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Biomedical subjects

F T Jensen

Publications and source records attributed to F T Jensen.

85 records · Page 5Linked to original sources
PubMed1978

Pulmonary embolism associated with elective surgery, detected by ventilation-perfusion scintigraphy.

The frequency of clinical and sub-clinical postoperative pulmonary embolism, demonstrated by combined pulmonary ventilation-perfusion scanning, and the prophylactic effect of low-dose heparin, were assessed in a randomised double-blind study in 43 patients aged over 40 years. Pulmonary embolism was demonstrated using combined ventilation-perfusion scanning in 4 out of 43 patients (9%). The incidence was 1 out of 19 patients in the heparin-treated group and 3 out of 24 patients in the placebo group. This difference was not significant. If post-operative perfusion scanning alone had been utilised for diagnosing pulmonary embolism, the frequency of pulmonary emboli would have been 33%, with 21% in the heparin group and 46% in the placebo group. This difference is not significant. It is concluded that perfusion scanning over-estimates the frequency of post-operative pulmonary embolism. The use of the more specific combined ventilation-perfusion scanning shows that asymptomatic postoperative pulmonary embolism does occur, but that the frequency is considerably lower than indicated by perfusion scanning alone. Combined ventilations-perfusion scanning must be performed in studies assessing the effects of various treatment regimes on the frequency of pulmonary embolism postoperatively. The small number of patients included in the study do not permit any conclusions concerning any prophylactic effect of low-dose heparin against pulmonary embolism.

Aged↗
PubMed1977

Cerebrospinal fluid lactate and pH in patients with acute severe head injury.

Cerebral ventricular fluid (CSF) lactate and pH were measured repeatedly in 21 comatose patients with severe head injury during the first three weeks after trauma. In addition, regional cerebral 133Xe blood flow (rCBF) was measured two to four times in each patient at various time intervals, depending on the indications for carotid angiography, and the pressure in the cerebral ventricular system (IVP) was measured continuously. The series was divided into three groups: (1) patients with local cortical cerebral lesions, (2) patients with brain-stem symptoms, and (3) patients with both local cortical lesions and brain-stem symptoms. The results showed that a high CSF lactate level in patients with severe acute brain injury suggested severe and extensive brain lesions and predicted a poor outcome of the injury. In the individual patients, increasing CSF lactate foreboded clinical deterioration, whereas decreasing CSF lactate indicated recovery. The CSF pH was decreased in most patients, but very low pH levels (below 7.20) were seen only in three patients who all had a poor outcome. Correlation was not observed between CSF lactate and rCBF or between CSF pH and rCBF. It is concluded that repeated determination of CSF lactate and pH during the post-traumatic period may be a valuable tool in the assessment of the course and outcome of the brain injury.

Adolescent↗
PubMed1977

The cerebrovascular CO2 reactivity during the acute phase of brain injury.

Using the intra-arterial 133xenon (133Xe) method, the cerebrovascular response to acute Paco2 reduction was studied in 26 unconscious, brain-injured patients subjected to controlled ventilation. The CO2 reactivity was calculated as delta in CBF/delta Paco2. The perfusion pressure was defined as the difference between mean arterial pressure and mean intraventricular pressure. Although the CO2 reactivities did not differ significantly from that in awake, normocapnic subjects, it was low in the acute phase of injury, especially in those patients with severe outcome in whom the brain-stem reflexes were often affected. An increase of the CO2 reactivity with time was observed, indicating normal response after 1-2 weeks. Chronic hypocapnia in six unconscious patients resulted in sustained CSF pH adaptation. The question whether a delay in CSF pH adapation exerts an influence on the CO2 reactivity, and the influence of cerebral lactacidosis on the CO2 response are discussed.

Adolescent↗
PubMed1977

The effects of PaCO2 reduction on regional cerebral blood flow in the acute phase of brain injury.

In 26 unconscious patients with brain injuries, regional cerebral blood flow (rCBF) was measured with a 16-channel Cerebrograph before and after acute reduction of PaCO2. The intra-arterial 133xenon washout technique was used, and CBF was calculated regionally as initial slope index or stochastic flow. The CO2 reactivity was calculated as deltaln CBV/deltaPaCO2. In supratentorial cortical lesions, an acute fall in PaCO2 increased the homogeneity of the regional flow pattern (decrease in the standard deviation of the regional flow values), and reduced the number of focal hyperaemic regions (tissue peaks). The CO2 reactivity in tissue peak regions was generally higher than in regions without tissue peaks. In severely injured patients with a poor outcome (dementia, vegetative survival or death), inverse steal reaction was accounted for in 11% of all regions, but only in 3% of the regions in patients who survived without dementia. Inverse steal reaction was most frequently seen during the first 3 days after the trauma. In repeated CBF studies, an increase in the CO2 reactivity with time was observed after the acute trauma. In comparison with the CO2 reactivity found in normocapnic awake subjects, this increase was higher than expected in several cases.

Adolescent↗
PubMed1977

Methodological aspects of tear flow determination by means of a radioactive tracer.

Theoretical considerations on a simplified biological system representing the tear pathways lead to the assumption of an exponential pattern of elimination of tracer substances from the conjunctival sac. The tracer used in the present study was technetium, Tc99m, as sodium pertechnetate. The detection system consisted of a gamma camera coupled to a digital system, a minicomputer and a magnetic tape unit. After instillation of 10 microliter normal saline solution containing Tc99m the decay of activity was followed by means of an activity-time function curve to which exponential curves were approximated by the computer. As a parameter for tear flow the fractional turnover rate was calculated from 7 to 15 min after instillation. An initial faster elimination was found in the first 7 min following instillation. Corrections for background radiation, evaporation of water and transconjunctival transport of Tc99m were estimated.

Animals↗
PubMed1977

Compartmental analysis of regional cerebral blood flow in patients with acute severe head injuries.

Bicompartmental analysis for the calculation of regional cerebral blood flow (rCBF) from 133Xe clearance in brain tissue has not been thoroughly explored in clinical studies. Most authors rely either on the average rCBF obtained by height/area analysis of the clearance curves or on the initial-slope flow index. Possibly the reason is that the validity of the bimodal flow distribution in abnormal brain tissue is considered questionable. In the present study, bicompartmental analysis, performed by a least-square computerized iterative approach, was used in the calculation of the flow and weight of the tissue of the brain of patients with severe head injuries. The analysis was found to give important information of the nature and course of the brain lesions even if the clearance curves did not have the normal bi-exponential shape, provided the results obtained were properly interpreted. In such cases, the values of the flow and relative weight could not be taken as flow and weight values of gray and white matter, but rather as indices of fast and slower flow components. The interpretation of the results was based on the identification of three types of 13-minute clearance curves, each being characteristic of a type of brain lesion. The clearance curves from fairly normal brain tissue appeared to be bi-exponential; curves from areas of severe cortical contusion had, in addition, an initial and rapid "third" component, a tissue peak, whereas curves from severely edematous brain tissue approached the monoexponential shape.

Adolescent↗
PubMed1977

[Mobile kidney diagnosis by renography with a gamma camera (author's transl)].

There were 15 nephroptosis patients examined by renography with a gamma camera, which appears to be of value in demonstrating if the mobility of the kidney causes changes in urinary flow or in renal blood flow. By means of gamma camera renography, it seems possible to distinguish between cases where the nephroptosis is a casual finding and cases where it has pathogenic significance.

Adolescent↗
PubMed1976

Dynamic changes in regional CBF, intraventricular pressure, CSF pH and lactate levels during the acute phase of head injury.

The authors measured regional cerebral 133xenon (133Xe) blood flow (rCBF), intraventricular pressure (IVP), cerebrospinal fluid (CSF) pH and lactate, systemic arterial blood pressure (SAP), and arterial blood gases during the acute phase in 23 comatose patients with severe head injuries. The IVP was kept below 45 mm Hg. The rCBF was measured repeatedly, and the response to induced hypertension and hyperventilation was tested. Most patients had reduced rCBF. No correlation was found between average CBF and clinical condition, and neither global nor regional ischemia contributed significantly to the reduced brain function. No correlation was found between CBF and IVP or CBF and cerebral perfusion pressure (CPP). The CSF lactate was elevated significantly in patients with brain-stem lesions, but not in patients with "pure" cortical lesiosn. The 133Xe clearance curves from areas of severe cortical lesions had very fast initial components called tissue peaks. The tissue peak areas correlated with areas of early veins in the angiograms, indicating a state of relative hyperemia, referred to as tissue-peak hyperemia. Tissue-peak hyperemia was found in all patients with cortical laceration or severe contusion but not in patients with brain-stem lesions without such cortical lesions. The peaks increased in number during clinical deterioration and disappeared during improvement. They could be provoked by induced hypertension and disappeared during hyperventilation. The changes in the tissue-peak areas appeared to be related to the clinical course of the cortical lesion.

Acid-Base Imbalance↗
PubMed1975

Elimination of scalp blood flow by headband during dynamic brain scintigraphy.

The effect of the application of a headband during brain scintigraphy was investigated in 11 healthy volunteers. In each person, extracranial recording of a bolus of 99mTc-pertechnetate injected intravenously was done on two occasions during a scintillation camera. On one occasion a narrow sphygmomanometer cuff encircling the head from brow to occiput and inflated to 300 mmHg was applied during measurements; another time, the procedure was identical except for the headband. A comparison between counting rates under the derived time-activity curves showed significantly lower values on headband application (p less than 0.01). Static scintigrams consisting of the first 300,000 counts recorded after bolus release with and without headband application show a clear delineation of the headband position with prevention of "halo" appearance about the cranial cavity. It has thus been possible by simple means to reduce the irrelevant radionuclide distribution which, especially during dynamic investigations of cerebral circulation, constitutes a source of error.

Cerebrovascular Disorders↗
PubMedDate not supplied

Selenium in the anterior pituitary of the rat after a single injection of 75Se sodium selenite.

In order to investigate the selenite metabolism in the anterior pituitary and compare it with other endocrine organs, rats were injected intraperitoneally with 75Se sodium selenite (5 mg/kg). The rats were whole body counted shortly after injection and recounted just before sacrifice, which was performed 2, 24, 48 h, and 4, 10, 20, 30, 40, 60, and 80 d after injection. Besides the anterior pituitary, the selenium content was also estimated in the thyroid gland, testis, adrenals, liver, kidney, and blood. The maximum selenium content was observed in all organs 2 h after injection, at which time the anterior pituitary contained 2.9 micrograms/g wet wt, compared to 13.5 micrograms/g wet wt in liver and .6 micrograms/mg wet wt in testis. The excretion of selenite from the anterior pituitary resembled that seen in most other organs investigated, i.e., an initial rapid excretion and a slower secondary phase resembling a first order reaction. Practically all selenium was excreted by 60 d after injection. The selenium content in pituitaries from untreated rats was estimated by PIXE analysis to be 2.2 +/- .1 micrograms dry wt and .48 +/- .03 micrograms/g wet wt. From the present study it can be concluded that selenium in the form of selenite accumulates in the anterior pituitary after a single intraperitoneal injection; selenite is excreted from the gland in a biphasic manner; practically all selenium is excreted within 60 d; and pituitaries from normal rats contain .48 micrograms selenium/g wet wt.

Adrenal Glands↗