Whether it’s today’s chemical, biological agent scare or tomorrow’s first responder call, firefighters are the chosen few who continually play Russian roulette with their health each time they don their hazardous material… suit or turnout gear. Each year governing committees amend standards to improve protective equipment. Yet, in spite of these good intentions, protective fabrics place an immeasurable health risk on the human body. As enigmatic as the term “heat stress” is, so is a “cure-all” solution.

Firefighters and EMTs are well versed on the facts and remedies of the minor heat illness occurrences… heat rash, heat cramps, tetany (painful muscle spasms caused by faulty calcium metabolism or diminished parathyroid function), heat syncope (fainting) and heat exhaustion. But, it’s the obscure damage that one serious heat related incident like heat stroke can cause that is shrouded in obscurity. In a 1995 Occupational Medicine article, the Cancer Registry of Norway reported a correlation between the incidence of kidney cancer and both exposure and cumulative exposure to hot environments and volatiles some 20 to 35 years before observation. The main findings of this study revealed heat stress and kidney cancer in the group with at least three years of total employment. A quote from this study stated, “Increased risk of kidney cancer has been reported from previous studies of workers in aluminum smelters and other hot environments such as foundries and coke ovens.” Studies published in the American Journal of Medicine suggest that Acute Respiratory Distress Syndrome (ARDS) and a variety of other critical conditions associated with ARDS are also linked to heat stroke. Recently, the Center for Disease Control revealed astounding facts about Chronic Fatigue Syndrome (CFS) that resemble the chronic effects of an individual who survives heat stroke. Medical research hints a correlation between continual exposure of heat that forces the individual to near exhaustion usually results in mild to serious physiologic and neurologic aftereffects. Typically described as exhaustion and poor stamina, the underlying factor in both a severe heat illness and CFS is their pathology involving our body’s cellular energy “storehouse”.

Research cannot well define the dysfunction of our body’s immune system when broached by a disruption caused by severe heat. It does, however, intimate that as our body experiences severe disruption, our natural killer cells that fight viruses can be suppressed or deficient, compromising our immune system. Commonalities discovered between CFS and sequelae (the medical term for recurrent complications frequently noticed in individuals who recover from a severe heat illness) are:

• Overall muscle discomfort, flaccid muscles, headaches and weakness
• Sleep disturbances or hypersomnolence (requiring excessive sleep hours and naps)
• Spatial disorientation, light headedness and dyslogia (speech impairment, reasoning, memory loss and/or the ability to concentrate)
• Chills and night sweats (a thermoregulatory problem)
• Skin sensitivity and sensitivity to heat and cold
• Irregular heart beat and recurrent chest and/or abdominal pain
• Lowered tolerance to alcohol, irritable bowel and/or diarrhea
• Weight fluctuation and menstrual cycle disruption

Our bodies are truly a complex chemical, electrical and biological organism. In the early stages of a severe heat illness, at the cellular level, tremendous hyperactivity and abnormalities are taking place. Excessive heat exposure radically denatures proteins, lipoproteins and phospholipids; it liquefies membranes and provokes electrolyte abnormalities that ultimately lead to cardiovascular collapse, multi-organ failure and finally death. Lipids (one of the principal structural materials of living cells) are transported by the lipoproteins throughout the blood, so disruption of our cells is not a good thing. As we destroy the lipoproteins that sheath the myelin in the neurotransmitters (nerve fibers), we destroy our communication central processing system. Potassium is essential for muscular contraction and function of the heart, skeletal and smooth internal organ muscles, as well as the osmotic pressure and ionic electrical balance. As heat stress persists, potassium levels peak and wane as muscle damage occurs. As these minerals work together to facilitate one another, abnormal levels of calcium, potassium, magnesium and phosphates could become significant enough to cause hypertension (persistent high blood pressure), cardiac arrhythmias or tachycardia (irregular or elevated heart rate) or be the precursor to mild stroke and require immediate treatment. As our electrolytes become imbalanced, the onset of vomiting and diarrhea can occur. If excess sweating has occurred, the level of sodium usually measures high unless plenty of water without sodium replenishment was previously ingested. Sodium helps maintain osmotic pressure of extracellular fluid, gastrointestinal absorption of certain sugars and proteins, cell permeability and muscle function. Liver damage is a consistent finding and hypoglycemia (low blood sugar) is very common and may be incited by liver failure.

Hemodynamic reports (the study of the forces involved in blood circulation) reveal in severe dehydration cases, abnormal coagulation occurs altering amino acids and causes cerebral edema (excess fluid in the brain cells or tissues). Prolonged intravascular coagulation or loss of blood to the lungs incites damage to the lung tissues and may predispose people to develop pulmonary problems like ARDS. Once this occurs, individuals require more positive inhalation pressure via mechanical ventilation. Serious heat damage is often associated with endotoxemia (the presence of endotoxins in the blood and tissues) that form an integral part of the cell wall of certain bacteria and are released when the cell destructs. Blood hemorrhaging in the skin (red bumps) can occur followed by blood in the urine. As dehydration increases, the viscosity of the blood changes (from oxygen rich, easily perfused fluid to a sludge-like substance). Vascular tone and capacity, in turn, alter blood pressure and cardiac output. If left untreated, the heart becomes tired and quits.

Neurologic complications vary from mental disorientation to delirium, unconsciousness, convulsions or a comatose state (displaying similar symptoms to that of sustaining a serious head injury). Those individuals may require tomography scans to determine the level of Central Nervous System (CNS) damage. Nerve damage can be as subtle to recovering victims as partial or permanent anhidrosis (cessation of sweating). From thereon, their ability to maintain thermal equilibrium may be compromised, especially when faced with heat stress conditions. Irreparable damage to the body’s heat-dissipating bodily mechanisms may be noted along with muscle coordination may be weak and affected in some or all quadrants of the body. One’s equilibrium and hand-eye coordination may be off. In some cases, lack of nerve conductivity in the lower limbs may be noted.

Neurologic disorders during heat related illnesses are further complicated by release of adrenaline (epinephrine – the most potent stimulant of our sympathetic nervous system). Adrenaline stress is extremely prevalent in high-risk occupations where tension, fear, anger, excitement and life threatening situations occur. Release of adrenaline changes the physiological responses and causes a magnitude of complex reactions including, but not limited to increased blood pressure, heart rate and force of blood vessel contraction, relaxation of bronchiolar and intestinal smooth muscles and other metabolic effects. According to John LoZito, Neurologist, a release of some adrenaline is good, but needless adrenaline incites hyperactivity akin to dropping a fuel drum on a bonfire further increasing susceptibility for more serious maladies: stroke, cardiac stress, etc.

Extreme dehydration causes retention of carcinogens and an imbalance of myoglobin (oxygen carrying proteins) in prominent organs like the bladder and colon. Loss of fluid prevents diluting and flushing of the toxins, predisposes one for constipation and urinary tract infections, as well as bladder and colon cancer. Kidney stones may form more readily as calcium, uric acid and other substances become concentrated and form crystals due to fluid loss. Heat damage incites sudden rhabdomolysis and intramuscular necrosis (destroying skeletal muscles and decay of muscle tissue also known as muscle wasting). Researchers have long purported good fluid intake neutralizes the cavity causing acids, flushes away sugar and inhibits the micro-organisms that cause gum disease and other oral hygiene problems. For individuals afflicted with asthma, drying of the nose, throat and lung tissues presumably incite more asthma attacks than with hydrated tissues or humid weather. Dehydration, measuring as little as one percent of one’s body weight in non-heat stress conditions can be the cause for headaches, fatigue, muscle cramps and the “blah” feeling. A net water loss of as little as four percent of one’s body weight can cause blood pressure to plummet quickly. These and a host of other disorders make simple nausea and headaches just a walk in the park.

The typical information from organizations like the National Institute of Health, OSHA, NIOSH, CDC, Worksafe Australia and others do not reflect the pathophysiology of how heat stress affects our body at the cellular level. Medical science has just begun to unravel the baneful mysteries of bodily reaction to heat, unfortunately many times after the fact.

This is the first part in a series of educational articles analyzing the in-depth effects of heat stress, including noteworthy considerations for firefighters and other emergency responders, by Kathryn Doherty. Kathryn is a graduate from the University of Oklahoma. She has conducted heat stress awareness seminars, consulted with companies and published numerous articles on this subject. Kathryn can be reached by email at: The50DegreeCo@aol.com