Heat syncope, or fainting due to heat, can be concerning. Learn its causes, prevention, and first aid tips. Expert advice at Meri Sehat.

Heat Syncope

Humza Khizer

Overview

People of the subcontinent are no strangers to heat and its effects. Heat-related illnesses, such as heat cramps, heat exhaustion, heat syncope, and dehydration frequently plague thousands across Pakistan and India. In 2015, Karachi, Pakistan, experienced its first heat epidemic. The heat spell caused a city-wide emergency, resulting in more than 1200 deaths over just 4 days<a href="#accordion">[1]</a>. Whereas, in India, 1,000 additional deaths were reported in Ahmedabad due to the extreme heat in 2010[1]. With the fast-approaching climate change, the mortality and morbidity rates of heat-related illnesses are expected to increase further. In the past two decades, a 50% increase in heat-related deaths has been reported among adults aged 65 years and older<a href="#accordion">[4]</a>. In 2018, an estimated 296,000 people died from extreme heat exposure worldwide<a href="#accordion">[4]</a>. 
&nbsp;

Research states heat waves as the second major cause of weather-related morbidity and mortality globally<a href="#accordion">[1]</a>. As per the latest publication by the United States Institute of Peace (USIP), the inevitable climate change has increased the severity of heat waves across Asia<a href="#accordion">[2]</a>. In 2022, both Pakistan and India reported a record 45 degrees Celsius - the highest ever in more than 100 years[2]. Moreover, China, Thailand, and Myanmar also broke all-time high records with temperatures rising above 40 degrees.

However, Asia is not the only victim. Heat emergencies pose a similar threat across the United States and countries in Western Europe. In the United States, there are an average of 702 heat-related deaths per year<a href="#accordion">[3]</a>. While more than 9,000 hospitalizations each year are due to heat[3].

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Due to climate change, extreme heat is now considered a growing public health concern. Especially, in low-income countries such as Pakistan where there are inadequate resources and finances for implementing heat-related emergency prevention strategies. The country currently ranks 7th on the list of top 10 countries with a 30.5 climate risk index score<a href="#accordion">[1]</a>. Karachi, in particular, is at high risk for heat-related emergencies due to urbanization and limited greenery. Between 2006 and 2015, temperatures in the city rose to 45&deg;Celsius between May and July, and the daily average humidity ranged between 30-95%<a href="#accordion">[1]</a>.

The high heat index coupled with high humidity is a common factor in the increased incidence of heat-related illnesses. 
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Heat syncope is a type of heat-related illness characterized by the loss of consciousness. The fainting episode occurs from exposure to high temperatures combined with <a href="https://merisehat.pk/disease/dehydration">dehydration</a>. Also called orthostatic dizziness, heat syncope is associated with the following signs and symptoms:

<ul>
	<li>Sweaty skin</li>
	<li>Tunnel Vision</li>
	<li>Low blood pressure</li>
	<li>Weak or decreased pulse</li>
	<li>Dizziness</li>
	<li>Light-headedness on change in position (e.g., when rising from a sitting position or standing too long)</li>
	<li>Fainting 
	&nbsp;</li>
</ul>

Furthermore, due to the syncope causing a loss of consciousness and dizziness, patients are at a higher risk of injury from falling.

Unlike people suffering from heat stroke or heat exhaustion, patients with heat syncope have an average body temperature. 
&nbsp;

Causes

The human body cools itself via conduction, radiation, convection, and evaporation. To increase the loss of heat through the skin, the small blood vessels present in the skin dilate. However, the continued dilation of blood vessels limits the blood supply to the brain. Thus, resulting in light-headedness and syncope. This commonly occurs when the patient has been standing for long periods, or from a sudden change in position, e.g., suddenly rising from a lying or sitting position in the heat. 
&nbsp;

Individuals who are not used to high temperatures and the elderly are more at risk of developing heat syncope. Other factors that increase the risk include:

<ul>
	<li>Occupations that require working outdoors, e.g., laborers</li>
	<li>Wearing heavy equipment (e.g. firefighting gear) during hot temperature</li>
	<li>Standing for long periods</li>
	<li>Exercising under direct sunlight</li>
	<li>Dehydration</li>
	<li>Alcohol</li>
	<li>Caffeine</li>
	<li>Pre-existing medical conditions e.g. <a href="https://merisehat.pk/disease/diabetes-type-1-and-2">Diabetes</a> 
	&nbsp;</li>
</ul>

Treatment

Most people suffering from heat syncope usually recover within 10 to 15 minutes with minor treatment and monitoring. First aid measures for heat syncope include the following:

<ul>
	<li>Follow the ABCs (Airway, Breathing, Circulation).</li>
	<li>Move the person to a cool or shaded area and make them sit or lie down.</li>
	<li>Make the person slowly slip juice, water, or an energy drink (with no caffeine).</li>
	<li>Remove any tight or extra clothing.</li>
	<li>If the person is unconscious, raise their legs to promote blood circulation to the heart.</li>
	<li>Monitor the patient&#39;s vitals. 
	&nbsp;</li>
</ul>

Individuals unacclimatized to high temperatures are at risk of developing heat syncope. Therefore, it is advised that they slowly acclimatize to exercising in the heat over 2 weeks by progressively increasing the intensity and duration of physical activity.

&nbsp;

The following measures can further help prevent heat syncope.

<ul>
	<li>Staying hydrated before and during exercise.</li>
	<li>Quitting alcohol.</li>
	<li>Avoiding caffeine.</li>
	<li>Wearing loose, light clothing in hot weather.</li>
	<li>Exercising during the cooler part of the day. 
	&nbsp;</li>
</ul>

Conclusion

Majority of Pakistan&rsquo;s population from the low socioeconomic class lives in small, overcrowded houses with a lack of water and electricity. Moreover, there is a lack of accessible and affordable healthcare services in the country. All these factors contribute to the high morbidity and mortality of heat-related illnesses in Pakistan. Many researchers suggest the implementation of a community-based approach to address this heat mortality and morbidity. One such intervention is the Heat Emergency Awareness and Treatment (HEAT) intervention.

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The HEAT intervention involves spreading awareness among communities, especially low-income households about the symptoms, risk factors, preventive measures, early signs, dietary modifications, and steps to manage possible heat illness.

A combination of community-based awareness sessions and heat wave preparedness plans is key to reducing the prevalence of heat-related illnesses in the country. 
&nbsp;

Key Points

<ul>
	<li>Due to climate change, extreme heat is now considered a growing public health concern.</li>
	<li>Heat-related illnesses, such as heat cramps, heat exhaustion, heat syncope, and dehydration frequently plague thousands across Pakistan and India.</li>
	<li>The high heat index coupled with high humidity is a common factor in the increased incidence of heat-related illnesses.</li>
	<li>Heat syncope is a type of heat-related illness characterized by the loss of consciousness.</li>
	<li>To increase the loss of heat through the skin, the small blood vessels in the skin dilate. However, the continued dilation of blood vessels limits the blood supply to the brain. Thus, resulting in light-headedness and syncope.</li>
	<li>Most people suffering from heat syncope usually recover within 10 to 15 minutes with minor treatment and monitoring.</li>
	<li>Individuals who are not used to high temperatures and the elderly are more at risk of developing heat syncope.</li>
	<li>A combination of community-based awareness sessions and heat wave preparedness plans is key to reducing the prevalence of heat-related illnesses in the country. 
	&nbsp;</li>
</ul>

[1] Khan UR, Ahmed N, Naeem R, et al. Heat Emergencies: Perceptions and Practices of Community Members and Emergency Department Healthcare Providers in Karachi, Pakistan: A Qualitative Study. Int J Environ Res Public Health. 2021;18(9):4736. Published 2021 Apr 29. doi:10.3390/ijerph18094736.

[2] How heat waves are destabilizing Asia. United States Institute of Peace.

[3] Heat & Health tracker. Centers for Disease Control and Prevention.

[4] Razzak JA, Agrawal P, Chand Z, Quraishy S, Ghaffar A, Hyder AA. Impact of community education on heat-related health outcomes and heat literacy among low-income communities in Karachi, Pakistan: a randomised controlled trial. BMJ Glob Health. 2022;7(1):e006845. doi:10.1136/bmjgh-2021-006845.