Words By Scott Smith
In Australia, traumatic injuries involving severe haemorrhage account for a significant number of preventable prehospital deaths 1. Prompt haemorrhage control, to minimise blood loss and maintain perfusion to vital organs, is the most fundamental and effective treatment for these patients 3. The use of arterial tourniquets for extremity haemorrhage has proven to decrease morbidity for both military and civilian populations 4. However, a significant number of preventable prehospital deaths from trauma are due to lower abdominal and junctional haemorrhage where arterial tourniquet is not applicable 5. Due to this limitation, there has been significant research into, and development of the design of tourniquets for occluding axillary and inguinal arteries and the abdominal aorta 6.
Pathophysiology of haemorrhage
Uncontrolled haemorrhage results in hypovolaemic shock which, in this context, is referred to as haemorrhagic shock 7. When haemorrhagic shock occurs, the body’s homeostatic response is activated, and compensatory mechanisms are employed 8. Reduced cardiac output triggers a release of catecholamines and subsequent compensatory cascade 9. A rise in heart rate, increased force of contraction, and vasoconstriction occur in order to maintain perfusion to vital organs 9. When haemorrhage occurs due to vascular damage a complex clotting cascade is initiated to achieve haemostasis 10. Haemostasis is crucial to maintain blood volume, blood pressure, and systemic perfusion 7.
A haemorrhagic traumatic injury may occur due to coagulation and fibrinolysis pathways being disproportionately affected, resulting in impaired haemostasis 11. The hinderance of haemostasis in haemorrhagic shock patients may stimulate an inflammatory response, further triggering the coagulation system while causing a reduction in fibrinogen 12. These concepts are collectively known as acute traumatic coagulopathy (ATC) and a recent study found that patients with ATC suffered increased morbidity, organ failure and required greater transfusion volumes 13.
In the initial presentation the clinical features of haemorrhagic shock may be absent or minimalised as compensatory mechanisms prevail 8. However, once the body is no longer able to continue to compensate for the increasing blood loss, tachycardia and hypotension will commonly present 9, 14. Catecholamine release, causing vasoconstriction to maintain perfusion to vital organs, may cause the skin to become pale and mottled with cold peripheries 7, 9. If haemorrhagic shock persists, perfusion may become inadequate to sustain oxygen exchange and anaerobic metabolism can occur 8. This may result in lactic acidosis, causing a decrease in the clotting ability of the blood 11. Additionally, an altered level of consciousness may occur due to the reduction in cerebral perfusion 11.
Tranexamic acid (TXA)
Patients experiencing tissue damage with massive blood loss are at an increased risk of developing hyperfibrinolysis 2. Hyperfibrinolysis results in excessive breakdown of the fibrin component of blood clots, due to excessive plasmin, and therefore impedes haemostasis 15. TXA is an antifibrinolytic drug that inhibits the breakdown of fibrin clots 16. It achieves this by binding to the lysine site on plasminogen and therefore preventing the formation of plasmin 17. The Clinical Randomisation of an Antifibrinolytic in Significant Haemorrhage (CRASH-2) trial in 2013 studied the effect of TXA on haemorrhaging trauma patients. The CRASH-2 trial noted that TXA improved mortality by approximately one-third of patients suffering traumatic injury associated with massive blood loss 18. Although only some haemorrhaging trauma patients will suffer hyperfibrinolysis and require TXA administration, even in the absence of hyperfibrinolysis TXA has been shown to be beneficial 19.
External Aortic Compression (EAC)
In the tactical setting, EAC using extremity tourniquets applied prior to the onset of shock increase survival rates by up to 90% 22. This decreases to 18% when an extremity tourniquet is applied after the onset of shock 20. In recent years, the most common cause of death for soldiers is due to haemorrhagic trauma at junctional or truncal areas where an extremity tourniquet cannot be applied. A report by van Oostendorp et al. in 2016 agreed that a similar outcome occurred in the civilian setting. Due to these findings other lifesaving interventions are required for junctional and truncal injury 21.
Manual external aortic compression
The use of manual EAC is not new and has been utilised for many years to control post-partum haemorrhage 22. Research has suggested that a haemorrhage located distally to the bifurcation of the descending abdominal aorta, thus involving the iliac arteries and femoral arteries, may be controlled using manual EAC 23. The procedure is easily taught, can be rapidly applied, is free of cost and requires no equipment. A study using Doppler ultrasonography found that with correct application of manual EAC, femoral blood flow ceased 24. However, there are limitations to its effectiveness. In order to sufficiently occlude the abdominal aorta in an adult male, it is necessary to apply 35-55 kilograms of pressure 25. While manual EAC pressure could be provided on scene it is neither safe nor possible to maintain during transportation 22,23.
Abdominal aortic and junctional tourniquet
Although effective, the shortcomings of manual EAC have instigated the development of tourniquets that can apply effective EAC and control inguinal and axillary haemorrhage 25. The AAJT, a belt like device, can be applied to areas requiring haemorrhage control where an extremity tourniquet cannot be placed. When applied correctly, the AAJT is effective in reducing distal blood flow while increasing mean arterial pressure, systemic vascular resistance and afterload 4 ,26. When applied to the patient the inbuilt wedge-shaped bladder is manually inflated with a bulb until the inbuilt pressure gauge registers sufficient pressure to occlude the underlying vasculature 25. Whilst relatively simple, the device is contraindicated in patients with abdominal aortic aneurisms, pregnancy and penetrating injuries to the abdomen. Due to the placement of the AAJT when used for EAC it may also increase work of breathing as it increases intra-abdominal pressure, and a study investigating the long-term consequences of abdominal aortic and junctional tourniquet for haemorrhage control in 2018 found that iatrogenic injury was caused by the AAJT if left applied for longer than the one hour recommended period. The injuries noted were ischaemic necrosis of bowel and muscle tissue and neural destruction causing paraplegia 26,27.
Prehospital severe haemorrhage requires prompt control to improve patient outcomes 3. Using state ambulance protocols from Queensland as an example, one gram of TXA can be administered to patients with traumatic injuries incurred within the last three hours, with a ‘coagulopathy of severe trauma score’ (COAST) equal to or greater than three 28. Studies conducted on the use of TXA support this timeframe and dosage 17,18,29. The CRASH-2 trial found that early TXA administration improved effectiveness. Therefore, the administration of TXA by paramedics in Australia may potentially result in positive outcomes for these types of patients.
Further, the use of manual EAC by paramedics in Queensland is indicated for post-partum haemorrhage 30. Due to the benefit and simplicity of using manual EAC for the control of lower trunk haemorrhage consideration to expand this scope of practice should be explored. As previously described, the use of manual EAC during transport is not only inefficient but could be dangerous to unrestrained paramedics and would therefore only considered a temporary on scene measure.
The introduction of the AAJT would require minimal training 31 . Equipping ambulance services with the AAJT would enable the rapid control of life-threatening abdominal and junctional haemorrhage. Once applied the AAJT does not require ongoing adjustments and the patient is able to be transferred to definitive care with the device in place. As the AAJT can cause ischaemic bowel necrosis and neural destruction if left on for longer than one hour, paramedics would need to make considerations for the application of AAJT to patients with transport times greater than 90 minutes. A risk analysis should be performing by the attending paramedics and the possibility of iatrogenic injury weighed against the possibility of exsanguination and death.
The use of TXA should continue and would possibly show increased benefits if used in combination with manual EAC and the AAJT. It is suggested that manual EAC be applied rapidly for lower trunk haemorrhage control while the AAJT is being prepared. As discussed, a proposed trial with the AAJT in paramedic care would be relevant as the application of this device is time critical and paramedics are often the first health care professionals on scene. The Balian et al. study investigating the use of AAJT by a Sydney helicopter retrieval service, concurs with this perspective 25. The device was used on patients already in traumatic cardiac arrest and, unfortunately, returned a 100% mortality rate. The authors contended that the delayed application of the AAJT due to the helicopter response time increased these mortalities and had the AAJT been applied by the first paramedics on scene the patients may have had more favourable outcomes.
Understanding the pathophysiology and clinical features of haemorrhage is beneficial to paramedics so that they may recognise severe haemorrhage and provide prompt management. The use of TXA, while beneficial for patients experiencing hyperfibrinolysis, is effective in all patients experiencing severe haemorrhage due to its anti-inflammatory actions. Traditionally patients with severe haemorrhage that cannot be controlled by extremity tourniquets have poor outcomes. Manual EAC is effective for lower truncal haemorrhage control, however, is not sustainable for long periods of time and during transport. The AAJT is a practical management option due to its simple application, efficacy, variety of placement locations and nil overall risk to the provider when in transit. Further research is required to determine if the conjunctive use of these haemorrhage control methods improves patient outcomes in the paramedicine setting.
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