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Biomedical subjects

B M Weiss

Publications and source records attributed to B M Weiss.

At least 37 records · Page 2Linked to original sources
PubMed1994

Risk and benefit of low systemic heparinization during open heart operations.

Heparin surface-coated perfusion equipment with improved thromboresistance was evaluated in 104 consecutive patients undergoing open heart operation in a prospective, randomized trial with low versus full systemic heparinization. Surgical procedures included coronary artery revascularization in 47 of 54 (87%) for low versus 44 of 50 patients (88%; not significant [NS]) for full, valve repair/replacement in 8 of 54 (15%) for low versus 5 of 50 patients (10%; NS) for full, left ventricular aneurysm repair in 1 of 54 (2%) for low versus 2 of 50 patients (4%; NS) for full, and other in 3 of 54 (6%) for low versus 3 of 50 patients (6%; NS) for full. Cross-clamp time was 39.2 +/- 10.7 minutes for low versus 39.5 +/- 10.5 minutes for full (NS). Cardiopulmonary bypass time was 68.6 +/- 20.1 minutes for low versus 69.3 +/- 16.6 minutes for full (NS). Lowest activated coagulation time during perfusion was 255 +/- 75 seconds for low versus 537 +/- 205 seconds for full (p < 0.0005). In the low group, the target activated coagulation time of more than 180 seconds was not reached during perfusion in 4 of 54 patients (7%), the lowest value being 164 seconds. No oxygenator failure occurred. Hospital mortality was 0 of 54 (0%) for low versus 1 of 50 patients (2%) for full (NS). Bleeding required surgical revision in 0 of 54 (0%) for low versus 4 of 50 patients (8%) for full (p = 0.05). Drainage (24 hours) was 790 +/- 393 mL for low versus 1,039 +/- 732 mL for full (p < 0.025).(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Coagulation↗
PubMed1994

Assisted circulation without systemic heparinization.

The need for improvements in materials and equipment for extracorporeal circulation has been obvious for years. Among the surfaces with biologically active compounds, those with heparin binding have been found sufficiently thromboresistant and particularly suitable for different types of artificial perfusion. Partial left heart bypass (LHBP) was performed in 10 anesthetized, acutely instrumented, and open-chested mongrel dogs (weight 23 to 50 kg) with a servo-controlled roller pump. The pump flow was maintained at 50 mL/kg/min for 6 hours. Heparin surface-coated equipment was used without additional heparin. For LHBP with a standard circuit, the total amount of heparin during the study period was (mean +/- SD) 487 +/- 124 IU/kg. The right atrial, pulmonary artery, and left ventricular end-diastolic pressures, cardiac output, left ventricular output, right and left ventricular stroke work, pulmonary gas exchange, and acid-base balance changed similarly with both systems. Blood loss (204 +/- 78 v 1,240 +/- 586 mL, P < 0.0005), volume substitution requirements (647 +/- 48 v 1,860 +/- 764 mL, P < 0.0025), and oxygen extraction ratio (mean 25.4 to 32.0 v 25.4 to 56.4%, P < 0.025) were significantly lower, and mean aortic pressure (mean 65 to 69 v 62 to 38 mmHg, P < 0.025) and hemoglobin concentration (mean 9.1 to 8.1 v 9.4 to 3.9 g/dL, P < 0.05) were significantly higher during 6 hours of LHBP without systemic heparinization. Low but stable oxygen delivery was provided with heparin-coated LHBP, whereas it showed a descending trend (mean 14.0 to 10.8 v 13.4 to 5.5 mL/kg/min, P < 0.1) with the standard circuit.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Cardiotomy suction versus red cell spinning during repair of descending thoracic aortic aneurysms.

Two consecutive series of patients undergoing repair of descending thoracic and thoracoabdominal aortic aneurysms with partial cardiopulmonary bypass and low systemic heparinization (activated coagulation time: ACT greater than 180 sec) for proximal unloading and distal protection were analyzed. During the surgical procedures, thoracic shed blood was recovered either with a red cell spinning autotransfusion device (n=10) or two pump suckers and Duraflo II heparin surface coated cardiotomy reservoirs (n=10). There were 5/10 acute lesions and 1/10 ruptures for the autotransfusion group versus 5/10 acute lesions and 2/10 ruptures for the cardiotomy group (NS). Extension of aortic resection (range 1-8) was 3.6+/-1.2 for autotransfusion versus 3.5+/-1.4 for cardiotomy suction (NS). Mean number of reimplanted patches for intercostal and visceral reperfusion was 0.3+/-0.6 for autotransfusion versus 0.6+/-1.0 for cardiotomy (NS). Perfusion time was 41+/-17 min for autotransfusion versus 60+/-19 min for cardiotomy (p less than 0.05) and cross clamp time was 33+/-14 min for autotransfusion versus 43+/-17 min for cardiotomy (p less than 0.01). Total heparin dose was for 9500+/-2100 IU for autotransfusion versus 9800+/-1300 IU for cardiotomy (NS). The mean of the lowest ACTs measured during perfusion was 281+/-121 sec for autotransfusion versus 258+/-58 sec for cardiotomy (NS). The total protamine dose given was 7800+/-2100 IU for autotransfusion versus 9700+/-1900 IU for cardiotomy (p less than 0.05). The volume of washed red cells prepared was 3186+/-1318 ml for autotransfusion versus 0 for cardiotomy (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

Perfusion with low systemic heparinization during resection of descending thoracic aortic aneurysms.

Two series of 20 consecutive patients with aneurysms of the descending thoracic aorta (TAA) and thoraco-abdominal aorta (TAAA) underwent multisegmental aortic repair using either simple normothermic crossclamping and rapid reanastomosis (historic) or partial cardiopulmonary bypass (CPB) with heparin coated perfusion equipment and low systemic heparinization (actual). Chronic lesions were present in 14/20 patients (70%) for simple versus 13/20 (65%) for CPB (NS). Acute lesions (symptomatic less than 24 h) were present in 6/20 patients (30%) for simple versus 7/20 (35%) for CPB (NS). Dissecting lesions were observed in 4/20 patients (20%) for simple versus 8/20 (40%) for CPB (NS). Aneurysmal lesions were found in 16/20 patients (80%) for simple versus 12/20 (60%) for CPB (NS). Mean number of aortic segments (n = 8) resected was 3.2 +/- 1.1 for simple versus 4.0 +/- 1.2 for CPB (P less than 0.01). Replacement of the transdiaphragmatic aorta was performed in 10/20 patients (50%) for simple and 13/20 patients (65%) for CPB (NS). A heparin loading dose of 5000 IU for simple versus 100 IU/kg bodyweight for CPB was used. In the latter group, the activated clotting time was kept above 180 s during a mean perfusion time of 46 +/- 28 min at a mean pump flow of 2.2 +/- 0.7 l/min. Thirty-day survival for all (transdiaphragmatic) was 12/20 (5/10) patients for simple versus 20/20 (13/13) for CPB (P less than 0.002, P less than 0.01). One-year survival (all) was 11/20 patients (55%) for simple versus 19/20 (95%) for CPB (P less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

Temporary lung support using an intravascular gas exchanger.

Severe respiratory failure may be difficult to overcome by conventional mechanical ventilation. As an alternative to the very demanding lung support using various modalities of extracorporeal circulation (ECMO, ECLA, etc.) we evaluated an intravascular gas exchanger (IVOX) in a "reversible" bovine model. Several degrees of hypoventilation were studied with and without intravascular gas exchange in 5 endotracheal intubated, anaesthetized, and volume-controlled ventilated animals (body weight 73 +/- 4 kg). After systematical heparinization (300 IU/kg body weight) the animals were instrumented with EKG electrodes, thermodilution pulmonary artery catheter with continuous measurement of O2-saturation, central venous and femoral arterial catheter, etc. The intravascular gas exchanger made from siliconized microporous polypropylene hollow fibres was placed in the caval veins under radiofluoroscopic control. The following scenarios were studied without and with intravascular gas exchange (gas inlet 100% O2): Normoventilation (with 14-20 strokes/min) at F10(2) 0.50 and at F10(2) 0.21; Hypoventilation (ventilator frequency reduced to 50% and tidal volume reduced to 50% of normoventilation) at F10(2) 0.50 and at F10(2) 0.21. Hemodynamics, mixed venous O2-saturation, arterial and venous blood gases, and gas-exchanger exhaust were analyzed after stabilization over 15 minutes (mean +/- standard deviation). Blood gas analyses showed significant improvement with intravascular gas exchange during hypoventilation at F10(2) 0.21: pH moved from 7.10 +/- 0.17 to 7.19 +/- 0.15*, PaCO2 moved from 9.9 +/- 4.2 kPa to 8.7 +/- 2.8*, PaO2 moved from 6.5 +/- 1.2 kPa to 7.3 +/- 0.8* and mixed venous O2-saturation moved from 33.9 +/- 16.0% to 48.1 +/- 4.6* (* = p less than 0.05 for without versus with intravascular gas exchange).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Reduction and elimination of systemic heparinization during cardiopulmonary bypass.

After extensive experimental evaluation, heparin-coated perfusion equipment was clinically evaluated with low or no systemic heparinization in three different groups of patients (n = 47). In group 1, resection of descending thoracic aortic aneurysms (n = 24) was performed with heparin-coated equipment used for left heart bypass (n = 12) or partial cardiopulmonary bypass (n = 12) for proximal unloading and distal protection (heparin 5000 IU, autotransfusion). All devices remained functional throughout the procedures and no systemic emboli were detected. The sole death (1 of 24, 4%) occurred in a patient with ruptured thoracoabdominal aortic aneurysm requiring operation in extremis. Paraparesis with spontaneous recovery occurred in one patient (1 of 24, 4%). In group 2, coronary artery revascularization randomized for low (activated clotting time greater than 180 seconds) versus full (activated clotting time greater than 480 seconds) systemic heparinization was prospectively analyzed in 22 patients. All patients recovered without sequelae, and no myocardial infarction was diagnosed. Low dose of heparin (8041 +/- 1270 IU versus 52,500 +/- 17,100 IU; p less than 0.0005) resulted in reduced protamine requirements (7875 +/- 1918 IU versus 31,400 +/- 14,000 IU; p less than 0.0005), reduced blood loss (831 +/- 373 ml versus 2345 +/- 1815 ml; p less than 0.01), reduced transfusion requirements of homologous blood products (281 +/- 415 ml versus 2731 +/- 2258 ml; p less than 0.001), and less patients transfused (5 of 12 versus 10 of 10; p less than 0.05). Lower D-dimer levels in the group perfused with low systemic heparinization (0.50 +/- 0.43 mg/L versus 1.08 +/- 0.59 mg/L; p less than 0.05) were attributed to the absence of cardiotomy suction in this group. In group 3, rewarming in accidental hypothermia by cardiopulmonary bypass was successfully performed without systemic heparinization in a patient with hypothermic cardiac arrest (23.3 degrees C) and intracranial trauma. We conclude that systemic heparinization for clinical cardiopulmonary bypass can be reduced and eliminated in selected patients if perfusion equipment with improved biocompatibility is used. Bypass-induced morbidity can be reduced.

Aged↗
PubMed1992

Improved biocompatibility of heparin surface-coated ventricular assist devices.

Heparin surface coated ventricular assist devices (VADs) and cannulas were evaluated in comparison to uncoated VADs in 10 bovine experiments (body weight 77 +/- 6 kg). All systems were primed with cristalloid solution. No systemic heparin was given. Left ventricular assist was started with a blood flow of 4.2 +/- 0.4 l/min and maintained over 6 hours. Besides hemodynamic monitoring, blood samples were taken at regular intervals for blood gas, hematological, biochemical and coagulation studies. All animals in the study group (coated) were assisted for the scheduled 6 hours without device failure. In the control group, however, total occlusion occurred in 1 VAD after 1 hour of left ventricular assist whereas the other 4 VADs remained functional throughout the protocol. Mixed venous oxygens saturation was preassist 56 +/- 12% for coated versus 63 +/- 11% for uncoated and the final value at 60 minutes after weaning was 58 +/- 16% versus 59 +/- 5% (NS). Mean hematocrit dropped from a baseline value of 33 +/- 4% for coated versus 29 +/- 8% for uncoated to 29 +/- 7% versus 30 +/- 5% (NS) after 6 hours of assist. There was no significant difference between the baseline values (5.7 +/- 3.0 mumol/l for coated versus 4.6 +/- 3.1 mumol/l for uncoated) and the 6-hour values (3.8 +/- 3.7 mumol/l versus 7.6 +/- 6.4 mumol/l) for mean plasma hemoglobine. The normalized platelet levels dropped after 10 minutes of assist to 91 +/- 21% for coated versus 94 +/- 49% for uncoated (NS) and 89 +/- 29% versus 65 +/- 44 at 6 hours (NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Experimental evaluation of heparin-coated cardiopulmonary bypass equipment with low systemic heparinization and high-dose aprotinin.

Cardiopulmonary bypass (n = 8 calves) with heparin-coated perfusion equipment, low-dose systemic heparinization (activated clotting time: ACT greater than 180 s) and high-dose aprotinin administration was evaluated in comparison to standard perfusion equipment with full-dose systemic heparinization (ACT greater than 480). All animals were perfused for 6 hours and similar values were observed for blood gases and mixed venous oxygen saturation in both groups. The heparin doses given in the study group before and during the 6 hours of perfusion totalized 14660 +/- 2553 IU as compared to 60833 +/- 5137 IU for the control group. No protamin was given in the study group whereas an equivalent of 27000 +/- 5805 IU was necessary to reverse heparin in the control group. There was no difference for prebypass hematocrit versus postbypass hematocrit in the two groups. Prebypass plasma hemoglobine was 8.4 +/- 2.1 mumol/L in the study group versus 10.0 +/- 3.8 mumol/L in the control group. After mixing with the priming volume, plasma hemoglobine was 8.6 +/- 2.5 mumol/L in the study group versus 6.7 +/- 1.6 mumol/L in the control group. The highest value was observed in the study group after 2 hours of perfusion (8.2 +/- 2.1 mumol/L) versus 5 hours of perfusion in the control group (7.4 +/- 3.6 mumol/L). Prebypass LDH levels of 1610 +/- 150 IU in the study group versus 1740 +/- 210 IU in the control group moved to 1870 +/- 200 IU in the study group at 24 hours after perfusion versus 2650 +/- 400 IU in the control group at 24 hours and decreased thereafter.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Clinical application of heparin-coated perfusion equipment with special emphasis on patients refusing homologous transfusions.

Clinical application of heparin-coated cardiopulmonary bypass equipment during perfusion with low systemic heparinization is reported with special emphasis on patients refusing any transfusion of homologous blood or blood products. Using the described technique, coronary artery revascularization was successfully performed in three Jehovah's witnesses. During perfusion, the activated clotting time (ACT) was maintained above 180 seconds. Prebypass haematocrit was 38 +/- 3% and dropped to 22 +/- 1% after seven days. Hence, cardiopulmonary bypass with low systemic heparinization may further reduce bypass induced morbidity and improve the final outcome in selected patients.

Aged↗
PubMed1991

Comparison of nalbuphine and fentanyl anesthesia for coronary artery bypass surgery. Hemodynamics, hormonal response, and postoperative respiratory depression.

To determine whether nalbuphine might replace fentanyl as the principal opioid for anesthesia during coronary artery bypass surgery, 20 patients undergoing myocardial revascularization were anesthetized with flunitrazepam and with a continuous infusion of either nalbuphine (an opioid agonist-antagonist) or fentanyl (a pure opioid agonist) in equipotent dosage ratio of 333:1. During endotracheal intubation, all patients given nalbuphine, but only one given fentanyl (P less than 0.05), required nitroglycerin to control arterial blood pressure. Two minutes after tracheal intubation, plasma values of epinephrine, norepinephrine, vasopressin, and cortisol did not change in the fentanyl group compared with the awake (baseline) levels, whereas catecholamines and vasopressin significantly increased with nalbuphine compared with the baseline and with the values in the fentanyl group. A steady state of anesthesia (30 min after intubation), when compared with the baseline, was characterized by unchanged systemic and pulmonary blood pressures and increased systemic vascular resistance with nalbuphine, by decreased systemic and pulmonary pressures and resistances with fentanyl, and by comparably decreased cardiac index with both opioids. Hormone values returned to baseline levels but norepinephrine remained significantly higher in the nalbuphine than in the fentanyl group. A bolus injection of either nalbuphine (2.5 mg/kg) or fentanyl (7.5 micrograms/kg) given during the steady-state period of anesthesia provoked only minimal hemodynamic changes. Before skin incision, 7 of 10 patients receiving nalbuphine required nitroglycerin to control arterial blood pressure. After sternotomy, both groups required nitroglycerin, but additional antihypertensive drugs were necessary mainly in the nalbuphine group.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, Intravenous↗
PubMed1991

Heparin-coated left heart bypass: renal function and hormonal response.

The effect of partial (50 ml/min/kg) left heart bypass (LHBP) on renal function, plasma renin activity (PRA), aldosterone, arginine vasopressin and atrial natriuretic peptide (ANP) response was studied in ten anesthetized, open-chested mongrel dogs (weight 23-50 kg) over a period of 6 h. Standard equipment with systemic heparinization (control), initially 300 IU/kg, was employed in five dogs, and heparin-coated equipment without additional heparin in the other five (heparin coated). Urine was continuously collected through a transurethral catheter. Urine samples and pulmonary artery blood samples for hormonal assays were taken at preset intervals before and during LHBP. The results in each group were summarized as median (25th-75th) and compared using the Mann-Whitney U test. In the control group higher blood loss required higher volume substitution. Urine output was maintained in heparin coated and slightly decreased at 3-4 h in control LHBP. Creatinine clearance at 3-5 h and free-water clearance at 3-6 h were significantly higher with heparin-coated LHBP. PRA, aldosterone and vasopressin peaked at 1-2 h of LHBP similarly in both groups, not exceeding the values before perfusion. PRA and aldosterone response was sustained during 6 h and the percentage changes corrected for hemodilution indicated a stronger response with standard equipment. Vasopressin concentrations were slightly but significantly higher in the control group at 1 and 6 h of perfusion. Corrected for hemodilution, vasopressin percentage changes were not different in the two groups. ANP, despite atrial unloading, rose similarly in both groups. There was a tendency to poorly sustained ANP response (control greater than heparin-coated) after 6 h of perfusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Aldosterone↗
PubMed1991

[Rest ventricular function in left heart bypass].

During partial left heart bypass (LHBP), the flow delivered by an assist device is easy to measure while residual left ventricular function (LVI) seems difficult to assess. In this study, we have attempted to define the separate right and left ventricular function during LHBP. In 6 anesthetized dogs, following thoracotomy and systemic heparinization, aorta and left atrium were cannulated and connected to the servo-controlled roller pump (modified Stöckert-System). Following saline infusion (30 ml/kg), LHBP was started and maintained at 50 ml/min/kg throughout 6 h. Standard hemodynamic parameters were continuously monitored. Cardiac output, blood gas analyses, hemoglobin and activated coagulation time were measured at regular intervals. LVI was calculated as the difference between cardiac output and assist-flow rate. Other derived variables were obtained using standard formulas. The Wilcoxon rank-test was used for the statistical analysis. The results, as median and 25th-75th percentile, are summarized in the graphics 1-6. Under the experimental conditions of this study, the flow performance and stroke work of the right ventricle remained unchanged, while the work-unloaded left ventricle maintained only a part of systemic perfusion. Neglecting the physiological shunt and its changes, which influences the difference between the left and right ventricular output, the simple formula to assess LVI during LHBP seems plausible.

Animals↗
PubMed1990

Superior hemodynamics in left heart bypass without systemic heparinization.

Open-chest left heart bypass was performed in 10 canine experiments (30 +/- 9 kg) by a servo controlled roller pump for 6 h at a pump flow of 50 ml/min per kg bodyweight. The surfaces of the tubing sets were either standard (with systemic heparinization) or with end-point attached heparin (no systemic heparin). Besides continuous monitoring of hemodynamics, a standard battery of blood samples was taken before bypass, after 10 min and every hour thereafter. There is no evidence of increased fibrin production in the group with end-point attached heparin surfaces perfused without systemic heparinization. Superior hemodynamics in left heart bypass performed without systemic heparinization appear to be due to improved hemostasis, reduced blood loss and therefore reduced transfusion requirements. Left heart bypass with heparin-coated equipment has been successfully used for resection of a thoracoabdominal aneurysm in six patients.

Animals↗
PubMed1990

Reduced blood loss and transfusion requirements with low systemic heparinization: preliminary clinical results in coronary artery revascularization.

In coronary artery revascularization, low systemic heparinization was compared to full systemic heparinization during perfusion with heparin surface-coated cardiopulmonary bypass equipment. Twelve patients were randomly assigned to two groups and perfused with low [activated clotting time (ACT) greater than 180 s] or full (ACT greater than 480 s) systemic heparinization. A standard battery of blood samples was taken before the procedure, after heparinization, and at regular intervals during and after cardiopulmonary bypass. No differences were seen between the two groups in regard to age, body surface area, preoperative hematocrit, duration of bypass, bypass hypothermia, cross-clamp time, and number of bypasses per patient. However, there were more internal thoracic artery (ITA) grafts in the group with low systemic heparinization (1.5 +/- 0.8 ITA grafts per patient versus 0.8 +/- 0.4 ITA grafts per patient with full heparinization; p less than 0.05). The oxygenator gradient at the end of perfusion (before weaning) was 107 +/- 40 mmHg for low versus 110 +/- 10 mmHg for full heparinization (difference not significant). The total amount of heparin used was 7200 +/- 1030 IU for low versus 51400 +/- 9700 IU for full (p less than 0.05). Postoperative hematocrit was 35.0 +/- 2.0% for low versus 24.7 +/- 2.7% for full (p less than 0.05). Total chest tube drainage was 428 +/- 153 ml/m2 for low versus 935 +/- 414 ml/m2 for full (p less than 0.05). Homologous transfusions of blood products were necessary in 3/6 patients for low versus 6/6 patients for full (p less than 0.10).(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Coagulation↗
PubMed1990

Performance characteristics of centrifugal pumps with heparin surface coating.

Heparin surface coating is one approach to improve the biocompatibility of existing blood pumps used for mechanical circulatory support. Experimental evaluation of centrifugal pumps with heparin surface coating was performed during open chest left heart bypass (3.7 L/min over 6 hours) in two series of bovine experiments. Eight calves (74 +/- 4 kg) were perfused either by heparin surface coated equipment without systemic heparinization or uncoated equipment with systemic heparinization (300 I. U,/kg bodyweight; ACT greater than 400 s). A standard battery of analyses was performed before and at regular intervals after onset of perfusion. At the end of perfusion all pump-heads were gently rinsed. There were no macroscopic clots for both groups whereas macroscopic clots were observed in uncoated tubings introduced for control in the group perfused without systemic heparinization. The hemodynamics were significantly better in the group perfused without systemic heparinization and maintained functional coagulation system. Clinical application of heparin surface coated equipment during resection of thoraco-abdominal aortic aneurysms is showing promising results in 12 patients.

Animals↗