title: Investigating the "Rule of W," a mnemonic for teaching on postoperative complications.
abstract: OBJECTIVE
  To identify the timing and relative frequency of common postoperative complications in a contemporary, diverse surgical population and develop a mnemonic for teaching and clinical decision support.
  
  
  METHODS
  We enrolled a cohort of general and vascular surgical patients undergoing elective, inpatient surgery in the American College of Surgeons National Surgical Quality Improvement Program database between 2005 and 2011. Index complications were noted by postoperative day (POD). Timing and incidence were compared within each day.
  
  
  RESULTS
  Among 614,525 patients, 51,173 (9.88%) experienced the following index complications over 30 days: pneumonia (n = 5947), urinary tract infection (n = 9459), superficial surgical site infection (sSSI) (n = 20,460), deep/organ space surgical site infection (dSSI) infection (n = 11,847), venous thromboembolism (n = 4478), kidney injury (n = 2620), and myocardial infarction (n = 1813). Median time to complication differed significantly for index complications (p < 0.0001). On POD 0, the most common complication was myocardial infarction (incidence 4.26/10,000 patient days; 95% CI: 3.75-4.78). On POD 1 and 2, pneumonia was the most common complication, with peak incidence on POD 2 (20.36; 95% CI: 19.22-21.51). On POD 3, pneumonia (16.3; 95% CI: 15.27-17.33) and urinary tract infection (15.5; 95% CI: 14.49-16.51) were significantly more common than other complications. On POD 4, the most common complication was sSSI (16.24; 95% CI: 15.20-17.28). From POD 5 to POD 30, sSSI and dSSI were the 2 most common complications. Risk of venous thromboembolism declined only slightly through POD 30.
  
  
  CONCLUSIONS
  We propose a mnemonic for postoperative complication timing and frequency, independent of fever, as follows: Waves (myocardial infarction), Wind (pneumonia), Water (urinary tract), Wound (sSSI and dSSI), and Walking (venous thromboembolism) in the order of likelihood.
authors.affiliation: Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota; Center for Surgery and Public Health, Brigham and Women's Hospital, Boston, Massachusetts. Electronic address: hyder.joseph@mayo.edu.
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Hyder
authors.affiliation: Center for Surgery and Public Health, Brigham and Women's Hospital, Boston, Massachusetts; Department of Surgery, Brigham and Women's Hospital, Boston, Massachusetts; Department of Surgery, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Elliot
authors.initials: E
authors.lastname: Wakeam
authors.affiliation: Harvard University, Cambridge, Massachusetts.
authors.forename: Vishal
authors.initials: V
authors.lastname: Arora
authors.affiliation: Center for Surgery and Public Health, Brigham and Women's Hospital, Boston, Massachusetts.
authors.forename: Nathanael D
authors.initials: ND
authors.lastname: Hevelone
authors.affiliation: Division of General Internal Medicine Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts; Division of Sleep Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts.
authors.forename: Stuart R
authors.initials: SR
authors.lastname: Lipsitz
authors.affiliation: Center for Surgery and Public Health, Brigham and Women's Hospital, Boston, Massachusetts; Department of Surgery, Brigham and Women's Hospital, Boston, Massachusetts.
authors.forename: Louis L
authors.initials: LL
authors.lastname: Nguyen
mesh_terms: D020000:Decision Support Systems, Clinical; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008568:Memory; D008875:Middle Aged; D011183:Postoperative Complications / Q000175:diagnosis / Q000453:epidemiology*; D058996:Quality Improvement; D013997:Time Factors; D014481:United States / Q000453:epidemiology; D014656:Vascular Surgical Procedures / Q000193:education*
keywords: Medical Knowledge; Patient Care; Practice-Based Learning and Improvement; complication timing; walking; water; wind; wound