Patterns of oxygen debt repayment in cardiogenic shock patients sustained with extracorporeal life support: A retrospective study.

Cardiogenic shock is the most frequent kind of shock in cardiac intensive care, and cardiac dysfunction and hypoxia are often seen in critically ill patients. Inadequate organ and tissue perfusion and hypoxia result in anaerobic metabolism with hyperlactatemia and oxygen debt accumulation. However, the role of accumulated oxygen debt in the course of cardiogenic shock and hypoxia has not been clearly described. Here, we first described the existence of several patterns of oxygen debt repayment in cardiogenic shock patients maintained by an extracorporeal life support system. Oxygen debt was computed from the lactate concentration at five time points, covering the first 26 h of ECLS. Patterns representing basic pathophysiological processes were independent of the cause of the primary insult. Groups of patients classified into specific patterns differed in terms of survival rate from 51.5% to only 4.6%. It is very important that the initial group not predetermine the fate of the patient and may change in the course of treatment due to 'between-cluster migration'. We believe that our finding of different patterns of oxygen debt repayment in cardiogenic shock patients may offer new insights for a more rational, goal-directed treatment of highly morbid conditions such as hypoxia and cardiogenic shock.

Last-minute cancellation of adult patients scheduled for cardiothoracic surgery in a large Dutch tertiary care centre.

OBJECTIVES: Unanticipated cancellation of a surgical procedure is a common problem, causing distress to the patient and increases in healthcare costs. However, limited evidence exists on the effects of last-minute cancellations of cardiothoracic surgical procedures in particular. The goal of this study was to gain insight into the prevalence of and the reasons for last-minute cancellations and to examine whether cancellation is associated with adverse medical outcomes. METHODS: Patients who were scheduled for elective cardiothoracic surgical procedures between January 2017 and June 2019 were evaluated. The reasons for the cancellations were assigned to the categories medically related or process related. We examined the differences in patient characteristics between those designated as no cancellation, medically related cancellations and process-related cancellations. Lastly, we examined the outcomes of patients who experienced a last-minute cancellation of a scheduled operation. RESULTS: A total of 2111 patients were included; of these, 301 (14.3%) had last-minute cancellations. In 78 (26%) cases, the cancellations were attributable to medical reasons (e.g. infection, comorbidities); 215 (71%) of the cancellations were process related (e.g. another patient in more urgent need of surgery, lack of staff). Almost 99% of the operations with a process-related cancellation were rescheduled compared to only 71.8% of the medically related cancelled operations (P < 0.001). Patients with a medically related cancellation had significantly higher 1-year mortality than patients who had no cancellation (unadjusted hazard ratio 2.50; 95% confidence interval, 1.30-4.78; P = 0.006); after adjustment for the EuroSCORE II, this effect remained significant. CONCLUSIONS: Last-minute cancellations were commonly seen in our cohort, and the reasons for cancellation were significantly related to adverse medical outcomes.

Is there a "safe" suction pressure in the venous line of extracorporeal circulation system?

Successes of extracorporeal life support increased the use of centrifugal pumps. However, reports of hemolysis call for caution in using these pumps, especially in neonatology and in pediatric intensive care. Cavitation can be a cause of blood damage. The aim of our study was to obtain information about the cavitation conditions and to provide the safest operating range of centrifugal pumps. A series of tests were undertaken to determine the points at which pump performance decreases 3% and gas bubbles start to appear downstream of the pump. Two pumps were tested; pump R with a closed impeller and pump S with a semiopen impeller. The performance tests demonstrated that pump S has an optimal region narrower than pump R and it is shifted to the higher flows. When the pump performance started to decrease, the inlet pressure varies but close to -150 mmHg in the test with low gas content and higher than -100 mmHg in the tests with increased gas content. The same trend was observed at the points of development of massive gas emboli. Importantly, small packages of bubbles downstream of the pump were registered at relatively high inlet pressures. The gaseous cavitation in centrifugal pumps is a phenomenon that appears with decreasing inlet pump pressures. There are a few ways to increase inlet pump pressures: (1) positioning the pump as low as possible in relation to the patient; (2) selecting appropriate sized venous cannulas and their careful positioning; and (3) controlling patient's volume status.

The effect of flow and pressure on the intraoxygenator flow path of different contemporary oxygenators: an in vitro trial.

INTRODUCTION: This study analyzed the effect of different flows and pressures on the intraoxygenator flow path in three contemporary oxygenators and its consequences for oxygen transfer efficiency. METHODS: In an experimental setup, intraoxygenator flow path parameters were analyzed at post-oxygenator pressures of 150, 200, and 250 mm Hg and at flows ranging from 2 L/min to the oxygenators' maximum permitted flow, with and without pulsatility. The oxygen gradient and the oxygen transfer per minute and per 100 mL blood were calculated using previously collected clinical data and compared with the flow path parameters. RESULTS: Increasing pressure did not affect the flow path parameters, whereas pulsatile flow led to significantly increased dynamic oxygenator blood volumes. Increased flow resulted in decreased values of the flow path parameters in all oxygenators, indicating increased flow through short pathways in the oxygenator. In parallel, oxygen transfer/100 mL blood decreased in all oxygenators (average 2.5 ± 0.4 to 2.4 ± 0.3 mL/dL, p > 0.001) and the oxygen gradient increased from 229 ± 45 to 287 ± 29 mm Hg, p > 0.001, indicating decreased oxygen transfer efficiency. Oxygen transfer/min increased (101 ± 15 to 143 ± 20 mL/min/m2, p > 0.001), however, due to the increased flow through the oxygenator. CONCLUSION: Varying trans-membrane oxygenator pressures did not lead to changes in the intraoxygenator flow path, while an increased flow exhibited lower flow path parameters resulting in less efficient use of the gas exchange compartment. The latter was confirmed by a decrease in O2 transfer efficiency during higher blood flows.

Peripheral cannulae selection for veno-arterial extracorporeal life support: a paradox.

Explosive penetration of veno-arterial extracorporeal life support in everyday practice has drawn awareness to complications of peripheral cannulation, resulting in recommendations to use smaller size cannulae. However, using smaller cannulae may limit the effectiveness of extracorporeal support and thereby the specific needs of the patient. Selection of proper size cannulae may therefore pose a dilemma, especially since pressure-flow characteristics at different hematocrits are lacking. This study evaluates the precision of cannula pressure drop prediction with increase of fluid viscosity from water flow-pressure charts by M-number, dynamic similarity law, and via fitted parabolic equation. Thirteen commercially available peripheral cannulae were used in this in vitro study. Pressure drop and flow were recorded using water and a water-glycerol solution as a surrogate for blood, at ambient temperature. Subsequently, pressure-flow curves were modeled with increased fluid viscosity (0.0031 N s m-2), and then compared by M-number, dynamic similarity law, and fitted parabolic equation. The agreement of predicted and measured values were significantly higher when the M-number (concordance correlation = 0.948), and the dynamic similarity law method (concordance correlation = 0.947) was used in comparison to the fitted parabolic equation (concordance correlation = 0.898, p < 0.01). The M-number and dynamic similarity based model allow for reliable prediction of peripheral cannula pressure drop with changes of fluid viscosity and could therefore aid in well-thought-out selection of cannulae for extracorporeal life support.

Oxygen delivery, oxygen consumption and decreased kidney function after cardiopulmonary bypass.

INTRODUCTION: Low oxygen delivery during cardiopulmonary bypass is related to a range of adverse outcomes. Previous research specified certain critical oxygen delivery levels associated with acute kidney injury. However, a single universal critical oxygen delivery value is not sensible, as oxygen consumption has to be considered when determining critical delivery values. This study examined the associations between oxygen delivery and oxygen consumption and between oxygen delivery and kidney function in patients undergoing cardiopulmonary bypass. METHODS: Oxygen delivery, oxygen consumption and kidney function decrease were retrospectively studied in 65 adult patients. RESULTS: Mean oxygen consumption was 56 ± 8 ml/min/m2, mean oxygen delivery was 281 ± 39 ml/min/m2. Twenty-seven patients (42%) had an oxygen delivery lower than the previously mentioned critical value of 272 ml/min/m2. None of the patients developed acute kidney injury according to RIFLE criteria. However, in 10 patients (15%) a decrease in the estimated glomerular filtration rate of more than 10% was noted, which was not associated with oxygen delivery lower than 272 ml/min/m2. Eighteen patients had a strong correlation (r >0.500) between DO2 and VO2, but this was not related to low oxygen delivery. Central venous oxygen saturation (77 ± 3%), oxygen extraction ratio (21 ± 3%) and blood lactate levels at the end of surgery (1.2 ± 0.3 mmol/l) showed not to be indicative of insufficient oxygen delivery either. CONCLUSIONS: This study could not confirm an evident correlation between O2 delivery and O2 consumption or kidney function decrease, even at values below previously specified critical levels. The variability in O2 consumption however, is an indication that every patient has individual O2 needs, advocating for an individualized O2 delivery goal.

Contemporary Oxygenator Design: Shear Stress-Related Oxygen and Carbon Dioxide Transfer.

Design of contemporary oxygenators requires better understanding of the influence of hydrodynamic patterns on gas exchange. A decrease in blood path width or an increase in intraoxygenator turbulence for instance, might increase gas transfer efficiency but it will increase shear stress as well. The aim of this clinical study was to examine the association between shear stress and oxygen and carbon dioxide transfer in different contemporary oxygenators during cardiopulmonary bypass (CPB). The effect of additional parameters related to gas transfer efficiency, that is, blood flow, gas flow, sweep gas oxygen fraction (FiO2 ), hemoglobin concentration, the amount of hemoglobin pumped through the oxygenator per minute-Qhb, and shunt fraction were contemplated as well. Data from 50 adult patients who underwent elective CPB for coronary artery bypass grafting or aortic valve replacement were retrospectively analyzed. Data included five different oxygenator types with an integrated arterial filter. Relationships were determined using Pearson bivariate correlation analysis and scatterplots with LOESS curves. In the Capiox FX25, Fusion, Inspire 8F, Paragon, and Quadrox-i groups, mean blood flows were 4.8 ± 0.9, 5.3 ± 0.7, 4.9 ± 0.7, 5.0 ± 0.6, and 5.7 ± 0.6 L/min, respectively. The mean O2 transfer/m2 membrane surface area was 44 ± 14, 51 ± 9, 60 ± 10, 63 ± 14, and 77 ± 18, respectively, whereas the mean CO2 transfer/m2 was 26 ± 14, 60 ± 22, 73 ± 29, 74 ± 19, and 96 ± 20, respectively. Associations between oxygen transfer/m2 and shear stress differed per oxygenator, depending on oxygenator design and the level of shear stress (r = 0.249, r = 0.562, r = 0.402, r = 0.465, and r = 0.275 for Capiox FX25, Fusion, Inspire 8F, Paragon, and Quadrox-i, respectively, P < 0.001 for all). Similar associations were noted between CO2 transfer/m2 and shear stress (r = 0.303, r = 0.439, r = 0.540, r = 0.392, and r = 0.538 for Capiox FX25, Fusion, Inspire 8F, Paragon, and Quadrox-i, respectively, P < 0.001 for all). In addition, O2 transfer/m2 was strongly correlated with FiO2 (r = 0.633, P < 0.001), blood flow (r = 0.529, P < 0.001), and Qhb (r = 0.589, P < 0.001). CO2 transfer/m2 in contrast was predominately correlated to sweep gas flow (r = 0.567, P < 0.001). The design-dependent relationship between shear stress and gas transfer revealed that every oxygenator has an optimal range of blood flow and thus shear stress at which gas transfer is most efficient. Gas transfer is further affected by factors influencing the O2 or CO2 concentration gradient between the blood and the gas compartment.

Preoperative hemoglobin level: the best predictor of transfusion of packed red cells.

Blood transfusions could have serious consequences for patients. A reduction in the transfusion rate could be accomplished by an optimized blood management. Clear guidelines and awareness among all employees at a single institution have resulted in a reduction in transfusion rates in recent years. Identification of the group of patients who still received a blood transfusion in recent years could result in a further reduction. This study enrolled 4022 patients undergoing cardiothoracic surgery between 2008 and 2013. Patients were divided into three groups: "no blood transfusion", "transfusion of packed red cells only" and "any other combinations of blood transfusion". In total, 16 variables were tested for their association with the administration of homologous blood. The variables associated with blood transfusion were included in a stepwise multinomial logistic regression analysis to find the variables with the strongest association. For the transfusion of packed red cells only and any other combinations of blood transfusion, the following predictors are found: gender, age, weight, type of surgery, reoperation, unstable angina pectoris, endocarditis, recent myocardial infarction, preoperative creatinine level, preoperative hemoglobin level and preoperative platelet count. The best predictor for the transfusion of packed red cells is preoperative hemoglobin level (4.1 to 7.8 mmol/l). For other blood products, the strongest association was found with type of surgery (aortic surgery, ventricular septal rupture and intracardiac tumour).

Vascular Occlusion Test to Dynamically Assess Microcirculation During Normothermic Pulsatile Cardiopulmonary Bypass.

OBJECTIVE: To evaluate parameters of the vascular occlusion test (VOT) before, during, and after pulsatile cardiopulmonary bypass (CPB). DESIGN: Prospective, observational study. SETTING: Single-center university hospital. PARTICIPANTS: Adult patients undergoing elective cardiac surgery with pulsatile CPB. INTERVENTIONS: An oximeter sensor and adult-sized pneumatic tourniquet were positioned at the right forearm. A VOT with a predefined ischemic time of 3 minutes was performed before, during, and after CPB. Changes in tissue oxygen saturation were recorded. MEASUREMENTS AND MAIN RESULTS: Thirty-four patients who underwent cardiac surgery were enrolled in the study. The lowest tissue oxygen saturation measured during the ischemic challenge differed among all 3 stages of surgery, with median values of 62.9% before, 57.5% during, and 59.3% after perfusion (p<0.05). Both occlusion (p<0.001) and reperfusion (p<0.05) slopes were steeper after bypass compared with before initiating bypass, whereas the reperfusion time remained constant among the different time points. CONCLUSIONS: The microcirculatory function as demonstrated by changes in VOT parameters was enhanced during and after normothermic pulsatile CPB. Clinical relevance, however, needs to be further explored.

Impact of Intraoperative Events on Cerebral Tissue Oximetry in Patients Undergoing Cardiopulmonary Bypass.

Previous studies showed that decreased cerebral saturation during cardiac surgery is related to adverse postoperative outcome. Therefore, we investigated the influence of intraoperative events on cerebral tissue saturation in patients undergoing cardiac surgery with cardiopulmonary bypass (CPB). A total of 52 adult patients who underwent cardiac surgery using pulsatile CPB were included in this prospective explorative study. Cerebral tissue oxygen saturation (SctO2) was measured in both the left and right cerebral hemisphere. Intraoperative events, involving interventions performed by anesthesiologist, surgeon, and clinical perfusionist, were documented. Simultaneously, in-line hemodynamic parameters (partial oxygen pressure, partial carbon dioxide pressure, hematocrit, arterial blood pressure, and CPB flow rates) were recorded. Cerebral tissue saturation was affected by anesthetic induction (p < .001), placement of the sternal retractor (p < .001), and initiation (p < .001) as well as termination of CPB (p < .001). Placement (p < .001) and removal of the aortic cross-clamp (p = .026 for left hemisphere, p = .048 for right hemisphere) led to changes in cerebral tissue saturation. In addition, when placing the aortic crossclamp, hematocrit (p < .001) as well as arterial (p = .007) and venous (p < .001) partial oxygen pressures changed. Cerebral tissue oximetry effectively identifies changes related to surgical events or vulnerable periods during cardiac surgery. Future studies are needed to identify methods of mitigating periods of reduced cerebral saturation.

Hemolysis during cardiac surgery is associated with increased intravascular nitric oxide consumption and perioperative kidney and intestinal tissue damage.

INTRODUCTION: Acute kidney injury (AKI) and intestinal injury negatively impact patient outcome after cardiac surgery. Enhanced nitric oxide (NO) consumption due to intraoperative intravascular hemolysis, may play an important role in this setting. This study investigated the impact of hemolysis on plasma NO consumption, AKI, and intestinal tissue damage, after cardiac surgery. METHODS: Hemolysis (by plasma extracellular (free) hemoglobin; fHb), plasma NO-consumption, plasma fHb-binding capacity by haptoglobin (Hp), renal tubular injury (using urinary N-Acetyl-ß-D-glucosaminidase; NAG), intestinal mucosal injury (through plasma intestinal fatty acid binding protein; IFABP), and AKI were studied in patients undergoing off-pump cardiac surgery (OPCAB, N = 7), on-pump coronary artery bypass grafting (CABG, N = 30), or combined CABG and valve surgery (CABG+Valve, N = 30). RESULTS: FHb plasma levels and NO-consumption significantly increased, while plasma Hp concentrations significantly decreased in CABG and CABG+Valve patients (p < 0.0001) during surgery. The extent of hemolysis and NO-consumption correlated significantly (r (2) = 0.75, p < 0.0001). Also, NAG and IFABP increased in both groups (p < 0.0001, and p < 0.001, respectively), and both were significantly associated with hemolysis (R s = 0.70, p < 0.0001, and R s = 0.26, p = 0.04, respectively) and NO-consumption (Rs = 0.55, p = 0.002, and R s = 0.41, p = 0.03, respectively), also after multivariable logistic regression analysis. OPCAB patients did not show increased fHb, NO-consumption, NAG, or IFABP levels. Patients suffering from AKI (N = 9, 13.4%) displayed significantly higher fHb and NAG levels already during surgery compared to non-AKI patients. CONCLUSIONS: Hemolysis appears to be an important contributor to postoperative kidney injury and intestinal mucosal damage, potentially by limiting NO-bioavailability. This observation offers a novel diagnostic and therapeutic target to improve patient outcome after cardiothoracic surgery.

The role of patient's profile and allogeneic blood transfusion in development of post-cardiac surgery infections: a retrospective study.

OBJECTIVES: We aimed to investigate the association of patient characteristics and allogeneic blood transfusion products in development of post-cardiac surgery nosocomial infections. METHODS: This retrospective study was conducted in 7888 patients undergoing cardiac surgery with median sternotomy and cardiopulmonary bypass. Multivariable logistic regression analysis was used for independent effect of variables on infections. RESULTS: A total of 970 (12.3%) patients developed one or several types of postoperative infections. Urinary (n = 351, 4.4%) and pulmonary tract infections (n = 478, 6.1%) occurred more frequently than sternal wound infections (superficial: n = 102, 1.3%, deep: n = 72, 0.9%) and donor site infections (n = 61, 0.8%). Interventions, including valve replacement (P = 0.002) and coronary artery bypass grafting combined with valve replacement (P = 0.012), were associated with increased risk of several types of postoperative infections. Patients' profiles changed substantially over the years; morbid obesity (P = 0.019), smoking (P = 0.001) and diabetes mellitus (P = 0.001) occur more frequently nowadays. Furthermore, surgical site infections showed to be related to morbid obesity (P < 0.001) and higher risk stratification (P = 0.031). Smoking (P < 0.001) and chronic obstructive pulmonary disease (P < 0.001) were related to pulmonary tract infections. In addition, diabetic patients developed more sepsis (P = 0.003) and advanced age was associated with development of urinary tract infections (P < 0.001). Even after correcting for other factors, blood transfusion was associated with all types of postoperative infection (P < 0.001). This effect remained present in both leucocyte-depleted and non-leucocyte-depleted transfusion. CONCLUSIONS: Our data showed that post-cardiac surgery infections occur more frequently in patients with predetermined risk factors. The amount of blood transfusions was integrally related to every type of postoperative infection.

Hypovolemia in extracorporeal life support can lead to arterial gaseous microemboli.

Next to severely decreased pump flow, hypovolemia in extracorporeal life support (ELS) can result in subatmospheric venous line pressure. Such pressure may lead to degassing and resultant gaseous microemboli (GME), with potential changes in neurological clinical outcome. CME activity resulting from degassing was investigated in relation to subatmospheric venous line pressure, partial oxygen pressure (pO2 ), and hematocrit in a model of a centrifugal pump-based circuit for long-term ELS. Additionally, a device that provides instantaneous volume buffer capacity during hypovolemia was evaluated in relation to GME appearance. An exponential relationship was found between decreasing venous line pressure and GME downstream of the centrifugal pump (P = 0.001). Arterial bubble activity appeared at subatmospheric venous line pressures of -200 mm Hg and less. A rising (pO2 ) increased formation of GME (P = 0.05). A rise in hematocrit, in contrast, did not affect embolic activity (P = 0.22). With simulated hypovolemia, volume buffer capacity added to the venous line dampened fluctuations of venous line pressure by approximately 40%, but a significant reduction in GME formation could not be found (P = 0.22). Moreover, the device enabled a 14% higher support flow. With ELS flow being related to patient volume status, hypovolemia can diminish support. A coherent decrease of venous line pressure triggers degassing of blood-dissolved gases and causes arterial GME, which can become massive during persistent conditions of limited venous return. Incorporation of a volume buffer capacity device into the extracorporeal support circuit enables a higher and more stable support flow in critically low patient filling.

Quantification of recirculation as an adjuvant to transthoracic echocardiography for optimization of dual-lumen extracorporeal life support.

PURPOSE: Proper cannula positioning in single site veno-venous extracorporeal life support (vv-ELS) is cumbersome and necessitates image guidance to obtain a safe and stable position within the heart and the caval veins. Importantly, image-guided cannula positioning alone is not sufficient, as possible recirculation cannot be quantified. METHODS AND RESULTS: We present an ultrasound dilution technique allowing quantification of recirculation for optimizing vv-ELS. CONCLUSION: We suggest quantification of recirculation in addition to image guidance to provide optimal vv-ELS.

Evaluation of a new condensed extra-corporeal circuit for cardiac surgery: a prospective randomized clinical pilot study.

This prospective randomized clinical pilot study was conducted to evaluate a recently introduced reduced volume CPB system that is coated with the biopassive Xcoating. Twenty-two patients undergoing coronary artery bypass grafting (CABG) with cardiopulmonary bypass (CPB), either with a fully heparin-coated CPB circuit (control, n=11) or with an Xcoating coated condensed extra-corporeal circuit (CondECC, n=11), were included. We examined activation of the complement system (C3bc and C4bc), activation of neutrophils (BPI), the acute phase response (interleukin (IL)-6, and acute phase proteins (LBP, AGP, and CRP)), myocardial tissue injury (troponin T), hemolysis (free hemoglobin (FHb)), and clinical outcome parameters. Preoperative risk profiles were identical for both patient groups. All patients went through the procedure without major complications and were discharged from the hospital. FHb and BPI levels at the end of pump support (p < 0.01) and at 15 min after the administration of protamine (p < 0.05) were significantly higher in the control group. In addition, FHb levels were still significantly elevated upon arrival on the cardiothoracic intensive care unit (CICU) in the control group (p < 0.05). C3bc and C4bc, acute phase proteins, IL-6, and troponin T concentrations, and clinical outcome variables were identical in both patient groups. In conclusion, the evaluated condensed extracorporeal circuit is a flexible and multifunctional CPB sytem that offers safe procedures. Furthermore, the results indicate improved biocompatibility of this option for extracorporeal circulation.