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  • Title: First report of intramyocardial pH in man. II. Assessment of adequacy of myocardial preservation.
    Author: Khuri SF, Josa M, Marston W, Braunwald NS, Smith B, Tow D, VanCisin M, Barsamian EM.
    Journal: J Thorac Cardiovasc Surg; 1983 Nov; 86(5):667-78. PubMed ID: 6632942.
    Abstract:
    Intramyocardial pH and temperature were continuously measured in the anteroseptal region in 40 patients undergoing aortic cross-clamping during cardiac operations. Myocardial protection was achieved with systemic cooling (25 degrees C) and multidose potassium cardioplegia (4 degrees C). A clinical myocardial preservation score was devised based on intraoperative and postoperative need for inotropic support, postoperative creatine kinase isoenzyme (CK-MB) and electrocardiographic changes, and radionuclide ventriculography. The patients were divided into three groups according to their preservation scores. Group I (n = 17) with good preservation (scores 0 to 2), Group II (n = 15) with fair preservation (scores 3 to 8), and Group III (n = 8) with poor preservation (scores 9 to 15). Baseline intramyocardial pH was similar in all groups (mean +/- SEM = 6.77 +/- 0.03). With the administration of cold potassium cardioplegia, intramyocardial pH rose above baseline in all three groups. The magnitude of this rise related directly to the adequacy of preservation and to the duration of the cross-clamp period. Patients with lowest preservation scores and shortest cross-clamp periods had the highest intramyocardial pH. In contrast, there was no relationship between myocardial temperature during cross-clamp and either intramyocardial pH or the preservation score. The integrated mean intramyocardial pH during cross-clamp was found to be the parameter that correlated most with the adequacy of preservation. The correlation between intramyocardial pH and myocardial temperature during the period of cross-clamping related to the length of this period; it was good (r = 0.76, p less than 0.01) in periods of 40 minutes or less and very poor in periods exceeding 60 minutes (r = 0.27, p greater than 0.10). It is concluded that (1) the magnitude of rise in intramyocardial pH during the period of aortic cross-clamping is a good indicator of the adequacy of myocardial preservation; (2) during periods of aortic cross-clamping exceeding 40 minutes, myocardial temperature is a poor indicator of adequacy of preservation, since progressive tissue acidosis may occur despite low myocardial temperatures; and (3) techniques and solutions that can effectively reduce the progression of tissue acidosis will, in most likelihood, enhance our ability to protect the ischemic myocardium during cardioplegic arrest.
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