Biomedical subjects

H R Winn

Publications and source records attributed to H R Winn.

At least 91 records · Page 5Linked to original sources

PubMed1995

Persistent feeding arteries to angiographically completely embolized arteriovenous malformation demonstrated by intraoperative color-flow Doppler testing: report of two cases.

Two cases of arteriovenous malformation (AVM) treated preoperatively by endovascular embolization that appeared to be completely occluded after embolization are presented. Seven and 12 days later, respectively, these patients underwent resection of their AVM. At the time of surgery, intraoperative color-flow Doppler studies revealed persistent feeding arteries to an active residual nidus of the AVM. The significance of this finding is presented in light of previous published literature.

Adult↗

PubMed1995

Alcohol use before and after traumatic head injury.

STUDY OBJECTIVE: To determine (1) the significance of blood alcohol level in the emergency department in history of alcohol abuse and (2) the significance of habitual alcohol use in head-injured patients before and after injury. DESIGN: Inception cohort study with 1-year follow-up. SETTING: Level I trauma center. PARTICIPANTS: One hundred ninety-seven hospitalized adult head-injury survivors with a broad spectrum of head-injury severity. RESULTS: Alcohol use and behavioral problems associated with alcohol use were assayed before injury and in the month and year after injury. The patients' blood alcohol levels in the ED were also examined. Preinjury alcohol abuse was frequent; 42% of the subjects were legally intoxicated while in the ED. The amount of drinking and magnitude of reported preinjury alcohol problems decreased soon after the injury but was followed by an increase by 1 year, although the amount of drinking did not return to the preinjury level (P < .0001). Patients with more severe head injuries decreased their drinking more than did those with less severe head injuries. The patients' blood alcohol levels in the ED were a good indicator of the magnitude of their preinjury alcohol problems (r = .51 to .59; each, P < .001). CONCLUSION: Preinjury habitual alcohol abuse is frequent in head-injured patients. Blood alcohol levels in the ED are indicative of history of problem drinking and might serve as a basis for treatment referral. The first weeks after injury in hospitalized patients may provide an opportunity to begin interventions because head-injured patients drink less at that time.

Adolescent↗

PubMed1995

Simultaneous measurements of pial arteriolar diameter and laser-Doppler flow during somatosensory stimulation.

We simultaneously measured pial arteriolar diameter and changes in cortical blood flow during activation of the somatosensory cortex by sciatic nerve stimulation. The pial vasculature was visualized with a closed-cranial window technique in chloralose-anesthetized rats (n = 13). Local blood flow was monitored with laser-Doppler flowmetry. During stimulation of the sciatic nerve (0.2 V, 5 Hz, 20 s), vascular diameter and laser-Doppler flow consistently displayed similar response profiles. With 0.5-ms stimulation pulses, the responses showed an initial peak followed by a smaller but sustained plateau dilation. In contrast, 5-ms pulses evoked a monotonically rising response. Our results support the concept that pial arteriolar diameter changes reflect cortical blood flow responses during somatosensory stimulation.

Animals↗

PubMed1995

Differential effects of alcohols on intracerebral arterioles. Ethanol alone causes vasoconstriction.

We compared the effect of the acute application of ethanol, methanol, 1-propanol, 1-butanol, urea, and mannitol (1-100 mM) on the basal tone of isolated-cannulated rat intracerebral arterioles to determine if the response of these arterioles to ethanol could be attributed to alteration of membrane fluidity or changes in osmolality. These arterioles spontaneously developed tone to 62.0 +/- 8.4% of passive diameter (44.2 +/- 11.9 vs. 70.9 +/- 14.7 microns). Ethanol caused a dose-dependent reduction in arteriolar diameter starting at 3 mM (p = 0.03), reaching a diameter of 81.4 +/- 3.0% of basal tone at 100 mM. In comparison, all other agents tested caused the arterioles to dilate, with the exception of 1-propanol, which produced inconsistent vessel responses. At 100 mM concentration, methanol, 1-butanol, urea, and mannitol dilated intracerebral arterioles by 116.1 +/- 12.7, 151.5 +/- 12.4, 131.1 +/- 17.0, and 149.8 +/- 6.6%, respectively. Thus, in a concentration range associated with acute intoxication, ethanol causes constriction of isolated intracerebral arterioles. The mechanism of action of ethanol cannot be accounted for solely based upon its physicochemical characteristics of osmolality or lipid solubility, but rather may reflect a more specific action on one or more cellular mechanisms responsible for determining basal intracerebral arteriolar tone. The characterization of the response of intracerebral arterioles to ethanol is important in view of epidemiologic links between ethanol consumption and cerebrovascular disease.

Animals↗

PubMed1995

Ketamine does not increase cerebral blood flow velocity or intracranial pressure during isoflurane/nitrous oxide anesthesia in patients undergoing craniotomy.

Ketamine's effect on cerebral hemodynamics is controversial. We hypothesized that ketamine would not increase intracranial pressure (ICP) and cerebral blood flow (CBF) velocity in anesthetized, ventilated patients. Twenty patients requiring craniotomy for brain tumor or cerebral aneurysm were studied. After induction with thiopental, anesthesia was maintained with isoflurane and nitrous oxide in oxygen. During controlled ventilation (PaCO2 34 +/- 1 mm Hg); middle cerebral artery blood flow velocity (VMCA), mean arterial blood pressure (MAP), bilateral frontooccipital processed electroencephalogram (EEG), and ICP were measured before and for 10 min after intravenous ketamine 1.0 mg/kg. Cerebral arteriovenous oxygen content difference (AVDO2) and cerebral perfusion pressure (CPP) were calculated. After ketamine, MAP, CPP, PaCO2, and AVDO2 were unchanged. ICP decreased from 16 +/- 1 mm Hg to 14 +/- 1 mm Hg (mean +/- SE; P < 0.001) and VMCA decreased from 44 +/- 4 cm/s to 39 +/- 4 cm/s (P < 0.001). Total EEG power decreased (P < 0.02). These results suggest that ketamine can be used in anesthetized, mechanically ventilated patients with mildly increased ICP without adversely altering cerebral hemodynamics.

Anesthesia, Inhalation↗

PubMed1995

L-NNA suppresses cerebrovascular response and evoked potentials during somatosensory stimulation in rats.

We studied the local cerebrovascular response and somatosensory-evoked potentials (SEPs) to stimulation of the sciatic nerve during both short- (< 30 min) and long-term (90-150 min) exposure to topically applied NG-nitro-L-arginine (L-NNA). The pial circulation was visualized through a cranial window in alpha-chloralose-anesthetized rats. The diameter of pial arterioles (25-45 microns) and laser-Doppler flow (LDF) in the hindlimb sensory cortex were simultaneously measured during sciatic nerve stimulation. Short-term (< 30 min) treatment with L-NNA (1 mM) abolished the dilation of pial arterioles induced by acetylcholine, whereas the response to sciatic nerve stimulation was not affected. When applied for > 30 min, L-NNA induced severe vasomotion and attenuated the vascular responses to sciatic nerve stimulation. Long-term exposure to topically (1 mM) or systemically (10 mg/kg i.v.) applied L-NNA also attenuated cortical SEPs to sciatic nerve stimulation. Thus L-NNA-induced inhibition of vascular responses may be secondary to suppression of neuronal activity and an L-arginine metabolite, such as nitric oxide, may be involved in neurotransmission in the cerebral cortex during somatosensory activity.

Animals↗

PubMed1995

Modulation of cerebral arteriolar diameter by intraluminal flow and pressure.

We determined whether cerebral arterioles in vitro adjust their diameters in response to changes in intraluminal flow rate and pressure. Intracerebral arterioles (38- to 55-microns diameter) were isolated from Sprague-Dawley rats and cannulated with a perfusion system that permitted separate control of intraluminal pressure and flow rates. Increasing pressure at 0 flow, in 20 mm Hg steps from 20 to 100 mm Hg, resulted in myogenic constriction, which was greatest at 60 mm Hg (approximately 20%). Increasing flow rate at a constant pressure of 60 mm Hg elicited a biphasic response. At flow rates of up to 10 microL/min, the arterioles dilated by up to 14.5 +/- 2.2% of their control diameter. At higher (> 10 microL/min) flow rates, however, a progressive restoration of resting diameter was observed. Application of the nitric oxide synthase inhibitor NG-mono-methyl-L-arginine (L-NMMA, 0.1 mmol/L) caused a 15.4 +/- 1.7% decrease in control diameter (at 60 mm Hg, zero flow). Although L-NMMA did not affect the responses to increases in pressure or to vasodilators (adenosine and pH 6.8 buffer), it abolished the dilator responses to flow rate increases and to acetylcholine. In contrast, inhibition of prostaglandin synthesis by indomethacin (10 mumol/L) had no effect on flow-induced dilation. These results show that changes in intraluminal flow rates and pressure can independently influence cerebral arteriolar tone and suggest that the flow-induced dilator responses of cerebral arterioles are mediated by an arginine metabolite, such as nitric oxide.

Animals↗

PubMed1995

A guide to placement of parietooccipital ventricular catheters. Technical note.

Accurate placement of parietooccipital ventricular catheters can be difficult and frustrating. To minimize the morbidity of the procedure and lengthen the duration of shunt function, the catheter tip should lie in the ipsilateral frontal horn. The authors describe a posterior ventricular guide (PVG) for placement of parietooccipital catheters that operates by mechanically coupling the posterior burr hole to the anterior target point. In a series of 38 patients who underwent ventriculoperitoneal shunting with the assistance of the guide, postoperative computerized tomography (CT) scanning revealed that 35 (92.0%) had accurate catheter placement. In comparison, a retrospective review of free-hand posterior catheter placement revealed good catheter position in only 22 of 43 patients (51.1%). The use of the guide added less than 5 minutes to the entire procedure, and there were no complications related to its use. The PVG is a simple and useful tool that aids in the placement of parietooccipital ventricular catheters.

Adolescent↗

PubMed1995

Classification and regression trees (CART) for prediction of function at 1 year following head trauma.

A cohort of 514 hospitalized head-injury survivors was identified based on their injury and 448 (87%) of them were followed for 1 year. Comprehensive neurobehavioral testing was performed 1 month and 1 year after injury. The authors developed predictions of six neuropsychological and two psychosocial outcomes 1 year after head injury. Prediction trees are presented for verbal IQ, Halstead's Impairment Index, and work status at 1 year. Early predictors of neurobehavioral outcome in survivors are similar to previously reported predictors of mortality. Extent (both depth and length) of coma and age are the medical and demographic variables most predictive of late outcome. Adding 1-month scores substantially improves prediction of neuropsychological variables. The classification and regression tree is a useful technique for predicting long-term outcome in patients with head injury. The trees are simple enough to be used in a clinical setting and, especially with 1-month scores, predictions are accurate enough for clinical utility.

Adolescent↗

PubMed1995

Improved outcome after rupture of anterior circulation aneurysms: a retrospective 10-year review of 224 good-grade patients.

Several significant diagnostic and therapeutic advances in the management of subarachnoid hemorrhage have emerged during the last 10 years. The present study was undertaken to determine whether these advances have improved overall outcome in patients of low surgical risk and what factors predict outcome. The authors retrospectively reviewed the management of good-grade patients seen at the Harborview Medical Center at the University of Washington, who suffered ruptured anterior circulation aneurysms between 1983 and 1993. The results in this series demonstrate that favorable outcomes occurred in 96.8% of patients designated Hunt and Hess Grade I, 88.3% of those assigned Grade II, and 81.3% of those deemed Grade III after rupture of anterior circulation aneurysms. On the basis of clinical and radiographic factors present at admission, correct prediction can be made about all favorable, but only 17% of unfavorable outcomes. During the decade under investigation, the authors observed a significant (p = 0.002) increase in the number of favorable outcomes: 74.5% of patients treated during the first management period (1983-1987); 87% of patients treated during the second period (1987-1990); and 93.5% of patients treated during the third management period (1990-1993) experienced favorable outcomes. Improvements in critical-care techniques and the management of vasospasm may be associated with the improved outcome observed during this series.

Adult↗

PubMed1995

Intracranial pressure changes induced during papaverine infusion for treatment of vasospasm.

The authors reviewed the cases of 21 patients who received intraarterial infusions of papaverine to determine the drug's effects on intracranial pressure (ICP), mean arterial blood pressure, pulse rate, and cerebral perfusion pressure (CPP). The study focused on patients with aneurysmal subarachnoid hemorrhage who developed clinical signs and symptoms of vasospasm, which was documented by cerebral angiography. In 18 patients, an average dose of 300 mg papaverine was administered over 20 to 35 minutes using a No. 5 French catheter inserted into the high cervical internal carotid artery or vertebral artery. Two other patients received superselective infusions via a microcatheter placed in the anterior cerebral artery. Sixteen patients (76%) experienced good angiographic results, and 11 (52%) obtained objective clinical improvement within 48 hours. Significant elevations in ICP, blood pressure, and pulse rate were noted during papaverine infusion. In contrast, no statistically significant sustained change in CPP was observed, although it tended to decrease during papaverine infusion. In one elderly patient, infusion of the common carotid artery resulted in profound bradycardia and hypotension with a subsequent significant increase in ICP and a marked decrease in CPP. The increase in ICP in these patients correlates well with changes seen in animal models and is probably related to increased cerebral blood flow. A careful, titrated infusion of papaverine, with constant reference to the patient's ICP, blood pressure, and pulse rate, minimizes the transient increase in ICP while maintaining adequate blood pressure and CPP. Failure to monitor these parameters during the infusion, with appropriate modification of the rate of titration, could potentially produce an uncontrolled change in ICP or CPP.

Adult↗

PubMed1995

Anesthetic-dependent pial arteriolar response to ethanol.

Anesthetic agents are often administered in the presence of ethyl alcohol, both in research and in the clinical setting. The authors tested the hypothesis that anesthetic agents may affect cerebrovascular responses to ethanol. A closed cranial window preparation in the rat was used to compare the response of pial arterioles to topically applied ethanol (0.01% to 1% vol/vol) in the presence of alpha-chloralose/urethane (50 and 600 mg/kg, respectively) or halothane (0.5% to 1%) anesthesia. Heart rate, mean arterial blood pressure, and blood gas levels were maintained stable and within the physiological range throughout each experiment. Ethanol induced significant vasoconstriction in alpha-chloralose/urethane-anesthetized animals (multivariate analysis of variance (MANOVA), p = 0.039); conversely, ethanol induced significant vasodilation of the pial arterioles in halothane-anesthetized animals (MANOVA, p = 0.017). These responses were significantly different from one another (MANOVA, p = 0.001). Thus, the choice of anesthetic agent alters the cerebrovascular response to ethanol, and care should be taken to ascertain the influence of anesthesia in both research and clinical settings.

Anesthetics↗

PubMed1995

Causes, prevention, and treatment of post-traumatic epilepsy.

Post-traumatic seizures often occur after severe head injury. Acutely, these seizures complicate management of the head-injured patient by increasing intracranial pressure and causing postictal decreases in level of consciousness. In the long term, epilepsy can have a negative effect on the patient's functioning and integration into society. The more severe the head injury, the more likely that post-traumatic seizures will occur. The risk of late seizures exceeds 30% for patients with penetrating head injury, intracerebral hematoma, subdural hematoma, depressed skull fracture, or seizure within the first week after injury. Late post-traumatic seizures are treated the same as any epileptic seizures of the same type. Phenytoin and carbamazepine are effective in preventing seizures in the first week after head injury, but are not effective in preventing late seizures. Both additional antiepileptic drugs and neuroprotective agents that may lessen the damage that leads to seizures are being investigated to determine if they are effective in preventing the occurrence of post-traumatic epilepsy.

Anticonvulsants↗

PubMed1994

Adenosinergic modulation of CA1 neuronal tolerance to glucose deprivation in organotypic hippocampal cultures.

Glucose deprivation produced neuronal degeneration of CA1 pyramidal neurons in hippocampal slice cultures. The effects of the adenosine agonist cyclohexyladenosine (CHA) and antagonist cyclopentylxanthine (CPX) on CA1 neuronal loss following hypoglycemia was examined using propidium iodide fluorescence as an indicator of cell death. The intensity of propidium iodide fluorescence in hippocampal area CA1 was quantified using Optimas image analysis software. Following 2 or 3 h of glucose deprivation, CPX significantly enhanced injury in the CA1 region while CHA provided significant protection. These results suggest that adenosine plays an important role in endogenous neuronal protection during hypoglycemic injury, and also supports a role for the use of adenosine agonists as neuroprotective agents.

Adenosine↗

PubMed1994

Employment following traumatic head injuries.

OBJECTIVE: Determine rates of, and factors predictive of, return to work in patients with civilian traumatic head injuries. DESIGN: Inception cohort study with 1- to 2-year follow-up. SETTING: Hospitalized patients in a level I trauma center. PATIENTS: Three hundred sixty-six hospitalized head-injured subjects who were workers before injury and 95 comparison subjects participated in prospective, longitudinal investigations of employment following head injury. Head-injured and comparison subjects were similar on basic demographics and preinjury employment status. The comparison subjects consisted of patients who sustained traumatic injury to the body but not to the head. MAIN OUTCOME MEASURE: Time taken to return to work following head injury. RESULTS: Survival methodology was used for analysis. Whether patients returned to work and when related to both the characteristics of the injured patients (eg, education, preinjury work history), the severity of head injury and associated neuropsychologic problems, and severity of other system injuries. More precise predictions were possible using the multivariate model. CONCLUSIONS: The present study provides a means of assessing employment potential predictively. This can be useful for clinical and research purposes. The results should be used cautiously and should stimulate discussions of appropriate use of services and resources to meet individual patients' needs.

Adult↗

PubMed1994

Effects of theophylline and cyclohexyladenosine on brain injury following normo- and hyperglycemic ischemia: a histopathologic study in the rat.

The present study was designed to determine the effects of theophylline, an adenosine receptor antagonist, and cyclohexyladenosine (CHA), an adenosine receptor agonist, on ischemic brain injury following normo- and hyperglycemic ischemia and reperfusion in fasted male Wistar rats. Moderate hyperglycemia was achieved by administering 17% D-glucose (3 g/kg i.p.), whereas normoglycemic animals received an equal volume of saline. The animals were further divided into two groups: One group was pretreated with either theophylline (0.20 mumol/g i.p.) or an equal volume of saline; the second group received either intraventricular CHA (6.25 nmol) or mock CSF prior to the onset of ischemia. During ischemia, pericranial temperature was maintained at 36 degrees C and EEG was monitored. Cerebral ischemia was induced for 15 min, after which flow was restored and the animals were allowed to recover completely. There were no significant differences in physiologic parameters among the groups studied. Five days following the ischemic episode, the rats were perfused with formalin and the brains subserially sectioned (8 microns) in the coronal plane and stained with celestine blue/acid fuchsin. Histopathologic analysis was performed in a blinded fashion to determine percentage of dead neurons. Hyperglycemic animals had significantly greater ischemic injury in CA1, cortex, and caudate than the normoglycemic group (p < 0.01). Moreover, rats pretreated with theophylline had a significantly (p < 0.01) higher percentage of dead neurons in CA1, cortex, and caudate than corresponding controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine↗

PubMed1994

Rapid infusion system for neurosurgical treatment of massive intraoperative hemorrhage.

Using an illustrative case of severe closed head injury that resulted in a posterior fossa epidural hematoma (EDH) and supratentorial epidural/subdural hematomas (SDH), the massive blood losses associated with operative repair of the torn sigmoid sinus and the significant fluid losses associated with refractory diabetes insipidus were treated by the intraoperative use of the Rapid Infusion System (RIS, Haemonetics). The RIS can rapidly infuse warm blood, crystalloid, or colloid at rates up to 1.5 L/min, thereby limiting the commonly associated hypotension, hypothermia, and coagulopathies. During the suboccipital craniectomy for evacuation of the EDH and repair of the sigmoid sinus, the patient required 18 units of blood replacement secondary to a large tear in the sigmoid sinus. During a separate craniotomy for evacuation of the SDH, the patient also developed diabetes insipidus, which increased the operative fluid replacement to 39 L. Despite these massive blood and fluid losses, the RIS limited the hypotension to less than 2 min and prevented hypothermia and the frequently associated coagulopathies. When used in a neurosurgical setting associated with massive blood and/or fluid losses, the RIS accomplishes three important objectives: (1) rapid infusion of intravenous fluids for maintaining perfusion pressure, (2) rapid warming of fluids despite high intravenous infusion rates of cold crystalloids, thereby preventing intraoperative hypothermia, and (3) continuous monitoring of infusion rates and totals.

Adult↗

PubMed1994

Decreased plasma protein binding of valproate in patients with acute head trauma.

1. One hundred and ten plasma samples were obtained from 50 patients treated with valproate for prophylaxis of post-traumatic head injuries. The samples were selected to include a wide range of albumin concentrations and were assayed for free and total valproate concentrations. Valproate binding parameters were determined from the Scatchard equation for one binding site using reweighted least squares analysis. 2. Plasma albumin concentrations were measured in 130 patients with head trauma. They started to decrease immediately after trauma, reaching a minimum at 5-7 days of approximately 24% of baseline value and did not return to normal until 1 month. 3. The free fraction of valproate varied six to seven-fold as albumin concentration ranged from 1.5 to 4.8 g 100 ml-1 (218-696 mumol l-1). The mean association constant for binding (Ka) was 0.008 mumol l(-1) and the mean number of binding sites (N) was 2.0. There values were similar to those reported for valproate in otherwise healthy patients with epilepsy. 4. Because of saturable protein binding of valproate, hypoalbuminaemia may necessitate the monitoring of free valproate concentrations to avoid toxicity when valproate is used in patients with acute head injury.

Acute Disease↗