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Physiology II
Cardiovascular Case E

hot tub fever 

the patient: a 36-year-old man 

chief complaint: syncope

history and clinical course: This 36-year-old University of New England faculty member had been in excellent health prior to the current episode of dizziness and fainting, which occurred in the hydrospa at the Campus Center. Following 20-25 minutes of moderately heavy exercise (swimming laps in the pool), the patient joined several faculty colleagues in the hydrospa and entered into a spirited and sometimes heated discussion of university budgetary negotiations. After about 20 min of continuous immersion up to shoulder level in the spa, the patient lifted himself to a sitting position on the rim of the spa with his lower legs still immersed. Shortly thereafter, his colleagues noticed that he was no longer participating in the discussion, and became concerned when he appeared to be losing consciousness. Before they could move to his aid, he had slipped nearly completely back into the spa. They quickly pulled him out of the spa, laid him supine on the tile floor, and notified the lifeguards. The patient demonstrated a rapid, shallow breathing pattern at this point, his skin was extremely flushed and very warm, and he had a heart rate of 132 beats/min. The lifeguards began cooling the patient with wet towels, and he quickly regained consciousness. Shortly thereafter he was able to walk unassisted back to the locker room. The patient suffered no apparent ill effects from the incident, except for a residual susceptibility to harassment by his colleagues. Interestingly, during the walk to the locker room, the patient's colleagues themselves experienced somewhat delayed symptoms of dizziness and loss of balance similar to those of the patient, although less severe and very short-lived; they vigorously denied any such sensations during subsequent interactions with the patient, however.

STUDY QUESTIONS  The Answers Below Are Just My Guess

1. What is a primary role of the cutaneous circulation that is relevant to this case?  The cutaneous circulation has been drastically increased to help cool the body (from exercise and spa contact).  The vasodilation in the skin started to cool the body after exercise, but now the body is picking up heat from the hot water and is heating up the body.

2. What is the status of this patient's cutaneous circulation immediately after exercise and after 20 minutes of immersion in the hot tub?  The cutaneous circulation is increased both after exercise and after being in the hot tub.

3. How does the demand for peripheral blood flow to the skin conflict with the central regulation of mean systemic arterial pressure?  The local control of vascular dilation in the cutaneous to cool the body is taking blood away from the central blood supply so it is decreasing SBP.  The central regulation wants the blood to return to the core but the local skin control is conflicting with that demand.

4. Why did the patient lose consciousness only after moving to a sitting position on the edge of the hot tub?  He was in a more sitting position on the side of the tub than when he was in the tub so the blood pooled in his feet giving him orthostatic hypotension.  With his feet still in the water, there continued to be vasodilation of the cutaneous blood vessels in his feet thus increasing still the pooling of blood in his feet.  There is also the possibility that when he was in the water up to his chest, that the pressure of the water could have helped maintain the blood return to the core (reduced the peripheral pooling) thus helped maintain his SBP until he took his body out of the water.

5. Why were symptoms delayed in his colleagues?  Two reasons.  First the man who fainted was already warm from the exercising before he got in the water so he reached a higher temperature before his colleagues.  Second, do to the excitement of seeing a colleague faint, there was a sympathetic response on the colleagues.  This caused vasoconstriction of the periphery thus maintaining SBP for a period of time (No cooling of the body was taking place at this time r/t cutaneous vasoconstriction).  Once the sympathetic response wore off (when the ordeal was over and they were walking back to the locker room) vasodilation returned to continue cooling off the body.  Now the people are standing so an orthostatic hypotension takes place.


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