271 research outputs found
Outer membrane proteins and lipopolysaccharides mediated antibody response against bovine Pasteurella multocida type B-2
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Role of Decompressive Craniectomy in severe Traumatic Brain Injury: An Institutional Experience
No full textObjective: The present study was designed to assess the outcome following the Decompressive Craniectomy procedures performed in our setup for patients presenting with severe traumatic brain injury.
Materials and Methods: This was a retrospective study wherein the medical records of adult patients that presented with an initial Glasgow Coma Scale (GCS) ? 8 and in whom decompressive craniectomy had been carried out for severe traumatic brain injury were retrospectively analyzed. Patients in whom decompressive craniectomy had been carried out for causes other than trauma and patients with initial GCS ? 9 were excluded from the study. The studied parameters included age, sex, initial GCS, computed tomography (CT) brain diagnosis, and the outcome according to the Glasgow coma outcome scale (GOS).
Results: The study included 12 patients, and of these 12 patients operated with Decompressive Craniectomy for severe traumatic brain injury only 2 survived. The mortality was 83.3%. The initial GCS and age were not statistically different between the survivors and the non-survivors. Based on the Glasgow Outcome Scale (GOS) only 1 patient had a good outcome. Overall, an unfavorable outcome based on the GOS score was seen in 91.7% of patients.
Conclusion: Our study concludes that Decompressive Craniectomy is associated with high mortality in patients presenting with severe traumatic brain injury and does not seem to offer a better alternative to standard medical management
Relationship between Postoperative Dexamethasone Following Posterior Spinal Surgery and Surgical Site Infection
No full textObjective: Studies have shown that postoperative dexamethasone administration in patients in whom posterior spinal surgical interventions have been carried out reduces the postoperative pain and decreases the analgesia requirement. Our study aimed to find out whether the use of postoperative steroids in patients that had undergone posterior spinal surgical procedures led to an increased incidence of wound infections.
Materials and Methods: The medical data of 52 patients in whom posterior spinal surgical interventions had been performed were retrospectively analyzed. The patients were divided into two groups. In the first group, postoperative dexamethasone had been administered after spinal surgery, and in the second group, no postoperative dexamethasone had been given. The two groups were then compared for their association with postoperative surgical site infection.
Results: Forty-five patients were included in the group in whom postoperative dexamethasone was given. Six (13.3%) of these patients developed postoperative surgical site infections. None of the seven patients in the second group in whom no postoperative dexamethasone had been administered developed postoperative wound infection. The difference in infection rate between the two groups did not reach statistical significance (p = 0.3).
Conclusion: An infection rate of 13.3% in the group of patients in whom postoperative dexamethasone had been administered is considerably high as compared to the 1 – 2% incidence quoted in the literature for simple laminectomy procedures. A prospective study with a larger sample size is needed to accurately define the relationship between postoperative dexamethasone administration and surgical site infection following posterior spinal surgery
A Study of Reduced Order 4D-VAR with a Finite Element Shallow Water Model
No full textForecast models often depend on unknown parameters, such as model initial and boundary conditions, or other tunable parameters not necessarily having any physical meaning. Calibration of these parameters to minimize errors between forecasted and observed states is called data assimilation. A common approach in this context are variational methods, of which four dimensional data variation (4D-VAR) is studied in this thesis. In 4D-VAR, a cost function is defined that penalizes misfits between observations and the corresponding numerical model results, obtained by running the model with the chosen configuration. Performing optimization with regard to this cost function yields an improved initial parameter set. Associated with this type of methods, however, are difficulties in connection with programming the adjoint model, which is needed to compute the exact gradient of the cost function. Additionally, having to integrate the adjoint model backwards in time adds significantly to the computational cost of the data assimilation process. To avoid manual implementation of adjoint code and to reduce computational complexity, approximation of the gradient calculation is considered through the use of proper orthogonal decomposition (POD), a flexible data-driven order reduction method. To facilitate this, a finite element model of the shallow water equations is tested with both the full adjoint 4D-VAR method and two different POD-reduced approaches. Twin experiments are performed and comparisons are made in terms of accuracy, computational complexity and sensitivity to perturbation and number of observation points.Applied mathematicsElectrical Engineering, Mathematics and Computer Scienc
P1586: COMPARISON OF FREQUENCY OF TRANSFUSION RELATED COMPLICATIONS IN THALASSEMIC AND NON-THALASSEMIC PATIENTS RECEIVING NON LEUKODEPLETED RED CELL CONCENTRATE.
No full textComplications Following Comparison of Surgery for Chronic Subdural Hematoma, With and Without Postoperative Drainage Tube
No full textObjectives: Chronic subdural hematoma (CSDH) is one of the most common entities treated in neurosurgery. Postoperative subdural drainage employed after burr hole evacuation for treating CSDH reduces recurrence, but whether it leads to increased surgical complications compared to no postoperative drainage is debatable. The present study was designed to assess whether postoperative subdural drainage leads to increased surgical complications following burr hole evacuation of CSDH compared to no drainage.
Materials and Methods: The medical records of 69 patients treated with burr hole evacuation for chronic subdural hematoma between July 2013 to April 2014 were retrospectively analyzed. The patients were divided into two groups. In group A patients, postoperative subdural drainage had been employed following burr hole evacuation of CSDH, while in group B patients there was no drainage. The two groups were then compared for the development of surgical complications other than recurrence.
Results: Sixteen patients developed complications. Acute Subdural hematoma formed in 3 patients. There was intraparenchymal drain insertion in 6 patients. An empyema developed in 2 patients, while one patient each developed an Extradural hematoma, fits, contusion, and hemorrhagic infarction. All the complications occurred in the group A patients receiving postoperative subdural drainage. Postoperative subdural drainage tube was found to be significantly associated (p = 0.0017) with complications.
Conclusion: We conclude that postoperative subdural drainage following burr hole evacuation of chronic subdural hematoma is associated with increased surgical complications compared to no drainage
Model reduced variational data assimilation for shallow water flow models
No full textIdentifying uncertain parameters in large-scale numerical flow models can be done using the variational method. However, for implementing the variational method the adjoint model have to be available, which requires highly complex computer code and maintenance and thus hampers its applications. To ease this problem, this thesis has explored several methods for efficiently identifying uncertain parameters in a large-scale tidal model of the entire European continental shelf which does not require the implementation of these complex adjoint code. In this study, as a first step an estimation method based on model reduction is developed and investigated for the estimation of diffusion coefficient in a simple 2D-advection diffusion model. Two projection based model reduction methods were considered, namely proper orthogonal decomposition (POD) and Balanced proper orthogonal decomposition (BPOD). In the POD based estimation method an ensemble of forward model simulations is used to determine an approximation of the covariance matrix of the model variability and a small number of the leading eigenvectors of this matrix is used to define a model subspace. By projecting the original model onto this subspace an approximate linear reduced model is obtained. Once the reduced model is available its adjoint can be implemented easily and the minimization problem is solved completely in reduced space with very low computational cost. BPOD is also a model reduction method which considers both inputs and outputs of the system while determining the reduce subspace. The estimation method has been extended by including BPOD procedure into the estimation procedure. Numerical results from a simple pollution model demonstrate that the POD based estimation approach successfully estimate the diffusion coefficient for both advection dominated problems as for diffusion dominated problems. Another important message in this study, although lots of effort had been made in constructing a reduced order model by the BPOD method, the minimization results demonstrated that both the POD and the BPOD methods performed similarly. Preliminary results showed the validity of the POD based model reduction methods for parameter estimation. As a next step, the POD based estimation method is used to calibrate numerical tidal models. Results from (twin) numerical experiments showed that the POD based calibration method performed very efficiently to estimate depth values in the selected regions of the model domain. The computational costs of the POD based calibration method are dominated by the generation of an ensemble of forward model simulations where the simulation period of the ensemble is equivalent to the timescale of the original model. It has also been found in the study that it is not needed to use a full simulations of the original model for the generation of the ensemble. The POD based calibration method has also been implemented for the estimation of the water depth and space varying bottom friction coefficient values in a very large-scale DCSM model. The recently designed large-scale spherical grid based water level model for the northwest European continental shelf (around 1000000 computational grid points) has been used for this purpose. This has been the first application of the POD based calibration method to a very large-scale model and with real data. Results from numerical experiments showed that the calibration method performs very efficiently. An overall improvement of more than 50\% was observed after the calibration in comparison with the initial model. The results also demonstrated that the POD based calibration method offered a very efficient minimization technique compared to the classical adjoint method without the burden of implementation of the adjoint. As a concluding step, to estimate depth values in the model DCSM, a Simultaneous perturbation stochastic approximation (SPSA) method has been used. The method uses stochastic simultaneous perturbation of all model parameters to generate a search at each iteration. SPSA is based on a highly efficient and easily implemented simultaneous perturbation approximation to the gradient. This gradient approximation for the central difference method uses only two objective function evaluations independent of the number of parameters being optimized. The results from experiments showed that SPSA has a lower convergence rate than POD based calibration method, however the computational cost in each iteration of the SPSA method is usually far less then the POD based calibration method. The results also demonstrated that the SPSA algorithm proved to be a promising optimization algorithm for model calibration for cases where adjoint code is not available for computing the gradient of the objective function.Applied mathematicsElectrical Engineering, Mathematics and Computer Scienc
Surgical Modality as a Determinant of Survival and Neurological Outcome Following the Evacuation of Acute Subdural Hematomas
No full textObjective: We designed the present study to compare the clinical outcomes of the craniotomy and the decompressive craniectomy procedures that we had performed in our department for evacuating traumatic acute subdural hematomas.
Material and Methods: We retrospectively analyzed the medical data of all the adult patients in whom a craniotomy or a decompressive craniectomy had been performed for evacuating acute traumatic subdural hematoma. The demographic data, the preoperative Glasgow Coma Scale (GCS), and the clinical outcome were studied.
Results: A craniotomy had been carried out in five patients for traumatic AcSDH evacuation while in twelve patients a decompressive craniectomy had been performed. The mean preoperative GCS was 9 in the patients that underwent a craniotomy, whereas the mean preoperative GCS in the decompressive craniectomy group was 6.8. The overall mortality was 47%. In the craniotomy group, 4 (80%) patients survived and 1 (20%) patient expired. In the decompressive craniectomy group, 5 (41.7%) patients survived and 7 (58.3%) patients expired. The outcome in all the 9 surviving patients was favorable based on the Glasgow Outcome scale and all of them were independent of follow-up.
Conclusion: Better clinical outcome was observed in patients who had undergone a craniotomy compared to those in whom a decompressive craniectomy had been performed. Patients that underwent a craniotomy were also in a better clinical status preoperatively compared to patients who underwent a decompressive craniectomy
Relationship between postoperative pneumocephalus and recurrence following chronic subdural hematoma evacuation
No full textObjective: Postoperative pneumocephalus has been reported as one of the possible causes of increased recurrence following burrhole evacuation of chronic subdural hematoma (ChSDH). The present study was designed to assess the relationship between postoperative pneumocephalus and recurrence following chronic subdural hematoma evacuation.
Materials and Methods: The medical records of sixty eight patients that had been operated for ChSDH evacuation with burrhole drainage were retrospectively analyzed. The area of the pneumocephalus was measured in the slice where the size of the pneumocephalus was the biggest. The patients were then divided into the recurrent and the non-recurrent groups and compared for their association with the postoperative pneumocephalus. Patients with a pneumocephalus size of > 4 cm2 and those with a size ? 4 cm2 were also compared with each other for recurrence.
Results:
Fourteen (20.6%) patients had recurrence following burrhole evacuation of ChSDH. The mean size of the pneumocephalus in the recurrent group was 7.88 ± 5.12 cm2 and in the non-recurrent group was 6.56 ± 5.56 cm2.The size of the pneumocephlus was not statistically different (p=0.42) between the two groups. We also compared patients with a pneumocephalus size of > 4 cm2 and those with a pneumocephalus size of ? 4 cm2 and again found that the relationship with recurrence was not significant (p=0.288).
Conclusion:
We conclude that postoperative pneumocephalus is not associated with recurrence following burrhole evacuation of chronic subdural hematoma.
Keywords: Postoperative pneumocephalus, burrhole evacuation, recurrence, chronic subdural hematom
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