Schottky barrier-gated high performance photodetectors using a water-borne polymeric colloid.

Here, we demonstrate the synergetic application of a cationic surfactant (CTAB) for the fabrication of a fast response organic photoconductor via an environmentally benign fabrication process. A water-borne colloid of the semiconducting polymer PBTTT was fabricated via a mini-emulsion process with CTAB as the surfactant, and deposited onto a Au-patterned substrate to complete the photoconductor device geometry. Due to the preferential adsorption of the ammonium cation of the CTAB molecules onto the Au surface, a dipole layer was created and thus the work function of Au was significantly reduced, as confirmed by ultraviolet photoelectron spectroscopic studies. We show that the resulting Schottky barrier between Au-CTAB and PBTTT can be used as an artificial 'gate' for a trap-limited photoconductive mechanism, leading to a fast temporal response of the photoconductor without sacrificing the efficient photoconductive gain-generating mechanism. As a result, a high detectivity of 4.92 × 10(10) Jones, as well as a high gain of 107, can be realized from the PBTTT-based organic photoconductor. This result opens the possibility of fabricating high performance and simple structured organic photodetectors via a nontoxic fabrication process.

Treatment before transfer: the patient with burns.

OBJECTIVES: To review pre-burns centre management, including assessment, resuscitation, and transfer. METHODS: A retrospective analysis of the notes of all the UK patients admitted to the Burns Centre in 1998, who had a body surface area burn of over 15% in adults (10% in children). RESULTS: There were 31 patients, 21 adults and 10 children, and the average burn size was 32% (12-96%). Fourteen were overestimated (average of 9%) and 13 underestimated by 7.5%. Twenty nine received intravenous fluids, 18 specified a formula, but it was only applied correctly in 10. The average time to the Burns Centre from the burn was 10 hours, and the time for resuscitation and transfer, eight hours. Documentation was generally poor. CONCLUSION: There has previously been considerable variation in the standard of initial burn management and there have been problems with burn percentage assessment and resuscitation formula application. A new proforma has been introduced to tackle these issues.

Total intravenous anaesthesia using 3-in-1 mixture of propofol, alfentanil and mivacurium.

INTRODUCTION: To avoid errors and confusion associated with 3 separate infusions, we conducted a feasibility study of total intravenous anaesthesia (TIVA) using 1 electrically-powered syringe pump to deliver a 3-in-1 mixture containing fixed proportions of propofol, alfentanil and mivacurium. MATERIALS AND METHODS: The 3-in-1 mixture was obtained by mixing 200 mg propofol, 1 mg alfentanil, 20 mg mivacurium, and making up to 40 mL with 5% dextrose solution. Electrical zone sensing sizer and light microscopy were used to compare emulsion instability of the 3-in-1 with control mixtures. In 50 ASA 1 patients, bolus infusions of 0.4 mL of the 3-in-1 mixture per kg body weight were given for induction of anaesthesia. All patients were subsequently intubated and ventilated with air-oxygen mixtures. Anaesthesia was maintained using a continuous infusion of the 3-in-1 mixture with the infusion rate titrated to satisfactory clinical response. Intravenous morphine 0.1 mg/kg was given for intra- and postoperative analgesia. Residual neuromuscular blockade was reversed using glycopyrronium and neostigmine at the end of surgery. RESULTS: The 3-in-1 mixtures remained stable for up to 5 hours after preparation. Induction and maintenance of anaesthesia were smooth, intubation conditions satisfactory, and intraoperative haemodynamic changes acceptable. Recovery from anaesthesia and neuromuscular blockade was rapid. There were no major intra- or immediate postoperative complications. CONCLUSIONS: The 3-in-1 mixtures remained stable for up to 5 hours after preparation. It may be feasible to provide TIVA using the 3-in-1 mixture for induction and maintenance of anaesthesia in ASA 1 patients.

Outpatient third molar surgery under local anaesthesia and conscious sedation using patient-controlled analgesia with alfentanil.

We examined the feasibility of intraoperative conscious sedation employing patient-controlled analgesia with alfentanil (PCA-alfentanil) in 20 adult outpatients undergoing third molar surgery under local anaesthesia. A loading dose of intravenous alfentanil 15 mg/kg was administered immediately before local anaesthetic administration using 2% lignocaine with 1:80,000 adrenaline. This was followed by a background alfentanil infusion of 0.05 mg/kg/min. On demand alfentanil doses were 4 mg/kg with lockout intervals of 3 minutes. All patients were mildly sedated, easily aroused verbally and co-operative throughout the surgery. None experienced any cardiovascular or respiratory complications related to PCA-alfentanil. Immediate postoperative complications included nausea, vomiting and pruritus. High patient comfort and acceptance scores suggest that the use of PCA-alfentanil can be a useful adjunct to local anaesthesia in adult outpatients undergoing third molar surgery.

Outpatient general anaesthesia for oral surgery.

Outpatient general anaesthesia (GA) is administered for extraction of carious teeth in children and straightforward dento-alveolar surgery such as removal of impacted teeth, cyst enucleation and dental implantology in adults. Although oral surgery is often performed under local anaesthesia, GA is indicated in conditions when local anaesthesia is ineffective and in uncooperative patients because of age, fear or anxiety, mental impairment or physical disability. Outpatient GA for oral surgery yields a high satisfaction score from the patients. The incidence of major morbidity is acceptably low because of proper patient and procedure selection, improved perioperative patient monitoring, and the use of newer, faster recovery anaesthetic agents with fewer side-effects. Effective pain management is important for optimal postoperative analgesia and patient satisfaction. The principles, conduct, and management of common problems of outpatient GA for oral surgery are discussed.

Postoperative vomiting (POV) in the paediatric outpatient general surgical population.

AIM: To determine the incidence of postoperative vomiting (POV) in the paediatric outpatient general surgical population, the factors affecting POV and the incidence of unplanned admissions contributed by POV. METHOD: One hundred and ninety-nine children below 13 yeas of age undergoing elective outpatient general surgical procedures were enrolled into this prospective study. Anaesthesia was induced either intravenously or via the inhalational route. It was then maintained with nitrous oxide, oxygen and isoflurane or halothane. The age, sex, body weight, duration of fasting, administration of trimeprazine, type of general surgical procedure, maintenance technique for general anaesthesia, duration of general anaesthesia, the administration of opiods or local anaesthetics and the incidence of POV were noted. The results were analysed initially with chi-squared test and subsequently subjected to multivariate logistic regression analysis and stepwise variable selection method. RESULTS: The incidence of POV was 8.5%. Duration of general anaesthesia greater than one hour was associated with a significantly higher incidence of POV. Postoperative emesis did not contribute to unplanned admissions in these day surgical patients.

Bone marrow harvesting using EMLA (eutectic mixture of local anaesthetics) cream, local anaesthesia and patient-controlled analgesia with alfentanil.

Bone marrow harvesting (BMH) was performed on 40 consecutive allogeneic or autologous donors using EMLA (eutectic mixture of local anaesthetics), local anaesthesia (LA) and patient-controlled analgesia with alfentanil (PCA-A). The effect of alkalinizing the LA solution on reducing pain during LA infiltration in the presence of EMLA was also investigated. EMLA 10 g with occlusive dressing was applied to the harvest sites at least 60 min before BMH. The PCA device was programmed to deliver an intravenous loading dose of 15 microg/kg alfentanil, followed by a background alfentanil infusion of 0.05 microg/kg/min. Demand dose was 4 microg/kg and lockout time was 3 min. Donors were randomized to receive either alkalinized (n = 19) or non-alkalinized (n=21) LA solution (lignocaine 1% with 1:100000 adrenaline). While post-operative nausea and vomiting were the only side-effects, all donors in both groups reported satisfactory pain scores during LA infiltration and satisfactory overall intra-operative comfort scores. They completed BMH using either regimen successfully, found this technique acceptable and would recommend this form of anaesthesia to others. Alkalinizing the LA solution did not significantly improve the pain scores during LA infiltration in the presence of EMLA. In conclusion, BMH can be performed safely using EMLA, LA and PCA-A without major complications.

Intravascular gas exchange.

Intravascular gas exchange, in which miniaturized hollow fibre oxygenators are inserted into the caval veins, has been proposed as a simpler and safer alternative to extracorporeal support in severe respiratory failure. One such device, the IVOX (intravascular oxygenator), has undergone clinical trials (160 implants) and, despite individual benefits, was found to be limited in its gas exchanging capacity. The peculiarities of oxygen physiology render pre-pulmonary oxygenation inefficient and variable, whereas carbon dioxide clearance is much more predictable. Several devices are currently undergoing development and may offer substantially enhanced gas exchange. The new devices, which may be several years from widespread clinical assessment, offer exciting therapeutic options in severe respiratory failure but are unlikely to completely replace extracorporeal techniques in the most severe forms of respiratory failure.

Cytotoxic and leishmanicidal aminoglycosteroids and aminosteroids from Holarrhena curtisii.

The EtOH extract of the leaves of Holarrhena curtisii yielded five new steroidal alkaloids: 17-epi-holacurtine (3), 17-epi-N-demethylholacurtine (4), holacurtinol (5), 3alpha-amino-14beta-hydroxypregnan-20-one (7), and 15alpha-hydroxyholamine (8), in addition to the known compounds, holacurtine (1), N-demethylholacurtine (2), and holamine (6). All eight compounds showed significant cytotoxic and leishmanicidal activities.

Conodiparines A-D, new bisindoles from Tabernaemontana. Reversal of vincristine-resistance with cultured cells.

Four new bisindoles of the vobasine-iboga type, conodiparines A-D were obtained from Tabernaemontana corymbosa which showed appreciable activity in reversing resistance in vincristine-resistant KB cells.

Is it feasible to use magnesium sulphate as a hypotensive agent in oral and maxillofacial surgery?

We report the results of a feasibility study using intravenous magnesium sulphate for deliberate hypotension in 16 ASA 1 patients undergoing major oral and maxillofacial surgery. All the patients received a standard nitrous oxide, oxygen, isoflurane, opioid and muscle relaxant anaesthetic. Magnesium sulphate was infused at 40 g/h until the mean arterial pressure reached 55 +/- 5 mmHg, followed by a maintenance dose of 5 g/h until 30 minutes prior to the end of surgery. The mean arterial pressure was significantly (P < 0.01) reduced by the magnesium sulphate when compared to baseline values. Control of the mean arterial pressure was satisfactory. No patient had reflex tachycardia, cardiac arrhythmia or rebound hypertension. In 14 patients the surgeons thought that the blood loss was less than when using other hypotensive anaesthetic techniques. In 2 patients the surgeons thought the blood loss was excessive. In another 2 patients, the surgeons thought that there was excessive facial swelling on completion of surgery. Postoperative muscle weakness and sedation were not problems clinically. Fourteen patients were extubated immediately after surgery and another 2 patients an hour later in the recovery room. Intraoperative urine output was well maintained. On completion of surgery, the prothrombin time was significantly increased (P < 0.05), and the partial thromboplastin time significantly decreased (P < 0.05) in all the patients (when compared to preoperative values); the clinical significance of this is unclear. The use of intravenous magnesium sulphate for deliberate hypotension is feasible in ASA 1 patients using a standard nitrous oxide, oxygen, isoflurane, opioid and muscle relaxant technique. This study forms the basis for a larger controlled study where the issues of postoperative sedation and weakness and coagulopathy can be dealt with in greater detail.

Reversal of multidrug resistance (MDR) by aspidofractinine-type indole alkaloids.

A series of indole alkaloids of the aspidofractinine-type was assessed for their potential in reversing MDR in vincristine-resistant KB cells. Of the compounds tested, kopsiflorine, kopsamine, pleiocarpine, 11-methoxykopsilongine, lahadinine A and N-methoxycarbonyl-11,12-methylenedioxy-delta 16,17-kopsinine were found to show appreciable activity.

Preoperative prediction of intra and postoperative red blood cell transfusion in surgical patients.

Anaesthetists were asked to predict the need for intra and postoperative red blood cell transfusion in 1706 patients before surgery. Each prediction was made using only the individual patient's medical history and physical examination, the results of routine preoperative laboratory investigations, and knowledge of the proposed surgical procedure. Only 159 patients (9.3%) received red blood cell transfusion. The sensitivity and specificity of this preoperative prediction were 85.5% and 96.6% respectively, whereas the positive and negative predictive values were 72.3% and 98.5% respectively. Using a stepwise logistic regression model, preoperative haemoglobin concentration, Surgical Table of the procedure, and age of patients were found to significantly determine the need for intra and postoperative red blood cell transfusion. It is recommended that type and screen should replace group and crossmatch procedures in surgical patients where no intra and postoperative red blood cell transfusion is predicted as necessary.

A questionnaire survey on practice of chest tube management.

AIM: With the aim towards better education of junior medical staff on chest tube management, we designed a questionnaire to survey their practice and at the same time to assess their level of understanding of the physical principles of chest tube and its drainage system. METHODS: The questionnaire was distributed to 130 junior medical staff (house officers, medical officers, trainee medical officers and specialist medical officers) from 7 Medical and Surgical Departments in Singapore General Hospital. Eighty-seven (66.9%) candidates responded. The mean age of the respondents was 27 +/- 2.1. They had an average of 3.2 +/- 1.9 years after basic medical qualification and 5 hospital postings. Nine respondents had obtained higher medical qualifications. RESULTS: About a quarter of the respondents, and 40% of those with higher medical qualifications gave appropriate answers. Ninety percent indicated that they received no lectures on chest tube management. Incomplete response ranged from 0% to 6%. CONCLUSION: To improve education on chest tube management, our results and the feedback we obtained from the respondents, suggest that lectures on important physical principles of chest tube and its drainage system should be delivered to all junior medical staff.

Bone marrow harvesting using local anaesthesia and PCA-alfentanil: a feasible alternative to general or regional anaesthesia.

We examined the feasibility of combined use of local anaesthesia (LA) and patient-controlled analgesia with alfentanil (PCA-alfentanil) for bone marrow harvesting (BMH) in 16 consecutive in-patient donors (nine allogeneic and seven autologous). A loading dose of alfentanil 15 micrograms/kg was delivered at the time of skin preparation followed by a background infusion of alfentanil 0.05 microgram/kg/min. On -demand bolus doses of alfentanil were 4 micrograms/kg with lockout intervals of 3 min. Local anaesthesia was achieved using 1% lignocaine (up to 7 mg/kg) with 1:200,000 adrenaline. All donors were mildly sedated during BMH, tolerated the procedure well, and experienced no cardiovascular or respiratory complications. Post-operative nausea and vomiting were the only side-effects. All donors indicated that the combined use of LA with PCA-alfentanil was acceptable for BMH. Our preliminary results suggest that although optimal PCA settings have yet to be determined, this technique may be a feasible and effective alternative for BMH in situations where general or regional anaesthesia is undesirable.

Clinical strategies in intravascular gas exchange.

Specific therapies in the management of acute pulmonary failure remain elusive, with attention being focused instead on novel supportive measures. The benefits of extracorporeal gas exchange support remain uncertain, and the perceived simplicity of intravascular gas exchange has, therefore, attracted much interest. Initial clinical experience with the intravascular oxygenator (IVOX) device confirms its safety and simplicity, but estimated mean gas-transfer values represent only 25% of basal gas-exchange requirements. The inherent limitations of IVOX as an oxygenator are discussed, providing a rationale for considering IVOX as primarily a CO2 removal device. Reappraisal of the clinical place of intravascular gas exchange and the identification of specific applications most likely to yield benefit to patients are suggested. Design modifications enhancing efficacy are anticipated, further strengthening the potential of intravascular gas-exchange devices in selected patients with pulmonary failure.

Use of patient-controlled analgesia with alfentanil for burns dressing procedures: a preliminary report of five patients.

The use of patient-controlled analgesia with alfentanil (PCA-alfentanil) as a form of pain relief for dressing procedures in patients during the acute phase of their burn injuries was investigated. Five ASA 1 and 2 patients with 10-30 per cent total body surface area (TBSA) thermal burns, had PCA-alfentanil for their dressing procedures after standard fluid resuscitation. One patient who did not receive a loading dose and a background infusion of alfentanil had unsatisfactory pain relief. Four patients had good pain relief after a loading dose of IV alfentanil 1 mg followed by a continuous background infusion of 200-800 micrograms/h. Demand dose ranged from 200 to 400 micrograms and lockout time ranged from 1 to 3 min. The total dose of alfentanil delivered ranged from 0.8 to 4.48 mg and duration of the dressings ranged from 30 to 60 min. All patients were mildly sedated, calm, communicative and cooperative during dressing procedures. None of them experienced hypotension or respiratory depression. One patient experienced nausea but no vomiting, no other adverse effects of alfentanil were noted. From the pilot study, PCA-alfentanil may be an effective form of pain relief for dressing procedures in patients during their acute phase of burn injuries. The optimal PCA-alfentanil setting has yet to be determined.

Cerebral resuscitation from cardiac arrest: treatment potentials.

In 1961, in Pittsburgh, PA, "cerebral" was added to the cardiopulmonary resuscitation system (CPR --> CPCR). Cerebral recovery is dependent on arrest and cardiopulmonary resuscitation times, and numerous factors related to basic, advanced, and prolonged life support. Postischemic-anoxic encephalopathy (the cerebral postresuscitation disease or syndrome) is complex and multifactorial. The prevention or mitigation of this syndrome requires that there be development and trials of special, multifaceted, combination treatments. The selection of therapies to mitigate the postresuscitation syndrome should continue to be based on mechanistic rationale. Therapy based on a single mechanism, however, is unlikely to be maximally effective. For logistic reasons, the limit for neurologic recovery after 5 mins of arrest must be extended to achieve functionally and histologically normal human brains after 10 to 20 mins of circulatory arrest. This goal has been approached, but not quite reached. Treatment effects on process variables give clues, but long-term outcome evaluation is needed for documentation of efficacy and to improve clinical results. Goals have crystallized for clinically relevant cardiac arrest-intensive care outcome models in large animals. These studies are expensive, but essential, because positive treatment effects cannot always be confirmed in the rat forebrain ischemia model. Except for a still-elusive breakthrough effect, randomized clinical trials of CPCR are limited in their ability to statistically document the effectiveness of treatments found to be beneficial in controlled outcome models in large animals. Clinical studies of feasibility, side effects, and acceptability are essential. Hypertensive reperfusion overcomes multifocal no-reflow and improves outcome. Physical combination treatments, such as mild resuscitative (early postarrest) hypothermia (34 degrees C) plus cerebral blood flow promotion (e.g., with hypertension, hemodilution, and normocapnia), each having multiple beneficial effects, achieved complete functional and near-complete histologic recovery of the dog brain after 11 mins of normothermic, ventricular fibrillation cardiac arrest. Calcium entry blockers appear promising as a treatment for postischemic-anoxic encephalopathy. However, the majority of single or multiple drug treatments explored so far have failed to improve neurologic outcome. Assembling and evaluating combination treatments in further animal studies and determining clinical feasibility inside and outside hospitals are challenges for the near future. Treatments without permanent beneficial effects may at least extend the therapeutic window. All of these investigations will require coordinated efforts by multiple research groups, pursuing systematic, multilevel research--from cell cultures to rats, to large animals, and to clinical trials. There are still many gaps in our knowledge about optimizing extracerebral life support for cerebral outcome.

Pseudomembranous necrotising bronchial aspergillosis complicating chronic airways limitation.

Pseudomembranous necrotising bronchial aspergillosis is a variety of invasive aspergillosis found in immunosuppressed patients. A case is presented of a 66 year old woman whose only underlying disease was chronic airways limitation. The pathological findings and clinical implications are discussed.