Anesthetic preconditioning: effects on latency to ischemic injury in isolated hearts.
BACKGROUND
Anesthetic preconditioning (APC) is protective for several aspects of cardiac function and structure, including left ventricular pressure, coronary flow, and infarction. APC may be protective, however, only if the duration of ischemia is within a certain, as yet undefined range. Brief ischemia causes minimal injury, and APC would be expected to provide little benefit. Conversely, very prolonged ischemia would ultimately cause serious injury with or without APC. Previous investigations used a constant ischemic time as the independent variable to assess ischemia-induced changes in dependent functional and structural variables. The purpose of the study was to define the critical limits of efficacy of APC by varying ischemic time.


METHODS
Guinea pig hearts (Langendorff preparation; n = 96) underwent pretreatment with sevoflurane (APC) or no treatment (control), before global ischemia and 120 min reperfusion. Ischemia durations were 20, 25, 30, 35, 40, and 45 min.


RESULTS
At 120 min reperfusion, developed (systolic-diastolic) left ventricular pressure was increased by APC compared with control for ischemia durations of 25-40 min. Infarction was decreased by APC for ischemia durations of 25-40 min, but not 20 or 45 min. APC improved coronary flow and vasodilator responses for all ischemia durations longer than 25 min, and decreased ventricular fibrillation on reperfusion for ischemia durations longer than 30 min.


CONCLUSIONS
Although APC protects against vascular dysfunction and dysrhythmias after prolonged ischemia, protection against contractile dysfunction and infarction in this model is restricted to a range of ischemia durations of 25-40 min. These results suggest that APC may be effective in a subset of patients who have cardiac ischemia of intermediate duration.
Kevin
Leo G
LG
Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, Wisconsin, USA.
Katz
Peter
P
Camara
Amadou K S
AK
Novalija
Enis
E
Riess
Matthias L
ML
Stowe
David F
DF
D000758:Anesthesia; D018685:Anesthetics, Inhalation / Q000494:pharmacology; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D003326:Coronary Circulation / Q000502:physiology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D019157:Ischemic Preconditioning, Myocardial; D008738:Methyl Ethers / Q000494:pharmacology; D017202:Myocardial Ischemia / Q000473:pathology*; D015428:Myocardial Reperfusion Injury / Q000473:pathology / Q000517:prevention & control; D000077149:Sevoflurane; D013997:Time Factors; D014693:Ventricular Fibrillation / Q000503:physiopathology; D016277:Ventricular Function, Left / Q000187:drug effects
D018685:Anesthetics, Inhalation; D008738:Methyl Ethers; D000077149:Sevoflurane