Update on conservative management of acoustic neuroma.

OBJECTIVE: To update the authors' experience with conservative management of acoustic neuromas. STUDY DESIGN: Retrospective chart review. SETTING: Private practice and tertiary care referral setting. INTERVENTION: Of 600 patients with acoustic neuroma, 102 were treated with the "wait and scan" treatment option. At least two magnetic resonance imaging scans were required of all patients. MAIN OUTCOME MEASURES: Change in tumor size over time was evaluated, as were clinical symptoms: hearing status, tinnitus, balance disturbance, aural fullness, vertigo, headache, and facial pain, numbness, or weakness. RESULTS: Of 102 patients, the average follow-up time interval was 28.5 months. Forty-five (44%) of 102 patients demonstrated a change in tumor size: an average total growth of 2.17 mm per year. In the remaining 54 patients (53%), no growth was demonstrated during a mean follow-up of 28.5 months. Three patients demonstrated actual tumor shrinkage. Of the 102 patients receiving conservative treatment, 85 (84%) reported hearing loss, 67 (66%) tinnitus, 37 (36%) balance disturbance, 29 (28%) aural fullness, 28 (27%) vertigo, 7 (7%) headache, 4 (4%) facial numbness, 2 (2%) facial weakness, and 0 (0%) facial pain. CONCLUSION: Conservative management-"wait and scan"-for selected patients with acoustic neuroma is a reasonable choice of management instead of radiation or microsurgery. In some situations the individual morbidities associated with surgery or radiation make those treatments not in the patient's best interests. A third option is necessary in patients who cannot or do not wish to undergo those other treatments.

Hepatobiliary elimination of trovafloxacin and metabolites following single oral doses in healthy volunteers.

Trovafloxacin, a fluoronaphthyridone derivative related to fluoroquinolones, has significant activity against gram-negative and gram-positive pathogens, including penicillin-resistant Streptococcus pneumoniae, anaerobes and atypical organisms, good tissue penetration and a long elimination half-life. Following oral administration, less than 10% of the dose is renally eliminated as unchanged drug. Hepatobiliary elimination of trovafloxacin was examined by comparing the time course and bile and serum concentrations of trovafloxacin and its metabolites following oral administration to three patients with in-dwelling nasobiliary catheters or T-tubes. Following a single 200 mg oral dose, the mean maximum plasma trovafloxacin concentration was 2.0+/-0.4 mg/l, the area under the concentration-time curve 22.0+/-5.5 mg x h/l and the elimination half-life 8.5 h. Values in bile for the same subjects were 27.8+/-9.6 mg/l, 327.7+/-142.9 mg x h/l and 10.7 h. Corresponding values for the N-acetyl metabolite in bile were 3.8+/-3.4 mg/l, 35.3+/-29.8 mg x h/l and 8.3 h. The mean bile : serum ratio of trovafloxacin was 14:9 and consistent with biliary elimination. Serum concentrations of trovafloxacin in this study were similar to those reported in healthy volunteers. Bile concentrations of trovafloxacin substantially exceeded those of the N-acetyl metabolite, suggesting efficient clearance of the metabolite or that hepatic metabolism of trovafloxacin is not extensive.

Concentrations of trovafloxacin in colonic tissue and peritoneal fluid after intravenous infusion of the prodrug alatrofloxacin in patients undergoing colorectal surgery.

BACKGROUND: Trovafloxacin is a new fourth-generation fluoroquinolone whose pharmacokinetics and in vitro activity suggest that it is well suited for antibiotic prophylaxis in elective colorectal surgery. Alatrofloxacin is a prodrug that is rapidly hydrolyzed to trovafloxacin in the body. METHODS: Twelve patients received a single dose of alatrofloxacin equivalent to 200 mg trovafloxacin by intravenous infusion over 1 hour. Surgery was started at various time points relative to infusion time to allow determination of trovafloxacin concentrations in serum, colonic tissue, and peritoneal fluid as a function of time. RESULTS: The concentration in the earliest colonic tissue sample (1.4 hours after dosing) was 1.4 microg/g. The maximum colonic tissue concentration was 2.8 microg/g in a sample taken 2 hours after dosing. Colonic tissue/serum concentration ratios in samples taken 2-10 hours after the end of infusion ranged from 0.8 to 1.47. Concentrations of trovafloxacin in peritoneal fluid ranged from below the level of quantitation to 2.1 microg/mL at the time of colonic tissue sampling and from below the level of quantitation to 2.5 microg/mL at the time of wound closure. Alatrofloxacin was well tolerated. CONCLUSIONS: After a single intravenous dose of alatrofloxacin equivalent to 200 mg trovafloxacin, trovafloxacin is distributed rapidly into colonic tissue and peritoneal fluids. Tissue concentrations approximate serum concentrations and decline in parallel for up to 10 hours after dosing.

The refeeding syndrome: an approach to understanding its complications and preventing its occurrence.

The refeeding syndrome (RS) is a complication of nutritional support that potentially causes considerable morbidity and mortality. Compensatory metabolic alterations secondary to chronic starvation predispose malnourished patients to RS. Providing nutritional support initiates an intracellular shift of potassium, magnesium, and phosphate that results in many adverse effects. The literature addressing RS focuses on only one electrolyte abnormality, hypophosphatemia; however, often all three electrolyte levels are perturbed. Thus RS should be characterized as a syndrome of generalized fluid and electrolyte imbalance. Recommended electrolyte supplementation and laboratory monitoring can help prevent the disorder in susceptible patients.

Operating modes of a charge-transfer-plate liquid-crystal phase modulator.

New results for an electron-beam-addressed liquid-crystal phase modulator are presented. Local, as well as global, control of liquid-crystal molecular reorientation is demonstrated, and the results of five different operating modes are discussed. Linear phase modulation with depths up to 30pi are demonstrated with this device, as are two-dimensional arrays of computer-generated spherical lenses with actively variable focal lengths. The spherical lenses were written without the use of specialized transfer functions to compensate for device nonlinearities. Applications are discussed in the context of adaptive optics in spaceborne systems.

Charge-transfer-plate spatial light modulators.

Charge-transfer-plate spatial light modulators (CTPSLM's) are a class of devices that employ chargetransfer plates as the interface between the charge-generation element and the light-modulation element. Both optically addressed and electrically addressed devices have been built. Chargegenerating elements for the optically addressed devices include photoconductors, photodiode and phototransistor arrays, optoelectronic integrated circuit chips, and photocathode-microchannel-plate assemblies. For electrically addressed devices, electron guns, very large-scale integrated circuits, thin-film transistors, and matrix electrodes are among the possible charge-generation elements. Lightmodulation elements used in CTPSLM's include liquid crystals, electro-optic organic and inorganic crystals, polymers, deformable membrane mirrors, oil films, multilayer dielectric films, and electroluminescent films. In principle, all combinations of charge-generation elements and light-modulating elements are possible. This paper explores the fundamental performance limitations of CTP technology, and describes the design, operation, and applications of five different CTPSLM's (three based on membrane-mirror technology and two on liquid-crystal technology).

Nutritional support of pulmonary patients: a multidisciplinary approach.

Pulmonary disease affects and is affected by the nutritional status of the patient. The relationships between nutrition, medications, complications, and the course of pulmonary disease itself are multifaceted and are the focus of concern for the nutritional support team. Nutritional support of patients with pulmonary disease demands the expertise of a multidisciplinary team in monitoring the nutritional status of patients, appropriately selecting feeding solutions and routines, selecting and administering medications, and planning and implementing nursing interventions. Recognition of the importance of the nutritional component of care for patients with pulmonary disease is the focus of this article.

Osmolality of oral drug solutions and suspensions.

The osmolality values of a variety of commonly used drug solutions and suspensions were determined. A total of 58 commercially available drug solutions and suspensions and electrolyte solutions for oral use were analyzed. Samples of each product were diluted 1:10 to a total volume of 100 microL with sterile water for irrigation and mixed thoroughly. The osmolality of 10-microL aliquots of each diluted mixture was determined at least in duplicate by vapor pressure osmometry. Only six (10%) of the products had osmolality values that were less than or equal to 1000 mOsm/kg (i.e., similar to the values of commercially available enteral formulas). The other products had osmolality values ranging from 1,050 to 10,950 mOsm/kg. Since many drug solutions and suspensions are hypertonic compared with normal gastrointestinal secretions, inappropriate administration could cause adverse gastrointestinal effects in patients receiving enteral nutrition support.

Treatment effects of parenteral vitamins in total parenteral nutrition patients.

To determine the prevalence of abnormal vitamin levels in an adult hospitalized population requiring total parenteral nutrition (TPN) and to assess the effect of routine parenteral vitamin therapy on vitamin levels, we studied 35 general surgical patients. Assays for 12 vitamins were performed both before and after a standard 10-day course of TPN. Patients were given nothing by mouth. The first 25 patients received a daily parenteral vitamin mixture tailored to the recommendations of the Nutrition Advisory Group of The American Medical Association (maintenance dose). The final 10 patients were given a parenteral multivitamin dose providing substantially greater amounts of most vitamins (repletion dose). Only 58% (190/324) of pre-TPN vitamin levels were normal, 25% were low, and 17% were high. No patient had fewer than two abnormal baseline levels. Vitamin levels did not correlate with serum albumin, body weight, or nitrogen balance. After 10 days of treatment, only 39% of low pre-TPN vitamin levels improved; most (45/62) of the low posttreatment levels were low at baseline. The higher repletion dose resulted in a significantly (p less than 0.01) greater percent increase in vitamin A, C, and pyridoxine levels. The prevalence of abnormal vitamin levels in this population is high (42%). Standard parenteral vitamin therapy leads to marginal improvement in abnormally low pre-TPN vitamin levels.

Urea nitrogen excretion in chair-adapted primates.

To evaluate the temporal pattern of urea excretion in chair-adapted primates (Macaque fascicularis) on continuous total parenteral nutrition (TPN), two groups of five animals were studied. Group I received continuous TPN (75 glucose kcal; 0.56 g nitrogen; and 100 ml fluid per kg per day) while Group II received a single morning isonitrogenous oral meal along with a continuous isovolemic intravenous infusion of 0.45% saline. Urine was collected hourly in group I for 2 days and every 4 hr in group II for 5 days and analyzed for urea content. Time series analysis revealed no periodicity of urea excretion in either group. Six animals were then studied for a total of 46 TPN days to define the relationship between the urea content of a single 3-hr morning urine aliquot and its respective content in a 24-hr collection. A significant linear relationship was found (r = +0.76, p less than 0.01). However, using this relationship, a reasonable estimate (+20%) of measured 24-hr urea output was achieved only 50% of the time using a single 3-hr urea output. Chair-adapted primates maintained on continuous TPN or a single oral meal with continuous saline infusion do not exhibit a periodic pattern of urea excretion. The variability in 3-hr urinary urea output in the chaired primate on continuous TPN does not consistently permit accurate estimation of the coincident 24-hr urinary urea output.

Nitrogen utilization from elemental diets.

Repletion experiments were performed in malnourished, chair-adapted primates to explore recently reported differences in nitrogen utilization from elemental diets. Two elemental diets were fed consecutively for 8 days through a gastrostomy. Diet C (maltodextrins, peptides, crystalline amino acids) resulted in: larger weight gain (F1,6 = 17.93, p less than 0.01); smaller decrease of serum albumin (F1,5 = 11.2, p less than 0.015), larger increase in total iron binding capacity (F1,6 = 30.6, p less than 0.002), and a more positive nitrogen balance (F1,6 = 30.4, p less than 0.002) than diet V (glucose oligosaccharides, crystalline amino acids). Diet C was considered to be more effective in the nutritional repletion of the study animals. Additional experiments were performed in normal human volunteers to investigate the metabolic fate of ingested glutamine and whether the rapid catabolism and excretion of the amido nitrogen of this amino acid, which constitutes 11.56% of total nitrogen in diet V, could explain the differences observed in primates in our study and in human subjects by other authors. Six normal volunteers were fed 15N amino glutamine, 15N alanine, or 15N H4Cl. Similar amounts of 15N from Gln and Ala were excreted in 10 hr. The amido group of glutamine does not seem to be metabolized differently from the alpha-amino group of alanine under the conditions of the study. The marked differences in nitrogen utilization from the study diets could not be explained by the presence of relatively large amounts of glutamine in one of them.

Impact of a nutritional support service on VA surgical patients.

The impact of a multidisciplinary Nutritional Support Service (NSS) on the reduction of complication was evaluated in 78 consecutive patients who received total parenteral nutrition (TPN) on the same VA surgical service. Patients were placed into one of three groups (pre-NSS, transition-NSS, post-NSS) based on the evolution of the NSS. A significant reduction in catheter sepsis was observed and was attributable to the establishment of an NSS, specifically, a nurse specialist and protocols for catheter insertion and care.