Introducing the fragility index-A case study using the Term Breech Trial

The fragility index (FI) is a sensitivity analysis of the statistically significant result of a clinical study. It is the number of hypothetical changes in the primary event of one of the two cohorts in a 1-to-1 comparative trial to render the statistically significant result non-significant (ie, to alter the P-value from ≤0.05 to >0.05). The FI can be compared with the patient drop-out rates and protocol violations, which, if much higher than the FI, may arguably suggest less robustness/stability of the trial's results. To illustrate the concept, we have chosen the Term Breech Trial (TBT) as a case study. The TBT results favor planned cesarean birth, as opposed to planned vaginal delivery, in the term singleton fetus with breech presentation. Our analysis shows that the FI of the TBT is 21, which is small in comparison to the number (hundreds) of protocol violations present. Some experts have suggested the inclusion of the FI in data analysis and subsequent discussion of clinical trial data. Routine use of such a metric may be valuable in encouraging readers to maintain a healthy degree of skepticism, especially when interpreting trial results which may directly influence clinical practice.

Update on surgical repair in functional mitral regurgitation

BACKGROUND

Functional mitral regurgitation (FMR) is common in patients with myocardial infarction or dilated cardiomyopathy, and portends a poor prognosis despite guideline-directed medical therapy (GDMT). Surgical or transcatheter mitral repair for FMR from recent randomized clinical trials showed disappointing or conflicting results.

AIMS

To provide an update on the role of surgical repair in the management of FMR.

MATERIALS AND METHODS

A literature search was conducted utilizing PubMed, Ovid, Web of Science, Embase, and Cochrane Library. The search terms included secondary/FMR, ischemic mitral regurgitation, mitral repair, mitral replacement, mitral annuloplasty, transcatheter mitral repair, and percutaneous mitral repair. Randomized clinical trials over the past decade were the particular focus of the current review.

RESULTS

Recent data underlined the complexity and poor prognosis of FMR. GDMT and cardiac resynchronization, when indicated, should always be applied. Accurate assessment of the interplay between ventricular geometry and mitral valve function is essential to differentiate proportionate FMR from the disproportionate subgroup, which could be helpful in selecting appropriate transcatheter intervention strategies. Surgical repair, most commonly performed with an undersized ring annuloplasty, remains controversial. Adjunctive valvular or subvalvular repair techniques are evolving and may produce improved results in selected FMR patients.

CONCLUSION

FMR resulted from complex valve-ventricular interaction and remodeling. Distinguishing proportionate FMR from disproportionate FMR is important in exploring their underlying mechanisms and to guide medical treatment with surgical or transcatheter interventions. Further studies are warranted to confirm the clinical benefit of appropriate surgical repair in selected FMR patients.

[Sufentanil during anesthetic induction of remifentanil-based total intravenous anesthesia: a randomized controlled trial]

BACKGROUND

Postoperative pain represents an important concern when remifentanil is used for total intravenous anesthesia because of its ultrashort half-life. Longer acting opioids, such as sufentanil, have been used during induction of remifentanil-based total intravenous anesthesia as a means to overcome this shortcoming. However, the effectiveness and safety of such strategy still lacks evidence from randomized clinical trials. Hence, we aimed to assess the postoperative analgesic efficacy and safety of a single dose of sufentanil administered during the induction of remifentanil-based total intravenous anesthesia.

METHODS

Forty patients, scheduled for elective open abdominal surgery, were randomized to receive remifentanil-based total intravenous anesthesia with or without a single dose of sufentanil upon induction. We assessed the postoperative morphine consumption administered through a patient-controlled analgesia pump. Self-reported pain scores and the occurrence of nausea, vomiting, pruritus, agitation, somnolence and respiratory depression were also assessed up to 2 days after surgery.

RESULTS

The mean difference between the sufentanil and control groups regarding morphine consumption in the post-anesthetic care unit and at 12, 24 and 48h after surgery were -7.2mg (95%CI: -12.5 to -2.1, p<0.001), -3.9mg (95%CI: -11.9 to 4.7, p=0.26), -0.6mg (95%CI: (-12.7 to 12.7, p=0.80), and -1.8mg (95%CI: (-11.6 to 15.6, p=0.94), respectively. Neither self-reported pain nor the incidence of adverse events were significantly different between groups at any time point.

CONCLUSION

Our findings suggest that the administration of sufentanil during induction of remifentanil-based total intravenous anesthesia is associated with decreased early postoperative opioid consumption.

Bias in Before-After Studies: Narrative Overview for Anesthesiologists

Before-after study designs are effective research tools and in some cases, have changed practice. These designs, however, are inherently susceptible to bias (ie, systematic errors) that are sometimes subtle but can invalidate their conclusions. This overview provides examples of before-after studies relevant to anesthesiologists to illustrate potential sources of bias, including selection/assignment, history, regression to the mean, test-retest, maturation, observer, retrospective, Hawthorne, instrumentation, attrition, and reporting/publication bias. Mitigating strategies include using a control group, blinding, matching before and after cohorts, minimizing the time lag between cohorts, using prospective data collection with consistent measuring/reporting criteria, time series data collection, and/or alternative study designs, when possible. Improved reporting with enforcement of the Enhancing Quality and Transparency of Health Research (EQUATOR) checklists will serve to increase transparency and aid in interpretation. By highlighting the potential types of bias and strategies to improve transparency and mitigate flaws, this overview aims to better equip anesthesiologists in designing and/or critically appraising before-after studies.

Use of Recombinant Activated Factor VII after Axillofemoral Bypass Grafting

Recombinant activated factor VII (rFVIIa) is a powerful prohaemostatic agent that theoretically predisposes to thrombosis after peripheral vascular surgery. We report the use of rFVIIa to reduce bleeding in a patient after axillofemoral bypass grafting for ruptured aorto-iliac pseudoaneurysm. Despite the increased risk of thrombosis, the patient made an uneventful recovery with preserved graft patency. The favourable result suggests that rFVIIa should be considered even in vascular surgical patients, if the risks of continued bleeding outweigh those of thrombosis. Better risk estimation is only possible if reports of rFVIIa use in vascular patients continue to appear and through controlled trials.

Right Upper Lobe Collapse Secondary to an Anomalous Bronchus after Endotracheal Intubation for Routine Surgery

Perioperative hypoxaemia is a common but serious problem with well recognised causes. However, an anomalous bronchus causing lobar collapse as a cause is seldom mentioned. A healthy young male patient was anaesthetised for a knee operation. He required reintubation immediately postoperatively for hypoxia. He was found to have right upper lobe collapse. Fibreoptic examination of the trachea demonstrated an anomalous bronchus as the cause. Intra-operatively, the endotracheal tube had been inserted too deeply and the bronchial orifice had been obstructed by the tip. It took several hours for the lung to re-expand. Greater awareness of this potential complication is needed.

Acute liver failure with extreme hyperbilirubinemia secondary to endocarditis-related severe mitral and tricuspid regurgitation: a challenge and an opportunity for surgeons

Hyperbilirubinemia is a known risk factor in patients undergoing open heart operations. Infective endocarditis often leads to valvular injury, such as rupture of chordae tendineae or leaflet perforation, which can cause acute heart failure in association with pulmonary hypertension and liver dysfunction. Here we present a patient with massive liver congestion, reflected by extreme hyperbilirubinemia, secondary to acute heart failure following mitral valve endocarditis that was successfully treated by emergency mitral and tricuspid valve repair.

Total Spinal Anesthesia Failure: Have You Assessed the Sensory Anesthesia in Sacral Dermatomes?

Intrathecal local anesthetic maldistribution is a well-known cause of spinal anesthesia failure (SAF). This could potentially result in sensory blockade restricted to the sacral dermatomes. We sought to determine the overall incidence of SAF and the role of sacral dermatomes in differentiating between total and partial failures. Of the 3111 spinals prospectively examined, 194 (6.2%) were classified as failures. Of the 72 presumed total failures based on the initial assessment, evaluation of the sacral dermatomes revealed sensory blockade in 32 (44%; 95% confidence interval, 32.7%-56.6%). Sacral dermatome assessment after SAF may be important in safely guiding subsequent anesthetic management.

Retrograde Extrusion of Coronary Thrombus During Urgent Aortocoronary Bypass Surgery: A Case Report

A 73-year-old man underwent urgent coronary artery bypass grafting after an acute myocardial infarction. An angiogram had revealed multivessel disease with a circumflex artery lesion suspected as the primary culprit. On separation from cardiopulmonary bypass, transesophageal echocardiography revealed a new mobile mass in the aortic root. Cardiopulmonary bypass was reinstituted and a large thrombus emanating from the left coronary ostium was surgically removed. We hypothesize that the thrombus had originated from coronary retrograde extrusion during venous grafting. This case illustrates an unusual source of emboli during coronary artery bypass grafting and emphasizes the importance of perioperative transesophageal echocardiography for the prevention of potentially catastrophic outcomes.

A technique of placing cuffed endotracheal tubes through in situ paediatric laryngeal mask airways

If tracheal intubation is not possible using direct laryngoscopy, one option is to use a laryngeal mask airway (LMA) through which an endotracheal tube (ETT) can be passed. In children, however, the size of an uncuffed ETT that can pass through the lumen of an LMA is sometimes too small for the trachea, resulting in gas leakage around the ETT. Using a cuffed ETT may reduce the gas leak but withdrawal of the LMA is then prevented by the pilot balloon. In this study, the largest sizes of cuffed and uncuffed Mallinckrodt™ ETTs that could pass with ease through various sizes of paediatric Classic™ and ProSeal™ LMAs were documented. For cuffed ETTs, withdrawal of the LMA was made possible by simply cutting off the pilot balloon. The ETT cuff-inflating mechanism was then repaired by passing a 20 or 22 gauge cannula into the cut end of the inflating tubing. The proximal end of the cannula was then connected to a one-way valve or a three-way stopcock. This technique of cutting off the pilot balloon of the cuffed ETT made it possible to use paediatric cuffed ETTs in exchange for the LMAs tested. The task was easy to perform. Subsequent repair of the cuff-inflation tubing was effective and could withstand high pressures. These findings indicate that it is possible to pass cuffed ETTs through paediatric LMA lumens, which can provide ventilation without gas leaks, unlike uncuffed ETTs.

Chest wall reconstruction with MatrixRib system: avoiding pitfalls

Reconstructions of the chest wall using commercially available artificial metallic rib systems are gaining in popularity. The MatrixRib system involves use of plates and screws to bridge any defect and provide support for the chest wall following resection. So far, there has been no publication focusing on describing the use of this new technology in a step-by-step approach. We describe our technique and discuss potential pitfalls and difficulties of using the system.

Angiogenic response to major lung resection for non-small cell lung cancer with video-assisted thoracic surgical and open access

Background. Angiogenic factors following oncological surgery is important in tumor recurrence. Vascular endothelial growth factor (VEGF), angiopoietin 1 (Ang-1), Ang-2, soluble VEGF-receptor 1 (sVEGFR1) and sVEGFR2 may influence angiogenesis. This prospective study examined the influence of open and video-assisted thoracic surgery (VATS) lung resections for early stage non-small cell lung cancer (NSCLC) on postoperative circulating angiogenic factors. Methods. Forty-three consecutive patients underwent major lung resection through either VATS (n = 23) or Open thoracotomy (n = 20) over an 8-month period. Blood samples were collected preoperatively and postoperatively on days (POD) 1 and 3 for enzyme linked immunosorbent assay determination of angiogenic factors. Results. Patient demographics were comparable. For all patients undergoing major lung resection, postoperative Ang-1 and sVEGFR2 levels were significantly decreased, while Ang-2 and sVEGFR1 levels markedly increased. No significant peri-operative changes in VEGF levels were observed. Compared with open group, VATS had significantly lower plasma levels of VEGF (VATS 170 ± 93 pg/mL; Open 486 ± 641 pg/mL; P = 0.04) and Ang-2 (VATS 2484 ± 1119 pg/mL; Open 3379 ± 1287 pg/mL; P = 0.026) on POD3. Conclusions. Major lung resection for early stage NSCLC leads to a pro-angiogenic status, with increased Ang-2 and decreased Ang-1 productions. VATS is associated with an attenuated angiogenic response with lower circulating VEGF and Ang-2 levels compared with open. Such differences in angiogenic factors may be important in lung cancer biology and recurrence following surgery.

Surgical emphysema as a cause of severe hypercapnia during laparoscopic surgery

Surgical emphysema is a well-recognised complication of laparoscopic surgery, but its impact on end-tidal carbon dioxide levels and carbon dioxide elimination is seldom reported and may not be fully appreciated by anaesthetists. Four cases are presented where extensive surgical emphysema occurred during laparoscopic surgery. The visual display of the anaesthetic record using the software program Monitor showed substantial rises in end-tidal carbon dioxide levels and allowed calculation of the carbon dioxide elimination, which increased two- to three-fold above normal levels. Having a visual record of carbon dioxide changes facilitated the recognition of surgical emphysema in three out of the four cases. Strategies such as estimating and tracking changes in carbon dioxide elimination from the minute ventilation and end-tidal carbon dioxide levels may assist in early identification, and palpating for surgical emphysema is recommended during laparoscopy if other causes of increased carbon dioxide levels are excluded.

Using illness scripts to teach clinical reasoning skills to medical students

BACKGROUND AND OBJECTIVES

Most medical students learn clinical reasoning skills informally during clinical rotations that have varying quality of supervision. We conducted a randomized controlled trial to determine if a workshop that uses "illness scripts" could improve students' clinical reasoning skills when making diagnoses of patients portrayed in written scenarios.

METHODS

In 2007--2008, 53 fourth-year medical students were randomly assigned to either a family medicine (intervention) or psychiatry (control) clerkship at The Chinese University of Hong Kong. Students in the intervention group participated in a 3-hour workshop on clinical reasoning that used illness scripts. The workshop was conducted with small-group teaching using a Web-based set of clinical reasoning problems, individualized feedback, and demonstration of tutors' reasoning aloud. The effectiveness of the intervention was assessed using the Diagnostic Thinking Inventory (DTI) and the measurement of individual students' performance in solving clinical reasoning problems (CRP).

RESULTS

The post-intervention overall DTI scores between groups were similar (mean difference 0, 95% confidence interval [CI]= -7.4 to 7.4). However, the total scores on the CRP assessment were 14% (95% CI=8% to 21%) higher in the intervention group than in controls.

CONCLUSION

A workshop on illness scripts may have some benefit for improving diagnostic performance in clinical reasoning problems.

Tips for teachers of evidence-based medicine: making sense of decision analysis using a decision tree

Decision analysis is a tool that clinicians can use to choose an option that maximizes the overall net benefit to a patient. It is an explicit, quantitative, and systematic approach to decision making under conditions of uncertainty. In this article, we present two teaching tips aimed at helping clinical learners understand the use and relevance of decision analysis. The first tip demonstrates the structure of a decision tree. With this tree, a clinician may identify the optimal choice among complicated options by calculating probabilities of events and incorporating patient valuations of possible outcomes. The second tip demonstrates how to address uncertainty regarding the estimates used in a decision tree. We field tested the tips twice with interns and senior residents. Teacher preparatory time was approximately 90 minutes. The field test utilized a board and a calculator. Two handouts were prepared. Learners identified the importance of incorporating values into the decision-making process as well as the role of uncertainty. The educational objectives appeared to be reached. These teaching tips introduce clinical learners to decision analysis in a fashion aimed to illustrate principles of clinical reasoning and how patient values can be actively incorporated into complex decision making.

The incidence of deep venous thrombosis in Chinese medical Intensive Care Unit patients

OBJECTIVE

To evaluate the incidence of deep venous thrombosis in critically ill, Intensive Care Unit patients of Chinese ethnicity.

DESIGN

Prospective, observational study.

SETTING

Intensive Care Unit in a Hong Kong teaching hospital.

PATIENTS

Consecutive adult Chinese medical patients not receiving pharmacological or mechanical prophylaxis for deep venous thrombosis.

MAIN OUTCOME MEASURES

Compression and duplex Doppler ultrasound examinations of the lower limbs within 24 hours of admission and twice weekly thereafter during their Intensive Care Unit stay. After discharge, a 1-week follow-up investigation was also performed. Demographic data and risk factors for deep venous thrombosis were prospectively recorded.

RESULTS

Over a 9-month study period, 80 patients were investigated. Deep venous thrombosis was detected by ultrasound examination in 15 (19%) of the patients (95% confidence interval, 14-23%). Nine of 15 had isolated below-knee deep venous thrombosis, and of these, five had bilateral involvement. Characteristics of patients with or without deep venous thrombosis were similar. Of the 15 patients who had a positive ultrasound examination, only four (27%) had clinical signs of deep venous thrombosis. Of the 65 patients without a positive ultrasound examination, only two (3%) had positive clinical signs (P=0.01). This yielded a moderate positive likelihood ratio of 9 (95% confidence interval, 2-43) and a small negative likelihood ratio of 0.76 (95% confidence interval, 0.56-1.03). There were no cases of pulmonary embolism. Hospital mortality in those with and without deep venous thrombosis was 33% and 28%, respectively.

CONCLUSIONS

In the absence of prophylaxis, the incidence of deep venous thrombosis in Chinese medical Intensive Care Unit patients is lower than that reported in similar Caucasian patients, but higher than expected. As clinical features are not able to reliably exclude the presence of deep venous thrombosis, early routine prophylaxis for deep venous thrombosis in Chinese medical Intensive Care Unit patients should be considered.

Hemostatic parameters after hepatectomy for cancer

BACKGROUND/AIMS

Epidural analgesia improves postoperative outcome, and should benefit patients undergoing hepatectomy for cancer. However, the combination of underlying disease, surgery, and blood loss after hepatectomy may lead to hemostatic changes that, theoretically, increase the risk of epidural hematoma. To quantify these changes, we retrospectively reviewed the records of 229 patients at the Prince of Wales Hospital, Hong Kong.

METHODOLOGY

We analyzed the hemostatic parameters of those in whom there were complete data (n=143) up to postoperative day 3.

RESULTS

We found considerable derangements in the international normalized ratio (INR), prothrombin time, activated partial thromboplastin time (aPTT), and platelet counts, with peak derangements occurring around postoperative day 2. The amount of liver resected and the preoperative Model for End-Stage Liver Disease score were predictors of peak INR > or = 1.5 in the postoperative period.

CONCLUSIONS

We conclude that commonly measured hemostatic parameters are deranged after hepatectomy for cancer. Because of the complex cancer- and surgery-related hemostatic changes, whether these changes indeed indicate increased risk of neuraxial hematoma associated with neuraxial blocks is unclear. We also found that most Chinese patients were managed adequately with patient-controlled intravenous morphine. Clinicians contemplating neuraxial block on patients undergoing hepatectomy for cancer must weigh the potential risks and benefits.

Effect of an integrated teaching intervention on clinical decision analysis: a randomized, controlled study of undergraduate medical students

A four-hour integrated teaching session on clinical decision analysis has been developed and introduced as part of the Life Long Learning Skills course for medical students at The Chinese University of Hong Kong. The feasibility and effectiveness of teaching the principles and practice of clinical decision analysis to final-year undergraduate medical students was evaluated. One hundred and thirty-two students were randomly assigned to medical (intervention) and surgical rotations (control) and were assessed two weeks before and three weeks following a teaching session. The students' performance was assessed in response to 10 A-type multiple choice question items that incorporated various clinical scenarios requiring decision making and interpreting cost-effectiveness ratios and sensitivity analysis graphs. More students in the intervention group improved their overall performance scores compared with those in the control group (23.4% vs. 7.4%; 16.1% difference; 95% confidence interval [CI], 3.8-28.5%; p = 0.01). Improvements were in interpretation of decision making (22.2% difference; 95% CI, 10.1-34.4%; p < 0.001). No improvements were seen for calculating cost-effectiveness ratios or interpreting sensitivity analysis graphs. The overall educational intervention was well received by students and effective in improving students' clinical decision analysis skills under simulated conditions.

Dynamic Airflow Limitation after Topical Anaesthesia of the Upper Airway

This prospective before-and-after observational study investigated the effect of upper airway anaesthesia on dynamic airflow. Six consenting ASA 1 adults, all authors of this study, underwent a series of Spirometric measurements before and after topical anaesthesia of the upper airway using lignocaine. Peak inspiratory flow rate, forced inspiratory flow between 25% and 75% of the maximum inhaled volume, forced expiratory volume at 1 second, and forced vital capacity in the supine and sitting positions were measured. The measured inspiratory parameters were significantly reduced after lignocaine topical anaesthesia of the upper airway. Expiratory flow parameters were not affected. We conclude that topical anaesthesia of the upper airway leads to dynamic inspiratory airflow limitation.

A mathematical model for fresh frozen plasma transfusion strategies during major trauma resuscitation with ongoing hemorrhage

BACKGROUND

Randomized controlled trials of how best to administer fresh frozen plasma (FFP) in the presence of ongoing severe traumatic hemorrhage are difficult to execute and have not been published. Meanwhile, coagulopathy remains a common occurrence during major trauma resuscitation and hemorrhage remains a major cause of traumatic deaths, suggesting that current coagulation factor replacement practices may be inadequate.

METHODS

We used a pharmacokinetic model to simulate the dilutional component of coagulopathy during hemorrhage and compared different FFP transfusion strategies for the prevention or correction, or both, of dilutional coagulopathy. Assuming the rates of volume replacement and loss are roughly equal, we derived the hematocrit and plasma coagulation factor concentration over time based on the rate of blood loss and replacement, the hematocrit and coagulation factor concentration of the transfusate, and the hematocrit and plasma factor concentration at the time when FFP transfusion begins.

RESULTS

Once excessive deficiency of factors has developed and bleeding is unabated, 1-1.5 units of FFP must be given for every unit of packed red blood cells (PRBC) transfused. If FFP transfusion should start before plasma factor concentration drops below 50% of normal, an FFP:PRBC transfusion ratio of 1:1 would prevent further dilution.

CONCLUSION

During resuscitation of a patient who has undergone major trauma, the equivalent of whole-blood transfusion is required to correct or prevent dilutional coagulopathy.

Total airway obstruction during local anesthesia in a non-sedated patient with a compromised airway

PURPOSE

To report a case of complete upper airway obstruction after topicalization with lidocaine in a completely conscious patient with partial upper airway obstruction.

CLINICAL FEATURES

A 69-yr-old man with a history of neck cancer and radiation presented for resection of recurrent neck tumour. No preoperative sedation was given. He had inspiratory and expiratory stridor but had no history of aspiration or swallowing problem. Phonation was distorted but effective. The surgeon was reluctant to perform an awake tracheostomy under local anesthesia. In preparation for a fibrescope-assisted orotracheal intubation, the non-sedated patient was given topical upper airway lidocaine during which he developed total airway obstruction and hypoxemia. He was immediately intubated with a fibrescope. His vocal cords were not edematous although the supraglottic structures appeared to be. The vocal cords were abducted and their movement was limited and not paradoxical. Tumour resection was uneventful upon successful tracheal intubation and general anesthesia. Tracheostomy at the end of the case was difficult, as expected. The patient tolerated the procedures and regained consciousness with no neurologic sequelae.

CONCLUSION

Dynamic airflow limitation associated with local anesthesia of the upper airway may lead to complete upper airway obstruction in a compromised airway. The main cause may be the loss of upper airway muscle tone, exacerbated by deep inspiration during panic.

Postthoracotomy pain syndrome

Postthoracotomy pain syndrome is relatively common and is seen in approximately 50% of patients after thoracotomy. It is a chronic condition, and about 30% of patients might still experience pain 4 to 5 years after surgery. In the majority of patients pain is usually mild and only slightly or moderately interferes with normal daily living. In a small subset of patients pain can be severe and can be described as a true disability to the extent that these patients are incapacitated. The exact mechanism for the pathogenesis of PTPS is still not clear, but cumulative evidence suggests that it is a combination of neuropathic and nonneuropathic (myofascial) pain. Trauma to the intercostal nerve during thoracotomy is the most likely cause. Because pain does not cause disability in the majority of patients, management is usually conservative. If pain is causing disability then multidisciplinary pain management involving the pain specialist, social worker, physical therapist, and a psychologist is required. It is mandatory to exclude recurrence of disease or malignancy as a cause for the pain prior to initiating treatment. As with most forms of neuropathic pain, treatment of PTPS is also difficult and patients might require more than one form of therapy to control pain and reduce disability. Based on current evidence, it is not possible to draw any firm conclusion regarding whether any form of analgesic or surgical technique can influence the generation of PTPS. Preemptive analgesia initiated prior to surgery shows promise and might help reduce the incidence of PTPS. Scientific evidence is steadily growing but there is still a need for large, prospective, randomized trials evaluating PTPS. Until more is known about this condition and how to prevent the central and peripheral nervous system changes that produce long-term pain after thoracotomy, patients must be warned preoperatively about the possibility of developing PTPS and how it might affect their quality of life after surgery. In addition, measures such as selecting the least traumatic and painful surgical approach, avoiding intercostal nerve trauma, and adopting an aggressive multimodal perioperative pain management regimen commenced before the surgical incision should be performed to prevent postthoracotomy pain syndrome.

Antioxidative and anti-endotoxin effects of propofol on endothelial cells

OBJECTIVE

To investigate the antioxidant and anti-endotoxin effects of propofol on endothelial cells and the possible mechanisms.

METHODS

Cultured endothelial cells were treated with hydrogen peroxide (H(2)O(2)), propofol + H(2)O(2), lipopolysaccharide (LPS) and propofol + LPS, respectively. Endothelial cell damage was monitored for possible lactic dehydrogenase (LDH) release. The transcription and the protein expression levels of endothelial nitric oxide synthase (eNOS) were measured.

RESULTS

LDH release was higher in groups treated with H(2)O(2) or LPS than in the control group. After pretreatment with propofol, the effects induced by H(2)O(2) were attenuated, but propofol did not decrease the LDH release induced by LPS. Both H(2)O(2) and LPS significantly increased the eNOS transcript levels and the increases were significantly attenuated after pretreatment with propofol. Both H(2)O(2) and LPS significantly increased the eNOS protein expression and the increase was attenuated after pretreatment with propofol.

CONCLUSION

Propofol could protect endothelial cells against oxidative stress by inhibiting eNOS transcription and protein expression, but could not antagonise endotoxin induced cell injuries.

Consequences of syringe size sensor malfunction in a modern infusion pump

Prompted by an actual case of potentially life-threatening infusion pump malfunction, we investigated the effects of wire breakage(s) within the syringe size sensor circuit in a Graseby 3400 infusion pump. The circuit wires within the sensor were systematically broken. The syringe sizes recognised by the sabotaged circuit and the actual sizes of syringes inserted into the pump were compared. Thirty-eight per cent of the possible wire breakages resulted in a smaller syringe size being recognized, causing the infusion rate to be too fast, and 38% of the possiblewire breakage resulted in a larger syringe size being recognized, causing the infusion rate to be too slow. The volume delivered for each different size of Terumo syringe as a function of distance travelled by the plunger was measured. The errors ranged from 0.4 to 2.6 times that of the expected rate. Only 1.3% of the possible wire breakage(s) were recognised as errors by the pump. The infusion rates were not affected in 22.5% of the cases. Wire breakage within the syringe size sensor in infusion pumps is yet another potential source of infusion error, with important safety implications.

Combined paravertebral lumbar plexus and parasacral sciatic nerve block for reduction of hip fracture in a patient with severe aortic stenosis

PURPOSE

To report the use of a combined paravertebral lumbar plexus and parasacral sciatic nerve block for reduction of hip fracture in an elderly patient with severe aortic stenosis.

CLINICAL FEATURES

In an 87-yr-old lady with severe aortic stenosis and fracture of the right trochanter due to a fall, a combined right-sided paravertebral lumbar plexus and parasacral sciatic nerve block was used successfully for operative reduction of the fracture. A moderate amount of phenylephrine was required to maintain adequate systemic blood pressure despite the largely unilateral nature of the blocks.

CONCLUSION

Combined paravertebral lumbar plexus and parasacral sciatic nerve block can be a viable alternative to general anesthesia and epidural or spinal block for hip surgery in patients with severe aortic stenosis.

Use of heliox in critical upper airway obstruction. Physical and physiologic considerations in choosing the optimal helium:oxygen mix

Heliox has a lower density than oxygen and nitrogen, and can improve ventilation rapidly in patients with critical upper airway obstruction. The choice of the best helium:oxygen ratio depends on whether the predominant problem is hypercarbia or hypoxia. In the former situation, 80% helium should be used, and in the latter, 100% oxygen is appropriate.