Current and Future Burdens of Heat-Related Hyponatremia: A Nationwide Register-Based Study

Dysnatremia in a changing climate: A global systematic review of the association between serum sodium and ambient temperature

OBJECTIVE

Both hyponatremia and hypernatremia have been reported to occur more frequently with higher ambient temperatures, although the underlying mechanisms are not well understood. Global temperatures are rising due to climate change, which may impact the incidence of dysnatremia worldwide. We aimed to identify, collate and critically appraise studies analyzing the relationship between climate measures (outdoor temperature, humidity) and serum sodium concentrations.

DESIGN

Systematic review, reported in accordance with PRISMA guidelines.

METHODS

MEDLINE and Embase were searched with relevant key terms. Studies assessing the effect on serum sodium measurement of elevated temperature or humidity versus a comparator were included.

RESULTS

Of 1466 potentially relevant studies, 34 met inclusion criteria, originating from 23 countries spanning all inhabited continents. The majority (30 of 34, 88%) reported a significant association between outdoor temperature and dysnatremia, predominantly lower serum sodium with increased ambient temperature. Humidity had a less consistent effect. Individuals aged above 65 years, children, those taking diuretics and antidepressants, those with chronic renal impairment or those undertaking physical exertion had increased vulnerability to heat-associated dysnatremia. The risk of bias was assessed to be high in all but four studies.

CONCLUSIONS

Higher ambient temperature is consistently associated with an increased incidence of hyponatremia. We infer that hyponatremia presentations are likely to rise with increasing global temperatures and the frequency of extreme heat events secondary to climate change. Evidence-based public health messages, clinician education and reduction in fossil fuel consumption are necessary to reduce the expected burden on healthcare services worldwide.

Assessment of 24 h Sodium and Potassium Urinary Excretion in Normotensive and Hypertensive Dominican Adults

Higher salt (sodium) intake has been associated with higher blood pressure (BP). The degree of association may be influenced by factors such as age, origin, and dietary components. This study aimed to evaluate the 24 h urinary sodium (Na) and potassium (K) excretion in normotensive and hypertensive Dominican adults and estimate their salt intake. 163 volunteers (18-80 years old) participated in a cross-sectional study. The 24 h Na and K urinary excretion were measured using an ion-selective electrode technique. Na and K urinary excretion (99.4 ± 46.5 and 35.0 ± 17.5 mmol/24 h) did not correlate with BP, except in the normotensive group, in which K correlated with SBP (0.249, p = 0.019). Na and K excretion were similar in normotensive and hypertensive subjects. When considering two age groups (18-45, 46-80 years), the Na-to-K molar ratio (3.1 ± 1.3) was higher in younger subjects (p = 0.040). Na-to-K ratio was associated with DBP in the total group (r = 0.153, p = 0.052), in the hypertensive group (r = 0.395, p < 0.001), and in the older group with SBP (0.350, p = 0.002) and DBP (0.373, p < 0.001). In the older group, Na-to-K ratio and DBP correlated after controlling for subjects with hypertension controlled by treatment (r = 0.236, p = 0.041). The Na-to-K ratio correlated, when salt intake was over 5 g/day (52.2%), with SBP (rho = 0.219, p = 0.044) and DBP (rho = 0.259, p = 0.017). Determinants of BP in the total sample were age (SBP, beta: 0.6 ± 0.1, p < 0.001; DBP, beta: 0.2 ± 0.1, p < 0.002), sex (SBP, beta: 11.2 ± 3.5, p = 0.001), body mass index (BMI) (SBP, beta: 1.0 ± 0.3, p < 0.001; DBP, beta: 0.4 ± 0.2, p = 0.01), and Na-to-K ratio (SBP, beta: 3.0 ± 1.1, p = 0.008; DBP, beta: -12.3 ± 4.0, p = 0.002). Sex and BMI were determinants in the younger group. Na-to-K molar ratio was determinant in the older group (SBP, beta: 6.7 ± 2.4, p = 0.005; DBP, beta: 3.8 ± 1.1, p < 0.001). The mean Na and salt intakes (2.3 and 5.8 g/day) were slightly higher and the K intake lower (1.4 g/day) than WHO recommendations.

[Climate change and (surgical) health in context]

BACKGROUND

The impacts of the climate crisis will result in a health crisis in addition to loss of habitats and increasing supply uncertainty. In this context, the health sector and especially surgery are relevant emitters of greenhouse gases, thus contributing to the magnitude of the climate crisis. Many reviews regarding the impacts on human health are available; however, a view from the surgical perspective has so far been underrepresented.

MATERIAL AND METHODS

This narrative review summarizes the relevance of climate-related changes for the surgical disciplines based on a literature search.

RESULTS

Immediate impacts are expected by the increasing number of extreme weather events, e.g., floods, droughts and wildfires. In these settings, surgery is a part of the disaster medicine chain but simultaneously the functionality of surgical departments can be impaired or even break down when they are themselves affected by extreme weather events. Heat waves cause an increase in surgical site infections, which may lead to postponement of elective surgery for patients at high risk. Collateral impacts are mirrored by an increase in the incidence of lung and skin cancers, which often need surgical treatment within a multidisciplinary setting. Additionally, there are indirect impacts that are of a very different nature, e.g., inadequate diet which leads to further deterioration of the greenhouse gas footprint of the health sector due to the necessity of bariatric surgical capacities.

CONCLUSION

The climate crisis represents a major challenge in surgery and all other medical disciplines. At the same time is it indispensable that the health sector and therefore surgery, take steps towards a zero emission pathway.