Hypoxaemia associated with one-lung anaesthesia: new discoveries in ventilation and perfusion

An Unusual Cause of End-Tidal Carbon Dioxide Rise During One-Lung Ventilation

A relatively common problem that may arise during one-lung ventilation is elevation of end-tidal carbon dioxide (ETCO2), which has several potential etiologies. This case report describes a 69-year-old woman with carcinoid tumor undergoing a robotic left lower lobectomy complicated by an acute rise in ETCO2 during one-lung ventilation, without an immediately identifiable cause. Thorough evaluation revealed CO2 leak through an open bronchial lumen resulting in an artificially high ETCO2 reading. This case report demonstrates the importance of performing a comprehensive assessment during acute changes in ETCO2 while also considering changes in the surgical field, which may contribute to these findings.

Effect of Deferasirox on Shunt Fraction During Thoracic Surgery With One-Lung Ventilation: A Randomized Controlled Study

Context Deferasirox, an iron chelator, can potentially reduce intraoperative right-to-left shunt and improve oxygenation in patients undergoing thoracic surgery requiring one-lung ventilation (OLV) by potentiating hypoxic pulmonary vasoconstriction (HPV). Aim The aim was to determine the effect of deferasirox on the intraoperative shunt fraction (SF) of patients undergoing thoracic surgery using OLV. Study design and settings This was a prospective, single-blind, randomized, controlled study. The study was conducted at a tertiary-care hospital. Methods Before surgery, 64 patients were allocated to two groups comprising 32 patients each. Group D patients were administered deferasirox, while those in group C were given a placebo. We included patients with the American Society of Anesthesiologists physical status III or IV, aged 18-60 years, undergoing elective thoracic surgery needing OLV. SF was the primary outcome variable. Secondary outcome variables were arterial oxygen tension (PaO₂), peripheral oxygen saturation (SpO₂), the ratio of PaO₂ and inspired oxygen concentration (P/F), and complications such as desaturation episodes, hypotension, and tachycardia. Results Baseline and postoperative values of outcome variables were statistically similar in both groups. Intraoperative values of SF were lower and PaO₂, SpO₂, and P/F were higher in group D. The incidence of intraoperative desaturation was lower in group D. Conclusion We conclude that pre-treatment with deferasirox reduces intraoperative SF and improves oxygenation during thoracic surgery using OLV.

Cardiac sympathetic denervation for untreatable ventricular tachycardia in structural heart disease. Strengths and pitfalls of evolving surgical techniques

Cardiac sympathetic denervation (CSD) is a valuable option in the setting of refractory ventricular arrhythmias in patient with structural heart disease. Since the procedure was introduced for non structural heart disease patients the techniques evolved and were modified to be adopted in several settings. In this state-of-the-art article we revised different techniques, their rationale, strengths, and pitfalls.

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

Background and Aims:

Baseline difference in the perfusion of two lungs is the cause of intra-operative shunt during one-lung ventilation (OLV). This study aimed to test the hypothesis that the gradient of end-tidal carbon dioxide (EtCO₂) between two lungs in lateral position (D-EtCO_2lateral) would predict the quantity of shunt and hence the drop in the oxygenation during OLV.

Methods:

An observational study was conducted to include consecutive 70 patients undergoing thoracic surgery using a double-lumen tube in a lateral position. D-EtCO_2lateral was calculated by subtracting EtCO₂ from the non-dependent lung from that of the dependent lung when ventilation parameters are the same for each lung. Oxygenation was assessed by measuring PaO₂/FiO₂ ratios (P/F ratio) at 10, 20 and 40 min after OLV. Correlations between D-EtCO_2lateral and P/F ratios were calculated. Receiver operating curves were analysed to test the ability of D-EtCO_2lateral to identify patients with a P/F ratio of <100 during OLV.

Results:

A moderate correlation was found between D-EtCO_2lateral and P/F ratios at 10 and 20 min of OLV. Among lung resection cases (n = 61), correlation was moderate at 10 (r = 0.64), and 20 min (r = 0.65) (P < 0.001) and became weak at 40 min (r = 0.489, P < 0.001). Areas under curve for D-EtCO_2lateral to predict the drop in P/F ratio <100 at 10, 20 and 40 min after OLV were 0.90 (cut-off: 2.5), 0.78 (cut-off: 3.5) and 0.78 (cut-off: 4.5), respectively.

Conclusion:

D-EtCO_2lateral could predict the drop in oxygenation in the early part of OLV in lung resection surgeries.

[Intraoperative Ventilation Approaches to One-lung Ventilation]

The management of thoracic surgery patients is challenging to the anesthetist, since one-lung ventilation (OLV) includes at least two major conditions: sufficient oxygenation and lung protection. The first is mainly because the ventilation of one lung is stopped while perfusion to that lung continues; the latter is related to the fact that the whole ventilation is applied to only a single lung. Recommendations for maintaining the oxygenation and methods of lung protection may contradict each other (e. g. high vs. low inspiratory oxygen fraction (FiO₂), high vs. low tidal volume, etc.). Therefore, a high degree of pathophysiological understanding and manual skills are required in the management of these patients.In light of recent clinical studies, this review focuses on a current protective strategy for OLV, which includes a possible decrease in FiO₂, lowered V_T, the application of positive end-expiratory pressure (PEEP) to the dependent and continuous positive airway pressure (CPAP) to the non-dependent lung and alveolar recruitment manoeuvres as well. Other approaches such as the choice of anaesthetics, remote ischemic preconditioning, fluid management and pain therapy can support the success of ventilatory strategy. The present work describes new developments that may change the classical approach in this respect.

Intraoperative Anesthetic Management of the Thoracic Patient

The intraoperative anesthetic management for thoracic surgery can impact a patient's postoperative course, especially in patients with significant lung disease. One-lung ventilation poses an inherent risk to patients, including hypoxemia, acute lung injury, and right ventricular dysfunction. Patient-specific ventilator management strategies during one-lung ventilation can reduce postoperative morbidity.

The Effects of Iloprost on Oxygenation During One-Lung Ventilation for Lung Surgery: A Randomized Controlled Trial

Hypoxemia can occur during one-lung ventilation (OLV) in thoracic surgery, leading to perioperative complications. Inhaled iloprost is a selective pulmonary vasodilator with efficacy in patients with pulmonary hypertension. The purpose of this study was to evaluate the effects of off-label inhaled iloprost on oxygenation during OLV in patients undergoing lung surgery. Seventy-two patients who were scheduled for elective video-assisted thoracoscopic lobectomy were assigned to receive an inhaled nebulizer of distilled water (control group), 10 μg iloprost (IL10 group), or 20 μg iloprost (IL20 group). Arterial and venous blood gas and hemodynamic analyses were obtained. Changes in partial pressure of oxygen in arterial blood (PaO₂), after the initiation of OLV and the resumption two-lung ventilation (TLV), were similar in all three groups. However, PaO₂ in the IL10 group was comparable to that in the control group, whereas PaO₂ in the IL20 group was significantly higher than that in the control group at 10, 20, and 30 min after administration of iloprost (275.1 ± 50.8 vs. 179.3 ± 38.9, p < 0.0001; 233.9 ± 39.7 vs. 155.1 ± 26.5, p < 0.0001; and 224.6 ± 36.4 vs. 144.0 ± 22.9, p < 0.0001, respectively). The shunt fraction in the IL20 group was significantly higher than that in the control group after administration of iloprost (26.8 ± 3.1 vs. 32.2 ± 3.4, p < 0.0001; 24.6 ± 2.2 vs. 29.9 ± 3.4, p < 0.0001; and 25.3 ± 2.0 vs. 30.8 ± 3.1, p < 0.0001, respectively). Administration of inhaled iloprost during OLV improves oxygenation and decreases intrapulmonary shunt.

Peep titration based on the open lung approach during one lung ventilation in thoracic surgery: a physiological study

BACKGROUND

During thoracic surgery in lateral decubitus, one lung ventilation (OLV) may impair respiratory mechanics and gas exchange. We tested a strategy based on an open lung approach (OLA) consisting in lung recruitment immediately followed by a decremental positive-end expiratory pressure (PEEP) titration to the best respiratory system compliance (C_RS) and separately quantified the elastic properties of the lung and the chest wall. Our hypothesis was that this approach would improve gas exchange. Further, we were interested in documenting the impact of the OLA on partitioned respiratory system mechanics.

METHODS

In thirteen patients undergoing upper left lobectomy we studied lung and chest wall mechanics, transpulmonary pressure (P_L), respiratory system and transpulmonary driving pressure (ΔP_RS and ΔP_L), gas exchange and hemodynamics at two time-points (a) during OLV at zero end-expiratory pressure (OLV_pre-OLA) and (b) after the application of the open-lung strategy (OLV_post-OLA).

RESULTS

The external PEEP selected through the OLA was 6 ± 0.8 cmH₂O. As compared to OLV_pre-OLA, the PaO₂/FiO₂ ratio went from 205 ± 73 to 313 ± 86 (p = .05) and C_L increased from 56 ± 18 ml/cmH₂O to 71 ± 12 ml/cmH₂O (p = .0013), without changes in C_CW. Both ΔP_RS and ΔP_L decreased from 9.2 ± 0.4 cmH₂O to 6.8 ± 0.6 cmH₂O and from 8.1 ± 0.5 cmH₂O to 5.7 ± 0.5 cmH₂O, (p = .001 and p = .015 vs OLV_pre-OLA), respectively. Hemodynamic parameters remained stable throughout the study period.

CONCLUSIONS

In our patients, the OLA strategy performed during OLV improved oxygenation and increased C_L and had no clinically significant hemodynamic effects. Although our study was not specifically designed to study ΔP_RS and ΔP_L, we observed a parallel reduction of both after the OLA.

TRIAL REGISTRATION

TRN: ClinicalTrials.gov , NCT03435523 , retrospectively registered, Feb 14 2018.

Anesthetic management of off-pump simultaneous coronary artery bypass grafting and lobectomy: Case report and literature review

RATIONALE

Survey data show approximately 10% patients with lung cancer may present concomitant coronary heart disease. Simultaneous surgery is a challenge for anesthetist. We review our experience in the anesthesia with 5 patients who required simultaneous off-pump coronary artery bypass grafting (OPCABG) and pulmonary resection for lung cancer.

PATIENT CONCERNS

Between 2014 and 2016, 5 patients with ASA (American Society of Anesthesiologists) grade II or III, underwent combined OPCABG and lung resection in the first Affiliated Hospital, Zhejiang University School of Medicine.

DIAGNOSES

All five patients were diagnosed with coronary heart disease and peripheral pulmonary carcinoma INTERVENTIONS:: Five patients received general anesthesia with double-lumen endobronchial tube for lung separation. The anesthetics were used, which caused slight hemodynamic fluctuations during induction of anesthesia; while during the maintenance of anesthesia, supplemented by Dexmedetomidine, the drug doses were titrated according to the depth of anesthesia. Guided by cardiac index (CI), stroke volume variation (SVV) and oxygen delivery (DO2), different strategies were taken at the different stage of surgery, during lung resection, SVV was kept about 13% to 15%, and less than 10% during OPCABG.

OUTCOMES

Five patients were transferred to intensive care unit (ICU) with intubation after surgery, duration of ventilation was 10 to 18 hours, and length of ICU stay and hospital stay were 1.8 to 2.5 ds and 11 to 16 ds, respectively. All of patients were discharged with not any perioperative complication.

LESSONS

In summary, anesthetists should focus on the maintenance of the balance between oxygen supply and demanding, which was achieved by close monitoring, titration of anesthetics and goal-directed fluid therapy during surgical procedures.

The oxygen reserve index (ORI): a new tool to monitor oxygen therapy

Supplemental oxygen is administered in the vast majority of patients in the perioperative setting and in the intensive care unit to prevent the potentially deleterious effects of hypoxia. On the other hand, the administration of high concentrations of oxygen may induce hyperoxia that may also be associated with significant complications. Oxygen therapy should therefore be precisely titrated and accurately monitored. Although pulse oximetry has become an indispensable monitoring technology to detect hypoxemia, its value in assessing the oxygenation status beyond the range of maximal arterial oxygen saturation (SpO₂ ≥97%) is very limited. In this hyperoxic range, we need to rely on blood gas analysis, which is intermittent, invasive and sometimes delayed. The oxygen reserve index (ORI) is a new continuous non-invasive variable that is provided by the new generation of pulse oximeters that use multi-wavelength pulse co-oximetry. The ORI is a dimensionless index that reflects oxygenation in the moderate hyperoxic range (PaO₂ 100-200 mmHg). The ORI may provide an early alarm when oxygenation deteriorates well before any changes in SpO₂ occur, may reflect the response to oxygen administration (e.g., pre-oxygenation), and may facilitate oxygen titration and prevent unintended hyperoxia. In this review we describe this new variable, summarize available data and preliminary experience, and discuss its potential clinical utilities in the perioperative and intensive care settings.

One-lung Ventilation for Thoracic Surgery: Current Perspectives

One-lung ventilation (OLV) is an anesthesiological technique that is increasingly being used beyond thoracic surgery. This requires specific skills and knowledge about airway management, maintenance of gas exchange and prevention of acute lung injury. Sometimes maintaining adequate gas exchange and minimizing acute lung injury may be opposing processes. Parameters validated for OLV titration still have not been found, but a multimodal approach based on low tidal volume, end-expiratory pressure application and alveolar recruitment maneuvers is considered the best way to ensure protective ventilation and reduce lung damage. The purpose of this review is to analyze all these factors using the latest scientific evidence and the opinions of the most influential authors.

Effects of stellate ganglion block on the peri-operative vasomotor cytokine content and intrapulmonary shunt in patients with esophagus cancer

OBJECTIVE

To investigate the effects of stellate ganglion block (SGB) on the peri-operative vasomotor cytokine content and intrapulmonary shunt in patients with esophagus cancer who underwent thoracotomy.

MATERIALS AND METHODS

Forty patients undergoing elective resection of esophageal cancer patients who had I~II American Society of Anesthesiologist (ASA) were randomly divided into total intravenous anesthesia group (group N, n=20) and total intravenous anesthesia combined with SGB group (group S, n=20, 0.12 mL/kg 1% lidocaine was used for SGB 10 min before induction). Heart rate (HR), mean arterial pressure (MAP), central venous pressure (CVP), mean pulmonary arterial pressure (MPAP) and continuous cardiac output (CCO) were continuously monitored. The blood from internal jugular vein was drawn respectively before induction (T0), and 30 min (T1), 60 min (T2) and 120 min (T3) after one-lung ventilation (OLV), and 30 min (T4) after two-lung ventilation. The contents of plasma endothelin (ET), nitric oxide (NO) and calcitonin gene-related peptide (CGRP) were detected with enzyme linked immunosorbent assay (ELISA). Meanwhile, arterial and mixed venous blood samples were collected for determination of blood gas and calculation of intrapulmonary shunt fraction (Qs/Qt).

RESULTS

During OLV, ET contents were increased significantly in two groups (P<0.05), and no significant difference was presented (P>0.05). NO content in group S was obviously higher than in group N at T3 (P<0.05), whereas CGRP content in group N was markedly lower than in group S at each time point (P<0.05). Qs/Qt was significantly increased in both groups after OLV, but there was no statistical significant regarding the Qs/Qt at each time point between two groups.

CONCLUSIONS

Total intravenous anesthesia combined with SGB is conducive to regulation of perioperative vasomotor cytokines in thoracotomy, and has little effect on intrapulmonary shunt at the time of OLV.

Hypoxemia during one-lung ventilation for robot-assisted coronary artery bypass graft surgery

BACKGROUND

Robot-assisted coronary artery bypass grafting requires continuous one-lung ventilation (OLV) to evacuate the thoracic cavity. Whether this ventilatory mode subjects patients to serious hypoxemia remains underinvestigated.

METHODS

From 2005 to 2010, all patients receiving robot-assisted coronary artery bypass graft surgery using OLV with active capnothorax for internal mammary artery harvesting and then passive pneumothorax for minithoracotomy direct-vision coronary bypass graft surgery were included. Patients' variables of oxygenation were monitored and compared throughout the whole surgical period. Persistent oxygen desaturation (arterial oxygen pressure <70 mm Hg) refractory to primary managements was defined as a hypoxemic event, and predictors of such events were identified by multivariate regression analysis.

RESULTS

A total of 255 consecutive patients were enrolled. Average oxygen saturation decreased modestly during the first stage of OLV with active capnothorax, causing hypoxemic events in 9 patients (4.3%) leading to death in 2 (0.8%), whereas it dropped drastically in the second stage of OLV with passive pneumothorax, resulting in hypoxemic events in 32 patients (12.6%) and death in 1 (0.4%). Multivariate regression analysis identified high pulmonary vascular resistance and low left ventricular ejection fraction as predictors of hypoxemia during internal mammary artery takedown, whereas prolonged procedure and chronic obstructive pulmonary disease were identified as predictors during minithoracotomy bypass grafting.

CONCLUSIONS

Robot-assisted two-stage coronary artery bypass surgery employing OLV could be complicated by serious hypoxemia especially at the minithoracotomy grafting stage and in patients with specific risk factors. Thus, when managing such patients, invasive monitoring and aggressive treatment of arterial desaturation are mandatory to ensure the patient's safety and procedural smoothness.

Anesthesia for thoracic surgery: a survey of middle eastern practice

Purpose:

The main objective of this survey is to describe the current practice of thoracic anesthesia in the Middle Eastern (ME) region.

Methods:

A prospective online survey. An invitation to participate was e-mailed to all members of the ME thoracic-anaesthesia group. A total of 58 members participated in the survey from 19 institutions in the Middle East. Questions concerned ventilation strategies during one-lung ventilation (OLV), anesthesia regimen, mode of postoperative analgesia, use of lung isolation techniques, and use of i.v. fluids.

Results:

Volume-controlled ventilation was favored over pressure-controlled ventilation (62% vs 38% of respondents, P<0.05); 43% report the routine use of positive end-expiratory pressure. One hundred percent of respondents report using double-lumen tube (DLT) as a first choice airway to establish OLV. Nearly a third of respondents, 31.1%, report never using bronchial blocker (BB) in their thoracic anesthesia practice. Failure to pass a DLT and difficult airway are the most commonly cited indications for BB use. Regarding postoperative analgesia, the majority 61.8% favor thoracic epidural analgesia over other techniques (P<0.05).

Conclusions:

Our survey provides a contemporary snapshot of the ME thoracic anesthetic practice.