INTRODUCTION AND EPIDEMIOLOGY
The elderly have worse outcomes following trauma because of physiologic changes that occur with aging. They are more susceptible to serious injury from low-energy mechanisms, less able to compensate from the stress of injury, and more likely to suffer complications during treatment and recovery. Emergency physicians should have a higher suspicion for injury and lower threshold for diagnostic testing and admission than in younger patients.
Studies have variously defined the lower limits of the geriatric age group to be as young as 55 years and as old as 80 years. Some have shown mortality to increase with individuals as young as 45 years of age.1 Regardless of the definition, caring for injured elders constitutes a large and growing portion of emergency medicine practice. The U.S. Census Bureau projects that those ≥65 years old will increase from 13% to 16% of the population by 2020 and to 20% by 2040.2,3 Geriatric patients represented 12% of the population in the Major Trauma Outcomes Study.4 Although the elderly are less likely to be involved in trauma, they are more likely to have fatal outcomes when injured, with a mortality rate twice that of younger patients. Those age 65 years and older consumed a disproportionate share of trauma hospitalizations (23%) and trauma costs (28%) relative to the 12% of the U.S. population they comprised in 1985.5
Part of the difficulty in describing the elderly population derives from the discrepancy between chronologic and physiologic age. Chronologic age is the actual number of years the individual has lived, whereas physiologic age describes the functional capacity of the patient's organ systems. Studies have shown a clear association between age and mortality. Comorbid diseases have been shown to be associated with increased mortality after minor and moderate injuries in all age groups.6
The physiologic changes of aging complicate recovery from injury and make assessment of injury more difficult. With age, myocytes are lost and replaced by collagen. This results in decreased contractility and compliance for any given preload.7 An 80-year-old person will have approximately 50% of the cardiac output of a 20-year-old, even without significant atherosclerotic coronary artery disease. Maximal heart rate and cardiac output decrease with age. Aging myocardium has a decreased chronotropic response to catecholamines and is dependent on preload (intravascular volume); hypovolemia can easily result in shock. Deterioration of the cardiac conduction system leads to atrial fibrillation and bundle-branch blocks. Medications, especially digoxin, β-blockers, and calcium channel blockers, impair the tachycardic response to catecholamines, both impairing the body's inability to compensate for hemorrhage and making heart rate an unreliable predictor of hypovolemia.
Chest wall compliance, respiratory muscle strength, and the capacity for oxygen exchange all decrease with age. The response to hypoxia may decline by 50% and that to hypercarbia by 40%, such that the patient may ...