Difficult intubation and extubation in adult anaesthesia.

OBJECTIVE: To provide an update to French guidelines about "Difficult intubation and extubation in adult anaesthesia 2006". DESIGN: A consensus committee of 13 experts was convened. A formal conflict-of-interest (COI) policy was developed at the onset of the process and enforced throughout. The entire guidelines process was conducted independent of any industry funding. The authors were advised to follow the principles of the Grading of Recommendations Assessment, Development and Evaluation (GRADE) system to guide assessment of quality of evidence. The potential drawbacks of making strong recommendations in the presence of low-quality evidence were emphasized. Few recommendations were ungraded. METHODS: The panel focused on 6 questions: 1) Why must oxygen desaturation be avoided during intubation and what preoxygenation and oxygenation techniques should be used to prevent it? 2) Should videolaryngoscopes be used instead of standard laryngoscopy with or without a long stylet to achieve a better success rate of intubation after the first attempt during anticipated difficult intubation off fiberoptic intubation? 3) Should TCI or target controlled inhalation anaesthesia (TCIA) be used instead of bolus sedation for airway control in the event of suspected or proven difficulty in a patient spontaneously breathing? 4) What mode of anaesthesia should be performed in patients with difficult intubation criteria and potentially difficult mask ventilation? 5) In surgical patients, what criteria predict difficulties encountered during postoperative tracheal extubation? 6) Should decision trees and algorithms be employed to direct decision-making for the management of difficult intubation, whether foreseen or not? (based on the information from the preceding five issues). Population, intervention, comparison, and outcomes (PICO) questions were reviewed and updated as needed, and evidence profiles were generated. The analysis of the literature and the recommendations were then conducted according to the GRADE® methodology. RESULTS: The SFAR Guideline panel provided 13 statements on difficult intubation and extubation in adult anaesthesia. After two rounds of discussion and various amendments, a strong agreement was reached for 99% of recommendations. Of these recommendations, five have a high level of evidence (Grade 1±), 8 have a low level of evidence (Grade 2±). No recommendation was provided for one question. CONCLUSIONS: Substantial agreement exists among experts regarding many strong recommendations for the best care of patients with difficult intubation and extubation in adult anaesthesia.

Prospective observational study of the effect of dual antiplatelet therapy with tranexamic acid treatment on platelet function and bleeding after cardiac surgery.

BACKGROUND: The bleeding impact of dual antiplatelet therapy (DAPT), aspirin and clopidogrel, maintained until coronary artery bypass graft surgery (CABG), is still a matter of debate. The lack of preoperative antiplatelet activity measurement and heterogeneity of antifibrinolytic protocols in prior studies make the conclusions questionable. The aim of this prospective study was to determine, after preoperative antiplatelet activity measurement, if the maintenance of DAPT until CABG increases bleeding in patients treated with tranexamic acid (TA). METHODS: This observational study included 150 consecutive patients, 89 treated with aspirin and 61 treated with DAPT, undergoing a first-time planned on-pump CABG with TA treatment. Antiplatelet activity was measured with platelet aggregation tests and quantification of VASP phosphorylation. Postoperative bleeding at 24 h was recorded and propensity score analysis was performed. RESULTS: Based on VASP assay, 54% of patients showed high on-clopidogrel platelet activity inhibition. Postoperative bleeding at 24 h increased by 22% in the DAPT group, compared with the aspirin group (680 [95% CI: 360-1670] vs 558 [95%CI: 267-1270] ml, P < 0.01), consistent with increased blood transfusion (21% vs 7%, P = 0.01); a higher incidence of mediastinitis did not reach statistical significance (15% vs 4%, P = 0.05). Bleeding correlated with the extent of clopidogrel antiplatelet effect, with the best correlation for the VASP assay. CONCLUSIONS: Maintenance of DAPT until the day of CABG in patients treated with TA, increased postoperative bleeding at 24 h in parallel with preoperative antiplatelet activity induced by clopidogrel.

Rodent auditory perception: Critical band limitations and plasticity.

What do animals hear? While it remains challenging to adequately assess sensory perception in animal models, it is important to determine perceptual abilities in model systems to understand how physiological processes and plasticity relate to perception, learning, and cognition. Here we discuss hearing in rodents, reviewing previous and recent behavioral experiments querying acoustic perception in rats and mice, and examining the relation between behavioral data and electrophysiological recordings from the central auditory system. We focus on measurements of critical bands, which are psychoacoustic phenomena that seem to have a neural basis in the functional organization of the cochlea and the inferior colliculus. We then discuss how behavioral training, brain stimulation, and neuropathology impact auditory processing and perception.

[Comparison of three ventilatory modes during immediate postoperative transfer of cardiac surgical patients]. / Comparaison de trois modes ventilatoires au cours du transport postopératoire immédiat du patient opéré de chirurgie cardiaque.

OBJECTIVE: Compare three ventilatory strategies during the immediate postoperative transfer of cardiac surgical patient. STUDY DESIGN: Prospective, comparative and observational study. PATIENTS AND METHODS: After approval by our local ethical committee, 330 patients undergoing on-pump cardiac surgery were consecutively included. Patients suffering from chronic obstructive pulmonary disease, exhibiting intraoperative hypoxemia or requiring nitric oxide were excluded. The ventilatory mode was left at the discretion of the anesthesiologist and included: controlled mechanical ventilation (FiO(2)=1, N=124) or (FiO(2)=0.6, N=106), and manual ventilation using rebreathing bag (N=100). A blood gas analysis was performed immediately prior to connecting patient at ventilator at the arrival in ICU. RESULTS: The mean duration of transfer was 3.9+/-1.4 min. Invasive pressure monitoring was used in all patients. The pulse oxymetry and electrocardiogram were respectively used in 78% and 24% of patients. PaO(2) values less than 100 mmHg and those more than 300 mmHg were more frequently found in patients ventilated by rebreathing bag (42%) and mechanical ventilation FiO(2)1 (52%), respectively. No significant difference was found between groups regarding PaCO(2) values. CONCLUSION: When rebreathing bag is used for transfer in ICU, severe decrease in PaO(2) may be observed. In absence of intraoperative hypoxemia, a mechanical ventilation with FiO(2)0.6 seems to be the most suitable ventilatory strategy for such short immediate postoperative transfer.

[How to succeed at funding a research year in anaesthesiology and critical care in France?]. / Du master au post-doctorat: comment assurer le financement d'une année de recherche en anesthésie-réanimation?

Good research needs good financial support. The research fellowship is a full-time job that leaves no time for another job to pay the rent. Funding the daily-life part of the fellowship is therefore a sine qua none condition for serenity and good research. Preparing grants applications for research is a crucial step towards success. There is however a lack of easily available information for personal funding application in Anesthesiology and Critical Care research. In this review, we aimed to present the different stages of this long process, from grant application to taxes payment.

Airway management in trauma.

Maintenance of a patent and prevention of aspiration are essential for the management of the trauma patient, that requires experienced physicians in airway control techniques. Difficulties of the airway control in the trauma setting are increased by the vital failures, the risk of aspiration, the potential cervical spine injury, the combative patient, and the obvious risk of difficult tracheal intubation related to specific injury related to the trauma. Endotracheal intubation remains the gold standard in trauma patient airway management and should be performed via the oral route with a rapid sequence induction and a manual in-line stabilization maneuver, to decrease the risks previously mentioned. Different techniques to control the airway in trauma patients are presented: improvement of the laryngoscopic vision, lighted stylet tracheal intubation, retrograde technique for orotracheal intubation, the laryngeal mask and the intubating laryngeal mask airways, the combitube and cricothyroidotomy. Management of the airway in trauma patients requires regular training in these techniques and the knowledge of complementary techniques allowing tracheal intubation or oxygenation to overcome difficult intubation and to prevent major complications as hypoxemia and aspiration.

Quartz resonator signatures under Newtonian liquid loading for initial instrument check.

The quartz crystal microbalance (QCM) has been increasingly utilized in the monitoring of the deposition of thin macromolecular films. Studies in the deposition of polymers, biomaterials, and interfacial reactions under electrochemical environment are some of the conditions for the study of these material and deposition properties at a lipid interface. Numerous studies have shown the difficulties in configuring an experimental setup for the QCM such that the recorded data reflect only the behavior of the quartz crystal and its load, and not some artifact. Such artifacts for use in liquids include mounting stress, surface properties such as hydrophobicity, surface roughness coupling to loading liquids, influence of compressional waves, and even problems with the electronic circuitry including the neglect of the quartz capacitance and the hysteretic effects of electronic components. It is thought useful to obtain a simple test by which the user could make a quick initial assessment of the instrument's performance. When a smooth quartz crystal resonator is immersed from air into a Newtonian liquid, the resonance and loss characteristics of the QCM are changed. A minimum of two experimental parameters is needed to characterize these changes. One of the changes is that of the resonant frequency. The second is characterized by either a change in the equivalent circuit resistance (DeltaR) or a change in the resonance dissipation (DeltaD). Two combinations of these observables, in terms of either Deltaf and DeltaR or Deltaf and DeltaD, which we define as Newtonian signatures of S(1) and S(2), are calculated to have fixed values and to be independent of the harmonic and of the physical values of the Newtonian liquid. We have experimentally determined the values of S(1) and S(2) using three different QCM systems. These are the standard oscillator, the network analyzer, and the QCM dissipation instrument. To test the sensitivity of these signatures to surface roughness, which is potential experimental artifact, we determined the values of S(1) and S(2) for roughened crystals and found that these signatures do reflect that experimental condition. Moreover, these results were qualitatively in accord with the roughness scaling factor described by Martin.

An evaluation of capnography monitoring during the apnoea test in brain-dead patients.

BACKGROUND AND OBJECTIVE: Diagnosis of brain death usually requires the absence of spontaneous respiratory movements during the apnoea test and an arterial carbon dioxide partial pressure above 60 mmHg. On the other hand, although capnography (end-tidal CO(2)) is currently monitored in intensive care unit patients, it has not been evaluated during the apnoea test in brain-dead patients. Therefore, the aim of this prospective study was first to investigate the usefulness of capnography monitoring, and secondly to evaluate the variation of the carbon dioxide partial pressure-end-tidal CO(2) gradient during the apnoea test in clinically brain-dead patients. METHODS: After local Ethics Committee approval, 60 clinically brain-dead patients were investigated. End-tidal CO(2) was continuously recorded before, during and after the apnoea test. Arterial blood gases were sampled immediately before and after the apnoea test for calculation of the carbon dioxide partial pressure-end-tidal CO(2) gradient. RESULTS: The apnoea test was clinically positive in 58 patients, whereas end-tidal CO(2) was equal to 0 during the apnoea. During the 20-min apnoea test, carbon dioxide partial pressure increased from 40 +/- 7 to 97 +/- 19 mmHg (P < 0.001) with a rate of 2.8 +/- 0.9 mmHg min(-1), end-tidal CO(2) increased from 31 +/- 6 to 68 +/- 17 mmHg (P < 0.001) and carbon dioxide partial pressure-end-tidal CO(2) gradient increased from 9 +/- 4 to 29 +/- 10 mmHg (P < 0.001). In two patients, the apnoea test was clinically negative because of the occurrence of spontaneous respiratory movements, whereas capnography showed contemporaneously significant increases in end-tidal CO(2). CONCLUSIONS: End-tidal CO(2) should be systematically monitored and recorded, at least for medico-legal considerations, during the apnoea test in brain-dead patients. The high variability in the carbon dioxide partial pressure-end-tidal CO(2) gradient increase precludes any extrapolation of the carbon dioxide partial pressure from the end-tidal CO(2) at the end of the apnoea test.

Comparison of the effects of mepivacaine and lidocaine on rat myocardium.

BACKGROUND AND OBJECTIVE: To compare the inotropic and lusitropic effect of lidocaine and mepivacaine on rat papillary muscle. METHODS: Effects of lidocaine and mepivacaine (10-8-10-3 M) were studied in rat left ventricular papillary muscles in vitro at a calcium concentration of 1 mmol, under low (isotony) and high (isometric) loads. RESULTS: Lidocaine induced a significant negative inotropic effect in isotonic and isometric conditions whereas mepivacaine did not. Mepivacaine only induced a negative inotropic effect when added as a bolus for the highest concentration and this effect was significantly more pronounced with lidocaine than with mepivacaine (active force at 10-3 M: 63 +/- 10 vs. 84 +/- 10% of baseline, P < 0.05). Increasing calcium concentration resulted in a greater positive inotropic effect in the control (199 +/- 11% of baseline) and mepivacaine groups (197 +/- 22% of baseline) when compared to the lidocaine group (163 +/- 19% of baseline, P < 0.05 vs. lidocaine and control groups), suggesting an impairment on intracellular Ca2+ handling by lidocaine. A negative lusitropic effect under low load was observed only for mepivacaine and suggested an impairment of sarcoplasmic reticulum function. Lidocaine and mepivacaine did not modify post-rest potentiation but significantly depressed the force-frequency relationship. CONCLUSIONS: The negative inotropic and lusitropic effects induced by lidocaine were more important than that of mepivacaine and may involve an impairment of intracellular Ca2+ handling.

Effects of a loading dose of morphine before i.v. morphine titration for postoperative pain relief: a randomized, double-blind, placebo-control study.

BACKGROUND: I.V. morphine titration (MT) allows adjustment of the dose needed for pain relief in the post-anaesthesia care unit (PACU). However, MT has limitations such as a delay to achieve pain relief. We thus assessed the effect of a fixed intraoperative loading dose of morphine administered before titration. METHODS: One hundred patients who were undergoing major orthopaedic surgery were included in a double-blind, randomized study comparing a loading dose of morphine (0.15 mg kg(-1)) with placebo administered intraoperatively. MT was then administered in the PACU followed by patient-controlled analgesia (PCA) over 24 h. Data are expressed as mean (sd). RESULTS: The initial VAS [41 (36) vs 52 (35), NS] was not decreased in the morphine group. The VAS was lower in the morphine group in the PACU and PCA periods. The time to achieve effective pain relief was not decreased in the morphine group. The total dose of morphine administered in the PACU (including the loading dose) was significantly increased in the morphine group (+31% in mg kg(-1), P<0.05). Morphine requirements during the PCA period were not different between groups. The incidence of sedation was increased and a severe episode of ventilatory depression occurred in the morphine group. CONCLUSIONS: A loading dose of morphine administered at the end of surgery slightly decreased the VAS but did not reduce the time to pain relief or morphine consumption within the first 24 h. This slight improvement in analgesia was obtained at the expense of morphine-related adverse events.

Capillary aging of the contacts between glass spheres and a quartz resonator surface.

The strength of the contacts between small glass spheres and the surface of a quartz crystal resonator has been probed based on the increase of resonance frequency induced upon sphere contact. The acoustic interaction between the sphere and the plate is modeled as a low-frequency coupled resonance; the dependence of the resonant parameters on overtone order lends support to this model. After exposing the sample to humid air and drying it again, the contact strength increases at least tenfold due to capillary forces--we observe a hysteretic form of the sand-castle effect. Repeated wet-dry cycles reveal logarithmic capillary aging with time. The experiments suggest that the drying of the liquid bridges leads to a contraction of small voids in the contact zone, subsequently increasing cohesion.

Anaesthesia for carotid endarterectomy: comparison of hypnotic- and opioid-based techniques.

BACKGROUND: Although the synergistic interaction between hypnotics and opioids for total i.v. anaesthesia has been repeatedly demonstrated, questions about different dose combinations of hypnotics and opioids remain. The optimal combination would be based on maximal synergy, using the lowest dose of both drugs and having the lowest incidence of side-effects. METHODS: The major goal of this prospective randomized study was to compare two different dose combinations of propofol and remifentanil (both administered by target controlled infusion (TCI)) in respect of haemodynamics during surgery and recovery, and the need for cardiovascular treatment in the recovery room. A secondary goal was to compare pain scores (VAS) and morphine consumption in the recovery room. Anaesthesia was induced in both groups using TCI propofol, adjusted to obtain a bispectral index score (BIS) value between 40 and 60. TCI for remifentanil commenced at an initial effect-site concentration of 0.5 ng ml(-1), and was adjusted according to haemodynamics. Patients were divided into one of two groups during anaesthesia: (i). Group H, hypnotic anaesthesia (n=23), propofol effect-site concentration maintained at 2.4 microg x ml(-1); and (ii). Group O, opioid anaesthesia (n=23), propofol effect-site concentration maintained at 1.2 microg x ml(-1). In both groups, remifentanil effect-site concentration was adjusted according to haemodynamics and changes in BIS value. RESULTS: In Group O, more episodes of intraoperative hypotension (P<0.02) and hypertension (P<0.01), and fewer episodes of tachycardia were observed. More patients in Group O required nicardipine administration for postoperative hypertension (8 patients in Group H vs 15 patients in Group O, P<0.04). During recovery, morphine titration was necessary in approximately 50% of patients. No significant difference between groups was observed concerning pain scores or requirement for morphine titration. CONCLUSIONS: Maintenance of anaesthesia predominantly with propofol and a low dose of remifentanil, both administered using TCI, is associated with greater stability in perioperative haemodynamics than anaesthesia predominantly with remifentanil alone. Postoperative pain was identical in both groups of patients who underwent relatively short duration, and relatively painless surgery.

A study of the structure of polymyxin B-dipalmitoylphosphatidylglycerol complexes by vibrational spectroscopy.

The effect of the antibiotic polymyxin B on dipalmitoylphosphatidylglycerol (DPPG) bilayers has been studied by Raman and infrared spectroscopies and small-angle X-ray diffraction. Each polymyxin B molecule binds five DPPG molecules at physiological pH and induces a macroscopic phase separation of the complex rather than a lateral phase separation. Below the phase transition of DPPG/polymyxin B bilayers, the results obtained show that the intermolecular vibrational coupling is high and suggest that the acyl chains of the bound lipid are interdigitated and that the hydrophobic tail of the antibiotic does not penetrate this tight assembly. On the other hand, the phase transition of DPPG is shifted down from 41 degrees C to 37 degrees C in the complexes and remains highly cooperative. Above the phase transition of the complexes, the conformation of the acyl chains of DPPG is slightly more disordered as a result of the penetration of the polymyxin chain, but the structure of the glycerol backbone of the lipid does not seem to be affected. However, the rotational rate of the lipid appears to be restricted by the peptide.