We retrospectively studied the influence of a decrease in hemoglobin(Hb)oxygen dissociation ability within the oxygen supply-demand balance of 25 patients without and 12 patients with diabetes mellitus(DM)who underwent open heart surgery under a normothermic cardiopulmonary bypass(CPB). Bound oxygen delivery(bound DO₂I), soluble oxygen delivery(soluble DO₂I), bound oxygen consumption(bound VO₂I), soluble oxygen consumption(soluble VO₂I), bound oxygen extraction ratio(bound O₂ER), soluble oxygen extraction ratio(soluble O₂ER)and the ratio of bound VO₂I to total VO₂I(%bound VO₂)were measured from cardiac output(CO), blood gas data, and perfusion indices obtained during CPB. The Hb oxygen saturation was determined as Hb oxygen fractional saturation(%O₂ Hb). The sum of bound DO₂ and soluble DO₂ was >300mL/min/m², the lactate value was <2.5mmol/L, and lactic acidosis was absent in both groups. Although HbA1_C was significantly higher in the DM than in the normal group, P50 did not significantly differ between the groups before CPB, indicating that P50 did not correlate with HbA1_C. On the other hand, P50 continued to decrease in the DM group after the start of CPB and significantly differed in the ICU. The Hb value did not significantly differ between the groups. However, bound O₂ER and %bound VO₂ were lower and %vO₂ Hb was higher in the DM than in the normal group during CPB. Bound O₂ER also decreased with increasing soluble DO₂I, and this decrease was greater in the DM group. These findings indicate that these differences were due to a decrease in the ability of Hb oxygen to dissociate. The decrease in P50 did not directly reflect the increase in HbA1_C, but it nevertheless suggests the presence of a complex compensatory mechanism. Although a sufficient amount of oxygen was supplied and the %vO₂ Hb remained at or above the reference value, our findings suggest that either oxygen intake was disrupted or oxygen was not utilized by tissues. In summary, dysoxia caused by the decreased ability of Hb oxygen dissociation in the DM group rendered evaluation of the oxygen supply-demand balance through monitoring only %vO₂ Hb and Pv-O₂ difficult. Furthermore, the decrease in Hb oxygen dissociation ability could be prevented by avoiding high soluble DO₂I(PaO₂).

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We developed an easy-to-use gravity drainage type hemodiafiltration method for correction of hyperkalemia(k≥ 5.5mmol/L)occurring during extracorporeal circulation in open heart surgery. The subjects of the present study were 11 consecutive patients(two men and nine women with a mean age of 63.6±12.9years)in whom this method was used for correction of hyperkalemia occurring during extracorporeal circulation. With the present method, substitution fluid(Sublood^®-BSG)was perfused outside the hollow fiber hemoconcentrator(MAQUET BC140 plus^®)by gravity counter-currently to the flow of blood, using a transfusion set(internal diameter of 3.0mm). The drop height was 150cm, and the blood flow rate was 400mL/min. The potassium added to the cardioplegic solution during extracorporeal circulation was 69.0±33.1mmol. Packed irradiated red blood cells, 5.5±3.6units, were transfused. Before applying this method, the maximum concentration of potassium was 6.41±0.76mmol/L. After its application, there was a significant decrease to 4.82±0.22mmol/L(p<0.0001)by the time of weaning from extracorporeal circulation. There were no significant differences in the concentrations of sodium, potassium, bicarbonate ion, or hydrogen ion concentration indices between the time immediately after the start of extracorporeal circulation and the time immediately before weaning. We conclude this novel method to be useful for correction of hyperkalemia occurring during extracorporeal circulation.

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