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Biomedical subjects

L Segadal

Publications and source records attributed to L Segadal.

15 recordsLinked to original sources
PubMed1992

Estimation of total body fluid shifts between plasma and interstitium in man during extracorporeal circulation.

Fluid transport between plasma and interstitium during extracorporeal circulation was studied in seven patients undergoing aortocoronary bypass grafting. The absolute shifts in plasma volume during hypothermia were determined as the difference between input and loss of fluid and the changes in blood volume. The change in haemoglobin concentration due to acute haemodilution when starting extracorporeal circulation was used to calculate the absolute blood and plasma volume. The Starling equation for exchange across the capillary wall was used to describe fluid shifts. The total fluid filtered during the 60- to 90-min period of extracorporeal circulation averaged 34.1 +/- 11.1 (s.d.) ml/min. The total body filtration coefficient from the Starling relationship averaged 0.046 +/- 0.012 ml/kg.mmHg.min (0.354 +/- 0.092 ml/kg.kPa.min). Haemodilution, reducing colloid osmotic pressure in plasma (COPP) by approximately 10 mmHg (1.3 kPa) will result in a loss of plasma fluid of around 2 1 per hour. When corrected for lower fluid viscosity due to hypothermia during extracorporeal circulation, CFC would be about 40% higher, and a filtered volume of nearly 3 1 in a normothermic 70-kg person would be expected. Crystalloid haemodilution for shorter periods of time does not produce excessive oedema and thus may be well tolerated.

Aged↗
PubMed1991

[Prevention of scars. A controlled long-term study of the effect of hydrocolloid occlusive bandages after thoracic surgery in children].

We examined the development of hypertrophic scarring in 38 children undergoing thoracic surgery. The patients were observed for average 14 months. A treatment group receiving hydrocolloid occlusive bandage (DuoDERM ConvaTec, Squibb) was compared with a control group. Although the difference between the groups did not reach statistical significance there was a clear tendency towards better prevention of hypertrophic scarring in the group treated with hydrocolloid occlusive bandage.

Adolescent↗
PubMed1991

Velocity distribution model for normal blood flow in the human ascending aorta.

During the study of velocities in the human ascending aorta it became necessary to establish a method for two-dimensional velocity profiles from discrete velocity data obtained from different heartbeats and with different techniques. A descriptive geometrical model was therefore developed and expanded to 16 elements each containing 16 constants by a serial optimising technique using a least-squares method. Published data from two different studies on velocity distribution in the ascending aorta comprising six subjects with normal aortic valves were used. Three-dimensional graphic displays of velocity profile at different time intervals of the heart cycle clearly show common features of distribution of velocity at a point 6 cm above the aortic valve. There was a pronounced skewness with clockwise rotation of the skewness direction during systole, reversed flow directed towards the left coronary sinus of Valsalva in late systole and early diastole concomitant with secondary flow augmentation along the opposite wall of the aorta. Consistent plane-symmetric features during the heart cycle could not be demonstrated.

Aorta↗
PubMed1988

Simultaneous measurement of velocity, diameter, flow and pressure in the ascending aorta of cats. Evaluation of an extractable Doppler ultrasound probe for continuous monitoring of aortic blood flow.

To evaluate an extractable Doppler ultrasound probe designed for monitoring postoperative aortic flow in infants, simultaneous measurements of velocity, diameter, electromagnetic flow estimates, and pressure in the ascending aorta were recorded in cats. Doppler flow calculators were designed to provide flow estimates based on preset constant or measured instantaneous aortic diameter. Doppler sample volume was extended to about 1.2 X 1.6 X 4.0 mm. By pharmacological interventions, a wide range of flow rates and pressures were obtained, some of which were outside physiological values. The prototype probe described here was well suited for implantation in aortas with outer diameter 8-12 mm. Correlation coefficients between Doppler and electromagnetic estimated flow for 140 samples were 0.908 and 0.959 for constant and instantaneous diameter, respectively. Mean difference between the two methods was calculated, as well as the 95% confidence limits (2SD) of the differences. Limits of agreement, in stable haemodynamic situations without drugs, were -20.0 and 22.4% of mean average flow for constant diameter Doppler flow estimates, and -14.5 and 15.1% of electromagnetic flow values for instantaneous diameter estimates. These limits increased when all samples were taken into account, but the limits for instantaneous diameter estimates were reduced from -33.1 and 32.4 to -23.9 and 19.3% after removal of data obtained during isoprenaline infusion, which introduced extreme high flow/low pressure situations. This Doppler method seems well suited for postoperative monitoring of aortic flow in infants. Errors observed in larger aortas with an asymmetric flow profile do not seem to be present in smaller vessels within normal values of flow and pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Blood velocity distribution in the human ascending aorta.

Mapping of blood velocities across the lumen of the ascending aorta was performed in eight patients during open-heart surgery. A Doppler ultrasound probe was constructed to measure velocities in 2 mm steps from the maximum convexity to the maximum concavity of aorta, 6 to 7 cm above the aortic valve. In five patients with angina and normal aortic valves, velocity profiles were very similar and showed the following main features: a skewed peak systolic velocity profile with the highest velocity along the left posterior wall, a bidirectional velocity profile in late systole and early diastole with retrograde velocities along the left posterior wall, and a sustained antegrade flow along the convexity well into diastole. The resultant mean velocity profile had the highest velocity at the convex side and a central minimum velocity. In patients with Medtronic-Hall tilting disc prostheses, where the larger opening was oriented backwards and to the right, mean flow velocity profile was skewed in the opposite direction of normal. Moreover, instant systolic velocity profiles were much more irregular and dependent on the exact orientation of the prosthesis. In one patient with aortic valvular disease, very irregular and different velocity profiles were found. Based on a symmetry assumption, overall mean velocity for the total cross section was computed, and the magnitude of error in estimation of total flow from measurement of velocities at different depths was calculated. To measure total flow in the aorta, i.e., cardiac output, by single-gated Doppler technique, the most representative sampling site was about one-third of the diameter from the convex wall.

Adult↗
PubMed1985

Continuous measurement of aortic blood velocity, after cardiac surgery, by means of an extractable Doppler ultrasound probe.

A new method has been developed for the continuous measurement of aortic blood velocity in patients following cardiac surgery. Using an extractable Doppler ultrasound probe placed on the ascending aorta, the changes in aortic velocity were recorded up to 24 h postoperatively, in 14 patients undergoing coronary bypass surgery. Volume flow rate is calculated from the mean velocity, the diameter of the aorta and the angle between the ultrasound beam and the direction of the blood flow, by means of an analogue flow calculator. Estimation of aortic flow showed a correlation of r = 0.79 with cardiac output measured by a thermodilution technique. The main advantage of the system is that it allows continuous monitoring of cardiac output, as well as short and long-term trend analyses, during the early postoperative period.

Aorta↗
PubMed1985

Budd-Chiari syndrome with obstruction of the inferior caval vein: successful treatment by cavosplenoatrial shunt.

A 27-year-old man had a 10-month history of recurrent ascites, massive edema, and extreme fatigue. The diagnosis of Budd-Chiari syndrome with severe stenosis of the retrohepatic part of the inferior caval vein had been established. Medical treatment had failed to prevent further deterioration. A single 14 mm Gore-Tex graft (W.L. Gore & Associates, Inc. Elkton, Md.) was used to establish a cavosplenoatrial shunt. The postoperative recovery was uneventful. All signs of ascites and edema disappeared within 8 weeks after surgery. In connection with repair of a ventral hernia 8 months later, a liver biopsy specimen revealed partial normalization of liver histology and an angiography demonstrated a patent shunt. Two and a half years after the initial operation he developed a bleeding peptic ulcer demanding emergency surgery. The shunt was again found patent. Three years after the first operation the patient is free of symptoms and working full time.

Adult↗
PubMed1979

Sick sinus syndrome treated with permanent pacemaker in 109 patients. A follow-up study.

During the last decade implantation of permanent pacemakers has become the treatment of choice for patients suffering from the sick sinus syndrome (SSS). We have followed up 112 SSS patients treated with permanent pacemakers in Haukeland Hospital in the period 1966--76. The pacemakers were later removed from three of the patients. In the remaining 109 patients the SSS was characterized by tachy-bradyarrhythmias (TBA) in 44 and bradyarrhythmias (BA) in 65. Before implantation, 68 patients had syncopes and 27 severe dizziness. After implantation, symptomatic improvement was apparent in 104 patients; only three still had syncopes. During the follow-up period (mean 34.4 months), 29 patients died (yearly mortality 9.3%). There was no significant difference in total mortality between patients with TBA and with BA. Concomitant disturbances in atrioventricular (AV) conduction occurred in 35.8% of the patients. Among 79 of 80 patients still alive, five had developed total AV block, 19 had stable atrial fibrillation, 12 of these were possibly pacemaker-independent (ventricular rate greater than 60/min). Systemic embolization was observed in 16 patients, more frequently in the TBA (12/44) than in the BA group (4/65) (p less than 0.001). It is concluded that permanent pacemakers have an excellent symptomatic effect in patients with SSS. The prognosis is mainly determined by the presence or absence of coronary heart disease and/or heart failure.

Adolescent↗
PubMed1979

Evaluation of the microsphere-method for determination of cardiac output.

Cardiac output was determined by means of radioactive microspheres, 15 +/- 5 microns in diameter. Blood flow in the ascending aorta was measured by an electromagnetic flowmeter. In eight cats thirty-eight simultaneous measurements were made of cardiac output and aortic flow. The observations correlated well (r = 0.89), with a mean difference of 5.2%, probably corresponding to coronary blood flow. Continuous flow recordings showed no alterations in aortic flow during the injections of microspheres; arterial blood pressure and heart rate remained unchanged even after six injections, each consisting of about 2 x 10(5) spheres per kg body weight. Tests for shunting of microspheres were performed and revealed shunt fractions in the systemic circulation of about 8%, with no significant shunting through the lungs. The microsphere method for determining cardiac output is thought to be an accurate method, suitable for small and medium sized animals.

Animals↗
PubMed1976

Complications with permanent endocardial electrode systems.

The different complications of endocardial electrode systems in 185 patients during the last seven years are discussed. The surgical technique for the now routinely used cephalic route is described. The choice of anaesthesia is discussed. In the last 39 implantations there have not been any displacements or retractions. Of the total number of patients only 3 required replacement of endocardial by myocardial electrodes. This was caused by unstable position and high stimulation threshold. Fracture of the electrode occurred in 4 cases. Stimulation of the diaphragm occurred in 10%, displacement and retraction of the electrodes in 6,5% and heart penetration or perforation in 3,8% of the patients. There was one death from cardiac tamponade due to electrode perforation of the right ventricle. One case had irreversible brain damage due to prolonged asystole during pulse generator replacement. Unimportant wound infections and haematomas occurred in 5 patients and phlebitis in 3 patients. More or less serious electrode complications have been seen in 56 of the 185 patients, 18 patients having more than one complication.

Electrodes, Implanted↗
PubMedDate not supplied

Instantaneous cross-sectional flow velocity profiles: a comparative study of two ultrasound Doppler methods applied to an in vitro pulsatile flow model.

Two methods based on different techniques for construction of cross-sectional flow velocity profiles from Doppler ultrasound signals were compared: an intraluminal method using pulsed-wave Doppler echocardiography and an extraluminal method using two-dimensional (color) Doppler ultrasound. The methods were applied to an in vitro pulsatile flow model. With the intraluminal method, pulsed Doppler recordings obtained throughout several flow pulses at different positions across a tube were digitized, and cross-sectional flow velocity profiles were obtained by matching the onset of flow velocity at the various positions. With the extraluminal method, cross-sectional flow velocity profiles were obtained by time interpolation between the digital flow velocity data obtained from several flow velocity maps. The first flow velocity map was recorded at onset of flow and the following maps were incrementally delayed with 20 msec from one flow pulse to the next. The time lag caused by the time needed to update each of the flow velocity maps was compensated for by time interpolation between the sequentially recorded flow velocity maps. The cross-sectional flow velocity profiles obtained with the two methods were compared at identical positions within the tube model at equal flow settings and throughout the pulsatile flow periods. At three different flow settings with peak flow velocity of 0.3, 0.5, and 0.7 m/sec, the difference (mean +/- SD) between the obtained velocities were 0.01 +/- 0.04, -0.01 +/- 0.05, and -0.03 +/- 0.07 m/sec, respectively. The findings suggest that cross-sectional flow velocity profiles from pulsatile flow velocity recordings can be obtained equally well with both methods.

Blood Flow Velocity↗