CARDIOVASCULAR JOURNAL OF AFRICA • Vol 21, No 1, January/February 2010
12
AFRICA
re-assessed, but this time in terms of a 50% rise in baseline
s-creatinine level (Table 4). Again, those patients with impaired
renal function were on average nine years older and their
EuroSCORE was higher. These patients’ estimated GFR was
26.6% lower than the group with no further impairment (55.8
vs 76.0 ml/min/1.73m
2
, respectively). It was disappointing not
to be able to demonstrate an influence from diabetes mellitus on
postoperative kidney dysfunction. Patients with left ventricular
function of less that 40% did have a higher chance of kidney
dysfunction after CABG. Patients with postoperative renal
dysfunction stayed in hospital on average two and a half days
longer than those with no dysfunction. In the series of Antunes,
renal dysfunction after surgery increased hospital stay by 3.4
days.
16
However, he defined postoperative impairment slightly
differently from us.
An important limitation was the size of the study popula-
tion. When the incidence of adverse effects or complications is
low, a study needs a large number of patients to be sufficiently
powered. We would have expected a difference in renal outcome
between diabetics and non-diabetics in terms of postoperative
renal impairment. The power of this study was perhaps just too
small to have demonstrated a statistical difference between 11.2
and 6.5% (Table 4). The same applies to mortality between those
who developed renal deterioration and those with unchanged
kidney function. Values of 1.2 and 5.9% (Table 4) were not suffi-
ciently different for the small number of patients in this study.
However, study populations of a few thousand are almost impos-
sible in one-man practices at a single institution.
17
Other data
missing in this study, such as haematocrit, incidence of hyperten-
sion and more detailed statistical analysis could perhaps clarify
the specific influence of GFR on the outcome after CABG.
Conclusion
In this group of patients who had isolated CABG, a fifth of them
had moderate to severe chronic kidney disease pre-operatively,
based on their GFR as estimated by the sMDRD. This confirms
the high prevalence of kidney co-morbidity in CABG patients.
Another one-fifth of the patients had stage 1 renal function pre-
operatively. Of the patients with chronic kidney disease, a quarter
developed renal impairment after the operation. They had a six-
times higher chance to develop renal impairment than those with
no or mild renal dysfunction before the operation. This postop-
erative deterioration of kidney function caused them to stay in
hospital on average two and a half days longer than the rest of the
patients. We conclude that GFR as estimated with the sMDRD is
a good predictor of renal impairment after CABG.
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