Fat contamination of pericardial suction blood and its influence on in vitro capillary-pore flow properties in patients undergoing routine coronary artery bypass grafting

AbstractObjective: Neurologic dysfunction after cardiopulmonary bypass might be due to arterial microembolization. Pericardial suction blood is a possible source of embolic material. Our aim was to determine the capillary-pore flow ability of pericardial suction blood. Methods: Pericardial suction blood from patients undergoing coronary bypass was collected, and pericardial suction blood and venous blood were sampled at the end of cardiopulmonary bypass and before reinfusion of pericardial suction blood. Pericardial suction blood was (n = 10) or was not (n = 10) prefiltered through a 30-μm cardiotomy screen filter before capillary in vitro analysis. Additionally, in 8 patients the plasma viscosity was measured, and in 5 of these patients, pericardial suction blood capillary deposits were evaluated by using a microscopy-imprint method and fat staining. Capillary flow was tested through 5-μm pore membranes. Tested components were plasma, plasma-eliminated whole-blood resuspension, and leukocyte/plasma-eliminated erythrocyte resuspension. Initial filtration rate and clogging slope expressed the blood-to-capillary interaction. Results: The plasma-flow profile of pericardial suction blood was highly impaired, with a 47% reduction in initial filtration rate (P <.001) and a 142% steeper clogging slope flow deceleration (P <.01). This difference was not due to a change in pericardial suction blood viscosity, such as by free hemoglobin, which corresponded to 5.7% of the erythrocytes. There were no differences in resuspended whole blood or erythrocytes. The cardiotomy filter had no effect. Microscopy suggested the presence of capillary fat deposits in pericardial suction blood that were not seen with venous plasma (P <.05). The pericardial suction blood volume was 458 ± 42 mL and contained 95.6 ± 9.3 g/L hemoglobin. Conclusions: The pericardial suction blood plasma capillary flow function was highly impaired by liquid fat. Pericardial suction blood hemoglobin appears worth recovering after fat removal, despite profound hemolysis.J Thorac Cardiovasc Surg 2002;124:377-8

Productivity in relation to organization of a surgical department : a retrospective observational study

Background Responsible and efficient resource utilization are important factors in healthcare. The aim of this study was to investigate how total case time differs between two differently organized surgical departments. Methods This is a retrospective observational study of a cohort of patients undergoing elective surgery for breast cancer or malignant melanoma in a university hospital setting in Sweden. All patients were operated on by the same set of surgeons but in two different surgical departments: a general surgery (GS) and a cardiothoracic (CT) surgery department. Patients were selected to the two departments from a waiting list in the order of referral for surgery. The effect of being operated on at the CT department compared to the GS department was estimated by linear regression. Results The final study cohort comprised 349 patients in the GS department and 177 patients in the CT department. Both groups were similar regarding surgical procedures, American Society of Anesthesiologists' score, body mass index, age, sex, and the skill level of the operating surgeon. These covariates were included in the linear regression model. The total case time, defined by the Procedural Time Glossary as room set-up start to room clean-up finish, was significantly shorter for the patients who underwent a surgical procedure at the CT department compared to the GS department, even after adjusting for the background characteristics of the patients and surgeon. After adjusting for the selected covariates, the average difference in total case time between the two departments was - 30.67 min (p = 0.001). Conclusions A significantly shorter total case time was measured for operations in the CT department. Plausible explanations may be more beneficial organizational factors, such as staffing ratio, skill mix in the operating room team, and working behavioral aspects regarding resource utilization.Peer reviewe

Fat contamination of pericardial suction blood in cardiac surgery : clinical and experimental studies in perspectives of transfusion logistics

Introduction: During cardiac surgery aided by cardiopulmonary bypass (CPB) the autotransfusion of pericardial suction blood (PSB) is regarded mandatory to limit allogeneic blood exposure. PSB is however proposed as a source of lipid microemboli and to contribute to brain damage. This thesis addresses the logistics of allogeneic blood transfusion during coronary artery bypass grafting (CABG), the embolic potential of reinfused PSB, and means to reduce PSB fat contamination, investigated both clinically and experimentally. Methods: Study I) Patients undergoing CABG surgery (n=2469) were included in a database study. The magnitude of surgical bleeding versus blood transfusion was analyzed to extract a subgroup of patients (n=982) in whom transfusions were independent from bleeding. Study II) PSB and venous-blood samples were collected from patients undergoing routine CABG (n=20). The in vitro capillary-flow properties of blood subcomponents and the effects of routine screen filtration were tested. PSB fat contamination was evaluated by imprint microscopy. Study III) Heat extracted liquid human fat or soya oil were mixed with mediastinal drain blood (n=20) and incubated in a temperature controlled column, to evaluate spontaneous density separation of fat. Study IV) The findings from study-III were applied to develop a fat-reducing system (FRS) using two stacked compartments. The FRS was experimentally tested (n=12), with similar methods as in study-III, and clinically evaluated (n=10). A single-chamber blood bag (n=10) served as reference. Results: Study I) A surgical bleeding of less than 400 mL showed no correlation to blood transfusion, although 64 of 982 patients still received allogeneic blood. The strongest predictors for this kind of transfusion were; female gender, weight ≤70 kg, CPB time ≥90 minutes, CPB temperature ≤32 ºC, and advanced age (P&lt;.001 - .038). Study II) The capillary-flow profile of PSB plasma was highly impaired compared to venous plasma (P&lt;.001). Conversely, blood-cell components showed no difference between PSB and venous blood. Routine screen filtration showed no ameliorating effect on capillary-flow resistance. Fat debris was detected on imprints in all PSB samples in contrast to venous plasma (P&lt;.05). Study III) After 10-min of incubation had 77% of added soya oil separated and found contained in the top 20% fraction of blood (P&lt;.001), aimed to be discarded. The density separation of human fat was less efficient compared to soya oil (P=.011). Fat also adsorbed to surface which was more pronounced at low temperature (P&lt;.001). The overall reduction of human fat was 70%. Study IV) PSB contained 1.5 mL fat suspended in 418 mL PSB. Of this fat was 24% surface-bound. Experimental analysis of the proposed FRS revealed an 83% fat-reduction which was clinically confirmed, suggesting 80% reduction (P=.001). The FRS also gave a small but significant erythrocyte-concentrating effect. Conclusions: Transfusion of allogeneic blood during CABG surgery appeared associated with an institutional, individual, and technical bias of an anticipated need and not only used to compensation for surgical bleeding. In part may this reflect a non-compliant CPB methodology and hemodilution. It was confirmed that PSB plasma contained fat, with a suggested embolic potential. Human fat was significantly reduced from mediastinal drain blood by spontaneous density separation and surface adsorption. The prototype FRS used for PSB incubation during CPB allowed an efficient fat reduction

Can the Oxygenator Screen Filter Reduce Gaseous Microemboli?

Gaseous microemboli (GME) define small bubbles as <200 μm in size. GME are reported to increase morbidity after cardiopulmonary bypass (CPB) and cardiac surgery. To prevent intrusion of GME into the systemic circulation during CPB, arterial line filtration is generally recommended. New trends in oxygenator design promote location of arterial filtration as an integral part of the oxygenator housing. The present experimental study aimed to evaluate the GME removal properties of an integrated arterial screen filter in a standard microporous oxygenator. The GME properties of Terumo Capiox® FX25 with an integrated arterial screen filter was assessed in an experimental setup and compared with Capiox® RX25, in which no arterial screen filter is present. A blood analog prime solution was recirculated using a roller pump at 4 and 6 L per minute flow rate, respectively, through a customized CPB circuit comprising oxygenator, reservoir, and connecting tubing. A controlled volume of air was introduced into the circuit. The GME activity was measured and computed using a Gampt BCC200® ultrasonic device placing one probe at the venous inlet and one other at the arterial outlet of the oxygenator. Transmembrane delta values of GME activity were used to calculate the removal efficacy based on counts and volume of GME. Use of screen filtration reduced the GME volume by 99.1% ± .1% compared with 98.0% ± .1% for controls at 4 L/min flow rate (p < .001). At 6 L/min, the reduction was 97.9% ± .1% compared with 97.0% ± .1% (p < .001). In contrast, the reduction of GME counts was less effective after screen filtration compared with controls: 89.6 ± .6% versus 91.4 ± .4% at 4 L/min and 55.6% ± 1.6% versus 76.0% ± 1.4% at 6 L/min, respectively (p < .001). The tested oxygenator with incorporated arterial screen filter reduced GME activity based on the calculated volume at the same time as counts of GME increased

Can We Rely on the Activated Clotting Time to Measure Heparin Anticoagulation? A Clinical Evaluation of Two ACT Monitors

The sensitivity to heparin during cardiopulmonary bypass (CPB) is determined by patient-specific characteristics and is assessed by the whole blood activated clotting time (ACT). We aimed to examine reliability measures between two different ACT monitors using Bland–Altman analysis: bias should not exceed 50 ± 50 seconds for measurements performed during CPB or 10 ± 10 seconds before and after CPB. The ACT response should be linear in relation to the concentration of heparin in plasma. Twenty patients (n = 20) aged 20–80 years and admitted for coronary artery bypass surgery were enrolled to this clinical observational study. ACT values and antifactor Xa were sampled: 1) before induction of anesthesia, 2) after heparin bolus, 3) during CPB at the start of rewarming, 4) at weaning from CPB, and 5) after heparin reversal. The evaluation comprised the Hemostasis Management System Plus™ (HMS, Medtronic Inc., Minneapolis, MN) and i-STAT™ (Abbott, Point of Care Inc., Princeton, NJ). Bias for the HMS Plus™ vs. i-STAT™ was +105 ± 119 seconds for measurements during CPB and +2.8 ± 11.7 seconds before and after CPB. Associated limits of agreement for the observed bias were ±235 and ±23 seconds, respectively. Inter-device correlation of ACT values was .46 (p < .001) during CPB; otherwise .48 (p = .02). Both devices produced ACT values unrelated (<10%) to the measured heparin concentration. The use of multivariable regression analysis demonstrated an independent association between the ACT measurement and hematocrit, however, not with the plasma concentration of heparin. ACT monitors demonstrate unacceptable bias differences, combined with wide limits of agreement. The ACT response correlated with hematocrit, but not with the actual heparin concentration

Plasma hyperosmolality during cardiopulmonary bypass is a risk factor for postoperative acute kidney injury : results from double blind randomised controlled trial

Introduction: The study objective was to investigate whether a Ringer’s acetate based priming solution with addition of Mannitol and sodium concentrate increases the risk of cardiac surgery associated kidney injury (CSA-AKI). Methods: This is a double blind, prospective randomized controlled trial from a single tertiary teaching hospital in Sweden including patients aged ≥65 years (n = 195) admitted for routine cardiac surgery with cardiopulmonary bypass. Patients in the study group received Ringer’s acetate 1000 mL + 400 mL Mannitol (60 g) + sodium chloride 40 mL (160 mmol) and heparin 2 mL (10 000 IU) 966 mOsmol (n = 98), while patients in the control group received Ringer’s acetate 1400 mL + heparin 2 mL (10 000 IU), 388 mOsmol (n = 97) as pump prime. Acute kidney injury was analysed based on the Kidney Disease Improving Outcomes (KDIGO 1-3) definition. Results: The overall incidence of CSA-AKI (KDIGO stage 1) was 2.6% on day 1 in the ICU and 5.6% on day 3, postoperatively. The serum creatinine level did not show any postoperative intergroup differences, when compared to baseline preoperative values. Six patients in the Ringer and five patients in the Mannitol group developed CSA-AKI (KDIGO 1-3), all with glomerular filtration rates &lt;60 mL/min/1.73 m2. These patients showed significantly higher plasma osmolality levels compared to preoperative values. Hyperosmolality together with patient age and the duration of the surgery were independent risk factors for postoperative acute kidney injury (KDIGO 1-3). Conclusions: The use of a hyperosmolar prime solution did not increase the incidence of postoperative CSA-AKI in this study, while high plasma osmolality alone increased the associated risk by 30%. The data suggests further examination of plasma hyperosmolality as a relative risk factor of CSA-AKI

Continuous Venous Oximetry: A Comparative Study Between the CDI 100 and the Bentley OxySat II

Two in-line oxygen saturation monitors, the CDI 100 and OxySat II, were evaluated in the clinical setting. Eighty-seven venous blood samples were drawn during 20 elective cardiopulmonary bypass procedures. Monitor readings were compared to OSM III co-oximeter values. The results revealed that saturation(%) determination was biased, -3.16 ± 2.21 SD for the CDI 100 and -0.34 ± 2.17 SD for the OxySat II. Hemoglobin (g/dl) and hematocrit (%) measurement, available only for the CDI 100, resulted in a bias of +5.54 ± 5.68 SD and +1.94 ± 1.78 SD, respectively. It was concluded that both monitors operated within clinically acceptable limits, with a more favorable outcome for the OxySat II

The Relationship Between Oxygen Transfer and FIO

On-line computation of body oxygen consumption (V̇O2) was performed in twelve (n=12) cardiac surgical patients utilizing cardiopulmonary bypass. Two in-line monitors, the CDI 400™ and CDI 100™ were interfaced with a personal computer. Arterial oxygen partial pressure, saturation and temperature from the CDI 400™ and venous saturation and hemoglobin values from the CDI 100™ enabled a real time computerized V̇O2 calculation. Paired V̇O2 and fractions of inspired oxygen (FIO) values made it possible to plot an oxygen transfer equation (OTE) for the AVECOR Affinity™ hollow fiber oxygenator. Regression analysis of 124 V̇O2-FIO2 pairs established the following relationship: V̇O2 = 368.4 * FIO2 - 15.6, with a correlation of 0.89 (p<0.001). This regression line presented as an OTE-plot suggests that the Affinity™ oxgenator is capable of transferring approximately 350 ml/min of oxygen at an FIO2 = 1.0. In conclusion, on-line CPB-monitoring interfaced with a personal computer may be used for real time V̇O2 - calculations and to establish an oxygen transfer equation of a given oxygenator

Our initial experience of monitoring the autoregulation of cerebral blood flow during cardiopulmonary bypass

Abstract Background: Cerebral blood flow is believed to be relatively constant within an upper and lower blood pressure limit. Different methods are available to monitor cerebral blood flow autoregulation during surgery. This study aims to critically analyze the application of the cerebral oxygenation index (COx), one of the commonly used techniques, using reference to data from a series of clinical registrations. Method: Cerebral blood flow was monitored using near infrared spectroscopy, while cerebral blood pressure was estimated by recordings obtained from either the radial or femoral artery in 10 patients undergoing cardiopulmonary bypass. The association between cerebral blood flow and blood pressure was calculated as a moving continuous correlation coefficient. A Cox index > 0.4 was regarded as a sign of abnormal cerebral autoregulation. Recordings were examined to discuss reliability measures and clinical feasibility of the measurements, followed by interpretation of individual results, identification of possible pitfalls and suggestions of alternative methods. Results and Conclusion: Monitoring of cerebral autoregulation during cardiopulmonary bypass is intriguing and complex. A series of challenges and limitations should be considered before introducing this method into clinical practice

Is a hyperosmolar pump prime for cardiopulmonary bypass a risk factor for postoperative delirium? : A double blinded randomised controlled trial

Objective: Postoperative delirium (POD) is common after cardiac surgery. We have previously identified plasma sodium concentration and the volume of infused fluids during surgery as possible risk factors. Both are linked to the selection and composition of the pump prime used for cardiopulmonary bypass (CPB). Present study aims to examine whether hyperosmolality increases the risk for POD. Design: Patients ≥65 years (n = 195) scheduled for cardiac surgery were prospectively enrolled into this double blinded randomised clinical trial. Study group received a pump prime containing mannitol and ringer-acetate (966 mOsmol) (n = 98) vs. ringer-acetate (388 mOsmol) (n = 97) in the control group. Postoperative delirium was defined according to DSM-5 criteria based on a test-battery pre- and postoperatively (days 1–3). Plasma osmolality was measured on five occasions and coordinated with the POD assessments. The primary outcome was the POD incidence related to hyperosmolality as the secondary outcome. Results: The incidence of POD was 36% in the study group and 34% in the control group, without intergroup difference (p=.59). The plasma osmolality was significantly higher in the study group, both on days 1 and 3 and after CPB (p&lt;.001). Post hoc analysis indicated that high osmolality levels increased the risk for delirium on day 1 by 9% (odds ratio (OR) 1.09, 95% CI 1.03–1.15) and by 10% on day 3 (OR 1.10, 95% CI 1.04–1.16). Conclusions: Use of a prime solution with high osmolality did not increase the incidence of POD. However, the influence of hyperosmolality as a risk factor for POD warrants further investigation