The Journal of ExtraCorporeal Technology No 56-4 | Page 18

156 M . Szpytma et al .: J Extra Corpor Technol 2024 , 56 , 149 – 158

Table 9 . Sub-analysis : Postoperative median troponin profiles for 120-minute aortic cross-clamp time .

Continuous variables are expressed median ( IQR ), categorical variables are expressed number (%). Abbreviations : HKB – hyperkalemic blood cardioplegia ; DNC – Del Nido cardioplegia ; AUC – area under curve .

Figure

3 . Troponin profile based on cardioplegia strategy for greater than 120-minute ischaemic time . Solid middle bar is the median , top and bottom of box the 75th and 25th percentile , with upper and lower adjacent values .

further 500 mL DNC at 90 min ischemic time was utilised . Following evaluation of our current data , departmental morbidity and mortality reviews and recent publications discussing redosing and timing of DNC for cases with extended AXC [ 20 , 21 ], we have developed our current multi-dose DNC dosing protocol .

The current dosing protocol stipulates that when the total ischemic time is expected to be less than 90 min a single 1000 mL induction DNC dose is used . If the ischemic time is expected to exceed 90 min a 1000 mL DNC induction dose is given followed by maintenance doses of 500 mL DNC administered at approximately 60 min intervals thereafter .

Limitations

This is a retrospective observational study with inherent limitations associated with the study design . Our report represents an evolving clinical practice reinforced by a culture of measurement and review , visible by multiple dosing protocol adjustments over time , with the most recent iteration of the delivery protocol being adopted in 2023 . The choice of variables for the propensity matching is an inherent limitation of the statistical methodology , and additionally , we have not performed sensitivity analyses on the route of cardioplegia administration or surgeon performing the procedure . The variation introduced by being unable to propensity match surgeons is an inherent limitation of the retrospective study design . It is important to note the median number of cardioplegia doses in the 90 min ACX time primary analysis was one , therefore inference on multi-dosing is based on the sub-analysis alone . With regards to clinical outcomes one of the major concerns regarding multidose DNC is lidocaine toxicity and its hypothesized results on myocardial contractility and arrhythmia . Arrhythmia and a quantitative reproducible measure of cardiac output such as inotropic requirements or cardiac index post-operatively were not included . Similarly , rates of return to theatre were higher in the DNC cohort however inferences on the manner and cause of this were not included . A further limitation is that we have not reported a 24-hour Troponin value as one of the two hospitals did not collect this time point , and our troponin profiles are not indexed to renal function nor type of procedure which can introduce confounders to their interpretation relative to these variables . Finally , a significant consideration is the learning curve for the operative team in adopting a new cardioplegic strategy , this will inadvertently introduce patient selection bias and additional confounders about timing of redosing , choice of cardioplegic agent , mode , and rate of delivery ; which cannot be accounted for in a retrospective study design .

Conclusion

This is the largest quantitative cohort study on DNC use in patients with prolonged AXC time in Australia or New Zealand and adds significantly to the limited international reports . Del Nido cardioplegia in more complex and longer procedures has demonstrated equivalent myocardial protection compared with multiple doses of HKB cardioplegia . This study is a quality assurance measure driven by clinical experience and our departmental morbidity and mortality review processes . Randomised , multi-centre trials are needed to develop an evidence-based protocol for multi-dose DNC .