Measurement of alveolar derecruitment in patients with acute lung injury: computerized tomography versus pressure–volume curve

INTRODUCTION: Positive end-expiratory pressure (PEEP)-induced lung derecruitment can be assessed by a pressure–volume (P–V) curve method or by lung computed tomography (CT). However, only the first method can be used at the bedside. The aim of the study was to compare both methods for assessing alveolar derecruitment after the removal of PEEP in patients with acute lung injury or acute respiratory distress syndrome. METHODS: P–V curves (constant-flow method) and spiral CT scans of the whole lung were performed at PEEPs of 15 and 0 cmH(2)O in 19 patients with acute lung injury or acute respiratory distress syndrome. Alveolar derecruitment was defined as the difference in lung volume measured at an airway pressure of 15 cmH(2)O on P–V curves performed at PEEPs of 15 and 0 cmH(2)O, and as the difference in the CT volume of gas present in poorly aerated and nonaerated lung regions at PEEPs of 15 and 0 cmH(2)O. RESULTS: Alveolar derecruitments measured by the CT and P–V curve methods were 373 ± 250 and 345 ± 208 ml (p = 0.14), respectively. Measurements by both methods were tightly correlated (R = 0.82, p < 0.0001). The derecruited volume measured by the P–V curve method had a bias of -14 ml and limits of agreement of between -158 and +130 ml in comparison with the average derecruited volume of the CT and P–V curve methods. CONCLUSION: Alveolar derecruitment measured by the CT and P–V curve methods are tightly correlated. However, the large limits of agreement indicate that the P–V curve and the CT method are not interchangeable

Low spatial resolution computed tomography underestimates lung overinflation resulting from positive pressure ventilation

Objective: In acute lung injury, lung overinflation resulting from mechanical ventilation with positive end-expiratory pressure (PEEP) can be assessed using lung computed tomography. The goal of this study was to compare lung overinflation measured on low and high spatial resolution computed tomography sections. Design: Lung overinflation was measured on thick (10-mm) and thin (1.5-mm) computed tomography sections obtained at zero end-expiratory pressure (ZEEP) and PEEP 10 cm H2O using a software including a color-coding system. Setting: A 20-bed surgical intensive care unit of a university hospital. Patients: Thirty mechanically ventilated patients with acute lung injury. Interventions: None. Measurements and Main Results: Overinflated lung volume was measured as the end-expiratory volume of lung regions with computed tomography attenuations < 900 Hounsfield units. Lung overinflation, expressed in percentage of the total lung volume, was significantly underestimated by thick computed tomography sections compared with thin computed tomography sections (0.4 1.6% vs. 3.0 4.0% in ZEEP and 1.9 4% vs. 6.8 7.3% in PEEP, p < .01). In patients with a diffuse loss of aeration, the overinflated lung volumes of thick and thin computed tomography sections were, respectively, 0.6 0.8 mL vs. 16 10 mL in ZEEP (p < .01) and 8 9 mL vs. 73 62 mL in PEEP (p < .05). In patients with a focal loss of aeration, this underestimation was more pronounced: 18 56 mL vs. 127 140 mL in ZEEP (p < .01) and 85 161 mL vs. 322 292 mL in PEEP (p < .01). Conclusions: In patients with acute lung injury, an accurate computed tomography estimation of lung overinflation resulting from positive pressure mechanical ventilation requires high spatial resolution computed tomography sections, particularly when the lung morphology shows a focal loss of aeration. (Crit Care Med 2005; 33:741–749

Co-infection with influenza-associated acute respiratory distress syndrome requiring extracorporeal membrane oxygenation

International audienceCo-infection frequency and impact among influenza-associated acute respiratory distress syndrome (ARDS) patients requiring extracorporeal membrane oxygenation (ECMO) are not known. This retrospective, observational analysis concerned data prospectively collected from patients admitted to our medical intensive care unit (ICU) who received ECMO support for influenza-associated ARDS between 2009 and 2016. Co-infection was defined as occurring within 48 hours following ICU admission. Among the 77 ARDS patients requiring ECMO support, 39 (51%) developed co-infections, with Staphylococcus aureus (18 (46%) of the co-infected) being the most prevalent pathogen. Panton–Valentin leukocidin (PVL)-producing S. aureus was isolated from ten patients (56% of S. aureus co-infections and 26% of all co-infections). Except for body mass index, initial disease severity and antibiotic treatment prior to admission, patients with co-infection were comparable to those without. Co-infection was associated with higher in-ICU mortality (62% vs. 29% without; p=0.006), and, on day 60, (median [interquartile range]) fewer ECMO-free days (0 [0–19] vs. 23 [0–46]; p=0.004) and fewer mechanical ventilation-free days (0 [0–0] vs. 6 [0–35]; p=0.003). Multivariable analyses retained age >49 years, pre-ECMO Simplified Acute Physiology Score II >70 and co-infection as independent predictors of hospital mortality. In conclusion, co-infection is frequent in ECMO-treated patients with influenza-associated ARDS, affecting ~50% of them, and is independently associated with poor outcome. S. aureus was the most frequently identified pathogen, with a high rate of PVL-positive S. aureus. Whether specific therapy targeting PVL-producing S. aureus should be given remains to be determined

Prone positioning monitored by electrical impedance tomography in patients with severe acute respiratory distress syndrome on veno-venous ECMO

International audienceBackground: Prone positioning (PP) during veno-venous ECMO is feasible, but its physiological effects have never been thoroughly evaluated. Our objectives were to describe, through electrical impedance tomography (EIT), the impact of PP on global and regional ventilation, and optimal PEEP level.Methods: A monocentric study conducted on ECMO-supported severe ARDS patients, ventilated in pressure-controlled mode, with 14-cmH2O driving pressure and EIT-based "optimal PEEP". Before, during and after a 16-h PP session, EIT-based distribution and variation of tidal impedance, VTdorsal/VTglobal ratio, end-expiratory lung impedance (EELI) and static compliance were collected. Subgroup analyses were performed in patients who increased their static compliance by ≥ 3 mL/cmH2O after 16 h of PP.Results: For all patients (n = 21), tidal volume and EELI were redistributed from ventral to dorsal regions during PP. EIT-based optimal PEEP was significantly lower in PP than in supine position. Median (IQR) optimal PEEP decreased from 14 (12-16) to 10 (8-14) cmH2O. Thirteen (62%) patients increased their static compliance by ≥ 3 mL/cmH2O after PP on ECMO. This subgroup had higher body mass index, more frequent viral pneumonia, shorter ECMO duration, and lower baseline VTdorsal/VTglobal ratio than patients with compliance ≤ 3 mL/cmH2O (P < 0.01).Conclusion: Although baseline tidal volume distribution on EIT may predict static compliance improvement after PP on ECMO, our results support physiological benefits of PP in all ECMO patients, by modifying lung mechanics and potentially reducing VILI. Further studies, including a randomized-controlled trial, are now warranted to confirm potential PP benefits during ECMO

Life-threatening massive pulmonary embolism rescued by venoarterial-extracorporeal membrane oxygenation

Abstract Background Despite quick implementation of reperfusion therapies, a few patients with high-risk, acute, massive, pulmonary embolism (PE) remain highly hemodynamically unstable. Others have absolute contraindication to receive reperfusion therapies. Venoarterial-extracorporeal membrane oxygenation (VA-ECMO) might lower their right ventricular overload, improve hemodynamic status, and restore tissue oxygenation. Methods ECMO-related complications and 90-day mortality were analyzed for 17 highly unstable, ECMO-treated, massive PE patients admitted to a tertiary-care center (2006–2015). Hospital- discharge survivors were assessed for long-term health-related quality of life. A systematic review of this topic was also conducted. Results Seventeen high-risk PE patients [median age 51 (range 18–70) years, Simplified Acute Physiology Score II (SAPS II) 78 (45–95)] were placed on VA-ECMO for 4 (1–12) days. Among 15 (82%) patients with pre-ECMO cardiac arrest, seven (41%) were cannulated during cardiopulmonary resuscitation, and eight (47%) underwent pre-ECMO thrombolysis. Pre-ECMO median blood pressure, pH, and blood lactate were, respectively: 42 (0–106) mmHg, 6.99 (6.54–7.37) and 13 (4–19) mmol/L. Ninety-day survival was 47%. Fifteen (88%) patients suffered in-ICU severe hemorrhages with no impact on survival. Like other ECMO-treated patients, ours reported limitations of all physical domains but preserved mental health 19 (4–69) months post-ICU discharge. Conclusions VA-ECMO could be a lifesaving rescue therapy for patients with high-risk, acute, massive PE when thrombolytic therapy fails or the patient is too sick to benefit from surgical thrombectomy. Because heparin-induced clot dissolution and spontaneous fibrinolysis allows ECMO weaning within several days, future studies should investigate whether VA-ECMO should be the sole therapy or completed by additional mechanical clot-removal therapies in this setting

Ischemic and hemorrhagic brain injury during venoarterial-extracorporeal membrane oxygenation

Abstract Background Structural neurological complications (ischemic stroke and intracranial bleeding) and their risk factors in patients receiving venoarterial-extracorporeal membrane oxygenation (VA-ECMO) are poorly described. Our objective was to describe frequencies, outcomes and risk factors for neurological complications (ischemic stroke and intracranial bleeding) in patients receiving VA-ECMO. Methods Retrospective observational study conducted, from 2006 to 2014, in a tertiary referral center on patients who developed a neurological complication(s) on VA-ECMO. Results Among 878 VA-ECMO-treated patients, 65 (7.4%) developed an ECMO-related brain injury: 42 (5.3%) ischemic strokes and 20 (2.8%) intracranial bleeding, occurring after a median [25th;75th percentile] of 11 [6;18] and 5 [2;9] days of support, respectively. Intracranial bleeding but not ischemic stroke was associated with higher mortality. Multivariable analysis retained only platelet level > 350 giga/L as being associated with ischemic stroke. Female sex, central VA-ECMO and platelets < 100 giga/L at ECMO start were independently associated with intracranial bleeding with respective odds ratios [95% CI] of 2.9 [1.1–7.5], 3.8 [1.1–10.2] and 3.7 [1.4–9.7]. In a nested case–control study, rapid CO2-level change from before-to-after ECMO start also seemed to be associated with intracranial bleeding. Conclusions Neurological events are frequent in VA-ECMO-treated patients. Ischemic stroke is the most frequent, occurs after 1 week on ECMO support, has no specific risk factor and is not associated with higher mortality. Intracranial bleeding occurs earlier and is associated with female sex, central VA-ECMO, low platelet count and rapid CO2 change at ECMO start, and high mortality. Level of evidence This study provides Class IV evidence that central VA-ECMO, low platelet count and rapid CO2 change at ECMO start are associated with intracranial bleeding and high mortality

Brain injury during venovenous extracorporeal membrane oxygenation

International audiencePurposeThe frequency of neurological events and their impact on patients receiving venovenous extracorporeal membrane oxygenation (VV-ECMO) are unknown. We therefore study the epidemiology, risk factors, and impact of cerebral complications occurring in VV-ECMO patients.MethodsObservational study conducted in a tertiary referral center (2006–2012) on patients developing a neurological complication (ischemic stroke or intracranial bleeding) while on VV-ECMO versus those who did not, and a systematic review on this topic.ResultsAmong 135 consecutive patients who had received VV-ECMO, 18 (15 assessable) developed cerebral complications on ECMO: cerebral bleeding in 10 (7.5 %), ischemic stroke in 3 (2 %), or diffuse microbleeds in 2 (2 %), occurring after respective medians (IQR) of 3 (1–11), 21 (10–26), and 36 (8–63) days post-ECMO onset. Intracranial bleeding was independently associated with renal failure at intensive care unit admission and rapid PaCO2 decrease at ECMO initiation, but not with age, comorbidities, or hemostasis disorders. Seven (70 %) patients with intracranial bleeding and one (33 %) with ischemic stroke died versus 40 % of patients without neurological event. A systematic review found comparable intracranial bleeding rates (5 %).ConclusionsNeurological events occurred frequently in patients on VV-ECMO. Intracranial bleeding, the most frequent, occurred early and was associated with higher mortality. Because it was independently associated with rapid hypercapnia decrease, the latter should be avoided at ECMO onset, but its exact role remains to be determined. These findings may have major implications for the care of patients requiring VV-ECMO

Predictors of insufficient peak amikacin concentration in critically ill patients on extracorporeal membrane oxygenation

International audienceBackground: Amikacin infusion requires targeting a peak serum concentration (Cmax) 8–10 times the minimal inhibitory concentration, corresponding to a Cmax of 60–80 mg/L for the least susceptible bacteria to theoretically prevent therapeutic failure. Because drug pharmacokinetics on extracorporeal membrane oxygenation (ECMO) are challenging, we undertook this study to assess the frequency of insufficient amikacin Cmax in critically ill patients on ECMO and to identify relative risk factors.Methods: This was a prospective, observational, monocentric study in a university hospital. Patients on ECMO who received an amikacin loading dose for suspected Gram-negative infections were included. The amikacin loading dose of 25 mg/kg total body weight was administered intravenously and Cmax was measured 30 min after the end of the infusion. Independent predicators of Cmax < 60 mg/L after the first amikacin infusion were identified with mixed-model multivariable analyses. Various dosing simulations were performed to assess the probability of reaching 60 mg/L < Cmax < 80 mg/L.Results: A total of 106 patients on venoarterial ECMO (VA-ECMO) (68%) or venovenous-ECMO (32%) were included. At inclusion, their median (1st; 3rd quartile) Sequential Organ-Failure Assessment score was 15 (12; 18) and 54 patients (51%) were on renal replacement therapy. Overall ICU mortality was 54%. Cmax was < 60 mg/L in 41 patients (39%). Independent risk factors for amikacin under-dosing were body mass index (BMI) < 22 kg/m2 and a positive 24-h fluid balance. Using dosing simulation, increasing the amikacin dosing regimen to 30 mg/kg and 35 mg/kg of body weight when the 24-h fluid balance is positive and the BMI is ≥ 22 kg/m2 or < 22 kg/m2 (Table 3), respectively, would have potentially led to the therapeutic target being reached in 42% of patients while reducing under-dosing to 23% of patients.Conclusions: ECMO-treated patients were under-dosed for amikacin in one third of cases. Increasing the dose to 35 mg/kg of body weight in low-BMI patients and those with positive 24-h fluid balance on ECMO to reach adequate targeted concentrations should be investigated