Medical, clinical question: Fever?

Question

A 4 year old is seen in a clinic with a temp of 103F. His skin is warm and flushed, his pulse is 120 bpm and respirations are shallow and rapis at 32 breaths per minute. His mom states that he has complained of a sore throat and has refused to drink or take meds to bring the temp down.

What are the physiological mechanisms of fever generation?

Is the warm, flushed skin, rapid heart rate, and respirations consistent with this level of fever?

After receiving an appropriate dose of Tylenol, the child begins to sweat, and the temp drops to 37.2C. What physiologic mechanisms are responsible for the drop in temp?

Answer 1

1.  A fever is caused when certain stimuli raise the hypothalamic set point for temperature.  These stimuli are certain cytokines (IL-1, IL-6, and TNF-alpha) or certain microbial toxins (e.g. bacterial wall fragments) and they cause the endothelium in the hypothalamus to generate prostaglandin E2.  This latter substance sets off a chain reaction that eventually raises the hypothalamus' set point.

2.  A fever is generated by (a) reducing heat loss by vasoconstriction and behaviours like putting on a jersey/jumper, and (b) increasing heat production by shivering, increasing muscle tone, and increasing the body's metabolic rate.

3.  A fever of 103 is very high, and I would say that the symptoms are consistent with this level of fever.  This part is debatable, though.

4.  There are two major mechanisms now responsible for the drop in temp.  Firstly, tylanol reduces prostaglandin production (more details in the reference below) and thus helps drop the hypothalamic set point back to normal.  With the body now perceiving the temperature as too high, it will aim to drop the temperature by means of things like vasodilatation, sweating (which encourages evaporation), and behavioural changes (e.g. taking off the jersey/jumper).