Start Of One-lung Ventilation Research Articles

Comparative effects of variable versus conventional volume-controlled one-lung ventilation on gas exchange and respiratory system mechanics in thoracic surgery patients: A randomized controlled clinical trial

BackgroundMechanical ventilation with variable tidal volumes (V-VCV) has the potential to improve lung function during general anesthesia. We tested the hypothesis that V-VCV compared to conventional volume-controlled ventilation (C-VCV) would improve intraoperative arterial oxygenation and respiratory system mechanics in patients undergoing thoracic surgery under one-lung ventilation (OLV). MethodsPatients were randomized to V-VCV (n = 39) or C-VCV (n = 39). During OLV tidal volume of 5 mL/kg predicted body weight (PBW) was used. Both groups were ventilated with a positive end-expiratory pressure (PEEP) of 5 cm H2O, inspiration to expiration ratio (I:E) of 1:1 (during OLV) and 1:2 during two-lung ventilation, the respiratory rate (RR) titrated to arterial pH, inspiratory peak-pressure ≤ 40 cm H2O and an inspiratory oxygen fraction of 1.0. ResultsSeventy-five out of 78 Patients completed the trial and were analyzed (dropouts were excluded). The partial pressure of arterial oxygen (PaO2) 20 min after the start of OLV did not differ among groups (V-VCV: 25.8 ± 14.6 kPa vs C-VCV: 27.2 ± 15.3 kPa; mean difference [95% CI]: 1.3 [−8.2, 5.5], P = 0.700). Furthermore, intraoperative gas exchange, intraoperative adverse events, need for rescue maneuvers due to desaturation and hypercapnia, incidence of postoperative pulmonary and extra-pulmonary complications, and hospital free days at day 30 after surgery did not differ between groups. ConclusionsIn thoracic surgery patients under OLV, V-VCV did not improve oxygenation or respiratory system mechanics compared to C-VCV.Ethical Committee: EK 420092019.Trial registration: at the German Clinical Trials Register: DRKS00022202 (16.06.2020).

Association between Oxygen Reserve index and arterial partial pressure of oxygen during one-lung ventilation: a retrospective cohort study.

We aimed to investigate the association between the Oxygen Reserve index (ORi) and arterial partial pressure of oxygen (PaO2) during one-lung ventilation in patients who underwent non-cardiac thoracic surgery requiring one-lung ventilation. This retrospective study assessed the eligibility of 578 adult patients who underwent elective non-cardiac thoracic surgery requiring one-lung ventilation at a tertiary hospital, and their electronic medical records were reviewed. The ORi monitor was used in all patients during anesthesia, and arterial blood gas analysis was routinely performed 15 min after the initiation of one-lung ventilation. The primary endpoint was the association between ORi and PaO2 which were measured simultaneously during one-lung ventilation. We also investigated the risk factors for PaO2 less than 150 mmHg during one-lung ventilation. Total of 554 patient were included in the analysis. The ORi value measured 15 min after the start of one-lung ventilation was significantly associated with PaO2 in the linear regression model (r2 = 0.5752, P < 0.001), and 0.27 of the ORi value could distinguish PaO2 ≥ 150 mmHg (sensitivity 0.909, specificity 0.932). Risk factors for PaO2 < 150 mmHg during one-lung ventilation included a lower ORi, older age, higher body mass index, left-sided one-lung ventilation, and lower hemoglobin concentrations. This study suggested that ORi could provide useful information on arterial oxygenation even during one-lung ventilation for non-cardiac thoracic surgery.

Impact of Lower Tidal Volumes During One-Lung Ventilation: A 2022 Update of the Meta-analysis of Randomized Controlled Trials

To clarify the influence of lower tidal volume (4-7 mL/kg) compared with higher tidal volume (8-15 mL/kg) during one-lung ventilation (OLV) on gas exchange and postoperative clinical outcome. Meta-analysis of randomized trials. Thoracic surgery. Patients receiving OLV. Lower tidal volume during OLV. Primary outcome was PaO2-to-the oxygen fraction (PaO2/FIO2) ratio at the end of the surgery, after the reinstitution of two-lung ventilation. Secondary endpoints included perioperative changes in PaO2/FIO2 ratio and carbon dioxide (PaCO2) tension, airway pressure, the incidence of postoperative pulmonary complications, arrhythmia, and length of hospital stay. Seventeen randomized controlled trials (1,463 patients) were selected. Overall analysis showed that the use of low tidal volume during OLV was associated with a significantly higher PaO2/FIO2 ratio 15 minutes after the start of OLV and at the end of surgery (mean difference 33.7 mmHg [p=0.02] and mean difference 18.59 mmHg [p < 0.001], respectively). The low tidal volume also was associated with higher PaCO2 values 15 minutes and 60 minutes after the start of OLV and with lower airway pressure, which was maintained during two-lung ventilation after surgery. Moreover, the application of lower tidal volume was associated with fewer postoperative pulmonary complications (odds ratio 0.50; p < 0.001) and arrhythmias (odds ratio 0.58; p=0.009), with no difference in length of hospital stay. The use of lower tidal volume, a component of protective OLV, increases the PaO2/FIO2 ratio, reduces the incidence of postoperative pulmonary complications, and should be considered strongly in daily practice.

USE OF VIDEO LARYNGOSCOPE FOR DIFFICULT AIRWAY MANAGEMENT IN THORACIC SURGERY: A CASE STUDY

We present the clinical case of a 76-year-old male with the following medical history: Active smoker (2 packs/day),moderate obesity, moderate COPD. arterial hypertension, mellitus diabetes 2, dyslipidemia. Lacunar stroke without neurological damage, infrarenal abdominal aortic aneurysm of 40 mm, under follow-up in policlinic of Vascular Surgery, 1st degree atrioventricular block, under follow-up by Cardiology. Normal Echocardiography. PET-CT: Hypermetabolic pulmonary nodule in RUL, suggestive of cancer. FUNCTIONAL TESTS: Moderate obstructive pattern. FEV1 2.20 (72%), FEV1/FVC 58. DLCO 5.80 (64%). AIRWAY EXPLORATION: Retrognatia, Mallampati III, significant cervical stiffness, thick neck and degree of movement of head and neck < 80°. Case Management: Placement of thoracic epidural catheter (T5-T6) prior to induction for analgesic control during intraoperative and postoperativeperiod. Non-invasive blood pressure monitoring, 5-lead ECG, temperature, peripheral oxygen saturation (SpO2), Bispectral Index (BIS) and Train-of-four (TOF). In the presence of predictors of possible difficult airway and ventilation, material is prepared for management of possible difficult airway Pre-oxygenation with face mask and FiO2 1 until EtO2 85 mmHg is reached. Rapid sequence induction was performed with intravenous midazolam, fentanyl, propofol and 1,2 mg/kg of rocuronium. After reaching TOF 0, direct laryngoscopy was initially performed but a Cormark-Lehane (CL) III was observed.Indirect laryngoscopy was then performed with a McGrath video laryngoscope with a n°4 disposable blade, showing a CL I. Subsequently, an 11 Fr airway exchange catheter was introduced through the vocal cords into the trachea; then, the proximal end of the airway exchange catheter was inserted into the endobronchial lumen of the 37Fr Vivasight DL, to permet its insertion into the trachea guided by this airway exchange catheter under the vision of the McGrath videolaryngoscope. Once the VivaSight DL was inserted into the trachea, the airway exchange catheter was removed and the VivaSight DL tube was turned left 90° and was inserted successful into the left main bronchus guided by embedded camera of this special type of DLT. Anesthesia maintenance was performed with inhalated sevoflurane and continuous intravenous infusion of remifentanil and rocuronium. Epidural elastomer of levobupivacaine 0.125% at 7 ml/h. Controlled ventilation is maintained in volume control mode, with Tidal Volume (TV) at 7 ml/kg ideal weight in two-lung ventilation and 5 ml/kg ideal weight in one-lung ventilation. Alveolar Recruitment Maneouvres (ARM) after intubation and at start of one-lung ventilation (OLV) were performed. Good mechanics and adequate gas exchange throughout the procedure, with no episodes of desaturation. After completion of surgery, reversal of neuromuscular blockade was achieved with sugammadex at 2 mg/kg. After checking TOF ratio> 90% and adequate level of consciousness, optimal respiratory mechanics and a 100% SpO2, extubation was performed without incident. He was transferred to the intensive care unit for post-surgical control during the first 24 hours.

The use of oxygen reserve index in one-lung ventilation and its impact on peripheral oxygen saturation, perfusion index and, pleth variability index

BackgroundOur goal is to investigate the use of the oxygen reserve index (ORi) to detect hypoxemia and its relation with parameters such as; peripheral oxygen saturation, perfusion index (PI), and pleth variability index (PVI) during one-lung ventilation (OLV).MethodsFifty patients undergoing general anesthesia and OLV for elective thoracic surgeries were enrolled in an observational cohort study in a tertiary care teaching hospital. All patients required OLV after a left-sided double-lumen tube insertion during intubation. The definition of hypoxemia during OLV is a peripheral oxygen saturation (SpO2) value of less than 95%, while the inspired oxygen fraction (FiO2) is higher than 50% on a pulse oximetry device. ORi, pulse oximetry, PI, and PVI values were measured continuously. Sensitivity, specificity, positive and negative predictive values, likelihood ratios, and accuracy were calculated for ORi values equal to zero in different time points during surgery to predict hypoxemia. At Clinicaltrials.gov registry, the Registration ID is NCT05050552.ResultsHypoxemia was observed in 19 patients (38%). The accuracy for predicting hypoxemia during anesthesia induction at ORi value equals zero at 5 min after intubation in the supine position (DS5) showed a sensitivity of 92.3% (95% CI 84.9–99.6), specificity of 81.1% (95% CI 70.2–91.9), and an accuracy of 84.0% (95% CI 73.8–94.2). For predicting hypoxemia, ORi equals zero show good sensitivity, specificity, and statistical accuracy values for time points of DS5 until OLV30 where the sensitivity of 43.8%, specificity of 64%, and an accuracy of 56.1% were recorded. ORi and SpO2 correlation was found at DS5, 5 min after lateral position with two-lung ventilation (DL5) and at 10 min after OLV (OLV10) (p = 0.044, p = 0.039, p = 0.011, respectively). Time-dependent correlations also showed that; at a time point of DS5, ORi has a significant negative correlation with PI whereas, no correlations with PVI were noted.ConclusionsDuring the use of OLV for thoracic surgeries, from 5 min after intubation (DS5) up to 30 min after the start of OLV, ORi provides valuable information in predicting hypoxemia defined as SpO2 less than 95% on pulse oximeter at FiO2 higher than 50%.

Dexmedetomidine combined with protective lung ventilation strategy provides lung protection in patients undergoing radical resection of esophageal cancer with one-lung ventilation

To investigate the effect of dexmedetomidine combined with pulmonary protective ventilation against lung injury in patients undergoing surgeries for esophageal cancer with one-lung ventilation (OLV). Forty patients with undergoing surgery for esophageal cancer with OLV were randomly divided into pulmonary protective ventilation strategy group (F group) and dexmedetomidine combined with protective ventilation strategy group (DF group; n=20). In F group, lung protective ventilation strategy during anesthesia was adopte, and in DF group, the patients received intravenous infusion of dexmedetomidine hydrochloride (0.3 μg · kg-1 ·h-1) during the surgery starting at 10 min before anesthesia induction in addition to protective ventilation strategy. Brachial artery blood was sampled before ventilation (T0), at 30 and 90 min after the start of OLV (T1 and T2, respectively) and at the end of the surgery (T3) for analysis of superoxide dismutase (SOD), malondialdehyde (MDA), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), arterial oxygenation pressure (PaO2), oxygenation index (OI) and lung compliance (CL). At the time points of T1, T2 and T3, SOD level was significantly higher and IL-6 level was significantly lower in the DF group than in F group (P &lt; 0.05). The patients in DF group showed significantly higher PaO2, OI and CL index than those in F group at all the 3 time points. Dexmedetomidine combined with pulmonary protective ventilation strategy can reduce perioperative lung injury in patients undergoing surgery for esophageal cancer with OLV by suppressing inflammation and oxidative stress to improve lung function and reduce adverse effects of the surgery.

Comparison of the effects of sevoflurane and propofol anesthesia on pulmonary function, MMP-9 and postoperative cognition in patients receiving lung cancer resection.

Effects of sevoflurane and propofol anesthesia on pulmonary function, matrix metalloproteinase-9 (MMP-9) and postoperative cognition were compared in patients undergoing simple resection of lower lobe of left lung. Retrospective method was used to analyze 58 cases of lung cancer patients treated by simple resection of lower lobe of left lung in the Second Hospital of Dalian Medical University from October 2016 to October 2017, and they were divided into two groups: Sevoflurane group (n=32) with sevoflurane anesthesia and propofol group (n=26) with propofol anesthesia. In the present study, the moment before induction of anesthesia (T1), before the start of one-lung ventilation (T2), before the end of one-lung ventilation (T3), after closed chest surgery (T4), 24 h after surgery (T5), calculate alveolar-arterial oxygen difference (A-aDO2), respiratory index (RI) and intrapulmonary shunt ratio (Qs/Qt), were compared between the two groups. The serum MMP-9 concentration at T1, T4 and T5 were detected by enzyme linked immunosorbent assay. The cognitive function of two groups was assessed by Mini-Mental State Examination (MMSE) 1 day before surgery and 1 and 10 days after surgery. The A-aDO2 level at T4 in sevoflurane group was significantly higher than that in propofol group (P<0.05). The RI level at T3, T4, the Qs/Qt and the MMP-9 level at T4 in the sevoflurane group was significantly higher than that in the propofol group (P<0.05). The MMSE score in sevoflurane group was significantly lower than that in propofol group 1 and 10 days after surgery (P<0.05). Propofol has little effect on pulmonary function and can decrease inflammatory factor MMP-9. Both sevoflurane and propofol have an effect on cognitive function after lung cancer resection, but propofol can reduce cognitive impairment in patients with lung cancer.

The effects of different inspired oxygen concentration on the pulmonary collapse and postoperative recovery of thoracoscopic surgery

Objective To investigate the effect of different inhalation oxygen concentration on the lung collapse and postoperative recovery of thoracoscopic surgery. Methods Patients who underwent elective thoracoscopic radical resection of lung cancer were randomly divided into group A (n=29) and group B (n=30). Patents in the group A received a gas mixture of oxygen and air (FiO2=50%) whereas and patients in the group B received 100% oxygen(FiO2=100%) until the start of one lung ventilation (OLV). Then, the dependent lungs were ventilated with 50% oxygen during OLV in both groups. The surgeon evaluated the lung collapse using LCS score and Campos score for lung collapse. They were scaled at 1 min after the opening of the pleura(T0), 10 min after the start of OLV (T1), 20 min after the start of OLV (T2) and 30 min after the start of OLV (T3). During two lungs ventilation, arterial blood gases were measured before anesthesia induction, at 10, 20, 30 min after initiation of OLV. The incidence of postoperative atelectasis by chest CT at the third day after operation, hospital length of stay(LOS) and the incidence of patchy consolidation were recorded. Results At T1 and T2, the LCS scores and Campos scales of group B were higher than scores of group A (P 0.05). The oxygen partial pressure of group B was higher than that of the group A before 20 min of OLV, but the difference were not significant after 20 min. The incidence of postoperative atelectasis, LOS and the incidence of patchy consolidation were not different (P>0.05) Conclusions The inhalation of 100% oxygen before the OLV can make the pulmonary collapse effect better, and it has no effect on postoperative recovery. Key words: Video assisted thoracic operation; Pulmonary collapse; Fraction of inspired oxygen; One lung ventilation

Effect of One-Lung Ventilation on Blood Sevoflurane and Desflurane Concentrations

To determine the blood sevoflurane and desflurane concentrations during one-lung ventilation (OLV). Randomized, single-blind study. Single university hospital. The study comprised 24 patients, 35 to 70years old who were scheduled for either a major abdominal surgery or thoracotomy. The patients were divided into the following 4 groups: sevoflurane two-lung ventilation (TLV), sevoflurane OLV, desflurane TLV, and desflurane OLV. Vaporizers were set at 1.5% sevoflurane or 6% desflurane. In the TLV groups, blood samples were taken in 10-minute intervals starting 40 minutes after the start of TLV (T1-T9) for blood gas analysis and gas chromatography. In the OLV groups, the first sample was collected at 40 minutes of TLV (T1), and other samples were collected in 10-minute intervals from the start of OLV (T2-T9). Saturation of peripheral oxygen (SpO2), hemodynamic variables, and inspired and end-tidal volatiles were recorded. The fraction uptake of the volatile agents (F) was calculated for each patient at the same time points. The mean arterial sevoflurane concentration in the sevoflurane OLV group at T1 decreased from 40.7 ± 4.4 to 30.2 ± 2.5 µg/mL at T3 (p = 0.014, 26% decrease). In the OLV desflurane group, the mean arterial desflurane concentration at T1 declined from 224.6 ± 44.8 to 159.8 ± 32 µg/mL at T3 (p=0.018, 29% decrease). However, the reduction of sevoflurane concentration compared with that of desflurane at T3 was not statistically significant (p = 0.31). In addition, the fraction uptake of the volatile agents values significantly increased at the start of OLV (p = 0.001). An OLV procedure causes a decrease in the both arterial and venous blood concentrations of sevoflurane and desflurane. This reduction is believed to be due to ventilation-perfusion mismatch.

Bronchial suction does not facilitate lung collapse when using a double-lumen tube during video-assisted thoracoscopic surgery: a randomized controlled trial.

Bronchial suction through the lumen of a bronchial blocker has been reported to accelerate lung collapse. The aim of the current study was to examine whether bronchial suction could also facilitate lung collapse when using a double-lumen tube (DLT). Eighty patients scheduled for elective video-assisted thoracoscopic surgery for lung cancer using a DLT for one-lung ventilation (OLV) were randomised into an arm that received bronchial suction and an arm that underwent spontaneous collapse (n=40 per arm). For bronchial suction, a pressure of -30 cmH2O was applied to the lumen of the non-ventilated lung during the first minute of OLV. The primary endpoint was the degree of lung collapse at 10 min after the start of OLV, assessed on a 10-point visual analogue scale (0: fully inflated; 10: complete collapse). Secondary outcomes included lung collapse at 1 and 5 min after the start of OLV, as well as occurrence of intraoperative hypoxemia. Median (interquartile range) lung collapse scores at 10 min were statistically greater in the bronchial suction arm than in the spontaneous collapse arm [9.0 (9.0-9.0) vs. 8.5 (8.0-9.0); P=0.004]. Lung collapse was also statistically greater in the bronchial suction arm at 5 min [8.0 (7.0-8.0) vs. 7.0 (6.25-7.0) min; P=0.002] and 1 min [4.0 (4.0-5.0) vs. 2.0 (2.0-2.0) min; P<0.001]. None of the patients experienced intraoperative hypoxemia and operative complications. Bronchial suction resulted in statistically greater but not clinically meaningful lung collapse when using a DLT. However, greater degree of lung collapse at 1-min could be helpful in reducing accidental injuries.

Importance of alveolar recruitment strategy revisited.

Low tidal volume, rather than high tidal volume, ventilation is often used for mechanical ventilation during surgery to avoid lung injury due to alveolar overdistention. Under general anesthesia with a muscle relaxant, there is a risk of compressing the lungs by diaphragmatic displacement, which can be aggravated in patients placed in the supine position. Such a risk becomes even higher during reduced tidal volume ventilation, causing alveolar atelectasis and hypoxemia. Therefore, positive end expiratory pressure (PEEP) is applied to prevent spontaneous closure of alveoli. In this volume, Jung et al. [1] reports on the importance of the alveolar recruitment strategy (ARS). The authors applied ARS before the start of one-lung ventilation (OLV), and compared the oxygenation score between high- and low-tidal volume groups. Repetitive open and closure of collapsed alveoli by positive pressure ventilation could cause damage to the capillary endothelium and alveolar epithelium. Excessive expansion and risk of alveolar injury may even occur during low tidal volume ventilation due to an uneven distribution of ventilated volume to already open alveoli. However, Jung et al. [1] showed that preemptive ARS commonly increases PaO2 without causing hemodynamic instability in groups with or without PEEP during OLV. The improvement in oxygenation was better in the group where ARS was combined with PEEP. Their study design and intriguing results will draw the attention of general readers of the journal. The ARS helps to open collapsed alveoli, which is effectively maintained by PEEP. Therefore, both ARS and PEEP maneuvers are compulsory to improve oxygenation and lung mechanics during general anesthesia [2]. Diverse ARS methods have been reported in recent clinical studies. The recommended ARS is peak inspiratory pressure up to 40 cmH2O at 10 respiratory cycles with 15-20 cmH2O PEEP. Adequate PEEP level following ARS is reportedly 5-20 cmH2O depending on the condition of the patient (i.e., pulmonary function and physical condition) and also the type of operation. The time to apply ARS is typically (1) immediately after intubation before confirming lung sounds, (2) after suctioning, or (3) just before extubation. Functional residual capacity is reduced in 50% of patients after tracheal suctioning, in which case combined ARS and PEEP effectively restores PaO2 [3]. Along with increased PaO2, several reports have indicated that ARS with PEEP during OLV decreases AaDO2, and decreases the alveolar dead space ventilation ratio [4,5,6]. In addition to OLV anesthesia, ARS with appropriate PEEP is required to improve PaO2 in patients with minimal lung injury during other surgeries with a high risk of atelectasis such as laparoscopic surgery [7,8,9], pediatric patients [10], and obese patients [9]. This preemptive ARS effect during low tidal volume OLV has been described previously [11]. Preemptive ARS can also be applied before pneumoperitoneum during laparoscopic surgery [8] with the purpose of improving oxygenation. However, high intrathoracic pressure during ARS may cause hemodynamic instability. Therefore, adjustment of the pressure and application duration should consider a patient's hemodynamic status and the potential risks [5]. In obese patients, higher pressures are required for adequate ARS and PEEP [9]. The risk of hemodynamic derangement by such high pressures can be prevented by intravascular volume replacement [12]. Interestingly, one study reported that applying ARS with PEEP to the donor lung in situ as well as after transplantation lowers the risk of primary graft dysfunction [13]. Several reports have suggested the beneficial effects of ARS with PEEP during general abdominal surgery to reduce post-operational complications [14]. In conclusion, applying ARS and PEEP during surgery or in patients vulnerable to atelectasis is helpful for improving oxygenation and lowering postoperative pulmonary complications. PEEP must be sustained to keep alveoli in their open state and optimize patient oxygenation. In addition, adequate ARS before applying PEEP is essential to maximize the benefits of PEEP.

Thoracotomy for lung lesion does not affect the accuracy of esophageal temperature

BackgroundThere are several sites for measuring body temperature. Correct reading of core temperature is imperative for patients undergoing major operations under anesthesia. In certain situations, the sites of measurement may be close to the surgical area, and thus the measurement is easily prejudiced by the influence environment. We hypothesized that the body temperature, if monitored in the esophagus, would be lower than obtained from the tympanic membrane during thoracotomy for lung pathology under general anesthesia. Materials and methodsThe study involved 32 patients, of American Society of Anesthesiologists (ASA) physical status I or II, who were to undergo elective thoracotomy for lung disorders. General anesthesia was induced with fentanyl, propofol, and rocuronium and maintained with sevoflurane in oxygen. The tympanic membrane probe was placed prior to when general anesthesia was administered, and the esophageal probe was inserted after administration of general anesthesia. Both the individualized temperatures were recorded at 5-minute intervals, and were compared at each change of surgical situation. ResultsThe tympanic membrane temperature was higher than esophageal temperature after initiation of one-lung ventilation (OLV) with statistical significance. The magnitude of decrease in temperature between two individualized temperatures, as compared from start of OLV, was greater in tympanic membrane temperature, especially at 30 minutes after OLV (p < 0.02, difference = –0.09 ± 0.22) and at the time point of the lowest temperature (p = 0.002, difference = −0.14 ± 0.24). There was no clinical difference of situation found (difference > 0.5°C) in the measuring sequences. ConclusionThe accuracy of esophageal temperature seemed not to be affected during thoracotomy for lung lesion, in comparison with that of tympanic temperature. From clinical viewpoints, the monitoring of esophageal temperature could be more reliable in such surgical situation.

One-lung ventilation does not result in cerebral desaturation during application of lung protective strategy if normocapnia is maintained

Previously a report has suggested that administration of lung protective strategy for one-lung ventilation(OLV) results in oxygen desaturation of the brain parenchyma. The aim of our work was to confirm that the maintenance of normocapnia during protective OLV strategy results in alteration of cerebral blood fl ow and cerebral oxygen saturation as compared to double-lung ventilation. Data were obtained from 24 patients undergoing thoracic surgery. Cerebral oxygen saturation (rSO2) was continuously monitored by INVOS 5100C Cerebral Oxymeter System along with measurement of cerebral blood fl ow velocity (MCAV) by transcranial Doppler sonography. Arterial blood samples were taken for blood gas analysis in the awake state, in the supine and lateral decubitus position during double-lung ventilation (DLV), and during OLV. When ventilation was changed from DLV to OLV, no significant change was observed in rSO2. A significant decrease of rSO2 was found compared to the value observed during DLV in lateral decubitus at the time point 60 minutes after the start of OLV. No clinically significant changes in the MCAV was observed throughout the course of the thoracic surgical procedure. OLV does not result in clinically relevant decreases in cerebral blood fl ow and cerebral oxygen saturation during application of lung protective ventilation if normocapnia is maintained.

Smoking as a risk factor for intraoperative hypoxemia during one lung ventilation

Smoking is associated with many intra and postoperative events, especially respiratory complications. Hypoxemia and airway damage are found to aggravate any pre-existing respiratory pathology among smokers. One lung ventilation (OLV) carries a 4-10 % risk of development of hypoxia. The purpose of this study was to predict the incidence of hypoxemia for smokers during OLV for patients undergoing video-assisted thoracoscopic surgery (VATS). Sixty patients undergoing VATS using OLV by double lumen tube were included in this pilot cross-sectional study. These patients were divided into 2 groups, group S which included 30 heavy smoker patients (smoking more than 20 cigarettes per day for more than 20 years) and group NS which included 30 non-smoker patients. Intra and postoperative arterial oxygen tension (PaO(2)), arterial carbon dioxide tension (PaCO(2)), and intraoperative peak airway pressure were compared between the 2 groups. PaO(2) was significantly higher in the non-smoker group than in the smoker group, both at the start and end of OLV. It was 173 ± 68 mmHg for NS compared with 74 ± 10.8 mmHg for S at the start of OLV; at the end of OLV it was 410 ± 78 mmHg for the former and 360 ± 72 mmHg for the latter (P < 0.05). From this study it can be concluded that for heavy smoker patients there was a significant reduction in arterial oxygen tension (PaO(2)) in comparison with non-smokers. However, hypoxemia reported for both groups was comparable.

Comparison of cardiac output as assessed by transesophageal echo-Doppler and transpulmonary thermodilution in patients undergoing thoracic surgery

Study Objective To evaluate the accuracy of cardiac index (CI) as measured by echo-transesophageal Doppler monitoring (echo-TDM) with CI measured by the transpulmonary thermodilution technique. Design Prospective, observational study. Setting University hospital. Patients 16 patients scheduled for elective lung cancer resection. Interventions Patients underwent two-lung ventilation (TLV) and one-lung ventilation (OLV). Measurements and Main Results CI measurements were analyzed using Bland-Altman plots. Absolute values of CI as measured by both devices were highly correlated (r 2 ranging from 0.72 to 0.77), as were relative changes in CI after the start of OLV (r 2 = 0.48, P = 0.006). Before, during, and after OLV, TDM-CI biases were 0.46 ± 0.28 L/min/m 2, 0.25 ± 0.18 L/min/m 2, and 0.35 ± 0.29 L/min/m 2, respectively. Limits of agreement remained stable throughout the three measurement periods (range −1.08 to 0.21 L/min/m 2). The mean percentage error of CI measurements was 21.9% compared with the thermodilution technique. Although no adverse events were reported, 11% of measurement sets were incomplete due to poor signal detection. Conclusions Echo-TDM is a safe technique, allowing continuous semi-invasive assessment of hemodynamic changes in most patients undergoing open-chest surgery. Doppler-derived CI values showed significant biases and moderate clinical agreement with transpulmonary thermodilution during TLV and OLV.

The Association Between the Initial End-Tidal Carbon Dioxide Difference and the Lowest Arterial Oxygen Tension Value Obtained During One-Lung Anesthesia With Propofol or Sevoflurane

The purpose of this study was to examine the correlation between the lowest PaO(2) value recorded during the first 45 minutes of one-lung ventilation (OLV) and the end-tidal CO(2) (ETCO(2)) difference between two-lung ventilation (TLV) and the early phase of OLV. A prospective, randomized study. A university hospital. Thirty-six patients scheduled for elective thoracic surgery. Thoracic surgery patients were randomly assigned to 1 of 2 groups (group P [n = 18], maintained with propofol; group S [n = 18], maintained with sevoflurane). After setting up, the authors measured arterial blood gases at F(I)O(2) = 1.0 as follows: during TLV and at 5 minutes, 15 minutes, 30 minutes, and 45 minutes after the start of OLV. ETCO(2) was recorded just before and at 3 minutes after the start of OLV. The authors examined the relationship between the initial ETCO(2) difference and the lowest PaO(2) value recorded during the first 45 minutes of OLV. There was a significant negative correlation between the lowest PaO(2) (x) value and the initial ETCO(2) difference (y) during OLV in each group (group P: y = -0.0203x + 7.2571, r(2) = 0.5351; group S: y = -0.0257x + 7.3158, r(2) = 0.6129). This correlation was not significantly different between the groups. The present study indicates that the ETCO(2) difference between TLV and early OLV has an association with impaired oxygenation later during OLV. This would be a simple and clinically convenient predictor of the lowest PaO(2) value likely to be reached during one-lung anesthesia with either propofol or sevoflurane.

The Use of Air in the Inspired Gas Mixture During Two-Lung Ventilation Delays Lung Collapse During One-Lung Ventilation

Collapse of the ipsilateral lung facilitates surgical exposure during thoracic procedures. The use of different gas mixtures during two-lung ventilation (2LV) may improve or impede surgical conditions during subsequent one-lung ventilation (OLV) by increasing or delaying lung collapse. We investigated the effects of three different gas mixtures during 2LV on lung collapse and oxygenation during subsequent OLV: Air/Oxygen (fraction of inspired oxygen [FIO(2)] = 0.4), Nitrous Oxide/Oxygen ("N(2)O," FIO(2) = 0.4) and Oxygen ("O(2)," FIO(2) = 1.0). Subjects were randomized into three groups: Air/Oxygen (n = 33), N(2)O (n = 34) or O(2) (n = 33) and received the designated gas mixture during induction and until the start of OLV. Subjects' lungs in all groups were then ventilated with FIO(2) = 1.0 during OLV. The surgeons, who were blinded to the randomization, evaluated the lung deflation using a verbal rating scale at 10 and 20 min after the start of OLV. Serial arterial blood gases were performed before anesthesia induction, during 2LV, and every 5 min, for 30 min, after initiation of OLV. The use of air in the inspired gas mixture during 2LV led to delayed lung deflation during OLV, whereas N(2)O improved lung collapse. Arterial oxygenation was significantly improved in the O(2) group only for the first 10 min of OLV, after which there were no differences in mean Pao(2) values among groups. De-nitrogenation of the lung during 2LV is a useful strategy to improve surgical conditions during OLV. The use of FIO(2) 1.0 or N(2)O/O(2) (FIO(2) 0.4) during 2LV did not have an adverse effect on subsequent oxygenation during OLV.

Propofol does not inhibit hypoxic pulmonary vasoconstriction in humans

The influence of increasing doses of propofol (from 6 to 12 mglkglh by continuous infusion) on hypoxic pulmonary vasoconstriction was studied in 10 patients prior to thoracic surgery. All patients were intubated with a left-sided double-lumen endobronchial tube. Initial anesthesia and muscle relaxation were accomplished by administering fentanyl, droperidol, and pancuronium. After 100% oxygen ventilation of both lungs for 20 min in a lateral decubitus position, the nondependent lung was deflated and one-lung ventilation was started. The dependent lung was continuously ventilated with 100% oxygen. Twenty minutes after the start of one-lung ventilation, propofol at an IV infusion rate of 6 mglkglh was added to the anesthetic technique. Thirty minutes later it was increased to 10 mglkglh and another 15 min later to 12 mglkglh. Then the propofol infusion was stopped. Thirty minutes later, two-lung ventilation was restarted to compare initial values. No changes in venous admixture or PaO, were observed during propofol infusion. There was no change in any respiratory or circulatory variables except systemic vascular resistance, which decreased significantly immediately after the propofol infusion commenced but returned to control values 15 min later for the rest of the observation period. After reestablishing two-lung ventilation, all variables did not differ from control values. In all patients, the hypoxic pulmonary vasoconstriction reflex was present after institution of one-lung ventilation and was not abolished after administration of propofol in doses from 6 to 12 mg/kg/h.