BGOTW #28

Blood Gas of the Week #28

A 13 year old castrated male domestic shorthair cat is presented laterally recumbent and minimally responsive. The owners report chronic vomiting that has increased in frequency recently. Historically the vomitus was yellow bile however recently there is partially to undigested food in the vomitus. The cat seemed lethargic in the last 24 hours but was still interactive last night. The owner awoke to find the cat in the current condition this morning.

On examination the cat is responsive only to noxious stimuli, has a very slow and shallow breathing pattern, absent femoral pulses with cold extremities, midrange pupils with sluggish PLR, very dry mucus membranes, generally poor body condition and coat quality, and you think you feel a bowel-associated mass, but are unsure if it is actually a mass or just a hard ball of feces. The heart sounds somewhat quiet, there are no breath soundsTriage vitals are as follows:

T 94.5F    P 100    R 8    mm grey    CRT >3     BCS 3/9    Weight 2.9kg   BP unable to obtain

Your fantastic technical team rapidly places an IV catheter, and blood is collected for analysis. Interpret the blood gas:

Step 1: Evaluate the pH

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The pH is very low at 7.12 – this is acidemia. 

 

Step 2: Determine the primary process

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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. There is both a metabolic acidosis and a respiratory acidosis. Both are contributing to the severely low pH:

 

Since there is both a metabolic acidosis and a respiratory acidosis, there are two primary problems: one or more metabolic processes causing acidosis, as well as decreased ventilatory capacity resulting in accumulation of CO2, also causing acidosis. This also means that we can’t calculate compensation.

So this is a Mixed acid-base disturbance characterized by a respiratory acidosis AND metabolic acidosis.

 

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.