Understanding casualty analysis

Death on the battlefield is a function of tactical scenarios, chances of being injured, severity of injuries and availability of treatment.1 Each of these elements has associated factors that may influence outcomes. The chance of injury is a factor of the kinetics and activity within a given military operation; severity of the injury is affected by weaponry and performance of protective equipment; and medical treatment is affected by the tactical environment, availability of care, timely evacuation and sophistication of resuscitative and surgical techniques. LSCO scenarios will negatively affect all these factors, significantly increasing battlefield deaths.

Battlefield mortality is stratified by location. Mortality before arrival at a medical treatment facility is considered ‘killed in action’ (KIA), after arrival is considered ‘died of wounds’ (DOW). Overall battlefield mortality is defined as the CFR: number of deaths (KIA+DOW)/total number injured (deaths and survivors).1

Defining good casualty care

A marker of battlefield medical success is a reduction in the KIA:DOW ratio. Over the last 23 years, KIA has been reduced by preventing exsanguination, early blood resuscitation, timely surgical intervention and robust data collection allowing for evidence-based improvement.6 These advances have enabled more severely injured casualties to survive the battlefield evacuation to reach surgical care, creating a subsequent slight increase in DOW%. An increase in DOW% is therefore reflective of more critically injured casualties surviving to hospital, a small number which may then die later in hospital despite the best medical efforts.7 8 Therefore, a small increase in DOW% is a marker of a successful medical trauma system and an indicator of improved overall survival. Improving the overall CFR lies in a reduction of KIA without a significant increase in DOW.2 6–10

When do battlefield deaths occur?

Understanding how and when casualties die after injury is critical to developing meaningful prevention and treatment strategies as well as focused research and innovation. Initial reports from the Russia–Ukraine war reveal familiar injury patterns.3 11 However, the significant increased proportion of extremity data suggests that the cohort with torso and head injuries are likely KIA. The increased timelines to the hospital mean that this cohort simply does not survive past the battlefield due to their time-critical life-threatening injuries. Despite changes in the character of conflict, injuries affect human physiology in predictable ways.12–16

Data from Operation HERRICK demonstrates that 57% of deaths occurred immediately and over 66% of battlefield deaths occurred within the first 10 min.16 This is replicated with US military data showing a KIA rate of 77%–87%; of these, 35% occurred instantaneously and 52% occurred before reaching a medical treatment facility.15 The unforgiving expediency of haemorrhagic death is also replicated in civilian trauma.17–19

Although battlefield injuries are highly lethal with many deaths due to non-survivable wounds, 25% of battlefield deaths were deemed potentially survivable through medical intervention.15 Medical survivability does not account for the tactical environment, a critical factor in determining timely treatment. The multifaceted logistical challenges facing soldiers in the Russia–Ukraine conflict highlight how potentially salvageable deaths might be tactically unpreventable.3 11 These same issues will likely exist in LSCO and must be accounted for by medical planners.

Previous improvements in casualty care

Focussing on prehospital haemorrhage control, transfusion and rapid evacuation to surgical care are the most data-driven aspects of previous improvements. For example, one of the best reported fatality improvements was seen in the US 75th Ranger Regiment over the past 20 years. Their success was due to early life-saving haemorrhage control, blood product resuscitation and robust prehospital data collection enabling a continuous cycle of quality improvement.6 However, practices within special operations forces (SOF) units may not be generalisable to LSCO scenarios. SOF units are typically characterised by highly trained small teams equipped to provide first-line medical care beyond the typical soldier’s capabilities. Since the vast majority of casualties will be in conventional forces, death rates in LSCO will be predictably higher than the Rangers’ experience in asymmetric operations.

Most potentially avoidable deaths occur early and efforts to mitigate haemorrhage are the primary method for improved outcomes.6 20–23 This understanding confirms the clear impact time has on mortality. 97% of British fatalities who were KIA and died on the battlefield died within 90 min. When looking at all combat casualties, irrespective of their geographical location of death, 90% died within 4 hours.10 16 Data on civilian trauma confers similar early death statistics.17–19 Specifically, data have shown that early access to medical treatment can decrease the KIA rate by 39%.2 6 The North Atlantic Treaty Organization clinical timelines recommend 10 min to initial first aid, 1 hour to advanced prehospital intervention and 2 hours to surgical intervention.24 Contemporary data reconfirms the benefit of prehospital haemorrhage control and blood transfusion,25 combined with early surgical intervention. Transport to a surgical team within 1 hour of injury was associated with a 66% reduction in 24-hour mortality.10 Similar survival benefit was demonstrated when blood transfusions were initiated within 15 min of injury.26

Effects of the changing environment

Globally, allies are being forced to face the reality of LSCO with high numbers of casualties that will not be treated within the current recommended medical timelines. Limitations include the capacity and protection of evacuation platforms, available providers and ethical evacuation priorities.3 An assumption of immediate medical evacuation is unrealistic and patient movement will likely be a series of multiple prolonged stages. Similarly, wargaming efforts in the Indo-Pacific arena anticipate the vulnerability of medical ships, decreased maritime surgical assets, long evacuation times and the complicated interface between maritime rescue and treatment capabilities.3 27

Changing expectations

Prehospital care advancements have occurred during smaller-scale operations with secured evacuation assets. However, LSCO has led to higher mortality estimates by eliminating these assumptions. Saving a soldier with a potentially survivable injury relies on the interplay between tactical survivability and medical survivability; separating one aspect from the other is an oversimplified fatal flaw that ignores the relevance of both. The advances in medical care are not able to overcome every tactical obstacle. Here lies the inconvenient truth of LSCO. Tactical survivability will be negatively impacted in LSCO due to prehospital care constraints, increased evacuation times and delayed surgical interventions. A potentially survivable injury in a tactically unsurvivable scenario is still considered unsurvivable. Mortality rates are projected to worsen due to increased tactical complexity affecting the preventability of death.28 As the battlefield complexity increases, one constant remains: human physiology. In trauma, the process of early death mostly results from exsanguination, neurological injury or ventilatory compromise. The ‘consistent curve of haemorrhagic deaths’ develops rapidly.19 Extending life-saving care to a 24-hour ‘golden day’ will increase mortality rates and reverse improvements in casualty fatality rates that were seen under faster delivery of medical care. Those with potentially survivable injuries will die: ‘unexpected survivors’ will become ‘expected deaths’ and, more worryingly, ‘expected survivors’ will become ‘unexpected deaths’. Potential solutions to the challenges of prolonged field care in LSCO must be viewed pragmatically. Clinical consequences must be highlighted when considering and articulating future battlefield risks associated with constrained medical planning for LSCO (Box 1).

Leveraging the lexicon

The ‘golden hour’, a sound bite coined by Cowley, has driven improvement in trauma systems,9 19 29 and has contemporary value.10 Such buzz phrases, from the ‘platinum 10 min’ to the ‘golden day’, can easily enter the lexicon without understanding the physiological basis for these aphorisms. Despite the lack of academic literature mentioning the ‘golden day’, this term has appeared in discussions by military leaders and risks being repeated by military commanders and medical planners. Because it sounds similar to the well-accepted beneficial term ‘golden hour’, the use of ‘golden day’ may falsely reassure that delays in evacuation can be mitigated without consequences. New challenges require a shift in expectations for dealing with increased casualties, contested evacuation and limited medical treatment. Clinicians must understand casualty data and communicate the complexity of battlefield mortality. Language that does not account for these facts should be removed from use to avoid confusion.

When planning combat operations, line commanders must be candidly informed of excess mortality during LSCO. The parameters associated with LSCO are significantly different from those seen over the last 30 years of combat, generating casualty numbers and death rates not seen since World War I, alongside increased risk to medical providers.