Background An intervention to potentiate hypoxic pulmonary vasoconstriction may reduce intrapulmonary shunt and hypoxemia during one-lung ventilation. Previous animal studies reported that repeated intermittent hypoxic stimuli potentiated hypoxic pulmonary vasoconstriction, but no clinical study has examined the effects of this intervention on hypoxemia during one-lung ventilation. We thus performed a single-center, parallel-group, double-blind, randomized controlled trial to investigate whether repeated intermittent hypoxic stimuli to the operative lung reduce hypoxemia during the subsequent one-lung ventilation for thoracoscopic surgery. Methods Patients undergoing one-lung ventilation were randomized into two groups (n = 68 each). Before one-lung ventilation, in the intermittent hypoxia group, the nondependent lung was not ventilated for 2 min and then ventilated for 2 min while the dependent lung was continuously ventilated. This was repeated five times. In the continuous normoxia group, both lungs were ventilated for 20 min. We measured SpO2, PaO2, FiO2, PaCO2, SaO2, and central venous oxygen saturation during one-lung ventilation. The primary outcome was the number of patients with hypoxemia defined as a SpO2 <95% during one-lung ventilation, which was analyzed with a chi-squared test. Results Hypoxemia was less frequent in the intermittent hypoxia group than in the continuous normoxia group during OLV [6/68 (8.8%) vs 17/68 (25.0%), risk ratio (95% CI) 0.35 (0.15–0.84), p = 0.012]. The PaO2 (p = 0.008 for 30 min and 0.007 for 60 min) and PaO2/FiO2 (p = 0.008 for both) were higher 30 and 60 min after starting one-lung ventilation, and the alveolar-arterial pressure gradient (p = 0.010) and shunt index (p = 0.008) were lower 30 min after starting one-lung ventilation in the intermittent hypoxia group than in the continuous normoxia group. Postoperative adverse events did not differ significantly between groups. Conclusions Repeated intermittent hypoxic stimuli to the operative lung seemed to potentiate hypoxic pulmonary vasoconstriction, and thus reduced hypoxemia during the subsequent one-lung ventilation.

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Protective ventilation is a prevailing ventilatory strategy these days and is comprised of small tidal volume, limited inspiratory pressure, and application of positive end-expiratory pressure (PEEP). However, several retrospective studies recently suggested that tidal volume, inspiratory pressure, and PEEP are not related to patient outcomes, or only related when they influence the driving pressure. Therefore, this review introduces the concept of driving pressure and looks into the possibility of driving pressure-guided ventilation as a new ventilatory strategy, especially in thoracic surgery where postoperative pulmonary complications are common, and thus, lung protection is of utmost importance.

http://cris.nih.go.kridentifier:KCT0001443.

Background and objectivesEpidural analgesia is the gold standard for post-thoracotomy pain management and can be started before or after surgical incision. This systematic review and meta-analysis investigated whether pre-emptive epidural analgesia before thoracotomy incision reduces acute and chronic post-thoracotomy pain in adults compared with epidural analgesia after incision.MethodsWe searched databases including MEDLINE, Embase, and CENTRAL for randomized controlled trials comparing epidural analgesia initiated before (pre-emptive group) and after (control group) thoracotomy incision in adults. The primary outcomes were the pain intensity during rest and coughing within 72 hours after surgery and the incidence of pain 1 to 6 months after surgery. Data were combined with random-effects meta-analyses. We rated the quality of evidence as high, moderate, low, and very low using the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) method.ResultsWe included 19 trials with 1062 participants involving 529 in the pre-emptive group and 533 in the control group. The pain intensity was significantly lower at rest within 72 hours after surgery (19 studies, n=1062) and during coughing within 48 hours after surgery (11 studies, n=638), and the incidence of pain was significantly lower 1 to 6 months after surgery (6 studies, n=276) in the pre-emptive group than in the control group. The quality of evidence was moderate or low in the primary outcomes.ConclusionsOur review provides low-quality evidence that pre-emptive epidural analgesia reduces the intensity of acute pain and the incidence of chronic pain after thoracotomy in adults.Protocol registration numberCRD42019131620.