Defining oliguria during cardiopulmonary bypass and its relationship with cardiac surgery-associated acute kidney injury.

BACKGROUND: While urine flow rate ≤0.5 ml kg-1 h-1 is believed to define oliguria during cardiopulmonary bypass (CPB), it is unclear whether this definition identifies risk for acute kidney injury (AKI) . The purpose of this retrospective study was to evaluate if urine flow rate during CPB is associated with AKI. METHODS: Urine flow rate was calculated in 503 patients during CPB. AKI in the first 48 h after surgery was defined by the Kidney Disease: Improving Global Outcomes classification. Adjusted risk factors associated with AKI and urine flow rate were assessed. RESULTS: Patients with AKI [n=149 (29.5%)] had lower urine flow rate than those without AKI (P<0.001). The relationship between urine flow and AKI risk was non-linear, with an inflection point at 1.5 ml kg-1 h-1 Among patients with urine flow <1.5 ml kg-1 h-1, every 0.5 ml kg-1 h-1 higher urine flow reduced the adjusted risk of AKI by 26% (95% CI 13-37; P<0.001). Urine flow rate during CPB was independently associated with the risk for AKI. Age up to 80 years and preoperative diuretic use were inversely associated with urine flow rate; mean arterial pressure on CPB (when <87 mmHg) and CPB flow were positively associated with urine flow rate. CONCLUSIONS: Urine flow rate during CPB <1.5 ml kg-1 h-1 identifies patients at risk for cardiac surgery-associated AKI. Careful monitoring of urine flow rate and optimizing mean arterial pressure and CPB flow might be a means to ensure renal perfusion during CPB. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov NCT00769691 and NCT00981474.

Radiation induced valvulitis with late leaflet rupture.

Various cardiac sequelae of mediastinal irradiation have been reported, from pericarditis to conduction defects. Despite the potentially fatal nature of some of these abnormalities, many may present with few or no symptoms. In this case report, the patient, who had received 4000 rads to the mediastinum 24 years previously, presented with worsening shortness of breath and two episodes of lightheadedness. Subsequently, he was found to have aortic valve rupture associated with fibrosis. A review of the literature indicates that valve rupture is a novel consequence of mediastinal radiation.

Amiodarone versus a beta-blocker to prevent atrial fibrillation after cardiovascular surgery.

BACKGROUND: Both amiodarone and beta-blockers have been shown to decrease the incidence of atrial fibrillation after cardiovascular surgery. However, the superior agent has not been identified. METHODS: We performed a pilot study on 102 patients (68 men, mean age 65 +/- 10 years, mean left ventricular ejection fraction 0.53 +/- 0.12) undergoing cardiovascular surgery (94 coronary artery bypass grafting [CABG], 5 valvular surgery only, and 3 CABG + valvular surgery). The patients were randomized to receive amiodarone (1 g/d intravenously x 48 hours, then 400 mg/d orally until discharge) or propranolol (1 mg intravenously every 6 hours x 48 hours, then 20 mg orally four times a day until discharge). Atrial fibrillation was defined as lasting longer than 1 hour or resulting in hemodynamic compromise. RESULTS: The incidence of postoperative atrial fibrillation was 16.0% (8/50) in the amiodarone group and 32.7% (17/52) in the propranolol group (P =.05). The mean length of stay was 8.8 +/- 3.5 days for amiodarone-treated patients and 8.4 +/- 2.7 days for propranolol-treated patients (P not significant). Serious adverse events were uncommon and similar in each group. CONCLUSION: Early intravenous amiodarone, followed by oral amiodarone, appears to be superior to propranolol in the prevention of postoperative atrial fibrillation. It is well tolerated and can be started at the time of surgery. However, the use of amiodarone did not result in a reduction in the length of hospital stay.

Atrial pacing for the prevention of atrial fibrillation after cardiovascular surgery.

OBJECTIVE: The purpose of this study was to determine the efficacy of atrial pacing in the prevention of atrial fibrillation following cardiovascular surgery. BACKGROUND: Although pharmacologic therapy has been used to help prevent postoperative atrial fibrillation, it suffers from limited efficacy and adverse effects. In the nonoperative setting, novel pacing strategies have been shown to reduce recurrences of atrial fibrillation and prolong arrhythmia-free periods in patients with paroxysmal atrial arrhythmias. METHODS: A total of 154 patients (115 men; mean age, 65 +/- 10 years; ejection fraction, 53 +/- 10%) undergoing cardiac surgery (coronary artery bypass surgery, 88.3%; aortic valve replacement, 4.5%; coronary bypass + aortic valve replacement, 7.1%) had right and left atrial epicardial pacing electrodes placed at the time of surgery. Patients were randomized to either no pacing, right atrial (RAP), left atrial (LAP) or biatrial pacing (BAP) for 72 h after surgery. Beta-adrenergic blocking agents were administered concurrently to all patients following surgery. RESULTS: There was a reduction in the incidence of postoperative atrial fibrillation from 37.5% in patients receiving no postoperative pacing to 17% (p < 0.005) in patients assigned to one of the three pacing strategies. The length of hospital stay was reduced by 22% from 7.8 +/- 3.7 days to 6.1 +/- 2.3 days (p = 0.003) in patients assigned to postoperative atrial pacing. The incidence of atrial fibrillation was lower in each of the paced groups (RAP, 8%; LAP, 20%; BAP, 26%) compared with patients who did not receive postoperative pacing (37.5%). CONCLUSION: Postoperative atrial pacing, in conjunction with beta-blockade, significantly reduced both the incidence of atrial fibrillation and the length of hospital stay following cardiovascular surgery. Additional studies are needed to determine the most effective anatomic pacing site.

The combination of propranolol and magnesium does not prevent postoperative atrial fibrillation.

BACKGROUND: Atrial fibrillation is a common complication of cardiovascular surgery. Beta-blockers have been shown to decrease the incidence of postoperative atrial fibrillation. However, the use of magnesium is more controversial. It was our hypothesis that adjunctive magnesium sulfate would improve the efficacy of beta-blockers alone in the prevention of postoperative atrial fibrillation. METHODS: We prospectively randomized 167 coronary artery bypass patients (mean age 61+/-10 years, 115 men) to receive propranolol alone (20 mg four times daily) or propranolol and magnesium (18 g over 24 hours). Magnesium was begun intraoperatively, and propranolol was started on admission to the intensive care unit. RESULTS: Using an intention-to-treat analysis, the incidence of postoperative atrial fibrillation was 19.5% in the propranolol-treated patients and 22.4% in propranolol + magnesium-treated patients (p = 0.65). Because combination therapy resulted in an excess of postoperative hypotension, which required withholding doses of propranolol, an on-treatment analysis was also performed. In this analysis, the incidence of atrial fibrillation was still not significantly different (18.5% in propranolol-treated patients and 10.0% in propranolol + magnesium-treated patients, p = 0.20). CONCLUSIONS: Adjunctive magnesium sulfate, in combination with propranolol, does not decrease the incidence of postoperative atrial fibrillation.

Changing practice of coronary bypass surgery and its impact on early risk and long-term survival.

Over the past 20 years, a steady evolution in cardiac surgical techniques for coronary bypass graft (CABG) surgery has occurred. Recent reports are refining our knowledge of early and late survival after CABG surgery. Studies have documented the changing importance of well-recognized risk factors. New models that take into account multiple factors and that predict early risk of CABG surgery with good reliability have been developed. Long-term survival has been related to factors such as age, gender, diabetes mellitus, race, smoking history, left ventricular function, estrogen treatment in women, and serum lipids. Several recent studies provide insight into decision making regarding CABG versus catheter interventions for both primary and secondary revascularization. Data concerning new techniques, such as minimally invasive surgery, document promising results but also the anticipated learning curve of new procedures. Overall, favorable short-term and long-term survival results after CABG surgery continue to be reported despite an increasing elderly and complex patient group undergoing cardiovascular surgical procedures.

Comparison of results and risk factors of cardiac surgery in two 3-year time periods in the 1990s.

With the increasing number of treatment options for heart disease, decision-making requires profiles of risk for conventional cardiac surgery. Refinements in techniques and clinical practices seem to have reduced surgical risk. This study was performed to determine current risk factors. From July 1, 1990, to June 30, 1996, 1,036 consecutive patients underwent 1,042 heart operations using standard incisions and cardiopulmonary bypass with cardioplegia. Univariate and multivariate analyses using a logistic regression model were performed to determine factors significant for combined 30-day and hospital mortality. To determine if there were trends in the results and the risk factors, the last 500 consecutive cases in the series were analyzed separately. Overall, 30-day mortality was 17 of 1,042 (1.6%) and combined 30-day and hospital mortality was 27 of 1,042 (2.6%). Significant risk factors for combined 30-day and hospital mortality by multivariate analyses were: emergent/resuscitative status, preoperative dialysis, left ventricular ejection fraction < or = 30%, valve operation, and creatinine > or = 1.5 mg/dl. Comparison with baseline characteristics of the patients undergoing the last 500 consecutive operations to the earlier 542 operations in the study group showed that risk factors had a very similar profile for the 2 groups. The overall 30-day mortality for the last 500 consecutive operations was 5 of 500 (1.0%) and combined 30-day and hospital mortality was 8 of 500 (1.6%). The significant risk factors by multivariate analyses were reduced to left ventricular ejection fraction < or = 30% and creatinine > or = 1.5 mg/dl. These results indicate that modern techniques and clinical practices have mitigated well-recognized risk factors in conventional cardiac surgery and this trend is ongoing.

Early discharge of patients with new-onset atrial fibrillation after cardiovascular surgery.

BACKGROUND: Atrial fibrillation is one of the most frequent complications after cardiovascular surgery. It may result in thromboembolic events, hemodynamic deterioration, and an increased length and cost of hospitalization. METHODS: We retrospectively studied 504 consecutive adult patients undergoing cardiovascular surgery to determine whether patients with new-onset postoperative atrial fibrillation could be safely discharged in atrial fibrillation after ventricular rate had been controlled and anticoagulation initiated. RESULTS: Postoperative atrial fibrillation occurred in 79 (16.2%) of the 487 survivors. Of these patients, 67 were discharged in sinus rhythm, whereas the remaining 12 were discharged in atrial fibrillation. Patients discharged in atrial fibrillation tended to be older, have higher Parsonnet risk scores, and have an increased incidence of valvular heart surgery. Despite this result, this cohort had a shorter length of hospital stay (7.3+/-2.0 days vs 10.9+/-9.3 days, p = 0.006), decreased hospital costs ($14,188+/-$2635 vs $23,016+/-$21,963, p = 0.002), and decreased hospital charges ($37,878+/-$7420 vs $58,289+/-$50,980, p = 0.003) compared with patients with atrial fibrillation discharged in sinus rhythm. In the 12 persons discharged home in atrial fibrillation, no repeat hospitalizations, bleeding complications, or thromboembolic events occurred. CONCLUSION: A strategy of early discharge of patients with persistent postoperative atrial fibrillation appears promising and deserves prospective testing on a larger scale.

Pericostal sutures to reinforce sternal closure after cardiac surgery.

BACKGROUND AND AIM OF THE STUDY: An increasing number of elderly and medically complex patients are undergoing cardiac surgery and are at increased risk for sternal dehiscence. A technique of sternal closure reinforcement with pericostal wires is described, and results are reviewed. METHODS: After placement of the standard peristernal wires, one or two sets of pericostal wires were placed around ribs in the mid-portion of the sternotomy to reinforce the closure. A retrospective study over a 6-year period was carried out to determine the incidence of sternal dehiscence and any associated complications. Pericostal wires were used in well over 50% of cases. RESULTS: The incidence of sternal dehiscence was 4 out of 1048 operations (0.38%). No adverse effects of the pericostal wires were identified. CONCLUSIONS: Frequent use of pericostal wires is associated with a low incidence of sternal dehiscence.

Risks of cardiac operations for elderly patients: reduction of the age factor.

BACKGROUND: Age has been considered an important risk factor for cardiac operations. Recent refinements have been designed to reduce cardiac, neurologic, and renal complications. METHODS: Analysis of cardiac surgical outcomes including mortality, length of stay, complications, and costs were undertaken for a consecutive series of 285 patients 70 years old and older and 568 patients younger than 70 years who underwent operation during 1991 through 1995. Management included antegrade and retrograde cold and warm blood cardioplegia, epicardial echocardiography, retrosternal dissection for reoperations, maintenance of "normal" arterial pressure, and measures to avoid renal dysfunction. Parsonnet risk stratification and multiple regression were used to account for risk factors. RESULTS: The 30-day mortality rate for elderly patients was 1.8% (5/285) and 1.8% (10/568) for patients less than 70 years old (p = not significant). The hospital mortality rate for the elderly patients was 3.2% (9/285) versus 2.5% (14/568) for the younger group (p = not significant). The frequencies of complications were not different. Over the 5-year period, length of stay decreased from 12.5 +/- 1.5 days to 8.9 +/- 0.9 days for patients 70 years old and older and from 11.5 +/- 0.1 to 6.4 +/- 0.3 days for patients less than 70 years old. Hospital charges for the elderly group were 13% higher. CONCLUSIONS: Modern cardiac surgical techniques and clinical practices have reduced the importance of the age factor.

Urinary thromboxane B2 in cardiac transplant patients as a screening method of rejection.

Noninvasive methods for regular monitoring of cardiac transplant patients for acute rejection are preferable to the only currently accepted method involving frequent endomyocardial biopsies. Thromboxane A2 (TXA2) is synthesized in large amounts by monocytes/macrophages during organ graft rejection. It enhances T-lymphocyte clonal expansion and cytotoxic function as well as upregulating the major histocompatibility class II expression on antigen presenting cells. Experimentally increased urinary excretion of TXA2 metabolites is associated with cardiac transplant rejection. We therefore compared urinary immunoreactive thromboxane B2 (i-TXB2) levels to the rejection score of the endomyocardial biopsies. In addition we graded the degree of activated lymphocytes in peripheral blood. Urinary i-TXB2 was significantly higher in patients exhibiting medium to severe rejection than in patients without rejection (1236 +/- 372 vs. 526 +/- 57 pg/mL). The urine i-TXB2 (704 +/- 48 pg/mL) of all patients who participated in this study, whose endomyocardial biopsy indicated rejection, was also significantly higher than in the non-rejecting group. Increased levels of urine i-TXB2 were associated with increased biopsy scores. Circulating activated lymphocytes was also significantly increased in patients with moderate/severe rejection compared to patients with no rejection (66 +/- 11 vs. 39 +/- 4 per mm (3)) (p < 0.01). Further, this study shows that urine i-TXB2 is associated with increased endomyocardial biopsy scores (acute rejection scores) and blood lymphocyte activation. Thus we conclude that urine i-TXB2 may be of potential value as a diagnostic screening test for helping identify cardiac transplant patients undergoing acute rejection.

Current surgical treatment of valvular heart disease.

Surgery for valvular heart disease has undergone important refinements during the past several years. The general indications for valvular surgery are the presence of symptoms that interfere with the patient's lifestyle and that cannot be controlled with medical therapy, and indications of a threat to continued survival, such as angina, dyspnea, effort syncope or progressive impairment of ventricular contractility. Infective endocarditis may also be an indication for valvular surgery in patients with congestive heart failure, recurrent embolism, persistent infection despite antibiotic therapy, large vegetations or progressive conduction defects. Surgical procedures for the treatment of valvular heart disease include reconstruction techniques and valve replacement procedures. Reconstructive surgery minimizes the amount of materials that must be implanted. Advances in myocardial preservation have reduced the risk of such complex cardiac surgical procedures as multiple valve replacements and valve replacements combined with coronary artery bypass surgery. Follow-up care is important to monitor valve function, fluid balance and anticoagulation.

Cardiac operations in patients aged 70 years and over: mortality, length of stay, and hospital charge.

BACKGROUND: With emphasis today on cost containment in health care, the results and costs of cardiac operations in elderly patients are being scrutinized. METHODS: Our computerized database was used to obtain the characteristics of patients undergoing cardiac operations from January 1990 to July 1994. A study group of 628 patients aged 70 years and over was identified, and comparisons were made between them and adult patients less than 70 years of age. RESULTS: In the elderly group the 30-day mortality was 33 of 628 (5.3%), and the overall hospital mortality was 40 (6.4%). During this time the 30-day mortality for all adult patients less than 70 years old was 49 of 1787 (2.7%; p < 0.003) and the hospital mortality was 59 (3.3%; p < 0.001). The mean length of postoperative hospital stay (days +/- standard error) in all surviving patients aged 70 years and over was 11.6 +/- 0.4 days, compared with 8.5 +/- 0.2 days in patients less than 70 years old (p < 0.001). Over the time of the study the length of stay in patients less than 70 years old declined from 9.6 +/- 0.4 to 7.2 +/- 0.6 days, whereas it stayed the same for elderly patients. The 30-day mortality and length of stay increased with the risk category of the Parsonnet model. The mean hospital charge for patients aged 70 and over was 114% of that for younger patients. CONCLUSIONS: Although mortality, length of stay, and hospital charge are increased in patients 70 years of age and over, they are not excessively so. The results support the continued performance of cardiac surgical procedures in select elderly patients.

Desmopressin acetate in cardiac surgery: a double-blind, randomized study.

Use of desmopressin acetate (DDAVP) for patients having cardiac surgery is controversial. We did a double-blind, randomized study of 83 patients having cardiac operations at Georgetown University Hospital. The effect of DDAVP on bleeding as compared to placebo was evaluated by blood loss, replacement volume, and laboratory tests. There were no significant differences in baseline and intraoperative data between the DDAVP (n = 40) and placebo (n = 43) groups. Total drainage for the first 24 postoperative hours was 1,214 mL (+/- 78) for the DDAVP group and 1,386 mL (+/- 116) for the placebo group (not significant). There were no significant differences in replacement therapy. In this study, administration of DDAVP did not decrease bleeding.

Reduction of conjugated dienes in lung transplantation: effect of BN 52021.

Oxygen-derived free radicals have been identified as the mediators of tissue injury during reperfusion in organ transplantation. Lipid peroxidation of cell membrane polyunsaturated fatty acids, generating conjugated dienes (CD), is a toxicity of oxygen-derived free radicals. The CD structure in fatty acyl moieties was measured by high-pressure liquid chromatography in samples of inferior pulmonary venous blood and pulmonary tissue to assess reperfusion injury and oxygen-derived free radical-mediated damage in a canine model of left lung allotransplantation. The cold ischemic preservation interval was 6 hours and the posttransplantation monitoring period was 6 hours. Twenty-eight size- and weight-matched adult male dogs underwent left lung allotransplantation and were randomized to receive pulmonary artery flush of modified Euro-Collins (EC) (40 mL/kg) or University of Wisconsin (UW) (40 mL/kg) solutions alone or with the addition of the platelet-activating factor antagonist BN 52021 (10 mg/kg). When employed, BN 52021 was administered to donors 30 minutes before harvest and recipients 30 minutes before reperfusion. Left and right inferior pulmonary venous blood samples were obtained at baseline before transplantation and at 1, 2, 4, and 6 hours after transplantation; tissue samples were obtained after euthanasia. Serum and tissue CD levels are expressed as mean fraction of the total hydroperoxide sample +/- standard error of the mean. At 6 hours after transplantation, the EC group's (n = 7) CD fraction was 0.28 +/- 0.03, whereas that of the EC + BN 52021 group (n = 7) was 0.12 +/- 0.03 (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Platelet activating factor antagonist enhances lung preservation in a canine model of single lung allotransplantation.

Optimal techniques for lung preservation are yet to be defined. Platelet activating factor is a phospholipid released by a variety of cells and produces pulmonary abnormalities similar to posttransplantation pulmonary dysfunction. We investigated the strength of the effect of the platelet activating factor antagonist BN 52021 as compared with that of deferoxamine, an iron chelator previously shown to improve lung preservation. Differential lung function and pulmonary hemodynamics were used to assess preservation after a 6-hour period of cold ischemic storage in a modified canine model of left lung allotransplantation. Thirty size- and weight-matched mongrel male dogs were used for 15 transplant procedures randomized to one of three preservation techniques. The University of Wisconsin solution was used as the basic flush solution for all experimental animals. BN 52021 was added to the flush solution in one group (10 mg/kg, n = 5) and deferoxime in another group (10 mg/kg, n = 5). No additives were used for the control animals (n = 5). BN 52021 and deferoxime were administered to respective donor animals 30 minutes before organ harvesting (10 mg/kg) and to recipient animals 30 minutes before reperfusion (10 mg/kg). The pulmonary artery flush solution was administered (40 ml/kg) over 4 minutes. Recipient animals received double-lumen endotracheal tubes and were monitored with balloon-tipped, flow-directed catheters in both pulmonary arteries and dual-angle ultrasonic flow probes around each pulmonary artery. Solid-state high-fidelity micromanometers were used to measure pressures in the pulmonary artery, the left atrium, and the left ventricle. Systemic arterial, right and left pulmonary venous, and mixed venous blood samples were analyzed at 1, 2, 4, and 6 hours after transplantation. Pulmonary venous oxygen tension of the transplanted lung for the control group was 202 +/- 81 mm Hg versus 282 +/- 53 mm Hg for the BN 52021 group 6 hours after transplantation (p less than 0.05). Pulmonary vascular resistance of the transplanted lung for the control group was 319 +/- 54 dynes.sec.cm-5 versus 149 +/- 71 dynes.sec.cm-5 for the BN 52021 group (p less than 0.05). Proton magnetic resonance spectroscopy was performed on segments of upper and lower lobes of the native and transplanted lung from recipient animals to determine total lung water content. The BN 52021 group had a total lung water content of 57.3% as compared with 51.9% for the deferoxime group (p = not significant) and 88.6% for the control group (p less than 0.05).(ABSTRACT TRUNCATED AT 400 WORDS)

Iron chelation therapy and lung transplantation. Effects of deferoxamine on lung preservation in canine single lung transplantation.

Reperfusion injury is a limiting factor in lung transplantation. Deferoxamine is an iron chelator that inhibits the formation of oxygen-derived free radicals. We investigated the effects of deferoxamine on posttransplantation lung function in a canine model of single lung transplantation. Twelve dogs underwent left lung transplantation after 20- to 24-hour hypothermic storage in a modified Euro-Collins solution. In six experiments donor and recipient received a 10 mg/kg dose of deferoxamine before harvest and transplantation, and 10 mg/kg was added to the preservation solution. Arterial oxygen tension, alveolar-arterial oxygen difference, pulmonary vascular resistance, and dynamic lung compliance were measured. Data were recorded for 6 hours after ligation of the native pulmonary artery. At the end of the study the mean arterial oxygen tension was 175.1 mm Hg for the deferoxamine treated group versus 71.1 mm Hg for the control group (p less than 0.001), and the alveolar-arterial oxygen difference was less in the deferoxamine-treated group: 502.3 versus 606.0 mm Hg (p less than 0.001). The mean pulmonary vascular resistance was lower throughout the study, and after 6 hours it was 455.1 dynes/sec/cm(-5) in the deferoxamine-treated group versus 663.7 dynes/sec/cm(-5) in the control group (p less than 0.035). Compliance was similar in both groups. We conclude that deferoxamine improves lung preservation and early posttransplantation function in canine single lung transplantation.