Cooling of the myocardium has long been recognized as cardioprotective during cardiac surgery. Cold cardioplegia is routinely used to protect the heart during aortic cross-clamping. Shumway [1] introduced additional topical cooling with ice-slush in 1959, aiming to enhance myocardial protection during intervals between cardioplegia doses. Although theoretically beneficial, several studies have reported potential detrimental effects of ice-slush application [2, 3, 4, 5, 6, and 7]. As a result, many centers have abandoned routine topical cooling, though controversy remains regarding its necessity. Studies to define evidence on the benefits of additional topical cooling is limited, especially in Eastern India. The present study aims to assess the outcomes of topical cooling with cold saline or ice-slush in patients undergoing aortic and/or mitral valve surgery, using markers of myocardial damage.

Intraoperative hypothermia during cardiopulmonary bypass (CPB) is employed to reduce metabolic rate and oxygen consumption, protecting vital organs from ischemic injury. Mild hypothermia (34–35 °C) decreases oxygen consumption, CO₂ production, and anesthetic use, while moderate hypothermia (32–34 °C) improves tissue oxygen delivery, reduces inotropic requirements, and facilitates early extubation. However, hypothermia can also prolong anesthesia recovery, increase cardiac morbidity, and impair coagulation. Meta-analyses indicate that even a 1 °C drop can raise blood loss and transfusion risk. Hypothermic CPB (25–32 °C) can induce reversible platelet dysfunction and inhibit clotting factors. Randomized trials have generally shown no significant differences in blood product use, extubation time, hospital stay, myocardial infarction, or mortality between patients with mild hypothermia (~34 °C) and normothermia. Some studies suggest that intraoperative temperatures of 32–35 °C may reduce ICU stay and transfusion requirements compared to >35 °C, but mortality and major complications appear unchanged. Pediatric studies comparing moderate (24 °C) and mild (34 °C) hypothermia also show no significant differences in systemic inflammatory response or organ injury. Overall, the optimal hypothermic strategy during CPB remains unclear, with wide variability in practice and debate over the role of additional topical cooling. Aims of the study to assess whether intraoperative topical myocardial cooling with ice-slush or cold saline provides additional cardioprotection beyond systemic hypothermia and cold cardioplegia, and its impact on postoperative myocardial and pulmonary function in aortic and mitral valve surgery with CPB.

Study Type:  Prospective observational study.

Study Place: Ward, ICU and OT of Department of Cardiothoracic and Vascular Surgery, IPGMER and SSKM Hospital, Kolkata

Study Population: All patients undergoing surgery for Aortic and/or mitral valve disease in the aforementioned department, keeping in mind the study period, inclusion and exclusion criteria.

Study Period: One and Half year (July 2022-January 2024)

Sample Size: 40 patients.

Inclusion Criteria:

• All patients presenting with aortic and/or mitral valve disease posted for surgery in the department of CTVS, IPGMER & SSKM Hospital, in the above mentioned study period.

Exclusion Criteria:

1. Any patient going in for emergency valve surgery, that is for endocarditis, vegetation, or acute mitral regurgitation caused by mitral valve prolapse (MVP).
2. Any patient having concomitant coronary disease undergoing concomitant CABG, to rule out the confounding factor of ischemic heart disease induced rise in markers of myocardial damage.
3. Any patient who is hemodynamically unstable preoperatively.
4. Re-do valve surgery cases as in stuck valve or prosthetic valve endocarditis.
5. Patients not willing to participate in the study.
6. Patients who are declared unfit to undergo operation.

Parameters to be Studied:

The following parameters will be compared between groups who received and did not receive topical hypothermia

• Post-operative (next morning) levels of cardiac specific creatinine kinase (CK-MB) and troponin I(Trop-I).
• Spontaneous restoration rate of sinus rhythm when weaning from CPB.
• Time to restore to sinus rhythm post cross clamp removal.
• Post CPB need of myocardial pacing.
• Post-operative rate of pulmonary morbidity (clearness or haziness of lung field) studied using post-operative day 1(POD 1) digital chest x ray films
• Post-operative diaphragm elevation studied using post-operative day 4(POD 4) digital chest x ray films.
• Rate of immediate post-operative mortality (within 5 days of operation).

Statistical Analysis:

Data were entered into Excel and analyzed using SPSS and GraphPad Prism. Numerical variables were summarized using means and standard deviations, while categorical variables were described with counts and percentages. Two-sample t-tests were used to compare independent groups, while paired t-tests accounted for correlations in paired data. Chi-square tests (including Fisher’s exact test for small sample sizes) were used for categorical data comparisons. P-values ≤ 0.05 were considered statistically significant.

Table 1: Association Between Demographic parameter: Topical Cooling

Table 2: Association between Surgery: Group

Table 3: Association between Sinus Rhythms Restored Spontaneously or not: Group

Table 4: Association between Pacing needed post CPB and Any events when coming off CPB: Group

Table 5: Association between POD1 Lung Fields, POD4 Diaphragm Elevated, and Mortality at POD5: Group

Table 6: Distribution of mean CK-MB POD1 (unit/L), Troponin I (Trop I) POD1(pg/mL) and Time to Restore Sinus Rhythm (min): Group

Figure 1: Association between Surgery: Group

Figure 2: Association between Sinus Rhythm Restored Spontaneously or not: Group

The two groups are broadly similar in age. The largest proportions in both groups fall in the 31–50 years range. The p-value of 0.7928 indicates no statistically significant difference in age distribution between the groups. Slightly more males are in the topical cooling group (65%) compared to the no topical cooling group (50%). The p-value of 0.3372 shows that this difference is not statistically significant.

Among patients in the No Topical Cooling group (n=20), 11 (55.0%) underwent Mitral Valve Replacement (MVR), 7 (35.0%) underwent Aortic Valve Replacement (AVR), and 2 (10.0%) underwent Double Valve Replacement (DVR). In the Topical Cooling group (n=20), 10 (50.0%) underwent MVR, 8 (40.0%) underwent AVR, and 2 (10.0%) underwent DVR. The difference in distribution of surgery types between the two groups was not statistically significant (p = 0.9445).

In the No Topical Cooling group (n=20), 18 patients (90.0%) had sinus rhythm restored, while 2 patients (10.0%) did not. In the Topical Cooling group (n=20), 16 patients (80.0%) had sinus rhythm restored, and 4 patients (20.0%) did not. The difference in the rate of sinus rhythm restoration between the two groups was not statistically significant (p = 0.37582).

Following cardiopulmonary bypass (CPB), pacing was required in 2 patients (10.0%) in the No Topical Cooling group compared to 5 patients (25.0%) in the Topical Cooling group. The difference was not statistically significant (p = 0.2118).

Regarding events while coming off CPB, 2 patients (10.0%) in the No Topical Cooling group and 3 patients (15.0%) in the Topical Cooling group experienced such events. This difference was also not statistically significant (p = 0.6325).

On postoperative day 1 (POD1), clear lung fields were observed in 10 patients (50.0%) in the No Topical Cooling group and 4 patients (20.0%) in the Topical Cooling group, whereas hazy lung fields were noted in 10 patients (50.0%) and 16 patients (80.0%), respectively. This difference was statistically significant (p = 0.0467), indicating a higher incidence of hazy lung fields in patients who received topical cooling.

On postoperative day 4 (POD4), diaphragmatic elevation was seen in 2 patients (10.0%) in the No Topical Cooling group and 6 patients (30.0%) in the Topical Cooling group. The difference, however, was not statistically significant (p = 0.1138).

There was no mortality observed in either group up to postoperative day 5 (POD5).

In the No Topical Cooling group, the mean CK-MB on POD1 was 45.38 ± 31.46 U/L, whereas in the Topical Cooling group, it was 89.82 ± 90.19 U/L; the difference was statistically significant (p = 0.0443), indicating that topical cooling actually caused myocardial damage rather than protection.

The mean Troponin I on POD1 in the No Topical Cooling group was 47.92 ± 17.95 pg/mL, compared to 53.85 ± 13.86 pg/mL in the Topical Cooling group, with no statistically significant difference (p = 0.2494).

The mean time to restore sinus rhythm was significantly shorter in the No Topical Cooling group (3.89 ± 1.64 min) compared to the Topical Cooling group (6.69 ± 3.81 min) (p = 0.0078, statistically significant), indicating that addition of topical cooling lead to functional myocardial damage rather than protection.

The present study was a prospective observational study. This study was conducted over a period of one and a half years (July 2022–January 2024) at the Ward, ICU, and OT of the Department of Cardiothoracic and Vascular Surgery, IPGMER and SSKM Hospital, Kolkata. The study population included all patients undergoing surgery for aortic and/or mitral valve disease in the aforementioned department, based on the defined inclusion and exclusion criteria. The sample size for the study was 40 patients.

In our study comprising 40 patients undergoing valve surgery, the two groups were broadly similar in age, with the majority belonging to the 31–50 years range. The p-value [0.7928] indicated no statistically significant difference in age distribution between the groups. Slightly more males were in the topical cooling group [65%] compared to the no topical cooling group [50%], though this difference was not statistically significant [p = 0.3372].

Among patients in the No Topical Cooling group, 11 [55.0%] underwent Mitral Valve Replacement [MVR], 7 [35.0%] underwent Aortic Valve Replacement [AVR], and 2 [10.0%] underwent Double Valve Replacement [DVR]. In the Topical Cooling group, 10 [50.0%] underwent MVR, 8 [40.0%] underwent AVR, and 2 [10.0%] underwent DVR. The distribution of surgical types was comparable between groups [p = 0.9445], confirming that both cohorts were well matched preoperatively.

Restoration of sinus rhythm after cardiopulmonary bypass [CPB] was achieved in 18 patients [90.0%] in the No Topical Cooling group and in 16 patients [80.0%] in the Topical Cooling group, with no significant difference between them [p = 0.3758]. Similar findings have been reported by Nikas et al. [2] and Allen et al. [6], who found that topical hypothermia did not enhance myocardial recovery when adequate systemic cooling and cold cardioplegia were used.

Pacing was required in 2 patients [10.0%] in the No Topical Cooling group and 5 patients [25.0%] in the Topical Cooling group, though this difference was not statistically significant [p = 0.2118]. Adverse events while coming off CPB occurred in 2 [10.0%] and 3 [15.0%] patients, respectively [p = 0.6325]. These results indicate that omitting topical cooling does not compromise intraoperative hemodynamic stability or rhythm recovery.

Postoperative findings showed more pulmonary changes among patients receiving topical cooling. On postoperative day 1, hazy lung fields were observed in 16 patients [80.0%] in the Topical Cooling group compared to 10 patients [50.0%] in the No Topical Cooling group, a statistically significant difference [p = 0.0467]. This suggests increased pulmonary congestion or atelectasis among those who received topical ice slush. Similar observations were made by Curtis et al. [3] and Kohorst et al. [4], who reported postoperative diaphragmatic elevation and phrenic nerve dysfunction following topical cardiac hypothermia.

By postoperative day 4, diaphragmatic elevation was noted in 6 patients [30.0%] in the Topical Cooling group versus 2 patients [10.0%] in the No Topical Cooling group [p = 0.1138]. Although not statistically significant, this trend supports previous findings that topical ice may induce phrenic nerve injury and transient diaphragmatic paralysis [3–5, 7]. No mortality occurred in either group up to postoperative day 5, indicating short-term safety of both approaches.

Analysis of postoperative cardiac biomarkers demonstrated significantly higher CK-MB levels in the Topical Cooling group on POD1 (89.82 ± 90.19 U/L) compared to the No Topical Cooling group (45.38 ± 31.46 U/L; p = 0.0443), suggesting increased myocardial enzyme release with topical cooling. Troponin I levels were higher in the Topical Cooling group (53.85 ± 13.86 pg/mL vs. 47.92 ± 17.95 pg/mL), but the difference was not statistically significant (p = 0.2494). Notably, the mean time to restore sinus rhythm was significantly shorter in the No Topical Cooling group (3.89 ± 1.64 min) compared to the Topical Cooling group (6.69 ± 3.81 min; p = 0.0078), indicating faster electrophysiological recovery without topical ice.

These findings suggest that omitting topical cardiac cooling does not adversely affect myocardial protection, rhythm recovery, or hemodynamic stability, rather it may reduce myocardial mechanical and electrophysiological damage, while also potentially reducing pulmonary complications.

Elevated markers of myocardial damage and adverse pulmonary outcomes with topical hypothermia have been reported previously by Kadan M et al [8].

The study design, statistical interpretation, and sample size were aligned with established clinical research methodology as per Hazra A et al [9] and Pourhoseingholi MA et al[10].

Overall, these results support the evolving literature questioning the routine use of topical hypothermia in valve surgery when adequate systemic hypothermia and cold cardioplegia are applied, as previously noted by Sarkar M et al[11].

We concluded that in patients having aortic and mitral valve surgery, no topical cardiac hypothermia during cardiopulmonary bypass is linked to a lower risk of myocardial injury, lower pulmonary morbidity, and a better outcome following surgery. These results establish topical hypothermia as an unnecessary addition in the management of myocardial protection during these high-risk procedures. To validate these findings and investigate the underlying processes thereof, more research is necessary.

1. Shumway NE, Lower RR. Hypothermia for extended periods of anoxic arrest. SurgForum 1959; I0:563.
2. Nikas DJ, Ramadan FM, Elefteriades JA. Topical hypothermia: Ineffective and deleterious as adjunct to cardioplegia for myocardial protection. Ann Thorac Surg. 1998; 65:2831.
3. Curtis JJ, Nawarawong W, Walls JT, et al. Elevated hemidiaphragm after cardiac operations: Incidence, prognosis, and relationship to the use of topical ice slush. Ann Thorac Surg.1989; 48:7648.
4. Kohorst WR, Schonfeld SA, Altmann M. Bilateral diaphragmatic paralysis following topical cardiac hypothermia. Chest.1984; 85:658.
5. Millis GH, Khan ZP, Desai J, Forsyth A, Ponte J. Effects of temperature on phrenic nerve and diaphragmatic function during cardiac surgery. Br J Anaesth. 1997; 79:72632.
6. Allen BS, Buckberg GD, Rosenkranz ER, et al. Topical cardiac hypothermia in patients with coronary disease. An unnecessary adjunct to cardioplegic protection and cause of pulmonary morbidity. J Thorac Cardiovasc Surg.  1992; 104:62631.
7. Canbaz S, Turgut N, Halici U, Balci K, Ege T, Duran E. Electrophysiological evaluation of phrenic nerve injury during cardiac surgery:a prospective, controlled, clinical study.BMC Surgery. 2004; 4:2.
8. Kadan M, Erol G, Oz BS, Arslan M. Effects of topical hypothermia on postoperative inflammatory markers in patients undergoing coronary artery bypass surgery. Cardiovasc J Afr. 2014 Mar-Apr; 25(2):67-72.
9. Hazra A, Using the confidence interval confidently, J Thorac Dis. 2017 Oct; 9 (10): 4125–4130.
10. Pourhoseingholi MA, Vahedi M, Rahimzadeh M. Sample size calculation in medical studies. Gastroenterol Hepatol Bed Bench 2013;6(1):14-17.
11. Sarkar M, Prabhu V. Basics of cardiopulmonary bypass. Indian J Anaesth. 2017 Sep; 61(9):760-767.