Current priming solutions for cardiopulmonary bypass contain a potent coronary vasodilator

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Abstract
We studied the effects of acetate (Ac), the buffer in crystalloids used during cardiopulmonary bypass (CPB) (e.g. Normosol-R and Plasma-Lyte, Ac = 27mEq/1), on coronary resistance (R) for the empty beating heart, and on vascular resistance (SVR) of 19 dogs on CPB. Control Rwith Ac = 0 (Rc) was obtained by adjusting flow to give a pressure of 90 ± 10mmHg (R = 532 ± 32 dynes.sec/cm5g, other Rs are given as a percentage of their respective Rc) . Continuous addition of Ac = 1.6 or 7.1 mEq/L of blood resulted in a rapid decrease in R to 34 ± 3 and 17 ± 2% of Rc, followed by a recovery to higher steady values of 53 ± 3 and 27 ± 2% respectively (p < 0.008). A bolus administration of 2mEq and 6mEq into the coronary circuit resulted in R dropping to 30 ± 5 and 17 ± 6% respectively. Rs obtained with Ac were compared to the Rs obtained for control 20sec reactive hyperaemia (35 ± 1 %), after 30 minutes global ischaemia (14 ± 1 %), and with the addition of bicarbonate (98 ± 2%). Ac did not change heart rate, but caused an increase in O2 consumption from 3.4 ± 0.4 to 4.8 ± 0.7ml/min/1 00g, (p < 0.038). Systemically, a bolus of 6mEq of Ac caused an immediate drop in SVR to 45 ± 5% of control. The property of Ac as a potent coronary and vascular dilator may need to be considered when Ac is used during cardiac surgery. Statistical comparisons were made with the paired t-test.