Search PubMed⌕ Search

Biomedical subjects

L Henriksen

Publications and source records attributed to L Henriksen.

At least 55 records · Page 3Linked to original sources
PubMed1984

Effect of acetazolamide on cerebral blood flow and cerebral metabolic rate for oxygen.

The aim of this study was to evaluate the effect of acetazolamide on cerebral blood flow (CBF) and cerebral metabolic rate for oxygen (CMRO2). CBF, arterial and jugular venous partial O2 pressure, partial CO2 pressure, pH, and O2 saturation percentage were measured in six patients before and 3 and 20 minutes after intravenous administration of 1 g of acetazolamide. CBF was measured by the intracarotid 133xenon injection technique. In addition, changes in CBF were estimated from the arteriovenous oxygen content difference. CBF increased in all patients after acetazolamide, by approximately 55 and 70% after 3 and 20 min, respectively. The CBF changes were of the same order whether calculated from the 133Xe clearance or from the arteriovenous oxygen differences (A-V)O2. CMRO2, calculated from (A-V)O2 differences and CBF, remained constant. Except for an increase in the venous oxygen saturation, the blood gases remained constant. Acetazolamide, in a dose sufficient to inhibit the erythrocyte carbonic anhydrase (EC 4.2.1.1), thus induced a rapid and marked increase in CBF, leaving CMRO2 unchanged. This effect of acetazolamide on CBF is probably explained by a decrease in brain pH rather than by brain tissue hypoxia due to inhibition of oxygen unloading in the brain capillaries.

Acetazolamide↗
PubMed1984

Acute cerebral dysfunction after open-heart surgery. A reaction-time study.

A sensitive measure of subtle CNS dysfunction, the continuous reaction time (CRT), was used in 19 patients to quantify the immediate effects of open-heart surgery and extracorporeal circulation (ECC) on the CNS. The control group comprised 17 patients undergoing thoracic surgical procedures without ECC. The reaction time was significantly prolonged after surgery both in the ECC patients and in the controls. CRT was unrelated to the duration of anaesthesia in both groups, but in the ECC group deterioration of CRT showed positive correlation with (a) the duration of ECC, (b) the duration of perfusion pressure below 50 mmHg during ECC and (c) the PCO2 during ECC. These three factors may be of pathogenetic significance in the development of CNS dysfunction following open-heart surgery. The acute changes in reaction time resolved within a week of surgery, but on questioning two months later half of the ECC patients reported intellectual disturbance, primarily impairment of memory and lability of mood.

Adolescent↗
PubMed1983

Controlled hypotension with sodium nitroprusside: effects on cerebral blood flow and cerebral venous blood gases in patients operated for cerebral aneurysms.

The effect on cerebral haemodynamics of arterial hypotension induced by sodium nitroprusside infusion was studied in nine patients at the end of operations for intracranial aneurysms under N2O-O2-halothane anaesthesia. Cerebral blood flow (CBF), using the intraarterial 133Xe injection method, and cerebral jugular venous blood gases were monitored before, during and after the induced hypotension. CBF and jugular venous oxygen tension (PvO2) remained constant during the hypotensive period. Following its termination, a 13% increase in CBF occurred (P less than 0.05) and PvO2 showed the same trend, a 5% increase (P less than 0.30). Regional CBF recordings (rCBF) in 16 small areas within the cerebral hemisphere were obtained at each measurement. In four of the patients, rCBF abnormalities were present in the form of hyperaemic regions, probably induced by the operation or the disease itself. The focal abnormalities were not accentuated during hypotension nor were ischaemic regions disclosed. It is concluded that sodium nitroprusside has only a minor influence on cerebral haemodynamics in the anaesthetized state.

Adolescent↗
PubMed1983

Brain hyperperfusion during cardiac operations. Cerebral blood flow measured in man by intra-arterial injection of xenon 133: evidence suggestive of intraoperative microembolism.

Cerebral blood flow (CBF) was measured by intra-arterial injection of xenon 133 in 29 patients during cardiac operations. Marked changes occurred in all patients. A normal and significant correlation with temperature and plasma PCO2 (p less than 0.01) support the reliability of the method. Mean CBF measured between sternotomy and the onset of extracorporeal circulation (ECC) was 38 ml/100 gm . min. The first minute of ECC was associated with a decrease in CBF in nine of 12 patients (p less than 0.02). During steady-state hypothermic ECC (temperature 29 degrees C), CBF increased unexpectedly to 64 ml/100 gm . min (p less than 0.01). Following rewarming steady-state normothermic ECC, mean CBF decreased to 42 ml/100 gm . min with signs of impairment of cerebral autoregulation. Ten and 20 minutes after termination of ECC, mean CBF was 40 and 41 ml/100 gm . min, respectively. Arterial PCO2 was found to be important in regulating CBF. The cerebral autoregulation maintained CBF down to arterial pressures of around 55 mm Hg. Below this level, CBF was significantly correlated with perfusion pressure (p less than 0.01). Multiple small emboli with a hyperemic border zone could cause a brain hyperperfusion, as seen in our patients during bypass. Measurements of CBF during ECC hold promise as a guide toward safer cardiac operations.

Adult↗
PubMed1983

Cerebral blood-flow tomography: xenon-133 compared with isopropyl-amphetamine-iodine-123: concise communication.

Tomographic maps of local cerebral blood flow (CBF) were obtained with xenon-133 and with isopropyl-amphetamine-iodine-123 (IMP) in 11 subjects: one normal, two tumor cases, and eight cerebrovascular cases. A highly sensitive four-face, rapidly rotating, single-photon emission tomograph was used. The Xe-133 flow maps are essentially based on the average Xe-133 concentration over the initial 2 min during and after an inhalation of the inert gas lasting 1 min. These maps agreed very well with the early IMP maps obtained over the initial 10 min following an i.v. bolus injection. The subsequent IMP tomograms showed a slight decrease in contrast amounting to appr. five percentage points in the CBF ratio between diseased and contralateral areas. It is concluded that Xe-133 is more practical: low cost, available on a 7-day basis, easily repeatable, quantifiable without the need for arterial sampling, and with low radiation exposure to patient and personnel. On the other hand, IMP gives an image of slightly higher resolution. It also introduces a new class of iodinated brain-seeking compounds allowing, perhaps, imaging of other functions more important than mere blood flow.

Amphetamines↗
PubMed1982

The effects of sodium nitroprusside on cerebral blood flow and cerebral venous blood gases. I. Observations in awake man during and following moderate blood pressure reduction.

Cerebral blood flow (CBF) and cerebral venous blood gases were studied in seven patients before, during and after intravenous sodium nitroprusside infusion. The 133Xe intra-arterial injection method was used for the CBF measurements. A dose of sodium nitroprusside (mean 1.0 mg, mean infusion time 20 min), which reduced mean arterial blood pressure by a mean of 17%, resulted in a 13% decrease in CBF (P less than 0.05). Measurements obtained 5 and 20 min after termination of the sodium nitroprusside infusion showed no signs of a hyperaemic rebound effect. Arterial PCO2, metabolic rate of oxygen, arterio-venous oxygen difference and venous PO2 remained unchanged during and after infusion. It is concluded that sodium nitroprusside has a minor effect on cerebral haemodynamics, an effect that might be mediated by the sympathetic nervous system.

Adolescent↗
PubMed1982

The effects of sodium nitroprusside on cerebral blood flow and cerebral venous blood gases. II. Observations in awake man during successive blood pressure reduction.

Cerebral blood flow (CBF) and cerebral venous blood gases were investigated in seven awake patients during hypotension induced with sodium nitroprusside. Infusion of the drug into the internal carotid artery produced no changes in cerebral haemodynamics. Intravenous nitroprusside infusion resulted in a decrease in both CBF and jugular venous PO2 (P less than 0.01, respectively). Reducing mean arterial blood pressure by 18% and 43% produced a mean CBF fall of 6% and 27% respectively. Arteriovenous oxygen difference increased in consonance with the CBF decrease (P less than 0.01). Arterial PCO2 fell during the infusion (P less than 0.01). At 18% blood pressure reduction, the observed PCO2 decrease of 0.25 kPa could account for the 6% CBF decrease. At 43% blood pressure reduction, PCO2 fell by 0.53 kPa, a decrease which could not explain the observed CBF fall of 27%. Dizziness and incipient fainting occurred in the patients at this point. It is concluded that sodium nitroprusside has a minor but significant effect on cerebral haemodynamics in normal awake man.

Adult↗
PubMed1982

Cerebral blood flow in chronic toxic encephalopathy in house painters exposed to organic solvents.

Cerebral blood flow (CBF) was studied in 11 controls and 9 house painters occupationally exposed to organic solvents for a mean of 22 years. They had mild to moderate intellectual impairment, and no or only minor cerebral atrophy was seen in a CT-scan of the brain. The 133Xe inhalation technique was used and the flow was calculated from the initial slope of the 133Xe wash out curve (ISI). ISI averaged 36.8 ml/100 g/min in the painters and 45.4 ml/100 g/min in the controls, representing a significant difference (P less than 0.05). The reduced CBF in these painters with slight to moderate intellectual impairment might be due to limited neuronal loss or to permanently decreased metabolism of the neurones.

Adult↗
PubMed1981

Cerebral blood flow following normovolemic hemodilution in patients with high hematocrit.

The effects on cerebral hemodynamics of venisection and a 4% albumin-saline infusion were studied in six patients with high hematocrit (mean, 51.5%). Cerebral blood flow (CBF) was measured using the xenon 133 intracarotid injection method. Blood gases were measured in arterial and jugular venous blood. Rapid two-stage hemodilution, which lowered mean hematocrit by 9 and 13%, resulted in CBF increases of 19 and 23%, respectively. Jugular venous partial pressure of oxygen and oxygen delivery capacity (CBF x arterial oxygen content) did not change significantly from baseline. The cerebral metabolic rate for oxygen increased slightly following stage 1 hemodilution but returned to baseline value following stage 2. The study lends no support to the concept that patients whose hematocrit is at the high end of the normal range have generalized cerebral hypoxia.

Adult↗
PubMed1981

Visual cortex activation recorded by dynamic emission computed tomography of inhaled xenon 133.

Regional cerebral blood flow (CBF) was studied tomographically with 133Xe administered by inhalation over a 1-min period at a concentration of 10 mCi/l. A fast rotating ("dynamic') single-photon emission computed tomograph with four detector heads was used, an instrument that has been found to be well suited for detecting focal ischemia. In the present study its ability to detect focal hyperemia was investigated in 13 normal subjects studied during rest and during visual stimulation. A flickering light "seen' with eyes open and closed, increased blood flow in the visual cortex by 35% and 22% respectively. Looking at different pictures displayed on a screen raised regional CBF by 26%. The most complex task, reading and copying a text, increased blood flow by 45%. Averaging the different tasks resulted in a mean regional CBF increase in the visual cortex of 35%. The result is comparable with that obtained by positron emission tomography. Both forms of isotope tomography offer unique possibilities of the study of brain function in health and disease, possibilities not matched by X-ray tomography. The low cost and ready availability of appropriate single-photon radionuclides (133Xe and 127Xe) are mentioned.

Cerebrovascular Circulation↗
PubMed1981

Regional cerebral blood flow during rest and skilled hand movements by xenon-133 inhalation and emission computerized tomography.

Regional cerebral blood flow (CBF) was studied in 16 normal adult volunteers during rest and in 10 the study was repeated during skilled hand movements. A fast-rotating ("dynamic"), single-photon emission computerized tomograph (ECT) with four detector heads was used. Xenon-133 was inhaled over a 1-min period at a concentration of 10 mCi/L. The arrival and washout of the radioisotope was recorded during four 1-min periods. Two slices, 2 cm thick, 7 and 12 cm above the orbitomeatal line were obtained in every study. CBF averaged 60 ml/100 g/min (SD +/- 11) in the lower slice and 51 ml/100 g/min (SD +/- 13) in the upper slice. A symmetric pattern comparing right to left sides was found in both slices. Finger tapping and writing with the right hand increased CBF in specific areas of the upper slice: in the contralateral hand area by 35 +/- 15% (p less than 0.025), and in the supplementary motor area on both sides by 34 +/- 15% (p less than 0.025).

Adult↗
PubMed1981

A method for calculating regional cerebral blood flow from emission computed tomography of inert gas concentrations.

Emission tomography of positron or gamma emitting inert gases allows calculation of regional cerebral blood flow (rCBF) in cross-sectional slices of human brain. An algorithm is presented for rCBF calculations from a sequence of time averaged tomograms using inhaled 133Xe. The approach is designed to avoid loss of information in brain areas with low flow rates. It is based on linearizing and scaling the early isotope distribution picture (recorded from 0 to 2 min) in rCBF units of ml/100 g/min. This is done by calculating the time constant ki for pixels with high count rate using the entire sequence of four 1 min pictures and using a fixed value for the brain:blood partition coefficient, lambda. The method is essentially based on the bolus distribution principle, and it allows the estimation of blood flow in ischemic areas. Application to positron emission tomography is discussed.

Cerebral Infarction↗
PubMed1981

Regional cerebral blood flow by radioxenon-113 inhalation and dynamic emission tomography.

A rapidly rotating single photon tomograph is described for atraumatic and three-dimensional measurements of rCBF in ml/100 g/min. The instrument has a high sensitivity permitting the recording of the uptake and washout of xenon-133 from the human brain during and after inhalation of the gas at a concentration of 10 mCi/l for 1 min. The algorithm used to calculate rCBF is described, and clinical results in particular in stroke cases are presented. The rapidly rotating tomograph is better suited for the study of focal cerebral ischemia than the conventional stationary detectors because superposition of tissue layers is avoided.

Brain Ischemia↗