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 Table of Contents  
Year : 2021  |  Volume : 7  |  Issue : 4  |  Page : 220-225

The effects of temperature and outcomes of patients presenting to the emergency department with heat-related illness: A retrospective cross-sectional study

1 Department of Emergency Department, Christian Medical College, Vellore, Tamil Nadu, India
2 Department of Radio Diagnosis, Christian Medical College, Vellore, Tamil Nadu, India

Date of Submission18-Jul-2020
Date of Acceptance20-Nov-2020
Date of Web Publication24-Dec-2021

Correspondence Address:
Dr. Kundavaram Paul Prabhakar Abhilash
Department of Emergency Medicine, Christian Medical College, Vellore - 632 004, Tamil Nadu
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/IJAM.IJAM_97_20

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Introduction: In a tropical country like India, heat-related illnesses are a common occurrence in the unforgiving summer months. Our study aimed to study the profile and outcome of patients with heat-related illnesses presenting to the emergency department (ED).
Materials and Methods: This retrospective, cross-sectional study included all patients with heat-related illnesses to the ED during the months of April, May, and June of 2016. Baseline demographic characteristics, computed tomography (CT) brain findings, and hospital outcome were noted.
Results: During the 3-month study period, 72 patients presented with heat-related illnesses. Two-thirds (46/72: 63.8%) suffered from heat stroke, whereas one-third (26/72: 36.2%) had heat exhaustion. Classical and exertional types were seen in 46% and 54% of heat strokes, respectively. The mean age (standard deviation) of the patients was 59.7 (13.3) years with a male preponderance (56.9%). Homemakers (37.5%) and manual laborers (20.8%) were most commonly affected. Hypotension at ED arrival was noticed in 20.8% (15/72), whereas tachycardia and tachypnea were noted in 80.5% (58/72) each. The findings on CT of the brain included acute infarcts (5/26: 19.6%) and an intra-cranial bleed (1/26: 3.8%). The mortality rate was 19.5% (14/72).
Conclusion: Heat-related illnesses cause significant mortality during the relentless hot summers of a tropical country like India. Homemakers and manual labors were the most affected group. Acute changes were seen in CT brain of a quarter of patients with heat stroke.
The following core competencies are addressed in this article: Patient care, Systems-based practice, Medical knowledge, Practice-based learning and improvement.

Keywords: Emergency department, heat exhaustion, heat-related illnesses, heat stroke

How to cite this article:
Raju F, Biju AC, Gunasekaran K, Mannam PR, George K, Abhilash KP. The effects of temperature and outcomes of patients presenting to the emergency department with heat-related illness: A retrospective cross-sectional study. Int J Acad Med 2021;7:220-5

How to cite this URL:
Raju F, Biju AC, Gunasekaran K, Mannam PR, George K, Abhilash KP. The effects of temperature and outcomes of patients presenting to the emergency department with heat-related illness: A retrospective cross-sectional study. Int J Acad Med [serial online] 2021 [cited 2023 Jun 4];7:220-5. Available from: https://www.ijam-web.org/text.asp?2021/7/4/220/333411

  Introduction Top

Heat-related illness (HRI) includes a broad spectrum of syndromes arising due to the disruption of the normal body thermoregulation due to exposure to high environmental heat. HRI mainly includes heat stroke, heat exhaustion, and heat cramps.[1],[2] The core pathophysiology is consequent to failure of thermoregulation at the level of the hypothalamus and is induced by extreme environmental heat. Severe HRIs (heat stroke and heat exhaustion) are characterized by hyperthermia, defined as the elevation of core body temperature above the normal range of 36°C–37.5°C.[1],[3],[4] It is important to differentiate this elevation of core body temperature from fever, which is a result of cytokine activation due to inflammation.[4] Heat cramps, characterized by brief episodes of cramps after exertion in a hot environment is an innocuous type at the lower end of the HRI spectrum.

A heat wave is a prolonged period of unusually and excessively hot weather, which may also be accompanied by high humidity.[5] The Indian subcontinent experiences relentless heat waves every summer.[6] A major heat wave that hit India in 2016 during the months of April and May during caused a record high temperature of 51.0°C (123.8°F) in the town of Phalodi, in the state of Rajasthan.[6] Over a 100 people died with more than a million affected by some degree of heat-related illness in many parts of the country, including Vellore, a city in North Tamil Nadu.[3] Heat waves causing heat stroke and other HRIs are not restricted to the tropical countries. There have been reports of heat stroke and heat-related deaths in as North as Chicago.[7],[8],[9] This is a common condition in the Middle East where many pilgrims to the Haj are affected every year.[10] There have been reports of heat-related deaths from Karachi and Nanjing, China too.[11],[12]

Most studies from India have described the entity of “heat stroke” alone; hence, we embarked on this study to describe the profile and outcome of the complete cohort of patients with severe HRI to the emergency department (ED). Description of acute radiological findings on computed tomography (CT) of the brain was another important objective of our study.

  Methodology Top

This was a retrospective, descriptive study conducted in the adult ED of a large tertiary care hospital in South India, which with 2,700 inpatient beds. The adult ED has 49 beds with about 75,000 admissions annually. This study was approved by the Institutional Review Board (IRB Min. No.10623 dated April 3, 2017) of Christian Medical College, Vellore, and patient confidentiality was maintained using unique identifiers and by password protected data entry software with restricted users. The manuscript strictly adheres to the STROBE guidelines.

Adults presenting with HRI, presenting during the period of April 2016 to May 2016 were included in the analysis. Heat stroke was defined as patients with core temperature >40°C (104°F) with the signs of central nervous system (CNS) dysfunction and exposure to environmental heat. Patients with exposure to environment heat with core temperature between 37°C and 40°C and normal mental status were considered to have heat exhaustion. Children and adolescents below 18 years of age were excluded. Data were retrieved from our electronic medical records called clinical work station, designed and maintained by the Medical Information Technology Department of Christian Medical College, Vellore. Details of history (age, sex, occupation, and comorbidities) and physical examination findings (rectal temperature, pulse rate, blood pressure, respiratory rate, and saturation) and demographic details were recorded on a standard data collection sheet. Other variables included sequential organ failure assessment (SOFA) score, occupation, triage priority, and outcome. Priority 1 included patients with airway, breathing and circulation compromised, core temperature ≥104°F, Glasgow Coma Scale <8, and exposure to severe environmental heat. Priority 2 included patients with airway, breathing and circulation is not compromised, dyspnea, high core temperature, and history of exposure to heat. All patients underwent laboratory tests (complete blood count, serum electrolytes, liver function test, serum creatinine, creatinine phosphokinase [CPK], and blood culture) as per the protocol of evaluation of patients of HRI in the ED. Relevant radiological tests such as CT of the brain were performed when required as per the decision of the treating physician. This was a retrospective, cross-sectional study, and therefore, we could not control exposure or outcome assessment, and instead relied on others for accurate record-keeping.

Based on a previous study by Dhainaut et al., assuming a mortality rate of 25%, and a precision of 5, using the formula 4pq/d2, the sample size was calculated to be 75.[13] The data were analyzed using the Statistical Package for the Social Sciences (IBM Corp. Released 2015. IBM SPSS, version 23.0, Armonk, NY). Continuous variables are presented as mean (standard deviation [SD]). Categorical and nominal variables are presented as percentages.

  Results Top

During the 2-month study period, the ED attended to 11,210 patients with 72 patients being HRI. Two thirds (46/72: 63.8%) suffered from heat stroke while one third (26/72: 36.2%) had heat exhaustion [Figure 1]. Classical and exertional types were seen in 46% (21/46) and 54% (25/46) of heat strokes, respectively. The mean (SD) age of the patients was 59.7 (13.3) years with a male preponderance (56.9%). Homemakers (37.5%) and manual laborers (20.8%) were most commonly affected [Table 1]. Hypotension at ED arrival was noticed in 20.8% (15/72), whereas tachycardia and tachypnea were noted in 80.5% (58/72) each. The severity at presentation was assessed by SOFA score. SOFA score of more than 5 was seen in 41.7% of patients [Table 1]. The leukocytosis was seen in 80.5% (53/72). 34.7% had serum creatinine >1.4 mg/dL indicating renal failure. Other laboratory investigations are shown in [Table 2]. The findings on CT of the brain included acute infarcts (5/26: 19.6%) and an intra-cranial bleed (1/26: 3.8%), as shown in [Table 2]. The number of patients presenting with HRI in relation to the daily temperature recorded in Vellore city is shown in [Figure 2]. The hospital outcome of heat stroke (classical and exertional types) and heat exhaustion is shown in [Table 3]. The overall in-hospital mortality rate was 19.5% (14/72). We performed a bivariate analysis for factors associated with mortality. However, age ≥60 years, male sex, exertional type of heat stroke, comorbidities such as diabetes, hypertension, and high-SOFA score were not statistically significant predictors of outcome [Table 4].
Figure 1: STROBE diagram

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Table 1: Baseline characteristics, examination findings and severity

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Table 2: Laboratory parameters and radiological findings

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Table 3: Hospital outcome of heat stroke and heat exhaustion

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Table 4: Bivariate analysis of factors associated with mortality (n=69)*

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Figure 2: Number of patients in relation to the maximum daily temperature of Vellore city

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  Discussion Top

Our study showed the profile and outcome of patients who presented to the ED with HRI during the heat wave period in 2016. Key findings of our study were that homemakers and manual labors were the most affected. CT brain findings of acute infarcts and bleed in one-fifth of patients on who an imaging of the brain was performed are another important feature of our study.

Our city, Vellore, being one of the hottest places in North Tamil Nadu has a high incidence of HRI during the unforgiving summer months of April and May. In our study, the higher mean age of patients (59.7 years) suggests the vulnerable group of patients to HRI. This vulnerable age group finding is consistent with other studies done on heat wave-related hospital admissions.[7],[14],[15] The male-to-female ratio of our study population (2:1) is predictable since, in a patriarchal society like India, men tend to do more laborious physical work outside and thus get directly exposed to the sun. However, distribution of occupation in our study suggests homemakers too being at a high risk of HRI. The reason of this finding can be attributed to the fact that these women work in equally hot environment of the kitchen in the confines of home without air-conditioning facilities also, age, other comorbidities, and ventilation in the house probably have a significant role in triggering episodes of HRI that require hospital admission.

Data on acute findings on CT brain among patients with HRI is scant. The CT imaging findings of our patients suggests the extent of involvement of CNS with acute infarct and intracranial bleed in a fifth of patients on whom imaging was performed. However, CNS imaging was not done on all patients it was left to the discretion of the treating physician. A larger sample of patients with CT brain being done would give us a better understanding of the true extent of pathological damage sustained by the brain.

In our study, a significant proportion of patients had leukocytosis, acute renal failure, and elevated levels of CPK and liver enzymes. Varghese et al. showed high levels of CPK (.1000 IU/l), metabolic acidosis, and elevated liver enzymes to be predictors of mortality among patients requiring intensive care unit admission.[16] A recent study by Sankar et al. too showed elevated liver enzymes, deranged renal parameters, electrolyte abnormalities (hyponatremia and hypokalemia) to be significant findings among patients admitted with HRI.[17]

We found a notable increase in the number of HRI patient admitted in the ED with increase in the average and peak temperature recordings in our area. Extremes of climate changes are known to have significant adverse events on health, with extreme high temperature wreaking havoc in tropical countries like India.[18] Hence, it is imperative for all, especially the vulnerable groups to take precautions to prevent dehydration that would eventually precipitate HRI. Public awareness of the warning symptoms and provision of hydration facilities by the roadside and at workplaces by the relevant authorities goes a long way in preventing deleterious health consequences of extreme heat.

Heat stroke can be considered as a potentially life-threatening condition if not treated with adequate cooling measures, which remain the cornerstone of therapy. Evaporative and conductive methods of cooling with water spray, ice packs, infusion of intravenous fluids in combination rapidly lowers the core temperature in a conducive, cool environment. There is no clarity on the superiority of one cooling method over another, but a combination of cooling measures is widely employed in most places.[19],[20] Future research must be directed toward finding the optimal combination of cooling techniques that would decrease the mortality rate of HRI.

Our study has certain limitations. The low sample size of HRI and that of radiological imaging being some of them. Missing charts are another limitation of our retrospective study. Nevertheless, our study provides a detailed understanding on the profile and outcome of patients with HRI and shows the correlation of the temperature levels with the incidence of HRI.

  Conclusion Top

Heat-related illnesses cause significant mortality during the relentless hot summers of a tropical country like India. Homemakers and manual labors were the most affected group. Acute changes were seen in CT brain of a quarter of patients with heat stroke. There was a direct correlation between the daily maximum temperature in our city and the number of patients with HRI. Hence, we recommend adequate preventive measures like hydration and cooling measures in the blistering heat of tropical summers to prevent this lethal condition.

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Conflicts of interest

There are no conflicts of interest.

Research quality and ethics statement

The authors of this manuscript declare that this scientific work complies with reporting quality, formatting and reproducibility guidelines set forth by the EQUATOR Network. The authors also attest that this clinical investigation was determined to require Institutional Review Board/Ethics Committee review, and the corresponding protocol/approval number is IRB Min. No.10623 dated 03.04.17. We also certify that we have not plagiarized the contents in this submission and have done a Plagiarism Check.

  References Top

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  [Figure 1], [Figure 2]

  [Table 1], [Table 2], [Table 3], [Table 4]


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