title: Association of Nurse-to-Patient Ratio with mortality and preventable complications following aortic valve replacement.
abstract: OBJECTIVE
  To examine hospital resources associated with patient outcomes for aortic valve replacement (AVR), including inpatient adverse events and mortality.
  
  
  METHODS
  We used the Nationwide Inpatient Sample to identify AVR procedures from 1998 to 2010 and the American Hospital Association Annual Survey to augment hospital characteristics. Primary outcomes included mortality and the development of adverse events, identified using standardized patient safety indicators (PSI). Patient and hospital characteristics associated with PSI development were evaluated using univariate and multivariate analyses.
  
  
  RESULTS
  An estimated 410,157 AVRs at 5009 hospitals were performed in the US between 1998 and 2010. The number of procedures grew annually by 4.72% (p=0.0003) in high volume hospitals, 4.48% in medium volume hospitals (p<0.0001), and 2.03% in low volume hospitals (p=0.154). Mortality was highest in low volume hospitals, 4.70%, decreased from 4.14% to 3.73% in medium and high volume hospitals, respectively (p=0.0002). Rates of PSIs did not vary significantly across volume terciles (p=0.254). Multivariate logistic regression analysis showed low volume hospitals had increased risk of mortality as compared with high volume hospitals (odds ratio [OR]: 1.42; 95% confidence interval [CI]: 1.01 to 2.00), while hospital volume was not associated with adverse events. PSI development was associated with small hospitals as compared with large (OR: 1.63, 95% CI: 1.16 to 2.28) and inversely associated with higher nurse-to-patient ratio (OR: 0.94, 95% CI: 0.90 to 0.99).
  
  
  CONCLUSIONS
  The volume-outcomes relationship was associated with mortality outcomes but not postoperative complications. We identified structural differences in hospital size, nurses-to-patient ratio, and nursing skill level indicative of high quality outcomes.
authors.affiliation: Stanford University School of Medicine, Stanford, California.
authors.forename: Nicole
authors.initials: N
authors.lastname: Arkin
authors.forename: Peter H U
authors.initials: PH
authors.lastname: Lee
authors.forename: Kathryn
authors.initials: K
authors.lastname: McDonald
authors.forename: Tina
authors.initials: T
authors.lastname: Hernandez-Boussard
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D001021:Aortic Valve / Q000601:surgery*; D002983:Clinical Competence / Q000706:statistics & numerical data; D005260:Female; D006276:Health Facility Size / Q000706:statistics & numerical data* / Q000600:supply & distribution*; D006295:Health Resources / Q000706:statistics & numerical data*; D019918:Heart Valve Prosthesis Implantation / Q000401:mortality* / Q000706:statistics & numerical data*; D006761:Hospitals / Q000706:statistics & numerical data* / Q000600:supply & distribution*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009726:Nurses / Q000706:statistics & numerical data* / Q000600:supply & distribution*; D061214:Patient Safety / Q000706:statistics & numerical data; D010361:Patients / Q000706:statistics & numerical data*; D011183:Postoperative Complications / Q000401:mortality / Q000517:prevention & control*; D011787:Quality of Health Care; D012306:Risk; D013997:Time Factors; D016896:Treatment Outcome; D014481:United States / Q000453:epidemiology