うっ血性心不全におけるヘモグロビン酸素解離能の検討

Studies on hemoglobin oxygen dissociation in patients with congestive heart failure

　生体が円滑にエネルギー代謝を進めるためには，末梢組織へ酸素が十分供給されなければならない。酸素摂取量は心拍出量と動静脈酸素含量較差との積で示される。うっ血性心不全においては一般に心拍出量は低下するが，動静脈酸素含量較差の増大により酸素摂取量は維持される。この動静脈酸素含量較差の増大に寄与するひとつの因子としてヘモグロビン酸素解離能が挙げられる。ヘモグロビン酸素解離能の亢進は，肺毛細血管におけるヘモグロビンと酸素との結合にはほとんど影響を及ぼさないが，末梢毛細血管におけるヘモグロビンからの酸素解離を容易とし，組織での酸素分圧を上昇，組織の酸素取り込みを促進する。本研究では各種心疾患に起因するうっ血性心不全患者を対象にして心不全の重症度別にP₅₀値，2,3-diphosphoglycerate （DPG）濃度などを測定し，心不全におけるヘモグロビン酸素解離能の臨床的意義を検討した。

The present study was designed to evaluate theclinical significance of hemoglobin oxygen dissocia-tion curve (ODC) in patients with congestiveheart failure (CHF). Materials consisted of 14 CHF patients due to various cardiac diseases and 57 nor-mal subjects. Blood sampling was performed from the antecubital vein for the measurements of P₅₀levels and 2,3 diphosphoglycerate (DPG) concen-trations. P₅₀ at 37℃, pH 7.4, PCO₂ 0 mmHg was determined using Hemox-Analyzer.

The P₅₀ level was higher in CHF patients than in normal subjects (28.7 mmHg vs 25.0 mmHg, p<0.005) and 2, 3-DPG concentration was higher in CHF patients than in normal subjects (17.7 μmole/gHb vs 12.8 μmole/gHb, p<0.005). A sig-nificant positive correlation was observed between 2,3-DPG concentration and P₅₀ level in CHF pa-tients (r=0.53, p<0.01), as well as in normal subjects (r=0.52, p<0.01). In CHF patients, the greater the severity of heart failure (New York Heart Association functional classification) was, the more rightward shift in ODC was noticed. The mean values of P₅₀ were 26.9 mmHg for class II, 27.8 mmHg for class III, and 29.0 mmHg for class IV, respectively.

A 2,3-DPG-mediated rightward shift of ODC in patients with CHF was considered as a compensa-tory adjustment to poor tissue blood flow by impair-ed cardiac output. In conclusion, the measurement of P₅₀ levels in CHF patients seems to be useful to assess the severity of cardiac dysfunction.