COMPARISON OF UW SOLUTION AND ST THOMAS SOLUTION IN THE RAT - IMPORTANCE OF POTASSIUM CONCENTRATION

Background University of Wisconsin solution ((UW) is in limited clinic al use for heart transplantation, but there are doubts about its effic acy and concerns about the effect of its high K+ concentration on endo thelium. St. Thomas' solution with or without aspartate is widely used and is of proven efficacy. Methods. Using a modified (starch-free) va riant of UW (MUW) we studied: (1) recovery of function with UW compare d with aspartate-containing St. Thomas' solution; (2) effect of elevat ion of K+ in St. Thomas' solution to the level in UW; and (3) effect o f reduction of K+ in UW and addition of Ca2+ or aspartate. isolated ra t hearts underwent 7 hours of arrest at 1 degrees C using MUW with or without 20 mmol/L aspartate or using aspartate-containing St. Thomas' solution. Results. Functional recovery with MUW (51.8% +/- 2.5%) was s uperior to that with aspartate-containing St. Thomas' solution (37.1% +/- 4.3%; p < 0.01). Addition of aspartate to MUW had no effect. Durin g 6 hours of arrest, lowering the K+ in MUW from 125 mmol/L to 20 mmol /L reduced functional recovery from 59.9% +/- 4.2% to 42.3% +/- 4.3% ( p < 0.01). The addition of 1 mmol/L Ca2+ had no effect. Elevation of K + in St. Thomas' solution produced more rapid arrest but no improvemen t in recovery. Conclusions. The protective effect of starch-free UW is greater (+13%) than that of aspartate-enriched St. Thomas' solution. Reduction of K+ in UW to lessen possible deleterious effects would dec rease its protective effect by about 30% to a level comparable with th at of St. Thomas' solution.