Electrocardiogram failure in the operating room - bench testing to prevent bed-side disaster.

Electrocardiogram (ECG) false alarms are common in electrically-hostile peri-operative environments. Newer integrated monitoring, with sophisticated hardware and software, has the potential to minimise artefacts. However, monitoring issues continue to occur, with the potential for critical incidents and unnecessary and harmful interventions. We describe the root cause analysis of a series of apparent ECG flatline asystolic events that appeared in the operating room shortly after the introduction of new intra-operative monitoring systems. Clinical events and biomedical laboratory testing revealed complete loss of ECG signal with increasing resistance. The new ECG systems had incorporated both software and hardware changes to improve the fidelity of signal acquisition and display, but had become much more sensitive to impedance changes. After we alerted the manufacturer, they added software and hardware updates that resulted in resolution of all incidents of ECG loss-of-signal.

Comparison of preoperative and intraoperative assessment of aortic stenosis severity by echocardiography.

BACKGROUND: General anaesthesia and surgically induced changes in cardiac loading conditions may alter flow across the aortic valve. This study examined how echocardiographic assessment of the severity of aortic stenosis (AS) changes during surgery. METHODS: Patients who underwent aortic valve replacement for any severity of AS between July 2007 and June 2015 were identified. Peak velocities, mean gradients, and dimensionless indices (DI) measured with preoperative transthoracic echocardiography (TTE) were compared with those measured with intraoperative transoesophageal echocardiography (TOE). Additionally, agreement of preoperative and intraoperative grading of AS based on these measurements was assessed. RESULTS: Data from 319 patients were analysed. On average, intraoperative TOE peak velocity and mean gradient were lower by 0.59 m s -1 and 12.5 mm Hg, respectively ( P <0.0001), compared with preoperative TTE measurements, whereas the difference in mean DI was minimal at 0.008. Preoperative and intraoperative grades of AS severity (mild, moderate, and severe) by peak velocity, mean gradient, and DI agreed in 53.3, 53.7, and 83.3% of patients, respectively. The TOE grade of AS severity by peak velocity and mean gradient was at least one lower than the TTE grade in 45.1 and 42.7% of patients, respectively. Significantly fewer patients had their severity of AS reclassified based on DI ( P <0.0001). CONCLUSIONS: Intraoperative TOE peak velocities and mean gradients are often significantly lower than preoperative TTE measurements, leading to underestimation of AS severity in nearly half of our study patients. The DI is a more reliable measurement of AS severity in the intraoperative setting.

Factors associated with poor adherence to antiviral treatment for hepatitis B.

Antiviral therapy for hepatitis B is effective and reduces the risk of progression to cirrhosis and liver cancer but is often required for an indefinite duration. Treatment adherence is important to prevent the development of resistance and optimize outcomes. Pharmacy adherence measures can be used to assess treatment adherence, with the medication possession ratio being less susceptible to bias than physician- or self-reported adherence. The aim of this study was to measure adherence in public hospital outpatients over a 3-year period and to examine factors associated with nonadherence. A retrospective study of pharmacy records of patients dispensed antiviral therapy for hepatitis B from four major hospitals in Melbourne between 2010 and 2013. Hospital record numbers were linked with and de-identified demographic information including age, sex, Indigenous status, country of birth, interpreter requirement, spoken language and postcode of residence. The medication possession ratio was the outcome measure with poor adherence defined <.90. Univariate logistic regression and multivariate logistic regression were performed to examine associations with nonadherence. Records of 1026 patients were included in the analysis. Twenty per cent of all participants met the definition of poor adherence. Significant factors affecting adherence included age <35 years (P=.002), hospital site and treatment by multiple doctors within shorter time periods. This is the largest study examining detailed factors associated with adherence to hepatitis B treatment. Understanding poor adherence in clinical settings, and the factors associated with lower adherence, is important to inform efforts towards promoting treatment adherence for hepatitis B.

Measurement of peak aortic jet velocity in the perioperative period-machine variability: implications for assessment of aortic stenosis severity.

Variation in echocardiography machines and probes are not well described in the perioperative period. We aimed to compare the estimation of severity of aortic stenosis with transthoracic echocardiography (TTE) using two semi-portable ultrasound machines. Experienced cardiac anaesthetists performed a limited transthoracic echocardiogram with two different semi-portable ultrasound machines in patients with known aortic stenosis. The peak aortic jet velocity with continuous-wave Doppler and the time taken to obtain an acceptable envelope were recorded. The Sonosite M Turbo often underestimated the peak jet velocities (median jet velocity [IQR] 2.25 m/s [1.95 to 3.4] versus 3.85 m/s (3 to 4.2); P <0.001) and required more time to get a satisfactory envelope than the GE Vivid I. There was no statistically or clinically significant difference between the velocities obtained from the Vivid I and those measured on the patient's formal cardiology preoperative transthoracic echocardiogram (median [IQR]: 3.95 m/s [3.0 to 4.7]; P=0.3). However, the velocities obtained by the M Turbo were significantly lower than those obtained by the formal preoperative transthoracic echocardiogram (P <0.001). With the expansion of transthoracic echocardiography amongst anaesthetists, underestimation of the peak aortic jet velocity can significantly underestimate the severity of aortic stenosis with potentially lethal clinical consequences. Semi-portable ultrasound machines with echocardiographic capability are not necessarily equivalent and can result in underestimation of severity of aortic stenosis.

The relationship between superior vena cava diameter and collapsibility and central venous pressure.

The aim of this study was to assess the relationship between superior vena cava (SVC) diameter, collapsibility and central venous pressure (CVP) in cardiac surgical patients. SVC maximum and minimum diameters, plus collapsibility with ventilation, were measured with transoesophageal echocardiography in the mid-oesophageal bicaval view with M-mode. Simultaneously, CVP was measured via the right atrial port of a pulmonary artery catheter. Measurements were possible in 91 out of 92 patients. The median CVP was 10 mmHg with a range of 2 to 19 mmHg. There was a weak, but statistically significant, correlation between CVP and SVC collapsibility index (r=-0.21, P=0.049). There was no statistically significant correlation between maximum SVC diameter and CVP. Maximum SVC diameter was statistically significantly correlated with weight (Pearson's r=0.28, P=0.008). There was no statistically significant correlation between CVP and age or body dimensions. Our findings indicate that SVC diameter and collapsibility are easily measured with transoesophageal echocardiography but do not reliably reflect CVP in anaesthetised cardiac surgical patients.

The utility of transoesophageal echocardiography for estimating right ventricular systolic pressure.

With the reduction in use of the pulmonary artery catheter, alternative methods of pulmonary pressure estimation are required. The use of echocardiographically-derived right ventricular systolic pressure has recently been questioned, but this technique has not been validated in anaesthetised surgical patients with transoesophageal echocardiography. One hundred measurements of right ventricular systolic pressure with transoesophageal echocardiography were compared with the pulmonary artery systolic pressure obtained simultaneously from a pulmonary artery catheter in patients undergoing cardiac surgery. Simultaneous right ventricular systolic pressure and pulmonary artery systolic pressure measurements were possible in all patients, and these measurements were strongly correlated (r = 0.98, p < 0.001), with minimal bias and narrow limits of agreement (approximately -5 to +5 mmHg), across a broad range of pulmonary pressures. Measurement of right ventricular systolic pressure using tranoesophageal echocardiography is readily achievable and closely correlates with pulmonary artery systolic pressure, with minimal bias, in cardiac surgical patients undergoing general anaesthesia and positive pressure mechanical ventilation of the lungs.

A randomised controlled trial of fluid restriction compared to oesophageal Doppler-guided goal-directed fluid therapy in elective major colorectal surgery within an Enhanced Recovery After Surgery program.

There is continued controversy regarding the benefits of goal-directed fluid therapy, with earlier studies showing marked improvement in morbidity and length-of-stay that have not been replicated more recently. The aim of this study was to compare patient outcomes in elective colorectal surgery patients having goal-directed versus restrictive fluid therapy. Inclusion criteria included suitability for an Enhanced Recovery After Surgery care pathway and patients with an American Society of Anesthesiologists Physical Status score of 1 to 3. Patients were intraoperatively randomised to either restrictive or Doppler-guided goal-directed fluid therapy. The primary outcome was length-of-stay; secondary outcomes included complication rate, change in haemodynamic variables and fluid volumes. Compared to restrictive therapy, goal-directed therapy resulted in a greater volume of intraoperative fluid, 2115 (interquartile range 1350 to 2560) ml versus 1500 (1200 to 2000) ml, P=0.008, and was associated with an increase in Doppler-derived stroke volume index from beginning to end of surgery, 43.7 (16.3) to 54.2 (21.1) ml/m(2), P <0.001, in the latter group. Length-of-stay was similar, 6.5 (5 to 9) versus 6 (4 to 9) days, P=0.421. The number of patients with any complication (minor or major) was similar; 0% (30) versus 52% (26), P=0.42, or major complications, 1 (2%) versus 4 (8%), P=0.36, respectively. The increased perioperative fluid volumes and increased stroke volumes at the end of surgery in patients receiving goal-directed therapy did not translate to a significant difference in length-of-stay and we did not observe a difference in the number of patients experiencing minor or major complications.

Molecular virology of hepatitis B virus, sub-genotype C4 in northern Australian Indigenous populations.

Indigenous Australians experience a significant health burden from chronic hepatitis B infection; however, the strain of hepatitis B virus (HBV) found among Indigenous Australians has not been well characterized. Blood samples were collected from 65 Indigenous Australians with chronic HBV infection from across the Top End of Australia's Northern Territory. Phylogenetic analysis of HBV from these samples revealed that 100% of the isolates were genotype C, sub-genotype C4, expressing the serotype ayw3. This strain is a divergent group within the HBV/C genotype, and has only been described in Indigenous Australians. Evidence of recombination was suggested by discordant phylogenetic clustering of the C4 sequences when comparing the full genome to the surface region and confirmed by recombination analysis which showed the surface gene region to be most closely related to genotype J, while the remaining regions of the genome were most similar to genotype C sequences. Mutational analysis revealed the presence of multiple mutations that have been linked with more rapid liver disease progression and an increased risk of hepatocellular carcinoma. These mutations were detected in the majority of sequences examined. Variants associated with vaccine failure were detected as the predominant viral quasi-species in 3/35 samples. In summary, the HBV C4 variant found in this population has a high potential to cause advanced liver disease and to escape vaccination programs. Further in vitro functional and natural history studies are warranted in order to determine the clinical and public health consequences of infection with the HBV C4 variant in these communities.

A validation of the use of names to screen for risk of chronic hepatitis B in Victoria, Australia, 2001 to 2010.

The burden of chronic hepatitis B (CHB) is increasing in Australia, particularly in those born in the Asia-Pacific region, and nearly half are undiagnosed. Primary care clinicians have a key role in diagnosing CHB, however identification of patients at risk is hindered by lack of awareness and limited information on country of birth in patient records. This study evaluates the potential of a validated list of names associated with Asian country of birth as a screening tool to predict risk of CHB, by comparing it with surveillance records for all people diagnosed with CHB or salmonellosis in Victoria from 2001 to 2010, and analysed using standard screening tools. Name list match was associated with CHB notification, with over 60% of cases having one name matching the list (sensitivity), and nearly one third matching both given name and surname; less than 15% and 2% of salmonellosis notifications matched for one name and both names, respectively (false positives). These results show that more than half of notified cases of CHB would have been identified by this name list, and that it could be used in support of initiatives to improve diagnosis of patients with diseases associated with country of birth when limited information is available.

Hepatitis D virus in Victoria 2000-2009.

BACKGROUND: Hepatitis D virus (HDV) coinfection can adversely affect prognosis and complicate management of chronic hepatitis B. The epidemiology and clinical practices surrounding HDV in Australia are poorly understood, with no robust estimates of the burden of disease, and the extent of appropriate testing and clinical follow up is unknown. AIMS: To determine the number of reported cases of HDV in Victoria, Australia between 2000-2009 and to explore screening practices in patients at risk of HDV infection over the same time period. METHODS: Data regarding HDV diagnoses in Victoria for 2000-2009 were obtained from notifiable disease surveillance and public health laboratory testing records. Notifications data were analysed to determine risk factors and demographics of HDV diagnoses where available, and laboratory records used to determine screening practices and follow up testing. RESULTS: Eighty-seven notifications for HDV were recorded between 2000 and 2009. The median age at diagnosis was 34 (interquartile range 27-44), and the majority of cases were men (77%) and born overseas (71.4% of those with country of birth reported). During the same period, 2314 Victorian residents were tested for HDV infection, with 110 (4.75%) found to be positive. Both the number of people testing positive and the number of tests conducted steadily increased between 2005 and 2009. Of those patients with positive HDV antibody results, less than half (44 patients, 40%) were subsequently evaluated for replicative infection by polymerase chain reaction. CONCLUSION: The number of people being tested for HDV has increased over the past decade; however, gaps in the appropriate follow-up of infected patients are apparent. Birth overseas has become an increasingly important risk factor in Victorian notifications, highlighting the need for routine testing of people living with chronic hepatitis B for HDV infection.

Left ventricular volume and ejection fraction assessment with transoesophageal echocardiography: 2D vs 3D imaging.

BACKGROUND: Developments in transducer technology have enabled the use of three-dimensional transoesophageal echocardiography (3D TOE) in the operating theatre. Transthoracic echocardiography (TTE) 3D left ventricular (LV) volumes and ejection fraction (EF) agree better with magnetic resonance imaging (MRI) measurements, with less intra- and inter-observer variability compared with 2D. This has not been validated with 3D TOE. The aim of this study was to assess the bias, limits of agreement, and reproducibility of 3D TOE and 2D TOE LV volumes and EF in cardiac surgical patients. METHODS: Sixty-three patients having cardiac surgery with TOE were evaluated. LV volumes and EF were calculated using modified Simpson's method on 2D mid-oesophageal four- and two-chamber views, xPlane, and from a 3D full-volume data set. Intra- and inter-observer variability were assessed in a subset of 17 patients. RESULTS: Real-time 3D TOE volume and EF assessment was possible in 59 of the 63 patients. Median end-diastolic volumes (EDVs) as measured by 2D, xPlane, and 3D techniques were 98.5, 94, and 97 ml. Median ESVs were 38.5, 40 and 35.6 ml. Median EFs were 58, 54 and 62.2%. There were no significant pairwise differences between these measurements. The limits of agreement for all comparisons were wide, and there were no statistically significant differences between the three methods in intra- or inter-observer variability. CONCLUSION: The intraoperative use of 3D TOE to estimate LV volumes and EF has small bias compared with 2D assessments, wide limits of agreement, and no clear advantages compared with standard 2D TOE imaging in terms of LV volume and EF assessment.

Observation of picometer vertical emittance with a vertical undulator.

Using a vertical undulator, picometer vertical electron beam emittances have been observed at the Australian Synchrotron storage ring. An APPLE-II type undulator was phased to produce a horizontal magnetic field, which creates a synchrotron radiation field that is very sensitive to the vertical electron beam emittance. The measured ratios of undulator spectral peak heights are evaluated by fitting to simulations of the apparatus. With this apparatus immediately available at most existing electron and positron storage rings, we find this to be an appropriate and novel vertical emittance diagnostic.

Magnetic linear dichroism in the angular dependence of core-level photoemission from (Ga,Mn)As using hard x rays.

We report a study of the electronic properties of the ferromagnetic semiconductor (Ga,Mn)As using magnetic linear dichroism in the angular dependence of Mn 2p photoemission under hard x-ray excitation. Bulk plasmon loss satellites demonstrate that the probed Mn ions are incorporated deep within the GaAs lattice, while the observed large dichroism indicates that the spectra originate from ferromagnetic substitutional Mn. Simulations of the spectra using an Anderson impurity model show that the ferromagnetic Mn 3d electrons of substitutional Mn in (Ga,Mn)As are intermediate between localized and delocalized.

Determining the orientation of a chiral substrate using full-hemisphere angle-resolved photoelectron spectroscopy.

Chiral interfaces and substrates are of increasing importance in the field of enantioselective chemistry. To fully understand the enantiospecific interactions between chiral adsorbate molecules and the chiral substrate, it is vital that the chiral orientation of the substrate is known. In this Letter we demonstrate that full-hemisphere angle-resolved photoemission permits straightforward identification of the orientation of a chiral surface. The technique can be applied to any solid state system for which photoemission measurements are possible.

Does the pulmonary artery catheter still have a role in the perioperative period?

The pulmonary artery catheter (PAC) was introduced into clinical practice in the early 1970s. Its use quickly expanded beyond patients with acute myocardial infarction to critically ill patients in the intensive care unit. Increasingly, it was used in the perioperative period in patients having major cardiac and noncardiac surgery. Publication of large observational studies suggested that patients with a PAC were more likely to suffer major morbidity or mortality, but this was difficult to assess because patients who had a PAC inserted were often sick, with more severe pathology, and were therefore more likely to die. The PAC is a monitoring device and information alone is unlikely to influence outcome unless it is linked to a proven therapy. Several thousand articles on the use of the PAC now exist, but in general, the quality of this literature is poor Much of the data are not randomised, have small sample sizes and include patients with greatly differing pathological states. It is unclear which, if any, of the PAC-guided therapies are actually beneficial for patients. Despite these flaws, there is no clear evidence of benefit, nor harm, in cardiac, intensive care or perioperative patients. Selected indications for the PAC may remain, such as complex cardiac surgery or solid organ transplantation. However, its routine use is difficult to justify and increasingly, most of the haemodynamic data available from the PAC can be obtained less invasively with echocardiography.

Evaluation of systolic murmurs using transthoracic echocardiography by anaesthetic trainees.

Focused transthoracic echocardiography by anaesthetists in the peri-operative period has recently been described; the data suggest that the specific skills required can be obtained by non cardiology physicians with limited training. Aortic stenosis is known to increase significantly the peri-operative risk in non-cardiac surgery. This study aimed to assess the ability of echocardiography naive trainee anaesthetists to recognise and assess the severity of aortic stenosis after a set amount of training. Five trainees underwent 2 h of didactic and hands-on teaching in evaluation of the aortic valve, after which they scanned 20 patients each. Their results were compared with those obtained by an experienced cardiac anaesthetist with echocardiography training and qualifications. There was 100% concordance between trainees and the consultant for assessment of clinically significant aortic stenosis, with no cases of misdiagnosis. There was also 90-100% agreement (kappa statistic 0.8-1) between the consultant and each trainee's assessment of clinically significant aortic stenosis based on a peak aortic velocity > 3 m.sec(-1). Anaesthesia trainees can be successfully and rapidly trained to recognise and estimate the severity of aortic stenosis.

Three years' experience of focused cardiovascular ultrasound in the peri-operative period.

Ultrasound applications in peri-operative medicine have become common place in modern anaesthesia practice. Anaesthetists have performed transoesophageal echocardiography in cardiac and selected non-cardiac surgery for over two decades. We aimed to assess the indications, impact on clinical management and accuracy of focused cardiovascular ultrasound performed by anaesthetists in the peri-operative period. One hundred and seventy patients over a 3-year period had a focused transthoracic echocardiogram. Adequate images to answer the clinical question were obtained in 167 out of 170 patients (98%). The undifferentiated systolic murmur was the commonest indication (98 out of 170, 58%). Some degree of aortic stenosis was present in 47 out of 170 (26%) of patients; mitral valve disease (30 out of 170 (18%)) and pulmonary hypertension (25 out of 170 (14%)) were also common. Changes in peri-operative management occurred in 140 out of 170 (82%) patients and major findings correlated with a formal cardiology transthoracic echocardiogram in 52 out of 57 (92%) patients. Focused cardiovascular ultrasound performed by anaesthetists in the peri-operative period accurately detects major cardiac pathology and significantly alters peri-operative management.

Focused transthoracic echocardiography in the perioperative period.

Ultrasound applications in perioperative medicine have expanded enormously over the past decade. Transoesophageal echocardiography has been performed by anaesthetists during cardiac surgery for over 20 years. With the increasing availability of portable ultrasound systems, the use of ultrasound to assist in vascular cannulation and regional anaesthesia has been well described. Portable ultrasound systems come with a range of probes for different applications, including transthoracic echocardiography. While transthoracic echocardiography has traditionally been the domain of cardiologists, its use has been increasing in critical care, the emergency room and, recently, by anaesthetists in the perioperative period. Unlike formal cardiology-based transthoracic echocardiography, focused, goal-directed transthoracic echocardiography is often more appropriate in the perioperative period to address a particular question and can be performed in just a few minutes. Transthoracic echocardiography allows rapid, noninvasive, point-of-care assessment of ventricular function, valvular integrity volume status and fluid responsiveness. It can help distinguish undifferentiated systolic murmurs preoperatively, give valuable information on the aetiology of unexplained hypotension and cardiovascular collapse and assess response to therapeutic interventions such as vasoactive drugs and volume resuscitation. Focused transthoracic echocardiography should include qualitative assessment of left and right ventricular function, an estimate of aortic valve gradient, right ventricular systolic pressure and intravascular volume status as minimum requirements. Transthoracic echocardiography is a valuable tool in the perioperative period and ideally the equipment and expertise should be available in all operating rooms.