204 T . Takeichi et al .: J Extra Corpor Technol 2023 , 55 , 201 – 205
Figure 4 . ECG of systemic hyperkalemia during CPB shows a blood potassium level of 9 mEq / L . ECG : Electrocardiogram ; CPB : Cardiopulmonary bypass .
and the subsequent suboptimal myocardial protection [ 2 , 3 ]. The flow to the sub-endocardium occurs during diastole . The compressive force exerted on the sub-endocardial muscle by fibrillation restricts the flow and oxygen delivery to the myocardium during the diastolic phase of ventricular fibrillation [ 7 ]. Imanaka et al . showed that the more prolonged VF time , CK-MB increased and the longest VF time was 146 min . However , such an extended period of VF did not cause severe myocardial damage [ 5 ]. Also , Hiraoka et al . reported that intraoperative myocardial protection under mild hypothermia and VF was not an inappropriate myocardial protection strategy compared to cardiac arrest with a cardioplegic solution [ 4 ].
On the other hand , the BH approach and systemic hyperkalemia avoid sub-endocardial hypoperfusion mismatches , which are commonly observed with VF . Additionally , during ischemic arrest , myocardial edema increases in the static diastolic state and may lead to cardiac dysfunction [ 6 ]. In the case of systemic hyperkalemia , provides complete electromechanical diastolic arrest with uniform myocardial protection as opposed to fibrillatory arrest without the fear of cardioplegia washout [ 8 , 9 ]. Some studies have suggested that preoperative cardiac surgery can be safely performed with previous CABG and internal thoracic artery ( ITA ) using systemic hyperkalemia and arrest without the ITA graft [ 8 – 10 ].
In this case , we employed systemic hyperkalemia for the complex reoperation and were able to safely perform myocardial protection . To achieve myocardial protection , we administered an initial dose of 10 mL of MgSO 4 and 500 mL of mixture solution and maintained a systemic potassium concentration of 9.0 mEq / L by continuously infusing a drop and administrated 10 mL of MgSO 4 every 30 min . The peak potassium level was 9.9 mEq / L , the minimum was 8.0 mEq / L , and the total potassium administered was 250 mEq . Weaning from CPB was easy and the maximum level of postoperative CK-MB was 19 . Some studies show that cardiac protection due to systemic hyperkalemia without aortic cross-clamp can be a safe option and protect the heart [ 8 , 11 ]. Moreover , compared to hypothermic cardiac arrest , hyperkalemia cardiac arrest is associated with decreased myocardial adenosine triphosphate level [ 12 ]. In our series , CK-MB was slightly increased . In terms of becoming 9.9 mEq / L of potassium level , we calibrated the CDI parameter at 30-minute intervals . However , since the potassium concentration of CDI can only be measured up to 8.0 mEq / L when we checked an arterial blood gas sample every 30 min , the peak potassium level was 9.9 mEq / L . In this case , as it was not possible to obtain cardiac arrest at a blood potassium concentration of 8.0 mEq / L , we maintained a blood potassium level of 9 mEq / L .
However , this method of systemic hyperkalemia to achieve cardiac arrest has some drawbacks . First of all , to maintain a mean arterial pressure above 70 mmHg , we used phenylephrine and noradrenaline . However other reports suggest that systemic hyperkalemia may reduce vascular tone by affecting potassium channels [ 13 , 14 ]. Next , it may take some time to decrease the systemic potassium concentration . In this case , we used DUF methods and glucose-insulin therapy to return to normal potassium levels . Intracellular potassium is moved to the extracellular compartment during rewarming , suggesting that hyperkalemia is caused by administered potassium as well as by transport from the intracellular compartment and its effective removal is crucially important . In fact , we took about 60 min to decrease the potassium level to 5.5 mEq / L . To prevent postoperative fatal arrhythmia due to hyperkalemia , the most important procedure is to remove excessive serum potassium during CPB [ 15 ]. However , it is difficult to decrease high potassium levels in a short time using DUF alone . A study has shown that the use of the gravity drainage type hemodiafiltration method is useful for correcting hyperkalemia occurring during extracorporeal circulation because of its simple structure [ 16 ].
We believe this strategy is useful in complex cases to protect the heart . However , some researches show that CPB under systemic hyperkalemia is safe , few studies have been reported on via right thoracotomy under systemic hyperkalemia CPB without aortic cross-clamping . Therefore , this technique warrants further evaluation .
Conflict of interest The authors declared no conflict of interest .
Funding The authors received no funding to complete this research .