Wednesday, May 21, 2008

In which I kid myself I am Mr D'Arcy.

We do love talking about the weather here in dear old Blighty. Well after all we seem to have so much of it and it’s so much safer than talking about politics, religion, or that other thing…

Here in Borchester it’s not at all uncommon to experience “four seasons in one day”, especially at this time of year. So to have five consecutive days of sunshine and actual warmth last week came as a bit of a surprise. Of course we are now back to “changeable” with “sunny spells” and “showers”, but it was nice while it lasted. Or at least it was for most of us. For one small group of our regular customers it has proved to be a bit of a challenge though.

To explain why, I need to take us back a couple of years. Around that time we got a brand shiny new test to play with here in GP land, the eGFR. It is a whizzy test to be sure. It tells us, by some clever sciency technique too complex for my little grey cells, how well a punter’s kidneys are filtering. This is a pretty useful piece of information, believe it or not. It is especially useful where a customer already has diseases known to muck up kidney function, like diabetes and some sorts or hypertension to name just a couple. And better yet, we have an evidence base of drugs to use to help improve renal function once it is shown to be “failing” as charted by a decline in eGFR.

The only thing is, in screening for other conditions, as we will often do in the elderly, we will ask to look at their blood chemistry (measuring other vitally important chemicals like sodium, potassium, urea and creatinine) and the lab now takes all that chemical soup and uses it to generate an eGFR result, even where that’s not what we were looking for. This in turn has revealed what we have actually known for a long time, but not previously quantified, which is that older folks' kidneys do not filter efficiently. This means that in the absence of any of the scary conditions alluded to above it is still quite possible to have a low eGFR and hence “renal disease” purely as a function of being older. And since we have a lovely evidence base for medicines that will help preserve renal function many of them are ending up medicated.

Now I know you all though sunshine was only medically important in things like rickets (good) and skin cancers and such (bad), but it seems also to have been having an effect on such medicated older patients. The class of drug most widely used in renal protection is the ACE (angiotensin converting enzyme inhibitors). And ACE drugs are known to lower blood pressure, and to do so disproportionately well in the elderly. Taking a little old lady, with “renal disease” (that’s little old kidneys to you and me) and bunging her on an ACE will likely improve her renal function a bit, and could drop her blood pressure a bit more than a bit. Now add in unseasonably warm weather (and them “not casting a clout”, May not yet being out and all) and a sort of "pressure cooker in reverse" effect takes place. So in this past week the surgery has seen a handful of little old ladies having a fit of the vapours as their blood pressure falls to “fainty” levels.

It’s called the law of unintended consequences. Still it’s kind of nice to think I can still cause ladies to swoon at my age….


Elaine said...

Do we get the wet shirt photo? ;-)

orchidea said...

Mmm. What a good idea, Elaine!

Doctor Jest said...

Hmm. Perhaps next "Spring Break" if you both promise to be very good.