Defining acidosis in postoperative cardiac patients using Stewart's method of strong ion difference.

OBJECTIVE: To define the true incidence and nature of acidosis in pediatric patients postcardiac surgery, using Stewart's direct method of measuring strong ion difference. We also wished to compare the ability of standard indirect methods (base deficit, lactate, anion gap, and corrected anion gap) to accurately predict tissue acidosis. DESIGN: A single-center prospective observational study. SETTING: A pediatric intensive care unit in a tertiary referral center. PATIENTS: Pediatric patients who had undergone cardiac surgery were studied in the immediate postoperative period. Patients who had undergone both open and closed cardiac surgery were included. INTERVENTIONS: Routine arterial blood gas analysis and laboratory electrolyte measurements were made in patients immediately on admission to the pediatric intensive care unit (PICU) after cardiac surgery and each morning until discharge from the PICU. MEASUREMENTS AND MAIN RESULTS: Figge's equations were used to calculate strong ion difference and total tissue acids (unmeasured acids and lactate). These direct methods then were compared to indirect measurements: base deficit, lactate anion gap, and anion gap corrected for albumin. We collected 150 samples from 44 patients. Tissue acidosis occurred overall in 60 of 150 samples. This was due to raised unmeasured acids alone in 44 of 60 (73.3%), raised lactate alone in six of 60 (10%), and a combination of the two in ten of 60 (16.6%). Hyperchloremia occurred in 19 of 150 samples overall and 12 of 25 (48%) samples immediately after cardiopulmonary bypass. Measured base deficit showed a poor correlation with true tissue acidosis (r = -.48, p <.001) and the worst discriminatory ability (area under the curve, 0.72; 0.62-0.82). Anion gap corrected for albumin had the best correlation (r =.95, p <.001) and highest area under the curve (0.90; 0.85-0.95). CONCLUSIONS: Metabolic acidosis occurs frequently postcardiac surgery and is largely due to raised unmeasured acids and less commonly raised lactate. Hyperchloremia is common, particularly after cardiopulmonary bypass. Base deficit correlates poorly with true tissue acidosis, and corrected anion gap offers the most accurate bedside alternative to Stewart's method of tissue acid calculation.     

Loss of neurofibromatosis 1 (NF1) gene expression in NF1-associated pilocytic astrocytomas

The critical role of the neurofibromatosis 1 (NF1) gene as a tumour suppressor has been clearly demonstrated for malignancies arising in NF1 patients. However, little is known about the more common benign tumours, such as the pilocytic astrocytoma. Most NF1-associated astrocytomas are benign and clinically non-progressive, though aggressive tumours are occasionally encountered. In this study, eight pilocytic astrocytomas from six individuals affected with NF1 were analysed for NF1 expression. All eight tumours demonstrated loss of neurofibromin expression by immunohistochemistry, which was confirmed in one case using Western blot analysis. Microsatellite analysis showed loss of a single NF1 allele (LOH) in two of four NF1-associated tumours. These results demonstrate that, in contrast to sporadic astrocytomas, loss of NF1 expression is an important primary genetic event in the pathogenesis of NF1-associated pilocytic astrocytomas.     

Simultaneous measurement of human joint force, surface electromyograms, and functional MRI-measured brain activation

Functional magnetic resonance imaging (fMRI) has been increasingly used in studying human brain function given its non-invasive feature and good spatial resolution. However, difficulties in acquiring data from peripheral (e.g. information from muscle) during fMRI studies of motor function hinder interpretation of fMRI data and designing more sophisticated investigations. Here we describe a system that was designed to concurrently measure handgrip force, surface electromyograms (EMG) of finger flexor and extensor muscles, and fMRI of human brain. The system included a pressure transducer built in a hydraulic environment, a heavily shielded EMG recording element, and a visual feedback structure for online monitoring of force and/or EMG signal, by the subject positioned in the scanner during an fMRI experiment. System evaluation and subsequent fMRI motor function studies have indicated that by using this system, high quality force and EMG signals can be recorded without sacrificing the quality of the fMRI data.     

Comparison of the internal state scale to clinician-administered scales in asthma patients receiving corticosteroid therapy

Mood symptoms are reported frequently in asthma patients, particularly during corticosteroid therapy. This investigation compared the Internal State Scale (ISS), a self-report measure of symptoms of mania and depression, to the Hamilton Rating Scale for Depression (HRSD), Young Mania Rating Scale (YMRS), and Brief Psychiatric Rating Scale (BPRS) in a group of asthma patients (n=60 at baseline) before, during, and after a 1-2 week burst of prednisone. The depression and well being subscales of the ISS correlated well with HDRS scores. The perceived conflict subscale correlated with the BPRS scores. However, none of the ISS subscales correlated consistently and specifically with the YMRS in this population. Possible explanations for differences observed in bipolar versus asthma patients given the ISS are discussed. These data suggest the ISS may be a useful tool for depression symptoms and overall psychopathology in asthma patients and in patients receiving corticosteroid therapy. However, its ability may be attenuated outside of the population for which it was designed.     

Dendritic and synaptic alterations of hippocampal pyramidal neurones in scrapie-infected mice

Neurone damage and eventual loss may underlie the clinical signs of disease in the transmissible spongiform encephalopathies (TSEs). Although neurone death appears to be through apoptosis, the trigger for this form of cell death in the TSEs is not known. Using two different murine scrapie models, hippocampal pyramidal cells were studied through microinjection of fluorescent dye, and synaptic integrity, using p38-immunoreactivity (p38-IR), both visualized using confocal laser scanning microscopy. Intradendritic distensions and dendritic spine loss were found to co-localize to areas of vacuolar and prion protein pathology in the hippocampus of mice infected with ME7 or 87 V scrapie. A significant reduction in p38-IR was found concomitantly in the hippocampus in ME7 scrapie mice. These results indicate that both pre- and post-synaptic sites are altered by scrapie infection; this would disrupt neuronal circuitry and may initiate apoptotic cell death, giving rise to the neurological disturbances manifested in clinical TSE cases.     

全科医生札记--布朗医生日记

生日贺卡每年12月27日我都会收到我的保险公司代理人送来的生日贺卡和一张冰淇淋店的优惠券。去年我开始为我的病人做同样的事情。将病人生日按顺序排列成单并输入计算机,每月打印2次,将过生日病人的名字标记出来,我的办公室管理员伊莎贝尔负责写病人的名字和地址,并在每张贺卡     

Changes in cortical activity during suppression in stereoblindness

Patients with strabismus or anisometropic amblyopia fixate and attend with one eye and suppress the image from the other eye. Here we use a visual evoked potential technique to show that patients who lack normal stereopsis retain suppressive binocular interactions but lack a characteristic form of non-linear binocular interaction that is present in normal observers. Oscillating grating targets presented at different temporal frequencies in the two eyes evoke a strong response in normal observers at a frequency equal to the sum of the two input frequencies for fusable targets but not for rivalrous ones. However increasing contrast in one eye reduces the response amplitude from the other eye under either fusable (dichoptic masking) or rivalrous conditions. Stereo-deficient observers lack the sum-frequency response, but retain dichoptic masking interactions. Dichoptic masking is stronger when the masker is presented to the patients' dominant rather than non-dominant eyes, suggesting that a subset of preserved binocular inhibitory interactions form the basis of clinical suppression.     

Australian experience with the Freehand System for restoring grasp in quadriplegia

BACKGROUND: The purpose of the present study was to document the value of an implanted multichannel neuroprosthesis (Freehand System) for restoring hand grasp in the first Australians to receive this device. METHODS: Hand function in C5 quadriplegic patients was assessed via measurement of pinch forces, a grasp release test and tests of activities of daily living (ADL). Comparisons were made between presurgery scores and scores recorded after rehabilitation when the neuroprosthesis was and was not in use. RESULTS: A significant difference for both lateral pinch (P = 0.003) and palmar grasp (P = 0.003) was found between forces recorded with and without the use of the neuroprosthesis after rehabilitation, but not between forces recorded presurgery and during rehabilitation without the neuroprosthesis. All subjects were able to grasp, move and release more objects within the 30-s test period with the neuroprosthesis than without it. Collective results for the eight ADL tests for all six subjects show that, in 35 of the 48 (73%) occasions, less physical assistance and/or adaptive equipment was required when the Freehand system was employed compared to when it was not used. In 41 of the 48 (85%) occasions, the six subjects expressed a preference for using the neuroprosthesis to perform these activities of daily living. Twelve months after rehabilitation, five of the six subjects still used the neuroprosthesis daily or every second day. CONCLUSION: The Freehand neuroprosthesis has provided useful hand function with few surgical and technical difficulties in these patients. Regular ongoing use of the device indicates user satisfaction.     

Technique of controlled reperfusion of the transplanted lung in humans

BACKGROUND: Reperfusion injury remains a significant and sometimes fatal problem in clinical lung transplantation. Controlled reperfusion of the transplanted lung using white cell-filtered, nutrient-enriched blood has been shown recently to significantly ameliorate reperfusion damage in a porcine model. We modified this experimental technique and applied it to human lung transplantation. METHODS: Approximately 1,500 mL of arterial blood was slowly collected in a cardiotomy reservoir during the lung implant, and mixed to make a 4:1 solution of blood:modified Buckberg perfusate. This solution was passed through a leukocyte filter and into the transplant pulmonary artery for 10 minutes, at a controlled rate (200 mL/min) and pressure (less than 20 mm Hg), immediately before removal of the vascular clamp. RESULTS: Five patients underwent lung transplantation (1 bilateral, 4 single lung) using this technique. All patients were ventilated on a 40% fraction of inspired oxygen within a few hours and extubated on or before the first postoperative day. CONCLUSIONS: Controlled reperfusion of the transplanted lung with white cell-filtered, nutrient-enriched blood has given excellent functional results in our small initial clinical series.