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Biomedical subjects

T Frøysaker

Publications and source records attributed to T Frøysaker.

At least 73 records · Page 4Linked to original sources
PubMed1984

Superior caval vein stenosis due to giant aneurysm of the right coronary artery.

Aneurysms of the coronary arteries may cause angina, myocardial infarction or sudden death due to thrombosis, embolization or rupture. The patient described herein may represent the first reported case of a large coronary artery aneurysm compressing the upper caval vein, and thereby producing a significant inflow gradient. The anatomical details were demonstrated by digital subtraction angiography (DSA). The patient successfully underwent resection of the aneurysm and reconstruction of the coronary artery with a saphenous vein bypass graft.

Aneurysm↗
PubMed1984

Catecholamine responsive adenylate cyclase in human myocardial preparations. Properties and optimalization of assay conditions.

In the present study we have investigated the conditions for optimal adenylate cyclase (AC) activity in preparations of human myocardial biopsies, with emphasis on both basal enzyme activity and isoproterenol response. Different preparation procedures (homogenates, membrane particles) of the same biopsy showed no difference in relative response to isoproterenol, although absolute activities, using protein concentration for normalization, showed some variance. The AC-receptor complexes of the preparations were also stable when stored on ice for 3 h, and both basal and stimulated AC activities were constant at a wide range of protein concentrations (2.9-31.9 micrograms/tube), and throughout 92 min incubation. The effects of varying Mg2+, guanyl nucleotides (GTP, GMP-P(NH)P), and ATP concentrations on myocardial AC activities were also investigated under both basal conditions as well as after isoproterenol stimulation. The apparent Km for the substrate (Mg X ATP) binding to the AC was approximately 0.1 mmol/l. Isoproterenol stimulated the AC activity by increasing Vmax (41 to 142 pmol/mg protein X min) without any change in the apparent Km. Maximal relative activation by isoproterenol was achieved at pH 6.5-7.0. The concentration of isoproterenol causing half maximal AC stimulation was approximately 0.1 micrograms/ml (2 X 10(-4) mmol/l). Half maximal inhibition of isoproterenol (4 micrograms/ml) stimulated AC activity was obtained by 0.025 micrograms/ml propranolol (8 X 10(-5) mmol/l). The sensitivity and precision of this assay should make it possible to measure AC activity as well as isoproterenol response in very small quantities of myocardial tissue. This could provide a method for studying receptor functions of sick hearts by endomyocardial biopsies.

Adenosine Triphosphate↗
PubMed1983

Cerebral damage following open-heart surgery in deep hypothermia and circulatory arrest.

Six patients undergoing aortic arch replacement during deep hypothermia and circulatory arrest were subjected to studies including serial determinations of total creatine kinase (CK) activity in the cerebrospinal fluid (CSF), monitoring of the intracranial epidural pressure and the cerebral perfusion pressure and clinical neurological evaluation. In two of four patients with postoperative pressure monitoring, a marked increase in pressure was seen. In one case this pressure rise terminated in brain tamponade six days postoperatively, despite aggressive treatment with steroids, mannitol and barbiturate. In comparison with patients undergoing surgery for valve replacement or aorto-coronary by-pass, some of the patients with aortic arch replacement clearly sustained more severe cerebral damage, as judged by clinical examination and autopsy findings as well as by assessment of the degree or extent of the neuronal damage from CK activity in CSF. Patients of this type are obvious candidates for postoperative neuro-intensive monitoring and care. Repeated pulsed Doppler flow velocity determinations in precerebral arteries, performed bedside, combined with monitoring of the cerebral perfusion pressure, provide a useful indication of the cerebral circulatory state in such situations.

Adult↗
PubMed1983

Monitoring of intracranial pressure after open-heart surgery.

Brain damage following open-heart surgery is receiving increasing attention. Efforts are being made to improve the setting for cardiac surgery so as to avoid such complications. When they occur, their recognition is retrospective, when the cerebral lesion is inevitable. Because heavy sedation is necessary, clinical supervision with respect to brain function is both difficult and unreliable in the early postoperative period. We therefore submitted 34 selected patients to neurosurgical intensive care supervision. The measures included postoperative monitoring of intracranial epidural pressure (EDP), of arterial blood pressure (BP) and of central venous pressure (CVP). In 25 patients there was rise in EDP during the first postoperative hours. Six of these patients received mannitol treatment and in three of them barbiturate was additionally given, in order to reduce EDP and improve the cerebral perfusion pressure (CPP = BP-EDP). Nevertheless EDP progressed to brain tamponade six days postoperatively in one case. In patients with raised EDP, weaning from the ventilator should be postponed until EDP has almost normalized. The EDP recording is a valuable guide in the postoperative management of the individual patient.

Blood Pressure↗
PubMed1983

The clinical significance of changes in cerebral perfusion pressure during open-heart surgery.

In 34 high-risk patients, the intracranial epidural pressure (EDP) and the cerebral perfusion pressure (CPP) were monitored in connection with open-heart surgery. The findings were clinically evaluated, with special attention to affection of the central nervous system. Reduction of EDP to 10-30 mmHg for periods up to 10 min at the start of extracorporeal circulation and transient rise of EDP in the early postoperative period were relatively well tolerated. Late postoperative EDP rise, on the other hand, denoted an unfavourable trend, associated with permanent cerebral damage. Mannitol and/or barbiturates are indicated when an early rise in postoperative EDP persists or a late rise occurs. Covariation of EDP and arterial blood pressure (BP) should be regarded as a warning sign, especially if it is pronounced or appears during the postoperative course. In such conditions it seems important to stabilize the CPP by reducing a high EDP and by careful management of BP variations, i.e. with use of vasopressors. Postoperative epileptiform seizures seem to be prognostically unfavourable.

Adolescent↗
PubMed1982

Aspects of cerebral perfusion in open-heart surgery.

A selected series of 25 patients undergoing open-heart surgery were subjected to continuous monitoring of arterial blood pressure (BP), central venous pressure (CVP) and intracranial epidural pressure (EDP). This gave continuous information on the cerebral perfusion pressure (CPP = BP-EDP). In all patients the start of the extracorporeal perfusion caused a rapid fall in CPP (30 mmHg or less in 22 patients, less than 10 mmHg in 5 patients). The combination of grave systemic hypotension and increased EDP contributed to these low CPP states, which varied in duration from 2 to 15 min. Spontaneous, as well as vasopressor-induced BP recovery was accompanied by a concomitant increase in EDP in 15 patients. This prolonged the low CPP state, making an evaluation of CPP from BP alone misleading under such conditions. Increasing EDP secondary to a rise in BP was also observed during termination of the extracorporeal circulation, particularly in 6 patients requiring an intra-aortic balloon pump in addition to large doses of vasopressors to obtain an acceptable BP. An increase in CVP to levels above EDP is transmitted intracranially, thus reducing the CPP. The recordings may improve insight into pathogenic mechanisms leading to harmful effects on the brain in connection with open-heart surgery.

Blood Pressure↗
PubMed1982

Use of Haemonetics Cell Saver for autotransfusion in cardiovascular surgery.

The Haemonetics Cell Saver was evaluated as a tool for the refining of blood shed during cardiovascular surgery. After blood filtration the red cells are concentrated, washed and re-infused as red cells suspended in normal saline (CS blood) with haematocrit around 60%. Platelets and plasma with desired and undesired components are removed. In 50 patients undergoing elective but complicated cardiovascular surgery an average of 4.4 units CS blood were produced. In 3 Jehovah's Witnesses the method was used in combination with immediate preoperative prebleeding and dextran infusion. No blood products were given. The haematocrit was maintained at a safe level subsequent to retransfusion. Platelet counts were never critically low and extremely low total protein did not lead to peripheral or pulmonary oedemas or coagulation problems. In an in vitro study it was shown that extreme dilution of coagulation factors is well tolerated before the clotting time (ACT) is affected. The Cell Saver proved to be an effective, reliable and safe device for autotransfusion of salvaged blood during cardiovascular surgery.

Adult↗
PubMed1982

Posterior left ventricular aneurysm due to occlusion of the circumflex coronary artery with recurrent ventricular tachycardia. Case report.

A 62-year-old male developed a large posterior left ventricular aneurysm diagnosed 6 months after a sustained myocardial infarction. Coronary angiography revealed a proximal occlusion of the circumflex artery, two 75% stenoses of the right coronary artery and a normal left anterior descending artery. The main clinical indication for surgery was residual bouts of ventricular tachycardia. A successful "mechanical conversion" of this arrhythmia by means of light precordial knocks in the apex region is reported. In this way the patient could be prepared for surgery without using myocardial depressant drugs. The aneurysm was resected, encircling endocardial ventriculotomy was performed and the right coronary artery was grafted. Nine months after the operation the patient is well without the need for antiarrhythmic drugs. The rarity of this condition is stressed and the possible mechanisms of ventricular tachycardia and its treatment in this particular case are discussed.

Coronary Disease↗
PubMed1981

Surgical treatment of aneurysms of the aortic arch.

A new approach to the challenge of surgical treatment of aneurysms of the aortic arch is described. Former techniques have been dependent on separate cannulation of the cerebral arteries, but induction of deep total body hypothermia to 15 degrees C and circulatory arrest is considered to give sufficient time for resection of the aneurysms and completion of the anastomoses. This is made possible by excising the aneurysms in such a way that the orifices of the three arch vessels are trimmed to leave a small cuff of tissue around the vessels, thereby reducing the number of anastomoses to three. The successful treatment of three patients with this method, is reported.

Adult↗
PubMed1980

Development of a canine model for long-term studies after mitral valve replacement with the hall-kaster prosthesis.

The present study was designed for long-term evaluation of the recently developed Hall-Kaster heart valve prosthesis. Mitral valve replacement was performed in 33 dogs. A detailed description of the operative procedure used is given. Extracorporeal circulation was instituted using a nonhemic priming volume resulting in an extreme hemodilution with hematocrit of about 15%. 19 of the animals died within 24 h, while 7 survived the observation period of 4--6 weeks. Thrombus on the valve was the major cause of early and late deaths. Anticoagulants were therefore given, and the therapy was made more extensive as the study progressed. The anticoagulation regime finally comprised warfarin administration preoperatively and throughout the experiment, and heparin infusion during the first 24 h postoperatively. Neomycin was used for preoperative sterilization of the gut. Later, cephalotin and penicillin were given. The use of these anticoagulants and antibiotics was found to be of major significance in providing us with a satisfactory canine model for long-term in vivo evaluation of the prosthesis.

Animals↗
PubMed1979

An ultrasound Doppler technique for the noninvasive determination of the pressure gradient in the Björk-Shiley mitral valve.

The accuracy in determining the pressure gradient in the Björk-Shiley mitral implant from noninvasive ultrasound Doppler data was explored in nine adult patients. Manometric and ultrasound data were collectd simultaneously, and identical diastolic periods were used to compare the manometric gradient (delta Pm) with the gradient obtained from ultrasound data (delta Pu). In the nine patients the mean diastolic value of delta Pm ranged from 2-12.5 mm Hg and the difference between the mean diastolic values of delta Pm and delta Pu was 0.3 +/- 1.0 mm Hg(SD). The results of the investigation indicated that the method is accurate and reliable in the nonivasive determination of the mean diastolic gradient in the Björk-Shiley mitral implant.

Blood Pressure↗
PubMed1979

In vivo haemodynamic evaluation of the Hall-Kaster central flow prosthetic heart valve.

The first in vivo haemodynamic observations of the recently developed Hall-Kaster central flow prosthetic heart valve are reported. Haemodynamic evaluation of valve function was performed both in acute and chronic experiments following implantation of the Hall-Kaster prosthesis in the mitral position in dogs. These studies showed a low transvalvular pressure gradient, an effective opening angle of about 70 degrees and good diastolic flow through both the large and small orifices of the prosthesis. A slow rotational movement was depicted by the disc during opening and closure.

Animals↗
PubMed1979

Aortic valve replacement. A randomized study comparing the Björk-Shiley and Lillehei-Kaster disc valves. Late haemodynamics related to clinical results.

In this study, 78 randomized patients with either Björk-Shiley (B-S) or Lillehei-Kaster (L-K) aortic disc valve prostheses were re-admitted for clinical and haemodynamic evaluation. The patients were selected that those with narrow aortic roots were over-represented. Cine-aortography was carried out in 75 patients and left ventricular catheterisation via the transseptal approach was performed in 42. The clinical improvement was striking, although the number of patients still incapacitated was relatively large in patients with the small L-K valves (Nos. 14 & 16). Peak-to-peak and mean systolic pressure differences across the valves were significantly lower in the B-S than in the L-K valves, particularly when the small valve sizes were compared. Left ventricular end-diastolic pressure (LVEDP), which was elevated in most patients before operation, decreased significantly to normal levels in the B-S group. In the L-K group, LVEDP did not decrease significantly and was on the average still above the normal level after operation, probably due to the relatively large pressure gradients. The study indicates that the L-K valves Nos. 14 & 16 in particular represents a resistance to flow that is too large to be acceptable in clinical practice.

Adult↗
PubMed1979

Clinical and haemodynamic observations after combined aortic and mitral valve replacement with the Björk-Shiley tilting disc valve prosthesis. Early and late results in 25 patients.

Combined mitral and aortic valve replacement with the Björk-Shiley tilting disc valve (pyrolite) was performed in 25 unselected patients characterized by markedly impaired functional capacity, hypokinetic central circulation and cardiomegaly before operation. Surgery was performed during extracorporeal circulation with deep hypothermia. The mitral valve was replaced first in all cases. There were no intra-operative deaths, but 2 patients died while still in hospital (8.0%). One patient died 2 months postoperatively due to progressive heart failure. The remaining patients--with the exception of one who had died of cancer of the ovary--were re-examined in average 28.7 (18-40) months postoperatively. Most patients had improved symptomatically and were in functional classes I-II (N.Y.H.A.). The haemodynamic findings indicated restoration to normal resting values of cardiac output, pulmonary artery pressure and pulmonary vascular resistance, but with an increase in left ventricular end-diastolic pressure (LVEDP). The mean diastolic gradient across the mitral prosthesis varied from 0 to 11 mmHg, while simultaneous pressure recordings from the left ventricle and the aorta, with one exception, disclosed no systolic pressure gradients (peak) across the aortic valve. Postoperative arterial thrombo-embolic complications occurred in 2 patients, resulting in only minor neurological sequelae.

Adult↗