Biomedical subjects

W Sorteberg

Publications and source records attributed to W Sorteberg.

23 records · Page 2Linked to original sources

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

Cerebral autoregulation dynamics in humans.

We studied the response of cerebral blood flow to acute step decreases in arterial blood pressure noninvasively and nonpharmacologically in 10 normal volunteers during normocapnia, hypocapnia, and hypercapnia. The step (approximately 20 mm Hg) was induced by rapidly deflating thigh blood pressure cuffs following a 2-minute inflation above systolic blood pressure. Instantaneous arterial blood pressure was measured by a new servo-cuff method, and cerebral blood flow changes were assessed by transcranial Doppler recording of middle cerebral artery blood flow velocity. In hypocapnia, full restoration of blood flow to the pretest level was seen as early as 4.1 seconds after the step decrease in blood pressure, while the response was slower in normocapnia and hypercapnia. The time course of cerebrovascular resistance was calculated from blood pressure and blood flow recordings, and rate of regulation was determined as the normalized change in cerebrovascular resistance per second during 2.5 seconds just after the step decrease in blood pressure. The reference for normalization was the calculated change in cerebrovascular resistance that would have nullified the effects of the step decrease in arterial blood pressure on cerebral blood flow. The rate of regulation was 0.38, 0.20, and 0.11/sec in hypocapnia, normocapnia, and hypercapnia, respectively. There was a highly significant inverse relation between rate of regulation and PaCO2 (p less than 0.001), indicating that the response rate of cerebral autoregulation in awake normal humans is profoundly dependent on vascular tone.

Adult↗

PubMed1988

Cerebral vasospasm after subarachnoid haemorrhage investigated by means of transcranial Doppler ultrasound.

Measurements of flow velocity in defined segments of the basal cerebral arteries can be obtained through the intact adult skull using 2 MHz pulsed Doppler ultrasound. We compared flow velocity in these vessels with findings from 56 cerebral angiographies obtained in 51 patients at from day 1 to day 21 after subarachnoid haemorrhage (SAH). The diameter of the proximal segment of the middle cerebral, anterior cerebral, and posterior cerebral arteries (MCA, ACA, and PCA, respectively) were measured from anteroposterior films produced in one angiographic laboratory. In patients investigated on day 1-2, the median MCA diameter was 2.8 mm with range 2.3-3.4 mm. The median flow velocity was 56 cm/s, range 36-88 cm/s (within normal limits). There was a clear inverse relationship between the MCA diameter and MCA flow velocity. Eleven of the 13 MCA's having diameter 1.5 mm or less showed flow velocity in excess of 140 cm/s. This seems a useful limit to diagnose pronounced MCA spasm (50% diameter reduction) with this method. Further clues to the severity of MCA spasm were obtained from the ratio calculated dividing the MCA flow velocity by the flow velocity in the ipsilateral, extracranial internal carotid artery (ICA), since spasm probably does not involve the neck vessels. This ratio was from 1.1 to 2.3, median 1.7 at day 1-2, but rose to over 10 in patients with the most severe MCA lumen narrowing. The PCA flow velocity was inversely related to the PCA diameter. Assessment of ACA spasm requires considering findings from both hemispheres combined, since the two proximal ACA's usually anastomose through the anterior communicating artery.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1986

A non-invasive Doppler ultrasound method for the evaluation of patients with subarachnoid hemorrhage.

Measurements of flow velocity in the basal cerebral arteries can be obtained non-invasively through the intact skull using 2 MHz pulsed Doppler ultrasound. We investigated 47 patients with subarachnoid hemorrhage and compared flow velocity with angiography. Flow velocity in the middle and posterior cerebral arteries (MCA and PCA) was inversely related to the lumen diameter. Further clues to diagnose MCA spasm were obtained from the ratio of MCA flow velocity divided by the velocity in the distal extracranial internal carotid artery. In the individual patient, the two anterior cerebral arteries should be considered together, since this communicating system often has unique possibilities for collateral flow. Recordings from large MCA aneurysms were obtained before angiography in 4 patients.

Adult↗