Change in stroke volume during alveolar recruitment maneuvers through transient continuous positive airway pressure or stepwise increase in positive end expiratory pressure in anesthetized patients: a prospective randomized double-blind study.

PURPOSE: Intraoperative alveolar recruitment maneuvers (ARM) used during protective ventilation strategy may have severe adverse hemodynamic effects, reported mainly during abrupt continuous positive airway pressure (CPAP). Stepwise increase and decrease in positive end expiratory pressure (PEEP) may be used. We compared the hemodynamic effects of these two maneuvers. METHODS: We enrolled patients scheduled for intermediate to high-risk surgery with continuous arterial pressure and stroke volume (esophageal Doppler) monitoring in a prospective, single-centre, randomized, double-blind study. After induction of anesthesia, we ensured preload independence of stroke volume before an ARM was randomly performed: 30 cm H2O CPAP for 30 sec (CPAP group) or stepwise increase in PEEP from 8 to 20 cm H2O with inspiratory pressure of 10 cm H2O followed by a stepwise decrease in PEEP from 20 to 8 cm H2O (STEP group). The primary outcome was the relative variation in stroke volume. RESULTS: Thirty-five patients were included in the CPAP and STEP groups. Mean (standard deviation) relative variation in stroke volume was -57 (24)% in the CPAP group and -32 (24)% in the STEP group (difference, -25; 95% confidence interval, -37 to -14; P < 0.001). Changes in systolic, mean, and diastolic arterial pressure over time were not different between groups. The ARM was stopped because of a systolic arterial pressure < 70 mm Hg in four patients in the CPAP group and in one patient in the STEP group. CONCLUSIONS: Alveolar recruitment maneuvers through stepwise increase and decrease in PEEP have a better hemodynamic tolerance than transient CPAP. TRIAL REGISTRATION: ClinicalTrials.gov (NCT04802421); first submitted 15 March 2021.

RéSUMé: OBJECTIF: Les manœuvres de recrutement alvéolaire (MRA) peropératoire utilisées pendant les stratégies de ventilation protectrice peuvent avoir des effets hémodynamiques indésirables graves, rapportés principalement lors d'une ventilation en pression positive continue (PPC ou CPAP en anglais) abrupte. L'augmentation et la diminution par étapes de la pression expiratoire positive (PEP) peuvent être utilisées. Nous avons comparé les effets hémodynamiques de ces deux manœuvres. MéTHODE: Nous avons recruté des patient·es devant bénéficier d'une chirurgie à risque intermédiaire à élevé avec monitorage continu de la tension artérielle et du volume d'éjection (Doppler œsophagien) dans le cadre d'une étude prospective, monocentrique, randomisée et à double insu. Après induction de l'anesthésie, nous nous sommes assurés de l'indépendance de précharge du volume d'éjection avant qu'une MRA ne soit effectuée au hasard : 30 cm H2O PPC pendant 30 secondes (groupe PPC) ou augmentation progressive de la PEP de 8 à 20 cm H2O avec pression inspiratoire de 10 cm H2O, suivie d'une diminution progressive de la PEP de 20 à 8 cm H2O (groupe STEP). Le critère d'évaluation principal était la variation relative du volume d'éjection. RéSULTATS: Trente-cinq personnes ont été incluses dans les groupes PPC et STEP. La variation relative moyenne (écart type) du volume d'éjection était de −57 (24) % dans le groupe PPC et de −32 (24) % dans le groupe STEP (différence, −25; intervalle de confiance à 95 %, −37 à −14; P < 0,001). Les changements dans la tension artérielle systolique, moyenne et diastolique au fil du temps n'étaient pas différents entre les groupes. Les MRA ont été arrêtées en raison d'une tension artérielle systolique < 70 mm Hg chez quatre patient·es du groupe PPC et chez une personne du groupe STEP. CONCLUSION: Les manœuvres de recrutement alvéolaire par augmentation et diminution par étapes de la PEP ont une meilleure tolérance hémodynamique que la PPC transitoire. ENREGISTREMENT DE L'éTUDE: ClinicalTrials.gov (NCT04802421); soumis pour la première fois le 15 mars 2021.

Performance Evaluation of a Dedicated Preclinical PET/CT System for the Assessment of Mineralization Process in a Mouse Model of Atherosclerosis.

PURPOSE: The purpose of this study was to assess the impact of positron emission tomography/X-ray computed tomography (PET/CT) acquisition and reconstruction parameters on the assessment of mineralization process in a mouse model of atherosclerosis. PROCEDURES: All experiments were performed on a dedicated preclinical PET/CT system. CT was evaluated using five acquisition configurations using both a tungsten wire phantom for in-plane resolution assessment and a bar pattern phantom for cross-plane resolution. Furthermore, the radiation dose of these acquisition configurations was calculated. The PET system was assessed using longitudinal line sources to determine the optimal reconstruction parameters by measuring central resolution and its coefficient of variation. An in vivo PET study was performed using uremic ApoE-/-, non-uremic ApoE-/-, and control mice to evaluate optimal PET reconstruction parameters for the detection of sodium [18F]fluoride (Na[18F]F) aortic uptake and for quantitative measurement of Na[18F]F bone influx (Ki) with a Patlak analysis. RESULTS: For CT, the use of 1 × 1 and 2 × 2 binning detector mode increased both in-plane and cross-plane resolution. However, resolution improvement (163 to 62 µm for in-plane resolution) was associated with an important radiation dose increase (1.67 to 32.78 Gy). With PET, 3D-ordered subset expectation maximization (3D-OSEM) algorithm increased the central resolution compared to filtered back projection (1.42 ± 0.35 mm vs. 1.91 ± 0.08, p < 0.001). The use of 3D-OSEM with eight iterations and a zoom factor 2 yielded optimal PET resolution for preclinical study (FWHM = 0.98 mm). These PET reconstruction parameters allowed the detection of Na[18F]F aortic uptake in 3/14 ApoE-/- mice and demonstrated a decreased Ki in uremic ApoE-/- compared to non-uremic ApoE-/- and control mice (p < 0.006). CONCLUSIONS: Optimizing reconstruction parameters significantly impacted on the assessment of mineralization process in a preclinical model of accelerated atherosclerosis using Na[18F]F PET. In addition, improving the CT resolution was associated with a dramatic radiation dose increase.