pH 7.51…lactate of 20??

Blood Gas!

This 74 year old gentleman attended the ED after phoning a friend because he ‘though he was having a stroke in both hands’.  Paramedics had to gain entry to the house, which was in a state of disrepair, cold, and unclean.  The patient was found on the floor, surrounded by vomit.  I tend to do a VBG in situations like this because I get an acid/base status and other useful information back faster than formal bloods.

His observations were essentially normal, apart from his 3 lead which was a veritable soup of short lived atrial arrhythmias, and PVCs.  He was also a bit cold 34 degrees C.  What is your interpretation of this gas?

pH 7.51
pCO2 60
pO2 28
BE 22
Na 145
K 2.2
AG 55.4
Cl 44
iCa 0.74
Gluc 9.8
Lac 20.0
HCO3- 40.8


My interpretation:

So starting from the top the patient is Alkalotic, with an elevated CO2.  This means they have to have a metabolic alkalosis with respiratory compensation.  Lets looks more closely at the metabolic component, the BE is 22, which means we have ‘22’ more bases than normal, we can also see that his bicarbonate is 40.8. (thats where they are coming from).

There are clues here.  We know that bicarbonate takes time to respond to problems.  This man must have a chronic problem causing his bicarbonate to go up.  We can infer this is a chronic metabolic alkalosis with a degree of respiratory compensation which is probably new.

Lets examine the AG – the gap is 55.4! Which is the highest gap I have EVER seen.  Remember that AG is calculated by adding the Na and K, and taking the chloride from bicarbonate.  Where is the source of the gap.  It’s predominantly from the Chloride.  Look it’s 44!  That’s less than HALF what it should be, I suspect that it’s not the only cause of the Gap here,  as we’ve got a lactate of 20 , pushing in the other direction and perversely helping to correct the alkalosis.

If you fancy you can calculate his SID which is 96!  High SID alkalosis is usually caused by gastric outlet obstruction, vomiting, excessive NG suctioning, diuretic mistakes,  primary hypoaldosteronism, or volume depletion.

This man has pyloric stenosis from untreated chronic H pylori, and acute renal failure secondary to volume depletion.  I think his gas shows a chronic metabolic alkalosis with respiratory compensation and a hyperlactaemia.   I have never seen this pattern in an adult before!


Na 147
K 2.1
Cl 51
Urea 33.8
Creat 542
Ca2+corr 2.1
Mg2+ 2.0
CRP <3




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