Enhanced Firefighter Rehab Trial: The Role of Aspirin in Preventing Heat Stress Induced Platelet Activation

Not Applicable

Completed

Conditions: Heat Stress Disorders

Interventions: Drug: Daily aspirin (ASA)
Other: Active cooling
Drug: Acute placebo
Other: Passive cooling
Drug: Daily placebo
Drug: Acute aspirin (ASA)

Registration Number: NCT01066923

Lead Sponsor: Dave Hostler

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.

Recruitment & Eligibility

Status: COMPLETED

Sex: All

Target Recruitment: 124

Inclusion Criteria

Apparently healthy males and females aged 18-49 years

Exclusion Criteria

History of heart disease, vascular disease, or sudden death including prior MI, coronary revascularization, congenital heart disease or history of stroke
Hypertension during screening: SBP>139 or DBP>89
Those who are taking medications that may be expected to blunt the physiologic response to a treadmill exercise test (e.g. beta blockers)
Prescription medication with known side effect of impaired thermoregulation
Positive pregnancy test at any time during the study
Resting ECG with clinical presentation suggesting coronary heart disease (e.g. pathologic Q wave)
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
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
At the discretion of the study physician for any other medical condition or prescription medication
Known history of platelet dysfunction
Aspirin allergy or intolerance

Study & Design

Study Type: INTERVENTIONAL

Study Design: PARALLEL

Arm && Interventions

Group	Intervention	Description
Daily ASA, Active cool, Acute ASA	Daily aspirin (ASA)	Two weeks of daily aspirin therapy prior to exercise, active cooling following exercise, aspirin immediately post exercise
Daily ASA, Active cool, Acute ASA	Active cooling	Two weeks of daily aspirin therapy prior to exercise, active cooling following exercise, aspirin immediately post exercise
Daily ASA, Active cool, Acute placebo	Active cooling	Two weeks of daily aspirin therapy prior to exercise, active cooling following exercise, placebo immediately post exercise
Daily ASA, Active cool, Acute placebo	Acute placebo	Two weeks of daily aspirin therapy prior to exercise, active cooling following exercise, placebo immediately post exercise
Daily ASA, Passive cool, Acute ASA	Passive cooling	Two weeks of daily aspirin therapy prior to exercise, passive cooling following exercise, aspirin immediately post exercise
Daily ASA, Passive cool, Acute placebo	Passive cooling	Two weeks of daily aspirin therapy prior to exercise, passive cooling following exercise, placebo immediately post exercise
Daily ASA, Passive cool, Acute placebo	Acute placebo	Two weeks of daily aspirin therapy prior to exercise, passive cooling following exercise, placebo immediately post exercise
Daily placebo, active cool, Acute ASA	Active cooling	Two weeks of daily placebo prior to exercise, active cooling following exercise, aspirin immediately post exercise
Daily placebo, active cool, Acute ASA	Daily placebo	Two weeks of daily placebo prior to exercise, active cooling following exercise, aspirin immediately post exercise
Daily placebo, active cool, Acute placebo	Active cooling	Two weeks of daily placebo prior to exercise, active cooling following exercise, placebo immediately post exercise
Daily placebo, active cool, Acute placebo	Daily placebo	Two weeks of daily placebo prior to exercise, active cooling following exercise, placebo immediately post exercise
Daily placebo, active cool, Acute placebo	Acute placebo	Two weeks of daily placebo prior to exercise, active cooling following exercise, placebo immediately post exercise
Daily placebo, Passive cool, Acute ASA	Passive cooling	Two weeks of daily placebo prior to exercise, passive cooling following exercise, aspirin immediately post exercise
Daily placebo, Passive cool, Acute ASA	Daily placebo	Two weeks of daily placebo prior to exercise, passive cooling following exercise, aspirin immediately post exercise
Daily placebo, Passive cool, Acute placebo	Passive cooling	Two weeks of daily placebo prior to exercise, passive cooling following exercise, placebo immediately post exercise
Daily placebo, Passive cool, Acute placebo	Daily placebo	Two weeks of daily placebo prior to exercise, passive cooling following exercise, placebo immediately post exercise
Daily placebo, Passive cool, Acute placebo	Acute placebo	Two weeks of daily placebo prior to exercise, passive cooling following exercise, placebo immediately post exercise
Daily ASA, Active cool, Acute ASA	Acute aspirin (ASA)	Two weeks of daily aspirin therapy prior to exercise, active cooling following exercise, aspirin immediately post exercise
Daily ASA, Passive cool, Acute ASA	Daily aspirin (ASA)	Two weeks of daily aspirin therapy prior to exercise, passive cooling following exercise, aspirin immediately post exercise
Daily ASA, Active cool, Acute placebo	Daily aspirin (ASA)	Two weeks of daily aspirin therapy prior to exercise, active cooling following exercise, placebo immediately post exercise
Daily ASA, Passive cool, Acute placebo	Daily aspirin (ASA)	Two weeks of daily aspirin therapy prior to exercise, passive cooling following exercise, placebo immediately post exercise
Daily ASA, Passive cool, Acute ASA	Acute aspirin (ASA)	Two weeks of daily aspirin therapy prior to exercise, passive cooling following exercise, aspirin immediately post exercise
Daily placebo, active cool, Acute ASA	Acute aspirin (ASA)	Two weeks of daily placebo prior to exercise, active cooling following exercise, aspirin immediately post exercise
Daily placebo, Passive cool, Acute ASA	Acute aspirin (ASA)	Two weeks of daily placebo prior to exercise, passive cooling following exercise, aspirin immediately post exercise

Primary Outcome Measures

Name	Time	Method
Platelet Closure Time	0, 30, 60, and 90 minutes post exercise
Vascular Function Measured by Peripheral Arterial Tonometry	Baseline, 30, 60, and 90 minutes post exercise	Reactive Hyperemia Index

Secondary Outcome Measures

Name	Time	Method
Activation of Coagulation	0, 30, 60, and 90 minutes post exercise	This measure was not collected. Equipment was not available.
Hyperthermia and Hemoconcentration Identified by Retinal Imaging	0, 30, 60, and 90 minutes post exercise	This measure was not collected. Equipment was not available.