Preoperative inspiratory muscular training to prevent postoperative hypoxemia in morbidly obese patients undergoing laparoscopic bariatric surgery. A randomized clinical trial.

BACKGROUND: Morbidly obese patients show an increased risk of postoperative hypoxemia and pulmonary complications when compared with normal weight subjects. The purpose of this study was to determine the effects of preoperative inspiratory muscular training (IMT) on postoperative arterial oxygenation in morbidly obese patients submitted to laparoscopic bariatric surgery. METHODS: Forty-four morbidly obese patients were randomly assigned to receive either preoperative usual care (control group, n = 21) or preoperative IMT (trained group, n = 23) for a month prior to the date of surgery. Data on oxygenation (PaO2/FiO2 ratio) were obtained at 1 h and at 12 h after surgery (PACU 1 h and PACU 12 h, respectively). Data on maximum static inspiratory pressure (MIP) were obtained before and after the training period, and at postanesthesia care unit (PACU) 12-h time point. RESULTS: PaO2/FiO2 was significantly higher in the trained group than in the control group, both at PACU 1 h (305.2 ± 77.6 vs. 248.8 ± 53.8, P = 0.008) and at PACU 12 h (333.5 ± 59.6 vs. 289.7 ± 79.6, P = 0.044). As a consequence, the percentage of patients with relative hypoxemia (PaO2/FiO2 lower than 300 mmHg) at the time of PACU discharge was higher in the control group (57 vs. 17 %, P: 0.006). MIP was significantly higher in the trained group compared with the control group at the preoperative time point (89.87 ± 19.00 vs. 77.00 ± 21.20 cm H2O, P = 0.04). CONCLUSIONS: Preoperative IMT improved postoperative oxygenation and increased inspiratory muscular strength in morbidly obese patients submitted to laparoscopic bariatric surgery.

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.

Myocardial oxidative stress protection by sevoflurane vs. propofol: a randomised controlled study in patients undergoing off-pump coronary artery bypass graft surgery.

CONTEXT: Myocardial oxidative stress plays an essential role in the pathogenesis of ischaemia-reperfusion injury associated with coronary artery bypass grafting (CABG). Both propofol and volatile anaesthetics have been shown to reduce reactive oxygen species in experimental and clinical studies. MAIN OBJECTIVE: To compare the influence of sevoflurane and propofol on myocardial oxidative stress markers (F2-isoprostanes and nitrates/nitrites) in coronary sinus blood samples from patients undergoing off-pump CABG. DESIGN AND SETTING: Randomised controlled clinical study of patients scheduled for off-pump CABG in a tertiary academic university hospital from June 2007 to August 2009. Forty patients consented to enrolment and were assigned to receive either propofol or sevoflurane. INTERVENTIONS: Upon completion of the proximal anastomosis, a retroplegia cannula was inserted in the coronary sinus to obtain blood samples, according to the study protocol. MAIN OUTCOME MEASURES: Markers of lipoperoxidation (F2-isoprostanes) and nitrosative stress (nitrates/nitrites) were measured in coronary sinus blood samples at three time points: after the end of the proximal anastomosis (T1), after completion of all grafts (T2) and 15 min after revascularisation (T3). RESULTS: Of the 40 recruited patients, 38 fully completed the study. In the sevoflurane group (n = 20), concentrations of oxidative stress markers in the coronary sinus remained almost constant and were significantly lower than those in the propofol group (n = 18) at all time points. F2-isoprostanes concentrations were as follows at T1: sevoflurane group 37.2 ±â€Š27.5 pg ml vs. propofol group 170.7 ±â€Š30.9 pg ml [95% confidence interval (CI) 112.16-155.08, P < 0.0001); at T2: sevoflurane group 31.94 ±â€Š24.6 pg ml vs. propofol group 171.6 ±â€Š29.7 pg ml (95% CI 119.78-159.63, P < 0.0001); and at T3: sevoflurane group 23.8 ±â€Š13.0 pg ml vs. propofol group 43.6 ±â€Š31 pg ml (95% CI 2.87-36.63, P = 0.023). CONCLUSION: In patients undergoing off-pump CABG, sevoflurane showed better antioxidative properties than propofol.

Adaptive support ventilation for gynaecological laparoscopic surgery in Trendelenburg position: bringing ICU modes of mechanical ventilation to the operating room.

BACKGROUND AND OBJECTIVE: The aim of the present study was to test the efficacy of adaptive support ventilation (ASV) to automatically adapt the ventilatory settings to the changes in the respiratory mechanics that occur during pneumoperitoneum and Trendelenburg position in gynaecological surgeries. METHODS: We prospectively studied 22 ASA I women scheduled for gynaecological laparoscopic surgery in the Trendelenburg position. After intravenous induction of general anaesthesia, patients were ventilated with ASV, a closed-loop mode of mechanical ventilation based on the Otis formula, designed to automatically adapt the ventilatory settings to changes in the patient's respiratory system mechanics, while maintaining preset minute ventilation. Respiratory mechanics variables, ventilatory setting parameters and analysis of blood gases were recorded at three time points: 5 min after induction (baseline), 15 min after pneumoperitoneum and Trendelenburg positioning (Pneumo-Trend) and 15 min after pneumoperitoneum withdrawal (final). RESULTS: A reduction of 44.4% in respiratory compliance and an increase of 29.1% in airway resistance were observed during the Pneumo-Trend period. Despite these changes in respiratory mechanics, minute ventilation was kept constant. ASV adapted the ventilatory settings by automatically increasing inspiratory pressure by 3.2 +/- 0.9 cmH(2)O (+19%), P < 0.01, respiratory rate by 1.3 +/- 0.5 breaths per minute (+9%) and the inspiratory to total time ratio (T(i)/T(tot)) by 43.3%. At final time, these parameters returned towards their baseline values. Adequate gas exchange was maintained throughout all periods. PaCO(2) increased moderately (+13%) from 4.4 +/- 0.6 (baseline) to 5.0 +/- 0.9 kPa (Pneumo-Trend), P < 0.01; and decreased slightly at final time (4.7 +/- 0.8 kPa), P < 0.05. Clinician's intervention was needed in only one patient who showed a moderate hypercapnia (PaCO(2) 6.9 kPa) during pneumoperitoneum. CONCLUSION: In healthy women undergoing gynaecologic laparoscopy, ASV automatically adapted the ventilatory settings to the changes in the respiratory mechanics, keeping constant the preset minute ventilation, providing an adequate exchange of respiratory gases and obviating clinician's interventions.

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 < or =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.