Clinical and experimental studies on cold cardioplegia by measuring intramyocardial gas tensions
Sudo, K.
Nihon Kyobu Geka Gakkai 30(1): 1-13
1982
ISSN/ISBN: 0369-4739 PMID: 6808060 Document Number: 194902
Although cold cardioplegia was widely used during open heart surgery, myocardial metabolism under this condition was not fully investigated. In order to assess the efficacy of cold cardioplegia in current practice, intramyocardial pO2 [O2 partial pressure] and pCO2 [CO2 partial pressure] were continuously measured with a mass spectrometer in 10 clinical cases undergoing open heart surgery and in 24 dogs, during cold cardioplegia. In clinical cases, cold hyperkalemic cardioplegic solution was infused in the amount of 20 ml/kg for initial and 10 ml/kg for subsequent infusions every 20 min. The mean myocardial temperature was thus reduced to 14.1 .+-. 2.0.degree. C. In experimental studies, the myocardial temperature was maintained at 10 .apprx. 15.degree. C in 10 dogs by the same method as in clinical cases (group A), at 20 .apprx. 25.degree. C in 9 dogs by repeated infusion of 20.degree. C cardioplegic solution (group B) and at 20 .apprx. 25.degree. C in 5 dogs by single infusion of 20.degree. C solution (group C). In comparison with groups B and C (0.71 .+-. 0.66, 1.63 .+-. 0.60 mm Hg/min), respectively, group A showed reduced increase rate of pCO2 during arrest (0.36 .+-. 0.16 mm Hg/min). Similar results were obtained in clinical cases (0.25 mm Hg/min). The recovery rate of pCO2 at 20 min after arrest in groups A, B and C were 130 .+-. 35, 147 .+-. 60, and 175 .+-. 82%, respectively. The pCO2 levels at 5 min after resuscitation in clinical cases were below the prearrest values. Immediately following the resumption of coronary perfusion, the pCO2 levels rose temporarily in clinical cases as well as in group A, this phenomenon was not observed in group C. In clinical cases, the pO2 values remained relatively high. These data suggest that the method of current clinical use has the following 2 benefits in regard to myocardial protection: inhibition of the aerobic and anaerobic metabolism of the myocardium by hypothermia and maintenance of low pCO2 level by washout of the metabolic products. It was also confirmed that the myocardial temperature between 20.degree. and 25.degree. C was not adequate for myocardial preservation, and that single dose infusion was also inadequate.