METHODS AND ANALYSIS: Hip fracture Accelerated surgical TreaTment And Care tracK (HIP ATTACK) is a multicentre, international, parallel-group randomised controlled trial (RCT). Patients who suffer a hip fracture are randomly allocated to either accelerated medical assessment and surgical repair with a goal of surgery within 6 hours of diagnosis or standard care where a repair typically occurs 24 to 48 hours after diagnosis. The primary outcome of this substudy is the development of AKI within 7 days of randomisation. We anticipate at least 1998 patients will participate in this substudy.

ETHICS AND DISSEMINATION: We obtained ethics approval for additional serum creatinine recordings in consecutive patients enrolled at 70 participating centres. All patients provide consent before randomisation. We anticipate reporting substudy results by 2021.

METHODS: The HIP fracture Accelerated surgical TreaTment And Care tracK (HIP ATTACK) trial was a randomized controlled trial designed to determine whether accelerated surgery for hip fracture was superior to standard care in reducing death or major complications. This substudy is a post-hoc analysis of 1392 patients (from the original study of 2970 patients) who had a cardiac biomarker/enzyme measurement (>99.9% had a troponin measurement and thus "troponin" is the term used throughout the paper) at hospital arrival. The primary outcome was all-cause mortality. The secondary composite outcome included all-cause mortality and non-fatal myocardial infarction, stroke, and congestive heart failure 90 days after randomization.

RESULTS: Three hundred and twenty-two (23%) of the 1392 patients had troponin elevation at hospital arrival. Among the patients with troponin elevation, the median time from hip fracture diagnosis to surgery was 6 hours (interquartile range [IQR] = 5 to 13) in the accelerated surgery group and 29 hours (IQR = 19 to 52) in the standard care group. Patients with troponin elevation had a lower risk of mortality with accelerated surgery compared with standard care (17 [10%] of 163 versus 36 [23%] of 159; hazard ratio [HR] = 0.43 [95% confidence interval (CI) = 0.24 to 0.77]) and a lower risk of the secondary composite outcome (23 [14%] of 163 versus 47 [30%] of 159; HR = 0.43 [95% CI = 0.26 to 0.72]).

CONCLUSIONS: One in 5 patients with a hip fracture presented with myocardial injury. Accelerated surgery resulted in a lower mortality risk than standard care for these patients; however, these findings need to be confirmed.