Improvement of blood loss volume estimation by paramedics using a pictorial nomogram: A developmental study

Abstract

Introduction: To propose and evaluate a nomogram to assist paramedics to visually estimate the external blood loss on a non-absorbent surface and to identify whether the nomogram improves visual estimation.

Methods: The study was a prospective, paired-control design (pre-training control group & post-training group), utilizing Emergency Medical Assistant (EMA) I and II trainees from the Hong Kong Fire Services Ambulance Command Training School. A nomogram (blood loss volume to area on a non-absorbent surface) was prepared to aid blood loss estimation. All participants estimated four scenarios of blood pools twice (A: 180mL; B: 470mL;C: 940mL; D: 1550mL) before and after using the nomogram. Every participant received two-minute training on how to use the nomogram correctly. The difference between the estimations and the actual volume in each scenario was calculated. The absolute percentage errors were used for direct comparison and identification of improvement between visual estimation and the use of the nomogram.

Results: Sixty-one participants with an average of 3-year paramedic field experience were recruited by convenience sampling. In combining all scenarios, the median of absolute percentage error of 61 participants was 43% (95%CI 38.0-50.9%) in visual estimation, while it was 23% (95%CI 17.4-27.0%) when using the nomogram. There was a significant reduction in absolute percentage error between visual estimation and the use of the nomogram (p<0.0001).

Conclusion: The nomogram significantly improved the estimation of external blood loss volume.

Keywords: Blood loss estimation; Haemorrhage; Hong Kong; Nomogram; Paramedics; Pre-hospital; Visual estimation.