Effect of administration of single dose Histidine-Tryptophane-Ketoglutarate (HTK) cardioplegia solution on serum sodium concentration, osmolarity and acid-base balance.

The introduction of cardiopulmonary bypass (CPB) in the 1950*s has allowed
induction of cardiac arrest by administering cardioplegia solution.¹
Cardioplegia solutions improve the tolerance to ischaemia and reperfusion by
preserving myocardial energy reserves, preventing osmotic and electrolyte
imbalances and buffering acidosis.
Histidine-tryptophane-ketoglucorate (HTK) and St. Thomas* cardioplegia solution
are used by default for most cardiothoracic procedures at the Catharina
Hospital Eindhoven. The chosen cardioplegia solution depends on the time-length
of the specific cardiothoracic procedure. Patients undergoing cardiothoracic
procedures in which the estimated aortic clamping time exceeds 120 minutes will
receive single dose HTK cardioplegia solution. These procedures include triple
valve surgery, double valve + coronary artery bypass grafting and aortic arch
surgery. Patients undergoing coronary artery bypass grafting or single valve
surgery alone will receive St. Thomas* cardioplegia solution as the aortic
clamping time is generally less than 120 minutes.

Cardioplegia with histidine-tryptophane-ketoglucorate (HTK) for cardiac arrest
has been widely used clinically and reported in more than 700.000 cases of open
cardiac surgery.2 It is simple to use, administered as one single dose, and it
is claimed to give sufficient myocardial protection for more than 2 hours of
cardiac arrest.3 Therefore, single dose cardioplegia administration is an
attractive option in more complex cardiac procedures as re-administration of
cardioplegia can disturb the technical flow of the operation. However, HTK
cardioplegia solution is hyponatremic (15 mmol/l) compared to serum sodium
concentration (140 mmol/l) and could lead to severe hyponatremia if
administered in high volumes. Rapid development of hyponatremia can lead to
cerebral swelling which can ultimately end in brain herniation and even death.4
Treatment of acute hyponatremia however is not straightforward in this case, as
HTK cardioplegia solution is slightly hypertonic (310 mosmol/kg).
Administration of this solution might therefore lead to isotonic hyponatremia,
in which correction of serum sodium levels would be harmful, as a hyperosmolar
state with cerebral shrinking as a consequence could be induced.
Besides one study from Lindner et al in 2012, measurement of serum sodium
concentration has never been correlated to serum osmolarity. In the
aforementioned study serum osmolarity was measured in only 7 out of 25
patients. In this study isotonicity during acute hyponatriemia after
cardioplegia with HTK solution was shown. However, a larger sample size would
be reasonable to confirm that administration of HTK cardioplegia solution will
lead to isotonic hyponatremia and does not need any correction indeed.
In this observational study we want to get more insight in the biochemical
disturbances (sodiumconcentration, acid-base balance and osmolarity) that the
cardiosurgical patient is exposed to in our own institution during every day
practice. Serum osmolarity is not a standard laboratory measurement in the
perioperative setting and data from earlies studies are sparse. We are striving
for improvement of our daily perioperative quality of care.

To analyse serum sodium concentration, serum osmolarity and arterial bloodgas
at different times before and after administration of HTK solution, to get more
insight of the impact of this solution on these biochemical parameters and to
improve our daily practice in management of hyponatremia after HTK cardioplegia
administration.
In addition, to evaluate the above mentioned parameters in time after
administration of St Thomas* cardioplegia solution. It*s not our intention to
compare HTK and St Thomas* results one to one, but to get more insight in the
consequences of our daily clinical practice.

Monocenter, prospective, observational study

Blood sampling will be done through an arterial line, which will be placed
standardly at the start of anesthesia for a cardiosurgical procedure.
Participation in this study therefore does not lead to additional risk.
Multiple bloodsampling may lead to anaemia. The needed volumes are small
however, and the numer of samples are limited. Most biochemical analyses can be
done from the bloodsamples taken at the Intensive Care for routine
postoperatieve laboratory testing. The maximum sampling volume will be 25 ml of
blood per patient in total. The risk of any disadvantageous health effect for
the patient is negligible.