Arindam Choudhury | Search PubMed

PubMed2005

Constructing a speculative kernel machine for pattern classification.

We propose and investigate the performance of a new geometry-based algorithm designed to identify potentially informative data points for classification. An incremental QR update scheme is used to build a classifier using a subset of these points as radial basis function centers. The minimum descriptive length and the leave-one-out error criteria are employed for automatic model selection. The proposed scheme is shown to generate parsimonious models, which perform generalization comparable to the state-of-the-art support and relevance vector machines.

Algorithms↗

PubMed2004

The effect of epidural bupivacaine on induction and maintenance doses of propofol (evaluated by bispectral index) and maintenance doses of fentanyl and vecuronium.

The growing interest in combining local and general anesthesia has led to studies investigating possible interactions between general anesthesia and local anesthetics administered via spinal, epidural, IV, or IM routes. However, no study has evaluated the effect of local anesthetics on all three components of balanced anesthesia, i.e., hypnosis, analgesia, and muscle relaxation. In this prospective, randomized, double-blind study, we investigated the effect of epidural bupivacaine on the dose requirement of propofol (as evaluated by using the bispectral index [BIS]), fentanyl, and vecuronium for general anesthesia. This study consisted of 30 adults, ASA physical status I and II, undergoing Whipple's pancreaticoduodenectomy for periampullary carcinoma lasting >4 h. An epidural catheter was placed between T9-10. Depending on the group allocation, 10 mL of the study drug was administered as a bolus followed by an infusion at 6 mL/h via the epidural catheter. Patients were divided into 2 groups of 15 each. Patients in the control group received epidural normal saline whereas those in the bupivacaine group received epidural bupivacaine 0.1%. Induction of anesthesia was performed with IV fentanyl 2 mug/kg and propofol titrated to achieve BIS between 40-50. Endotracheal intubation was facilitated by the IV administration of vecuronium 0.1 mg/kg and patient's lungs were ventilated with 66% nitrous oxide in oxygen. After intubation, infusion of propofol 1% was titrated to maintain BIS between 40-50. Inadequate analgesia was defined as an increase in systolic blood pressure and/or heart rate by >20% of baseline values in response to surgical stimulus and was treated with bolus fentanyl 0.5 mug/kg. Neuromuscular monitoring was used to assess the need for additional doses of vecuronium. Data were analyzed by using the Student's t-test and P </= 0.05 was considered significant. The requirement of propofol for induction and maintenance of anesthesia in the bupivacaine group was 1.3 +/- 0.3 mg/kg and 2.4 +/- 0.9 mg . kg(-1) . h(-1), respectively, compared with 2.4 +/- 0.6 mg/kg and 4.4 +/- 1.6 mg . kg(-1) . h(-1) observed in the control group (P < 0.05). Significant reduction was also observed in the requirement of vecuronium and fentanyl during maintenance in the bupivacaine group (P < 0.05). We conclude that epidural bupivacaine given before induction of anesthesia reduces the requirement of propofol, fentanyl, and vecuronium during general anesthesia.

Adult↗

PubMed2002

An unusual case of Bouveret's syndrome.

A 69-year-old man presented to the emergency department with a 12-hour history of severe abdominal pain. His medical history was significant for a small-bowel obstruction that resolved with conservative therapy 4 months prior to admission. In the distant past, a Billroth II gastric resection was performed for ulcer disease. He was hypothermic, and laboratory studies showed elevated serum liver and pancreatic enzymes. A CT scan of the abdomen demonstrated fat stranding and a small amount of free air in the area of the pancreas. Gram-negative rods subsequently grew from blood cultures. A presumptive diagnosis of necrotising pancreatitis was made, and supportive care was instituted. Follow-up CT scan performed several days later demonstrated a large filling defect in the stomach. Endoscopy showed this defect to be a giant gallstone, and the diagnosis of Bouveret's syndrome was made. The patient underwent laparotomy. A duodenal perforation in the posterior aspect of the fourth portion was identified. The perforation had been caused by chronic impaction of the giant stone. The stone was removed through the perforation, and the perforation was closed in multiple layers. Drainage of the retroperitoneum was effected through large catheters placed through the flank. The presentation, diagnostic evaluation, treatment, and complications of this condition are discussed.

Aged↗