Marina Soro

The Predictive Performance of a Pharmacokinetic Model for Manually Adjusted Infusion of Liquid Sevofluorane for Use with the Anesthetic-Conserving Device (AnaConDa) : A Clinical Study

BACKGROUND: The Anesthetic-Conserving Device (AnaConDa) can be used to administer inhaled anesthetics using an intensive care unit (ICU) ventilator. We evaluated the predictive performance of a simple manually adjusted pump infusion scheme, for infusion of liquid sevoflurane to the AnaConDa. METHODS: We studied 50 ICU patients who received sevoflurane via the AnaConDa. They were randomly divided into three groups. A 6-h infusion of liquid anesthetic was adjusted according to the infusion scheme to a target end-tidal sevoflurane concentration of 1% (Group 1%, n = 15) and 1.5% (Group 1.5%, n = 15). The initial rate was adjusted to reach the target concentration in 10 min and then the infusion was reduced to the first hour maintenance rate and readjusted once each hour afterwards. The actual concentrations were measured in the breathing circuit and compared with the target values. In the third group (n = 20) we used the model to increase and decrease the target concentration (±0.3%) for 3 h and evaluated the actual change in concentration achieved. The ability of the infusion scheme to provide the target concentration was quantified by calculating the performance error (PE). Infusion scheme performance was evaluated in terms of accuracy (median absolute PE, MDAPE) and bias (median PE, MDPE). RESULTS: Performance parameters (mean ± sd, %) were for 1%, 1.5%, increase of concentration by 0.3% and decrease of concentration by 0.3% groups, respectively: MDAPE 5.3 ± 5.5, 2.6 ± 4.0, 5.0 ± 5.6, 5.5 ± 5.4; MDPE −5.3 ± 5.5, −2.3 ± 4.1, −0.1 ± 7.1, 0.2 ± 5.4. No significant differences were found between means of all performance parameters when the 1% and 1.5% groups were compared. CONCLUSIONS: There is an excellent 6-h predictive performance of a simplified pharmacokinetic model for manually adjusted infusion of liquid sevoflurane when using the AnaConDa to deliver sevoflurane to ICU patients.

Cardioprotective effect of sevoflurane and propofol during anaesthesia and the postoperative period in coronary bypass graft surgery: a double-blind randomised study.

Context Volatile anaesthetics may have direct cardioprotective properties due to effects similar to ischaemic preconditioning and postconditioning. Clinical results in cardiac surgery patients are controversial and may be related to the timing of administration of anaesthetics intraoperatively. Objective We hypothesised that the cardioprotective effect of sevoflurane in coronary bypass graft surgical patients would be greater if administration during anaesthesia continued in the ICU for at least 4 h postoperatively until weaning from mechanical ventilation. Design Double-blind, double-dummy, prospective, randomised and controlled clinical trial. Setting In a single centre between June 2006 and June 2007. Patients Seventy-five adult patients were assigned randomly to receive anaesthesia and postoperative sedation either with propofol (control, n = 37) or sevoflurane (n = 36). Interventions Myocardial biomarkers were measured before surgery, at the time of admission to the intensive care unit and at 6, 24, 48 and 72 h. The need for inotropic support, and lengths of stay in the intensive care unit and hospital were also recorded. Main outcome measures Elevation of myocardial biomarkers was the primary endpoint. The secondary endpoints were haemodynamic events and lengths of stay in the intensive care unit and hospital. Results Necrosis biomarkers increased significantly in the postoperative period in both groups with no significant differences at any time. Inotropic support was needed in 72.7 and 54.3% of patients in the propofol and sevoflurane groups, respectively (P = 0.086). There were no significant differences in haemodynamic variables, incidence of arrhythmias, myocardial ischaemia or and lengths of stay in the ICU and hospital between the two groups. Conclusion In patients undergoing coronary bypass graft surgery, continuous administration of sevoflurane as a sedative in the ICU for at least 4 h postoperatively did not yield significant improvements in the extent and time course of myocardial damage biomarkers compared to propofol.

Programming pressure support ventilation in pediatric patients in ambulatory surgery with a laryngeal mask airway

BACKGROUND:Anesthesia workstations with pressure support ventilation (PSV) are available, but there are few studies published on how to program flow-triggered PSV using a laryngeal mask airway (LMA) under general anesthesia in pediatric patients. METHODS:We studied 60 ASA I and II patients, from 2 mo to 14 yr, scheduled for ambulatory surgery under combined general and regional anesthesia with a LMA. Patients were classified according to their body weight as follows: Group A ≤10 kg, Group B 11–20 kg, and Group C >20 kg. All were ventilated in PSV using the following settings: positive end-expiratory pressure of 4 cm H2O, the minimum flow-trigger without provoking auto-triggering, and the minimum level of pressure support to obtain 10 mL/kg of tidal volume. RESULTS:The flow-trigger most frequently used in our study was 0.4 L/min, ranging from 0.2 to 0.6 L/min. We found no correlation between the flow-trigger setting and the patient’s age, weight, compliance, resistance, or respiratory rate. There was a good correlation between the level of pressure support (Group A = 15 cm H2O, Group B = 10 cm H2O and Group C = 9 cm H2O) and age (P < 0.001), weight (P < 0.001), dynamic compliance (P < 0.001), and airway resistances (P < 0.001). CONCLUSIONS:PSV with a Proseal™ LMA in outpatient pediatric anesthesia can be programmed simply using the common clinical noninvasive variables studied. However, more studies are needed to estimate the level of pressure support that may be required in other clinical situations (respiratory pathology, endotracheal tubes, or other types of surgeries) or with other anesthesia workstations.

Sevoflurane, but not propofol, reduces the lung inflammatory response and improves oxygenation in an acute respiratory distress syndrome model: a randomised laboratory study.

CONTEXT Acute respiratory distress syndrome is characterised by activation of the inflammatory cascade. The only treatment that reduces the mortality rate associated with this syndrome is lung protective ventilation, which requires sedation of patients. Sedation in critical care units is usually induced intravenously, although there is reason to believe that inhaled anaesthetics are a suitable alternative. Sevoflurane has recently been shown to modulate the lung inflammatory response in a model of lung injury more favourably than propofol. OBJECTIVE The goal of this study was to confirm whether or not sevoflurane is more effective than propofol in ameliorating the inflammatory response in an animal model of acute respiratory distress syndrome. DESIGN A prospective, randomised, controlled study. SETTING Research foundation laboratory at the Hospital Clínico Universitario, Valencia, Spain. EXPERIMENTAL ANIMALS Sixteen Landrace/large white crossbred pigs weighing 30 to 45 kg. INTERVENTIONS Animals were allocated randomly to one of two groups: one sedated with intravenous propofol 5 to 7 mg kg−1 h−1 (group P) and the other with sevoflurane, administered using an AnaConDa device to obtain an end-tidal concentration of 1.5% (group S). Monitoring, lung protective ventilation and anaesthetic management were identical in both groups. MAIN OUTCOME MEASURES The PaO2/FiO2 ratio and cytokine concentrations in bronchoalveolar lavage specimens were determined at 10, 150 and 240 min after confirmation of acute respiratory distress syndrome (PaO2/FiO2 <26.7 kPa). RESULTS At 240 min, median and interquartile range (IQR) concentrations of cytokines in bronchial lavage specimens in group S were lower than those in group P [interleukin-1&bgr; (IL-1&bgr;) 53, IQR 16–140 vs. 311, IQR 183–637 pg ml−1, P = 0.04; tumour necrosis factor-&agr; 347, IQR 161–433 vs. 552, IQR 475–649 pg ml−1, P = 0.04; and IL-6 101, IQR 76–282 vs. 580, IQR 369–701 pg ml−1, P = 0.03]. The polymorphonuclear neutrophil count was also lower in group S (P = 0.007), which also had a higher PaO2/FiO2 ratio. TRIAL REGISTRATION GE-015/09. CONCLUSION In an animal model of acute respiratory distress syndrome, sevoflurane ameliorates the lung inflammatory response and improves oxygenation to a greater extent than propofol.

Low-flow anesthesia and reduced animal size increase carboxyhemoglobin levels in swine during desflurane and isoflurane breakdown in dried soda lime.

UNLABELLED After institutional approval, we studied the effect of animal size, anesthetic concentration, and fresh gas flow (FGF) rate on inspired carbon monoxide (CO) and carboxyhemoglobin (COHb) during anesthesia in swine, using soda lime previously dried to 1 +/- 0.1% water content. To ascertain the effect of anesthesia, eight adult pigs were anesthetized with either 1 minimum alveolar anesthetic concentration (MAC) desflurane or isoflurane and, to characterize the effect of the FGF rate, it was doubled in four pigs. To determine the effect of animal size, four small and four large pigs received 1 MAC desflurane or isoflurane, and to determine the effect of the anesthetic concentration, a group of four swine was exposed to 0.5 MAC. CO and COHb concentrations were larger with desflurane (5500 +/- 980 ppm and 57.90% +/- 0.50%, respectively) than with isoflurane (800 ppm and 17.8% +/- 2.14%, respectively), especially in the small animals. Increasing the FGF rate significantly reduced peak CO and COHb concentrations resulting from both anesthetics; however, when each anesthetic was reduced to 0.5 MAC, the concentrations obtained were similar. We conclude that CO intoxication is more severe with desflurane than with isoflurane, that small animals are at higher risk for CO poisoning, and that low FGF can increase COHb concentrations. IMPLICATIONS The present study shows that the use of desflurane with desiccated carbon dioxide absorbents in pediatric anesthesia can produce a dangerous carbon dioxide intoxication, especially with low-flow anesthesia.

Rationale and study design for an individualized perioperative open lung ventilatory strategy (iPROVE): study protocol for a randomized controlled trial

BackgroundPostoperative pulmonary and non-pulmonary complications are common problems that increase morbidity and mortality in surgical patients, even though the incidence has decreased with the increased use of protective lung ventilation strategies. Previous trials have focused on standard strategies in the intraoperative or postoperative period, but without personalizing these strategies to suit the needs of each individual patient and without considering both these periods as a global perioperative lung-protective approach. The trial presented here aims at comparing postoperative complications when using an individualized ventilatory management strategy in the intraoperative and immediate postoperative periods with those when using a standard protective ventilation strategy in patients scheduled for major abdominal surgery.MethodsThis is a comparative, prospective, multicenter, randomized, and controlled, four-arm trial that will include 1012 patients with an intermediate or high risk for postoperative pulmonary complications. The patients will be divided into four groups: (1) individualized perioperative group: intra- and postoperative individualized strategy; (2) intraoperative individualized strategy + postoperative continuous positive airway pressure (CPAP); (3) intraoperative standard ventilation + postoperative CPAP; (4) intra- and postoperative standard strategy (conventional strategy). The primary outcome is a composite analysis of postoperative complications.DiscussionThe Individualized Perioperative Open-lung Ventilatory Strategy (iPROVE) is the first multicenter, randomized, and controlled trial to investigate whether an individualized perioperative approach prevents postoperative pulmonary complications.Trial registrationRegistered on 5 June 2014 with identification no. NCT02158923.

The accuracy of the anesthetic conserving device (AnaConDa©) as an alternative to the classical vaporizer in anesthesia.

BACKGROUND: The Anesthetic Conserving Device—AnaConDa® (ACD)—has been compared with a conventional vaporizer. However, the accuracy of the administered concentration of volatile anesthetics was not examined. In the present study we measured the accuracy of the ACD when used as a portable vaporizer. METHODS: This prospective study included 30 ASA I–III patients scheduled for elective surgery under general anesthesia. The patients were randomly organized into 3 groups of 10 patients per group. In each group, the sevoflurane infusion rate was adjusted to deliver 1.0 vol%, 1.5 vol%, and 2.0 vol% alveolar concentration. Hemodynamic data, bispectral index, and end-tidal sevoflurane concentrations were recorded every 2 minutes. RESULTS: We analyzed 801 data points from 30 patients. The mean difference between the end-tidal sevoflurane concentration and the target concentration was −11.0 ± 9.3% of the target when the target was 1.0 vol%, −5.4 ± 6.4% when the target was 1.5 vol%, and −4.0 ± 7.4% when the target was 2.0 vol%. No significant differences were found in the error at the different target concentrations. CONCLUSIONS: We found that the ACD may be a valid alternative to the conventional vaporizer. The ACD is very simple to use, delivery rate needs to be adjusted only once per hour, and the anesthetic savings are independent of the circuit characteristics and fresh gas flow rate.

effects of prone position on alveolar dead space and gas exchange during general anaesthesia in surgery of long duration

Background and objective: We investigated the effects of prone position on respiratory dead space and gas exchange in 14 anaesthetized healthy patients undergoing elective posterior spinal surgery of more than 3 h of duration. Methods: The patients received a total intravenous anaesthetic with propofol/remifentanil/cisatracurium. They were ventilated at a tidal volume of 8–10 mL kg−1, zero positive end‐expiratory pressure and an inspired oxygen fraction of 0.4. Physiological, airway and alveolar dead spaces were calculated by analysis of the volumetric capnography waveform. Measurements were made in supine position (20 min after the beginning of mechanical ventilation) and 30, 120 and 180 min after turning to prone position. Results: We found that the alveolar dead space/tidal volume ratio did not change. PaO2/FiO2 increased, although not statistically significantly. Dynamic compliance was reduced due to a reduction in tidal volume and an increase in plateau pressure. Conclusions: Patients undergoing surgery in prone position for a duration of 3 h under general anaesthesia including muscle relaxation and mechanical ventilation without positive end‐expiratory pressure have stable haemodynamics and no significant changes in the alveolar dead space to tidal volume ratio. Oxygenation tended to improve.

Protection strategies during cardiopulmonary bypass: ventilation, anesthetics and oxygen.

Purpose of review To provide an update of research findings regarding the protection strategies utilized for patients undergoing cardiopulmonary bypass (CPB), including perioperative ventilatory strategies, different anesthetic regimens, and inspiratory oxygen fraction. The article will review and comment on some of the most important findings in this field to provide a global view of strategies that may improve patient outcomes by reducing inflammation. Recent findings Postoperative complications are directly related to ischemia and inflammation. The application of lung-protective ventilation with lower tidal volumes and higher positive end-expiratory pressure reduces inflammation, thereby reducing postoperative pulmonary complications. Although inhalation anesthesia has clear cardioprotective effects compared with intravenous anesthesia, several factors can interfere to reduce cardioprotection. Hyperoxia up to 0.8 FiO2 may confer benefits without increasing oxidative stress or postoperative pulmonary complications. During the early postoperative period, inhalation anesthesia prior to extubation and the application of preventive noninvasive ventilation may reduce cardiac and pulmonary complications, improving patients’ outcomes. Summary Lung-protective mechanical ventilation, inhalation anesthesia, and high FiO2 have the potential to reduce postoperative complications in patients undergoing CPB; however, larger, well powered, randomized control trials are still needed.

WHO Needs High FIO2

World Health Organization and the United States Center for Disease Control have recently recommended the use of 0.8 FIO2 in all adult surgical patients undergoing general anaesthesia, to prevent surgical site infections. This recommendation has arisen several discussions: As a matter of fact, there are numerous studies with different results about the effect of FIO2 on surgical site infection. Moreover, the clinical effects of FIO2 are not limited to infection control. We asked some prominent authors about their comments regarding the recent recommendations.