1 Perioperative anaesthetic management of mediastinal masses in adults. Erdös G et al. Eur J Anaesthesiol. 2009 Aug; 26(8):627-32.
The authors of this review have developed a methodology to guide management of the adult with a mediastinal mass. The preoperative protocol recommends detailed interdisciplinary team consultation and possible preoperative irradiation/chemotherapy. Concerning features on symptom review include respiratory distress in the supine position and superior vena cava syndrome. Correlation of the clinical and radiological findings (CT) +/-echocardiography and dynamic testing (pneumotachgraphs) should enable risk stratification. A cross-sectional tracheal area less than 50% of normal can predict frequent perioperative respiratory complications. Consideration must be given regarding safe transport to theatre, positioning, haemodynamic monitoring and lower extremity intravenous access. The authors prefer to secure the airway awake with a reinforced ETT and avoid all muscle relaxants if possible. Should complications arise, attempts should be made for rapid surgical decompression and/or repositioning and it is possible that a rigid bronchoscope or extracorporeal circulation may be required. HDU/ICU should be available and rapid extubation is preferred by the authors. Their recommendations are based both on available literature and their own clinical experiences and thus are limited to the level of expert opinion.
Take home message: Safe anaesthesia for a mediastinal mass requires meticulous preoperative assessment and a detailed plan to manage serious haemodynamic or respiratory decompensation as a consequence of tumour compression syndromes.
2 Practical use of the raw electroencephalogram waveform during general anesthesia: the art and science. Bennett C et al. Anesth Analg. 2009 Aug;109(2):539-50.
This review article attempts to educate clinicians so that they are better equipped to problem solve when faced with an unexpectedly high or low quantitative EEG index (qEEGI) number from either a BIS or spectral entropy monitor. The authors emphasize that clinical judgement is crucial when using qEEG, as is a clear mental picture of the expected raw EEG and knowledge of common EEG artifacts. Beta-band activity (13-30 Hz) predominates in the EEG of an awake subject (fuzzy flat line). As the sedative/hypnotic drug concentration increases, the beta activity slows to spindle-like/alpha waves (short bursts of activity with frequency of around 7-14 Hz) and then slows further to the theta range (3.5-7 Hz). Delta waves (1-4 Hz) are the hallmark of slow wave sleep and deeper anaesthesia, where the whole EEG slowly wanders up then down around the base-line. Burst suppression and isoelectricity are features of progressively deeper anaesthesia. The presence of spindle-like waves and background slow delta waves, with no fast waves, are probably the most important EEG signs of anaesthesia. Common artifacts include EMG signal (frontalis, masseter or extraocular muscles), cerebral pathology and certain drugs i.e ketamine. Of note, cerebral ischaemia is accurately detected by BIS with a decreasing of the qEEGI due to cortical inactivation. Given this background, the authors conclude that it is not possible to adequately monitor a patient by blind obedience to the processed number.
Take home message: Optimal use of qEEG monitors, such as BIS and M-entropy, requires an understanding of expected raw EEG changes during anaesthesia as well as potential sources of non-EEG artifact.
For related reading this month: - Nishiyama T. Cerebral state index vs. bispectral index during sevoflurane-nitrous oxide anaesthesia. Eur J Anaesthesiol. 2009 Aug;26(8):638-4 - Cirodde A et al. Is your patient sleeping? Eur J Anaesthesiol. 2009 Aug;26(8):704-6.
3 Neuraxial techniques in obstetric and non-obstetric patients with common bleeding diatheses. Choi S et al. Anesth Analg. 2009 Aug;109(2):648-60.
This article is a valuable resource considering the paucity of published data regarding the provision and safety of neuraxial techniques in patients with common bleeding diatheses. The data presented are cautiously reassuring, at least in the obstetric population. Upon review of 507 neuraxial techniques in patients with haemophilia, vWD or ITP there was a single case of spinal haematoma after diagnostic LP in an undiagnosed haemophiliac infant resulting in permanent paraplegia. The remaining cases proceeded uneventfully, however factor levels had spontaneously normalized, were replaced or appropriate therapy initiated (i.e. DDAVP) and platelet counts were >50-60X109/L in the vast majority of predominantly obstetric cases. There is very little data pertaining to severe vWD (type II/III) and non-obstetric cases. The effects of publication bias and negative reporting cannot be discounted and it is important to consider that the evidence presented is Level IV at best. This article is a strong prompt for large scale, multi-institutional, international detailed data collection of outcome after neuraxial techniques in patients with abnormal clotting to enable reliable evidence based recommendations to be made in the future.
Take home message: Based on available evidence, predominantly from the obstetric population, haemorrhagic complications after neuraxial techniques in patients with known haemophilia, vWD or ITP appear infrequent when factor levels are more than 0.5 IU/mL for Factor VIII/IX levels, vWF levels and ristocetin co-factor activity levels, or when the platelet count is more than 50 X109/L. before block performance.
4 Perioperative hemodynamic monitoring with transesophageal Doppler technology. Schober P et al. Anesth Analg. 2009 Aug;109(2):340-53.
This review is effectively ‘transoesophageal Doppler (TOD) 101’. The various devices commercially available (CardioQ, HemoSonic 100, Waki TO) enable calculation of CO based on the measured frequency shift between the emitted and received ultrasound frequency to determine blood flow velocity in the aorta and subsequently calculates stroke distance, stroke volume and CO. It is important to consider that individual CO measurements obtained with TOD may differ considerably from CO values derived by thermodilution so that the two techniques are not interchangeable. However, there is a strong positive correlation between TOD and the reference methods suggesting that the direction of changes in CO can be traced by TOD. Thus, TOD may be used as a trend monitor rather than a device for the exact measurements of CO. With adequate training and experience estimates of preload, afterload (based on flow-time corrected) and contractility (based on peak velocity, mean acceleration) can be made using TOD. Changes in stroke volume secondary to a volume bolus can help clarify estimates of haemodynamic variables in equivocal cases. However, TOD does not allow direct visual estimation of ventricular filling, contractility, or valvular function, which might be desirable in patients with complex cardiac pathophysiology or extended surgery. The shortcomings of TOD need to be considered to avoid misinterpretations of the measured data. Despite limitations of TOD, especially in cases of aortic pathology and various illness states, current evidence suggests that Doppler-guided fluid replacement has the potential to improve patient outcome with several studies showing that its use associated with reduction of postoperative complications, length of stay and morbidity.
Take home message: Transoesphageal Doppler allows the continuous trend monitoring of CO and other advanced haemodynamic variables to guide fluid administration and therapy with vasoactive and inotropic drugs.
For related reading this month: - Biais M et al. A comparison of stroke volume variation measured by Vigileo/FloTrac system and aortic Doppler echocardiography. Anesth Analg. 2009 Aug;109(2):466-9. - Mayer J et al. Uncalibrated arterial pressure waveform analysis for less-invasive cardiac output determination in obese patients undergoing cardiac surgery. Br J Anaesth. 2009 Aug;103(2):185-90.
See also: March Journal Watch (6)
5 Anesthesia for noncardiac surgery in adults with congenital heart disease. Cannesson M et al. Anesthesiology. 2009 Aug;111(2):432-40.
This review discusses the implications of the increasing number of adult patients with CHD present for noncardiac surgery. CHD lesions can be functionally classified into those that produce left to right shunts (acyanotic) and those that produce cyanosis (right to left shunts). The long-term consequences of CHD which effect anaesthesia mangement include pulmonary hypertension, increased bleeding and thrombosis risk, heart failure and dysrhythmias. Common objectives of intraoperative management are promotion of tissue oxygen delivery by preventing arterial desaturation, maintaining a balance between pulmonary and systemic flows and optimizing haematocrit. In addition, knowledge of the specific palliative repairs including the Blalock-Taussig shunt, Fontan circulation and Mustard or Senning procedure are required to determine appropriate monitoring and assess haemodynamic goals. Single ventricle anatomy and physiology is probably, along with Eisenmenger syndrome, the most challenging CHD for the anaesthetist to manage. Other specific considerations include the requirement for meticulous deairing of intravenous lines in patients with shunts to prevent systemic air embolization and endocarditis prophylaxis. Notably, the American Heart Association has recently published updated guidelines for the prevention of infective endocarditis. The major change is now only specific cardiac conditions associated with the highest risk for adverse outcomes should continue following antibiotic prophylaxis.
Take home message: Adults with moderate or severe CHD requiring non-cardiac surgery are at high risk, particularly those with poor functional class, pulmonary hypertension, congestive cardiac failure, and cyanosis; and these patients should receive care from a multidisciplinary team in a regional adult CHD centre.
6 Prognostic value of brain natriuretic peptide in noncardiac surgery: a meta-analysis. Ryding AD et al. Anesthesiology. 2009 Aug;111(2):311-9.
This metanalysis was designed to assess the prognostic value of elevated BNP or NT-proBNP levels in predicting mortality and major adverse cardiovascular events (MACE). Data from 15 publications (n=4,856) were included in the analysis. The metanalysis concluded that preoperative BNP elevation is associated with significantly increased risk of short-term MACE, cardiac mortality and all-cause mortality as well as longer term MACE and all cause mortality after major non-cardiac surgery. Generally accepted normal values for BNP (less than 100 pg/ml and NT-Pro-BNP (less than 300 pg/ml) would have a negative predictive value of at least 95-99% for short term MACE. The authors are hopeful that measurement of BNPs may be a simple method of risk stratifying patients before non-cardiac surgery and deciding which patients would benefit from further investigation of ventricular function and or inducible ischaemia.
Take home message: It is likely that BNP elevation identifies patients with impaired cardiac function or a significant ischaemic burden who may have poor outcomes when challenged with the haemodynamic and pro-inflammatory stresses of general anaesthesia and major surgery.
For related reading this month: - Oscarsson A et al. N-terminal fragment of pro-B-type natriuretic peptide is a predictor of cardiac events in high-risk patients undergoing acute hip fracture surgery. Br J Anaesth. 2009 Aug;103(2):206-12.
See also: Feb Journal Watch (6); April Journal Watch (8)
7 Predictors of cardiac events in high-risk patients undergoing emergency surgery. Oscarsson A et al. Acta Anaesthesiol Scand. 2009 Aug;53(8):986-994.
The aim of this observational study was to determine the perioperative incidence of myocardial damage (via TnI levels) and LV myocardial dysfunction (via NT-proBNP levels) in high risk patients having emergency surgery (n=211). Even within this high risk group (ASA III/IV, mean age 80.4, >75% abdominal or orthopaedic surgery) it is alarming to observe that 14% of these patients had a major adverse cardiac event (MACE). Post-operative TnI was elevated in 22/26 of the patients who suffered MACE. Even more interesting, 64% of these patients had a pathological TnI before surgery. A TnI elevation significantly increased the risk of major adverse cardiac event (MACE) to 33% vs 3% in patients with normal TnI and significantly increased 30 day mortality to 23% vs 7%. Increased preoperative NT-proBNP concentrations were seen in 59% of the patients. Elevated NT-proBNP was an independent predictor of myocardial damage post-operatively, OR 6.2 (2.1-18) and resulted in an increased risk of MACE (21% vs 2.5%) in patients with NT-proBNP <1800 pg/ml. Two independent predictors of death within 30 days from surgery were identified: Cr >170 micromol OR 2.8 (1-7.7) and hypoxaemia in recovery room OR 11.7 (2.1-64). Importantly, most patients with TnI elevations had neither clinical symptoms of myocardial ischaemia nor evidence of ECG abnormalities. This study had a small sample size, missing data and was susceptible to selection bias.
Take home message: The combination of of TnI and NT-proBNP in the peri-operative period may prove to be a useful supplement to aid risk stratification and a reliable way of monitoring patients at high risk of cardiac complications. This study suggests more frequent perioperative ordering of these tests should be considered, especially in the emergency setting.
For related reading this month: - Oscarsson A et al. N-terminal fragment of pro-B-type natriuretic peptide is a predictor of cardiac events in high-risk patients undergoing acute hip fracture surgery. Br J Anaesth. 2009 Aug;103(2):206-12
8 Anaesthesia for deep brain stimulation and in patients with implanted neurostimulator devices. Poon CC et al. Br J Anaesth. 2009 Aug;103(2):152-65.
This article provides an update on the increasingly common procedure of deep brain stimulator (DBS) insertion. Indications include Parkinson’s disease and other illnesses such as essential tremor, intractable epilepsy and chronic pain with refractory symptoms. For insertion, an awake or sedative technique with a scalp block is currently preferred because it facilitates neurological testing and intraoperative microelectrode recording (MER) used to map correct electrode position. Intra-operative priorities include good pain control, meticulous patient positioning and padding, attention to thermal control, and avoidance of excessive fluid administration to prevent bladder distension. With respect to drugs for sedation, benzodiazepines should be avoided. It is not yet clear whether propofol interferes with MER however dexmedetomidine attenuates the haemodynamic and neuroendocrine responses as well as reliably producing conscious sedation so some experts feel it is an ideal sedative for DBS implantation. Intra-operative risks include neurological complications (intracranial haemorrhage, seizures) and cardiovascular complications (uncontrolled hypertension, VAE) as well as airway compromise. To reduce the risk of intracranial haemorrhage, good hypertensive control is mandatory and antihypertensive medication should be continued perioperatively. Care is required in the management of patients who already have a DBS implanted, as it can interfere with other monitoring and therapeutic devices i.e. MRI, electrocautery, PPM/ICDs.
Take home message: In addition to standard and neurological monitoring, important considerations during ‘awake’ DBS insertion include pain control, suitable drugs for sedation and optimal blood pressure control.
9 Previously undiagnosed aortic stenosis revealed by auscultation in the hip fracture population--echocardiographic findings, management and outcome. McBrien ME et al. Anaesthesia. 2009 Aug;64(8):863-70.
This paper explores some of the common issues surrounding hip fracture surgery in elderly, debilitated patients. The authors employed a retrospective observational study design to investigate the outcome of 272 hip fracture patients between 2001-2005 who were identified with previously undiagnosed aortic stenosis revealed as a result of cardiac auscultation and subsequent bedside echocardiography. These results were then compared with a control group of 3698 patients without (diagnosed) AS. The study revealed an incidence of previously undiagnosed aortic stenosis, as revealed by auscultation and confirmed by echocardiography, of 6.9% in hip fracture patient presentations and 30% of the patients who had an echocardiogram ordered to investigate a previously undiagnosed heart murmur were found to have AS. Obviously patients with undiagnosed AS may have remained undiagnosed due to failure to identify a murmur on ausculatation. The 30-day mortality rate for the total hip fracture population admitted in the 4-year period, including those patients who were managed without surgical fixation, was 7.3% and notably, there were no statistically significant trends towards higher 30-day mortality rates or 1 year mortality rates with diagnosis of AS or as the severity of aortic stenosis increased. The authors surmise that an explanation for this finding is that the diagnosis of AS had implications on choice of anaesthetic technique with highly significant trends identified towards general over spinal anaesthesia and towards use of invasive blood pressure measurement intraoperatively, as severity of AS increased. Peripheral nerve blocks were utilized in 60-70% of AS patients and the authors state they believe all hip fracture patients should receive nerve blockade for postoperative analgesia unless otherwise contraindicated. The predicted disadvantages of TTE prior to NOF surgery were evident in this study with median time from injury to surgery approximately 5 days for all patients, greatly exceeding recommended targets of 48 hours. The main limitations of this study are missing data, unknown true rate of positive AS diagnosis and retrospective, observational study design. It is potentially interesting to consider the results of this study in view of the increased interest in anaesthetist driven TTE/heartscan.
Take home message: The authors of this paper recommend echocardiography is made available to assess patients with suspected or known aortic stenosis prior to anaesthesia for repair of their hip fracture without causing delay to surgery which is in keeping with 2001 NCEPOD recommendations.
See also: June Journal Watch (6)
10 Fentanyl: destiny or devil? Editorial: Groban L et al. Anesth Analg. 2009 Aug;109(2):301-2.
Morphine-based cardiac anesthesia provides superior early recovery compared with fentanyl in elective cardiac surgery patients. Murphy GS et al. Anesth Analg. 2009 Aug;109(2):311-9.
This RCT sought to determine whether the choice of intraoperative opioid (morphine or fentanyl) influences early recovery after uncomplicated cardiac surgery. Ninety patients were randomized to receive either morphine (40 mg) or fentanyl (600 mcg) as part of a standardised opioid-isoflurane anaesthetic. The patients were all planned for extubation Day 1. Compared with patients given fentanyl, those receiving morphine had higher global quality of recovery scores especially in the dimensions of pain, emotional state and physical comfort. As the accompanying editorial emphasizes, there is a growing body of evidence that suggests a significant role for opioids in stimulating preconditioning. However the receptors involved in preconditioning are activated by morphine not fentanyl which means morphine may have greater potential for cardioprotection and modulating the proinflammatory response. The study was not powered to detect a difference in complication rate or outcome.
Take home message: This study suggests overall recovery after cardiac surgery is enhanced when morphine, rather than fentanyl, was administered as part of a balanced anaesthetic technique.
Other articles of potential specific interest:
OBSTETRIC - Visser WA et al. Spinal anesthesia for intrapartum Cesarean delivery following epidural labor analgesia: a retrospective cohort study. Can J Anaesth. 2009 Aug;56(8):577-83
Written by Maryanne Balkin, September 2009
Feedback welcome: M.Balkin@alfred.org.au
Disclaimers:
1 Best attempts are made to include articles representative of recent publications but no attempt is made to include every important article.
2 Commentary & take home message is only one of many possible opinions/interpretations of the literature.
For other 2009 editions of journal watch: http://www.anaesthesiacases.com.au/cpd