Clinical trial NCT01066923: Enhanced Firefighter Rehab Trial: The Role of Aspirin in Preventing Heat Stress Induced Platelet Activation
Official title: Enhanced Firefighter Rehab Trial: Aspirin Versus Placebo
Study type: INTERVENTIONAL
Overall status: COMPLETED
Phase: NA
Conditions: Heat Stress Disorders
Keywords: firefighter
heat stress
platelet activation
aspirin
Lead sponsor: University of Pittsburgh
Sponsor class: OTHER
Collaborators: name: Federal Emergency Management Administration
name: Eyemarker Systems, Inc
First posted: 2010-02-10
Enrollment: 124
Sex: ALL
Minimum age (years): 18
Maximum age (years): 49
Standard ages: ADULT
Accepts healthy volunteers: yes
Allocation: RANDOMIZED
Intervention model: PARALLEL
Primary purpose: PREVENTION

Brief summary: The purpose of this study is to determine if aspirin taken by firefighters prevents platelets from becoming sticky when body temperature rises during work in protective clothing.

Detailed description: Firefighters have the highest rate of line-of duty death (LODD) in the United States. More than half of these LODD are cardiovascular related occurring disproportionately around fire suppression activities. In addition, shift work, lifestyle factors, and the exposures associated with fire suppression (e.g. smoke, chemicals) may predispose the firefighter to earlier onset of heart disease or cause a pro-inflammatory state leading to endothelial dysfunction.

Fire suppression activities exacerbate cardiovascular strain and endothelial dysfunction and provide potential triggers for ischemic events (e.g. myocardial infarction, stroke). There is a rapid rise in heart rate following the activation of a fire company which may persist for as long as 20 minutes. Even in cases where heavy work is not being performed, the repetitive upper body exercise associated with tool use raises heart rate disproportionately to oxygen consumption.

Finally, there is a rapid rise in core body temperature from increased physical activity, environmental heat and impaired thermoregulation that has been shown to cause vasoconstriction and activate coagulation during heat stress (12, 13). This has recently been demonstrated in firefighters working in thermal protective clothing. The combination of triggers created during fire suppression may result in heart attack or stroke, especially in firefighters with risk factors for cardiovascular disease.

Interventions beyond basic fireground rehab may be required to minimize the effect of these triggers and enhance a firefighter's health and wellness. Fireground rehab typically focuses on cooling and rehydration of the firefighter following fire suppression or training with the assumption that these interventions will correct the underlying pathophysiology. Effective fireground rehab must deliver appropriate interventions and monitor the progress of the firefighter. While correcting hyperthermia and hypohydration are essential for continued performance, it is not clear if these therapies correct alterations in platelet or endothelial function or if other interventions are necessary to correct these physiological disturbances. Furthermore, the options for monitoring the firefighter beyond simply measuring heart and respiratory rate are limited. In our FEMA-funded Fireground Rehab Evaluation (FIRE) Trial, we demonstrated that five commercially available thermometers did not reliably measure or estimate core temperature following uncompensable heat stress (UHS) making it impossible to gauge the effectiveness of rehab interventions.

Eligibility criteria: Inclusion Criteria:

1. Apparently healthy males and females aged 18-49 years

Exclusion Criteria:

1. History of heart disease, vascular disease, or sudden death including prior MI, coronary revascularization, congenital heart disease or history of stroke
2. Hypertension during screening: SBP\>139 or DBP\>89
3. Those who are taking medications that may be expected to blunt the physiologic response to a treadmill exercise test (e.g. beta blockers)
4. Prescription medication with known side effect of impaired thermoregulation
5. Positive pregnancy test at any time during the study
6. Resting ECG with clinical presentation suggesting coronary heart disease (e.g. pathologic Q wave)
7. Known history of gastrointestinal disease or disorder i.e. diverticulitis which creates a theoretical risk of the core temperature capsule becoming lodged in the digestive tract
8. Medications and supplements known to alter endothelial function (e.g. arginine, omega 3 fatty acids, NSAIDS, tobacco products. This exclusion may be disregarded for subjects willing to stop taking the supplement for the duration of the study
9. At the discretion of the study physician for any other medical condition or prescription medication
10. Known history of platelet dysfunction
11. Aspirin allergy or intolerance

Primary outcomes:
measure: Platelet Closure Time
timeFrame: 0, 30, 60, and 90 minutes post exercise
measure: Vascular Function Measured by Peripheral Arterial Tonometry
timeFrame: Baseline, 30, 60, and 90 minutes post exercise
Secondary outcomes:
measure: Activation of Coagulation
timeFrame: 0, 30, 60, and 90 minutes post exercise
measure: Hyperthermia and Hemoconcentration Identified by Retinal Imaging
timeFrame: 0, 30, 60, and 90 minutes post exercise
Other outcomes:
Locations:
city: Pittsburgh
country: United States
facility: University of Pittsburgh, Emergency Responder Human Performance Lab
state: Pennsylvania
Study officials:
affiliation: University of Pittsburgh
name: David Hostler, PhD
role: PRINCIPAL_INVESTIGATOR
References:
citation: Olafiranye O, Hostler D, Winger DG, Wang L, Reis SE. Effect of aspirin on acute changes in peripheral arterial stiffness and endothelial function following exertional heat stress in firefighters: The factorial group results of the Enhanced Firefighter Rehab Trial. Vasc Med. 2015 Jun;20(3):230-6. doi: 10.1177/1358863X15571447. Epub 2015 May 4.
citation: Hostler D, Suyama J, Guyette FX, Moore CG, Pryor RR, Khorana P, McEntire SJ, Comer D, Reis SE. A randomized controlled trial of aspirin and exertional heat stress activation of platelets in firefighters during exertion in thermal protective clothing. Prehosp Emerg Care. 2014 Jul-Sep;18(3):359-67. doi: 10.3109/10903127.2013.869644. Epub 2014 Feb 18.