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Biomedical subjects

I Birdi

Publications and source records attributed to I Birdi.

At least 19 recordsLinked to original sources
PubMed1998

Hemodynamic performance of the 21-mm St. Jude BioImplant prosthesis using dobutamine Doppler echocardiography.

This study examines the hemodynamic performance of small size St. Jude BioImplant aortic prostheses using dobutamine echocardiography. Eleven patients (3 women, mean age 75 years) who had undergone aortic valve replacement with a size 21-mm St. Jude BioImplant aortic prostheses at 10.8 +/- 5.1 months (SD) previously were studied. Dobutamine infusion was started at a rate of 5 microg/kg/min and increased to 10 microg/kg/min, and subsequently to 20 microg/kg/min at 15-minute intervals. Pulsed and continuous-wave Doppler studies were performed at rest and at the end of each stage. Effective orifice area, mean gradient, and the performance index across each prosthesis were calculated and cardiac output was determined by Doppler measurement of flow in the left ventricular outflow tract. Stress dobutamine increased heart rate and cardiac output by 51% and 56%, respectively (both p <0.0001), and the mean transvalvular gradient increased from 30.1 +/- 7.5 mm Hg at rest to 49.3 +/- 11.5 mm Hg at maximum stress (p <0.0005). The performance index increased progressively from 0.29 +/- 0.05 at rest to 0.40 +/- 0.10 at maximum stress (p <0.0005). Regression modeling analyses demonstrated that the maximum stress gradient was independent of all variables except the resting gradient (p = 0.03). Body surface area had no effect on the changes in cardiac output, effective orifice area, or transprosthetic gradient at maximum stress. Thus, these data demonstrate that the size 21-mm St. Jude BioImplant prosthesis exhibits suboptimal hemodynamic performance with transvalvular gradients consistent with mild to moderate aortic stenosis, both at rest and under stress conditions.

Adrenergic beta-Agonists↗
PubMed1997

Left ventricular volume reduction surgery.

Left ventricular volume reduction has recently been introduced as a surgical treatment for end stage dilated cardiomyopathy. This operation involves the resection of a slice of viable left ventricular myocardium in order to reduce the wall tension imposed upon the contracting heart chamber. Early results are encouraging, but clinical evaluation on a larger scale is required. In the present article, we describe the indications, surgical principles and results of left ventricular volume reduction surgery with reference to our group's experience.

Animals↗
PubMed1997

Biochemical markers of myocardial injury during cardiac operations.

The evaluation of myocardial damage in relation to cardiac operation from a clinical and a research perspective is of great importance, particularly for the evaluation of different cardioprotective strategies. Although measurements of serum biochemical markers have often been used, their value has been limited by their lack of sensitivity and specificity in the presence of skeletal muscle damage. A newer range of markers are now available that may reliably indicate both perioperative myocardial infarction, as well as more subtle degrees of subclinical myocyte injury. In this review, the application of biochemical markers for clinical and research purposes during cardiac operation is considered.

Biomarkers↗
PubMed1997

Influence of normothermic systemic perfusion during coronary artery bypass operations: a randomized prospective study.

OBJECTIVES: Normothermic cardiopulmonary bypass has been proposed as a more physiologic technique than hypothermic bypass for the maintenance of the body during cardiac surgery. The aims of this study were to investigate the effects of systemic perfusion temperature on clinical outcome after coronary revascularization. METHODS: Three hundred patients (mean age 60 +/- 9 years, 88% male) were prospectively randomized into three groups: hypothermia (28 degrees C, n = 100), moderate hypothermia (32 degrees C, n = 100), and normothermia (37 degrees C, n = 100). All patients received cold antegrade St. Thomas' Hospital crystalloid cardioplegic solution, and patients in the normothermic group were actively rewarmed during cardiopulmonary bypass (nasopharyngeal temperature 37 degrees C). RESULTS: No differences were found between groups with respect to mortality (1%), intraaortic balloon pump use, perioperative infarction rates, focal neurologic deficits (1%), intubation time, intensive care unit stay, and postoperative hospital stay. Further stepwise regression analysis identified age and intensive care unit stay as important predictors of the variability in postoperative stay (both R2 = 0.114; p < 0.001), whereas perfusion temperature remained a nonsignificant explanator. Normothermic perfusion necessitated larger doses of phenylephrine to maintain arterial pressure above 50 mm Hg during cardiopulmonary bypass (p < 0.0001 vs 28 degrees C, p < 0.01 vs 32 degrees C) but less requirement for electrical defibrillation during reperfusion (p < 0.05 vs 32 degrees C, p < 0.01 vs 28 degrees C). Total chest drainage was not different between groups, but patients undergoing normothermic cardiopulmonary bypass required less transfusion of blood (p < 0.05 vs 28 degrees C and 32 degrees C) and platelets (p < 0.04 vs 32 degrees C, p < 0.001 vs 28 degrees C) in the postoperative period. CONCLUSIONS: Cardiopulmonary bypass temperature did not influence early clinical outcome after routine coronary artery bypass operations. Normothermic systemic perfusion was associated with an increased requirement for vasoconstrictors and reduced requirements for electrical defibrillation and transfusion of blood products.

Bicarbonates↗
PubMed1997

Cardiac troponin T and troponin I release during coronary artery surgery using cold crystalloid and cold blood cardioplegia.

OBJECTIVE: To evaluate and compare myocardial protection using cold crystalloid and blood cardioplegia by measuring release of cardiac Troponin T and Troponin I during coronary artery surgery. METHODS: Forty two patients undergoing myocardial revascularization were prospectively randomised into two groups in whom myocardial protection was achieved with either antegrade cold (4 degrees C) crystalloid (CCP) (n = 21) St. Thomas' I cardioplegic solution. Serial venous blood samples were collected for measurement of cardiac Troponin T and Troponin I, prior to induction of anesthesia and at 4, 12, 24 and 48 h after removal of the aortic cross clamp. RESULTS: There were no hospital deaths in the two groups and one patient in each group suffered a perioperative myocardial infarction. Rising levels of Troponin T and Troponin I were found in all patients. Serum concentrations increased as early as 4 h after removal of the aortic cross clamp, and reached a peak at 12 h postoperatively in both groups. These levels subsequently declined, but remained higher than preoperative values at 48 h. There were no differences between the two groups with respect to serum Troponin T and I release at 4, 12, 24 and 48 h, area under the respective curves, and peak Troponin T and I release. Serum Troponin levels were significantly higher in patients with unstable angina and in two patients who suffered a perioperative myocardial infarction. CONCLUSION: Serum release of cardiac Troponin T and Troponin I is significantly raised in low risk patients undergoing myocardial revascularization. This release is similar when either cold crystalloid or cold blood cardioplegia are used. This may imply that both methods offer identical protection to the myocardium in a low risk group of patients.

Aged↗
PubMed1997

Hemodynamics of St. Jude Medical prostheses in the small aortic root: in vivo studies using dobutamine Doppler echocardiography.

BACKGROUND AND AIMS OF THE STUDY: The well known correlation between prosthetic valve orifice area and transvalvular pressure drop has raised concerns about the presence of significant residual gradients when only a small-sized prosthesis can be implanted, particularly in patients with a large body surface area. The aim of this study was to study the hemodynamic performance of small-size St. Jude Medical aortic prostheses using dobutamine echocardiography. METHODS: Fifteen patients (14 females, one male, of mean age 67 years) who had undergone aortic valve replacement with size 19 mm St. Jude Medical prostheses at a mean of 19 +/- 8 (SD) months previously were studied. Dobutamine infusion was started at a rate of 5 micrograms/kg/min and increased to 10 and subsequently to 20 micrograms/kg/min at 15-min intervals. Pulsed and continuous-wave Doppler studies were performed at rest and at the end of each stage. Effective orifice area (EOA) and mean gradient across each prosthesis were calculated, and cardiac output (CO) was determined by Doppler measurement of flow in the left ventricular outflow tract. RESULTS: Dobutamine-stress increased heart rate and cardiac output by 57% and 86% respectively (both p < 0.0005), and mean transvalvular gradient increased from 22.0 +/- 4.9 mmHg at rest to 41.9 +/- 9 mmHg at maximum stress (p < 0.0001). Regression modeling analyses demonstrated that maximum stress gradient was independent of all variables except resting gradient (p = 0.0068). Body surface areas had no effect on the changes in cardiac output, effective orifice area or transprosthetic gradient at maximum stress. CONCLUSIONS: These data demonstrate that the size 19 mm St. Jude Medical prosthesis exhibits favorable hemodynamic performance. Transvalvular gradients remained within a clinically acceptable range, both at rest and under stress conditions. Moreover, in the patient population studied, overall hemodynamic performance indicates that with St. Jude Medical aortic valves, patient-prosthesis mismatch is unlikely to be a problem of clinical importance.

Adult↗
PubMed1996

Effects of cardiopulmonary bypass temperature on pulmonary gas exchange after coronary artery operations.

BACKGROUND: Pulmonary dysfunction is one aspect of the postoperative morbidity associated with cardiopulmonary bypass. Normothermic systemic perfusion can result in shorter intubation times, which have been attributed to improved pulmonary gas exchange, but the influence of perfusion temperature on pulmonary gas exchange itself is not known. METHODS: Pulmonary gas exchange was assessed using alveolar-arterial oxygen pressure gradients in 45 patients undergoing routine coronary revascularization who were randomized to undergo cardiopulmonary bypass at 28 degrees C, 32 degrees C, or 37 degrees C. This was part of a more comprehensive study of the effects of temperature on bodily systems. The gradients were estimated preoperatively with the patients breathing air, again over a period between 2 and 4 hours postoperatively during mechanical ventilation with three different oxygen concentrations (30%, 40%, and 60%), and again 1 hour after extubation while breathing the same three oxygen concentrations. RESULTS: Preoperative alveolar-arterial oxygen pressure gradients on air were 24.4 +/- 8.2 mm Hg (mean +/- standard deviation) (28 degrees C), 24.5 +/- 20.4 mm Hg (32 degrees C), and 20.5 +/- 9.5 mm Hg (37 degrees C). Postoperatively, during ventilation and after rewarming, the gradients increased with the increase in inspired oxygen fraction concentrations (30% to 60%) from 67.1 +/- 12.0 mm Hg to 193.1 +/- 30.5 mm Hg (28 degrees C), from 76.4 +/- 20.6 mm Hg to 246.7 +/- 47.7 mm Hg (32 degrees C), and from 79.0 +/- 18.0 mm Hg to 222.9 +/- 40.5 mm Hg (37 degrees C), respectively. A similar pattern was noted 1 hour after extubation, when the gradients increased from 72.4 +/- 12.5 mm Hg to 256.6 +/- 26.5 mm Hg (28 degrees C), from 75.7 +/- 13.9 mm Hg to 252.7 +/- 38.3 mm Hg (32 degrees C), and from 69.1 +/- 19.3 mm Hg to 253.1 +/- 33.0 mm Hg (37 degrees C). There were no significant differences in alveolar-arterial oxygen pressure gradient between the three groups during ventilation or after extubation. CONCLUSIONS: Cardiopulmonary bypass perfusion temperature does not influence alveolar-arterial oxygen pressure gradients in the first 12 hours after routine coronary artery bypass grafting in patients with uncompromised pulmonary and left ventricular function.

Carbon Dioxide↗
PubMed1996

Normothermic techniques during open heart operations.

There has been considerable interest in the use of normothermic techniques during cardiac operations, both as a means of myocardial protection and as a more physiologic environment for other organs during cardiopulmonary bypass. Although a limited number of uncontrolled studies have suggested superior clinical results compared with conventional hypothermic regimens, these claims have not been thoroughly investigated using randomized protocols. The limited available data suggest that the successful use of warm blood cardioplegia requires adequate delivery of the solution to all parts of the myocardium at optimal flow rates to maintain aerobic arrest, so those who advocate the use of normothermic arrest must pay particular attention to ensure that their myocardial protection is effective. The advantages of employing normothermic systemic perfusion in regard to factors such as improved hemodynamic performance and reduced blood loss postoperatively need to be balanced against concerns regarding the inadequacy of cerebral protection offered by this method.

Blood Coagulation↗
PubMed1996

The effects of cardiopulmonary bypass temperature on neuropsychologic outcome after coronary artery operations: a prospective randomized trial.

UNLABELLED: The effect of systemic perfusion temperature on postoperative cognitive function was investigated in 96 adult patients undergoing elective coronary revascularization with cardiopulmonary bypass at 28 degrees C, 32 degrees C, or 37 degrees C. Neuropsychologic performance was assessed 1 day before the operation and 6 weeks after the operation. Five tests were adapted from the Wechsler Adult Intelligence Scale and two from the Wechsler Memory Scale. RESULTS: No patients had major neurologic complications. Ninety-three patients completed the five Wechsler Adult Intelligence Scale tests, but only 70 went on to complete the Wechsler Memory Scale tests as well. In these, there was an effect of cardiopulmonary bypass temperature on the number of neuropsychologic tests in which there was a preoperative to postoperative deterioration (p = 0.021), the number with bypass at 37 degrees C being significantly greater than the number with bypass at 32 degrees C (p = 0.015). Subsidiary analyses using a multivariate linear model examined the effect of cardiopulmonary bypass temperature on the magnitude of change, with or without allowing for other possible confounding influences. There was an adverse effect of normothermic (37 degrees C) versus moderately hypothermic (32 degrees C) perfusion---more convincingly displayed in the analyses of all seven scores rather than just the Wechsler Adult Intelligence Scale scores. Further cooling to 28 degrees C conferred no additional benefit in terms of cognitive function. The importance of the deterioration is open to question.

Body Temperature↗
PubMed1996

Comparison of hemodynamic performances of St. Jude Medical and CarboMedics 21 mm aortic prostheses by means of dobutamine stress echocardiography.

Dobutamine stress Doppler echocardiography was used to compare the hemodynamic performance of two small aortic bileaflet prostheses. Nineteen patients (14 female, mean age 64 years) who had undergone aortic valve replacement with 21 mm bileaflet valve prostheses (St. Jude Medical valve, n = 9, or CarboMedics valve, n = 10) were studied. Dobutamine infusion was started at a rate of 5 micrograms.kg-1.min-1 and increased to 10 and 20 micrograms.kg-1.min-1 at 15-minute intervals. Under maximum stress, heart rate and cardiac output increased by 70% and 120%, respectively, and mean arterial blood pressure decreased by 9%. Pulsed-wave and continuous-wave Doppler studies were performed at rest and at the end of each stage. Velocity ratio, effective orifice area, performance index, and discharge coefficient of the valve were calculated, and peak and mean velocities and pressure drops across the prostheses were measured. Dobutamine infusion produced similar increases in cardiac output in all patients. Effective orifice areas, discharge coefficients, and performance indexes were comparable for the two valve groups both at rest and maximum stress. Transvalvular velocities and pressure drops were also similar in the two valve groups. Transvalvular pressure drops were also comparable in patients with large body surface area. Dobutamine stress echocardiography is useful in the evaluation of the hemodynamic performance of prosthetic heart valves. St. Jude Medical and CarboMedics 21 mm prostheses have equally favorable hemodynamic performances in most patients under conditions of high cardiac output.

Aged↗
PubMed1995

Evaluation of the hemodynamic performance of small CarboMedics aortic prostheses using dobutamine-stress Doppler echocardiography.

BACKGROUND: The well-known correlation between prosthetic valve orifice area and transvalvular gradients has raised concerns about the presence of significant residual gradients when the size of the prosthesis that can be implanted is limited by the presence of a small aortic annulus. METHODS: Dobutamine-stress Doppler echocardiography was used to evaluate the hemodynamic performance of small CarboMedics aortic prostheses (19 mm and 21 mm) in 18 patients (16 women; mean age, 64 years) who had undergone aortic valve replacement 23.5 +/- 19 months (standard deviation) previously. Dobutamine infusion was started at a rate of 5 micrograms.kg-1.min-2 and increased to 10 and 20 micrograms.kg-1.min-2 at 15-minute intervals. Pulsed and continuous wave Doppler studies were performed at rest and at the end of each stage. Effective orifice area, performance index, and discharge coefficient of both valves were calculated, and peak and mean velocity and pressure drop across the prostheses were measured. RESULTS: Heart rate and cardiac output increased by 74% and 94%, respectively, and mean arterial blood pressure decreased by 9% at maximum stress. Effective orifice area, discharge coefficient, and performance index were comparable in both valve sizes at rest and maximum stress. Also, there was no significant difference in mean transvalvular pressure drop (gradient) for 19-mm and 21-mm prostheses at rest (8.1 +/- 8.4 and 4.8 +/- 3.8 mm Hg) or maximum stress (15.1 +/- 14.2 and 8.8 +/- 5.8 mm Hg, respectively). No significant correlation could be demonstrated between transvalvular pressure drop and patient's body surface area. CONCLUSIONS: These data show that 19-mm and 21-mm CarboMedics aortic prostheses exhibit equally favorable hemodynamic performance with minimal pressure gradient, both at rest and under stress conditions.

Aged↗
PubMed1995

In-hospital audit underestimates early postoperative morbidity after cardiac surgery.

BACKGROUND: The demand for open heart surgery has driven current practice towards early postoperative discharge and interhospital transfer to maximise patient throughput. The extent to which this redirects morbidity to other healthcare providers is unknown. OBJECTIVE: To define the incidence of inhospital and early postoperative morbidity within 6 weeks of primary hospital discharge after cardiac surgery. DESIGN: Prospective inhospital data for 322 consecutive adult patients undergoing cardiac surgery were compared with retrospective information obtained by postal questionnaire. RESULTS: Mean (SD) primary postoperative hospital stay was 8.3 (3.1) days. There were 13 inhospital deaths (4%), and three patients died within 6 weeks of primary discharge. Retrospective information was obtained from 297 patients (96%). Of these, 77% patients were discharged home directly, while 23% were transferred to other hospitals for continued medical care. Mean (SD) hospital stay after transfer was 12 (8.4) days and required 741 additional hospital bed days. Thirty nine patients (13%) were readmitted to hospital, requiring a further 275 hospital bed days. The readmission rate was lower in patients sent home directly (10%), than in those who were transferred (22%; P < 0.001). CONCLUSIONS: Inhospital audit underestimates early morbidity after cardiac surgery. The burden transferred to other healthcare providers is considerable and has important financial implications for purchasers.

Cardiac Surgical Procedures↗
PubMed1995

Cardiopulmonary bypass perfusion temperature does not influence perioperative renal function.

BACKGROUND: The recent introduction of normothermic cardiopulmonary bypass (CPB) perfusion has raised concerns regarding the associated risk of renal dysfunction through its potential to exacerbate the systemic inflammatory response and end-organ injury. This study was designed to investigate the influence of CPB perfusion temperature on renal function. METHODS: A prospective, randomized, controlled trial of CPB perfusion temperature (28 degrees C, 32 degrees C, and 37 degrees C) was performed in 30 patients undergoing routine coronary artery bypass grafting with normal preoperative renal function. Creatinine clearance was measured before induction of anesthesia, during CPB, and during every 12-hour period thereafter for 48 hours postoperatively. Glomerular and tubular function were assessed further by measurement of urinary creatinine, albumin, total protein, and retinol binding protein levels preoperatively, during CPB, and on days 1 and 3 postoperatively. RESULTS: Creatinine clearance increased on CPB by 51% (28 degrees C), 185% (32 degrees C), and 112% (37 degrees C) (all p < 0.01 versus preoperative values) and returned to preoperative values by 24 hours postoperatively in all three groups. Urinary albumin/creatinine ratios rose significantly from a mean of 0.4 +/- 0.1 (standard deviation) to 10 +/- 12.5 (28 degrees C), from 0.55 +/- 0.3 to 5.2 +/- 4.9 (32 degrees C), and from 0.96 +/- 0.8 to 7.8 +/- 7.0 (37 degrees C) during CPB (all p < 0.001) but decreased gradually thereafter. Also, urinary total protein/creatinine ratios rose significantly from a mean of 0.009 +/- 0.007 to 0.034 +/- 0.02 (28 degrees C), from 0.01 +/- 0.006 to 0.026 +/- 0.01 (32 degrees C), and from 0.011 +/- 0.008 to 0.033 +/- 0.02 (37 degrees C) during CPB (all p < 0.005); however, there was a further increase by 24 hours, and ratios decreased gradually thereafter. Similarly, urinary retinol binding protein/creatinine ratios rose significantly in all three groups during CPB (all p < 0.0001) and increased further by 24 hours. There was no statistically significant difference between the renal markers in the three temperature groups in any of the observations. CONCLUSION: These data suggest that cardiopulmonary bypass perfusion temperature does not influence renal function in patients undergoing coronary artery bypass grafting.

Aged↗