By C. Vatras. Furman University. 2018.
Children who are diagnosed with a shunt malfunction are taken promptly to the operating room for shunt revision purchase 25mg strattera otc. The presence of a ﬂuid collection in the subcutaneous tissue in proximity to the shunt track is sugges- tive buy strattera 40 mg lowest price. A collapse of the valve without quick reﬁlling of CSF may indicate a shunt obstruction buy strattera 18 mg low cost. Finally order 10 mg strattera with mastercard, the shunt reservoir can be accessed by a 23- or 25-gauge butterﬂy needle. The presence of spontaneous ﬂow with good respiratory variations up the tubing or in a manometer connected to the butterﬂy indicates patency of the ventricular catheter. If there is no CSF ﬂow up the manometer and the ventricles are large, a presumed shunt obstruction is conﬁrmed. In some institutions, a nuclear medicine patency study may be performed to evaluate a presumed shunt malfunc- tion, by occluding the valve and injecting through the butterﬂy needle a radioactive isotope, such as indium [111In] into the reservoir. The radioactive isotope can then be traced from the ventricular system, through the shunt device, and into the distal collection site. Uncommon Shunt Complications Table 4 lists several uncommon shunt complications. Subdural hygromas and hema- tomas may develop after the insertion of a ventricular shunt into a child with very large ventricles and a thin cerebral cortical mantle. Treatment of symptomatic subdural hygromas and hematomas consists of changing the shunt valve to a higher 34 Avellino pressure setting and=or by introducing a catheter into the subdural effusion and connecting it to the distal shunt system. Ventricular catheter migration out of the ventricular system occurs if the shunt has not been properly ﬁxed at the burr hole site where it exits the skull. Abdominal pseudocysts can develop around the distal end of the peritoneal catheter. They often develop in young children secondary to indolent bacterial infec- tions. In addition to presenting with a clinical picture of a shunt infection, the patient may also complain of abdominal pain and distension. The cysts may be percutaneously aspirated, and the ﬂuid can be cultured. Given the indolent nature of the likely infections, treatment is no different from any other shunt infection. Ascites, similarly, may be indicative of an indolent infection, or it may be secondary to CSF overproduction and=or inadequate peritoneal absorption. Hernias can also develop within 3 months of shunt insertion, and are treated like any other hernia. Perforation of intraperitoneal organs is a rare but well-recognized complication. Treatment of Posthemorrhagic Hydrocephalus (PHH) Premature infants weighing 0. First, serial lumbar punctures and=or ventricular taps are performed to normalize ICP; approximately 5–15 mL of CSF must be removed daily to adequately temporize the PHH. The infant’s ICP can be assessed by palpation of the anterior fontanelle and detection of the cranial suture splaying; and ventriculomegaly can be followed by serial cranial ultrasounds. Ventriculosubgaleal shunts can safely temporize PHH while avoiding exter- nal drainage or frequent CSF aspirations. A ventricular catheter connected to a sub- cutaneous reservoir can be accessed for daily CSF aspirations with a risk of infection of less than 5%. A ventriculoperitoneal shunt should be considered when the CSF is cleared of posthemorrhagic debris, CSF protein is <1000 mg=dL, the infant weighs >1. Treatment of Hydrocephalus Associated with Myelomeningocele Approximately 85% of infants with myelomeningoceles develop symptomatic hydro- cephalus, and approximately 50% have obvious hydrocephalus at birth. Treatment is usually with a ventriculoperitoneal shunt, although recent evidence suggests that endoscopic third ventriculostomies may have a useful role. Historically, shunt place- ment is deferred until after the myelomeningocele is repaired; however, contempor- ary evidence suggests that the risks of shunt complications are not signiﬁcantly increased if the shunt is placed at the same time as the myelomeningocele closure. In many centers, the shunt is placed in neonates with ventriculomegaly at the time of the myelomeningocele closure with the hope that a shunt will prevent a CSF leak from the repaired myelomeningocele site.
The tools that will ultimately deﬁne the success of the project are analytical models of biological pro- cesses that have predictive power – virtual cells order strattera 25 mg with amex, tissues 10mg strattera otc, organs and systems buy generic strattera 10 mg. This will extend buy strattera 18 mg visa, and partially replace, the traditional approach to bio- medical research that is based on studying living cells or tissues in vitro, or on obtaining data from human volunteers in vivo, by introducing ‘in silico’ experiments (a term, derived from the currently prevailing silicon- based computer chips). Much of the ‘input’ data is already available from many decades of bio-medical research. More will follow and, with the development of new experimental tools and technologies, the insight into sub-cellular, genetic and molecular levels of biological activity is becom- ing increasingly detailed. Virtual biological systems will be produced by describing in great detail the constituent parts and their interrelation according to the laws of conservation of energy, mass, and momentum. Such models can be used to perform in silico experiments, for example by monitoring the response of a system or its components to a deﬁned intervention. Model ‘output’ – predictions of biological behaviour – is then validated against in vitro or in vivo data from the real world. A conﬁrmation of the modelling-derived predictions would allow the performance of new in silico experiments, either with a higher degree of conﬁdence or at a higher level of functional integration. Rejection of model output would help to pinpoint where the model needs reﬁnement, either by providing new input data, or by direct model improvement. Subsequently, the in silico experiment could be repeated with a higher degree of conﬁ- dence, until the model satisfactorily reﬂects the tested aspect of reality. This is a steady iterative process between the virtual organ and the real thing. Its prime objectives are the development of our understanding of a biological system like the heart, and the improvement of its in silico description. Through this multiple iteration, virtual organ models mature towards a tool that can be used with a high degree of conﬁdence for research, development or clinical applications by scientists and doctors who do not need to be specialists in model development or validation. A patient who recently recovered from a minor heart attack is suffering from periods of ectopic ventricular beats, originating from what is believed to be a small area of post-ischaemic ﬁbrosis in the free wall of the left ventricle. The subsequent section on ‘The utility of virtual organs’ will address more general aspects that can be appreciated without knowledge of the detail presented next. The making of the virtual heart 135 The extent and localisation of the area is investigated and conﬁrmed, using catheter impedance tracking of ventricular wall tissue properties and non- invasive monitoring of cardiac dimensions and relative catheter location. A small area of increased ﬁbrosis is diagnosed and mapped in real time to a patient-speciﬁc 3D virtual heart model. Using the virtual heart, optimal pattern and localisation for the tissue ablation are established with the aim of maximising the anti-arrhythmic effect while mini- mising the energy levels of the procedure. Using the same catheter, a minimal tissue area is ablated, obliterating the ectopic focus and terminating the arrhythmia. The whole, minimally-invasive procedure took only 12 minutes, and the patient made – as typical for 97 per cent of cases – a full recovery. Cardiac models are amongst the most advanced in silico tools for bio-med- icine, and the above scenario is bound to become reality rather sooner than later. Both cellular and whole organ models have already ‘matured’ to a level where they have started to possess predictive power. We will now address some aspects of single cell model development (the ‘cars’), and then look at how virtual cells interact to simulate the spreading wave of electri- cal excitation in anatomically representative, virtual hearts (the ‘trafﬁc’). Less well known is the fact, that this mechanical activity is tightly controlled by an electrical process called ‘excitation’. In the normal heart, electrical excitation originates in specialised pace- maker cells and spreads as an electrical wave throughout the whole organ. This electrical signal determines the timing and, to a degree, the force of cardiac contraction. Thus, the heartbeat is a consequence of an electrical process (which does, however, go completely unnoticed in day-to-day life). In 1928, two Dutch engineers, van der Pol and van der Mark, described the heartbeat by comparing it to a simple oscillator. This approach, which was revolution- ary at the time, gave rise to a whole family of models of the heartbeat and of the operation of other periodically active, electrically excitable cells (like neurones or skeletal muscle cells). This approach is, at the same time, the great advantage and a major limitation of membrane potential models. As they are rather compact, models of this type were the ﬁrst to be used in investigations of the spread of excitation in multi-dimensional ‘tissue’ representations consisting of relatively large numbers of interconnected excitable elements; their role in assessing biophysical behaviour like cardiac impulse propagation is undiminished.
No doubt it is possible to instruct students in ‘basic steps’ order strattera 40 mg free shipping, such as the importance of introductions generic 40mg strattera overnight delivery, shaking hands order 25mg strattera visa, sitting down generic 10mg strattera visa, listening attentively, etc. Perhaps in the past such conduct would have been regarded as simple good manners, which students might have been expected to acquire at home rather than at medical school. However, it may be fairly argued that the manifest lack of such elementary civility towards their patients among many doctors justifies including such instruction in the curriculum. Nevertheless, it is difficult to imagine that it would be necessary to spend more than a few minutes in an overcrowded curriculum on such tuition. Such skills fall into the category of things that can be learned by observation and reflection in clinical situations, not taught in a classroom (McCormick 1996). Indeed the very attempt to teach them in such a formal way underestimates the subtleties of doctor-patient communication which generations of doctors have painstakingly acquired through the sort of apprenticeship experience that is now so disparaged. The net effect of the promotion of comic- book communication skills is to elevate the banal while degrading what is profound in medical practice (Willis 1995:127). Clinical governance Clinical governance means the extension into the medical world of new mechanisms of regulation through audit that have been developed in business. These amount, according to Michael Power, professor of accountancy at the London School of Economics, to ‘the spread of a distinct mentality of administrative control, a pervasive logic which has a life of its own over and above specific practices’ (Power 1994). Power describes an ‘audit explosion’ in the late 1980s and early 1990s, as the term ‘began to be used in Britain with growing frequency in a wide variety of contexts’ (Power 1997: 3). A perception of a general deterioration in professional confidence and public trust in business and in services, in both private and public sectors, resulted in a quest for external guarantees of quality and probity. But audit is not a neutral process: when people subject their work to external monitoring, they inevitably find that this process leads to a reorganisation of their work to comply with the requirements of audit. As Power writes, ‘audit is not simply a solution to a technical problem; it also makes possible ways of redesigning the process of government’ (Power 1997:11). Though audit is designed to reassure, Power argues that it has ambivalent implications for relations of trust. Where trust is lacking, people hope that it can be restored through audit. The audit society tends to create ‘an inflationary spiral’ of trust in more remote sources of reassurance, or to put it another way, it fosters increasing distrust: 151 THE CRISIS OF MODERN MEDICINE Assumptions of distrust sustaining audit processes may be self-fulfilling as auditees adapt their behaviour strategically in response to the audit process, thereby becoming less trustworthy. In a detailed study of the impact of the ideology of audit on the world of health, Power notes that this has created ‘an enormous environmental disturbance’ (Power 1997:108). He comments on the attempt to adapt medical audit to managerial purposes that this ‘fragile practice’ was ‘never intended as a public accountability device’ (Power 1997:109). As medical audit has been assimilated into clinical governance, concerns about the quality of patient care have become subordinate to the managerial performance imperatives. Power concludes that faith in audit as a means of regulating medical performance reflects wider social anxieties, affecting doctors and patients as well as managers and politicians, and the ‘need to create images of control in the face of risk’ (Power 1997: 121). Other commentators have warned that this process may have adverse effects producing ‘inspection overload’ and irrevocable damage to cultures of trust (Day, Klein 1990). The processes of clinical governance are not only time- consuming, but potentially demoralising, as the presence of a shadowy third party in doctor-patient relations has a subtly corrosive effect on professional authority. Some have expressed concerns that guidelines can stifle innovation and encourage defensive practice (this is certainly likely to increase if departures from national guidelines become the basis for litigation) (Fletcher, Fletcher 1990). Others fear that ‘insufficient attention will be paid to the sometimes nebulous concepts of trust and culture in a headlong rush for the more tangible appeals of measurement, monitoring and coercive control mechanisms’ (Davies, Mannion 1999). In a brief commentary on ‘the perils of checklist medicine’, London GP Iona Heath has pointed out some of the dangers of the preoccupation with guidelines on doctor-patient relationships (Heath 152 THE CRISIS OF MODERN MEDICINE 1995). As she observes, ‘guidelines are constructed from evidence from research derived from studies of populations and are predicated on the notion of a composite patient which may have little immediate relevance to the troubled person who presents in the consulting room’. She warns that guidelines ‘depersonalise individual patients and turn them into diseases’ and that the managerial use of guidelines to monitor practice ‘implies levels of coercion and control which are potentially destructive of the fragile good that is the doctor-patient relationship’. Revalidation The proposed system of revalidation will have far-reaching consequences for the professional standing of doctors and for our relations with our patients. For GPs, it will take the form of ‘a continuous process with an episodic submission and assessment of fitness to continue in general practice’ (RCGP November 1999:5). Assessment will take place against detailed standards of acceptable and unacceptable conduct under the headings of ‘professional competence’, ‘good relations with patients and colleagues’ and ‘professional ethical obligations’ (RCGP October 1999:1). The immediate response to these questions from supporters of the new system is that the proposed reforms are necessary to restore public confidence in doctors and the NHS in response to ‘a progression of “rogue dolors” and health care scandals through the media’ (Smith 1999).
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