Re: [HSF] BT shunt – neonate

[Prasanna Simha M]

If you assume a SpvO2 of 100 %, SaO2 = SpaO2 (approx as there is no
effective left to right shunt) ,SvO2 in a cyanotic 50-60 % then for a  Qp/Q
of 1:1 would be around 70 -80 %
Qp/Qs = systemic av difference / pulmonary AV difference = (Sa02
-Sv02/Spvo2-SpaO2) = 80 -60 /100 - 80
So in  a single ventricle physiology a saturation of around 80 -85 % (and at
times lower) would result in a balalnced circulation whereas in a TOF a
slightly higher  value may be accepted because of small PA's and neonatal
resistance would give a value between 89 -82 % . Higher thanthat would lead
to pulmonary overcirculation. The goal is to keep Qp/Qs < 1.5
Additional values like  Omega  (Oxygen excess factor) can also be used to
optimize oxygen delivery
oxygen delivered/oxygen consumed = CaO2/(CaO2-CsvO2) = SaO2/ (SaO2- SvO2)
which should be kept below 3.0


On Jan 27, 2008 4:11 PM, Prasanna Simha M <prasannasimha at gmail.com> wrote:

> In a cyanotic patient a saturation @ 92 %represents a Qp/Qs of 1:1 and
> also below 92 % the O2 release curve shows a sharp dip.
> Prasanna
>
>
> On Jan 27, 2008 3:56 PM, Nasser F. Abou'Seada <nfaabouseada at gmail.com>
> wrote:
>
> > Prasanna
> > would you elaborate on the 92% figure please ?
> >
> > NFA
> >
> > On Jan 26, 2008 11:03 AM, Prasanna Simha M <prasannasimha at gmail.com>
> > wrote:
> >
> > > unremitting spells or as a part of  a palliative staged procedure  for
> > eg
> > > as
> > > a part of a Norwood etc.In a neonate a 3 or 3.5mm shunt is enough. The
> > > shunt
> > > should give a Sat not greater than 92 %
> > > Prasanna
> > >
> > > On Jan 26, 2008 10:24 PM, james le <jamesle2007 at yahoo.com> wrote:
> > >
> > > >
> > > >
> > > >   What are the situations when we may  need  CPB   to perform  BT
> > shunt
> > > in
> > > > neonates?
> > > >
> > > >  How can we assess  excessive  flow from the shunt  before it leads
> > to
> > > >  elevation of serum lactate? Can ECHO assessment  help?
> > > >
> > > >
> > > >
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-- 
Prasanna Simha M