Study on ultrasound assisted precipitation of CL-20 and its effect on morphology and sensitivity.

Applying ultrasound to crystallizing systems offers significant advantages for modifying and improving the processes as well as quality of products. This paper reports on ultrasound assisted reprecipitation of CL-20 to obtain fine particles as well as to achieve desired morphology, which will improve insensitivity characteristics. In this study, CL-20 has been reprecipitated by sonication process and has been characterized by DSC, SEM and particle size analysis. The results are compared with control CL-20 sample (unsonicated). SEM photographs revealed that sonication process offer uniform crystalline morphology without any agglomeration. The particle size of sonicated CL-20 sample obtained is around 5+/-1 microm with a narrow particle size distribution. The DSC thermogram of sonicated and unsonicated sample is identical. CL-20 samples were subjected to impact and friction sensitivity experiments, the results indicate the sensitivity characteristics reduced considerably. Ultrasonic assisted crystallization technique reduces the time of reprecipitation considerably with an enhanced recovery of CL-20 with a very narrow particle size distribution.

Preparation and thermal studies on tetranitrodibenzo tetraazapentalene (TACOT): a thermally stable high explosive.

Thermally stable high explosive, tetranitro-2,3,5,6-dibenzo-1,3a,4,6a-tetraazapentalene (TACOT) was synthesized and characterized during this work. Thermo analytical techniques (TG and DSC) were applied to study the thermal decomposition behaviour of TACOT in comparison with benchmark thermally stable high explosive 1,3,5-triamino-2,4,6-trinitrobenzene (TATB). Kinetic parameters such as reaction order, activation energy and pre-exponential factors were computed from the thermal data. The activation energy for TACOT (292 kJ/mol) was found 1.5 times to that of TATB (200 kJ/mol), which can account for its higher thermal stability and can be attributed to pentalene moiety in the former.

Establishment of process technology for the manufacture of dinitrogen pentoxide and its utility for the synthesis of most powerful explosive of today--CL-20.

This paper reviews the recent work done on the synthesis as well as characterization of dinitrogen pentoxide (DNPO). The physico-chemical characteristics of DNPO are also discussed. The review brings out the key aspects of N2O5 technology with relevance to realize modern and novel HEMs. The paper also includes the aspects related with establishing the synthesis facility of dinitrogen pentoxide at HEMRL by gas phase interaction of N2O4 with O3. The process parameters for the synthesis of N2O5 at 50 g/batch have been optimized. The synthesized dinitrogen pentoxide has been characterized by UV [204, 213, 258 nm (pi-->pi*) 378 and 384 nm (n-->pi*)] and IR (1428, 1266, 1249, 1206, 1044, 822, 750, 546 and 454 cm(-1)) spectroscopy. The DSC clearly showed the sublimation of N2O5 at 32 degrees C. The nitration studies on 2,6,8,12-tetraacetylhexaaza tetracyclo[5,5,0,0(3,11)0(5,9)]dodecane (TAIW) proved its viability in 2,4,6,8,10,12-hexanitro-2,4,6,8(10,12))-hexaazatetracyclo [5,5,0,0(3,11)0(5,9)]dodecane (CL-20) synthesis. The synthesized CL-20 and its precursors have also been subjected to hyphenated TG-FTIR studies to understand decomposition pattern.

Effect of extended perioperative antibiotic prophylaxis on intravascular catheter colonization and infection in cardiothoracic surgery patients.

Intravascular catheter-related infections (CRI) account for one third of nosocomial bloodstream infections in England. UK Department of Health guidelines state that antibiotic prophylaxis is not required during placement, or use of, central venous catheters, to prevent CRI. However, some clinicians continue to use antibiotics in an attempt to prevent CRI. We investigated the effect of extended routine perioperative antibiotic prophylaxis in cardiothoracic patients on rates of intravascular catheter (IVC) colonization and infection. Investigations were undertaken in patients undergoing uncomplicated cardiothoracic surgery during July 2001-February 2002. Patients who received three doses of cefuroxime as perioperative prophylaxis were compared with those who received extended cefuroxime prophylaxis until the IVC was removed. Patients were not randomized into groups, but received the different prophylaxis regimens according to the usual practice of the consultant cardiothoracic surgeon. A roll tip method was used to determine IVC colonization. Of 191 patients who fulfilled the inclusion criteria, 12 were excluded because data were incomplete. One hundred and forty-six patients received routine prophylaxis, and 33 prophylaxis until the IVC was removed. Twenty-three out of 146 (16%) IVCs in the 'routine' group and four out of 33 (12%) in the 'extended' group became colonized; no IVC-related bloodstream infections occurred during the survey. The duration of IVC placement and the types of operation performed in the two groups were not significantly different (P > 0.05). In routine cardiothoracic surgery patients, extending routine perioperative antibiotic prophylaxis until all IVCs have been removed does not influence rates of IVC colonization.

The left atrial roof incision: an asset for minimally invasive mitral valve surgery.

BACKGROUND: The focus in minimally invasive mitral valve surgery has been on reducing thoracic incisions. Several cardiac incisions described in these procedures do not conform with the philosophy of "minimal invasiveness". We describe the left atrial roof incision which has the potential of facilitating an excellent mitral valve exposure through a limited cardiac incision, without major cardiac trauma. The safety, efficacy and technical ease of this technique for minimally invasive mitral valve surgery is evaluated. METHODS: From July 1998 to December 2000, 95 consecutive patients underwent mitral valve surgery by the same surgeon. The patients were divided into 2 groups on the basis of the cardiac incision used for correction of mitral valve disease. Group I patients had left atrial roof incision and group II patients had the traditional paraseptal incision. Each group was further classified into the minimally invasive sternotomy and standard sternotomy subgroups. The clinical variables and complications in the 2 groups were compared. RESULTS: There were 40 male and 55 female patients with a mean age of 63 +/-12yrs (range 29 to 88yrs). LARI was used for mitral valve exposure in 81 patients (85%). In 18 patients (19%), surgery was by minimally invasive technique. The mitral valve was replaced in 82% of patients and repaired in 18%. LARI provided a better exposure of the mitral valve in its anatomical and physiological disposition, without distortion. There was no significant difference in the cross clamp times and postoperative complications between the 2 groups. More patients in the LARI group regained sinus rhythm at discharge. CONCLUSION: LARI is safe and technically easy to perform. It provides an excellent exposure of the mitral valve and left heart cavities in its anatomical disposition with minimal cardiac trauma, making it ideal for minimally invasive mitral surgery.

Mediastinal haematoma in Ehlers-Danlos syndrome.

A patient with Ehlers-Danlos syndrome presented acutely with clinical and radiological features suggestive of aortic dissection. Further investigations including computerised tomography and aortography showed mediastinal haematoma with no evidence of aortic dissection. He was treated conservatively with no complications. The typical clinical and radiological features are reviewed and an emphasis is made on accurate diagnosis to allow prompt, appropriate management.

Coronary ostial stenosis: surgical considerations.

To investigate the clinical significance of coronary ostial stenosis, we reviewed eight patients with such lesions, including three with isolated stenosis at the orifice of the coronary artery. There were five male and three female patients, with an average age of 46.25 years (range 32-69 years). Their symptoms consisted mainly of angina (6 patients), with dyspnoea and palpitation being the presenting features in the remaining two patients. All patients underwent preoperative coronary angiography which confirmed stenosis at the level of the orifice with absence of reflux of contrast medium into the sinus of Valsalva as the main features. Delay in the appreciation of stenosis of the orifice of the right coronary artery resulted in the death of two patients, whose diagnosis was confirmed at post mortem examinations. Stenosis of the orifice of the right coronary artery was present in seven patients, with two patients also having stenosis of the orifice of the left coronary artery. The remaining patient had isolated stenosis of the left coronary arterial orifice. Coronary artery bypass grafting was performed in five patients, including two who had patch angioplasty to the right coronary artery. The patient with isolated stenosis of the orifice of the left coronary artery had patch angioplasty only. Follow-up of up to three years in the surviving patients showed good functional results. The ease with which it is possible to miss right coronary ostial stenosis is emphasized and angiographic features are reviewed.

Left ventricular outflow tract obstruction from mitral prosthesis.

A case of left ventricular outflow tract obstruction six years following mitral valve replacement is presented. Clinical features, echocardiographic and angiographic studies preoperatively all suggested aortic valve disease. The diagnosis of left ventricular outflow tract obstruction by the strut of the mitral prosthesis was made intraoperatively. Enlargement of the aortic root and aortic valve replacement resulted in good symptomatic and echocardiographic improvement.

Re-operation for recurrent coronary artery and graft disease. A review of 73 patients in a group of 2573 consecutive first operations.

Between January 1980 and December 1986, 2573 patients underwent simple first time coronary artery bypass grafting, of whom 73 (65 males and 8 females) aged 34-69 years (mean 51.3 yrs) had repeat bypass grafts at Wythenshawe Hospital, Manchester. Of these 73 patients, 15 had a previous myocardial infarction, 5 hyperlipidaemia, 4 systemic hypertension, and 12 had a strong family history of ischemic heart disease. There was an overall deterioration of left ventricular function at the time of reoperation. The interval between the two operations was 5-131 months (mean 34.2 mths); recurrence of angina occurred earlier (mean 18.4 mths). Vessels grafted at the first operation were LAD (59), RCA (46), circumflex (41) and diagonal (13). The corresponding data at reoperation were LAD (55), RCA (46), circumflex (28) and diagonal (10). Blocked grafts were seen in 67 patients and new lesions noticed in 29. Reoperation was done using saphenous vein (129), internal mammary artery (5), arm veins (2) and tubular Gortex grafts (2). One patient had concurrent excision of a left ventricular aneurysm. Coronary anastomoses were performed with elective ventricular fibrillation (47) or cardioplegic arrest (91). Aortic cross clamp time varied from 0-92 minutes. Seven patients required intra-aortic balloon support. These patients died in the first 30 days, an operative mortality rate of 4.1%, and two 18 months after surgery. Sixty-eight percent of patients seen at 1 year were totally symptom free. We conclude that reoperation for coronary artery disease can be done with a low mortality and good immediate relief of symptoms.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiographic, electrocardiographic and surgical features of single coronary artery producing myocardial ischaemia.

A patient is described in whom an unstenosed single coronary artery was associated with angina and syncope. Full clinical documentation of the patient with ambulatory electrocardiography, angiography, surgical findings and stress testing before and after bypass grafting are described.

Internal mammary artery conduit: an additional surgical procedure in difficult coarctation of the aorta.

Between October 1986 and February 1987 two young men with coarctation of the aorta and a hypoplastic isthmus were treated by a combined resection and isthmusplasty with implantation of the left internal mammary artery to the distal aorta. An appreciable drop in the systolic gradient was seen in both patients after the mammary artery anastomosis and haemodynamic variables across the repair continued to improve postoperatively. Digital transvenous subtraction angiography five months after operation showed a satisfactory mammary artery conduit across the repaired coarctation.

Postoperative neuralgia in the leg after saphenous vein coronary artery bypass graft: a prospective study.

The degree of cutaneous sensory deficit in the leg was assessed after removal of the long saphenous vein in 50 consecutive patients undergoing coronary artery bypass vein grafts randomly assigned subcutaneous sutures or a single layer of sutures. Removal of the vein and repair of the leg incision were done by the same team of surgeons. In group 1 (25 patients) the leg incision was repaired with "00" Dexon subcutaneous and "00" prolene subcuticular sutures while in group 2 (25 patients) closure was effected by a single layer of interrupted "00" nylon sutures. All had crepe pressure bandage from the base of the toes to the groin for the first 24 hours followed by TED stockings for six to eight weeks. Sutures were removed on the eighth postoperative day. Cutaneous sensation in the leg and ankle was assessed 48 hours, seven days, and six to eight weeks after surgery, and a final comparison of the cosmetic effects and sensory perception after one year or more was made in 37 patients. There were no major differences between the groups at 48 hours in sensory abnormalities (anaesthesia, hyperaesthesia, and pain) but sensory recovery was significantly better in group 2 at the second and third assessments. There was some reduction in sensory abnormalities at the final review in group 1. No appreciable difference was noted in the quality of the scar between the two groups. We conclude that cutaneous sensation is better preserved by repairing the leg incision in a single layer. Subcutaneous sutures may produce neuropraxia of the long saphenous nerve by direct pressure as healing progresses.

Surgical ligation of the patent ductus arteriosus in low birth weight pre-term infants. A review of 67 consecutive cases.

Between March 1978 and October 1983, sixty-seven low birth weight infants (600-1500 gm) with gestational age of 26-33 weeks had surgical ligation of PDA in our unit. Thirty-six (54%) had previous failed indomethacin therapy. Congestive cardiac failure (61), respiratory distress syndrome (48) and failure to thrive (34) were the presenting features. Nine patients had severe acidosis (pH 6.8-7.18) on admission. A trans-pleural approach was used in all. Ventilation was required for 1-13 days. There were no intra-operative deaths. Sixteen (24%) died of the problems of prematurity. The others have continued to thrive. We believe that ligation of PDA is a safe and effective procedure in the low birth weight premature infant, but should only be undertaken in a well set up paediatric cardiac surgical unit.

Surgical management of severe coarctation of the aorta in the first month of life.

Between March, 1978, and April, 1982, 48 neonates under 4 weeks of age were operated upon for severe coarctation of the aorta in our unit. Of these, 36 babies were in severe congestive cardiac failure and 11 had renal failure. Angiocardiography and echocardiography demonstrated intracardiac lesions in 29 patients. All had a patent ductus arteriosus. Surgical relief of the coarctation was effected within 48 hours of diagnosis. Those in severe cardiac and renal failure were intubated and ventilated in the intensive care unit before the operation. Continuous monitoring of the central venous and arterial pressures and rectal and skin temperature and periodic checks on the acid-base status were instituted, and acidosis was corrected carefully with a 4.2% solution of sodium bicarbonate. A dopamine infusion (4 to 8 micrograms/kg/min) was used to assist the renal and cardiac functions. Five babies were treated with prostaglandin E for 24 to 46 hours before the operation. Forty-five patients had subclavian flap repair of the coarctation and the other three had repair by polytetrafluoroethylene (PTFE) patch angioplasty. The patients were ventilated for 1 to 8 days postoperatively. Dopamine support was given to all the immediate postoperative period. Three patients with associated cardiac lesions died in the first 48 hours after operation. Three other patients died on the sixth, eighth, and eleventh postoperative days of noncardiac causes. Of the 42 survivors, three required revision of the repair because of restenosis 3 to 18 months later. Three patients with ventricular septal defect had closure of the defect within 8 months after birth. We believe that coarctation of the aorta presenting soon after birth should be treated by a combination of active resuscitation and early surgical relief, and that continuous monitoring for early detection and correction of hypoxia and acidosis is essential to achieve satisfactory results.

Management of neonatal posterolateral diaphragmatic hernia.

From March 1978 to April 1982 13 neonates with a left posterolateral diaphragmatic hernia were seen in respiratory distress within 12 hours of birth. Each had severe acidosis and hypoxia. They were immediately intubated and ventilated. Arterial and central venous lines were inserted, the acidosis was partially corrected, and a dopamine infusion of 4-8 micrograms/kg/min was begun immediately. Continuous monitoring of arterial and venous pressures, core and skin temperatures, blood gases, and pH was instituted. Diaphragmatic defects were repaired by direct suture in nine neonates and by Gore-Tex patches in four. The left lung in all patients was hypoplastic. Ventilation and inotropic support were continued for four to five days after operation and close control of acid-base balance was maintained. All but one survive and are doing well. We consider the key to survival to be management of the dangerous combination of acidosis (by enhancing peripheral and renal perfusion with dopamine) and hypoxia (by prolonged assisted ventilation).