Review article: Environmental heatstroke and long‐term clinical neurological outcomes: A literature review of case reports and case series 2000–2016

Abstract

Global temperatures are rising; extreme environmental heat can result in adverse health effects including heatstroke. Acute effects of heat are well recognised, but there is less understanding of potential long-term adverse outcomes. Our aim was to review recent medical literature for clinical cases of environmental heatstroke with a focus on neurological outcome. Structured search strategies were designed to retrieve publications of heatstroke case reports using Ovid Medline and Embase (2000-2016). One thousand and forty-nine abstracts were identified, and after application of exclusion criteria 71 articles deemed relevant. Ninety cases were identified from 71 articles. 100% presented with acute neurological symptoms; 87.8% presented with non-neurological symptoms. 44.4% patients recovered fully, 23.3% died, 23.3% suffered convalescent or long-term neurological sequelae, and in 8.9% no long-term follow up was available. 57.1% of the patients who died or had a neurological deficit had no documented co-morbidity. Patterns of neurological deficits included 66.7% patients with motor dysfunction, 9.5% cognitive impairment, 19% both motor and cognitive impairment and 4.7% other. In total 71.4% of the impaired patients had long-term cerebellar dysfunction. Adverse long-term neurological outcomes were common in surviving patients presenting with environmental heatstroke. Permanent neurological deficits were present in 34.4% of survivors where outcome was known; many were young, healthy individuals. Cerebellar injury was common suggesting cerebellar structures are vulnerable to heat. These findings highlight that people of all ages and pre-morbid states are at risk of severe heat-related illness. In the face of climate change, effective interventions for heat-related illness, including both treatment and prevention are necessary.

Long-Term Cardiovascular Diseases of Heatstroke: A Delayed Pathophysiology Outcome

“…A decrease in functional status at two years follow up, resulting in the need for elderly institution care, has also been reported in NEHS patients [8] . These outcomes are in line with other studies that have also shown that the cerebellum is particularly susceptible to heat cytotoxicity leading to permanent damage [7,9]. Myocardial dysfunction in HS hospitalized patients has been reported, with elevated cardiac troponin levels representing myocardial damage [10][11][12][13].…”

“…The combination of heat cytotoxicity and the body's inflammatory and coagulation pathways response leads to multiple organ dysfunction, including encephalopathy, rhabdomyolysis, acute kidney injury, hepatic injury, circulatory failure, cardiac injury and disseminated intravascular coagulopathy (DIC) [3] . In a recent review of persistent neurological impairment in HS patients, Lawton et al found cerebellar dysfunction in 35% of survivors, consisting of cerebellar dysarthria and ataxia, with some patients in a coma for up to two years [7] . A decrease in functional status at two years follow up, resulting in the need for elderly institution care, has also been reported in NEHS patients [8] .…”

The association between heat stroke and subsequent cardiovascular diseases

“…Brain tissue is vulnerable to heat [28]. Almost all patients with HS experienced acute neurological disturbances, and up to 23.3% of the HS patients suffered long-term neurological sequelae [8]. The patterns of neurological deficits included motor dysfunction in 66.7% of the patients, cognitive impairment in 9.5% and both motor and cognitive impairment in 19%.…”

“…The patterns of neurological deficits included motor dysfunction in 66.7% of the patients, cognitive impairment in 9.5% and both motor and cognitive impairment in 19%. Long-term cerebellar dysfunction was found in 71.4% of those HS patients [8]. A previous study indicated that AIS was also increased after a critical illness, such as sepsis [29].…”

“…Heat stroke (HS) is the most severe HRI and has been defined as a patient with profound central nervous system abnormalities and severe hyperthermia (core temperature typically but not always > 40°C) [7]. HS is associated with high mortality, and survivors may retain chronic neurological sequelae [8].…”