INDICES> Plasma Expanders in Shock? (3)

[Kirsten Myhr <myhr@online.no>]

INDICES> Plasma Expanders in Shock? (3)
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Dear George,

Treating shock is not easy. There are also different types of shock which
should not necessarily be treated the same way. Here is a copy from British
National Formulary (NB free online at http://bnf.vhn.net).
SHOCK. Shock is a medical emergency associated with a high mortality. The
underlying causes of shock such as haemorrhage, sepsis or myocardial
insufficiency should be corrected. The profound hypotension of shock must
be treated promptly to prevent tissue hypoxia and organ failure. Volume
replacement is essential to correct the hypovolaemia associated with
haemorrhage and sepsis but may be detrimental in cardiogenic shock.
Depending on haemodynamic status, cardiac output may be improved by the use
of sympathomimetic inotropes such as adrenaline (epinephrine), dobutamine
or dopamine (see notes above). In septic shock, when fluid replacement and
inotropic support fail to maintain blood pressure, the vasoconstrictor
noradrenaline (norepinephrine) may be considered. In cardiogenic shock
peripheral resistance is frequently high and to raise it further may worsen
myocardial performance and exacerbate tissue ischaemia.

The use of sympathomimetic inotropes and vasoconstrictors should preferably
be confined to the intensive care setting and undertaken with invasive
haemodynamic monitoring.

For advice on the management of anaphylactic shock, see section 3.4.3.
<http://bnf.vhn.net/bnf/documents/bnf.732.html>
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There was an article in the Lancet in March discussing colloids and acute
renal failure and it could be of interest. It also has many good
references, a.o. to the article Joel referred to:

Schortgen F et al. Effects of hydroxyethylstarch and gelatin on renal
function in severe sepsis: a multicentre randomised study. Lancet 2001;
357: 911-6.

It compares hydroxyethylstarch (HES) with gelatin (Haemaccel). It says that
'whether crystalloids or colloids are preferable and whether one colloid is
better than the others have been debated for three decades. No conclusive
data on outcomes and adverse events are available to settle the issue.'
Their study was not powered to detect a difference in mortality, but they
could conclude that HES was an independent risk factor for acute renal
failure in patients with severe sepsis or septic shock.

I have located five recent Cochrane reviews on the subject:
Bunn F, Alderson P, Hawkins V. Colloid solutions for fluid resuscitation
(http://www.update-software.com/abstracts/ab001319.htm)
Reviewers' conclusion: From this review, there is no evidence that one
colloid solution is more effective or safe than any other, although the
confidence intervals are wide and do not exclude clinically significant
differences between colloids. Larger trials of fluid therapy are needed it
clinically significant differences in mortality are to be detected or
excluded.

Alderson P, Schierhout G, Roberts I, Bunn F. Colloids versus crystalloinds
for fluid resuscitation in critically ill patients
(http://www.update-software.com/abstracts/ab000567.htm)
Reviewers' conclusion: There is no evidence from randomised controlled
trials that resuscitation with colloids reduces the risk of death compared
to crystalloids in patients with trauma, burns and following surgery. As
colloids are not associated with an improvement in survival, and as they
are more expensive than crystalloids, it is hard to see how their continued
use in  these patient types can be justified outside the context of
randomised controlled tirals.

Kwan I, Bunn F, Roberts I. Timing and volume of fluid administration for
patients with bleeding following trauma.
(http://www.update-software.com/abstracts/ab002245.htm)
Reviewers' conclusion: We found no evidence from randomised controlled
trials to support early or larger volume of intravenous fluid
administration in uncontrolled haemorrhage. There is continuing uncertainty
about the best fluid administration strategy in bleeding trauma patients.
Further randomised controlled trials are needed to establish the most
effective fluid resuscitation strategy.

Whattling PJ. Intravenous fluids for abdominal aortic surgery.
(http://www.update-software.com/abstracts/ab000991.htm)
Reviewers' conclusion: Further studies are required, with sufficient sample
size and power, to draw any further conclusions. There are no studies
examining the effects of combination fluid therapy.

Although you are not asking about albumin, there was a Cochrane review on
that in BMJ in 1998 that could also provide information on treatment of
critically ill patients in general. Cochrane Injuries Group Albumin
Reviewers. Human albumin administration in critically ill patients:
systematic review of randomised controlled trials. BMJ 1998; 317: 235-40.
Reviewers conclusion: There is no evidence that albumin administration
reduces the risk of death in critically ill patients with hypovolaemia,
burns or hypoalbuminaemia, and a strong suggestion that it may increase the
risk of death. These data may suggest that the use of human albumin in
critically ill patients should be urgently reviewed and that it should not
be used outside the context of a rigorously conducted randomised controlled
trial.

In Norway as far as I can see from a quick look at the recommendations in
our national formulary would be to give Ringer acetate (for some reasons
this is preferred to lactate) or sodium chloride for dehydration up to 5-6
litres. In cases of blood loss, treatment should also start with
crystalloids and only when blood loss is more than 20% will colloids be
added (but crystalloids continued as well), then erythrocytes and albumin
when blood loss is more than 50%. The risks of using blood products other
than plasma and albumin has caused indications to be tightened, which has
actually proven that in the past it was overused.

I think it is fair to conclude from all these references that there is
still a lot to be done in this area. For your own question, it also means
that there is little to support a demand for colloids. Particular care
should be taken where there is a risk of acute renal failure.

Kirsten

Kirsten Myhr
Head of Eastern Region Drug Information Centre

RELIS Ost
Ulleval University Hospital
0407 Oslo, Norway
Tel.: +47 23 01 64 11(o)   Fax: +47 23 01 64 10
+47 22 56 05 85 (h)   mobile: +47 416 38 747
myhr@online.no
www.relis.no




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