Tidal Volume Lowering by Instrumental Dead Space Reduction in Brain-Injured ARDS Patients: Effects on Respiratory Mechanics, Gas Exchange, and Cerebral Hemodynamics.

BACKGROUND: Limiting tidal volume (VT), plateau pressure, and driving pressure is essential during the acute respiratory distress syndrome (ARDS), but may be challenging when brain injury coexists due to the risk of hypercapnia. Because lowering dead space enhances CO2 clearance, we conducted a study to determine whether and to what extent replacing heat and moisture exchangers (HME) with heated humidifiers (HH) facilitate safe VT lowering in brain-injured patients with ARDS. METHODS: Brain-injured patients (head trauma or spontaneous cerebral hemorrhage with Glasgow Coma Scale at admission < 9) with mild and moderate ARDS received three ventilatory strategies in a sequential order during continuous paralysis: (1) HME with VT to obtain a PaCO2 within 30-35 mmHg (HME1); (2) HH with VT titrated to obtain the same PaCO2 (HH); and (3) HME1 settings resumed (HME2). Arterial blood gases, static and quasi-static respiratory mechanics, alveolar recruitment by multiple pressure-volume curves, intracranial pressure, cerebral perfusion pressure, mean arterial pressure, and mean flow velocity in the middle cerebral artery by transcranial Doppler were recorded. Dead space was measured and partitioned by volumetric capnography. RESULTS: Eighteen brain-injured patients were studied: 7 (39%) had mild and 11 (61%) had moderate ARDS. At inclusion, median [interquartile range] PaO2/FiO2 was 173 [146-213] and median PEEP was 8 cmH2O [5-9]. HH allowed to reduce VT by 120 ml [95% CI: 98-144], VT/kg predicted body weight by 1.8 ml/kg [95% CI: 1.5-2.1], plateau pressure and driving pressure by 3.7 cmH2O [2.9-4.3], without affecting PaCO2, alveolar recruitment, and oxygenation. This was permitted by lower airway (- 84 ml [95% CI: - 79 to - 89]) and total dead space (- 86 ml [95% CI: - 73 to - 98]). Sixteen patients (89%) showed driving pressure equal or lower than 14 cmH2O while on HH, as compared to 7 (39%) and 8 (44%) during HME1 and HME2 (p < 0.001). No changes in mean arterial pressure, cerebral perfusion pressure, intracranial pressure, and middle cerebral artery mean flow velocity were documented during HH. CONCLUSION: The dead space reduction provided by HH allows to safely reduce VT without modifying PaCO2 nor cerebral perfusion. This permits to provide a wider proportion of brain-injured ARDS patients with less injurious ventilation.

Lung ultrasound to monitor the development of pulmonary atelectasis in gynecologic oncologic surgery.

BACKGROUND: Atelectasis formation is considered the major cause of hypoxemia during general anesthesia (GA). Gynecologic oncologic surgery (GOS) often requires pneumoperitoneum and steep bed angulation that further reduce lung compliance by shifting bowels and diaphragm. The aim of our study was to assess the impact of intraoperative variables on lung aeration using lung ultrasound (LUS) score and their correlation with postoperative oxygenation in women undergoing GOS. METHODS: In this prospective observational study 80 patients scheduled for GOS were enrolled. After three minutes pre-oxygenation, propofol-sufentanil-sevoflurane GA and standard mechanical ventilation (MV) were administered (tidal volume of 8 mL/kg of predicted body weight, FiO2 40%, I:E ratio of 1:2 and PEEP 5 cm H2O). A 0-36 LUS score was calculated considering 12 pulmonary areas, and arterial blood gas analysis were performed before GA (T1) and in recovery room (T2). RESULTS: LUS score increased significantly between T1 (1.79±2.39) and T2 (11.08±4.40, ΔLUS=9.29±4.10, P<0.05), mostly in basal and posterior areas. Changes in LUS score correlated significantly with time of MV (r=0.246, P<0.05), cumulative time in TR position (r=0.321, P<0.05) and worsening in oxygenation (ΔPaO2/FiO2, r=-0.260, P<0.05). ΔLUS score significantly correlated with colloid infusion. The linear regression analysis showed that TR time can predict ΔLUS score (F1,78=8.97, P=0.004). No correlation was found with pneumoperitoneum, apnea time at induction and TR angle. CONCLUSIONS: Aeration loss after GOS detected using LUS correlates with TR time, MV time, colloid infusion and worsening in oxygenation.

Utility of ultrasound-guided transversus abdominis plane block for day-case inguinal hernia repair.

BACKGROUND: The transversus abdominis plane (TAP) block is a regional anesthesia technique that effectively reduces the pain intensity and use of analgesia in abdominal surgery. The aim of this study was to determine the utility of the ultrasound-guided TAP block in improving the efficacy of the ultrasound-guided ilioinguinal/iliohypogastric nerve (IIN/IHN) block for intraoperative anesthesia and postoperative pain control in day-case inguinal hernia repair (IHR). METHODS: We conducted a descriptive study of patients undergoing elective primary unilateral open IHR. Fifty-nine patients were divided into two groups according to the anesthetic technique used: ultrasound-guided TAP block plus ultrasound-guided IIN/IHN block (TAP group) vs. ultrasound-guided IIN/IHN block alone (IIN/IHN group). The outcome measures were the adequacy of anesthesia during surgery and postoperative analgesia. RESULTS: Four patients (12.5%) in the TAP group and 10 patients (37.0%) in the IIN/IHN group experienced inadequate anesthesia and needed systemic sedation (P < 0.05). No significant differences in additional local anesthetic volume were found between the two groups. Patients in the TAP group reported lower pain scores at the end of surgery (0.4 ± 0.8 vs. 2.1 ± 2.5, P < 0.01), at 2 hours after surgery (0.8 ± 1.3 vs. 3.0 ± 2.2, P < 0.01), at discharge (1.4 ± 1.2 vs. 4.3 ± 2.2, P < 0.01), and at 24 hours (1.5 ± 1.1 vs. 4.5 ± 2.3, P < 0.01). CONCLUSIONS: The combination of the TAP and IIN/IHN blocks is associated with better intraoperative anesthesia and lower postoperative pain scores compared with the IIN/IHN block alone.