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Three Part Question

In [adult patients with classical heat-stroke] is [rectal thermometry] [accurate at recording core body temperature]?

Clinical Scenario

A 50 year old male is brought in by ambulance after a collapse. It is a hot day and the patient had been playing 5-aside football when he collapsed. In the Emergency Department he is a assessed, having a rectal temperature of 41.5°C and a GCS of 4. The patient is hot and not sweating. A diagnosis of heatstroke is made. You wonder if rectal thermometry is the most accurate available method for recording the patient’s core body temperature.

Search Strategy

Ovid Medline® 1950 to June Week 2 2009
Ovid Embase 1980 to 2009 Week 25
Ovid EBM Reviews- Cochrane Central Register of Controlled Trials 2nd Quarter 2009
Ovid EBM Reviews - Cochrane Database of Systematic Reviews 2nd Quarter 2009
EBSCOHost CINAHL Plus

Medline® search strategy;
1. heat stroke.mp. or exp Heat Exhaustion/ or exp Heat Stroke/
2. (rectal adj1 temperature).mp. [mp=title, original title, abstract, name of substance word, subject heading word]
3. exp Body Temperature/ or core body temperature.mp.
4. rectal temperature.mp. or exp Thermometers/
5. 4 or 3 or 2
6. 1 and 5
7. limit 6 to (english language and humans)
8. 7 and "Heat Stroke".sa_suba.
9. 8 and "Heat Exhaustion".sa_suba.
10. 8 or 9

Embase search strategy;
1. heat stroke.mp. or exp Heat Exhaustion/ or exp Heat Stroke/
2. (rectal adj1 temperature).mp. [mp=title, abstract, subject headings, heading word, drug trade name, original title, device manufacturer, drug manufacturer name]
3. exp Body Temperature/ or core body temperature.mp.
4. rectal temperature.mp. or exp Thermometers/
5. 4 or 3 or 2
6. 1 and 5
7. limit 6 to (human and english language)
8. 7 and "Heat Stroke".sa_suba.

Cochrane search strategy;
1. heat stroke.mp. or exp Heat Exhaustion/ or exp Heat Stroke/
2. (rectal adj1 temperature).mp. [mp=ti, ot, ab, sh, hw, kw, tx, ct]
3. exp Body Temperature/ or core body temperature.mp.
4. rectal temperature.mp. or exp Thermometers/
5. 4 or 3 or 2
6. 1 and 5

CINAHL Plus search strategy;
1.(MH "Heat Stroke") or (MH "Heat Exhaustion") AND (rectal temperature OR themometer)

Search Outcome

The search returned 1009 results (Medline 570, Embase 425, Cochrane 8, Cinahl 6) 8 of which were relevant, mainly relating to heat exhaustion in athletes. There were, however, 4 results of good quality suitable for inclusion. Two comparative studies compared rectal temperature (Trec) with tympanic temperature (Tty), whilst another compared Trec with temporal artery temperature (TAT). An observational field study compared a wide range of devices simultaneously against a well calibrated Trec gold standard. Search outcome data is largely based on exertional heat exhaustion in athletes and does not cater well for the heat wave patient, typically elderly and suffering purely from classical heat stroke. A further search of the literature journal articles deliberating heat stroke specifically, however no good quality data on heat stroke was found.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Hansen R.D., Olds T.S., Richards D.A., Richards C.R., Leelarthaepin B. 1996 Germany	12 collapsed ‘fun-runners’ monitored by both Trec and Tty	Comparative Study	On admission	Tty was (mean+/-SEM) 1.2+/-0.3degrees°C lower than Trec	Weak for BET as not looking at heatstroke. Focus on one manufacturer’s IR tympanic thermometry device.
			Subsequent monitoring	Tty correlated significantly with Trec Trec significantly lower than Tty after admission
			In diagnosing exertional heat exhaustion	Tty ≥37.1°C predicted Trec ≥38°C (sens 0.93 spec 0.63) 38°C diagnostic EHE, therefore Tty misdiagnosing condition
Ronneberg K., Roberts W.O., McBean A.D., Center B.A. 2008 United States	60 collapsed marathon runners with Trec measured in 2 consecutive annual races along with temporal artery temperature (TAT) device	Comparative Study	Trec	17 hyperthermic runners indentified (Trec ≥39.4°C) mean ± SD Trec of 40.7°C ± 0.94°C	Focus on one manufacturer’s TAT device alone.
			TAT	2 hyperthermic runners identified mean ± SD TAT temperature of 37.4°C ± 1.3°C
			Normothermic collapsed runners	No statistical correlation between Trec and TAT measurements in the 43/60 normothermic runners (P=0.37)
Newsham K.R., Saunders J.E., Nordin E.S. 2002 United States	10 volunteers exercising in a treatment room of 32°C (27°C wet bulb) with regular Trec and Tty recordings before, during and after exercise and removal from warm environment.	Comparative Study	Before exercise	Tty 37.3°C Trec 37.3°C	Weak for BET as data not applicable for thermoregulatory failure (heatstroke) patients.
			During exercise	Both device measurements strongly correlated (P<0.001)
			Temperature rise	Tty >1.9°C Trec >1.5°C Statistically significant (P=0.03)
			Peak temperature	Tty 39.2°C Trec 38.9°C Not statistically significant (P>0.05)
			After exercise	Notable Trec ‘lag’ whereby Trec continued to rise for 5-10minutes (average +0.1°C) Tty returned to pre-exercise levels quickly, Trec very similar at end of cold-environment rest period than during exercise itself. Suggests Trec unreliable measurement of core temperature during rapid cooling treatments.
Casa D.J., Becker S.M., Ganio M.S., Brown C.M., Yeargin S.W., Roti M.W., Siegler J., et al. 2007 United States	25 patients, simultaneous testing of devices in the oral, axilla, aural, gastrointestinal, forehead, temporal and rectal regions. Measurements taken as per instructions as well as how observed in road races. Forehead temperature also measured on the athletic field (direct sunlight)- other measurements in covered pavilion.	Observational Field Study	Device invalid if Trec and Tdevice difference ±0.27°C, Trec taken as criterion standard
			Expensive oral device	-1.2°C
			Inexpensive oral device	-1.67°C
			Expensive axillary device	-2.58°C
			Inexpensive axillary device	-2.07°C
			Aural device	-1.00°C
			Temporal device according to instruction manual	-1.46°C
			Temporal device modified method	-1.36°C
			Forehead temperature on athletic field	+0.6°C
			Gastrointestinal	-0.19°C
			Forehead in pavilion	-0.14°C

Comment(s)

Rectal temperature is often cited as the gold standard for core body temperature measurement. Both exertional and classical heatstroke rely on an accurate measurement of core body temperature for diagnosis alongside neurological involvement. A reliable core body temperature is also important in differentiating between heat exhaustion and heat stroke, as well as monitoring the success of cooling therapies. The studies cited here suggest that rectal temperature is the best available method for the measurement of core body temperature. It is invasive and more time consuming to undertake however the best evidence suggests a wild variation when comparing other devices (such as oral, tympanic and axillary measurement) against Trec. In the medical emergency that is heatstroke it is critical the core body temperature measurement can be trusted and as such all other devices could well be mistrusted. The concept of ‘rectal lag’ in rapid cooling situations seems to require further investigation to ensure hypothermia is not inadvertently induced during the treatment of heatstroke reliant on a solely rectal measurement of core body temperature.

Clinical Bottom Line

Rectal thermometry represents the most accurate, reliable and rapidly available method of core body temperature measurement. Rectal thermometry should always be used when diagnosing heat stroke and in monitoring the effects of cooling therapies.

References

1. Hansen R.D., Olds T.S., Richards D.A., Richards C.R., Leelarthaepin B. Infrared thermometry in the diagnosis and treatment of heat exhaustion International Journal of Sports Medicine. 17(1)(pp 66-70), 1996. Date of Publication: 1996.
2. Ronneberg K., Roberts W.O., McBean A.D., Center B.A. Temporal artery temperature measurements do not detect hyperthermic marathon runners. Medicine and Science in Sports and Exercise. 40(8)(pp 1373-1375), 2008. Date of Publication: 2008.
3. Newsham K.R., Saunders J.E., Nordin E.S. Comparison of rectal and tympanic thermometry during exercise. Southern Medical Journal 95(8)(pp 804-810), 2002.
4. Casa D.J., Becker S.M., Ganio M.S., Brown C.M., Yeargin S.W., Roti M.W., Siegler J., Blowers J.A., Glaviano N.R., Huggins R.A., Armstrong L.E., Maresh C.M. Validity of devices that assess body temperature during outdoor exercise in the heat. Journal of Athletic Training. 42(3)(pp 333-342), 2007. Date of Publication: Jul 2007.