J Thorac Cardiovasc Surg 1994;108:795-796
© 1994 Mosby, Inc.
Continuous monitoring of coronary sinus oxygen saturation during warm heart surgery
T. Miyairi, MD,
T. Miwa, MD,
T. Takayama, MD,
K. Ka, MD,
K. Itoh, MD
Department of Thoracic and Cardiovascular Surgery
Department of Anesthesia
Kanagawa Children's Medical Center
232 Yokohama, Japan
To the Editor:
Warm heart surgery has been proposed by Lichtenstein and his colleagues
1 to be the alternative strategy to the conventional hypothermic cardiac arrest technique during cardiac operations. That modality of myocardial protection is said to maintain myocardial preservation by eliminating the period of ischemia, avoiding the side effects of hypothermia and abolishing reperfusion injury. 2 However, because the normothermic heart is far more vulnerable to anaerobic conditions than is the hypothermic heart, 3 care should be taken to avoid ischemic myocardial damage during warm heart surgery.
Recently, we have performed warm heart surgery in patients with congenital heart disease with the aid of on-line monitoring of coronary sinus oxygen saturation (SO2). We used an intravascular optic catheter (SAT-2, 4F, Baxter Healthcare Corporation, Santa Ana, Calif.) placed in the coronary sinus under direct vision. Coronary sinus SO2 level was carefully observed during the continuous perfusion of warm blood cardioplegic solution.
Although the heart was supposed to be maintained under aerobic conditions during warm heart surgery, we found that the coronary sinus SO2 level varied incessantly throughout operative procedure. With the heart beating, the coronary sinus SO2 level was about 40%. After the induction of cardioplegic arrest, its level was kept about 70% to 80% during complete electromechanical cardiac arrest. However, the occurrence of ventricular fibrillation, beating, or other electrical activity immediately lowered the coronary sinus SO2 level below 50% (Fig. 1.). If the coronary sinus SO2 level drops without myocardial electrical activity, an oxygen debt must have been incurred from insufficient oxygen supply, such as cardioplegic infusion failure or coronary artery compression by an inappropriate surgical maneuver. Such problems necessitate immediate recognition and amendment. We try to keep the coronary sinus SO2 level in an appropriate range (above 60%, below 80%) by adjusting the concentration of potassium and infusion rate of the cardioplegic solution. If we need to decrease or even totally interrupt the infusion of cardioplegic solution for good visualization of the operative field, we take care not to prolong the ischemic time (coronary sinus SO2 below 60%) more than 10 minutes.
View larger version (28K):
[in this window]
[in a new window]
|
Fig. 1. Changes in the coronary sinus blood oxygen saturation (ScsO2). The ScsO2 level was about 40% with the heart beating after aortic crossclamping, and its level immediately increased to 70% to 80% with cardioplegic arrest. Ventricular fibrillation (Vf)lowered its level to below 50%.
|
|
Thus, by continuously monitoring the level of coronary sinus SO2, we can regulate the cardioplegic infusion condition to maintain the heart in a virtually aerobic state, minimize myocardial damage by limiting the ischemic period, and detect the occurrence of incidental myocardial ischemia without delay during normothermic cardiac arrest. We believe that continuous measurement of coronary sinus blood SO2 is mandatory for the safe practice of warm heart surgery.
References
-
Lichtenstein SV, El Dalati H, Panos A, Slutsky AS. Long cross-clamp times with warm heart surgery [Letter]. Lancet 1989;1:1443.[Medline]
-
Lichtenstein SV, Ashe KA, El-Dalati H, Cusimano RJ, Panos A, Slutsky AS. Warm heart surgery. J THORAC CARDIOVASC SURG 1991;101:269-74.[Abstract]
-
Cooley DA, Reul GJ, Wukasch DC. Ischemic contracture of the heart: "stone heart." Am J Cardiol 1972;29:575-7.[Medline]
