Variation in the practice of preoperative medical consultation for major elective noncardiac surgery: a population-based study

Background — Patients scheduled for major elective noncardiac surgery frequently undergo preoperative medical consultations. However, the factors that determine whether individuals undergo consultation and the extent of interhospital variation remain unclear.

Methods — The authors used population-based administrative databases to conduct a cohort study of patients, aged 40 yr or older, who underwent major elective noncardiac surgery in Ontario, Canada, between April 2004 and February 2009. Multilevel logistic regression models were used to identify patient- and hospital-level predictors of consultation.

Results — Within the cohort of 204,819 patients who underwent surgery at 79 hospitals, 38% (n = 77,965) underwent preoperative medical consultation. Although patient- and surgery-level factors did predict consultation use, they explained only 5.9% of variation in consultation rates. Differences in rates across hospitals were large (range, 10-897 per 1,000 procedures), were not explained by surgical procedure volume or hospital teaching status, and persisted after adjustment for patient- and surgery-level factors. The median odds of undergoing consultation were 3.51 times higher if the same patient had surgery at one randomly selected hospital as opposed to another.

Conclusions — One-third of surgical patients undergo preoperative medical consultation. Although patient- and surgery-level factors are weak predictors of consultation use, the individual hospital is the major determinant of whether patients undergo consultation. Additional research is needed to better understand the basis for this substantial interhospital variation and to determine which patients benefit most from preoperative consultation.