Why is it important to be careful with sodium intake in heat-related illnesses?

Proper Sodium Management in Heat-Related Illnesses

In heat-related illnesses, maintaining appropriate sodium balance is critical as both insufficient and excessive sodium intake can worsen outcomes and increase mortality risk.

Why Sodium Balance Matters in Heat Exposure

• Extensive sweating during heat exposure leads to significant sodium losses that must be replaced to maintain fluid balance and prevent complications 1
• Sodium supplementation is essential for heavy sweaters to maintain sodium balance and prevent muscle cramping when exercise in heat lasts longer than 1 hour 1
• Effective rehydration requires more than just water intake - sufficient electrolytes (especially sodium) must be consumed to offset sweat-related losses and better retain and distribute ingested water 1

Dangers of Improper Sodium Management

Risks of Insufficient Sodium Replacement

• Inadequate sodium intake during prolonged heat exposure can lead to:
  • Muscle cramping, especially when exercise lasts longer than 1 hour 1
  • Impaired fluid retention and distribution throughout the body 1
  • Hyponatremia (low blood sodium), which can cause confusion, seizures, and even death in severe cases 2

Risks of Excessive Sodium or Water Intake

• Hypernatremia (high blood sodium) is associated with significantly decreased one-year survival rates (45% vs. 57% in those with normal sodium levels) 3
• Overly aggressive fluid intake without adequate sodium can lead to exercise-associated hyponatremia, which can be mistaken for heat exhaustion 2
• Symptoms of hyponatremia can mimic heat illness, leading to incorrect treatment 2

Practical Recommendations for Sodium Management

• Athletes and individuals exposed to heat should aim to consume a solution containing 0.5–0.7 g/L of sodium during activity 1
• For those experiencing muscle cramping, increase sodium supplementation to 1.5 g/L of fluid 1
• Include 30–60 g/h of carbohydrates in hydration regimen for exercise lasting longer than 1 hour, and up to 90 g/h for events lasting over 2.5 hours 1
• After exercise in heat, rehydration should include sodium, carbohydrates, and protein 1

Special Considerations

• Athletes with high sweat rates may require higher sodium intake than public health recommendations suggest 1
• Incomplete between-match rehydration is often unavoidable when multiple same-day activities occur with short rest periods 1
• In these cases, begin the first activity well-hydrated and well-nourished, with sufficient sodium levels, and immediately begin appropriate post-activity rehydration 1
• A cold carbohydrate-protein replacement drink with a small, easily digestible salty snack can be more effective than solid food when there is little recovery time 1

Monitoring and Prevention

• Simple monitoring techniques such as daily morning body mass and urine specific gravity can provide useful insights into hydration state 1
• For competitions lasting several days, monitoring sodium status becomes increasingly important 1
• Recognize that medications like non-steroidal anti-inflammatory drugs and diuretics can increase heat illness risk and affect sodium balance 1
• Current or recent illness, especially those involving gastrointestinal distress, can increase risk of sodium imbalances during heat exposure 1

Emergency Situations

• In cases of suspected heat illness with altered mental status, obtaining point-of-care serum sodium may improve recognition of hyponatremia and guide appropriate management 2
• Depending on severity of symptoms, exercise-associated hyponatremia can be managed by fluid restriction, oral hypertonic broth, or with intravenous 3% saline 2
• Rapid measurement of serum sodium concentration is mandatory to appropriately guide electrolyte resuscitation in heat-related emergencies 3