Predicting haemorrhage in pre-hospital traumatic patients: evaluation of the novel heart-to-arm time index

Background Early recognition of hypovolaemia in trauma patients is very important. However, the most often used clinical signs, such as hypotension and tachycardia, lack specificity and sensitivity. Methods We propose a non-invasive index of hypovolaemia, the heart to arm time (iHAT), based on a modified pulse transit time indexed to heart rate. Pulse transit time is the sum of pre-ejection period and vascular transit time. Following pre-load reductions due to hypovolaemia, ventricular diastolic filling time increases causing an increase in pre-ejection-period, pulse transit time, and hence iHAT. One hundred and four consecutive patients with suspected major trauma were enrolled. The primary aim was to evaluate the use of the iHAT for detecting haemorrhage in major trauma. The secondary end point was to compare the specificity and sensitivity of iHAT compared to commonly used indexes. Results iHAT was calculated in 84 subjects, 11 of whom were haemorrhagic. iHAT discriminated haemorrhagic from non-haemorrhagic group (46.8% vs. 66.9%, P < 0.0001). The cut-off for iHAT with the best compromise between sensitivity (90.9%) and specificity (100%) was reached at the 58.78% level. Comparing haemorrhagic and non-haemorrhagic patients, the area under the ROC curve was 0.952 for iHAT, 0.835 for heart rate, and 0.911 for systolic blood pressure, showing no significant differences. Conclusions iHAT is a non-invasive index that can identify haemorrhage in trauma patients with high sensitivity and specificity. These data should be considered as an exploration, but any conclusion should be validated in a new set of consecutive patients.