Perfusion

Objectives: We evaluated the impact of aortic cross-clamping time (XCT) and cardiopulmonary bypass time (CPBT) on the immediate and late outcome after adult cardiac surgery and attempted to identify their safe time limits.

Methods: This study includes 3280 patients who underwent adult cardiac surgery of various complexities. Myocardial protection was achieved with tepid continuous antegrade/retrograde blood cardioplegia.

Results: Receiver operating characteristics (ROC) curve analysis showed that XCT (area under the curve, AUC: 0.66), CPBT (AUC: 0.73) and CPBT with unclamped aorta (AUC: 0.77) were significantly associated with 30-day postoperative mortality. XCT of increasing 30-minute intervals (Odds Ratio (OR) 1.21, 95%C.I. 1.01-1.52) and CPBT of increasing 30-minute intervals (OR 1.47, 95%C.I. 1.27-1.71) were independent predictors of 30-day mortality. The best cutoff value for XCT was 150 min (30-day death: 1.8% vs. 12.2%, adjusted OR 3.07, 95%C.I. 1.48-6.39, accuracy 91.5%) and for CPBT 240 min (30-day death: 1.9% vs. 31.5%, adjusted OR 8.78, 95%C.I. 4.64-16.61, accuracy 96.0%). These parameters were significantly associated also with postoperative morbidity, particularly with postoperative stroke.

Conclusions: XCT and CPBT are predictors of immediate postoperative morbidity and mortality. In our experience, cardiac procedures with CPBT<240 min and XCT<150 min were associated with a rather low risk of immediate postoperative adverse events independently of the complexity of surgery patient’s operative risk.

Attenuated inflammatory response and decreased platelet activation have been claimed repeatedly when biocompatible circuits are used for cardiopulmonary bypass. We evaluated five Health Canada approved biocompatible circuit coatings (BCC) against an un-coated control group to determine their effectiveness in improving post-operative outcomes.

Patients were assigned to the Control group or one of the 5 coated circuit groups: 40 Control; 33 Trillium; 32 Phisio; 34 Bioline; 33 X; and 11 GBS. Measured outcomes included: ventilator time; ICU time; post-operative chest tube drainage and transfusion volume; high sensitivity C-reactive protein (hsCRP); tau protein; and pre- and 72-hour post-operative anti-saccadic eye movement test comparisons.

Results: 183 patients were enlisted into the study. One arm of the study (GBS) was abandoned after 11 patients on account of inconsistent pressure excursions within the oxygenator and the excessive consumption of platelets necessitating transfusion. Patients in the X-coated group had significantly longer ventilator and intensive care unit (ICU) time compared to the three remaining coated circuit study groups. Though not significant, patients in the X group also demonstrated the highest post-operative chest tube losses, the most platelet transfusions, the highest tau protein levels and the lowest post-operative anti-saccadic eye movement test (ASEMT) results compared to the three remaining coated groups. The patients in the Trillium, Bioline and Phisio groups showed an improvement in ventilator and ICU time relative to the Control group. The diabetic patients in the Trillium, Bioline and Phisio groups showed an improvement in bleeding relative to the diabetic patients in the Control group.

Conclusion: We compared all 5 coated circuits approved for clinical use in Canada against an uncoated control circuit. Three of the 5 coated circuits (Trillium, Phisio and Bioline BCC) were found to improve ventilator and ICU time compared to Control. Further studies are indicated to validate these results and their impact upon approval criteria, purchasing choices and safe clinical practice, especially as applied to higher risk diabetic patients.

Background: Biocompatible surfaces play an important role in the inflammatory response during cardiopulmonary bypass (CBP), with the arterial filter contributing a large surface area of the circuit. Different filter-coating materials designed to improve blood-filter biocompatibility are currently used in CPB circuits. This study evaluates eight biocompatible coatings used for arterial filters and their effects on blood components during circulation. Methods: Arterial filters were randomly assigned in eight independent heparin-bonded tubing loops and perfused by a single swine (n=8). Arterial blood was routed simultaneously, but separately, into each circuit and circulated for 30 minutes at 37°C. Blood samples were drawn for CBC, ACT, and TAT III measurements at baseline, post-heparinization and post-circulation. At study completion, filters were imaged using multiphoton microscopy. Results: RBC, platelet, and WBC counts, and TAT III complex were all decreased after 30 minutes of circulation; however, WBC count was the only parameter that showed statistically significant differences between the filters. Circulating WBC reduction ranged from 6% (Carmeda and Trillium) to 41% (Terumo-X-coating) with corresponding microscopic confirmation of increased WBC entrapment. Conclusion: All eight filter coatings altered the blood components to varying degrees. Selection of the most effective filter, in conjunction with a heparin-bonded circuit for CPB, may decrease the intraoperative foreign-surface activation of blood cells.

The aim of this prospective, animal study was to compare brain tissue oxygen tension (PbtO₂) with cerebral near infrared spectroscopy (NIRS) and mixed venous oxygen saturation (SVO₂) during venoarterial extracorporeal membrane oxygenation (VA ECMO) in a porcine model. This was accomplished using twelve immature piglets with surgically implanted catheters placed in the superficial cerebral cortex to measure brain PbtO₂ and microdialysis metabolites. The NIRS sensor was placed overlying the forehead to measure cerebral regional saturation index (rSO₂i) while SVO₂ was measured directly from the ECMO circuit. Animals were placed on VA ECMO followed by an initial period of stabilization, after which they were subjected to graded hypoxia and recovery. Our results revealed that rSO₂i and SVO₂ correlated only marginally with PbtO₂ (R²=0.32 and R²=0.26, respectively) while the correlation between rSO₂i and SVO ₂ was significantly stronger (R²=0.59). Cerebral metabolites and rSO₂i were significantly altered during attenuation of PbtO ₂, p<0.05). A subset of animals, following exposure to hypoxia, experienced markedly delayed recovery of both rSO₂i and PbtO ₂ despite rapid normalization of SVO₂. Upon further analysis, these animals had significantly lower blood pressure (p=0.001), lower serum pH (p=0.01), and higher serum lactate (p=0.02). Additionally, in this subgroup, rSO₂i correlated better with PbtO₂ (R²=0.76). These findings suggest that, in our ECMO model, rSO₂i and SVO ₂ correlate reasonably well with each other, but not necessarily with brain PbtO₂ and that NIRS-derived rSO₂i may more accurately reflect cerebral tissue hypoxia in sicker animals.

Introduction: Recirculation (R), the shunting of arterial blood back into to the venous lumen, commonly occurs during veno-venous extracorporeal membrane oxygenation (VV-ECMO) and renders the monitoring of the venous line oxygen saturation no longer reflective of patient mixed venous oxygen saturation (S_VO₂). Previously, we failed to prove the hypothesis that, once R is known, it is possible to calculate the S_VO₂ of a patient on VV-ECMO. We hypothesize that we can calculate S_VO₂ during VV-ECMO if we account for and add an additional correction factor to our model for dissolved oxygen content. Therefore, the purpose of this study is to derive a more accurate model that will allow clinicians to determine S_VO₂ during VV-ECMO when ultrasound dilution is being used to quantify R. Methods : Using an extracorporeal circuit primed with fresh porcine blood, two stocks of blood were produced; (1) arterial blood (AB), and (2) venous blood (VB). To mimic recirculation, the AB and VB were mixed together in precise ratios using syringes and a stopcock manifold. Six paired stock AB/VB sets were prepared. Two sets were mixed at 20% R increments and 4 sets were mixed at 10% R increments. The partial pressure of oxygen (pO₂ ) and oxygen (O₂) saturation of the stock blood and resultant mixed blood was determined. The original model was modified by modeling the residual errors with linear regression. Results: When using the original model, as the partial pressure of arterial oxygen (P_aO ₂) of the stock AB increased, the calculated S_VO₂ was higher than actual, especially at higher R levels. An iteration of the original model incorporating the P_aO₂ level (low, medium, high) and R was derived to fit the data. Conclusions : The original model using R and circuit saturations for the calculation of S_VO ₂ in VV-ECMO patients is an oversimplification that fails to consider the influence of the high pO₂ of arterial blood during therapy. In the future, further improvements in this model will allow clinicians accurately to calculate S_VO₂ in conjunction with recirculation measurements.

Background: The CardioWest temporary total artificial heart (TAH-t) replaces both native ventricles of the heart and is more beneficial for a select group of patients than most other typical ventricular assist devices (VADs). This review will expand on the current literature and highlight the chronology of this device. The CardioWest TAH-t has been implanted in over 715 patients at 30 multiple institutional centers worldwide as a bridge-to-transplant (BTT) since 1993. The mechanical flow dynamics of the device are manufactured and designed differently from other traditional VADs, allowing increased outputs and normal filling pressures, allowing for sufficient organ and tissue perfusion and dramatic recoveries, allowing patients to return to an almost normal quality of life. Results: There was a 79% survival to transplant achievement in the protocol group who received the TAH-t versus a 46% in the control group (P < 0.001). Furthermore, there was a 70% survival rate at one year in the protocol group versus 31% in the control group (P < 0.001). The one- and five-year survival rates after transplantation were 69% and 34%, respectively, in the control group and 86% and 64%, respectively, in the protocol group. Conclusion: It is evident that the advancement of modern engineering and medicine has made way for a reliable and durable device that provides a promising future in the field of end-stage heart failure.

It is well known that extracorporeal surfaces have the ability to bind such drugs as fentanyl, nitroglycerine and propofol. Adsorption of the injectable anesthetic agent Diprivan® (propofol) onto uncoated and heparin-coated extracorporeal surfaces during cardiopulmonary bypass (CPB) has been previously investigated; however, propofol adsorption onto synthetic-coated extracorporeal surfaces has not been published previously. The focus of this investigation was on the interaction of propofol and the synthetic biomimetic coating from the Sorin Group called Mimesys® (phosphorylcholine (PC)). A randomized series of six in vitro experiments were done with propofol using both PC-coated circuits without arterial filters and those with arterial filters. The circuits were identical in all experiments and priming remained the same, with 750 mls of normal saline and 1250 mls of fresh bovine blood (hematocrit 41.0 ± 1.0%). After circulation and collection of baseline samples, the first (low) dose of 4 mg (4000 mcg) of Diprivan 1% was added to the perfusate, followed by the second (high) dose of 40 mg (40,000 mcg) and the final challenge (extreme dose) of 356 mg (356,000 mcg) of Diprivan.

Drug assay was done by an independent laboratory, using the standardized method of High Performance Liquid Chromatography (HPLC). Measurements of total propofol were done at baseline, 20 minutes, 40 minutes and 60 minutes after each injection. Oxygenator performance was also measured prior to the addition of propofol and repeated after exposure to 4 mg, 40mg and 356 mg propofol for 60 min, 120 min and 180 minutes of circulation. Results indicate that phosphorylcholine coating does not prevent the adsorption of propofol during extracorporeal circulation and the oxygenator’s gas exchange ability is not affected by prolonged exposure to an extreme dose of the medication during high flow extracorporeal circulation.

The minimally invasive Heartport (HP)-assisted technique has become first choice option for mitral valve surgery in many centres.The pool of patients potentially treated using HP techniques, however, is still limited by the presence of peripheral vessel disease, expecially in the elderly population. Alternative approaches to using the HP technique safely in such a subset of patients, therefore, should be evaluated. Here, we present our preliminary experience using the axillary artery as an alternative site of cannulation for HP-assisted redo mitral valve surgery in patients with concomitant peripheral vessel disease.

A 27-year-old, G₃P ₂A₀ female with acute Staph aureus (SA) endocarditis successfully underwent CPB-assisted aortic valve replacement with a bioprosthetic aortic valve at 22 weeks’ gestation. This patient’s presentation of acute endocarditis complicated by septic shock, congestive heart failure, severe aortic insufficiency, multiple septic embolic events and borderline renal failure appeared on the daunting background of chronic heavy tobacco usage, hepatitis C positivity, long-term IV drug abuse and a pregnancy into its twenty-second week. Optimal treatment strategies implemented for both mother and fetus throughout the perioperative period contributed to a successful outcome for both.