Managing the military patient with syncope

Risk factors for reflex syncope in the British Army

INTRODUCTION

Reflex syncope in the UK Armed Forces is reportedly higher than comparable militaries and civilian populations and is significantly more common in soldiers who take part in State Ceremonial and Public Duties (SCPD) compared with other British Army service personnel (SP). This study aimed to investigate individual susceptibility factors for syncope in soldiers who regularly take part in SCPD.

METHODS

A retrospective cohort study was performed in 200 soldiers who perform SCPD. A questionnaire was undertaken reviewing soldiers' medical history and circumstances of any fainting episodes. A consented review of participants' electronic primary healthcare medical record was also performed. Participants were divided into two groups (syncope, n=80; control, n=120) based on whether they had previously fainted.

RESULTS

In the syncope group orthostasis (61%) and heat (35%) were the most common precipitating factors. The most common interventions used by soldiers were to maintain hydration (59%) and purposeful movements (predominantly 'toe wiggling'; 55%). 30% of participants who had previously fainted did not seek definitive medical attention. A history of migraines/headaches was found to increase the risk of reflex syncope (OR 8.880, 1.214-218.8), while a history of antihistamine prescription (OR 0.07144, 0.003671-0.4236), non-white ethnicity (OR 0.03401, 0.0007419-0.3972) and male sex (OR 0.2640, 0.08891-0.6915) were protective.

CONCLUSION

This is the first study, in the British Army, to describe, categorise and establish potential risk factors for reflex syncope. Orthostatic-mediated reflex syncope is the most common cause in soldiers who regularly perform SCPD and this is further exacerbated by heat exposure. Soldiers do not use evidence-based methods to avoid reflex syncope. These data could be used to target interventions for SP who have previously fainted or to prevent fainting during SCPD.

Reflex syncope in the UK Armed Forces

INTRODUCTION

Reflex syncope is the most common subtype of syncope and, despite not being associated with increased mortality, often results in significant morbidity and costly diagnostics. Reflex syncope can be of concern for certain occupational groups and may be exacerbated by some occupations. Reflex syncope in the military is anecdotally common but the extent in the UK Armed Forces (UKAF) is unknown. The aim of this study was to assess the incidence and prevalence of reflex syncope in the UKAF.

METHODS

A retrospective search of the Defence Medical Information Capability Programme using prespecified read-codes was performed at defence primary healthcare centres over the period of 1 January 2019 to 1 January 2020. Data were obtained on 76 103 service personnel (SP) (53% of the UKAF).

RESULTS

The overall syncope case rate for the UKAF was 10.5 per 1000 person-years (p-yrs). In comparing services there was a significantly increased risk of syncope in the British Army (10.7 per 1000 p-yrs) compared with the Royal Air Force (8.6 per 1000 p-yrs) (p=0.0365), SP who served overseas (16.7 per 1000 p-yrs) in comparison with UK medical centres (10.3 per 1000 p-yrs) (p<0.0001), and British Army units that regularly took part in State Ceremonial and Public Duties (15.8 per 1000 p-yrs vs 10.2 per 1000 p-yrs) (p=0.0035). Army training units conferred a significantly reduced risk of syncope (p<0.0001).

CONCLUSIONS

These data are the first to define the incidence and prevalence of syncope in the UKAF. Orthostasis and heat are probable triggers, although recruits are potentially protected. These data offer opportunities to improve the health and well-being of SP, with economic, logistical and reputational benefits for the UKAF. Further research to identify personnel at risk of future syncopal events may allow for targeted use of countermeasures.

The effect of water temperature on orthostatic tolerance: a randomised crossover trial

Purpose

Bolus water drinking, at room temperature, has been shown to improve orthostatic tolerance (OT), probably via sympathetic activation; however, it is not clear whether the temperature of the water bolus modifies the effect on OT or the cardiovascular responses to orthostatic stress. The aim of this study was to assess whether differing water temperature of the water bolus would alter time to presyncope and/or cardiovascular parameters during incremental orthostatic stress.

Methods

Fourteen participants underwent three head-up tilt (HUT) tests with graded lower body negative pressure (LBNP) continued until presyncope. Fifteen minutes prior to each HUT, participants drank a 500 mL bolus of water which was randomised, in single-blind crossover fashion, to either room temperature water (20 °C) (ROOM), ice-cold water (0–3 °C) (COLD) or warm water (45 °C) (WARM). Cardiovascular parameters were monitored continuously.

Results

There was no significant difference in OT in the COLD (33 ± 3 min; p = 0.3321) and WARM (32 ± 3 min; p = 0.6764) conditions in comparison to the ROOM condition (31 ± 3 min). During the HUT tests, heart rate and cardiac output were significantly reduced (p < 0.0073), with significantly increased systolic blood pressure, stroke volume, cerebral blood flow velocity and total peripheral resistance (p < 0.0054), in the COLD compared to ROOM conditions.

Conclusions

In healthy controls, bolus cold water drinking results in favourable orthostatic cardiovascular responses during HUT/LBNP without significantly altering OT. Using a cold water bolus may result in additional benefits in patients with orthostatic intolerance above those conferred by bolus water at room temperature (by ameliorating orthostatic tachycardia and enhancing vascular resistance responses). Further research in patients with orthostatic intolerance is warranted.

Association of Occupational Distress and Low Sleep Quality with Syncope, Presyncope, and Falls in Workers

Syncope and presyncope episodes that occur during work could affect one's safety and impair occupational performance. Few data are available regarding the prevalence of these events among workers. The possible role of sleep quality, mental stress, and metabolic disorders in promoting syncope, presyncope, and falls in workers is unknown. In the present study, 741 workers (male 35.4%; mean age 47 ± 11 years), employed at different companies, underwent clinical evaluation and blood tests, and completed questionnaires to assess sleep quality, occupational distress, and mental disorders. The occurrence of syncope, presyncope, and unexplained falls during working life was assessed via an ad hoc interview. The prevalence of syncope, presyncope, and falls of unknown origin was 13.9%, 27.0%, and 10.3%, respectively. The occurrence of syncope was associated with an increased risk of occupational distress (adjusted odds ratio aOR: 1.62, confidence intervals at 95%: 1.05-2.52), low sleep quality (aOR: 1.79 CI 95%: 1.16-2.77), and poor mental health (aOR: 2.43 CI 95%: 1.52-3.87). Presyncope was strongly associated with occupational distress (aOR: 1.77 CI 95%: 1.25-2.49), low sleep quality (aOR: 2.95 CI 95%: 2.08-4.18), and poor mental health (aOR: 2.61 CI 95%: 1.78-3.84), while no significant relationship was found between syncope or presyncope and metabolic syndrome. These results suggest that occupational health promotion interventions aimed at improving sleep quality, reducing stressors, and increasing worker resilience might reduce syncope and presyncope events in the working population.

Heat Adaptation in Military Personnel: Mitigating Risk, Maximizing Performance

The study of heat adaptation in military personnel offers generalizable insights into a variety of sporting, recreational and occupational populations. Conversely, certain characteristics of military employment have few parallels in civilian life, such as the imperative to achieve mission objectives during deployed operations, the opportunity to undergo training and selection for elite units or the requirement to fulfill essential duties under prolonged thermal stress. In such settings, achieving peak individual performance can be critical to organizational success. Short-notice deployment to a hot operational or training environment, exposure to high intensity exercise and undertaking ceremonial duties during extreme weather may challenge the ability to protect personnel from excessive thermal strain, especially where heat adaptation is incomplete. Graded and progressive acclimatization can reduce morbidity substantially and impact on mortality rates, yet individual variation in adaptation has the potential to undermine empirical approaches. Incapacity under heat stress can present the military with medical, occupational and logistic challenges requiring dynamic risk stratification during initial and subsequent heat stress. Using data from large studies of military personnel observing traditional and more contemporary acclimatization practices, this review article (1) characterizes the physical challenges that military training and deployed operations present (2) considers how heat adaptation has been used to augment military performance under thermal stress and (3) identifies potential solutions to optimize the risk-performance paradigm, including those with broader relevance to other populations exposed to heat stress.