Reliability and sensitivity of frozen-section pancreatic biopsy

A collaborative Veterans Administration and University of California, Davis Medical Center group of 586 patients with histologically proved pancreatic carcinoma was reviewed. During laparotomy, 159 patients underwent 251 frozen-section pancreatic biopsies with subsequent permanent section examination of the same tissue block. All 112 positive frozen-section diagnoses were corroborated on permanent sectioning. The 47 patients with false-negative biopsy specimens were equally divided between sampling and interpretation error. We conclude that in this group of 159 pancreatic cancer patients, 30% failed to be correctly diagnosed by intraoperative frozen-section biopsy. This failure was due to patient sampling and interpretation error in equal proportion. Interpretation error rates were not influenced by the type or number of biopsies. Patient sampling error is apparently reduced by repeated biopsy, and specimen sampling error occurred less frequently with wedge biopsy.     

Endoscopically guided sinonasal cultures: a direct comparison with maxillary sinus aspirate cultures.

Sinusitis is a common medical problem that can at times be challenging to treat. Although most cases respond to empiric therapy, success is not achieved universally. If empiric therapy fails, it is important to identify the causative bacterial pathogen. Antral puncture is the traditional diagnostic method to recover and identify pathogens in sinusitis; however, it remains a painful, invasive test with potential complications. In contrast, rigid sinonasal endoscopy permits recovery of mucopus emanating from the sinus ostia with little pain and few possible complications. Endoscopy also affords important visual information that can confirm or refute a historical/clinical diagnosis of sinusitis. Although previous studies have shown poor correlation between nasal cavity swab cultures and maxillary sinus aspiration cultures, few investigations have compared endoscopically guided middle meatal cultures with cultures obtained from maxillary sinus aspiration. Thirteen patients with maxillary sinusitis in one or both sinuses underwent endoscopically guided culture of the middle meatus and maxillary sinus puncture with aspiration and culture (16 total study samples). Results from the microbiologic analysis were compared. Endoscopically guided middle meatal cultures accurately identified the predominant bacterial pathogen and correlated with the cultures from maxillary sinus aspiration in more than 90% of infections. These preliminary results suggest that endoscopically guided sinonasal cultures hold promise as a viable alternative to maxillary sinus aspiration. Endoscopically guided cultures appear to be an effective, noninvasive diagnostic tool for otolaryngologists managing sinusitis.     

Enhanced recovery of pseudomonas from blood cultures

Pseudomonas and staphylococcal septicaemia are frequent complications of paediatric patients with significant burns. Early diagnosis and appropriate treatment afford the greatest likelihood of clinical response. Blood cultures from these patients may be negative or may become positive only after prolonged incubation. To evaluate more rapid culture methods for precise diagnosis, an in vitro study was done. The effects of venting and/or rotating on low inocula blood cultures was evaluated. Both venting and rotating contributed to more rapid bacterial growth and the effects were additive, affording a much more rapid and, therefore, potentially more useful culture method.     

Analysis of anaerobic blood cultures in burned patients

The utility of anaerobic blood culturing is often debated in the general population, but there is limited data on the modern incidence, microbiology, and utility of obtaining routine anaerobic blood cultures for burned patients. We performed a retrospective review of the burned patients electronic medical records database for all blood cultures drawn between January 1997 and September 2005. We assessed blood cultures for positivity, organisms identified, and growth in aerobic or anaerobic media. 85,103 blood culture sets were drawn, with 4059 sets from burned patients. Three hundred and forty-five single species events (619 total blood culture isolates) were noted in 240 burned patients. For burned patients, four isolates were obligate anaerobic bacteria (all Propionibacterium acnes). Anaerobic versus aerobic culture growth was recorded in 310 of 619 (50.1%) burned patient blood culture sets. 46 (13.5%) of the identified organisms, most of which were not obligate anaerobic bacteria, were identified from solely anaerobic media. The results of our study suggest that the detection of significant anaerobic bacteremia in burned patients is very rare and that anaerobic bottles are not needed in this population for that indication. However anaerobic blood cultures systems are also able to detect facultative and obligate aerobic bacteria; therefore, the deletion of the anaerobic culture medium may have deleterious clinical impact.     

Guideline for the optimal use of blood cultures

The incidence of sepsis is increasing globally, with high morbidity and mortality. Prompt, accurate detection of bacteraemia and fungaemia is imperative for improving patient care, yet health care professionals lack training in correct blood culture techniques. These guidelines discuss the clinical importance of blood cultures, the indications for their use and the correct technique for optimal yield of pathogenic micro-organisms that cause sepsis.     

Near-infrared spectrometric determination of blood pH

BACKGROUND: Reflectance near-infrared spectroscopy (600-2200 nm) can noninvasively probe deep into tissues. Blood is the predominant absorber of near-infrared light in biological tissues. We investigated the feasibility of using reflectance near-infrared spectroscopy to measure blood pH in vitro. METHODS: Reflectance near-infrared spectra (600-2200 nm) were obtained with a fiberoptic probe immersed in diluted human packed red blood cells maintained at 37 degrees C. Changes in pH (6.800-7.600) were induced by: (1) varying the partial pressure of carbon dioxide by the bubbling of mixtures of humidified carbon dioxide and nitrogen gas through the blood; and (2) adding 1 N HCl/NaOH. Humidified oxygen gas was bubbled through the blood to generate variations in oxygen saturation. After each titration of pH, the spectrum was recorded and blood was sampled for the measurement of: pH, pCO(2), and pO(2) using blood gas analysis; and hemoglobin concentration and oxygen saturation using co-oximetry. Samples from three separate pH titrations were combined (120 total samples) and analyzed using partial least-squares analysis to generate a mathematical model relating spectral changes to pH (calibration set). This model was then used to predict the pH of a set of 36 pH titrations (prediction set). RESULTS: Quantitative and qualitiative analyses of the spectra in the calibration set found that spectral changes in the wavelength range, 650-1050 nm, were directly related to changes in pH. First-derivative-treated spectra from the calibration set, analyzed using partial least-squares analysis, generated a mathematical model with a cross-validated r(2) of 0.939 and a standard error of calibration of 0.046 pH unit. When this model was applied to the prediction set, with an offset correction, the r(2) was 0.936 with a standard error of prediction of 0.050 pH unit. CONCLUSION: Blood pH can be predicted in vitro with clinical significance using reflectance near-infrared spectroscopy (650-1050 nm) within a standard error of 0.050 pH unit.     

Absence of direct antioxidant effects from volatile anesthetics in primary mixed neuronal-glial cultures

BACKGROUND: Volatile anesthetics decrease ischemic brain injury. Mechanisms for this protection remain under investigation. The authors hypothesized that volatile anesthetics serve as antioxidants in a neuronal-glial cell culture system. METHODS: Primary cortical neuronal-glial cultures were prepared from fetal rat brain. Cultures were exposed to iron, H2O2, or xanthine-xanthine oxidase for 30 min in serum-free media containing dissolved isoflurane (0-3.2 mm), sevoflurane (0-3.6 mm), halothane (0-4.1 mm), n-hexanol, or known antioxidants. Cell damage was assessed by release of lactate dehydrogenase (LDH) and trypan blue exclusion 24 h later. Lipid peroxidation was measured by the production of thiobarbituric acid-reactive substances in a cell-free lipid system. Iron and calcium uptake and mitochondrial depolarization were measured after exposure to iron in the presence or absence of isoflurane. RESULTS: Deferoxamine reduced LDH release caused by H2O2 or xanthine-xanthine oxidase, but the volatile anesthetics had no effect. Iron-induced LDH release was prevented by the volatile anesthetics (maximum effect for halothane = 1.2 mm, isoflurane = 1.2 mm, and sevoflurane = 2.1 mm aqueous phase). When corrected for lipid solubility, the three volatile anesthetics were equipotent against iron-induced LDH release. In the cell-free system, there was no effect of the anesthetics on thiobarbituric acid-reactive substance formation in contrast to Trolox, which provided complete inhibition. Isoflurane (1.2 mm) reduced mean iron uptake by 46% and inhibited mitochondrial depolarization but had no effect on calcium uptake. CONCLUSIONS: Volatile anesthetics reduced cell death induced by oxidative stress only in the context of iron challenge. The likely reason for protection against iron toxicity is inhibition of iron uptake and therefore indirect reduction of subsequent intracellular oxidative stress caused by this challenge. These data argue against a primary antioxidant effect of volatile anesthetics.     

Volume sensitivity of blood pressure in end-stage renal disease

BACKGROUND: The influence of interdialysis (ID) volume expansion on the blood pressure (BP) change and on the BP level at the end of the ID time period was studied in 167 chronic haemodialysis patients. Our analysis focused on 120 patients not receiving antihypertensive drugs (untreated group). The remaining 47 patients were receiving antihypertensive medication (treated group). METHODS: The ID weight gain was considered equivalent to the volume gain. In each patient the mean ID BP change (as percent change of initial BP) and the mean ID volume expansion related to the lean body mass (ml.kg-1) were determined from 25 consecutive ID time periods. The individual volume sensitivity of BP was expressed as the BP change divided by the volume expansion. Basal overhydration was estimated as mean ID initial weight minus dry weight. RESULTS: All patients gained volume during ID time periods and the BP was increased in 91%. The change of mean BP (MBP) was directly correlated with volume expansion (r = 0.45, P < 0.00001) only in the untreated group. These patients showed a volume sensitivity unrelated with age, serum urea and calcium concentrations and haematocrit. Sensitivity of diastolic BP (DBP), an indicator of the capacity to respond to volume expansion by vasoconstriction (autoregulatory process), exhibited a negative correlation with the initial DBP level (r = -0.36, P < 0.0001) and with the serum potassium (in women, r = -0.35, p < 0.02). These factors appeared to counteract the volume-induced DBP response. The MBP levels at the end of ID time periods were independent of volume expansion and basal overhydration. Hypertensive patients showed a higher sensitivity than normotensive patients (0.35 +/- 0.2 versus 0.20 +/- 0.19% per ml.kg-1, P < 0.005). Final MBP showed a positive correlation with initial MBP and, to a smaller extent, with serum urea concentration. CONCLUSIONS: In our study the ID change of BP is partially dependent on volume gain. Volume sensitivity is a measure of the BP responsiveness and is higher in hypertensive patients. Final BP depends on the height of initial BP and other factors accounting for volume sensitivity, whose precise nature remain to be clarified.