Anaesthesia and Intensive Care

This study assessed the relationships between body mass index (BMI) and different outcomes after adult cardiac surgery by linking detailed preoperative comorbidity data with the long-term mortality and morbidity outcomes of 2131 consecutive patients who had elective cardiac surgery at a major cardiac surgical hospital in Western Australia. Patients with a high BMI had more comorbidities and were more likely to have had coronary artery bypass grafting than valve surgery. A total of 143 patients (6.7%) died during a median follow-up period of 30 months. The major causes of death were congestive heart failure (25.9%), myocardial infarction (14.7%), infection (23.8%) and cancer (13.9%). BMI had no association with long-term mortality, after adjusting for important confounders including the Charlson Comorbidity Index. BMI had a relatively linear relationship with the risk of new-onset atrial fibrillation (odds ratio 1.05 per point increment, 95% confidence interval 1.03 to 1.05) and venous thromboembolism (odds ratio 1.20, 95% confidence interval 1.14 to 1.26). BMI was the second most important predictor after age and accounted for 22% of the variability in the risk of atrial fibrillation. BMI had an inverse relationship with the risk of requiring allogeneic blood transfusion, postoperative intra-aortic balloon pump, or surgical re-exploration. In summary, BMI had differential associations with different short- and long-term outcomes after elective adult cardiac surgery. After adjusting for important confounders including the presence of cancers, we did not observe any ‘obesity paradox’ and patients with a high BMI were not associated with an increased probability of long-term survival.

Previous reports on the prognostic value of diabetes mellitus for cardiac complications after vascular surgery show divergent results, especially in regards to the role of type 2 diabetes as a cardiac risk factor, which remains unclear. The aim of this study was to assess the impact of type 2 diabetes on 30-day cardiac complications after vascular surgery.

Patients undergoing elective vascular surgery between 2002 and 2011 were included in this retrospective cohort study. Previous diagnosis of type 1 and 2 diabetes and use of oral glucose-lowering medications and insulin were recorded. Patients with type 1 diabetes were excluded from the analysis. The main outcome parameter was cardiac complications, a composite of cardiovascular death, non-fatal myocardial infarction, congestive heart failure, severe arrhythmia and asymptomatic troponin release within 30 days of surgery. In multivariate analysis, corrections were made for comorbidities, demographics, medication use and surgical risk.

Of 1462 patients, 329 (22.5%) patients had type 2 diabetes. Cardiac complications occurred in 155 (13.7%) patients without diabetes and in 68 (20.7%) with type 2 diabetes. In multivariate analysis, type 2 diabetes was associated with a significantly increased risk of 30-day cardiac complications (odds ratio 1.80; 95% confidence interval 1.25 to 2.60). Results were similar for type 2 diabetes patients managed with (odds ratio 1.84; 95% confidence interval 1.01 to 3.37) and without (odds ratio 1.79; 95% confidence interval 1.19 to 2.70) insulin.

Type 2 diabetes is an independent risk factor for cardiac complications after vascular surgery and should be treated as such in preoperative cardiac risk stratification.

Left ventricular filling and thus diastolic function are frequently monitored and managed in critical care. However, scant data exist regarding possible screening tests for diastolic dysfunction in the intensive care unit (ICU). The present study aimed to evaluate plasma b-type natriuretic peptide (BNP) as a marker of diastolic dysfunction in a single-centre cohort of ‘non-cardiac’ ICU patients. The ICU is non-cardiac in that it provides mixed medical/surgical services with the exception of cardiology, cardiac surgery and solid organ transplantation.

Clinical data were recorded over the first 24 hours of ICU stay for 32 consecutive patients. Transthoracic echocardiogram and blood collection for BNP assay were then performed. Diastolic dysfunction was demonstrated in 34% (n=11). Mean ± standard deviation BNP values were higher with diastolic dysfunction (238±195 vs 72±78 pg/ml; P=0.003). A BNP threshold of >43 pg/ml yielded a sensitivity of 80% and a specificity of 59%; area under the receiver operating characteristic curve was 0.82. BNP correlated independently with E/e’ (R = 0.425; P=0.015) (E/e’: peak early transmitral velocity [E]/early diastolic mitral annular velocity [e']) but not left ventricular ejection fraction (P=0.8), illness severity (Acute Physiological and Chronic Health Evaluation II; P=0.3) or fluid balance (P=0.4).

Diastolic dysfunction was common in this cohort of non-cardiac ICU patients and was independently associated with a significantly higher BNP. The potential application as a screening test for diastolic dysfunction is likely to require a threshold lower than previously proposed for heart failure.

The synthetic glucocorticoid dexamethasone is administered to many patients receiving a general anaesthetic to reduce the risk of postoperative nausea and vomiting. Dexamethasone is known to suppress the hypothalamic-pituitary-adrenal axis; however, the duration of this suppression following the standard anti-emetic intravenous dose of 4 to 8 mg used with anaesthesia is unknown.

A randomised controlled double-blind crossover trial assessing the effects of 8 mg intravenous dexamethasone versus saline control was performed in ten healthy male volunteers. The adrenal, thyroid and gonadal axes and glucose levels were assessed over a four-day period after dexamethasone administration.

All participants had normal baseline hypothalamic-pituitary-adrenal axis function. No difference in Cortisol levels was demonstrated at four or eight hours after dexamethasone administration compared with placebo. At 24 hours post dexamethasone, the Cortisol had dropped to less than 5% of baseline and returned to normal during the subsequent day. Increased plasma glucose levels were also observed in the dexamethasone group as compared with placebo.

A dose of 8 mg of dexamethasone results in significant suppression of the hypothalamic-pituitary-adrenal axis and elevated plasma glucose levels. The Cortisol suppression is maximal at approximately 24 hours post dose.

Phenytoin is regularly employed in the critically ill for prophylaxis against or treatment of seizure disorders. No prior studies have examined current dosing practices in an Australasian intensive care unit (ICU) setting. The aims of this study were to: a) describe the adequacy of contemporary dosing in respect to free and total serum phenytoin concentrations; b) identify factors associated with therapeutic drug concentrations; and c) examine the accuracy of predictive equations that estimate free concentrations in this setting. All patients receiving a loading dose of phenytoin in a tertiary-level ICU were eligible for enrolment; 53 patients were enrolled in the study. Serum samples to determine free and total phenytoin concentrations (measured by high performance liquid chromatography) were then drawn prior to the following dose. Free concentrations below the recommended target (<1 mg/1) were considered as suboptimal. The most common indication for phenytoin loading was traumatic brain injury (49%) and the mean administered dose was 14.5 (3.66) mg/kg. Twenty-six patients (49%) had suboptimal trough free concentrations, although this subgroup was significantly heavier and therefore received a lower per kilogram dose (12.8 [3.1] vs 16.3 [3.4] mg/kg, P=0.001). In multivariate analysis, larger weight adjusted doses (P=0.018), higher albumin concentration (P=0.034) and receiving phenytoin for an indication other than seizure (P=0.035), were associated with a greater likelihood of adequate concentrations. In conclusion, phenytoin dosing remains complex in critically ill patients, although lower per kilogram loading doses are strongly associated with free concentrations below the desired target.

Acute respiratory failure with bilateral pulmonary infiltrates is a clinical problem with a wide differential diagnosis. We evaluated whether open lung biopsy offered a diagnosis and therapeutic guidance in cases of unclear diagnosis after non-invasive tests. For this purpose, we reviewed 60 cases of open lung biopsy performed between 2002 and 2009 in patients with acute respiratory failure and bilateral infiltrates at the intensive care unit of Ghent University Hospital. Pathological diagnosis was classified as specific or non-specific and its contribution to therapy and decision-making was evaluated by a panel of three intensive care unit physicians. We found that a specific pathological diagnosis was present in 39 open lung biopsy patients (65%; 95% confidence interval 52 to 76%): idiopathic interstitial pneumonia in 24 patients, malignancy in four patients, pulmonary infectious disease in nine patients, and a combination of specific diagnoses in two patients. Open lung biopsy contributed to patient management in 53 cases (88%) as it led to the initiation, modification or discontinuation of therapeutic drugs in 36, and contributed to the decision to continue or withdraw ventilator support in 17. Complications of open lung biopsy were noted in 14 patients (23%). We conclude that open lung biopsy was a useful diagnostic intervention in of a selected group of patients with acute respiratory failure and bilateral infiltrates of unclear clinical diagnosis, as it offered a specific diagnosis in 65%.

Lipid emulsions have been used to treat cardiovascular collapse due to local anaesthetic toxicity. However, there are few data available on the comparative efficiency of the partitioning properties of available lipid emulsions in clinical use. This in vitro study compared the buffering properties of the lipid emulsions Clinoleic™ 20% (Baxter, Old Toongabbie, NSW) and Intralipid® 20% (Fresenius Kabi, Pymble, NSW) using both bupivacaine (Marcain® 0.5%, AstraZeneca, North Ryde, NSW) and ropivacaine (Naropin® 1%, AstraZeneca, North Ryde, NSW). The concentration of anaesthetic in buffer before and after mixing with lipid was quantified using chromatographic analysis. Bupivacaine was more effectively bound by the lipid agents, with a 40% reduction in initial concentration. Ropivacaine demonstrated a 20% reduction in concentration with the addition of lipid agents. Importantly, there was no significant difference between Intralipid and Clinoleic in terms of their buffering behaviour, suggesting equivalent binding efficacy.

Cricothyroidotomy is infrequently performed in the intensive care unit but may be a lifesaving procedure. The aim of this study was to determine the number of attempts required by trainees to gain adequate skills for a successful cricothyroidotomy (defined as lung inflation <60 seconds). The effect of training on time to completion of cricothyroidotomy was also studied. After viewing a demonstration video on the procedure, each participant attempted cricothyroidotomy five times consecutively on a manikin with a pre-assembled Melker cricothyroidotomy kit. Time from ‘skin’ palpation to ‘lung’ inflation was recorded for 30 participants. Time to completion of cricothyroidotomy decreased over consecutive attempts within each participant (F_4df=39.6; P <0.001) and between participant variability in times recorded at each attempt also decreased (P=0.04). Overall improvement in time to completion was seen even between the fourth and fifth attempts (mean difference −6.3 seconds; P <0.001). All participants were successful by the fifth attempt, by which stage all but two had been successful on two consecutive attempts. Age, years of postgraduate practice and level of seniority appeared to be associated with earlier success. Consecutive attempts on a manikin led to an improvement in the time to completion of cricothyroidotomy and rate of a successful outcome (<60 seconds). We recommend that clinicians undergo at least five training attempts on a manikin to gain proficiency in cricothyroidotomy.

When evaluating assessments, the impact on learning is often overlooked. Approaches to learning can be deep, surface and strategic. To provide insights into exam quality, we investigated the learning approaches taken by trainees preparing for the Australian and New Zealand College of Anaesthetists (ANZCA) Final Exam. The revised two-factor Study Process Questionnaire (R-SPQ-2F) was modified and validated for this context and was administered to ANZCA advanced trainees. Additional questions were asked about perceived value for anaesthetic practice, study time and approaches to learning for each exam component. Overall, 236 of 690 trainees responded (34%). Responses indicated both deep and surface approaches to learning with a clear preponderance of deep approaches. The anaesthetic viva was valued most highly and the multiple choice question component the least. Despite this, respondents spent the most time studying for the multiple choice questions. The traditionally low short answer questions pass rate could not be explained by limited study time, perceived lack of value or study approaches. Written responses suggested that preparation for multiple choice questions was characterised by a surface approach, with rote memorisation of past questions. Minimal reference was made to the ANZCA syllabus as a guide for learning. These findings indicate that, although trainees found the exam generally relevant to practice and adopted predominantly deep learning approaches, there was considerable variation between the four components. These results provide data with which to review the existing ANZCA Final Exam and comparative data for future studies of the revisions to the ANZCA curriculum and exam process.

This survey was designed to evaluate the factors affecting mental health and welfare in Australian anaesthetists and to investigate current sources of support.

An electronic survey was sent to 500 randomly selected Fellows and trainees of the Australian and New Zealand College of Anaesthetists. Questions were related to: anxiety, stress, depression, substance misuse, self-medication, suicide, reporting illness, and help-seeking. Current psychological wellbeing was assessed using the Kessler Psychological Distress Scale (K10).

A total of 191 completed surveys were received (a response rate of 38%): 26% had attended their general practitioner for mental health issues, of whom half had been diagnosed with a mental illness; 7% of all respondents were currently prescribed medication for this; 25% had previously self-prescribed psychoactive medication; 17% admitted to using alcohol to deal with stress, anxiety or depression; and 8% responded that mental illness had at some point impaired clinical care. Sixteen percent of all respondents reported previous suicidal ideation.

Despite a low response rate, and the possibility of responder bias, the mental health of Australian anaesthetists would appear to be subject to common and persistent risk factors, many of which are well described in previous studies. We identify general practitioners as particularly valuable in targeting initiatives for improvements in mental health and welfare. The significant prevalence of suicidal ideation and reluctance to approach senior colleagues with concerns about mental health or welfare issues are specific causes for concern and suggest that further investigation, education and a potential review of support networks is required.

We suspected that many high blood pressure measurements taken in our anaesthetic pre-assessment clinic and immediately prior to induction of anaesthesia were unusually elevated due to a ‘white coat’ effect. These high blood pressure measurements were causing late cancellations of surgery, even though white coat measurements may not be representative of the patient's usual blood pressure or of their risk of end-organ damage due to hypertension. In this audit, patients with high blood pressure in our pre-admission clinic were provided with training and a home blood pressure monitor to use prior to surgery. These were compared to the pre-admission clinic measurements to determine the incidence of white coat hypertension. We also compared home to general practice blood pressure monitoring where possible. Fifty-two patients were provided with monitors. Fifty-one of these took at least five measurements at home. Thirty-four (66%) patients had average measurements at home at least 20 mmHg lower than pre-admission clinic measurements. A total of 33% of general practice clinic measurements were also ≥20 mmHg higher than average home measurements. White coat hypertension was common in our audit population. Relying on average home blood pressure measurements rather than ‘one off in-hospital measurements may have helped to prevent the postponement or cancellation of surgery for 13 patients who had recorded blood pressure ≥ 180/110 mmHg in our pre-admission clinic.

The origin of New Zealand's paediatric intensive care medicine lay in the formal establishment of Auckland Hospital's Central Respiratory Unit within the hospital's Infectious Diseases Unit (December 1958). It was initially established for the care of critically ill children, chiefly with airway and respiratory disorders or tetanus. Senior Specialist Anaesthetist Matthew Spence soon took charge, his first annual report (1960) briefly describing six children among 19 admissions and another six consulted on elsewhere. Rapid build-up of paediatric admissions—36 in 1963 becoming 104 in 1969—is detailed through Dr Spence's admirable annual reports for that period, which also provide the evidence of his organisational brilliance and personal commitment to development of the unit. Treatment for children, approximately a third of all admissions, soon included management of brain swelling from meningitis, intractable convulsions, traumatic brain injury, etc. Critically ill children were occasionally flown into Auckland; others were cared for regionally as further intensive care units developed throughout New Zealand. Successive additions to medical staffing gradually resulted in four full-time intensivists after Dr Spence's retirement in 1983. Dr James Judson computerised record-keeping from 1984 and developed a large database, containing details of children with numbers approaching 2000. At the end of 1991, the (now) Department of Critical Care Medicine completed its paediatric role over three decades, with care of children passing to a paediatric intensive care unit in the new Auckland paediatric hospital (soon to be called “Starship”). Regional intensive care units still make a substantial contribution to paediatric intensive care countrywide.

In a single centre over two years, four children (7 to 10 years old) with upper limb osteosarcoma underwent chemotherapy followed by forequarter amputation. All patients had preoperative pain and were treated with gabapentin. Nerve sheath catheters were placed in the brachial plexus intraoperatively and left in situ for five to 14 days. After surgery, all patients received local anaesthetic infused via nerve sheath catheters as part of a multimodal analgesia technique. Three of the four patients were successfully treated as outpatients with the nerve sheath catheters in situ. All four children experienced phantom limb pain; however, it did not persist beyond four weeks in any patient.