E. Enevoldsen

Transcranial doppler recordings in raised intracranial pressure

The pulsatility index (PI) registreted by the transcranial doppler (TCD) was examined in relation to arterial pCO2 (paCO2) and epidural pressure (ICP). In 10 normal subjects PI was studied during variations in paCO2. In 10 neurosurgical patients with head injuries concomitant measurements of PI and ICP were obtained. The results showed a negative exponential correlation between PI and paCO2. PI changed with 3.2% pr mmHg paCO2. A positive exponential correlation between PI and ICP was observed. PI changed with 2.4% pr mmHg ICP. In the subgroup of patients with raised ICP (15 mmHg <) p

Retrograde catheterization of the right internal jugular vein for serial measurements of cerebral venous oxygen content

Serial measurements of CBF and metabolism require multiple cerebral venous blood samples. Retrograde catheterization of the right internal jugular vein is easily performed at a point 2.5–3 cm lateral to, and 2 cm above, the medial end of the right clavicula. Complications are few and minor. In 1/80 (1.25%) cases the carotid artery was punctured during cannulation. Insertion of the catheter for 16–18 cm reduces contamination with extracerebral blood to a minimum.

Cerebral blood flow and metabolism following subarachnoid haemorrhage: cerebral oxygen uptake and global blood flow during the acute period in patients with SAH.

Forty‐eight patients with subarachnoid haemorrhage were studied with repeated rCBF and CMRO2 measurements. Cortical rCBF was measured using xenon‐inhalation technique. CMRO2 was calculated as AVDO2 x CBF. When first studied the 29 conscious patients showed relative hyperaemia with CBF at 50 ml and reduced CMRO2 at 2.17 ml. In the following week CBF decreased to 41. CMRO2 remained reduced and constant. The 19 unconscious patients showed initially pronounced reduction in CMRO2 to 1.26, followed by gradual increase to 1.73 in 4–5 days. Simultaneously CBF increased from 18 ml to slightly above 30 ml. In the conscious patients the early reduction in CMRO2 and the concomitant luxury perfusion may be explained by global ischaemia because of very high ICP at the time of the haemorrhage. The reduced CBF in the unconscious group could be due to increased ICP, as ventricular drainage increased CBF to levels of relative hyperaemia as demonstrated in one case. As no decrease in CMRO2 was seen during the first 2 weeks, it is suggested that ischaemia at the time of aneurysm rupture is the most important single factor in reduction of global CMRO2.

Relation between angiographic cerebral vasospasm and regional CBF in patients with SAH

The relation between angiographically determined cerebral vasopasm following a subarachnoid hemorrhage and regional cerebral blood flow (CBF) was studied in 63 investigations of 45 patients. The CBF was measured using the intra‐arterial 133‐Xe clearance technique within one hour of angiography. A positive correlation between regional CBF and diameter of major supplying vessel was observed. However, in the 13 cases with focal vasospasm the reduction in CBF was global and not restricted to the area of the spastic vessel. The cerebral oxygen extraction was reduced but independent of the degree of vasopasm, speaking against vasopasm as the cause for the reduction in CBF. The observed association between reduction in CBF and vasospasms could be caused by a common factor responsible for development of both. Thus, it is proposed that the amount of blood escaping at time of aneurysm rupture determines 1) the amount of reduction in cerebral oxygen uptake and thereby the reduction in CBF and 2) the degree of vasopasm. If so a correlation, yet not causal, between reduction in CBF and degree of vasospasm, will be observed.

Cerebral blood flow and metabolism following subarachnoid haemorrhage : effect of subarachnoid blood

The amount of effused blood following a subarachnoid haemorrhage (SAH) was estimated in 48 patients by cerebral computerized tomographic scanning. The cerebral oxygen consumption (CMRO2) was calculated as arteriovenous difference for oxygen multiplied by mean cerebral blood flow measured by the 133–Xe inhalation technique. A significant negative correlation was observed between CMRO2 and amount of subarachnoid blood, with additional reduction in CMRO2 in case of ventricular bleeding. Cerebral blood flow on admission, opposed to CMRO2, showed no correlation to amount of blood on CT scan. A correlation was observed for blood flow measured at day 5 and further on, indicating a restored coupling between flow and metabolism. The clinical (Hunt) grade on admission and the outcome correlated to the amount of blood. These observations suggest that the acute reduction in CMRO2 following a SAH is mainly determined by the amount of blood escaping during the aneurysm rupture, and that the cerebral blood flow level a few days after SAH mainly is determined by the initial reduction in oxygen uptake.

Spasm index in subarachnoid haemorrhage: consequences of vasospasm upon cerebral blood flow and oxygen extraction

Abstract A spasm index, defined as transcranial Doppler detected flow velocity in the middle cerebral artery divided by regional cortical cerebral blood flow (CBF), was used on 24 patients with subarachnoid haemorrhage (SAH). The aim was to estimate degree and time course of vasospasm, even in cases with great day‐to‐day variation in CBF, and correlate to CBF and oxygen extraction. All patients showed increase in spasm indices with peak index in the second or third week. The index seemed stable in spite of day‐to‐day fluctuations in CBF. Severe vasospasm were associated with poor clinical condition, reduced CBF (<30) and high AVDO2. The same picture could be seen with minor degree of vasospasm, probably, in some cases, due to high intracranial pressure. The results suggests that the spasm index is useful in monitoring patients with subarachnoid haemorrhage, and that severe vasospasm has a negative influence on clinical condition, CBF and oxygen extraction

A neuropsychological study of 12 patients with transient ischemic attacks before and after EC/IC bypass surgery

ABSTRACT – A neuropsychological study of 12 patients with transient ischemic attacks from the carotid artery territory was carried out about 2 months following their latest attack, about a week before STA/MCA bypass operation, and again 3 months postoperatively. The results suggest that the TIA patients as a group were slightly intellectually impaired preoperatively. After the operation, a minor neuropsychological improvement had taken place although they still were not fully intellectually rehabilitated.

Reversible ischemic neurological deficit and minor strokes before and after EC/IC bypass surgery

ABSTRACT Thirty‐three patients with reversible ischemic deficits or completed minor strokes had their cerebral function measured neuropsychologically a few days before and 3 months after extra‐intra cranial bypass surgery. Three months post‐operatively bypass patency was demonstrated by angiography. Ten patients were operated on the right side and 23 on the left side. The right hemisphere patients were found to be neuropsychologically intact or only slightly impaired before, as well as after, the operation whereas the left hemisphere patients pre‐operatively had impaired verbal sequential thinking, reduced capacity for repetition, verbal learning, and mental arithmetic. Post‐operatively they improved significantly on 5 of 15 tests and performed no worse on any test than the control group. Consequently, they, too, had post operatively no or only slight neuropsychological impairment.

The Lower Limit of Cerebral Autoregulation During Treatment of Severe Hypertension

The lower mean blood pressure limit of CBF autoregulation is about 60 torr in normal man. In hypertensive patients the lower limit is shifted towards higher blood pressures.