>
> It's reassuring to know that there is much debate, on exactly, which
> inotrope to use!
>
> Is this a personal, intuitive thing?
Yes
>
> I like to think of things like; a 'wide open circulation', that needs
> 'tightening' (sepsis), with the use of predominately alpha action
> (Noradrenaline and Adrenalin to an extent). Or a failing pump
> that requires
> a positive inotrope; doputamine, with adrenaline to
> counteract the side
> effects of opening up the circulation;if required because of low BP!
Sort of. However, if you're already on full throttle, pushing the pedal
harder won't help much.
>
> Of course nitrates are used to 'off load the heart', and
> presumably decrease
> LV diastolic filling pressures (ultimately, leading to
> over-stretch, and
> hence decreased LV function, if LV ED pressures are raised -
> {but who knows
> whats going off, without PA line}).
Yes. there is a dilated cardiomyopathy. Shrink the size of end diastolic
volume and you make the pump work harder (this is a basic law of physics and
I can never remember whose it is. Would someone please help me on this- the
thing that says a balloon gets easier to inflate as it gets bigger- this has
effects at volumes where the Starling curve is still on the unstroke).
>
> Does anyone ever use Noradrenaline without PA line?
> For that matter does anyone ever use inotropes blindly without CVP?
Use inotropes without CVP (CVP is not really an improvement on JVP in
experienced hands and selected patients; just easier to measure).
Noradrenaline a little bit different- you know you're bringing up BP, but
want to know the cost in terms of cardiac output. I suppose you could use
one of the non invasive doppler things instead, but I don't have one of them
yet.
> LVF is likely to be due to pump failure ( beware of valve
> problems)- so
> logically can you make a broken pump, pump harder with inotropes?
Not if the patient already has maximal drive. More to the point- do you want
to drive an ischaemic heart harder. Remember- nobody has ever shown any
benefit of inotropes in cardiogenic shock (except possibly for a few hours
awaiting transplant). (Indeed the large Italian study that looked at
inotropes in septic shock showed that goal directed therapy aimed at much
lower goals had significant benefits in terms of outcomes).
> Physiologists - correct me if I'm wrong in my rational use of
> inotropes...please!!
You can only be rational if you know what an inotrope does. The stuff in the
books from lab rats and healthy volunteers tells you little about the
effects in patients with shock, high circulating catecholamine levels and a
lot of nitric oxide in the tissues.
Matt Dunn
Warwick
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