Kinetics of tissue oxygenation index during fast and slow cardiopulmonary bypass initiation.

INTRODUCTION: Despite being a daily clinical application in cardiac operating theaters, an evidence-based approach on how to optimally initiate the heart-lung machine (HLM) to prevent critical phases of cerebral ischemia is still lacking. We therefore designed a study comparing two different initiation times for starting the cardiopulmonary bypass (CPB). METHODS: We conducted a monocentric, randomized, and prospective study comparing the impact of two initiation times, a rapid initiation of 15 s and a slow initiation of 180 s to reach the full target flow rate of 2.5 L/min/m2 times the body surface area, on cerebral tissue oxygenation by near infrared spectroscopy measurements. RESULTS: The absolute values in tissue oxygenation index (TOI) showed no difference between the groups before and after the CPB with a 10% drop in oxygenation index in both groups due to the hemodilution through the HLM priming. Looking at the kinetics a rapid initiation of CPB produced a higher negative rate of change in TOI with a total of 21% in critical oxygenation readings compared to 6% in the slow initiation group. CONCLUSION: In order to avoid critical phases of cerebral ischemia during the initiation of CPB for cardiac procedures, we propose an initiation time of at least 90 s to reach the 100% of target flow rate of the HLM.

Prospective clinical study testing the efficacy and safety of a new formula to increase the precision of oxygen therapy in the initiation phase of cardiopulmonary bypass.

INTRODUCTION: During cardiopulmonary bypass (CPB), supranormal concentrations of oxygen are routinely administered with the intention to prevent cellular hypoxia. However, hyperoxemia may have adverse effects on patient outcome. Oxygen settings are based on the perfusionist's individual work experience rather than profound recommendations and studies analyzing the effect of oxygen levels are in need of methodological improvement. We aimed to advance perfusion technique by developing and clinically applying a formula for tailored oxygen therapy in CPB. METHODS: A formula to precalculate the oxygenator setting before CPB was developed. The newly-derived formula was then evaluated in a prospective, single-center pilot study to test whether a predefined arterial partial oxygen pressure (PaO2) of 150-250 mmHg could be reached. 80 patients were enrolled in the study between April and September 2021. RESULTS: The mean oxygen fraction calculated for the setting of the gas blender was 52% ±0,12. The mean PaO2 after initiation of the CPB was 193 ± 99 mmHg (min-max: 61-484, median 163 mmHg). 38.75% of the values were in the desired PaO2 corridor of 150 to 250 mmHg. 8.75% of all PaO2 values were below <79.9 mmHg, 31.25% between 80 and 149.9 mmHg, 38.75% between 150 and 249.9 mmHg and 21.25%>250 mmHg. CONCLUSIONS: Conceptually, perfusion technique should be goal-directed, guided by objective parameters and formulas. Although the optimal CPB oxygenation target remains unknown, it is nevertheless important to develop strategies to tailor oxygen therapy to aid in creating evidence as to what level of oxygen is best for patients during CPB. The formula we derived needs further adjustments to increase results in the target range.

Cavoatrial hypernephroma resection on cardiopulmonary bypass: Mild/normo-versus moderate hypothermia.

INTRODUCION: Renal cell carcinoma (RCC) is one of the most prevalent malignant tumors. It extends up into the systemic veins and right atrium. Surgical extraction of such extensions is usually carried out using cardiopulmonary bypass (CPB) with moderate hypothermic (MH) being frequently applied in order to obtain a clear surgical field. However, due to obvious disadvantages of hypothermia, approaches with mild/normothermia (NT) during CPB have also been established. The current study aims to compare the outcomes of patients undergoing RCC tumor and extensions resection using MH versus NT. MATERIAL AND METHODS: This is a retrospective, non-randomized study. All patients who underwent RCC tumor and extensions resection for stage III or IV (Staehler) RCC in a single center between 2006 and 2020 were included. During surgery, MH or NT were applied. CPB was realized using aortic and bicaval cannulation. We compared the procedural times, transfusion requirements and postoperative outcomes, respectively between the MH and NT groups. RESULTS: A total of 24 consecutive patients (n(NT) = 12, n(MH) = 12) were included in the study (median age NT 68.5 and MH 66.5). The study only showed a significant difference in heart-lung machine times (median CPB time NT 45.5 min and MH 110.0 min, p = 0.004). All other results, loss of drainage, administration of blood products, as well as the postoperative course and mortality were comparable in both groups. CONCLUSION: The results showed a high perioperative and long-term mortality. The perioperative course was similar after surgery with NT or MH. Therefore, NT which minimizes potential complications of MH should be preferred.

Current Application of NIRS and CPB Initiation Times in German Cardiac Surgery Centers: A Survey.

Near-infrared spectroscopy (NIRS) has been widely used in cardiac surgery to monitor cerebral oxygen supply. The initiation and perioperative management of cardiopulmonary bypass (CPB) constitute critical events in modifying the normal physiology of adequate blood and oxygen supply to the brain. First, little is known about how frequent NIRS is really used. Second, there are varying practices on how to initiate CPB. We therefore conducted a survey in Germany to get an idea of NIRS usage in cardiac surgery for the duration of initiation of CPB protocols. A web-based e-mail survey using commercial SurveyMonkey® (SurveyMonkey, San Mateo, CA) software was conducted in August 2017 including all German cardiac surgery centers. About 75% of the perfusion departments do not use NIRS as a standard monitoring device. It is usually reserved for clinical scenarios where cerebral perfusion might be impaired such as aortic arch surgery or carotid artery stenosis. Only one-third of the departments use a standardized duration of initiation of CPB despite a common belief of potential harm with fast initiation. The usual applied time to initiate CPB ranges from 30 to 120 seconds. Our survey revealed that the NIRS technology is only used in specific types of cardiac surgery to this date. In addition, there is a clear need for scientific studies on how to initiate CPB in the best way for the patient.