[Clinical aspects of global ischemia of the heart].
The vast majority of modern surgical open-heart procedures require a period of global myocardial ischaemia due to the interruption of the coronary circulation, since a bloodless operative field is of great importance for delicate surgical techniques. Several cardiac protective measures have been applied in order to minimize ischaemic damage to the heart muscle: 1. Intermittent myocardial ischaemia, combined with mild to moderate hypothermia: ischaemic periods of 15-30 min at 28-32 degrees C are tolerated. Multiple ischaemic periods are possible after intermittent (3-5 min) reperfusion. 2. Deep hypothermia, combined with ischaemia: myocardial cooling to 18-23 degrees C protects the heart for ischaemic periods of up to 45-60 min. 3. Cardioplegic arrest, combined with hypothermia: a great variety of cardioplegic solutions are still used today in clinical practice. a. Interruption of electrical activity: most cardioplegic solutions use K+ (15-35 mmol/l); complete suppression of electrical processes is not always achieved. b. Interruption of electrical activity and buffering of glycolytic end products. St. Thomas-, Kirklin-Solution, blood cardioplegia and their multiple variations can result in an 3-5 fold tolerance to myocardial ischaemia. c. Interruption and blockade of electro-mechanical activity, combined with an effective buffering. Bretschneider-HTK cardioplegia equilibrates the extracellular space due to a 6-10 min infusion of the cold, crystalloid solution and allows uninterrupted ischaemic periods of more than 2 h under clinical conditions. In order to achieve optimal cardiac tolerance to global ischaemia a careful protocol of perioperative myocardial proection has to be followed. Most heart centers use a combination of hypothermia and effective cardioplegia.
Hellberg
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Abteilung für Herz- und Gefässchirurgie, Robert-Bosch-Krankenhaus, Stuttgart.
D002314:Cardioplegic Solutions / Q000008:administration & dosage; D004562:Electrocardiography; D006324:Heart Arrest, Induced / Q000379:methods*; D006331:Heart Diseases / Q000601:surgery*; D006801:Humans; D007036:Hypothermia, Induced / Q000379:methods; D009203:Myocardial Infarction / Q000517:prevention & control; D011183:Postoperative Complications / Q000517:prevention & control
D002314:Cardioplegic Solutions
Klinik der globalen Ischämie des Herzens.