Page 24 - ANZCP GAZETTE DECEMBER 2023

The average preop haemoglobin in the two groups was the same (13.35 g/dL). The lowest mean Hb on CPB was observed in the microplegia group (9.44 g/dl) but did not reach clinical significance. There was a higher amount of blood product usage in the del Nido group (23.9% vs 27.4%).
Figure 1: Average aortic cross clamp time between the patients in the Del Nido and microplegia group.
The microplegia group had an increased aortic clamp time of 82.60 minutes compared to the Del Nido group of 64.24 minutes. The difference of 20 minutes did reach clinical significance (P = 0.0014).
Figure 2: Average change in Haemoglobin between the Del Nido and Microplegia group.
All haemoglobin levels decreased on bypass. The lowest average haemoglobin was observed in the microplegia group. There was no statistically significant difference at any point between the two groups.
Figure 3: Percentage change in haemoglobin during the duration of bypass.
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During CABG the most remarkable percent change in haemoglobin was observed in the microplegia group (29.29 vs 28.24%) but did not reach clinical significance.
Discussion:
Myocardial protection during cardiac surgery is essential to decrease the adverse clinical outcomes during cardiac surgery. The use of Del Nido cardioplegia is gaining popularity however, few randomised control trials have been published on it cardioprotective effects on the myocardium.
This study found that the use of Del Nido cardioplegia positively impacted both the aortic cross clamp and bypass time in CABG surgery which is consistent with the current literature (1). This is likely due to the decreased requirement for redosing. The average cross- clamp time for the two groups was 72.44 minutes. Only one dose of del Nido was likely to be required, whereas 3-4 doses of microplegia would have been given. This is advantageous as it causes fewer disruptions to the procedure. Furthermore studies conducted by Al-Sarraf et al. have shown that prolonged cross clamp times is correlated with poorer clinical outcomes in cardiac patients (10-11).
Del Nido also had similar clinical outcomes regarding the change in haemoglobin, blood product usage and length of ICU stay; and a significant difference was no observed between the two groups. The greatest change in haemoglobin was observed in the microplegia group.
These results were unexpected, given that Del Nido has a larger crystalloid component (1000ml) which causes a greater degree of haemodilution and during the induction dose and subsequently a lower haematocrit . (12). The results may be explained by increased plasmalyte usage in the microplegia group which, this study did not measure.
Conclusion: The results from this study were similar to the current literature, only the X-clamp time reached clinical significance. The decreased time was likely due to the single administration associated with the del Nido protocol. Both groups had similar clinical outcomes in terms of change in haemoglobin and length of ICU stay.
Limitations: There are several limitations to this study. Firstly this was a single centre, non-randomised retrospective study therefore it may not be representative of all techniques and outcomes. Furthermore there was no randomisation of cardioplegia used among surgeons. There was also no direct measure of myocardial injury as our institution doesn’t routinely measure post-operative troponin T levels. A multi-centre randomized control study comparing del Nido cardioplegia to conventional cardioplegia would further our understanding.