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The yield stress-pH and zeta potential-pH behaviour of α-alumina and zirconia dispersions with adsorbed small ionic molecular additives such as phosphate and pyrophosphate were determined. The result for adsorbed citrate was included for comparison. Adsorbed phosphate at high surface coverage increased the maximum yield stress of low surface area α-Al2O3 (AKP30 and AA07) dispersions slightly. This increase is attributed to the intermolecular hydrogen bonding between phosphates adsorbed on interacting particles. With high surface area ZrO2 (Tosoh) dispersions, however, the adsorbed phosphate decreased the maximum yield stress. This is due to its very rough surface morphology limiting the extent of intermolecular hydrogen bonding between adsorbed phosphate layers. Unlike phosphate, pyrophosphate reduces the maximum yield stress of AKP30 α-Al2O3. This is due to the presence of intramolecular hydrogen bonding, thereby impeding effective bridging. A similar result is observed with citrate. The adsorbed pyrophosphate acts as an effective steric barrier keeping interacting particles further apart, thereby weakening the van de Waals attraction. These dispersions with the presence of non-DLVO forces, that is bridging and steric, did not affect the linear relationship between yield stress and the square of the zeta potential as predicted by the yield stress-DLVO force model. However the relative importance of these non-DLVO forces affect the value of the critical zeta potential at the point of transition from flocculated to dispersed state. © 2011 Canadian Society for Chemical Engineering [ABSTRACT FROM AUTHOR]

The effect of branched polyethylenimine (PEI) of molecular weight (Mw) 600, 1800 and 70,000 on the surface forces interacting between 'uniform size' spherical silica particles in water was investigated via the yield stress and zeta potential techniques. This silica has a point of zero charge at pH approximately 2.0. All PEIs caused the zeta potential-pH curve and the high pH zero zeta potential to shift to a higher pH and the extent of the shift increases with increasing PEI concentration and is not affected by PEI Mw. PEI adsorption on silica is low or negligible at pH less than 3.5 and this is due to a very low negative charge density. Adsorption of PEI beyond 3.5 caused a maximum zeta potential to occur at pH between 4 and 6. The maximum yield stress located at the point zero zeta potential is many times larger than that with no added PEI. It ranged from 20 to 42 times for low Mw PEI and as high as 68 times for Mw 70,000. At low surface coverages, the force responsible for the high yield stress is charged patch-bridging attraction. At complete surface coverage, particle bridging via hydrogen bond and unlike charged attraction between monomeric, dimeric and tetrameric silicate ions with the adsorbed PEI layers of the interacting particles was responsible.

Introduction: The study aims to show that total knee arthroplasty using computer-assisted surgical navigation without intramedullary rodding is safer than conventional intramedullary techniques in preventing venous thromboembolism., Methods: 30 patients were grouped into groups of 10. Groups A and B had conventional intramedullary rodding of the femur and/or tibia. Group C had no rodding of the femur and tibia using computer-assisted surgical navigation. The degree, duration and size of the embolic shower were captured by a transoesophageal echocardiography probe. The echogenic emboli were graded according to the Mayo Clinic score. Haemodynamic parameters such as pulse oximetry oxygen saturation, end-tidal carbon dioxide, heart rate and mean arterial pressure were also recorded., Results: There was a significant difference in the size of the emboli and the Mayo Clinic score when comparing the groups with intramedullary rodding and those without. There was also a significant difference in the pulse oximetry oxygen saturation and heart rate when the group without intramedullary rodding was compared with groups with rodding., Conclusion: Surgical navigation total knee arthroplasty may be safer than conventional total knee replacement with intramedullary rodding in preventing venous thromboembolism.

Introduction: Postoperative nausea and vomiting (PONV) is one of the commonest complaints following anaesthesia, and can result in morbidity like wound dehiscence, bleeding, pulmonary aspiration of gastric contents, fluid and electrolyte disturbances, delayed hospital discharge, unexpected hospital admission, and decreased patient satisfaction., Method: A literature search was done on the Medline and relevant articles chosen., Results: Despite the vast amount of research done in this field and the variety of antiemetic drugs available, PONV still has a high incidence. Many factors are associated with PONV. Quantifying the relative impact of risk factors on PONV has resulted in the development of risk models, which can stratify risk categories and hence allow the anaesthetist to identify those patients at higher risk for PONV. The management of PONV requires a multi-modal approach which can include the use of less emetogenic anaesthetic techniques, balanced analgesia, appropriate intravenous hydration, the use of pharmacotherapy and possibly non-pharmacologic methods., Conclusions: The use of risk models facilitates the judicious use of pharmacotherapy to ameliorate PONV especially in the high-risk patient and may lead to a more cost effective and efficient means of managing PONV.

Recently, the use of thermal energy to shrink the redundant glenohumeral joint capsule in patients with instability has generated a great deal of interest. Proponents assert that the procedure avoids the need for an open stabilization and it may be used as an adjunct to an open or arthroscopic capsulolabral repair. The use of nonablative thermal energy to shrink soft-tissue collagen appears to induce ultra-structural and mechanical changes at or above 60 degrees C. The microscopic changes reflect the unwinding of the collagen triple helix and loss of the fiber orientation. The fibrils contract into a shortened state and reactive fibroblasts have been shown to grow into this treated area and synthesize the collagen matrix. The biomechanical properties of the tissue do not appear to be detrimentally altered if shrinkage is limited to less than 15% and if ablation or excess focal treatment is avoided. The endpoint of optimal shrinkage is not known and clinical estimations of tissue changes and volumetric reduction are used as guides to treatment. The first clinical follow-up study was only recently published in the peer-reviewed literature and prior preliminary reports were optimistic regarding the use of thermal energy for the treatment of glenohumeral instability. Thermal capsular shrinkage has been used as an adjunct to a capsulolabral repair, as well as an isolated treatment for the disorders of internal impingement and multidirectional instability. Additional evaluation is necessary to determine the optimal quantity of energy needed for tissue shrinkage without inadvertent tissue destruction. The long-term clinical effect, mechanical properties, and durability of the newly produced collagen need to be analyzed further. The basic science and clinical applications of this newly applied technology are reviewed in this article.

For Achilles tendon surgery, an S-shaped incision may be made crossing the midline proximal to the transverse skin creases above the top of the heel counter. This incision provides wide exposure of the tendon and enables wound closure with minimal skin tension. After surgery, direct external pressure on the wound and dependent swelling of the Achilles tendon region, which may increase risks for wound dehiscence and infection, are minimized by laying the patient in the lateral decubitus or prone position to elevate the heel.

The one-bone forearm procedure can be a successful salvage option for forearm stability in selected patients and is indicated if instability and bone loss are irreparable by other means. We report a case of a dysfunctional arm secondary to radical débridement of the ulna after osteomyelitis treated successfully with a one-bone forearm procedure and followed up for 8 years.

The most common method used in the treatment of acute patellar tendon ruptures is primary end-to-end repair. The use of the Acufex ACL guide (Acufex Microsurgical, Mansfield, MA) provides efficient and accurate placement of transosseous drill holes in the patella and minimizes the risk, tourniquet time, and surgical time of acute patellar tendon repairs.

The results of a retrospective study of fall incidence during a 1-year period in a psychiatric hospital in Singapore are reported, involving 309 patients who fell one or more times during their stay. The profile of inpatients involved in falls was identified. Data were derived from standard incident forms completed whenever patients had a fall. A total of 348 falls were identified for the 1-year period. Results revealed higher fall rates in younger male epileptic patients; elderly female patients, age 70 and older with depression or dementia; individuals with concomitant medical conditions; and patients taking three types of medication. The majority of falls occurred when the activity level was high in the ward. Young epileptic patients and elderly depressed patients were prone to repeated falls. These results have the potential to assist in identifying patients at high risk and in designing and implementing strategies to prevent such incidents.

Since 1997 some of our cardiac anaesthetists have, whenever possible, extubated the patients early after cardiac surgery to improve their level of comfort, to allow an early return of the cardiopulmonary physiological function, and to help reduce health care costs. After a few months of implementing this practice, an audit was carried out to evaluate the success of early extubation after coronary artery bypass graft (CABG) surgery. Over a 6-month period starting from May 1997, the perioperative data of 110 consecutive patients with good or moderate left ventricular function scheduled for elective CABG were prospectively collected and analysed. The anaesthetic regime was according to the preference of the anaesthetists. Initially consent was obtained from the surgeons when the extubation criteria were fulfilled, but subsequently as the practice became more accepted by the surgeons, extubation was initiated by the anaesthetists. Within 4 hours of admission into the intensive care unit (ICU), 50 (45.5%) of the 110 patients satisfied the early extubation criteria and were extubated. The extubation criteria are described in the article. For the remaining patients, the median duration of mechanical ventilation was 14.3 hours. The profiles of the two groups of patients and the possible reasons for not extubating early are discussed. Forty-five per cent of the patients with moderate to good ventricular function were extubated safely within 4 hours of admission into the ICU after CABG surgery. With gradual acceptance of the practice and a change in mindset amongst all the care givers, more patients can benefit from this practice. This article highlights the challenges associated with changing institutional practices with respect to the postoperative care of cardiac patients.

Purpose: We report a case of a 33 yr old woman with pulmonary hypertension secondary to uncorrected right coronary artery to pulmonary artery fistula who underwent two successful operative deliveries under general anesthesia., Clinical Features: This woman underwent an emergency Caesarean section at 32 wk gestation because she presented in NYHA Class IV, heart failure and premature labour. She did not have antenatal follow-up. For her second pregnancy, she was managed from the first trimester of pregnancy by the cardiologist, obstetrician and anesthesiologist. She received oral furosemide and digoxin from eight weeks gestation. Pregnancy was managed to term before she progressed to NYHA Class IV and cardiac failure at 37 wk gestation. She had a Caesarean section under general anesthesia. She received rapid sequence induction of anesthesia and tracheal intubation with 0.1 mg x kg(-1) etomidate, 2 mg x kg(-1) succinylcholine and maintenance with nitrous oxide 50% in oxygen, isoflurane 1% and 0.1 mg x kg(-1) vecuronium. Fentanyl, 2 microg x kg(-1) helped to obtund the hypertensive response to intubation. Analgesia was provided with 1 mg x kg(-1) morphine. Glyceryl trinitrate infusion, 10-30 microg x min(-1) was used in addition to the anti-heart failure therapy. End-tidal capnography, electrocardiogram, pulse oximetry, continuous arterial blood pressure and pulmonary arterial catheter provided hemodynamic monitoring. The lungs were mechanically ventilated for 24 hr postoperatively. She received anti-heart failure therapy which she continued after discharge. She was NYHA class II upon discharge. She defaulted from further follow-up., Conclusion: Although the literature advocates, in this situation, controlled vaginal delivery utilising epidural analgesia, we describe the successful outcome for operative delivery under general anesthesia in a patient with secondary pulmonary hypertension and heart failure.

Purpose: The incidence of thrombotic events following cardiopulmonary bypass (CPB) in patients receiving surgical repair or palliation of congenital heart defects (CHD) is as high as 16%. Protein C, an intrinsic anticoagulation protease which, when activated, breaks down factor Va of the coagulation system, aids in maintaining a normal procoagulant/anticoagulant balance. Resistance of factor Va to degradation by activated protein C occurs and predisposes to thrombotic events. The resistance of factor Va to such degradation is, in the majority of cases, due to a genetic mutation referred to as factor V Leiden (FVLeiden). The presence of FVLeiden can be diagnosed using a DNA based assay. The prevalence of FVLeiden in the with CHD has not been determined. The objective of this study was to determine the prevalence of FVLeiden in patients with CHD., Methods: Two hundred consecutive patients with CHD undergoing surgical repair or palliation requiring cardiopulmonary bypass were studied. Blood was taken before administration of homologous blood transfusion and assayed using a DNA based method with polymerase chain reaction amplification for the FVLeiden mutation., Results: The prevalence of FVLeiden in our study population was 9/200 (4.5%). None of these patients demonstrated thrombotic complications. However, three patients (1.5%) without the FVLeiden mutation developed postoperative thrombotic complications., Conclusions: The prevalence of FVLeiden in patients is 4.5% that is not different from that of the population at large. There was no identifiable association with the occurrence of postoperative thrombotic events.

A case of heparin resistance and its management during cardiopulmonary bypass is reported. A patient with a history of post-infarct angina and arrhythmias was treated with intravenous heparin infusion for five days prior to myocardial revascularisation surgery. He required 13,500 IU/kg of heparin to increase his activated clotting time to a therapeutic level for safe institution of cardiopulmonary bypass. This phenomenon of heparin resistance was postulated to be due to consumption of circulating antithrombin III as a result of prior heparinisation. Treatment with fresh frozen plasma restored heparin effectiveness.

This 50-year-old man was on enteral full-strength Ensure through the jejunostomy tube. The enteral feed was accidentally infused through the peripheral intravenous line. He went into a septic state with hypotension, hypoxemia, and increased pulmonary shunting requiring ventilatory and inotropic support. We instituted two cycles of plasmapheresis in an attempt to remove any foreign antigen and toxins present. This resulted in improved oxygenation, rapid recovery, and discharge from intensive care. His blood culture grew Klebsiella species that was consistent with the organism grown from the culture of the Ensure feeds.

The degree of sedation in 191 day-stay children after oral premedication were compared. One hundred and forty-six were 1-5 years old (Group 1) and were randomised to receive either chloral 40 mg/kg, midazolam 0.2 mg/kg, promethazine 1 mg/kg, trimeprazine 3 mg/kg or placebo. Forty-five were 5-12 years old and were randomised to receive either trimeprazine 3 mg/kg, midazolam 0.2 mg/kg or placebo (Group 2). The children were assessed using four categories: asleep or drowsy, awake but calm, crying or anxious and oversedated or obstructed airway. They were assessed on leaving the ward, at separation from the parents, at induction, in the recovery room and one and two hours after returning to the ward. In Group 1, it was found that chloral and trimeprazine gave the best degree of sedation but the sedative effect of trimeprazine lasted longer into the post operative period. In Group 2, it was found that the children did not require deep sedation and the anxiolysis obtained with midazolam was adequate.