Heat, Humidity and Protecting the Heart

[J.Adderton, BSN, MSN]

The hot and humid "dog days of Summer" can cause heat stress in healthy people. For those with existing heart disease, typical Summer weather can be downright dangerous. Studies have shown heat and humidity are hard on the heart. Heart disease, especially heart failure and ventricular dysfunction, make it harder for the body to cool in Summer weather. According to the American Heart Association, a heat wave lasting just 2 days increases the likelihood of a premature heart-associated death.

Heat and Heart Stress

The body sheds extra heat through the involuntary process of radiation and evaporation. This process cools the body but adds some stress to the heart. In individuals with heart disease, the stress can be significant.

Radiation (Circulation)

Heat naturally moves from warm to cooler areas. If the air around us is cooler, our bodies use radiation to release heat into the air. This transfer will stop when air temperature reaches body temperature. The heart has to pump harder and faster to reroute blood flow to the skin for heat release.

Evaporation (Heat)

Sweat cools the body through evaporation. Just one teaspoon of sweat can cool the body by 2 degrees a day with low humidity. Evaporation is less effective on humid days when the air is heavy with water vapor. This process of cooling places additional strain on the heart. Sweat pulls sodium, potassium and other minerals needed for water balance out of the body. To counter this loss, the body holds onto water by retaining fluid.

Heart Problems and Problems Coping

Healthy people most likely adjust to hot Summer days without missing a beat. However, those with heart disease may have difficulty coping with the added physical stress. The following factors may further contribute:

• Heart muscle damage can decrease the heart's ability to circulate enough blood to adjust to hot weather.
• Narrowed arteries can limit blood flow to the skin
• Common heart medications may interfere with the ability to regulate heat.
• Beta blockers slow heart rate and blood may not circulate fast enough for effective heat exchange.
• Diuretics may worsen dehydration
• Some antihistamines and antidepressants reduce or block sweating
• In certain conditions (I.e. dementia, Alzheimer's Disease, Parkinson's Disease) thirst signals may not be sent due to the brain's slow response to dehydration.

Balancing Heat and Diuretics

Congestive heart failure brings additional strain on hot days. Since the heart is weaker, the body has a harder time cooling. The risk for heat stroke, heat exhaustion and dehydration is greater with heart failure. Also, diuretics may increase the risk for dehydration and high sodium levels.

Patient education should include compliance with physician instructions for fluid intake during hot weather. Diuretics and fluid intake may need to be adjusted to compensate for increased sweating and water loss.

What to Watch For

Nurses have a responsibility to educate heart patients on what to watch for during hot weather.

• Weakness and/or dizziness
• Nausea and vomiting
• Cool skin
• Headaches
• Dark urine
• Muscle cramps
• High fever*
• Uncharacteristic behavior*
• Confusion*
• Rapid respirations*
• Rapid pulse*
• Seizures and unconsciousness*

*May indicate heat stroke

Be Proactive and Safe

Nurses are the constant across all areas of healthcare. Therefore, nurses carry the responsibility of educating heart patients on precautions to take on hot days. Patient education may include:

• Avoid activity outdoors during the hottest part of the day
• Consider exercising indoors or try out a water work-out in the pool
• Talk to your physician about guidelines for staying hydrated, especially if fluid intake is restricted
• When sweating, drink sports drinks to replace electrolytes
• Don't wait until you are thirsty to drink
• Consider other sources of hydration such as popsicles or fruit juice
• Avoid alcohol and caffeine to reduce risk of dehydration
• Wear loose, light-weight and light-colored clothing
• If going outdoors, use sunblock
• Talk to your doctor about your specific self-care needs during hot weather
• Keep informed of you local humidity levels
• Check on a friend or neighbor and ask them to do the same for you

Patient education should also include tips on maintaining a cool environment.

• Stay indoors with air-conditioning as much as possible.
• Don't rely on fans as the primary source of cooling
• If your home is not air-conditioned, contact your local health department to locate a local air-conditioned shelter
• Limit the use of stove and oven for cooking and laundry dryers
• Cool down with cool baths or showers
• If time must be spent outdoors, avoid the hottest part of the day and find a shady area

Conclusion

Hot and humid weather can be dangerous for anyone, but the risk is greater for those with heart disease. Be prepared to educate your patients on how to prevent over-stressing the heart while beating the dog days of Summer.

Protect Your Heart

CDC Information Related to Extreme Heat

Heat is hard on the heart: Simple precautions can ease the strain

[caliotter3]

Timely and informative. Thanks for sharing.