1. Minimally invasive cardiac output monitoring in the perioperative setting. Anesth Analg. 2009 Mar;108(3):887-97. [Abstract]
Minimally invasive CO monitoring appears to be a topical issue with the increasing popularity of ‘goal directed fluid therapy’. The article discusses the principles and limitations of 5 methods of “non-invasive” measurement of CO: oesophageal Doppler-deltexa, hemosonic, pulse contour analysis-FloTrac, PiCCO (requires CVC+central arterial line), indicator/lithium dilution-LiDCO (also uses pulse contour analysis), thoracic bioimpedence-bioZ and partial non-rebreathing systems/Fick principle-NICO. It becomes obvious that some methods have more evidence of reliability and accuracy behind them and some are not truly ‘non-invasive’. The article emphasizes the sensitivity of SV & CO when compared with arterial BP and HR as measures of adequate intravascular volume status.
Take home message: The author states that the oesophageal Doppler and arterial pulse contour devices seem to have the greatest potential at replacing the PAC for CO measurement in the OR.
Further reading about this topic this month: Editorial: Goal-directed perioperative fluid management: why, when, and how? Anesthesiology. 2009 Mar;110(3):453-5 [Article]
2. Risk associated with preoperative anemia in noncardiac surgery: a single-center cohort study. Anesthesiology. 2009 Mar;110(3):574-81. [Article]
This is a retrospective observational study of 7,759 patients. Patients for this study were selected from an acute pain database, including patients receiving PCA and epidurals, so it only considered patients having major surgery. This may explain the very high incidence of preoperative anaemia: 39.5% for men & 39.9% for women. The analysis used both logistic regression and propensity score analyses to adjust for perioperative confounders, including RBC transfusions, and it found that anaemia was associated with more than two-fold greater odds of dying within 90 days of surgery.
Take home message: Anaemia is independently associated with increased mortality in this study, however it is possible that preoperative anaemia was associated with adverse outcomes simply because it is a marker of severity of illness. However, this study does add to the body of evidence that suggest anaemia and its treatment with allogeneic blood transfusion contribute to morbidity & mortality.
For further reading about this topic this month: Perioperative management of acute and chronic anemia: has the pendulum swung too far? Can J Anaesth. 2009 Mar;56(3):183-189
3. Noninfectious serious hazards of transfusion. Anesth Analg. 2009 Mar;108(3):759-69.
This review of non-infectious serious hazards of transfusion (NISHOTs) divides NISHOTS into immune (haemolytic transfusion reactions-febrile or not, allergic reactions, TRALI, PTP, GVHD, TRIM, alloimmunisation & michochimerism) and non-immune mediated (all potential Cx of massive transfusion +sepsis, mistransfusion, ‘old’ blood storage lesions). Studies suggest that transfusions are rarely beneficial for Hb≥10 g/dL and are generally indicated for Hb≤7 g/dL. Multiple factors must be considered when transfusing patients with Hbs between 7-10 g/dL including individual patient factors, NISHOTs, infectious complications, blood supply issues and other cost/benefit analyses.
Take home message: It is becoming increasingly relevant to conduct a thorough risk-benefit analysis for every transfusion we authorize, so it is important to remember that current evidence shows a patient is up to 1000-fold more likely to experience a NISHOT than an infectious complication of transfusion.
4. Perioperative management of antiplatelet agents in noncardiac surgery. Eur J Anaesthesiol. 2009 Mar;26(3):181-7.
This article gives a brief overview of the impact of antiplatelet Rx on surgery & anaesthesia. The first part discusses available antiplatelet drugs: ADP receptor antagonists-thienopyridines, glycoprotein IIb/IIIa receptor antagonists, agents that increase intraplatelet levels of cAMP and COX-1 inhibitors. The second part discusses the perioperative impact of these agents and assessment of risk of thrombosis vs haemorrhagic risk in relation to cardiac stents, neuraxial anaesthesia, ambulatory surgery & emergency surgery.
Take home message: When considering administration of perioperative antiplatelet therapy in the elective setting, consideration must be given to the likelihood of thrombosis vs potential for haemorrhage, and consequences of such.
5.Video and optic laryngoscopy assisted tracheal intubation - the new era. Anaesth Intensive Care. 2009 Mar;37(2):219-233.
This review gives a brief summary of several well established videolaryngoscopes including the glidescope, the McGrath, the Pentax Airway Scope and an optic laryngoscope, the airtraq. It also gives information about FOB, the CTrach and Bonfils fiberscope. Unfortunately the review is lacking in a detailed critical analysis of the available evidence pertaining to usefulness of these devices in clinical practice.
Take home message: Current evidence suggest videolaryngoscopes are likely to become standard equipment for the difficult intubation trolley in the future, as they already are in many parts of the world.
For further reading about this topic this month: The ASA difficult airway algorithm: is it time to include video laryngoscopy and discourage blind and multiple intubation attempts in the nonemergency pathway? Anesth Analg. 2009 Mar;108(3):1052 Intubation difficulties in obese patients. Anesth Analg. 2009 Mar;108(3):1051; author reply 1051-2 Videolaryngoscopy in the management of the difficult airway: a comparison with the Macintosh blade. Eur J Anaesthesiol. 2009 Mar;26(3):218-22.
6. The effect of residual neuromuscular blockade on the speed of reversal with sugammadex. Anesth Analg. 2009 Mar;108(3):846-51.
Editorial: Patient safety revisited: reliability is paramount. Anesth Analg. 2009 Mar;108(3):702-3
This article presents data from post hoc analysis of multicentre observational study. The results indicate that, despite the fact that patients received sugammadex 4 mg/kg at least 15 mins after the last dose of rocuronium, sugammadex only completely reversed neuromuscular blockade in ≤5mins in 84% of patients NB: this is the dose recommended by the manufacturer for this level of block. Time to reversal was quicker in patients with ≥1 twitch vs patients with 0 twitches on TOF. The range for reversal in the 0 twitch group was 0.8-22.3 minutes. The discussion emphasizes the requirement for the manufacturers to perform additional comparative studies to establish the benefits of sugammadex over neostigmine-glycopyrrolate with respect to clinically meaningful outcome variables.
Take home message: This study indicates response to sugammadex in this dose range can be unreliable. As stated by Brull in the editorial: for any drug data, including sugammadex, it is critical for the clinician to note the variability (range) of responses to drugs, not just the mean data.
For further reading about this topic this month- A collection of comprehensive articles relating to neuromuscular blockade, reversal of blockade and monitoring of blockade have been published in a supplement to the March edition of Anaesthesia. In addition providing a wealth of up to date information, the supplement is definitely intended to provide promotional material for sugammadex. Notably, the US FDA issued a non-approvable letter to Schering-Plough for sugammadex in August 2008. Articles worth reading include: Antagonism of non-depolarising neuromuscular block: current practice. Anaesthesia. 2009 Mar;64 Suppl 1:22-30. Sugammadex in clinical practice. Anaesthesia. 2009 Mar;64 Suppl 1:45-54. Monitoring neuromuscular block: an update. Anaesthesia. 2009 Mar;64 Suppl 1:82
7. A comparison of propofol and remifentanil target-controlled infusions to facilitate fiberoptic nasotracheal intubation. Anesth Analg. 2009 Mar;108(3):852-
Editorial: Opioid or propofol: what kind of drug for what kind of sedation? Manual dosing or target-controlled infusion? Anesth Analg. 2009 Mar;108(3):704-6.
There seems to be as many ways to sedate a patient for awake FOB as there are anaesthetists. This RCT (n=60), is interesting in that it describes a protocol for safe sedation of 59/60 patients using single agent therapy (either remi or propofol) by aiming for stable effect site concentrations. Notably, the final target conc’n (Schnider) for propofol was 3.9+/-1.4 mcg/ml ie. borderline general anaesthesia. The final remi conc’n was 2.4+/-0.8 ng/mL. Only catch is that the remifentanil option requires remifentanil (Minto) TCI. Oversedation was less of a problem and recall was higher when remifentanil was used.
Take home message: For awake FOB (a noxious & stimulating procedure), both remifentanil and propofol TCI monotherapy can be rapidly titrated to achieve good intubating conditions and patient comfort but remifentanil allows for more patient cooperation making it safer when spontaneous ventilation is paramount.
8. Effect of epidural analgesia in patients with traumatic rib fractures: a systematic review and meta-analysis of randomized controlled trials. Can J Anaesth. 2009 Mar;56(3):230-242
A metanalysis of RCTs looking at the effect of epidural analgesia in patients with traumatic rib fractures. Unfortunately only eight studies met eligibility criteria (n=232), which limits the study’s statistical power. The conclusions were that epidural analgesia did not significantly affect mortality, ICU LOS, hospital LOS & duration of mechanical ventilation was only decreased if epidurals not using LA were excluded. Hypotension was significantly associated with use of thoracic epidural analgesia with LA.
Take home message: There is no level 1 evidence currently available to suggest patients with traumatic rib fractures have a better outcome with epidural analgesia.
9. Editorial: British consensus guidelines on intravenous fluid therapy for adult surgical patients (GIFTASUP)-Cassandra’s view. Anaesthesia. 2009 Mar;64 (3):235-238.
GIFTASUP are guidelines recently published in the UK and are intended to improve perioperative fluid prescribing. This editorial states that the guidelines should be mandatory reading for anyone involved in fluid management and that the guidelines are extensive, informative and have an excellent bibliography of references. However, it is critical of the assessment of levels of evidence used and feels that it results in a dissociation between the recommendations and the evidence and provides and illusion of knowledge and certainty where little exists.
Link to guidelines: http://www.ics.ac.uk/downloads/2008112340_GIFTASUP%20FINAL_31-10-08.pdf
Summary: http://journal.ics.ac.uk/pdf/1001013.pdf
Take home message: GIFTASUP contains a wealth of selected information relating to perioperative fluid management, but it may be prudent to take the recommendations as suggestions and realize that much of the evidence base may be limited the level of expert opinion.
10. Diagnosing metabolic acidosis in the critically ill: bridging the anion gap, Stewart, and base excess methods. Can J Anaesth. 2009 Mar;56(3):247-256.
This is a great article for anyone who is interested in critical care acid-base derangements, but has been overwhelmed by the confusing explanation of the Stewart physicochemical approach to metabolic acidosis available in textbooks. It offers simple equations that claim to reliably identify multiple complex acid-base derangements. The author also emphasizes the fact that a metabolic acidosis due to unmeasured anions is a predictor of mortality.
Take home message: When attempting to interpret complex metabolic acid-base derangements, the modified base excess approach may best combine the ease of use with clinical effectiveness while staying true to the principles of acid-base physiology.
11. Intraoperative fraction of inspired oxygen is a modifiable risk factor for surgical site infection after spinal surgery. Anesthesiology. 2009 Mar;110(3):556-62.
This is a small (n=104), retrospective case-control study. Cases & controls were not matched for any criteria, so the study has some obvious limitations. However, after multivariate analysis, administration of FiO2 less than 50% had the strongest association with SSI followed by ASA≥3, prolonged procedure duration, obesity, razor shave before surgery, posterior approach, lumbar-sacra operative level & instrumentation.
Take home message: An FiO2 >50% is a simple and low cost intervention for spinal surgery that is associated with a decreased risk of surgical site infection in this study.
12. Practice advisory on anesthetic care for magnetic resonance imaging: a report by the Society of Anesthesiologists Task Force on Anesthetic Care for Magnetic Resonance Imaging. Anesthesiology. 2009 Mar;110(3):459-79. [Article]
This is a practice advisory intended to assist anaesthesia related decision making in the MRI suite. It emphasizes the importance of having pre-procedure screening for patient and personnel, as well as having a detailed plan that includes: compatible monitoring, airway management, inhalational vs intravenous anaesthesia, positioning of patient/anaesthetist/equipment and management of emergencies either with the patient or the magnet (projectile, quench, fire).
Take home message: The MRI suite is a hazardous place to conduct anaesthesia due to direct and indirect effects of the strong magnetic field present. Hazards include noise, heating, potential for projectiles, medically unstable patients and limitations in compatible anaesthesia equipment/monitoring as well as availability of emergency assistance.
Other articles of potential specific interest:
Ultrasound guidance compared with electrical
neurostimulation for peripheral nerve block: a systematic review
and meta-analysis of randomized controlled trials. Br J
Anaesth. 2009 Mar;102(3):408-17.
Cardiac surgery in the parturient. Anesth Analg. 2009 Mar;108(3):777-85.
Editorial: Is fast-track cardiac anesthesia now the global standard of care? Anesth Analg. 2009 Mar;108(3):689-91.
Patient sex an its influence on general anaesthesia. Anaesth Intensive Care. 2009 Mar;37(2):207-218. Transfusion-related acute lung injury: current concepts for the clinician. Anesth Analg. 2009 Mar;108(3):770-6.
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