A new attempt for myocardial cooling during cardiac surgery
Maeta, H.; Iriyama, T.; Itoh, T.; Okamura, K.; Ijima, H.; Sakurai, J.; Mitsui, T.; Hori, M.
Nihon Kyobu Geka Gakkai 30(1): 21-27
1982
ISSN/ISBN: 0369-4739 PMID: 7097061 Document Number: 183477
A combination of the topical myocardial cooling and the cold cardioplegia has now become a routine method for myocardial preservation. Rapid uniform cooling of the heart and keeping myocardium in ideal hypothermia are the most important requirements of myocardial protection during cardiac surgery. A new superfine myocardial thermosenser and a cooling coil which showed good results in clinical use was designed. The superfine myocardial thermosensor (MTS) is made of string-typed thermocouples (chromelalumel) covered with Inconel. It is only 0.25 mm thick and can be inserted into any depth or any part of myocrdiaum. Relationship between the electromotive force and the temperature meausred by a mercury thermometer had an excellent correlation at over 7.degree. C. The MTS is fixed firmly enough with only 1 suture to the myocardium and is removable easily and safely under the heart beating. Myocardial cooling coil is made of a vinyl chloride tube (5 mm in diameter) and formed like a basket. The left ventricle is wrapped by this coil and lifted up from the pericardium. This coil is connected to a heat-exchanger and a roller pump. The pericardial cavity is irrigated continuously with cold saline through the coil. Overflowed water is aspirated by another suction tube and flows back to the heat-exchanger. Then myocardial cooling was induced by the flow of saline at 3.degree.-6.degree. C and a flow rate of 300-400 ml/min through this intrapericardial irrigation circuit. Myocardial temperatures monitored by the MTS were maintained at 8 to 15.degree. C, although the rectal temperature was kept at over 25.degree. C. The use of cooling coil enabled the duration of aortic cross clamping to prolong up to 3 h. In the control group without the cooling coil, myocardial temperature was quickly elevated and became unstable. Two out of 25 cases in the control group resulted in myocardial infarction. The protection of myocardium was improved by lifting the left ventricle up from the pericardium, irrigating the pericardial cavity through the cooling coil with cold saline and isolating the heart from heat input by draining the blood through the individual caval cannulation and the left atrial vent, under the continuous monitoring of the myocardial temperature by the MTS.