A. David Mendelow, Benjamin H. Eidelman and Thomas A. McCalden
✓ The effect of intracarotid infusion of dexamethasone on cerebral blood flow and cerebral oxygen utilization was measured in baboons using the xenon-133 clearance technique. The cerebrovascular response to intracarotid infusion of 5-hydroxytryptamine (5-HT) was then determined during simultaneous infusion of the steroid. Infusion of dexamethasone alone and infusion with 5-HT produced no significant change in cerebral blood flow or cerebral oxygen utilization when compared to baseline values. The study indicates that neither dexamethasone nor 5-HT with dexamethasone modify cerebral blood flow when infused via the internal carotid artery.
A. David Mendelow, John O. Rowan, Lilian Murray and Audrey E. Kerr
✓ Simultaneous recordings of intracranial pressure (ICP) from a single-lumen subdural screw and a ventricular catheter were compared in 10 patients with severe head injury. Forty-one percent of the readings corresponded within the same 10 mm Hg ranges, while 13% of the screw pressure measurements were higher and 46% were lower than the associated ventricular catheter measurements. In 10 other patients, also with severe head injury, pressure measurements obtained with the Leeds-type screw were similarly compared with ventricular fluid pressure. Fifty-eight percent of the dual pressure readings corresponded, while 15% of the screw measurements were higher and 27% were lower than the ventricular fluid pressure, within 10-mm Hg ranges. It is concluded that subdural screws may give unreliable results, particularly by underestimating the occurrence of high ICP.
Iain Robert Chambers, Lynne Treadwell and A. David Mendelow
Object. Intracranial pressure (ICP) and cerebral perfusion pressure (CPP) are frequently monitored in severely head injured patients. To establish which one (ICP or CPP) is more predictive of outcome and to examine whether there are significant threshold levels in the determination of outcome, receiver—operating characteristic (ROC) curves were used to analyze data in a large series of head-injured patients.
Methods. Data were obtained from a total of 291 severely head injured patients (207 adults and 84 children). Outcome was categorized as either independent (good recovery or moderate disability) or poor (severely disabled, vegetative, or dead) by using the Glasgow Outcome Scale; patients were also grouped according to the Marshall computerized tomography scan classification.
Conclusions. The maximum value of a 2-minute rolling average of ICP readings (defined as ICPmax) and the minimum value of the CPP readings (CPPmin) were then used to calculate the sensitivity and specificity of the ROC curves over a range of values. Using ROC curves, a threshold value for CPPmin of 55 mm Hg and for ICPmax of 35 mm Hg appear to be the best predictors in adults. For children the levels appear to be 43 to 45 mm Hg for CPPmin and 35 mm Hg for ICPmax. Higher levels of CPPmin seem important in adults with mass lesions. These CPP thresholds (45 mm Hg for children and 55 mm Hg for adults) are lower than previously predicted and may be clinically important, especially in children, in whom a lower blood pressure level is normal. Also, CPP management at higher levels may be more important in adults with mass lesions. A larger observational series would improve the accuracy of these predictions.
A. David Mendelow, David I. Graham, Ursula I. Tuor and William Fitch
✓ The purpose of this study was to determine in subhuman primates whether hemodynamic mechanisms (as compared with embolic mechanisms) contribute to cerebral ischemia following carotid artery occlusion or stenosis. Following carotid artery occlusion there was loss of cerebral autoregulation: cerebral blood flow (CBF) measured with the xenon-133 technique became passively dependent upon the mean arterial blood pressure (MABP) over an MABP range of 30 to 110 mm Hg. By contrast, autoregulation was preserved in normal animals and in animals with a 90% carotid artery stenosis. Regional CBF was measured with carbon-14-labeled iodoantipyrine autoradiography in normotensive baboons, in hypotensive animals, and in hypotensive animals with carotid artery occlusion or stenosis. With carotid artery occlusion and hypotension, reduced levels of local CBF were seen ipsilaterally in the boundary zones between the anterior and middle cerebral arteries with 35% of the area of an anterior section through the hemisphere displaying a CBF value of less than 20 ml/100 gm/min. Comparable values with hypotension were 21% with carotid artery stenosis, 20% with no proximal vascular lesion, and 1% in normotensive animals. These areas of reduced CBF corresponded with areas of boundary-zone ischemia seen with light microscopy. The study suggests that while hemodynamic ischemia develops with carotid artery occlusion, it does not occur with even a 90% carotid artery stenosis or in normal animals.
Thomas A. Kingman, A. David Mendelow, David I. Graham and Graham M. Teasdale
✓ Cerebral blood flow (CBF) was measured at different times during the first 150 minutes following an experimental space-occupying lesion produced with a 50-µl microballoon in rats. Local CBF was measured with the carbon-14-labeled iodoantipyrine quantitative autoradiographic technique. A region of local ischemia developed around the mass, while the remote effects of the mass were minimal. The focal ischemic lesion enlarged with time, and simulated removal of the lesion within this design did not alleviate the ischemia.
E. J. Sinar, A. David Mendelow, David I. Graham and Graham M. Teasdale
✓ Late pathophysiological events after the production and subsequent removal of an intracerebral mass were investigated using a mechanical microballoon model to simulate intracerebral hemorrhage. Immediately following balloon inflation in the caudate nucleus of rats, there was a significant increase in intracranial pressure to 14 ± 1 mm Hg (mean ± standard error of the mean), accompanied by a reduction in cerebral blood flow (CBF) in the ipsilateral frontal cortex, as measured by the hydrogen-clearance technique. Carbon-14-iodoantipyrine autoradiography revealed a significant reduction in the CBF of the ipsilateral caudate nucleus 4 hours after balloon inflation: 31% of the caudate nucleus had a CBF of less than 20 ml ⋅ 100 gm−1 ⋅ min−1 compared to only 1% in the sham-treated control group (balloon insertion without inflation). The rats with an intracerebral mass exhibited a significant increase in the volume of ischemic damage in the ipsilateral caudate nucleus (17.1% of total volume) compared to only 1.7% in the sham-treated group; however, there was no evidence of cerebral edema. Ischemic damage and reduced CBF persisted for 4 hours after transient inflation of a microballoon in the caudate nucleus. This suggests that ischemic damage occurs at the time of formation of the lesion and is not prevented by its early removal.
Philip Barlow, A. David Mendelow, Audrey E. Lawrence, Marion Barlow and John O. Rowan
✓ Recordings from two different types of subdural pressure monitor with simultaneous intraventricular pressure (IVP) tracings are compared in 20 head-injured patients. In the first 10 patients a fluid-filled catheter was placed subdurally and connected to an external transducer, and in the second 10 the Gaeltec model ICT/b solid state miniature transducer was used. The latter system has the advantage that both zero and calibration checks can be carried out after insertion. Only 44% of the fluid-filled catheter readings corresponded with IVP in series of 10-mm Hg ranges, while 53% of readings were lower; this tendency was more marked at higher pressures. With the Gaeltec transducer, 72% of subdural pressure readings corresponded with IVP, while only 9% were lower and 19% were higher than IVP. The differences may have been due to technical causes or to true pressure differentials. The subdural catheter appears too unreliable for routine clinical use, but the Gaeltec transducer may be a satisfactory alternative to ventricular pressure monitoring.
Patrick Mitchell, Richard Kerr, A. David Mendelow and Andy Molyneux
The present purpose is to define the sensitivity of the superiority of coil embolization observed in the International Subarachnoid Aneurysm Trial (ISAT) according to the rate of late rebleeding over a reasonable range, and to find the range of rebleeding rates for which it may be overturned. In the ISAT, coil embolization appears to be safer than clip ligation at 1 year, and clip occlusion has better long-term efficacy at preventing rebleeding. This leaves open the question of which is better in the longer term.
The authors calculate the life expectancy of patients following a subarachnoid hemorrhage (SAH) and compare the life expectancy of those who underwent coil embolization with those who underwent clip ligation in the ISAT cohort.
The 1-year poor outcome rate following treatment climbs rapidly with advancing age. A consequence is that the absolute difference between the poor outcome rates after coil embolization and clip occlusion is lower in those < 50 years of age (3.3%) than it is for those > 50 years of age (10.1%). This difference may be enough to give clip application the advantage in the < 40-year-old group despite the small size of the difference in 1-year rebleeding rates thus far observed (0.152%).
When treating ruptured cerebral aneurysms, the advantage of coil embolization over clip ligation cannot be assumed for patients < 40 years old. In this age range the difference in the safety of the 2 procedures is small, and the better long-term protection from SAH afforded by clip placement may give this treatment an advantage in life expectancy for patients < 40 years of age.
Biodun Ogungbo, Barbara Gregson, Alison Blackburn, Jane Barnes, Ramon Vivar, Robin Sengupta and A. David Mendelow
Object. The authors reviewed the management protocols for young adults who presented with subarachnoid hemorrhage (SAH) at the Regional Neurosurgery Unit in Newcastle during a study period of 9 years. Aneurysmal SAH is uncommon in the age group selected (18–39 years) and, therefore, the performance of these patients has not been extensively reported in the literature. The authors also evaluated the good-grade rebleed rate (an index of management efficiency) in this cohort of patients.
Methods. The Newcastle neurosurgical unit serves a population of close to 3 million people, and an average of 180 patients with SAH are seen each year. The majority of patients are transferred from other hospitals in the region. This study includes patients admitted between January 1990 and December 1998. A total of 1609 patients were admitted during this period, of whom 295 (18.4%) between the ages of 18 and 39 years constituted the study population of young adults.
Two hundred ninety-five young adults presented with SAH; 181 (61.4%) were women and 114 (38.6%) were men, a ratio of 3:2. Of 246 patients in whom this value was recorded, 15 (6.1%) presented with a history of hypertension, and there was an association between hypertension and the occurrence of multiple aneurysms (Fisher two-tailed exact test, p = 0.008). Thirty-five patients (11.9%) presented with a hematoma on computerized tomography scans; of these, 20 (57%) were women and 15 were men.
In six patients the lesion had rebled before treatment. The good-grade rebleed rate was three (1.7%) of 178. The overall favorable outcome rate was 83.8% (Glasgow Outcome Scale [GOS] 4 and 5) and unfavorable outcome occurred in 16.2% (GOS 1–3), with a total of 40 deaths in this group (13%). Age had no influence on outcome in young adults. Comparing the outcome at discharge with the follow-up evaluation at 6 months revealed that patients in the moderate and severe disability groups continued to improve and many achieved good recovery.
Conclusions. In this report the authors detail the outcome of a large number of young adults with SAH. The incidence of SAH was higher in the female population, although the ratio was not as high as previously reported. The authors have also demonstrated a progressive increase in the incidence of aneurysmal SAH with age, even in young adults. Hypertension but not age influenced the occurrence of multiple aneurysms. The good-grade rebleed rate is low, although it is not zero. Generally, a satisfactory outcome was obtained and significant continuing improvements were noted between discharge and follow-up evaluation. This reflects the power of recovery in young adults. These are people whose economic productivity and fertility are at peak levels and therefore the financial and social burden occasioned by less-than-perfect outcomes is large.