B . Ali et al .: J Extra Corpor Technol 2024 , 56 , 84 – 93 87
defibrillation ( DC Shock ), the total volume of cardioplegia , and the number of doses , cardiopulmonary bypass time , and aortic cross-clamp time , and mortality . In addition , the incidence of atrial fibrillation ( AF ) and atrial flutter ( AFL ), mechanical ventilation support time , total ICU stay , and mortality were also assessed postoperatively . All parameters were followed during the ICU stay except mortality was followed up till patient discharge from the hospital . We focused on tracking patient mortality only up to the point of discharge rather than extending through 30 days post-operation , as is standard in the Society of Thoracic Surgeons ( STS ) guidelines for surgical mortality reporting . This decision was based on several factors specific to our research objectives and constraints . Firstly , our primary aim was to assess the immediate impact of intervention on patient survival , emphasizing the perioperative period and inhospital outcomes . Moreover , logistical limitations , including the availability of follow-up data and resource constraints , influenced our decision to limit the scope to in-hospital mortality .
Sample size
To calculate our sample size , we used the differences between the 24-h postoperative troponin levels in del Nido and St . Thomas cardioplegia [ 20 ]. The levels were 4.2 (± 2.86 ) and 8.7 (± 6.21 ) ng / mL , respectively . We needed 30 patients in each group to detect a statistical difference in the two-sided test with a 5 % alpha error and 90 % power . However , we decided to include more patients in this observational study to obtain more reliable results with greater precision and power . Therefore , we chose a sample size of 40 patients for each group .
Recruitment and allocation
The clinical team identified potential candidates for cardiac surgery either by referral or from the inpatient waiting list . A member of the research team then approached these patients and offered them the to participate in the study . After obtaining consent , eligible patients were randomly assigned to receive either routine del Nido or modified del Nido Cardioplegia Solution once their eligibility was confirmed . This study was approved by the Research Ethical Committee of the School of Medicine-Shiraz University of Medical Science ( ID : IR . SUMS . MED . REC . 1401.534 ) and was registered in the Iranian Registry of Clinical Trials ( Code : IRCT20230719058845N1 ).
Randomization and blinding
The study randomly assigned 120 patients into three groups of 40 each , using block randomization generated via www . sealedenvelope . com in blocks of 6 ( 6 20 = 120 ) and each block had 20 random codes for either control or Intervention groups . Sealedenvelope . com is a British organization that collaborates with academic institutes and the National Health Service ( NHS ) of the UK . Their primary focus is to support clinical trials by offering various services through a web-based platform . These services include randomization , allocation concealment , code-break services , and case report management . Sealed Envelope plays a crucial role in supporting clinical trials and ensuring their success [ 21 ].
In order to ensure the randomization of the study , codes were generated and sealed in envelopes prior to the day of surgery . On the day of the surgery , perfusionists were entrusted with the responsibility of opening the seals and preparing the cardioplegia solution in accordance with the instructions provided in the randomized codes . This method of code randomization helped to eliminate bias and improve the validity of the study results .
Treatment allocation was concealed from study personnel and participants . The intervention type was blinded by the surgical team , patients , anesthetists , nurses , and laboratory staff . The post-operative care was provided by a specialized team , also blinded to the intervention type . Quality control was performed on data entry for consistency and accuracy .
Follow-up assessment
The routine del Nido and modified del Nido cardioplegic solutions had different baseline solutions . Despite this difference , both solutions were deemed safe , and the outcomes were regularly audited by the lead investigator every five interventions . The study investigators evaluated the possibility of adverse events to prevent any negative consequences for patients . However , administering a single dose was still effective in preserving the myocardium for an extended period during ischemia when using an aortic cross-clamp and during the follow-up phase no patient was excluded or dropped out .
Statistical analysis
We used different methods to describe the data depending on whether it was a quantitative or qualitative variable . We used mean and SD for symmetrical distributions , while we used median and IQR for asymmetric distributions . Qualitative variables were described using frequencies and percentages . To compare means between groups , we used a one-way analysis of variance with Tukey ’ s post hoc analysis . For asymmetric data , we complemented it with the Kruskal-Wallis test and the Dunn test . For comparing proportions among groups , we used Pearson ’ s X 2 test , if the minimum expected count was less than 5 , we used Fisher ’ s exact test . For repeated measures , we used the repeated measure ANOVA test , complemented by the Bonferroni test . We set the significance level at 5 %, and we analyzed the data using SPSS V . 25 .
Results
In this study , a total of 120 participants , elected for isolated CABG surgery were included , and randomly allocated into three groups , 40 in each group ; Control Group ( n = 40 ), Intervention Group A ( n = 40 ), and Intervention Group B ( n = 40 ) with no potential dropout or exclusion throughout follow-up . The control group received normal saline-based del Nido Cardioplegia Solution ( dNCS ) also known as rdNCS , Intervention Group A received lactated-based dNCS ( rldNCS ), while Intervention Group B received plain Ringer-based dNCS ( prdNCS ) ( Figure 1 ).
The mean age of the rdNCS group was 63 (± 6.1 ), rldNCS group 61 (± 10.1 ), and prdNCS group 62 (± 8.7 ) respectively , and observed with an insignificant difference among the