Cirugia no cardiaca, hipotension y necrosis miocardica
More than one in five patients at high cardiovascular risk show signs
of heart muscle necrosis immediately after undergoing non-cardiac
elective surgery, Australian research has found.
Seventy nine patients out of 352 undergoing elective surgery at a
Sydney hospital showed elevation in a high-sensitivity troponin T assay
(hs-TnT) in the 48 hours after their operation.
Only seven patients (2%) showed clinical evidence of MI, so without the
very sensitive hs-TnT assay, the myocardial necrosis in the others
would not have been detected, said the authors, led by Professor David
Brieger of Concord Repatriation General Hospital.
Myocardial necrosis was more likely to occur in older patients; if
there had been a period of hypotension during the operation; and if the
operation was an orthopaedic procedure, the authors found.
Intraoperative hypotension (defined as systolic blood pressure of 100mg
Hg or less) occurred in 70% of patients, lasting for about half an hour
on average. Increasing the period of hypotension “strongly predicted
myocardial necrosis.”
The findings suggested “The most common mechanism [for the myocardial
necrosis] is likely to be a mismatch between myocardial oxygen supply
and demand rather than thrombus formation on vulnerable plaque”, the
authors said.
The authors measured hs-TNT in all the patients before the surgery and
found that 31% had raised levels (greater than 14ng/litre). Having
elevated levels before the operation did not increase the likelihood of
myocardial damage during the operation.
The authors commented that a high incidence of perioperative cardiac
events after orthopaedic surgery had been reported in other studies.
They speculated that subclinical fat embolism could be an underlying
cause.
All of the patients were on antiplatelet therapy and 80% were taken off
this before the operation. The authors commented that this went against
current guidelines, although no link was found between anti-platelet
therapy cessation and perioperative myocardial necrosis in their cohort.
Heart 2012: doi:10.1136/heartjnl-2011-301577
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