Page 88 - JSOM Winter 2021

event and thanks to the increase in staff, our operating capac- the ability of performing effective medical interventions by
ities increased. Our center took charge of almost all victims. tactically engaged first responders. Best practices among sol-
Patient diversion concerned only three patients transferred to diers and athletes use work-rest cycles and hydration strategies
a nearby hospital for minor orthopedic surgery. to succeed in hot environments. According to data collected
in this trial and in studies available in literature, it is reason-
able to speculate that an aerobically fit soldier may require not
Care Under Heat: Focused Discussion on less than 45–60 minutes of rest and rehydration before return-
Heat Stress and Performance of Combat Medics ing at near-baseline physiological parameters when exposed
Maj. Jacopo Frassini, MD – NATO Centre of Excellence for to a 30-minute continuous submaximal physical activity at
Military Medicine
WBGT of 28–31°C. In the same range of WBGT, rehydration
Introduction: Most modern allied military land operations requires not less than 1500 gr of fluids to replenish the sweat
have been taking place in hot climates. Harsh environmen- loss, mainly occurring during the first 30 minutes in the recov-
tal conditions degrade both human performance and health. ery phase. The importance of maintaining a 3–5 hour/week
In the fight, heat stress, exertion and dehydration can rapidly aerobic fitness for faster post-exertional recovery should be
compromise mental and physical skills. Combat medics are strengthened in individuals who favour mainly isometric and
frequently subject to an additional burden in providing effec- resistance training, which does not seem to provide benefits in
tive lifesaving interventions while constrained in their tactical this regard. Soldiers, especially if critical to the medical safety
engagement. Aims: (1) Investigate the factors that can facili- of the unit, should be aware of the additional cardiovascu-
tate the recovery to near-baseline physiological status between lar burden in the heat and be able to self-regulate their effort
combat activations of highly trained elite warfighters in hot in order to avoid exercising at maximal heart rate and risk
outdoor conditions. (2) Discuss the implications on the prepa- premature exhaustion. Conclusion: Awareness of the problem
ration of combat medics in order to sustain their mental/phys- and structured training profiles are essential to prepare com-
ical performance in the heat. Methods: A group of 33 SOF bat medics to sustain reliable performance levels and avoid
operators were monitored during a 30-minute submaximal incapacitation when providing casualty care in environmen-
self-paced aerobic exercise (running) and the subsequent 60 tal conditions at high risk of heat stress. Further studies are
minutes of recovery when a fixed amount of water was ad- needed to address the detriment more specifically for special-
ministered. Each participant took a test at low and one at high ized medical skills in realistic tactical conditions. (Main Ref.:
heat stress exposures, calculated using the Wet Bulb Globe Frassini J, Nocca P. Physical Activity, Hydration and Thermal
Temperature (WBGT) Index. Variations of heart rate were de- Stress. GMedMil 2015;165(3):275-294).
tected with the use of a dynamic 12-lead ECG recorder, along
with periodic measures of blood pressure, body weight and Junctional Tourniquet use in the
running distance. Experimental conditions of the trial did not Modern Combat Environment
consider the additional heat stress generated by the tactical Major Rich Hilsden, Trauma Surgeon,
protective gear and by the exact combat tempo. Results: The Canadian Armed Forces
peak heart rate reached at maximum effort was significantly
higher in the test conducted at higher heat stress level (174.6 ± odern conflicts have changed the injury patters seen in
10.2 bpm vs. 166 ± 9.9 bpm; p < 0.001). The most relevant Mcombat casualties. Many patients are the victims of blast
difference was noticed among those participants that did not injuries and improvised explosive devices. These weapons
reduce the running distance in hot conditions, rapidly reaching cause multiple amputations and pelvic disruption resulting in a
their maximal heart rate. During the first 3 minutes into the devastating injury pattern. Junctional injuries are injuries that
recovery phase, heart rate dropped 52 bpm on average inde- occur between the extremities and the torso. Junctional hem-
pendently of the heat stress level and proceeded with a slope orrhage is a challenge to control with external compression
of –1.1 bpm/min. In the first 15–20 minutes of rest the curves and is not amenable to conventional tourniquet application. A
of heart rate at high and low heat stress (WBGT respectively junctional tourniquet is an external compression device which
of 22.1 ± 1.2°C and 28.6 ± 1.9°C) maintained a parallel sep- compresses the aorta or ileac artery restricting blood flow and
aration of about 8.5 bpm. The weight loss was used to assess preventing hemorrhage. These devices have recently been in-
the hydration status. At mean WBGT values of 28.6°C, the corporated into combat casualty care.
average total weight loss was 1520 ± 200 gr. No significant Outcomes: The combat vascular surgery working group out
difference between the tests at high and low WBGT values of Western University set out to align the experience of com-
was noticed at the end of the effort, while increased losses bat injuries with the new capability of junctional tourniquets.
were registered during the recovery at higher heat stress levels. We suggest an algorithmic approach for the use of junctional
In the recovery phase and independently from the WBGT val- tourniquets in combat casualty care. Patient Population: This
ues, the heart rate returned to baseline values after 45–60 min- research applies to all military personal potentially exposed
utes and the body weight stabilized between 30–45 minutes, to combat threats which may result in junctional injuries.
with faster results in the subjects with 3 to 5 hours of aerobic Conclusions: The vascular surgery working group successfully
training per week. The trend in systolic and diastolic blood developed clinical decision tools for the use of junctional tour-
pressure values reflected the loss in body weight. Discussion: niquets though the phases of combat casualty care, up to the
Recent studies have shown that at increasing levels of WBGT receiving surgical facility. Firstly, junctional tourniquets should
there is a reduction in physical/mental performance and an not be considered during the care under fire phase. Once the
increased incidence of exertional heat illness. The dynamic environment has shifted to tactical field care, and beyond,
situations where the combat medics operate often involve re- junctional tourniquets should be available, and their use con-
peated physical efforts with intensity and duration that vary sidered. The most frequently considered case is the application
according to the circumstances with limited possibility for re- of a junctional tourniquet for a wound above the level which
hydration and rest. Thus, heat stress has the potential to affect a conventional tourniquet could be applied, and after pressure

86 | JSOM Volume 21, Edition 4 / Winter 2021