12 C . W . Striker and J . A . Reagor : J Extra Corpor Technol 2025 , 57 , 9 – 13
Figure 3 . Magnesium levels within age brackets . Magnesium levels for infant ( 30 days to 1 year of age ), child ( 1 – 12 years of age ), teenager ( 13 – 17 years of age ), and adult ( 18 or more years of age ) subjects with Draw 1 magnesium levels in the left figure and Draw 2 on the right .
( p = 0.089 ); however , ninety-nine samples displayed hypermagnesemia . The effect of magnesium administration was significant ( p < 0.001 ), raising magnesium levels well above normal in almost all cases . When the magnesium levels were broken into age groups , similar trends continued with higherthan-normal magnesium levels at D1 and again at D2 ( Figure 3 ).
Discussion
Cardioplegic solutions are utilized to ameliorate metabolic injury of the myocardium during ischemia while providing a still , bloodless operative field . The efficacy of these solutions is demonstrated in the quiescence of cardiac activity and the propensity for post-ischemic recovery of acceptable ventricular function . Over time , cardioplegic solutions have been developed to improve recovery of the myocardium by attenuating myocardial reperfusion injury .
A major advancement in pediatric cardiac surgery was the introduction of del Nido cardioplegia . dNC was developed at the University of Pittsburgh during the 1990 ’ s to address the needs of immature myocardium in neonates , infants , and pediatric patients [ 1 , 3 ]. A characteristic of immature myocardium is a higher sensitivity to intracellular calcium related to an underdeveloped sarcoplasmic reticulum [ 1 , 3 ]. In its formulation , dNC seeks to decrease intracellular calcium by including magnesium , a calcium-competing ion , and polarizing agents such as lidocaine [ 1 ]. Secondarily , dNC safely accommodates longer myocardial ischemic times thereby aiding surgical efficiency [ 1 , 3 – 5 ]. dNC is a Plasmalyte solution ( Baxter Healthcare , Deerfield , IL ) with the following additives : mannitol , magnesium , sodium bicarbonate , potassium chloride , and lidocaine as listed in Table 1 . These components were utilized with the following rationale . Mannitol , a free radical scavenger , exhibits osmotic properties which may reduce cardiac myocyte edema . Magnesium , a calcium channel blocker , attenuates the buildup of intracellular calcium in an effort to reduce diastolic stiffness postcross-clamp removal , which may result in poor filling and decreased cardiac function [ 1 , 6 ]. Sodium bicarbonate helps to maintain an adequate intracellular pH during anaerobic metabolism . Potassium chloride is utilized to establish a rapid depolarizing arrest by inhibiting the movement of sodium and potassium across the cellular membrane . Lidocaine assists in the blockade of the sodium channels and stabilizes the cellular membrane preventing intracellular movement of calcium and sodium , specifically during hyperkalemic arrest . dNC is delivered in a 1:4 ratio of blood to crystalloid ( 1 ).
Although dNC is most widely used in pediatric cardiac surgery and was initially developed for the immature myocardium , it has gained attention in adult cardiac surgery . Shu , Hong , Shen et al ., demonstrate shorter ICU length of stay , less ventricular arrhythmia , increased hemodynamic stability resulting in earlier extubation , and decreased sternal wound infection ( possibly due to less glucose ) with del Nido over St . Thomas Solution [ 7 ]. Cayir and Yuksel demonstrated that the requirement for intraoperative defibrillation post cross-clamp removal was significantly less for adult cardiac CPB patients with the use of dNC over St . Thomas solution [ 5 ]. These findings are consistent with Buel , Striker , and O ’ Brien ’ s study in the congenital pediatric population [ 4 ]. Additionally , surgical efficiency is improved due to less dosing frequency of dNC over St . Thomas Solutions [ 5 ].
Magnesium is often administered following the release of the aortic cross-clamp for the prevention of dysrhythmias and ventricular dysfunction due to hypomagnesemia [ 8 – 10 ]. Hypomagnesemia post-CPB can be exacerbated by diuresis , hemodilution , and ultrafiltration during CPB . Previous studies have demonstrated that the administration of magnesium prior to cessation of CPB results in fewer arrhythmias and improved ventricular function [ 9 – 11 ]. These studies , however , did not use a magnesium-based cardioplegic solution such as dNC . As such , it is essential to determine if exogenous magnesium administration post aortic cross-clamp removal is necessary as hypermagnesemia can result in undesired effects such as arrhythmia and / or hypotension [ 12 ].
Continual evaluation of our clinical practices , specifically following an alteration in cardioplegic solutions , and considering the adverse effects of hypermagnesemia , it was prudent to ascertain magnesium levels on CPB . Under our current protocol , we hypothesized that the administration of exogenous magnesium post cross-clamp removal , in the setting of cardioplegic arrest with dNC solution , may result in hypermagnesemia . These data validate this hypothesis specifically with the use of a buffered Plasmalyte prime and dilutional ultrafiltration