74 M. Bagherinasab et al.: J Extra Corpor Technol 2026, 58, 73--78
This research aimed to evaluate the effects of two different initiation timings-- rapid and slow-- on the measurements of the cerebral tissue oxygenation( TOI via NIRS) index( TOI) and the incidence of neurological complications following on-pump cardiac surgery.
CPB. Prior to cannulation, complete heparinization was achieved by administering 400 IU / kg of body weight in heparin, ensuring an activated clotting time( ACT) exceeding 450 s. The ACT was measured using the Medtronic HMS Plus system, employing kaolin as the activator.
Material and methods
This randomized, monocentric, double-blind, and prospective study was carried out at the Baqiyatallah University Hospital for Cardiac Surgery over the period from October 2023 to April 2024. The research protocol received evaluation and approval from the Research Ethics Committees of Golestan University of Medical Sciences, assigned the ethics code IR. GOUMS. REC. 1402.126, on July 25, 2023.
Written informed consent was obtained from all participants prior to their involvement. The inclusion criteria encompassed adult individuals aged 18 years and older who were scheduled to undergo non-emergency coronary artery bypass graft( CABG) surgery, which involved arterial cannulation of the aorta and single venous cannulation of the right atrium. Exclusion criteria included individuals with a prior diagnosis of neurological conditions, such as stroke, as well as those exhibiting any stenosis in the carotid or cerebral arteries. Furthermore, significant calcification of the aorta was another factor for exclusion. Anemia, defined as a hemoglobin level below 10 g / dL or a hematocrit( HCT) value under 30 %, also disqualified certain participants. Moreover, patients requiring preoperative cardiac support systems, such as intra-aortic balloon pumps, extracorporeal membrane oxygenation, or ventricular assist devices, were considered ineligible for the study.
Demographic and medical information were collected for each patient participating in the study. Prior to the commencement of the study, a randomization process was implemented for Groups A and B, as outlined below:
( A) Cardiopulmonary bypass initiation time of 180 s is required to achieve the full target flow rate.
( B) Cardiopulmonary bypass should be initiated within 30 s to achieve the desired target flow rate.
Study protocol
The configuration of our HLM was established using a LivaNova S5( LivaNova PLC, London, United Kingdom) in conjunction with a Sorin Inspire 8F( LivaNova PLC, London, United Kingdom) oxygenator module, which features an integrated arterial filter and an open hard-shell venous reservoir. The HLM circuit was primed with 1,000 mL of Ringer’ slactate solution, which contained 10,000 IU of heparin. Prior to the commencement of extracorporeal circulation, the priming solution was warmed to a temperature of 37 ° C, and the fraction of inspired oxygen was established at 0.8, with a gas flow rate of 2 L / min. In Group A, the flow rate was incrementally increased every 45 s by 25 % of the total flow, ultimately achieving the desired flow rate of 100 % at the 180-second mark. Similarly, in Group B, the flow rate was incrementally increased every 3.75 s by 25 % of the total flow, achieving the target flow rate of 100 % within 30 s. The venous clamp was adjusted to a closure of 10 % to reduce the diameter of the venous conduit before the removal of the clamp on the arterial side. Subsequently, the clamp on the venous side was carefully released, ensuring that the patient remained isovolemic during the initiation of CPB, thereby preserving pulsatility throughout the measurement period.
Cerebral blood flow autoregulation is closely associated with viscosity, especially in relation to hemodilution, as well as with the partial pressure of carbon dioxide( PaCO 2)[ 2 ]. Consequently, it is essential to alter only one variable for the purpose of comparative analysis while ensuring that PaCO 2 levels remain constant. In this study, we maintained PaCO 2 within the range of 30--35 mmHg. This lower range was intentionally maintained to standardize cerebral autoregulatory conditions and minimize the confounding influence of hypercapnia-induced cerebral vasodilation. The desired flow rate was determined based on the calculated cardiac output for each patient. This output was derived by applying a cardiac index of 2.4 L / min / m 2, which was multiplied by the body surface area formula developed by DuBois and DuBois.
Anesthesia and surgery protocol
All patients received anesthesia according to a standardized protocol. The perioperative management of anesthesia involved the establishment of both arterial and venous lines, monitoring via transesophageal echocardiography, and the administration of norepinephrine in conjunction with saline infusions, aimed at maintaining the mean arterial pressure within the range of 60--80 mmHg. Each patient underwent a midline sternotomy, accompanied by a standardized cannulation technique for
Data collection
The demographic information collected encompassed variables such as age, sex, history of diabetes mellitus, ejection fraction, hypertension, body surface area, and preoperative creatinine levels. The evaluation of arterial blood oxygen pressure( Pao 2), hematocrit concentrations, and fluctuations in the TOI was performed at five-minute intervals every 30 min during the first three minutes after the commencement of CPB. The B-Capta online blood gas monitoring system, developed by LivaNova, was employed to facilitate precise assessments of the PaO 2 and temperature in the arterial line, as well as measurements of saturation, HCT, hemoglobin, and temperature in the venous line. The TOI was evaluated using NIRS( NIRO-200NX, Hamamatsu Photonics K. K., Hamamatsu City, Japan). This evaluation necessitated the placement of the appropriate electrodes on the left and right foreheads. Initial observa-