The Toronto Risk Score for adverse events following cardiac surgery

To develop and validate an objective and reliable measure of acuity that will identify high-risk patients and predict length of stay following all cardiac surgery procedures.

Logistical regression analysis of 12,683 patients undergoing cardiac surgery between 1996 and 2000 was used to identify the independent predictors of postoperative adverse events (AEs, defined as death, myocardial infarction, low cardiac output syndrome, postoperative renal failure, stroke or deep sternal wound infection). The rounded ORs for each of the 18 predictors of AEs were summed to calculate the Toronto Risk Score (TRS) for each patient. Weighted linear regression was used to determine the relationship between TRS and length of stay in the 4378 patients who underwent cardiac surgery between 2001 and 2002.

TRS was significantly associated with cardiovascular intensive care unit length of stay (R2=0.85, slope=0.42, intercept=0.4; P<0.001). For each unit increase in TRS, cardiovascular intensive care unit length of stay increased by 0.4+/-0.05 days. TRS was also significantly associated with total postoperative length of stay (R2=0.88, slope=0.71, intercept=4.9; P<0.001). TRS captured a significant increase in acuity from 1996 and 2000 (5.12+/-3.5) to 2001 and 2002 (5.54+/-3.5; P<0.001). Despite increased acuity, AEs were reduced in 2001 and 2002 (8.1%) compared with 1996 to 2000 (9.8%; P=0.012).

The TRS is a valid measure of acuity that can identify patients who are at high risk of experiencing an AE and having prolonged length of stay after any cardiac surgery procedure, capture changes in acuity over time and allow for continuous quality performance evaluation.