Blood Gas of the Week #21
A 3 year old, castrated male domestic shorthair cat is presented because the owner noted that the cat had not moved from a spot on the floor in the last 12 hours. He has a 1 week history of poor appetite, and 3 day history of vomiting.
The triage technician’s brief assessment suggests the cat is near death so cat and owner are brought directly to the treatment area so that obtaining a brief history and consent can occur simultaneously with the doctor’s assessment and initiation of resuscitation. The cat is stuporous, with slow shallow breathing, the smell of ketones on his breath, and non-palpable pulse. He groans when his abdomen is palpated, and he is quite edematous making peripheral access difficult. A jugular catheter is immediately placed, blood collected, and resuscitation initiated. Vital signs obtained while the catheter was being placed are as follows:
T 96.8F P 105 R 12 mm grey CRT prolonged BCS 7/9 Weight 7.4kg BP unable to obtain
Just as your technician tells you she can’t get the blood pressure to read your STAT blood work comes back as follows. Interpret the blood gas.
Step 1: Evaluate the pH
The pH is very low at 6.88 – this is acidemia.
Step 2: Determine the primary process
Acidemia can be caused by a high pCO2 or a low bicarbonate. This patient has both a high pCO2 and a low bicarbonate – so this is a mixed acid-base disturbance.
Case Discussion
This cat was ultimately found to have a pancreatic abscess, diabetes (possibly due to the injury to his pancreas, although this might have been pre-existing) and subsequent acute kidney injury. So why the mixed disturbance? The metabolic acidosis is not surprising since he is in kidney failure, has an abscess, and is diabetic with circulating ketones. By the time he was presented he was late in the course of his illness and had a very depressed level of consciousness and depressed respirations. His slow and shallow breathing was not enough to breathe off his CO2, resulting in a simultaneous respiratory acidosis.
