Michael M. Mohseni

A biological hybrid model for collagen-based tissue engineered vascular constructs

Various approaches to tissue engineering a small diameter blood vessel have historically relied upon extended culturing periods and/or synthetic materials to create mechanical properties suitable to withstand the hemodynamic stresses of the vasculature. In this work, we present the concept of a construct-sleeve hybrid (CSH) graft, which uses a biological support to provide temporary reinforcement while cell-mediated remodeling of the construct occurs. Support sleeves were fabricated from Type I collagen gels and crosslinked with glutaraldehyde, ultraviolet, or dehydrothermal treatments. Uniaxial tensile testing of acellular sleeves revealed increased stiffness moduli and tensile stresses with crosslinking treatments. A second collagen layer containing cells was molded about the sleeve to create a CSH. After in vitro culture, CHSs with uncrosslinked (UnXL) and glutaraldehyde treated (Glut) sleeves exhibited significant increases in mechanical strength (20.4-fold and 121-fold increases in ultimate stress, respectively) compared to unreinforced control constructs. Burst testing produced similar findings with peak pressures of 100 and 650mmHg in the UnXL and Glut CSHs, respectively. Construct compaction, cell viability, and histological examination demonstrated that the function of most cells remained unimpaired with the incorporation of the biological support sleeve.

Effect of Antibiotic Pretreatment on Cerebrospinal Fluid Profiles of Children With Bacterial Meningitis

OBJECTIVE. The goal of this study was to evaluate the effect of antibiotic administration before lumbar puncture on cerebrospinal fluid profiles in children with bacterial meningitis. METHODS. We reviewed the medical records of all children (1 month to 18 years of age) with bacterial meningitis who presented to 20 pediatric emergency departments between 2001 and 2004. Bacterial meningitis was defined by positive cerebrospinal fluid culture results for a bacterial pathogen or cerebrospinal fluid pleocytosis with positive blood culture and/or cerebrospinal fluid latex agglutination results. Probable bacterial meningitis was defined as positive cerebrospinal fluid Gram stain results with negative results of bacterial cultures of blood and cerebrospinal fluid. Antibiotic pretreatment was defined as any antibiotic administered within 72 hours before the lumbar puncture. RESULTS. We identified 231 patients with bacterial meningitis and another 14 with probable bacterial meningitis. Of those 245 patients, 85 (35%) had received antibiotic pretreatment. After adjustment for patient age, duration and severity of illness at presentation, and bacterial pathogen, longer duration of antibiotic pretreatment was not significantly associated with cerebrospinal fluid white blood cell count, cerebrospinal fluid absolute neutrophil count. However, antibiotic pretreatment was significantly associated with higher cerebrospinal fluid glucose and lower cerebrospinal fluid protein levels. Although these effects became apparent earlier, patients with ≥12 hours of pretreatment, compared with patients who either were not pretreated or were pretreated for <12 hours, had significantly higher median cerebrospinal fluid glucose levels (48 mg/dL vs 29 mg/dL) and lower median cerebrospinal fluid protein levels (121 vs 178 mg/dL). CONCLUSIONS. In patients with bacterial meningitis, antibiotic pretreatment is associated with higher cerebrospinal fluid glucose levels and lower cerebrospinal fluid protein levels, although pretreatment does not modify cerebrospinal fluid white blood cell count or absolute neutrophil count results.

Prevalence of hyponatremia, renal dysfunction, and other electrolyte abnormalities among runners before and after completing a marathon or half marathon.

Background: Prior reports on metabolic derangements observed in distance running frequently have small sample sizes, lack prerace laboratory measures, and report sodium as the sole measure. Hypothesis: Metabolic abnormalities—hyponatremia, hypokalemia, renal dysfunction, hemoconcentration—are frequent after completing a full or half marathon. Clinically significant changes occur in these laboratory values after race completion. Study Design: Observational, cross-sectional study. Methods: Consenting marathon and half marathon racers completed a survey as well as finger stick blood sampling on race day of the National Marathon to Fight Breast Cancer (Jacksonville, Florida, February 2008). Parallel blood measures were obtained before and after race completion (prerace, n = 161; postrace, n = 195). Results: The prevalence of prerace and postrace hyponatremia was 8 of 161 (5.0%) and 16 of 195 (8.2%), respectively. Hypokalemia was not present prerace but was present in 1 runner postrace (1 of 195). Renal dysfunction occurred prerace in 14 of 161 (8.7%) and postrace in 83 of 195 (42.6%). Among those with postrace renal dysfunction, 45.8% (38 of 83) were classified as moderate or severe. Hemoconcentration was present in 2 of 161 (1.2%) prerace and 6 of 195 (3.1%) postrace. The mean changes in laboratory values were (postrace minus prerace): sodium, 1.6 mmol/L; potassium, −0.2 mmol/L; blood urea nitrogen, 2.8 mg/dL; creatinine, 0.2 mg/dL; and hemoglobin, 0.3 g/dL for 149 pairs (except blood urea nitrogen, n = 147 pairs). Changes were significant for all comparisons (P < 0.01) except potassium (P = 0.08) and hemoglobin (P = 0.01). Conclusions: Metabolic abnormalities are common among endurance racers, and they may be present prerace, including hyponatremia. The clinical significance of these findings is unknown. Clinical relevance: It is unclear which runners are at risk for developing clinically important metabolic derangements. Participating in prolonged endurance exercise appears to be safe in the majority of racers.

Diagnostic value of immature neutrophils (bands) in the cerebrospinal fluid of children with cerebrospinal fluid pleocytosis

OBJECTIVE. We evaluated the diagnostic utility of the presence and number of cerebrospinal fluid (CSF) bands in distinguishing bacterial from aseptic meningitis among children with CSF pleocytosis. METHODS. We identified retrospectively a cohort of children 29 days to 19 years of age with CSF pleocytosis (≥10 × 106 leukocytes per L) who were treated in the emergency departments of 8 pediatric centers between January 2001 and June 2004 and whose CSF was evaluated for the presence of bands. We performed bivariate and multivariate analyses to determine the ability of CSF bands to distinguish bacterial from aseptic meningitis. RESULTS. Among 1116 children whose CSF was evaluated for the presence of bands, 48 children (4% of study patients) had bacterial meningitis. Bacterial meningitis, compared with aseptic meningitis, was associated with a greater CSF band proportion (0.03 vs 0.01; difference: 0.02; 95% confidence interval: 0.00–0.04) and CSF absolute band count (392 × 106 cells per L vs 3 × 106 cells per L; difference: 389 × 106 cells per L; 95% confidence interval: −77 × 106 cells per L to 855 × 106 cells per L). In addition, 29% of patients with bacterial meningitis, compared with 18% of patients with aseptic meningitis, had any bands detected in the CSF. After adjustment for other factors associated with bacterial meningitis, however, CSF band presence, CSF absolute band count, and CSF band proportion were not independently associated with bacterial meningitis. CONCLUSION. In this multicenter study, neither the presence nor quantity of CSF bands independently predicted bacterial meningitis among children with CSF pleocytosis.

Viral meningitis: Which patients can be discharged from the emergency department?

BACKGROUND Even in an era when cases of viral meningitis outnumber bacterial meningitis by at least 25:1, most patients with clinical meningitis are hospitalized. OBJECTIVE We describe the clinical characteristics of an unusual outbreak of viral meningitis that featured markedly elevated cerebrospinal fluid white blood cell counts (CSF WBC). A validated prediction model for viral meningitis was applied to determine which hospital admissions could have been avoided. METHODS Data were collected retrospectively from patients presenting to our tertiary care center. Charts were reviewed in patients with CSF pleocytosis (CSF WBC > 7 cells/mm(3)) and a clinical diagnosis of meningitis between March 1, 2003 and July 1, 2003. Cases were identified through hospital infection control and by surveying all CSF specimens submitted to the microbiology laboratory during the outbreak. RESULTS There were 78 cases of viral meningitis and 1 case of bacterial meningitis identified. Fifty-eight percent of the viral meningitis cases were confirmed by culture or polymerase chain reaction to be due to Enterovirus. Mean CSF WBC count was 571 cells/mm(3), including 20 patients with a CSF WBC count > 750 cells/mm(3) (25%) and 11 patients with values > 1000 cells/mm(3) (14%). Sixty-four of 78 patients (82%) were hospitalized. Rates of headache, photophobia, nuchal rigidity, vomiting, and administration of intravenous fluids in the Emergency Department were no different between admitted and discharged patients. Only 26/78 (33%) patients with viral meningitis would have been admitted if the prediction model had been used. CONCLUSIONS Although not all cases of viral meningitis are necessarily suitable for outpatient management, use of a prediction model for viral meningitis may have helped decrease hospitalization by nearly 60%, even though this outbreak was characterized by unusually high levels of CSF pleocytosis.

Cardiac Tamponade as the Initial Manifestation of Systemic Lupus Erythematosus

A 14-year-old black girl presented with the chief complaint of malaise, shortness of breath, and sore throat. She was seen 4 days prior in the same Emergency Department (ED) when she was started on amoxicillin for presumed pharyngitis. Upon evaluation by the emergency physician, the patient was tachypneic, with a blood pressure of 116/57 mm Hg, heart rate of 163 beats/min, and temperature of 36.9 C. Oxygen saturation was 98% on room air. Physical examination was significant for wheezing in all lung fields. Initially, reactive airway disease was presumed, and the patient received three albuterol nebulizer treatments. After no improvement and continued tachycardia, chest X-ray study was obtained, revealing marked cardiomegaly (Figure 1). Additionally, electrocardiogram was performed, which revealed sinus tachycardia, PR depression, and electrical alternans (Figure 2). Arrangements were made for transfer to a nearby Pediatric Intensive Care Unit (PICU). The patient continued to decompensate while in the ED, however, ultimately becoming unresponsive and asystolic, requiring cardiopulmonary resuscitation and intubation. Emergent pericardiocentesis was performed, with removal of 675 mL of blood and subsequent return of spontaneous circulation. Repeat chest X-ray study imaging revealed a marked decrease in size of the cardiac silhouette (Figure 3). Despite resuscitative efforts at the treating

Severe hypophosphatemia and acute neurologic dysfunction in a marathon runner.

INTRODUCTION The differential diagnosis of acute neurologic dysfunction in endurance athletes is broad but includes heatstroke, cerebrovascular accident, and electrolyte disturbance, among others. Although hyponatremia has been established as a reason for altered mental status (AMS) in endurance events, hypophosphatemia alone, to our knowledge, has not been reported as a cause of neurologic disturbance. We present a case of acute weakness and paresthesias mimicking stroke in a marathon runner with severe hypophosphatemia.

Concurrent Spontaneous Pneumomediastinum and Pneumorrhachis

BACKGROUND Spontaneous pneumomediastinum with concurrent pneumorrhachis (air in the spinal canal) and subcutaneous emphysema can be an alarming presentation, both clinically and radiographically. These clinical entities often require only conservative measures after ruling out any worrisome underlying causes. Management often involves appropriate imaging, hospital admission, and sub-specialty consultation as needed to help determine any potential causes for the presentation that may require anything more than a period of medical observation. CASE REPORT A 20-year-old man presented to the Emergency Department (ED) with acute onset of chest pain. Physical examination was significant for subcutaneous emphysema across the anterior chest wall. Radiographs of the neck revealed extensive soft tissue emphysema extending into the upper mediastinum. Computed tomography (CT) of the neck with contrast revealed a small amount of air within the central canal of the spinal cord, in addition to extensive pneumomediastinum and subcutaneous emphysema. The patient remained stable and was discharged home on hospital day 2, after significant threats for morbidity or mortality were ruled out. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: Spontaneous pneumomediastinum, pneumorrhachis, and subcutaneous emphysema are rare clinical entities, but each requires thorough investigation in the ED to rule out any underlying life-threatening cause. A conservative treatment approach is appropriate for most patients without evidence of cardiorespiratory compromise or neurologic deficits accruing due to these problems.

Acute pericarditis following endoscopy

The differential diagnoses for patients presenting with chest discomfort after endoscopy remain broad. In addition to infectious, traumatic and bleeding complications, intrinsic cardiac pathology should be considered. Though rare, pericarditis and pericardial tamponade are additional entities that the clinician should consider when evaluating these patients. We present a 74-year-old man who arrived to the emergency department with substernal chest discomfort that began shortly after upper and lower endoscopy the previous day. Biopsies were obtained during the procedure (ileal and colonic mucosa) without complication. The patient reported worsening chest discomfort with deep inspiration or lying flat. ECG was significant for diffuse ST-segment elevation and PR depression. Cardiac workup was otherwise negative; the patient improved with conservative measures. In this case report, we describe a little known complication after upper endoscopy. By highlighting the clinical features of pericarditis in this setting, the provider can be alert to recognise and promptly treat this clinical entity.

Splenic torsion: a rare cause of abdominal pain

Splenic torsion is an exceedingly rare but clinically important disease process that should be recognised promptly by the treating physician. In this condition, there is twisting of the spleen along its vascular pedicle, subsequently leading to abdominal pain in the setting of organ ischaemia. Vascular thrombosis and splenic infarction may ensue. Torsion has been described in cases of a known wandering spleen. Abnormal development of the splenic suspensory ligaments may predispose a patient to a wandering spleen. Treatment of splenic torsion is typically surgical, with goals of preservation of the spleen if possible. We present a case of a young woman who presented with left-sided chest and abdominal pain and was found to have splenic torsion with complete splenic infarction. Surgical intervention was required, and splenectomy was performed. In this case presentation, we outline the multidisciplinary approach needed to care for the patient with this rare condition.