Recombinant activated factor VII for the rapid correction of coagulopathy in nonhemophilic neurosurgical patients

OBJECTIVE

Coagulopathy is a significant contraindication for neurosurgery. Unfortunately, many coagulopathic patients require urgent neurosurgical intervention. Standard use of blood products, including fresh-frozen plasma or prothrombin complexes, to correct the coagulopathy often leads to significant delays in treatment. Recombinant activated factor VII (rFVIIa) is a medication originally designed to treat bleeding in hemophiliacs but also seems to correct a wide variety of coagulopathies rapidly and safely in nonhemophilic patients.

METHODS

The medical records of nine patients with coagulopathy requiring urgent neurosurgical intervention were reviewed retrospectively. Each patient was given a dose ranging from 40 to 90 microg/kg of rFVIIa before undergoing surgery. Pre-rFVIIa coagulation and post-rFVIIa coagulation parameters were obtained. Once correction of the coagulopathy was verified, each patient underwent the appropriate neurosurgical procedure.

RESULTS

The average age of the patients was 40.9 years; six were women. The causes of the coagulopathy included anticoagulant medication, liver dysfunction, and dilutional coagulopathy after traumatic hemorrhage. Neurosurgical indications included intraparenchymal/intraventricular hemorrhage, hydrocephalus, diffuse cerebral edema, and epidural hematoma. Post-rFVIIa coagulation parameters obtained as early as 20 minutes after infusion of the medication showed normalization of values. There were no procedural or operative complications and no postoperative hemorrhagic complications. No associated thromboembolic or other complications with the use of rFVIIa were observed.

CONCLUSION

The use of rFVIIa for the urgent surgical treatment of coagulopathic patients is quite promising. Further studies, including randomized, prospective trials using rFVIIa to address issues such as optimal dosing, efficacy, surgical indications, cost-effectiveness, morbidity, and mortality are needed.

The impact of provider volume on mortality after intracranial tumor resection

OBJECTIVE

Policies of regionalization and selective referral for a number of "high-risk" surgical procedures are being explored and implemented as a result of significant variation in postoperative mortality between high- and low-volume providers. The effect of provider volume on outcomes after intracranial tumor resection is unknown and warrants investigation.

METHODS

By use of the Nationwide Inpatient Sample for 1996 and 1997, patients (older than 19 yr) who had a diagnosis of a malignant central nervous system neoplasm and underwent craniotomy or craniectomy were included. Hospital volume and surgeon volume were categorized by quartiles (very low, low, high, or very high volume). Unadjusted and case mix-adjusted analyses were performed with regard to postoperative in-hospital mortality.

RESULTS

The crude in-hospital mortality was 2.8% for a total of 7547 patients. The mean patient age was 55.8 years (66.5% <65; 33.5% >/=65). Mortality for very low- to very high-volume hospitals was as follows: 3.8, 3.2, 2.4, and 1.8% (P < 0.001). Mortality for very low- to very high-volume surgeons was as follows: 4.1, 3.9, 3.1, and 1.4% (P = 0.003). Predictors of mortality in a logistic regression model were emergent admission (odds ratio [OR], 2.97; 95% confidence interval [CI], 2.02-4.38; P < 0.001), and age 65 years or greater (OR, 1.63; 95% CI, 1.16-2.30; P = 0.005). The risk of mortality was reduced for very high-volume hospitals (OR, 0.58; 95% CI, 0.35-0.97; P = 0.038) and very high-volume surgeons (OR, 0.42; 95% CI, 0.22-0.84; P = 0.012).

CONCLUSION

Higher-volume providers have superior outcomes after surgical resection of malignant intracranial tumors. This reduction was maintained despite adjustment for case mix. As the regionalization of high-risk surgery moves forward, it is important for neurosurgeons to maintain leadership roles in the development of specialty-specific data collection and health policy initiatives that improve and reduce variation in outcomes.

Surgeon volume as an indicator of outcomes after carotid endarterectomy: an effect independent of specialty practice and hospital volume

BACKGROUND

High-volume hospitals have been shown to have superior outcomes after carotid endarterectomy (CEA), but the contribution of surgeon volume and specialty practice to CEA outcomes in a national sample is unknown.

STUDY DESIGN

Using the National Inpatient Sample for 1996 and 1997, 35,821 patients who underwent CEA (ICD-9-CM code 3812) and had data for unique surgeon identification were studied. Surgeons were categorized in terms of annual CEA volume as low-volume surgeons (< 10 procedures), medium-volume surgeons (10 to 29), and high-volume surgeons (> or = 30). Data from cardiac, general, neurologic, and vascular surgical practices were analyzed. In-hospital mortality, postoperative stroke, and prolonged length of stay (> 4 days) were the primary outcomes variables. Unadjusted and case-mix adjusted analyses were performed.

RESULTS

The overall in-hospital mortality was 0.61%. CEA was performed annually by high-volume surgeons in 52% of patients, by medium-volume surgeons in 30% of patients, and by low-volume surgeons in 18% of patients. Observed mortality by surgeon volume was 0.44% for high-volume surgeons, 0.63% for medium-volume surgeons, and 1.1% for low-volume surgeons (p < 0.001). The postoperative stroke rate was 1.14% for high-volume surgeons, 1.63% for medium-volume surgeons, and 2.03% for low-volume surgeons (p < 0.001). Surgeon specialty had no statistically significant effect on mortality or postoperative stroke. In the logistic regression model, increased risk of mortality was associated with emergent admission (odds ratio [OR] = 2.1; 95% confidence interval [CI] 1.6 to 2.8, p < 0.001), patient age > 65 years (OR = 2.0; 95% CI 1.3 to 3.1, p = 0.001), low-volume surgeon (OR = 1.9; 95% CI 1.4 to 2.5, p < 0.001), and COPD (OR = 1.8; 95% CI 1.3 to 2.5, p = 0.001). Low hospital CEA volume (< 100) was not a significant risk factor in the multivariate analysis.

CONCLUSIONS

More than 50% of the CEAs in the United States are performed by high-volume surgeons with superior outcomes. Health policy efforts should focus on reducing the number of low-volume surgeons, regardless of surgeon specialty or total hospital CEA volume.

Antiplatelet therapy: an alternative to heparin for blunt carotid injury

BACKGROUND

Blunt carotid injuries (BCIs) are uncommon. Most single-center studies are small and highlight the use of anticoagulation for treatment. In a retrospective review, we identified 22 patients who presented with BCI and assessed neurologic and survival outcomes on the basis of injury grade and treatment with anticoagulation or antiplatelet therapy.

METHODS

Patient demographics were identified using the trauma registry at a single Level I trauma center. Chart reviews assessed neurologic function, modalities used for diagnosis, and treatment. Neurologic outcomes were graded good (minimal to no deficit), fair (moderate deficit needing some assistance), poor (requiring institutionalization), and dead.

RESULTS

Twenty-two adult trauma patients were diagnosed with BCI, for an incidence of 0.45% in the 8-year study period. All BCI patients underwent head computed tomography and four-vessel cerebral arteriography. Eight patients were not anticoagulated, five because of intracranial injuries, two who had surgical CCA repairs, and one with an aortic injury. Full anticoagulation with heparin was attempted in seven patients, with four major bleeding complications requiring cessation of heparin and blood transfusions. Seven patients received antiplatelet therapy. No difference in neurologic outcome was observed between those receiving anticoagulation and those receiving antiplatelet therapy. Bleeding complications from full anticoagulation were higher than with antiplatelet agents (p = 0.05).

CONCLUSION

Contrary to previous reports, we did not observe improved outcomes with full anticoagulation compared with antiplatelet therapy. Anticoagulation was associated with increased extracranial bleeding complications. The risks and possible benefits, as well as timing, of anticoagulation or antiplatelet therapy for BCI should be carefully weighed by the major care providers of the patient with multiple injuries.

Role of topical steroids in reducing dysfunction after nerve injury

OBJECTIVE

To determine the efficacy of topical dexamethasone in reducing nerve dysfunction after axonotmesis injury.

STUDY DESIGN

A three-armed, blinded study including sham, control, and test groups was designed using the rat sciatic nerve crush injury model.

METHODS

Twenty-two rats were randomly assigned to a control group or a topical steroid group. A standardized sciatic nerve crush injury was performed under sterile conditions on each animal. A separate group of five rats underwent a sham operation to isolate the crush injury as the source of postoperative dysfunction in the control and steroid groups. All animals underwent walking track analysis with calculation of the sciatic functional index (SFI) before surgery and through the postoperative recovery period. Dexamethasone saturated Gelfoam was placed at the site of injury in the topical steroid group. The functional performance of each group was compared throughout the recovery period.

RESULTS

No morbidity associated with topical application of steroids at the injury site was noted. The topical steroid group had improved recovery at postoperative days 14, 18, and 22. This difference was statistically significant at day 14. At the termination of the study, there was a clear trend toward superior recovery for the steroid group compared with controls (90% vs. 73%), but this difference did not reach statistical significance.

CONCLUSIONS

Clinical use of topical steroids to reduce postoperative nerve dysfunction warrants further study.

Distance learning for hospital managers

Telemedicine technology enabled this class to meet. The Chapel Hill instructor could not have traveled to Scotland Neck for the classes, and the class members could not have taken time away from their jobs to travel to Chapel Hill. The technology allowed the participants to fit the classes into their schedules. For the group of managers at this small, isolated hospital, the experience of participating in a management class with an expert was a positive one. They were introduced to standard management practices, learned new skills, and formed a support group/team onsite. The students felt close to the leader, yet the physical distance made her an outsider in a way that encouraged frankness. The technology seemed to foster the best of both worlds--intimacy, yet physical distance and, thus, safety. These new managers were able to take part in a course that taught tangible skills for improving their job performance and, more important, afforded access to resources outside of Halifax County. They were able to step away from their daily routine and interact with outsiders and each other in new ways, without the stress and expense of travel. The results of this pilot study indicate that distance learning is feasible for courses of this kind. Staff burnout and turnover are chronic problems in rural facilities, with isolation contributing to job dissatisfaction. Distance learning offers exciting possibilities for addressing these problems in healthcare settings across the country.

Effect of hematocrit on calculation of cerebral blood flow and lambda in xenon CT

Knowledge of the patient's hematocrit is necessary for calculation of cerebral blood flow (CBF) with xenon CT, and is a potential source of error. This study quantifies the effect of hematocrit on the calculation of CBF and lambda, and determines if the magnitude of the effect is dependent on actual CBF or lambda. The effect of hematocrit was measured empirically using software employing the numerical calculation method. CBF and lambda were found to be inversely related to hematocrit. The percent error produced by an inaccurate hematocrit is greater for lower actual CBF values.

Increased cerebral blood flow but no reversal or prevention of vasospasm in response to L-arginine infusion after subarachnoid hemorrhage

OBJECT

The reduction in the level of nitric oxide (NO) is a purported mechanism of delayed vasospasm after subarachnoid hemorrhage (SAH). Evidence in support of a causative role for NO includes the disappearance of nitric oxide synthase (NOS) from the adventitia of vessels in spasm, the destruction of NO by hemoglobin released from the clot into the subarachnoid space, and reversal of vasospasm by intracarotid NO. The authors sought to establish whether administration of L-arginine, the substrate of the NO-producing enzyme NOS, would reverse and/or prevent vasospasm in a primate model of SAH.

METHODS

The study was composed of two sets of experiments: one in which L-arginine was infused over a brief period into the carotid artery of monkeys with vasospasm, and the other in which L-arginine was intravenously infused into monkeys over a longer period of time starting at onset of SAH. In the short-term infusion experiment, the effect of a 3-minute intracarotid infusion of L-arginine (intracarotid concentration 10(-6) M) on the degree of vasospasm of the right middle cerebral artery (MCA) and on regional cerebral blood flow (rCBF) was examined in five cynomolgus monkeys. In the long-term infusion experiment, the effect of a 14-day intravenous infusion of saline (control group, five animals) or L-arginine (10(-3) M; six animals) on the occurrence and degree of cerebral vasospasm was examined in monkeys. The degree of vasospasm in all experiments was assessed by cerebral arteriography, which was performed preoperatively and on postoperative Days 7 (short and long-term infusion experiments) and 14 (long-term infusion experiment). In the long-term infusion experiment, plasma levels of L-arginine were measured at these times in the monkeys to confirm L-arginine availability. Vasospasm was not affected by the intracarotid infusion of L-arginine (shown by the reduction in the right MCA area on an anteroposterior arteriogram compared with preoperative values). However, intracarotid L-arginine infusion increased rCBF by 21% (p < 0.015; PCO2 38-42 mm Hg) in all vasospastic monkeys compared with rCBF measured during the saline infusions. In the long-term infusion experiment, vasospasm of the right MCA occurred with similar intensity with or without continuous intravenous administration of L-arginine on Day 7 and had resolved by Day 14. The mean plasma L-arginine level increased during infusion from 12.7+/-4 microg/ml on Day 0 to 21.9+/-13.1 microg/ml on Day 7 and was 18.5+/-3.1 microg/ml on Day 14 (p < 0.05).

CONCLUSIONS

Brief intracarotid and continuous intravenous infusion of L-arginine did not influence the incidence or degree of cerebral vasospasm. After SAH, intracarotid infusion of L-arginine markedly increased rCBF in a primate model of SAH. These findings discourage the use of L-arginine as a treatment for vasospasm after SAH.

The role of performance assessment in the regulation of underground disposal of radioactive wastes: an international perspective

Much has been written about the development and application of quantitative methods for estimating under uncertainty the long-term radiological performance of underground disposal of radioactive wastes. Until recently, interest has been focused almost entirely on the technical challenges regardless of the role of the organization responsible for these analyses. Now the dialogue between regulators, the repository developer or operator, and other interested parties in the decision-making process receives increasing attention, especially in view of some current difficulties in obtaining approvals to construct or operate deep facilities for intermediate or high-level wastes. Consequently, it is timely to consider the options for regulators' review and evaluation of safety submissions, at the various stages in the site selection to repository closure process, and to consider, especially, the role for performance assessment (PA) within the programs of a regulator both before and after delivery of such a submission. The origins and broad character of present regulations in the European Union (EU) and in the OECD countries are outlined and some regulatory PA reviewed. The issues raised are discussed, especially in regard to the interpretation of regulations, the dangers from the desire for simplicity in argument, the use of regulatory PA to review and challenge the PA in the safety case, and the effects of the relationship between proponent and regulator. Finally, a very limited analysis of the role of PA in public hearings is outlined and recommendations are made, together with proposals for improving the mechanisms for international collaboration on technical issues of regulatory concern.

Use of hydroxyapatite bone cement to prevent cerebrospinal fluid leakage through the frontal sinus: technical report

OBJECTIVE

To test the efficacy of a simple technique of frontal sinus obliteration during low frontal craniotomy using hydroxyapatite cement instead of more traditional methods, such as pericranial flaps, free muscle or adipose grafts, lumbar drainage, or fibrin glue.

METHODS

Eight patients undergoing low frontal craniotomy for intradural surgery had the frontal sinus obliterated by careful removal of mucosa followed by filling of the sinus with hydroxyapatite bone cement. No other adjuncts for preventing cerebrospinal fluid leakage through the sinus were used.

RESULTS

At an average follow-up of 9 months, there were no cerebrospinal fluid leaks, infections, instances of resorption, or cosmetic deformities.

CONCLUSION

Hydroxyapatite bone cement seems to be a simple and effective method for frontal sinus obliteration and prevention of cerebrospinal fluid leakage.

Combined transarterial and transvenous embolisation of jugulotympanic paragangliomas

SUMMARY

Paragangliomas of the jugular region present a greater challenge to the surgeon than paragangliomas in other locations. Because of the vascular nature of the tumour, bleeding can be substantial not only from arterial inflow to the tumour, but also from venous bleeding, if not embolised prior to surgery. Six patients were treated with combined transarterial and transvenous embolisation followed by surgical resection. In each instance, the diagnosis of jugulotympanic paraganglioma was suspected based on MR features. Substantial reduction in loss of blood appears to result from the combined transarterial and transvenous embolisation approach.

Basilar artery perforation as a complication of endoscopic third ventriculostomy

The morbidity and mortality associated with third ventriculostomy has decreased significantly over the past 75 years since its introduction by Walter Dandy. Now more commonly performed using an endoscopic method, the significant morbidity of third ventriculostomy has dropped to approximately 5%; essentially that associated with ventriculoscopy in general. However, the possible complication of massive subarachnoid hemorrhage resulting from perforation of the basilar artery or its branches in the course of fenestration of the floor of the third ventricle has only recently been reported. In our case, subsequent to a vascular injury, a pseudoaneurysm developed at the site of vascular perforation, which was then appropriately controlled. The patient has since made a full recovery. Our goal is to remind the endoscopist of this unusual complication and to discuss our management strategies.

Surgical exposure of the petrous internal carotid artery: practical application for skull base surgery

When exposing the horizontal petrous carotid artery in preparation for intrapetrous carotid bypass, the surgeon has no definite landmarks to localize the perimeter of the cochlea. The results of this study provide a practical, consistent, and safe method to maximize carotid artery exposure while minimizing cochlear injury. We measured the carotid-cochlea distance (mean, 4.3 mm) and the carotid-cochlear angle (mean, 10.8 degrees) in 33 temporal bones in which the extended middle fossa approach had been performed. We correlated this distance to the width of a Sheehy weapon knife, which can be easily measured intraoperatively. Twenty-five temporal bones were imaged prior to surgical exposure using a new computed tomography (CT) protocol that can be used for preoperative assessment of the carotid-cochlear anatomy. The carotid-cochlea distance and carotid-cochlear angle measured on CT are compared with postsurgical measurements.

Loss of nitric oxide synthase immunoreactivity in cerebral vasospasm

To determine the distribution of nitric oxide synthase (NOS) in the primate cerebral artery nervi vasorum and to examine the potential role of NOS in cerebral vasospasm after subarachnoid hemorrhage (SAH) in primates, the distribution of NOS immunoreactivity (NOS-IR) in the major cerebral arteries was examined immunohistochemically in cynomolgus monkeys by the use of whole, mounted preparations of the circle of Willis. In four normal monkeys, NOS-IR was localized to the endothelial and adventitial layers of the large cerebral arteries. On the abluminal side, NOS-IR staining was densely concentrated in perivascular nerve fibers (nervi vasorum) of the anterior circulation. Staining was less prominent in the posterior circulation. In six monkeys with vasospasm on Day 7 after placement of preclotted arterial blood to form an SAH around the right middle cerebral artery (MCA) (42% +/- 8.3% decrease of MCA area, mean +/- standard deviation), NOS-IR was virtually absent in nerve fibers around the spastic right MCA but was normal on the contralateral side. In five monkeys in which vasospasm resolved by Day 14 after SAH (36% +/- 14% decrease of right MCA area on Day 7, and 5% +/- 14% decrease on Day 14), NOS-IR was also absent in the right MCA adventitial nerve fibers and remained normal in the left MCA. Adventitial NOS-IR was also normal in cerebral vessels of a sham-operated, nonspastic monkey. These findings provide further evidence that nitric oxide (NO) functions as a neuronal transmitter to mediate vasodilation in primates and indicate a role for adventitial NO in the pathogenesis of cerebral vasospasm after SAH in humans.

Nitric oxide mediation of chemoregulation but not autoregulation of cerebral blood flow in primates

The authors sought to develop a model for assessing in vivo regulation of cerebral vasoregulation by nitric oxide (NO), originally described as endothelial-derived relaxing factor, and to use this model to establish the role of NO in the regulation of cerebral blood flow (CBF) in primates. By using regional intraarterial perfusion, the function of NO in cerebral vasoregulation was examined without producing confounding systemic physiological effects. Issues examined were: whether resting vasomotor tone requires NO; whether NO mediates vasodilation during chemoregulation and autoregulation of CBF; and whether there is a relationship between the degree of hypercapnia and hypotension and NO production. Twelve anesthetized (0.5% isoflurane) cynomolgus monkeys were monitored continuously for cortical CBF, PaCO2, and mean arterial pressure (MAP), which were systematically altered to provide control and experimental curves of chemoregulation (CBF vs. PaCO2) and autoregulation (CBF vs. MAP) during continuous intracarotid infusion of 1) saline and 2) an NO synthase inhibitor (NOSI), either L-n-monomethyl arginine or nitro L-arginine. During basal conditions (PaCO2 of 38-42 mm Hg) NOSI infusion of internal carotid artery (ICA) reduced cortical CBF from 62 (saline) to 53 ml/100 g/per minute (p<0.01), although there was no effect on MAP. Increased CBF in response to hypercapnia was completely blocked by ICA NOSI. The difference in regional (r)CBF between ICA saline and NOSI infusion increased linearly with PaCO2 when PaCO2 was greater than 40 mm Hg, indicating a graded relationship of NO production, increasing PaCO2, and increasing CBF. Diminution of CBF with NOSI infusion was reversed by simultaneous ICA infusion of L-arginine, indicating a direct role of NO synthesis in the chemoregulation of CBF. Hypotension and hypertension were induced with trimethaphan camsylate (Arfonad) and phenylephrine at constant PaCO2 (40 +/- 1 mm Hg). Autoregulation in response to changes in MAP from 50 to 140 mm Hg was unaffected by ICA infusion of NOSI. In primates, cerebral vascular tone is modulated in vivo by NO; continuous release of NO is necessary to maintain homeostatic cerebral vasodilation; vasodilation during chemoregulation of CBF is mediated directly by NO production; autoregulatory vasodilation with hypertension is not mediated by NO; and increasing PaCO2 induces increased NO production.

Effect of intracarotid nitric oxide on primate cerebral vasospasm after subarachnoid hemorrhage

The continuous release of nitric oxide (NO) is required to maintain basal cerebrovascular tone. Oxyhemoglobin, a putative spasmogen, rapidly binds NO, implicating loss of NO in the pathogenesis of cerebral vasospasm after subarachnoid hemorrhage (SAH). If vasospasm is mediated by depletion of NO in the vessel wall, it should be reversible by replacement with NO. To investigate this hypothesis, the authors placed blood clots around the right middle cerebral artery (RMCA) of four cynomolgus monkeys; four unoperated animals served as controls. Arteriography was performed before and 7 days after surgery to assess the presence and degree of vasospasm, which was quantified in the anteroposterior (AP) projection by computerized image analysis. On Day 7, cortical cerebral blood flow (CBF) in the distribution of the right MCA was measured during four to six runs in the right internal carotid artery (ICA) of brief infusions of saline followed by NO solution. Arteriography was performed immediately after completing the final NO infusion in three of the four animals with vasospasm. Right MCA blood flow velocities were obtained using transcranial Doppler before, during, and after NO infusion in two vasospastic animals. After ICA NO infusion, arteriographic vasospasm resolved (mean percent of preoperative AP area, 55.9%); that is, the AP areas of the proximal portion of the right MCA returned to their preoperative values (mean 91.4%; range 88%-96%). Compared to ICA saline, during ICA NO infusion CBF increased 7% in control animals and 19% in vasospastic animals (p < 0.002) without significant changes in other physiological parameters. During NO infusion, peak systolic right MCA CBF velocity decreased (130 to 109 cm/sec and 116 to 76 cm/sec) in two vasospastic animals. The effects of ICA NO on CBF and CBF velocity disappeared shortly after terminating NO infusion. Intracarotid infusion of NO in a primate model of vasospasm 1) increases CBF, 2) decreases cerebral vascular resistance, 3) reverses arteriographic vasospasm, and 4) decreases CBF velocity in the vasospastic artery without producing systemic hypotension. These findings indicate the potential for the development of targeted therapy to reverse cerebral vasospasm after SAH.

Development of a CELSS bioreactor: oxygen transfer and micromixing in parabolic flight

The gas exchange portion of a phase-separated loop bioreactor was tested with respect to oxygen mass transfer and micromixing in accelerations of 0.01g, 1g, and 2g. A plot of the overall mass transfer coefficient versus gravity indicates the rate of oxygen transfer does not change as a function of acceleration. Also, it was determined that the micromixing did not exhibit significant changes in the various gravitational fields. These observations indicate the loop bioreactor should function independent of acceleration.

Treatment of cranial dural arteriovenous fistulae by interruption of leptomeningeal venous drainage

Cranial dural arteriovenous fistulae (AVF's) of the tentorial incisura or the dura of the middle fossa have a much higher incidence of draining via leptomeningeal veins than do AVF's of the transverse-sigmoid sinuses or the cavernous sinus. Such a drainage pattern is associated with an increased incidence of intracranial hemorrhage and progressive focal neurological deficits. Patients with cranial dural AVF's often undergo surgical excision and/or endovascular embolization for elimination of the AVF. Since these lesions are frequently large and involve the skull base or adjacent dural sinuses, extensive surgery is often required. In contrast, spinal dural AVF's with only intradural venous drainage to the medullary venous system are treated successfully by simply interrupting the vein that drains the dural AVF as it enters the subarachnoid space. The authors identified a subgroup of patients with cranial dural AVF's in whom the AVF was drained only by leptomeningeal veins, and sought to establish whether simple interruption of the vein draining the blood from the AVF into the subarachnoid space is effective and lasting treatment in this subgroup of patients, as it is in patients with spinal dural AVF's. Four adult patients with symptomatic cranial dural AVF's (two petrotentorial, one middle fossa floor, and one posterior fossa base) were identified on arteriography as having fistulae that were supplied by the internal and/or external carotid arteries and drained only via leptomeningeal veins (two entered the petrosal vein, one a cerebellar hemispheric vein, and one a mesencephalic vein). All patients underwent interruption of the vein draining the dural AVF as it penetrated the dura to enter the subarachnoid space, and experienced neurological improvement after surgery. Repeat arteriography at 1 to 2 weeks (three patients), 3 months (3 patients), 12 to 15 months (three patients), and 4 years (two patients) revealed no residual AVF and no evidence of abnormal blood flow. Many cranial dural AVF's with leptomeningeal venous drainage (the type with the most aggressive behavior) are drained only by leptomeningeal veins. This subgroup of patients can be identified by selective arteriography and requires only interruption of the draining vein as it enters the subarachnoid space for successful, lasting elimination.

Primary extraosseous pulmonary osteogenic sarcoma: CT findings

This is a report of a primary extraosseous osteogenic sarcoma of the lung. The patient presented with fever and productive cough. Chest radiography and CT showed a cavitary lesion with an air-fluid level. The lesion was treated as an abscess. Despite aggressive antibiotic therapy and drainage, the patient continued to deteriorate rapidly. At autopsy the lesion was found to be a primary extraosseous pulmonary osteogenic sarcoma.

Effect of dissolved oxygen control on growth and antibiotic production in Streptomyces clavuligerus fermentations

A proportional-integral control system was used to control dissolved oxygen in a fermentor at constant shear and mass transfer conditions. Growth and antibiotic production in Streptomyces clavuligerus were studied at different dissolved oxygen levels during the fermentation. Three protocols were employed: no-oxygen control to provide a base case, oxygen controlled to a preset saturation level throughout the fermentation, and oxygen controlled at a high level only during the growth phase. The last protocol was aimed at optimizing the consumption of oxygen. Lower specific growth rates and cephamycin C yields were obtained when dissolved oxygen was controlled at 50% throughout the fermentation, compared to the base case. A 2.4-fold increase in the final cephamycin yield was observed when dissolved oxygen was controlled at saturation levels during the growth phase, compared to the experiments without dissolved oxygen control. This enhancement in yield was independent of the dissolved oxygen (DO) level after exponential growth, in the range of 50-100% saturation. The most effective control strategy, therefore, was to control DO only during active growth when the biosynthetic enzymes were probably synthesized.

Stereotactic radiosurgery of small intracranial tumors: neuropathological correlation in three patients

The mechanism by which radiosurgery can stop the growth of some tumors is poorly understood, in part because postmortem neuropathological findings in patients have been reported only rarely. To define further the effects of radiosurgery, we present the correlation among clinical, neuroimaging, and neuropathological data in three patients with different intracranial tumors who died between 2 and 39 weeks after radiosurgery. The target volumes in two patients with malignant tumors showed sharply demarcated coagulative necrosis. In the third patient, who had a benign acoustic nerve tumor, neuropathological examination found intratumoral hemorrhage and cyst formation, but no necrosis. Radiosurgery appears to cause acute necrosis of malignant cells, although its effectiveness may be limited by the infiltrative nature of some tumors. In benign tumors, necrosis following radiosurgery is relatively delayed, and may not be required for growth arrest.

Controlled ecological life support systems (CELSS) in high pressure environments

Future space habitats may be constructed in high pressure environments. The biological components of any controlled ecological life support systems (CELSS) used in these habitats will have to be able to grow and metabolize normally for the CELSS to operate.

The maximization of the productivity of aquatic plants for use in controlled ecological life support systems (CELSS)

Lemna minor (common duckweed) and a Wolffia sp. were grown in submerged growth systems. Submerged growth increased the productivity unit volume (P/UV) of the organisms and may allow these plants to be used in a controlled ecological life support system (CELSS).

Gas bubble coalescence in reduced gravity conditions

The effects of low gravity, as produced by a reduced gravity aircraft, the KC135, on the formation and coalescence of gas bubbles were examined over a range of gas-liquid ratios and with various medium constituents. These effects will influence design considerations of fermentors operating in reduced gravity conditions.

A multimodality projection console for the radiology conference room

A multimodality projection console for the radiology conference room is described. The configuration of the TV camera, view boxes, switches, and adjacent lectern allows better transmission and easier manipulation of images during consultation and lecture sessions with the faculty, and house officers.

The effect of radiation on the long term productivity of a plant based CELSS

Mutations occur at a higher rate in space than under terrestrial conditions, primarily due to an increase in radiation levels. These mutations may effect the productivity of plants found in a controlled ecological life support system (CELSS). Computer simulations of plants with different ploidies, modes of reproduction, lethality thresholds, viability thresholds and susceptibilities to radiation induced mutations were performed under space normal and solar flare conditions. These simulations identified plant characteristics that would enable plants to retain high productivities over time in a CELSS.

Control of nitrate concentration in fermentations of Corynebacterium glutamicum

A nitrate control system has been devised for the maintenance of stable nitrate concentrations throughout fed-batch fermentations of Corynebacterium glutamicum. The feedback control system was based on the use of a nitrate-ion-selective electrode to directly monitor the nitrate levels in the fermentor and an automatic controller to activate a nitrate feed pump. The electrode which was used for controlling the nitrate level was stable through-out the fermentation period. The apparent maximum specific growth rate, biomass production, protein production, biomass yields on glucose and nitrate, and amino acid production were all optimal at approximately 50mM nitrate.

Gas transfer in microgravity fermentations

Fermentations performed under microgravity conditions may be used in future long duration space missions for recycling expendable life support materials. These fermentations will differ from similar fermentations performed at one gravity in the manner in which gas transfer in the fermentor is carried out.

Image communications. What is needed and why

Better communications are essential in the new medical environment. Methods to make more efficient the throughput in an existing department, foster confidence of patients, and improve the communications and efficiency of referring physicians are needed. The most difficult and thus the driving component of the new communications environment is image transmission. Concepts of picture archiving and communications systems, or PACS, arising from digital technology make possible unique and ubiquitous solutions to image communications. Better quality control and improved interpretation throughout the system, including the offices of referring physicians, will be possible. Radiologists are in a position to mold this new medical industry.

Cell division in Deinococcus radiodurans and a method for displaying septa

The study of sections, freeze-cleaved, and whole-cell preparations of Deinococcus radiodurans supported the contention that septa close assymmetrically and originate from discrete opposing locations on the cell surface. Tetrads and the larger associations (sheets) of cells in some strains were formed by alternate and synchronized divisions in two planes. The polarity initiating the second division in cells of the Sark strain, in particular, was often expressed in slower growing cells before completion of the first division so that the advancing margins of the first septum were diverted towards the nearest new pole; the resulting gap was closed later on, and consequently, the cell compartments of this coccus were in communication for some time after two rounds of nuclear segregation. Freeze cleaving showed that the initial generation of septa involved a short sulcus in the plasma membrane and not a circumferential infolding. The shape and form of the developing septum was inferred from sections but was displayed in whole-cell preparations by a technique which selectively and positively stained a septal component. Positive staining of the septum with uranyl salts was appreciable when the relative stainability of the peripheral wall (mainly peptidoglycan) was reduced by pretreatment with salts of low atomic weight metals (0.01-1.0%, w/v) such as cobalt, copper, iron, or zinc. Examination of these whole-cell preparations by stereoscopy showed that the septal diaphragm closes as a slit or long oval, and the advancing margin shows curvature towards the next axis of division. The mechanism and exact site of this positive staining was not elucidated; vancomycin blocking of the uncross-linked peptides of peptidoglycan was almost as effective as the transition metal salts as a foretreatment for staining septa.

Isolation and characterization of the plasma membrane and the outer membrane of Deinococcus radiodurans strain Sark

Deinococcus radiodurans strain Sark, although gram-positive, has a complex cell wall profile that includes an outer membrane-like structure. The outer cell envelope layers formed blebs throughout the growth cycle, which were shed as large vesicles (0.5-3.5 micron m in diameter) from approximately 5% of the cell population. Instability was accentuated by treatment with 10% NaCl, which released the outer membrane from all cells without disrupting the peptidoglycan layer, and provided an outer membrane fraction uncontaminated by plasma membrane. Cells so treated formed protoplasts after sequential treatment with 6 M urea, trypsin, and the supernatant from batch cultures of Lysobacter enzymogenes 495. The plasma membrane was isolated from lysed protoplasts. The absence of presence of catalase activity, and differences in lipid composition, were used to differentiate between plasma membrane and outer membrane.

Unusual polar lipids of Micrococcus radiodurans strain Sark

The polar lipids of Micrococcus radiodurans strain Sark appear to be unique in that common bacterial phospholipids such as phosphatidylethanolamine, phosphatidylserine, phosphatidylcholine, and phosphatidylinositol are absent. Of the 13 polar lipids detected, 5 contain phosphorus and carbohydrate, 4 contain carbohydrate and no phosphorus, and 1 contains phosphorus as well as sulfur. None of the polar lipids contain free choline or amino groups and none are sensitive to phospholipases C or D. Of eight selected polar lipids tested, all were found to be labile to milk alkali, suggesting the presence of ester linkages. It is suggested that the unusual lipid profile of M. radiodurans strain Sark may be useful in taxonomic considerations.