Repeated intermittent hypoxic stimuli to operative lung reduce hypoxemia during subsequent one-lung ventilation for thoracoscopic surgery: A randomized controlled trial

Abstract

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.

The Use of Oxygen Reserve Index in One-Lung Ventilation and Its Impact On Peripheral Oxygen Saturation, Perfusion Index and Pleth Variability Index

“…For calculation of sample size, a hypoxemia rate of 30% after OLV, and a 10% precision at 95% con dence intervals, an alpha error of 0.05, and a power of 80%, the number of patients for the study was calculated as 28 patients. [8, 10,15]…”

“…Masimo Rainbow Signal Extraction Technology introduced the device. [13][14][15][16] ORi is a parameter-driven from this device that is between 0 and 1 values, and it is sensitive to the changes in arterial oxygenation in the blood, with the range of 100 to 200 mmHg. [2,[8][9][10]13,[18][19][20][21] When oxygenation is in the moderate hyperoxic content showing an arterial blood oxygenation value of 100-240 mmHg in arterial blood gas analysis, the pulse oximeter SpO2 value remains 100%, whereas there is a decrease in the value of ORi.…”

“…The third set of values was after general anesthesia induction with a 100% mask ventilation before laryngoscopy. [8- 10,15] The other ten different timepoints are also determined during anesthesia maintenance throughout the thoracic operation. These include; 5 minutes after tracheal intubation during two-lung ventilation in the supine position and 5 minutes after placing the patient in a lateral position with two-lung ventilation; at 1 minute after OLV placement, at two minutes after OLV placement, and afterward at ve minutes 10 minutes, 15 minutes, 30 minutes, 45 minutes, 60 minutes and 90 minutes.…”

“…The incidence of thromboembolic complications, arrhythmia, pneumonia, the duration of hospital and intensive care unit stay were recorded. [9,13,[15][16][17][18] Intravenous ephedrine (Ephedrine, Osel Pharmaceutical, Turkey) at a dose of 10 mg bolus injections were considered if SBP was less than 90 mmHg. Hypotension was de ned as a decrease in MAP more signi cant than 20% after anesthesia induction and treated with intermittent bolus doses of 5 mg ephedrine.…”

“…The necessary closure related procedure, including necessary suturing, aspiration, and irrigation of uids and blood, are performed. [13,15,18] 2.5 The Ethical Considerations Trakya University Faculty of Medicine University Ethical Committee agreed and approved the study in February 2020. All patients approved the fully informed written consent to participate in the study.…”