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H K Pedersen

Publications and source records attributed to H K Pedersen.

At least 19 recordsLinked to original sources
PubMed2001

Hemispheric differences for visual matrix processing: stimulus size and spatial frequency effects.

Hemispheric processing differences were assessed by presenting square matrices that varied in size and the number of filled-in cells. Subjects judged whether the matrix contained an even or odd number of filled cells. Experiment 1 employed relatively small matrix sizes (2 x 2, 3 x 3, and 4 x 4), and Experiment 2 employed relatively large matrix sizes (4 x 4, 6 x 6, and 8 x 8). Response time was shorter and error rates lower for left visual field/right hemisphere (LVF/RH) presentations compared to right visual field/left hemisphere (RVF/LH) presentations, with the larger matrices demonstrating the strongest visual field/hemispheric effects. Increases in the number of filled cells contributed to increases for the LVF/RH response time advantage only for the larger arrays. Analysis of the data from both studies collapsed across the number of filled cells produced highly consistent LVF/RH advantages for both response time and error rate, with stronger LVF/RH advantages found for the larger matrix sizes of both studies. The findings suggest that visual stimulus spatial frequency is a key determinant of hemispheric processing advantages, but that this factor is constrained by stimulus size variation. Theoretical implications with respect to the hemispheric processing double filtering by frequency model are discussed.

Adult↗
PubMed2001

CTA in patients with acute subarachnoid haemorrhage. A comparative study with selective, digital angiography and blinded, independent review.

PURPOSE: Minimal- or non-invasive methods replacing intra-arterial digital subtraction angiography (IA-DSA) would be of great importance in patients suffering from acute subarachnoid haemorrhage (SAH). The aims of this study were to compare CTA with IA-DSA in patients with acute SAH, to compare CTA interpretations with those of blinded, independent reviewers and to evaluate improvement in CTA diagnostics after 1 year of experience with CTA. MATERIAL AND METHOD: During 2 years 162 patients with SAH underwent CTA as well as IA-DSA. Independent blinded review of 77 patients was performed for 1 year. RESULTS: Totally 144 aneurysms were demonstrated in 119 patients at IA-DSA, while 43 patients had normal intracranial arteries. Initially 131 aneurysms were detected at CTA while 2 normal, tortuous arteries were misinterpreted as aneurysms, giving a sensitivity of 91% and a specificity of 95%. At independent blinded review the observer agreement was 87% and the kappa value 0.68. CONCLUSION: CTA in SAH is of great value in demonstrating vascular anatomy and the exact size of an aneurysm. However, IA-DSA is still needed for diagnostic evaluation in aneurysms smaller than 5 mm in diameter, especially in those located near bony structures.

Acute Disease↗
PubMed2000

Improving postoperative MR imaging of pituitary macroadenomas: comparison of full and reduced dose of gadopentetate dimeglumine.

The aim of this study was to evaluate the efficacy of contrast-medium (CM)-ehanced MR imaging of operated pituitary macroadenomas with reduced dose of gadopentetate dimeglumine. In a prospective study 18 patients were examined with coronal T1-weighted MR imaging prior to and following intravenous CM injections. Two sets of contrast-enhanced coronal images were obtained in each patient; the first set after 50% of the recommended dose of 0.1 mmol/kg body weight (b.w.) had been administered, and the second set immediately after additional CM had been given to make up a total dose of 0.1 mmol/kg b.w. The images were evaluated by three neuroradiologists. The SIPAP classification system was used to evaluate tumour extension, whereas tumour margin conspicuity was scored using an arbitrary scale of 1-5 (1 = indistinct, 5 = well defined). Signal intensity measurements obtained from the most enhancing part of the adenomas demonstrated increased enhancement with increased CM dose. Tumour delineation scores were significantly better on the reduced- and full-dose images than on pre-CM injection images, but, with one exception, tumour extension was identified as the same on all imaging sequences. Postoperative MR imaging of large macroadenoma residues can routinely be performed without intravenous CM. When CM is indicated a reduced dose of gadopentetate dimeglumine should provide sufficient diagnostic information.

Adenoma↗
PubMed1997

Cardiovascular effects of MnDPDP and MnCl2 in dogs with acute ischaemic heart failure.

PURPOSE: To examine the cardiovascular effects of MnDPDP in a model of acute heart failure in the dog, and to compare these effects with those of MnCl2. MATERIAL AND METHODS: The study involved slow i.v. infusion of either 10, 60 and 300 mumol/kg of MnDPDP, or 1, 6 and 30 mumol/kg MnCl2, in increasing doses to groups of 5 dogs. Acute ischaemic heart failure was first induced by injection of polystyrene microspheres (50 +/- 10 microns) into the left coronary artery until a stable left ventricular end-diastolic pressure of approximately 20 mm Hg was achieved. The following test parameters were measured: left ventricular end-diastolic pressure; the first derivatives of maximum rate of left ventricular contraction and relaxation; mean aortic pressure; pulmonary artery pressure; right atrial pressure; cardiac output; heart rate; QT-time; PQ-time; QRS-width; and plasma catecholamines. RESULTS: Slow infusion of MnDPDP at doses up to and including 12 times the clinical dose was well tolerated in dogs without further depression of cardiovascular function during acute ischaemic heart failure. At 300 mumol/kg, i.e. 60 times the human dose, only minor haemodynamic and electrophysiological effects were seen, and these were similar to those seen after administration of 30 mumol/kg MnCl2. CONCLUSION: The present study suggests that slow infusion of MnDPDP should not cause further deterioration of cardiac function in patients with heart failure.

Acute Disease↗
PubMed1996

[Spread of an imported multiresistant Staphylococcus aureus to other hospitals via secondary colonized patients].

UNLABELLED: A secondary spread of an imported methicillin-resistant Staphylococcus aureus strain (MRSA) to two other patients occurred within a Danish surgical ward in spite of isolation of a multitraumatized index-patient immediately after arrival from a hospital in the Mediterranean area. The two other colonized patients were later transferred to other hospitals in Denmark where it became apparent that they had developed serious infections with the MRSA strain. IN CONCLUSION: to prevent spread of imported MRSA within Danish hospitals, strict adherence to isolation procedures and a high level of general hygiene is essential not only when patients are transferred from hospitals situated in endemic areas of MRSA abroad, but also when admitted from Danish hospital wards where known cases of colonisation or infection with MRSA exist.

Cross Infection↗
PubMed1996

Coronary arteriography with an oxygenated contrast medium: cardiac effects in dogs with and without acute ischemic heart failure.

RATIONALE AND OBJECTIVES: We investigated the possible cardiac effects of oxygen addition to contrast media (CM) during coronary arteriography in dogs that did and did not have ischemic heart failure. METHODS: Acute ischemic heart failure was induced by injecting small plastic microspheres into the left coronary artery of 18 dogs. Hemodynamic and electrophysiologic measurements were performed during a single injection before and during heart failure and during a single injection and five rapidly repeated CM injections during heart failure. Iohexol supplemented with electrolytes (iohexol + electrolytes = IPE), oxygenated IPE (IPE+O), Ringer acetate, and oxygenated Ringer acetate were injected into the left coronary artery. RESULTS: Single injections of IPE and IPE+O induced small hemodynamic and electrophysiologic effects. However, repeated injections of IPE and IPE+O increased left ventricular inotropy (maximum value of the first derivative of the left ventricular pressure) by 36% and 39%, reduced heart rate by 7% (for both), and lengthened QTc time (corrected QT interval) by 39 and 38 msec, respectively. A comparison of IPE and IPE+O revealed no statistically significant differences. CONCLUSION: Although electrolyte addition to nonionic CM may reduce the risk of cardiac complications during coronary arteriography, oxygenation does not seem to significantly further reduce this risk.

Animals↗
PubMed1996

Electrolyte addition to nonionic contrast media. Cardiac effects during experimental coronary arteriography.

Although the incidence of serious adverse effects is low during clinical coronary arteriography, life-threatening cardiovascular complications occasionally occur. Ventricular fibrillation (VF) is most often seen during contrast media (CM) injection through a wedged catheter. A simulated wedged catheter model in dogs has therefore been developed. Further, patients with heart failure are at greater risk for CM-related side effects during coronary arteriography. Thus, an acute ischemic heart failure model has been used. The present thesis was designed to investigate the cardiac electrophysiologic and hemodynamic effects of CM during selective coronary arteriography in normal and failing hearts, and in particular the role of electrolyte addition to nonionic CM. The risk of spontaneously induced VF and the arrhythmogenic mechanisms were studied when using iso-osmolal and low-osmolal CM having different contents of electrolytes, and after pretreatment with antiarrhythmic drugs. Further, effects of adding electrolytes to nonionic CM during single and fast repeated injections in normal and failing hearts were studied. Also possible effects of oxygenating CM were studied. CM injection in a wedged catheter situation had a high risk for VF. Probably, VF was due to induced regional electrophysiologic changes in ventricular activation and repolarization. Pretreatment with antiarrhythmic drugs did not prevent VF. However, addition of low concentrations of electrolytes to nonionic CM reduced the risk for VF in a wedged catheter situation. The results indicate that side-effects of CM during coronary arteriography are related mainly to the passive washout of cardiac electrolytes. Electrolyte shifts during coronary arteriography may change the myocardial Na/Ca balance and cellular calcium control. The nonionic, iso-osmolal CM iodixanol, with a balanced content of sodium and calcium and the low-osmolal, nonionic CM iohexol, also with a balanced content of electrolytes, had about the same low risk for inducing VF and presented a much lower risk for inducing VF than did iohexol and ioxaglate in a wedged catheter situation. Single injection of iohexol with a balanced eletrolyte addition induced only minimal electro-physiologic changes and was well tolerated hemodynamically. Repeated intracoronary CM injections during ischemic heart failure were associated with similar additive electrophysiologic and hemodynamic changes as when using iohexol without electrolyte supplement. Oxygenated and nonoxygenated CM presented the same risk for inducing VF. Only minor electrophysiologic and hemodynamic differences could be detected during wedged catheter injection. In conclusion, addition of key electrolytes to nonionic CM can reduce the risk of cardiac complications during coronary arteriography. Oxygenation of CM does not seem to significantly further reduce the risk.

Animals↗
PubMed1995

Contrast-medium-induced ventricular fibrillation: arrhythmogenic mechanisms and the role of antiarrhythmic drugs in dogs.

RATIONALE AND OBJECTIVES: Small electrolyte additions to a nonionic contrast medium reduce the risk of ventricular fibrillation (VF) during wedged catheter injection of a contrast medium. The current study was designed to further investigate contrast-medium-induced VF by studying the effect of pretreatment with different antiarrhythmic drugs. METHODS: During a simulated wedged catheter situation, iohexol was injected into the anterior descending branch of the left coronary artery in five open-chest, anesthetized dogs pretreated with lidocaine, propranolol, amiodarone, almokalant, or verapamil. RESULTS: Wedging the catheter for 60 sec did not induce VF. However, all 15 wedged catheter injections with iohexol induced VF within 28 sec (19 +/- 1 [mean +/- standard error of the mean]) despite pretreatment with antiarrhythmic drugs. Prior to VF, conduction was slowed and monophasic action potential duration lengthened in the contrast-medium-perfused myocardium, although no significant changes occurred in the control area. CONCLUSION: The combination of catheter wedging and long-lasting contrast medium injection has a high risk of causing VF. Although adding a small amount of electrolytes to nonionic contrast media can reduce the risk of VF, antiarrhythmic drug therapy may not have a protective effect.

Action Potentials↗
PubMed1995

Additive hemodynamic and electrophysiologic effects of repeated intracoronary contrast media injections in dogs with heart failure.

RATIONALE AND OBJECTIVES: We investigated the cardiac effects of single and repeated contrast media injections in dogs with heart failure and compared the effects of iohexol with iohexol supplemented with electrolytes (30 mmol/l NaCl, 0.15 mmol/l CaCl2, 0.9 mmol/l KCl, and 0.1 mmol/l MgCl2; iohexol + electrolytes [IPE]). Although it has a higher osmolality than iohexol, IPE appears to be safer when injected through a wedged catheter. METHODS: Acute ischemic heart failure was induced by injections of small plastic microspheres into the left coronary artery of 16 anesthetized dogs. Iohexol, IPE, and Ringer acetate were injected into the left coronary artery either as a 5-ml single injection or repeatedly five times, once every 10th second. RESULTS: Single injections of iohexol and IPE induced small hemodynamic and electrophysiologic effects. However, repeated injections of iohexol and IPE increased the maximum rate of isovolumetric contraction by 46% and 36%, reduced heart rate by 8% and 7%, and lengthened QTc (the Q-T interval corrected for heart rate) time by 44 and 39 msec, respectively. No statistically significant differences were found in a comparison of IPE and iohexol. CONCLUSION: During heart failure, repeated injections of iohexol and IPE induced similar additive hemodynamic and electrophysiologic effects without inducing arrhythmias or serious hemodynamic changes.

Animals↗
PubMed1995

Cardiac electrophysiology, arrhythmogenic mechanisms and roentgen contrast media.

Contrast media (CM) affect normal cardiac electrophysiology when injected into the coronary arteries. High-osmolality CM cause more pronounced electrophysiological effects than do low-osmolality CM. Further, both high- and low-osmolality ionic CM have more pronounced effects than the nonionic CM. The CM-induced electrophysiological effects involve regional disturbances of depolarization and repolarization, thereby causing disturbances of impulse conduction as well as dispersion of refractoriness. Recent experimental studies have demonstrated that the addition of sodium or a balanced electrolyte supplement to nonionic CM reduces the risk of ventricular fibrillation (VF), particularly when the CM is injected in a wedged catheter situation. The reduced risk of VF may be due to the small and transient lengthening of repolarization seen in the CM-perfused area of the myocardium. Iodixanol, which is an isotonic nonionic dimer supplemented with NaCl and CaCl(2), is as well tolerated as iohexol during free coronary flow. However, when flow is restricted, such as when CM is injected through a wedged catheter, the risk of VF is less with iodixanol than with iopamidol, iohexol and ioxaglate.

Animals↗
PubMed1995

Cardiac effects of adding electrolytes and oxygen to iohexol in a dog model of contrast media-induced ventricular fibrillation.

We investigated whether addition of a balanced electrolyte supplement and oxygen to the nonionic contrast medium iohexol reduces the risk of ventricular fibrillation (VF), and studied regional electrophysiology prior to the VF event. Twenty ml of each test solution were infused at a rate of 0.5 ml/s into the left anterior descending coronary artery (LAD) in 8 anesthetized dogs. LAD was externally occluded during infusion, to simulate a wedged catheter situation. ECG, hemodynamics, regional epicardial monophasic action potential duration (MAPD) and ventricular activation times (VAT) were calculated. All infusions with iohexol caused VF within 27 s. Five of 12 infusions with iohexol + 30 mmol NaCl, 3 of 11 infusions with iohexol+electrolytes (IPE) NaCl, KCl, CaCl2 and MgCl2) and 4 of 11 infusions with IPE with oxygen addition (IPE+O2) caused VF after 45 s. Iohexol did not change MAPD prior to the VF event. Iohexol + 30 mmol NaCl and the IPE solutions lengthened MAPD initially, but at the time of the VF event MAPD were normalized or shortened. We conclude that electrolyte supplement to iohexol may prevent VF, probably by lengthening MAPD.

Action Potentials↗
PubMed1994

Contrast media-induced ventricular fibrillation: an experimental study of the effects of dimeric contrast media during wedged catheter injection in dogs.

RATIONALE AND OBJECTIVES: We investigated the cardiac effects of an ionic dimer, ioxaglate and two nonionic dimers, iotrolan, and iodixanol. METHODS: During a simulated wedged catheter situation, 22 ml of each contrast medium was injected into the left anterior descending branch of the left coronary artery in seven open-chested, anesthetized dogs. RESULTS: Of 13 injections with each contrast medium, ioxaglate induced ventricular fibrillation in 11 after 34 +/- 5 sec, iotrolan in 6 after 42 +/- 4 sec, and iodixanol in 3 after 61 +/- 1 sec. Ioxaglate markedly lengthened monophasic action potential duration in contrast medium-perfused myocardium. Iotrolan, and iodixanol induced biphasic changes, first lengthening and then shortening action potential duration. The electrophysiological changes occurred later when using iodixanol. CONCLUSIONS: The risk of ventricular fibrillation during long-lasting contrast media exposure to the myocardium, as in a wedged catheter situation, appears to be much lower with iodixanol compared with ioxaglate and also lower than when using iotrolan.

Animals↗
PubMed1994

Cardiac effects of coronary arteriography with electrolyte addition to iohexol. A study in dogs with and without heart failure.

Electrolyte addition to nonionic contrast media has been suggested to further reduce the incidence of ventricular fibrillation during coronary arteriography. The present study was designed to investigate the effects of adding 30 mM NaCl, 0.9 mM KCl, 0.15 mM CaCl2 and 0.1 mM MgCl2 to iohexol on cardiac electrophysiology and hemodynamics (iohexol+electrolytes = IPE). Contrast media were injected into the left main coronary artery in 9 open-chest, anesthetized dogs before and after induction of acute ischemic heart failure. IPE increased left ventricular inotropy (LV dP/dtmax) with no initial decrease, even during heart failure. During heart failure IPE induced the same hemodynamic effects as iohexol without electrolyte addition. IPE slightly lengthened epicardial monophasic action potential duration before heart failure. We conclude that IPE appears to be well tolerated hemodynamically. The electrophysiologic differences between IPE and iohexol are small when the injection time is not longer than 5 s.

Animals↗
PubMed1993

Repeated intracoronary injections of contrast media. Additive hemodynamic and electrophysiologic effects in a dog model.

RATIONALE AND OBJECTIVES: Coronary arteriography in patients implies several selective injections into the coronary arteries. The authors investigate whether repeated injections cause additive cardiac hemodynamic and electrophysiologic effects in dogs. METHODS: Five repeated injections of 5 mL iohexol (Omnipaque 350 mgI/mL, Nycomed Imaging AS, Oslo, Norway), ioxaglate (Hexabrix 320 mgI/mL, Laboratory Guerbet, Cedex, France), and sodium meglumine-diatrizoate (Renografin-76 370 mgI/mL, Squibb Diagnostics, Princeton, NJ) were given into the left coronary artery in 7 anesthetized dogs and were compared with the effects after a 5 mL single injection of the same medium. Left ventricular (LV) pressures, LV dP/dtmax (inotropy) and epicardial monophasic action potential were recorded, from which monophasic action potential duration (MAPD) was measured. RESULTS: Repeated injections of ioxaglate and sodium meglumine-diatrizoate did not potentiate initial decrease in LV pressures and inotropy, but the secondary increase in LV inotropy increased more after repeated injections than after a single injection. Repeated injections of iohexol increased LV inotropy more than a single injection. All contrast media prolonged MAPD more after repeated injections than after single injections. MAPD was prolonged 30 sec after the last injection. CONCLUSION: Repeated injections of contrast media cause greater cardiac hemodynamic and electrophysiologic effects than a single injection during selective coronary arteriography.

Action Potentials↗
PubMed1992

[Diagnostic imaging of the gastrointestinal and biliary tracts. Pattern of examinations during the period 1975-90].

The procedures used for imaging of the gastrointestinal tract, the gall bladder and the bile ducts were registered in six Norwegian hospitals during the period 1975-90. Data obtained from all hospitals showed a significant decrease in radiological examinations of the stomach and the large bowel, and a dramatic decrease of such examinations in the case of the gall bladder and bile ducts. The changes are mainly due to the increasing use of newer methods such as ultrasonography, gastroscopy and colonoscopy. The shift in the pattern of examinations, as shown in the present study, may well have many implications for patients and for the health service as a whole.

Biliary Tract Diseases↗
PubMed1992

Radiological examinations of the urinary tract. Changes during the last 24 years.

Procedures for imaging the urinary tract have been recorded in six Norwegian hospitals for the last 24 years. For three of the hospitals, data were collected from 1965 to 1989, and for the other three from 1966, 1971 and 1975, respectively. There was a significant reduction in the number of intravenous pyelograms, voiding cystograms, and renal angiograms, but the number of retrograde pyelograms and plain radiographs of the urinary tract remained constant. Computed tomography of the urinary tract increased during the first years, but after the introduction of ultrasonography, the number of computed tomograms decreased. Ultrasonographic examinations of the urinary tract are still rapidly increasing, and seem to have replaced some of the other imaging techniques. The present results should be taken into consideration when planning the health care for the future.

Angiography↗
PubMed1992

Restenosis after percutaneous transluminal coronary angioplasty.

Restenosis after percutaneous transluminal coronary angioplasty was demonstrated in 61 (29%) of 210 successfully treated patients. Mostly it occurred within 4 months after treatment and in arteries less than 3 mm in diameter. Careful clinical follow-up is therefore particularly important early after angioplasty of smaller arteries. Redilation can be performed without increased risk of restenosis.

Angioplasty, Balloon, Coronary↗