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Blood Gas Interpretation and Temperature Measurements

Three Part Question

In [interpreting arterial blood gases in adults] does [patient temperature entered into the gas analyser] influence [clinical management of the patient]

Clinical Scenario

Blood gas analysers are typically preset to assume a patient’s temperature is normothermic at 37 degrees centigrade. In clinical practice the temperature of the patient is infrequently taken at the time of sample or entered into the analyser. With emergency departments exposed to patients presenting with temperature extremes, you wonder whether the temperature entered into the gas analyser has a significant effect on results and subsequent clinical management.

Search Strategy

Medline 1966 to December week 1 2010 using the OVID interface, From 1966 to Current, Embase mkikl,1865 to December week 1 2010 using the OVID interface.
(Blood Gas/ Blood Gas Analysis) AND (Axilla temperature/ or body temperature/ or body temperature measurement/ or core temperature/ or high temperature/ or low temperature/ or incubation temperature/ or temperature/ or temperature dependence/ or temperature measurement/ or tympanic temperature). LIMIT to human and adult and English language.

396 articles were found, none of which contained evidence-based studies relevant to the question.

Search Outcome

396 articles were found, none of which contained evidence-based studies relevant to the question.


Personal experience demonstrates there are inconsistencies and variations in the way blood gases are processed in clinical practice. There is literature supporting the use of temperature correction during cardiopulmonary bypass or during a deep hypothermic circulatory arrest, where the patient is cooled to severe hypothermia (TH, Baltal M, Bilen A, Seydaoglu G, Incesoz M, Tasdelen A, Aslamaci S. (2003). Comparison of alpha-stat and pH-stat cardiopulmonary bypass in relation to jugular venous oxygen saturation and cerebral glucose-oxygenation utilization. Anesthesia and Analgesia; 96: 644–650). The solubility of oxygen and carbon dioxide in the blood increases as temperature decreases and vice versa; therefore, temperature changes can cause shifts in the Oxygen Haemoglobin Dissociation Curve (Guyton A, Hall J. (2000). Textbook of Medical Physiology. Philadelphia: WB Saunders). CO2 production in hypothermic situations is low due to a reduced metabolic rate and inversely high in hyperthermia situations, thus affecting the acid-base balance. This causes a lower PaCO2 causing a respiratory alkalosis in the acute stage and an acidosis in high PaCO2 environments (. Bookallil MJ. (1999). pH and temperature, Royal Prince Alfred Hospital, The University of Sydney. Therefore, using temperature correction may add to confusion and mislead the interpreter as to what is actually occurring at a physiological level. Furthermore, there is little actual evidence on normal partial pressures of gases at varying temperatures (Williams JJ, Marshall BE. (1982). A fresh look at an old question. Anesthesiology; 56: 1–2.) . Temperature correction will affect the results, the extent of which is variable and dependant on several factors. If there is no standard local guideline regarding the use of temperature correction, there is a risk that when blood gases are examined, there may be inconsistencies in the way information is acted upon. Further clinical studies into temperature correction are required to formally evaluate the question.

Clinical Bottom Line

Although there are no clinical studies directly related to patient temperature correction and blood gas measurements, the evidence suggests results vary according to temperature. A standardised approach should be adopted by emergency departments to ensure consistency in result interpretation and clinical management.