1 Post-traumatic stress disorder in aware patients from the B-aware trial. Leslie K et al. Anesth Analg. 2010 Mar;110(3):823-8.
The trauma of awareness: history, clinical features, risk factors, and cost. Editorial: Ghoneim M. Anesth Analg. 2010 Mar;110(3):666-7.
Post-traumatic stress disorder after intraoperative awareness and high-risk surgery. Editorial: Mashour GA. Anesth Analg. 2010 Mar;110(3):668-70.
This matched-cohort study reports the long-term psychological follow-up of patients who experienced awareness in the B-aware trial. The primary outcome, incidence of post-traumatic stress disorder (PTSD), was diagnosed with a face-face interview of awareness patients using the clinician administered PTSD scale. Follow-up occurred a median of 5.3 years after initial surgery and revealed that 6 of the 13 confirmed awareness patients had died. The incidence of PTSD in five of the seven available awareness patients (71%) was higher than the incidence found in control patients (OR 13.3, CI 1.4-650; p=0.02). The accompanying editorial by Ghoneim draws attention to the debilitating psychological and physical repercussions associated with PTSD and emphasizes the importance of providing treatment and identifying risk factors that predispose patients to this poor outcome. Each surviving awareness patients was matched with 3 or 4 controls for age, sex, surgery type, date of surgery and hospital. Surprisingly, the incidence of PTSD in the control population of 25 patients was 12%. The other accompanying editorial by Mashour comments that the high incidence of PTSD in the control group is consistent with the literature for high-risk surgery patients, especially those who spend time ventilated in ICU. However because of the lack of a ‘control group for the control group’, the data regarding PTSD in the surgical population should be interpreted cautiously. Given the fact that 3 of the 5 awareness patients felt that symptoms of PTSD were present early after surgery, but did not report psychiatric sequelae within 30 days of surgery, the authors recommend that awareness patients should be advised to seek counseling regardless of how long it takes symptoms of PTSD to emerge.
Take home message: A high proportion of patients develop PTSD after intra-operative awareness events and therefore require psychological follow-up.
For related reading this month: Mashour GA et al. A novel classification instrument for intraoperative awareness events. Anesth Analg. 2010 Mar;110(3):813-5.
2 Relation between preoperative and intraoperative new wall motion abnormalities in vascular surgery patients: a transesophageal echocardiographic study. Galal W et al. Anesthesiology. 2010 Mar;112(3):557-66. [Article]
Not all perioperative myocardial infarctions can be prevented with preoperative revascularization. Editorial Subramaniam B et al. Anesthesiology. 2010 Mar;112(3):524-6.
In this observational study, a cohort of high-risk vascular surgery patients (n=54) underwent preoperative dobutamine stress echocardiography (DSE) and intraoperative multi-plane transoesophageal echocardiology (TOE). The locations of LV rest abnormalities and new wall motion abnormalities (NWMA) were scored using a protocol based seven-wall model. Outcome for a composite endpoint of adverse cardiac events (troponin release, MI, cardiac death) was subsequently assessed during a 30-day follow-up period. The composite cardiac endpoint occurred in 26% of patients (26%, 11% and 6% for troponin release, MI and cardiac death respectively). The authors demonstrated that, although preoperative DSE can predict patients who are at risk for perioperative myocardial infarction (PMI), it could not predict the location of those PMI in 54 consecutive patients undergoing vascular surgery. In contrast, NWMA detected by intraoperative TOE had 100% positive predictive value and better agreement with the location of PMI compared with preoperative DSE. Notably, no events of cardiac death or post-operative MI occurred in patients without intraoperative NWMA. The explanation of this finding is that preoperative DSE is good for the diagnosis of significant coronary artery obstruction and identification of patients at risk of MI, but it may fail to identify the myocardial territory at risk from rupture of a non-obstructive coronary artery plaque-an aetiology thought to be commonly responsible for PMI. The accompanying editorial highlights that the agreement of location of PMI, a major focus of this study, was based on only 6 patients. The editorialist also suggests that the current challenge for high risk patients is to establish a comprehensive strategy with long-term beta-blockade, statin therapy and targeted preoperative revascularization, keeping in mind the added risk of coronary stent thrombosis or dual antiplatelet therapy. In addition, the author feels that this study suggests that intraoperative TOE may be a sensitive method for identification of patients at risk for PMI.
Take home message: This study found that preoperative DSE predicted NWMA and MI associated with surgery, but did not predict the location of ischaemia and infarction suggesting the potential superiority of optimized medical therapies over preoperative invasive revascularisation options for prevention of PMI.
See also: Jan 09 Journal Watch (1) June 09 Journal Watch (6) Sep 09 Journal Watch (11)
3 The effect of bispectral index monitoring on long-term survival in the B-aware trial. Leslie K et al. Anesth Analg. 2010 Mar;110(3):816-22.
Deep hypnosis as a sign of "imbalance" in balanced anesthesia. Editorial: Kurata J. Anesth Analg. 2010 Mar;110(3):663-5.
This post-hoc analysis of the B-Aware trial tested the hypothesis that BIS monitoring improved survival. The investigators analyzed data from the trial with added follow-up data on the prognosis (death, MI, CVA) from 1947 patients. The authors found that BIS monitoring itself did not affect survival but propensity score analysis indicated that, in patients with a BIS decrease of <40 for >5 minutes, there was an association with decreased survival (a hazard ratio for death of 1.42; CI 1.02-1.95; p=0.39) and increased rates of myocardial infarction and stroke compared with those patients who did not show such a BIS decrease. The authors’ propose that these results suggests anaesthetists should avoid low BIS values by careful titration of hypnotic drugs. An alternative explanation is that low BIS values reflect underlying disease processes and trauma, and that these factors, rather than anaesthetic dosing, affect survival. It is worth noting that the B-aware trial studied high-risk surgical patients who had a relatively high 30-day mortality. The study population also included a large number of patients having cardiac surgery. Limitations of the study included inability to follow-up 17% of the original study patients, patients were not randomized to differing BIS values and BIS values were manually recorded. The accompanying editorial suggests anaesthetic titration within the BIS range between 40 and 60 should play an important role in preventing awareness while treating hypotension and highlights that low BIS values maybe useful as one of the many premonitory signs of insufficient circulation. However, the editorial also states that correlation between the BIS values and other intraoperative indices for circulation or organ perfusion would have made the present data more informative in addressing the meaning of excessively low BIS values. The editorialist also suggests the impact of deep hypnosis on the prognosis of surgical patients must await a future RCT that controls for other predictive factors.
Take home message: Preliminary evidence suggests titration of anaesthesia to BIS target range of 40-60 may improve postoperative outcomes.
4 Practice advisory for the prevention, diagnosis, and management of infectious complications associated with neuraxial techniques: a report by the American Society of Anesthesiologists Task Force on infectious complications associated with neuraxial techniques. Anesthesiology. 2010 Mar;112(3):530-45. [Article]
Direct extracts from Practice advisory:
“PRACTICE advisories are systematically developed reports that are intended to assist decision-making in areas of patient care. Advisories are based on a synthesis of scientific literature and analysis of expert opinion, clinical feasibility data, open forum commentary, and consensus surveys. Advisories developed by the American Society of Anesthesiologists (ASA) are not intended as standards, guidelines, or
absolute requirements. Practice advisories are not supported by scientific literature to the same degree as standards or guidelines because of the lack of sufficient numbers of adequately controlled studies. Practice advisories are subject to periodic revision as warranted by the evolution of medical knowledge, technology, and practice.
Advisory Statements for Prevention
History and physical examination relevant to the procedure and review of relevant laboratory studies should be conducted to identify patients who may be at risk of infectious complications before performing neuraxial techniques. Consider alternatives to neuraxial techniques for patients at high risk. When neuraxial techniques are selected in a known or suspected bacteremic patient, consider administering preprocedure antibiotic therapy. Selection of neuraxial technique should be determined on a case-by-case basis, including consideration of the evolving medical status of the patient. Lumbar puncture should be avoided in the patient with a known epidural abscess. Aseptic techniques should always be used during preparation of equipment (e.g. ultrasound) and the placement of neuraxial needles and catheters, including (1) removal of jewelry (e.g., rings and watches), hand washing, and wearing of caps, masks (covering both mouth and nose and consider changing before each new case), and sterile gloves; (2) use of individual packets of antiseptics for skin preparation; (3) use of chlorhexidine (preferably with alcohol) for skin preparation, allowing for adequate drying time#; (4) sterile draping of the patient; and (5) use of sterile occlusive dressings at the
catheter insertion site.** Bacterial filters may be considered during extended continuous epidural infusion. Limit the disconnection and reconnection of neuraxial delivery systems to minimize the risk of infectious complications. Consider removing unwitnessed accidentally disconnected catheters. Finally, catheters should not remain in situ longer than clinically necessary.
Advisory Statements for Diagnosis
Daily evaluation of patients with indwelling catheters for early signs and symptoms (e.g., fever, backache, headache, erythema, and tenderness at the insertion site) of infectious complications should be performed throughout their stay in the facility.†† To minimize the impact of an infectious complication, promptly attend to signs or symptoms. If an infection is suspected: (1) remove an in situ catheter and consider culturing the catheter tip, (2) order appropriate blood tests, (3) obtain appropriate cultures, and (4) if an abscess is suspected or neurologic dysfunction is present, imaging studies should be performed and consultation with other appropriate specialties should be promptly obtained.
Advisory Statements for Management
Appropriate antibiotic therapy should always be administered at the earliest sign or symptom of a serious neuraxial infection. Consultation with a physician with expertise in the diagnosis and treatment of infectious diseases should be considered. If an abscess is present, surgical consultation should be obtained to determine whether percutaneous drainage of the abscess or surgery (e.g., laminectomy) is warranted.“
Take home message: Due to the limited evidence base for prevention, diagnosis and management of infectious complications of neuraxial techniques, practice advisory statements may be helpful but ultimately decisions need to be made after expert case-by-case evaluation.
See also: Feb 09 Journal Watch (3)
5 Urgent surgery in patients with a recently implanted coronary drug-eluting stent: a phase II study of 'bridging' antiplatelet therapy with tirofiban during temporary withdrawal of clopidogrel. Savonitto S et al. Br J Anaesth. 2010 Mar;104(3):285-91.
This small observational pilot study (n=30) tested the hypothesis that the IV perioperative administration of the glycoprotein IIb/IIIa receptor blocker, tirofiban, allows the safe withdrawl of clopidogrel in patients with a recently implanted coronary drug-eluting stent (DES) who need urgent surgery. Thirty patients with a recently implanted DES (median 4 months) and high-risk characteristics for stent thrombosis underwent urgent major surgery (abdominal, cardiac, vascular, orthopaedic, urological, gynae. ENT) or eye surgery (2 patients). Clopidogrel was withdrawn 5 days before surgery and tirofiban started 24 hours later, continued until 4 hours before surgery, and resumed 2-20 hours after surgery (required in 13 patients) until oral clopidogrel was resumed (loading dose 300 mg). The use of aspirin was decided by the surgeon. There were no cases of the composite endpoint (death, MI, stent thrombosis, or surgical re-exploration due to bleeding) during the index admission. There was one case of major bleeding (post-hemicolectomy) and one case of minor bleeding (post-nephrotomy) as per the thrombolysis in myocardial infarction (TIMI) criteria.
The strategy was resource intensive-patients were admitted 4 days preoperatively for administration of tirofiban and placed in CCU/ICU until resumption of clopidogrel where they had daily 12 lead ECG monitoring and measurement of CK-MB (not troponin). Of note, although administered for up to 384 hours in this study, tirofiban is only approved for 72 hours of administration. The zero rate of cardiac ischaemic event should be interpreted cautiously because of the limited number of patients treated and lack of control group.
Take home message: Observational evidence suggests a ‘bridging strategy’ using IV tirofiban may allow temporary withdrawal of clopidogrel in patients with a recently implanted DES without substantially increasing the risk of bleeding.
See also: Jan 09 Journal Watch (10) March 09 Journal Watch (4)
6 To continue or discontinue aspirin in the perioperative period: a randomized, controlled clinical trial. Oscarsson A et al. Br J Anaesth. 2010 Mar;104(3):305-12.
This double-blind placebo controlled RCT (n=220) was undertaken to try and assess the incidence of perioperative myocardial damage in patients with or without low-dose aspirin treatment in the perioperative period. Patients with at least 1 coronary risk factor were given aspirin (75 mg) or placebo for 7 days before high or intermediate risk non-cardiac surgery and it was continued until the third postoperative day. Patients previously on aspirin were restarted on aspirin therafter. Patients were followed up with troponin levels preoperatively and at 12, 24, 48 hours after surgery, ECGs preoperatively, immediately postoperatively and at 24 and 48 hrs postoperatively and then telephone interview and medical record review at 30 days after surgery. Study patients underwent advanced bowel surgery, gastric surgery, prostate surgery, cystectomy, nephrectomy, hip or knee arthroplasty and intra-abdominal or pelvic cancer surgery. Postoperative myocardial damage (defined by troponin elevation ≥0.04 mcg/l) was the primary endpoint. Secondary endpoints were incidence of major adverse cardiac event (MACE), CVA/TIA, perioperative blood loss and blood product transfusions. Four patients (3.7%) in the aspirin group and 10 patients in the placebo group had elevated troponin levels in the postoperative period-a difference that was not statistically significant. Two patients (1.8%) in the aspirin group and 10 patients (9%) in the placebo group had a MACE during the first 30 postoperative days represented a statistically significant difference between groups (p=0.02). The incidence of perioperative CVA was also statistically significantly higher in the placebo group (0.049). Treatment with aspirin resulted in a 7.2% absolute risk reduction (CI 1.3-13%) or a relative risk reduction of 80% (CI 9.2-95%). Numbers needed to treat were 14. Unfortunately of the planned 540 patients, the study was terminated early, primarily because during the study period, new recommendations for high-risk patients taking aspirin were published recommending a continuation of aspirin during the perioeprative period. In addition, patients with coronary stents were excluded as per 2006 guidelines. Eight and 9 patients did not complete allocated therapy in the aspirin and placebo groups respectively but analysis was intention-to-treat. A notable feature was the trend to more patients with insulin dependent diabetes included in the placebo group (p=0.06). Two patients (2%) in the aspirin group, both having prostate surgery, suffered bleeding which required reoperation. None of the patients in the placebo group required reoperation, however this difference was not statistically significant (p=0.24). Notably, the study was not powered to evaluate bleeding complications. 90% of all patients included in the study were taking aspirin preoperatively and there is a rebound phenomenon documented whereby abrupt cessation of aspirin results in an increase in thromboxane A2 activitiy and a decrease in fibrinolysis, resulting in increased platelet adhesion and aggregation. Bearing this, and the pro-coagulant state that exists perioperatively in mind, it is unclear whether poorer outcome observed in this study maybe more associated with cessation of chronic aspirin therapy than lack of administration of aspirin in the perioperative period. Despite limitations of this study, not least of all which was the failure to substantiate the primary endpoint, it is unlikely an adequately powered RCT will be conducted in high-risk patients given the existing evidence to support perioperative aspirin therapy so assessment of bleeding potential vs cardiac risk will need to be on a case by case basis.
Take home message: The decision to cease aspirin therapy in high-risk patients having intermediate-high risk surgery should be carefully considered.
7 Perioperative fluid prescription, complications and outcomes in major elective open gastrointestinal surgery. Warrillow SJ et al. Anaesth Intensive Care. 2010 Mar;38(2):259-65.
Fluid therapy--art or science? Editorial: Duncan AW. Anaesth Intensive Care. 2010 Mar;38(2):239-40.
This observational study retrospectively assesses fluid administration and fluid balance in elderly patients undergoing major elective surgery (n=100). The authors document complications and outcomes in a cohort of patients with a relatively high incidence of co-morbidities. In contrast to recent evidence-based recommendations suggesting conservative fluid prescription (≤3L over first 24 hours), the investigators found that relatively large volumes of fluid were administered intra-operatively (median 4.2 L) and in the first 24 hours post-operatively (median 6.3 L). Overall, 32% of patients suffered a major complication including pulmonary congestion/oedema, severe sepsis, pneumonia, ileus, arrhythmias, delirium, abdominal sepsis and anastomotic leaks and additional 35% experienced a minor complication. Complications were twice as frequent in patients having non-colorectal surgery, especially anastomotic leaks, sepsis, pneumonia and pulmonary congestion. Limitations of this study include the relatively small sample size, single-centre data collection and retrospective/observational design. The accompanying editorial suggests that “anaesthetists and intensivists must apply art as well as science to adapt fluid regimens in order to optimize fluid balance for individual patients.”
Take home message: There is mounting evidence to suggest excessive perioperative fluid administration is associated, not only with cardiorespiratory complications, but also a range of general surgical complications.
For related reading: Nov 09 Journal Watch (6)
AIRWAY
Stricker PA et al. Lingual tonsil. Anesthesiology. 2010 Mar;112(3):746.
Marsland C et al. Proficient manipulation of fibreoptic bronchoscope to carina by novices on first clinical attempt after specialized bench practice. Br J Anaesth. 2010 Mar;104(3):375-81.
Broomhead RH et al. Confirmation of the ability to ventilate by facemask before administration of neuromuscular blocker: a non-instrumental piece of information? Br J Anaesth. 2010 Mar;104(3):313-7. -
Hamaekers AE et al. Achieving an adequate minute volume through a 2 mm transtracheal catheter in simulated upper airway obstruction using a modified industrial ejector. Br J Anaesth. 2010 Mar;104(3):382-6.
Xue FS et al. Re: Awake orotracheal intubation with the Bonfils fibrescope in patients with a difficult airway. Eur J Anaesthesiol. 2010 Mar;27(3):305-6.
Tsai CJ et al. A comparison of the effectiveness of dexmedetomidine versus propofol target-controlled infusion for sedation during fibreoptic nasotracheal intubation. Anaesthesia. 2010 Mar;65(3):254-9.
Xue FS et al. A simple maneuver to facilitate tracheal intubation using the Airtraq((R)) laryngoscope with a reinforced endotracheal tube. Can J Anaesth. 2010 Mar;57(3):278-279.
Bustamante S et al. Sequential rotation to insert a left double-lumen endotracheal tube using the GlideScope(R). Can J Anaesth. 2010 Mar;57(3):282-283.
GENERAL TOPICS
Reuter DA et al. Cardiac output monitoring using indicator-dilution techniques: basics, limits, and perspectives. Anesth Analg. 2010 Mar;110(3):799-811.
Wong AK et al. Preoperative Takotsubo cardiomyopathy identified in the operating room before induction of anesthesia. Anesth Analg. 2010 Mar;110(3):712-5. -
Hessel EA 2nd et al. Takotsubo (stress) cardiomyopathy and the anesthesiologist: enough case reports. Let's try to answer some specific questions! Anesth Analg. 2010 Mar;110(3):674-9.
Daly MJ et al. Takotsubo cardiomyopathy in two preoperative patients with pain. Anesth Analg. 2010 Mar;110(3):708-11.
Goins KM et al. Unexpected cardiovascular collapse from massive air embolism during endoscopic retrograde cholangiopancreatography. Acta Anaesthesiol Scand. 2010 Mar;54(3): 385-88.
Wallet F et al. Factors associated with noninvasive ventilation failure in postoperative acute respiratory insufficiency: an observational study. Eur J Anaesthesiol. 2010 Mar;27(3):270-4.
Unterbuchner C et al. The use of sugammadex in a patient with myasthenia gravis. Anaesthesia. 2010 Mar;65(3):302-5.
Sweeney BP. Neuromuscular blockade and minimal monitoring. Anaesthesia. 2010 Mar;65(3):308.
DI Marco P et al. Knowledge of residual curarization: an Italian survey. Acta Anaesthesiol Scand. 2010 Mar;54(3): 307-12.
White SM et al. Anaesthesia for proximal femoral fracture in the UK: first report from the NHS Hip Fracture Anaesthesia Network. Anaesthesia. 2010 Mar;65(3):243-8.
Weingarten TN et al. Anesthesia and myotonic dystrophy type 2: a case series. Can J Anaesth. 2010 Mar;57(3):248-55.
Babitu UQ et al. Patients' understanding of technical terms used during the pre-anaesthetic consultation. Anaesth Intensive Care. 2010 Mar;38(2):349-53.
OBSTETRICS
Butwick AJ et al. Minimum effective bolus dose of oxytocin during elective Caesarean delivery. Br J Anaesth. 2010 Mar;104(3):338-43.
Dennis A et al. Intravenous labetalol is available in Australia. Anaesth Intensive Care. 2010 Mar;38(2):397.
PAEDIATRICS
Crosby G et al. At the sharp end of spines: anesthetic effects on synaptic remodeling in the developing brain. Anesthesiology. 2010 Mar;112(3):521-3.
Briner A et al. Volatile anesthetics rapidly increase dendritic spine density in the rat medial prefrontal cortex during synaptogenesis. Anesthesiology. 2010 Mar;112(3):546-56.
Levy RJ et al. Detection of carbon monoxide during routine anesthetics in infants and children. Anesth Analg. 2010 Mar;110(3):747-53.
PAIN
Kissin I. The development of new analgesics over the past 50 years: a lack of real breakthrough drugs. Anesth Analg. 2010 Mar;110(3):780-9.
Scholz J et al. Preclinical research on persistent postsurgical pain: what we don't know, but should start studying. Anesthesiology. 2010 Mar;112(3):511-3. -
Kehlet H et al. Persistent postsurgical pain: the path forward through better design of clinical studies. Anesthesiology. 2010 Mar;112(3):514-5. -
Rappaport BA et al. ACTION on the prevention of chronic pain after surgery: public-private partnerships, the future of analgesic drug development. Anesthesiology. 2010 Mar;112(3):509-10.
Dworkin RH et al. Preventing chronic postsurgical pain: how much of a difference makes a difference? Anesthesiology. 2010 Mar;112(3):516-8.
PERIOPERATIVE MEDICINE
Killen J et al. New insulin analogues and perioperative care of patients with type 1 diabetes. Anaesth Intensive Care. 2010 Mar;38(2):244-9.
Sear JW et al. Recommendations on perioperative beta-blockers: differing guidelines: so what should the clinician do? Br J Anaesth. 2010 Mar;104(3):273-5.
Boldt J. Use of albumin: an update. Br J Anaesth. 2010 Mar;104(3):276-84
REGIONAL ANAESTHESIA
Wadhwa A et al. A simple approach to the sciatic nerve that does not require geometric calculations or multiple landmarks. Anesth Analg. 2010 Mar;110(3):958-63.
Borgeat A et al. Case scenario: neurologic complication after continuous interscalene block. Anesthesiology. 2010 Mar;112(3):742-5.
Tsui BC et al. Ultrasound imaging for regional anesthesia in infants, children, and adolescents: a review of current literature and its application in the practice of neuraxial blocks. Anesthesiology. 2010 Mar;112(3):719-28
Jlala HA et al. Effect of preoperative multimedia information on perioperative anxiety in patients undergoing procedures under regional anaesthesia. Br J Anaesth. 2010 Mar;104(3):369-74.
Groves ND et al. Effect of informational internet web pages on patients' decision-making: randomised controlled trial regarding choice of spinal or general anaesthesia for orthopaedic surgery. Anaesthesia. 2010 Mar;65(3):277-82.
Errando CL, Perez-Caballero P. Cranial subdural haematoma after spinal anaesthesia: perhaps not so rare complication. Eur J Anaesthesiol. 2010 Mar;27(3):307-8.
Harris B et al. Site marking by anaesthetists preparing for peripheral nerve blockade. Anaesthesia. 2010 Mar;65(3):312.
Cohen SP et al. Incidence and root cause analysis of wrong-site pain management procedures: a multicenter study. Anesthesiology. 2010 Mar;112(3):711-8.
Ali M et al. Prospective, randomized, controlled trial of thoracic epidural or patient-controlled opiate analgesia on perioperative quality of life. Br J Anaesth. 2010 Mar;104(3):292-7.
LITERATURE REVIEW (from non-anaesthesia journals in past 12 months)
Meyhoff CS et al; PROXI Trial Group. Effect of high perioperative oxygen fraction on surgical site infection and pulmonary complications after abdominal surgery: the PROXI randomized clinical trial. JAMA. 2009 Oct 14;302(14):1543-50.
NEUROANAESTHESIA
Wu CT et al. A comparison of 3% hypertonic saline and mannitol for brain relaxation during elective supratentorial brain tumor surgery. Anesth Analg. 2010 Mar;110(3):903-7.
TRAUMA ANAESTHESIA
Hiller J et al. A retrospective observational study examining the admission arterial to end-tidal carbon dioxide gradient in intubated major trauma patients. Anaesth Intensive Care. 2010 Mar;38(2):302-6.
Written by Maryanne Balkin, April 2010
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 2010 editions of journal watch: http://www.anaesthesiacases.com.au/cpd