How to preoxygenate in operative room: healthy subjects and situations "at risk".

Intubation is one of the most common procedures performed in operative rooms. It can be associated with life-threatening complications when difficult airway access occurs, in patients who cannot tolerate even a slight hypoxemia or when performed in patients at risk of oxygen desaturation during intubation, as obese, critically-ill and pregnant patients. To improve intubation safety, preoxygenation is a major technique, extending the duration of safe apnoea, defined as the time until a patient reaches an arterial saturation level of 88% to 90%, to allow for placement of a definitive airway. Preoxygenation consists in increasing the lung stores of oxygen, located in the functional residual capacity, and helps preventing hypoxia that may occur during intubation attempts. Obese, critically-ill and pregnant patients are especially at risk of reduced effectiveness of preoxygenation because of pathophysiological modifications (reduced functional residual capacity (FRC), increased risk of atelectasis, shunt). Three minutes tidal volume breathing or 3-8 vital capacities are recommended in general population, mostly allowing achieving a 90% end-tidal oxygen level. Recent studies have indicated that in order to maximize the value of preoxygenation (i.e, oxygenation stores) obese and critically-ill patients can benefit from the combination of breathing 100% oxygen and non-invasive positive pressure ventilation (NIV) with end-expiratory positive pressure (PEEP) in the proclive position (Trendelenburg reverse). Recruitment manoeuvres may be of interest immediately after intubation to limit the risk of lung derecruitment. Further studies are needed in the field of preoxygenation in pregnant women.

How to choose an anesthesia ventilator?

During the past few years, many manufacturers have developed a new generation anesthesia ventilators or anesthesia workstations with innovative technology and introduced so-called new ventilatory modes in the operating room. The aim of this article is to briefly explain how an anesthesia ventilator works, to describe the main differences between the technologies used, to describe the main criteria for evaluating technical and pneumatic performances and to list key elements not to be forgotten during the process of acquiring an anesthesia ventilator.

What are the main "machine dysfunctions" to know?

The incidents related to the medical devices are common during anesthesia and in intensive care unit. These incidents are rarely the cause of complications because monitoring detects them early; alternative scenarios allow bearing these problems. Although the incidence of these complications has much declined, these incidents are serious adverse events and at the origin of life-threatening complications. Improper use of medical devices is the main factor that promotes the onset of these complications. To maintain a high level of security, it is necessary to use and control procedures according to the manufacturer recommendations. This is part of a strategy involving users, biomedical engineers and manufacturers. Several actions are effective in preventing the occurrence of these incidents: the control before use, the continuation of the performance of the equipment, use based on the recommendations of the experts and manufacturers and appropriate training. This strategy is best applied by a clinical expert who has extensive technical knowledge. This expert is a key player for users learning and allows establishing and maintaining rules of use in collaboration with medical staff and biomedical engineers and manufacturers.

[Esophageal cancer surgery: evolution of pain management, hemodynamics and ventilation practices during 16 years]. / Œsophagectomie carcinologique : 16ans d'évolution des pratiques anesthésiques ventilatoires, hémodynamiques et analgésiques.

OBJECTIVE: To describe the evolution of perioperative anesthesia practices in for esophageal cancer surgery. PATIENTS AND METHODS: We conducted an observational retrospective study in a single center evaluating main perioperative practices during 16 years (1994-2009). Statistical analysis was done on 4 chronologic quartiles of same sample size. RESULTS: Two hundred and seven consecutive patients were included during the 4 periods 1994-1997 (n=52), 1997-1999 (n=52), 1999-2003 (n=52) and 2004-2009 (n=51). The main significant evolutions between the first and the fourth period were observed: (i) in ventilation: lower tidal volume (9.6[8.6-10.6] vs 7.6[7.0-8.3] mL/kg of ideal body weight (IBW), p<0.01), increased use of Positive End Expiratory Pressure (0 vs 83%, p<0.001) and increased use of post-operative non-invasive ventilation (0 vs 51%, p<0.001); (ii) in hemodynamic management: lower fluid replacement (20.6 [16.0-24.6] vs 12.6 [9.7-16.2] mL/h/kg of IBW, p<0.001); (iii) in analgesia: increased use of epidural thoracic anesthesia (31 vs 57%, p<0.001). Peroperative bleeding, type of fluid replacement, length of mechanical ventilation, length of stay in intensive care unit, ventilatory free days and mortality at day 28 didn't change. CONCLUSIONS: During these previous years, anesthesia practices in ventilation, hemodynamics and analgesia for esophageal cancer surgery have changed.

[Risk of barotrauma when using non-reinhalation Waters valves: a comparative study on bench test]. / Risque barotraumatique avec des valves de non-réinhalation de Waters: étude comparative sur banc d'essai.

OBJECTIVE: Manual ventilation is delivered in the operating room or the intensive care unit to intubated or non-intubated patients, using non-rebreathing systems such as the Waters valve. New generation Waters valves are progressively replacing the historic Waters valve. The aim of this study was to evaluate maximal pressure delivered by these 2 valves. TYPE OF STUDY: Bench test. MATERIAL AND METHOD: Thirty-two different conditions were tested, according to 2 oxygen flow rates (10 and 20L/min), without (static condition) or with manual insufflations (dynamic condition) and 4 valve expiratory opening pressures. The primary endpoint was maximal pressure measured at the exit of the valve, connected to a model lung and a bench test. RESULTS: Measured pressures were different for most evaluated conditions. Increasing oxygen flow from 10 to 20L/min increased maximal pressure for both valves. Increasing valve expiratory opening pressure induced a significant increase in maximal pressure for the new generation valve (from 4 to 61cmH2O in static conditions and from 18 to 68cmH2O in dynamic conditions). For the historic valve, maximal pressure increased significantly but remained below 15cmH2O in both static and dynamic conditions. CONCLUSION: Use of new generation Waters valves should be different from historic Waters valves. Indeed, barotrauma could be caused by badly adapted valve expiratory opening pressure settings.

A multicentre observational study of intra-operative ventilatory management during general anaesthesia: tidal volumes and relation to body weight.

We conducted an observational prospective multicenter study to describe the practices of mechanical ventilation, to determine the incidence of use of large intra-operative tidal volumes (≥10 ml.kg(-1) of ideal body weight) and to identify patient factors associated with this practice. Of the 2960 patients studied in 97 anaesthesia units from 49 hospitals, volume controlled mode was the most commonly used (85%). The mean (SD) tidal volume was 533 (82) ml; 7.7 (1.3) ml.kg(-1) (actual weight) and 8.8 (1.4) ml.kg(-1) (ideal body weight)). The lungs of 381 (18%) patients were ventilated with a tidal volume>10 ml.kg(-1) ideal body weight. Being female (OR 5.58 (95% CI 4.20-7.43)) and by logistic regression, underweight (OR 0.06 (95% CI 0.01-0.45)), overweight (OR 1.98 (95% CI 1.49-2.65)), obese (OR 5.02 (95% CI 3.51-7.16)), severely obese (OR 10.12 (95% CI 5.79-17.68)) and morbidly obese (OR 14.49 (95% CI 6.99-30.03)) were the significant (p ≤ 0.005) independent factors for the use of large tidal volumes during anaesthesia.

[ARDS and influenza A (H1N1): patients' characteristics and management in intensive care unit. A literature review]. / Grippe A (H1N1) et SDRA: caractéristiques des patients admis en réanimation et prise en charge. Revue de la littérature.

Novel influenza A (H1N1) at the origin of the 2009 pandemic flu developed mainly in subjects of less than 65 years contrary to the seasonal influenza, which usually developed in elderly patients of more than 65 years. Elderly subjects are partly protected by old meetings with close stocks. Influenza A(H1N1) can arise in serious forms within 60 to 80% of cases a fulminant acute respiratory distress syndrome (ARDS) "malignant and fulminant influenza" in subjects without any comorbidity, which makes the gravity and the fear of this influenza. The fact that this influenza A (H1N1) can develop in healthy young patients and evolve in few hours to a severe ARDS with a refractory hypoxemia gave to the foreground the possible interest of the recourse to extracorporeal oxygenation (ECMO) in some selected severe ARDS (5-10%). The first publications of patients admitted in intensive care unit (ICU) for severe influenza A (H1N1) often associated to an ARDS reported a mortality rate from 15 to 40%. This mortality variability may be explained in part by different studied populations, ARDS characteristics and human and material resources in the ICUs between the countries. Indeed, the highest mortality rates (30-40%) have been reported by in Mexico which were affected the first by pandemic flu and which were not prepared. A bacterial pneumonia was associated to H1N1 influenza in approximately 30% of the cases as at admission in ICU or following the days of the admission justifying an early antibiotherapy associated to the antiviral treatment by oseltamivir (Tamiflu). Obesity, pregnancy and respiratory diseases (asthma, COPD) seem to be associated to the development of a severe viral pneumonia due to influenza A (H1N1) often with ARDS. Older age, high APACHE II and SOFA scores and a delay of initiation of the antiviral treatment by oseltamivir are associated to higher morbidity and mortality. Other analyses of the results obtained from the first published papers included more patients and future studies would permitted to better define the role of therapeutics such as steroids and ECMO.