RESUMEN
STUDY OBJECTIVE: During laparoscopic surgery, the role of PEEP to improve outcome is controversial. Mechanistically, PEEP benefits depend on the extent of alveolar recruitment, which prevents ventilator-induced lung injury by reducing lung dynamic strain. The hypotheses of this study were that pneumoperitoneum-induced aeration loss and PEEP-induced recruitment are inter-individually variable, and that the recruitment-to-inflation ratio (R/I) can identify patients who benefit from PEEP in terms of strain reduction. DESIGN: Sequential study. SETTING: Operating room. PATIENTS: Seventeen ASA I-III patients receiving robot-assisted prostatectomy during Trendelenburg pneumoperitoneum. INTERVENTIONS AND MEASUREMENTS: Patients underwent end-expiratory lung volume (EELV) and respiratory/lung/chest wall mechanics (esophageal manometry and inspiratory/expiratory occlusions) assessment at PEEP = 0 cmH2O before and after pneumoperitoneum, at PEEP = 4 and 12 cmH2O during pneumoperitoneum. Pneumoperitoneum-induced derecruitment and PEEP-induced recruitment were assessed through a simplified method based on multiple pressure-volume curve. Dynamic and static strain changes were evaluated. R/I between 12 and 4 cmH2O was assessed from EELV. Inter-individual variability was rated with the ratio of standard deviation to mean (CoV). MAIN RESULTS: Pneumoperitoneum reduced EELV by (median [IqR]) 410 mL [80-770] (p < 0.001) and increased dynamic strain by 0.04 [0.01-0.07] (p < 0.001), with high inter-individual variability (CoV = 70% and 88%, respectively). Compared to PEEP = 4 cmH2O, PEEP = 12 cmH2O yielded variable amount of recruitment (139 mL [96-366] CoV = 101%), causing different extent of dynamic strain reduction (median decrease 0.02 [0.01-0.04], p = 0.002; CoV = 86%) and static strain increases (median increase 0.05 [0.04-0.07], p = 0.01, CoV = 33%). R/I (1.73 [0.58-3.35]) estimated the decrease in dynamic strain (p ≤0.001, r = -0.90) and the increase in static strain (p = 0.009, r = -0.73) induced by PEEP, while PEEP-induced changes in respiratory and lung mechanics did not. CONCLUSIONS: Trendelenburg pneumoperitoneum yields variable derecruitment: PEEP capability to revert these phenomena varies significantly among individuals. High R/I identifies patients in whom higher PEEP mostly reduces dynamic strain with limited static strain increases, potentially allowing individualized settings.
RESUMEN
BACKGROUND: Arteriovenous fistula (AVF) for haemodialysis (HD) induces a volume/pressure overload which impairs bi-ventricular function and increases systolic pulmonary arterial pressure (PAPS) and left ventricular mass (LVM). In the presence of high blood flow (Qa) AVF (> 1.5 L/min/1.73 m2) and cardio-pulmonary recirculation (>20%), high-output congestive heart failure (CHF) may occur and AVF flow reduction is recommended. Proximal Radial Artery Ligation (PRAL) is an effective technique for distal radio-cephalic (RC) AVF flow reduction. METHODS: we evaluated six HD and four transplant patients with high-flow RC AVF and symptoms of CHF who underwent PRAL. We compared echocardiographic (ECHO) findings before (T0) and 1 and 6 months (T1,T6) after PRAL. Preoperative ECHO was performed before (T0b) and after AVF anastomosis manual compression (T0c). RESULTS: At T1 AVF flow reduction rate was 58.4% ± 13% and 80% of patients reported improved CHF symptoms. ECHO data showed an improvement of tricuspid annular plane systolic excursion (TAPSE) at T1 (p = 0.03) and a reduction of PAPS at T6 (p = 0.04). TAPSE improved after AVF anastomosis compression during preoperative ECHO (p = 0.03). Delta of TAPSE at the dynamic manoeuvre at T0 directly correlated with early (1 month after PRAL, p = 0.01) and late (6 months after PRAL, p = 0.04) deltas of TAPSE. CONCLUSIONS: AVF flow reduction after PRAL induces immediate regression of CHF symptoms, early improvement of TAPSE and late improvement of PAPS, suggesting a prevalent right sections involvement in CHF. Preoperative TAPSE modification after AVF anastomosis compression could represent a useful evaluation tool to determine which patients would benefit of PRAL.