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Biomedical subjects

L Henriksen

Publications and source records attributed to L Henriksen.

70 records · Page 4Linked to original sources
PubMed1976

Local reflex in microcirculation in human cutaneous tissue.

Blood flow in cutaneous tissue measured by the local 133Xenon washout technique decreased about 35 per cent during venous stasis of 40 mmHg in three normal subjects. The response was unaffected by block of the nerve three cm proximally to the labeled area. When the tissue was infiltrated with lidocaine or with phentolamine, blood flow remained constant, indicating that the decrease in blood flow is due to an arteriolar vasoconstrictor response to increase in venous transmural pressure. Local venous stasis elicited a vasoconstrictor response in an adjoining area not affected by the stasis. The response was blocked by lidocaine applied to the side of stasis. In 2 chronically sympathectomized patients, the vasoconstrictor response was abolished in the denervated limbs but present on the non-operated side (1 patient with unilateral sympathectomy). The results indicate that the vasoconstrictor response to an increase in venous transmural pressure is due to a local nervous mechanism involving sympathetic adrenergic fibres, most likely a sympathetic axon reflex.

Blood Pressure↗
PubMedDate not supplied

Do as I say: parent smoking, antismoking socialization, and smoking onset among children.

This study examined relationships between smoking and antismoking practices of parents and early onset of smoking among elementary-grade children. The parent practices we investigated were direct modeling of cigarette smoking and antismoking socialization variables, such as setting rules to eliminate cigarette smoking in the home, awareness of children's smoking behaviors, and making clear the disciplinary consequences of cigarette smoking. Surveying a sample of 1.213 third- and fifth-grade children, we found (1) children's risk of early onset of smoking increases with level of exposure to parent smoking models; (2) if one or both parents are current smokers, children who have never tried smoking have significantly greater risk of intending to smoke, perceiving easy access to cigarettes, and being ambivalent about smoking; (3) risk rates for children of former smokers indicate that parents' quitting smoking does not eradicate the effects of parent modeling; and (4) children whose parents engage in antismoking socialization have significantly lower rates of smoking onset, even if parents are current smokers. The implications of these results for preventive intervention and future research are discussed.

Age of Onset↗
PubMedDate not supplied

Reliability of children's self-reported cigarette smoking.

Youth who first smoke cigarettes during childhood are a high risk for habitual smoking. Evaluating the reliability of children's smoking initiation is essential to research efforts to explain or prevent smoking onset. The present study is the first to establish reliability of self-reported smoking behavior with questionnaire data from elementary school children (N = 1,184). Data from a longitudinal investigation are used to examine the consistency of children's self-reported smoking across items and over time. Both cross-sectional and longitudinal analyses demonstrate that children report having tried smoking and lifetime use remarkably consistently. However, only about half the children reliably estimated their grade at first use. The study results suggest that some but not all standard questionnaire items yield reliable self-report data about initial smoking behavior from respondents as young as 8 to 11 years.

Age Factors↗
PubMedDate not supplied

Regional cerebral blood flow assessed by 133Xe inhalation and emission tomography: normal values.

Regional cerebral blood flow (rCBF) in the cerebral hemispheres and the cerebellum was measured by single photon emission computed tomography with inhalation of 133Xe in 39 normal volunteers at test. The goal of this study was to assess the normal flow pattern and its variations. Five parallel tomographic slices through the brain were recorded with a resolution element of 1.7 X 1.7 X 2.0 cm (full width at half maximum). The blood flow distribution showed that the predominantly gray matter areas displayed flow approximately double that of the predominantly white matter regions. The CBF distribution was practically symmetrical with a side-to-side difference averaging 1.4 +/- 1.4 ml/100 g/min. This means that a difference exceeding 4.2 ml/100 g/min (approximately 9% of mean CBF) is abnormal with a confidence level of below 5%. The measured average CBF and cerebellar blood flow were 56 +/- 7 and 54 +/- 6 ml/100 g/min (mean +/- 1 SD), respectively. A significant correlation was found between CBF and PCO2, and between CBF and age. Repeat measurements in an additional 30 subjects showed a day-to-day variability of -0.2 +/- 6.4 ml/100 g/min of the difference between the first and the second measurement. This corresponds to random methodological and biological errors of 6.4/square root 2 = 4.6 ml/100 g/min and is a measure of the overall intraindividual variability. Xenon-133 tomography is atraumatic and affords rCBF images free of the superposition artifacts that practically invalidate the nontomographic approaches in the studies of cerebrovascular disease. The rCBF tomograms are blurred, particularly due to Compton scatter. Relative to this factor, the errors caused by local variations in the tissue:blood partition coefficient are less important.

Adult↗
PubMedDate not supplied

Regional cerebral blood flow in stroke by 133Xenon inhalation and emission tomography.

A rapidly rotating single-photon emission tomograph was used to study regional cerebral blood flow by 133Xenon inhalation. Using a rotation speed of 180 degrees/5 sec a tomographic picture of the average Xenon concentration in 3 slices is obtained. By taking a sequence of 4 one-minute tomograms during and after a one-minute 133Xenon inhalation period a flow-dependent variation in local isotope concentration is seen. This sequence is used for calculating CBF by a deconvolution procedure. The CBF maps have a spatial resolution of approximately 1.7 cm (FWHM). This preliminary study comprises normal subjects and 10 unselected patients with stroke. The CBF tomograms localized appropriate ischemic areas in all 10 patients. In one patient the conventional x-ray tomogram was negative, while the flow tomogram clearly showed a decreased flow in consonance with the clinical findings. Regional cerebral blood flow measured tomographically by 133Xenon inhalation circumvents the extra-cranial contamination and the superposition of intracranial tissues that hamper 133Xenon inhalation flow studies using stationary detectors.

Adult↗
PubMedDate not supplied

Regional cerebral blood flow in patients with transient ischemic attacks studied by Xenon-133 inhalation and emission tomography.

Cerebral blood flow CBF was studied in 14 patients with transient ischemic attacks TIA and arteriosclerotic neck vessel disease. CBF was measured by a rapidly rotating single photon emission computerized tomograph using Xenon-133 inhalation. This method yields images of 3 brain slices depicting CBF with a spatial resolution of 1.7 cm. Based primarily on the clinical evidence and on the angiographical findings embolism was considered the pathogenetic factor in 10 cases, whereas chronic hemodynamic insufficiency rendered symptomatic by postural factors probably accounted for the symptoms in 4 patients. Of the 14 patients, all studied days to weeks after the most recent TIA, four showed hypoperfused areas on the CBF-tomograms and with roughly the same location hypodense areas on CT-scanning, i.e. areas of complete infarction. However, an additional five patients showed reduction of CBF in areas with no abnormality on the CT-scan. The abnormal blood flow pattern was found to be unchanged after clinically successful reconstructive vascular surgery. This suggests the presence of irreversible ischemic tissue damage without gross emollition (incomplete infarction). It is concluded, that TIAs are often harmful events, as no less than 9 of the 14 patients studied had evidence of complete and/or incomplete infarction. Thorough examination and rational therapy should be instituted as soon as possible to prevent further ischemic lesions.

Adult↗
PubMedDate not supplied

CBF before and after extracranial-intracranial bypass surgery in patients with ischemic cerebrovascular disease studied with 133Xe-inhalation tomography.

Cerebral blood flow (CBF) was studied by 133Xenon inhalation tomography in 22 patients with symptoms of ischemic cerebrovascular disease before and after establishment of an extracranial-intracranial bypass shunt. Selection of patients for shunting was based on angiographically demonstrated arterial occlusions and on the finding of focal low flow areas corresponding to the clinical symptoms, that consisted mainly of minor stroke with good remission and with or without subsequent TIAs. It was required that the area of low flow should clearly exceed the CT lesion present in practically all cases. Following surgery, the permanent neurologic deficits remained unchanged, while the TIAs stopped in all but one case. Two patients showed a definite increase of CBF in the low flow area while another two showed a questionable increase. All the other cases, 18 of the 22, showed an unchanged tomographic flow map with no trend towards diminution in extension or severity of the focal hypoperfused area. A persistent low flow in areas with no corresponding CT lesion following alleviation of a possible flow impediment is interpreted to represent an incomplete infarction or diaschisis.

Adult↗
PubMedDate not supplied

Cardiovascular and respiratory effects of terbutaline in patients after open-heart surgery.

In 10 patients after mitral or/and aortic valve replacement, terbutaline was given intramuscularly (10 mcg/kg body wt.) to see what cardiovascular and respiratory effects were produced. A marked cardiovascular effect was seen. Increase in heart rate (20%) was of sinus or atrial origin, no ventricular arrhythmias were seen. Cardiac index rose (46%) left and right stroke work increased (18%, 31%); systemic and pulmonary vascular resistance decreased (32%, 19%); Arterial oxygen tension decreased from 134 to 102 mmHg (24%); O2-consumption remained unchanged. Except for an increase in compliance no changes in respiratory dynamics occurred in the total respiratory system. Terbutaline's cardiovascular effects, its low toxicity, lack of ventricular arrhythmias and unchanged oxygen consumption, indicate that it could be useful to patients where an increase in cardiac output and improvement in peripheral circulation is needed.

Adult↗
PubMedDate not supplied

The cardiovascular and respiratory effects of fenoterol in patients after open-heart surgery.

Fenoterol (a selective beta-2-adrenergic drug) was given intravenously (2 mcg/kg body weight/15 min) to 7 normotensive patients after open-heart surgery in order to study the cardiovascular and respiratory effects. A marked cardiovascular effect was seen without changes in venous or arterial pressure. The increased heart rate (46%) was of sinus or atrial origin; no ventricular arrhythmias were seen. The cardiac index rose by 91%; left and right ventricular stroke work increased by 26% and 54% respectively; systemic and pulmonary vascular resistance decreased by 31% and 23% respectively; arterial oxygen tension decreased from 264 to 205 mm Hg; oxygen consumption rose 31%. No changes occurred in respiratory dynamics, in the total respiratory system of patient and tubes. The cardiovascular effect of fenoterol, without a corresponding increase in end-diastolic filling pressure and resistance against systolic ejection of the left ventricle, as well as the absence of ventricular arrhythmias, indicate that the drug may be useful as a supplement to other sympathomimetic compounds in normal use.

Cardiac Surgical Procedures↗