Cardiopulmonary Bypass Procedures Research Articles

Normothermia versus hypothermia during cardiopulmonary bypass: A randomized, controlled trial

To evaluate the influence of perfusion temperature on systemic effects of cardiopulmonary bypass (CPB), 30 patients undergoing elective coronary artery bypass grafting were randomly assigned to either normothermic (warm, n = 14, 36 degrees C) or hypothermic (cold, n = 16, 28 degrees C) CPB. Serial hemodynamic measurements and blood samples were obtained before, during and after the CPB procedure. During CPB, there were no differences between both groups in the need for vasopressors (norepinephrine, phenylephrine), urinary output, or fluid balance. In the early postoperative period, normothermic CPB patients had significantly lower systemic vascular resistance and higher cardiac index measurements (mean +/- standard error: systemic vascular resistance, 880 +/- 27 versus 1,060 +/- 57 dyne.s.cm-5, p = 0.025; cardiac index, 3.6 +/- 0.1 versus 2.9 +/- 0.1 L.min-1.m-2, p = 0.01) without differences in the administration of vasoactive drugs. Blood loss was significantly higher in patients after hypothermic CPB (median [range] body surface area: 370 [180-560] versus 490 [280-2,120] mL/m2, p = 0.0006), with a greater need for transfusion of erythrocytes and fresh frozen plasma. Plasma levels of tumor necrosis factor and soluble tumor necrosis factor receptors increased during and after CPB, independent of perfusion temperature. This study suggests a significant influence of CPB temperature and respective perfusion management on postoperative hemodynamics and blood loss. Normothermic CPB is not associated with additional systemic adverse effects.

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.

Circulating cytokines in patients undergoing normothermic cardiopulmonary bypass

To determine the cytokine release during normothermic cardiopulmonary bypass, we have measured plasmatic levels of tumor necrosis factor-α and interleukins-1β, 6, and 8 in 10 patients during the first 24 hours after the start of bypass. Arterial blood samples were collected at intervals before, during, and after bypass. Interleukin-1β was not detectable in the plasma, and traces of tumor necrosis factor-α were detected in only three patients at times independent of the cardiopulmonary bypass procedure. Circulating endotoxin remained undetectable. Plasma interleukin-6 and interleukin-8 rose significantly from 2 until 24 hours after the start of bypass (p < 0.05) and peaked respectively at 4 and 2 hours after the beginning of bypass (interleukin-6, 268.1 ± 131.43 pg/ml; interleukin-8, 370 ± 420 pg/ml; mean peak ± standard deviation). Peak values of interleukin-6 and interleukin-8 were correlated neither with the duration of aortic crossclamping or the bypass procedure nor with the hemodynamic parameters recorded at the same times. This study shows that normothermic cardiopulmonary bypass does not induce systemic release of tumor necrosis factor-α and interleukin-1β. A local production of these cytokines cannot be excluded, because interleukin-6 and interleukin-8 are produced by stimulated macrophages and monocytes in response to tumor necrosis factor-α and interleukin-1β. Our results, at normothermia, show a similar pattern of interleukin-6 and interleukin-8 release when compared with release during hypothermic cardiopulmonary bypass. Interleukin-8, an important chemotactic neutrophil factor, might play a role in reperfusion injuries observed in lungs and heart after cardiopulmonary bypass. (J THORAC CARDIOVASC SURG 1994;108:636-41)

Effect of prophylactic epsilon-aminocaproic acid on blood loss and transfusion requirements in patients undergoing first-time coronary artery bypass grafting: A randomized, prospective, double-blind study

The prophylactic use of aprotinin has recently been reported to be associated with a significant decrease in blood loss in patients undergoing cardiopulmonary bypass procedures. One of the primary effects of aprotinin is prevention of plasmin degradation of platelet function. Because aprotinin is commercially unavailable in the United States at this time, we evaluated epsilon-aminocaproic acid with respect to decreased perioperative blood loss. We prospectively randomized 40 patients undergoing first-time coronary artery bypass grafting without prior sternotomy into two groups: one group ( n = 21) received prophylactic and preincision epsilon-aminocaproic acid and the other ( n = 19) received a placebo. No significant differences existed between patient groups with respect to age, body surface area, cardiopulmonary bypass time, and aortic crossclamp time. Cumulative blood loss at 4, 8, 12, and 24 hours after chest closure was significantly less in the epsilon-aminocaproic acid group (426 ± 242 ml versus 634 ± 224 ml, p = 0.002, at 12 hours). Only one patient receiving epsilon-aminocaproic acid was given blood or blood components compared to five patients in the placebo group ( p < 0.02). D-dimers and fibrin split products were significantly less prevalent in the epsilon-aminocaproic acid group (at 4 hours: 0/20 versus 7/16, p < 0.002 and 5/20 versus 12/19, p < 0.05, respectively). None of the patients had a perioperative myocardial infarction or cerebrovascular accident. The prophylactic administration of epsilon-aminocaproic acid results in a significant decrease in blood loss in patients undergoing first-time coronary artery bypass grafting, and blood transfusion requirements are significantly less. It may be important to administer epsilon-aminocaproic acid before skin incision to be optimally effective. (J THORAC CARDIOVASC SURG 1994;108:99-108)

Mechanism of stroke complicating cardiopulmonary bypass surgery

Stroke is a devastating complication of cardiopulmonary bypass (CPB) surgery which occurs in 1 to 5% of cases. Strategies to reduce its incidence require a knowledge of the underlying pathology and aetiology. To determine the incidence, pathology and aetiology of stroke complicating CPB. Prospective review of clinical, operative and cranial CT scan findings in all cases of stroke complicating CPB procedures in our institution over an 18 month period. Twenty-one (1.6%, 95% CI 0.9-2.3%) cases of stroke were identified from 1336 CPB procedures. Cranial CT scan, performed in all but one patient, was normal in three patients or consistent with ischaemic stroke in 17 patients. There were no cases of haemorrhagic infarction or intracerebral haemorrhage. It was difficult to differentiate embolic and borderzone infarcts in two cases. After considering the clinical, operative and CT scan features together, 12 (57%, 95% CI 36-78%) of the cases were felt to be embolic in origin and nine (43%, 95% CI 22-64%) due to hypoperfusion in a borderzone. This study demonstrates that stroke remains an important complication of CPB procedures with an incidence in our series of 1.6%. The pathologic type of stroke is predominantly ischaemic in nature due to either cerebral embolism or borderzone infarction. Strategies for stroke prevention in patients undergoing CPB should be targeted primarily at these two mechanisms.

Leucocyte depleting filters and cardiothoracic surgery

Leucocyte filtration technology is now beginning to be used in cardiothoracic surgery. The leucocyte depletion of banked homologous blood has been shown to reduce its immunosuppressive effects, along with a range of other benefits. Use of such a blood product appears to be an attractive option during cardiopulmonary bypass (CPB) as this procedure is recognized as causing immune disturbance and long-term immunosuppression. White-cell removal filters also appear to have a novel application in the reduction of neutrophil-mediated damage associated with CPB procedures. A strong database from animal work has been recently supplemented by human data that shows clinical benefits from autologous white-cell removal by filtration.

Comparison of three blood-processing techniques during and after cardiopulmonary bypass

The return of extracorporeal circuit blood at the termination of cardiopulmonary bypass is an important feature of blood conservation during open heart procedures. However, the relative benefits and disadvantages of different circuit blood salvage methods remain unclear. Accordingly, the purpose of this study was to examine whether quantifiable differences exist between three different circuit blood-salvaging techniques: direct infusion, centrifugation, and ultrafiltration. Sixty patients with very similar preoperative characteristics were randomly assigned to each of the three groups, and blood coagulation screens, plasma profiles, and respiratory function were determined at 20 minutes and at 6 and 18 hours after cardiopulmonary bypass. Early after cardiopulmonary bypass (20 minutes), the plasma colloid osmotic pressure and fibrinogen and platelet concentrations were significantly higher with ultrafiltration ( p < 0.05) versus those observed for the other two methods. The plasma thromboplastin times were significantly ( p < 0.05) longer after cardiopulmonary bypass with centrifugation as compared to direct infusion and ultrafiltration. However, the coagulation profiles and plasma composition normalized by 18 hours after cardiopulmonary bypass with all three blood-salvaging methods. There were no significant differences in terms of blood utilization or chest tube drainage over the entire postoperative period among any of the circuit blood-salvaging methods. These results suggest that ultrafiltration of postcardiopulmonary circuit blood may preserve plasma colloid pressure and platelet concentration in the early postoperative period, but these differences do not persist. Thus, for routine cardiopulmonary bypass procedures, direct infusion, centrifugation, and ultrafiltration may all be satisfactory methods of circuit blood salvage.

Cardiopulmonary bypass and thyroid hormone metabolism

Early investigations involving patient response to thyrotropin-releasing hormone during cardiac operations prompted researchers to consider that the cardiopulmonary bypass (CPB) procedure may affect this response. Results from several studies indicate that total T 3 (active thyroid hormone) concentration are significantly reduced during and after CPB (ie, the euthyroid sick syndrome). Inhibition of the monodeiodinase pathway during CPB, and subsequent inhibition of peripheral thyroxine to T 3 conversion may partly explain these findings. These data prompted the investigation of intravenous T 3 administration to patients undergoing CPB. Clinical trials to date have shown that intravenous T 3 administered during or after CPB improves cardiac output and contractility. This article reviews the studies of thyroid hormone before, during and after CPB operations.

Pharmacokinetics of intravenous vancomycin in pediatric cardiopulmonary bypass surgery

The purposes of this investigation were to characterize the disposition of vancomycin in children undergoing cardiopulmonary bypass (CPB) surgery and to determine whether a 15-mg/kg intravenous dose provides adequate serum concentrations during and after CPB. Six children (age range, 0.8 to 4.8 years) received intravenous vancomycin 15 mg/kg 1 to 2 hours before CPB surgery. Serial blood samples (mean, 10/patient) were collected before, during and after CPB surgery. The mean (+/- SD) vancomycin concentrations at the end of the infusion and 5 hours after the infusion were 27.3 +/- 5.7 and 5.9 +/- 3.0 mg/liter, respectively. The initiation of CPB resulted in an abrupt decrease (44.5%) in serum vancomycin concentrations; however, concentrations remained constant (range, 6.2 to 14.1 mg/liter) throughout the rest of the CPB procedure. The mean (+/- SD) values for the apparent volume of distribution, total body clearance and elimination half-life were 0.59 +/- 0.15 liter/kg, 2.94 +/- 0.93 ml/min/kg and 2.4 +/- 0.8 hours, respectively. These values were similar to those reported in the literature for children not undergoing CPB surgery. A single vancomycin dose of 15 mg/kg before pediatric CPB surgery provides serum concentrations greater than 5 mg/liter throughout the duration of the CPB procedure. To sustain these concentrations subsequent dosing of vancomycin is necessary within 6 hours after the initial vancomycin dose.

Cardiopulmoitary bypass procedures in dialysis patients

To determine the operative outcome of chronic renal failure patients, we retrospectively reviewed twenty-five consecutive adult patients with chronic renal failure dependent on maintenance hemodialysis (21) or peritoneal dialysis (3), who underwent cardiopulmonary bypass procedures over a five-year period in our institution. The operations included isolated coronary artery bypass grafting in 16 patients; aortic valve replacement in 3; aortic valve replacement plus mitral valve replacement in 1; aortic valve replacement, mitral valve replacement, and coronary artery bypass grafting in 2; aortic valve replacement and coronary artery bypass grafting in 1, mitral valve replacement and coronary artery bypass grafting in 1, and repair of a thoracoabdominal aortic aneurysm in 1 patient. Fourteen operations were elective, and 11 were urgent or emergent. The number of patients with good (>0.50), fair (0.30 to 0.50), and poor (<0.30) left ventricular ejection fractions were 13, 9, and 3, respectively. There were 0, 7, 7, and 11 patients in New York Heart Association functional classification I, II, III, and IV, respectively. All patients were dialyzed within 24 hours before operation. All but 3 patients were managed by immediate postoperative peritoneal dialysis via a Technoff catheter placed intraoperatively (18 patients) or via a preexisting Technoff catheter (4 patients). This was then switched to hemodialysis when clinical conditions stabilized. Univariate analysis of 22 preoperative and intraoperative variables, followed by a multivariate analysis with a stepwise logistic regression model, was performed using the 30-day or in-hospital operative mortality as the dependent variable. The urgency of the operation and New York Heart Association class IV were found to be independent variables associated with increased operative mortality. There were no operative deaths among the 14 patients having elective operation; 4 of the 11 patients having nonelective operation died postoperatively, constituting a 36% operative mortality for this subgroup. All operative deaths occurred in the patients in preoperative New York Heart Association class IV (4/11 or 36%). This study demonstrated that elective cardiopulmonary bypass operations can be performed in chronic renal failure patients with excellent operative outcome, when done with careful perioperative management. Patients having nonelective operations and patients in the most advanced stage of their cardiac diseases had substantial operative mortalities in this series. The overall operative mortality of the 296 cases reported in the English-language literature thus far is 9%.

Platelet protection by low-dose aprotinin in cardiopulmonary bypass: Electron microscopic study

To evaluate the effect of low-dose aprotinin during cardiopulmonary bypass on platelet function and clinical hemostasis, 30 patients undergoing various cardiopulmonary bypass procedures employing bubble oxygenators were randomized to receive either low-dose aprotinin (2 × 10 6 KIU in the cardiopulmonary bypass priming solution, 15 patients [group A]) or placebo (15 patients [group B]). Blood samples were collected before and after cardiopulmonary bypass to assess platelet count and aggregation on extracellular matrix, which was studied by a scanning electron microscope. On a scale of 1 to 4 preoperative mean platelet aggregation grades were similar in both groups (3.8 ± 0.5 and 3.5 ± 0.5 for groups A and B, respectively). Postoperatively, platelet aggregation on extracellular matrix decreased slightly in group A (2.8 ± 1.3; p < 0.01) and significantly in group B (1.3 ± 0.5; p < 0.001). Eleven of the 15 patients in group A remained in aggregation grade 3 or 4 compared with none of the group B patients. Platelet count was similar in both groups preoperatively and postoperatively. Total 24-hour postoperative bleeding and blood requirement were lower in the aprotinin group (487 ± 121 mL and 2.3 ± 1.0 units) than in the placebo group (752 ± 404 mL and 6.8 ± 5.1 units; p < 0.01). These results show that the use of low-dose aprotinin during cardiopulmonary bypass provides improved postoperative hemostasis, which might be related to the protection of the platelet aggregating capacity.

OCULAR FINDINGS IN NEONATES AFTER EXTRACORPOREAL MEMBRANE OXYGENATION

Extracorporeal membrane oxygenation (ECMO) is a modified, prolonged cardiopulmonary bypass procedure used to treat newborns who have reversible cardiac or respiratory failure. The venoarterial bypass technique requires cannulation of both the right carotid artery and the internal jugular vein, and after decannulation these vessels are permanently ligated. Left-sided retinal vascular changes after ECMO have been reported, and were attributed to ligation of these vessels. A retrospective review of the results of ocular examinations of 86 infants who had undergone ECMO therapy at Childrens Hospital in Los Angeles between March, 1987 and May, 1991 was conducted. Normal findings were noted in 73 infants. One infant had bilateral retinal vascular tortuosity, and 12 infants had incidental ocular findings, but there was no evidence of left-sided retinal hemorrhage, venous congestion, or tortuosity. Our results suggest that left-sided retinal vascular changes after ECMO do not occur, occur only rarely, or clear rapidly and result in no permanent retinal damage. To unequivocally rule out the possibility that ECMO can cause transitory retinal vascular changes, we recommend further prospective studies, with ocular examinations performed before, during, and after ECMO.

Extracorporeal membrane oxygenation for cardiac failure after congenital heart operation

Despite continuing improvement in myocardial protection and surgical technique, the repair of complex congenital heart lesions can result in cardiopulmonary compromise refractory to conventional therapy. In a 29-month period, 24 patients (aged 14 hours to 6 years) were treated with extracorporeal membrane oxygenation (ECMO) 28 times for profound cardiopulmonary failure. Four patients required ECMO after each of two cardiopulmonary bypass procedures. Seventeen patients required ECMO to be initiated in the operating room: 12 (71%) were weaned successfully from ECMO, and 8 (47%) survived. Seven patients had ECMO initiated in the intensive care unit: 6 (86%) were weaned, and 5 (71%) survived. Serial echocardiograms demonstrated substantial recovery of cardiac function in 18 of 21 instances (86%) of ventricular failure from myocardial dysfunction. Overall, 18 of 24 patients (75%) were successfully weaned from ECMO including all 4 who underwent 2 ECMO treatments. We conclude that ECMO can successfully salvage children who have serious cardiopulmonary failure immediately after a congenital heart operation and that long-term survival is possible after two ECMO treatments.

Response to heparinization in adults and children undergoing cardiac operations

The activated clotting time is an unreliable index of anticoagulation status during cardiopulmonary bypass procedures. However, modem instrumentation (Hemotec Hepcon HMS) now allows the monitoring of free heparin levels via automated protamine titration. In the present study, the standard procedure of anticoagulation at Killingbeck Hospital, Leeds, was investigated. Twenty-two pediatric patients and 20 adult patients undergoing open heart procedures involving cardiopulmonary bypass were given empirical doses of heparin (3 mg/kg body weight bolus), and activated clotting time was maintained at a level greater than 450 seconds using the Hemochron Timer. Heparin neutralization was performed at the termination of the bypass period using an empirical equivalent (3 mg/kg) of protamine sulfate. Mean free heparin concentration (± standard deviation) fell from 2.26 (± 0.45) mg/kg to 1.39 (± 0.34) mg/kg over the period 10 to 40 minutes on bypass in children. In adults, free heparin level declined from 2.56 (± 0.58) mg/kg to 1.81 (± 0.58) mg/kg over the same period. The biological half-life for heparin was 60 minutes in adults and 35 minutes in pediatric patients. Empirical protamine dosing resulted in excess protamine administration when compared with Hepcon titrated dose requirements: for children: median (range), 80 (12 to 350) versus 33 (12 to 97) mg, p < 0.001; and for adults: 350 (200 to 500) versus 130 (61 to 237) mg, p < 0.001. In conclusion, empirical heparin administration (3 mg/kg) does not result in “steady-state” anticoagulation during cardiopulmonary bypass, and empirical administration of protamine takes no account of interindividual differences in heparin sensitivity and biological half-life, which may be assessed using the Hepcon HMS.

Cyanide Toxicity from Sodium Nitroprusside: Risks and Management

To review the risks, manifestations, and treatment of cyanide toxicity from nitroprusside therapy. All English case reports identified in Index Medicus (MEDLINE) of cyanide intoxication related to nitroprusside from 1970 to the present were reviewed. In addition, literature regarding the incidence, risks, and treatment of cyanide toxicity from nitroprusside is presented. Numerous cases of cyanide toxicity associated with nitroprusside have been reported. The overall incidence appears to be infrequent; however, certain patients may be at high risk. Risk factors may include hypoalbuminemia, cardiopulmonary bypass procedures, or the administration of moderate to high doses of nitroprusside. Treatment of cyanide toxicity requires the cessation of nitroprusside and, for severe toxicity, use of the cyanide antidote kit. Cyanide toxicity from nitroprusside may be prevented by concomitant administration of sodium thiosulfate infusions.

Need for invasive cardiological assessment and intervention: a ten year review.

The uptake of invasive cardiological investigation and cardiopulmonary bypass procedures by the North West Surrey Health District was audited over the years 1979-88. Growth was almost continuous throughout the ten year period. The need within the district each year for coronary angiography seemed to be between 111 and 171 and for surgical revascularisation of the myocardium between 63 and 96 procedures; the first figure is the mean of the second quinquennial period (1984-88) and the second figure the total for 1988. After correction for the standardised mortality ratio and catchment area, the national requirement should lie between 690 and 1070 coronary angiograms and 390 and 600 coronary artery bypass graft operations per million population each year. There is a further national requirement for 70 valvar heart operations and 30 miscellaneous procedures per million population each year. Owing to delays in the provision of services, 20 patients died of a cardiovascular cause while they were on the waiting list for investigation or surgery. In the United Kingdom the annual target to be achieved by 1990 was 300 coronary artery bypass procedures per million population.

Is Blood Conservation Optimally Utilized?

Blood conservation and the subsequent prevention of transfusion have assumed an increasingly important role in cardiac surgery. The concern is one of preventing transmission of transfusion related diseases and of conserving an extremely valuable resource (1,2). Cardiac surgery with cardiopulmonary bypass has become the most common operation performed, thus attracting much analysis of transfusion practices. It is estimated that of the approximately 250,000 cardiopulmonary bypass procedures done in the United States each year, the majority require transfusion of blood products (3). It has been calculated that the cardiac surgery services throughout the United States use somewhat over 10% of all the blood product resources that are transfused in this country (4,5). Many methods of blood conservation have been described (Table 1), but there still exists a wide variance in blood product utilization for adult patients undergoing cardiopulmonary bypass procedures. A review of the literature reveals average packed red blood cell transfusion rates from 0.3 up to 8 units per patient (4,6-8). If we further add the transfusion of platelets, fresh frozen plasma, and cryoprecipitate, the total donor exposure to the patient goes up substantially more. A varied patient population has been cited as the reason for these discrepancies but it has been demonstrated in similarly matched groups of patients receiving transfusions, that the patterns were based to some extent upon "prevailing practice" rather than on need (9,10). The purpose of this study was to identify which methods of blood conservation were being practiced in a major metropolitan area within the United States where the risk of transfusion related disease is relatively high. Secondly, to stratify the frequency of use of particular blood conservation methods in order to estimate how often a particular method was utilized and by what percentage of respondents. Finally, to increase the awareness of the options and difficulties associated with current modalities of transfusion practice and blood conservation.

Infection control in cardiopulmonary bypass procedures

Infection control in cardiopulmonary bypass procedures

The Effect of Lysed Platelets on Neutralization of Heparin In Vitro with Protamine as Measured by the Activated Coagulation Time (ACT)

The effect of lysed platelets on the activated coagulation time (ACT) was studied in heparinized whole blood during titration with protamine. Frozen-thawed washed platelet suspension, or a chromatography fraction thereof, or autologous frozen-thawed platelet-rich plasma was added in various dilutions to freshly drawn blood anticoagulated with 3,000 USP units/l heparin. After a 10 min incubation, the amount of protamine needed to restore the ACT to baseline ("protamine titration dose") was determined. We found that the protamine titration dose decreased in proportion to the amount of lysed platelet material added; expressed as a percentage of the total number of platelets present, each unit increase in lysed platelets produced a 1.7% +/- 0.8 (SD) reduction in the protamine dose needed to normalize the ACT. A heparin activity assay showed that this effect was not due to anti-heparin activity of lysed platelets such as platelet factor 4 (PF4). Our data indicate that the procoagulant activity of platelet membranes reduced the sensitivity of the ACT to heparin. These findings suggest that membranous platelet microparticles may cause an inaccurate calculation, based on the ACT, of a protamine dose to reverse heparin anticoagulation in cardiopulmonary bypass procedures.

Clinical comparison of two devices for detection of microemboli during cardiopulmonary bypass

Detection of gaseous microemboli during cardiopulmonary bypass procedures is important for the clinical evaluation of equipment such as oxygenators and cardiotomy reservoirs. Comparison of published data can be difficult if different detectors are used. Two devices reported in the literature, the Technique Laboratories TM-8 and the Hatteland BD-100, are compared during clinical procedures. The relationship between the outputs of these devices was linear over two ranges, the difference in output amounted to a standard deviation of 11% in the lower range and 38% in the upper range.