Parameters:
(1) external temperature of the great toe in °C (monitored with a surface probe taped to the toe)
(2) rectal temperature representing core temperature (monitored with a rectal temperature probe)
(3) ambient environmental temperatures (usually 21-25 °C or 70-77°F)
Measurements:
(1) gradient (difference) between rectal and great toe temperatures
(2) gradient between great toe temperature and ambient temperature
(3) Burton index (Joly and Weil, 1969)
In a healthy adult in a room with stable temperature, the difference (rectal temperature) – (great toe surface temperature) is in the range of 3.5 – 4.4°C (Kholoussy et al).
Joly and Weil found that a poor prognosis occurred in patients with both:
(1) a toe temperature 3 hours after admission < 27°C and
(2) a difference between the toe and ambient temperature < 2°C
Burton index =
= ((toe temperature) – (ambient temperature)) / ((rectal temperature) – (toe temperature)
The great toe temperature can also serve as an estimate of cardiac index with the r value 0.71 (Joly and Weil, 1969):
cardiac index in L per min per meter square BSA =
= (0.286 * (toe temperature in °C)) – 5.24
Vincent et al (1988) found the gradient between toe and ambient temperature correlated with cardiac index with a r value of 0.63.
cardiac index in L per min per meter square BSA =
= 1.58 + (0.07 * ((toe temperature) – (ambient temperature)))
Factors limiting accuracy or usefulness of the great toe measurements:
(1) peripheral vascular disease
(2) central hypothermia
(3) use of vasoactive drugs
(4) the type of shock (not useful in septic shock)
(5) quality of the attachment for the toe thermistor
(6) amount of movement and rubbing against blankets
