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Biomedical subjects

David W Newell

Publications and source records attributed to David W Newell.

At least 37 records · Page 2Linked to original sources
PubMed2005

Superficial temporal artery to middle cerebral artery bypass.

The superficial temporal artery to middle artery bypass is a technique that allows the blood supply from the extracranial carotid circulation to be routed to the distal middle cerebral artery branches. The procedure allows blood flow to bypass proximal lesions of the intracranial vasculature. The performance of this bypass requires specialized microvascular training and the use of microvascular techniques. The techniques involved in performing these procedures include microdissection of the superficial temporal artery in the scalp, microdissection of the recipient middle cerebral artery branches near the sylvian fissure, and anastomosis techniques using either microvascular sutures or a microanastomotic device. The successful completion of the bypass and subsequent patency requires meticulous attention to technical details.

Journal Article↗
PubMed2005

Rotational vertebrobasilar ischemia: hemodynamic assessment and surgical treatment.

OBJECTIVE: Rotational vertebrobasilar insufficiency is a severe and incapacitating condition. Proper investigation and management are essential to reestablish normal posterior circulation hemodynamics, improve symptoms, and prevent stroke. We present a series of 10 patients with rotational vertebrobasilar ischemia who were treated surgically and emphasize the importance of transcranial Doppler in the diagnosis and management of this condition. METHODS: All patients presented with symptoms of vertebrobasilar insufficiency induced by head turning. Transcranial Doppler documented a significant decrease in the posterior cerebral artery velocities during head turning that correlated with the symptoms in all patients. A dynamic cerebral angiogram was performed to demonstrate the site and extent of vertebral artery compression. RESULTS: The surgical technique performed was tailored to each individual patient on the basis of the anatomic location, pathogenesis, and mechanism of the vertebral artery compression. Five patients underwent removal of osteophytes at the level of the subaxial cervical spine, one patient had a discectomy, two patients had a decompression only at the level of C1-C2, and two patients had a decompression and fusion at the C1-C2 level. CONCLUSION: The transcranial Doppler is extremely useful to document the altered hemodynamics preoperatively and verify the return of normal posterior circulation velocities after the surgical decompression in patients with rotational vertebrobasilar ischemia. Surgical treatment is very effective, and excellent long-term results can be expected in the vast majority of patients after decompression of the vertebral artery.

Aged↗
PubMed2004

Basilar artery vasospasm and delayed posterior circulation ischemia after aneurysmal subarachnoid hemorrhage.

BACKGROUND AND PURPOSE: The clinical and hemodynamic impacts of basilar artery (BA) vasospasm (VS) after aneurysmal subarachnoid hemorrhage (SAH) are ill-defined. The purpose of the present study was to evaluate the relationship between BA-VS and regional cerebral blood flow (rCBF) with posterior circulation after aneurysmal SAH. METHODS: Daily transcranial Doppler (TCD) measurements of posterior and anterior circulation arteries were conducted in 162 patients with aneurysmal SAH. rCBF to the brain stem (BS) and other brain territories was assessed by multiple single-photon emission computed tomography with (99m)Tc ethyl cysteinate dimer single-photon emission computed tomography (ECD-SPECT) imaging during the course of VS. RESULTS: SPECT imaging showed delayed BS hypoperfusion in 29 patients (17.9%). Of them, 23 patients (79.3%) were found to have BA-VS. Patients with very high BA flow velocities (FVs; >115 cm/s) had a 50% chance of developing delayed BS ischemia. BA-VS was found at a higher rate in patients who experienced reduced rCBF in the cerebellum (56.3%), thalamic nuclei (68.4%), and occipital lobe (81.8%). Although patients with delayed BS hypoperfusion did not present with a higher clinical grade, their clinical outcome was significantly worse (Glasgow Outcome Score after 30 days 2.48+/-1.16 versus 3.3+/-1.27; P=0.001). CONCLUSIONS: These findings suggest for the first time that BA-VS after aneurysmal SAH is associated with hypoperfusion to BS and other posterior circulation territories. The risk for delayed BS ischemia increased significantly when TCD BA-FVs were >115 cm/s.

Adult↗
PubMed2004

Impact of surgical clipping on survival in unruptured and ruptured cerebral aneurysms: a population-based study.

BACKGROUND AND PURPOSE: The management of aneurysms is controversial because little is known about the impact of clipping on long-term outcome. This study was designed to evaluate long-term survival of patients with aneurysms undergoing clipping in a statewide population. METHODS: We used a retrospective design using an administrative database to identify patients hospitalized with aneurysms (1987 to 2001). Time-to-event analysis was used to determine the risk of death from all causes and from neurological causes. RESULTS: 4619 patients (mean age 54.7+/-15.3, 66.3% female) were hospitalized with cerebral aneurysms. Survival among patients with ruptures was significantly lower compared with patients with unruptured aneurysm (P<0.001) with adjusted hazard ratio (HR) of death after clipping 40% higher (HR: 1.4; 95% CI: 1.2, 1.7) in patients with rupture compared with those that were unruptured. Survival estimates for unruptured patients who underwent clipping were significantly higher than among those unruptured patients who did not undergo clipping (P<0.001), with adjusted HR of death 30% higher in patients with unruptured aneurysm that were not clipped compared with unruptured patients who were clipped (HR: 1.3; 95% CI: 1.1, 1.6). Patients with unruptured aneurysm who underwent clipping and survived beyond the 30-day postoperative period were less likely to die from neurologically related causes (5.6 versus 2.3%, P<0.001). Patients with ruptures and aneurysms who underwent clipping have a higher rate of death compared with the general population in the long-term. CONCLUSIONS: Short-term and long-term mortality after clipping of cerebral aneurysms is higher than previously reported. Patients with unruptured aneurysms who undergo clipping have improved survival compared with those who do not undergo clipping. This study supports the use of early intervention in the management of patients with unruptured aneurysms.

Aneurysm, Ruptured↗
PubMed2004

Ophthalmic artery blood flow velocity increases during hypocapnia.

PURPOSE: The effects of anesthetic management on blood flow to the optic nerve have not been well-studied. The ophthalmic artery provides the majority of the blood supply to the optic nerve via several smaller branches. Retinal blood flow has been shown to react to carbon dioxide (CO(2)) similar to intracranial vessels, but insufficient data exist for the ophthalmic artery. The purpose of this study is to examine the CO(2)-reactivity of the ophthalmic artery. METHODS: Eight healthy awake subjects aged 28 to 50 yr were tested for CO(2)-reactivity in the ophthalmic artery using transcranial Doppler (TCD) insonation of blood flow velocity (V(op)), while simultaneously recording the V(op) of the middle cerebral artery (V(mca)) as an internal control. V(op) and V(mca) recordings were made under hypocapnic, normocapnic and hypercapnic conditions. RESULTS: The CO(2)-reactivity slope of V(mca) was 3.27% per mmHg PaCO(2). From normocapnia to hypercapnia, V(op) did not change significantly (mean +/- SD, 18 +/- 4 cm*sec(-1) to 18 +/- 6 cm*sec(-1)), (end-tidal CO(2), etCO(2), = 43 +/- 5 mmHg to 53 +/- 4 mmHg, respectively). In contrast, V(op) increased significantly under hypocapnic conditions (etCO(2) = 26 +/- 4 mmHg) to 25 +/- 5 cm*sec(-1) (P < 0.05). The CO(2)-reactivity slope of V(op) from normocapnia to hypocapnia was 2.57% per mmHg. CONCLUSIONS: This study demonstrates that V(op) increases with hypocapnia, but is unaffected by hypercapnia. The anastomoses of the ophthalmic artery with the external carotid artery, which displays a relatively fixed resistance, may account for these findings.

Adult↗
PubMed2004

Cerebral autoregulation in pediatric traumatic brain injury.

OBJECTIVE: The aims of this study were to document the incidence of impaired cerebral autoregulation in children with traumatic brain injury using transcranial Doppler ultrasonography and to examine the relationship between autoregulatory capacity and outcome in children following traumatic brain injury. DESIGN: Prospective cohort study. SETTING: Harborview Medical Center (level I pediatric trauma center) in Washington state. PATIENTS: Thirty-six children <15 yrs old with traumatic brain injury: Glasgow Coma Scale score <9 (n = 12, group 1), Glasgow Coma Scale score 9-12 (n = 12, group 2), and Glasgow Coma Scale score 13-15 (n = 12, group 3). INTERVENTIONS: Cerebral autoregulation testing was conducted during extracranial surgery. Mean middle cerebral artery flow velocities were measured using transcranial Doppler as mean arterial pressure was increased to whichever variable was greater: 20% above baseline or a set value (80 mm Hg for <9 yrs and 90 mm Hg for 9-14 yrs). Autoregulatory capacity was quantified by the Autoregulatory Index. Autoregulatory Index <0.4 was considered impaired cerebral autoregulation. Discharge outcome using the Glasgow Outcome Scale score was considered good if the Glasgow Outcome Scale score was > or =4. MEASUREMENTS AND MAIN RESULTS: Twenty-four (67%) of 36 children had an Autoregulatory Index > or =0.4. The incidence of impaired cerebral autoregulation was 42% (five of 12) in group 1, 42% (five of 12) in group 2, and 17% (two of 12) in group 3. Ten (42%) of the 24 children with intact cerebral autoregulation had a good outcome compared with only one of 12 (8%) children with impaired cerebral autoregulation (p =.04). Six of 12 (50%) children with impaired cerebral autoregulation had hyperemia compared with one of 24 (4%) children with intact cerebral autoregulation (p <.01). Hyperemia was associated with poor outcome (p =.01). CONCLUSIONS: The incidence of impaired cerebral autoregulation was greatest following moderate to severe traumatic brain injury. Impaired cerebral autoregulation was associated with poor outcome. Hyperemia was associated with impaired cerebral autoregulation and poor outcome.

Adolescent↗
PubMed2004

Is there a sex difference in the course following traumatic brain injury?

Traumatic brain injury (TBI) is a significant cause of death and disability in the United States. Sex has not been thoroughly examined as a factor that may influence outcome following TBI. Clinical studies involving humans that have focused on sex and TBI outcome have yielded inconclusive results, yet sex-related physiologic differences have been demonstrated in animal studies. The purpose of this study is to examine the interaction of sex and age in relation to outcome at 3 and 6 months postinjury in a population of individuals with TBI. The sample includes 157 subjects (124 males, 33 females), 16 to 89 years of age, admitted to a level 1 trauma center following TBI. Physiologic data and information about injury severity and clinical course were gathered during hospitalization. Outcome was assessed at 3 and 6 months postinjury using the Extended Glasgow Outcome Scale (GOSE) and Functional Status Examination (FSE). In this sample, there was a significant relationship between sex and age with respect to functional outcome at 6 months following TBI, controlling for initial injury severity. Females age 30 years or older had significantly poorer outcome as measured by the GOSE (P = 0.031) and the FSE (P = 0.037) than either males or younger females. There was also a very different rate of recovery, with women age 30 years and older, on average, showing no improvement between 3 and 6 months postinjury. Further study is needed to elucidate the reasons why sex may affect outcome following TBI.

Adolescent↗
PubMed2004

Superficial temporal artery to middle cerebral artery bypass.

The superficial temporal artery to middle cerebral artery bypass is an elegant procedure that was developed and first performed by M. Gazi Yaşargil. It has been used by neurosurgeons for more than 30 years in the management of neurovascular disorders such as cerebrovascular ischemic disease, moyamoya disease, and complex intracranial aneurysms. Mastering the technique requires not only precise and fine skills but also devoted training in the microsurgery laboratory. The technique presented in this article evolved from the long and vast experience of the senior author (DWN) in performing superficial temporal artery to middle cerebral artery bypasses for a variety of cerebrovascular conditions.

Anastomosis, Surgical↗
PubMed2004

Severe posttraumatic craniocervical instability in the very young patient. Report of three cases.

Children younger than 3 years of age represent a distinct subpopulation of patients at particular risk for high cervical and craniovertebral injuries. There are few descriptions of survivors of severe craniocervical trauma among the very young, and scarce data exist regarding management after initial emergency stabilization. The authors describe three children, age 1 to 32 months, who presented with craniocervical junction injuries. Variable neurological findings were observed at presentation (cranial nerve deficits, obtundation, and moderate-to-severe quadriparesis). All three were treated with prolonged immobilization and have recovered with minimal to no neurological deficit.

Child, Preschool↗
PubMed2003

Dynamic pressure--flow velocity relationships in the human cerebral circulation.

BACKGROUND AND PURPOSE: The pressure-flow velocity relationship in the cerebral circulation is characterized by the critical closing pressure (CCP), which is the pressure at which flow ceases, and the linear slope of a plot between pressure and flow velocity. It has been suggested, but not validated, that CCP can be determined from arterial blood pressure (ABP) and transcranial Doppler (TCD) recordings during the cardiac cycle. We studied a group of patients in whom ventricular fibrillation (VF) was induced. The time interval before defibrillation enabled calculation of CCP from data in which flow approached zero. These estimates were compared with values calculated before and after fibrillation and during regular heartbeats. METHODS: TCD velocities and ABP in the radial artery were recorded before, during, and after 28 episodes of VF in 13 patients. CCPs were calculated by 3 different methods: (1) linear extrapolation from data during VF (gold standard); (2) linear extrapolation from normal heartbeat data; and (3) first harmonic Fourier filtering of normal heartbeat data. RESULTS: The CCP during VF calculated from long diastoles was 32.9+/-11 mm Hg (mean+/-SD). The regular heartbeat estimate was 6.0+/-4.3 mm Hg lower (P<0.05). The CCP estimate with the use of a Fourier filter was 1.4+/-3.9 mm Hg (P=NS) lower than during VF. During hyperemia after defibrillation, the CCP decreased by 13.3 mm Hg, while velocity increased by 63%. The decrease in CCP could explain half of the increase in flow velocity during hyperemia. CONCLUSIONS: CCP can be accurately estimated from regular heartbeat data and is an important factor in regulation of the cerebral circulation.

Adult↗
PubMed2003

The ISAT trial.

Explore the source record for details and available documents.

Angioplasty↗
PubMed2003

Cerebral blood flow and dynamic cerebral autoregulation during ethanol intoxication and hypercapnia.

More than one-third of patients diagnosed with head injury are intoxicated with ethanol. Most clinical and animal studies have shown alcohol to have a deleterious impact in the setting of cerebrovascular trauma; however, there are also data showing neuroprotective effects in low ethanol doses. Human studies using imaging modalities suggest that small doses of alcohol produce cerebral vasodilatation and higher doses cerebral vasoconstriction. The aim of this study was to investigate the effect of ethanol intake on dynamic cerebral autoregulation and velocities in the middle cerebral arteries, and compare these changes with the effects of hypercapnia. Dynamic cerebral autoregulation and cerebral blood flow velocities were analysed before and after alcohol intake (1.1 g/kg of body weight) in six adult volunteers. Cerebral blood flow velocities in both middle cerebral arteries were monitored continuously by transcranial Doppler. A value for dynamic cerebral autoregulation was calculated from the rate of increase in middle cerebral artery velocities after a rapid-step decrease in arterial blood pressure. A sudden decrease in blood pressure was achieved by the release of previously inflated large blood pressure cuffs around the subject's thighs. Three volunteers were also tested before alcohol intake with CO(2) challenge (breathing 6% CO(2)) during the autoregulation procedure. Blood alcohol level reached 90 mg/dl approximately 60 min after ethanol ingestion. Cerebral blood velocities increased by 8% from baseline for uncorrected end-tidal (et) CO(2) and by 24% for correction to et CO(2)=40. Dynamic cerebral autoregulation measured as an autoregulation index decreased from 4.3+/-1.3 to 2.9+/-1.1 (p=0.089), which did not reach statistical significance. During hypercapnic conditions, dynamic cerebral autoregulation dropped from 4+/-0.8 to 0.9+/-0.9. In conclusion, mild alcohol intoxication caused cerebral vasodilatation with a subsequent increase in cerebral blood flow of 8-24%. Dynamic cerebral autoregulation was not found to be significantly impaired by ethanol. Hypercapnia almost completely destroys the physiological autoregulatory mechanism. A mild hyper-ventilation to etCO(2)=34-36 may be a compensatory contra-measure for ethanol-induced vasodilatation in the setting of head trauma.

Adult↗
PubMed2003

Comparison of anterior and posterior approaches in cervical spinal cord injuries.

This study reports the results of 52 patients with unstable cervical spine injuries and associated spinal cord injuries randomized to either anterior or posterior stabilization and fusion. All patients had achieved reduction and had unstable injuries that were thought to require surgical stabilization. Patients requiring a specific approach for either reduction or decompression were not included. Frankel grades and ASIA motor index scores were followed in each patient as well as fusion status, changes in alignment, and pain at final follow-up. Neurologic improvement was noted in each group with no significant differences. In the anterior group, 70% improved at least 1 Frankel grade and 57% improved 1 Frankel grade in the posterior group. There were two nonunions in the anterior group (90% fusion) and none in the posterior group (100% fusion), although this was not statistically different. Seven patients in each group complained of pain at the final follow-up. There were no significant differences in fusion rates, alignment, neurologic recovery, or long-term complaints of pain in patients treated with either anterior or posterior fusion and instrumentation.

Adult↗
PubMed2003

Autoregulatory response and CO2 reactivity of the basilar artery.

BACKGROUND AND PURPOSE: Transcranial Doppler has been extensively used to measure cerebrovascular control mechanisms, including autoregulation in humans and in patients with cerebrovascular diseases. There have been sufficient reports on the measurement of normal autoregulatory response (AR) and CO2 reactivity (CR) of the middle cerebral artery (MCA) but few reports of these indices for the basilar artery (BA). We measured AR and CR in the BA in healthy volunteers to determine normal values and compared them with simultaneous measurements made in the MCA. METHODS: Sixteen normal subjects were enrolled. Time-averaged mean velocities of maximum blood flow in the BA and MCA were continuously and simultaneously monitored by using transcranial Doppler along with continuous measurement of mean arterial blood pressure (MABP). Values were obtained during rest, alterations of end-tidal PaCO2 (ETCO2), and acute decrease and recovery of MABP. AR was evaluated by using the thigh cuff method and graded by the standard dynamic autoregulatory index (ARI), with values between 0 and 9. CR was measured as percentage change in time-averaged mean velocity per mm Hg ETCO2. RESULTS: The mean age of 16 subjects was 27.38+/-8.50 years. Average baseline values for MABP and ETCO2 were 82.29+/-7.10 and 42.75+/-3.77 mm Hg, respectively. Mean ARI was 4.62+/-1.26 for the BA and was 4.77+/-1.23 for the MCA (n=15) (P=0.598). Average CR was 2.54+/-0.39%/mm Hg ETCO2 for the BA and 2.51+/-0.29%/mm Hg ETCO2 for the MCA (n=16) (P=0.686). CONCLUSIONS: Our study demonstrates that ARI and CR values for the BA are similar to those for the MCA.

Adult↗
PubMed2003

Transient rotational compression of the vertebral artery caused by herniated cervical disc. Case report.

Of the many causes of vertebrobasilar insufficiency (VBI), extrinsic compression of the vertebral artery (VA) is relatively uncommon. A syndrome of VBI caused by extrinsic compression of the VA secondary to head rotation has been termed positional vertebrobasilar ischemia. The authors present a case of transient VBI caused by herniation of a cervical disc. Transcranial Doppler ultrasonography was used preoperatively to confirm the diagnosis and intraoperatively to monitor cerebral perfusion and to confirm that adequate decompression of the VA had been achieved.

Brain Ischemia↗
PubMed2002

The impact of aneurysmal subarachnoid hemorrhage on functional outcome.

Despite advances in the management of aneurysmal subarachnoid hemorrhage (SAH), a significant percentage of survivors are left with persistent cognitive, behavioral, and emotional changes that affect their day-to-day lives. This article describes outcome at 3 months after aneurysmal SAH in 61 patients, using the Extended Glasgow Outcome Scale (GOSE) and the Functional Status Examination (FSE). The GOSE provides a measure of overall functional outcome but does not address the specifics of functional limitations. The FSE, in addition to identifying functional limitations, provides insight into factors contributing to them and the extent to which SAH survivors perceive them as affecting their day-to-day activities. The findings of this study demonstrate that SAH survivors have considerable limitations in functional status in almost all areas of daily living at 3 months following SAH. The limitations were attributed to a variety of physical, cognitive, and emotional factors, and they were reported to be moderately to severely bothersome in almost half of the individuals. The findings highlight the need for appropriate rehabilitation, education, and support for SAH survivors and their families to enhance coping and improve quality of life, given the substantial and persistent impact of SAH.

Adult↗