Have pre-anaesthetic lab tests been relevant for choosing anaesthetic protocols?

Hello there!

Keeping on the discussion about the video lesson “ Patient Assessment ” - Anaesthesia Unravelled, we point out this quite interesting paper, from Alef et al (2008) , to make some "concerns“ about the relevance of laboratory tests for the decision of a anesthetic protocol.

The authors analysed 1537 lab tests (haematological and biochemical) of dogs that would be undergoing anaesthesia, and 84% out of them got normal exams. Only 10% had haematological changes, but almost all close to the reference range for the specie. Regarding serum urea and creatinine, less than 10% had levels above those considered normal. The serum FA and ALT were considered higher from the reference in about 30-40% of the patients, but with little change in the anaesthetic protocol. In summary, only 0.2% of the animals had their anaesthetic protocol changed, in 0.8%, the anaesthesia was postponed, and in 1.5%, the animals required preoperative therapy. Such a small amount, isn't it?

Some points to consider :
- The vast majority of them were considered ASA 1-2 (85%);
- The mean age was 5.8 years;
- Despite the low percentage of changing protocols, they happened at all.

So, why do run pre-anaesthetic exams for?
I'm sure they are so important because a small percentage of our patients could benefit from this. However, in my opinion, the most important point is that we must know about the "baseline" patient condition before give them some drug. This is the only way to know if the anaesthetic procedure would have any influence on the perianaesthetic period or even trigger any problem in the post-anaesthetic one.

However, in view of this paper, even considering it is a bit old (more than 10 years) and anaesthetic drugs have been safer nowadays, chances to change anaesthetic protocols in dogs under 2 years old, because of lab tests, are practically null. Conversely, dogs over 10 years old could get lab test changes, which is expected.

In summary, asking for lab tests could depend on the situation, the professional and the patient condition. Obviously, I believe the anaesthetist will feel much more confident to anaesthetise their patient with preoperative exams on their hands. But we should think about how much money these exams could weigh on the price of a small procedure, like spay or castration, for a low-income owner. Again, I am not in favour of neglecting pre-anaesthetic lab exams ... just to think about...

Read up this paper!

Tips? Comments? Do it please!

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