Baby, It’s Hot Outside.

As a person with arthritis among other maladies, I regularly see my rheumatologist. “A rheumatologist is a board certified internist or pediatrician who is qualified by additional training and experience in the diagnosis and treatment of arthritis and other diseases of the joints, muscles, and bones,” according to HSS at https://www.hss.edu/rheumatology-rheumatologist.asp. During my appointment, she mentioned that my GFR (Glomerular Filtration Rate) was 46.

Panic! It’s almost always in the low 50s. She calmed me down by telling me that GFR is usually lower during the Arizona heat (I know, I know: but it’s a dry heat.) of the summer. I don’t know why I was surprised. It made sense.

Think about it. Let me re-enforce this with a statement taken from study on PubMed at https://pubmed.ncbi.nlm.nih.gov/21617334/.

“However, the percent change in eGFR from spring to summer was greater in hypertensive patients with CKD… than in those without CKD …. “

PubMed is part of the National Institutes of Health’s National Library of Medicine’s National Center for Biotechnology Information.

I know hypertension (high blood pressure) is included in this statement, but the fact that GFR is lowered t than it’s lowered in those without hypertension leads us to the realization that those without hypertension DO have lower GFRs during the summer heat.

Another study from EuropePMC at https://europepmc.org/article/med/28946962 tells us:

“Recurrent dehydration in people regularly exposed to high temperatures seems to be resulting in an unrecognised cause of proteinuric chronic kidney disease, the underlying pathophysiological mechanism of which is becoming better understood. However, beyond heat waves and extreme temperatures, there is a seasonal variation in glomerular filtration rate that may contribute to the onset of renal failure and electrolyte disorders during extremely hot periods.”

Here are a couple of definitions you may need to understand the above statement. The first is from The Mayo Clinic at https://www.mayoclinic.org/symptoms/protein-in-urine/basics/definition/sym-20050656.

“Protein in urine — known as proteinuria (pro-tee-NU-ree-uh) — is excess protein found in a urine sample. Protein is one of the substances identified during a test to analyze the content of your urine (urinalysis).

Low levels of protein in urine are normal. Temporarily high levels of protein in urine aren’t unusual either, particularly in younger people after exercise or during an illness.

Persistently high levels of protein in urine may be a sign of kidney disease.”

The following definition is from MedicineNet at https://www.medicinenet.com/script/main/art.asp?articlekey=10691.

“Pathophysiology: Deranged function in an individual or an organ due to a disease.”

So, it looks like dehydration is a key factor in lowering the GFR during the summer heat. We know that dialysis patients need to limit their liquid intake, but what about those of us who are not on dialysis but do have CKD (Chronic Kidney Disease)?

I went to MedicalNewsToday at https://www.medicalnewstoday.com/articles/153363#symptoms for some facts about dehydration:

“Around three-quarters of the human body is water.

The causes of dehydration include diarrhea, vomiting, and sweating.

Individuals more at risk of dehydration include athletes, people at higher altitudes, and older adults.

Early symptoms of dehydration include dry mouth, lethargy, and dizziness.”

Did you notice “sweating” and for those of a certain age like me “older adults”?

So, I gather I’m sweating out more liquids than I’m taking in. But how does that work exactly? I thought I was drinking sufficient amounts of fluid.

Biology Online at https://www.biologyonline.com/dictionary/sweating was a bit of an eye opener.

“Sweating is a way of our body to regulate body temperature. It is commonly used as a synonym for perspiration but in stricter sense perspiration pertains to the water loss as a cooling mechanism of the body and therefore It (sic) includes both the release of watery, salty fluid through the pores of the skin from the sweat glands and the evaporation of water from the skin (trans-epithelial) and respiratory tract. Thus, there exist two forms of perspiration, the sensible and the insensible water loss. In sweating, the process always entails the loss of both water and solutes…. The salty fluid is secreted as droplets or moist on the skin and is called as sweat. Environmental cues that could stimulate the body to produce sweat are high temperature and humidity of the surroundings.”

Oh, solutes. Those include the electrolytes that are so important to us as CKD patients. Orthology at https://orthology.com/myth-debunked-need-electrolytes-work/ offers us a simple explanation:

“The warmer the weather and the more you sweat, the more likely you’ll need electrolyte replacement. Again, this is just a general guideline and will differ by individual, activity and other factors. Pay attention to signs that your electrolyte levels are too low, such as muscle cramps, fatigue, dizziness, nausea or mental confusion.”

Aha, it’s excessively hot out. We drink more, but more sweat is being produced the higher the temperature is. When we sweat or perspire (since the two words are often used interchangeably), we are also exuding electrolytes. Now it all makes sense. An imbalance of electrolytes could lower your GFR. I turned to Tampa Cardio at https://tampacardio.com/causes-electrolyte-imbalance-body/ for confirmation.

“Electrolyte imbalances can cause a wide range of symptoms, some mild and some potentially life threatening. Electrolyte imbalances are commonly caused by loss of fluids through prolonged diarrhea, vomiting, sweating or high fever.”

But we’re already having problems with our electrolytes. No wonder excessive heat affects our GFR. As the University of Michigan’s Michigan Medical at https://www.uofmhealth.org/conditions-treatments/kidney/fluid-and-electrolyte-disorders states:

“Changes in the body’s levels of minerals including potassium, magnesium, calcium and sodium—and the corresponding impact these have on the body’s function, muscle strength and heart rhythm can be associated with disorders of kidney or endocrine glands.

Got it. Let’s all just stay in the air conditioning so we don’t lower our GFRs even more than the excessive heat does. In Arizonia, that probably means until November this year. That was a joke (I hope).

Until next week,

Keep living your life!

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