Hadrien Rozé

Extracorporeal membrane oxygenation for pandemic influenza A(H1N1)-induced acute respiratory distress syndrome: a cohort study and propensity-matched analysis.

RATIONALE Many patients with severe acute respiratory distress syndrome (ARDS) caused by influenza A(H1N1) infection receive extracorporeal membrane oxygenation (ECMO) as a rescue therapy. OBJECTIVES To analyze factors associated with death in ECMO-treated patients and the influence of ECMO on intensive care unit (ICU) mortality. METHODS Data from patients admitted for H1N1-associated ARDS to French ICUs were prospectively collected from 2009 to 2011 through the national REVA registry. We analyzed factors associated with in-ICU death in ECMO recipients, and the potential benefit of ECMO using a propensity score-matched (1:1) cohort analysis. MEASUREMENTS AND MAIN RESULTS A total of 123 patients received ECMO. By multivariate analysis, increasing values of age, lactate, and plateau pressure under ECMO were associated with death. Of 103 patients receiving ECMO during the first week of mechanical ventilation, 52 could be matched to non-ECMO patients of comparable severity, using a one-to-one matching and using control subjects only once. Mortality did not differ between the two matched cohorts (odds ratio, 1.48; 95% confidence interval, 0.68-3.23; P = 0.32). Interestingly, the 51 ECMO patients who could not be matched were younger, had lower Pa(o(2))/Fi(o(2)) ratio, had higher plateau pressure, but also had a lower ICU mortality rate than the 52 matched ECMO patients (22% vs. 50%; P < 0.01). CONCLUSIONS Under ECMO, an ultraprotective ventilation strategy minimizing plateau pressure may be required to improve outcome. When patients with severe influenza A(H1N1)-related ARDS treated with ECMO were compared with conventionally treated patients, no difference in mortality rates existed. The unmatched, severely hypoxemic, and younger ECMO-treated patients had, however, a lower mortality.

Doppler resistive index to reflect regulation of renal vascular tone during sepsis and acute kidney injury

IntroductionRenal resistive index (RI), determined by Doppler ultrasonography, directly reveals and quantifies modifications in renal vascular resistance. The aim of this study was to evaluate if mean arterial pressure (MAP) is determinant of renal RI in septic, critically ill patients suffering or not from acute kidney injury (AKI).MethodsThis prospective observational study included 96 patients. AKI was defined according to RIFLE criteria and transient or persistent AKI according to renal recovery within 3 days.ResultsMedian renal RIs were 0.72 (0.68-0.75) in patients without AKI and 0.76 (0.72-0.80) in patients with AKI (P=0.001). RIs were 0.75 (0.72-0.79) in transient AKI and 0.77 (0.70-0.80) in persistent AKI (P=0.84). RI did not differ in patients given norepinephrine infusion and was not correlated with norepinephrine dose. RI was correlated with MAP (ρ= -0.47; P=0.002), PaO2/FiO2 ratio (ρ= -0.33; P=0.04) and age (ρ=0.35; P=0.015) only in patients without AKI.ConclusionsA poor correlation between renal RI and MAP, age, or PaO2/FiO2 ratio was found in septic and critically ill patients without AKI compared to patients with AKI. These findings suggest that determinants of RI are multiple. Renal circulatory response to sepsis estimated by Doppler ultrasonography cannot reliably be predicted simply from changes in systemic hemodynamics. As many factors influence its value, the interest in a single RI measurement at ICU admission to determine optimal MAP remains uncertain.

Clinical review: Update on neurally adjusted ventilatory assist - report of a round-table conference

Conventional mechanical ventilators rely on pneumatic pressure and flow sensors and controllers to detect breaths. New modes of mechanical ventilation have been developed to better match the assistance delivered by the ventilator to the patients needs. Among these modes, neurally adjusted ventilatory assist (NAVA) delivers a pressure that is directly proportional to the integral of the electrical activity of the diaphragm recorded continuously through an esophageal probe. In clinical settings, NAVA has been chiefly compared with pressure-support ventilation, one of the most popular modes used during the weaning phase, which delivers a constant pressure from breath to breath. Comparisons with proportional-assist ventilation, which has numerous similarities, are lacking. Because of the constant level of assistance, pressure-support ventilation reduces the natural variability of the breathing pattern and can be associated with asynchrony and/or overinflation. The ability of NAVA to circumvent these limitations has been addressed in clinical studies and is discussed in this report. Although the underlying concept is fascinating, several important questions regarding the clinical applications of NAVA remain unanswered. Among these questions, determining the optimal NAVA settings according to the patients ventilatory needs and/or acceptable level of work of breathing is a key issue. In this report, based on an investigator-initiated round table, we review the most recent literature on this topic and discuss the theoretical advantages and disadvantages of NAVA compared with other modes, as well as the risks and limitations of NAVA.

Case Scenario: Management of Intraoperative Hypoxemia during One-lung Ventilation

H YPOXEMIA that may reasonably be defined by an arterial hemoglobin oxygen saturation of less than 90% occurs in 5–10% of patients during one-lung ventilation (OLV). The physiopathology of hypoxemia is complex, and the management of intraoperative hypoxemia during OLV remains a challenge for anesthesiologists. In life-threatening hypoxemia, correct oxygenation should be restored rapidly. This may require discontinuing surgery to eliminate reversible causes of hypoxemia. Several strategies can then be applied to prevent and correct hypoxemia during OLV.

Neuro-ventilatory efficiency during weaning from mechanical ventilation using neurally adjusted ventilatory assist

BACKGROUND Neuro-ventilatory efficiency (NVE), defined as the tidal volume to electrical diaphragm-activity ratio (VT/EAdi) at the beginning and end of the weaning process after acute hypoxaemic respiratory failure, may provide valuable information about patient recovery. METHODS This observational study included 12 patients breathing with neurally adjusted ventilatory assist (NAVA). When a spontaneous breathing trial (SBT) with pressure support of 7 cm H2O and PEEP was unsuccessful, NAVA was used and the level was adjusted to obtain an EAdi of ∼60% of maximal EAdi during SBT. VT and EAdi were recorded continuously. We compared changes in NVE between NAVA and SBT at the first failed and first successful SBT. RESULTS When patients were switched from NAVA to SBT, NVE was significantly reduced during both unsuccessful and successful SBT (-56 and -38%, respectively); however, this reduction was significantly lower when SBT was successful (P=0.01). Between the first and last day of weaning, we observed that NVE decreased with NAVA [40.6 (27.7-89.5) vs 28.8 (18.6-46.7); P=0.002] with a significant decrease in NAVA level, whereas it remained unchanged during SBT [15.4 (10.7-39.1) vs 19.5 (11.6-29.6); P=0.50] with significant increases in both EAdi and VT and no difference in respiratory rhythm. CONCLUSIONS These results suggest that in patients after respiratory failure and prolonged mechanical ventilation, changes in VT and NVE, between SBTs are indicative of patient recovery. Larger clinical trials are needed to clarify whether changes in NVE reliably predict weaning in patients ventilated with NAVA.

Factors associated with early graft dysfunction in cystic fibrosis patients receiving primary bilateral lung transplantation

OBJECTIVES Primary graft dysfunction (PGD) occurs in 10-25% of cases and remains responsible for significant morbidity and mortality after lung transplantation. Our goal was to explore donor and recipient variables and procedure factors that could be related to early graft failure in cystic fibrosis patients receiving bilateral lung transplantation, the PGD grade being derived from the PaO(2)/FiO(2) ratio measured at the sixth post-operative hour. METHODS Data from 122 cystic fibrosis patients having undergone lung transplantation in six transplant centres in France were retrospectively analysed. Donor and recipient variables, procedure characteristics and anaesthesia management items were recorded and analysed with regard to the PaO(2)/FiO(2) ratio at the sixth post-operative hour. Recipients were divided into three groups according to this ratio: Grade I PGD, when PaO(2)/FiO(2) >300 mmHg or extubated patients, Grade II, when PaO(2)/FiO(2) = 200-300 mmHg, and Grade III, when PaO(2)/FiO(2) <200 mmHg or extracorporeal membrane oxygenation still required. RESULTS Forty-eight patients were Grade I, 32 patients Grade II and 42 patients Grade III PGD. Otos donor score, recipient variables and procedure characteristics were not statistically linked to PaO(2)/FiO(2) at the sixth post-operative hour. Ischaemic time of the last implanted graft and the lactate level at the end of the procedure are the only factors related to Grade III PGD in this group. CONCLUSIONS Hyperlactataemia most probably reflects the severity of early PGD, which leaves graft ischaemic time as the only factor predicting early PGD in a multicentre population of cystic fibrosis lung graft recipients.

Reducing tidal volume and increasing positive end-expiratory pressure with constant plateau pressure during one-lung ventilation: effect on oxygenation

BACKGROUND It is no longer safe to use large tidal volumes (V(T)) (>8 ml kg(-1)) for one-lung ventilation (OLV), and limiting plateau pressure should be a major objective. Due to the specificity of OLV, the use of positive end-expiratory pressure (PEEP) remains controversial. This study determined whether at the same low plateau pressure, reducing V(T) and increasing PEEP were not inferior to larger V(T) and lower PEEP ventilation in terms of oxygenation. METHODS This prospective, randomized, non-inferiority, cross-over trial included 88 patients undergoing open thoracotomy who received two successive ventilatory strategies in random order: V(T) (8 ml kg(-1) of ideal body weight) with low PEEP (5 cm H(2)O), or low V(T) (5 ml kg(-1)) with a high PEEP. Respiratory rate and PEEP were, respectively, adjusted to maintain constant ventilation and plateau pressure. The primary endpoint was the ratio under each ventilatory strategy. RESULTS The non-inferiority of low-V(T) ventilation could not be established. The mean adjusted ratio was lower overall during low-V(T) ventilation, and differences between the two ventilatory modes varied significantly according to baseline (T0). Decreased oxygenation during low V(T) was smaller when baseline values were low. Systolic arterial pressure was not lower during low-V(T) ventilation. CONCLUSION During OLV, lowering V(T) and increasing PEEP, with the same low plateau pressure, reduced oxygenation compared with larger V(T) and lower PEEP. This strategy may reduce the risk of lung injury, but needs to be investigated further.

Pressure-controlled ventilation and intrabronchial pressure during one-lung ventilation†

BACKGROUND Pressure-controlled ventilation (PCV) has been suggested to reduce peak airway pressure (P(peak)) and intrapulmonary shunt during one-lung ventilation (OLV) when compared with volume-controlled ventilation (VCV). At the same tidal volume (V(T)), the apparent difference in P(peak) is mainly related to the presence of a double-lumen tracheal tube. We tested the hypothesis that the decrease in P(peak) observed in the breathing circuit is not necessarily associated with a decrease in the bronchus of the dependent lung. METHODS This observational study included 15 consecutive subjects who were ventilated with VCV followed by PCV at constant V(T). Airway pressure was measured simultaneously in the breathing circuit and main bronchus of the dependent lung after 20 min of ventilation. RESULTS PCV induced a significant decrease in P(peak) [mean (sd)] measured in the breathing circuit [36 (4) to 26 (3) cm H(2)0, P<0.0001] and in the bronchus [23 (4) to 22 (3) cm H(2)O, P=0.01]. However, the interaction (ventilatory mode x site of measurement) revealed that the decrease in P(peak) was significantly higher in the circuit (P<0.0001). Although the mean percentage decrease in P(peak) was significant at both sites, the decrease was significantly lower in the bronchus [5 (6)% vs 29 (3)%, P<0.0001]. CONCLUSIONS During PCV for OLV, the decrease in P(peak) is observed mainly in the respiratory circuit and is probably not clinically relevant in the bronchus of the dependent lung. This challenges the common clinical perception that PCV offers an advantage over VCV during OLV by reducing bronchial P(peak).

Acquired deficit of antithrombin and role of supplementation in septic patients during continuous veno-venous hemofiltration.

Continuous renal replacement therapy (CRRT) is widely used in the management of septic patients with acute renal failure (ARF). Short filter lifespan (<24 hours) is a major concern and may result of a procoagulating state. The aim of this study was to investigate the relationship between antithrombin (AT) deficit and early filter clotting, and whether supplementation of AT could increase filter lifespan. Two different methods for supplementation, bolus and continuous infusion were also compared. We conducted a two-center prospective study from March 2003 to May 2004. Twenty-seven patients with septic shock and ARF were included and treated by CRRT. Unfractionated heparin (UHF) was used for anticoagulation. The initial level of AT was low with a median level at 45.4% (16%–69%). Low AT activity was associated with shorter filter lifespan. Supplementation led to a longer filter lifespan (15.2–33.2 hours) (p < 0.05). Continuous infusion provided better results: 48.5 vs. 27.8 hours for bolus method. This study suggests that AT measurement should be considered in continuous veno-venous hemofiltration with clotting problems as supplementation could increase filter lifespan by more than 100%. Continuous infusion is preferable. Cost effectiveness should be evaluated shortly.

Diffuse Cerebral Microbleeds after Extracorporeal Membrane Oxygenation Support

Extracorporeal membrane oxygenation (ECMO) is used to provide cardiac and/or pulmonary support in patients refractory to conventional therapies (1, 2). We describe here four patients who demonstrated extensive cerebral microbleeds in the context of persistent coma after ECMO support. Unexpectedly, all patients recovered full consciousness and had (for three of them) no or slight disabilities 1 year after intensive care unit (ICU) discharge.