bluuebunny/crossref_metadata_2025 huggingface dataset:
View of the Larynx Obtained using the Miller Blade and Paraglossal Approach, Compared to that with the Macintosh Blade
Authors: Achen B. , Terblanche O. C. , Finucane B. T.
Published: January 2019

The purpose of this study was to determine if laryngoscopy using a Miller blade with a paraglossal approach would yield an improved view of the larynx compared to that obtained with a Macintosh blade using the standard approach.

One-hundred and sixty-one patients, scheduled for elective surgery requiring tracheal intubation, voluntarily participated in this study. Patients were randomly assigned to one of the two groups (Miller vs. Macintosh). A standard general anaesthetic was administered. Comparisons were made of the percentage of the vocal cords visible at laryngoscopy. The view of the airway was also graded using the Cormack and Lehane scale. Statistical analysis using Fisher's exact test was performed. A P value <0.05 was considered statistically significant. The time required to complete intubation and complications if any, were also recorded. Laryngoscopy using the Miller blade allowed 100% of the vocal cords to be viewed in 78%> of cases, whereas this was achievable in only 53% with the Macintosh blade (P=0.0014). The Miller blade enabled greater than 25% of the vocal cords to be seen in 95% of the cases, whereas this was achievable in only 80% with the Macintosh laryngoscope (P=0.003). A grade 1 Cormack and Lehane view of the larynx was obtained in 96.5% of cases in the Miller group compared with 85% in the Macintosh group (P=0.02).

Direct laryngoscopy using the Miller blade and paraglossal approach, afforded a much-improved view of the larynx in the majority of cases. For this reason trainees should learn laryngoscopy using both blades.
Effect of Open-Chest Surgery in the Lateral Position on Blood Propofol Concentration during Target-Controlled Infusion of Propofol
Authors: Tan L. H. , Cokis C. J. , Weightman W. M. , Manopas A. R. , Paech M. J. , Nazir H. S. , Hackett L. P.
Published: January 2019

Our research hypothesis was that single lung ventilation during thoracic surgery in the lateral position increases the blood concentration of propofol during target-controlled infusion.

Thirty adult patients in two tertiary referral hospitals undergoing open-chest surgery were studied. Anaesthesia was induced and maintained with propofol using a Diprifusor (Graseby 3500) computer-controlled pump set to deliver a blood concentration of 4 μg.ml-1. Blood samples were taken with the patient positioned in 1) the supine position 20 minutes after induction (supine); 2) the lateral position just prior to one-lung ventilation (lateral); 3) the lateral position five minutes after commencing one-lung ventilation (OLV5) and 4) the lateral position 20 minutes after commencing one-lung ventilation (OLV20). Propofol concentrations were determined by high performance liquid chromatography.

The target-controlled infusion target level was maintained at 4 μg.ml-1 during the study period for all cases. The mean (SD) propofol blood concentration (μg.ml-1) at each stage was 5.5 (1.5) supine, 5.3 (1.1) lateral, 5.3 (1.2) OLV5 and 5.1 (1.2) OLV20. Repeated measures ANOVA showed an F value 1.9, lambda 5.5 and P value 0.15. Post hoc analysis did not identify a significant difference between the sample times.

During target-controlled infusion of propofol, mean blood propofol concentrations did not change significantly from those obtained with the patient supine after up to 50 minutes in the lateral position during thoracic surgery, or 20 minutes after commencing one-lung ventilation.
Comparison of Intensive Care Outcome Prediction Models Based on Admission Scores With those Based on 24-Hour Data
Authors: Duke G. J. , Piercy M. , Digiantomasso D. , Green J. V.
Published: January 2019

We compared the performance of six outcome prediction models - three based on 24-hour data and three based on admission-only data - in a metropolitan university-affiliated teaching hospital with a 10-bed intensive care unit. The Acute Physiology and Chronic Health Evaluation models, version II (APACHE II) and version III-J, and the Simplified Acute Physiology Score version II (SAPS II) are based on 24-hour data and were compared with the Mortality Prediction Model version II and the SAPS version III using international and Australian coefficients (SAPS IIIA).

Data were collected prospectively according to the standard methodologies for each model. Calibration and discrimination for each model were assessed by the standardised mortality ratio, area under the receiver operating characteristic plot and Hosmer-Lemeshow contingency tables and chi-squared statistics (C10 and H10). Predetermined criteria were area under the receiver operating characteristic plot >0.8, standardised mortality ratio 95% confidence interval includes 1.0, and C10 and H10 P values >0.05.

Between October 1, 2005 and December 31, 2007, 1843 consecutive admissions were screened and after the standard exclusions, 1741 were included in the analysis. The SAAPS II and SAPS IIIA models fulfilled and the APACHE II model failed all criteria. The other models satisfied the discrimination criterion but significantly over-predicted mortality risk and require recalibration. Outcome prediction models based on admission-only data compared favourably to those based on 24-hour data.
Efficacy of Low Dose Levobupivacaine (0.1%) for Axillary Plexus Block using Multiple Nerve Stimulation
Authors: Zhao X. , Wang Y.-W. , Chen H. , Zhang Z. , You X.-M. , Luo K. , Jin Y.-J.
Published: January 2019

The purpose of this study was to investigate if low doses of levobupivacaine (0.1%) produce complete sensory blockade in preoperative axillary brachial plexus block and to compare the effect of different doses of levobupivacaine on sensory and motor blockade.

A total of 110 patients scheduled for elective forearm or hand surgery were randomly allocated to receive 36 ml or 72 ml of levobupivacaine 0.1% or 36 ml of levobupivacaine 0.25%. In each group, volumes were equally distributed in the four nerve territories. In all patients, the sensory and motor block was assessed at five, 10, 20 and 30 minutes after the placement of axillary block.

Complete sensory block was obtained in 94.4% of patients receiving 36 ml of levobupivacaine 0.1%, 92.1% of those receiving 72 ml of levobupivacaine 0.1%, and 97.1% of those receiving 36 ml of levobupivacaine 0.25%. There was no significant difference either in the onset of the sensory and motor block or duration of the sensory and motor block.

This study demonstrates that 36 ml of levobupivacaine 0.1% (36 mg) is as effective as higher doses and volumes in axillary brachial plexus blockade.
Comparison of Stress in Anaesthetic Trainees between Hong Kong and Victoria, Australia
Authors: Chia A. C. L. , Irwin M. G. , Lee P. W. H. , Lee T. H. W. , Man S. F.
Published: January 2019

A postal survey was sent to anaesthetic trainees in Hong Kong and Victoria, Australia to compare work-related stress levels. Demographic data were collected. Anaesthetist-specific stressors, Maslach Burnout Inventory and Global Job Satisfaction scores were used for psychological testing. The response rates from Hong Kong and Melbourne were 64 of 133 (48.1%) and 108 of 196 (55.1%), respectively. Victorian respondents were older with greater family commitments, but more advanced in fulfilling training requirements. Hong Kong respondents, being faced with both the challenge of dual College requirements, exhibited consistently higher indices of stress (P <0.001) and less job satisfaction (P <0.001). Common occupational stressors related to dealing with critically ill patients and medicolegal concerns. Higher stress scores observed in Hong Kong trainees related to service provision and a perceived lack of resources. Despite the complex nature of stress, its antecedents and manifestations, an inverse relationship between emotional exhaustion and job satisfaction was evident in correlation analysis (P <0.001). This survey suggests that stress was present in some trainees in both areas. Hong Kong trainees may benefit from local development to address mental wellbeing as being important to fulfil this highly competitive training program.
Effect of the Mode of Administration of Inhaled Anaesthetics on the Interpretation of the FA/FI Curve – a GasMan® Simulation
Authors: Van Zundert T. , Hendrickx J. , Brebels A. , De Cooman S. , Gatt S. , De Wolf A.
Published: January 2019

The effects of blood solubility, cardiac output and ventilation on the rise of the alveolar towards the inspired concentration, the FA/FI curve, of an inhaled anaesthetic are often thought to reflect how these factors affect wash-in of the central nervous system compartment and, therefore, speed of induction because If is the partial pressure ultimately attained in the central nervous system (FVRG). These classical FA/FI curves assumed a constant FI. We used GasMan® to examine whether changes in solubility, cardiac output and ventilation affect the relationship between the FA/FI curve and FVRG differently while either FI or FA are kept constant.

Using GasMan®, we studied the effects of solubility (desflurane vs isoflurane), cardiac output (5 vs 10 l.min-1) and minute ventilation (4 vs 8 l.min-1) on FA, FI FA/FI. and FVRG with either FI kept constant or FA kept constant (at 1 minimum alveolar concentration). High fresh gas flows were used to avoid rebreathing, so that the delivered concentration matched FI.

Despite similar effects on the FA/FI curve, the effects on FVRG differed. With constant FI, lower solubility or higher ventilation results in a higher FVRG and a higher cardiac output results in a lower FVRG With constant FA, solubility has only a minimal effect on FVRG; an increase in cardiac output hastens the rise of FVRG to the same plateau value; and a change in ventilation has minimal effect on FVRG.

Despite similar effects on the FA/FI curve, the effects of solubility, cardiac output and ventilation on the FVRG are different when either FI or FA are kept constant. With the FI kept constant, induction of anaesthesia is slower with a higher cardiac output, but with FA kept constant, induction of anaesthesia is faster with a higher cardiac output. The introduction of an end-expired closed-loop feedback administration of inhaled anaesthetics makes this distinction clinically relevant.
The Effect of Dexmedetomidine on Agitation during Weaning of Mechanical Ventilation in Critically ill Patients
Authors: Shehabi Y. , Nakae H. , Hammond N. , Bass F. , Nicholson L. , Chen J.
Published: January 2019

Ventilated patients receiving opioids and/or benzodiazepines are at high risk of developing agitation, particularly upon weaning towards extubation. This is often associated with an increased intubation time and length of stay in the intensive care unit and may cause long-term morbidity. Anxiety, fear and agitation are amongst the most common non-pulmonary causes of failure to liberate from mechanical ventilation. This prospective, open-label observational study examined 28 ventilated adult patients in the intensive care unit (30 episodes) requiring opioids and/or sedatives for >24 hours, who developed agitation and/or delirium upon weaning from sedation and failed to achieve successful extubation with conventional management. Patients were ventilated for a median (interquartile range) of 115 [87 to 263] hours prior to enrolment, Dexmedetomidine infusion was commenced at 0.4 μg/kg/hour for two hours, after which concurrent sedative therapy was preferentially weaned and titrated to obtain target Motor Activity Assessment Score score of 2 to 4. The median (range) maximum dose and infusion time of dexmedetomidine was 0.7 μg/kg/hour (0.4 to 1.0) and 62 hours (24 to 252) respectively. The number of episodes at target Motor Activity Assessment Score score at zero, six and 12 hours after commencement of dexmedetomidine were 7/30 (23.3%), 28/30 (93.3%) and 26/30 (86.7%), respectively (P <0.001 for 6 and 12 vs 0 hours). Excluding unrelated clinical deterioration, 22 episodes (73.3%) achieved successful weaning from ventilation with a median (interquartile range) ventilation time of 70 (28 to 96) hours after dexmedetomidine infusion. Dexmedetomidine achieved rapid resolution of agitation and facilitated ventilatory weaning after failure of conventional therapy. Its role as first-line therapy in ventilated, agitated patients warrants further investigation.
Incidence of Residual Neuromuscular Blockade in a Post-Anaesthetic Care Unit
Authors: Yip P. C. , Hannam J. A. , Cameron A. J. D. , Campbell D.
Published: January 2019

We conducted a prospective observational study to assess the incidence of residual neuromuscular blockade (RNMB) in a post-anaesthetic care unit (PACU) of a tertiary hospital. The subjects were 102 patients undergoing general anaesthesia with neuromuscular blockade (NMB). The procedural anaesthetists were unaware of their patients’ inclusion in the study, and the choice of muscle relaxant and use of reversal agents were at the anaesthetists’ discretion. On arrival to the PACU, the train-of-four ratio was assessed using electromyography, repeated every five minutes until the train-of-four ratio exceeded 0.9. RNMB was defined as a train-of-four ratio < 0.9. The requirement for airway support, incidence of desaturation while in the PACU and time to eligibility for PACU discharge were recorded. The mean interval between the last dose of relaxant and arrival in the PACU for patients with RNMB was 81 minutes. An intermediate-acting muscle relaxant had been used for most patients. Despite this, RNMB was observed in 31% (95% confidence interval 25 to 47%) of patients. Our findings suggest that RNMB in the PACU is common. As RNMB may predispose to postoperative complications, anaesthetists should utilise quantitative monitoring to assess neuromuscular blockade and optimise reversal use. Anaesthetists should be aware that intervals between the last dose of relaxant of well over one hour do not exclude the possibility of RNMB, even when using intermediate-acting neuromuscular blockade agents.
Episodic Waveforms in the Electroencephalogram during General Anaesthesia: A Study of Patterns of Response to Noxious Stimuli
Authors: Mackay E. C. , Sleigh J. W. , Voss L. J. , Barnard J. P.
Published: January 2019

Previous studies of the electroencephalogram (EEG) during anaesthesia have identified two distinct patterns of change in response to a noxious stimulus, a classical arousal pattern and a paradoxical arousal pattern. We developed methods of EEG analysis to quantify episodic EEG patterns – namely sleep spindle-like (‘10 Hz-score’) and burst-suppression-like fluctuations in high frequencies (‘high frequency variation index’) – and used traditional power spectral quantification of non-episodic delta waves. We studied 30 healthy adult patients undergoing elective surgery under general anaesthesia with propofol, fentanyl (1.0, 2.5 or 4.0 μg/kg, n=10 for each group), muscle relaxant and sevoflurane. Prefrontal EEG data were recorded during the operation and analysed for changes in episodic patterns before and after noxious stimuli (intubation and incision). Before noxious stimuli, the EEG patterns varied markedly between patients and were not strongly correlated to calculated effect-site concentrations of fentanyl, propofol or sevoflurane. Noxious stimuli reduced the 10Hz-score from 0.25 to 0.20 (P=0.01) after intubation and from 0.33 to 0.27 (P=0.01) after incision; and high frequency variation index from 2.8 to 2.0 (P=0.02) after incision – the classical arousal pattern. The nociception-induced reduction in spindles was greater in the low-dose fentanyl group (P=0.01). There was less tachycardia in the high-dose fentanyl group (P=0.002). It is possible to quantify such episodic EEG patterns during general anaesthesia and in this study noxious stimulation tended to reduce the prevalence of these patterns.
Preoperative Estimated Glomerular Filtration Rate and RIFLE-Classified Postoperative Acute Kidney Injury Predict Length of Stay Post-Coronary Bypass Surgery in an Australian Setting
Authors: Moore E. M. , Simpson J. A. , Tobin A. , Santamaria J.
Published: January 2019

We investigated the influence of preoperative estimated glomerular filtration rate and postoperative acute kidney injury on outcomes after coronary bypass surgery in a local setting, with the focus on length of stay.

A retrospective analysis of prospectively collected data for 3302 consecutive patients who underwent coronary artery bypass graft surgery (June 1997 through to January 2007) at St Vincent's Public Hospital, Melbourne, was undertaken. Preoperative estimated glomerular filtration rate was calculated and categorised using US National Kidney Foundation cut-offs for chronic kidney disease (normal function; mild, moderate and severe dysfunction). Postoperative acute kidney injury was categorised using serum creatinine RIFLE criteria (no acute kidney injury, risk, injury and failure). Postoperative intensive care and hospital length of stay was determined.

The hazard ratios for time to hospital discharge up to one month decreased (indicating a longer length of stay) as severity of preoperative renal dysfunction category increased when compared to those with normal renal function: mild hazard ratio=1.02 (95% confidence interval: 0.91 to 1.15, P=0.70), moderate 0.87 (0.76 to 1.00, P=0.047), severe 0.47 (0.35 to 0.64, P < 0.001). Hazard ratios also decreased as severity of postoperative acute kidney injury category increased, when compared to those with no acute kidney injury: risk 0.67 (0.58 to 0.77, P <0.001), injury 0.52 (0.41 to 0.65, P <0.001), failure 0.35 (0.20 to 0.60, P <0.001).

The increasing severity of preoperative renal dysfunction and postoperative acute kidney injury were associated with increased hospital length of stay. This has implications for resource use, informed consent and case selection.
Hyperbaric Oxygen Therapy in the Treatment of Post Cardiac Surgical Strokes – a Case Series and Review of the Literature
Authors: Gibson A. J. , Davis F. M.
Published: January 2019

Strokes remain an uncommon but significant complication of cardiac surgery. Cerebral air embolism is the likely aetiology in the majority of cases. Hyperbaric oxygen therapy is the recognised treatment for cerebral air embolism associated with compressed air (SCUBA) diving accidents and is therefore also the standard of care for iatrogenic causes of air embolism. It follows that there is a logic in treating post-cardiac surgical stroke patients with hyperbaric oxygen.

The aim of this retrospective review was to examine the outcomes of 12 such patients treated in the Christchurch Hospital hyperbaric unit and to appraise the evidence base for the use of hyperbaric oxygen therapy in this setting.

Despite delays of up to 48 hours following surgery before the institution of hyperbaric oxygen therapy, 10 of the 12 patients made a full neurological recovery or were left with mild residual symptoms, with nine returning to their previous level of care. One patient remained hemiplegic and there was one early neurological death.

There is a paucity of prospective data in this area, but based on sound pathophysiological principles and clinical experience, we believe that patients suffering a stroke following open cardiac surgery should be considered for hyperbaric oxygen therapy.
‘Speaking Valve’ Aspiration in a Laryngectomy Patient
Authors: Kadam V. Rao , Lambert P. , Pant H. , O'Reilly M.
Published: January 2019

Tracheo-oesophageal speech using a one-way speaking valve is a common mode of speech rehabilitation for laryngectomy patients. Aspiration of this device can cause significant airway obstruction and pose anaesthetic and surgical challenges during its retrieval. In this case report, we describe our management of a patient who had had a laryngectomy who aspirated his speaking valve through his stoma. Emergency retrieval of the valve was performed, during which difficulties were encountered, first in obtaining an adequate seal for pre-oxygenation, and second in maintaining adequate oxygen saturation. We discuss some innovative techniques that could be used to address these issues.
Duropleural Fistula Revealed by Neurological Manifestations: An Unusual Cause of Pleural Effusion
Authors: Maskin L. P. , Raimondi A. , Hlavnicka A. , Díaz M. F. , Roura N. , Wainsztein N.
Published: January 2019

Symptomatic pleural collection of cerebrospinal fluid is a rare but accepted complication in hydrocephalic paediatric patients treated with ventriculopleural shunts. Few cases have been described in adults, usually as complication of trauma, tumours or spinal surgery, particularly post-laminectomy. It should be considered in the differential diagnosis of pleural effusion after neurosurgical procedures involving the spine. We describe two patients with large cerebrospinal fluid collections in the pleural cavity caused by postoperative duropleural fistula, who presented with neurological symptoms, cerebrospinal fluid pressure headache and meningitis.
Formal and Informal Fallacies in Anaesthesia
Authors: Gibbs N. M.
Published: January 2019

Formal and informal fallacies refer to errors in reasoning or logic, which result from invalid arguments. Formal fallacies refer to arguments that have an invalid structure or ‘form’, while informal fallacies refer to arguments that have incorrect or irrelevant premises. There are many formal and informal fallacies that could theoretically occur in anaesthesia practice or in the appraisal of anaesthesia research. This paper describes several such potential fallacies. It is possible that a greater awareness, recognition and discussion of these logic-based errors will lead to improved patient safety and more informed appraisal of clinical research.
Anti-Emetic Dexamethasone and Postoperative Infection Risk: A Retrospective Cohort Study
Authors: Corcoran T. B. , Truyens E. B. , Ng A. , Moseley N. , Doyle A. C. , Margetts L.
Published: January 2019

Nausea and vomiting are common complications of anaesthesia. Dexamethasone is an effective prophylaxis but is immunosuppressive and may increase postoperative infection risk. This retrospective cohort study examined the association between the administration of a single intraoperative anti-emetic dose of dexamethasone (4 to 8 mg) and postoperative infection in 439 patients undergoing single procedure, non-emergency surgery in a university trauma centre. Exclusion criteria included comorbidities, immunosuppressive medications or procedures that confer an increased infection risk. In the 10-week study period and three-month follow-up period, there were 98 documented infections (22.3% of the cohort), of which 43 were detected only on post-discharge follow-up. Anti-emetic dexamethasone was given to 108 patients (24.6%). Stepwise, multivariate logistic regression modelling identified significant associations between female gender, symptomatic reflux, respiratory disease and the risk of infection. The adjusted odds ratio for dexamethasone was 0.88 (0.5 to 1.5, P=0.656). We did not demonstrate an association between anti-emetic doses of dexamethasone and postoperative infection.
A Retrospective Study to Determine Whether accessing Frequency Affects the Incidence of Microbial Colonisation in Peripheral Arterial Catheters
Authors: Koh D. B. C. , Robertson I. K. , Watts M. , Davies A. N.
Published: January 2019

Peripheral arterial catheters are used for the continuous monitoring of blood pressure and repeated blood sampling in critically ill patients, but can be a source of catheter-related bloodstream infection. A common assumption is that the more frequently an arterial catheter is accessed, the greater the likelihood of contamination and colonisation to occur. We sought to determine whether the accessing frequency has an influence on the rate of colonisation in a peripheral arterial catheter.

A retrospective, unmatched, nested case control study was conducted in our intensive care unit. The intensive care unit charts of 96 arterial catheters from 83 patients were examined to measure the number of times each respective arterial catheter was accessed. Multivariate Cox proportional hazards regression was used to compare the rate of accessing of arterial catheters and account for varying arterial catheter in situ duration. Arterial catheters which had a high access rate of 8.1 or more times/day (five colonised of 32 patients: hazards ratio 1.69, 95% confidence interval 0.52 to 5.49; P=0.77), or a medium access rate of 6.7 to 8.0 times/day (six colonised of 32 patients: hazards ratio, 1.35, 95% confidence interval, 0.37 to 4.92: P=0.65) were not significantly more colonised when compared to arterial catheters which had a low access rate of 0 to 6.6 times/day (six colonised of 32 patients), adjusted for arterial catheter insertion site and place in hospital where the arterial catheter insertion was performed.

We were unable to demonstrate that the accessing frequency of an arterial catheter was a major predisposing factor for the likelihood of colonisation. Other mechanisms other than hub colonisation should be investigated further.
Warming the Epidural Injectate Improves First Sacral Segment Block: A Randomised Double-Blind Study
Authors: Han S. S. , Lee S. C. , Ro Y. J. , Min S. W. , Huh J.
Published: January 2019

This study investigated the effect of local anaesthetic temperature on block of the first sacral segment. Twenty-four patients undergoing lumbar epidural anaesthesia at L2-3 or L3-4 were randomly divided in double-blind fashion into two groups to receive 22 ml of lignocaine 2% with adrenaline 1:200,000, sodium bicarbonate and fentanyl, at either 21°C (cold group) or 37°C (warm group). The sensory block was assessed by loss of sensation to pinprick and the pain threshold after repeated electrical stimulation at L2, S1 and S3 dermatomes. Motor block was evaluated using the modified Bromage scale. Patient characteristics were comparable between the groups. Onset of block at the first sacral segment (S1) was faster in the warm group than in the cold (10 vs 17.5 minutes, P <0.001). The pain threshold at S1 was significantly higher in the warm group. We concluded that epidural lignocaine 2% with adrenaline 1:200,000, sodium bicarbonate and fentanyl injected at 37°C hastens S1 block within 10 minutes of administration.
Changes in Case-Mix and Outcomes of Critically Ill Patients in an Australian Tertiary Intensive Care Unit
Authors: Williams T. A. , Ho K. M. , Dobb G. J. , Finn J. C. , Knuiman M. W. , Webb S. A. R.
Published: January 2019

Critical care service is expensive and the demand for such service is increasing in many developed countries. This study aimed to assess the changes in characteristics of critically ill patients and their effect on long-term outcome. This cohort study utilised linked data between the intensive care unit database and state-wide morbidity and mortality databases. Logistic and Cox regression was used to examine hospital survival and five-year survival of 22,298 intensive care unit patients, respectively. There was a significant increase in age, severity of illness and Charlson Comorbidity Index of the patients over a 16-year study period. Although hospital mortality and median length of intensive care unit and hospital stay remained unchanged, one- and five-year survival had significantly improved with time, after adjusting for age, gender, severity of illness, organ failure, comorbidity, ‘new’ cancer and diagnostic group. Stratified analyses showed that the improvement in five-year survival was particularly strong among patients admitted after cardiac surgery (P=0.001). In conclusion, although critical care service is increasingly being provided to patients with a higher severity of acute and chronic illnesses, long-term survival outcome has improved with time suggesting that critical care service may still be cost-effectiveness despite the changes in case-mix.
Perioperative Melatonin Use
Authors: Jarratt J.
Published: January 2019

Melatonin is a substance chiefly produced by the pineal gland and has a key role in the sleep-wake cycle. It also has an important antioxidant role. Exogenous melatonin has a short half-life and is available in a range of preparations. Newer analogues targeted for the recently discovered melatonin MT1 and MT2 receptors have also been developed. Exogenous melatonin is used as a resynchronisation agent in jet lag and for other sleep disturbances.

Perioperatively, melatonin has been used as a premedicant, sedative and analgesic. It decreases paediatric emergence delirium. The antioxidant properties of melatonin are being investigated for use in sepsis and reperfusion injuries. It would appear that patients on melatonin supplements should continue taking them perioperatively because there may be benefits.

Melatonin and its analogues will be increasingly encountered in the perioperative setting.
The Development of a System to Guide Volatile Anaesthetic Administration
Authors: Kennedy R. R. , French R. A.
Published: January 2019

We have developed and deployed within our operating rooms a system which provides real-time estimates of effect-site levels of inhalational anaesthetic agents along with forward predictions of end-tidal and effect-site concentrations. The initial aim of this project was to provide users of inhalational agents with tools similar to those available in target-controlled infusion systems. This paper describes the development and implementation of the system and outlines evaluation and uses of the system.

The prototype was developed by combining a locally developed data logging and trend display system with a model of uptake developed as a teaching tool in 1982. This uptake model performs as well as contemporary models of propofol uptake and distribution. Following initial evaluation, the system has been deployed in over half our operating rooms and uses data gathered from the Datex/GE Anaesthesia Delivery Unit anaesthetic machines. We have conducted a number of studies of the system itself, explored aspects of the underlying models, and used the system to investigate effect-site guided anesthesia and as a tool for data collection in other studies.

The system has been well accepted locally and has been shown to facilitate faster changes in inhalational levels. We have also seen a significant decrease in fresh gas flow rates over recent years and attribute this in part to the predictive system, which simplifies the task of determining the appropriate combination of gas flow and vapour dial setting. The system also provides a useful platform for a range of research projects.
Empirical Aspects of Linking Intensive Care Registry Data to Hospital Discharge Data without the use of Direct Patient Identifiers
Authors: Bohensky M. A. , Jolley D. , Sundararajan V. , Pilcher D. V. , Evans S. , Brand C. A.
Published: January 2019

In the field of intensive care, clinical data registries are commonly used to support clinical audit and develop evidence-based practice. However, they are often restricted to the intensive care unit episode only, limiting their ability to follow long-term patient outcomes and identify patient readmissions. Data linkage can be used to supplement existing data, but a lack of unique patient identifiers may compromise the accuracy of the linkage process. The aim of this study was to assess the quality of linking the Australia/New Zealand critical care registry to a state financial claims database using a method without direct patient identifiers and to identify possible sources of bias from this method. We used a linkage method relying on indirect patient identifiers and compared the accuracy of this method to one that also included the patient medical record number and date of birth.

The overall linkage rate using the method with indirect identifiers was 92.3% compared to 94.5% using the method with direct identifiers. Factors most strongly associated with not being a correct link in the first method included patients at one study hospital, admissions in 2002 and 2003 and having a hospital length of stay of 20 days or more. Linking the Australia/New Zealand critical care without direct patient identifiers is a valid linkage method that will enable the measurement of long-term patient survival and readmissions. While some sources of bias have been identified, this method provides sufficient quality linkage that will support broad analyses designed to signal future in-depth research.
Responses to Dural Puncture during Institution of Combined Spinal-Epidural Analgesia: A Comparison of 27 Gauge Pencil-Point and 27 Gauge Cutting-Edge Needles
Authors: van den Berg A. A. , Ghatge S. , Armendariz G. , Cornelius D. , Wang S.
Published: January 2019

Pencil-point spinal needles are popular for combined spinal-epidural analgesia because they cause less dural puncture headache than cutting-edge spinal needles. However, many parturients move, grimace, vocalise or experience paraesthesia or dysaesthesia during dural puncture when performing ‘needle through needle’ combined spinal-epidural analgesia. We compared dural puncture responses induced by pencil-point and cutting-edge needles (both 27 gauge).

With institutional approval, 115 parturients presenting for elective caesarean section or labour analgesia were audited. After lignocaine infiltration, a Tuohy-type needle was inserted to loss of resistance to saline at a mid-lumbar interspace, and either a 27 gauge cutting-edge or 27 gauge pencil-point needle was inserted ‘needle through needle’ through the dura. During dural penetration, the occurrence of patient movement, grimacing or vocalisation was noted by a blinded observer, as was the patient's response to the question “Did you feel that?” asked by the anaesthetist.

The audit comprised two similar groups of patients (caesarean section, n=30; labour analgesia, n=85). In both groups, grimacing and movement during thecal penetration occurred more frequently with pencil-point needles (P <0.05 and P <0.025, respectively). Pooled data analysis revealed that pencil-point and cutting-edge needles induced grimacing and movement in 17 (22%) and 2 (5%), spontaneous vocalisation in 4 (5%) and 1 (3%) and was perceived by 13 (17%) and 3 (8%) parturients (P <0.025, P=NS, P=NS), respectively. Overall, 34 and 6 objective and subjective patient responses (P <0.005) occurred when inserting these needles, respectively.

Dural puncture by a 27 gauge pencil-point needle inserted ‘needle through needle’ when instituting combined spinal-epidural analgesia induces more iatrogenic responses than a 27 gauge cutting-edge needle.
Perioperative Mortality Score: Data Collection and Cost
Authors: Achuthan S. , Smirk A. , Keeble A. , Leslie K.
Published: January 2019

The perioperative mortality score aims to predict mortality in elderly patients undergoing noncardiac surgery using three preoperative risk factors (age, albumin and American Society of Anesthesiologists physical status) and then modify this risk assessment if any of three postoperative complications occur (unplanned intensive care unit admission, systemic inflammation and acute renal failure). In order to determine the cost of routine perioperative mortality score calculation in future research, we audited the incidence of clinician-initiated preoperative albumin, pre- and postoperative creatinine and postoperative white cell count testing in patients aged ≥70 years presenting for elective and emergency noncardiac surgery requiring at least overnight admission over a three-month period. We recruited 637 noncardiac surgical patients. All laboratory tests required for perioperative mortality score calculation were performed in only 47% of patients and the total cost of testing all untested patients was A$12,057 (A$18,927 per 1000 patients). Preoperative hypoalbuminaemia was present in 11% of tested patients, acute renal impairment in 24% of tested patients and high white cell count in 33% of tested patients. These results may be used to inform future research or clinical use of the score.
Clinical Determination of Brain Death
Authors: Dobb G. J.
Published: January 2019

In 2010 an article in the Canadian Journal of Anesthesia1 presented case reports of two patients who appeared to regain spontaneous respiration after they had been determined to be brain dead. The criteria used were those described in the recommendations from the Canadian Council for Donation and Transplantation2. The article was accompanied by an editorial3 that acknowledged the challenges faced by the physicians who determined that brain death had occurred, but concludes that in both cases several of the criteria were either misinterpreted or overlooked. However, it is clearly pertinent to ask if these reports have any implications for the clinical determination of brain death in Australia and New Zealand as described in the Australian and New Zealand Intensive Care Society (ANZICS) Statement on Death and Organ Donation4.
Effect of a Blood Conservation Device in Patients with Preserved Admission Haemoglobin in the Intensive Care Unit
Authors: Mukhopadhyay A. , See K. C. , Chan Y. H. , Yip H. S. , Phua J.
Published: January 2019

An important iatrogenic cause of anaemia in the intensive care unit is loss of the discarded blood during phlebotomy via indwelling vascular catheters. A closed system blood conservation device has previously been shown to reduce the need for blood transfusion and to blunt the decrease of haemoglobin in intensive care unit patients. However, such a device may not benefit patients who are admitted with a relatively preserved haemoglobin.

In this sub-group analysis of a before-and-after study, 128 patients had admission haemoglobin ≥115 g/l and did not receive any blood transfusions while in the intensive care unit. In the control group of 50 patients a blood conservation device was not used, while in the active group of 78 patients the device was used. Use of the blood conservation device did not affect the haemoglobin trends when both groups were compared using the general linear model.

For patients with admission haemoglobin ≥115 g/l, use of a blood conservation device does not affect the subsequent rate of haemoglobin decline in the intensive care unit. These patients are unlikely to benefit from the use of such devices.
Intrabronchial Airway Pressures in Intubated Patients during Bronchoscopy under Volume Controlled and Pressure Controlled Ventilation
Authors: Nakstad E. R. , Opdahl H. , Skjønsberg O. H. , Borchsenius F.
Published: January 2019

Bronchoscope insertion through an endotracheal tube increases airflow resistance. Constant tidal volume (TV) ventilation can be maintained by augmenting the inspiratory pressure, but increased outflow resistance cannot be compensated for. Air trapping distal to the tube may lead to higher airway pressures in volume controlled (VC) mode and reduced TV in pressure controlled (PC) mode. Increased end-expiratory airway pressures will not be detected by ventilator pressure sensors.

In mechanically ventilated and sedated patients, the effects of bronchoscope insertion on intrabronchial pressures were recorded by a pressure transducer distal to the endoscope. In half of the patients, the ventilator was set in VC mode prior to bronchoscope insertion, keeping the previous TV constant. In the other half, the ventilator was set in PC mode, keeping previous peak inspiratory pressures constant. All patients underwent sequences of VC-PC-VC or PC-VC-PC ventilation with two-minute intervals between mode-changes.

In VC mode, bronchoscope insertion increased peak airway pressure from 29 cmH2O (22 to 43) to 41 cmH2O (36 to 49) (P=0.012) and end-expiratory airway pressure from 11 cmH2O (6 to 18) to 22.5 cmH2O (15 to 30) (P=0.012). There were no significant changes in TV, PaCO2 or PaO2 after two minutes. In PC mode, peak airway pressure was unchanged and end-expiratory airway pressure increased from 9.5 cmH2O (7 to 10) to 10.5 cmH2O (9 to 18) (P=0.017). Median TV was reduced from 673 ml (585 to 800) to 450 ml (408 to 560) (P=0.012); median PaCO2 increased from 5.7 kPa to 6.5 kPa (P=0.012).

Using distal measurement, positive end-expiratory airway pressure increased markedly in VC mode but only marginally in PC mode after bronchoscope insertion.
Brugada Syndrome – A Review of the Implications for the Anaesthetist
Authors: Carey S. M. , Hocking G.
Published: January 2019

Brugada syndrome is characterised by specific electrocardiogram changes in the right precordial leads, a structurally normal heart and susceptibility to ventricular arrhythmias that may cause syncope or sudden death in otherwise fit young adults. Perioperative pharmacological and physiological changes may precipitate these events. Arrhythmias and symptoms typically occur at rest or sleep when vagal activity predominates. Although the condition is rare, the implications are serious and may result in death. Individual case reports describe diverse anaesthetic management. In this paper we critically appraise the literature to identify unifying features and determine whether specific management can be recommended. We found 18 clinical reports of anaesthesia including a total of 28 patients, most under general anaesthesia. Those with an implanted defibrillator should have it deactivated. All patients should have external defibrillator pads applied continuously throughout the perioperative period. Electrolyte imbalances should be corrected preoperatively. Propofol infusions for maintenance of general anaesthesia are probably safe if duration and dose are limited. Sevoflurane may be the preferred volatile anaesthetic. Autonomic changes, inadequate analgesia, light anaesthesia and postural changes should be all be minimised. The patient should be warmed or cooled to maintain normothermia. An isoprenaline infusion is advocated for intraoperative ST changes. Regional anaesthesia is possible if the dose is limited and systemic absorption restricted. Lignocaine is the drug of choice while bupivacaine is relatively contraindicated. Ropivacaine is possibly also not safe. Prolonged regional anaesthesia may therefore require continuous catheter techniques. Five-lead electrocardiogram monitoring and ST trend analysis should continue into the postoperative period.
Obesity and Obstetric Anaesthesia
Authors: Mace H. S. , Paech M. J. , Mcdonnell N. J.
Published: January 2019

Obesity is increasing in the population as a whole, and especially in the obstetric population, among whom pregnancy-induced physiological changes impact on those already present due to obesity. In particular, changes in the cardiovascular and respiratory systems during pregnancy further alter the physiological effects and comorbidities of obesity. Obese pregnant women are at increased risk of diabetes, hypertensive disorders of pregnancy, ischaemic heart disease, congenital malformations, operative delivery, postpartum infection and thromboembolism. Regional analgesia and anaesthesia is usually preferred but may be challenging. Obese pregnant women appear to have increased morbidity and mortality associated with caesarean delivery and general anaesthesia for caesarean delivery in particular, and more anaesthesia-related complications. This article summarises the physiological and pharmacological implications of obesity and pregnancy and describes the issues surrounding the management of these women for labour and delivery.
Observational Study of Admission and Triage Decisions for Patients Referred to a Regional Intensive Care Unit
Authors: Howe D. C.
Published: January 2019

The objectives of this study were to identify factors associated with decisions concerning triage and admission to the intensive care unit and to describe the outcome of patients referred to intensive care unit for admission. The study was a single-centre, prospective, observational study. It was performed in the general intensive care unit of a tertiary regional hospital, over the period of February to June 2009. The patients were non-elective, acute medical in-patients.

For 100 patients referred, only 36 were admitted to the intensive care unit. The remaining 64 were declined admission: nine were declined admission because they were assessed as too sick to benefit, 41 were declined admission because they were assessed as too well to benefit and 14 were deemed to potentially benefit from intensive care unit admission but were not admitted (‘triage’). Patients most likely to receive triage decisions were medical in-patients who had expressed wishes about end-of-life care, who were functionally limited with co-morbid conditions affecting their performance status. Patients referred by Resident Medical Officers were also more likely to receive a triage decision.

Age, gender, Aboriginal and Torres Strait Islander status, diagnostic category and reason for referral did not impact on admission or triage decisions. Bed status in intensive care unit at the time of referral affected neither admission nor triage decisions. Hospital mortality in patients deemed too well to benefit from intensive care unit was 7.3%, suggesting that all patients referred for consideration of admission to intensive care unit should be classified as ‘high risk’.
Oesophageal Balloon Tracheoplasty in Early Tracheal Stenosis following Percutaneous Tracheostomy
Authors: Mahanta V. , Howson C.
Published: January 2019

Percutaneous tracheostomy is an efficient technique used in intensive care units. Although a safe procedure, serious early and late complications can occur. A rare complication is suprastomal stenosis following inadvertent tracheal cartilage fracture resulting in stenosis. Management is complicated, often requiring specialised equipment. While surgical treatment techniques are evolving, none are universally applicable. We report a case of early tracheal stenosis following percutaneous tracheostomy, treated successfully using a novel technique of oesophageal balloon tracheoplasty.

To our knowledge, this is the first reported case of immediate post percutaneous tracheostomy suprastomal stenosis treated with balloon tracheoplasty using an oesophageal balloon catheter which is readily available in most endoscopy units.
Calcitonin for Acute Neuropathic Pain Associated with Spinal Cord Injury
Authors: Humble S. R.
Published: January 2019

Neuropathic pain associated with spinal cord injury is caused by complex neural mechanisms and is often refractory to standard therapy. Salmon calcitonin was an effective treatment for neuropathic symptoms in this case series of three patients with recent spinal cord injury. Salmon calcitonin is already used to help manage pain after limb amputation and also after vertebral fractures and it is perhaps surprising that it has not been trialled previously for spinal cord injury pain. Calcitonin is thought to exert its effect by modulation of the serotonergic system and is generally well tolerated and convenient to administer. This underutilised drug may be a very useful adjuvant for neuropathic pain associated with spinal cord injury.
Changes in Microvascular Blood Flow during Coupled Plasma Filtration and Adsorption
Authors: Berlot G. , Bianco N. , Tomasini A. , Vassallo M. C. , Bianco F.
Published: January 2019

A 51-year-old man with septic shock underwent three consecutive sessions of coupled plasma filtration-adsorption each lasting 12 hours. Sublingual microvascular perfusion was assessed using the orthogonal polarisation spectral imaging technique at three different times: immediate pre-coupled plasma filtration-adsorption phase, two hours following commencement and two hours after its termination. The video images of the sublingual microcirculation were analysed by an investigator blinded to the time of image acquisition. The De Backer's score was calculated. During the coupled plasma filtration-adsorption, the number of perfused vessels increased compared with the pre-coupled plasma filtration-adsorption period, but decreased again after its termination. It is arguable that the elimination of septic mediators during the procedure could account for the observed variations.