Driving Pressure Is Associated with Outcome during Assisted Ventilation in Acute Respiratory Distress Syndrome.

WHAT WE ALREADY KNOW ABOUT THIS TOPIC: Higher driving pressure during controlled mechanical ventilation is known to be associated with increased mortality in patients with acute respiratory distress syndrome.Whereas patients with acute respiratory distress syndrome are initially managed with controlled mechanical ventilation, as they improve, they are transitioned to assisted ventilation. Whether higher driving pressure assessed during pressure support (assisted) ventilation can be reliably assessed and whether higher driving pressure is associated with worse outcomes in patients with acute respiratory distress syndrome has not been well studied. WHAT THIS ARTICLE TELLS US THAT IS NEW: This study shows that in the majority of adult patients with acute respiratory distress syndrome, both driving pressure and respiratory system compliance can be reliably measured during pressure support (assisted) ventilation.Higher driving pressure measured during pressure support (assisted) ventilation significantly associates with increased intensive care unit mortality, whereas peak inspiratory pressure does not.Lower respiratory system compliance also significantly associates with increased intensive care unit mortality. BACKGROUND: Driving pressure, the difference between plateau pressure and positive end-expiratory pressure (PEEP), is closely associated with increased mortality in patients with acute respiratory distress syndrome (ARDS). Although this relationship has been demonstrated during controlled mechanical ventilation, plateau pressure is often not measured during spontaneous breathing because of concerns about validity. The objective of the present study is to verify whether driving pressure and respiratory system compliance are independently associated with increased mortality during assisted ventilation (i.e., pressure support ventilation). METHODS: This is a retrospective cohort study conducted on 154 patients with ARDS in whom plateau pressure during the first three days of assisted ventilation was available. Associations between driving pressure, respiratory system compliance, and survival were assessed by univariable and multivariable analysis. In patients who underwent a computed tomography scan (n = 23) during the stage of assisted ventilation, the quantity of aerated lung was compared with respiratory system compliance measured on the same date. RESULTS: In contrast to controlled mechanical ventilation, plateau pressure during assisted ventilation was higher than the sum of PEEP and pressure support (peak pressure). Driving pressure was higher (11 [9-14] vs. 10 [8-11] cm H2O; P = 0.004); compliance was lower (40 [30-50] vs. 51 [42-61] ml · cm H2O; P < 0.001); and peak pressure was similar, in nonsurvivors versus survivors. Lower respiratory system compliance (odds ratio, 0.92 [0.88-0.96]) and higher driving pressure (odds ratio, 1.34 [1.12-1.61]) were each independently associated with increased risk of death. Respiratory system compliance was correlated with the aerated lung volume (n = 23, r = 0.69, P < 0.0001). CONCLUSIONS: In patients with ARDS, plateau pressure, driving pressure, and respiratory system compliance can be measured during assisted ventilation, and both higher driving pressure and lower compliance are associated with increased mortality.

A Calibration Technique for the Estimation of Lung Volumes in Nonintubated Subjects by Electrical Impedance Tomography.

BACKGROUND: Electrical impedance tomography (EIT) is a bedside monitoring technique of the respiratory system that measures impedance changes within the thorax. The close correlation between variations in impedance (ΔZ) and lung volumes (Vt) is known. Unless Vt is measured by an external reference (e.g., spirometry), its absolute value (in milliliters) cannot be determined; however, measurement of Vt would be useful in nonintubated subjects. OBJECTIVE: To validate a simplified and feasible calibration method of EIT, which allows estimation of Vt in nonintubated subjects. MATERIALS AND METHODS: We performed a prospective study on 13 healthy volunteers. Subjects breathed 10 times in a nonexpandable "calibration balloon" with a known volume while wearing the EIT belt. The relationship between ΔZ and the balloon volume was calculated (ΔZ/Vt). Subsequently, subjects were connected to a mechanical ventilator by a mouthpiece under different settings. Vt was calculated from EIT measurements (VtEIT) by means of the ΔZ/Vt coefficient and compared with the value obtained from the ventilator (Vtflow). RESULTS: There was a close correlation between Vtflow and VtEIT (r2 = 0.89). The fit equation was VtEIT = 0.9 × Vtflow +10.1. The highest correlation was found at positive endexpiratory pressure (PEEP) 0 (mean: VtEIT = 0.93 × Vtflow) versus PEEP 8 (mean: VtEIT = 0.8 × Vtflow), p = 0.01. No differences in the fit equation were found between pressure support ventilation (PSV) 0 and PSV 8, p = 0.50. Further analysis showed no statistically significant differences between sex, height, and BMI. CONCLUSION: A simple and fast EIT calibration technique enables reliable, noninvasive monitoring of Vt in nonintubated subjects.

Safety of anesthesia for children with mucopolysaccharidoses: A retrospective analysis of 54 patients.

BACKGROUND: Complications are common during anesthesia for patients with mucopolysaccharidoses. San Gerardo Hospital (Italy) is a reference center for mucopolysaccharidoses with a dedicated pediatric anesthesia service. AIMS: This study aims to evaluate the safety of anesthesia for mucopolysaccharidoses patients, describe their anesthetic management at our institution, and assess risk factors for complications. METHODS: The anesthetic charts of mucopolysaccharidoses patients admitted from January 1999 to December 2014 were retrospectively analyzed. We retrieved patients' demographics; location and type of the procedure; anesthetic approach airway management and occurrence of difficult intubation and complications and outcome at hospital discharge. A generalized linear mixed model was performed to assess risk factors for complications and difficult intubation. RESULTS: Fifty-four consecutive children were included. The anesthetic charts of 232 procedures (52% radio-diagnostics, 15% orthopedics, 15% ear-nose-throat surgery, 10% neurosurgery, and 8% general surgery) were analyzed. Each patient underwent a median of 4 (1-6) procedures. The median age at the first procedure was 2 (1-5), and overall age was 5 (2-8) years old. One hundred and twenty-five (54%) procedures were performed in remote locations. General anesthesia was utilized for 100 (43%) procedures. No death was recorded. Twenty-one (9%) procedures had respiratory complications. Remote location anesthesia was associated with increased risk for complications (odds ratio 5.405 [1.355-28.571], P = .016). All planned intubations (n = 65) were successful. Nineteen (29%) of those were defined difficult. All emergency intubations (n = 3) failed and were rescued by laryngeal mask airways. Older age was associated with an increased risk of difficult intubation (OR 1.200 [1.019-1.436], P = .028). CONCLUSION: Patients with mucopolysaccharidoses are at high risk for anesthesia-related complications. Remote location anesthesia is associated with increased risk for complications, and older age is associated with increased risk for difficult intubation.

Sedation and general anesthesia for patients with Cornelia De Lange syndrome: A case series.

Cornelia De Lange syndrome (CdLS) is a rare congenital disease characterized by typical facial dysmorphism, developmental disability, and limb deficiency defects. Various congenital malformations and medical complications have been described with gastroesophageal reflux as the major one. CdLS patients often require multiple high-risk anesthetic procedures. At San Gerardo Hospital (Monza, Italy) the management of CdLS patients is routinely organized through a standard protocol and a dedicated pediatric anesthesia team has been implemented. We report on a retrospective descriptive analysis of the anesthetic records of the CdLS patients admitted to San Gerardo Hospital from January 2010 to December 2015. We retrieved: demographics, genetic profiles, type of procedures, anesthetic approaches, anesthetics usage and complications. Data are reported as median (interquartile range) values. Twenty-seven patients (11 female), with age 12 (7-15) years old, weight 24 (14-35) kg, and severity score of 25 (18-32) were included. NIBPL mutations were the most frequently represented. We analyzed 58 procedures (30 esophagogastroduodenoscopies, 8 evoked auditory potential tests, 5 radiodiagnostics, 5 catheters positioning, 4 bronchoscopies) managed by sedation (36) and general anesthesia (6). Each patient underwent one (1-2) anesthetic procedure. Propofol (59%), sevoflurane (31%), fentanyl (24%), and ketamine (10%) were used. Three out of six endotracheal intubations were difficult. The only documented intraoperative complications were three episodes of desaturation (oxygen saturation <90%) occurring during sedations and were managed without the need for an invasive control of the airways. Implementation of a specific management protocol and a dedicated allowed to provide anesthesia to CdLS patients without the occurrence of major complications. © 2016 Wiley Periodicals, Inc.

Safe ECMO femoral decannulation by placement of inferior vena cava filter via internal jugular vein.

Veno-arterial extracorporeal membrane oxygenation (ECMO) is a lifesaving treatment in patients with cardiogenic shock or cardiac arrest caused by massive pulmonary embolism. In these patients, positioning an inferior vena cava filter is often advisable, especially if deep venous thrombosis is not resolved at the time of the ECMO suspension. Moreover, in ECMO patients, a high incidence of deep venous thrombosis at the site of venous cannulation has been reported, and massive pulmonary embolism following ECMO decannulation has been described. Nonetheless, an inferior vena cava filter cannot be positioned as long as an ECMO cannula is inside the inferior vena cava. Thus, we developed a strategy to allow placement of an inferior vena cava filter through the internal jugular concurrently with the removal of the femoral venous ECMO cannula. In two women supported by veno-arterial ECMO for cardiac arrest secondary to pulmonary embolism, this novel approach allowed for safe ECMO decannulation.

Extracorporeal carbon dioxide removal through ventilation of acidified dialysate: an experimental study.

BACKGROUND: Extracorporeal (EC) carbon dioxide (CO(2)) removal (ECCO(2)R) may be a powerful alternative to ventilation, possibly avoiding the need for mechanical ventilation and endotracheal intubation. We previously reported how an infusion of lactic acid before a membrane lung (ML) effectively enhances ECCO(2)R. We evaluated an innovative ECCO(2)R technique based on ventilation of acidified dialysate. METHODS: Four swine were sedated, mechanically ventilated, and connected to a venovenous dialysis circuit (blood flow, 250 ml/min). The dialysate was recirculated in a closed loop circuit including a ML (gas flow, 10 liters/min) and then returned to the dialyzer. In each animal, 4 different dialysis flows (DF) of 200, 400, 600, and 800 ml/min were evaluated with and without lactic acid infusion (2.5 mEq/min); the sequence was completed 3 times. At the end of each step, we measured the volume of CO(2)R by the ML (V(co2)ML) and collected blood and dialysate samples for gas analyses. RESULTS: Acid infusion substantially increased V(co2)ML, from 33 ± 6 ml/min to 86 ± 7 ml/min. Different DFs had little effect on V(co2)ML, which was only slightly reduced at DF 200 ml/min. The partial pressure of CO(2) of blood passing through the dialysis filter changed from 60.9 ± 3.6 to 37.1 ± 4.8 mm Hg without acidification and to 32.5 ± 5.3 mm Hg with acidification, corresponding to a pH increase of 0.18 ± 0.03 and 0.03 ± 0.04 units, respectively. CONCLUSIONS: Ventilation of acidified dialysate efficiently increased ECCO(2)R of an amount corresponding to 35% to 45% of the total CO(2) production of an adult man from a blood flow as low as 250 ml/min.