An 80-year-old woman is brought to the emergency department following a burn injury. The patient lives alone in an apartment. Earlier today, her clothes caught fire while she was cooking. The patient's neighbor heard her screaming and helped extinguish the fire, but the patient had already sustained burns on her face, arms, and body. She has a history of Parkinson disease and osteoporosis. Temperature is 37.4 C (99.3 F), blood pressure is 140/84 mm Hg, pulse is 110/min, and respirations are 18/min. Oxygen saturation is 95% on room air. On examination, the patient is in distress and anxious. There are partial- to full-thickness burns involving the lower face, neck, both arms, and anterior chest and abdomen. Which of the following age-related cardiopulmonary changes is most likely to increase this patient's mortality risk?
Physiologic age-related cardiovascular changes | |
Aortic stiffening |
|
Mild concentric LVH* |
|
Conduction cell degeneration |
|
Reduced baroreceptor sensitivity & adrenergic responsiveness |
|
*A soft S4 is a normal finding in the elderly. EF = ejection fraction; HTN = hypertension; LVH = left ventricular hypertrophy; SV = stroke volume. | |
With advancing age, the cardiopulmonary system undergoes physiologic changes that can lead to reduced ability to cope with critical illness (eg, severe burns). One of the major changes in the cardiovascular system involves decreased responsiveness to adrenergic stimuli, which contributes to a lower maximal heart rate and reduced maximal cardiac output.
Critical illness often involves a hypermetabolic state (ie, increased resting energy expenditure) and a marked decrease in intravascular blood volume (eg, evaporative losses with severe burn injury, vascular leakage with sepsis), both of which necessitate a sympathetic-mediated increase in heart rate and contractility to help maintain organ and tissue perfusion. The attenuation of this response with age likely contributes to poorer critical illness outcomes in elderly patients.
(Choices B and E) Compliance of the aorta and other large arteries decreases with age, resulting in isolated systolic hypertension and an increase in left ventricular afterload. In response to the increased afterload, mild concentric left ventricular hypertrophy occurs, resulting in increased left ventricular wall thickness. The reduced arterial compliance also decreases blood volume retained in the arterial system, which increases susceptibility to hypotension during critical illness.
(Choices C and F) Degeneration of lung elastin with age causes alveolar enlargement and increased air trapping. The alveolar enlargement decreases the percentage of the alveolar surface in contact with alveolar capillaries, reducing gas exchange surface area. This effect, combined with reduced alveolar ventilation due to increased air trapping, increases ventilation-perfusion mismatching.
(Choice D) Diaphragmatic strength decreases with age. This has little effect on resting tidal volumes, but it increases the susceptibility to respiratory fatigue during periods of respiratory stress (eg, critical illness).
Educational objective:
Physiologic age-related changes in the cardiopulmonary system can lead to reduced ability to cope with critical illness. These changes include reduced maximal heart rate and cardiac output due to decreased responsiveness to adrenergic stimuli, reduced retention of arterial blood volume due to decreased arterial compliance, and reduced respiratory strength and gas exchange efficiency.