I am grateful to Dr Cowley and his colleagues for publishing an interesting article on the "Interpretation of arterial blood gas results" and to medical student Camilli Simini for encouraging the use of acid base nomograms as an aid to interpretation in her rapid response.
I would like to point out a potential patient saftey issue in failing to appreciate the difference bewteen Standard and Actual HCO3-. Dr Cowley and coauthors emphasise the use of standard bicarbonate (sHCO3-) whereas the inpretation of most acid base nomograms requires the actual bicarbonate.
Standard refers to standard conditions and is the concentration in whole blood that has been equilibrated at 37 degrees C with a PCO2 of 40 mmHg (5.3 kPa) with oxygen to give full saturation of haemoglobin.
Actual bicarbonate is claculated by the gas analyser from the Henderson Hasselbach equation using pH and PCO2 [1].
[1] Lawrrie, A. and Golda, B.P. Actual or Standard Bicarbonate. Lancet 1979 Jul 28;2(8135):201-2.
Competing interests:
No competing interests
22 March 2013
Eugene Lloyd
Senior Teaching Fellow/Specialty Doctor Emergency Medicine
University of Bristol/North Bristol NHS Trust
School of Physiology and Pharmacology, Medical Sciences Building, University Walk, Bristol, UK, BS8 1TD
Rapid Response:
Re: Interpreting arterial blood gas results
Dear Editor,
I am grateful to Dr Cowley and his colleagues for publishing an interesting article on the "Interpretation of arterial blood gas results" and to medical student Camilli Simini for encouraging the use of acid base nomograms as an aid to interpretation in her rapid response.
I would like to point out a potential patient saftey issue in failing to appreciate the difference bewteen Standard and Actual HCO3-. Dr Cowley and coauthors emphasise the use of standard bicarbonate (sHCO3-) whereas the inpretation of most acid base nomograms requires the actual bicarbonate.
Standard refers to standard conditions and is the concentration in whole blood that has been equilibrated at 37 degrees C with a PCO2 of 40 mmHg (5.3 kPa) with oxygen to give full saturation of haemoglobin.
Actual bicarbonate is claculated by the gas analyser from the Henderson Hasselbach equation using pH and PCO2 [1].
[1] Lawrrie, A. and Golda, B.P. Actual or Standard Bicarbonate. Lancet 1979 Jul 28;2(8135):201-2.
Competing interests: No competing interests