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Exertional heat illness in half marathon runners: experiences of the Great North Run
  1. Rachel Hawes1,
  2. Jeni McMorran2,
  3. Chris Vallis3,4
  1. 1Critical Care & PHEM, Northern Deanery, Newcastle upon Tyne, UK
  2. 2High Dependency Unit, Newcastle General Hospital, UK
  3. 3Royal Victoria Infirmary, Newcastle upon Tyne, UK
  4. 4BUPA Great North Run, Newcastle upon Tyne, UK
  1. Correspondence to Dr Rachel Hawes, Anaesthetic Department, Cheriton House, James Cook University Hospital, Marton Road, Middlesbrough, UK; rachelhawes{at}doctors.org.uk

Abstract

Exertional heat illness is a potentially fatal condition. Large numbers of competitors in the Great North Run are affected annually. This article briefly discusses the patient demographics, presentation and treatment of large numbers of patients with a simple, effective regime.

  • Environmental medicine
  • environmental medicine
  • expedition medicine
  • mass gathering medicine
  • military
  • nursing
  • pre-hospital

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Introduction

Exertional heat illness is a well described phenomenon in the prehospital environment in military and sporting events.1 It is defined as a core temperature >40°C 10 min after cessation of exercise, and covers a broad range of clinical conditions from minor heat cramps and symptoms of lethargy to severe heat exhaustion, multiple organ failure and death.

The pathophysiology of hyperthermia is well understood2–4 but the evidence base around its treatment is still limited.5 Severe heat illness is a poorly documented problem in half marathons and presents a different biochemical profile to full marathon runners.6

The BUPA Great North Run (GNR) is the world's largest half marathon with over 54 000 entrants annually. The GNR medical team has extensive experience in managing hyperthermic athletes using a simple but effective system. The treatment pathway and availability of near patient biochemistry testing has had a crucial impact on minimising the need for emergency department attendance. The vast majority of athletes are treated successfully on location and very few require hospital admission.

Description of the GNR

The GNR is a unidirectional, half marathon open to adult runners of all standards. The course is roughly west to east, and due to time of year held and geographical location the maximum temperatures rarely peak above 18°C.

Entrants receive pre-event information on health, training and circumstances in which they should not run. New runners and those with existing medical conditions are advised to take advice from their GP.

Medical set-up

As most collapses occur within the final 2 km, the Field Hospital is situated at the finish line. On arrival, runners are immediately triaged by Paramedics using a system based on major incident medical management and support (MIMMS).7

Teams are arranged to receive large numbers of patients in rapid succession, each team consisting of six medical and nursing personnel overseeing three trolleys, set out in a star formation with the heads together. This allows for accommodation of patients admitted in sequence in different stages of treatment.

As water is involved in cooling, electrical equipment is minimal and patient monitoring is based on clinical examination and mercury rectal thermometers, the most accurate measure of core temperature in the prehospital setting.8 Three resuscitation bays are equipped to an emergency department standard for patients that do not respond rapidly to initial treatment or require additional support.

The Physiotherapy team treat the severe muscle cramps that accompany reperfusion of lower limbs.

Treatment

Management involves an ‘airway, breathing, circulation’ (ABC) approach, insertion of a large bore intravenous cannula and venous blood sampling9 for serum electrolytes and glucose. Infusion of 1L of 0.9% saline occurs concomitantly with removal of clothing and copious tepid sponging.

Cooling ceases at 39°C to avoid ‘overshoot’. This phase typically takes 30 min. Patients rarely need more than 2000 ml of intravenous fluids to replace their depleted volume.

Observations continue until the Glasgow Coma Score (GCS) has returned to 15 and cardiorespiratory parameters are within normal limits. If recovery is not complete within 2 h, hospital admission is arranged.

Most patients are discharged to the recovery area within 60 min of arrival and discharged home, accompanied, within 2 h.

Numbers

In 2009, 55 runners in similar male to female proportions were admitted to the Field Hospital with core temperatures >41°C. All but four were discharged home within 2 h. These were admitted to hospital and discharged within 24 h.

Nearly all patients with core temp >41°C had some cognitive dysfunction and delirium was common. This was transitory in the majority but, rarely, has been severe, requiring sedation. Diarrhoea and muscle cramps occurred frequently on cooling and reperfusion. There has never been a death or intensive care unit (ICU) admission from hyperthermia.

Runners invariably have high/normal serum sodium and haematocrit (>50%), suggesting dehydration. Hyponatraemia is an anomalous finding. Bicarbonate is low and anion gap demonstrates a metabolic acidosis.

Long-term follow-up has been difficult as race entrants travel from around the UK and internationally and submission of general practitioner (GP) details is voluntary.

Discussion

The proportion of heat illness to runners is the highest in all UK half marathons and several factors are postulated. The course follows the same direction as the prevailing wind. Its evaporative and cooling effects are therefore diminished, compounded by the ‘mass effect’ created by the large numbers of entrants, resulting in a packed course and reduced airflow between runners.

The majority of patients with hyperthermia were not fun runners nor elite athletes but well prepared club runners, who possibly overexert themselves trying to achieve a personal best, overheat, lose decision-making ability and the situation deteriorates.

During the course of a half marathon, runners have insufficient time to drink enough water to become hyponatraemic, which limits their metabolic derangement and perhaps facilitates the rapid recovery times.

Conclusions

We have found the above method to be simple, safe, effective, minimising the need for ED attendance and easily reproducible with minimal resources in the prehospital environment.

References

Footnotes

  • Competing interests None.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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