Pre-cardiopulmonary Bypass Research Articles

Alteration of the neonatal pulmonary physiology after total cardiopulmonary bypass

Objectives: The purpose of this study was to analyze the mechanisms associated with lung injury after cardiopulmonary bypass and to propose strategies of prevention. Methods: Thirty-two neonatal piglets underwent 90 minutes of hypothermic cardiopulmonary bypass without aortic crossclamping. Five experimental groups were defined: group I had standard cardiopulmonary bypass (control), group II received continuous low-flow lung perfusion during cardiopulmonary bypass, group III treatment was similar to that of group I with maintenance of ventilation, group IV received pneumoplegia, and group V received nitric oxide ventilation (30 ppm) after cardiopulmonary bypass. Data drawn from hemodynamic and gas exchange values and muscular and pulmonary tissular levels of adenosine triphosphate (in micromoles per gram) and myeloperoxidase (in international units per 100 mg) were used for comparisons before and 30 and 60 minutes after cardiopulmonary bypass. Pulmonary and systemic vascular endothelial functions were assessed in vitro after cardiopulmonary bypass on isolated rings of pulmonary and iliac arteries. Results: Pulmonary vascular resistance index, cardiac index, and oxygen tension were better preserved in groups II, IV, and V. All groups disclosed a significant decrease in lung adenosine triphosphate levels and an increase in myeloperoxidase activity whereas these levels stayed within pre–cardiopulmonary bypass ranges in muscular beds. Endothelium-dependent relaxation was preserved in systemic arteries but was strongly affected in pulmonary arteries after cardiopulmonary bypass. None of the methods that aimed to protect the pulmonary vascular bed demonstrated any preservation of pulmonary endothelial function. Conclusion: Cardiopulmonary bypass results in ischemia-reperfusion injury of the pulmonary vascular bed. Lung protection by continuous perfusion, pneumoplegia, or nitric oxide ventilation can prevent hemodynamic alterations after cardiopulmonary bypass but failed to prevent any of the biochemical disturbances. (J Thorac Cardiovasc Surg 1997;114:1061-9)

Sinus Venosus Atrial Septal Defect?

Sinus Venosus Atrial Septal Defect?

Relationship between leukocyte count and patient risk for excessive blood loss after cardiac surgery.

To evaluate the relationship between leukocyte counts and risk for excessive blood loss after cardiac surgery when including numerous demographic, operative, and laboratory factors in the comparison. A prospective, clinical evaluation. A point-of-care laboratory and the cardiac surgical unit of a university-affiliated tertiary center. Patient-related and hematologic variables were measured, using blood specimens obtained from 89 hospitalized patients who underwent cardiac surgery involving cardiopulmonary bypass. None. Demographic, operative, and transfusion-related data were recorded for each patient. Routinely obtained measurements of laboratory-based prothrombin time, partial thromboplastin time, complete blood count, and bleeding time were recorded. Hemoglobin concentration, platelet count, and red and white blood cell counts were measured with an on-site instrument before initiation (pre-cardiopulmonary bypass) and before discontinuation (end-cardiopulmonary bypass) of cardiopulmonary bypass. Hematocrit was calculated using recorded variables, and white blood cell percent change values were calculated using white blood cell counts from both periods, using the following formula: [(end-cardiopulmonary bypass - pre-cardiopulmonary bypass)/pre-cardiopulmonary bypass] x 100. When we excluded four patients who had a surgical source of post-cardiopulmonary bypass bleeding, significant (p < .0001) relationships were observed between white blood cell count (r2 = .46) and white blood cell percent change values (r2 = .71) and cumulative mediastinal chest tube drainage in the first 4 postoperative hours in 85 patients. Bayes theorem was used to evaluate the predictive ability of hematologic measurements in identifying patients with excessive bleeding (n = 24), defined as >1000 mL of cumulative chest tube drainage in the first 24 postoperative hours, when compared with patients without excessive bleeding (n = 61). Demographic and operative variables were similar between these patients except that patients with excessive bleeding required more red blood cell, platelet, and plasma transfusions during the postoperative interval. Significantly (p < .0001) greater white blood cell percent change values were obtained in the excessive bleeding cohort (119 +/- 93 percent change) when compared with patients without excessive bleeding (28 +/- 36 percent change). On-site measurements of white blood cell count, as an index of the inflammatory response to extracorporeal circulation, may be useful in identifying patients at increased risk for excessive bleeding. Further studies are needed to examine whether white blood cell counts during multiple cardiopulmonary bypass periods may identify patients with an exaggerated inflammatory response to extracorporeal circulation. By using this information, physicians may be able to intervene with anti-inflammatory medications and blood preservation techniques.

Effects of Nitric Oxide After Cardiac Transplantation in the Setting of Recipient Pulmonary Hypertension

Background. Recipient pulmonary hypertension secondary to chronic congestive heart failure is a significant risk factor for right ventricular failure after cardiac transplantation. In this study, the hemodynamic and inotropic effects of nitric oxide (NO) were examined after bicaval cardiac transplantation in the setting of monocrotaline pyrrole-induced recipient chronic pulmonary hypertension.Methods. Twenty dogs underwent 10 successfully completed transplantation experiments. Recipients underwent pulmonary artery injection of 3 mg/kg monocrotaline pyrrole 4 months before transplantation. Measurements were taken 1 hour after cessation of cardiopulmonary bypass and after NO inhalation. Pulmonary vascular impedance was calculated using Fourier analysis, and cardiac function was assessed with load-insensitive means (preload recruitable stroke work).Results. At the time of transplantation, the precardiopulmonary bypass levels of pulmonary vascular resistance in recipient animals were significantly greater when compared with donor levels, and were further significantly increased after cardiopulmonary bypass. Three recipients died after transplantation secondary to acute right ventricular failure. In the surviving animals, NO led to significant improvements in pulmonary vascular resistance and vascular impedance, which occurred in association with significant increases in transpulmonary efficiency. No significant changes were observed in right and left ventricular preload recruitable stroke work after NO inhalation.Conclusions. These data suggest that NO may be an effective means to improve vascular impedance and pulmonary vascular efficiency after cardiac transplantation in the setting of recipient chronic pulmonary hypertension.(Ann Thorac Surg 1997;63:1546–55)

Effects of Nitric Oxide After Cardiac Transplantation in the Setting of Recipient Pulmonary Hypertension

Background. Recipient pulmonary hypertension secondary to chronic congestive heart failure is a significant risk factor for right ventricular failure after cardiac transplantation. In this study, the hemodynamic and inotropic effects of nitric oxide (NO) were examined after bicaval cardiac transplantation in the setting of monocrotaline pyrrole-induced recipient chronic pulmonary hypertension.Methods. Twenty dogs underwent 10 successfully completed transplantation experiments. Recipients underwent pulmonary artery injection of 3 mg/kg monocrotaline pyrrole 4 months before transplantation. Measurements were taken 1 hour after cessation of cardiopulmonary bypass and after NO inhalation. Pulmonary vascular impedance was calculated using Fourier analysis, and cardiac function was assessed with load-insensitive means (preload recruitable stroke work).Results. At the time of transplantation, the precardiopulmonary bypass levels of pulmonary vascular resistance in recipient animals were significantly greater when compared with donor levels, and were further significantly increased after cardiopulmonary bypass. Three recipients died after transplantation secondary to acute right ventricular failure. In the surviving animals, NO led to significant improvements in pulmonary vascular resistance and vascular impedance, which occurred in association with significant increases in transpulmonary efficiency. No significant changes were observed in right and left ventricular preload recruitable stroke work after NO inhalation.Conclusions. These data suggest that NO may be an effective means to improve vascular impedance and pulmonary vascular efficiency after cardiac transplantation in the setting of recipient chronic pulmonary hypertension.(Ann Thorac Surg 1997;63:1546–55)

Pulmonary vascular permeability after cardiopulmonary bypass and its relationship to oxidative stress.

To assess the relationship between oxidative stress resulting from cardiopulmonary bypass and the onset of increased pulmonary vascular permeability. Prospective, controlled study. Adult intensive care unit of a postgraduate teaching hospital. Ten patients undergoing surgery requiring cardiopulmonary bypass, and seven normal subjects. Cardiopulmonary bypass in ten patients undergoing surgery. Protein accumulation index was measured in patients after surgery and in normal subjects as a marker of increased pulmonary vascular permeability. Plasma markers of lipid peroxidation (lipid peroxides and thiobarbituric acid-reactivity), plasma chelatable iron, total non-heme iron, transferrin, and primary plasma proteinaceous antioxidant activities were measured before and after cardiopulmonary bypass, and compared with those values found in normal subjects. Protein accumulation index was significantly higher (1.79 +/- 0.54 [SEM]) in the postcardiopulmonary bypass patients compared with healthy subjects (0.33 +/- 0.07, p < .05). Concentrations of lipid peroxides precardiopulmonary bypass were similar to those concentrations in control patients (0.020 +/- 0.003 vs. 0.031 +/- 0.002 nmol/mg protein), but were significantly increased postcardiopulmonary bypass (0.114 +/- 0.010 nmol/mg protein, p < .01). Thiobarbituric acid-reactive substances were higher precardiopulmonary bypass than those in controls (0.052 +/- 0.01 vs. 0.019 +/- 0.01), and increased postcardiopulmonary bypass (0.072 +/- 0.012), although they did not reach significance. Bleomycin-chelatable iron, indicative of transient plasma iron-overload, was only found in one patient (6.5 mumol/L) postcardiopulmonary bypass. Total plasma non-heme iron concentrations before cardiopulmonary bypass were similar to those concentrations in normal control patients (0.19 +/- 0.03 vs. 0.22 +/- 0.015 nmol/mg of protein), and significantly increased postcardiopulmonary bypass (0.48 +/- 0.08, p < .01). Transferrin concentrations were lower in cardiopulmonary bypass patients (2.43 +/- 0.17 vs. 2.89 +/- 0.03 g/L) than in controls and significantly decreased postcardiopulmonary bypass (1.55 +/- 0.09 g/L, p < .01). High plasma iron concentrations with a lower level of transferrin, postcardiopulmonary bypass, gave significantly increased mean percentage iron-saturation of transferrin, increasing from 27.1% to 61.7% (p < .01). Proteinaceous primary antioxidant activities, measuring iron-binding and iron-oxidizing protection of peroxidizing lipid membranes, were both significantly decreased postcardiopulmonary bypass (83.7 +/- 3.71% pre and 26.6 +/- 8.42% post, p < .01, and 51.2 +/- 2.96% pre and 29.0 +/- 2.94% post, p < .01, respectively). In 90% of the cardiopulmonary bypass patients, there was a significant correlation between the percent increase in iron saturation of transferrin and the protein accumulation index. Pulmonary vascular permeability was significantly increased in patients postcardiopulmonary bypass compared with normal subjects. This patient population also had significantly increased plasma markers of lipid peroxidation compared with normal subjects. Cardiopulmonary bypass induced further increases in lipid peroxidation products but a substantial decrease in proteinaceous primary antioxidants. In the majority of patients, there was a significant correlation between the iron saturation of transferrin and the protein accumulation index.

Control of Oxygen Cytotoxicity With Allopurinol and Superoxide Dismutase: A Canine Model of Global Myocardial Ischemia-Reperfusion Injury

The purpose of this study was to assess the effects of acute pharmacological interventions on the ischemia-reperfusion damage in a canine model of hypothermic global myocardial ischemia. Three experimental groups each consisting of seven animals were subjected to 2 h of global ischemia followed by 1 h of reperfusion. Group A (control) used Tyers' isoosmolar potassium cardioplegia solution; group B received allopurinol (40 mg/kg), 95% intravenously (IV) systemically with 5% added to the final infusion of Tyers' solution. In group C, superoxide dismutase (6.5 mg/kg) was used, one third of the total dose in the final delivery of the Tyers' cardioplegia solution and two thirds IV during the initial 5 min of reperfusion. In all three groups, myocardial temperature was maintained between 15 and 19°C. Methods of evaluation included hemodynamic and echocardiographic parameters of ventricular function. Assessment was performed at three time periods: pre-cardiopulmonary bypass (control), 60 min postreperfusion and immediately post-volume loading (at 2 h after cardiopulmonary bypass). No significant deterioration of myocardial function was observed in either of the experimental groups after the use of these preservation techniques. Comparison of regression slopes based on analysis of covariance for myocardial performance, systolic function, and diastolic compliance did not demonstrate any significant differences between the groups. Two hours of global ischemia was not sufficient to cause measurable damage to the myocardium on the basis of which the pharmacological intervention with allopurinol and superoxide dismutase could be evaluated. The controversy surrounding the use of allopurinol and superoxide dismutase is discussed with the findings of this experimental protocol and is brought up for scientific dialogue.

Platelet Activating Factor and Thromboxane B2 Production After Cardiopulmonary Bypass

Platelet-activating factor (PAF) is believed to have a central role in the pathogenesis of ischemia-reperfision injury. The purpose of this study was to investigate the relationships among production of PAF, thromboxane B2 (TαB2), and cardiopulmonary sequelae in patients undergoing coronary artery bypass graft surgery (CABGS). Venous blood from nine patients (eight men, one woman) undergoing scheduled CABGS, was sampled from central venous catheters before anesthetic induction, pre-cardiopulmonary bypass (CPB), 10 and 30 minutes post-CPB, 10 and 30 minutes post-aortic declamping, and 120 minutes and 24 hours after the conclusion of CPB. Plasma levels of PAF and TαB2 were determined by radioimmunoassay kits (Amersham Canada Ltd.). PAF and TαB2 were significantly different between high-risk patients (group I; Canadian Cardiovascular Society class 3-4; n = 4) and low-risk patients (group II; Canadian Cardiovascular Society class 2; n = 5): group I PAF = 960 pg/mL, group II PAF = 159 pg/mL (P = 0.0029); group I TαB2 = 320 pg/mL, group II TαB2 = 229 pg/mL (P = 0.0262). Group I PAF was significantly greater than group II PAF: before CPB = 825 pg/mL (group I), 138 pg/mL (group II); during initiation of CPB = 1600-2015 pg/mL (group I), 158-200 pg/mL (group II) (P = 0.0143). Correlations between duration of CPB and peak PAF (r = 0.7049, P = 0.0339), peak PAF level, and time to extubation (r = 0.8863, P = 0.0079) were significant. PAF levels were different in patients requiring postoperative epinephrine (2124 ± 700 pg/mL) or dopamine (667 ± 266 pg/mL) (P = 0.0042). The production of PAF is determined by preoperative patient characteristics and duration of CPB. Increased levels of PAF in patients with unstable angina, left main coronary artery disease, or recent myocardial infarction are associated with the need for increased inotropy and prolonged ventilatory support following CABGS. The degree of PAF production during CPB may be a factor in postoperative instability in high-risk patients.

Relative Changes in Cerebral Blood Flow During Cardiac Operations Using Xenon-133 Clearance Versus Transcranial Doppler Sonography

Background. Changes in cerebral blood flow (CBF) during cardiac operations have implications in terms of postoperative neurologic and neuropsychological dysfunction. Current techniques of CBF measurement are cumbersome and invasive. Transcranial Doppler sonography offers a noninvasive means of assessing changes in CBF. The aim of this study was validation of this technique with existing methods of CBF measurement during cardiac operations. Methods. We compared the changes in CBF using xenon-133 clearance with changes in middle cerebral artery velocity by transcranial Doppler sonography (V MCA) using pH-stat and alpha-stat acid-base management during cardiopulmonary bypass. Measurements were taken (1) before bypass, (2) at 28°C on bypass, (3) at 37°C on bypass, and (4) after bypass. Relative changes in CBF and V MCA, calculated as the percent change from the prebypass baseline value normalized to 100%, were used in this analysis. Results. During the hypothermic phase of cardiopulmonary bypass, CBF and V MCA increased by 45.9% and 51.8%, respectively ( p < 0.001), during pH-stat acid-base management but decreased by only 26.4% and 22.4%, respectively ( p < 0.0001), during alpha-stat acid-base management. Linear regression analysis of the absolute changes in CBF (mL·100 g −1·min −1) and V MCA (cm/s) showed a significant correlation ( r = 0.60; r 2 = 0.36; p < 0.0001), but a better correlation was obtained when relative changes in CBF and V MCA were compared ( r = 0.89; r 2 = 0.79; p < 0.0001). Conclusions. Measurements of V MCA, expressed as relative changes of a pre-cardiopulmonary bypass level (using the noninvasive transcranial Doppler sonographic technique), can be used to examine CBF changes during cardiopulmonary bypass. (Ann Thorac Surg 1997;63:167–74)

Perioperative lymphocyte adenylyl cyclase function in the pediatric cardiac surgical patient.

To examine intraoperative and postoperative lymphocyte adenylyl cyclase activities in children undergoing repair of congenital cardiac defects with hypothermic cardiopulmonary bypass. A prospective study. Tertiary university pediatric hospital. Twelve children were enrolled into the study to examine intraoperative lymphocyte adenylyl cyclase activities and 12 children were enrolled to examine postoperative lymphocyte adenylyl cyclase activities. None. Basal (unstimulated), isoproterenol, and prostaglandin E-1 stimulated adenylyl cyclase activities, and plasma norepinephrine and epinephrine concentrations were measured. Intraoperative basal (unstimulated), beta-adrenergic receptor-stimulated (in response to isoproterenol), and prostaglandin E1 (PGE1)-stimulated lymphocyte adenylyl cyclase activities all increased during cardiopulmonary bypass, then decreased immediately after cardiopulmonary bypass. In the postoperative group, a significant decrease in basal (unstimulated), beta-adrenergic receptor- and PGE1-stimulated adenylyl cyclase activities were observed on postoperative day 1 as compared with precardiopulmonary bypass values. In the pediatric cardiac surgical patient, there was an intraoperative enhancement of lymphocyte adenylyl cyclase activities. This increase in adenylyl cyclase activities was followed by reduced lymphocyte adenylyl cyclase activities, including beta-adrenergic receptor desensitization, postoperatively, as we have previously documented in adults.

Atrial Fibrillation Following Coronary Artery Bypass Graft Surgery

To determine the incidence, predictors, and cost of atrial fibrillation and flutter (AFIB) following coronary artery bypass graft (CABG) surgery. Prospective observational study (MultiCenter Study of Perioperative Ischemia). Twenty-four university-affiliated hospitals in the United States from 1991 to 1993. A total of 2417 patients undergoing CABG with or without concurrent valvular surgery selected using a systematic sampling interval. Detailed preoperative, intraoperative, and postoperative data collected on standardized reporting forms. The overall incidence of postoperative AFIB was 27 percent. Independent predictors of postoperative AFIB included advanced age (odds ratio [OR], 1.24 per 5-year increase; 95 percent confidence interval [CI], 1.18-1.31); male sex (OR, 1.41; 95 percent CI, 1.09-1.81); a history of AFIB (OR, 2.28; 95 percent CI, 1.74-3.00); a history of congestive heart failure (OR, 1.31; 95 percent CI, 1.04-1.64); and a precardiopulmonary bypass heart rate of more than 100 beats per minute (OR, 1.59; 95 percent CI, 1.00-2.55). Surgical practices such as pulmonary vein venting (OR, 1.44; 95 percent CI, 1.13-1.83); bicaval venous cannulation (OR, 1.40; 95 percent CI, 1.04-1.89); postoperative atrial pacing (OR, 1.27; 95 percent CI, 1.00-1.62); and longer cross-clamp times (OR, 1.06 per 15 minutes; 95 percent CI, 1.00-1.11) also were identified as independent predictors of postoperative AFIB. Patients with postoperative AFIB remained an average of 13 hours longer in the intensive care unit and 2.0 days longer in the ward when compared with patients without AFIB. Postoperative AFIB is common after CABG surgery and has a significant effect on both intensive care unit and overall hospital length of stay. In addition to expected demographic factors, certain surgical practices increase the risk of postoperative AFIB. Randomized controlled trials are necessary to determine if modification of these surgical practices, especially in patients at high risk, would decrease the incidence of postoperative AFIB.

Intraoperative Ventricular Tachycardia Responsive to Adenosine

Intraoperative Ventricular Tachycardia Responsive to Adenosine

762-3 Modified Ultrafiltration Reduces Airway Pressures and Improves Lung Compliance After Congenital Heart Surgery

Following surgery for congenital heart disease (CHD) decreased Dynamic Compliance (DC) (Δvolume/Δpressure) results in increased airway pressures, impaired cardiovascular function and prolonged mechanical ventilation. Modified ultrafiltration (MUF) reduces total body water, promotes hemoconcentration after separation from cardiopulmonary bypass (CPB), and may improve cardiorespiratory performance. MUF is accomplished by connecting the arterial cannula in series to a roller pump, an ultrafilter and the venous cannula. To determine the acute effects of CPB and MUF on respiratory mechanics (RM) after surgery for CHD, 18 pts were evaluated. The control (CTL) group consisted of 7 pts age 1 wk–9 mo and wgt 2.5–7 kg. The 11 successive pts who underwent MUF were aged 1 wk–9 yrs and wgt 3.5–23.9 kg. Diagnoses of the study group included TOF (3), AVSD (2), AS (1), cor triatriatum (1), DORV (1), HLHS (1), MS (1) and truncus arteriosus (1). RM were measured in the OR using a pneumotach and RM monitor. The peak airway pressure and peak end expiratory pressure were obtained Pre CPB, Post CPB and Post MUF (20 min post CPB in CTL group) with the tidal volume held constant. Following 17 ± 2 min of MUF, the HCT increased from 17 ± 1 to 39 ± 3% p = 0.0002. Group Pre CPB DC Post CPB DC Post MUF or 20 min post CPB DC CTL (n = 7) 4.8 ± 0.8 3.7 ± 0.5 * 3.8 ± 0.4 * MUF (n = 11) 11.3 ± 33 8.0 ± 2.2 # 10.1 ± 2.3 τ * = P &lt; 0.05 vs Ctl Pre CPB # = P&lt; 0.05 τ = p = ns vs MUF Pre CPB In the CTL group there was a significant reduction in DC after CPB which persisted 20 min after CPB. However, in the MUF group the reduction in DC after CPB was reversed by MUF. MUF improves DC, possibly due to a reduction in lung water. By increasing DC, MUF allows a reduction in airway pressures thereby potentially decreasing the negative impact of elevated airway pressures on cardiovascular function and improving cardiorespiratory interactions. These acute findings suggest that MUF may improve cardiorespiratory function thereby decreasing length of ventilation and length of hospital stay. Randomized studies are therefore indicated.

Cardiorespiratory response of intravenous angiotensin-converting enzyme inhibitor enalaprilat in hypertensive cardiac surgery patients

Twenty-four patients undergoing elective coronary artery bypass surgery were studied. Either the angiotensin-converting enzyme (ACE) inhibitor enalaprilat, 0.06 mg/kg, ( n = 12), or saline solution (=control group; n = 12), was randomly and blindly administered intravenously when the mean arterial blood pressure (MAP) increased to 90 mmHg after induction of anesthesia. Cardiorespiratory parameters were studied before injection, during the subsequent 30 minutes, precardiopulmonary bypass (CPB), post-CPB, and at the end of surgery. MAP was significantly reduced 5 minutes after administration of enalaprilat. The peak reduction of blood pressure was observed after 30 minutes (from 98 ± 4 to 68 ± 8 mmHg). Even immediately before CPB (112 ± 12 minutes after injection of enalaprilat), MAP and systemic vascular resistance were significantly lower than baseline values. Heart rate remained almost unchanged in both groups. Cardiac index increased slightly in the enalaprilat patients (maximum: +0.75 L/min/m 2 20 minutes after injection). Filling pressures (central venous pressure, pulmonary capillary wedge pressure) were also significantly reduced by enalaprilat. There were no differences from the control patients with regard to changes in right ventricular hemodynamics (right ventricular ejection fraction, right ventricular end-diastolic volume, right ventricular end-systolic volume), pulmonary gas exchange (PaO 2), or intrapulmonary right-to-left shunting (Qs/Qt). VO 2 increased only in the enalaprilat patients (from 179 ± 28 to 230 ± 30 mL/min) ( p < 0.05). Cardiorespiratory parameters did not differ between the two groups post-CPB. No significant differences in the use of inotropes or vasoconstrictors were found during the entire investigation period. It is concluded that intravenous (IV) administration of the ACE inhibitor enalaprilat was effective in reducing blood pressure in patients with coronary artery disease with hypertension after induction with fentanyl/midazolam. Lack of a reflex increase in heart rate and reduction in left ventricular afterload indicated a decrease in myocardial oxygen consumption, which is of particular importance in coronary artery surgery patients. Improved tissue perfusion can be assumed because of the increase in oxygen consumption, whereas pulmonary gas exchange remained unchanged. Thus, IV enalaprilat enlarges the armamentarium for treating hypertension and can be recommended in patients with coronary artery disease undergoing cardiac surgery.

Total intravenous anesthesia using propofol and alfentanil for coronary artery bypass surgery

Total intravenous anesthesia (TIVA) using alfentanil and propofol was used in 10 patients undergoing coronary artery bypass grafting. In an attempt to diminish unwanted side effects, lower doses were chosen than if either drug had been used alone. Anesthesia was induced with alfentanil, 75 μg/kg, followed by a sleep dose of propofol (mean dose 0.5 mg/kg). Maintenance in the precardiopulmonary bypass (CPB) period was achieved by infusions of propofol (6 mg/kg/h) and alfentanil (100 μg/kg/h). These were decreased by two thirds on commencement of CPB, and increased to half the initial rate on rewarming to 32°C. Additional boluses of alfentanil were used to control breakthrough hypertension. The mean arterial pressure (MAP) and left ventricular stroke work index (LVSWI) fell significantly on induction. MAP but not LVSWI returned to baseline levels at skin incision. The cardiac index (Cl) was maintained. A degree of myocardial depression was suggested by a fall in LVSWI despite maintaining preload, and by the failure of CI to increase in the presence of a reduced SVR. Anesthesia was satisfactory in all but one patient who developed break-through hypertension on sternotomy with transient ST segment depression, and awareness after CPB despite a plasma alfentanil concentration of 450 ng/mL. Mean time to wakening was 55 minutes. The study indicated that TIVA using propofol and alfentanil in the dosages described provides satisfactory basal anesthesia for coronary artery bypass surgery in patients with good left ventricular function, but requires additional pharmacologic manipulation, particularly with boluses of alfentanil, to control breakthrough hypertension.

Neutrophil Lactoferrin Release During Open Heart Surgery Is Unrelated to Complement Activation

The relationship between neutrophil activation and complement activation during open heart surgery was evaluated by measuring plasma lactoferrin and C3a des Arg (C3a) in 30 adult patients undergoing coronary artery surgery. Measurements were made before induction of anesthesia, before cardiopulmonary bypass, at the end of bypass, and 10 min after protamine infusion. Changes in the measured parameters thus reflected activation during the three distinct phases of cardiac surgery: pre cardiopulmonary bypass, the bypass phase, and the heparin neutralization phase. A major rise in lactoferrin occurred in the pre bypass period, from 99 +/- 13 (mean +/- SEM) to 647 +/- 48 ng/ml (p < 0.001). During this time, C3a levels did not rise significantly (384 +/- 22 to 439 +/- 36 ng/ml). The bypass procedure resulted in a rise of both lactoferrin and C3a levels, with lactoferrin reaching 1,092 +/- 69 ng/ml and C3a increasing to 1,884 +/- 179 ng/ml after bypass (p < 0.001 for both). In individual patients, however, the changes in lactoferrin during bypass did not correlate with changes in C3a levels (r = -0.06). After protamine infusion, C3a levels reached 3,301 +/- 324 ng/ml, while the plasma lactoferrin levels declined to 522 +/- 57 ng/ml. Thus, during open heart surgery, neutrophil activation, as measured by plasma lactoferrin concentration, does not correlate with complement activation resulting from the bypass procedure or the protamine neutralization of heparin. The potential clinical relevance of the neutrophil granular release of lactoferrin is discussed.

Myocardial Metabolic and Hemodynamic Changes During Propofol Anesthesia for Cardiac Surgery in Patients with Reduced Ventricular Function

This study examined the hypothesis that the use of propofol for induction and maintenance of anesthesia in patients with reduced ejection fraction (< 0.5) undergoing coronary artery revascularization would not be associated with a greater degree or incidence of myocardial ischemia as compared to patients receiving a moderate dose sufentanil-enflurane anesthetic technique. Two groups of patients were assigned randomly to receive one of two propofol anesthetic regimes. Group A (n = 21) received propofol 1-2 mg/kg as the induction drug and sufentanil 0.03 micrograms.kg-1.min-1 (fixed rate) plus propofol 50-200 micrograms.kg-1.min-1 (variable rate) infusions for maintenance of anesthesia. Group B (n = 21) received sufentanil 5 micrograms/kg for induction and propofol 50-200 micrograms.kg-1.min-1 (variable rate) infusion for maintenance of anesthesia. For comparison, a third group (Group C, n = 18) was studied subsequently. This group received sufentanil 5 micrograms/kg for induction of anesthesia which was maintained with enflurane. Adverse hemodynamic changes (hypertension, tachycardia) were managed by additional propofol (Groups A and B), sufentanil (Group C), or vasopressors (hypotension). Hemodynamic and myocardial metabolic profiles were measured when awake and sedated and at postinduction, postintubation, postincision, poststernotomy, and precardiopulmonary bypass times. Ischemia was assessed by measuring myocardial lactate production. The incidence of myocardial lactate production was reduced in Group B as compared to Group C (Group A, 45/126; Group B, 23/126; Group C, 58/107; P < 0.05). Myocardial lactate flux declined in all groups as surgery progressed; but apart from the reduction in flux (indicative of increased ischemia) noted in Group C versus Group B postinduction, no between-group differences were detected.(ABSTRACT TRUNCATED AT 250 WORDS)

Platelet Dysfunction During Cardiopulmonary Bypass Surgery With Special Reference to Platelet Membrane Glycoproteins

Changes in platelet membrane glycoproteins (GPIb, GPIIb/IIIa, and GMP-140) were evaluated using flow cytometry after binding with monoclonal antibodies in 22 adult patients undergoing cardiopulmonary bypass (CPB) surgery. The amount of GPIb on platelets decreased significantly during CPB, reaching a minimum level of 64 +/- 26% of the pre CPB value at 120 min of CPB. There was no significant change in the amount of GPIIb/IIIa on platelets. In accordance with these changes, ristocetin induced agglutination decreased to 56.7 +/- 16.2% of the pre CPB value during CPB. However, there were no significant changes in ADP and collagen induced aggregation throughout the procedure. The number of the activated platelets expressing GMP-140 on their surfaces increased significantly during CPB. There was an upper limit to the amount of GMP-140 expression on each platelet in the circulating blood, suggesting that excessively activated platelets are removed from the circulation. The authors conclude that CPB reduces the amount of GPIb on platelets, which results in platelet dysfunction. In addition, removal of excessively activated platelets from the circulation may lead to thrombocytopenia after CPB.

Does transesophageal echocardiography improve postoperative outcome in patients undergoing coronary artery bypass surgery?

The incidence and characteristics of ischemic episodes as detected by transesophageal echocardiography (TEE) and their relationship to postoperative myocardial infarction (MI) and adverse clinical outcome were studied in patients under-going coronary artery bypass grafting (CABG). Seventeen of 50 patients had 21 TEE-defined ischemic episodes: 4 patients (8%) had 4 ischemic episodes in the pre-cardiopulmonary bypass (CPB) period, and 15 patients (30%) had 17 ischemic episodes in the post-CPB period, whereas 19 patients had 20 ECG ischemic episodes: 3 patients (6%) had 3 ischemic episodes in the pre-CPB period and 17 (34%) had 17 ischemic episodes in the post-CPB period. In 14 patients, ischemic episodes were detected by both TEE and ECG. Clinicians were made aware of the TEE data and appropriate treatments were undertaken during ischemic episodes: of the 15 patients with TEE-defined post-CPB ischemia, 4 had an additional saphenous vein graft placed, 8 had an intra-aortic balloon pump (IABP) inserted, 3 were given sublingual nifedipine, and 13 received nitroglycerin. These treatments resulted in improvement in regional wall motion abnormalities (RWMA) by the end of surgery in 11 of the 15 patients (73%), including the 4 with postoperative MI and 2 who died with cardiogenic shock. The authors conclude that: (1) significantly more patients had TEE-defined ischemic episodes in the post-CPB period (30%) than in the pre-CPB period (8%); (2) a poor graft and/or inadequate myocardial protection were strongly suggestive of post-CPB ischemia, which was significantly related to adverse outcome; and (3) TEE was a useful tool enabling detection of problem areas at an early stage and timely and appropriate treatment to support and sustain patients.

The P3a wave of the auditory event-related potential reveals registration of pitch change during sufentanil anesthesia for cardiac surgery.

The N1 and P3 waves of the auditory event-related potential provide information on consciousness and cortical function. The N1 wave is reduced during states of low vigilance. The P3 wave occurs only for stimuli that somehow capture the subject's attention. There are two types of P3:P3a and P3b. The P3a predominates frontally and probably occurs when the subject simply notices the stimulus. The P3b predominates parietally and indicates conscious awareness of the evoking stimulus. The N1 and P3 were recorded in 12 patients during cardiac surgery under sufentanil anesthesia to search for unintentional awareness. The study was limited to the period before cardiopulmonary bypass. After premedication with diazepam, morphine, and scopolamine, sufentanil was used for induction (mean dose, 7.9 micrograms/kg) and maintenance (4 micrograms/kg) of anesthesia. No other anesthetics were administered. Recordings were obtained before induction, during induction after loss of consciousness, after tracheal intubation before incision, and before cardiopulmonary bypass. The N1 was attenuated significantly by sufentanil but was not abolished. The P3b occurred only during preinduction. There was no P3 during induction. There was a P3a during postintubation and precardiopulmonary bypass. The attenuation of N1 from induction onward reflects a decrease in the level of arousal caused by sufentanil. A P3a during postintubation and precardiopulmonary bypass indicates that pitch discrimination at the cortical level occurs but does not prove that conscious awareness has occurred. Whether or not the P3a reflects the regaining of consciousness is not known.