A lucky covariance estimator based on cumulative coherence.

The performance of adaptive acoustic localization methodologies depends on the quality of the covariance matrix being inverted. This paper demonstrates a technique to improve covariance estimation using the principles of lucky signal processing and the cumulative coherence. Lucky processing, popularized in astro-photography, is a technique that increases signal quality by selectively keeping only a small fraction from a pool of potential snapshots. Cumulative coherence, a measure of how well a set of vectors is described by its subsets, provides the measure of "data quality" that enables the lucky processing. This approach was applied to covariance estimation on an acoustic array by taking a fixed duration sample of data and creating a dense set of snapshots with higher than usual overlap. From these densely sampled snapshots, the "luckiest" ones were found using cumulative coherence, and the covariance was averaged as normal. Using data from the SWellEX-96 experiment, this new estimator was compared with standard practice. It was found that the lucky covariance estimate was successful at adaptive matched field processing and produced a less ambiguous processor output than the conventional estimator. The lucky covariance estimate had a higher estimated signal-to-noise ratio, especially when the source was at longer ranges from the array.

Incidence and outcome of weaning from mechanical ventilation according to new categories.

Weaning from mechanical ventilation was categorised as simple, difficult or prolonged by an international task force of the American Thoracic Society/European Respiratory Society/European Society of Intensive Care Medicine/Society of Critical Care Medicine/Sociéte de Réanimation de Langue Française in 2007. This new classification has not been tested in clinical practice. The objective of the present study was to determine the incidence and outcome of weaning according to the new categories. We included medical and surgical patients who required mechanical ventilation in a prospective, multicentre, 6-month cohort study. From an initial cohort of 510 patients, 257 intubated patients started weaning. Of these patients, the cumulative incidences of simple, difficult, and prolonged weaning were 152 (59%), 68 (26%) and 37 (14%), respectively. Hospital mortality was increased in patients with prolonged (32%) but not difficult (9%) weaning in comparison with those with simple weaning (13%), overall p = 0.0205. In a multivariate logistic regression model, prolonged but not difficult weaning was associated with an increased risk of death. Ventilator-free days and intensive care unit (ICU)-free days were decreased in both difficult and prolonged weaning. In conclusion, the new weaning category prolonged weaning is associated with increased mortality and morbidity in the ICU. The new category difficult to wean was associated with increased morbidity, but not mortality.

Robust time reversal focusing in the ocean.

Recent time-reversal experiments with high-frequency transmissions (3.5 kHz) show that stable focusing is severely limited by the time-dependent ocean environments. The vertical focal structure displays dynamic variations associated with focal splitting and remerging resulting in large changes in focal intensity. Numerical simulations verify that the intensity variation is linked to the focal shift induced by phase changes in acoustic waves resulting from sound speed fluctuations due to internal waves. A relationship between focal range shift, frequency shift, or channel depth changes is illustrated using waveguide-invariant theory. Based on the analysis of experimental data and numerical simulations, methods for robust time-reversal focusing are developed to extend the period of stable focusing.

The effects of norepinephrine on hemodynamics and renal function in severe septic shock states.

OBJECTIVE: To investigate the effect of norepinephrine (NE) on hemodynamics, oxygen metabolism and renal function in patients with severe septic shock. DESIGN: Prospective study. SETTING: Post-operative ICU in a municipal general hospital. PATIENTS: The study included 56 patients with extreme low resistance states due to abdominal sepsis, who remained hypertensive (MAP < 60 mmHg) despite optimal fluid therapy and dopamine > 20 micrograms/kg/min and cumulative doses of dopamine and dobutamine > 30 micrograms/kg/min, respectively. INTERVENTIONS: After registration of baseline values dopamine was reduced to 2.5 micrograms/kg/min, and norepinephrine was administered starting at a dose of 0.05 micrograms/kg/min until a mean arterial pressure of more than 60 mmHg could be maintained. MEASUREMENTS AND RESULTS: During norepinephrine infusion (dosage ranging between 0.1-2 micrograms/kg/min, mean dose rate: 0.4 micrograms/kg/min) mean arterial pressure and systemic vascular resistance index increased significantly (p < 0.001). After 8 h a significant increase in stroke volume (p < 0.05) and decrease in heart rate (p < 0.05) could be observed. There was no significant change in cardiac index (CI), oxygen delivery (O2AVI) and oxygen consumption (VO2I). Creatinine clearance increased significantly (p < 0.005) from a control value of 75 +/- 37 ml/min to 102 +/- 43 ml/min after 48 h NE-treatment. CONCLUSION: Our results suggest that norepinephrine can be used safely in the treatment of severe septic shock states. Mean arterial pressure and glomerular filtration rate improved markedly without deleterious effects on CI, O2AVI and VO2I.

[Noradrenaline in the "high output-low resistance" state of patients with abdominal sepsis]. / Noradrenalin im "High Output-Low Resistance State" beim septischen Abdominalpatienten.

We investigated the impact of norepinephrine administration on hemodynamics, oxygen metabolism and renal function in patients in severe septic shock. PATIENTS AND METHODS. Twenty-six patients with extremely low resistance who were between 24 and 87 years of age were included in the study. In 7 patients, acute necrotizing pancreatitis and superinfection was diagnosed; 19 patients suffered from diffuse peritonitis. The entrance criteria for the study were: a mean arterial pressure (MAP) of below 60 torr or, in chronic hypertensive patients, a decrease in systolic pressure of more than 50 torr compared to previous values, despite volume optimization, and dopamine greater than 20 micrograms/kg per min and cumulative doses of dopamine/dobutamine greater than 30 micrograms/kg per min, respectively. Cases with tachycardia greater than 140/min were also included in the study even when the inotropic medication dose was lower. After registration of baseline values, dopamine was reduced to 2.5 micrograms/kg per min, and norepinephrine was administered starting at a dose rate of 0.05 micrograms/kg per min, until a MAP of greater than 60 torr could be maintained. RESULTS. Of the 26 patients investigated, 16 survived; 10 patients with persisting sepsis died due to multiple organ failure (mortality: 38.5%). During the study period, a norepinephrine dosage ranging between 0.1 and 2 micrograms/kg per min was necessary to stabilize the arterial pressure. The mean dose rate was 0.3 micrograms/kg per min. The mean arterial pressure and systemic vascular resistance index showed a statistically significant increase of 30 and 20%, respectively, just after 1 h and distinctly remained above the initial values in the further course. The cardiac index remained constant or increased slightly. After 24 h a statistically significant increase in stroke volume and a decrease in heart rate could be observed. Creatinine clearance increased significantly from the control value of 73 +/- 48 ml/min to 114 +/- 37 ml/min after 48 h under norepinephrine treatment. O2-delivery and O2-consumption did not change significantly, although they showed a slight tendency to increase. CONCLUSION. When patients are in a septic high output-low resistance condition, particular attention must be paid to maintaining sufficient mean arterial pressures. Our results suggest that this essential goal can be achieved by norepinephrine. The mean arterial pressure and glomerular filtration rate improved markedly, and there was no evidence of bad effects such as an increased afterload on critical parameters like cardiac index, O2-delivery and O2-consumption.

[Concerning the malignancy of villous tumors of the large intestine]. / De la malignité des tumeurs villeuses du gros intestin.

The analysis of a personal series of 83 villous tumors of the rectum and the colon showed that half of them were degenerated. Malignancy was, once out of twice, at the intraepithelial stage ("in situ" epithelioma) or at the intramucous stage (micro-carcinoma) and once out of twice invasive. No more than the rectal touch or the endoscopic aspect, biopsy enables a regular recognition of this degeneration, nor of its invasion degree. Therefore villous tumor must be removed surgically, to give to the anatomopathologist a whole and well-oriented specimen, which allows him to say if this excision is enough or if it must be completed. In no case, a villous tumor must be removed endoscopically by any physical means, nor even resected with the diathermical ansa if it is pedonculated.

[Technic of the surgical excision of villous tumors]. / Technique d'exérèse chirurgicale des tumeurs villeuses.

Villous tumours of the colon and rectum are characterized by a high incidence of malignancy (50%) and by their tendency to recur. Invasive malignant villous tumours require wide excision in the same way as adenocarcinomas. Non-invasive tumours (stage 0 and stage I) should be treated like benign villous tumours. Villous tumours of the colon, i.e. situated more than 15 cm from the anus, are removed by a short colonic resection. Villous tumours of the rectum which are small and pedunculated or sessile, situated less than 8 cm from the anus can be excised via the trans-anal route, provided a margin of healthy mucosa is removed around the villous zone. High rectal tumours which are very large or diffuse are removed by a trans-sacral approach, low extensive tumours are removed by a coccyperineal or trans-sphincteric approach. Recurrences (30 to 40%) always occur after incomplete excision, especially after a trans-anal resection. Benign tumours can also recur, although remaining benign, and require a further local excision.

[Colonic occlusions. Retrospective cooperative study of 497 cases]. / Les occlusions coliques. Etude rétrospective coopérative de 497 cas.

A retrospective multicenter study involving 12 digestive surgery centers was conducted on 497 cases of colon obstruction. The most frequent cause of colon obstruction was colo-rectal cancer (71 p. cent of cases), but many other etiologies were involved, including 61 cases of torsion and 37 patients with occlusive sigmoiditis. Differential clinical and radiological features in each etiological group are discussed, the results of therapy undertaken analyzed, and a reasonable line of conduct proposed, adapted to each situation, with the objective of attempting to reduce mortality which still affects 25 p. cent of cases operated upon.

[Surgical treatment of acute complicated colitis. Report on twenty-eight cases (author's transl)]. / Traitement chirurgical des colites aiguës compliquées. A propos de vingt-huit observations.

Experience with 28 patients with acute diffuse complicated colitis operated on in emergency or semi emergency by the same surgical team is reviewed. The forms with colonic dilatation are the most numerous but do not resume the serious complications which may occur in the course of non specific inflammatory diseases of the colon. The operative mortality in this series was 10,7% (3/28). Peritoneal sepsis was the most significant factor contributing to mortality. It appears that the keystone to successful management is to prevent colonic perforation. Protracted medical management may be at last partly responsible for this complication. Failure of intensive medical therapy to induce rapid improvement constitutes an indication for definitive surgical treatment.

[A case of sudden unexplained death following retro-sternal esophagoplasty (author's transl)]. / Un cas de mort subite inexpliquée après cesophagoplastie rétro-sternale.

A recent case of deadly syncope, overcome five days after a colic retro-sternal esophagoplasty for caustic stenosis of the esophagus, and remaining unexplained even at the post-mortem examination, reminds the same cases formerly published. Its report is done for the purpose of inciting other authors to publish similar facts that they could have observed. These collected cases would lead to consider the possible responsibility of the retro-sternal way and put its indications back into question.

Surgical treatment of colonic diverticulitis: a report of 205 cases.

In a series of 205 patients treated for colonic diverticulitis, 101 presented acute complications, 35 chronic complications and 69 attacks of diverticulitis without complications. The treatment prescribed for the acute septic complications (generalized peritonitis, perisigmoidic abscess) as well as for acute occlusions consists of two-stage surgery: drainage and emergency colostomy, then secondary colectomy in elective conditions. Massive incoercible hemorrhages were treated by emergency hemostatic resection, guided by selective mesenteric arteriography. Chronic complications (inflammatory stenosing tumor, external or internal fistulas) are ideally treated by a one-stage colic resection. As postoperative mortality and morbidity rates are high and caused by acute conditions, it is justifiable to perform a prophylactic colic resection.

[Sphincterial conservation in surgery of carcinoma of the rectum (author's transl)]. / La conservation sphinctérienne dans la chirurgie du cancer du rectum.

The present study reports the results of several methods used to perform abdominal resection (with anastomosis fastened by means of sutures and clip-gun) abdomino-transanal method designed to preserve sphincter function (Babcok,, Toupet, Duhamel), anterior abdomino-perineal resection and tumorectomy. The indications of these different surgical techniques are discussed and the authors point out the necessity to do not give up the carcinologic needs to the sphincteral preservation.