On Tourniquets and Lives Saved

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“Tourner” French verb for “to turn” derived from the Old French torner, from the Latin tornare

Though tourniquets were likely in use since Roman times, the term “tourniquet” was originally turned by Louis Petit, the 18th century inventor of the screw tourniquet.  Though numerous design advancements have occurred and new devices have been made in the centuries that have followed, the basic principles of tourniquet use are essentially unchanged.  A tourniquet applies an external pressure to a limb (usually) that exceeds the arterial pressure in that extremity.  In this way the inflow of arterial blood to an extremity is stopped.  For a surgeon, in the setting of a prospective extremity surgery, this allows for the creation of a bloodless operative field.  For Emergency Medicine providers, tourniquets can aid in the exploration of extremity wounds, allowing the identification of injuries to tendons, joints, and vascular structures.  And perhaps most importantly, tourniquets applied proximal to the site of penetrating traumatic extremity injuries can cease bleeding from arterial injuries.  And with decreased bleeding from major vascular structures comes the likelihood of increased survival.  This is especially important in prehospital emergency medicine, where direct application of pressure to penetrating traumatic injuries is unpractical due to resource limitations (there are only so many hands to care for the patient). To look at the impact of tourniquets on survival, Kragh, et al (2011) conducted an observational study of battlefield casualties over the course of 2 non-consecutive 6 month spans.  They found increased survival with the prehospital application of a tourniquet (89% vs 78%) and found increased survival when the tourniquets were applied before the presence of shock.  These findings are limited somewhat, however, by the observational nature of the study, survivor bias, and questions of applicability to civilian injuries.

Are tourniquets safe?  

As with most questions of safety, the answers are somewhat complicated.  The first thing you must know is that not all tourniquets are created equally.  McEwen and Casey (2009) compared pressures applied from pneumatic surgical tourniquets and those applied by non-pneumatic tourniquets typically used in the prehospital environment and on the battlefield.  They found that non-pneumatic tourniquets applied a maximum pressure of 700 mmHg whereas pneumatic tourniquets applied a maximum pressure of 250 mmHg.  The authors propose that the higher pressures applied by the non-pneumatic tourniquets could result in increased risk of injury to the patient.

Kragh, J et al (2008) sought to measure complications of non-pneumatic “battlefield” tourniquets through the use of a prospective survey of casualties at a combat support hospital in Baghdad in 2006.  They followed 232 patients who had 428 tourniquets applied to 309 injured limbs and found relatively few complications.  They found no association with tourniquet time and the presence of clots, myonecrosis, rigor, pain, renal failure, or amputation.  Their data showed no statistically significant association between tourniquet time and fasciotomy.  The fasciotomy rate, however, for time <2 hours was 28% (75 of 272) and for >2 hours was 36% (9 of 25).  This could represent a trend towards increased fasciotomy rates with increased time though the true difference is difficult to ascertain given the small numbers in the > 2 hour group.  A retrospective review of a military trauma registry conducted by Kragh et al (2011) found that from 2003 to 2006 there were significant increases in the rate of fasciotomies in extremity injuries (monthly rates of fasciotomies increased from 5% to 30%).  Controlling for Injury Severity Score (ISS) and limb Abbreviated Injury Severity Score (AIS) the authors found that fasciotomy rates doubled after tourniquet placements in the field.  The authors state, however, that “the greater increase with injury severity than tourniquet use indicates that injury severity contributed more that fasciotomy rates than tourniquet use.”   Apart from the concern for the development of myonecrosis and possible subsequent fasciotomy from tourniquet use, transient nerve palsies are also a possibility with the application of a tourniquet.  Kragh et al (2008) found that 1.4% of limbs in their cohort had the development of a transient nerve palsy at the site of the tourniquet.  There were no reports of permanent nerve injury.

What guidelines exist for their application? 

The Eastern Association for the Surgery of Trauma (EAST) most recently updated their guidelines for the management of penetrating traumatic extremity injuries in 2012.

In cases of hemorrhage from penetrating lower extremity trauma in which manual compression is unsuccessful, tourniquets may be used as a temporary adjunct for hemorrhage control until definitive repair. (Level 3 Recommendation)

In citing the potential harms of tourniquet use, EAST notes:

“The complication rate for tourniquet use is exceedingly low and limited to transient nerve palsy. The authors recommended that ischemic time be kept as short as possible and that tourniquets be replaced with bandages when appropriate.”

How do you apply the Combat Tourniquet carried on Air Care?

Below are a series of videos that should help you learn how to apply the CAT tourniquet carried on Air Care.  This first video is a "procedural slide set" in which you will see a series of pictures narrated by Dr. Calhoun that demonstrate the key steps for proper application of the tourniquet.  There are nuances to the application and to application on the upper vs lower extremity but it boils down to placing it proximal to the site of injury and avoiding placing it over bony prominences (poorer compression of vascular structures and increased risk of nerve injury).

This second video shows you the application of the tourniquet from a first person view as filmed by a GoPro.  Cool? Yes.  Hopefully helpful as well.

References

  1. Fletcher, I & Healy, T. (1983). The Arterial Tourniquet. Annals of the Royal College of Surgeons of England. vol 65. 409-417.
  2. Fox N, Rajani RR, Bokhari F, Chiu WC, Kerwin A, Seamon MJ, Skarupa D, Frykberg E, Eastern Association for the Surgery of Trauma. Evaluation and management of penetrating lower extremity arterial trauma: an Eastern Association for the Surgery of Trauma practice management guideline. J Trauma Acute Care Surg. 2012 Nov;73(5 Suppl 4):S315-20.
  3. Kragh, J., Walters, T., Baer, D., Fox, C., Wade, C., Salinas, J., & Holcomb, J. (2008) Practical Use of Emergency Tourniquets to Stop Bleeding in Major Limb Trauma. The Journal of Trauma Injury, Infection, and Critical Care. Feb Supp, S38-S50
  4. Kragh, J., Wade, C., Baer, D., Jones, J., Walters, T., Hsu, J., Wenke, J., Blackbourne, & Holcomb, J. Fasciotomy Rates in Operations Enduring Freedom and Iraqi Freedom: Association with Injury Severity and Tourniquet Use. 25 (3). 134-139.
  5. McEwen J and Casey V. Measurement of hazardous pressure levels and gradients produced on human limbs by non-pneumatic tourniquets. Proc 32nd Conf Can Med Biol Eng Conf (Calgary, Canada), 2009, pp 1-4.
  6. http://www.tourniquets.org/
  7. http://en.wiktionary.org/wiki/tourner