Screening for familial intracranial aneurysms.
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Aneurysm, Ruptured↗
Biomedical subjects
P J Kirkpatrick
Publications and source records attributed to P J Kirkpatrick.
Time to reconsider treatment options for intracranial aneurysms.
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Adult↗
Neuropathological findings after intracerebral implantation of microdialysis catheters in sheep forebrain.
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Animals↗
Evaluation of carotid endarterectomy with sequential MR perfusion imaging: a preliminary 12-month follow up.
AIM: The clinical benefit of carotid endarterectomy is partially determined by peri-operative mortality and morbidity. Post-operative abnormalities in cerebral perfusion may be a risk factor for cerebral haemorrhage, and may be estimated from Bolus Arrival Time (BAT) as demonstrated by MR perfusion imaging. We aimed to use MR perfusion imaging to determine the temporal extent of these changes. MATERIALS AND METHODS: A single slice gradient recalled echo sequence was employed in five patients who underwent carotid endarterectomy. Sequential studies were undertaken pre-operatively, 3-5 days post carotid endarterectomy, and additionally at 3, 6 and 12 months. RESULTS: Asymmetric BATs were demonstrated in 3/5 patients, changes occurring as late as 6 to 12 months after carotid endarterectomy. These changes were not associated with either clinical or conventional MR morphological complications. CONCLUSIONS: MR perfusion imaging is able to demonstrate changes in BAT characteristics for up to 12 months after carotid endarterectomy. The clinical significance and underlying cause of these changes, including any association with post carotid endarterectomy hyperaemia, remains unknown.
Aged↗
Monitoring of brain metabolism during aneurysm surgery using microdialysis and brain multiparameter sensors.
The aim of the study was to monitor brain metabolism during aneurysm clipping using microdialysis and multiparameter sensors, particularly to investigate the effects of temporary clipping of vessels. Microdialysis catheters (n = 10) and Paratrend brain multiparameter (O2, CO2, pH and temperature) sensors (n = 15) were inserted into the cerebral cortex via a specially designed triple bolt prior to craniotomy. Baseline brain O2 levels ranging from 15-45 mmHg (2.0-6.0 kPa) and glucose levels from 0.5-3 mmol l-1 were stable during uneventful periods. The mean lactate/pyruvate (L/P) ratio ranged from 32 to 65 (normal < 30), indicating a tendency towards anerobic metabolism in all patients. Overall, short periods of temporary clipping (< 3 min; n = 6) were well tolerated producing no significant reduction in brain O2 (pre-clip mean 23 mmHg (3.0 kPa) vs. post-clip mean 20 mmHg (2.6 kPa)) or elevation of the L/P ratio (pre-clip mean 42 vs. post-clip mean 43). Two patients with prolonged temporary clipping showed derangements in the Paratrend parameters associated with increases in the L/P ratio. The results demonstrated that the monitored variables remained stable during uneventful procedures, including transient temporary clipping, but adverse events such as prolonged temporary clipping resulted in pronounced changes in brain metabolism. Monitoring of metabolism during aneurysm surgery may be of benefit in selected patients.
Adult↗
Measuring brain tissue oxygenation compared with jugular venous oxygen saturation for monitoring cerebral oxygenation after traumatic brain injury.
UNLABELLED: Jugular bulb oximetry is the most widely used method of monitoring cerebral oxygenation. More recently, measurement of brain tissue oxygenation has been reported in head-injured patients. We compared the changes in brain tissue oxygen partial pressure (PbO2) with changes in jugular venous oxygen saturation (SjVO2) in response to hyperventilation in areas of brain with and without focal pathology. Thirteen patients with severe head injuries were studied. A multiparameter sensor was inserted into areas of brain with focal pathology in five patients and outside areas of focal pathology in eight patients. A fiberoptic catheter was inserted into the right jugular bulb. Patients were hyperventilated in a stepwise manner from a PaCO2 of approximately 35 mm Hg to a PaCO2 of 22 mm Hg. There was no significant change in cerebral perfusion pressure or arterial partial pressure of oxygen with hyperventilation. In areas without focal pathology, there was a good correlation between changes in SjVO2 and PbO2 (deltaSjVO2 and deltaPbO2; r2 = 0.69, P < 0.0001). In areas with focal pathology, there was no correlation between deltaSjVO, and APbO2 (r2 =0.07, P = 0.23). In this study, we demonstrated that measurement of local tissue oxygenation can highlight focal differences in regional cerebral oxygenation that are disguised when measuring SjVO2. Thus, monitoring of PbO2 is a useful addition to multimodal monitoring of patients with traumatic head injury. IMPLICATIONS: Brain oxygenation is currently monitored by using jugular bulb oximetry, which attracts a number of potential artifacts and may not reflect regional changes in oxygenation. We compared this method with measurement of brain tissue oxygenation using a multiparameter sensor inserted into brain tissue. The brain tissue monitor seemed to reflect regional brain oxygenation better than jugular bulb oximetry.
Adult↗
Critical closing pressure in cerebrovascular circulation.
OBJECTIVE: Cerebral critical closing pressure (CCP) has been defined as an arterial pressure threshold below which arterial vessels collapse. Hypothetically this is equal to intracranial pressure (ICP) plus the contribution from the active tone of cerebral arterial smooth muscle. The correlation of CCP with ICP, cerebral autoregulation, and other clinical and haemodynamic modalities in patients with head injury was evaluated. METHOD: intracranial pressure, arterial blood pressure (ABP) and middle cerebral artery blood flow velocity were recorded daily in ventilated patients. Waveforms were processed to calculate CCP, the transcranial Doppler-derived cerebral autoregulation index (Mx), mean arterial pressure (ABP), intracranial pressure (ICP), and cerebral perfusion pressure (CPP). RESULTS: Critical closing pressure reflected the time related changes in ICP during plateau and B waves. Overall correlation between CCP and ICP was mild but significant (R=0.41; p<0.0002). The mean difference between ABP and CCP correlated with CPP (R=0.57, 95% confidence interval (95% CI) for prediction 25 mm Hg). The difference between CCP and ICP, described previously as proportional to arterial wall tension, correlated with the index of cerebral autoregulation Mx (p<0.0002) and CPP (p<0.0001). However, by contrast with the Mx index, CCP-ICP was not significantly correlated with outcome after head injury. CONCLUSION: Critical closing pressure, although sensitive to variations in ICP and CPP, cannot be used as an accurate estimator of these modalities with acceptable confidence intervals. The difference CCP-ICP significantly correlates with cerebral autoregulation, but it lacks the power to predict outcome after head injury.
Adolescent↗
Hemodynamic characterization of intracranial pressure plateau waves in head-injury patients.
OBJECT: Plateau waves of intracranial pressure (ICP) are often recorded during intensive care monitoring of severely head injured patients. They are traditionally interpreted as meaningful secondary brain insults because of the dramatic decrease in cerebral perfusion pressure (CPP). The aim of this study was to investigate both the hemodynamic profile and the clinical consequences of plateau waves. METHODS: One hundred sixty head-injured patients were studied using continuous monitoring of ICP; almost 20% of these patients exhibited plateau waves. In 96 patients arterial pressure, ICP, and transcranial Doppler (TCD) blood flow velocity were studied daily for 20 minutes to 3 hours. Sixteen episodes of plateau waves in eight patients were recorded and analyzed. The dramatic increase in ICP was followed by a profound fall in CPP (by 45%). In contrast, flow velocity fell by only 20%. Autoregulation was documented to be intact both before and after plateau but was disturbed during the wave (p < 0.05). Pressure-volume compensatory reserve was always depleted before the wave. Cerebrovascular resistance decreased during the wave by 60% (p < 0.05) and TCD pulsatility increased (p < 0.05). Plateau waves did not increase the probability of an unfavorable outcome following injury. CONCLUSIONS: The authors have confirmed that the plateau waves are a hemodynamic phenomenon associated with cerebrovascular vasodilation. They are observed in patients with preserved cerebral autoregulation but reduced pressure-volume compensatory reserve.
Adolescent↗
Cognition following subarachnoid hemorrhage from anterior communicating artery aneurysm: relation to timing of surgery.
OBJECT: This study was conducted to define neuropsychological changes following operation for subarachnoid hemorrhage (SAH) caused by rupture of an anterior communicating artery (ACoA) aneurysm and to assess the influence of the timing of surgery to clip the aneurysm. METHODS: Cognitive outcome was evaluated using the Cambridge Neuropsychological Test Automated Battery in patients with an ACoA aneurysm that had caused an SAH. Adult patients younger than 70 years of age who had achieved a favorable neurological outcome (Glasgow Outcome Scale scores of 4 or 5) were studied 6 to 24 months postsurgery. Patients were divided into early (Days 0-3) and late surgery groups (after Day 3) according to the timing of surgery after the ictus. Neuropsychological analysis was performed by reviewers who were blinded to the timing of surgery. Forty-seven patients whose mean age was 51.5 years were tested. They were compared with age- and intelligence quotient (IQ)matched controls by using premorbid IQ as estimated on the National Adult Reading Test. Patients showed deficiencies in several tasks of verbal fluency, pattern recognition, and spatial working memory; this profile of deficits was similar to that seen in patients who underwent temporal lobe excisions. However, there was no significant difference in cognitive performance between the early and late surgery groups. CONCLUSIONS: After open surgery for ruptured ACoA aneurysms, patients who have achieved a favorable neurological outcome still exhibit significant cognitive deficits, primarily in tests sensitive to temporal lobe dysfunction. However, early surgery does not carry a higher risk of neuropsychological disability.
Adult↗
Preliminary evaluation of a prototype spatially resolved spectrometer.
Near infrared spectroscopy (NIRS) has become an established research tool and is now being explored in several clinical settings [7]. However, until recently NIRS has not been fully quantified and changes have been difficult to interpret [4]. A new development by Hamamatsu Photonics, called the Spatially Resolved Spectrometer (SRS), proposes to be able to give a quantitative measure of oxygen saturation. We have incorporated the SRS into a multimodality monitoring system in three different clinical situations: 1) patients undergoing routine cardiopulmonary bypass, 2) head injured patients and 3) patients undergoing right-sided carotid endarterectomy. The importance of this investigation is in the development of the SRS machine which shows potential as a useful clinical tool. The results demonstrated good correlation between SRS and jugular venous oximetry (SjO2) in about 50% of patients. Although these results are encouraging, this study suggests that the SRS, in its present form, is not a reliable clinical monitor of cerebral oxygen saturation.
Brain↗
Resolving extra- and intracranial signal changes during adult near infrared spectroscopy.
Extracranial tissues have a significant effect on cerebral near infrared spectroscopy (NIRS) measurements in adults. Carotid surgery provides the opportunity to determine the relative contributions from the intra- and extracranial vascular territories. To assist, a specifically gated Laser Doppler flowmetry probe can be inserted between the NIRS optodes to co-monitor cutaneous blood flow associated with external carotid artery (ECA) clamping, whilst transcranial Doppler can be employed to monitor relative changes in the intracranial blood flow seen during internal carotid artery (ICA) clamping. Established criteria for severe cerebral ischemia (SCI) following carotid cross clamping was applied to 703 consecutive patients undergoing carotid surgery for high grade stenosis. Ipsilateral frontal NIRS recorded the difference (Total-deltaHbdiff) in concentrations of oxy- and deoxy-hemoglobin. Interrupted time series analysis following clamping of the ECA and ICA allowed the different vascular components of Total-deltaHbdiff (ECA-deltaHbdiff and ICA-deltaHbdiff) to be identified. Data from 76 patients was suitable. Sixteen (21%) patients fulfilled the criteria for SCI. Patients who demonstrated an ICA-deltaHbdiff of > 6.8 micromol l(-1) all showed SCI. No patient with an ICA-deltaHbdiff < 5.0 micromol l(-1) showed SCI. Thus an ICA-deltaHbdiff threshold of 6.8 micromol l(-1) provided a 100% specificity for SCI, whereas an ICA-deltaHbdiff < 5.0 micromol l(-1) was 100% sensitive for excluding SCI. When Total-deltaHbdiff was used without removing the ECA component, thresholds for SCI could not be resolved. NIRS can provide quantified thresholds for severe ischemia in the adult brain provided the extracranial component is removed.
Aged↗
Factors implicated in deaths from subarachnoid haemorrhage: are they avoidable?
The major causes of death following subarachnoid haemorrhage are the effects of the initial bleed, aneurysmal rebleeding and delayed cerebral ischaemia. Although in many cases the causes are unavoidable, in others they are potentially preventable. By conducting a Regional Audit of patients who have died from subarachnoid haemorrhage, we have attempted to quantify these concerns. The medical records and CT scans of 200 patients who died from subarachnoid haemorrhage in hospitals in the East Anglian Region over a 5-year period were analysed, with particular regard to the identification of potentially avoidable factors, including radiologically confirmed rebleeding, marked hydrocephalus, and poor fluid and electrolyte resuscitation. Thirty-three patients presented with World Federation of Neurosurgical Societies (WFNS) Grade V with fixed pupils. These patients were deemed unsalvageable. Of the remainder, 106 were good grade (WFNS I-III) at initial presentation, 77 (73%) of whom died as a result of rebleeding (mean 10.4 days post-bleed) indicating delays in transfer and definitive treatment. Of the 61 poor grade patients (WFNS IV and V with reactive pupils) marked hydrocephalus occurred in 15 (25%) and poor resuscitation in 37 (61%). These were considered contributing factors to their poor clinical condition. Rebleeding was the main cause of death in the good grade patients, and correctable factors were identified which are known to contribute to a poor clinical condition in poor grade patients. The need for more rapid and active clinical intervention is indicated.
Adolescent↗
The management of minor traumatic brain injury.
Minor traumatic brain injury accounts for the majority of the one million head trauma attendances at A&E departments in the United Kingdom. Guidelines have been established listing criteria for skull films, admission to hospital, computed tomography, and neurosurgical consultation. These are currently undergoing revision and were the subject of a satellite symposium to the J Douglas Miller memorial meeting held in October 1996 in Edinburgh. In the East Anglia Region the current guidelines have been issued as memo-cards for A&E officers. The aim of admission is to observe for deterioration, predominantly caused by intracranial haematomas. The indicators for the development of such lesions are an impaired level of consciousness and presence of a skull fracture. Such patients should therefore undergo regular and frequent neurological observations, and be admitted for at least 12 hours. Following discharge, routine follow up should be considered to identify and treat patients with postconcussion symptoms and signs. The possible way forward for the management of these patients is adopting a greater emphasis on preventative aspects, and establishing, implementing, and auditing evidence based guidelines. Improved teaching in the form of formal induction seminars and computerised teaching aids is required, and a better understanding of the aetiology and treatment of the postconcussion syndrome.
Brain Injuries↗
Cerebral perfusion pressure in head-injured patients: a noninvasive assessment using transcranial Doppler ultrasonography.
OBJECT: The authors studied the reliability of a new method for noninvasive assessment of cerebral perfusion pressure (CPP) in head-injured patients in which mean arterial blood pressure (ABP) and transcranial Doppler middle cerebral artery mean and diastolic flow velocities are measured. METHODS: Cerebral perfusion pressure was estimated (eCPP) over periods of continuous monitoring (20 minutes-2 hours, 421 daily examinations) in 96 head-injured patients (Glasgow Coma Scale score < 13) who were admitted to the intensive care unit. All patients were sedated, paralyzed, and ventilated. The eCPP and the measured CPP (ABP minus intracranial pressure, measured using an intraparenchymal microsensor) were compared. The correlation between eCPP and measured CPP was r=0.73; p < 10(-6). In 71% of the examinations, the estimation error was less than 10 mm Hg and in 84% of the examinations, the error was less than 15 mm Hg. The method had a high positive predictive power (94%) for detecting low CPP (< 60 mm Hg). The eCPP also accurately reflected changes in measured CPP over time (r > 0.8; p < 0.001) in situations such as plateau and B waves of intracranial pressure, arterial hypotension, and refractory intracranial hypertension. A good correlation was found between the average measured CPP and eCPP when day-by-day variability was assessed in a group of 41 patients (r=0.71). CONCLUSIONS: Noninvasive estimation of CPP by using transcranial Doppler ultrasonography may be of value in situations in which monitoring relative changes in CPP is required without invasive measurement of intracranial pressure.
Adolescent↗
Defining thresholds for critical ischemia by using near-infrared spectroscopy in the adult brain.
OBJECT: Signal changes in adult extracranial tissues may have a profound effect on cerebral near-infrared spectroscopy (NIRS) measurements. During carotid surgery NIRS signals provide the opportunity to determine the relative contributions from the intra- and extracranial vascular territories, allowing for a more accurate quantification. In this study the authors applied multimodal monitoring methods to patients undergoing carotid endarterectomy and explored the hypothesis that NIRS can define thresholds for cerebral ischemia, provided extracranial NIRS signal changes are identified and removed. Relative criteria for intraoperative severe cerebral ischemia (SCI) were applied to 103 patients undergoing carotid endarterectomy. METHODS: One hundred three patients underwent carotid endarterectomy. An intraoperative fall in transcranial Doppler-detected middle cerebral artery flow velocity (%deltaFV) of greater than 60% accompanied by a sustained fall in cortical electrical activity were adopted as criteria for SCI. Ipsilateral frontal NIRS recorded the total difference in concentrations of oxyhemoglobin and deoxyhemoglobin (Total deltaHb(diff)). Interrupted time series analysis following clamping of the external carotid artery (ECA) and the internal carotid artery (ICA) allowed the different vascular components of Total deltaHb(diff) (ECA deltaHb(diff) and ICA deltaHb(diff)) to be identified. Data obtained in 76 patients were deemed suitable. A good correlation between %deltaFV and ICA deltaHb(diff) (r = 0.73, p < 0.0001) was evident. Sixteen patients (21%) fulfilled the criteria for SCI. All patients who demonstrated an ICA deltaHb(diff) of greater than 6.8 micromol/L showed SCI, and in two patients within this group nondisabling watershed infarction developed, as seen on postoperative computerized tomography scans. No patient with an ICA deltaHb(diff) less than 5 micromol/L exhibited SCI or suffered a stroke. Within the resolution of the criteria used an ICA deltaHb(diff) threshold of 6.8 micromol/L provided 100% specificity for SCI, whereas an ICA deltaHb(diff) less than 5 micromol/L was 100% sensitive for excluding SCI. When Total deltaHb(diff) was used without removing the ECA component, no thresholds for SCI were apparent. CONCLUSIONS: Carotid endarterectomy provides a stable environment for exploring NIRS-quantified thresholds for SCI in the adult head.
Adult↗
Evaluation of carotid endarterectomy with sequential MR perfusion imaging: a preliminary report.
BACKGROUND AND PURPOSE: Current indications for carotid endarterectomy are determined by balancing the relative risks of surgery with the benefits of reduced risk of subsequent stroke. Our purpose was to use MR perfusion imaging to assess patients being considered for carotid endarterectomy and to monitor sequential changes in MR perfusion characteristics after surgery. In particular, we wished to determine whether this technique could be used to detect changes that might be related to post-carotid endarterectomy hyperemia. METHODS: We used a single-section gradient-recalled echo sequence to investigate 14 patients being examined before possible surgery for carotid artery disease. In the 12 patients in whom carotid endarterectomy was performed, sequential studies were performed 3 to 5 days after surgery and at 3 months. Analysis of bolus-arrival-time (BAT) images was performed. RESULTS: Significant delays in preoperative BAT images of 0.89 seconds (range, 0.05 to 3.22 seconds) were apparent between hemispheres. Excluding the two patients with contralateral internal carotid artery (ICA) occlusion, early arrival, possibly indicating postoperative hyperemia, was seen in five patients immediately after carotid endarterectomy but resolved within 3 to 5 months after surgery. CONCLUSION: MR perfusion imaging shows differences in BAT between hemispheres in patients with ICA stenosis. Changes in perfusion characteristics after carotid endarterectomy are complex, and early BAT on the operative side can occur soon after endarterectomy in over half those patients without an occluded contralateral vessel. The significance of these findings with regard to patient outcome and risk of postoperative hyperemia requires further investigation.
Aged↗
Use of near-infrared spectroscopy in the adult.
Adult near-infrared spectroscopy is a potential method for observing changes in cerebral oxygenation non-invasively. Access of light to the adult brain requires requires penetration through extracranial tissues; hence the detection of changes in cerebral chromophore concentration can only be achieved by using near-infrared spectroscopy in the reflectance-mode thereby adding variables which are difficult to control. These include the effects of variable anatomy, different intra-optode distances and the presence of an extra- to intracranial collateral blood supply. Although movements of oxygenated haemoglobin concentration following specific cerebral stimuli can be demonstrated, the challenge of separating changes which occur within the extracranial compartment from those occurring in the intracranial compartments remains. Our experience with near-infrared spectroscopy in the three adult clinical scenarios of carotid endarterectomy, head injury and carbon dioxide stress testing will be presented. The influence of extracranial contamination is demonstrated, as are the methods we have developed to help control for extracranial contamination. Provisional experience with spatially resolved spectroscopy technology will also be presented.
Adult↗
Uncomplicated carotid endarterectomy is not associated with neuropsychological impairment.
Whether neuropsychological changes follow carotid artery surgery is unclear, in part because of complications by multiple perioperative variables. Therefore, we carried out a detailed analysis of patients who underwent carotid artery surgery in which we attempted to control for the most important variables by excluding patients with a preoperative stroke and by adopting a standard operative technique without use of intraoperative carotid shunts. Thirty inpatients with symptomatic carotid artery disease admitted for carotid endarterectomy were assessed with a comprehensive battery of neuropsychological tests administered immediately before and after (48-72 h) surgery. No carotid bypass shunt was inserted during the operation. The battery included dementia and depression screening tests, standardised neuropsychological measures including Verbal Fluency and the National Adult Reading Test, and a battery of contemporary computerised tasks designed to measure different aspects of memory and attention from the Cambridge Neuropsychological Test Automated Battery (CANTAB). No significant difference was found in the cognitive scores postoperatively as compared with the patients' preoperative scores or compared with scores of a control group matched by age and intelligence.
Aged↗