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

Betül Akbuğa Özel

Status: Completed

Conditions: Blood Loss

Treatments: Other: The MAR method

Study type: Interventional

Funder types: Other

Identifiers

NCT06855472

KA17/92

Details and patient eligibility

About

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)

Full description

Preliminary Preparation:

For this study, the Professional Skills Laboratories were used as the physical setting. The scenarios were set up at three different stations, each positioned in a separate corner of a large room. Room dividers separated the stations, and each had a designated entrance and exit to prevent participants who had completed their estimations from encountering those who had not yet participated.

Two researchers designed three distinct simulated environments and scenarios for the study. A synthetic blood product was used to enhance the realism of the simulated blood loss cases. In line with the MAR method's design principles, all three stations featured flat, non-absorbent surfaces.

• Station 1: An acrylic (plexiglass) surface with 75 ml of blood.
• Station 2: A flat, varnished wood surface with 150 ml of blood.
• Station 3: A vinyl surface with 750 ml of blood.

Research Staff:

Three faculty researchers were present in the simulation area, overseeing orientation training for investigators and participants and coordinating activities at each station. Additionally, three medical student investigators were assigned to record blood volume estimates and estimation times.

Randomization:

Out of 237 eligible participants, 140 met the inclusion criteria and consented to participate. Since students from both departments had similar academic levels, ages, educational backgrounds, and no prior formal training in external blood loss estimation, the researchers used a non-stratified selection method. Participants were randomly assigned into two equal groups of 70 using a block randomization method (1:1 ratio) via the online service https://researchrandomizer.com/.

To assign participants, group names were written on paper, placed in a bag, and selected blindly.

• Group 1: Control group (Visual Estimation method), (n1:70).
• Group 2: Experimental group (MAR method), (n2:70). Group assignments were revealed to participants only when they arrived at the simulation room. To ensure allocation concealment, an independent researcher conducted both the randomization and group assignment before the trial began. While faculty researchers who prepared the stations knew the actual blood volumes, participants and study investigators who recorded the data were blinded to this information.

Study Description:

Student investigators at the stations received a 20-minute orientation before the study, covering its purpose, workflow, data form usage, and chronometer operation. Investigators recorded data in real-time as estimations were made. Neither participants nor investigators knew the actual blood volumes at the stations (double-blind design). At the start of the study, both groups received a 10-minute briefing, including:

• Signing the consent form
• Explaining the study's purpose
• Introducing the simulation lab and research team

To clearly describe the procedures, the study is presented in two distinct periods. Period I was conducted to obtain the primary outcomes based on the primary objectives of the study. During this period::

• Group 1 (Control): Estimated blood loss using the Visual Estimation (VE) method.
• Group 2 (Experimental): Received 1-2 minutes of MAR method training separately, then estimated blood loss using the MAR method at all three stations.

Investigators at each station recorded blood volume estimates and estimation times for both groups. Researcher analysed data providing intergroup records (Visual estimation method [n1] vs MAR method [n2]) and intragroup records (Visual method [n1] vs MAR method [n1])

Period II process was conducted to obtain the secondary outcomes based on the secondary objectives of the study. In this period::

•Group 1 (Previously Control): Received 1-2 minutes of MAR method training separately, then estimated blood loss using the MAR method at all three stations.

Investigators recorded blood volume estimates and estimation times. For secondary outcomes, data from 140 participants (MAR method [n2] plus MAR method [n1]) were analyzed to determine whether gender, height, and weight influenced blood loss estimates and estimation durations using the MAR method.

Enrollment: 237 patients

Sex: All

Volunteers: Accepts Healthy Volunteers

Inclusion criteria

• 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

Exclusion criteria

• 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

Trial design

Primary purpose: Other

Allocation: Randomized

Interventional model: Parallel Assignment

Masking: Double Blind

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237 participants in 2 patient groups

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

No Intervention group

Description:

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 group

Description:

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.

Treatment:

Other: The MAR method