Incidence,characteristics and risk factors for alveolar recruitment maneuver-related hypotension in patients undergoing laparoscopic colorectal cancer resection

BACKGROUND Alveolar recruitment maneuvers(ARMs)may lead to transient hypotension,but the clinical characteristics of this induced hypotension are poorly understood.We investigated the characteristics of ARM-related hypotension in patients who underwent laparoscopic colorectal cancer resection.AIM To investigate the characteristics of ARM-related hypotension in patients who underwent laparoscopic colorectal cancer resection.METHODS This was a secondary analysis of the PROtective Ventilation using Open Lung approach Or Not trial and included 140 subjects.An ARM was repeated every 30 min during intraoperative mechanical ventilation.The primary endpoint was ARM-related hypotension,defined as a mean arterial pressure(MAP)<60 mmHg during an ARM or within 5 min after an ARM.The risk factors for hypotension were identified.The peri-ARM changes in blood pressure were analyzed for the first three ARMs(ARM_(1,2,3))and the last ARM(ARMl_(ast)).RESULTS Thirty-four subjects(24.3%)developed ARM-related hypotension.Of all 1027 ARMs,37(3.61%)induced hypotension.More ARMs under nonpneumoperitoneum(33/349,9.46%)than under pneumoperitoneum conditions(4/678,0.59%)induced hypotension(P<0.01).The incidence of hypotension was higher at ARM_(1)points than at non-ARM_(1)points(18/135,13.3%vs 19/892,2.1%;P<0.01).The median percentage decrease in the MAP at ARM1 was 14%.Age≥74 years,blood loss≥150 mL and peak inspiratory pressure under pneumoperitoneum<24 cm H_(2)O were risk factors for ARM-related hypotension.CONCLUSION When the ARM was repeated intraoperatively,a quarter of subjects developed ARM-related hypotension,but only 3.61%of ARMs induced hypotension.ARM-related hypotension most occurred in a hemodynamically unstable state or a hypovolemic state,and in elderly subjects.Fortunately,ARMs that were performed under pneumoperitoneum conditions had less impact on blood pressure.

Lung recruitment maneuver effects on respiratory mechanics and extravascular lung water index in patients with acute respiratory distress syndrome

BACKGROUND：Animal experiments showed that recruitment maneuver （RM） and protective ventilation strategy of the lung could improve oxygenation and reduce extravascular lung water. This study was to investigate the effects of RM on respiratory mechanics and extravascular lung water index （EVLWI） in patients with acute respiratory distress syndrome （ARDS）. METHODS：Thirty patients with ARDS were randomized into a RM group and a non-RM group. In the RM group, after basic mechanical ventilation stabilized for 30 minutes, RM was performed and repeated once every 12 hours for 3 days. In the non-RM group, lung protective strategy was conducted without RM. Oxygenation index （PaO2/FiO2）, peak inspiratory pressure （PIP）, Plateau pressure （Pplat）, static pulmonary compliance （Cst） and EVLWI of patients before treatment and at 12, 24, 48, 72 hours after the treatment were measured and compared between the groups. Hemodynamic changes were observed before and after RM. One-way ANOVA, Student＇s t test and Fisher＇s exact test were used to process the data. RESULTS：The levels of PaO2/FiO2 and Cst increased after treatment in the two groups, but they were higher in the RM group than in the non-RM group （P〈0.05）. The PIP and Pplat decreased after treatment in the two groups, but they were lower in the RM group than in the non-RM group （P〈0.05）. The EVLWI in the two groups showed downward trend after treatment （P〈0.05）, and the differences were signifcant at all time points （P〈0.01）; the EVLWI in the RM group was lower than that in the non-RM group at 12, 24, 48 and 72 hours （P〈0.05 or P〈0.01）. Compared with pre-RM, hemodynamics changes during RM were significantly different （P〈0.01）; compared with pre-RM, the changes were not significantly different at 120 seconds after the end of RM （P〉0.05）. CONCLUSIONS： RM could reduce EVLWI, increase oxygenation and lung compliance. The effect of RM on hemodynamics was transient.

Effect of post recruitment maneuver ventilation by different tidal volume on lung vascular endothelial diastole function in rats with acute lung injury

BACKGROUND： This study aimed to observe the effect of recruitment maneuver （RM） and post-RM ventilation at different tidal volume on lung vascular diastole endothelial function in rats with acute lung injury （ALI）.METHODS： A ALl rat model was produced by intravenous infusion of lipopolysaccharide （6 mg/ kg）. Twenty-five rats were randomly divided into five groups： control group （n=5）, ALl group （n=5）, low tidal volume group （LV group, VT 6 mL/kg, n=5）, sustained inflation （SI） with low tidal volume group （SI＋LV group, VT 6 mL/kg, n=5）, and SI with moderate tidal volume group （SI＋MV group, VT 12 mL/ kg, n=5）. RM was performed with SI, airway pressure 30 cmH2O for 30 seconds, and positive end- expiratory pressure （PEEP） was set to 5 cmH2O. Lung tissue was taken after 5 hours of mechanical ventilation. Mean arterial blood pressure （MAP） was monitored during the experiment. Endothelin-1 （ET-1）, endothelial nitricoxide synthase （eNOS）, Ach-induced endothelium-dependent relaxation response of isolated pulmonary artery rings were determined at 5 hours. RESULTS：LPS increased ET-1 level, decreased the expression of eNOS in lung tissue, impaired the Ach-induced endothelium-dependent relaxation response in the pulmonary artery, without obvious effect on systemic hemodynamics. SI＋LV significantly reduced LPS-induced elevation of ET-1 level, increased the expression of eNOS, significantly improved endothelial dysfunction, and improved the dysfunction of endothelium-dependent relaxation in the pulmonary artery. CONCLUSIONS：RM with a high or low tidal volume ventilation could improve the lung vascular endothelial function of rats with acute lung injury, and RM with low tidal volume ventilation could lower significantly the injury of lung vascular endothelial diastole function in rats with acute lung injury.

What Does a First Order Model Tell Us about PEEP Wave Maneuvers?

Patients with acute respiratory distress syndrome (ARDS) are currently treated with a lung protective ventilation strategy and the application of positive end-expiratory pressure (PEEP), sometimes in combination with recruitment maneuvers. In this study, the respiratory system elastance and airway resistance of each breath before, during and after a specific recruitment maneuver (PEEP wave maneuver) were analyzed in two patient groups, ARDS and control group. A reduction of elastance after the maneuver was observed in ARDS patients. In addition, only healthy lungs exhibited a reduction of the elastance during the course of the maneuver, while the lungs of ARDS patients didn’t show that reduction of elastance. The capability of PEEP wave maneuvers to improve lung ventilation was shown and the dynamic behavior of the elastance after the maneuver was illustrated. Healthy lungs adapt faster to changes in mechanical ventilation than the lungs of ARDS patients.

Clinical efficacy and safety of recruitment maneuver in patients with acute respiratory distress syndrome using low tidal volume ventilation： a multicenter randomized controlled clinical trial

Background The recruitment maneuver （RM） has been shown to improve oxygenation in some patients with acute respiratory distress syndrome. But there is a lack of standardization and lack of clinical studies to prove the improvement on clinical outcome. We conducted this study to evaluate the clinical efficacy and safety of the RM in patients with acute respiratory distress syndrome （ARDS） using Iow tidal volume ventilation.Methods We randomly assigned 110 patients with ARDS from 14 Chinese intensive care units （ICUs） at the tertiary teaching hospitals. Patients with PaO2 ≤200 mmHg at FiO2 1.0 and PEEP ≥10 cmH2O were included in the study.Patients were randomized into two groups： control group and RM group. The tidal volume was set to 6-8 mi per kilogram of predicted body weight （PBW） in both groups. RM was performed by continuous positive airway pressure （CPAP） of 40 cmH2O maintained for 40 seconds. RMs was conducted every eight hours for the first five days, or stopped within five days if the patient reached the weaning standard.Results One hundred and ten patients had completed the requirements for the primary study goals, 55 from the RM group and 55 control patients. Baseline characteristics remained similar in the two groups. In the RM group the PaO2/FiO2 was significantly increased compared to baseline at 120 minutes after RM on day one and day two （P=0.007and P=0.001）. There were no significant differences between the RM and control group in hospital mortality （41.8% vs.56.4%, P=0.13）, 28-day mortality （29.1% vs. 43.6%, P=0.11） and ventilator-free days at day 28 （10.8±10.1 vs. 7.4±10.0,P=0.08）. ICU mortality （32.7% vs. 52.7%, P=0.03）, the rate of survival with unassisted breathing for at least 48 consecutive hours at day 28 （58.2% vs. 36.2%, P=0.02）, and nonpulmonary organ failure-free days at day 28 （17.4±11.1vs. 13.0±12.0, P=0.03） favored the RM group. There was no significant difference in mean blood pressure and heart rate before RM and at 30, 60, 120 minutes after RM. There was no incidence of barotraumas.Conclusions RM was safe and useful for improving oxygenation in patients with ARDS who were ventilated with a low tidal volume, with a beneficial impact on their clinical outcome.

Positive End-expiratory Pressure Titration after Alveolar Flecruitment Directed by Electrical Impedance Tomography

Background： Electrical impedance tomography （EIT） is a real-time bedside monitoring tool, which can reflect dynamic regional lung ventilation. The aim of the present study was to monitor regional gas distribution in patients with acute respiratory distress syndrome （ARDS） during positive-end-expiratory pressure （PEEP） titration using EIT. Methods： Eighteen ARDS patients under mechanical ventilation in Department of Critical Care Medicine of Peking Union Medical College Hospital from January to April in 2014 were included in this prospective observational study. After recruitment maneuvers （RMs）, decremental PEEP titration was performed from 20 cmH20 to 5 cmH20 in steps of 3 cmH20 every 5-10 min. Regional over-distension and recruitment were monitored with EIT. Results： After RMs, patient with arterial blood oxygen partial pressure （PaO2） ＋ carbon dioxide partial pressure （PaCO2） 〉400 mmHg with 100% of fractional inspired oxygen concentration were defined as RM responders. Thirteen ARDS patients was diagnosed as responders whose PaO2 ＋ PaCO2, were higher than nonresponders （419 ± 44 mmHg vs. 170 ±73 mmHg, P 〈 0.0001）. In responders, PEEP mainly increased-recruited pixels in dependent regions and over-distended pixels in nondependent regions. PEEP alleviated global inhomogeneity of tidal volume and end-expiratory lung volume. PEEP levels without significant alveolar derecruitment and over-distension were identified individually. Conclusions： After RMs, PEEP titration significantly affected regional gas distribution in lung, which could be monitored with EIT. EIT has the potential to optimize PEEP titration.