Doppler echocardiography for surveillance of acute cardiac allograft rejection: a 28-year single-center experience.

Background: Endomyocardial biopsies (EMB) are recommended for the detection of acute cardiac rejection (ACR) despite limited sensitivity. We report the long-term post-transplant results of Doppler echocardiography as a noninvasive alternative of routine EMB. Methods: Two cohorts of heart transplantation (HT) recipients were chronologically defined as follows: the Dual Monitoring Cohort (DMC) from January 1990 to December 1997 included patients who underwent routine EMB and Doppler echocardiography within 24 hours for ACR surveillance; and the "Echo-First Cohort" (EFC), including patients transplanted from January 1998 to December 2018 with Doppler echocardiography as first-line approach for ACR surveillance. Echocardiographic measurements of interest were collected: early diastolic (E) wave peak velocity; pressure half time (PHT) and isovolumetric relaxation time (IVRT). Post-transplant outcomes were reviewed and the Kaplan-Meier approach was used for survival estimates. Inter-operator variability for ultrasound measurements was investigated. Data were collected from medical records from January 2019 to December 2020. Results: A total of 228 patients were included, 99 patients in the DMC and 129 in the EFC. Overall, 5-, 10- and 15-year survival rates were 65.4%, 55.5% and 44.1% respectively, without any significant difference between the two cohorts (log rank test, P=0.71). Echocardiography variables and EMB findings were associated with a mean area under the receiver operating characteristic curve (AUC-ROC) of 0.73 [95% confidence interval (CI): 0.54-0.91], 0.74 (95% CI: 0.54-0.94) and 0.75 (95% CI: 0.57-0.94) respectively for E wave, PHT and IVRT. IVRT and PHT were significantly decreased, and E wave significantly increased, in case of histologically proven ACR. Inter-operator variability was not significant for E wave and IVRT measurements (P=0.13 and 0.30 respectively). Conclusions: Doppler echocardiography as a first-line method for surveillance of ACR did not impair long-term results after HT. These findings suggest that this non-invasive approach might be a reasonable alternative to systematic EMB, limiting risk and improving the quality of life.

Probabilistic Prediction of Gastrointestinal Ischemia after Cardiothoracic Surgery.

BACKGROUND: Gastrointestinal ischemia (GIisch) is challenging to diagnose in patients after cardiothoracic surgery. Computed tomography angiography (CTA) carries substantial false-negative and false-positive rates. The aim of the study was to evaluate if a combination of readily available variables improves the diagnosis of GIisch after cardiothoracic surgery. METHODS: This retrospective study included patients receiving intensive care after cardiothoracic surgery. GIisch was confirmed by surgical and/or endoscopic findings. A GIisch prediction score was developed using the Spiegelhalter-Knill-Jones system in a training cohort then tested in a validation cohort (patients without obvious signs of GIisch on CTA). RESULTS: The training cohort comprised 125 consecutive patients with suspected GIisch in 2008 to 2019, including 85 with confirmed GIisch. CTA, performed in 92 patients, had a high false-negative rate of 17/60 (28%) and a lower false-positive rate of 7/32 (22%). The score included cardiopulmonary bypass, negatively associated with GIisch, and six variables positively associated with GIisch: intraoperative mean arterial pressure < 50 mm Hg, aspartate aminotransferase > 15 N, lactate increase in 24 hour > 20%, and 3 CTA findings, namely, bowel dilation, bowel wall thickening, and mesenteric vasoconstriction. The area under the receiver operating characteristic was 0.82 (95% confidence interval [CI], 0.51-0.93) in the training cohort and 0.82 (95% CI, 0.68-0.96) in the validation cohort (n = 34 patients). Reliability of the predicted probabilities was greatest for probabilities ≤ 30% or ≥ 70%. CONCLUSION: In patients receiving intensive care after cardiothoracic surgery, GIisch cannot be ruled out based solely on CTA findings. A scoring system combining CTA findings with other variables may improve the diagnosis of GIisch in this population.

Circuit change during extracorporeal membrane oxygenation: single-center retrospective study of 48 changes.

BACKGROUND: Bleeding and thrombosis induce major morbidity and mortality in patients under extracorporeal membrane oxygenator (ECMO). Circuit changes can be performed for oxygenation membrane thrombosis but are not recommended for bleeding under ECMO. The objective of this study was to evaluate the course of clinical, laboratory, and transfusion parameters before and after ECMO circuit changes warranted by bleeding or thrombosis. METHODS: In this single-center, retrospective, cohort study, clinical parameters (bleeding syndrome, hemostatic procedures, oxygenation parameters, transfusion) and laboratory parameters (platelet count, hemoglobin, fibrinogen, PaO2) were collected over the seven days surrounding the circuit change. RESULTS: In the 274 patients on ECMO from January 2017 to August 2020, 48 circuit changes were performed in 44 patients, including 32 for bleeding and 16 for thrombosis. Mortality was similar in the patients with vs. without changes (21/44, 48% vs. 100/230, 43%) and in those with bleeding vs. thrombosis (12/28, 43% vs. 9/16, 56%, P = 0.39). In patients with bleeding, numbers of bleeding events, hemostatic procedures, and red blood cell transfusions were significantly higher before vs. after the change (P < 0.001); the platelet counts and fibrinogen levels decreased progressively before and increased significantly after the change. In patients with thrombosis, numbers of bleeding events and red blood cell transfusions did not change after membrane change. No significant differences were demonstrated between oxygenation parameters (ventilator FiO2, ECMO FiO2, and PaO2) and ECMO flow before vs. after the change. CONCLUSIONS: In patients with severe and persistent bleeding, changing the ECMO circuit decreased clinical bleeding and red blood cell transfusion needs and increased platelets and fibrinogen levels. Oxygenation parameters did not change significantly in the group with thrombosis.

Including Organ Dysfunctions in a Predictive Score for Nosocomial Pneumonia After Cardiothoracic Surgery.

BACKGROUND: Clinical diagnosis of ICU-acquired pneumonia after cardiothoracic surgery is challenging. Johanson criteria (chest radiograph infiltrate, purulent tracheal secretions, fever, and leukocytosis) fail in half the cases. A high Clinical Pulmonary Infection Score (CPIS) and ≥ 2-point increase in Sequential Organ Failure Assessment (SOFA) score (SOFA↑ ≥ 2) may improve diagnosis. The aim of the study was to evaluate whether CPIS or SOFA↑ ≥ 2 contributes to predict ICU-acquired pneumonia in subjects after cardiothoracic surgery. METHODS: We used a prospective observational design. Spiegelhalter-Knill-Jones scoring systems including CPIS or SOFA↑ ≥ 2, together with other clinical and laboratory variables, were developed in a derivation cohort. A positive quantitative pulmonary sample culture was required to confirm ICU-acquired pneumonia. Area under the receiver operating characteristic curve (AUROC) was computed for each of the 2 scoring systems. The best system was evaluated in a validation cohort. RESULTS: Derivation and validation cohorts included 172 and 108 subjects, with 410 and 216 suspected ICU-acquired pneumonia episodes, respectively. AUROC was 0.53 ± 0.03 for CPIS (P = .29) and 0.54 ± 0.03 for SOFA↑ ≥ 2 (P = .29). Adding purulent tracheal secretions and leukocytosis to SOFA↑ ≥ 2 (SOFA model) increased AUROC to 0.65 ± 0.03 (P < .001). Adding catecholamine use to CPIS (CPIS model) increased AUROC only slightly, to 0.57 ± 0.03. The probabilities predicted by the SOFA model were reliable, especially when high or low. CONCLUSIONS: A clinical scoring system including at least SOFA↑ ≥ 2 increase barely improved ICU-acquired pneumonia prediction in subjects after cardiothoracic surgery.

Oxygenation versus driving pressure for determining the best positive end-expiratory pressure in acute respiratory distress syndrome.

OBJECTIVE: The aim of this prospective longitudinal study was to compare driving pressure and absolute PaO2/FiO2 ratio in determining the best positive end-expiratory pressure (PEEP) level. PATIENTS AND METHODS: In 122 patients with acute respiratory distress syndrome, PEEP was increased until plateau pressure reached 30 cmH2O at constant tidal volume, then decreased at 15-min intervals, to 15, 10, and 5 cmH2O. The best PEEP by PaO2/FiO2 ratio (PEEPO2) was defined as the highest PaO2/FiO2 ratio obtained, and the best PEEP by driving pressure (PEEPDP) as the lowest driving pressure. The difference between the best PEEP levels was compared to a non-inferiority margin of 1.5 cmH2O. MAIN RESULTS: The best mean PEEPO2 value was 11.9 ± 4.7 cmH2O compared to 10.6 ± 4.1 cmH2O for the best PEEPDP: mean difference = 1.3 cmH2O (95% confidence interval [95% CI], 0.4-2.3; one-tailed P value, 0.36). Only 46 PEEP levels were the same with the two methods (37.7%; 95% CI 29.6-46.5). PEEP level was ≥ 15 cmH2O in 61 (50%) patients with PEEPO2 and 39 (32%) patients with PEEPDP (P = 0.001). CONCLUSION: Depending on the method chosen, the best PEEP level varies. The best PEEPDP level is lower than the best PEEPO2 level. Computing driving pressure is simple, faster and less invasive than measuring PaO2. However, our results do not demonstrate that one method deserves preference over the other in terms of patient outcome. CLINICAL TRIAL NUMBER: #ACTRN12618000554268 . Registered 13 April 2018.

Extubation Failure Prediction by Echography of the Diaphragm After Cardiothoracic Surgery: The EXPEDIA Study.

BACKGROUND: Successful extubation is difficult to predict. Ultrasound measurement of the diaphragm thickening fraction (DTF) might help predict weaning failure after cardiothoracic surgery. METHODS: We assessed the predictive performance of diaphragm ultrasound in a derivation cohort of 50 prospectively included cardiothoracic surgery subjects ready for a weaning trial and in a validation cohort of 39 subjects ventilated for ≥ 48 h. DTF was assessed by ultrasound during pressure support ventilation (PSV) then during a T-piece spontaneous breathing trial (SBT). DTF was the percentage change in diaphragm thickness between expiration and inspiration and DTFmax, the higher DTF value of the 2 hemidiaphragms. DTFmax during SBT (static study) and the difference in DTFmax between PSV and SBT (dynamic study) were analyzed. RESULTS: In the derivation cohort, DTFmax during SBT was 25.6 ± 17.3% in subjects with successful extubation and 65.2 ± 17.3% in those with weaning failure (difference 39.7 [95% CI 27.4-51.9], P < .01). During SBT, DTFmax ≥ 50% was associated with weaning failure (area under the receiver operating characteristic curve [AUC] 0.94 ± 0.05). In the dynamic study, a ≥ 40% DTFmax increase was associated with weaning failure (AUC 0.91 ± 0.06). In the validation cohort, DTFmax during SBT was 20.3 ± 17.1% in subjects with successful extubation and 82.0 ± 51.6% in those with weaning failure (difference 61.8 [95% CI 41.6-82.0], P < .01). During SBT, DTFmax ≥ 50% predicted weaning failure (AUC 0.99 ± 0.02). In the dynamic study, a ≥ 40% increase in DTFmax predicted weaning failure (AUC 0.81 ± 0.09). CONCLUSIONS: Measuring DTFmax during SBT and the DTFmax change when switching from PSV to SBT may help predict weaning failure after cardiothoracic surgery. The study was registered on ANZCTR. CLINICAL TRIAL REGISTRATION NUMBER: U1111-1180-1999.

Effect of Recruitment Maneuvers and PEEP on Respiratory Failure After Cardiothoracic Surgery in Obese Subjects: A Randomized Controlled Trial.

BACKGROUND: Obesity may increase the risk of respiratory failure after cardiothoracic surgery. A recruitment maneuver followed by PEEP might decrease the risk of respiratory failure in obese subjects. We hypothesized that the routine use after heart surgery of a recruitment maneuver followed by high or low PEEP level would decrease the frequency of respiratory failure in obese subjects. METHODS: In a pragmatic, randomized controlled trial, we assigned obese subjects (ie, with body mass index [BMI] ≥ 30 kg/m2) in the immediate postoperative period of cardiothoracic surgery to either volume control ventilation with 5 cm H2O of PEEP (control group) or a recruitment maneuver followed by 5 or 10 cm H2O of PEEP in the intervention arms (RM5 and RM10 groups, respectively). The primary outcome was the proportion of subjects with postextubation respiratory failure, defined as the need for re-intubation, bi-level positive airway pressure, or high-flow nasal cannula within the first 48 h. RESULTS: The study included 192 subjects: 65 in the control group (BMI 33.5 ± 3.2 kg/m2), 66 in the RM5 group (BMI 34.5 ± 3.2 kg/m2, and 61 in RM10 group (BMI 33.8 ± 4.8 kg/m2). Postextubation respiratory failure occurred in 14 subjects in the control group (21.5% [95% CI 13.3-35.3]), 21 subjects in the RM5 group (31.8% [95% CI 21.2-44.6]), and 9 subjects in the RM10 group (14.7% [95% CI 7.4-26.7]) (P = .07). The recruitment maneuver was stopped prematurely due to severe hypotension in 8 (12.1%) RM5 subjects and in 4 (6.6%) RM10 subjects (P = .28). There were no significant differences between the 3 groups for the frequencies of atelectasis, pneumonia, and death in the ICU. CONCLUSIONS: The routine use after heart surgery of a recruitment maneuver followed by 5 or 10 cm H2O of PEEP did not decrease the frequency of respiratory failure in obese subjects. A recruitment maneuver followed by 5 cm H2O of PEEP is inappropriate.

Neuromuscular Blockade Monitoring in Acute Respiratory Distress Syndrome: Randomized Controlled Trial of Clinical Assessment Alone or With Peripheral Nerve Stimulation.

BACKGROUND: Whether train-of-four (TOF) monitoring is more effective than clinical monitoring to guide neuromuscular blockade (NMB) in patients with acute respiratory distress syndrome (ARDS) is unclear. We compared clinical monitoring alone or with TOF monitoring to guide atracurium dosage adjustment with respect to drug dose and respiratory parameters. METHODS: From 2015 to 2016, we conducted a randomized controlled trial comparing clinical assessments every 2 hours with or without corrugator supercilii TOF monitoring every 4 hours in patients who developed ARDS (Pao2/Fio2 <150 mm Hg) in a cardiothoracic intensive care unit. The primary outcome was the cumulative atracurium dose (mg/kg/h). Secondary outcomes included respiratory parameters during the neuromuscular blockade. RESULTS: A total of 38 patients in the clinical + TOF (C + TOF) group and 39 patients in the clinical (C) group were included in an intention-to-treat (ITT) analysis. The cumulative atracurium dose was higher in the C + TOF group (1.06 [0.75-1.30] vs 0.65 [0.60-0.89] mg/kg/h in the C group; P < .001) compared to C group, as well as the atracurium daily dose (C + TOF - C group mean difference = 0.256 mg/kg/h [95% confidence interval {CI}, 0.099-0.416], P = .026). Driving pressures during neuromuscular blocking agent (NMBA) administration did not differ between groups (P = .653). Intensive care unit (ICU) mortality was 22% in the C group and 27% in the C + TOF group (P = .786). Days on ventilation were 17 (8-26) in the C group and 16 (10-35) in the C + TOF group. CONCLUSIONS: In patients with ARDS, adding TOF to clinical monitoring of neuromuscular blockade did not change ICU mortality or days on mechanical ventilation (MV) but did increase atracurium consumption when compared to clinical assessment alone. TOF monitoring may not be needed in all patients who receive neuromuscular blockade for ARDS.

Ultrasound Assessment of Respiratory Workload With High-Flow Nasal Oxygen Versus Other Noninvasive Methods After Chest Surgery.

OBJECTIVE: To compare the respiratory workload using the diaphragm thickening fraction (DTf) determined by sonography during high-flow nasal oxygen (HFNO), standard oxygen therapy (SOT), and noninvasive bilevel positive airway pressure support (BIPAP) in patients with acute respiratory failure (ARF) after cardiothoracic surgery. DESIGN: Prospective controlled clinical trial. SETTING: A French 23-bed cardiothoracic surgical intensive care unit. PARTICIPANTS: Nonintubated patients with ARF after cardiothoracic surgery or while awaiting lung transplantation. INTERVENTIONS: HFNO (50 L/min), SOT via a standard facemask, and BIPAP (pressure support, 4 cmH2O; positive end-expiratory pressure [PEEP], 4 cmH2O), with FIO2 kept constant were successively applied and compared. With BIPAP, pressure support or PEEP increments up to 8 cmH2O were compared with baseline settings. Each measurement was made after stable breathing for 5 minutes. MEASUREMENTS AND MAIN RESULTS: Fifty patients aged 60.0 ± 12.2 years were enrolled, including 14 (28%) with obesity. Mean PaO2/FIO2 was 153 ± 55 mmHg. DTf was lower with HFNO and BIPAP than with SOT (respectively 21.2% ± 15.1% v 30.9% ± 21.1% and 17.8% ± 19.1% v 30.9% ± 21.1%, p < 0.001) and was not different with HFNO versus BIPAP (p = 0.22). With BIPAP, increasing pressure support to 8 cmH2O decreased DTf (21.0% ± 14.3% v 28.8% ± 19.8%, p = 0.009), whereas increasing PEEP to 8 cmH2O did not (25.2% ± 17.2% v 28.8% ± 19.8%, p = 0.79). Tidal volume increased to 10.6 ± 3.4 mL/kg with 8 cmH2O pressure support v 8.8 ± 2.7 mL/kg with 4 cmH2O pressure support (p < 0.001). CONCLUSION: HFNO provides a comparable respiratory workload decrease compared with BIPAP at lower levels of pressure support and PEEP compared with SOT. Increasing BIPAP pressure support may provide higher levels of assistance but carries a risk of overdistension.