Impact of metabolic indices on central artery stiffness: independent association of insulin resistance and glucose with aortic pulse wave velocity

AIMS/HYPOTHESIS

Non-invasive measures of aortic stiffness reflect vascular senescence and predict outcome in diabetes. Glucose-mediated elastic artery sclerosis may play an integral role in the development of macrovascular complications. We used carotid-femoral pulse wave velocity ((cf)PWV) to quantify independent associations of fasting glucose, post-challenge glucose and derived insulin resistance (HOMA-IR) with aortic stiffness.

METHODS

(cf)PWV was measured using a 4 MHz continuous wave Doppler ultrasound probe within groups with newly identified age- and sex-matched normal glucose metabolism (NGM), impaired glucose regulation (IGR) and diabetes mellitus populations (n = 570, mean age 59.1, 56% male).

RESULTS

After multivariate adjustment, IGR and diabetes were associated with significant aortic stiffening compared with NGM (adjusted (cf)PWV+/-SE: NGM, 9.15 +/- 0.12 m/s; IGR 9.76 +/- 0.11 m/s, p < 0.001; diabetes, 9.89 +/- 0.12 m/s, p < 0.001). IGR stratification indicated that impaired fasting glucose (IFG; 9.71 +/- 0.12 m/s) and post-challenge (impaired glucose tolerance; 9.82 +/- 0.24 m/s) categories had similar (cf)PWV (p = 0.83). Modelled predictors of (cf)PWV were used to assess independent metabolic associations with arterial stiffness. Fasting glucose concentration (beta = 0.10; 95% CI 0.05, 0.18; p = 0.003), 2 h post-challenge glucose (beta = 0.14; 95% CI 0.02, 0.23; p < 0.001) and HOMA-IR (beta = 0.20, 95% CI 0.05, 0.53; p < 0.001) were independently related to (cf)PWV after adjustment for age, sex, mean arterial pressure, heart rate, body mass index, renal function and antihypertensive medication.

CONCLUSIONS/INTERPRETATION

IGR characterised by fasting or post-challenge hyperglycaemia is associated with significant vascular stiffening. Post-challenge glucose and HOMA-IR are the most powerful metabolic predictors of arterial stiffness, implying hyperglycaemic excursion and insulin resistance play important roles in the pathogenesis of arteriosclerosis.

Explaining racial disparities in incidence of and survival from out-of-hospital cardiac arrest

A prospective observational study of 4,653 consecutive cases of out-of-hospital cardiac arrest (OOHCA) occurring in New York City from April 1, 2002, to March 31, 2003, was used to assess racial/ethnic differences in the incidence of OOHCA and 30-day survival after hospital discharge among OOHCA patients. The age-adjusted incidence of OOHCA per 10,000 adults was higher among Blacks than among persons in other racial/ethnic groups, and age-adjusted survival from OOHCA was higher among Whites compared with other groups. In analyses restricted to 3,891 patients for whom complete data on all variables were available, the age-adjusted relative odds of survival from OOHCA among Blacks were 0.4 (95% confidence interval: 0.2, 0.7) as compared with Whites. A full multivariable model accounting for demographic factors, prior functional status, initial cardiac rhythm, and characteristics of the OOHCA event explained approximately 41 percent of the lower age-adjusted survival among Blacks. The lower prevalence of ventricular fibrillation as the initial cardiac rhythm among Blacks relative to Whites was the primary contributor. A combination of factors probably accounts for racial/ethnic disparities in OOHCA survival. Previously hypothesized factors such as delays in emergency medical service response or differences in the likelihood of receipt of cardiopulmonary resuscitation did not appear to be substantial contributors to these racial/ethnic disparities.

Steady-state pharmacokinetics of once-daily fosamprenavir/ritonavir and atazanavir/ritonavir alone and in combination with 20 mg omeprazole in healthy volunteers*

OBJECTIVES

Use of proton pump inhibitors in HIV-infected patients is common. The purpose of this study was to determine the steady-state pharmacokinetics of once-daily (qd) fosamprenavir/ritonavir (FPV/r) and atazanavir/ritonavir (ATV/r) alone and in combination with 20 mg qd omeprazole (OMP) in healthy volunteers.

DESIGN AND METHODS

A prospective, open-label, single-site, two-period, crossover pharmacokinetic study was carried out in healthy volunteers. Subjects received either qd FPV/r 1400 mg/200 mg or ATV/r 300 mg/100 mg in the morning for 14 days and then 20 mg OMP in the evening for an additional 7 days. The pharmacokinetics were assessed over 24 h on days 14 and 21. Following a 2-week washout, subjects repeated the process with the other regimen. Trough protease inhibitor (PI) concentrations were taken on day 16 of each period to assess the impact of a single dose of OMP on ATV and amprenavir (APV) concentrations. Plasma ATV and APV pharmacokinetic parameters were assessed by noncompartmental analysis; geometric mean ratios (GMRs; PI+OMP/PI; 90% confidence interval) were calculated between days 14 and 21.

RESULTS

Nineteen healthy, non-HIV-infected volunteers were evaluated. OMP reduced ATV exposure [area under the concentration curve at 0-24 h (AUC0-24 h)] and the minimum drug concentration (Cmin) by 27% each. In contrast, APV exposure and Cmin were decreased by 4 and 2%, respectively. Four subjects (21%) experienced greater than 50% declines in both ATV AUC0-24 h and Cmin after the addition of OMP; this was not observed in any subject following receipt of FPV/r. No alterations in APV or ATV trough concentrations were observed following a single dose of OMP.

CONCLUSIONS

The addition of 20 mg OMP administered in the evening has minimal effect on APV pharmacokinetics. In contrast, ATV pharmacokinetics were altered; a number of ATV-treated subjects experienced pronounced declines in exposures upon the addition of 20 mg OMP administered in the evening, whereas others experienced little to no change.

Germline mutations in the ribonuclease L gene in families showing linkage with HPC1

Although prostate cancer is the most common non-cutaneous malignancy diagnosed in men in the United States, little is known about inherited factors that influence its genetic predisposition. Here we report that germline mutations in the gene encoding 2'-5'-oligoadenylate(2-5A)-dependent RNase L (RNASEL) segregate in prostate cancer families that show linkage to the HPC1 (hereditary prostate cancer 1) region at 1q24-25 (ref. 9). We identified RNASEL by a positional cloning/candidate gene method, and show that a nonsense mutation and a mutation in an initiation codon of RNASEL segregate independently in two HPC1-linked families. Inactive RNASEL alleles are present at a low frequency in the general population. RNASEL regulates cell proliferation and apoptosis through the interferon-regulated 2-5A pathway and has been suggested to be a candidate tumor suppressor gene. We found that microdissected tumors with a germline mutation showed loss of heterozygosity and loss of RNase L protein, and that RNASEL activity was reduced in lymphoblasts from heterozyogous individuals compared with family members who were homozygous with respect to the wildtype allele. Thus, germline mutations in RNASEL may be of diagnostic value, and the 2-5A pathway might provide opportunities for developing therapies for those with prostate cancer.

Small bowel perforation from a migrated biliary stent

Stenting of the biliary tract is performed for a variety of benign and malignant disorders. Although uncommon, proximal and distal migration of these stents is known to occur. We report a case of jejunal perforation from a distally migrated biliary stent.

The spectrum of pathogenic mutations in SPINK5 in 19 families with Netherton syndrome: implications for mutation detection and first case of prenatal diagnosis

The Comèl-Netherton syndrome is an autosomal recessive multisystemic disorder characterized by localized or generalized congenital ichthyosis, hair shaft abnormalities, immune deficiency, and markedly elevated IgE levels. Life-threatening complications during infancy include temperature and electrolyte imbalance, recurrent infections, and failure to thrive. To study the clinical presentations of the Comèl-Netherton syndrome and its molecular cause, we ascertained 19 unrelated families of various ethnic backgrounds. Results of initial linkage studies mapped the Comèl-Netherton syndrome in 12 multiplex families to a 12 cM interval on 5q32, thus confirming genetic homogeneity of Comèl-Netherton syndrome across families of different origins. The Comèl-Netherton syndrome region harbors the SPINK5 gene, which encodes a multidomain serine protease inhibitor (LEKTI) predominantly expressed in epithelial and lymphoid tissues. Recently, recessive mutations in SPINK5 were identified in several Comèl-Netherton syndrome patients from consanguineous families. We used heteroduplex analysis followed by direct DNA sequencing to screen all 33 exons and flanking intronic sequences of SPINK5 in the affected individuals of our cohort. Mutation analysis revealed 17 distinct mutations, 15 of which were novel, segregating in 14 Comèl-Netherton syndrome families. The nucleotide changes included four non-sense mutations, eight small deletions or insertions leading to frameshift, and five splice site defects, all of which are expected to result in premature terminated or altered translation of SPINK5. Almost half of the mutations clustered between exons 2 and 8, including two recurrent mutations. Genotype-phenotype correlations suggested that homozygous nucleotide changes resulting in early truncation of LEKT1 are associated with a severe phenotype. For the first time, we used molecular data to perform prenatal testing, thus demonstrating the feasibility of molecular diagnosis in the Comèl-Netherton syndrome.

Elevated concentration of intraocular cortisol obtained by sequential parabulbar injection in rabbit model

BACKGROUND

Parabulbar injections of corticosteroids yield a high intraocular concentration, but the half-life is short. We determined the concentration of cortisol that might be obtained by sequential parabulbar infusions of hydrocortisone.

MATERIALS AND METHODS

Single parabulbar injections of hydrocortisone sodium succinate were made in a rabbit model and the time of maximum concentration and half-life determined in the retina-choroid, vitreous, serum, and the tissues of the paired eye by radio-immune assay. Based upon the half-life, sequential injections were made at 3 hour intervals to obtain a steady concentration.

RESULTS

The maximum concentration of cortisol in the ocular tissues occurred two hours after a single injection and was 98 times greater in the choroid-retina and 72 times greater in the optic nerve than in the paired eye and the serum. The half-life of cortisol was 15 minutes. Elevated levels could be sustained by sequential injections at 3 hour intervals.

CONCLUSION

Sequential injections of hydrocortisone through a retained parabulbar catheter could make it possible to titrate and maintain a therapeutic level of cortisol in the eyes of patients with posterior uveitis or optic neuritis.

Significant absorption of topical tacrolimus in 3 patients with Netherton syndrome

BACKGROUND

Tacrolimus is a macrolide immunosuppressant approved in oral and intravenous formulations for primary immunosuppression in liver and kidney transplantation. Topical 0.1% tacrolimus ointment has recently been shown to be effective in atopic dermatitis for children as young as 2 years of age, with minimal systemic absorption. We describe 3 patients treated with topical 0.1% tacrolimus who developed significant systemic absorption.

OBSERVATION

Three patients previously diagnosed as having Netherton syndrome were treated at different centers with 0.1% tacrolimus ointment twice daily. Two patients showed dramatic improvement. All patients were found to have tacrolimus blood levels within or above the established therapeutic trough range for oral tacrolimus in organ transplant recipients. None of these patients developed signs or symptoms of toxic effects of tacrolimus.

CONCLUSIONS

Patients with Netherton syndrome have a skin barrier dysfunction that puts them at risk for increased percutaneous absorption. The Food and Drug Administration recently approved 0.1% tacrolimus ointment for the treatment of atopic dermatitis. Children with Netherton syndrome may be misdiagnosed as having atopic dermatitis. These children are at risk for marked systemic absorption and associated toxic effects. If topical tacrolimus is used in this setting, monitoring of serum tacrolimus levels is essential.

Approximating large convolutions in digital images

Computing discrete two-dimensional (2-D) convolutions is an important problem in image processing. In mathematical morphology, an important variant is that of computing binary convolutions, where the kernel of the convolution is a 0-1 valued function. This operation can be quite costly, especially when large kernels are involved. We present an algorithm for computing convolutions of this form, where the kernel of the binary convolution is derived from a convex polygon. Because the kernel is a geometric object, we allow the algorithm some flexibility in how it elects to digitize the convex kernel at each placement, as long as the digitization satisfies certain reasonable requirements. We say that such a convolution is valid. Given this flexibility we show that it is possible to compute binary convolutions more efficiently than would normally be possible for large kernels. Our main result is an algorithm which, given an m x n image and a k-sided convex polygonal kernel K, computes a valid convolution in O(kmn) time. Unlike standard algorithms for computing correlations and convolutions, the running time is independent of the area or perimeter of K, and our techniques do not rely on computing fast Fourier transforms. Our algorithm is based on a novel use of Bresenham's (1965) line-drawing algorithm and prefix-sums to update the convolution incrementally as the kernel is moved from one position to another across the image.

The mode selection trial (MOST) in sinus node dysfunction: design, rationale, and baseline characteristics of the first 1000 patients

BACKGROUND

More than 200,000 permanent pacemakers will be implanted in the United States in 2000 at a cost of more than $2 billion. Sick sinus syndrome (SSS) will likely account for approximately half of all cases necessitating implantation. Pacemaker technology permits the selection of ventricular (single-chamber) or dual-chamber devices. However, clinical and outcomes data are inadequate to support a clear recommendation that one or the other type of device be used.

METHODS

The Mode Selection Trial (MOST) is a single-blind study supported by the National Heart, Lung, and Blood Institute designed to enroll 2000 patients with SSS. All patients will receive a DDDR pacemaker programmed to VVIR or DDDR before implantation. The average time of follow-up will be 3 years. MOST has a >90% power to detect a 25% reduction in the primary end point-nonfatal stroke or total (all cause) mortality-in the DDDR-treated group. Secondary end points will include health-related quality of life and cost effectiveness, atrial fibrillation, and development of pacemaker syndrome. Prespecified subgroups for analysis will include women and the elderly. Enrollment was completed in October 1999, with a total of 2010 patients.

RESULTS

The median age of the first 1000 enrolled patients is 74 years, with 25% of patients 80 years or older. Women comprise 49%, and 17% are nonwhite, predominantly black (13%). Before pacemaker implantation, 22% of patients reported a history of congestive heart failure, 11% coronary angioplasty, and 25% coronary bypass surgery. Supraventricular tachycardia including atrial fibrillation was present in 53% of patients. A prior stroke was reported by 12%. Antiarrhythmic therapy was in use in 18% of patients.

CONCLUSIONS

MOST will fill the clinical need for carefully designed prospective studies to define the benefits of dual-chamber versus single-chamber ventricular pacing in patients with SSS. The MOST population is typical of the overall pacemaker population in the United States. Thus the final results of MOST should be clinically generalizable.

Therapeutic drug monitoring of once daily gentamicin in serum and saliva of children

Gentamicin is widely used in paediatric medicine and therapeutic monitoring is mandatory due to the narrow margin of safety. Saliva sampling may be of potential interest, especially in children in whom blood sampling is often difficult. Experience with once daily intravenous administration of aminoglycosides has grown in recent years. Gentamicin levels were measured in serum and saliva of 55 children treated with the drug (5 mg/kg per day), administered intravenously in three different regimens: thrice (n = 19), twice (n = 18), and once daily (n = 18). No correlation was found between serum gentamicin concentrations and saliva levels when the drug was administered twice or thrice daily, however, there was good correlation when the drug was administered once daily (r2 = 0.96, P < 0.0001).

CONCLUSION

In children with uncomplicated infections treated with once daily gentamicin, trough concentrations of the drug can be monitored in saliva.

Internal sphincterotomy is superior to topical nitroglycerin in the treatment of chronic anal fissure: results of a randomized, controlled trial by the Canadian Colorectal Surgical Trials Group

PURPOSE

This was a multicenter, randomized, controlled trial to compare the effectiveness of topical nitroglycerin with internal sphincterotomy in the treatment of chronic anal fissure.

METHODS

Patients with symptomatic chronic anal fissures were randomly assigned to 0.25 percent nitroglycerin tid or internal sphincterotomy. Both groups received stool softeners and fiber supplements and were assessed at six weeks and six months.

RESULTS

Ninety patients were accrued, but 8 were excluded from the analysis because they refused internal sphincterotomy after randomization (6), the fissure healed before surgery (1), or a fissure was not observed at surgery (1). There were 38 patients in the internal sphincterotomy group (22 males; mean age, 40.3 years) and 44 patients in the nitroglycerin group (15 males; mean age, 38.7 years). At six weeks 34 patients (89.5 percent) in the internal sphincterotomy group compared with 13 patients (29.5 percent) in the nitroglycerin group had complete healing of the fissure (P = 5x10(-8)). Five of the 13 patients in the nitroglycerin group relapsed, whereas none in the internal sphincterotomy group did. At six months fissures in 35 (92.1 percent) patients in the internal sphincterotomy group compared with 12 (27.2 percent) patients in the nitroglycerin group had healed (P = 3x10(-9)). One (2.6 percent) patient in the internal sphincterotomy group required further surgery for a superficial fistula compared with 20 (45.4 percent) patients in the nitroglycerin group who required an internal sphincterotomy (P = 9x10(-6)). Eleven (28.9 percent) patients in the internal sphincterotomy group developed side effects compared with 37 (84 percent) patients in the nitroglycerin group (P<0.0001). Nine (20.5 percent) patients discontinued the nitroglycerin because of headaches (8) or a severe syncopal attack (1).

CONCLUSIONS

Internal sphincterotomy is superior to topical nitroglycerin 0.25 percent in the treatment of chronic anal fissure, with a high rate of healing, few side effects, and low risk of early incontinence. Thus, internal sphincterotomy remains the treatment of choice for chronic anal fissure.

Treatment of acute asthma. A new look at the old and at the new

beta-Agonists remain the mainstay of therapy for acute asthma and, for most patients, standard doses are acceptable. Although the onset of action of systemic steroids is still not clear, steroids promote recovery and should be given to patients with acute illness. Intravenous magnesium sulfate appears to improve pulmonary function in the most severely ill patients but is not useful in patients with more moderate episodes. Ipratropium bromide is a weak bronchodilator that still needs to be tested as an adjunct to standard treatment regimens before its role in adults with asthma can be determined; given its ease of use and favorable safety profile it could be considered for patients with more severe acute illness. Aminophylline has not been found by most studies to improve outcomes and the narrow therapeutic range and unfavorable safety profile relegate it to a last-line agent or no use at all. Helium-oxygen mixtures currently have no role in moderately ill patients but have a theoretical advantage as a temporizing measure in severely ill patients. Drugs used in the management of chronic asthma, such as inhaled steroids and leukotriene-modifying agents, are making their way into the acute treatment arena, and other newly developed specific mediator inhibitors or blockers deserve attention. The use of isomers of beta-agonists is another area that is attracting attention and study. Systemic steroids are used to prevent relapse after emergency department discharge and the addition of other agents such as leukotriene-modifying agents or inhaled steroids may further prevent the need for urgent visits or hospitalization. The search for optimal treatment strategies for acutely ill patients is challenging and exciting and, with more attention and resources being devoted to this area, newer treatments will be found that will eventually have a greater impact on the high morbidity associated with acute asthma.

Heterotopic pregnancy presenting as an acute abdomen: a diagnostic masquerader

Simultaneous intrauterine and extrauterine pregnancy is called heterotopic pregnancy. It is a rare complication of pregnancy, especially in the absence of predisposing factors. It is known to present with a variety of symptoms and signs often leading to a delay in establishing the correct diagnosis. We report the case of a 29-year-old woman, known to be 14 weeks pregnant, presenting with acute abdominal pain. The confirmation of a viable intrauterine pregnancy led to a general surgery consultation. A heterotopic ruptured right ectopic tubal pregnancy was found. Right salpingectomy was performed. The patient recovered uneventfully. The intrauterine pregnancy was not affected. This case illustrates the variable presentation of heterotopic pregnancy and the need for general surgeons to be suspicious of pregnancy related complications, even in the presence of a viable intrauterine pregnancy.

En passant synaptic varicosities form directly from growth cones by transient cessation of growth cone advance but not of actin-based motility

Formation of terminal synapses at sites such as the neuromuscular junction involves transformation of the motile growth cone into the nonmotile synaptic terminal. However, transformation does not need to be the mechanism when a neurite forms multiple widely spaced synaptic varicosities along a target in an en passant configuration. Synaptic varicosities could form here by specialization of the neurite after the growth cone has advanced past the site. We examined this issue by using cocultures of identified sensory (SN) and motor (L7) neurons from Aplysia. Living SNs were labeled with fluorescent dye and their neurites were observed at high resolution every few minutes growing along the axon of L7, allowing a fine-grained analysis of the behavior of the growth cone at the sites of synapse formation. All varicosities whose formation was observed indeed developed from the growth cone. Sensory varicosities were shown by electron microscopy to contain features characteristic of active zones for transmitter release within a day of their formation on the motor axon. Growth cone advance slowed or stopped transiently during varicosity formation, but the motile activity of the peripheral region of the growth cone (veils and filopodia) was maintained. These results suggest that target "stop signals" involved in the formation of synapses, at least of the en passant variety, may be of a different type from the growth inhibitory molecules, such as the collapsins, which guide axons to their targets.

Internal fixation of phalangeal fractures using titanium miniplates

Although widely utilized in the treatment of metacarpal fractures, plate fixation in phalangeal fractures remains controversial. Increased potential for infection, breakage, and added soft-tissue trauma leading to increased joint stiffness have been cited as important negative factors. A retrospective analysis of titanium plate fixation of phalangeal fractures over a 7-year period is presented. From 1991 to 1998, 16 fractures (13 men, 3 women; age range, 19-70 years) were managed with plate fixation using the Profyle titanium plating system as the primary modality of treatment. All plates were seated dorsally using an extensor tendon-splitting approach. The average follow-up period after surgery was 5 months (range, 3-28 months). Fracture patterns varied: 31% (5 of 16) were open fractures and 69% (11 of 16) were closed. Complications occurred in 25% of patients (4 of 16) and consisted of pain or other trigger that required removal of hardware, flexion contracture at the proximal interphalangeal joint, and extensor lag. There were no instances of hardware failure, infection, or malunion. The quality of recovery of joint motion was assessed using the Total Active Flexion Scale: nine digits were graded excellent, another six were categorized as good, and only one digit was judged as poor. A review of the current literature is presented along with suggested guidelines for the application of miniplate fixation for fractures of the phalanges.

Contemporaneous positron emission tomography and MR imaging at 1.5 T

Simultaneous acquisition of positron emission tomography (PET) and magnetic resonance (MR) images using an MR-compatible PET system will obviate the need for image registration and will allow unique studies of structure and function of living organisms in one setting. Here we report on simultaneous acquisition of PET and MR images on a clinical 1.5 T system using a 54 mm diameter prototype MR-compatible PET system (McPET). Phantom experiments were performed in order to determine the effect of the McPET system on MR images. The results demonstrated the system to be fully MR compatible, in both its detector head construction and operation. The McPET construction offers a promising method for design of a large-scale MR-compatible PET system that will be useful in functional studies of the brain.

Intravitreal gas injection diminishes hyaluronic acid

OBJECTIVES

To determine if compression of the vitreous by an intraocular gas bubble diminishes the concentration of hyaluronic acid (NaHA).

MATERIALS AND METHODS

Eighteen albino rabbits had air, xenon or perfluoroethane (C2F6) injected into the vitreous to displace 12.5% to 90% of the vitreous volume. After the gas was absorbed, the vitreous was analyzed for NaHA by the Carbazole method (1, 13).

RESULTS

A 90% displacement diminished the NaHA concentration by 18.6%. Lesser displacements caused a lesser loss, but the differences are not significant.

CONCLUSION

Intraocular gas injections, both large and small, reduce the concentration of NaHA and destabilize the vitreous structure.

Research fundamentals: III. elements of a research protocol for clinical trials

A clinical trial is a powerful technique for evaluating the effectiveness of an experimental intervention. The initial stages of planning a clinical trial involve choosing and refining a research question, selecting a study design, and deciding on appropriate statistical tests and sample sizes. The success of the study depends upon how well these issues are thought out in advance, and how they can be put into practice. The protocol is the written document that allows the investigator to communicate details of how the research question will be answered. In the following article, the basic components of the research protocol are described. Issues related to quality control, data entry, and pilot testing are discussed. This is the third in a series of research fundamental concept papers, written by members of the SAEM Research Committee.

Research fundamentals: II. Choosing and defining a research question

This is the second in a series of articles developed by members of the SAEM Research Committee to describe a stepwise approach to the research process. This series is aimed at junior academic emergency physicians (EPs), as well as nonacademic EPs with an interest in the research process. This article describes the development of a testable research hypothesis. While a multitude of sources provide interesting questions for consideration, choosing and refining the research question, so that it can be tested adequately and answered completely, are difficult tasks.

Comparison of the Maxair Autohaler to wet nebulizer in patients with acute asthma

STUDY OBJECTIVE

Patients with acute asthma often have difficulty using a conventional metered-dose inhaler. The Maxair Autohaler (3M Pharmaceuticals; St. Paul, MN) is a hand-held breath-actuated device developed to help patients coordinate drug administration. The study objective is to compare the efficacy of the Autohaler with inhaled beta-agonist administered by wet nebulizer in treating acute asthma exacerbations.

DESIGN

Parallel, randomized, placebo-controlled clinical trial.

SETTING

Emergency department (ED) of a university-affiliated hospital.

PARTICIPANTS

Patients aged 18 to 55 years presenting to the ED with acute asthma and an FEV1 40 to 70% on hospital arrival.

INTERVENTIONS AND MEASUREMENTS

Patients were given either six puffs of the Maxair Autohaler (1,200 microg pirbuterol) plus saline solution by nebulizer (active Autohaler group) or six puffs placebo by Autohaler plus 2,500 microg albuterol via nebulizer (active nebulizer group). Treatment was repeated at 30 and 60 min, with clinical evaluation performed before each treatment and again at 120 min. At 120 min, the protocol was completed.

RESULTS

Twenty-four patients were enrolled, with 5 excluded because of protocol violations. Baseline FEV1 percent predicted values for the active Autohaler group were 53% vs 51% for the active nebulizer group (p=not significant [NS]). At time 120 min, values were 66% for Autohaler and 64% for nebulizer (p=NS). The average time to administer Autohaler was 2.9 min, vs 9.1 min for nebulizer. No patient was excluded because of the inability to use the Autohaler device adequately.

CONCLUSION

In patients with moderate asthma exacerbations, similar improvements in pulmonary function are obtained when beta-agonists are given by either the Maxair Autohaler or a wet nebulizer device.

Low levels of serum ionized magnesium are found in patients early after stroke which result in rapid elevation in cytosolic free calcium and spasm in cerebral vascular muscle cells

Ninety-eight patients admitted to the emergency rooms of three urban hospitals with a diagnosis of either ischemic stroke or hemorrhagic stroke exhibited early and significant deficits in serum ionized Mg2+ (IMg2+), but not total Mg, as measured with a unique Mg2+-sensitive ion-selective electrode. Twenty-five percent of these stroke patients exhibited >65% reductions in the mean serum IMg2+ found in normal healthy human volunteers or patients admitted for minor bruises, cuts or deep lacerations. The stroke patients also demonstrated significant elevation in the serum ionized Ca2+ (ICa2+)/IMg2+ ratio, a sign of increased vascular tone and cerebrovasospasm. Exposure of primary cultured canine cerebral vascular smooth muscle cells to the low concentrations of IMg2+ found in the stroke patients, e.g. 0.30-0.48 mM, resulted in rapid and marked elevations in cytosolic free calcium ions ([Ca2+]i) as measured with the fluorescent probe, fura-2, and digital image analysis. Coincident with the rise in [Ca2+]i, many of the cerebral vascular cells went into spasm. Reintroduction of normal extracellular Mg2+ ion concentrations failed to either lower the [Ca2+]i overload or reverse the rounding-up of the cerebral vascular cells. These results suggest that changes in Mg2+ metabolism play important roles in stroke syndromes and in the etiology of cerebrovasospasm associated with cerebral hemorrhage.

Determination of size of aortic emboli and embolic load during coronary artery bypass grafting

BACKGROUND

Embolic signals have been detected within both the aortic lumen and the intracranial vasculature during coronary artery bypass grafting. Total numbers of these emboli have been reported. The present study examined the size of individual emboli and the total volume of embolization.

METHODS

Using transesophageal echocardiography, we continuously monitored the aortic lumen of 10 patients undergoing isolated coronary artery bypass grafting. We manually analyzed 720,000 individual echo frames over a 4-minute period after the release of aortic clamps to track and to calculate the volume of 657 individual particles. The embolic load for the entire procedure was calculated from mean volume based on analysis of 1,508 particles. We simultaneously monitored the middle cerebral artery using transcranial Doppler ultrasonography and compared numbers of emboli detected by the two techniques.

RESULTS

Particle diameter ranged from 0.3 to 2.9 mm (mean, 0.8 mm), and particle volume from 0.01 to 12.5 mm3 (mean, 0.8 mm3). Twenty-eight percent of particles measured 1 mm or more, 44% measured 0.6 to 1.0 mm, and only 27% measured 0.6 mm or less in diameter. Aortic embolic load for the procedure ranged from 0.6 cm3 to 11.2 cm3 (mean, 3.7 cm3). Estimated cerebral embolic load for the procedure ranged from 60 to 510 mm3 (mean, 276 mm3). The fraction of aortic emboli entering the cerebral circulation was very variable (3.9% to 18.1%). Seventy-six percent of the embolic volume after the release of clamps occurred over a 20-second period. Only 1 patient was encephalopathic perioperatively. This patient had the largest estimated cerebral embolic load (510 mm3) and the second largest aortic embolic load (8.4 cm3).

CONCLUSIONS

We determined the size of individual intraaortic embolic particles and the total volume of embolization during coronary artery bypass grafting, and found the proportion entering the cerebral circulation to be very variable. The constitution of these particles and the neurologic impairment resulting from such embolization remains to be determined.

Choroidal concentration of interferon after retrobulbar injection

PURPOSE

To determine whether recombinant human interferon alpha-2a (IFN alpha-2a) would diffuse into the choroid in significant amounts from a retrobulbar depot.

METHODS

One million international units of IFN alpha-2a were injected into the retrobulbar space of the eyes of 17 rabbits, and choroidal and serum concentrations were measured at 1, 2, 4, 8, 12, and 24 hours. The same dose of IFN alpha-2a was injected subcutaneously into 10 rabbits, and choroidal and serum concentrations were measured at the same intervals for comparison. Parabulbar and ocular tissues were studied by light microscopy for evidence of local toxicity.

RESULTS

Peak concentration IFN alpha-2a in the choroid after retrobulbar injection occurred at 2 hours and averaged 32,000 IU/mg. Peak concentration in the serum occurred at 4 hours and averaged 227 IU/ml. Concentrations in choroid and serum fell rapidly, and IFN alpha-2a was not detectible at 24 hours. No IFN alpha-2a was detected in the choroid of the paired eye, and only a trace (< 50 IU/mg) was found in either eye after subcutaneous injection. Light microscopy revealed some lymphocytes in the fat adjacent to the retrobulbar depot after six daily injections of IFN alpha-2a or saline. Sclera, choroid, and retina appeared unaffected.

CONCLUSIONS

IFN alpha-2a diffuses into the choroid from a retrobulbar depot in significant amounts. The serum concentration from a retrobulbar injection is < 1% of the choroidal concentration. The retrobulbar route to the choroid may be optimal for testing the effect of IFN alpha-2a on choroidal neovascularization.