Impact of Modified Hot Shot Delivery Before Cross Clamp Removal in Patients Undergoing Cardiac Surgery

Cardiac surgery performed with cardiopulmonary bypass (CPB) requires effective myocardial protection to minimize ischemic and reperfusion injury. ¹  Despite advances in surgical techniques, perioperative myocardial dysfunction remains a major determinant of postoperative morbidity and mortality, prolonging intensive care unit (ICU) stay and increasing resource utilization.² Traditional cardioplegia strategies, although widely used, may not provide complete protection against ischemia-induced myocardial damage, particularly during the critical period of aortic cross-clamp removal.³

One strategy to augment myocardial recovery is the administration of a “Hot Shot” (HS), a terminal warm blood cardioplegia solution delivered immediately before cross-clamp removal.³ The HS technique has been reported to improve metabolic recovery, reduce reperfusion arrhythmias, and decrease enzyme release, though results have been inconsistent across studies.⁴ A Modified Hot Shot (MHS), in which additives are included in the warm blood solution, has been proposed to further enhance myocardial protection.⁵ The modification aims to optimize metabolic support during reperfusion and reduce ischemia-related injury, thereby improving clinical outcomes.⁶

Although several reports support the use of terminal warm blood cardioplegia, evidence regarding the additional benefits of the modified HS formulation is limited, especially in South Asian populations where differences in patient characteristics and perioperative practices may influence outcomes.⁷ Furthermore, most available studies have small sample sizes or focus primarily on biochemical markers rather than clinically significant endpoints.⁸ Thus, the potential role of MHS in improving both biochemical and clinical outcomes requires further clarification.

The present study aimed to evaluate the impact of MHS administration before aortic cross-clamp removal in patients undergoing cardiac surgery. Specifically, we compared intraoperative and postoperative outcomes, including arrhythmia rates, enzyme release, need for intra-aortic balloon pump (IABP) support, ICU stay, renal complications, and mortality, between patients receiving standard HS and those receiving MHS.

Table 1. Inclusion and Exclusion Criteria

Abbreviations: CPB, cardiopulmonary bypass; HS, Hot Shot; MHS, Modified Hot Shot.

Interventions:
All operations were performed using standard CPB techniques with moderate systemic hypothermia. Myocardial protection was provided using intermittent cold blood cardioplegia. Immediately prior to aortic cross-clamp removal, patients received either HS or MHS solution.

• HS: Conventional warm blood cardioplegia delivered at 37°C, in a volume of approximately [insert from thesis, e.g., 200 mL].
• MHS: Warm blood cardioplegia supplemented with metabolic additives (Table 2), administered under the same conditions as HS.

Table 2. Composition of Modified Hot Shot (MHS) Solution

Abbreviations: MHS, Modified Hot Shot; ATP, adenosine triphosphate.

Data Collection:

Preoperative characteristics (age, sex, comorbidities, baseline ejection fraction, renal function), intraoperative variables (type of surgery, CPB and cross-clamp times, cardioplegia details), and postoperative outcomes were extracted from hospital records.

Study Endpoints:

The primary outcomes were markers of myocardial injury, including perioperative arrhythmias, postoperative creatine kinase-MB (CK-MB), and troponin levels. Secondary outcomes included intra-aortic balloon pump (IABP) requirement, ICU stay, renal failure requiring dialysis, and in-hospital mortality.

Statistical Analysis:

Data were analyzed using SPSS version 26.0 (IBM Corp., Armonk, NY, USA). Continuous variables were assessed for normality using the Shapiro–Wilk test. Normally distributed data were expressed as mean ± standard deviation (SD) and compared using the independent-samples t-test. Non-normally distributed variables were presented as median (interquartile range [IQR]) and analyzed using the Mann–Whitney U test. Categorical data were reported as frequencies and percentages, and compared with the chi-square or Fisher’s exact test, as appropriate. A p-value <0.05 was considered statistically significant.

Ethical Considerations:

The study protocol was approved by the Institutional Review Board of King Edward Medical University (Ref No: 113/RC/KEMU). Given the retrospective nature of the study, the need for individual informed consent was waived. All data were de-identified to ensure confidentiality.

Baseline Characteristics:

Baseline demographic and preoperative clinical characteristics were comparable between the two groups (Table 3). There were no significant differences in age, sex distribution, prevalence of hypertension, diabetes, or baseline ejection fraction. Preoperative renal function and comorbidity burden were also similar across the groups.

Table 3: Baseline and Preoperative characteristics of patients undergoing CPB

Abbreviations: Body Mass Index (BMI), Ejection Fraction (EF), Hemoglobin (Hb), Prothrombin Time (PT), Creatinine Clearance Ratio (CCR), Serum Glutamic Pyruvic Transaminase (SGPT), Serum Glutamic Oxaloacetic Transaminase (SGOT), White Blood Cells (WBCs), Activated Clotting Time (ACT)

Intraoperative Variables:

Key intraoperative parameters are summarized in Table 4. Cardiopulmonary bypass (CPB) and aortic cross-clamp times did not differ significantly between the HS and MHS groups as show in Figure1 and Figure 2. The type of surgical procedure performed was evenly distributed. Both groups received comparable volumes of cardioplegia solution, differing only in the composition of the final Hot Shot dose.

Table 4: Intraoperative Variables

Abbreviations: Hemoglobin (Hb), Cross Clamp (X clamp), Cardiopulmonary Bypass (CPB), Temperature (T)

Figure 1: Distribution of aortic cross-clamp times among study patients

Distribution of aortic cross-clamp times among study patients. The histogram illustrates the frequency of patients across different cross-clamp time intervals

Figure 2: Distribution of cardiopulmonary bypass (CPB) times among study patients

Distribution of cardiopulmonary bypass (CPB) times among study patients. The histogram demonstrates the spread of CPB times recorded during surgery. Abbreviation: CPB, cardiopulmonary bypass.

Postoperative Outcomes:

Postoperative outcomes are presented in Table 5. Patients in the MHS group demonstrated significantly lower incidence of arrhythmias compared with the HS group. Similarly, as shown in Figure 3 and Figure 4, biochemical markers of myocardial injury were reduced in the MHS group, with lower mean CK-MB and troponin levels in the early postoperative period (p<0.005 for both). The need for intra-aortic balloon pump (IABP) support was significantly less frequent in the MHS group (p<0.05). ICU stay was also shorter among patients receiving MHS (p<0.005).

Table 5: Post-Operative Variables, Complications and Mortality

Abbreviations: Hemoglobin (Hb), Activated Clotting Time (ACT), Fresh Frozen Plasma (FFPs), Minutes (min), Serum Glutamic Pyruvic Transaminase (SGPT), Serum Glutamic Oxaloacetic Transaminase (SGOT), White Blood Cells (WBCs), Creatine Kinase-Myoglobin Binding (CK-MB), Potassium (K), Intra-Aortic Ballon Pump (IABP)

Figure 3: Postoperative distribution of CK-MB levels in HS and MHS groups

Postoperative distribution of CK-MB levels in Hot Shot (HS) and Modified Hot Shot (MHS) groups. The graph displays the comparative frequency distribution of CK-MB enzyme levels following surgery. Abbreviations: HS, Hot Shot; MHS, Modified Hot Shot; CK-MB, creatine kinase–MB.

Patients receiving MHS had a significantly lower incidence of postoperative renal failure requiring dialysis (p<0.05). Other postoperative complications, including low cardiac output syndrome, bleeding requiring re-exploration, and respiratory complications, were less frequent in the MHS group, although the differences were not statistically significant. Overall, in-hospital mortality did not differ significantly between the two groups (HS vs. MHS, p=0.3).

Figure 4: Postoperative distribution of troponin-T levels in HS and MHS groups

Postoperative distribution of troponin-T levels in HS and MHS groups. The histogram illustrates the frequency distribution of troponin-T enzyme levels in the immediate postoperative period. Abbreviations: HS, Hot Shot; MHS, Modified Hot Shot.

This study evaluated the efficacy of Modified Hot Shot (MHS) delivery compared with conventional Hot Shot (HS) in patients undergoing cardiac surgery with cardiopulmonary bypass (CPB). The principal findings were that MHS significantly reduced the incidence of postoperative arrhythmias, lowered CK-MB and troponin levels, decreased the need for intra-aortic balloon pump (IABP) support, shortened intensive care unit (ICU) stay, and reduced renal complications. Importantly, overall mortality was similar between groups.

The concept of terminal warm blood cardioplegia, or the “Hot Shot,” has been widely studied as a strategy to improve metabolic recovery and reduce ischemia-reperfusion injury.9 Several clinical trials have demonstrated reductions in arrhythmias and improved myocardial recovery with HS use, although the magnitude of benefit has varied.10,11 In the present study, we observed that the addition of metabolic substrates and electrolytes in the MHS formulation provided incremental benefit beyond standard HS, particularly in reducing enzyme release and postoperative morbidity.

Biochemical markers such as CK-MB and troponin are established indicators of myocardial injury.12 Consistent with our findings, previous studies have shown that optimized reperfusion strategies are associated with lower enzyme release, reflecting improved myocardial protection.13 The reduced enzyme levels in the MHS group likely reflect better metabolic support during reperfusion, attributable to the inclusion of glutamate and aspartate, which enhance oxidative metabolism and ATP regeneration.14

Arrhythmia reduction in the MHS group also aligns with earlier work highlighting the stabilizing effect of magnesium in cardioplegia solutions.15 By limiting calcium influx and stabilizing cell membranes, magnesium supplementation may prevent reperfusion arrhythmias and support early hemodynamic stability.16 These mechanisms provide a plausible explanation for the lower IABP requirement observed in the MHS group.

Renal dysfunction remains a significant complication after cardiac surgery, contributing to morbidity and mortality.17 In our study, patients receiving MHS had a lower incidence of renal failure requiring dialysis. Although the exact mechanism is uncertain, it may relate to improved myocardial performance and reduced systemic inflammatory burden, thereby preserving renal perfusion. Previous literature supports the link between effective myocardial protection and better renal outcomes.18

Despite these advantages, we did not observe a mortality difference between groups. This finding is consistent with prior studies where myocardial protection strategies reduced morbidity but did not significantly affect short-term survival.19,20 Mortality in contemporary cardiac surgery is influenced by multiple perioperative and patient-related factors, and a single modification in cardioplegia is unlikely to independently shift this endpoint. 21

The present study has important clinical implications. Incorporating MHS into surgical protocols may improve perioperative outcomes, reduce postoperative complications, and shorten ICU stay. These benefits not only enhance patient recovery but also contribute to reduced healthcare costs and resource utilization, which is especially relevant in resource-limited healthcare systems.

However, several limitations merit consideration. First, this was a retrospective single-center study, which carries inherent risk of selection and information bias. Second, the follow-up was limited to the in-hospital period; longer-term outcomes such as late survival, ventricular function, and quality of life were not assessed. Third, the study did not include detailed hemodynamic or biochemical analyses that could further clarify the mechanisms underlying the observed benefits. Finally, although the groups were well matched at baseline, unmeasured confounders cannot be excluded

The Modified Hot Shot strategy was associated with superior perioperative myocardial protection compared with conventional Hot Shot. Patients receiving MHS experienced reduced arrhythmias, lower cardiac enzyme release, shorter ICU stay, and fewer renal complications, without a significant difference in mortality. These findings suggest that MHS may be a valuable adjunct in routine cardiac surgical practice. Future randomized controlled trials with larger cohorts and long-term follow-up are needed to validate and expand upon these results.

1.     Khilji SA, Ghaffar MF. Enhancement of myocardial recovery with terminal ‘hot shot’cardioplegia. Journal of Shalamar Medical & Dental College-JSHMDC. 2024 Dec 31;5(2):89-94. https://doi.org/10.53685/jshmdc.v5i2.229

2.     Elkhouly M, Fouad A. Effect of Antegrade direct hotshot Graft Perfusion in On-pump Coronary Artery Bypass Grafting. The Egyptian Journal of Hospital Medicine. 2022 Jul 1;88(1):3765-70. 10.21608/ejhm.2022.252038

3.     Mirmohammadsadeghi P, Mirmohammadsadeghi M. Effects of single antegrade hot shot in comparison with no hot shot administration during coronary artery bypass grafting. Arya Atherosclerosis. 2015 May;11(3):186. PMID: 26405451

4.     Kalogerakos PD, Kokkinakis S, Akoumianakis E, Karagkounis T, Gavalaki A, Kiparakis M, Akoumianakis I, Lazopoulos L, Gaitanaki T, Andreou A, Lasithiotakis K. Network meta-analysis of cardioplegic methods, in elective isolated coronary artery bypass grafting. Perfusion. 2025 Jul 8:02676591251359901. https://doi.org/10.1177/02676591251359

5.     Qasim A, Sharfi MH, Ibtesam-E-Fajar, Farrukh R, Mushtaq S, Rafique A. Correlation of Cardiopulmonary Bypasses and Cardiac Troponin I in Predicting Post-Op Arrhythmia. Pak J Med Health Sci. 2023;17(02):750. doi:10.53350/pjmhs2023172750 pjmhsonline.com

6.     Lu P, Lu X, Li B, Wang C, Wang X, Ji Y, et al. High-Sensitivity Cardiac Troponin T in Prediction and Diagnosis of Early Postoperative Hypoxemia after Off-Pump Coronary Artery Bypass Grafting. J Cardiovasc Dev Dis. 2022;9(12):416. doi:10.3390/jcdd9120416 PMC

7.     Li Y, Li Y, Hu Q, Zheng S, Tian B, Meng F, Chen Z, Han J, Wang S, Zhang H, Xu C, Jia Y, Jiao Y, Fu J, Meng X. Association of early elevated cardiac troponin I concentration and longitudinal change after off-pump coronary artery bypass grafting and adverse events: a prospective cohort study. J Thorac Dis. 2020;12(11):6542-6551. doi:10.21037/jtd-20-1691 Journal of Thoracic Disease

8.     Mahrose R, Shorbagy MS, Shahin KM, et al. Warm blood cardioplegia versus cold crystalloid cardioplegia for coronary artery bypass grafting (CABG) in patients with low ejection fraction. Ain-Shams J Anesthesiol. 2020;12:18. doi:10.1186/s42077-020-00069-8 SpringerOpen

9.     Del Nido cardioplegia versus cold blood cardioplegia in adult cardiac surgery: a meta-analysis of randomized clinical trials. J Cardiothorac Surg. 2024;19(356). doi:10.1186/s13019-024-02846-0 BioMed Central

10.   Frontiers | Increased levels of NT-proBNP and troponin T 2 years after coronary artery bypass grafting complicated by mediastinitis. Front Cardiovasc Med. 2023;10:1008825. doi:10.3389/fcvm.2023.1008825 Frontiers

11.   Effect of terminal warm reperfusion (hot shot) and remote ischemic preconditioning, either separately or combined, on myocardial recovery in adult cardiac surgery. J Egyptian Soc Cardiothorac Surg. 2017;3:230-235. doi:10.1016/j.jescts.2017.07.005 OUCI

12.   Troponin-I release after cardiac surgery with different surgical techniques and post-operative neurological outcomes. McGill J Med. 2020 Dec 1;9(2). doi:10.26443/mjm.v9i2.658 mjm.mcgill.ca

13.   Soliman, Rabie1,2,; Abukhudair, Walid3. The Perioperative Effect of Magnesium sulfate in Patients with Concentric Left Ventricular Hypertrophy Undergoing Cardiac Surgery: A Double-Blinded Randomized Study. Annals of Cardiac Anaesthesia 22(3):p 246-253, Jul–Sep 2019. | DOI: 10.4103/aca.ACA_34_18.

14.   Borden II RA, Ball C, Grady PM, Toth AJ, Lober C, Bakaeen FG, Tong MZ, Soltesz EG, Blackstone EH, Roselli EE. Microplegia vs 4: 1 blood cardioplegia: effectiveness and cost savings in complex cardiac operations. The Annals of Thoracic Surgery. 2020 Oct 1;110(4):1216-24. https://doi.org/10.1016/j.athoracsur.2020.02.006

15.   Walker LJ, Young PJ. Fluid administration, vasopressor use and patient outcomes in a group of high-risk cardiac surgical patients receiving postoperative goal-directed haemodynamic therapy: a pilot study. Anaesthesia and Intensive Care. 2015 Sep;43(5):617-27. https://doi.org/10.1177/0310057X15043005

16.   Sharma P, Chauhan A, Guleria K, Mehta S, Verma Y, Jaswal S. A Randomized control study to compare delNido and Saint Thomas cardioplegia solutions in isolated valvular heart surgery. European Journal of Cardiovascular Medicine. 2023 Jul 1;13(3).

17.   Sharma A, Dixit S, Mittal S, Sharma M, Sharma D, Mawar KK. DelNido cardioplegia versus St Thomas cardioplegia solution in double valve replacement: a single centre experience. Perfusion. 2021 Jul;36(5):476-81. https://doi.org/10.1177/0267659120961921

18.   Haider A, Khwaja IA, Khan AH, Yousaf MS, Zaneb H, Qureshi AB, Rehman H. Efficacy of whole-blood Del Nido cardioplegia compared with diluted Del Nido cardioplegia in coronary artery bypass grafting: A retrospective monocentric analysis of Pakistan. Medicina. 2021 Aug 31;57(9):918. https://doi.org/10.3390/medicina57090918

19.   Yang Q, He GW, Underwood MJ, Yu CM. Cellular and molecular mechanisms of endothelial ischemia/reperfusion injury: perspectives and implications for postischemic myocardial protection. American journal of translational research. 2016 Feb 15;8(2):765. PMID: 27158368

20.   Ruetzler, Kurt MD*,†; Khanna, Ashish K. MD, FCCP, FCCM†,‡; Sessler, Daniel I. MD†,§. Myocardial Injury After Noncardiac Surgery: Preoperative, Intraoperative, and Postoperative Aspects, Implications, and Directions. Anesthesia & Analgesia 131(1):p 173-186, July 2020. | DOI: 10.1213/ANE.0000000000004567

21.   Engelman DT, Ali WB, Williams JB, Perrault LP, Reddy VS, Arora RC, Roselli EE, Khoynezhad A, Gerdisch M, Levy JH, Lobdell K. Guidelines for perioperative care in cardiac surgery: enhanced recovery after surgery society recommendations. JAMA surgery. 2019 Aug 1;154(8):755-66. doi:10.1001/jamasurg.2019.1153