BGOTW #14
A 6 year, castrated male Labrador retriever mix is presented for acute-onset head tilt, abnormal gait, and vomiting. On examination he shows a left head tilt, horizontal nystagmus with fast phase to the right, and vestibular ataxia. He vomits partially digested food during the exam. The remainder of the examination is unremarkable.
T 102.3 P 140 R pant mm pink CRT 1.5s BCS 6/9 Weight 27kg BP 142/86 (105mmHg)
Interpret the blood gas:
Step 1: Evaluate the pH
The patient’s pH is 7.43 – in the normal range. There are two possibilities when we see a normal pH
- The patient’s acid-base status is normal OR
- The patient has a mixed acid-base status
The biggest mistake that people make is looking only at the pH, and stopping when they see it is normal. When you do this, you will miss many mixed disturbances that could give you clues about what is going on with the patient.
Step 2: Determine the primary process
Compensation should not take the pH back to completely normal. When we have a mixed acid-base disturbance we have more than one primary process happening (as opposed to a simple disturbance where there is a primary process and a compensatory process). So we need to look at the respiratory component and the metabolic component to define the different problems.
Respiratory component: In this patient the pCO2 is 31, a mild respiratory alkalosis
Metabolic component: In this patient the bicarbonate is 19 – just a touch low suggesting a metabolic acidosis
Step 3: Name the process (we can’t calculate compensation here because this is a mixed disturbance)
Want to learn about reading blood gases? You’ve come to the right place. Every week a new blood gas case will be posted. The scenario will post on Monday and the solution will post on Wednesday.
New to blood gasses? Check out the quick guide to acid-base interpretation here.
