Analysis of the Efficacy of Pressure Pad vs Pressure Bandage Immobilisation for Snake Bite First Aid in Healthy Volunteers.

Condition(s) studied

Investigational drug(s) / intervention(s)

Pressure bandage immobilisation first aid: Pressure Bandage Immobilisation Technique (PBI): 1. An elastic bandage of 100mm width will be applied to the full length of the involved limb, starting from the fingers or toes and moving proximally until the whole limb is bandaged, bandaging over clothing if required. 2. The desired pressure of the bandage (\~60mmHg) will be obtained by utilising "smart" bandages which have special markings that take on the shape of a square when the bandage is applied at this pressure/tension. Prior to use on each subject, the accuracy of this process will be confirmed via pressure manometry using an infant blood pressure cuff bladder placed under the wraps of the elastic bandage and connected to a manometer as per Canale et al. 3. Splinting of the limb will be performed using a sling for the arm, and a wooden splint for the leg.

Pressure pad first aid: Pressure Pad Technique (PP): 1. A square gauze pad of 5 sheets thickness with an overall size of 80x80mm will be applied to the injection site. 2. The gauze pad will be secured using an elastic bandage of 100mm width at a tension of \~60mmHg using a "smart" bandage. Prior to use on each subject, the accuracy of this process will be confirmed via pressure manometry using an infant blood pressure cuff bladder placed under the wraps of the elastic bandage and connected to a manometer as per Canale et al. 3. Splinting of the limb will be performed using a sling for the arm, and a wooden splint for the leg.

Control - no first aid: Control (no first aid technique applied): 1. Imaging will be done with the subject lying supine and still without the application of either bandaging technique 2. Splinting of the limb will be performed using a sling for the arm, and a wooden splint for the leg.

Study summary

Snake bite affects thousands of Australians every year, but few die as a result due to high quality first aid and timely medical care. Good first aid should be simple, standardised, use minimal or readily available equipment, and be able to be utilised effectively with no or minimal training by the rescuer. Over time the first aid methods used to manage snake bite in Australia have been questioned due to issues with efficacy, and some emerging evidence of harm from their use. There is little experimental data in the literature to support current first aid practices, and what exists suggests further research is required. This study aims to examine and compare the effectiveness of two first aid methods by tracking the movement of a mock venom through the body when each first aid method is used. This will provide important information about the suitability of current techniques used in Australia and whether a proposed simpler alternative technique is as effective. Currently, initial treatment of snake bite involves early first aid with the application of a pressure bandage and immobilisation (PBI) of the limb. There is limited data to support the basis of this technique and emerging evidence of harm when applied incorrectly. This project sets out to evaluate PBI compared to another technique involving the application of a pressure pad (PP) at the bite site (which is easier to do, and used in many countries outside of Australia). The project aims to determine whether each technique is effective, and whether the PP technique is at least as effective as PBI. To do this 24 participants will be recruited to undergo study with mock venom injected into their hand or foot and having either PBI or PP applied. The mock venom will then be traced with a gamma camera to determine rate of flow through the lymphatic system, which is how venom travels in the body. It is expected that the project will demonstrate the efficacy of both techniques, and that the PP will be at least as effective as PBI. This will provide a basis for change in the current first aid recommendations for snake bite first aid in Australia, and improve the care provided.

Eligibility

Primary outcome measure(s)

• Time for mock venom to reach regional lymph nodes following injection — From the date of enrolment until all scans are completed (minimum of 12 weeks, maximum of 18 months).
  Time (in seconds) will be recorded from the injection of Tn-99m sulfur colloid until signal is detected at the regional lymph nodes for the relevant limb, and then until there is evidence of entry to the systemic circulation (as demonstrated by signal detection in the liver). Times will be judged by the reporting radiologist on the basis of the time stamp on the relevant image relating to signal detection at the relevant location. Each scan will run for up to 30 minutes, with intervention scans having the first aid technique removed at this point and running for a further 30 minutes. This allows demonstration of movement of mock venom through the lymphatic system after removal of first aid if the initial application of first aid is efficacious enough to completely retard mock venom movement. Distance from injection site to either groin or axilla (as relevant) will also be measured at each scan so that a lymphatic flow rate is able to be calculated

Trial sites (1)