Ventilatory Influence on Cerebral Oxygenation During VATS
Condition: Thoracic Diseases
MeSH terms: Thoracic Diseases
Study type: Interventional

Summary: 
      During (OLV) in (VATS) ; many physiological factors may increase risk of hypoxemia such as
      positioning and intrapulmonary shunt thus compromising cerebral blood flow and oxygenation,
      resulting in postoperative neurocognitive dysfunctions. The authors hypothesized that
      increasing (EtCO2) is the most convenient and powerful method for the management of cerebral
      desaturation. Methods: Seventy patients undergoing VATS were enrolled in this randomized
      controlled trial. Mechanical ventilation was adjusted to maintain an EtCO2 of 33-38 mm Hg in
      group I and an EtCO2 of 39-45 mm Hg in group II. Regional cerebral oxygenation was monitored
      using near-infrared spectroscopy (O3TM, Masimo, Irvine, CA) placed on the patient's forehead.
    

Detailed description: 
      All patients were operated on by the same surgical team. Patients with severe bronchial
      asthma, chronic obstructive pulmonary disease, severe renal insufficiency, severe liver
      dysfunction, cerebrovascular disease, coagulopathy, uncontrolled diabetes mellitus,
      uncontrolled hypertension or cardiovascular disease, mental disabilities, hearing impairment
      were excluded. Patients were seen on the day of surgery in the preoperative area prior to
      administration of premedication. A 16 or 18-gauge peripheral venous cannula and a 20-gauge
      radial artery were inserted to all patients preoperatively. Randomization was done by sealed
      envelope method and the patients were divided into two groups; group I (targeted EtCO2 32-38
      mmHg) and group II (targeted EtCO2 39-45 mmHg).

      In the operating room, Patients were monitored by 5 lead electrocardiogram, invasive arterial
      blood pressure (IABP) through the arterial catheter and (Masimo®, Irvine, CA) which provides
      non-invasive continuous technologies for monitoring and measuring many physiological
      variables such as arterial oxygen saturation (SpO2), heart rate (HR) and hemoglobin
      concentration (Hb%) from the (RD Rainbow® SET Pulse Co-Oximeter), end tidal CO2 by capnometer
      (Nomoline sampling line Masimo ®, CA), noninvasive blood pressure, body temperature, (O3 ®,
      Masimo, Irvine, CA) attached to the patient to provide continuous monitoring of regional
      cerebral oxygen saturation (rSO2) of the two hemispheres by a near-infrared spectroscopy
      sensors connected to regional oximetry system. The sensors were placed bilaterally on
      patient's forehead after the skin of the forehead had been wiped with an alcohol swab and
      allowed to dry as recommended by the manufacturer, and (SedLine ®, Masimo, CA) brain function
      monitoring by Patient State Index (PSI) which is a processed EEG parameter affected by the
      anesthetic agents.

      Before general anesthesia, an epidural catheter was inserted at T5, 6 or T6, 7 interspace and
      a test dose of 3 ml of 2% lidocaine with epinephrine was given to exclude intrathecal or
      intravascular positioning of the catheter, for perioperative administration of 4-8 ml/ h of
      bupivacaine 0.125%. After preoxygenation for 2 minutes, anesthesia was induced in all
      patients with propofol 1.5-2 mg /kg, fentanyl 3-5 micg/ kg, and rocuronium 0.6-0.8 mg/ kg. A
      left-sided double-lumen tube (DLT) (39F for males and 37F for females) (Broncho-Cath;
      Mallinckrodt Medical Ltd, Athlone, Ireland) was used for endotracheal intubation and checked
      by fibreoptic bronchoscope (Olympus company, Tokyo, Japan) and auscultation. The patient was
      then positioned in left or right lateral decubitus position according to the surgical side
      and the DLT was rechecked again. Maintenance anesthesia was provided by sevoflurane to keep a
      patient state index (Psi) measured by (SedLine, Masimo®, CA) level between 25-50. Additional
      doses of fentanyl to a total of 7-15 micg/kg and rocuronium boluses were given to control the
      depth of anesthesia and to maintain stable neuromuscular block.

      Initially, all patients were applied with two-lung ventilation using a constant-flow,
      volume-controlled ventilation mode with a tidal volume 8 mL/kg of the actual body weight, an
      inspiratory to expiratory (I:E) ratio of 1:2, a respiratory rate of 12 breaths/min, oxygen
      flow rate of 1.5 L/min, and FiO2 (fraction of inspiratory oxygen) of 1.0 without PEEP. OLV
      was initiated with skin incision, and the tube lumen of the dependent non ventilated lung was
      opened to room air. During OLV, tidal volume was reduced to 7 mL/kg, respiratory rate of
      12-15 breaths/min, PEEP of 5 cm H2 O, FiO2 of 1.0, oxygen flow rate of 1.5 L/min, I:E 1:2.
      Then patients were assigned a ventilation strategy designed to achieve an EtCO2 of 32-3 8mm
      Hg or of 39-45mmHg in group I or II respectively throughout the intraoperative period by
      (MAQUET FLOW i anesthesia delivery system). This could be achieved by changing the
      respiratory rate and inspiratory: expiratory (I:E) ratio . rSO2 values obtained and After
      achieving and maintaining the target EtCO2 for 3 minutes baseline %ΔrSO2 was considerd and
      recorded every 10 minutes till the end of surgery. Although the data were available to both
      the anesthetist, there were no specific recommendations made on possible interventions by the
      study team. Peak inspiratory pressure (PIP) was monitored using a side stream spirometry
      device (MAQUET FLOW-i). If PIP >30 cmH2O, the volume controlled ventilation mode was changed
      to a pressure-controlled mode to achieve a targeted VT. Intraoperative fluid replacement by
      lactated Ringer's solution or hydroxyethyl starch solution was infused at rate of 8-10
      ml/kg/h.

      rSPO2, PSi, SpO2, mean BP, and HR were recorded before anesthesia, 5 minutes after
      intubation, 5 minutes after putting the patient in lateral position, after initiating OLV,
      after achieving and maintaining this target ETCO2 for 3 minutes, and every 10 min till the
      end of surgery . Hypotension (defined as more than 20% drop in mean ABP from baseline values
      obtained on admission to the operating room) was treated with ephedrine in 4 mg increments.
      We used ephedrine rather than phenylephrine as a previous study showed that cerebral oxygen
      saturation decreases after phenylephrine but remains unaffected after ephedrine in
      anaesthetized patients.

      ABG analysis by (ABL 800, Radiometer, Copenhagen, Denmark. PaO2, PaCO2 , pH, serum lactate,
      HCO3 concentration, haemoglobin concentration (Hb) ,and sodium and potassium ion
      concentrations. ABG was performed before anesthesia, after induction of anesthesia when the
      patient was in supine position, after positioning in the lateral decubitus position during
      two lung ventilation (TLV), 15 minutes after one lung ventilation (OLV) and every 15 minutes
      till the end of surgery. All the patients were in lateral position with head down 10º during
      surgery. If SpO2 decreased below 92% and lasted 30 seconds during OLV, surgery was
      temporarily interrupted and two-lung ventilation was resumed. At the end of surgery patient
      turned supine and neuromuscular block was antagonized with sugamadex 2mg/kg. At the time of
      closure of thoracic cavity, two-lung ventilation was started and both lungs were re-expanded
      by hand bagging in all patients. Aldrete scores were recorded by post anesthesia care unit
      (PACU) nurses blinded to group assignment on arrival to the PACU and then every 15 min
      thereafter until discharge from PACU. Patients were followed up for any complications of lung
      during their hospital stays. Delirium was assessed using a validated and widely used
      Confusion Assessment Method (CAM) rating scale, adapted from Inouye et al, immediately on
      arrival to hospital, then within 18-24 hours after surgery. Diagnosis of delirium requires
      the presence of both acute onset with fluctuating course and inattention, together with
      either disorganized thinking or altered level of consciousness. A single trained interviewer,
      blinded to randomization and proficient and trained in CAM, conducted all the assessments
      preoperatively when each patient arrived at the hospital and on the next day after surgery.
    

Intervention name(s): Monitoring of regional cerebral oxygenation
Intervention type(s): Diagnostic Test
Intervention description(s): Regional cerebral oxygenation was monitored using near-infrared spectroscopy (O3TM, Masimo, Irvine, CA) placed on the patient's forehead.
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: Triple (Participant, Care Provider, Outcomes Assessor)
Primary purpose: Diagnostic
Keywords: OLV