Intracellular pH measurement during cardiac arrest in ventricular myocardium by Bretschneider's cardioplegic solution...

Intracellular pH (pHi) has been measured in human or cat ventricular muscle during 60, 120 and 180 minutes of cardiac arrest by Bretschneider's cardioplegic solution HTK or St. Thomas solution with and without procaine. In 319 control measurements in modified Tyrode's solution pHi (mean, S.D.) was 7.38 +/- 0.02 (n = 128) during the first hour, 7.36 +/- 0.03 (n = 112) during the second hour and 7.35 +/- 0.03 (n = 79) in the third hour. The pHi in right ventricular muscle of the cat and left ventricular human muscle did not differ significantly during the time of measurements (Bretschneider HTK). The values (human/cat) in the first hour were 6.85 +/- 0.03 for both groups, 6.72 +/- 0.04/6.68 +/- 0.04 during the second hour and 6.70 +/- 0.03/6.67 +/- 0.05 in the third hour of measurement. The values for the St. Thomas solution with/without procaine were 6.83 +/- 0.02/6.74 +/- 0.03 in the first hour, 6.79 +/- 0.02/6.82 +/- 0.04 during the second hour and 6.68 +/- 0.03/6.82 +/- 0.02 in the third hour. An important difference to all other solutions was the observation made under the St. Thomas solution with procaine, that after recovery to normal values pHi decreased between the 2.-5. minute to values of 6.39-6.48 when the preparations were superfused with Tyrode's solution again. No recovery within 1 hour was observed. This fall in pHi was accompanied by a contracture.