Biomedical subjects
J L Peters
Publications and source records attributed to J L Peters.
Letter: Myocardial oxygen consumption.
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Transapical left ventricular bypass (TALVB) without an auxiliary ventricle.
A simple transapical left ventricular bypass system employing a roller pump, transapical LV withdrawal catheter, and outflow filter for continuous blood filtration, has been developed and evaluated in unanesthetized sheep for periods beyond 2 wks. The system provides continuous partial LV bypass and is capable of totally maintaining the circulation in the presence of a vasodilator or when total bypass is desired. Blood damage is minimal and blood transfusions have not been required. The transapical withdrawal catheter has been left in the LV apex beyond 4 mos and demonstrates thrombus formation and myocardial histological changes which suggest this catheter should be removed after pumping or long-term anticoagulation provided.
Use of artificial heart for basic cardiovascular research.
Improved technology in artificial heart development and implantation studies in unanesthetized calves have stimulated a new model for cardiovascular research. Independent control of the left and right ventricles, replacement of the natural right atrium with an artificial atrium (with a compliant inner diaphragm) are illustrated as examples of new methods to study the cardiovascular system. Preliminary results in three calves suggest that synchronous ventricular pumping is not required for total circulatory maintenance. In four calves a passive artificial right atrium was shown to decrease outflow obstruction to the right ventricle. A compliant inner deiapragm demonstrated a reduction in the amplitude of the atrial C and V waves. The effects of volume and drug infusion on peripheral vascular response in the presence of controlled artificial heart pumping (which does not respond to direct neural or hormonal influences) further illustrate the efficacy of this preparation as a new model for cardiovascular research.
Comparative evaluation of artificial ventricles in the United States.
A cooperative, comparative evaluation of nine artificial ventricles was performed on two standardized mock circulations. The ventricles included five air-driven diaphragm types, three sack types and a mechanically driven type. The slopes of the ventricular output curves varied from 0.04 to 0.88 at 0 to 5 Torr filling pressure and the maximum ventricular output varied from 3.8 to 11.9 liters/min at 100 Torr outflow pressure. All ventricles had decreased output with increased outflow pressures (70 to 130 Torr). Hemolysis index ratio (HI test/HI std) for HI std equals 0.024 plus or minus .005 (plus or minus 1 SD) g/100 liters (N equals 12), was +21.5 and +6.9 for a Dacron cloth and fibril heart, respectively, +2.0 to +2.86 for three sack ventricles, and +3.2 for a smooth diaphragm ventricle. The mechanical ventricle with a sinusoidal driving waveform and smooth surface had the lowest hemolysis, HI equals 0.008 plus or minus 0.003 (plus or minus 1 SD) (N equals 6). Sack ventricles caused marked hemolysis if the walls touched during systole. Ventricular dimensions varied: weight 116 to 700 g, length 9.2 to 18.7 cm, and volume 235 to 430 ml. Performance data was returned to each individual laboratory which resulted in modification of ventricular design in at least three instances. Comparative, standardized testing of artificial ventricles may shorten development time and provide performance criteria for application in man.
Consequences of the diaphragm driven artificial heart-animal implantation and mock circulation studies.
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Hemic and spirometric profiles in calves used for cardiovascular research.
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Artificial heart with hemispherical ventricles II and disseminated intravascular coagulation.
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Electroencephalographic sleep in clinically stable schizophrenic patients: two-weeks versus six-weeks neuroleptic-free.
EEG sleep studies in schizophrenic patients are influenced by alterations in clinical state and medication status. The current study defines longitudinal alterations in electroencephalographic (EEG) sleep for 10 healthy men who were schizophrenic patients who remained relatively clinically stable during a double-blind neuroleptic withdrawal study. Clinical assessments and EEG sleep studies were performed at baseline on haloperidol, and then at 2-week and 6-week drug-free periods. Sleep continuity and rapid eye movement (REM) sleep measures declined not only between the haloperidol baseline and 2-week drug-free conditions, but continued to decline from 2-week to 6-weeks neuroleptic-free. Alterations in EEG sleep from the 2-week to 6-week haloperidol-free assessments did not correlate with changes in clinical symptoms suggesting effects related to drug-withdrawal or subclinical state changes. These results show that despite relative clinical stability over time, the EEG sleep of schizophrenic patients continues to change following withdrawal of a neuroleptic and is dependent on the duration of the drug-free interval.
Clonidine improves memory function in schizophrenia independently from change in psychosis. Preliminary findings.
This study provides initial evidence that the alpha 2-adrenergic receptor agonist, clonidine, enhances memory functioning in hospitalized schizophrenics. Ten patients were tested while drug free and while on stable doses of clonidine (0.4-1.4 mg/day) for approximately 3 weeks. Throughout the duration of the study, all patients, as well as the examiner, were blind to medication status. Memory test scores were significantly better during the clonidine trials. This improvement occurred independently of change in psychosis. Clonidine does not improve memory in normal adults or in young and unimpaired animals, but has been shown to improve memory in Korsakoff's patients and non-human primates who are old or have dorsolateral prefrontal cortical lesions. The present results have implications for the role of the noradrenergic system in memory as well as for our understanding of the nature of the cognitive deficits associated with schizophrenia.
Lack of CNS depression from large doses of trimethaphan in sheep.
It is not uncommon to observe prolonged CNS depression for several hours following controlled hypotension and halothane anesthesia for neurosurgery. The present study evaluates possible contribution of large doses of trimethaphan to CNS depression. Four adult sheep were placed on transapical left ventricular bypass (TALVB) withdrawing blood from the apex of the left ventricle through a roller pump, Pall Ultipor filter, and returning the blood to a carotid artery. In the awake and unanesthetized animals, 1 to 2 gm of trimethaphan were administered IV during each experiment while maintaining mean arterial pressure at 60 to 75 torr. Two sheep stood up and knelt down without obvious correlation with dose of trimethaphan administered at the time; two remained standing and continued eating during the trimethaphan infusion. Cardiovascular recovery from these large doses of trimethaphan was within 15 to 30 minutes after the conclusion of drug infusion. The data strongly suggest that large doses of trimethaphan have no significant CNS depression in the awake and unanesthetized sheep.
Management of colonic injury following percutaneous nephrolithotomy.
Injury to the colon during percutaneous nephrolithotomy is rare. There are no definitive management guidelines for this injury. We report a case of left-sided colonic injury diagnosed following percutaneous nephrolithotomy and suggest a treatment algorithm.
Effects of retrovenous myocardial drug delivery after coronary artery occlusion in sheep.
Retrovenous (RV) myocardial delivery of blood and drugs into the coronary sinus (CS) through a 3 lumen balloon catheter was evaluated in sheep (no coronary collaterals) for protection from ventricular fibrillation (VF) during coronary artery occlusion. The balloon was asynchronously inflated (CS occlusion) for 5 sec and then deflated for 5 sec with 1 cc/sec of flow. The left anterior descending coronary artery was occluded with inflation of a percutaneous transluminal coronary angiography balloon and therapy started immediately. In a control group (no therapy, n = 4) all developed VF by 30 min after coronary artery occlusion. The drugs lidocaine (L), esmolol (E), adenosine (A), and deferoxamine (D) were evaluated for effects on eliminating developing VF with intravenous (i.v.) administration compared with RV administration with venous blood (VB) or arterial blood (AB). The percent survival after CA occlusion (no VF) was: L i.v., 0%; L RV with VB, 43%; L RV with AB, 17%; E i.v., 50%; E RV with VB, 70%; A. i.v., 29%; A RV with VB, 88%; D i.v., 17%; and D RV with AB, 80%. There was a trend toward lower myocardial necrosis (seen by tetrazolium stain and/or light microscopy) in the RV survivors (especially with VB) compared with the group i.v. survivors. These data suggest that RV antiarrhythmic drug delivery is a feasible alternative to i.v. administration during CA occlusion.
Rhythmic fluctuations in blood pressure in the decapitate dog.
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Total maintenance of circulation in the closed-chest animal with ventricular fibrillation.
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Tattooing: a Nova Scotia experience.
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