Nitrous Oxide for Identifying the Intersegmental Plane in Segmentectomy: A Randomized Controlled Trial
Condition: Pulmonary Nodule, Solitary; Pulmonary Nodule, Multiple; Lung Cancer
MeSH terms: Multiple Pulmonary Nodules; Solitary Pulmonary Nodule
Study type: Interventional

Summary: 
      Lung cancer is currently one of the most common malignant tumors in the world. In recent
      years, with the popularity of high-resolution CT, more and more early-stage lung cancers have
      been found. Anatomic pneumonectomy is gradually popular because it can completely remove lung
      nodules and preserve lung function to the greatest extent. During the surgery, the precise
      and rapid determination of intersegmental border is one of the key technologies. Improved
      inflation-deflation method is currently the most widely used method in clinical practice.
      Previous studies demonstrated that increasing the concentration of nitrous oxide in mixtures
      of N2O/O2 will lead to a faster rate of collapse. The rapid diffusion properties of N2O would
      be expected to speed lung collapse and so facilitate surgery. This study was designed to
      explore three types of inspired gas mixture used during two-lung anesthesia had an effect on
      the intersegmental border appearance time during pneumonectomy and its feasibility and
      safety: 75% N2O (O2: N2O = 1: 3), 50% N2O (O2: N2O = 1: 1), 100% oxygen.
    

Detailed description: 
      This randomized parallel group trial enrolled lung cancer patients scheduled to receive
      thoracoscopic anatomic segmentectomy at The First Affiliated Hospital of Nanjing Medical
      University. When anesthesia induction was completed, intubation was carried out using an
      appropriate-size double-lumen endobronchial tube (DLT) and the position of the DLT was
      confirmed with fiberoptic bronchoscopy and adjusted as needed. OLV of the dependent lung with
      FiO2=1.0 was begun in the lateral position, by clamping the DLT to the nonventilated lung
      proximally and opening the distal port of the DLT lumen to the atmosphere. Tidal volumes were
      5 mL/kg ideal bodyweight (male: height -100, and female: height - 105) without positive end
      expiratory pressure (PEEP). In order to avoid possible confounding effects of inhalation of
      volatile anesthetics on oxygenation, all subjects received total intravenous anesthesia.

      According to preoperative 3D-CTBA evaluation of bronchial and vascular structure of pulmonary
      nodules and pulmonary segments, the target segmental bronchus, arteries and intra-segment
      veins were accurately identi-fied and dissected by ligation or stapler cutting. After that,
      the anesthesiologist began to make preparations for the lung inflation. The portable nitrous
      oxide concentration detector (TD600-SH-B-N2O) was installed to detect N2O concentration
      (vol%), and then adjusted the anesthesia machine to the manual control mode. The flow of the
      selected gas mixture was set to 8L/min (Group75 set to N2O:O2=6:2, Group50 set to N2O:O2=4:4,
      Group0 set to O2=8), avoiding the interference of the total gas flow. When the N2O
      concentration detector reached the predetermined gas concentration, and then the collapsed
      lung was re-expanded completely with controlled airway pressure under 20 cmH2O (1cm H2O=0.098
      kPa) by the anesthesiologist. This procedure took approximately 1 min, and then FiO2=1.0 was
      performed after the initiation of the OLV.
    

Intervention name(s): nitrous oxide
Intervention type(s): Procedure
Intervention description(s): During one-lung ventilation with an open chest, the nonventilated lung collapses initially due to elastic recoil, which quickly brings the lung down to its closing capacity. Remaining gas in the lung is then removed by absorption into the pulmonary capillary blood. The rapid diffusion properties of N2O（Blood gas distribution coefficient is 0.47）would be expected to speed lung collapse and so facilitate surgery. The previous study suggested that increasing the concentration of N2O in mixtures of N2O/O2 will lead to a faster rate of collapse. When using nitrous oxide in oxygen during lung ventilation, ongoing oxygen uptake by blood shunting will serve to increase the partial pressure of nitrous oxide in parts of the lung that are still expanded. This will soon result in a partial pressure gradient for nitrous oxide uptake also, with a consequent faster rate of lung collapse than would occur in a patient being ventilated with 100% oxygen.
Other intervention name(s): oxygen
Intervention MeSH terms: Nitrous Oxide
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Triple (Participant, Investigator, Outcomes Assessor)
Primary purpose: Supportive Care
Keywords: pulmonary nodule; lung cancer; nitrous oxide; thoracoscopic anatomic segmentectomy