Biomedical subjects
Publications and source records attributed to M G Nelson.
A technique is presented for intraoperative management of an axilloaxillary by-pass graft when performing a median sternotomy for myocardial revascularization. This method allows continual perfusion of both upper extremities during the operation thereby preventing the potential complications of upper extremity or cerebral ischemia.
Pancreatic injuries secondary to blunt trauma are challenging to diagnose. In many cases, the diagnosis is missed or delayed due to the subtle symptoms and signs of pancreatic injury. Blunt pancreatic injuries may evolve over a period of time and can be a source of extensive morbidity and mortality. Most radiologic and laboratory studies have been notoriously nonspecific in diagnosing pancreatic injuries. This article discusses three patients we treated with pancreatic transection secondary to blunt trauma, who underwent computed tomography (CT) of the abdomen on admission. The pertinent CT findings and utility of CT as a diagnostic tool in these three cases of blunt pancreatic injuries are reviewed. Abdominal CT scanning can accurately identify pancreatic injuries secondary to blunt trauma, allowing expeditious surgical intervention. A high index of suspicion for pancreatic injury combined with careful interpretation of abdominal CT scans can provide valuable information about pancreatic injury during the initial trauma assessment.
The hereditary deficiency of erythrocyte pyrimidine 5' nucleotidase has been investigated using an HPLC anion-exchange procedure designed to measure both red cell nucleotide content and enzymic activity. Red cell nucleotide profiles were determined using a low pH phosphate buffer salt-gradient system in 20 min, whereas a low pH buffer alone permitted the determination of enzymic activity with each of six different nucleotide substrates in less than 4 min. Both the red cell nucleotide profiles and the enzymic activity of haemolysates from two affected brothers and their children agreed well with previously published values. This unified approach should prove useful for detailed studies of deficiencies involving isoenzymes of pyrimidine nucleotidase.
The Travenol Hem-O-Scan and the Instrumentation Laboratory (IL) system for determination of the oxygen dissociation curve and P50 values have been evaluated. Using the Hem-O-Scan, an oxygen dissociation curve and P50 value may be obtained on 2 microliter of blood in 40 min, though the pH is not measured. In the IL system, approximately 3 ml of blood is required to establish four points on the oxygen dissociation curve in 80 min, and pH data are available. Both systems give reproducible results for P50, giving standard deviations of 0.786 mm Hg for the Hem-O-Scan and 0.949 mm Hg for the IL system, compared with 1.740 mm Hg for the manual system. Good agreement was found between the manual method and Hem-O-Scan (t = 0.363, degrees of freedom = 19, 0.8 greater than P greater than 0.7; r = 0.892, P less than 0.001). There was also satisfactory agreement between the IL system and the Hem-O-Scan (t = 0.370, degrees of freedom = 20, 0.8 greater than P greater than 0.7; r = 0.760, P less than 0.001). P50 values obtained by the manual and by both automated technics agree well with published values.
A system of processing the laboratory data of a busy haematology department serving a teaching group of hospitals and the general practitioners of the district is described. The system, which has been in routine use for over two years, is based on a dedicated CTL8030 computer sited in the laboratory utilising Lynwood visual display units (VDUs) for both input and access to the data files. Data from the Coulter 'S' is fed by an interface to the computer and to other data handling modules. Manual test results are entered via VDUs, mainly by laboratory staff who also validate all data. Access is available to all data for answering telephone requests. Data are retained on the disc file for 48 hours only, and cumulative reporting was not planned into the system as deliberate policy. Quality control of the Coulter 'S' output is maintained both throughout the day and retrospectively at the end of each working day using both whole blood patient blood transfusion profiles, a record of blood and product usage, worksheets, quality control information, end-of-day listing in alphabetical order plus statistical information for administrative purposes. Since its introduction the system has been remarkably free from breakdown as a result of hardware failure. A number of fail safe/fallbacks have been included in the system.
Two systems for quality control have been compared, viz., the whole-blood control preparation method and the algorithm method using the geometric moving average XB and a new estimator Y. The system involving whole-blood controls has the advantage of simplicity of operation, but the economic cost of commercial preparations is often high. The algorith system has the advantage that results of all the test samples are used in the calculation; to some extent, this provides a buffer against random variation. The number of count-outs in a given channel is related to the precision of the channel, which in turn is a function of the number of determinations and calculations required for that result. An error of around 1% is introduced into the result each time a calculation is performed. A successful quality control scheme should contain elements of both control preparation and algorithm methods.
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For counting erythrocytes the instrument was precise, with a mean coefficient of variation of 1.21%. Erythrocyte counts showed close agreement with results obtained on a Coulter A electronic counter of proven accuracy. When the Celloscope 401 was modified by the manufacturers to eliminate electrical interference from other laboratory equipment, satisfactory precision and accuracy for white cell counting was obtained. Using cetrimide diluent the coefficient of variation was 1.6% but when using saponin/saline diluent the coefficient of variation was 3.5%. For leucocyte counting there was close agreement between duplicate tests performed on the Celloscope 401 and the Coulter S. The instrument was capable of satisfactory precision and accuracy in platelet counting, provided that the sedimentation method was used to obtain a platelet-rich plasma. The best results were obtained if a two-step dilution was carried out with a first dilution in 10% EDTA and a second in 2.5 mM cocaine in water. Using this method the precision study indicated a coefficient of variation of 3.11%. Close agreement was obtained between platelet counts on the Celloscope 401 when compared with the results obtained either by phase-contrast microscopy or using another electronic counter. Allowing for predilution and duplicate counts on each sample, the rate of throughput was approximately 32 samples per hour. Throughout the test period, the instrument remained electronically and mechanically stable.
The output from a Coulter model S is captured by a specially designed silent interface which visualizes the results, automatically prints the data on a continuous paper roll and transmits the information to a card punch located in a data processing room. Further requested test data and patient identification data are subsequently added manually to the punch card. The completed deck of cards is used in an off-line batch mode on a dedicated laboratory computer to format report documents, produce ward listings, and quality control information. A punch card off-line method is also described for blood group and related data.
The Fisher Hem-Alyzer is a multitest sequential discrete analyser with automatic printout of digitized results on paper tape. The instrument is well designed, soundly constructed, and reliable in routine use. Cross contamination from the sampler probe or between the cuvettes is minimal. Accuracy and precision are both highly satisfactory. Although the standard rate of throughput is 32 specimens per hour the instrument can be used at irregular intervals to analyse smaller batches or even individual specimens. In a routine daily service the Hem-Alyzer was capable of handling a workload of 200 specimens per day, requiring three hours of laboratory technician time. The Hem-Alyzer produces only three parameters. By not determining the packed cell volume it is not possible to incorporate the derived indices (MCV and MCHC) into the system and this, in the long term, is bound to be a disadvantage.
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The Technicon AutoAnalyzer SMA-4 has been systematically evaluated. Carry-over from the sample cups was found to be within an acceptable range. The precision and accuracy of the four parameters determined by the instrument have been investigated. The haemoglobin results were found to be accurate. There was good agreement with leucocyte counts performed on the model A Coulter electronic cell counter. After certain modifications had been made in the manifold, satisfactory degrees of accuracy were also obtained for the erythrocyte counts. Although the determination of the haematocrit by conductance is influenced by a variety of factors, the mean coefficient of variation was found to be 0.83% and 95% of the results agreed within +/- 2% of those obtained by the microhaematocrit centrifugation method.A logistic assessment of the SMA-4 when it was put into routine use indicated the need to select blood samples without excess anticoagulant, to calibrate the instrument before each run, to test for instrumental drift, to use a rapid method of correcting stoppages, and, if concurrent reporting is carried out, to employ the part-time services of a second operator. The presence of dust in the environment was found to have a deleterious effect on both the mechanical and electronic components of the system requiring preventive maintenance. It should be possible, by interfacing an analogue-digital converter and automatic punch, to produce data compatible with records.
A method of processing haematological laboratory data based on the IBM 870 system is described. As the cards are being punched with the identification particulars of the patient and source of the sample, a worksheet is automatically generated on which the tests are indicated. The results of the laboratory tests are recorded by the technician on the worksheet and reproduced on the punch cards which are subsequently used for the automatic printout of the results on self-adhesive preprinted labels. The resulting report is clear and legible and is transferred onto the request/report document. The data processing is carried out by clerk/typists who have been trained as punch card operators. The present workload of approximately 2,000 items of information obtained from some 170 samples per day is handled by one punch card operator in less than three hours. The punch cards are manipulated in a sorter for quality control purposes and are stored for subsequent retrieval of information.
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