Introduction

The cardiac surgeries procedures require the patient to be connected to the cardiopulmonary bypass machine (CPB) [1]. This technique provides the patient with oxygenated blood flow to his body while giving the surgeon a motionless, bloodless surgical field. The CPB circuit consists of arterial and venous cannulae, venous reservoir, blood oxygenator, heat exchanger (HE), pumps, arterial filter and cardioplegia delivery system [2]. The heat exchangers are composed of two pathways, one for the perfusate (blood or cardioplegia mixture) and one for water. These pathways are separated by material that allows efficient thermal exchange between the fluids. For currently commercially used heat exchangers, stainless steel is the most popular because of its combination of good heat exchange coefficient, ease of fabrication in either pleated or tubular form and biocompatibility. To control the temperature of the perfusate, water of desired temperature is circulated through the heat exchanger, cooling or warming the perfusate [3]. To increase the efficiency, the water flows in the opposite direction relative to the perfusate, maximizing the temperature differential throughout the transit. Cardioplegia delivery can be administered through a stand-alone pump then mixed with blood from the oxygenator or a blood cardioplegia solution can be pre-mixed in a soft reservoir [4]. The major property for comparison of commercially used heat exchangers are their thermal specifications e.g. thermal performance or heat transfer coefficient [5]. Although the manufacturers provide some basic information on the conditions under which the HEs should be operated, the thermal specifications are rarely listed [6]. In this context we evaluated the performance in terms of thermal exchange of Mistral Cardioplegia Heat Exchanger and delivery system disposable (Eurosets, Srl, Medolla, Italy), between the set value and the expected temperature value in the myocardial solution in relation to the flow, hematocrit and pressure in the various delivery systems for the blood and crystalloid solution and in terms safety relative at the incidence of adverse event.

Materials and Methods

Population and Study Design

This study was conducted according to the guidelines of the Declaration of Helsinki. The Internal Review Board (Anthea Hospital, GVM Care & Research review board, Bari, Italy) approved this research (September 2023). From September 2022 to August 2023 were collected and analyzed the consecutive uses of Mistral Cardioplegia Heat Exchanger (Eurosets, Srl, Medolla, Italy) device in a single cardiothoracic surgery center Anthea Hospital Gvm Care & Research, Bari, Italy. We collected 100 cardiac surgery procedures involved the use of myocardial protection techniques with Mistral Cardioplegia Heat Exchanger and delivery system disposable (Eurosets, Srl, Medolla, Italy). Fifty patients used the Mistral Cardioplegia Heat Exchanger, for St. Thomas Blood cardioplegic solution, managed with the temperature of 28 (°C), twenty-five used closed delivery system and twenty-five with soft shell reservoir delivery system; Fifty patients used the Mistral Cardioplegia Heat Exchanger, for Crystalloid Custodiol HTC ® cardioplegic solution managed with the temperature of 4 (°C), twenty-five were used closed delivery system and twenty-five with soft shell reservoir delivery system (Fig. 1). We evaluated the performance in terms of thermal exchange during cardioplegia administration, between the set value and the expected temperature value during the myocardial solution administration in relation to the flow, hematocrit, pressure and volume in the various delivery systems for the blood and crystalloid solution and in terms safety relative at the incidence of adverse event. The cardioplegic solutions were selected in relation to the internal protocol and scientific evidence, an expected clamping time < 90 min for St. Thomas Blood cardioplegic solution and an expected clamping time > 120 min for Custodiol HTC ® solution. The closed delivery system for blood cardioplegia was selected in patient with body surface area less than < 1.8 m2.

Fig. 1
figure 1

Study settings

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Mistral Cardioplegia Heat Exchanger Features

The Mistral device is a cardioplegia heat exchanger for Adult and Paediatric patients. It is used as component to perform the various cardioplegia techniques during cardiopulmonary bypass. The device is capable of varying the temperature of the cardioplegia solution used to arrest the heart according to the extracorporeal circulation needs. The low priming quantity, the small contact surface and the treatment with phosphorylcolin (Agile coating) make MISTRAL particularly suitable in situations where high heat exchange performance and higher biocompatibility are required. The stainless steel tube-bundle structure guarantees high heat exchange efficiency and extremely easy air removal (debubbling during priming). The device comes complete with a bubble catcher specifically designed to reduce embolic activity and enhance device safety. The Mistral device has been designed and is guaranteed for 6 h of use (Fig. 2).

Fig. 2
figure 2

Mistral cardioplegia heat exchanger features

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Statistical Analysis

Continuous data were expressed as mean ± standard deviation or a median with the interquartile range and categorical data as percentages. Cumulative survival was evaluated with the Kaplan–Meier method. All reported p-values were two-sided, and p-values of < 0.05 were considered to indicate statistical significance. All statistical analyses were performed with SPSS 22.0 (SPSS Inc., Chicago, IL, USA).

Results

The patients with St. Thomas blood cardioplegia solution at 28 °C (set value) Vs the patients with crystalloid Custodiol HTC ® solution at 4 °C (set value) reported a mean value for the cardiopulmonary bypass time of: 93 ± 12 Vs 140 ± 17 (min.), p-value = 0.025; the cross-clamp time was: 65 ± 8 Vs 109 ± 15 (min.), p-value = 0.029; the expected temperature value (°C) during blood cardioplegia for closed blood delivery system Vs soft shell reservoir delivery system was: 28 ± 0.91 Vs 28 ± 0.1, p-value = 0.91; the blood cardioplegia flow was during administration (ml/min): 180 ± 40 Vs 190 ± 50, p-value = 0.88; Hematocrit during cardioplegia administration (%), 27.8 ± 0.7 Vs 28.1 ± 0.3, p-value = 0.89; administration pressure (mmHg), 126 ± 30 Vs 129 ± 38, p-value = 0.088; volume for single infusion (ml), 845 ± 120 Vs 899 ± 38, p-value = 0.093. The expected temperature value (°C) during crystalloid Custodiol HTC ® solution for closed delivery system Vs soft shell reservoir delivery system was: 4 ± 0.97 Vs 4 ± 0.13, p-value = 0.97; the crystalloid cardioplegia flow was (ml/min): 180 ± 56 Vs 189 ± 32, p-value = 0.082, administration pressure (mmHg), 52 ± 23 Vs 49 ± 33, p-value = 0.079; volume for single infusion (ml) 1991 ± 240 Vs 2130 ± 330, p-value = 0.089. No adverse event was reported in both groups and subgroups.

Discussion

When Bigelow or Melrose proposed arresting the heart in order be able to operate under direct vision, they were aware that if they are going to interrupt the coronary circulation using a cross-clamp, they must find a way to protect the heart (hence the term myocardial protection) and the body (in particular the brain, cerebral protection) [7]. Two-thirds of the answer was already provided by developing cardiopulmonary bypass machines, which maintained systemic circulation, decompressed the heart, and reduced its work and oxygen consumption. They had to find the final third of the answer. Bigelow suggested hypothermia, whereas Melrose suggested cardioplegia, and along the line, non-cardioplegic techniques then developed. Indications of myocardial protection include open-heart surgery, e.g., aortic valve replacement, mitral valve repair [8]. The term 'open' refers to the ability to access the heart chambers' inside and address intracardiac pathologies, which is only possible after arresting the heart using cardioplegia. In other words, if the heart is not arrested, this doesn't qualify as open-heart surgery; instead, it used to be called closed heart surgery [9, 10]. The term closed heart surgery has been replaced by others, such as beating heart surgery or bypass surgery [11]. Also, arresting the heart alone is considered an 'open heart ' even if the chambers are not breached, such as coronary artery bypass grafts [12]. In this study, we demonstrated the effectiveness and efficiency of the mistral device. The topic inherent to exchange efficiency and clinical safety in heat exchangers for cardioplegia is not addressed exhaustively in the literature, often the studies presented deal with in vitro tests or animal studies, in this context we have presented a collection of data based on clinical practice.

Conclusions

The results of this study suggested that the Mistral Cardioplegia Heat Exchanger and delivery systems disposable for cardioplegia (Eurosets, Srl, Medolla, Italy) were effectiveness and efficiency in the management of myocardial protection techniques in terms of temperature and delivery. The systems used were safety and not reported adverse event during the procedures.