The Combat Application Tourniquet (CAT) is an effective tool to help control severe blood loss from the body's extremities. If used correctly, the CAT has the ability to save lives. A general misconception of the CAT is that it will result in the casualty requiring amputation of their extremity; this is false. Amputation is more often required as a result of the injury itself, not because of the tourniquet.

To be able to use a tourniquet effectively and ensure patient safety when using the device, there are considerations that should be understood. There are indications, directions for use and contraindications, all applicable for CAT tourniquet use. The CAT should be a LAST RESORT for blood control management. Applying direct pressure to the injury and elevating the extremity above the heart should be attempted prior to utilizing the CAT.

Upon identification of a life-threatening haemorrhage, the practitioner should assess and manage the patient using a structured ‘MARCH’ approach as follows:

• M: Massive Haemorrhage

• A: Airway

• R: Respiration (Breathing)

• C: Circulation

• H: Hypothermia

The simple 5-step approach to a CAT application is as follows and is demonstrated in Figure 1:

• Route the CAT over the limb, above the injury with the band threaded through the buckle.

• Pull the band tight around the limb itself so that no more than three fingers should be able to fit underneath the strap itself. It is important to note the strap should not cross the rod when following around the limb and can be left hanging free. If the strap is not tight enough, remove and re-attempt step 2.

• Twist the rod until bleeding ceases; this does not indicate an absence of blood—only cessation of active bleeding.

• Twist the rod, secure it in between the buckles and lock it into place. It is important not to cover the buckles for this purpose. Following this, reassess the distal part of the limb and palpate for a pulse. If a distal pulse is present, the tourniquet is not effective and re-tightening or application of a second tourniquet should be considered.

• Cover the clips with the ‘time strap’ and note the time of application.

Managing risks of CAT

The CAT tourniquet should only be used when indicated. If used inappropriately, the patient could continue to bleed or even lose a limb.

A tourniquet can safely be left on an extremity for 2–4 hours without release. This is a vital aspect of the application and necessitates the requirement for the timing strap. This is an item that should be applied first when managing a patient to prevent further exsanguination.

As with any medical procedure, it is recommended that consent be obtained from the patient. However, considering the mechanism of injury and complications associated with massive blood loss, the patient may not be able to consent. Patient consent should not delay the application of the CAT in cases of life-threatening injury in an emergency setting. As this is a time-critical procedure, it may be required to assume implied consent for these patients in order for their best interests to be prioritised.

A more detailed list of complications of tourniquet use includes but is not limited to:

• Permanent nerve and muscle injury

• Rhabdomyolysis

• Compartment syndrome

• Skin necrosis

• Reperfusion injury

• Pain and paresthesias.

These may lead to ischaemic injury causing the loss of viability of the limb and resulting in amputation. The cause of the physiological and pathophysiological effects is loss of perfusion to the limb because of a significant compressive force. This limits perfusion causing ischaemia and death of cells. These complications can make the risk/benefit decision challenging for the practitioner; however, they also reinforce the necessity of the presence of appropriate indications.

Frequent and constant training on this device is important as knowledge of mechanical skills can be rapidly lost when not reinforced.

An old and inappropriate practice still commonly exists. Periodic loosening of a tourniquet to provide ‘reperfusion’ was thought to be beneficial but instead resulted in the patient losing extensive blood volume. With the timeframe of 2–4 hours, there is no need to release a tourniquet in any environment other than a controlled environment with appropriate surgical staff.

The CAT is a lifesaving device that can be used by almost anyone in the pre-hospital environment but does have serious adverse effects if used incorrectly. Personnel is required to have training on the device as well as recognise what a life-threatening bleed entails. The device can be left for an extended period of time without adjustment but does require monitoring of the wound itself. The CAT is a device that can buy time, allowing the patient to reach definitive care such as emergency surgery. Without a tourniquet device, the patient will have a higher chance of bleeding out and dying before definitive care can be provided.

Disclaimer: This article has been developed for educational purposes only. It is not a substitute for professional medical advice. Should you have questions or concerns about any topic described here, please consult your medical professional.