This study includes data from 90 patients operated in the Cardiosurgery Department of the Medical Center Hospital of the Presidential Administration of the Republic of Kazakhstan were included in the study. All patients underwent mitral, aortic valve replacement/plasty under cardiopulmonary bypass (CPB) conditions. This research work was conducted between 2020 and 2022. To calculate the sample size, the investigators used the formula n=t2\*D\*N/confidence interval\*N+t2\*α, which will allow to identify the static significance of the study.
All patients were divided into 3 groups according to the type of anaesthesia: the first (1) group patients anaesthetised with propofol (P), the second group with sevoflurane (S), and the last one is with isoflurane (I).
The study was conducted in 5 stages:
1. Initial haemodynamic parameters and oxygen transport function of the patient's blood before anaesthesia were determined;
2. After tracheal intubation;
3. Before the CPB;
4. After the CPB;
5. The post-operative period until the patient is transferred to the specialized department.
Before induction into anaesthesia, haemodynamic monitoring was started on admission to the operating theatre using a Nihon Kohden monitor (Japan). The right radial artery was catheterised for invasive monitoring of systemic arterial pressure and arterial blood sampling, and a catheter was then inserted into the central jugular vein (under ultrasound machine control) and guided into the right atrium for mixed venous blood sampling.
Cardiac stroke volume was determined by transthoracic echocardiography (CS=end diastolic volume - end systolic volume). Cardiac output (CO=CS x heart rate), cardiac index (CI=CO/body surface area) were determined. the investigators determined blood oxygen content using the formula CaO2 (arterial ABB) and CvO2 (central mixed venous ABB) = \[(1.34 × Hb × SO2) + (PO2 × 0.031)\] / 100. Arteriovenous difference = CaO2-CvO2. Oxygen delivery was determined using the formula (DO2 = CI\* CaO2). Oxygen consumption (VO2 = Cardiac index (CI)\*AVD or VO2 = CO × (CaO2 - CvO2) \~ CO × Hb × 1.34 × (SaO2 - SvO2) / 100).
In the second stage, after tracheal intubation, indirect calorimetry was used to determine VO2, energy expenditure during anaesthesia using a Spirometry device (Oxford, UK), which was connected to an endotracheal tube and continuously showed oxygen demand and energy expenditure. A transesophageal echocardiography sensor was used to determine cardiac output. Additionally, the cardiac output was determined by Fick's formula. The same tests (cardiac output, cardiac index, consumption, oxygen delivery, energy expenditure) were performed in the third and fourth stages of anaesthesia. In the last stage, the consumption of muscle relaxants and opioid analgesics was calculated to assess the pharmaco-efficiency of anaesthetics. The time of extubation and the time of transfer of the patient to the specialized department were determined.
All patients continued antihypertensive medication both before and on the day of surgery to prevent the development of withdrawal syndrome and to reduce the risk of perioperative myocardial ischaemia.
