The effect of PaCO2 on cerebral perfusion: an experimental swine model.

Adequate cerebral perfusion is of particular concern to the clinician and is a major factor in postoperative morbidity. Cerebral circulation has the ability to autoregulate blood flow in order to maintain nutrient delivery and prevent high intravascular pressures. The focus of this study was to characterize the impact of gradually changing arterial CO2 levels on cerebral perfusion. A total of eight porcine subjects were placed into either a normothermic group (NG, N = 4, rectal temperature = 35.4+/-1.2 degrees C) or a hypothermic group (HG, N = 4, 30.6+/-0.6 degrees C). After initiation of cardiopulmonary bypass, the PaCO2 values sequentially varied between 24 and 56 mmHg. Arterial, venous, and internal jugular blood gas data were collected at 4 mmHg increments, and relative cerebral blood flow was calculated as CBF = 1 (CarterialO2-CjugularO2)(-1) Physiological parameters were similar in both groups across all test conditions: mean arterial pressure-NG 81.6+/-11.9 mmHg versus HG 73.4+/-7.0 mmHg, p = NS, and systemic oxygen consumption-HG 110.6+/-30.0 mL min versus NG 136.4+/-37.9 mL min(-1), p = NS. No significant differences were found in CBF in the NG (21.8+/-4.4 mL min(-1) 100 gL at PaCO2 = 56 mmHg versus 20.5+/-5.0 mL min(-1) 100 g(-1) at PaCO2 = 24 mmHg) or the HG (24.3+/-9.5 mL min(-1) 100 g(-1) at PaCO2 = 56 mmHg versus 25.6+/-12.0 mL min(-1) 100 g(-1) at PaCO2 = 24 mmHg). In conclusion, the alteration of PaCO2 under both hypothermic and normothermic conditions resulted in no significant differences in 1 (CarterialO2 - CjugularO2)(-1) in this model.

An in vitro study of the effects of isoflurane on oxygen transfer.

A common anesthetic technique utilized during cardiopulmonary bypass (CPB) includes the use of various inhalation agents, such as isoflurane. The purpose of this study was to evaluate the effects of this agent on oxygen transfer during CPB. An in vitro model was designed using bovine blood. Blood flow was held constant at 2 l/min, while gas flow was manipulated at 1 and 3 l/min. The percentage of inspired oxygen (FiO2) was set at 50 and 100%, and isoflurane was manipulated to 1.0, 3.0 and 5.0%. Blood gas analysis, oxygen transfer, and inlet and outlet isoflurane concentrations were measured at each of the given conditions. A total of 12 trials with four oxygenators were conducted. In the four oxygenators used in our study, no significant differences in oxygenator performance were found. At conditions of 1 I/min gas flow, 50% FiO2 and 1% isoflurane, there were no significant changes in O2 transfer between baseline and measurements taken during isoflurane administration (100.18 +/- 12.49 vs 102.35 +/- 10.99 ml O2/min, p=0.8031). At 3 I/min gas flow, 100% FiO2 and 5% isoflurane, no significant differences were found (142.35 +/- 10.76 vs 154.04 +/- 8.95 ml O2/min, p=0.1459). The only significant differences found for oxygen transfer were between 50 and 100% FiO2, all other conditions being set equal (102.35 +/- 10.99 vs 137.68 +/- 8.62 ml O2/min, p=0.0023). In conclusion, increasing concentrations of isoflurane up to 5% does not affect the efficiency of oxygen transfer in an in vitro circuit. Further studies are necessary to evaluate the effects in an in vivo setting.

Quantitative evaluation of hypothermia, hyperthermia, and hemodilution on coagulation.

The purpose of this study was to investigate the effects of temperature change on the coagulation time of blood at two different hematocrit levels by using various coagulation-monitoring devices. The devices used in this study were the Bayer Rapid Point Coag Analyzers, Hemochron Jr. Signature, Hemochron Response, Medtronic ACT II, and Haemoscope Thrombelastograph. One unit of human bank blood was used in this study. The hematocrit level was adjusted to 40% and 20%. A control bath and experimental bath were set up. Control blood was maintained at 37 degrees C and tested every 45 +/- 15 min throughout the experimental period of 6 h to demonstrate the stability of the model. The experimental blood was tested at temperature points of 37, 32, 27, 32, 37, 42, and 37 degrees C. Activated clotting time (ACT) tended to increase when the temperature was initially decreased from 37 to 27 degrees C, which reached a statistically significant level when measured by the Hemochron Response at both the 20% (147 +/- 10.7 to 159.3 +/- 11.0, p < .0332) and 40% hematocrit level (130 +/- 14.9 to 152.1 +/- 19.7, p < .0148). ACT was decreased significantly (p < .05) when the temperature was increased to 42 degrees C as measured by all machines except the Hemochron Jr. Signature at the 20% hematocrit level. ACT was significantly higher (p < .05) at a 20% hematocrit level as compared to that at a 40% hematocrit level on all devices for the majority of temperature points. These data suggested that hypothermia only increased ACT when measured by a macrosample device requiring a milliliter sample (Hemochron Response). However, hemodilution induced anticoagulatory effects and hyperthermia caused an acceleration in coagulation by all devices utilized in this study.

Effect of partial-filling autotransfusion bowls on the quality of reinfused product.

Intraoperative autotransfusion is used in a variety of surgical procedures with the quantity of blood loss dependent upon numerous factors. These procedures may or may not produce a full autotransfusion bowl. The inadequate removal of contaminants has been correlated to the incomplete filling of bowls, resulting in a condition called "Salvaged Blood Syndrome." The purpose of this study was to assess the quality of aspirated whole blood after processing with an autotransfusion system using various fill volumes and two wash volumes. An in vitro circuit was designed to mimic the mechanical effects of extracorporeal flow on blood. Twenty-four Baylor-style bowls were filled at 400 mL min(-1) and washed at 300 mL min(-1). Two wash volumes, 1000 and 2000 mL, and three bowl volumes: low, mid, and full, were used in this study. The bowl volumes were determined by using red cell quantities of 60, 100, and 135 mL for the low-fill, mid-fill, and full bowls, respectively. Samples were drawn pre-autotransfusion and post-autotransfusion and analyzed for plasma-free hemoglobin, IL-8, white blood cell count, platelet count, albumin, and total protein. All data were analyzed using one-way analysis of variance (ANOVA) with significance accepted at p > or = .05. Plasma-free hemoglobin levels and hematocrit were concentrated significantly (p < .05) as bowl volume increased. A significant difference in IL-8 levels was found in the wash volumes in the low-fill bowls (p < .02). Platelet count was significantly decreased between the full bowl with 1000 mL wash and the full bowl with 2000 mL wash (p < .0004). Total protein reduction was significantly less in the low-fill bowl with 1000 mL wash as compared to the other bowl treatments (p < .05). In conclusion, the quality of the washed product did not vary significantly between fill or wash volumes, with the exception of the low-fill bowl with 1000 mL wash.

Effects of ultrafiltration on enoxaparin: an in vitro analysis.

The use of low molecular weight heparins (LMWH) as an anticoagulant in the heparin-resistant patient poses challenges during cardiopulmonary bypass (CPB). The ultrafiltrability of LMWH has not been previously examined. The purpose of this study was to determine the effects of continuous ultrafiltration on the concentraton of a LMWH, enoxaparin. An in vitro analysis was performed using fresh whole human blood and an extracorporeal circuit containing four parallel ultrafiltrators and a cardiotomy reservoir with an integrated heat exchanger. Constant conditions included temperature (37 degrees C), flow (0.20 L-min(-1)) transmembrane pressure (200 mmHg), and hematocrit (25 +/- 2%). Samples were collected at the inlet, outlet, and ultrafiltrate line at one and three min for one control trial and again for each of the four hemoconcentrators following the bolus of enoxaparin. Coagulation measurements included a viscoelastic monitor (TEG), activated clotting time (ACT), activated partial thromboplastin time (aPTT), and quantitative analysis utilizing a membrane-based electrode for potentiometric measurement of polyanionic concentrations of enoxaparin. Enoxaparin concentration, from inlet to outlet, increased from 2.95 +/- 0.64 to 5.89 +/- 0.95 (p < .001) at 1 min and 4.24 +/- 0.49 to 7.89 +/- 0.606 (p < .001) at 3 min. Kinetic clot activity, as assessed by the TEG index, decreased from -3.8 +/- 2.5 vs. -10.5 +/- 6.0; (p < .01) pre- to postultrafiltrator samples after 3 min. ACT and aPTT results demonstrated no significant change. In conclusion, this study demonstrates enoxaparin is concentrated with the use of continuous ultrafiltration. Functional coagulation studies also indicate a concentrating effect, primarily via the TEG.

An update on perfusion safety: does the type of perfusion practice affect the rate of incidents related to cardiopulmonary bypass?

Cardiopulmonary bypass (CPB) techniques vary among adult and pediatric patients undergoing cardiac surgery. This may result in a differential conduct of CPB between various aged patients. The present study reports on perfusion incidents occurring in hospitals using extracorporeal circulation. An 80 question survey was mailed to chief perfusionists at all 1030 US cardiac surgical centers. Respondents were asked to report on device use and incidents occurring during a 2-year period from July 1996 to June 1998. Five hundred and twenty-four completed surveys were returned with the age of surgical patients operated on at each hospital defined as either an adult (n=407), pediatric (n=17), or combined-adult and pediatric (n=100). Centrifugal pumps were used as the primary systemic pumps in 54% of adult, 12% of pediatric, and 36% of combined centers. In-line blood gas monitoring was used in 76% of all pediatric hospitals, but in only 30% of adult facilities. Incident rates occurred once per every 120.9, 83.9, and 220.2 cases in adult, pediatric, and combined centers, respectively. Mortality rates related to CPB occurred 2.7 times higher in adult and pediatric centers as compared to combined hospitals. Arterial dissection was the number one cause of death in both pediatric and combined hospitals, while coagulation disturbances resulted in the highest mortality for adult procedures. Results of this study show that the lowest incident rates occur at hospitals performing combined adult and pediatric CPB.

The effect of priming techniques of ultrafiltrators on blood rheology: an in vitro evaluation.

The increased interest of using ultrafiltration during cardiopulmonary bypass ICPB) has mandated a re-evaluation of the hematological effects of this blood conservation process. 'Rinse-free' ultrafiltrators can be primed using either crystalloid or blood prior to use. It is unknown whether one priming technique results in superior results in ultrafiltration quality. An in vitro circuit was designed to evaluate the Sorin/COBE HC1400 (n=6), the Lifestream HC70 (n=6), and the Terumo/Sarns HC11 (n=6). All test conditions were conducted at a blood flow rate of 250 ml/min and a transmembrane pressure of 250 mmHg. Samples were drawn and analyzed at four distinct time points for hematocrit, total protein, plasma free hemoglobin, interleukin-6 (IL-6), interleukin-8 (IL-8), and tumor necrosis factor-alpha (TNFalpha). The HC11 had significantly greater percent increases in hematocrit under the blood priming protocol (29.2+/-7.9) than either the HC1400 (11.0+/-7.8, p<0.03) or the HC70 (11.9+/-7.8, p<0.04). When crystalloid priming was compared to blood priming, the HC1400 and HC70 produced significant percent increases in hematocrit and total protein levels. The HC1400 devices produced significantly less plasma free hemoglobin when primed with crystalloid rather than blood (43.6+/-38.3 vs 21.3+/-5.6, p<0.01). There were no significant differences between devices or priming techniques for IL-6, IL-8 or TNFalpha levels. In conclusion, the efficiency of the ultrafiltrators was elevated when primed with crystalloid before use. Cytokine levels were relatively unchanged with priming techniques, while plasma free hemoglobin levels were reduced with those devices previously primed with crystalloid.

An experimental evaluation of continuous cardiotomy reservoir ultrafiltration.

Ultrafiltration has been suggested as a means to reduce the morbidity associated with blood activation. However, the application of ultrafiltration to the highly activated blood of the cardiotomy suction subcircuit has not been investigated. The purpose of this study was to determine whether cardiotomy reservoir ultrafiltration (CRUF) would be effective in altering cytokine levels. Six swine, undergoing 90 min of cardiopulmonary bypass (CPB), were divided into two groups; one group was assigned to receive CRUF (N = 3), the other was to serve as controls and did not receive ultrafiltration (N = 3). Blood samples were analyzed for hematocrit, plasma-free hemoglobin, total protein, interleukin-8 (IL-8), and tumor necrosis factor alpha (TNF-alpha). Samples were taken pre-bypass, postheparinization, every 30 min during CPB, post-CPB and postprotamine. All data were analyzed using a one-way analysis of variance (ANOVA), with significance accepted at p < .05. There were no significant differences found between treatment and control groups for plasma-free hemoglobin levels (22.4 +/- 22.2 vs. 14.6 +/- 14.4; 40.1 +/- 26.1 vs. 40.0 +/- 19.3). After 90 min of ultrafiltration, there was a significant decrease in TNF-alpha (261.6 +/- 119.6 vs. 71.8 +/- 11.4; p = .02). Although IL-8 levels decreased from throughout the experiment, concentrations did not reach statistical significance. In conclusion, CRUF can be used without increasing cellular destruction, and can decrease certain cytokine levels. Our results suggest that further clinical studies should be undertaken utilizing this technique with a larger sample size.

The effect of volume replacement on serum protein concentration during cardiopulmonary bypass.

Although controversy exists concerning the optimal total protein and colloid osmotic pressure that should be maintained during cardiopulmonary bypass (CPB), the primary volume expanders remain albumin and 6% hetastarch. The purpose of this study was to quantify the effect of adding boluses of volume replacement agents under various conditions to total serum protein values during CPB. A standard CPB circuit was utilized in eight 45-kg swine that had a priming volume (physiologic saline solution) of 2309 +/- 245 mL. Volumetric alterations occurred throughout the CPB period by the addition of combinations of physiologic saline solution, 6% hetastarch or 5% swine albumin. Pre- and postadministration samples were assayed for total serum protein, total protein, and albumin throughout the CPB period and at pre- and postvolume administration times. There was a significant decline in total serum protein with the initiation of CPB (6.14 +/- 0.49 g/dL vs. 3.40 +/- 0.43 g/dL, p < .0001). Addition of 12.5 g of swine albumin (N = 5) to two different swine increased total serum protein significantly when compared to adding 500 mL of 6% hetastarch (N = 6) (swine albumin 12.4 +/- 6.3% vs. hetastarch 3.3 +/- 2.1%, p < .005). A reduction in total serum protein occurred after hemodilution with varying amount of physiologic saline solution: 250-450 mL (7.4 +/- 4.5%), 451-650 mL (9.6 +/- 5.6%), and 651-1050 mL (19.4 +/- 4.0%). In summary, knowledge of total serum protein concentration and estimated circulating blood volume can be used to guide albumin and hetastarch administration following hemodilution.

In vitro evaluation of the Medtronic cardioplegia safety system.

Myocardial preservation demands the precise and accurate delivery of cardioplegic solutions to provide nutritive delivery and metabolic waste removal. The purpose of this study was to evaluate the performance characteristics of the Medtronic CSS Cardioplegia Safety System in an in vitro setting. The CSS was evaluated under the following conditions: blood to crystalloid ratios of 1:0, 1:1, 4:1, 8:1, 0:1; potassium concentrations of 10, 20, and 40 mEq L-1; volumetric delivery collection at 100, 250, 500, 750, and 990 mL/min; pressure accuracy at 100 and 300 mmHg; and system safety mechanisms. Measured and predicted values from the CSS were compared using one way ANOVA, with statistical significance accepted at p < or = 0.05. The measured values for the tested ratios and volume collections were all within the manufacturer's technical parameters. Potassium concentration results were all within expected values except at 100 mL/min, where the measured value of 17.1 +/- 2.1 mmol was lower than the expected 20.0 +/- 0.2 mmol (p < .034). As flow rates changed, the CSS line pressure error was constant (0.5 to 3.7%), and the only significant difference was observed at 100 mmHg, 500 mL/min (102.3 +/- 1.7 vs. 100.0 +/- 0.0 mmHg, P < .003). The device performed accurately and reliably under all simulated safety conditions, including bubble detection, over pressurization and battery backup. In conclusion, the performance of the CSS was within the manufacturer's specifications for the majority of the tested conditions and operated safely when challenged under varying conditions.

Factors affecting perfusionists' decisions on equipment utilization: results of a United States survey.

The decision to utilize extracorporeal equipment is influenced by a number of factors, including clinical efficacy, cost effectiveness, and personal judgment. The purpose of this study was to report the results of a national survey that examined factors affecting perfusionists' decisions on equipment utilization. An 80-question survey was mailed to chief perfusionists at 1030 U.S. hospitals performing open-heart surgery. 524 completed surveys were returned, which represented 797 hospitals (78.8%) and 671,290 procedures over a 2-year period (July 1996-June 1998). Within the survey, 36 questions pertained to equipment utilization and served as the basis for this report. The perfusion equipment that had seen the greatest reduction in use were; heparin-coated circuits (HCC) (12.0%), in-line blood gas monitors (9.7%), soft-shell venous reservoirs (SSVR) (7.2%), and in-line arterial hemoglobin monitors (6.3%). Cost was the major determinant affecting the decision for the following devices: in-line blood gas monitors (82.4%), cardioplegia in-line delivery filters (75.0%), in-line arterial hemoglobin monitors (69.7%), HCC (55.6%), and SSVR (43.2). Ineffectiveness was the major reason reported for discontinuation of arterial-line bubble traps (64.7%), venous reservoir level detectors (50.0%), and arterial-line pressure manometers with pump shutdown (50.0%). 438 respondents discontinued use of one or more of 29 different devices during the past 2 years. Cost was the major reason in 52.7% of the cases, ineffectiveness in 33.1%, and 14.2% were in a category labeled "other." The pressures brought upon by the changing healthcare structure have influenced perfusionists' equipment selection, with cost being a major factor affecting clinical decisions for certain device utilization.

Pre-operative coagulopathy management of a neonate with complex congenital heart disease: a case study.

Severe coagulation defects often develop in neonates undergoing cardiac surgery, both as a result of the surgical intervention, and as pre-existing defects in the hemostatic mechanisms. The following case report describes a newborn patient with complex congenital heart disease and respiratory failure whose pre-operative coagulopathy was aggressively managed prior to surgical correction. A 5-day-old, 2.5 kg child presented with interrupted aortic arch, ventricular septal defect, atrial septal defect, and patent ductus arteriosus. On admission, he was in respiratory arrest suffering from profound acidemia. In addition, the child was hypothermic (30.1 degrees C), septic (Streptococcus viridans), and coagulopathic (disseminated intravascular coagulation-DIC). The patient was immediately intubated and initial coagulation assessment revealed the following: prothrombin time (PT) 48.9 s (international normalized ratio (INR) 15.7), activated partial thromboplastin time (aPTT) >106 s, platelet count 30,000 mm(3), fibrinogen 15 mg dL(-1) and antithrombin III (AT-III) 10%. Before cardiac surgery could be performed, the patient's DIC was corrected with the administration of cryoprecipitate (15 ml), fresh frozen plasma (300 ml), and platelets (195 ml). In spite of the large transfusion of fresh frozen plasma, the AT-III activity, measured as a percentage, remained depressed at 33. Initial thromboelastographic (TEG) determination revealed an index of +2.02, and following 100 IU administration of an AT-III concentrate, declined to -2.32. Sequential TEG profiles were performed over several days, with the results used to guide both transfusion and medical therapy. The congenital heart defect correction was subsequently performed with satisfactory initial results, but the patient developed a fungal infection and expired on the 16th post-operative day. The present case describes techniques of coagulation management for a newborn with both a severe hemostatic defect and congenital heart disease.

The effects of continuous blood gas monitoring during cardiopulmonary bypass: a prospective, randomized study--Part I.

The use of continuous in-line blood gas management (CILBGM) is steeped in controversy concerning its potential utility and impact on patient outcomes. The purpose of this study was to determine whether the use of CILBGM results in improved quality of patient care. Fifty-nine patients were enrolled in a Institutional Review Board-approved, prospective, randomized study. An in-line blood gas monitor (CDI 500) was placed into the arterial and venous lines for all patients. Blood gas monitoring in the control group was managed by intermittent sampling (every 20-30 min), while the treatment group was managed with continuous monitoring. There were no differences between groups in preoperative, surgical, anesthetic, or perfusion variables. The accuracy of the in-line monitor was comparable to laboratory analysis for arterial blood gas parameters (N = 160; pH bias = 0.00; PaCO2 bias = -1.1 mmHg; and PaO2 bias = 0.7 mmHg). There was less deviation from target values (pH = 7.40, PaCO2 = 40 mmHg, PaO2 = 150-200 mmHg) when in-line monitoring was used versus intermittent sampling (N = 784; pH deviation = 0.05 +/- 0.03 vs. 0.03 +/- 0.01, p < 0.0001; PaCO2 deviation = 4.0 +/- 2.9 mmHg vs. 2.0 +/- 0.9 mmHg, p < 0.0001; and PaO2 deviation = 22.7 +/- 16.9 mmHg vs. 11.7 +/- 8.3 mmHg, p < 0.0001). In conclusion, the results of part I of this study demonstrate that the use of CILBGM results in more accurate blood gas management during CPB.

The effects of continuous blood gas monitoring during cardiopulmonary bypass: a prospective, randomized study--Part II.

The impact of blood gas management during cardiopulmonary bypass (CPB) on patient care has not been examined and remains controversial. The purpose of this study was to determine whether precise blood gas management during CPB influences patient outcome. Fifty-nine patients were enrolled in an Institutional Review Board-approved, prospective, randomized study. An in-line blood gas monitor (CDI 500) was placed into the arterial and venous lines for all patients. Blood gas monitoring in the control group was managed by intermittent sampling (every 20-30 min), while the treatment group was managed with continuous monitoring. Blood gas control and measured parameters were as follows: pH 7.40 +/- 0.05, PaCO2 40 +/- 5 mmHg, PaO2 200 +/- 50 mmHg. The treatment group had the CDI 500 guide clinical decisions. Compared to the control group, the treatment group consisted of significantly more diabetic (7% vs. 47%, p < or = 0.001), renal failure (3% vs. 13%, p < or = 0.01), and chronic obstructive pulmonary disease patients (7% vs. 20%, p < or = 0.01). Internal thoracic artery utilization was higher in treatment patients than control patients (67% vs. 95%, p < or = 0.02). No other differences existed in demographic, pharmacological, surgical, or anesthetic parameters. In the perioperative period, the control group required antiarrythmic support more frequently than the treatment group (10% vs. 0%, p < or = 0.05). Compared to the control group, the treatment group required antiarrythmic (18% vs. 10%, p < or = 0.05) and cardiac glycoside therapy (11% vs. 0%, p < or = 0.05) less frequently in the postoperative period. Although treatment patients required less intraoperative pacing and cardioversion and spent less time on mechanical ventilation, in the intensive care unit (ICU), and in the hospital than control patients, statistical significance was not achieved. In conclusion, the use of continuous, in-line blood gas monitoring resulted in improvement in a number of postoperative outcome variables, although ICU and hospital stay was not effected.

Co-administration of aprotinin and epsilon-aminocaproic acid during cardiopulmonary bypass in a swine model.

Despite the beneficial effects of pharmacological interventions to prevent bleeding and to reduce the need for autogeneic blood, there are concerns that these agents induce a prothrombotic state. The purpose of this study was to examine the coagulation phenomena influenced by the coadministration of epsilon-aminocaproic acid (EACA) and aprotinin during cardiopulmonary bypass (CPB). A swine model of CPB was utilized in this study. During 120 min of CPB, treatment animals (N = 5) received 6 x 10(6) Kiu of aprotinin and 30 grams of EACA; whereas, control animals (N = 3) received an equal volume of 0.9% saline. Indices of thrombogenicity included hematological variables, gross pathology, and circuit examination for the presence of thrombus. The application of both antifibrinolytics resulted in an increase use of heparin. Total heparin requirements were significantly different between treatment group (58,800 +/- 3493 iu) versus control group (51,000 +/- 3464 iu). D-dimer concentration was also significantly higher in the control group (500-1000 ng mL-1) than in the treatment group (250-500 ng mL-1) at 5 and 30 min postprotamine. Other coagulation markers tested were not observed to be statistically significant between groups. Thromboelastographic (TEG) index decreased in the treatment group during the surgical procedure and bypass from 2.74 +/- 2.9 to -1.36 +/- 4.1 as compared to an increase from 2.62 +/- 2.9 to 4.05 +/- 0.4 in the control group. Pathologic analysis revealed occurrences of thrombus formation in small vessels in the lung and kidney glomeruli of treatment animals. The concurrent use of both aprotinin and EACA may induce a prothrombotic or coagulant state as determined by histological assessment.

The effects of nitric oxide on coagulation during simulated extracorporeal membrane oxygenation.

Extracorporeal membrane oxygenation (ECMO) is associated with profound alterations in hemostasis, with platelet dysfunction often being implicated as a causative factor for transfusion. Nitric oxide (NO) has shown to be a rapid yet temporary inhibitor of platelet function. The purpose of this study was to evaluate the effects of NO on platelet number and function in an in vitro ECMO model. Eight silicone membrane oxygenators were primed with fresh, heparinized, bovine blood and allowed to circulate for 48 hours. The treatment group (NO) consisted of four oxygenators that had an end concentration of 20 ppm NO applied to the sweep gas. Platelet counts, methemoglobin levels, plasma-free hemoglobin levels, activated clotting times, and thromboelastographic (TEG) studies were performed at baseline, 1, 6, 12, and 24 h. Scanning electron microscopy (SEM) was performed on sample areas from each oxygenator. The treatment group maintained an average of 25% higher platelet counts than the control group (85.1 +/- 32.0, x 10(3) versus 66.5 +/- 30.9 x 10(3)) although statistical significance was not achieved. Methemoglobin levels were significantly elevated in the treatment circuit at hours 12 and 24 (p < .05). This could be attributed to the lack of a biological interaction that would break down this toxic by-product. TEG indices steadily declined in both groups from baseline (-0.4 +/- 3.6) to (-17.2 +/- 3.3 p < .0007) treatment and (-20 +/- 4.5, p < .0001) control, with the treatment circuit maintaining only slightly improved indices over the most of the study. SEM data showed increased fibrin and cellular deposits in the control group (p = .05) when compared with the treatment group. NO added to the sweep gas of a simulated ECMO circuit at 20 ppm had little effect on the maintenance of platelet number and function.

Outcome analysis of coronary artery bypass grafting: minimally invasive versus standard techniques.

Minimally invasive coronary artery bypass grafting (MIDCAB) procedures are purported to result in improvements in patient management over standard techniques. A comparative study was performed on risk-stratified patients treated with either technique. Following institutional review board approval, a retrospective random chart review was conducted on 27 MIDCAB and 37 standard coronary artery bypass grafting (CABG) patients who were operated on over a 12-month period at the University of Nebraska Medical Center. Risk stratification was accomplished by dividing the two patient populations, MIDCAB and 'standard', into one of four subgroups based on a preoperative risk score. Risk stratification was achieved by dividing the patient populations into one of four subgroups: good, fair, poor and high risk. Both groups received similar operations and surgical interventions, except for the inclusion of cardiopulmonary bypass (CPB). Approximately 200 parameters were collected and analyzed in the following categories: anthropometric, operative and postoperative outcomes. The MIDCAB group had a significantly lower number of vessels bypassed (2.0+/-0.7 vs 3.4+/-0.9, p < 0.0001). Total postoperative blood product transfusions trended higher in the standard group (6.1+/-12.6 U) when compared to the MIDCAB patients (2.3+/-5.5 U, p < 0.15), although not statistically significant. Postoperative inotrope use was significantly less in the MIDCAB group (19% vs 59%, p < 0.002). Ventilator time in the MIDCAB group was 10.5+/-5.4 h vs 15.0+/-12.3 h in the standard group (p < 0.07). The MIDCAB group had an overall greater length of stay, but was only statistically different within the poor-risk subgroup (12.2+/-10.7 vs 7.5+/-3.9, p < 0.04). The results of this study show that when CPB is not utilized in treating patients undergoing CABG procedures, the benefits in regards to patient outcomes are unclear. This necessitates the need for further work when comparing outcomes for risk-stratified patients.

An in vitro evaluation of a self-contained cardioplegia delivery device.

Focus on improved myocardial protection has prompted the development of delivery systems which can accommodate the demands of increasingly refined cardioprotective strategies. The purpose of this study was to evaluate the Sorin Blood Cardioplegia Console (BCC) for accuracy and precision in the delivery of cardioplegia solutions. An in vitro model was designed to evaluate the following performance characteristics of the BCC: delivery volume (blood and crystalloid) at 50, 250, 375, and 500 ml/min flow rates; potassium end-delivery concentration at blood:crystalloid ratios of 4:1, 8:1, and 16:1; intermittent cardioplegia delivery; and heat transfer of the internal heater/cooler. Differences in blood and cardioplegia volumes between measured and calculated values across all flow rates tested were found to be statistically significant and ranged from 1.4 to 21.5 ml; however, the differences were within the accepted variance of the instrument (+/- 5%). Across all tested ratios, the measured end-potassium concentrations were all within 1 mEq of the expected values, except for the 16:1 ratio at 50 ml/min, which had a 2.52 mEq variance. All significant differences were within the accepted variance of the instrument (+/- 5%). In conclusion, the BCC accurately and delivered cardioplegia volumes and potassium concentrations across all tested conditions with reproducible performance.

Cardioplegia flow dynamics in an in vitro model.

The flow of fluids in extracorporeal circuits does not conform to conventional Poiseuille mechanics which confounds calculating cardioplegia (CP) flow distribution. The purpose of this study was to quantify CP flow dynamics in a model simulating coronary atherosclerosis across varying sized restrictions. An in vitro preparation was designed to assess hydraulic fluid movement across paired restrictions of 51, 81 and 98% lumen reductions. Volume data were obtained at variable flow, temperature, viscosity and pressure conditions. CP delivered through 14- and 18-gauge (GA) conduits at 8 degrees C and 100 mmHg infusion pressure revealed that both four to one and crystalloid CP solutions had significantly less total percentage flow through the 14-GA conduit, p < 0.0001 and p < 0.001, respectively. Overall, 4:1 CP exhibited the most favorable fluid dynamics at 8 degrees C in that it delivered the highest percentages of total CP flow through the smaller lumen conduit. At both 8 degrees C and 37 degrees C delivery, blood CP resulted in the least homogeneous fluid distribution at all delivery parameters. The results in relation to blood viscosity indicate that, although the 8 degrees C blood CP had a significantly greater viscosity than 37 degrees C blood CP, it did not produce an effect in fluid distribution. These data show that increasing the cardioplegic solution hematocrit causes an inhomogeneous fluid distribution regardless of delivery temperature or infusion pressure.

Removal of hepatocarcinoma cells from blood via cell washing and filtration techniques.

Utilization of autotransfusion during tumor resection remains controversial due to viability of carcinoma cells remaining in collected blood. The purpose of this study was to evaluate autotransfusion techniques combined with leukocyte depleting filters (LDF) for removal of hepatocarcinoma cells from autotransfusate. An in vitro model was created by contaminating expired human erythrocytes with cultured hepatocarcinoma (HEP G2) cells. Autotransfusion devices evaluated were Cobe BRAT2, Sorin STAT-P, and Fresenius CATS. Autotransfusate collected from varying processing conditions were filtered using the Pall Leukoguard RS or Pall Purecell RCQ LDF. Carcinoma concentrations were quantified via Coulter Counter technology. The CATS exhibited higher concentrations of cancer cells in the autotransfusate prior to washing, a 449% increase. This was significantly higher than either the BRAT2 or STAT-P, 350% and 315% respectively. Post washing HEP G2 concentrations in the BRAT2 were significantly higher than the STAT-P and CATS. Doubled wash volumes removed more HEP G2 cells in all trials, reaching statistical significance only in the CATS. LDF resulted in a significant 75% reduction of HEP G2 cells, with no difference between filters. While combination use of autotransfusion devices and leukocyte depleting filters did result in a product with concentrated hematocrit, no technique removed all hepatocarcinoma cells.