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By Jay MacNeal with Todd Daniello, Ken Hanson, Mitch Li, Sean Marquis, John Pakiela, Matt Smetana and Chris Wistrom

Firefighters are subjected to a variety of high-stress situations during training, performing technical rescues and operating on the fireground. Firefighters wearing structural gear are at high risk of thermal stress that, combined with heavy or even mild physical exertion, can rapidly lead to dehydration and other fluid balance illnesses.

While an ounce of prevention is worth a pound of cure, it is easy to get behind in fluid consumption quite rapidly. The use of aggressive prehydration and rehydration strategies is paramount to preventing serious illness.

One of the questions commonly considered is the use of oral versus intravenous fluids for firefighter rehab. Frankly, the question is poorly studied in the circumstances of firefighter exertion, dehydration and other fluid balance illnesses.

Although it may seem faster and more effective, rapid boluses of intravenous fluids are not without risks. Let’s examine what we know about hydration.

Fluid balance

We live in an age of energy drinks, workout optimizers and highly caffeinated beverages. The lifestyle choice to drink these alternatives to water tends to keep us, paradoxically, in a relative state of dehydration from the very beginning of our shifts.

In fact, a high percentage of firefighters arrive at training in a significantly dehydrated state, and firefighters lose a significant amount of body mass because of firefighting operations [1]. Firefighters are at risk of serious illness or injury because of these circumstances.

While most departments around the country are getting better at rehabilitation processes, firefighters often still avoid the formal process. Whether from fear of being taken out of the action or of missing a particularly exciting fireground activity, or due to the general mentality of being 10 feet tall and bulletproof, we still are far more likely to die from cardiac stress on the job than from any direct fire suppression activity.

Fluid balance is an important piece of that cardiac stress algorithm. Cardiac output is the amount of blood the heart pumps through the circulatory system in a minute. The amount of blood put out by the left ventricle of the heart in one contraction is called the stroke volume.

The stroke volume and the heart rate determine the cardiac output. If stroke volume is decreased due to dehydration and hypovolemia, the only way the body can compensate is to increase the heart rate. This leads to less blood supply to the heart, as the heart gets most of its supply in the diastole phase.

When cardiac output is decreased, the cooling capacity of the body is also reduced. It is a vicious cycle.

Oral fluids: Water or sports drinks?

To beat the vicious cycle of thermal load and dehydration hypovolemia, we need to maintain adequate hydration. Understanding how best to do that is important. Oral hydration was the first means of hydration and arguably may still be the best. There is an entire multibillion dollar industry dedicated to just that.

But when should sports drinks should be used instead of water? Most firefighters and EMS providers have heard of hyponatremia (abnormally low sodium levels) in athletes after drinking only water. Although rare, in extreme situations, fluid replacement with only water can lead to hyponatremia and when severe, seizures, coma and possibly death. Anecdotally, many people overcompensate to prevent hyponatremia by drinking only sports drinks.

A study of 488 runners in the Boston marathon showed that 0.6 percent had critical hyponatremia at the end of the run [2]. These runners were more likely to have consumed more than three liters of water, have slower finishing times and be at extremes of BMI. This study of marathon runners suggests that the individual’s physical fitness plays a role in sodium regulation.

Another sodium issue is hypernatremia, abnormally high concentration of blood sodium levels, which is a very real threat on the fireground as well. Concentration of blood sodium levels through essential fluid loss can and will lead to a hypernatremic state which also leads to dysrhythmias, seizures, coma and death.

Intravenous hydration fluids

Other than treating a medical emergency, is there a reason for IV fluids in rehab operations? Fluid replacement studies have been done in the athletic population. Although not a direct correlation to the fire service, there are some similarities. More importantly, at least one study has been done in the fire service.

In the Hostler study, subjects were given water, sports drink or IV rehydration therapy. Firefighters were dressed in protective gear and asked to complete a variety of upper and lower body exercises in a timed exercise period to reflect firefighting scene duties.

There was no difference in performance in the three study groups [3], thus the study showed no benefit to intravenous therapy over oral fluid consumption.

The routine use of intravenous therapy cannot be recommended as best practice [4,5]. Given the lack of benefit of intravenous hydration, the use of intraosseous or rectal fluid administration is also not recommended.

Best fluid options for fireground rehab

Based on the research, water, is in most situations the ideal rehydration beverage for firefighters receiving fireground rehab. Sports drinks can be beneficial but should not totally replace the use of water from company-level or formal rehab operations.

The avoidance of caffeinated beverages is highly recommended. The diuretic effect of caffeine can be counterproductive to hydration efforts.

Pre-hab for firefighters

Prior to heavy exertion, many athletes will prehydrate. Firefighters and EMS providers do not have the benefit of scheduled responses. Maintaining hydration during non-emergency operations is an important piece of response planning.

Implementation of a pre-hab strategy to drink a bottle of water while en route to an incident that is likely to cause a large thermal load seems to be a reasonable strategy. The amount of water should not be excessive to the point of causing nausea.

Video: Gordon Graham on firefighter hydration

Conclusion

Although it can be tempting to provide rapid rehydration with intravenous or intraosseous fluids, there is unlikely to be any benefit in most routine rehab situations. It is reasonable and a best practice to practice moderation, consume a combination of commercially available sports drinks and water or in some cases to dilute an electrolyte drink with water. Perhaps Grandma was right: moderation is the key.

Any provider not able to manage his or her hydration with oral fluid consumption will likely require additional medical support. Any responder requiring intravenous fluids is at risk of electrolyte imbalance and should be transported to the nearest appropriate medical facility for formal evaluation and treatment.

References

1. Quantifying dehydration in the fire service using field methods and novel devices.
2. Hyponatremia among runners in the Boston Marathon.
3. Comparison of rehydration regimens for rehabilitation of firefighters performing heavy exercise in thermal protective clothing: A report from the Fireground Rehab Evaluation (FIRE) trial
4. Intravenous fluid use in athletes.
5. R Kenefick et al, Rapid IV versus Oral Rehydration: Responses to Subsequent Exercise Heat Stress Med@Science in Sports & Exercise 2006