We thank Drs. Lynes and Griffiths for their comments on our study . It was a retrospective analysis of a convenience sample of patients undergoing hip fracture surgery who received pre-operative, goal-focused transthoracic echocardiography (TTE) against a matched cohort who did not. As we discussed, the study design restricts our analysis of the data to ‘hypothesis generation’ or ‘proof of concept’. We firmly believe that a randomised controlled trial is required to accept or reject our hypothesis that pre-operative echocardiography can reduce mortality in such patients. They suggest that the Nottingham Hip Fracture Score (NHFS) is useful as it demonstrated a ‘reasonable predictive value’ for 30-day mortality in nearly 5000 hip fracture surgery patients at a single centre , but limitations include validation in a single centre and reliance on pre-operative recording of seven variables. In a follow-up study, 8% of patients were excluded due to missing data such as admission mini-mental state examination and haemoglobin concentration . However, ASA status produced very similar predictions to NHFS in the initial study (AUC 0.719 and SE 0.0184 for NHFS and 0.718 and 0.0163 for ASA status) . The ASA status predicts incidence and severity of adverse outcomes in multiple centres [4, 5], is the most universally applied risk-scoring system, and was consistently reported in hip fracture surgery patients in our hospital databases. However, the results of our matching produced two cohorts with very similar demographic profiles.
Hypovolaemia is a common pre-operative finding in these patients (40–50%) , resulting from a combination of blood loss at the fracture site, delay in presentation to hospital and reluctance by medical staff to administer fluids. However, our contention is that clinical assessment of important cardiac disease and haemodynamic state (including hypovolaemia) is frequently incorrect compared with TTE . In our study of 64 patients , clinical diagnosis of hypovolaemia was missed in 34% (commonly leading to an unplanned fluid bolus), and hypovolaemia was mistaken for cardiac failure in 5% leading to restriction of a planned fluid bolus. Unlike the studies performed by Canty et al., Sinclair et al. and Venn et al. [1, 8, 9], in the study by Parker et al.  the amount of fluid given (crystalloid or gelatin colloid) was not guided by ultrasound assessment of intravascular volume, which may be the reason it failed to show an outcome difference. As discussed in our paper , TTE-guided fluid therapy is unlikely to be the sole contributor to the associated improved outcome.
Our retrospective study method and the potential unreliability of death registry data to ascertain the cause of death precluded us from commenting on the latter. We did not record anaesthetic or surgical staff's experience level, and retrospective data retrieval of this type is unreliable.
We cannot determine from our data why echocardiography may reduce mortality. However, echocardiography provides a higher level of diagnostic information to the treating medical team, on which to base clinical decisions. Importantly, it changes anaesthetists' peri-operative management from ‘reactive management’ to ‘proactive management’ . For example, undiagnosed aortic stenosis or cardiac failure can lead to a haemodynamic catastrophe, requiring rescue management to restore haemodynamic stability; however, the anaesthetist is likely to manage a patient with known severe aortic stenosis proactively to avoid haemodynamic compromise. Peri-operative cardiac failure is a strong predictor of postoperative mortality  and its avoidance by ‘TTE-guided proactive management’ could represent a mechanism of reduction in mortality associated with pre-operative TTE.