C0MPARISON OF THE TROPONIN I LEVELS DURING CORONARY ARTERY BYPASS GRAFT IN CARDIAC SURGERY PROCEDURES, REALISED WITH AND WITHOUT EXTRACORPOREAL CIRCULATION
U. BORRELLI(5), J. FIJALKOWSKI(5), M.
DETROUX(1), P. NACKERS(2),
B. COLINET(2), S. NIKIS(2), M. JAKUBIAK(2), C. MIESSE(2), G. SAÏDANE(2),
B. GILLIEAUX(2), S. JENNES(2), E. WIJTENBURG(1), A. BODSON(3),
M. BOEUR(3), P. STRUYVEN(3), V. RIZZI(3), H. YAZIDI(3), A. DE CONINCK(4)
1 - Department of Cardiovascular Surgery
2 - Department of Anesthesia & Reanimation
3 - Department of Clinical Microbiologic Laboratory
4 - Statistics
5 - Department of Perfusion
Department of Cardiovascular Surgery, St-Joseph Hospital, Gilly - Belgium
INTRODUCTION
Since 1997, we have been using a specific protocol of intermittent warm
blood cardioplegia during normothermic extracorporeal circulation (ECC) for
coronary artery bypass graft (CABG), valvular cardiac surgery and
ascendant aorta aneurysm. That protocol consists in a constant concentration of
potassium chloride (KCl) and to add sulphate of magnesium (MgSo4).That
cardioplegia protocol has been giving us a lot of satisfaction because it can be
easily adapted and modulated in function of the quality of the cardiac arrest,
the clamping time, the patient’s potassium concentration, the injection pressure
of the cardioplegia solution and even for less frequent intricate cardiac
pathologies. The quality of the myocardial protection by that technique has
already been evaluated in our hospital in a previous study (1). The results were
then very satisfying and to confirm those results, we decided to carry out this
prospective nonrandomized study.
METHODS
Patients
Between February 2002 and May 2002, 30 patients with coronary bypasses have been incorporated in this trial, distributed into two groups of 15 patients whose caracteristics were comparable (table II): 15 patients were operated with normothermic ECC, aortic crossclamping and intermittent anterograde warm blood cardioplegia (ECC Group). The other 15 patients were operated without ECC (OPCAB Group) with a stabilisation system (Octopus 3, Medtronic Minneapolis - USA) and under protection of an intracoronary shunt (Clearview, Medtronic Minneapolis - USA). We have compared the quality of the myocardial protection in both groups by measuring the troponin I levels at different moments: before incision, 10 minutes after protamine, 15 hours after surgery, in the 2nd postoperative day and the 3rd postoperative day.
Materials
We used:
1. ECC in open system with oxygenator with small contact surface D 903 Avant
(Phosphorylcholine, Dideco Mirandola - It).
2. A complete surface treated (Phosphorylcholine, Dideco Mirandola - It) circuit
combined with a total priming reduction of the ECC (500 ml).
3. The method for autologous retrograde priming with ECC compact. The circuit of
cardioplegia placed in a roller pump and connected to the oxygenator with the
following components:.
• A bubble trap with recirculation line to the venous resevoir
• A measure of the injection pressure
• A connection for an electrical syringe (infusor)
• 54 ml of KCl 2 mEq / ml = 2 mmol / ml or 0.149gr / ml
• 6 ml of MgSo4 = 14.7 mEq or 1.8 gr
KCl concentration / ml: 1.8 mEq or mmol / ml
The reference table for cardioplegia is inspired by the method of Professor A.M. Calafiore (2), without KCl loading dosis, by adding MgSo4 and intermediate stages. In this table we calculated the mean value of the administered KCl during the two minutes of cardiolplegia perfusion. The choice of the concentration of KCl to be administered, depends upon the pathology, the patient’s kalemia, the injection pressure and the cardiac arrest.
After control of the patient’s kalemia, the first minute of antegrade perfusion is an evaluation of the function of the aortic valve and the cardiac arrest, by the flow-pressure ratio (1,3). She can lead to an adaptation of KCl or to a retrograde perfusion. During antegrade cardioplegia, the flow of the blood pump is 250 to 300 ml per minute and the pressure of the cardioplegia circuit is 150 mmHg. The expression of a perfusion of good quality is the ratio between flow and pressure, a high ratio being the sign of a loss, a low ratio being the sign of a resistance.
During the first cardioplegia, the energetic needs
are less, the heart being perfused prior to clamping. After 1 minute of
cardioplegia perfusion, the KCl pump is stopped, while the blood pump continues
during 20 last seconds. In presence of small movements of the heart during the
20 last seconds, we inject 1g of MgSo4 in the cardioplegia circuit (1,3), to
become an ionic stabilisation on the level of the membranes and to obtain an end
to those movements. In the next periods of cardioplegia, the KCl pump is stopped
after 100 seconds of cardioplegia perfusion, the blood pump continuing during
the last 20 seconds. From the third cardioplegia, after control of the kalemia
and the cardiac arrest, the speed of the KCl syringue pump is lowered to 150 ml
per hour. If there is renewed cardiac activity during the first minute of
perfusion, the speed of the KCl syringue pump can be risen to 280 ml per hour
for the rest of this cardioplegia. In certain cardiac pathologies, a washing of
KCl can exist between the periods of cardioplegia due to a collateral perfusion
of the heart. Cardioplegia is administered every 15 to 20 minutes. During
retrograde cardioplegia (1,3), monitoring and the pulsatile form of the coronary
sinus pressure curve are the signs of the good quality of the perfusion. The
injection pressure has to be superior to 30 mmHg and inferior to 50 mmHg, for a
flow of 250 to 300 ml per minute, depending of the pathology. For hypertrophic
hearts, injection pressure has to be superior to 40 mmHg and inferior to 50 mmHg,
for a flow of 250 to 350 ml per minute.
Next retrograde cardioplegia is administered by a KCl syringue pump at a speed
of 150ml per hour.
Statistical analysis were performed using the software Sas and Statview. Data
are expressed as mean ± standard deviation, unless otherwise noted. P values <
of 0.05 or less were considered significant. Analysis was performed using the
tests no parametric of Mann-Whitney.
RESULTS
Due to one patient with a more complex pathology, the mean postoperative number of days of Intensive Care is a little higher in the OPCAB Group. Apart from this patient, the duration of postoperative hospitalization is similar in the two groups.
10 minutes after protamine, the troponin I values for the ECC Group are superior to the troponin I values of the OPCAB Group. This is explained by the fact that, for the OPCAB Group, there is a continuous washing of troponin I and thus a moderate systemic value.
In the ECC Group to the contrary, there is a
pooling of troponin I in the heart and thus a higher systemic value upon
declamping. It is important to note that there is no difference between the two
groups at the 15th postoperative hour and this untill the third postoperative
day. ECC Group undergoing 4,3 anastomoseses (+ 0,7 SD) and a mean aortic
clamping time of 87,9 minutes (± 19,6 SD), OPCAB Group undergoing 2,3
anastomoses (± 0,9 SD).
The results show that there is no significant difference between the two groups
on the first post-operative day: ECC Group: 2,311 ± 1,209 ng / ml (mean ± SD),
OPCAB Group: 2.625 ± 2.245 ng / ml (mean ± SD).
CONCLUSIONS
This study is an analysis of the adaptation of a technique of cardioplegia in our hospital. It is not our purpose to demonstrate a superiority against the other techniques of cardioplegia. It is important to verify the good quality of antegrade and retrograde cardioplegia perfusion, controlling the flow-pressure ratio. For the small movements of the heart, the injection of 1g of MgSo4 in the cardioplegia circuit during the last 20 seconds of perfusion, permits an ionic stabilisation on the level of the membranes and thus an end to the movements. Despite the different pathologies encountered, the kaliemia, the enzymatic values and the post-operative cardiac index of the patients stay in the norms. The measured values of Troponin I show that there is not a significant difference between the 2 groups. Since 1997, we have also used this method of myocardial protection with succes by patients with more complex pathologies than in this study. To confirm those encouraging results, it should be good to make a larger prospective study
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