Persistent back pain and sciatica in the United States: patient characteristics

Low back pain is an extremely common, seriously disabling, nonfatal public health problem worldwide. The National Low Back Pain Study was a multicenter study of a large, heterogeneous group of patients who have been referred to either a neurosurgeon or an orthopedic surgeon for the evaluation and treatment of a persistent complaint of low back pain. In this paper, we characterize persistent low back pain patients and their complaints, describe the impact of persistent low back pain on the patients' functional and psychological status, report on the patients' medical characteristics, and identify treatments that are currently prescribed for these patients. Persistent low back pain is most common among people in their mid-to-late thirties and early-to-mid forties. The patients are mostly white, well educated, and generally affluent. The majority are gainfully employed, but some quit working because of pain and those who do tend to be less educated, and more likely to be involved in litigation. The average patient has had low back pain intermittently for 10 years. The pain is usually well localized but its severity varies considerably. Besides pain, most persistent low back pain patients report a variety of motor and sensory deficits. Patients also report significant functional impairment at work, at play, and at home. The typical patient does not, however, display significant psychological distress. Most patients have consulted multiple health care providers, have received a variety of treatments, and have used a variety of medications to alleviate pain; a few have been subjected to more aggressive treatment measures including surgery, intradiscal therapy, and narcotic and psychoactive drugs. None of these treatments has been effective. Physical examinations of these patients do not provide significant clues for making a definitive diagnosis. Nonspecific abnormalities such as muscle spasm, tenderness, and trigger points are quite common, but motor weakness and sensory deficits in the lower extremities, and reflex changes in the knees and ankles, are much less common. The classic combination of reflex changes, motor weakness, and sensory deficits associated with specific protruded discs are extremely rare even though one of three patients had a diagnosis of disc herniation. Diagnostic imaging studies revealed that the majority of persistent low back pain patients have spondylotic abnormalities involving root compression or lumbar instability or both, with root compression as the primary cause of the complaint. Myofascial syndrome and lumbar instability were the next most common diagnoses. After a thorough evaluation by specialists in spinal disorders, three of five persistent low back pain patients were prescribed an additional course of conservative therapy, one of five was prescribed surgery, and the rest were prescribed no treatment. Persistent low back pain patients appear to be a distinct group of low back pain patients who are different from patients who have similar nonpersistent acute symptoms and those who have the chronic pain syndrome characterized by significant behavioral and psychological co-morbidities.

Divalent metal ions and the internal equilibrium of the hammerhead ribozyme

Thermodynamics of RNA cleavage/ligation were measured for a self-cleaving hammerhead ribozyme in the presence of Ca2+, Co2+, Mg2+, and Mn2+. The internal equilibrium, the ratio of cleaved to ligated RNA, decreases with increasing concentrations of each of the four divalent metal ions in a hyperbolic dependence that shows saturation. The metal ion dependence is not due to changes in ionic strength, and the value of the equilibrium constant at saturation is different for each metal ion. The concentration required to achieve half-saturation of the equilibrium is also different for each metal ion, and the order of apparent metal ion dissociation constants correlates with those measured for dissociation of the same metal ions complexed with tRNA and nucleotides. We interpret the divalent metal ion dependence of the equilibrium in terms of a thermodynamic model invoking noncooperative metal ion dissociation from the cleaved RNA. Thus, at 10 mM Mg2+, a commonly employed condition for hammerhead kinetic studies, metal ion dissociation contributes substantially to the free energy of the equilibrium and drives the hammerhead reaction toward cleaved RNA. Temperature dependencies of the equilibrium reveal that while the entropy and enthalpy changes of the equilibrium depend on the identity of the divalent metal ion, in each case a large entropic driving force overcomes an unfavorable change in enthalpy. This agrees with thermodynamics previously measured for an intermolecular hammerhead in the presence of Mg2+ [Hertel, K. J., & Uhlenbeck, O. C. (1995) Biochemistry 34, 1744-1749].

Kinetic characterization of intramolecular and intermolecular hammerhead RNAs with stem II deletions

A method is described to obtain intramolecular cleavage rates for the hammerhead ribozyme during in vitro transcription. By avoiding RNA purification and renaturation, the potential for formation of inactive conformations of the RNA is minimized. By showing that an intramolecular hammerhead and a closely related intermolecular hammerhead cleave at the same rate under a given set of conditions, we confirm that both reactions probably have the same rate-limiting step. An in vitro selection strategy was used to isolate active hammerheads from a library of molecules where six randomized nucleotides replaced stem-loop II. The sequence and number of nucleotides which replace stem-loop II have large effects on hammerhead cleavage activity. The relative activities of three sequences selected from the intramolecular library are the same when the sequences are transferred into an intermolecular hammerhead background.

Effects of maturation on cyclic GMP-dependent vasodilation in ovine basilar and carotid arteries

The present experiments examine the effects of maturation on cyclic GMP (cGMP)-mediated vasodilation in 688 segments of common carotid (COM) and basilar (BAS) arteries taken from newborn (3- to 7-d-old) and nonpregnant adult sheep. The main finding is that maximum efficacy for relaxation decreased with maturation in both artery types for the nitric oxide releasing vasodilators S-nitroso-N-acetyl-penicillamine and nitroglycerin. These decreases could not be explained by changes in the -log ED50 concentrations for either vasodilator. Determination of the time course of cGMP responses to S-nitroso-N-acetyl-penicillamine or nitroglycerin at 10 microM revealed that the peak cGMP responses to these agents (range: 5.3 +/- 0.8 to 8.3 +/- 1.6 pmol/mg of protein) also did not vary significantly with age. However, cGMP attained peak values more rapidly in adult (COM: 50 s; BAS 30 s) than in newborn (COM: 60-80 s: BAS, 40-60 s) segments and returned to baseline more slowly in newborn than in adult segments, suggesting that maturation accelerates cGMP turnover. Correspondingly, baseline levels of cGMP were higher in newborn (COM: 1.0 +/- 0.1; BAS: 3.3 +/- 0.5 pmol/mg of protein) than in adult (COM: 0.3 +/- 0.1; BAS: 1.7 +/- 0.2 pmol/mg of protein) segments. Despite these differences in cGMP time course, rates of relaxation in response to S-nitroso-N-acetyl-penicillamine and nitroglycerin did not vary significantly with age, indicating that the temporal relation between cGMP and relaxation is different in newborn and adult arteries.(ABSTRACT TRUNCATED AT 250 WORDS)

Pregnancy alters cerebrovascular adaptation to high-altitude hypoxia

We have previously shown alterations in cerebrovascular composition, contractility, and endothelial function in normoxic pregnant (P) and chronically hypoxic nonpregnant (HNP) adult sheep compared with nonpregnant normoxic controls (NP). This study focuses on a fourth group, pregnant sheep exposed to chronic high-altitude hypoxia (HP) (110 days at 3,820 m). The combined challenges of pregnancy and high-altitude hypoxia resulted in significant alterations in cerebrovascular function that were not simply the summation of the responses seen in the P and HNP animals. Compared with NP, HP arteries had increased protein content and increased intracranial arterial wall thickness. Both P and HP arteries showed increased contractility, while HNP artery maximum tensions were depressed. Endothelial function was depressed in the P common carotid and was enhanced in all HNP arteries. In contrast, an increased endothelial response was shown only in the HP common carotid. Thus, for contractility, the effects of pregnancy predominated in the HP arteries. For endothelial function, hypoxia effects were dominant in the common carotid but not in the intracranial arteries. Clearly, cerebrovascular characteristics are dynamic in nature, with artery-specific responses to both pregnancy and hypoxia.

Proposed toxic oxidant inhibitors fail to reduce brain edema

Toxic oxidants (oxygen free radicals) have been implicated in the formation of brain edema from ischemia-reperfusion injury or tumor growth. We investigated the ability of an iron chelator, a calcium channel blocker, and a xanthine oxidase inhibitor to reduce formation of brain edema following a cold lesion in cats. The agents were given independently of each other in an attempt to inhibit the Haber-Weiss reaction, prevent Ca++ modulated uncoupling of oxidative phosphorylation, and inhibit the generation of toxic oxidants via xanthine oxidase, respectively. Pentastarch-deferoxamine conjugate at a dose of 50 mg/kg was given 15 minutes before and 60 minutes after the cold lesion. Nimodipine was given at a dose of 1 mg/kg 1 hour before and 2 hours after the cold lesion. Allopurinol was given at a dose of 50 mg/kg 24 hours before, at the time of the lesion and, 24 and 48 hours after the lesion. Gravimetric measurements of multiple brain areas were performed at 24 hours post-lesion in the pentastarch-deferoxamine and nimodipine groups and at 72 hours post-lesion in the allopurinol group. None of these agents led to significant reduction in brain edema formation as measured with a gravimetric column of kerosene and bromobenzene. Pentastarch-deferoxamine conjugate was utilized to avoid the confounding effects of arterial hypotension which is seen with intravenous deferoxamine. There was even a suggestion of increased edema in the periventricular white matter in animals treated with nimodipine. Taken together, independent inhibition of the Haber-Weiss reaction, of calcium channels, or of xanthine oxidase does not reduce formation of brain edema in the cold lesion model.

The effects of topical dexamethasone on experimental brain tumors and peritumoral brain edema

To determine if topical dexamethasone administered to brain tumor beds would not only control peritumoral edema and suppress tumor growth but also prevent systemic steroid complications, we studied experimental brain tumors produced in 102 rabbits by implanted VX2 carcinoma cells. We separated 58 animals into three groups: 1) untreated rabbits (n = 15), 2) systemic dexamethasone-treated (4 mg/kg/day) rabbits (n = 18), and 3) topical dexamethasone-treated (2.5 microliters/h, osmotic pump) rabbits (n = 25). We administered systemic or topical dexamethasone from the third day or from the seventh day after tumor implantation, and sacrificed the animals on the 13th day. We compared survival in these three groups with that of another 44 rabbits, beginning treatment on the seventh day. We measured brain water content in the white matter of the sacrificed rabbits by the specific gravity method. We measured the length and width of the brain tumors of all the rabbits and estimated tumor volume. Systemic and topical dexamethasone administered from the third day produced statistically significant inhibition of tumor volume as well as a mean reduction in peritumoral brain edema in most tested sites. Systemic and topical dexamethasone treatment resulted in a statistically significant increase in survival relative to the untreated group. These results suggest that topical dexamethasone is efficacious in a brain tumor model and its administration to brain tumor beds constitutes a new therapeutic modality.

Therapeutic effects of local delivery of dexamethasone on experimental brain tumors and peritumoral brain edema

To determine if dexamethasone administered by osmotic pump directly to brain tumors would control peritumoral edema and at the same time suppress tumor growth and prolong survival, the authors studied experimental brain tumors produced in 102 rabbits by implanting VX2 carcinoma cells. Of these, 58 animals were separated into three treatment groups: Group 1 included 15 untreated rabbits; Group 2 included 18 rabbits treated with systemic dexamethasone (4 mg/kg/day); and Group 3 included 25 rabbits treated with local dexamethasone (0.24 mg/day) delivered by osmotic pump. Systemic or local dexamethasone was administered from Day 3 or Day 7 after tumor implantation, and animals were sacrificed on Day 13. A survival study was performed with 44 rabbits separated into the same treatment groups, beginning drug delivery on Day 7. Brain water content in the white matter of sacrificed animals was measured by the specific gravity method. The length and width of the brain tumors in all animals were measured and the tumor volume estimated. Findings showed that systemic and local dexamethasone administered from Day 3 or Day 7 was associated with a significant (5% level) inhibition of tumor volume as well as a mean reduction of brain edema in most tested sites. Systemic and local dexamethasone therapy also resulted in a significant (5% level) increase in survival time relative to the untreated group. These short-term results suggest that locally delivered dexamethasone may constitute a clinically important therapeutic modality.

Frameless stereotaxic integration of CT imaging data: accuracy and initial applications

To evaluate the spatial accuracy of a rapid interactive method of transferring computed tomographic (CT) information between its display on a computer screen to its source (test object, operating field), a multidimensional computer combined with a six-jointed position-sensing mechanical arm was tested with a Plexiglas model consisting of 50 rods of varied height and known location, a plastic replica of the skull, and, subsequently, three patients. The median error value between image and real location was 1-2 mm (P > .95), regardless of the registration target sites. The accuracy, however, increased with the selection of widespread registration points, and 95% of all errors were below 3.70 mm (P > .95). The results compare favorably with the four most commonly used stereotaxic framed units. A misregistration error of 0.3-2.2 mm was found during intraoperative correlation between anatomy on the CT display and actual anatomic location in the operative field.

Lumbar and cervical spondylosis and spondylotic myelopathy

The problem of chronic spondylitic spinal disease is markedly underrepresented in the literature. The principal focus is on procedures and diagnostic techniques. It has been suggested that the classic clinical syndromes are rare and that interventional protocols based on them are likely to be inadequate. New diagnostic techniques have revolutionized the evaluation of patients: magnetic resonance imaging is now the standard whereas myelography use is being steadily reduced. It is clear that the outcome of spinal surgery for herniated disk, in expert hands, is excellent. Nevertheless, there is an emphasis on minimally invasive and percutaneous techniques to try to avoid major surgery, which has been the standard. The natural history of these problems is still understood incompletely. Long-term follow-ups are generally not available and the value of nearly every form of conservative care remains unproven.

Spinal cord stimulation for chronic, intractable pain: experience over two decades

Over the past two decades, spinal cord stimulation devices and techniques have evolved from single-channel systems, with electrodes requiring laminectomy, into programmable "multichannel" systems with electrodes that may be placed percutaneously. We have reviewed our experience in 320 consecutive patients treated with these devices at our institution between 1972 and 1990. Technical details of treatment as well as patient characteristics have been assessed as predictors of clinical outcome and of hardware reliability by univariate and multivariate statistical methods. Current follow-up has been obtained at intervals from 2 to 20 years (mean, 7.1 yr) postoperatively on 205 patients. All clinical outcome measures have been based on disinterested third-party interview data--standard analog pain ratings, employment status, activities of daily living, and use of analgesics. At 7-year mean follow-up, 52% of the 171 patients who received permanent implants reported at least 50% continued pain relief. A majority had maintained improvements in activities of daily living and analgesic use. Analysis of hardware reliability for 298 permanent implants revealed significantly fewer clinical failures (P < 0.001) and technical failures (in particular, electrode migration and malposition, P = 0.025) as single-channel implants have evolved into programmable, multichannel devices. Our analysis of technical and clinical prognostic factors may be useful to the clinician in selecting patients for this procedure.

Cerebrovascular adaptations to high-altitude hypoxemia in fetal and adult sheep

In the fetus and infant, high-altitude hypoxemia is associated with increased cerebrovascular morbidity. To test the hypothesis that this increased morbidity involves changes in cerebrovascular endothelial and smooth muscle function, we examined middle cerebral, posterior communicating, basilar, and common carotid arteries obtained from 23 normoxic fetuses, 19 hypoxemic fetuses maintained at high altitude (3,820 m) from 30 days gestation to near term (approximately 143 days), 55 normoxic non-pregnant adults, and 24 hypoxemic nonpregnant adults maintained at the same altitude and duration as the hypoxemic fetuses. Long-term hypoxemia was associated with several significant changes in both fetal and adult arteries, including a generalized increase in base-soluble protein (5-50%), a depression of the maximum potassium-induced tensions (16-49%), and a depression of the relaxation responses to S-nitroso-N-acetylpenicillamine (1-11%), which releases nitric oxide into solution upon hydration. Altitude acclimatization significantly enhanced amine-to-potassium ratios (the ratio of tension produced by 10 microM serotonin with 20 microM histamine to that produced by 122 mM potassium) only in adult cerebral arteries (51-87%) and significantly depressed potassium-induced stresses (up to 41%) and serotonin/histamine-induced tensions (20-37%) only in fetuses. Endothelium-dependent relaxations to A23187 were significantly depressed in hypoxemic fetuses (4-11%) but were significantly enhanced in hypoxemic adults (2-14%). We conclude that chronic hypoxemia depresses both vascular smooth muscle and endothelial function to a greater extent in fetal than in adult cerebral arteries and that this effect could contribute to the greater postnatal vulnerability to asphyxic and hypertensive insults seen in hypoxemic neonates.

Self-cleaving catalytic RNA

We describe the structures and catalytic properties of several naturally occurring self-cleaving RNA motifs that give 2', 3' cyclic phosphate products. The hammerhead and hairpin motifs are derived from plant pathogenic RNAs and the delta motif is part of the human hepatitis delta element. A fourth motif from Neurospora is less well characterized. By assembling the self-cleaving RNAs from more than one oligoribonucleotide, the cleavage reaction can be examined under a variety of conditions and catalytic turnover can be demonstrated. Mutagenesis and chemical methods to introduce modified nucleotides allowed the structural requirements to be deduced. The role of divalent cations in the catalytic mechanism is discussed.

Non-glial tumors of the brain: tumors of the cerebellopontine angle and meningiomas

The principal non-glial tumors of the brain are meningiomas and acoustic schwannomas. Advances in the management of meningiomas have included endovascular techniques for embolization to reduce blood loss, radical surgical approaches, and the recognition of the high recurrence rate of these tumors. Advances in the management of acoustic tumors have been in preservation of VIIth nerve function, improved preservation of hearing, and the availability of stereotactic radiosurgical techniques as an alternative. There is still a substantial discussion concerning the route of surgery for acoustic tumors and not all agree that hearing preservation is a reasonable goal at present.

The utility of magnetic resonance imaging in the diagnosis of intranasal meningoencephaloceles

We present three patients in whom the diagnosis of intranasal meningoencephalocele was made by magnetic resonance imaging. The initial clinical evaluation and computed tomographic examinations of these patients failed to distinguish between chronic inflammation and intranasal meningoencephalocele. Although both computed tomography and magnetic resonance imaging are used to distinguish between normal, inflammatory, and neoplastic tissue in the nasal cavity and paranasal sinuses, limitations do exist and these are the focus of our communication. A clear understanding of the efficacy of these radiographic modalities will enhance surgical planning and can preclude severe complications.

Preoperative risks predict neurological outcome of carotid endarterectomy related stroke

The aim of this study was to determine if preoperative risk factors are predictors of poor stroke outcome after carotid endarterectomy. In addition, the effect of other stroke risk factors on stroke severity was determined. A retrospective review of carotid endarterectomy results spanning 10 years, encompassing 561 patients, and reporting the combined results of all surgeons at our institution was performed. Patients were assigned to one of four groups. There were 227 patients with no preoperative risks (Group 1), 61 with angiographic risks (Group 2), 196 with medical risks with or without angiographic risks (Group 3), and 77 with neurological risks with or without medical/angiographic risks (Group 4). Other risks associated with stroke occurrence were recorded including: intraoperative risks (cross-clamp time, use of shunt, use of glucose solutions), surgical complications (carotid occlusion/thrombus or ligation), and medical complications (hypoxia, myocardial infarct). Stroke incidence was 5% with 2% (11 patients) and 3.4% (19 patients) having good and poor outcomes, respectively. Stroke incidence was highest in Groups 2 and 4 (10 and 14%, respectively), and Group 4 had the highest incidence of poor-outcome stroke (12%). Cross-clamp time, intraoperative shunt placement, and intraoperative glucose administration were similar among preoperative risk groups and were not primary determinants of stroke severity. The most common medical complication was myocardial infarction, which had the highest incidence in Groups 3 and 4 (6.1 and 5%, respectively). The highest incidence of surgical complications occurred in Groups 2 and 4, carotid thrombosis being the most common event (16 patients). Surgical complications were more commonly associated with stroke than were medical complications.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of emulsion concentration on biodistribution of perflubron in tumor-bearing mice

Perflubron (perfluoroocytlbromide, PFOB) emulsion concentrations of 100%, 90%, or 60% w/v were administered to mice with and without 3 types of murine malignant tumor implants, and the distribution in blood, tumor, lung, liver and spleen were studied 48 hours after a dose of 10 or 3 g/Kg of PFOB. The most important changes were seen in the blood where the PFOB concentration [PFOB] was decreased in tumor bearing mice (TBM). Blood [PFOB] was also decreased in TBM and normal mice (NM) that received the 60% emulsion. Liver [PFOB] was increased in TBM. Lung [PFOB] was directly proportional to the emulsion concentration with the 10g/Kg dose. No major differences were seen in the biodistribution between the 100% and 90% emulsions using 10g/Kg, in spite of differences in composition and manufacturing history.

Hypoxia inhibits calcium influx in rabbit basilar and carotid arteries

We examined the hypothesis that hypoxia inhibits Ca2+ influx in isolated rabbit common carotid, internal carotid, and basilar arteries. In arteries mounted for measurement of isometric tension and exposed to 122 mM K+ in Ca(2+)-free Krebs, cumulative addition of Ca2+ produced Ca(2+)-force relations that were right-shifted by hypoxia (PO2 approximately 15 Torr) with no decrease in maximum force attained. In arteries precontracted with 122 mM K+, exposure to hypoxia produced relaxations whose rates and magnitudes were enhanced by reductions in bath Ca2+ from 8.0 to 0.8 mM. Using an ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid method for 3-min 45Ca influx measurements, modified for use in rabbit basilar and carotid arteries, we found that resting levels of Ca2+ influx (mumol.min-1.kg dry wt-1) were significantly higher in basilar (67 +/- 1, n = 10) than in internal carotid (27 +/- 1, n = 12) or common carotid (33 +/- 1, n = 12) arteries. K+ stimulation increased Ca2+ influx more than two-fold compared with control in all three artery types, and hypoxia inhibited this increase by 74% in basilar, 49% in internal carotid, and 33% in common carotid arteries. Exposure to 10 microM serotonin and 100 microM uridine 5'-triphosphate (UTP) also increased Ca2+ influx, but these increases were less than observed during K+ contractions and averaged 10 (basilar), 31 (internal carotid), and 82% (common carotid) above control. Hypoxia completely inhibited serotonin- and/or UTP-induced increases in Ca2+ influx in basilar and internal carotid segments and inhibited 47% of this increase in the common carotid segments.(ABSTRACT TRUNCATED AT 250 WORDS)

Prolonged shelf stability and biocompatibility of a concentrated injectable fluorocarbon emulsion

A four-year-old 100% w/v concentrated emulsion of perfluorooctylbromide (PFOB, perflubron) stored at 5 degrees C, when submitted to the close-to-total exchange-perfusion test in conscious rats (Hct 3-5%) still resulted in 75% survival. Particle size and size distribution, viscosity, pH were still in the acceptable range.

Cyclooxygenase inhibition with ibuprofen: effect on biodistribution of perflubron emulsions in mice with mammary tumor

The biodistribution of Perflubron (perfluorocytylbromide, PFOB) was studied by infusing 10 or 3 g/Kg doses of 90% and 100% w/v emulsions into Balb C mice with and without malignant mammary tumor implants. PFOB concentrations were measured in blood, liver, spleen, lung and tumor, and X-rays were taken 48 hours after infusion. Ibuprofen (IBU) was given intraperitoneally 10 mg/Kg dialy for 3 days to study the effects of cyclooxygenase blockade. The results showed that the blood [PFOB] in tumor-bearing mice (TBM) was only 3.6% of that measured in normal mice (NM), and the liver [PFOB] was increased by 59%. The lung [PFOB] increase with IBU therapy in NM was highly significant. IBU therapy resulted in a 98% and 468% increase in blood [PFOB] in normal and TBM, respectively. Smaller but statistically significant changes occurred in blood [PFOB] with saline and sham injections. Tumor [PFOB] was lower by 17% (P = .028) in mice treated with IBU. Smaller decreases were seen with saline and sham injections but did not achieve statistical significance. In conclusion, the presence of this malignant tumor resulted in changes that might influence the usefulness of PFOB as a contrast agent and as an adjuvant for radiation and chemotherapy. This study shows that cyclooxygenase inhibition significantly modified the pharmacodynamics of PFOB emulsions in blood, tumor and lung. The changes seen in the saline placebo and sham category were attributed to stress from procedures.

Pregnancy-induced changes in ovine cerebral arteries

We examined the effects of pregnancy on the ovine cerebral vasculature by comparing several characteristics of isolated endothelium-intact segments of three intracranial arteries including the middle cerebral (MCA), posterior communicating (PC), and basilar (BAS) arteries taken from pregnant sheep (138-143 days gestation, term approximately 145 days) and nonpregnant controls. For comparison, segments of the extracranial common carotid (COM) artery were also studied. With pregnancy, vessel water content increased (5.4-5.8%) in all arteries except the PC. Additionally, cellular protein content increased in all arteries (4.4-50.0%). Arterial stiffness, as determined by passive stress-strain determinations, was significantly decreased during pregnancy in the MCA but not in the larger arteries. Maximum contractile responses, when normalized to vessel wall cross-sectional area, were consistently greater in arteries from pregnant than in those from nonpregnant animals (10.1-49.7%). Relaxation to the endothelium-independent guanylate cyclase stimulator S-nitroso-N-acetyl penicillamine (SNAP) increased with pregnancy only in the distal MCA (approximately 17%). Endothelium-dependent relaxation to the calcium ionophore A23187 decreased only in the larger and more proximal COM (-39%). Thus pregnancy was associated with an increase in production of contractile force, a decrease in peripheral vascular stiffness, a decrease in the relaxant response to A23187 in the COM, and an increase in the relaxant response to SNAP in the MCA. Together, these findings indicate that pregnancy has widespread and important vessel specific cerebrovascular consequences that affect not only arterial composition, but also contractility and endothelial reactivity.

Iohexol cervical myelography in adult outpatients

The incidence of adverse reactions following standard film or screen cervical myelography with iohexol in 32 adult outpatients was reported. Iohexol at a dose of 1,080-3,000 mg of iodine was administered via a lateral C1-C2 approach in 26 patients and via a lumbar route in 6 patients. All 32 patients underwent postmyelographic cervical spine computed tomography and were discharged after the procedure was completed. No adverse reactions occurred in 53.1% of patients. The most common adverse reaction was headache (31.3%); other minor adverse reactions included exacerbation of pre-existing pain (12.5%), neck stiffness (9.4%), and vomiting (6.3%). Good to excellent technical quality was seen on all myelograms and computed tomographic scans. Outpatient cervical myelography with iohexol appears to be a safe and cost-effective alternative to inpatient examination.

Spinal cord compression complicating subarachnoid infusion of morphine: case report and laboratory experience

The intraspinal administration of morphine has been employed increasingly in the management of intractable pain of malignant as well as benign origin. We have encountered a previously unreported clinical complication: spinal cord compression by an inflammatory tissue mass surrounding a subarachnoid infusion catheter administering morphine, leading to paraplegia. The patient was referred to our institution after catheter and pump implantation for chronic, intractable pain associated with pre-existing lumbar arachnoid fibrosis, after multiple myelograms and surgeries. The patient may, therefore, have had an underlying propensity to foreign body reactions. We have encountered a similar phenomenon, however, in a canine laboratory model. The pathological features in both our patient and our laboratory preparation, with inflammatory tissue masses around the tip of the catheter but not around proximal subarachnoid segments, suggest an effect related to infusion, as opposed to infection or the presence of the catheter. We review the pathological features in both settings and the pertinent literature.

Failed back surgery syndrome

The failed back or postlaminectomy syndrome is obviously multidimensional. Failure of therapy may result from structural abnormalities in the back, psychosocial influences, or a combination of both. The causes of back pain are largely unknown. Correlations with diagnostic studies are uncertain. The lack of precise diagnoses is reflected in a multiplicity of nonspecific treatments, mostly of unproven value. Our current disability-litigation system adds greatly to the problem. Patients are rewarded for nonfunction. Some physicians become advocates for patients, others for insurance carriers and employers. Decisions concerning appropriate treatment are often made by patients, attorneys, the disability determination system, employers, and judges for extraneous reasons, which include financial gain or personal bias and often reflect lack of current information. Even when correct decisions are made, there is a lack of adequate programs for diagnosis and comprehensive treatment of these individuals. The failed back syndrome is not likely to disappear quickly. Large numbers of these patients require care. The best available evaluation includes thorough, but not overly minute investigation using the best current imaging techniques. These studies combined with the history and physical examination should provide a reasonably accurate assessment of the patient's condition. Concomitant evaluation of psychosocial issues is mandatory, and those who treat these patients without understanding the importance of the various comorbidities discussed are likely to be detrimental. Reparative surgery has real, but limited use. Nerve root compression and instability are the only two conditions demonstrated to be correctable at the present time. However, even when a potentially remediable lesion is found, these patients should undergo a reasonable attempt at physical rehabilitation with attention to both local factors and general function. The best data available today suggest that most of the patients suffering from failed back syndrome are incapacitated by psychiatric, psychologic, and social/vocational factors, which relate to the back complaint only indirectly. Those currently suffering from this problem can be best treated by comprehensive programs that address these complex psychosocial issues. New additions to this category can be reduced by rigorous attention to physical abnormalities, so that surgery is undertaken only for clear indications, and appreciation of the importance of the psychologic aspects of disability from low back pain. The smaller group suffering principally from physical abnormalities can be improved by reparative surgery or pain-relieving procedures if intensive conservative rehabilitation efforts fail. All surgical procedures fail occasionally, and as long as there is a need for reparative surgery, some patients will fail to benefit or be worsened by the procedures.(ABSTRACT TRUNCATED AT 400 WORDS)

Developmental changes in ovine cerebral artery composition and reactivity

We have examined age-related changes in segments of common carotid (Com), basilar (Bas), posterior communicating (PC), and middle cerebral (MC) arteries taken from 14 near-term fetal lambs, 62 newborn lambs 3-7 days old, and 42 adult nonpregnant sheep. Transition from fetal to newborn life was associated with a decreased water content in all arteries ranging from 0.6% (Com) to 2.3% (Bas), no change in the relative content of cellular protein, an increase in wall thickness ranging from 4% (MC) to 26% (Com), an increase in maximum contractile tension ranging from 18% (MC) to 82% (Com), an increase in stiffness, an increase in the maximum active stress ranging from 6% (Bas) to 43% (Com), a decrease in the amine-to-potassium ratio (calculated as the maximum response to 10 microM serotonin with 20 microM histamine divided by the maximum response to 122 mM K+) ranging from 8% (Bas) to 51% (Com), and a decrease in the norepinephrine-to-potassium ratio ranging from 2.1% (Bas) to 56% (Com). Thus developmental changes associated with the transition from fetal to newborn life were much more pronounced in the larger, more proximal Com than in the smaller, more distal cerebral arteries, suggesting that, at term, the cerebral arteries are more mature both functionally and structurally than the Com arteries. Similarly, the transition from newborn to adult life was associated with much greater changes in Com characteristics than with those of the cerebral arteries. These studies demonstrate that the effects of aging vary considerably along the cerebrovascular tree and that conclusions based on developmental studies of large systemic arteries cannot be freely extrapolated to the smaller arteries of the circle of Willis.

The Johns Hopkins Hospital

The role of The Johns Hopkins University as an innovative school with a basic mission of scientific research is discussed. Its principle that research is best performed by faculty and students at a graduate level gave birth to the revolutionary concept of a research university. Against this background, the hospital and later the medical school were founded. The innovations that emerged from this medical education structure are touched on.

Interstitial delivery of dexamethasone in the brain for the reduction of peritumoral edema

Controlled-release polymers have facilitated the interstitial delivery of drugs within the central nervous system. In the present study, dexamethasone was incorporated into ethylene-vinyl acetate polymers, which were then implanted adjacent to a 9L gliosarcoma in the brain of Fischer 344 rats. The effect of interstitial delivery of dexamethasone on peritumoral edema was assessed and compared to the effect of dexamethasone delivered systemically. Eighty-five rats underwent intracranial implantation of the 9L gliosarcoma. Five days later, the animals were randomly assigned to one of four treatment groups: Group 1 received intracranial implantation of controlled-release polymers containing dexamethasone; Group 2 received intraperitoneal implantation of controlled-release polymers containing dexamethasone; Group 3 received serial intraperitoneal injections of dexamethasone; and Group 4 received sham treatment. The animals were sacrificed 3 days after initiation of therapy and their brains were removed for measurement of the water content (edema) in the tumor-bearing and contralateral hemispheres. Brain and plasma samples were analyzed by reverse-phase high-performance liquid chromatography to determine the tissue and plasma concentrations of dexamethasone. Measurement of the release kinetics of dexamethasone from the ethylene-vinyl acetate polymers in an in vitro system showed that the drug was released in a controlled, tapering fashion. During the first 3 days of controlled release in vitro, 330 micrograms of a total content of 7.5 mg of dexamethasone was released into the medium. Analysis of tissue for drug levels demonstrated, however, that the interstitial delivery of this fractional amount of dexamethasone within the brain resulted in levels 19 times higher than those achieved by administering the full dose of 7.5 mg systemically over a 3-day period. Conversely, the systemic administration of dexamethasone resulted in plasma levels 16 times higher than those measured in the interstitial delivery of dexamethasone in the brain. Brain-water content determinations showed that the interstitial controlled release of the fractional amount of dexamethasone within the brain was as effective in controlling peritumoral edema as systemic administration of the full dose by serial intraperitoneal injections. The study demonstrates the following: 1) controlled-release polymeric carriers deliver biologically active dexamethasone in a sustained fashion; 2) very high concentrations of dexamethasone in brain tissue can be achieved using interstitial polymer-mediated drug delivery while minimizing plasma concentrations of this drug which are sometimes associated with serious systemic side effects; and 3) peritumoral brain edema can be effectively treated by the interstitial delivery of dexamethasone directly within the tumor bed.

Failed back surgery syndrome: 5-year follow-up in 102 patients undergoing repeated operation

The indications for repeated operation in patients with persistent or recurrent pain after lumbosacral spine surgery are not well established. Long-term results have been reported infrequently, and in no case has mean follow-up exceeded 3 years. We report 5-year mean follow-up for a series of repeated operations performed between 1979 and 1983. Patient characteristics and modes of treatment have been assessed as predictors of long-term outcome. One hundred two patients with "failed back surgery syndrome" (averaging 2.4 previous operations), who underwent a repeated operation for lumbosacral decompression and/or stabilization, were interviewed by a disinterested third party a mean of 5.05 years postoperatively. Successful outcome (at least 50% sustained relief of pain for 2 years or at last follow-up, and patient satisfaction with the result) was recorded in 34% of patients. Twenty-one patients who were disabled preoperatively returned to work postoperatively; 15 who were working preoperatively became disabled or retired postoperatively. Improvements in activities of daily living were recorded, overall, as often as decrements. Loss of neurological function (strength, sensation, bowel and bladder control) was reported by patients more often than improvement. Most patients reduced or eliminated analgesic intake. Statistical analysis (including univariate and multivariate logistic regression) of patient characteristics as prognostic factors showed significant advantages for young patients and for female patients. Favorable outcome also was associated with a history of good results from previous operations, with the absence of epidural scar requiring surgical lysis, with employment before surgery, and with predominance of radicular (as opposed to axial) pain.(ABSTRACT TRUNCATED AT 250 WORDS)

Dorsal root ganglionectomy for failed back surgery syndrome: a 5-year follow-up study

Dorsal root ganglionectomy has been suggested as a method for the treatment of chronic intractable radicular pain, with theoretical advantages over dorsal rhizotomy, which does not interrupt ventral root afferents. The indications for these procedures in patients with persistent pain following lumbosacral spine surgery are not well established. Long-term results have been reported infrequently, and no published series has a mean follow-up period of more than 30 months. The authors have reviewed their experience with a series of 13 patients with failed back surgery syndrome, in whom dorsal root ganglionectomy was performed. Patients were selected on the basis of clinical presentation and diagnostic root blocks suggesting a monoradicular pain syndrome. Follow-up data were obtained at a mean of 5.5 years following dorsal root ganglionectomy. Follow-up interviews to assess outcome were conducted by a disinterested third party. Treatment "success" (at least 50% sustained relief of pain and patient satisfaction with the result) was recorded in two patients at 2 years after surgery and in none at 5.5 years. Equivocal success (at least 50% relief, without clearcut patient satisfaction) was recorded in one patient at 2 and at 5.5 years postoperatively. Improvements in activities of daily living were recorded in a minority of patients. Loss of sensory and motor function was reported frequently by patients. A minority of patients had reduced or eliminated analgesic intake. These results suggest that dorsal root ganglionectomy has a limited role in the management of failed back surgery syndrome, and that methods to select patients to receive this procedure should be refined or alternative approaches should be considered.

Effect of light/dark cycles on expression of nitrate assimilatory genes in maize shoots and roots

The level of nitrate reductase (NR) and nitrite reductase (NiR) varied in both shoot and root tissue from nitrate-fed Zea mays L. grown under a 16-hour light/8-hour dark regime over a 10-day period postgermination, with peak activity occurring in days 5 to 6. To study the effect of different light regimes on NR and NiR enzyme activity and mRNA levels, 6-day-old plants were grown in the presence of continuous KNO(3) (10 millimolar). Both shoot NRA and mRNA varied considerably, peaking 4 to 8 hours into the light period. Upon transferring plants to continuous light, the amplitude of the peaks increased, and the peaks moved closer together. In continuous darkness, no NR mRNA or NR enzyme activity could be detected by 8 hours and 12 hours, respectively. In either a light/dark or continuous light regime, root NRA and mRNA did not vary substantially. However, when plants were placed in continuous darkness, both declined steadily in the roots, although some remained after 48 hours. Although there was no obvious cycling of NiR enzyme activity in shoot tissue, changes in mRNA mimicked those seen for NR mRNA. The expression of NR and NiR genes is affected by the light regime adopted, but light does not have a direct effect on the expression of these genes.

Fifteen years of transcutaneous electrical stimulation for pain control

Transcutaneous electrical stimulation was reintroduced into medical practice in the early 1970s. Since that time, numerous studies, both controlled and uncontrolled, have suggested its utility for the treatment of pain related to acute musculoskeletal injury, postoperative pain, pain of peripheral vascular origin, pain of myocardial ischemia and chronic pain of a variety of causes. Pain of labor in delivery is affected equivocally. Pain complicating cancer has not been reliably relieved. A small number of controlled studies fail to demonstrate benefit, but the preoponderance of evidence suggests that electrical stimulation of the peripheral nervous system is a useful adjunct in the management of many pain states. Most studies indicate that the resultant analgesia is not opioid-dependent. Pain threshold and perception both appear to be reduced. The physiological mechanism by which pain is affected is not defined; local neural blockade, branch block in the dorsal horn and activation of a central inhibitory system have all been postulated.

Surgical resection of intrinsic brain stem lesions: an overview

A major limitation to the effective treatment of intrinsic mass lesions of the brain stem has been the inability to clearly define the pathological anatomy radiographically. The improved soft tissue resolution offered by magnetic resonance imaging, as compared with axial computed tomography, now makes it possible not only to accurately distinguish anatomical relationships, but also to predict the pathological nature of the lesion. Accordingly, we have been encouraged to pursue a more aggressive approach to intrinsic lesions of the brain stem that appear well circumscribed on magnetic resonance imaging scan. The object of this paper is to report the successful treatment of four intrinsic lesions of the brain stem and to present an overview of the relevant published experience.

Pseudarthrosis of the cervical spine after anterior arthrodesis. Treatment by posterior nerve-root decompression, stabilization, and arthrodesis

Nineteen consecutive patients who had a symptomatic pseudarthrosis after a failed anterior cervical arthrodesis were treated by a posterior nerve-root decompression and arthrodesis. The indications for the operation were radiculopathy in the absence of myelopathy and evidence of a pseudarthrosis on lateral flexion and extension radiographs. The average duration of follow-up was forty-four months (range, twenty-four to fifty-four months). A solid fusion was achieved in all patients, and the radiculopathy was relieved in all but one. The motor weakness that had been present in four patients preoperatively resolved completely.

Stabilization of nitrate reductase in maize roots by chymostatin

Nitrate reductase (NR) in maize (Zea mays cv W64A x W182E) roots has been stabilized in vitro by the addition of chymostatin to extraction buffer. Contrary to previous observations, levels of NR were higher in the mature root than in root tip sections when chymostatin was included in the extraction buffer. Two forms of NR were identified, an NADH monospecific NR found mainly in the 1cm root tip and an NAD(P)H bispecific NR found predominantly in mature regions of the root. During the first 10 days of seedling growth, NR activity in the root ranged from 50 to 80% of the activities found in the leaf (a maximum of 2.4 micromoles NO(-) (2) produced per hour per gram fresh weight was measured at 4 days).

The molecular basis of brain injury and brain edema: the role of oxygen free radicals

This review article outlines basic concepts and pathophysiological aspects of the chemistry of oxygen free radicals in all forms of brain injury and brain edema. Recent experimental studies have demonstrated that oxygen free radicals may be important mediators of brain injury and brain edema, and pharmacological antagonism of oxygen free radicals shows beneficial therapeutic results. A number of fundamental questions need to resolved, and advanced techniques for detecting oxygen free radicals will be needed. No clinical data are available, but oxygen free radical scavengers may possibly become a critical therapeutic modality for brain injury and brain edema.

Three-dimensional CT imaging in postsurgical "failed back" syndrome

One hundred consecutive patients with postsurgical "failed back" syndrome (PSFBS) without fusion and 100 patients with PSFBS with fusion were evaluated with direct CT, two-dimensional (2D) multiplanar, and three-dimensional (3D) imaging. In the patients with and without fusion, 3D images were found to best display the following: the surgical procedure and its extent, lateral neural foraminal narrowing, and fractures of the posterior elements. The 3D images enabled optimal demonstration of fusion: solidity, pseudarthrosis, incorporation of transverse processes and facet joints, and transitional syndrome. In the patients without fusion, 3D images provided improved appraisal of surgical results in 31%; it showed additional fracture(s) in 9%, better displayed lateral neural foraminal narrowing in 42%, and showed additional posterior element fractures in 11% as compared to axial and 2D multiplanar reconstructed (MPR) scans. Three-dimensional imaging uncovered incomplete fusion in 17%, transitional syndrome in 13%, and pseudarthrosis in 6%. Thus, the 3D imaging provided additional information over the direct axial and MPR images (2D images) in 56 of 100 patients without fusion and 76 of 100 patients with fusion. At our institution, this imaging modality is now routinely performed in this patient population.

Acute management of intracranial hemorrhage in patients receiving thrombolytic therapy: case reports

Intracranial hemorrhage is an uncommon complication of antithrombotic therapy. We present two patients who suffered life-threatening intracranial bleeding as a complication of thrombolytic/anticoagulant treatment. Early diagnosis and treatment appear to be crucial factors for survival. We suggest an approach to perioperative management for intracranial hemorrhage resulting from antithrombotic therapy.

Effects of the arachidonate lipoxygenase inhibitor BW755C on traumatic and peritumoural brain oedema

The abstract BW755C is a novel non-steroidal anti-inflammatory agent. It inhibits synthesis of prostaglandins and leukotrienes by inhibition in the cyclooxygenase and lipoxygenase pathways of arachidonic acid metabolism. Cold injury induced vasogenic oedema was produced in 18 cats. The animals were sacrificed at six and twenty-four hours. One group was treated with BW755C. Seventeen white rabbits bearing an experimental brain tumour VX-2 carcinoma were treated for five consecutive days from the eight day after tumour injection to the thirteenth day. Untreated tumour bearing rabbits were used as control. Brain water content was measured by specific gravity method. BW755C did not reduce the water content following cold injury. There was no effect upon peritumoural oedema. The use of this novel blocking agent with diffuse effects in the arachidonic cascade was not beneficial for the reduction or prevention of brain oedema.

Oxygen free radicals in the genesis of peritumoural brain oedema in experimental malignant brain tumours

Disruption of blood brain barrier with increased vascular permeability is associated with genesis of peritumoural oedema. Oxygen free radicals play a role in increased vascular permeability. Recent studies have suggested that tumour cells can produce superoxide radicals and free radical scavengers such as superoxide dismutase (SOD) and catalase in tumour cells are impaired. In this study, we investigated the role of oxygen free radicals in the genesis of peritumoural brain oedema in experimental malignant brain tumours using V x 2 carcinoma cells and 9L glioma cells. In vitro data indicate that the V x 2 carcinoma cell and the 9L glioma cells produce superoxide radicals detected by nitroblue tetrazolium. Electron spin resonance spectroscopy using DMPO as a spin trap demonstrated that SOD activity was significantly lower in subcutaneous larger 9L glioma tumours than in normal brains and 9L glioma brain tumours. In the subcutaneous tumours, SOD activity was lower in the central portion of the tumour than in the peripheral portion of the tumour. In conclusion, we are not sure whether oxygen free radicals are major causative factors of peritumoural brain oedema, but the demonstration of oxygen free radicals in brain tumour cells needs further investigation.

Uncommon tumors of the skull base and uncommon approaches to them

The recognition of a number of uncommon tumors of the skull base is now relatively simple because of three-dimensional computed tomography and magnetic resonance imaging with enhancement. The radiographic classification of these tumors is reviewed, and their treatment is discussed. Although the basic approach to these tumors is the same--radical surgery with decompression of neural and vascular structures--the authors present various operative techniques for gaining access to and removing these tumors. They also examine the role of radiotherapy in supplementing surgical treatment.

Oxygen-free radicals in traumatic brain oedema

Oxygen-free radicals have been implicated as causative factors in ischaemic and traumatic processes. Oxygen-free radical scavengers can be used potentially to treat brain oedema. We investigated the effects of superoxide dismutase and dimethylthiourea on brain oedema. Vasogenic brain oedema was produced in 44 cats by a cortical freezing lesion. Animals were separated into three groups: (1) cold-induced oedema with sacrifice at 6, 24 and 48 h; (2) cold-induced oedema with sacrifice at 6, 24 and 48 h: subgroup A was pretreated with 10,000 u./kg polyethylene glycol and superoxide dismutase; subgroup B received a bolus injection of free superoxide dismutase (4 mg/kg) and then 1 mg/kg/min for 20 min; (3) cold-induced oedema with sacrifice at 6 and 24 h: this group was pretreated with 500 mg/kg dimethylthiourea. Brain water content was measured by the specific gravity method. Detection of superoxide radicals was carried out by the direct cortical application of nitroblue tetrazolium. Free and polyethylene glycol-superoxide dismutase did not prevent the development of brain oedema, but superoxide radicals were detected in the cold lesion. Dimethylthiourea prevented the development of brain oedema in the white matter adjacent to the lesion at 6 h but not at 24 h. These findings indicate that oxygen-free radicals are generated by the brain following cold injury and the demonstration of these radicals offers an important clue in the genesis of traumatic brain oedema.

A century of change in neurosurgery at Johns Hopkins: 1889-1989

Neurosurgical admissions to The Johns Hopkins Hospital during the first year of its existence, the first and last years of Harvey Cushing's practice, the last years of Walter Dandy's practice, the last years of Earl Walker's tenure, and the current neurosurgical case load are reviewed. Sixteen patients with neurosurgical problems were admitted during the first year of the hospital's existence. In the first year of Harvey Cushing's staff appointment, 38 neurosurgical patients were admitted. Infection, trauma, and trigeminal neuralgia were the most common neurosurgical problems at that time. When Harvey Cushing retired in 1912, his practice had grown to 100 operations per year. By the end of Walter Dandy's tenure, the surgical volume was much larger, more than 500 major operations per year. The development of neurosurgery virtually can be mirrored in the practice of neurosurgery under Harvey Cushing and Walter Dandy. From its humble beginnings in the treatment of trauma and infection, neurosurgery has expanded to cover all forms of intracranial disease, virtually every aspect of spinal disease, vascular disease (both intracranial and extracranial), and peripheral nerve injury. The centennial celebration at Johns Hopkins may be considered a centennial for neurosurgery. As we reflect upon our foundations, it is worthwhile to ask what changes we will contribute to the further development of neurosurgery in the next century.

Separation of craniopagus Siamese twins using cardiopulmonary bypass and hypothermic circulatory arrest

Occipitally joined craniopagus Siamese twins were separated with the use of cardiopulmonary bypass and hypothermic circulatory arrest. The 7-month-old infants shared a large sagittal venous sinus that precluded conventional neurosurgical approach because of risk of exsanguination and air embolism. After craniotomy and preliminary exposure of the sinus, each twin underwent sternotomy and total cardiopulmonary bypass with deep hypothermia. Hypothermic circulatory arrest allowed safe division and subsequent reconstruction of the sinus remnants. Several unusual problems were encountered, including transfusion of a large blood volume from one extracorporeal circuit to the other through the common venous sinus, deleterious warming of the exposed brain during circulatory arrest, and thrombosis of both pump oxygenators. Both infants survived, although recovery was complicated in each by neurologic injury, cranial wound infection, and hydrocephalus. This case demonstrates the valuable supportive role of cardiopulmonary bypass and hypothermic circulatory arrest in the management of complex surgical problems of otherwise inoperable patients.

Protective effect of the iron chelator deferoxamine on cold-induced brain edema

Oxygen free radicals such as superoxide radical and iron-catalyzed hydroxyl radical generated by the superoxide system have been implicated in the genesis of brain edema. Therefore, deferoxamine (DFO), an iron chelator, could potentially be used to treat brain edema. To examine this hypothesis, vasogenic brain edema was produced in 48 cats by a cortical freezing lesion. The animals were separated into three groups: Group 1 comprised 14 cats that received no DFO and were sacrificed at 6 or 24 hours; Group 2 consisted of 12 cats that were treated with DFO (50 mg/kg/ml, intravenously) at 15 minutes before the lesion was made and 60 minutes later and were sacrificed at 6 or 24 hours; and Group 3 included 12 cats that were treated with DFO (50 mg/kg/ml, intravenously) at 15 minutes after the lesion was produced and 60 minutes later and were sacrificed at 6 or 24 hours. The effect of DFO on arterial blood pressure was also studied in the remaining 10 cats. Brain water content in eight sampling areas was measured by the specific gravity method. Blood-brain barrier disruption was assessed by spread of Evans blue dye with planimetry. Specific gravity values at 6 and 24 hours were significantly higher in Group 2 than in Group 1 animals. Areas of Evans blue dye extravasation at 6 and 24 hours were significantly reduced in Group 2 relative to Group 1. Group 3 cats showed improvement in specific gravity values and Evans blue extravasation at 6 hours, but not at 24 hours. The iron chelator DFO prevented early development of brain edema; thus, this oxygen free radical scavenger may provide a foundation for a new therapy for brain edema.

Hemodynamic effects of intravenous lecithin-based perfluorocarbon emulsions in dogs

We evaluated and compared the acute hemodynamic effects of perfluorooctylbromide-100% (PFOB), a fluorocarbon emulsified in lecithin without pluronic-F68 (F68), to those of a standard iodinated contrast agent, renografin-76% (R76), and Fluosol-DA 20% (Fluosol), a fluorocarbon emulsified in part by F68. Five open chest dogs were instrumented to evaluate hemodynamic changes after iv injection of PFOB (1 ml.1 g/kg) and R76 (1 ml.0.37 g of iodine/kg). Fluosol (1 ml.0.2 g/kg) was given to two of the five dogs at the end of their study. Fluosol caused transient hemodynamic collapse in both dogs. R76 caused the known transient effect of hypotension (-15.4 +/- 3.3%) followed by hypertension (6.5 +/- 2.7%) and an increase in aortic flow (29.3 +/- 3.9% at 30 sec). PFOB caused minimal, clinically insignificant decrease in aortic flow (4 +/- 1% at 10 sec).