A young French Bulldog is sedated prior to surgery.
A pre-anaesthetic blood test can reveal hidden or undetected health problems that are not obvious from a physical examination alone. Image ©iStock.com/DenGuy

Have you ever noticed that, sometimes after starving, the haematocrit (Hct) and haemoglobin (Hgb) levels appear a little high on pre-anaesthetic bloods prior to a surgical procedure that morning?

If so, make sure you look at the figures.

If, like us, your laboratory machine produces a band with a red marker in the middle indicating some elevation, make sure you also look at the absolute figures.

I recently saw a nine-year-old boxer that, after a surgical procedure, developed redder and redder skin and mucous membranes. She had high Hct and Hgb on pre-anaesthetic bloods and subsequently turned out to have polycythaemia vera with, eventually, a Hct of 84.9.

Four episodes of venipuncture (taking 200ml to 300ml of initially very viscous blood on each occasion), plus treatment with hydroxycarbamide, and she was feeling much better.

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