Acid-base changes in ischemic myocardium and intervention with hypothermia or bicarbonate
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S Mochizuki1, M Taniguchi, S Seki
1Department of Medicine, Aoto Hospital, Jikei University, School of Medicine, Tokyo, Japan.
Insights
Correcting acid-base changes by lowering PCO2 or increasing HCO3- improved heart function recovery after ischemia. Lactate production was the main source of H+ during ischemia.
Area of Science:
- Cardiology
- Physiology
- Biochemistry
Background:
- Ischemia and reperfusion injury significantly impact myocardial contractility.
- Acid-base balance plays a crucial role in cardiac function during ischemic events.
- Understanding the effects of correcting hydrogen ion (H+) levels is vital for cardiac protection.
Purpose of the Study:
- To investigate the effects of ischemia and reperfusion on acid-base balance and myocardial contractility.
- To evaluate the efficacy of correcting H+ levels (via PCO2 reduction or HCO3- increase) on cardiac recovery.
- To identify the primary source of H+ production during myocardial ischemia.
Main Methods:
- Utilized a working heart model to induce global myocardial ischemia.
- Applied different reperfusion strategies: normothermia, hypothermia, and normothermia with sodium bicarbonate (NaHCO3) administration.
- Measured acid-base parameters in coronary effluent and assessed myocardial contractility (LV pressure, LV dP/dt).
Main Results:
- A strong correlation was observed between decreased coronary flow, reduced LV pressure, and altered acid-base status (increased PCO2, H+; decreased HCO3-).
- Lactate production showed a highly significant correlation with H+ accumulation.
- Hypothermia and NaHCO3 treatment significantly enhanced myocardial contractility recovery and reduced H+ increment compared to normothermia.
Conclusions:
- Lactate production is identified as the predominant source of H+ during myocardial ischemia.
- Correction of H+ levels, through hypothermia or NaHCO3, can mitigate ischemic damage and improve recovery.
- Interventions aimed at correcting acid-base balance may reduce reperfusion injury.
Abstract:
Effects of ischemia and reperfusion on acid-base changes in relation to myocardial contractility, and the effects of correcting H+ were studied by lowering PCO2 or increasing HCO3- levels. The hearts were perfused by working heart mode and whole heart ischemia was induced by use of a one way valve followed by myocardial warming (37 degrees C, normothermia), cooling (18 degrees C, hypothermia) or warming plus 2.1 mM NaHCO3 for 15 min. The hearts were then reperfused for 20 min. Coronary effluent was collected through pulmonary artery cannulation and used for the measurement of acid-base changes. There were close correlations between the decrease in coronary flow and LV pressure, LV dP/dt. Close correlations were also observed between the decline in LV pressure and the rise in PCO2, H+, and the decline in HCO3-. A highly significant correlation was seen between H+ and lactate production. Myocardial contractility decreased to the same extent in 3 groups during ischemia, whereas its recovery rate in both the hypothermia and HCO3- -treated groups were significantly higher than in the normothermia group. The increment of H+ was significantly less in both the hypothermia and HCO3- -treated groups than in normothermia. These results indicate that lactate production is the major H+ producing source and the correction of H+ could minimize the ischemic insult and at the same time contribute to the reperfusion injury.