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Review:
P.J. Devereaux, Lee Goldman, Salim Yusuf, Ken Gilbert, Kate Leslie, and Gordon H. Guyatt
Surveillance and prevention of major perioperative ischemic cardiac events in patients undergoing noncardiac surgery: a review
CMAJ 2005; 173: 779-788 [Abstract] [Full text] [PDF]
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[Read eLetter] Intraoperative perturbations in regional and systemic tissue energetics.
Richard G Fiddian-Green   (6 October 2005)

Intraoperative perturbations in regional and systemic tissue energetics. 6 October 2005
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Richard G Fiddian-Green
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Re: Intraoperative perturbations in regional and systemic tissue energetics.

richardfg{at}hotmail.com Richard G Fiddian-Green

Optimisation of cardiac output and oxygen delivery to >600 ml/min/m2 would seem to improve outcome in those having cardiac surgery and might do so by similar means in those having non-cardiac surgery (1). This was not considered in this article.

It has been suggested that exposure of the open wound during surgery to a hypocarbic hyperoxic environment might raise the tissue pH and thereby increase the myocardial workload and by inference intravascular volume because of the need of an increase in regional blood flow to accommodqate the increased demand for nutrient delivery. The hyperoxic environment might compound the problem by increasing the generation of free radicals (2).

However "in adult patients undergoing cardiac surgery with cardiopulmonary bypass, regional myocardial ischemic acidosis before aortic crossclamping, during aortic crossclamping, and at discontinuation of cardiopulmonary bypass are independently associated with reduced long- term postoperative survival. Reversing or avoiding myocardial acidosis during cardiac surgery improves long-term patient survival"(3).

Perhaps optimisation works by eliminating any dehydration and improving the body's capacity to accommodate the hypothetical increase in demand for an increase in intravascular volume induce by an exposed wound but exposing patients to the risks of volume overload when the wound is closed and the process reversed.

Anaesthetic agents might have similar effects for many would appear to compromise oxidative phosphorylation but this effect might be beneficial if it indeed induces preconditioning(4). But the issues are complex (5).

As safe as modern anaesthesia and surgery have become there remain unpredictable risks even in the young without co-morbidities. Greater attention to the optimisation of regional and systemic tissue energetics might help to limit these remaining risks of surgery including the cardic events addressed in this article.

1. Editorial by Tom Treasure, Professor of cardiothoracic surgery and David Bennett, Professor of intensive care. Reducing the risk of major elective surgery. BMJ 1999;318:1087-1088 ( 24 April ). 2. Product of a tissue alkalosis induced by hypocarbia? Richard G Fiddian-Green CJA Online, 21 Dec 2004 re: T Tsubo, T Kudo, A Matsuki and T Oyama Decreased glucose utilization during prolonged anaesthesia and surgery Canadian Journal of Anesthesia, Vol 37, 645-649

3. Khuri SF, Healey NA, Hossain M, Birjiniuk V, Crittenden MD, Josa M, Treanor PR, Najjar SF, Kumbhani DJ, Henderson WG. Intraoperative regional myocardial acidosis and reduction in long-term survival after cardiac surgery. J Thorac Cardiovasc Surg. 2005 Feb;129(2):372-81.

4. Riess ML, Kevin LG, McCormick J, Jiang MT, Rhodes SS, Stowe DF. Anesthetic preconditioning: the role of free radicals in sevoflurane- induced attenuation of mitochondrial electron transport in Guinea pig isolated hearts. Anesth Analg. 2005 Jan;100(1):46-53.

5. Richard G Fiddian-Green Preconditioning: priming of the protonmotive force by ATP synthase reversal? http://www.heartjnl.com/cgi/eletters/77/4/314#323, 4 Jul 2004

Conflict of Interest:

None declared