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Biomedical subjects

A Dahl

Publications and source records attributed to A Dahl.

At least 19 recordsLinked to original sources
PubMed1992

A comparison of regional cerebral blood flow and middle cerebral artery blood flow velocities: simultaneous measurements in healthy subjects.

Blood flow velocities were measured in both middle cerebral arteries (MCAs) of 36 healthy subjects using transcranial Doppler ultrasound. Measurements were first made using a hand-held probe. Velocities were then studied bilaterally with fixed probes under resting conditions and during simultaneous regional CBF (rCBF) measurements. A significant (p < 0.05) positive correlation was found between MCA flow velocities and rCBF in the estimated perfusion territory of this artery. The correlation coefficient was highest when the measurements were performed simultaneously (p < 0.001) or when velocities recorded with a hand-held probe were adjusted to take into account the significant velocity increase induced by the CBF study situation. The increased velocities during CBF measurements cannot be fully explained by the moderate but significant PCO2 increase. Other possible mechanisms are increased blood flow due to mental activation or MCA vasoconstriction secondary to stimulation of the sympathetic nervous system. The effect of mental activation and PCO2 differences should therefore be considered when comparing the results of repeated velocity and CBF measurements.

Adult↗
PubMed1992

Effect of pre- vs postoperative inguinal field block on postoperative pain after herniorrhaphy.

The analgesic effects of an identical inguinal field block, performed before or immediately after inguinal herniorrhaphy, were evaluated in 32 healthy patients in a double-blind, randomized study. During surgery, all patients received a light general anaesthesia with thiopentone, alfentanil and nitrous oxide in oxygen. After induction of general anaesthesia, patients were allocated randomly to receive an inguinal field block with lignocaine, either 15 min before operation or immediately after operation, after closure of the surgical wound, but before the patients were awake. Pain score on a visual analogue scale and on a verbal scale at rest, during mobilization from supine into sitting position and during cough was assessed 1, 2, 4, 6, 8 and 24 h, and 7 days after operation. No significant differences between the groups were observed in VAS scores or verbal pain scores during rest or ambulation at any time. There was no significant difference in time to first request for morphine or total morphine consumption. These results do not show pre-emptive analgesia with a conventional inguinal field block to be of clinical importance compared with a similar block administered after operation.

Adult↗
PubMed1992

Cerebral blood flow findings in moyamoya disease in adults.

Three adult patients with moyamoya disease are described. They presented with intracerebral hematoma, cerebral infarction and subarachnoid hemorrhage, respectively. Subarachnoid hemorrhage is rare in moyamoya and is usually the result of aneurysm rupture. No aneurysm was found in our patient. Regional cerebral blood flow (rCBF) and the cerebral perfusion reserve assessed by the acetazolamide test, were significantly reduced in all three patients. The areas with most reduced baseline rCBF and most impaired vasoreactivity did not always correspond to the site of the vascular accident, indicating that these CBF changes were at least in part due to the moyamoya disease and/or its underlying causes, and not solely to the vascular accidents.

Adult↗
PubMed1992

A comparison of transcranial Doppler and cerebral blood flow studies to assess cerebral vasoreactivity.

BACKGROUND AND PURPOSE: The aim of this study was to determine the ability of transcranial Doppler ultrasonography when used to assess cerebral vasoreactivity. The results of this method were compared with regional cerebral blood flow measurements. METHODS: Forty-three patients with symptoms suggesting cerebrovascular disease took part. Transcranial Doppler findings in the middle cerebral arteries were compared with regional cerebral blood flow in the corresponding perfusion territories before and after acetazolamide administration. RESULTS: There was a significant positive correlation between the absolute increase in cerebral blood flow in milliliters per 100 g per minute and the percent increase in velocity (r = 0.63). The right-left, side-to-side difference of the acetazolamide response obtained by the two methods also showed a positive correlation (r = 0.80). Control limits obtained from healthy subjects were used for both the blood flow increase (absolute values and asymmetry in absolute values) and the velocity increase (percent increase and asymmetry in percent increase). The two methods then agreed in their evaluation of vasoreactivity in 74 (86%) of the 86 middle cerebral artery perfusion territories; 20 (23%) were assessed by both methods as having a reduced vasodilatory reserve. Eleven hemispheres with a slightly reduced regional cerebral blood flow response to acetazolamide were not detected by transcranial Doppler, whereas all territories with a marked reduction were identified by Doppler. Only one hemisphere with a normal cerebral blood flow increase after acetazolamide administration was assessed by Doppler as having reduced vasoreactivity. CONCLUSIONS: Transcranial Doppler and the acetazolamide test may be used in clinical situations to assess cerebral vasoreactivity.

Acetazolamide↗
PubMed1990

Cluster headache: transcranial Doppler ultrasound and rCBF studies.

Transcranial Doppler and rCBF examinations were carried out in 25 cluster headache patients. Spontaneous and glyceryl trinitrate (nitroglycerin) provoked attacks were accompanied by a bilateral decrease in middle cerebral artery blood flow velocities. This decrease was more pronounced on the symptomatic side but the difference did not reach statistical significance. Mean hemispheric blood flow and rCBF were within normal limits during provoked attacks and similar to those found when patients were attack-free. During cluster periods middle cerebral artery velocities were significantly higher on the symptomatic side. Glyceryl trinitrate caused a bilateral middle cerebral artery velocity decrease which was significantly greater on the symptomatic side. Attacks provoked by glyceryl trinitrate appeared to begin when the vasodilatory effect of this substance was receding.

Adult↗
PubMed1989

Blood velocity and regional blood flow in defined cerebral artery systems.

Cerebral artery blood velocity and regional blood flow (rCBF) were investigated in 17 normal subjects. Blood velocity was measured with 2 MHz pulsed Doppler ultrasound in the proximal segments of the middle, anterior and posterior cerebral artery (MCA, ACA, and PCA) and in the distal extracranial internal carotid artery (ICA). The rCBF in the regions of interest tentatively corresponding to the perfusion territories of these vessels was estimated using 133Xe inhalation and a rapidly rotating single photon emission computer tomograph. Concomitant capnograph recordings showed that the end-expiratory pCO2 was higher during the rCBF than during the blood velocity examinations. This differences was highly significant. While there was no significant correlation between blood velocity and rCBF when these clear differences in pCO2 were disregarded, we did find significant positive correlations when the data were normalized to a standard pCO2 (5.3 kPa) using accepted formulas. The best correlation was found for the MCA (r = 0.630, p less than 0.001) and the PCA (r = 0.73, p less than 0.001), with a lower correlation in the ACA (r = 0.49, p less than 0.01) and the ICA (r = 0.41, p less than 0.05). The estimated blood velocity (V) given rCBF = 0 was not significantly different from 0. The results support the validity of expressing the relationship between blood velocity (V) and rCBF in defined cerebral artery systems as: V = 1/60 (rCBF) T (A)-1, where A represents the area of the lumen of the vessel segment where the velocity is being measured, and T denotes the size of the brain region being perfused from this artery.

Adult↗
PubMed1989

Effect of acetazolamide on cerebral artery blood velocity and regional cerebral blood flow in normal subjects.

The effect of intravenous acetazolamide 1 g on cerebral artery blood velocity and regional blood flow (rCBF) was investigated in eight normal subjects. Blood velocity was measured with 2 MHz pulsed Doppler in the proximal segments of the middle, anterior and posterior cerebral artery (MCA, ACA, and PCA) and in the distal extracranial internal carotid artery (ICA). The rCBF in the regions of interest tentatively corresponding to the perfusion territories of these vessels was estimated using 133Xe inhalation and a rapidly rotating single photon emission computer tomograph. Both blood velocity and rCBF increased after acetazolamide. There was no significant difference between the percentage ICA blood velocity increase (22 +/- 12%) and the percentage rCBF increase in the ICA region of interest (25 +/- 9%). In the MCA, ACA, and PCA, however, blood velocity increased more (mean increase 36-42%) than the rCBF in the corresponding regions of interest (mean increase 24-26%). These differences were highly significant suggesting a direct and site specific effect of acetazolamide in narrowing the lumen of the proximal MCA, ACA, and PCA, but not of the extracranial ICA. We also propose that the effect of acetazolamide induces reciprocal changes in the extent of adjacent perfusion territories in individual brain hemispheres. Data compiled from all subjects investigated at two very different perfusion levels (before and after acetazolamide) revealed a significant positive correlation between blood velocity and rCBF.

Acetazolamide↗
PubMed1989

Effect of nitroglycerin on cerebral circulation measured by transcranial Doppler and SPECT.

We used a combination of transcranial Doppler ultrasonography and single-photon emission computed tomography to noninvasively assess changes in the diameter of the middle cerebral artery induced by sublingual nitroglycerin in 10 healthy subjects. Nitroglycerin reduced mean blood flow velocities without concurrently changing regional cerebral blood flow in the perfusion territory of this vessel. Our results strongly suggest that nitroglycerin causes vasodilatation of the basal intracranial arteries.

Adult↗
PubMed1988

Inhibition of nasal and liver cytochrome P-450 mono-oxygenases by dioxolanes.

1. A series of six alkyl-substituted dioxolanes were studied for their inhibitory effects on mono-oxygenase activities in vitro with nasal and hepatic microsomes from rats and rabbits. 2. Carbon monoxide binding and hexamethylphosphoramide (HMPA) N-demethylase activity were most susceptible to inhibition by the test compounds. 3. Inhibition of HMPA N-demethylase activity in both nasal and liver microsomes increased with lipophilicity of the inhibiting compound. In olfactory mucosa, the bulk of the substituent at the 4-position also seemed to have an effect on inhibition. 4. Mono-oxygenase activity in the nasal mucosa was inhibited more readily than that in the liver.

Animals↗
PubMed1987

The effect of the tricyclic antidepressant drug, nortriptyline on left ventricular ejection fraction and left ventricular volumes.

Eight patients with major depression but otherwise healthy underwent radionuclide cardiography before and during nortriptyline treatment. The second examination was performed when the nortriptyline plasma concentration was within the therapeutic range (60-150 micrograms X l-1). Heart rate, arterial blood pressure, left ventricular ejection fraction, left ventricular volumes, systolic pressure-volume ratio, and cardiac output were determined. Heart rate increased in mean by 13% (P less than 0.05). All other variables were unchanged. We conclude that nortriptyline in therapeutic doses produces no major adverse effect on left ventricular function. Routine radionuclide cardiography might be a suitable method to detect among those treated with tricyclic antidepressants the occasional susceptible patient. This may particularly apply to patients with known heart disease and to elderly patients.

Adult↗
PubMed1985

Autosomal recessive non-progressive ataxia with an early childhood debut.

The case histories and clinical studies are given of 7 consanguineous patients, 4 adults and 3 children, with a rather uniform clinical picture of nonprogressive cerebellar ataxia manifesting in early childhood. Most patients have in addition slight spastic signs, short stature and normal intelligence. There are no signs of other organ pathology, biochemical aberrations, endocrine- or immunopathology. CT-scan and PEG show cerebellar atrophy. The pedigree analysis indicates an autosomal recessive mode of inheritance. The condition falls between the ataxic syndromes in the cerebral palsy range and the heredo-ataxias. Until now, no similar disorders seems to have been described.

Adolescent↗