions in Pietermaritzburg and Port Moresby were emergencies, compared with less than 30% in New Zealand and Geelong. Also, Pietermaritzburg and Port Moresby had much younger patient populations (P < .001). A total of 8,655 deaths were recorded within 30 days, and 8-20% of in-hospital deaths occurred on the same day as the first operation. In-hospital POMR ranged approximately 9-fold, from 0.38 per 100 admissions in New Zealand to 3.44 per 100 admissions in Pietermaritzburg. In New Zealand, in-hospital 30-day POMR underestimated total 30-day POMR by approximately one third. The difference in POMR if procedures were used instead of admission episodes ranged from 7 to 70%, although this difference was less when central line and pacemaker insertions were excluded. Age older than 65 years and emergency admission had large, independent effects on POMR but relatively little effect in multivariate analysis on the relative odds of in-hospital death at each site.
  
  
  CONCLUSIONS
  It is possible to collect POMR in countries at all level of development. Although age and admission urgency are strong, independent associations with POMR, a substantial amount of its variance is site-specific and may reflect the safety of operative and anesthetic facilities and processes. Risk-adjustment is desirable but not essential for monitoring system performance. POMR varies depending on the choice of denominator, and in-hospital deaths appear to underestimate 30-day mortality by up to one third. Standardized approaches to reporting and analysis will strengthen the validity of POMR as the principal indicator of the safety of surgery and anesthesia care.
authors.affiliation: Monash University & Barwon Health, Melbourne, Australia.
authors.forename: Roshan
authors.initials: R
authors.lastname: Ariyaratnam
authors.affiliation: Department of Clinical Sciences in Lund, Paediatric Surgery and Global Paediatrics, Faculty of Medicine, Lund University, Children's Hospital, Lund, Sweden.
authors.forename: Charlotta L
authors.initials: CL
authors.lastname: Palmqvist
authors.affiliation: Perioperative Mortality Review Committee, Health Quality and Safety Commission, Department of Population Health, University of Otago, Christchurch, New Zealand.
authors.forename: Phil
authors.initials: P
authors.lastname: Hider
authors.affiliation: Department of Surgery, Pietermaritzburg Metropolitan Trauma Service, Pietermaritzburg Metropolitan Hospital Complex, Nelson R. Mandela School of Medicine, University of KwaZuluNatal, Pietermaritzburg, South Africa.
authors.forename: Grant L
authors.initials: GL
authors.lastname: Laing
authors.affiliation: Deakin University and Barwon Health, University Hospital Geelong, Geelong, Australia.
authors.forename: Douglas
authors.initials: D
authors.lastname: Stupart
authors.affiliation: Perioperative Mortality Review Committee, Health Quality and Safety Commission New Zealand, Department of Anaesthesia, Hutt Valley District Health Board, Lower Hutt, New Zealand.
authors.forename: Leona
authors.initials: L
authors.lastname: Wilson
authors.affiliation: Department of Surgery, Pietermaritzburg Metropolitan Trauma Service, Pietermaritzburg Metropolitan Hospital Complex, Nelson R. Mandela School of Medicine, University of KwaZuluNatal, Pietermaritzburg, South Africa.
authors.forename: Damian L
authors.initials: DL
authors.lastname: Clarke
authors.affiliation: Department of Clinical Sciences in Lund, Paediatric Surgery and Global Paediatrics, Faculty of Medicine, Lund University, Children's Hospital, Lund, Sweden.
authors.forename: Lars
authors.initials: L
authors.lastname: Hagander
authors.affiliation: Department of Surgery, Deakin University and Barwon Health, University Hospital Geelong, Geelong, Australia.
authors.forename: David A
authors.initials: DA
authors.lastname: Watters
authors.affiliation: The Alfred Hospital & Monash University, Melbourne, Australia; Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore. Electronic address: rgruen@ntu.edu.sg.
authors.forename: Russell L
authors.initials: RL
authors.lastname: Gruen
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D066264:Datasets as Topic; D019049:Developed Countries / Q000706:statistics & numerical data; D003906:Developing Countries / Q000706:statistics & numerical data; D017052:Hospital Mortality; D006801:Humans; D008875:Middle Aged; D059035:Perioperative Period; D012107:Research Design / Q000592:standards; D020379:Risk Adjustment; D013514:Surgical Procedures, Operative / Q000401:mortality*; D055815:Young Adult