Management of Defects

A traceability matrix comes into its own when managing defects. If, at the planning stage, requirements, test cases and hazards have been mapped then it is a relatively straight-forward task to link the defect back to the hazard and understand the 

The techniques for carrying out a safety assessment on a defect are largely the same as for evaluating the risk for any hazard or indeed an incident in live service. At the very least one should consider  

Whether the defect affects a clinical business process known to be associated with significant clinical risk. 

Whether a clinician would rely upon the part of the system affected to deliver safe clinical care. 

The frequency with which the defect would be triggered during normal operation of the system. 

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Nature In some types of engineering and management-science problems, we may be concerned with a random variable which represents a proportion, for example, the proportional number of defective items per day. The method described previously relates to a single proportion. In this subsection two proportions will be considered. 

The urea cycle is essential for the detoxification of ammonia 678 Urea cycle defects cause a variety of clinical syndromes, including a metabolic crisis in the newborn infant 679 Urea cycle defects sometimes result from the congenital absence of a transporter for an enzyme or amino acid involved in the urea cycle 680 Successful management of urea cycle defects involves a low-protein diet to minimize ammonia production as well as medications that enable the excretion of ammonia nitrogen in forms other than urea 680... 

This example clearly shows that developing and accepting a hypothesis based on accurate and complete information is necessary for setting an acceptable technical solution. If the plant manager could have persuaded the resin manufacturer to develop a new resin that was similar to the incumbent resin, then the defect would still be there, the cost of the troubleshooting process would have been extremely high, the supplier would have incurred unnecessary development costs, and a high level of defective parts would still have occurred because the root cause would not have been removed. 

A serious complication of HIV infection is HIV-associated thrombocytopenia, This results from immune-mediated platelet destruction and decreased or defective platelet production due to infection of megakaryocytes with HIV-1 (211). HIV-related thrombocytopenia may be associated with an accelerated progression to AIDS and decreased survival rates. Hence management of thrombocytopenia in AIDS patient is crucial to prevent severe complications, Severe bleeding complications in HIV-infected hemophilia patients treated with protease inhibitors... 

The vast majority of ventricular septal defects (VSD) are congenital. Acquired VSDs are almost always a consequence of septal rupture following myocardial infarction, traumatic VSDs as a consequence of sharp or blunt chest trauma are exceptionally rare. Typically the post myocardial infarction ventricular septal defect (PMIVSD) occurs within the first week after the event (41). In the current era of thrombolysis about 0.2% of patients develop a VSD as a result of septal necrosis. Medical management of these patients is limited and carries a 30-day mortality of 94% compared with 47% who were treated surgically (42). 

The management of ventricular extra beats is based on recognition of the quinidine-like basis of the conduction defect In the series reported above (40) all 13 patients with ventricular arrhythmias responded to intravenous infusion of lidocaine (mean dose 2.0 mg/minute). This alone might account for the absence of deaths in this series. 

Topical anesthesia not only provides adequate surface anesthesia before debridement, it also has the beneficial effect of loosening the corneal epithelium. If both tetracaine and proparacaine are on hand, tetracaine is the preferred agent due to its greater effect on the corneal epithelium. Debridement may be accomplished with either a moistened cotton-tipped applicator or an Algerbrush. Both techniques effectively remove loose and damaged epithelial tissue. Debridement should be followed by irrigation and management of the corneal defect as an abrasion (see Chapter 26). 

In the first instance, it is used to confirm a diagnosis when dealing with a patient with a metabolic problem. When the routine chemical screens indicate the presence of abnormal metabolites or raised levels of the usual metabolites, then MS can positively confirm their identity and thus a diagnosis, or, should it be a new inborn error, point to the metabolic pathways which are affected. In many of the organic acidurias described, the defect leads to gross excretion of one or more compounds and, as quantitative extraction is not necessary for their detection, simple solvent or other methods are normally used. In some instances it is vital that analysis be carried out quickly so as to indicate the most suitable clinical management of an acutely ill patient. 

PoUer L, More JR. A study of Naphtionin in the management of the bleeding defect in patients with thrombocytopenia. J Chn Pathol 1964 17 680-4. 

Propofol infusion syndrome mimics the mitochondrial myopathies, in which there are specific defects in the mitochondrial respiratory chain. The clinical features of mitochondrial myopathy result from a disturbance in lipid metabolism in cardiac and skeletal muscle. These patients generally remain well until stressed by infection or starvation, although subclinical biochemical abnormalities of mitochondrial transport can be demonstrated. It has been suggested that early management of critically iU children may not include adequate calorific intake to balance the increase in metabolic demands, and that in susceptible children the diversion of metabolism to fat substrates may cause the propofol infusion sjmdrome. It is unclear if the dose or duration of propofol infusion alters this effect. As adults have larger carbohydrate stores and require lower doses of propofol for sedation, this may account for the relative rarity of the sjmdrome in adults. The authors suggested that adequate early carbohydrate intake may prevent the propofol infusion syndrome (71). 

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