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Biomedical subjects

B K Semb

Publications and source records attributed to B K Semb.

At least 19 recordsLinked to original sources
PubMed1993

A randomized study of neuropsychological function in patients undergoing coronary bypass surgery.

Fifty-four male patients were examined by an extensive battery of neuropsychological tests before and 1 and 6 months after coronary artery surgery. The patients were randomized to one of three methods of extracorporeal circulation (ECC): bubble oxygenation without an arterial line filter (Group I, n = 17), bubble oxygenation with an arterial filter (Group II, n = 17), or membrane oxygenation without an arterial filter (Group III, n = 20). The mean age was 59 (range 44-69) years. At 1 month nine patients (17%) and at 6 months four patients (7%) had neuropsychological deficits (reduction of 1 standard deviation in two or more tests). Postoperative intellectual dysfunction was found in groups I, II, and III at 1 and 6 months in 24% and 12%, 12% and 6%, and 15% and 5%, respectively. The differences between groups were not statistically significant. Significantly more patients in the membrane oxygenator group than in the bubble-oxygenator group without a filter performed better in the test for attention, visual scanning, and psychomotor speed and in the test for learning and memory at 1-month follow-up. In conclusion, there exists a risk of neuropsychological dysfunction after ECC, with improvement within the first 6 months, which is independent of the type of oxygenation and the use of arterial line filtration during ECC in this low-risk group.

Adult↗
PubMed1992

Magnetic resonance imaging of the brain before and after open heart operations.

Magnetic resonance imaging of the brain was performed in 29 adult male patients before and 1 week after elective coronary artery bypass grafting to study the cerebral effect of cardiopulmonary bypass. The mean age of the patients was 60 years (range, 45 to 69 years). During cardiopulmonary bypass, either a bubble oxygenator without an arterial line filter (n = 9), a bubble oxygenator with a depth adsorption filter (n = 10), or a flat-sheet membrane oxygenator without a filter (n = 10) was used. The mean bypass time was 88 minutes (standard deviation, 31 minutes) and did not differ significantly between the three groups. Preoperative magnetic resonance imaging revealed high signal intensity foci on T2-weighted images (white matter abnormalities) in 17 (59%; 95% confidence limits, 39% to 76%) of the 29 patients, all of which were nonspecific and of the common type considered to be related to aging, and all were unchanged at the postoperative examination. Preoperative and postoperative frontal horn indices, bicaudate diameters, and third ventricle widths did not differ significantly regardless of oxygenator type or whether or not an arterial line filter was used during cardiopulmonary bypass. Two patients (7%; 95% confidence limits, 1% to 23%), both receiving bubble oxygenation (1 without a filter and 1 with an arterial line filter) sustained a cerebral infarction during cardiopulmonary bypass.

Aged↗
PubMed1992

Central nervous system damage during cardiac surgery assessed by 3 different biochemical markers in cerebrospinal fluid.

Three cerebral biochemical markers, adenylate kinase (AK), neuron-specific enolase (NSE) and protein S-100, were determined in the cerebrospinal fluid (CSF) of male patients 24 h after coronary artery bypass grafting to investigate the extent of possible center nervous system (CNS) damage and relation to the type of oxygenator and the use of an arterial line filter. The patients were randomized into three groups for extracorporeal circulation (ECC); bubble oxygenator without an arterial line filter (Group I, n = 30), bubble oxygenator with a filter (Group II, n = 29) and a flat-sheet membrane oxygenator without a filter (Group III, n = 33). Pathologically high CSF levels of AK and NSE were found 24 h after ECC in respectively 93% and 95% of the patients. All protein S-100 concentrations were within the normal range. Isolated high CSF concentrations of AK, NSE and protein S-100 were observed in group I. Levels of AK and NSE were the lowest in group III, although there was no statistical difference between the groups. In conclusion, our study suggested that CNS damage caused by ECC involved neurons rather than glial cells. AK and NSE in the CSF seemed to be markers of ischaemic neuronal damage. Postoperative levels of biochemical markers in the CSF tended to be the lowest in the flat-sheet membrane oxygenator group.

Adenylyl Cyclases↗
PubMed1991

Early neurological and electroencephalographic changes after coronary artery surgery in low-risk patients younger than 70 years.

Between September 1986 and January 1988 neurological examination and electroencephalography (EEG) was performed before and one week after coronary artery bypass grafting in 66 patients younger than 70 years. Twenty patients were randomized to a bubble oxygenator without an arterial line filter (Group I), 22 patients to a bubble oxygenator with a depth adsorption filter (Group II), and 24 patients to a membrane oxygenator without a filter (Group III). No patient suffered a major stroke but early central nervous system dysfunction occurred after the operation in four patients (20%) in Group I, in four patients (18%) in group II and in two patients (8%) in group III. The difference between group I and III was not statistically significant but a larger number of patients in the groups might alter this. Our prospective study demonstrated a significant incidence of neurologic dysfunction in a low risk patient population undergoing standard coronary artery bypass surgery.

Adult↗
PubMed1989

In vitro flow characteristics of the Jarvik-7 prosthesis with respect to filling pressure, stroke frequency, and systolic duration.

The Jarvik-7 total artificial heart (TAH), as an implantable substitute for the natural heart, has become the most widely used prosthesis. Although the performance of the Jarvik-7 prosthesis has been described experimentally as well as clinically, the interrelationship between cardiac output, filling pressure, stroke frequency and systolic duration in a wider perspective has not been reported. Our in vitro evaluation of the pump demonstrates the relation between cardiac output and right filling pressure in the range of 2-17 mm Hg with a stroke frequency varying between 60-130 beats per minute with 40% and 50% systolic duration. With respect to complete ventricular filling, a safer and wider range of right filling pressures and stroke frequencies could be employed to produce various cardiac output values at 50% systolic duration as compared to 40% systolic duration. When complete diastolic filling was present, particularly with a high stroke frequency and a low systolic duration, an increase of the left filling pressure to an extent which in a clinical situation would probably cause pulmonary oedema, was observed. By using a right Jarvik-7/70 ml ventricle and a left Jarvik-7/100 ml ventricle, this buildup of the left filling pressure was completely avoided.

Blood Pressure↗
PubMed1987

Three-year clinical results with the Monostrut Björk-Shiley prosthesis.

Between November 1981 and June 1983, 351 patients underwent valve replacement with the Monostrut Björk-Shiley prosthesis. There were 214 aortic valve replacements, 101 mitral valve replacements, and 31 double (aortic and mitral) valve replacements. Four patients had valve implanted in the tricuspid position, and one patient underwent exchange of a valved, extracardiac conduit. Mean age was 61 years (range 2 to 78) and 186 (53%) were male. Concomitant procedures were performed in 52 patients (15%) and 17 (5%) were emergency operations. Early mortality (4.3%) was related to New York Heart Association Functional Class IV, emergency operation, or the presence of a concomitant procedure. Follow-up was 100% and covered 870 patients-years (mean 2.6 years per operative survivor). Postmortem examination was performed in 38 (79%) of the 48 fatalities. Only one patient suffered a sudden, unexplained death. The 3 year survival rate (early mortality excluded) was 88.6% (aortic valve replacement 89.2%, mitral valve replacement 89.3%, and double valve replacement 82.5%). The 3 year freedom from thromboembolism in patients receiving anticoagulants was as follows: aortic valve replacement 97.5%, mitral valve replacement 92.8%, and double valve replacement 100%. There were no instances of valve thrombosis or fatal embolism. In contrast, there were two instances of aortic valve thrombosis among 34 patients having aortic valve replacement without anticoagulation. The 3 year freedom from valve failure (modified Stanford definition) was as follows: aortic valve replacement 96.0%, mitral valve replacement 93.9%, and double valve replacement 89.7%. There were no mechanical failures. In conclusion, the Monostrut Björk-Shiley valve showed a low incidence of complications. There were no mechanical failures, no fatal emboli, and, when anticoagulants were administered, no valve thromboses.

Actuarial Analysis↗
PubMed1986

Evaluation of left ventricular function in children. Description of the method and normal values.

Thirteen patients between 5 and 13 years were presented as a normal material for statical and dynamical echocardiographic measurements including left ventricular internal diameter in diastole and systole, shortening fraction, cardiac output, mean VCF, maximal normalized and not normalized rates of increase and decrease of diameter. The data were compact and normally distributed, and the rates of diameter change were independent of patients' age and BSA, and may therefore be used as general reference.

Adolescent↗
PubMed1986

Echocardiographic assessment of cardiac function in open chest dogs.

Echocardiographic parameters of left ventricular function were compared with standard parameters in 5 open chest dogs. Cardiac output by echo compared with thermodilution showed a close correlation of r = 0.952. Peak rate of decrease of left ventricular diameter (RDD) correlated with dp/dtmax r = 0.826, and "normalized" RDD with dp/dtmax r = 0.873. The peak rates of increase of LV diameter (RID) and "normalized" RID correlated less with dp/dtmin, r = 0.610 and r = 0.642 respectively. Because of significant differences between the dogs, and because the results from all dogs induced into different hemodynamic states during the investigation were all pooled, the method proved reliable even under borderline conditions. We therefore think it may also be used in clinical situations.

Animals↗
PubMed1986

Echocardiographic assessment of left ventricular function in left ventricular volume load and the immediate changes after operation.

Cardiac function and changes following surgery was studied with computerized M-mode echocardiography in 12 patients with volume load of the left ventricle. Half of them had congenital lesions, the other half aortic regurgitation. Left ventricular (LV) shortening fraction and LV ejection time were significantly reduced postoperatively and came close to normal mean values. Also cardiac output and LV diameters normalized or at least started its normalization. The computerized values for rates of decrease and increase of left ventricular diameter were reduced postoperatively (p less than 0.01 and p less than 0.05 respectively) compared to elevated preoperative values. The study shows that relief of volume load on the left ventricle immediately leads to normalization of left ventricular function, especially if the myocardium was intact preoperatively.

Adolescent↗
PubMed1986

Evaluation of left ventricular function in chronical pressure load and the immediate changes after operative relief.

Cardiac function and changes following surgery was studied with computerized M-mode echocardiography in 10 patients with left ventricular pressure load, mainly valvular aortic stenosis. Six of the patients were below 15 years of age. In the adults an unfavourable reduction of shortening fraction and VCF was encountered, whereas no such reaction was seen in the pediatric group. Both groups had a significant (p less than 0.005) drop in LV ejection time. In general, however, the study demonstrated a different reaction to surgery in children and adults, the peak rate of decrease of diameter (RDD) increased in children, and remained more or less unchanged in adults, and the normalized RDD acted similarly. The time for NRDD after QRS onset was reduced in all patients, but more obvious in children. The peak rate of increase of diameter (RID) was unchanged in both groups, but demonstrated an insignificant fall on the first postoperative day in adults. The study demonstrates different ways of reacting to surgery in pressure loaded adult and childhood left ventricles. We think these differences can be explained by less damaged myocardium in the pediatric age group.

Adolescent↗
PubMed1986

Verapamil effects on left ventricular performance in patients with congestive heart failure studied with echocardiography before and after cardiac surgery.

Cardiac effects of a single dose of verapamil was studied with digitalization of M-mode echocardiograms in 6 patients before and after surgery, along with pharmacological examinations. Corresponding to the different distribution volume and excretion pre- and postoperatively, the cardiodepressive effect on the contraction of the left ventricle was more pronounced and lasted longer postoperatively. Probably due to initial reduction of peripheral resistance, there was an initial improvement of ventricular contractility indices. Obviously depending on serum concentration, maximal cardiodepression occurred at 35-40 ng/ml, and no effect could longer be found as the values reached 20 ng/ml, pre- as well as postoperatively.

Adult↗
PubMed1986

Mechanical failure of the Björk-Shiley valve. Incidence, clinical presentation, and management.

The experience after implantation of 3,334 Björk-Shiley valves over a 15 year period is described. With a 99.2% follow-up (covering 17,511 patient-years, mean follow-up time 6.3 years) and an autopsy rate of 75% among all fatalities, altogether 19 cases of mechanical failure were documented. There were no mechanical failures among the standard Delrin Björk-Shiley valve (n = 271), the aortic standard Pyrolyte Björk-Shiley (n = 739), or the Monostrut Björk-Shiley valve (n = 377). One of the mitral standard Pyrolyte valves (n = 430) fractured. Among the 1,461 convexo-concave valves, 18 fractured (6/884 with an opening angle of 60 degrees and 12/577 with an opening angle of 70 degrees). The actuarial incidence of mechanical failure at 5 years was 0.6% (with an upper 95% confidence limit of 1.2%) for the 60 degree convexo-concave valve and 2.8% (upper 95% confidence limit of 4.4%) for the 70 degree convexo-concave valve (p less than 0.01). Two groups of valves were especially affected by this complication; the 23 mm aortic 60 degree convexo-concave valve (5 year actuarial incidence 2.2%, upper 95% confidence limit 4.7%) and the 29 to 31 mm mitral 70 degree convexo-concave valve (8.3%, upper 95% confidence limit 14.2%). The hazard function presently indicates a constant (60 degree convexo-concave) or decreasing (70 degree convexo-concave) tendency for mechanical failure. The time interval between the first symptom of mechanical failure and circulatory collapse was significantly (p less than 0.01) shorter after aortic failure than after mitral failure, and no patient with a fractured aortic prosthesis survived long enough to undergo reoperation. The incidence of mechanical failure among patients dying suddenly (but with an autopsy) was 9.6% (95% confidence limits 4.9%-16.6%), and most cases of sudden death were unrelated to the prosthesis. The management of patients with suspected mechanical failure is described. Prophylactic re-replacements are discussed but cannot be generally recommended at present.

Adult↗
PubMed1985

Echocardiographic assessment of cardiac function and morphology in patients with generalised lipodystrophy.

Because cardiomegaly has been observed in lipodystrophic patients we studied cardiac morphology and function with one- and two-dimensional echocardiography in addition to general cardiologic examination in a series of seven patients. Muscular hypertrophy with increased chamber size and myocardial indentations were found. Two patients had asymmetrical septal hypertrophy (ASH), and two patients demonstrated systolic anterior movement (SAM) of the mitral valve. Wall motion analysis showed anomalities in four patients during contraction, in three during the early relaxation phase. Since pathological findings, probably increasing with age, were made in the majority of the patients, these findings add an additional unfavourable aspect to the syndrome.

Adolescent↗
PubMed1985

Angiographic and echocardiographic observations in surgical patients with atrial myxoma.

In a series of 18 patients with atrial myxoma (16 left, 2 right) the tumors were consistently identified by right ventriculography and generally visualized by left ventriculography in patients with left atrial myxoma examined owing to concomitant mitral insufficiency caused by tumor invasion at the site of mitral valve closure. Echocardiography was suited to early diagnosis of suggested tumor. Pseudoaneurysms in the cerebral and coronary arteries, apparently caused by myxomatous emboli with weakening of vessel lumen, were noted in several patients; therefore, selective coronary and cerebral arteriography should be performed preoperatively in patients with symptoms of thromboembolism. We stress that echocardiography should be performed routinely after surgery to disclose recurrences, while arteriographic control studies should be added in cases with vascular anomalies seen preoperatively.

Adult↗
PubMed1985

Assessment of prosthetic mitral valve pressure gradients by means of ultrasound Doppler technique and on-line spectral analysis.

The blood speed through prosthetic mitral valves was determined using ultrasound Doppler techniques combined with on-line spectral analysis. Spectral analysis was particularly suitable for maximum velocity estimation due to its superior ability in discriminating between Doppler signals and white background noise. From a simplified Bernoulli equation the corresponding transprosthetic pressure drop was calculated and estimates were compared against pressure gradients obtained by conventional intracardiac catheterization. A close relationship between the ultrasonic- and the manometric transprosthetic pressure gradients was found, but the ultrasonic method tended to systematically underestimate the pressure gradients slightly.

Blood Flow Velocity↗
PubMed1985

Gas bubble detection in fluid lines by means of pulsed Doppler ultrasound.

A pulsed Doppler instrument running at 1.5 MHz resonance frequency was used for detection of microbubbles within a recirculating fluid line. Glass beads of nominal 200 microns were injected to get a statistical calibration level of the set-up. This is achieved by identifying the peak intensity of the bubble size histogram which reflected the microsphere size.

Gases↗
PubMed1985

Comparison of bubble release from various types of oxygenators.

A comparative study of microbubble release from various types of oxygenators was performed using ultrasonic Doppler techniques. Bubble count versus amplitude histograms were calculated to derive the statistical distribution of the relative microbubble sizes. To compare the different oxygenators with respect to differences in microbubble releases, several key parameters as, temperature, liquid flow rate, gas to flow relationship, liquid level within the oxygenator, were altered one at a time to indicate different and oxygenator related sensitivities with respect to variations of the key parameters.

Extracorporeal Circulation↗