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Pragliola et al. Vessel Plus 2019;3:22 I http://dx.doi.org/10.20517/2574-1209.2019.003 Page 3 of 9

Table 1. Composition of the del Nido cardioplegia
Del Nido formulation Plasma-Lyte a solution 1000 mL
Plasma Lyte A Solution 1 L Sodium 140 mEq
Mannitol 20 % (16.3 mL) Potassium 5 mEq
Magnesium Sulfate 50% (4 mL) Magnesium 3 mEq
Sodium Bicarbonate 8.4% (13 mL) Cloride 98 mEq
Potassium Cloride 2 mEq/L (13 mL) Gluconate 23 mEq
Lidocaine 1% (13 mL) Acetate 27 mEq
Blood : Crystalloid 1:4

As known Potassium increases the resting potential of myocytes to about -46 mV, well above the depolarization
threshold of – 65 mV. In doing so it leaves the cells in a state of arrest. Hence, indirectly potassium blocks the
+
inward current of Na during the phase 0 of the myocardial action potential

Lidocaine
Lidocaine is a class I antiarrhythmic drug that directly blocks the Na channels in phase 0. Its half-life is
+
relatively long and is obviously increased by the absence of coronary circulation. It also blocks the so called
“window” channels which remain open during the depolarized arrest and allow some Na and Ca inward
2+
+
current in the cell. Lidocaine therefore allows for prolonged periods of cardiac arrest and participates in the
control of intracellular accumulation of calcium during the ischemic period.

Magnesium
Magnesium is a natural Calcium channels blocker. Contrary to the skeletal muscle, the cardiac myocyte is
largely dependent from extracellular calcium for its contraction. Calcium ions enter the cardiac myocyte
during phase 2 plateau of the action potential through L-Type channels which are blocked by Magnesium
ions. In doing so Magnesium prevents the contraction of the myocytes and accumulation of Calcium in the
cell. Interestingly both paediatric and “aged” cardiomyocytes have an altered homeostasis of Calcium which
can be modulated by Magnesium

Mannitol
Mannitol is a common additive to cardioplegia solutions. Its usage prevents cellular oedema and scavenges
free radicals. The cell membrane of immature myocardium has high concentration of poly unsaturated fatty
acids providing more sites for oxidative damage, on the other hand oxidative stress is believed to be potent
promoter of myocardial aging.

1:4 Blood ratio
The addition of blood to crystalloid cardioplegia is far beyond the simple concept of substrates and oxygen
deliver to the arrested heart. As the haemoglobin dissociation curves are altered during hypothermia, the
oxygen deliver is minimal and dependent from the gas dissolved in the solution. However, blood proteins
and the other components have several potential benefits which include buffering from proteins and carbonic
anhydrase contained in red cells, free radicals scavenge and more favourable rheological properties. In
addition, as a result of the lower haematocrit compared to the classic solution with a 4:1 ratio, the DNC has
a very low Calcium content which enhances the effects of Lidocaine and Magnesium.

DELIVER AND TECHNICAL ASPECTS
With the widespread use of blood cardioplegias the perfusionist can easily arrange a circuit to deliver the
DNC basic crystalloids components in a 4:1 ration with the patient’s derived oxygenated blood (> 150 mmH
pO2). Sample circuits drawings are available in the literature from the original Boston Children Hospital
and the Cleaveland Clinic . Table 1 depicts the current setting in use in our Centre. The DNC is usually
[11]