Pharmacodynamics and effectiveness of topical nitroglycerin at lowering blood pressure during autonomic dysreflexia

STUDY DESIGN

Secondary analysis of prospectively collected observational data assessing the safety of an autonomic dysreflexia (AD) management protocol.

OBJECTIVES

To estimate the time to onset of action, time to full clinical effect (sustained systolic blood pressure (SBP) <160 mm Hg) and effectiveness of nitroglycerin ointment at lowering blood pressure for patients with spinal cord injuries experiencing AD.

SETTING

US Veterans Affairs inpatient spinal cord injury (SCI) unit.

METHODS

Episodes of AD recalcitrant to nonpharmacologic interventions that were given one to two inches of 2% topical nitroglycerin ointment were recorded. Pharmacodynamics as above and predictive characteristics (through a mixed multivariate logistic regression model) were calculated.

RESULTS

A total of 260 episodes of pharmacologically managed AD were recorded in 56 individuals. Time to onset of action for nitroglycerin ointment was 9-11 min. Time to full clinical effect was 14-20 min. Topical nitroglycerin controlled SBP <160 mm Hg in 77.3% of pharmacologically treated AD episodes with the remainder requiring additional antihypertensive medications. A multivariate logistic regression model was unable to identify statistically significant factors to predict which patients would respond to nitroglycerin ointment (odds ratios 95% confidence intervals 0.29-4.93). The adverse event rate, entirely attributed to hypotension, was 3.6% with seven of the eight events resolving with close observation alone and one episode requiring normal saline.

CONCLUSIONS

Nitroglycerin ointment has a rapid onset of action and time to full clinical effect with high efficacy and relatively low adverse event rate for patients with SCI experiencing AD.

Risk factors for osteoporotic fractures in persons with spinal cord injuries and disorders

Clinical risk factors for fracture were explored among Veterans with a spinal cord injury. At the end of 11 years of follow-up, the absolute risk of fracture was approximately 20 %. Among the clinical and SCI-related factors explored, a prior history of fracture was strongly associated with incident fracture.

INTRODUCTION

Few studies to date have comprehensively addressed clinical risk factors for fracture in persons with spinal cord injury (SCI). The purpose of this study was to identify risk factors for incident osteoporotic fractures in persons with a SCI that can be easily determined at the point of care.

METHODS

The Veteran's Affairs Spinal Cord Dysfunction Registry, a national database of persons with a SCI, was used to examine clinical and SCI-related risk factors for fracture. Incident fractures were identified in a cohort of persons with chronic SCI, defined as SCI present for at least 2 years. Cox regression models were used to estimate the risk of incident fractures.

RESULTS

There were 22,516 persons with chronic SCI included in the cohort with 3365 incident fractures. The mean observational follow-up time for the overall sample was 6.2 years (median 6.0, IQR 2.9-11.0). The mean observational follow-up time for the fracture group was 3.9 years (median 3.3, IQR 1.4-6.1) and 6.7 years (median 6.7, IQR 3.1-11.0) for the nonfracture group. By the end of the study, which included predominantly older Veterans with a SCI observed for a relatively short period of time, the absolute (i.e., cumulative hazard) for incident fractures was 0.17 (95%CI 0.14-0.21). In multivariable analysis, factors associated with an increased risk of fracture included White race, traumatic etiology of SCI, paraplegia, complete extent of SCI, longer duration of SCI, use of anticonvulsants and opioids, prevalent fractures, and higher Charlson Comorbidity Indices. Women aged 50 and older were also at higher risk of sustaining an incident fracture at any time during the 11-year follow-up period.

CONCLUSIONS

There are multiple clinical and SCI-related risk factors which can be used to predict fracture in persons with a SCI. Clinicians should be particularly concerned about incident fracture risk in persons with a SCI who have had a previous fracture.

Development and validation of a computerized algorithm for International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI)

STUDY DESIGN

Validation study.

OBJECTIVES

To describe the development and validation of a computerized application of the international standards for neurological classification of spinal cord injury (ISNCSCI).

SETTING

Data from acute and rehabilitation care.

METHODS

The Rick Hansen Institute-ISNCSCI Algorithm (RHI-ISNCSCI Algorithm) was developed based on the 2011 version of the ISNCSCI and the 2013 version of the worksheet. International experts developed the design and logic with a focus on usability and features to standardize the correct classification of challenging cases. A five-phased process was used to develop and validate the algorithm. Discrepancies between the clinician-derived and algorithm-calculated results were reconciled.

RESULTS

Phase one of the validation used 48 cases to develop the logic. Phase three used these and 15 additional cases for further logic development to classify cases with 'Not testable' values. For logic testing in phases two and four, 351 and 1998 cases from the Rick Hansen SCI Registry (RHSCIR), respectively, were used. Of 23 and 286 discrepant cases identified in phases two and four, 2 and 6 cases resulted in changes to the algorithm. Cross-validation of the algorithm in phase five using 108 new RHSCIR cases did not identify the need for any further changes, as all discrepancies were due to clinician errors. The web-based application and the algorithm code are freely available at www.isncscialgorithm.com.

CONCLUSION

The RHI-ISNCSCI Algorithm provides a standardized method to accurately derive the level and severity of SCI from the raw data of the ISNCSCI examination. The web interface assists in maximizing usability while minimizing the impact of human error in classifying SCI.

SPONSORSHIP

This study is sponsored by the Rick Hansen Institute and supported by funding from Health Canada and Western Economic Diversification Canada.

Morbidity following lower extremity fractures in men with spinal cord injury

The Veterans Affairs Spinal Cord Dysfunction Registry from 2002 to 2007 was reviewed to determine whether men with spinal cord injury (SCI) and lower extremity fractures had an increased risk of complications compared to those without fractures. We determined that fractures are associated with significant consequences, particularly during the first month postfracture.

INTRODUCTION

Despite increasing longevity, patients with SCI have a substantial number of illnesses and comorbid conditions. Lower extremity fractures are frequent events in these patients. However, whether these fractures are associated with any increased risk of complications in SCI is not certain. The purpose of this report was to determine the impact of lower extremity fractures on morbidities in men with SCI.

METHODS

A population-based, nested, case-control (1,027 cases and 1,027 propensity-matched controls) of men enrolled in the Veterans Affairs Spinal Cord Dysfunction Registry from fiscal years 2002 to 2007 was reviewed to determine whether lower extremity fractures were associated with an increased risk for complications.

RESULTS

In propensity score models matched for demographic (age, race) and SCI-related injury factors (level/completeness of SCI), Veterans Affairs-service connection status, and comorbidities, at 1 month following the fracture, there was an increased risk for respiratory infections, pressure ulcers, urinary tract infections, thromboembolic events, depression, and delirium (p ≤ 0.03 for all). Over 12 months, the only complication more common in fracture cases was pressure ulcers (p < 0.01), with an absolute difference of less than 2 % when compared to controls. There was no significant increased risk of cardiac arrhythmias at any time examined following fracture (≥0.12).

CONCLUSIONS

Lower extremity fractures are associated with significant consequences in men with SCI during the first month postfracture, but they do not persist for a long term, except for pressure ulcers. Targeted interventions to prevent complications should be considered following lower extremity fractures in SCI, particularly in the first month following fracture.

Bloodstream infections and setting of onset in persons with spinal cord injury and disorder

STUDY DESIGN

A retrospective cohort study.

OBJECTIVE

Health-care-associated (HCA) bloodstream infection (BSI) has been shown to be a distinct epidemiologic category in the general adult population, but few studies have examined specific patient populations. The objective of this study was to assess characteristics associated with BSI that occurred in the hospital (hospital-acquired, HA BSI), from health-care contact outside the hospital (HCA BSI) or in the community (community-acquired, CA BSI) in veterans with spinal cord injury and disorder (SCI&D).

SETTING

Two United States Department of Veterans Affairs hospitals.

METHODS

All patients with SCI&D with a positive blood culture admitted to study hospitals over a 7-year period (1 October 1997 to 30 September 2004). Demographics, medical characteristics and causative organisms were collected.

RESULTS

Four hundred and thirteen episodes of BSI occurred in 226 patients, with a rate of 7.2 BSI episodes per 100 admissions: 267 (64.7%) were HA BSI, 110 (26.6%) were HCA BSI and 36 (8.7%) were CA BSI. Antibiotic resistance was more common in those with HA BSI (65.5%) compared with that in those with HCA (49.1%, P=0.001) and CA BSI (22.2%, P<0.0001). Methicillin resistance in Staphylococcus aureus was highly prevalent; HA BSI (84.5%), HCA BSI (60.6%) and CA BSI (33.3%).

CONCLUSION

HCA BSI comprises one-quarter of all BSIs in hospitalized patients with SCI&D. Although those with HCA and CA BSI share similarities, several differences in medical characteristics and causal microorganism are noted. Treatment and management strategies for HCA and CA infections need to vary.

Management of community-acquired pneumonia in persons with spinal cord injury

STUDY DESIGN

Retrospective case series.

OBJECTIVES

Respiratory disorders are the leading cause of death in persons with spinal cord injury (SCI), but the epidemiology and medical management of pneumonia in persons with chronic SCI is not well characterized. We describe the clinical presentation of persons with SCI with community-acquired pneumonia (CAP), characterize its management and compare practice to recommendations for CAP in the general population.

SETTING

Three United States Veterans Affairs Medical Centers with specialized SCI services.

METHODS

Chart abstraction was performed for all persons with chronic SCI seen at participating centers for treatment of CAP during a 2-year period. Collected data included presenting signs and symptoms, laboratory and imaging results, initial antibiotic therapy, secretion mobilization techniques, in-patient vs outpatient management, length of stay, and mortality.

RESULTS

In all, 41 persons with SCI received treatment for CAP during the study period. A total of 32 (78.0%) patients were admitted for treatment; two (4.8%) required intubation and mechanical ventilation. Initial antibiotic coverage met guideline recommendations for only half of inpatients and infrequently provided adequate antipseudomonal coverage. Microbiologic testing was performed on 26 cases (63.4%) and demonstrated a specific pathogen in only five cases (12.2% of total). Three cases (7.3%) died during treatment for CAP, and 16 (42.1%) of 38 CAP survivors died within a median follow-up of 3 years.

CONCLUSION

The majority of chronic SCI patients who present to specialized SCI centers with CAP are admitted for treatment. Short-term mortality is comparable to CAP in the general population.

Lactate supply as a determinant of the distribution of intracellular pH within the hepatic lobule

When isolated livers from starved rats are perfused with lactate at constant perfusate pH and P(co(2)), there is a marked gradient of cell pH (pH(i)) along the length of the lobular radius, with periportal cells being substantially more alkaline than perivenous cells. In the present studies, the perivenous 21% of the lobular volume was destroyed by retrograde digitonin perfusion, and antegrade perfusion restored. pH(i) was determined by (31)P-NMR. The remaining periportal cells, the site of gluconeogenesis from lactate, had a substantially higher mean pH(i) (7.42) than did the intact liver (7.23). When lactate was removed from the perfusate, mean pH(i) decreased to 7.25. The corresponding concentration of cell bicarbonate fell with a half-time of approximately 5 min. When lactate was re-introduced mean pH(i) rose to 7.34. We conclude that a major contributor to periportal alkalinity under these conditions is proton consumption during gluconeogenesis from lactate ions.

Factors associated with sleep apnea in men with spinal cord injury: a population-based case-control study

OBJECTIVE

To characterize a population of spinal cord injury (SCI) patients with sleep apnea, and to determine associated factors and comorbidities.

STUDY DESIGN

Population-based retrospective case-control study.

SUBJECTS

584 male patients served by a Veterans Affairs SCI service.

MEASURES

Medical records were reviewed for sleep apnea diagnosis, demographic information, neurologic characteristics, and treatments received. Sleep study reports were not available to determine the nature of abnormal respiratory events (ie central, obstructive, hypoventilation). For each case with tetraplegia, a control tetraplegic subject without sleep apnea diagnosis was selected.

RESULTS

We identified 53 subjects with diagnosed sleep apnea: 42 tetraplegic, 11 paraplegic. This represented 14.9% of all tetraplegic and 3.7% of all paraplegic patients in the population (P<0.0001 for comparison of tetraplegic and paraplegic proportions). In tetraplegic subjects, sleep apnea was associated with obesity and more rostral motor level, but not with ASIA Impairment Scale. Medical comorbidities associated with sleep apnea in non-SCI patients, such as hypertension, were more common in case subjects. Less than half of case subjects were receiving some form of treatment. For motor-complete tetraplegics, long-term positive airway pressure treatment was less common with motor level C5 and above compared to C6 and below.

CONCLUSION

In this population, sleep apnea has been frequently diagnosed, particularly in tetraplegic subjects. The true prevalence is likely to be considerably higher, since this study considered only previously diagnosed cases. Sleep apnea was associated with obesity and higher neurologic level, but not ASIA Impairment Scale. Medical comorbidities were more frequent in this group, and treatment acceptance was poor with higher level motor-complete injuries. Since the type of sleep apnea (central or obstructive) was not distinguished, we cannot comment on the prevalence and associations based on specific types of sleep apnea.

Clinician judgments of functional outcomes: how bias and perceived accuracy affect rating

OBJECTIVE

To evaluate the accuracy of clinician judgments of patient function, the susceptibility of judges to bias, and the relation between a judge's degree of belief in his/her accuracy of classification to observed accuracy when using the FIM instrument.

PARTICIPANTS

Fifty rehabilitation professionals.

SETTING

3 urban medical centers.

DESIGN

Four randomized experiments among subjects to examine the effect of potentially biasing information on FIM ratings of patient vignettes. Participants answered 60 true/false questions regarding patient function and FIM score and indicated confidence in the accuracy of their answers.

INTERVENTIONS

Manipulation of patient information.

MAIN OUTCOME MEASURES

The standard FIM 7-point scale, observed proportion of correct responses to the 60 true/false questions, and a 6-category confidence scale for each of the 60 questions were used as dependent measures.

RESULTS

FIM ratings assigned to others biased participants' FIM ratings of patient vignettes. Functional ability was overestimated when ratings in other domains were high and underestimated when they were low. Participants were overconfident in their ability to answer FIM questions accurately across all professional disciplines.

CONCLUSION

Bias and poor judgment of level accuracy play a significant role in clinician ratings of patient functioning. Blind ratings and training in debiasing are potential solutions to the problem.

Neurological worsening due to infection from renal stones in a multiple sclerosis patient

Symptomatic bladder dysfunction occurs in the majority of patients with multiple sclerosis (MS). Although guidelines have been established for diagnosis and management of bladder dysfunction in these patients, they are sometimes overlooked in the primary care setting, leading to severe, life threatening complications. A 64-year-old male with a 31-year history of spastic quadriparetic MS and neurogenic bladder dysfunction managed with an indwelling catheter, presented to the hospital with worsening neurological function. He had developed increased weakness and cognitive impairment several weeks after being treated for a urinary tract infection (UTI). He had become unable to perform any activities of daily living or drive his power wheelchair. After an extensive work-up, he was found to have a large (14 x 18 x 30 cm) retroperitoneal abscess and multiple renal stones, including a large obstructing calculus in the collecting system near the ureteropelvic junction, and he underwent nephrectomy and abscess drainage. Of note, he had been found to have multiple renal stones and hydronephrosis on renal ultrasound 3 years earlier, but he had received no treatment. Following drainage of the abscess, his upper extremity neurological function returned to baseline, his cognitive status improved, and he regained the ability to perform activities of daily living. Patients with paralysis from MS, much like those with traumatic spinal cord injuries, are at grave risk of mortality and morbidity from undiagnosed and under-treated urinary complications. This case demonstrates that evaluation and appropriate treatment for complications of neurogenic bladder should be part of routine care for patients with MS. Current recommendations for evaluation and management of bladder dysfunction in patients with MS will be reviewed.

Sleep apnea syndrome in chronic spinal cord injury: associated factors and treatment

OBJECTIVE

To determine the prevalence of sleep apnea in a sample of persons with chronic spinal cord injury (SCI) of varying injury levels and degrees of impairment.

DESIGN

Cross-sectional study.

SETTING

Inpatient SCI rehabilitation unit.

PARTICIPANTS

Twenty men with SCI (motor complete and incomplete; American Spinal Injury Association classes A-D) of at least 1 year's duration, randomly selected from patients with SCI undergoing elective hospitalization.

MAIN OUTCOME MEASURES

Apnea index, determined by sleep study (including chest wall movement, airflow, oxygen saturation), and daytime sleepiness, determined by Epworth sleepiness score.

RESULTS

Eight subjects (40%) had sleep apnea, manifested by elevated apnea index (mean +/- SD, 17.1 +/- 6.9) and excessive daytime sleepiness. Sleep apnea was commonly diagnosed in motor-incomplete injuries. A trend (p = .07) existed toward a greater prevalence of sleep apnea with tetraplegia. Age and body mass index were not associated with sleep apnea.

CONCLUSION

The prevalence of sleep apnea in men with chronic SCI admitted for nonrespiratory elective hospitalization is high relative to the general population.

Investigation of human low-density lipoprotein by (1)H nuclear magnetic resonance spectroscopy: mobility of phosphatidylcholine and sphingomyelin headgroups characterizes the surface layer

The resolution of the trimethyl headgroup resonance of phosphatidylcholine (PC) and sphingomyelin (SM) in the intact human low-density lipoprotein (LDL) (1)H NMR spectrum at 600 MHz enabled the investigation of LDL surface structure and phospholipid-apoB interactions. We have previously shown that a higher proportion of PC headgroups (25-35% of total PC in LDL) compared to SM were tightly bound to apoB and therefore NMR-invisible [Murphy, H. C., et al. (1997) Biochem. Biophys. Res. Commun. 234 (3), 733-737]. In the present study, we have investigated the mobility of phospholipid (PL) headgroups, using (1)H NMR spin-spin (T(2)) relaxation measurements, in LDL isolated from nine volunteers. We show that both PC and SM exist in two additional and distinct environments indicated by the biexponential behavior of the relaxation decays in each case. The data showed that 36% of PC headgroups had a short T(2) component, mean T(2) of 31 ms, and 64% had a longer T(2) component of 54 ms. Approximately 15% of SM headgroups had a short T(2) component (mean T(2) of 27 ms) and 85% had a longer T(2) component of 78 ms. Therefore the majority of SM headgroups (85%) were more mobile than PC (P < 0.001) and since PC headgroups in organic media were more mobile than SM, we conclude that the characteristic high mobility of LDL SM is not an intrinsic property but arises from a high degree of order in molecular packing of the surface PL of human LDL. We suggest that because PC and SM interact differentially with cholesterol and possibly with neighboring phospholipids, this results in the formation of relatively long-lived microdomains of PL in vivo.

Hepatic intralobular mapping of fructose metabolism in the rat liver

Detailed mapping of glucose and lactate metabolism along the radius of the hepatic lobule was performed in situ in rat livers perfused with 1.5 mM lactate before and during the addition of 5 mM fructose. The majority of fructose uptake occurred in the periportal region; 45% of fructose taken up in the periportal half of the lobular volume being converted into glucose. Periportal lactate uptake was markedly decreased by addition of fructose. Basal perivenous lactate output, which was derived from glucose synthesized periportally, was increased in the presence of fructose. During fructose infusion there was a small decrease in cell pH periportally, but acidification of up to 0.5 pH units perivenously. The evidence suggests that in situ the apparent direct conversion of fructose into lactate represents, to a substantial extent, the result of periportal conversion of fructose into glucose and the subsequent uptake and glycolysis to lactate in the perivenous zone of some of that glucose. (31)P NMR spectroscopy showed that the cellular concentration of phosphomonoesters changes very little periportally during fructose infusion, but there was an approximate twofold increase perivenously, presumably due to the accumulation of fructose 1-phosphate. It may be inferred that fructokinase activity is expressed throughout the hepatic lobule.

Fetal programming of hepatic lobular architecture in the rat demonstrated ex vivo with magnetic resonance imaging

We demonstrate that MRI imaging at sub-millimetre resolution can distinguish between periportal and perivenous zones of the rat liver lobule. This made it possible to measure the hepatic lobular radius in ex-vivo perfused fixed livers using MRI. Comparisons of histomorphometric and MRI measurements of lobular radius were in good agreement, although MRI measurements were significantly smaller (P< 0.001). Male rats whose mothers were fed 40% of the protein of controls during gestation and lactation, had a significantly larger hepatic lobular radius than that of controls [449+/-11 microm vs. 373+/-9 microm (mean +/- SEM), respectively, p<0.001, n = 12; histomorphometry data]. The proton T(2) in periportal and perivenous zones was mapped both before and after antegrade or retrograde perfusion of 10 ml of digitonin (4 mg ml(-1)). Only the T(2) of the hypointense regions increased significantly following antegrade perfusion of digitonin and conversely only that of the intense regions following retrograde perfusion. Digitonin causes permeabilization of cells in specific hepatic zones, determined by the direction of perfusion. The intense and hypointense regions of the hepatic MR images thus arise from the perivenous and periportal zones of the hepatic lobule, respectively.

Neurologic recovery and neurologic decline after spinal cord injury

Physicians caring for patients with spinal cord injury facilitate neurologic recovery by optimizing nutrition and general health, by coordinating active exercise and functional training to enhance the underlying synapse growth, reversal of muscle atrophy, and motor learning, and by controlling interfering spasticity. SCI physicians also must monitor for neurologic decline during initial rehabilitation and later in life, diagnose promptly and accurately such decline, and orchestrate the appropriate intervention.

Zonation of gluconeogenesis, ketogenesis and intracellular pH in livers from normal and diabetic ketoacidotic rats: evidence for intralobular redistribution of metabolic events in ketoacidosis

The intralobular distribution of metabolism was examined in the livers from rats with severe diabetic ketoacidosis (DKA), perfused at pH 6.8, and compared with that in livers from normal starved animals perfused at either pH 7.4 or 6.8. With lactate and palmitate as substrates, the perivenous uptake of periportally synthesized glucose seen in normal livers at pH 7.4 was abolished during DKA; indeed, gluconeogenesis was most active in the perivenous region. Whereas in normal livers perfused at pH 7.4 the periportal region showed a markedly elevated intracellular pH (pH(i)) compared with the perivenous zone, this distribution of pH(i) was reversed in DKA, with an intermediate distribution in normal livers perfused at pH 6. 8. 3-Hydroxybutyrate was generated throughout the lobule. Some acetoacetate generated periportally was converted to 3-hydroxybutyrate more perivenously. A steep gradient of oxygen uptake along the radius of the lobule was apparent in all three groups; oxygen uptake was greatly decreased perivenously despite adequate oxygen supply. These findings are consistent with our previous observations of the lobular co-location of high pH(i) and gluconeogenesis, and might offer an explanation of how high gluconeogenic rates can continue in spite of severe systemic acidosis in DKA. The findings provide direct evidence for a marked redistribution of intralobular metabolism in DKA.

Physical and psychological predictors of exercise dosage in healthy adults

PURPOSE

The purpose of this study was to examine the exercise dose-response issue in a sample of 121 regular exercisers categorized as relatively low, moderate, or high dosage physical activity participants.

METHODS

Male and female students, faculty, and staff of a midwestern university, currently engaging in various exercise modalities at least two times per week, were assessed on a variety of factors hypothesized to impact one's degree of exercise involvement.

RESULTS

ANOVA procedures indicated that low and high dosage groups differed significantly on the variables of age, exercise history, positive affect, and the locus of causality and stability attributional dimensions. Groups did not differ significantly in terms of body mass index, exercise efficacy, perceptions of either personal or external control over exercise behavior, or negative affective reactions to exercise behavior.

CONCLUSIONS

Taken together, the findings of this study suggest that individuals who exercise at varying doses of physical activity may be differentiated by certain demographic, behavioral, physiological, and psychological variables.

Seating pressures with conventional and dynamic wheelchair cushions in tetraplegia

OBJECTIVE

To compare pressure relief from a dynamic wheelchair cushion to a tilt-in-space wheelchair with conventional cushions.

STUDY DESIGN

Repeated measures analysis.

SETTING AND SUBJECTS

Spinal cord injury unit; 16 tilt-in-space wheelchair users with motor-complete tetraplegia.

MAIN OUTCOME MEASURES

Interface pressure at ischial tuberosities.

RESULTS

Mean ischial pressure with subjects seated upright on the dynamic cushion during the low ischial pressure phase was lower than tilted pressure on the gel cushion, but it was not significantly different from tilted pressure on the dry-flotation cushion (dynamic/upright, 71 mm Hg; gel/tilted, 86 mm Hg; dry-flotation/tilted, 74 mm Hg; p<.05 dynamic vs. gel). Mean ischial pressure with subjects upright on the dynamic cushion during the high ischial pressure phase was significantly greater than the gel/upright and dry-flotation/upright conditions (dynamic/upright, 157 mm Hg; gel/upright, 128 mm Hg; dry-flotation/upright, 111 mm Hg; p<.001).

CONCLUSION

The dynamic cushion produces similar pressure relief over the ischial tuberosities during the low pressure phase to a tilt-in-space wheelchair and conventional cushions. The dynamic cushion may be an alternative to a tilt-in-space wheelchair for some individuals.

Proton NMR spectroscopic analysis of multiple acyl-CoA dehydrogenase deficiency--capacity of the choline oxidation pathway for methylation in vivo

Proton NMR spectra of urine from subjects with multiple acyl-CoA dehydrogenase deficiency, caused by defects in either the electron transport flavoprotein or electron transport flavoprotein ubiquinone oxidoreductase, provide a characteristic and possibly diagnostic metabolite profile. The detection of dimethylglycine and sarcosine, intermediates in the oxidative degradation of choline, should discriminate between multiple acyl-CoA dehydrogenase deficiency and related disorders involving fatty acid oxidation. The excretion rates of betaine, dimethylglycine (and sarcosine) in these subjects give an estimate of the minimum rates of both choline oxidation and methyl group release from betaine and reveal that the latter is comparable with the calculated total body methyl requirement in the human infant even when choline intake is very low. Our results provide a new insight into the rates of in vivo methylation in early human development.

Recovery of ambulation in motor-incomplete tetraplegia

OBJECTIVE

To determine the effect of age and initial neurologic status on recovery of ambulation in patients with motor-incomplete tetraplegia.

STUDY DESIGN

Inception cohort study.

SETTING

Urban, tertiary care hospital with Regional Spinal Cord Injury Center.

PATIENTS

One hundred five patients with American Spinal Injury Association (ASIA) C or D tetraplegia at admission or within 72 hours of injury.

MAIN OUTCOME MEASURE

Ambulatory status at time of discharge from inpatient rehabilitation.

RESULTS

Ninety-one percent (30/33) of ASIA C patients younger than 50 years of age became ambulatory by discharge, versus 42% (13/31) ASIA C patients age 50 or older (p < .0001). All (41/41) patients initially classified as ASIA D became ambulatory by discharge.

CONCLUSION

For patients with ASIA D tetraplegia, prognosis for recovery of independent ambulation is excellent. For patients with ASIA C tetraplegia, recovery of ambulation is significantly less likely if age is 50 years or older.

Gluconeogenesis, glucose handling, and structural changes in livers of the adult offspring of rats partially deprived of protein during pregnancy and lactation

Maternal protein restriction is a model of fetal programming of adult glucose intolerance. Perfused livers of 48-h- starved adult offspring of rat dams fed 8% protein diets during pregnancy and lactation produced more glucose from 6 mM lactate than did control livers from rats whose dams were fed 20% protein. In control livers, a mean of 24% of the glucose formed from lactate in the periportal region of the lobule was taken up by the most distal perivenous cells; this distal perivenous uptake was greatly diminished in maternal low protein (MLP) livers, accounting for a major fraction of the increased glucose output of MLP livers. In control livers, the distal perivenous cells contained 40% of the total glucokinase of the liver; this perivenous concentration of glucokinase was greatly reduced in MLP livers. Intralobular distribution of phosphenolpyruvate carboxykinase was unaltered, though overall increased activity could have contributed to the elevated glucose output. Hepatic lobular volume in MLP livers was twice that in control livers, indicating that MLP livers had half the normal number of lobules. Fetal programming of adult glucose metabolism may operate partly through structural alterations and changes in glucokinase expression in the immediate perivenous region.

Evidence for distinct behaviour of phosphatidylcholine and sphingomyelin at the low density lipoprotein surface

This study demonstrates that the use of high field 1H NMR spectroscopy permits individual detection of phosphatidylcholine and sphingomyelin molecules at the surface of native low density lipoprotein (LDL) particles. Distinct behaviour was observed for the choline head group -N(CH3)3 resonances of these different phospholipids revealing preferential immobilisation for phosphatidylcholine. This suggests the existence of reversible and irreversible phosphatidylcholine-apolipoprotein B interactions and is consistent with microdomain formation at the surface monolayer of LDL. The novel resonance assignment and results show that 1H NMR can provide efficient and practical means for future studies on the structure and dynamics at the LDL surface.

A method for determination in situ of variations within the hepatic lobule of hepatocyte function and metabolite concentrations

A method is described for the production of detailed maps of intralobular variations of hepatocyte function and metabolite concentrations, based on variable destruction by digitonin of the lobule from the centrilobular direction. Instead of the conventional approach, in which isolated hepatocytes are then prepared and studied in suspension, perfusion is continued after digitonin treatment and the function of the unaffected lobular remnants is determined, or mean metabolite concentrations are measured by 31P-NMR. These measurements are plotted against the degree of destruction, determined precisely after each study by automated quantitative histomorphometry. These plots are transformed into curves of the function or metabolite concentration of nominal single cells at any point along the radius of the lobule. Gluconeogenesis from lactate remained stable, although reduced, even after 85-90% lobular destruction, predominated periportally and disappeared by 50% along the radius of the lobule. In 31P-NMR studies, employing 1.5 mM lactate as substrate, narrowing of the intracellular P1 resonance was observed as digitonin destruction increased; this was attributed to a decrease in the intralobular heterogeneity of the intracellular pH, which fell from approx. 7.9 to < 7.4 along the first 16% of the lobular radius (from the periportal end) and to < 7.3 in the remainder of the lobule. The ATP concentration rose, and then fell, along the radius of the lobule in a centripetal direction. The method is potentially generally applicable to a wide range of hepatocellular functions and to the measurement of metabolite concentrations, most conveniently those susceptible to estimation by NMR.

Cerebral energy metabolism in isovaleric acidaemia

A newborn infant with an acute metabolic encephalopathy caused by isovaleric acidaemia had severe impairment of cerebral energy metabolism. This was detected by phosphorus and proton magnetic resonance spectroscopy. After treatment she made excellent clinical recovery, her spectroscopic abnormalities resolved, and she was neurologically normal at the age of 1 year.

Propionylcarnitine excretion is not affected by metronidazole administration to patients with disorders of propionate metabolism

Propionylcarnitine (PC) excretion has been measured during a clinical trial of metronidazole therapy in two patients with propionic acidaemia and two patients with methylmalonic aciduria. All patients were in good metabolic control and were receiving L-carnitine. While total propionate excretion was reduced by up to 40% in all four patients during metronidazole therapy, the excretion of propionylcarnitine remained largely unchanged. PC comprised up to 80% of total propionate excretion in patients with propionic acidaemia.

CONCLUSION

These results suggest an extra-hepatic source and/or differing compartmentation for PC formation from those for the production of other metabolites of propionyl-CoA.

Detection of propan-1,2-diol in neonatal brain by in vivo proton magnetic resonance spectroscopy

Cerebral in vivo proton magnetic resonance spectroscopy of 13 newborn infants displaying seizures and receiving phenobarbitone, in one case supplemented by phenytoin, showed signals from propan-1,2-diol (the injection vehicle for both these anticonvulsants). Subsequent in vitro spectroscopy of cerebro spinal fluid (CSF) from one of these infants also showed signals from this substance. The estimated in vivo propan-1,2-diol concentration (approximately 3 mM) was less than that measured in the CSF sample (14.4 mM). These observations suggest that propan-1,2-diol may accumulate in cerebral tissue and misidentification of its signals in both in vivo and in vitro proton spectra may confuse diagnoses of metabolic or other disorders.

Purchasers look at physician hospital organizations

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An investigation of argininosuccinic acid anhydrides in argininosuccinic acid lyase deficiency by 1H-NMR spectroscopy

Argininosuccinate (ASA) is excreted in large amounts in the urine of patients with argininosuccinate lyase (EC 4.3.2.1) deficiency (ASLD). Previous workers have reported the presence of anhydrides of ASA in the urine of patients with this disorder. We have used 1H-NMR spectroscopy to investigate the presence of these compounds in untreated urine. Our results indicate that the anhydrides were absent from urine and are artifacts produced by the conditions prevailing in the methods of analysis previously used to investigate the urine from patients with ASLD. We have also attempted to reproduce the conditions that might promote the transition to the anhydrides in the urine from a patient with ASLD and in solutions of argininosuccinate. Resolution of ASA and the two anhydrides is possible and a spectrum of the urine from a patient with ASLD shows that the anhydrides are present at below 1% of the total ASA under normal physiological conditions.

Investigation of urea cycle enzyme disorders by 1H-NMR spectroscopy

High resolution proton nuclear magnetic resonance spectroscopy (1H-NMR) has been used to study patients with inborn errors of the urea cycle to evaluate further the diagnostic potential of this technique. The 1H-NMR metabolic profile from the urine of patients with citrullinaemia and argininosuccinic aciduria consistently demonstrated the presence of the diagnostic metabolites citrulline, N-acetylcitrulline and argininosuccinate, respectively. The profile from the urine of patients with ornithine carbamoyl transferase deficiency, is potentially diagnostic, but orotate was only detected in samples from three out of four patients. The characteristic fingerprint that each of the metabolites produces is unlike that of any other we have seen, including analogues of the metabolites which are structurally very similar such as arginine, ornithine and aspartate. The level of excretion of the metabolites from the patients with citrullinaemia and argininosuccinic aciduria has been well within the range of NMR detection.

Responses of retinal and visual pathway potentials of the guinea pig to nitrogen and helium at high pressure

Electroretinographic, optic chiasm, and visual cortex potentials were monitored in the awake guinea pig as nitrogen pressures were raised to 16 ATA and held for 30 min. Pressurization to 90 ATA with helium in 10-ATA increments followed. We sought to (a) quantify the depressant effect of nitrogen on the retina as compared to the central visual pathway, and (b) to test for pressure reversibility. The electroretinogram was reduced approximately 15%, the chiasm potential by 15%, and the cortical response by 32% in 16 ATA nitrogen, and latent periods for the three signals increased an average of 5-8%. Helium at pressure did not restore the amplitude of the electroretinogram or optic chiasm response, but the visual cortex potential returned to control levels near 90 ATA total pressure. Reversal of the nitrogen-induced latency increases by helium was partially effective up to 40 ATA. Control latent periods were not reached. Further attenuation of the electroretinogram and chiasm response amplitudes, and increased latencies of all signals were observed at 50-90 ATA.