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Biomedical subjects

A Piwnica

Publications and source records attributed to A Piwnica.

At least 91 records · Page 5Linked to original sources
PubMed1986

[Protective effects of inhibitors of oxygen free radicals on the ischemic and reperfused heart. Applications to cardioplegia].

Oxygen free radicals play an important role in the induction of myocardial lesions by the sequence ischaemic-reperfusion. The aim of this study was to determine whether the protection afforded by a cardioplegic solution could be improved by the addition of different anti-oxygen free radical agents. Forty isolated, perfused, rat hearts' isovolumic contraction systems were divided into 5 groups of 8. In 4 groups, cardioplegia was stopped for 90 minutes in normothermia and then reperfused for 45 minutes. These hearts received a single initial injection of either standard cardioplegic solution or a solution enriched with dismutase peroxide (200,000 U/l), reduced glutathione (0.1 mM) or peroxidase (6,000 U/l). The fifth group of hearts was continually aerobically reperfused and served as a non-ischaemic control group. Based on post-ischaemic values of the pressure developed (maximal systolic-diastolic pressure), LVdP/dt, diastolic pressure and coronary flow, the best myocardial protection was observed in those hearts given cardioplegic solution enriched with peroxidase, the haemodynamic indices being comparable to those of the non-ischaemic controls. These results confirm that myocardial protection with cardioplegic solutions can be improved by the addition of anti-oxygen free radical agents, especially peroxidase which inactivates both hydrogen peroxide (precursor of the very cytotoxic hydroxyl radical) and some hydroperoxides, so interrupting the self-sustaining chain of lipidoperoxidation and limiting the damaging effects of this reaction on the cardiac cell membranes.

Animals↗
PubMed1986

Comparison of perioperative and postoperative phasic blood flow in aortocoronary venous bypass grafts by means of pulsed Doppler echocardiography with implantable microprobes.

Although graft dimension and hemodynamic variables have been suggested as important determinants of the functional results of aortocoronary bypass grafting, there is no easy-to-use bedside method of monitoring phasic blood flow in coronary bypass grafts. We developed a miniaturized implantable silicone pulsed Doppler flow probe linked to a classic 8 MHz pulsed Doppler system. This apparatus has an adjustable range-gated time system that permits accurate measurement of diameter (D, in mm), cross-sectional blood flow velocity (Vm, in cm/sec), and coronary bypass graft flow (CBGF, in ml/min) as pi D2/4 X Vm X 60. Ten patients (55 +/- 7.2 years SD) with preoperative left ventricular ejection fractions over 45% received the implantable flow probes during the aortocoronary venous bypass procedure. Closure of the chest altered systolic and diastolic components of flow velocity and CBGF decreased from 131 +/- 65.8 to 94 +/- 55 ml/min (-28%; p less than .01). Comparison between early postoperative values (intensive care unit) and values 6 days later showed significant increases in diameter from 4.2 +/- 0.9 to 5.3 +/- 0.9 mm (p less than .01) and in CBGF from 130 +/- 112 to 204 +/- 86 ml/min (p less than .01). We conclude that the implantable pulsed Doppler microprobe is a sensitive bedside method for monitoring aortocoronary bypass graft diameter and blood flow in the postoperative period.

Blood Flow Velocity↗
PubMed1986

Cancer of the kidney invading the vena cava and heart. Results after 11 years of treatment.

Between October, 1973, and October, 1983, 18 patients with cancer of the kidney or adrenal gland that had invaded the vena cava, and in 11 cases had reached the heart, were operated on by seven surgical teams. The surgical excision in all patients was performed with extracorporeal circulation, circulatory arrest and deep hypothermia. No deaths occurred. If there are no detectable metastases before operation, the 5 year survival rate is 75% as compared to 6 months with medical treatment. This clinical situation is not uncommon, as 3% to 10% of cancers of the kidney invade the inferior vena cava and 40% of them reach the heart. The possibility of curing the cancers with minimal operative risk should prompt a systematic search for venous invasion with any cancer of the kidney.

Adolescent↗
PubMed1985

[Peroperative echocardiography in cardiac surgery].

Echocardiography is not only useful for pre-operative evaluation of cardiac lesions and to control the quality of some surgical procedures; used peroperatively, it contributes to our knowledge of cardiac function at different stages of the operation. It has taught us that the ischaemic cardiac arrest observed in cardiopulmonary bypass results in reduction of left ventricular compliance and that this can be prevented by potassium-induced cardioplegia. It has also shown that immediately after cardiac valve replacement, the left ventricular "pump" function is reduced in aortic and mitral regurgitation and increased in stenosis. In addition, it has provided evidence that closure of the pericardium and sternum is accompanied with a fall in left ventricular compliance and with disturbances in haemodynamics. The few post-operative studies reported have shown that end-expiratory positive pressure reduces the size of both right and left ventricular cavities. Per--and post--operative studies of left ventricular regional kinetics have not yet been carried out, but this seems to be a good field of application for trans-oesophageal echocardiography.

Cardiac Surgical Procedures↗
PubMed1985

Effect of nifedipine in hypothermic cardioplegia: a phosphorus-31 nuclear magnetic resonance study.

The ability of nifedipine to enhance myocardial protection was assessed on isolated perfused rat hearts subjected to 180 min of hypothermic (20 degrees C), global ischemia, followed by 45 min of normothermic reperfusion. Intracellular pH, ATP, Pi and phosphocreatine content were serially measured at 4 min intervals by phosphorus-31 nuclear magnetic resonance spectroscopy and correlated with simultaneously recorded hemodynamic parameters. Addition of nifedipine (0.075 mumol/l and 0.5 mumol/l) to Saint Thomas' cardioplegic solution reduced Pi accumulation during ischemic arrest and increased phosphocreatine levels during reperfusion. Post-ischemic functional recovery was not improved at a drug concentration of 0.075 mumol/l and was depressed at 0.5 mumol/l. These results clearly show that the presence of nifedipine in Saint Thomas' cardioplegic solution does not provide significant additional myocardial protection under hypothermic conditions.

Adenosine Triphosphate↗
PubMed1985

Surgery for prosthetic valve endocarditis.

Infectious endocarditis is the main complication after prosthetic valvular replacement. 2 problems remain unsolved: 1. Diagnostic: Fever, heart failure and paravalvular leaks should be indications for re-operations. 2. Technical: perfect fixation of the prosthetic valve is a surgical challenge. The difficulties as shown here are the cause for so many operative techniques. Early surgical intervention is the best method to prevent myocardial failure.

Abscess↗
PubMed1985

Suppression of arrhythmias within hours after a single oral dose of amiodarone and relation to plasma and myocardial concentrations.

In 65 patients a single oral dose of amiodarone (30 mg/kg) produced an antiarrhythmic effect on supraventricular or ventricular arrhythmias within 3 to 8 hours and lasted for 17 to 19 hours. On the second day a 15-mg/kg dose reproduced this effect within 3 to 9 hours. Plasma concentration of amiodarone increased to a maximum (2.2 +/- 1.7 mg/liter) mean +/- standard deviation) at 6 +/- 3.5 hours and plasma levels of N-desethylamiodarone (NDA) rose to 0.2 +/- 0.08 mg/liter at 12 +/- 6.4 hours. Sixty-one other patients were given a single 30-mg/kg dose 7 hours to 4 days before open heart surgery. Biopsies of the right atrial and left ventricular walls were taken during surgery. Myocardial concentration of amiodarone was maximal in the atrium after 7 hours (13 +/- 8 mg/kg) and in the ventricle after 24 hours (17 +/- 11 mg/kg). NDA myocardial concentration increased progressively until 24 hours and then remained stable over 4 days (1.5 mg/kg). The amiodarone myocardial to plasma concentration ratio was similar in the atrium and in the ventricle and averaged 22 and 10 for amiodarone and NDA, respectively. A significant relation existed between amiodarone concentration and the effect on ventricular premature complexes (r = 0.74, p less than 0.001) and between amiodarone plasma concentration and the effect on the atrioventricular conduction (r = 0.58, p less than 0.001). The plasma concentration of amiodarone corresponding to a 60% decrease in arrhythmias averaged 1.5 to 2 mg/liter.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1985

Limitations of fluorocarbons in reducing myocardial infarct size.

The effects of the oxygen-carrier fluorocarbons on myocardial infarct size were assessed in non-exchange-transfused dogs subjected either to a 3-hour occlusion of the left anterior descending coronary artery (LAD) followed by 2 hours of reperfusion (protocol I) or to a 5-hour permanent LAD occlusion (protocol II). Fluorocarbon administration was begun 30 minutes after LAD occlusion and was continued over the entire period of ischemia. After 5 hours, the hearts were excised and areas of necrosis were visualized by triphenyl tetrazolium chloride staining while risk regions were assessed by radiolabeled microspheres injected after coronary occlusion just before the onset of therapy, and further, in protocol I, by thallium-201 perfusion imaging performed at the end of fluorocarbon administration. In protocol I experiments, the ratio of necrotic area to area at risk was 81 +/- 35% (mean +/- standard deviation) in control saline-treated dogs (n = 6) and 67 +/- 27% in fluorocarbon-treated dogs (n = 6) (difference not significant). There was no significant difference between risk regions measured after and before fluorocarbon treatment. In protocol II, the ratio of necrotic area to area at risk was 47 +/- 30% in control dogs (n = 5) and 63 +/- 29% in fluorocarbon-treated dogs (n = 5) (difference not significant). However, in control dogs, the ratio of necrotic area to area at risk increased from 47 +/- 30% in the dogs that underwent permanent occlusion to 81 +/- 35% in the group that underwent reperfusion (p less than 0.001) while this ratio was similar in the corresponding subsets of fluorocarbon-treated animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

[Fatal hypoxemia following extracorporeal circulation for aortocoronary bypass. A case].

A lethal case of acute respiratory distress syndrome of the adult following extracorporeal circulation for aorto-coronary bypass is reported. This case illustrates the two mechanisms currently thought to be responsible for this pathology: (1) the passage of blood over the synthetic fibres of the cardiopulmonary bypass machine activates the complement, and the systemic inflammatory reaction that ensues accounts for the increased permeability of the alveolar capillary membrane; (2) the haemodilution inherent in extracorporeal circulation explains the hypoproteinaemia usually observed at the end of the procedure; the resulting fall in capillary osmotic pressure upsets the equilibrium of pressures in the capillary vessels.

Coronary Artery Bypass↗
PubMed1985

Increased injury of hypertrophied myocardium with ischemic arrest: preservation with hypothermia and cardioplegia.

Many patients undergoing cardiac surgery have some degree of myocardial hypertrophy. To assess the response of hypertrophied myocardium to simulated cardiac surgery, left ventricular hypertrophy was induced in rats by aortic banding, and ventricular function was measured by means of the isolated, isovolumic heart perfusion technique. The hypertrophied hearts had a greater susceptibility to ischemic injury than nonhypertrophied control hearts, as manifested by a greater degree of diastolic contracture during the recovery period after 30 minutes of ischemic arrest at 37 degrees C. Hypothermia without cardioplegia during a 2-hour arrest did not completely preserve diastolic function in the hypertrophied hearts, but cardioplegia combined with hypothermia completely protected the hypertrophied hearts against 2 hours of ischemia. The results suggest a need for both hypothermic and cardioplegic preservation techniques in patients with myocardial hypertrophy who have cardiac surgical procedures requiring a significant period of myocardial ischemia.

Animals↗
PubMed1985

Enhanced cardioplegic protection by a fluorocarbon-oxygenated reperfusate: a phosphorus-31 nuclear magnetic resonance study.

Prolonged global ischemia results in a defect in oxygen extraction during early reperfusion. This study was thus undertaken to assess the effects of maintaining cardioplegia at the onset of reoxygenation in view of channeling available energy toward reparative cell processes rather than mechanical activity. Twenty-four isolated perfused rat hearts were subjected to 120 min of 15 degrees C ischemia. Group I (control) was reperfused with the standard Krebs perfusion medium whereas in groups II and III the initial reperfusate consisted of an oxygenated alkaline cardioplegic solution prior to the resumption of Krebs perfusion. Oxygenation of the cardioplegic reperfusate was ensured by fluorocarbons at a concentration of 10% (O2 content: 5.5 vol %; group II) or 20% (O2 content: 9 vol %; group III). In addition to hemodynamical determinations, high-energy phosphates and intracellular pH were monitored serially by phosphorus-31 nuclear magnetic resonance spectroscopy. After 30 min of reperfusion postischemic recovery of aortic flow was better in group II (74.0 +/- 5.9% of control) than in group I (59.1 +/- 5.4% of control, P less than 0.05). This functional improvement correlated with a higher postischemic increase in phosphocreatine levels (103.21 +/- 11.21% vs 74.12 +/- 3.59%, at 3 min of reperfusion, P less than 0.05) without significant differences in total ATP content. Group III hearts exhibited a slow recovery as evidenced by a severe depression in aortic flow, coronary arteriovenous difference, and total phosphate content during the 15 initial minutes of reperfusion. These results show that the protection provided by cardioplegia can be improved by a fluorocarbon-oxygenated cardioplegic reperfusate.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗
PubMed1985

Fluorocarbons: a potential treatment of cerebral air embolism in open-heart surgery.

This study was designed to assess whether an oxygenated fluorocarbon solution could reduce ischemic brain damage related to arterial air embolism. Air embolism was produced by injecting air bubbles into the carotid artery of barbiturate-anesthetized rats breathing 100% oxygen. Results were assessed on electrocorticogram. In an additional set of experiments, mass spectrometry was used to provide continuous monitoring of intracerebral tissue oxygen (PO2) and carbon dioxide (PCO2) tensions and intermittent measurement of cerebral blood flow (CBF). Fluorocarbon or saline solution (containing the emulsifying agent of fluorocarbons) was given intravenously after the initial air embolism (0.2 ml), and injections of air (0.1 ml) were repeated thereafter every five minutes. The maximal amount of air required to achieve complete and irreversible flattening of the electrocorticogram was 1.60 +/- 0.06 ml (mean +/- standard error of the mean) in the saline-treated rats and 5.20 +/- 0.44 ml in the fluorocarbon-treated group (p less than 10(-7)). In the second experiment, air embolism caused CBF to rise in both groups, the average percent of increase being higher in treated (41.6%) than in control animals (38.3%) (p less than 0.02). However, in the control group, the increase in CBF did not prevent intracerebral tissue PO2 from decreasing by 7.4 +/- 7.0% over the same period; conversely, in the fluorocarbon group, PO2 levels fell by only 2.5 +/- 3.7% (p less than 0.001 versus controls), but this time-averaged percentage was calculated over a longer period of cumulative ischemia because of the greater number of air emboli tolerated by treated animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Acute thrombosis of a St. Jude Medical aortic prosthesis in a pregnant woman.

A 24-year-old, 4-months pregnant woman developed an acute thrombosis of a St. Jude Medical aortic valve prosthesis. Upon admission, she was in cardiogenic shock. A thrombectomy was achieved in emergency under cardiopulmonary bypass. The patient survived but not the fetus. Diagnosis, surgical procedure, anticoagulation drugs and valve prostheses in pregnant women are discussed.

Adult↗
PubMed1985

31P-NMR study of high-energy phosphorylated compounds metabolism and intracellular pH in the perfused rat heart.

Using 31P-NMR and haemodynamical measurements, this work assesses different aspects of myocardial preservation improvement during a global ischaemia, based on a simultaneous and correlated study of high-energy phosphorylated compounds, intracellular pH and left ventricular function. Isolated perfused working rat hearts were subjected to 2 or 3 h of hypothermic ischaemia followed by 30 or 45 min of reperfusion. A study of the influence of pH and buffer used in cardioplegic solutions has demonstrated a better preservation of high-energy phosphates and an improved functional recovery when using a pH 7.0, glutamate - containing solution. Protection provided by cardioplegia can be enhanced by the appropriate use of a fluorocarbon-oxygenated cardioplegic reperfusate. The use of nifedipine, a calcium antagonist, in the cardioplegic solutions, does not provide any additional protection under hypothermic conditions.

Adenosine Triphosphate↗