A 67-year-old man is brought to the hospital after he developed sudden-onset altered mental status. The patient was taking care of some yardwork alongside his 17-year-old grandson during a hot summer day. The grandson does not have any symptoms. On examination, the patient's temperature is 41 C (105.8 F), blood pressure is 90/60 mm Hg, pulse is 120/min, and respirations are 24/min. Examination shows warm and dry skin. The patient is not oriented to time, place, or person. Deep tendon reflexes and muscle tone are normal. Which of the following findings in this patient most likely explains why the patient developed symptoms while his grandson remained asymptomatic?

Question

A 67-year-old man is brought to the hospital after he developed sudden-onset altered mental status.  The patient was taking care of some yardwork alongside his 17-year-old grandson during a hot summer day.  The grandson does not have any symptoms.  On examination, the patient's temperature is 41 C (105.8 F), blood pressure is 90/60 mm Hg, pulse is 120/min, and respirations are 24/min.  Examination shows warm and dry skin.  The patient is not oriented to time, place, or person.  Deep tendon reflexes and muscle tone are normal.  Which of the following findings in this patient most likely explains why the patient developed symptoms while his grandson remained asymptomatic?

Quizplus · Accepted Answer

11ec160b_3b19_55c0_9249_413d55a25203_MD0001_00 This elderly patient developed hyperthermia and altered mental status while working outside on a hot summer day. This presentation suggests exertional heat stroke, a life-threatening multisystem disorder characterized by hyperthermia (typically >40 C [104 F]) associated with central nervous system dysfunction (eg, encephalopathy, as seen in this disoriented patient). Other classic manifestations of heat stroke include tachycardia, tachypnea, hypotension, flushing, and end-organ dysfunction (eg, pulmonary edema, renal or hepatic failure). Diaphoresis may or may not be present on examination, depending on hydration status. Normal thermoregulatory response to elevated temperatures include increased sweating and increased cardiac output. Furthermore, there is significant peripheral vasodilation and splanchnic vasoconstriction, which shunts blood to the periphery to aid with heat transfer. However, elderly patients are at particularly high risk of developing heat-related illness due to several features of normal aging that impair this response, including: Tonic contraction of the peripheral vasculature, which limits heat transfer to the skin Reduced sweat gland density, which limits the ability to dissipate heat via evaporation Loss of rete pegs and dermal capillaries, which reduces the effective epidermal area available for heat transfer In addition, many elderly patients have medical conditions (eg, congestive heart failure) or are taking medications that may limit cardiac output (eg, beta blockers), diaphoresis (eg, anticholinergics), or blood volume available for heat transfer (eg, diuretics). (Choices B and E) Appropriate responses to elevated temperature include decreased vasodilation (ie, vasoconstriction) of the splanchnic vasculature, which promotes blood flow from the internal organs to the skin, and peripheral vasodilation, which allows for heat dissipation. (Choice C) Loss of subcutaneous fat also often occurs with aging and reduces the ability to retain heat and allows increased heat transfer to the skin; however, this promotes cooling (and places elderly patients at increased risk for hypothermia). (Choice D) An increased number of sweat glands would promote cooling in patients with hyperthermia; however, sweat glands are typically reduced with aging, not increased. Educational objective: Elderly patients are at increased risk of developing heat-related illness due to several features of normal aging that impair normal thermoregulatory mechanisms, including tonic contraction of the peripheral vasculature, reduced sweat gland density, and reduced effective epidermal area available for heat transfer.

A 67-Year-Old Man Is Brought to the Hospital After He