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Biomedical subjects

O Henriksen

Publications and source records attributed to O Henriksen.

At least 217 records · Page 12Linked to original sources
PubMed1982

Subcutaneous blood flow over 24-hour periods in patients with severe leg ischaemia.

This paper describes a method for studying the clearance of 133Xenon from the subcutaneous tissue of the calf and foot over 24-h periods. The average blood flow over this period can be estimated from the clearance constant obtained. Two series of measurement of the radioactivity are made, the first 2 h after the injection of 1-2 mCi 133Xenon in saline and the second 18-24 h later. The distance between the detector and the depot is reproduced using a cylinder 20 cm long. The median washout rate of the isotope (k) in 25 patients was 2.57 X 10(-3) min-1 for the calf and 2.39 X 10(-9) min-1 for the foot. The median difference between repeated measurements in the same patient ws 0.24 X 10(-3) min-1 in the calf and 0.43 X 10(-3) min-1 in the foot. This method, which can be used to estimate the average blood flow over 24 h while the patient undertakes his normal activities, should be useful in assessing the effect of therapy on the blood flow to the limb.

Adult↗
PubMed1982

Determination of the subcutaneous tissue to blood partition coefficient in patients with severe leg ischaemia by a double isotope washout technique.

Knowledge of the tissue to blood partition coefficient (lambda) is essential for calculation of the perfusion coefficient in a single tissue based on measurements of the washout of locally injected isotopes. No measurements of lambda for Xenon in subcutaneous tissue in the leg have been done in patients with occlusive arterial disease. In 12 patients with occlusive arterial disease in the legs lambda for Xenon was determined in subcutaneous tissue in the calf region and foot as the ratio between the washout rate constant of 131I-Antipyrine and 133Xe. A mixture of the two indicators was injected subcutaneously laterally on the calf and in the first interosseous space on the foot. The time until the curves followed a monoexponential course varied between 15 and 45 min in the calf and 5 and 45 min in the foot. The calculated lambda for Xe showed a great variance between individuals in calf as well as foot. Mean value was 3.7 ml X g-1 (range: 1 X 7-10 X 7) in the calf and 2 X 7 ml X g-1 (range: 1 X 2-4 X 9) in the foot. It is concluded that lambda measurements are necessary for determination of subcutaneous blood flow from 133Xe washout curves in these patients. Determination of lambda is especially important when comparisons are made between individuals.

Aged↗
PubMed1982

Clinical and pharmacokinetic observations on sodium valproate - a 5-year follow-up study in 100 children with epilepsy.

Results of clinical and pharmacokinetic observations on sodium valproate (VPA) are reported from a long-term study in 100 children with epilepsy. VPA is the drug of choice in patients with absences. VPA may preferably be chosen as the first drug in patients with atonic seizures partly because all treatment of these seizures is uncertain, and the effect of VPA may be striking, without side effects. When starting with VPA the great problem of drug interactions is avoided. Treating patients with intractable epilepsy has shown that VPA may be effective in all seizure types regardless of the EEG-findings. However, generalized paroxysms of spike and wave complexes in the EEG are a good prognostic sign especially when fairly regular. Side effects are few when using enteric coated tablets, but toxic effects may be serious. Control schemes of blood and liver functions are necessary. Drug fasting serum level monitoring is mandatory, especially when VPA is given in combination with other anti-epileptic drugs as interactions with these are pronounced. Optimal clinical effect is usually seen on serum levels between 300 and 600 microgram mol/l, which may be obtained by giving 10-20 mg/kg daily assuming that the patient is receiving VPA monotherapy, which should always be aimed at. Comedication may have to be withdrawn to obtain therapeutic serum levels of VPA due to drug interactions.

Adolescent↗
PubMed1982

Effect of spinal sympathetic blockade upon postural changes of blood flow in human peripheral tissues.

The effect of head-up tilt upon subcutaneous and skeletal muscle blood flow in the crus was studied before and during epidural blockade in 10 subjects. Relative changes in blood flow were estimated by the local 133Xe washout technique. In subcutaneous tissue head-up tilt induced a decrease in blood flow of about 40% and there was no difference in the vascular response to head-up tilt before and during epidural blockade. In skeletal muscle tissue essentially the same was found as head-up tilt decreased blood flow by about 26% the response being uninfluenced by epidural blockade. In 3 patients local nervous blockade was induced by Lidocaine in 133Xe labelled subcutaneous tissue on one side. During epidural blockade and tilt blood flow increased by 12% whereas blood flow decreased by 30% on the control side. Thus epidural blockade had no influence on the vasoconstrictor response in subcutaneous tissue and skeletal muscle to head-up tilt whereas local blockade was able to prevent the response. Local mechanisms including the local veno-arteriolar reflex appear to play an important role for the observed maintenance of arterial blood pressure in the tilted position during central sympathetic blockade.

Anesthesia, Epidural↗
PubMed1982

Experimental osteoarthritis in the rabbit. A study of 133xenon washout rates from the synovial cavity.

Synovial perfusion in 6 rabbit knees, with experimentally induced osteoarthritis (joint instability), was studied by recording the initial 133Xe washout rates from the joint space. The unstable osteoarthritic knee was compared with the contralateral sham operated control knee at intervals of 6 to 96 weeks postoperatively. Within the first half year the ratio between the 133Xe washout rates in the osteoarthritic and control joints was significantly increased. These findings were supported by the increased blood flow to the joint region, visualized by scintigraphy of osteoarthritic rabbits given 99mTc-microspheres intracardially. However, methodological sources of error do not allow any conclusions regarding the much less increased 133Xe washout rates found in advanced osteoarthritis. The initially increased synovial blood flow coincided with the existence of joint effusion and the early development of osteophytes, all conditions supposed to be a consequence of posttraumatic synovitis. Attention is drawn to these pathogenic phenomena in studies dealing with the initial changes in experimental models of osteoarthritis and to a possible etiological significance.

Animals↗
PubMed1981

Local regulation of blood flow in subcutaneous tissue in patients with acute myocardial infarction.

1. Local regulation of subcutaneous blood flow in the forearm was studied in the acute phase of myocardial infarction. Blood flow was measured by the local 133Xe-washout technique. 2. Plasma concentrations of noradrenaline and adrenaline were increased on day 1, suggesting an increase in sympathetic neuronal activity, but gradually returned to normal thereafter. 3. Subcutaneous blood flow on day 1 was far below normal (38%) and steadily increased to reach normal at day 7 after coronary occlusion. The sympathetic vasoconstrictor activity that caused the initial reduction in flow could be blocked by proximal nervous blockade, increasing the subcutaneous blood flow by 130, 63 and 14% on days 1, 3 and 7 respectively after coronary occlusion. A normal response to decrease in arterial perfusion pressure was observed, suggesting that intrinsic vascular reactions responsible for autoregulation of blood flow were not affected by the increase in sympathetic vasoconstrictor activity. The vasoconstrictor response to increase in venous transmural pressure could not be demonstrated on day 1 after coronary occlusion but gradually reappeared during the following days. 4. Abolition of the vasoconstrictor response is most likely to be due to a centrally elicited increase in sympathetic activity, as a normal vasoconstrictor response was obtained after proximal nervous blockade. Thus the local sympathetic reflex mechanism underlying the vasoconstrictor response appears to be suppressed by a centrally elicited increase in sympathetic discharge rate.

Adult↗
PubMed1981

Constriction of collateral arteries induced by "head-up tilt" in patients with occlusive arterial disease of the legs.

The effect of head-up tilt on leg blood flow and segmental arterial blood pressures was studied in 21 patients with occlusion or severe stenosis of the common or superficial femoral artery. Arterial pressure was measured directly in the brachial artery, common femoral artery and popliteal artery. Relative change in blood flow in the leg during tilt was estimated by changes in arterio-venous oxygen differences and by the indicator dilution technique in nine patients. Head-up tilt caused a decrease in leg blood flow of 36% corresponding to an increase in total vascular resistance of 57%. Tilt did not change the pressure gradient from femoral to popliteal artery in the patients with occlusion of the superficial femoral artery, indicating that the flow resistance offered by the collateral arteries had increased. In a bilateral sympathectomised patient the increase in collateral resistance was almost absent indicating that the constriction of the collateral arteries is mainly mediated via sympathetic vasoconstrictor fibres.

Aged↗
PubMed1981

Effect of intra-arterially induced alpha-receptor blockade upon resistance in collateral arteries in patients with occlusion of the superficial femoral artery.

The effect of intra-arterially phentolamine inducing alpha-receptor blockade upon the resistance in collateral arteries bypassing an occlusion of the femoral artery was studied in five patients. The patients were placed on a tilt table and the measurements were performed with the patients in supine position and titled 40 degrees (head-up). Arterial blood pressure was measured directly in the brachial-common femoral-and popliteal artery. Relative blood flow was calculated as the relative change in arterio-venous oxygen saturation. Head-up tilt caused a decrease in blood flow of about 35% corresponding to an increase in total vascular resistance of 38%. Resistance in collateral arteries increased by 45%. In supine position alpha-receptor blockade reduced collateral resistance by 17%. However, the title-induced constriction of the collateral arteries was blocked by 87%. The results indicate that the constriction of the collateral arteries bypassing an occlusion of the superficial femoral artery is mainly mediated via sympathetic adrenergic vasoconstrictor fibres.

Adrenergic alpha-Antagonists↗
PubMed1981

Effect of lower body negative pressure upon local regulation of blood flow in human subcutaneous tissue.

Local regulation of subcutaneous blood flow in the forearm was studied during lower body negative pressure (LBNP) in 7 young healthy male subjects in supine position. Blood flow was measured on the forearm by the local 133Xe washout technique. LBNP of -40 and -60 mmHg induced a decrease in the 133Xe washout rate of 34 and 50% respectively. This response to LBNP could be blocked by proximal nervous blockade indicating that the vasoconstriction observed was due to a central sympathetic reflex mechanism. The vasoconstrictor response to increase in venous transmural pressure induced by lowering the arm (veno-arteriolar reflex mechanism) could not be demonstrated during 40 mmHg LBNP. The abolishment of this reflex is most likely due to centrally elicited increase in sympathetic activity as a normal veno-arteriolar reflex was elicited following proximal nervous blockade.

Adult↗
PubMed1981

Effect of orthostatic blood pressure changes upon capillary filtration-absorption rate in the human calf.

The effect of postural changes upon fluid filtration rate in the calf was studied in 3 healthy subjects placed in supine position. Volume changes in the calf were measured by a water plethysmograph. Relative changes in blood flow in subcutaneous tissue and anterior tibial muscle were measured by the local 133Xe washout technique. Lowering the calf from 5-25 cm caused a linear increase in filtration rate whereas blood flow in subcutaneous tissue of the segment studied and anterior tibial muscle remained constant. Based on this average CFC was about 0.0012 ml X min-1 X 100 g-1 X mmHg-1. Further lowering of the calf caused a decrease in blood flow in subcutaneous tissue and skeletal muscle by about 50% corresponding to an increase in total vascular resistance by about 100%. During these circumstances the increase in infiltration rate was reduced by about 33%. The resulted indicate that the local veno-anterior reflex responsible for the observed vasoconstriction in the tissue under study together with intrinsic vascular mechanisms reduces transcapillary fluid filtration in the lower position. The mechanism appears to be mainly due to a reduction of the increase in mean capillary pressure whereas CFC seems to remain almost constant.

Axons↗
PubMed1981

Duration of increase in vascular volume during venous stasis.

Duration of increase in vascular volume in the crus following application of venous stasis was studied in 3 healthy subjects placed in a supine position. Changes in calf volume during venous stasis was measured by plethysmography. In one series of experiments changes in vascular volume were studied by measurements of accumulation of 133Xenon proximal to a depot located in the anterior tibial muscle. In another series of experiments changes in activity of 99mTc-labelled erythrocytes were used as indicator for changes in vascular volume. Following application of venous stasis in the horizontal position the rate of increase in calf volume declined to a steady level after about 5 min. Both the studies with 133Xenon and with 99mTc-erythrocytes indicate that vascular volume continued to increase for 3, 3.5 and 5 min following venous stasis of 20, 30 and 40 mmHg, respectively. When the crus was lowered 50 cm below heart level the duration of increase in vascular volume following an additional increase in venous pressure induced by venous stasis was shorter than in the horizontal position. When the calf is placed at heart level the results indicate that for up to 5 min after application of venous stasis of 40 mmHg both increase in vascular volume and transcapillary fluid filtration contribute to the observed increase in calf volume. Using the rate of increase in calf volume within 5 min after induction of venous stasis thus leads to overestimation of CFC. After 5 min vascular volume appears to remain constant and the observed increase in calf volume seems to be solely due to a net increase in interstitial fluid volume.

Axons↗
PubMed1981

Augmented vasoconstrictor response to changes in vascular transmural pressure in patients with essential arterial hypertension.

The vasoconstrictor response to increase in venous transmural pressure in subcutaneous tissue was studied in 9 patients with essential arterial hypertension. Subcutaneous blood flow was measured on the distal part of the forearm and at the lateral malleolus by the local 133Xe washout technique. Increase in venous transmural pressure was obtained by lowering the area under study 40 cm below midaxillary line in the recumbent subject. Average mean arterial pressure +/- 1 S.E. was 133 +/- 6 mmHg. The fractional increase in vascular resistance induced by arteriolar constriction was more pronounced in the hypertensive patients that in a normotensive control group. "Minimal vascular resistance" in the papaverine relaxed vascular bed was higher in the hypertensive patients than in the controls. Distensibility of the papaverine relaxed resistance vessels was diminished in the patients. Follow-up studies after 6-18 months of anti-hypertensive treatment indicate that the vasoconstrictor response as well as "minimal vascular resistance" are normalized, whereas the distensibility of the papaverine relaxed arterioles remained unaltered in the hypertensive patients. The results indicate that the arteriolar smooth muscle cells of hypertensive patients are subjected to reversible hypertrophy whereas the reduced distensibility of the resistance vessels is due to irreversible structural changes.

Adult↗
PubMed1981

Reduced systolic blood pressure in fingers of patients with generalized scleroderma (acrosclerosis).

Segmental systolic blood pressure was measured on upper arm, wrist, proximal and middle pahlanx in 10 patients suffering from generalized scleroderma of the acrosclerosis type and in 5 normal. Systolic pressure was measured by the strain-gauge technique before and after abolition of sympathetic vasoconstrictor activity by local heating and by nerve block. Arm and wrist pressures were equal in the two groups, but a significant reduction in finger pressure was found in the patients. Finger pressure was unaltered after sympathetic blockade, both in the patients and in the normals. The pressure drop from wrist to finger in the patients suggests an increased flow resistance in the palmer arch and digital arteries which was probably not caused by an augmented sympathetic vasoconstrictor activity, as sympathetic blockade did not influence finger systolic pressure. Sympathectomy cannot be expected to relieve Raynaud's attacks in these patients.

Adult↗
PubMed1980

Excess cumulative blood flow and repayment during reactive hyperemia in human cutaneous tissue.

The influence of duration of vascular occlusion upon the reactive hyperemic response in human cutaneous tissue was studied in 6 subjects. Blood flow in cutaneous tissue was measured dorsally on the distal phalanx of the second finger by the local 133Xenon washout technique. Post-occlusive blood flow, calculated from the steepest part of the 133Xenon washout curve just after release of vascular occlusion, reached a maximum value when duration of vascular occlusion was 12 min. However, excess cumulative blood flow, i.e. the integrated blood flow during reactive hyperemia minus integrated pre-ischemic blood flow for a period corresponding to the duration of the reactive hyperemic response, increased with increasing duration of vascular occlusion from 3 to 24 min. Fractional repayment, i.e. excess cumulative blood flow divided by pre-ischemic blood flow times duration of vascular occlusion, was not correlated significantly to duration of vascular occlusion. However, there was a significant inverse correlation between fractional repayment and pre-occlusive blood flow, indicating that, besides metabolic factors, pre-ischemic blood flow in cutaneous tissue is influenced by other factors, such as heat regulation.

Adult↗
PubMed1980

Cold hypersensitivity after sympathectomy for Raynaud's disease.

Two patients with socially handicapping Raynaud's disease underwent bilateral upper thoracic sympathectomy. One to two days after the operation, both developed local hypersensitivity to cold in the form of a rebound. The cold hypersensitivity persisted in one of the patients, although complete degeneration of vasoconstrictor fibres was proven by absence of the sympathetic veno-arteriolar reflex after sympathectomy. Pre-operative sympathetic blockade could not predict the outcome of sympathectomy.

Adult↗
PubMed1980

Local regulation of blood flow in peripheral tissue.

Patients suffering from proximal occlusive arterial disease with rest pain in the foot get relief from their pain when the foot is lowered. The rest pain suggests ischemia of the foot. Lassen & Westling (1969) proposed that during lowering blood flow increases in ischemic areas and decreases in nonischemic areas. The relief of rest pain during lowering is in all probability due to this increase blood flow in ischemic areas. That flow really increases in the critical tissue areas was shown by Henriksen in 1974. The flow decrease in non-threatened areas was also demonstrated in this study. Since then, postural blood flow regulation in peripheral tissue has been studied in much detail and a clearer understanding of the mechanisms underlying this favourable redistribution of flow observed in such patients has emerged. A review of these studies is presented.

Arterial Occlusive Diseases↗