Nikiforov UV, Kisluchine VV, Chaus NI
Validation of a new method to measure cardiac output during
extracorporeal detoxification
42nd Annual Conference of the ASAIO
ASAIO J
(May) 42:(2):81 1996
Cardiac output measurements during dialysis might be useful for several
reasons. (1) Postdialysis
urea rebound correlates inversely with cardiac output
(George et al)
, (2) low cardiac output may mean increased mortality and propensity
to access thrombosis,
(3) high cardiac output in the absence of vasodilators may be a sign of an
undesirably elevated
shunt flow, and (4) cardiac output may be predictive of hypotension (see
Stakisaitis et al, ASN
abstract, 1995).
One way to measure cardiac output non-invasively during dialysis is by
impedance. Another is by
echocardiography. Pulse wave analysis using the Windkessel model using
either the brachial or
digital artery wave form is another. In this abstract, Nikiforov et al
validate the use of the
Transonics
impedance dilution device
, developed by Krivitski to measure cardiac output. The method is
straightforward. Saline
in the blood changes its acoustic properties and alters transmission speed.
A sensor is placed on
the arterial blood line. After calibrating with a small (5 ml) saline
injection proximal to the
sensor, a larger injection (10-20 ml) is given into the venous line. Some of
the injected saline
passes through the sensor after going through the cardiopulmonary circuit.
The dilution trace can
be used to compute the cardiac output, as in standard thermodilution or dye
dilution methodology.
Cardiac output was measured by thermodilution and by impedance dilution in 11
post-operative cardiac
patients undergoing dialysis or hemofiltration. A very good correlation
between the two methods was
reported (r=0.97). The number of measurements is not given. The range of
cardiac outputs is
reported as 2-8 L/min.
Comment: The thermodilution cardiac output itself is not reliable, and
should be phased
according to the respiratory cycle to produce accurate results.
Nevertheless, in the absence of
more detail, these are encouraging results. If the method can be modified to
dispense with the
actual injection technique (i.e., sudden backflush of dialysate, or some
other automated method),
this method would be useful for episodic determinations of cardiac output
during dialysis. However,
an impedance method would be still better if CO is being monitored to prevent
hypotension, as then
minute to minute changes in CO can be followed.
Interestingly, there was a second abstract at ASAIO validating the same
technology against an
ascending aortic flow probe in anesthetized pigs (page 85, Kisloukhine and
Dean), also showing
excellent results.
(John T. Daugirdas, M.D., University of Illinois at Chicago)
To go back use the BACK button on your browser.
Otherwise click on the desired link to this article below:
42nd Annual Conference of the ASAIO
Basic hemodialysis :
Complications (acute)