The MAR Method Versus the Visual Estimation Method in Predicting External Blood Loss

NCT06855472 | Completed

• 1 other identifier: KA17/92
• Study Type: interventional
• Target: 237
• Locations: 1 country
• Sites: 2

Brief Summary

The goal of this educational clinical trial is to determine whether the MAR method is more effective than the Visual Estimation method for estimating blood loss. It also aims to assess whether factors such as gender, weight, and height influence blood loss estimates when using the MAR method. The main research questions it aims to answer are:

• Does the MAR method provide more accurate blood loss estimates than the Visual Estimation method on flat, non-absorbent surfaces?
• Does the MAR method take longer to estimate blood loss compared to the Visual Estimation method?
• Do demographic factors such as gender, height, and weight affect blood loss estimates using the MAR method?
• Do these demographic factors also influence the time required for estimation using the MAR method? Researchers will compare the MAR method with the Visual Estimation method to determine whether the MAR method is a useful tool for accurately estimating external blood loss in clinical skill training. Participants will:
• Sign an Informed Consent Form at the start of the study
• Receive a 10-minute orientation session
• Receive a 2-minute MAR method training (for the intervention group-)
• Use either the MAR method or the Visual Estimation method for up to 60 seconds at each of the three stations
• Receive a 2-minute MAR method training (for the control group)
• Use the MAR method for up to 60 seconds at each of the three stations (for the control group)

Conditions

Blood Loss

Keywords

blood loss; clinical skills; emergency medicine; medical students; paramedics; randomized controlled trial; simulation training

Outcome Measures

Primary Outcomes (2)

• Blood loss volume estimate

  Blood loss volume estimates using the MAR and Visual Estimation (VE) methods were recorded in milliliters (ml). The participants had 60 seconds to complete their estimations at each station. Participants' verbal estimates were documented by researchers at each station on the study record form. Blood loss volume estimates obtained using Group 1's VE method (n1:70) Group 2's MAR method (n2:70) were compared between the groups. Blood loss volume estimates obtained using Group 1's VE method and MAR method (n1:70) were then compared within the group.

  From enrollment to the completion of method application in 20 minutes.

• Blood loss estimation time

  The blood loss estimation times for the MAR and VE methods were recorded in seconds. The participants had 60 seconds to complete their estimations at each station. A chronometer was used for each measurement. Blood loss estimation times obtained using Group 1's VE method (n1:70) and Group 2's MAR method (n2:70) were compared between the groups. Blood loss estimation times obtained using Group 1's VE method and MAR method (n1:70) were then compared within the group.

  From enrollment to the completion of method application in 20 minutes.

Secondary Outcomes (2)

• Blood loss volume estimate of each participant using the MAR method

  From enrollment to the completion of method application in 25 minutes.

• Blood loss estimation time of each participant using the MAR method

  From enrollment to the completion of method application in 25 minutes.

Study Arms (2)

Group 1: Visual Estimation Method (Control), (n1:70)

NO INTERVENTION

The Visual Estimation Method is the most commonly used technique for estimating external blood loss. It relies on quick visual assessment rather than precise measurement, providing an estimate within seconds.

Group 2: The MAR Method (Intervention), (n2:70)

EXPERIMENTAL

The MAR (Merlin, Alter, Raffel) method, which was first described by Merlin et al. in 2009, is an alternative clinical skill recommended for estimating the amount of external blood loss on flat surfaces and does not depend on visualization. The method can learn within 1-2 minutes. In this method, the participants are given 60 sec to complete their estimations.

Other: The MAR method

Interventions

The MAR method OTHER

The study was conducted in three isolated stations. Two faculty researchers designed the scenarios, while three others supervised training. Medical student investigators recorded blood loss estimates and estimation times. Before the study, investigators received 20-minute training. Participants and investigators were blinded to actual blood volumes. Group 1 and Group 2 attended a 10-minute briefing, including consent and study introduction. The study had two phases. In Phase 1, Group 1 used the Visual Estimation (VE) method, while Group 2 received a 2-minute MAR method training before making estimations. In Phase 2, Group 1 was trained in the MAR method and repeated estimations.A data form recorded demographics, blood loss estimates, and estimation times. Group 1's VE data and Group 2's MAR data were compared between groups, while Group 1's VE and MAR data were analyzed within the group. Combined MAR data from both groups were used to assess the impact of gender, height, and weight.

Group 2: The MAR Method (Intervention), (n2:70)

Eligibility Criteria

• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Child (0-17), Adult (18-64), Older Adult (65+)

You may qualify if:

• Being a second-year paramedic or medical student
• No prior theoretical or practical training in estimating external blood loss
• Willingness to participate in the study

You may not qualify if:

• Not being a second-year paramedic or medical student
• Having received theoretical or practical training in estimating external blood loss
• Declining to participate in the study

Sponsors & Collaborators

• Betül Akbuğa Özel: lead
• Baskent University: collaborator

Study Sites (2)

Baskent University

Ankara, Ankara, 06790, Turkey (Türkiye)

Location

Ankara Yıldırım Beyazıt University, Faculty of Medicine, Ankara Bilkent City Hospital, Department of Emergency Medicine

Ankara, Ankara, 06800, Turkey (Türkiye)

Location

Related Publications (6)

• Merlin MA, Alter SM, Raffel B, Pryor PW 2nd. External blood loss estimation using the MAR Method. Am J Emerg Med. 2009 Nov;27(9):1085-90. doi: 10.1016/j.ajem.2008.07.039.

  PMID: 19931755 BACKGROUND

• Yeung CY, Yim WW, Chan SY, Lo RSL, Leung LY, Hung KKC, Graham CA. Improvement of blood loss volume estimation by paramedics using a pictorial nomogram: A developmental study. Injury. 2017 Dec;48(12):2693-2698. doi: 10.1016/j.injury.2017.10.045. Epub 2017 Oct 31.

  PMID: 29108791 BACKGROUND

• Ashburn JC, Harrison T, Ham JJ, Strote J. Emergency physician estimation of blood loss. West J Emerg Med. 2012 Sep;13(4):376-9. doi: 10.5811/westjem.2011.9.6669.

  PMID: 22942938 BACKGROUND

• Williams B, Boyle M. Estimation of external blood loss by paramedics: is there any point? Prehosp Disaster Med. 2007 Nov-Dec;22(6):502-6. doi: 10.1017/s1049023x0000532x.

  PMID: 18709938 BACKGROUND

• Shafi S, Kauder DR. Fluid resuscitation and blood replacement in patients with polytrauma. Clin Orthop Relat Res. 2004 May;(422):37-42. doi: 10.1097/01.blo.0000129149.15141.0c.

  PMID: 15187831 BACKGROUND

• Akbuga Ozel B, Ozel G, Mamak Ekinci EB, Demirtola AE, Sahin G, Aksoy G, Yanikyurek I, Karaaslan MU. The MAR method versus the visual estimation method in predicting external blood loss: a randomized controlled study. Sci Rep. 2025 Aug 24;15(1):31091. doi: 10.1038/s41598-025-16169-0.

  PMID: 40851079 DERIVED

Related Links

• Merlin MA, Alter SM, Raffel B, Pryor PW 2nd. External blood loss estimation using the MAR Method. Am J Emerg Med. 2009 Nov;27(9):1085-90.

MeSH Terms

Conditions

Hemorrhage

Condition Hierarchy (Ancestors)

Pathologic Processes; Pathological Conditions, Signs and Symptoms

Study Officials

• Betul Akbuga Ozel, Asst.Prof.

  Ankara Yıldırım Beyazıt University, Faculty of Medicine, Ankara Bilkent City Hospital, Department of Emergency Medicine

  PRINCIPAL INVESTIGATOR

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: DOUBLE
• Who Masked: PARTICIPANT, INVESTIGATOR
• Masking Details: Participant: Second-year paramedic student or second-year medical student, having received no theoretical or practical training in predicting external blood loss (N:237) Investigator: Student, provided planned training to participants, recorded outcome parameters Researcher: faculty member, prepared three different simulated environments and scenarios, provided planned training to investigators, oversaw flow of participants across study arms and recorded outcome parameters
• Purpose: OTHER
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: SPONSOR INVESTIGATOR
• PI Title: Assistant Professor, MD, FTBEM, MSc, PhD

Model Details: Our study does not involve treatment, prevention, diagnosis, supportive care, screening, or medical devices. Instead, it is a randomized controlled trial that focuses on clinical skills training for estimating external blood loss in emergency medicine. The study designed a monocenter, double-blind, randomized, parallel-group, and controlled clinical educational study.

Study Record Dates

• First Submitted: February 18, 2025
• First Posted: March 3, 2025
• Study Start: May 7, 2017
• Primary Completion: May 7, 2017
• Study Completion: May 10, 2017
• Last Updated: March 6, 2025

Record last verified: 2025-02

Data Sharing

• IPD Sharing: Will not share

Locations

TU (2)