Clinical trial NCT06376123: Nomogram for Prediction of Alveolo-arterial Gradient During One-lung Ventilation
Official title: Nomogram for Prediction of Alveolo-arterial Gradient During One-lung Ventilation
Study type: OBSERVATIONAL
Overall status: NOT_YET_RECRUITING
Conditions: One-lung Ventilation
Keywords: One lung ventilation
Alveolo-arterial gradient
Nomograms
Lead sponsor: Bezmialem Vakif University
Sponsor class: OTHER
First posted: 2024-04-19
Enrollment: 40
Sex: ALL
Minimum age (years): 18
Maximum age (years): 100
Standard ages: ADULT
OLDER_ADULT
Accepts healthy volunteers: no
Observational model: CASE_ONLY
Time perspective: PROSPECTIVE
Sampling method: NON_PROBABILITY_SAMPLE
Study population: The study includes patients with pulmonary diseases, indicated for surgery. Among them are pulmonectomy, segmentectomy, lobectomy or wedge resections. All these types of surgery require one-lung (non-operating lung) ventilation. The patients should be electively operated, aged more that 18 years and must have no other pulmonary conditions (like fibrosis, pneumonia, lung oedema or interstitial lung disease) that could interfere with Alveolo-arterial gradient calculations.

Brief summary: The cause of hypoxia during one-lung ventilation is a common anaesthetic problem seen during thoracic surgery and is associated with increased fraction of shunted blood. This shunt occurs because the lung not participating in respiration stops saturating the blood with oxygen. The importance of our study is to collect some of the patient's parameters on a nomogram in the preoperative period, to predict the shunt fraction that will occur during one-lung ventilation and to make preparations and interventions accordingly.

Detailed description: The shunt that occurs during one lung ventilation varies for each patient and depends on many parameters. In this study, our aim was to predict the level of shunting during anaesthesia using readily available preoperative data. It is important to predict the hypoxia that will develop due to the shunt and to plan the methods that can be applied to reduce the shunt in terms of patient safety. One of the most reliable data reflecting the shunt level is the gradient of alvelo- arterial oxygen concentration. The calculation of alveolo-arterial oxygen gradient (A-a O2 gradient) is based on easily accessible parameters (pO2, pCO2, FiO2, age). The secondary aim of the study is to follow how the A-a O2 gradient (oxygen difference between alveolar and arterial blood) changes over time during surgery.

Demographic data, planned operation, comorbidities, side of surgery, ASA score, preoperative haemoglobin level, FEV1 (forced expiratory volume in 1 minute), FEV1/FVC (forced expiratory volume in 1 minute/forced vital capacity) ratio and EF (ejection fraction) will be recorded before surgery.FEV1, FEV1/FVC ratio values will be measured by spirometry test. Spirometry is a preoperative test routinely performed in all patients undergoing one lung ventilation. EF will be measured by preoperative echocadiography, which is also performed during the preoperative preparation of all patients scheduled for lung surgery. Patients undergoing VATS (video-assisted thoracotomy) surgery with planned lung resection, lobectomy, pulmonectomy, segmentectomy will be included in the study and all will be operated in the lateral decubitus position.

Once the patient is on the operating table, routine haemodynamic monitoring (heart rate, non-invasive blood pressure and blood oxygen saturation) will be performed.

The patient will then have an arterial cannula inserted for invasive arterial monitoring. It is a routine practice in major surgeries for blood gas monitoring, haemorrhage monitoring and monitoring of sudden blood pressure fluctuations. After insertion of the arterial cannula, blood gas will be taken in room air and arterial pO2 (partial oxygen pressure), arterial pCO2 (partial carbon dioxide pressure) and arterial SpO2 (oxygen saturation) will be recorded. At the same time, a venous blood sample (from any vein in the upper limb) will be taken in room air and vSpO2 (venous blood oxygen saturation) will be recorded.

All patients will undergo general anaesthesia and orotracheal intubation with a double lumen tube.

For anaesthesia induction, 1 mcg/kg fentanyl, 2 mg/kg propofol and 0.6 mg/kg rocuronium will be administered .After adequate mask ventilation and complete muscle relaxation, a double lumen intubation tube will be placed into the trachea by direct laryngoscopy. After the position of the tube and whether it is in the correct bronchus is supported by bronchoscopy, the patient will be connected to the mechanical ventilator and lateral decubitus (provided that the side to be operated on remains on top) will be given. Ventilator parameters will be selected the same for all patients. During two-lung ventilation, tidal volume 8 ml/kg, respiratory rate 12, peep 5, and FiO2 (fraction of inspired oxygen) = 60%. During one-lung ventilation, tidal volume will be set to 6 ml/min, respiratory rate 15, peep 5, and FiO2 = 70%. All patients will be ventilated in volume control mode.

At this stage, EtCO2 (end-tidal carbon dioxide) will be measured separately in both lungs. For this, first the airway from the lower lung will be clamped and the EtCO2 value will be recorded (dEtCO2 - dependent lung EtCO2). Then, vice versa, the airway from the lower lung will be clamped and the EtCO2 value obtained (ndEtCO2 - non-dependent lung EtCO2) will be recorded. The difference between these two values, D-EtCO2 (delta - end-tidal carbon dioxide) will be added to the data.

After these steps, one-lung ventilation will be started and the first A-a oxygen gradient will be recorded.

Eligibility criteria: Inclusion Criteria:

* Patients scheduled for elective VATS surgery.
* Age over 18 years.
* ASA 1-4 patients.

Exclusion Criteria:

* Patient refusal.
* Age below 18 years.
* Conditions that may impair oxygen diffusion: pulmonary oedema, fibrosis, interstitial lung disease, pneumonia.
* Emergency surgery.

Primary outcomes:
measure: Alveolo-arterial gradient
timeFrame: After intubation
measure: Alveolo-arterial gradient
timeFrame: After switching to one-lung ventilation.
Secondary outcomes:
measure: Alveolo-arterial gradient change
timeFrame: After switching to one lung ventilation
measure: Alveolo-arterial gradient change
timeFrame: The end of surgery
Other outcomes:
Locations:
city: Istanbul
country: Turkey
facility: Bezmialem Vakif University Dragos Hospital
state: Maltepe
Study officials:
affiliation: Anesthesiology and Reanimation Department, MD
name: Nigar Kangarli, MD
role: PRINCIPAL_INVESTIGATOR
References:
citation: Parab SY, Chatterjee A, Saxena RS. The utility of gradient of end-tidal carbon dioxide between two lungs in lateral decubitus position in predicting a drop in oxygenation during one-lung ventilation in elective thoracic surgery- A prospective observational study. Indian J Anaesth. 2021 Oct;65(10):744-749. doi: 10.4103/ija.ija_591_21. Epub 2021 Oct 29.
citation: Karzai W, Schwarzkopf K. Hypoxemia during one-lung ventilation: prediction, prevention, and treatment. Anesthesiology. 2009 Jun;110(6):1402-11. doi: 10.1097/ALN.0b013e31819fb15d.
citation: Alday E, Nieves JM, Planas A. Oxygen Reserve Index Predicts Hypoxemia During One-Lung Ventilation: An Observational Diagnostic Study. J Cardiothorac Vasc Anesth. 2020 Feb;34(2):417-422. doi: 10.1053/j.jvca.2019.06.035. Epub 2019 Jun 28.