Effect of positive end expiratory pressure on non-hypoxic apnea time and atelectasis during induction of anesthesia in infant: A randomized controlled trial

INTRODUCTION

This study aimed to assess the impact of positive-end-expiratory pressure (PEEP) on the non-hypoxic apnea time in infants during anesthesia induction with an inspired oxygen fraction of 0.8.

METHODS

This age stratified randomized controlled trial included patients under 1 year of age. Preoxygenation was performed using an inspired oxygen fraction of 0.8 for 2 min. Inspired oxygen fraction of 0.8 was administered via a face mask with volume-controlled ventilation at a tidal volume of 6 mL.kg-1, with or without 7 cmH2O of PEEP. Tracheal intubation was performed after 3 min of ventilation; however, it was disconnected from the breathing circuit. Ventilation was resumed once the pulse oximetry readings reached 95%. The primary outcome was the non-hypoxic apnea time, defined as the time from the cessation of ventilation to achieving a pulse oximeter reading of 95%. The secondary outcome measures included the degree of atelectasis assessed by ultrasonography and the presence of gastric air insufflation.

RESULTS

Eighty-four patients were included in the final analysis. In the positive end-expiratory pressure group, the atelectasis score decreased (17.0 vs. 31.5, p < .001; mean difference and 95% CI of 11.6, 7.5-15.6), while the non-hypoxic apnea time increased (80.1 s vs. 70.6 s, p = .005; mean difference and 95% CI of -9.4, -16.0 to -2.9), compared to the zero end-expiratory pressure group, among infants who are 6 months old or younger, not in those aged older than 6 months.

DISCUSSION

The application of positive end-expiratory pressure reduced the incidence of atelectasis and extended the non-hypoxic apnea time in infants who are 6 months old or younger. However, it did not affect the incidence of atelectasis nor the non-hypoxic apnea time in patients aged older than 6 months.

Determinants and Practice Variability of Oxygen Administration during Surgery in the United States: A Retrospective Cohort Study

BACKGROUND

The best approaches to supplemental oxygen administration during surgery remain unclear, which may contribute to variation in practice. This study aimed to assess determinants of oxygen administration and its variability during surgery.

METHODS

Using multivariable linear mixed-effects regression, the study measured the associations between intraoperative fraction of inspired oxygen and patient, procedure, medical center, anesthesiologist, and in-room anesthesia provider factors in surgical cases of 120 min or longer in adult patients who received general anesthesia with tracheal intubation and were admitted to the hospital after surgery between January 2016 and January 2019 at 42 medical centers across the United States participating in the Multicenter Perioperative Outcomes Group data registry.

RESULTS

The sample included 367,841 cases (median [25th, 75th] age, 59 [47, 69] yr; 51.1% women; 26.1% treated with nitrous oxide) managed by 3,836 anesthesiologists and 15,381 in-room anesthesia providers. Median (25th, 75th) fraction of inspired oxygen was 0.55 (0.48, 0.61), with 6.9% of cases less than 0.40 and 8.7% greater than 0.90. Numerous patient and procedure factors were statistically associated with increased inspired oxygen, notably advanced American Society of Anesthesiologists classification, heart disease, emergency surgery, and cardiac surgery, but most factors had little clinical significance (less than 1% inspired oxygen change). Overall, patient factors only explained 3.5% (95% CI, 3.5 to 3.5%) of the variability in oxygen administration, and procedure factors 4.4% (95% CI, 4.2 to 4.6%). Anesthesiologist explained 7.7% (95% CI, 7.2 to 8.2%) of the variability in oxygen administration, in-room anesthesia provider 8.1% (95% CI, 7.8 to 8.4%), medical center 23.3% (95% CI, 22.4 to 24.2%), and 53.0% (95% CI, 52.4 to 53.6%) was unexplained.

CONCLUSIONS

Among adults undergoing surgery with anesthesia and tracheal intubation, supplemental oxygen administration was variable and appeared arbitrary. Most patient and procedure factors had statistical but minor clinical associations with oxygen administration. Medical center and anesthesia provider explained significantly more variability in oxygen administration than patient or procedure factors.

EDITOR’S PERSPECTIVE

Clinical validation of the Air-Test for the non-invasive detection of perioperative atelectasis in children

BACKGROUND

The incidence of anesthesia-induced atelectasis in children is high and closely related to episodes of hypoxemia. The Air-Test is a simple maneuver to detect lung collapse. By a step-reduction in FiO2 to 0.21, a fall in pulse-oximetry hemoglobin saturation <97% unmasks the presence of collapse-related shunt in healthy lungs. The aim of this study was to validate the Air-Test as a diagnostic tool to detect perioperative atelectasis in children using lung ultrasound as a reference.

METHODS

We first assessed the Air-Test in a retrospective cohort of 88 anesthetized children (Retrospective study) followed by a prospective study performed in 72 children (45 postconceptional weeks to 16 years old) using a similar protocol (Validation study). We analyzed the performance of the Air-Test to detect atelectasis by an operating characteristic curve (ROC) analysis, using lung ultrasound consolidation score as reference.

RESULTS

Preoperative SpO2 was normal in both studies (retrospective 98.7±0.6%, validation 99.0±0.9%). The Air-Test, with a SpO2 cut point <97%, resulted positive in 67 patients in the retrospective study (SpO2 93.3±2.1%) and in 59 in the validation study (SpO2 94.9±1.8%); both P<0.0001. In the validation study, the Air-Test showed a sensitivity of 0.91 (95% CI 0.85-0.92), specificity of 1.00 (95% CI 0.84-1) and an area under the curve (AUC) of 0.98 (95% CI 0.97-1.00). AUC between both studies was similar (P=0.16).

CONCLUSIONS

The Air-Test is a noninvasive and accurate method to detect atelectasis in healthy anesthetized children. It can be used as a screening tool to individualize patients that can benefit from lung recruitment maneuvers.

Oxygenation during general anesthesia in pediatric patients: A retrospective observational study

STUDY OBJECTIVE

Protocols are used in intensive care and emergency settings to limit the use of oxygen. However, in pediatric anesthesiology, such protocols do not exist. This study aimed to investigate the administration of oxygen during pediatric general anesthesia and related these values to PaO2, SpO2 and SaO2.

DESIGN

Retrospective observational study.

SETTING

Tertiary pediatric academic hospital, from June 2017 to August 2020.

PATIENTS

Patients aged 0-18 years who underwent general anesthesia for a diagnostic or surgical procedure with tracheal intubation and an arterial catheter for regular blood withdrawal were included. Patients on cardiopulmonary bypass or those with missing data were excluded. Electronic charts were reviewed for patient characteristics, type of surgery, arterial blood gas analyses, and oxygenation management.

INTERVENTIONS

No interventions were done.

MEASUREMENTS

Primary outcome defined as FiO2, PaO2 and SpO2 values were interpreted using descriptive analyses, and the correlation between PaO2 and FiO2 was determined using the weighted Spearman correlation coefficient.

MAIN RESULTS

Data of 493 cases were obtained. Of these, 267 were excluded for various reasons. Finally, 226 cases with a total of 645 samples were analyzed. The median FiO2 was 36% (IQR 31 to 43), with a range from 20% to 97%, and the median PaO2 was 23.6 kPa (IQR 18.6 to 28.1); 177 mmHg (IQR 140 to 211). The median SpO2 level was 99% (IQR 98 to 100%). The study showed a moderately positive association between PaO2 and FiO2 (r = 0.52, p < 0.001). 574 of 645 samples (89%) contained a PaO2 higher than 13.3 kPa; 100 mmHg.

CONCLUSIONS

Oxygen administration during general pediatric anesthesia is barely regulated. Hyperoxemia is observed intraoperatively in approximately 90% of cases. Future research should focus on outcomes related to hyperoxemia.

Postoperative Supplemental Oxygen in Liver Transplantation (PSOLT) does not reduce the rate of infections: results of a randomized controlled trial

BACKGROUND

Despite inconsistent evidence, international guidelines underline the importance of perioperative hyperoxygenation in prevention of postoperative infections. Further, data on safety and efficacy of this method in liver transplant setting are lacking. The aim was to evaluate efficacy and safety of postoperative hyperoxygenation in prophylaxis of infections after liver transplantation.

METHODS

In this randomized controlled trial, patients undergoing liver transplantation were randomly assigned to either 28% or 80% fraction of inspired oxygen (FiO₂) for 6 postoperative hours. Infections occurring during 30-day post-transplant period were the primary outcome measure. Secondary outcome measures included 90-day mortality, 90-day severe morbidity, 30-day pulmonary complications, durations of hospital and intensive care unit stay, and 5-day postoperative bilirubin concentration, alanine and aspartate transaminase activity, and international normalized ratio (INR) (clinicatrials.gov NCT02857855).

RESULTS

A total of 193 patients were included and randomized to 28% (n = 99) and 80% (n = 94) FiO₂. With similar patient, operative, and donor characteristics in both groups, infections occurred in 34.0% (32/94) of patients assigned to 80% FiO₂ as compared to 23.2% (23/99) of patients assigned to 28% FiO₂ (p = 0.112). Patients randomized to 80% FiO₂ more frequently developed severe complications (p = 0.035), stayed longer in the intensive care unit (p = 0.033), and had higher bilirubin concentration over first 5 post-transplant days (p = 0.043). No significant differences were found regarding mortality, duration of hospital stay, pulmonary complications, and 5-day aspartate and alanine transaminase activity and INR.

CONCLUSIONS

Postoperative hyperoxygenation should not be used for prophylaxis of infections after liver transplantation due to the lack of efficacy.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02857855. Registered 7 July 2016.

Dual effects of supplemental oxygen on pulmonary infection, inflammatory lung injury, and neuromodulation in aging and COVID-19

Clinical studies have shown a significant positive correlation between age and the likelihood of being infected with SARS-CoV-2. This increased susceptibility is positively correlated with chronic inflammation and compromised neurocognitive functions. Postmortem analyses suggest that acute lung injury (ALI)/acute respiratory distress syndrome (ARDS), with systemic and lung hyperinflammation, can cause significant morbidity and mortality in COVID-19 patients. Supraphysiological supplemental oxygen, also known as hyperoxia, is commonly used to treat decreased blood oxygen saturation in COVID-19 patients. However, prolonged exposure to hyperoxia alone can cause oxygen toxicity, due to an excessive increase in the levels of reactive oxygen species (ROS), which can overwhelm the cellular antioxidant capacity. Subsequently, this causes oxidative cellular damage and increased levels of aging biomarkers, such as telomere shortening and inflammaging. The oxidative stress in the lungs and brain can compromise innate immunity, resulting in an increased susceptibility to secondary lung infections, impaired neurocognitive functions, and dysregulated hyperinflammation, which can lead to ALI/ARDS, and even death. Studies indicate that lung inflammation is regulated by the central nervous system, notably, the cholinergic anti-inflammatory pathway (CAIP), which is innervated by the vagus nerve and α7 nicotinic acetylcholine receptors (α7nAChRs) on lung cells, particularly lung macrophages. The activation of α7nAChRs attenuates oxygen toxicity in the lungs and improves clinical outcomes by restoring hyperoxia-compromised innate immunity. Mechanistically, α7nAChR agonist (e.g., GAT 107 and GTS-21) can regulate redox signaling by 1) activating Nrf2, a master regulator of the antioxidant response and a cytoprotective defense system, which can decrease cellular damage caused by ROS and 2) inhibiting the activation of the NF-κB-mediated inflammatory response. Notably, GTS-21 has been shown to be safe and it improves neurocognitive functions in humans. Therefore, targeting the α7nAChR may represent a viable therapeutic approach for attenuating dysregulated hyperinflammation-mediated ARDS and sepsis in COVID-19 patients receiving prolonged oxygen therapy.

Prevention of Surgical Site Infections in Neonates and Children: Non-Pharmacological Measures of Prevention

A surgical site infection (SSI) is an infection that occurs in the incision created by an invasive surgical procedure. Although most infections are treatable with antibiotics, SSIs remain a significant cause of morbidity and mortality after surgery and have a significant economic impact on health systems. Preventive measures are essential to decrease the incidence of SSIs and antibiotic abuse, but data in the literature regarding risk factors for SSIs in the pediatric age group are scarce, and current guidelines for the prevention of the risk of developing SSIs are mainly focused on the adult population. This document describes the current knowledge on risk factors for SSIs in neonates and children undergoing surgery and has the purpose of providing guidance to health care professionals for the prevention of SSIs in this population. Our aim is to consider the possible non-pharmacological measures that can be adopted to prevent SSIs. To our knowledge, this is the first study to provide recommendations based on a careful review of the available scientific evidence for the non-pharmacological prevention of SSIs in neonates and children. The specific scenarios developed are intended to guide the healthcare professional in practice to ensure standardized management of the neonatal and pediatric patients, decrease the incidence of SSIs and reduce antibiotic abuse.

Intraoperative High Fraction of Inspiratory Oxygen is Independently Associated with Worse Outcome After Living-Donor Liver Transplantation: A Retrospective Study

Background

Ischemia and reperfusion injury is an important factor that determines graft function after liver transplantation, and oxygen plays a crucial role in this process. However, the relationship between the intraoperative high fraction of inspiratory oxygen (FiO₂) and living-donor-liver-transplantation (LDLT) outcome remains unclear.

Patients and Methods

A total of 199 primary adult-to-adult LDLT cases in Kyoto University Hospital between January 2010 and December 2017 were enrolled in this study. The intraoperative FiO₂ was averaged using the total amount of intraoperative oxygen and air and defined as the calculated FiO₂ (cFiO₂). The cutoff value of cFiO₂ was set at 0.5.

Results

Between the cFiO₂ <0.5 (n = 156) and ≥0.5 group (n = 43), preoperative recipients’ background, donor factors, and intraoperative parameters were almost comparable. Postoperatively, the cFiO₂ ≥0.5 group showed a higher early allograft dysfunction (EAD) rate (P = 0.049) and worse overall graft survival (P = 0.036) than the cFiO₂ <0.5 group. Although the cFiO₂ ≥0.5 was not an independent risk factor for EAD in multivariable analysis (OR 2.038, 95%CI 0.992–4.186, P = 0.053), it was an independent risk factor for overall graft survival after LDLT (HR 1.897, 95%CI 1.007–3.432, P = 0.048).

Conclusion

The results of this study suggest that intraoperative high FiO₂ may be associated with worse graft survival after LDLT. Avoiding higher intraoperative FiO₂ may be beneficial for LDLT recipients.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00268-022-06544-7.

Error traps in pediatric one-lung ventilation

With the advent of thoracoscopic surgery, the benefits of lung isolation in children have been increasingly recognized. However, because of the small airway dimensions, equipment limitations in size and maneuverability, and limited respiratory reserve, one-lung ventilation in children remains challenging. This article highlights some of the most common error traps in the management of pediatric lung isolation and focuses on practical solutions for their management. The error traps discussed are as follows: (1) the failure to take into consideration relevant aspects of tracheobronchial anatomy when selecting the size of the lung isolation device, (2) failure to execute correct placement of the device chosen for lung isolation, (3) failure to maintain lung isolation related to surgical manipulation and isolation device movement, (4) failure to select appropriate ventilator strategies during one-lung ventilation, and (5) failure to appropriately manage and treat hypoxemia in the setting of one-lung ventilation.

Lung Navigation Ventilation Protocol to Optimize Biopsy of Peripheral Lung Lesions

BACKGROUND

Computed tomography-to-body divergence caused by respiratory motion, atelectasis, diaphragmatic motion and other factors is an obstacle to peripheral lung biopsies. We examined a conventional ventilation strategy versus a lung navigation ventilation protocol (LNVP) optimized for intraprocedural 3-dimensional image acquisition and bronchoscopic biopsy of peripheral lung nodules.

METHODS

A retrospective, single center study was conducted in consecutive subjects with peripheral lung lesions measuring <30 mm. Effects of ventilation strategies including atelectasis and tool-in-lesion confirmation were assessed using cone beam computed tomography images. Diagnostic yield was also evaluated. Complications were assessed through 7 days.

RESULTS

Fifty subjects were included (25 per group) with 27 nodules in the conventional group and 25 nodules in the LNVP group. Atelectasis was assessed by 2 blinded readers: [reader 1 (R1) and reader 2 (R2)]. Atelectasis was more prevalent in the conventional ventilation group, both for dependent atelectasis (R1: 64% and R2: 68% vs. R1: 36% and R2: 16%, P=0.00014) and sublobar/lobar atelectasis (R1: 48% and R2: 56% vs. R1: 20% and R2: 32%, P=0.01). Similarly, the target lesion was obscured due to atelectasis more often in the conventional ventilation group (R1: 36% and R2: 36% vs. R1: 4% and R2: 8%, P=0.01). Diagnostic yield was 70% for conventional ventilation and 92% for LNVP (P=0.08).

CONCLUSION

LNVP demonstrated markedly reduced dependent and sublobar/lobar atelectasis and lesions either partially or completely obscured by atelectasis compared with conventional ventilation. Future prospective studies are necessary to understand the impact of protocolized ventilation strategies for bronchoscopic biopsy of peripheral lung lesions.

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

Background

Our 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).

Methods

Fifty 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.

Results

Hypoxemia 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.

Conclusions

During 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%.

Can Erythropoietin Reduce Hypoxemic Neurological Damages in Neonates With Congenital Heart Defects?

Congenital heart defects (CHD), the most common cause of birth defects with increasing birth prevalence, affect nearly 1% of live births worldwide. Cyanotic CHD are characterized by hypoxemia, with subsequent reduced oxygen delivery to the brain, especially critical during brain development, beginning in the fetus and continuing through the neonatal period. Therefore, neonates with CHD carry a high risk for neurological comorbidities, even more frequently when there are associated underlying genetic disorders. We review the currently available knowledge on potential prevention strategies to reduce brain damage induced by hypoxemia during fetal development and immediately after birth, and the role of erythropoietin (EPO) as a potential adjunctive treatment. Maternal hyper-oxygenation had been studied as a potential therapeutic to improve fetal oxygenation. Despite demonstrating some effectiveness, maternal hyper-oxygenation has proven to be impractical for extensive clinical application, thus prompting the investigation of specific pathways for pharmacological intervention. Among those, the role of antioxidant pathways and Hypoxia Inducible Factors (HIF) have been studied for their involvement in the protective response to hypoxic injury. One of the proteins induced by HIF, EPO, has properties of being anti-apoptotic, antioxidant, and protective for neurons, astrocytes, and oligodendrocytes. In human trials, EPO administration in neonates with hypoxic ischemic encephalopathy (HIE) significantly reduced the neurological hypoxemic damages in several reported studies. Currently, it is unknown if the mechanisms of pathophysiology of cyanotic CHD are like HIE. Neonates with cyanotic CHD are exposed to both chronic hypoxemia and episodes of acute ischemia-reperfusion injury when undergo cardiopulmonary bypass surgery requiring aortic cross-clamp and general anesthesia. Our review supports future trials to evaluate the potential efficiency of EPO in reducing the hypoxemic neurologic damages in neonates with CHD. Furthermore, it suggests the need to identify early biomarkers of hypoxia-induced neurological damage, which must be sensitive to the neuroprotective effects of EPO.

Principles for minimizing oxygen debt: can they translate to clinical application and improve outcomes?

Oxygen delivery is dependent on pulmonary gas exchange, cardiac output, blood oxygen-carrying capacity, and tissue oxygen extraction. Reduction in oxygen delivery or higher oxygen consumption can initiate complex protective cellular processes precipitating oxygen debt. In critically ill and potentially surgical patients, stress and consequent hormonal or metabolic changes can trigger oxygen debt which is associated with worse morbidity and mortality. Increase in oxygen delivery by augmenting cardiac output or by increasing fraction of inspired oxygen (FiO₂) can help reduce oxygen debt. However, the extent of oxygen debt in an individual patient is poorly defined and difficult to measure. Furthermore, large heterogeneity in clinical trials assessing outcomes benefit of increasing oxygen delivery limits our ability to recommend goal directed fluid therapy aimed at increasing cardiac ouput or higher FiO₂. To understand and prevent oxygen debt in critically ill and surgical patients, we need to develop continuous monitoring techniques to assess the balance of oxygen delivery and consumption. Furthermore, methods of increasing oxygen delivery like goal-directed fluid therapy, higher FiO₂ and anemia prevention should be rigorously evaluated with focus on establishing outcomes benefit.

ORi™: a new indicator of oxygenation

In the perioperative period, hypoxemia and hyperoxia are crucial factors that require attention, because they greatly affect patient prognoses. The pulse oximeter has been the only noninvasive monitor that can be used as a reference of oxygenation in current anesthetic management; however, in recent years, a new monitoring method that uses the oxygen reserve index (ORi™) has been developed by Masimo Corp. ORi is an index that reflects the state of moderate hyperoxia (partial pressure of arterial oxygen [PaO2] between 100 and 200 mmHg) using a non-unit scale between 0.00 and 1.00. ORi monitoring performed together with percutaneous oxygen saturation (SpO2) measurements may become an important technique in the field of anesthetic management, for measuring oxygenation reserve capacity. By measuring ORi, it is possible to predict hypoxemia and to detect hyperoxia at an early stage. In this review, we summarize the method of ORi, cautions for its use, and suitable cases for its use. In the near future, the monitoring of oxygen concentrations using ORi may become increasingly common for the management of respiratory function before, after, and during surgery.

Practical Review of Mechanical Ventilation in Adults and Children in The Operating Room and Emergency Department

BACKGROUND

During general anesthesia, mechanical ventilation can cause pulmonary damage through mechanism of ventilator-induced lung injury which is a major cause of postoperative pulmonary complications, which varies between 5 and 33% and increases significantly the 30-day mortality of the surgical patient.

OBJECTIVE

The aim of this review is to analyze different variables which played key role in safe application of mechanical ventilation in the operating room and emergency setting.

METHOD

Also, we wanted to analyze different types of population that underwent intraoperative mechanical ventilation like obese patients, pediatric and adult population and different strategies such as one lung ventilation and ventilation in trendelemburg position. The peer-reviewed articles analyzed were selected according to PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses) from Pubmed/Medline, Ovid/Wiley and Cochrane Library, combining key terms such as: "pulmonary post-operative complications", "protective ventilation", "alveolar recruitment maneuvers", "respiratory compliance", "intraoperative paediatric ventilation", "best peep", "types of ventilation". Among the 230 papers identified, 150 articles were selected, after title - abstract examination and removing the duplicates, resulting in 94 articles related to mechanical ventilation in operating room and emergency setting that were analyzed.

RESULTS

Careful preoperative patient's evaluation and protective ventilation (i.e. use of low tidal volumes, adequate PEEP and alveolar recruitment maneuvers) has been shown to be effective not only in limiting alveolar de-recruitment, alveolar overdistension and lung damage, but also in reducing the onset of pulmonary post-operative complications (PPCs).

CONCLUSION

Mechanical ventilation is like "Janus Bi-front" because it is essential for surgical procedures, for the care of critical care patients and in life-threatening conditions but it can be harmful to the patient if continued for a long time and where an excessive dose of oxygen is administered into the lungs. Low tidal volume is associated with minor rate of PPCs and other complications and every complication can increase length of Stay, adding cost to NHS between 1580 € and 1650 € per day in Europe and currently the prevention of PPCS is only weapon that we possess.

Evidence-Based Guideline on Critical Patient Transport and Handover to ICU

The perioperative period is a time in which significant physiological change occurs. Improper transfer of information at this point can lead to medical errors. Planning and preparation for critical patient transport to ICU is vital to prevent adverse events. Critical patient transport to ICU must be as safe as possible and should not cause additional risks. It needs good communication, planning, and appropriate staffing with standard monitoring. Evidence shows inconsistency and variability on the use of standardized protocols during critical patient transfer and handover to the ICU. There is a variety of controversial approaches about the need of sedation, use of end-tidal CO₂ monitoring, and manual versus mechanical ventilation based on different evidence. The objective of this review was to recommend safer options of critical patient transfer to the ICU that help reduce patient morbidity and mortality. Methods. Google Scholars, PubMed through HINARI, and other search engines were used to search high-quality evidence that help reach appropriate conclusions. Discussion. Critical patient transfer and handover to ICU is a complex procedure that needs experienced hands, availability of appropriate team members, standard monitoring, and necessary emergency and patient-specific medications. Appropriate and adequate transfer of patient information to the receiving team decreases patient morbidity and mortality when the transfer team uses standardized checklist. Conclusion. Involvement of senior physicians, use of standard monitoring, and appropriate transfer of information have been shown to decrease critical patient morbidity and mortality.

Effect of spontaneous breathing on atelectasis during induction of general anaesthesia in infants: A prospective randomised controlled trial

BACKGROUND

Atelectasis occurs commonly during induction of general anaesthesia in children, particularly infants.

OBJECTIVES

We hypothesised that maintaining spontaneous ventilation can reduce atelectasis formation during anaesthetic induction in infants. We compared spontaneous ventilation and manual positive-pressure ventilation in terms of atelectasis formation in infants.

DESIGN

Randomised controlled study.

SETTING

Single tertiary hospital in Seoul, Republic of Korea, from November 2018 to December 2019.

PATIENTS

We enrolled 60 children younger than 1 year of age undergoing general anaesthesia, of whom 56 completed the study. Exclusion criteria were history of hypoxaemia during previous general anaesthesia, development of a respiratory tract infection within 1 month, current intubation or tracheostomy cannulation, need for rapid sequence intubation, preterm birth, age within 60 weeks of the postconceptional age and the presence of contraindications for rocuronium or sodium thiopental.

INTERVENTION

Patients were allocated randomly to either the 'spontaneous' group or 'controlled' group. During preoxygenation, spontaneous ventilation was maintained in the 'spontaneous' group while conventional bag-mask ventilation was provided in the 'controlled' group. After 5 min of preoxygenation, a lung ultrasound examination was performed to compare atelectasis formation in the two groups.

RESULTS

Atelectasis after preoxygenation was seen in seven (26.9%) of 26 patients in the 'spontaneous' group and 22 (73.3%) of 30 patients in the 'controlled' group (P = 0.001). The relative risk of atelectasis in the 'spontaneous' group was 0.39 (95% CI 0.211 to 0.723). Regarding ultrasound pictures of consolidation, the total score and sum of scores in the dependent regions were significantly lower in the 'spontaneous' group than in the 'controlled' group (P = 0.007 and 0.001, respectively).

CONCLUSION

Maintaining spontaneous ventilation during induction of general anaesthesia has a preventive effect against atelectasis in infants younger than 1 year of age, particularly in the dependent portions of the lungs.

TRIAL REGISTRATION

Clinicaltrials.gov (identifier: NCT03739697).

Morbidity and mortality after anaesthesia in early life: results of the European prospective multicentre observational study, neonate and children audit of anaesthesia practice in Europe (NECTARINE)

BACKGROUND

Neonates and infants requiring anaesthesia are at risk of physiological instability and complications, but triggers for peri-anaesthetic interventions and associations with subsequent outcome are unknown.

METHODS

This prospective, observational study recruited patients up to 60 weeks' postmenstrual age undergoing anaesthesia for surgical or diagnostic procedures from 165 centres in 31 European countries between March 2016 and January 2017. The primary aim was to identify thresholds of pre-determined physiological variables that triggered a medical intervention. The secondary aims were to evaluate morbidities, mortality at 30 and 90 days, or both, and associations with critical events.

RESULTS

Infants (n=5609) born at mean (standard deviation [sd]) 36.2 (4.4) weeks postmenstrual age (35.7% preterm) underwent 6542 procedures within 63 (48) days of birth. Critical event(s) requiring intervention occurred in 35.2% of cases, mainly hypotension (>30% decrease in blood pressure) or reduced oxygenation (SpO₂ <85%). Postmenstrual age influenced the incidence and thresholds for intervention. Risk of critical events was increased by prior neonatal medical conditions, congenital anomalies, or both (relative risk [RR]=1.16; 95% confidence interval [CI], 1.04-1.28) and in those requiring preoperative intensive support (RR=1.27; 95% CI, 1.15-1.41). Additional complications occurred in 16.3% of patients by 30 days, and overall 90-day mortality was 3.2% (95% CI, 2.7-3.7%). Co-occurrence of intraoperative hypotension, hypoxaemia, and anaemia was associated with increased risk of morbidity (RR=3.56; 95% CI, 1.64-7.71) and mortality (RR=19.80; 95% CI, 5.87-66.7).

CONCLUSIONS

Variability in physiological thresholds that triggered an intervention, and the impact of poor tissue oxygenation on patient's outcome, highlight the need for more standardised perioperative management guidelines for neonates and infants.

CLINICAL TRIAL REGISTRATION

NCT02350348.

Predictors of hypoxemia after general anesthesia in the early postoperative period in a hospital in Ethiopia: an observational study

BACKGROUND

Early postoperative hypoxemia is a common problem after general anesthesia. The identification of factors associated with an increased occurrence of it might help healthcare professionals to hypoxemia risk patients, therefore this study aims to assess the incidence and factors associated with early postoperative hypoxemia among surgical procedures.

METHODS

A prospective cohort study design was conducted from February 1, 2020 to June 30, 2020, on a total of 424 patients who underwent surgery under general anesthesia in Debre Tabor Comprehensive Specialized Hospital. The data was collected using a structured checklist. Bivariable and multivariable logistic regressions were used to check the association.

RESULTS

The incidence of early postoperative hypoxemia was 45.8%. Patients having a BMI of 25-29.9 kg/m2 and BMI of 30-39.9 kg/m2, patients having a chronic disease, current smokers, SPO2 reading before induction of less than 95%, emergency surgery, and the absence of oxygen therapy during the period of transfer and/or in the post anesthesia care unit were significantly associated with an increased risk of hypoxemia in the early postoperative period.

CONCLUSIONS

The incidence of early postoperative hypoxemia was high in Debre Tabor Comprehensive Specialized Hospital. Obese patients, patients having a chronic disease, current smokers, and lower oxygen saturations before induction, emergency surgery, and the absence of oxygen therapy were the main predictors of an increased occurrence of early postoperative hypoxemia.

O2 No Longer the Go2: A Systematic Review and Meta-Analysis Comparing the Effects of Giving Perioperative Oxygen Therapy of 30% FiO2 to 80% FiO2 on Surgical Site Infection and Mortality

OBJECTIVE

To determine the effects of perioperative high (80%) versus low (30%) fraction of inspired oxygen (FiO₂) on surgical site infection (SSI) and mortality in adult surgical patients.

BACKGROUND

The routine use of high fraction perioperative oxygen in patients is "standard of care" and recommended by the World Health Organisation; however, whether there is truly any benefit to this therapy has been challenged by some authors. Questions have also been raised about the possibility of harm from oxygen therapy.

METHOD

Randomised control trials comparing high-to-low FiO₂ were located by searching MEDLINE, Embase, CENTRAL and Web of Science. The primary outcomes were SSI up to 15 days and up to any time point postoperatively and mortality up to 30 days. The data were analysed using random effects meta-analysis.

RESULTS

Twelve studies involving 10,212 participants were included. At 15 days postoperatively, and at the longest point of post-operative follow-up, there was no statistically significant reduction in the risk of SSI when comparing patients who received a perioperative FiO₂ of 30% to those with an FiO₂ of 80% (RR 1.41, 95% CI 1.00-2.01, p 0.05 and RR 1.23, 95% CI 1.00-1.51, p 0.05). There was no statistically significant difference in mortality between the 30% FiO₂ and the 80% FiO₂ groups (RR 1.12, 95% CI 0.56-2.22, p 0.76).

CONCLUSION

This meta-analysis showed no statistically significant difference in post-operative SSI or mortality when comparing patients receiving an FiO₂ of 80% to those receiving an FiO₂ of 30%.

Ventilation in pediatric anesthesia: A French multicenter prospective observational study (PEDIAVENT)

INTRODUCTION

Protective ventilation is now a standard of care in adults. However, management of ventilation is heterogeneous in children and little is known regarding the mechanical ventilation parameters actually used during pediatric anesthesia.

AIM

The aim of the study was to assess current ventilatory practices during pediatric anesthesia in France and to compare them with pediatric experts' statements, with a specific focus on tidal volume.

PATIENTS AND METHODS

We conducted a prospective multicenter observational study, regarding the ventilatory management and the mechanical ventilation parameters, over two days (21 and 22 June 2017) in 29 pediatric centers in France. All children undergoing general anesthesia during these 2 days were eligible; those who required extracorporeal circulation or one-lung ventilation were excluded.

RESULTS

A total of 701 children were included; median [IQR] age was 60 [24-120] months. Among the patients in whom controlled ventilation was used, 254/515 (49.3%) had an expired tidal volume >8 mL/kg and 44 children (8.8%) an expired tidal volume ≥10 mL/kg. Lower weight and use of a supraglottic airway device were significantly associated with provision of a tidal volume ≥10 mL/kg (odds ratio 0.94, 95% confidence interval [0.92; 0.97], P < .001 and 2.28 [1.20; 4.31], P = .012, respectively). The positive end-expiratory pressure was set at a median [IQR] of 4 [3-5] cmH₂ O; it was <3 cmH₂ O in 15.7% of children and not used in 56/499 (9.3%). Among intubated children, 57 (18.3%) received a tidal volume < 10 mL/kg with a positive end-expiratory pressure ≥3 cmH₂ O in association with recruitment maneuvers.

CONCLUSIONS

Ventilatory practices in children were heterogenous, and a large proportion of children were not ventilated as it is currently recommended by some experts.

Effects of the intermediate care unit on the oldest-old general surgical patients: a retrospective, pre- and postintervention study

BACKGROUND

Whether the intermediate care unit (IMCU) is beneficial for the oldest-old (aged ≥ 80 years) general surgical patients still remains unknown. We aimed to investigate the impacts of IMCU on the clinical outcomes and cost in this population.

METHODS

A retrospective, pre- and postintervention study was performed in this population in a university teaching hospital. The primary outcome was the occurrence of life-threatening complications including death or unplanned ICU admission after the surgeries. Secondary outcomes included the comparisons of the hospitalization expenses, the hospital length of stay (LOS) and the postoperative LOS between the pre-IMCU group and the IMCU group.

RESULTS

Two hundred and seventeen patients were enrolled, including 98 in the pre-IMCU group and 119 in the IMCU group. After the introduction of IMCU, the occurrence of life-threatening complications significantly dropped from 11.2 to 2.5% (P = 0.012). The total hospitalization expenses showed a nonsignificant decreasing trend in the IMCU group (pre-IMCU group: 85856.3 ± 66583.7 RMB vs IMCU group: 78936.4 ± 36710.4 RMB). The treatment fee was much lower in the IMCU group (IMCU group: 4930.0 ± 4280.2 RMB vs pre-IMCU group: 7378.2 ± 10096.7 RMB, P = 0.017). Both the hospital LOS (IMCU group: 20.3 ± 10.3 days vs pre-IMCU group: 19.5 ± 9.0 days) and the postoperative hospital LOS (IMCU group: 12.0 ± 8.1 days vs pre-IMCU group: 11.2 ± 7.0 days) were not statistically different in the two groups.

CONCLUSIONS

The allocation of the oldest-old surgical patients who do not need organ support therapy in the ICU to IMCU rather than in the standard wards was associated with a significant decrease in postoperative life-threatening complications and treatment fee.

TRIAL REGISTRATION

This study was registered at https://www.chictr.org.cn (ChiCTR2000030639).

Recognizing Risks and Optimizing Perioperative Care to Reduce Respiratory Complications in the Pediatric Patient

There have been significant advancements in the safe delivery of anesthesia as well as improvements in surgical technique; however, the perioperative period can still be high risk for the pediatric patient. Perioperative respiratory complications (PRCs) are some of the most common critical events that can occur in pediatric surgical patients and they can lead to increased length of hospitalization, worsened patient outcomes, and higher hospital and postoperative costs. It is important to determine the various factors that put pediatric patients at increased risk of PRCs. This will allow for more detailed and accurate informed consent, optimized perioperative management strategy, improved allocation of clinical resources, and, hopefully, better patient experience. There are only a few risk prediction models/scoring tools developed for and validated in the pediatric patient population, but they have been useful in helping identify the key factors associated with a high likelihood of developing PRCs. Some of these factors are patient factors, while others are procedure-related factors. Some of these factors may be modified such that the patient’s clinical status is optimized preoperatively to decrease the risk of PRCs occurring perioperatively. Fore knowledge of the factors that are not able to be modified can help guide allocation of perioperative clinical resources such that the negative impact of these non-modifiable factors is buffered. Additional training in pediatric anesthesia or focused expertise in pediatric airway management, vascular access and management of massive hemorrhage should be considered for the perioperative management of the less than 3 age group. Intraoperative ventilation strategy plays a key role in determining respiratory outcomes for both adult and pediatric surgical patients. Key components of lung protective mechanical ventilation strategy such as low tidal volume and moderate PEEP used in the management of acute respiratory distress syndrome (ARDS) in pediatric intensive care units have been adopted in pediatric operating rooms. Adequate post-operative analgesia that balances pain control with appropriate mental status and respiratory drive is important in reducing PRCs.

Tracheal extubation in children: Planning, technique, and complications

Although poorly described in textbooks and rarely a topic of lecture, tracheal extubation is a critical phase of anesthetic care. It should therefore be carefully planned taking into account simple physiology-based principles to maintain the upper airway patent and avoid lung de-recruitment, but also the pharmacology of all anesthetic agents used. Although the management of most of its complications can be learned in a clinical simulation environment, the basic techniques can so far only be taught at the bedside, in the operating room. In this paper, the process of extubation is described in successive steps: preparation, return to adequate spontaneous ventilation, awake versus deep extubation, timing according to the child's breathing cycle, extubation in the operating room or in the Postanesthesia Care unit, child's management immediately after extubation, diagnosis and treatment of the early complications, and finally, how to prepare for a difficult reintubation.

Early Hyperoxia in Patients with Traumatic Brain Injury Admitted to Intensive Care in Australia and New Zealand: A Retrospective Multicenter Cohort Study

BACKGROUND

Early hyperoxia may be an independent risk factor for mortality in critically ill traumatic brain injury (TBI) patients, although current data are inconclusive. Accordingly, we conducted a retrospective cohort study to determine the association between systemic oxygenation and in-hospital mortality, in critically ill mechanically ventilated TBI patients.

METHODS

Data were extracted from the Australian and New Zealand Intensive Care Society Centre for Outcome and Resource Evaluation Adult Patient Database. All adult TBI patients receiving mechanical ventilation in 129 intensive care units between 2000 and 2016 were included in analysis. The following data were extracted: demographics, illness severity scores, physiological and laboratory measurements, institutional characteristics, and vital status at discharge. In-hospital mortality was used as the primary study outcome. The primary exposure variable was the 'worst' partial arterial pressure of oxygen (PaO2) recorded during the first 24 h in ICU; hyperoxia was defined as > 299 mmHg. Adjustment for illness severity utilized multivariable logistic regression, the results of which are reported as the odds ratio (OR) 95% CI.

RESULTS

Data concerning 24,148 ventilated TBI patients were extracted. By category of worst PaO2, crude in-hospital mortality ranged from 27.1% (PaO2 40-49 mmHg) to 13.3% (PaO2 140-159 mmHg). When adjusted for patient and institutional characteristics, the only PaO2 category associated with a significantly greater risk of death was < 40 mmHg [OR 1.52, 1.03-2.25]. A total of 3117 (12.9%) patients were hyperoxic during the first 24 h in ICU, with a crude in-hospital mortality rate of 17.8%. No association was evident in between hyperoxia and mortality in adjusted analysis [OR 0.97 (0.86-1.11)].

CONCLUSIONS

In this large multicenter cohort of TBI patients, hyperoxia in the first 24 h after ICU admission was not independently associated with greater in-hospital mortality. Hypoxia remains associated with greater in-hospital mortality risk and should be avoided where possible.

Effect of different fraction of inspired oxygen on development of atelectasis in mechanically ventilated children: A randomized controlled trial

BACKGROUND

The use of high fraction of inspired oxygen (F_I O₂ ) can cause direct pulmonary toxicity and pulmonary complications. The purpose of this study was to evaluate the effect of different F_I O₂ on development of intraoperative atelectasis in mechanically ventilated children using lung ultrasound.

METHODS

In this randomized controlled, patient- and sonographer-blinded trial, 86 children (≤6 years) undergoing noncardiac surgery were allocated into a low (n = 43) or high (n = 43) F_I O₂ group. The low F_I O₂ group consistently received 30% air-oxygen mixture during preoxygenation, ultrasound-guided recruitment maneuver, and mechanical ventilation. The high F_I O₂ group received 100% oxygen during preoxygenation and ultrasound-guided recruitment maneuver and 60% air-oxygen mixture during mechanical ventilation. Positive end-expiratory pressure of 5 cm H₂ O was applied in both groups. Lung ultrasound was performed one minute after the start of mechanical ventilation and at the end of surgery in both groups. Primary outcome was significant atelectasis incidence (consolidation score of ≥2 in any region) on the postoperative lung ultrasound. Secondary outcomes included significant atelectasis incidence on the preoperative lung ultrasound, incidences of intra- and postoperative desaturation, and incidences of postoperative fever and postoperative pulmonary complications.

RESULTS

Significant atelectasis incidence on the postoperative lung ultrasound was similar between the low and high F_I O₂ groups (28% vs 37%; Pearson chi-square value = 0.847; P = .357; OR 1.531; 95% CI 0.617-3.800). Significant atelectasis incidence on the preoperative lung ultrasound was also similar between the groups (12% vs 9%; Pearson chi-square value = 0.124; P = .725; OR 0.779; 95% CI 0.194-3.125). There were no statistically significant differences in the other secondary outcomes.

CONCLUSIONS

F_I O₂ did not affect significant atelectasis formation in mechanically ventilated children who received ultrasound-guided recruitment maneuver and positive end-expiratory pressure.

Effects of inspired oxygen concentration during emergence from general anaesthesia on postoperative lung impedance changes evaluated by electrical impedance tomography: a randomised controlled trial

We evaluated the effects of three different inspired oxygen concentrations (40%, 80%, and 100%) at anaesthesia emergence on postoperative lung volumes as measured by global impedance of electrical impedance tomography (EIT). This is a randomised, controlled, and assessor-blinded study in single-centre from May 2017 to August 2017. Seventy-one patients undergoing elective laparoscopic colorectal surgery with healthy lung condition were randomly allocated into the three groups based on the concentration of inspired oxygen applied during anaesthesia emergence: 40%-, 80%- or 100%-oxygen. End-expiratory lung impedance (EELI) with normal tidal ventilation and total lung impedance (TLI) with full respiratory effort were measured preoperatively and before discharge in the post-anaesthesia care unit by EIT, and perioperative changes (the ratio of difference between preoperative and postoperative value to preoperative value) were compared among the three groups. Postoperative lung impedances were significantly reduced compared with preoperative values in all patients (P < 0.001); however, perioperative lung impedance reduction (%) did not differ among the three oxygen groups. The mean reduction ratio in each 40%-, 80%-, and 100%-oxygen group were 37% ± 13%, 41% ± 14%, and 46% ± 14% for EELI (P = 0.125) and 40% ± 20%, 44% ± 17% and 49% ± 20% for TLI (P = 0.276), respectively. Inspired oxygen concentrations applied during anaesthesia emergence did not show a significant difference in postoperative lung volume as measured by EIT in patients undergoing laparoscopic colorectal surgery with healthy lungs.Trial registration cris.nih.go.kr (KCT0002642).

Physiologically driven, altitude-adaptive model for the interpretation of pediatric oxygen saturation at altitudes above 2,000 m a.s.l

Measuring peripheral oxygen saturation (SpO2) with pulse oximeters at the point of care is widely established. However, since SpO2 is dependent on ambient atmospheric pressure, the distribution of SpO2 values in populations living above 2000 m a.s.l. is largely unknown. Here, we propose and evaluate a computer model to predict SpO2 values for pediatric permanent residents living between 0 and 4,000 m a.s.l. Based on a sensitivity analysis of oxygen transport parameters, we created an altitude-adaptive SpO2 model that takes physiological adaptation of permanent residents into account. From this model, we derived an altitude-adaptive abnormal SpO2 threshold using patient parameters from literature. We compared the obtained model and threshold against a previously proposed threshold derived statistically from data and two empirical data sets independently recorded from Peruvian children living at altitudes up to 4,100 m a.s.l. Our model followed the trends of empirical data, with the empirical data having a narrower healthy SpO2 range below 2,000 m a.s.l. but the medians never differed more than 2.3% across all altitudes. Our threshold estimated abnormal SpO2 in only 17 out of 5,981 (0.3%) healthy recordings, whereas the statistical threshold returned 95 (1.6%) recordings outside the healthy range. The strength of our parametrized model is that it is rooted in physiology-derived equations and enables customization. Furthermore, as it provides a reference SpO2, it could assist practitioners in interpreting SpO2 values for diagnosis, prognosis, and oxygen administration at higher altitudes.NEW & NOTEWORTHY Our model describes the altitude-dependent decrease of SpO2 in healthy pediatric residents based on physiological equations and can be adapted based on measureable clinical parameters. The proposed altitude-specific abnormal SpO2 threshold might be more appropriate than rigid guidelines for administering oxygen that currently are only available for patients at sea level. We see this as a starting point to discuss and adapt oxygen administration guidelines.

Respiratory complications of anaesthesia

Postoperative pulmonary complications are a major determinant of outcome for patients and consume huge resources within hospital, particularly in critical care. Prediction and anticipation of postoperative pulmonary complications are vital for patient selection and, in some cases, for informed patient consent. Being able to assess the likelihood of postoperative pulmonary complications also allows research into methods to reduce them by allowing allocation of patients to the appropriate arms of research trials. Some patients have pre-operative characteristics or belong to patient groups such as those with chronic obstructive pulmonary disease or obstructive sleep apnoea, where techniques and evidence-based guidance to avoid or reduce complications are becoming established. Intra-operative ventilation and the use of lung-protective ventilation may be helpful during major surgery, but studies looking at reduced tidal volumes, recruitment and levels of positive end-expiratory pressure, have this far only led to a degree of consensus in terms of tidal volume, although parameters that predispose to postoperative pulmonary complications are becoming clearer. Optimal postoperative care in terms of analgesia, positioning, physiotherapy and mobilisation is another developing area. Techniques such as continuous positive airways pressure, non-invasive ventilation and high-flow nasal humidified oxygen appear to show some benefit, but the exact roles, pressures and timings of each are currently being explored. Much remains to be researched and developed into evidence-based practice.

Short-duration hyperoxia causes genotoxicity in mouse lungs: protection by volatile anesthetic isoflurane

High concentrations of oxygen (hyperoxia) are routinely used during anesthesia, and supplemental oxygen is also administered in connection with several other clinical conditions. Although prolonged hyperoxia is known to cause acute lung injury (ALI), whether short-duration hyperoxia causes lung toxicity remains unknown. We exposed mice to room air (RA or 21% O₂) or 60% oxygen alone or in combination with 2% isoflurane for 2 h and determined the expression of oxidative stress marker genes, DNA damage and DNA repair genes, and expression of cell cycle regulatory proteins using quantitative PCR and Western analyses. Furthermore, we determined cellular apoptosis using TUNEL assay and assessed the DNA damage product 8-hydroxy-2'-deoxyguanosine (8-Oxo-dG) in the urine of 60% hyperoxia-exposed mice. Our study demonstrates that short-duration hyperoxia causes mitochondrial and nuclear DNA damage and that isoflurane abrogates this DNA damage and decreases apoptosis when used in conjunction with hyperoxia. In contrast, isoflurane mixed with RA caused significant 8-Oxo-dG accumulations in the mitochondria and nucleus. We further show that whereas NADPH oxidase is a major source of superoxide anion generated by isoflurane in normoxia, isoflurane inhibits superoxide generation in hyperoxia. Additionally, isoflurane also protected the mouse lungs against ALI (95% O₂ for 36-h exposure). Our study established that short-duration hyperoxia causes genotoxicity in the lungs, which is abrogated when hyperoxia is used in conjunction with isoflurane, but isoflurane alone causes genotoxicity in the lung when delivered with ambient air.

Association between perioperative hyperoxia and cerebrovascular complications after laparotomy-A post-hoc follow-up study

BACKGROUND

Perioperative hyperoxia has been linked to increased long-term mortality. Vasoconstrictive and cellular side effects to hyperoxia have been suggested to increase the risk of coronary and cerebral ischemia. The aim of this post-hoc analysis of a large randomized trial was to compare the effects of 80% vs 30% perioperative oxygen on the long-term risk of stroke or transient cerebral ischemia (TCI) in patients undergoing abdominal surgery.

METHODS

A total of 1386 patients were randomized to 80% or 30% perioperative oxygen during acute or elective open abdominal surgery. Median follow-up was 3.9 years. Primary outcome was a composite of the long-term occurrence of stroke or TCI. Secondary outcomes included long-term mortality without stroke or TCI, and incidences of neurological admission, psychiatric admission, and dementia. Outcomes were analyzed in Cox regression models.

RESULTS

Stroke or TCI occurred in 20 (3.0%) patients given 80% oxygen vs 22 (3.2%) patients given 30% oxygen with an adjusted hazard ratio (HR) of 0.96 [95% CI 0.52-1.76]. Composite secondary outcome of death, stroke, or TCI had a HR of 1.21 [95% CI 1.00-1.47] for 80% compared to 30% oxygen. HRs for secondary outcomes were HR 1.14 [95% CI 0.79-1.64] for neurological admission, 1.34 [95% CI 0.95-1.88] for psychiatric admission and 0.54 [95% CI 0.16-1.80] for dementia.

CONCLUSION

Stroke or TCI did not seem related to perioperative inspiratory oxygen fraction. Due to few events, this study cannot exclude that perioperative hyperoxia increases risk of mortality, stroke, or TCI after abdominal surgery.

Hyperoxia reduces salivary secretion by inducing oxidative stress in mice

OBJECTIVE

The aim of this study was to determine the effects of prolonged hyperoxia on salivary glands and salivary secretion in mice.

DESIGN

Male C57BL/6 J mice were kept in a 75% oxygen chamber (hyperoxia group) or a 21% oxygen chamber for 5 days. We measured the secretion volume, protein concentration, and amylase activity of saliva after the injection of pilocarpine. In addition, we evaluated the histological changes induced in the submandibular glands using hematoxylin and eosin and Alcian blue staining and assessed apoptotic changes using the TdT-mediated dUTP nick end labeling (TUNEL) assay. We also compared the submandibular gland expression levels of heme oxygenase-1 (HO-1), superoxide dismutase (SOD)-1, and SOD-2 using the real-time polymerase chain reaction.

RESULTS

In the hyperoxia group, salivary secretion was significantly inhibited at 5 and 10 min after the injection of pilocarpine, and the total salivary secretion volume was significantly decreased. The salivary protein concentration and amylase activity were also significantly higher in the hyperoxia group. In the histological examinations, enlargement of the mucous acini and the accumulation of mucins were observed in the submandibular region in the hyperoxia group, and the number of TUNEL-positive cells was also significantly increased in the hyperoxia group. Moreover, the expression levels of HO-1, SOD-1, and SOD-2 were significantly higher in the hyperoxia group.

CONCLUSION

Our results suggest that hyperoxia reduces salivary secretion, and oxidative stress reactions might be involved in this.

Effects of lowering inspiratory oxygen fraction during microvascular decompression on postoperative gas exchange: A pre-post study

BACKGROUND

Despite many previous studies, the optimal oxygen fraction during general anesthesia remains controversial. This study aimed to evaluate the effects of lowering intraoperative fraction of inspired oxygen on postoperative gas exchange in patients undergoing microvascular decompression (MVD).

METHODS

We conducted a pre-post study to compare postoperative gas exchange with different intraoperative oxygen fractions. From April 2010 to June 2017, 1456 consecutive patients who underwent MVD were enrolled. Starting in January 2014, routine oxygen fraction was lowered from 1.0 to 0.3 during anesthetic induction/awakening and from 0.5 to 0.3 during anesthetic maintenance. Postoperative gas exchange, presented as the minimum value of PaO2/FIO2 ratio within 48 hours, were compared along with adverse events.

RESULTS

Among 1456 patients, 623 (42.8%) patients were stratified into group H (high FIO2) and 833 (57.2%) patients into group L (low FIO2). Intraoperative positive end-expiratory pressure was used in 126 (15.1%) patients in group H and 90 (14.4%) patients in group L (p = 0.77).The minimum value of PaO2/ FIO2 ratio within 48 hours after surgery was significantly greater in the group L (226.13 vs. 323.12; p < 0.001) without increasing any adverse events.

CONCLUSION

In patients undergoing MVD, lowering routine FIO2 and avoiding 100% O2 improved postoperative gas exchange.

Effects of Supplemental Perioperative Oxygen in Preventing Transient Hypoparathyroidism After Total Thyroidectomy

Background

Thyroidectomy is one of the most common endocrine procedures performed worldwide. Post-operative hypocalcemia is a troublesome complication of thyroid surgery. Few studies have considered the role of supplemental oxygen in preventing postoperative hypocalcemia in patients undergoing thyroidectomy.

Materials and methods

This was a randomized controlled study comparing the use of high flow supplemental oxygen (FiO₂ 80%) with low flow oxygen (FiO₂ 30%) in preventing transient postoperative hypocalcemia. Seventy-eight patients undergoing thyroidectomy during the year 2017 in Surgery Unit-1, Holy Family Hospital were included in the study.

Results

Transient hypoparathyroidism was present in 20.5% (n=8/39) in group 1 while it was present in 59.0% (n=23/39) in group 2 patients. Patients in group 1 (FiO₂ 80%) demonstrated a significantly lower percentage of transient hypoparathyroidism than group 2 (FiO₂ 30%) (P=0.001).

Conclusion

Our study concluded that high flow supplemental oxygen (FiO₂ 80%) significantly decreases the risk of developing postoperative transient hypocalcemia.

Continuous vital sign monitoring after major abdominal surgery-Quantification of micro events

INTRODUCTION

Millions of patients undergo major abdominal surgery worldwide each year, and the post-operative phase carries a high risk of respiratory and circulatory complications. Standard ward observation of patients includes vital sign registration at regular intervals. Patients may deteriorate between measurements, and this may be detected by continuous monitoring. The aim of this study was to compare the number of micro events detected by continuous monitoring to those documented by the widely used standardized Early Warning Score (EWS).

METHODS

Fifty patients were continuously monitored with peripheral arterial oxygen saturation (SpO₂ ), heart rate (HR), and respiratory rate (RR) the first 4 days after major abdominal cancer surgery. EWS was monitored as routine practice. Number and duration of events were analyzed using Fisher's exact test and Wilcoxon rank sum test.

RESULTS

Continuous monitoring detected a SpO₂ <92% in 98% of patients vs 16% of patients detected by EWS (P < .0001). Micro events of SpO₂ <92% lasting longer than 60 minutes were found in 58% of patients by continuous monitoring vs 16% by the EWS (P < .0001). Fifty-two percent of patients had micro events of SpO₂ <85% lasting longer than 10 minutes. Continuous monitoring found tachycardia in 60% of patients vs 6% by the EWS. Frequency of events for bradycardia, tachypnea, and bradypnea showed similar patterns.

CONCLUSION

Very low SpO₂ and tachycardia in post-operative patients are common and under-diagnosed by the EWS. Continuous monitoring can discover these micro events and potentially contribute to earlier detection and, potentially, result in prevention of clinical complications.

Comparison of clinical scores in their ability to detect hypoxemic severe OSA patients

BACKGROUND

Severe obstructive sleep apnea (sOSA) and preoperative hypoxemia are risk factors of postoperative complications. Patients exhibiting the combination of both factors are probably at higher perioperative risk. Four scores (STOP-Bang, P-SAP, OSA50, and DES-OSA) are currently used to detect OSA patients preoperatively. This study compared their ability to specifically detect hypoxemic sOSA patients.

METHODS

One hundred and fifty-nine patients scheduled for an overnight polysomnography (PSG) were prospectively enrolled. The ability of the four scores to predict the occurrence of hypoxemic episodes in sOSA patients was compared using sensitivity (Se), specificity (Sp), Youden Index, Cohen kappa coefficient, and the area under ROC curve (AUROC) analyses.

RESULTS

OSA50 elicited the highest Se [95% CI] at detecting hypoxemic sOSA patients (1 [0.89-1]) and was significantly more sensitive than STOP-Bang in that respect. DES-OSA was significantly more specific (0.58 [0.49-0.66]) than the three other scores. The Youden Index of DES-OSA (1.45 [1.33-1.58]) was significantly higher than those of STOP-Bang, P-SAP, and OSA50. The AUROC of DES-OSA (0.8 [0.71-0.89]) was significantly the largest. The highest Kappa value was obtained for DES-OSA (0.33 [0.21-0.45]) and was significantly higher than those of STOP-Bang, and OSA50.

CONCLUSIONS

In our population, DES-OSA appears to be more effective than the three other scores to specifically detect hypoxemic sOSA patients. However prospective studies are needed to confirm these findings in a perioperative setting.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov: NCT02050685.

The Relationship Between Oxygen Reserve Index and Arterial Partial Pressure of Oxygen During Surgery

BACKGROUND

The use of intraoperative pulse oximetry (SpO2) enhances hypoxia detection and is associated with fewer perioperative hypoxic events. However, SpO2 may be reported as 98% when arterial partial pressure of oxygen (PaO2) is as low as 70 mm Hg. Therefore, SpO2 may not provide advance warning of falling arterial oxygenation until PaO2 approaches this level. Multiwave pulse co-oximetry can provide a calculated oxygen reserve index (ORI) that may add to information from pulse oximetry when SpO2 is >98%. This study evaluates the ORI to PaO2 relationship during surgery.

METHODS

We studied patients undergoing scheduled surgery in which arterial catheterization and intraoperative arterial blood gas analysis were planned. Data from multiple pulse co-oximetry sensors on each patient were continuously collected and stored on a research computer. Regression analysis was used to compare ORI with PaO2 obtained from each arterial blood gas measurement and changes in ORI with changes in PaO2 from sequential measurements. Linear mixed-effects regression models for repeated measures were then used to account for within-subject correlation across the repeatedly measured PaO2 and ORI and for the unequal time intervals of PaO2 determination over elapsed surgical time. Regression plots were inspected for ORI values corresponding to PaO2 of 100 and 150 mm Hg. ORI and PaO2 were compared using mixed-effects models with a subject-specific random intercept.

RESULTS

ORI values and PaO2 measurements were obtained from intraoperative data collected from 106 patients. Regression analysis showed that the ORI to PaO2 relationship was stronger for PaO2 to 240 mm Hg (r = 0.536) than for PaO2 over 240 mm Hg (r = 0.0016). Measured PaO2 was ≥100 mm Hg for all ORI over 0.24. Measured PaO2 was ≥150 mm Hg in 96.6% of samples when ORI was over 0.55. A random intercept variance component linear mixed-effects model for repeated measures indicated that PaO2 was significantly related to ORI (β[95% confidence interval] = 0.002 [0.0019-0.0022]; P < 0.0001). A similar analysis indicated a significant relationship between change in PaO2 and change in ORI (β [95% confidence interval] = 0.0044 [0.0040-0.0048]; P < 0.0001).

CONCLUSIONS

These findings suggest that ORI >0.24 can distinguish PaO2 ≥100 mm Hg when SpO2 is over 98%. Similarly, ORI > 0.55 appears to be a threshold to distinguish PaO2 ≥150 mm Hg. The usefulness of these values should be evaluated prospectively. Decreases in ORI to near 0.24 may provide advance indication of falling PaO2 approaching 100 mm Hg when SpO2 is >98%. The clinical utility of interventions based on continuous ORI monitoring should be studied prospectively.

Perioperative hyperoxia: perhaps a malady in disguise

Oxygen is an element, which is used liberally during several medical procedures. The use of oxygen during perioperative care is a controversial issue. Anesthesiologists use oxygen to prevent hypoxemia during surgical procedures, but the effects of its liberal use can be harmful. Another argument for using high oxygen concentrations is to prevent surgical site infections by increasing oxygen levels at the incision site. Although inconclusive, literature concerning the use of high oxygen concentrations during anesthesia show that this approach may cause hemodynamic changes, altered microcirculation and increased oxidative stress. In intensive care it has been shown that high oxygen concentrations may be associated with increased mortality in certain patient populations such as post cardiac arrest patients. In this paper, a review of literature had been undertaken to warn anesthesiologists about the potential harmful effects of high oxygen concentrations.

Ascorbic Acid Attenuates Hyperoxia-Compromised Host Defense against Pulmonary Bacterial Infection

Supraphysiological concentrations of oxygen (hyperoxia) can compromise host defense and increase susceptibility to bacterial infections, causing ventilator-associated pneumonia. The phagocytic activity of macrophages is impaired by hyperoxia-induced increases in the levels of reactive oxygen species (ROS) and extracellular high-mobility group box protein B1 (HMGB1). Ascorbic acid (AA), an essential nutrient and antioxidant, has been shown to be beneficial in various animal models of ROS-mediated diseases. The aim of this study was to determine whether AA could attenuate hyperoxia-compromised host defense and improve macrophage functions against bacterial infections. C57BL/6 male mice were exposed to hyperoxia (≥98% O₂, 48 h), followed by intratracheal inoculation with Pseudomonas aeruginosa, and simultaneous intraperitoneal administration of AA. AA (50 mg/kg) significantly improved bacterial clearance in the lungs and airways, and significantly reduced HMGB1 accumulation in the airways. The incubation of RAW 264.7 cells (a macrophage-like cell line) with AA (0-1,000 μM) before hyperoxic exposure (95% O₂) stabilized the phagocytic activity of macrophages in a concentration-dependent manner. The AA-enhanced macrophage function was associated with significantly decreased production of intracellular ROS and accumulation of extracellular HMGB1. These data suggest that AA supplementation can prevent or attenuate the development of ventilator-associated pneumonia in patients receiving oxygen support.

Hyperoxic oxidative stress during abdominal surgery: a randomized trial

PURPOSE

The hypothesis of our study is that during anesthesia, administration of 80 % oxygen concentration increases oxidative stress more than 40 % oxygen.

METHODS

Forty ASA I-II patients were included in a randomized, single-blind study. Expiratory tidal volumes (ETV) were measured before induction and after extubation. After ventilation with 0.8 FiO2 and intubation, mini-bronchoalveolar lavage (mini-BAL), arterial blood gas (ABG), and blood samples were taken. Patients were randomly assigned to receive 0.8 (group I) or 0.4 (group II) FiO2 during management. Before extubation, mini-BAL, ABG, blood samples were taken. PaO2/FiO2, lactate, malondialdehyde (MDA), protein carbonyl (PCO), superoxide dismutase (SOD), total sulfhydryl (T-SH), non-protein sulfhydryl (NPSH), and protein sulfhydryl (PSH) were measured. In both groups, mean arterial pressure and heart rate values were recorded with 30-min intervals.

RESULTS

ETV values were higher in group II after extubation. PaO2/FiO2 values were higher in group II after extubation compared to group I. In both groups, plasma PCO, SOD, and T-SH levels increased significantly before extubation, whereas the increase in MDA was not significant between groups. Plasma PCO, T-SH, and lactate levels were higher in group I, and plasma SOD, and PSH were higher in group I before extubation. In both groups, MDA, SOD, T-SH, and NPSH levels in mini-BAL increased significantly before extubation. Between-group comparisons, PCO, T-SH, PSH, and NPSH were significantly higher in the BAL samples of group II, and MDA levels were higher in group I.

CONCLUSIONS

We found that 80 % FiO2 decreased ETV and PaO2/FiO2 and increased lactate levels and oxidative stress more, inhibiting antioxidant response compared to 40 % FiO2.

Novel Pulse Oximetry Sonifications for Neonatal Oxygen Saturation Monitoring: A Laboratory Study

OBJECTIVE

We aimed to test whether the use of novel pulse oximetry sounds (sonifications) better informs listeners when a neonate's oxygen saturation (SpO2) deviates from the recommended range.

BACKGROUND

Variable-pitch pulse oximeters do not accurately inform clinicians via sound alone when SpO2 is outside the target range of 90% to 95% for neonates on supplemental oxygen. Risk of blindness, organ damage, and death increase if SpO2 remains outside the target range. A more informative sonification may improve clinicians' ability to maintain the target range.

METHOD

In two desktop experiments, nonclinicians' ability to detect SpO2 range and direction of change was tested with novel versus conventional sonifications of simulated patient data. In Experiment 1, a "shoulder" sonification used larger pitch differences between adjacent saturation percentages for SpO2 values outside the target range. In Experiment 2, a "beacon" sonification used equal-appearing pitch differences, but when SpO2 was outside the target range, a fixed-pitch reference tone from the center of the target SpO2 range preceded every fourth pulse tone.

RESULTS

The beacon sonification improved range identification accuracy over the control display (85% vs. 60%; p < .001), but the shoulder sonification did not (55% vs. 52%).

CONCLUSION

The beacon provided a distinct auditory alert and reference that significantly improved nonclinical participants' ability to identify SpO2 range.

APPLICATION

Adding a beacon to the variable-pitch pulse oximeter sound may help clinicians identify when, and by how much, a neonate's SpO2 deviates from the target range, particularly during patient transport situations when auditory information becomes essential.

Cyclic and constant hyperoxia cause inflammation, apoptosis and cell death in human umbilical vein endothelial cells

BACKGROUND

Perioperative high-dose oxygen (O2 ) exposure can cause hyperoxia. While the effect of constant hyperoxia on the vascular endothelium has been investigated to some extent, the impact of cyclic hyperoxia largely remains unknown. We hypothesized that cyclic hyperoxia would induce more injury than constant hyperoxia to human umbilical vein endothelial cells (HUVECs).

METHODS

HUVECs were exposed to cyclic hyperoxia (5-95% O2 ) or constant hyperoxia (95% O2 ), normoxia (21% O2 ), and hypoxia (5% O2 ). Cell growth, viability (Annexin V/propidium iodide and 3-(4,5-dimethythiazol-2-yl)-2,5-diphenyl tetrazolium bromide, MTT) lactate dehydrogenase (LDH), release, cytokine (interleukin, IL and macrophage migration inhibitory factor, MIF) release, total antioxidant capacity (TAC), and superoxide dismutase activity (SOD) of cell lysate were assessed at baseline and 8, 24, and 72 h. A signal transduction pathway finder array for gene expression analysis was performed after 8 h.

RESULTS

Constant and cyclic hyperoxia-induced gradually detrimental effects on HUVECs. After 72 h, constant or cyclic hyperoxia exposure induced change in cytotoxic (LDH +12%, P = 0.026; apoptosis +121/61%, P < 0.01; alive cells -15%, P < 0.01; MTT -16/15%, P < 0.01), inflammatory (IL-6 +142/190%, P < 0.01; IL-8 +72/43%, P < 0.01; MIF +147/93%, P < 0.01), or redox-sensitive (SOD +278%, TAC-25% P < 0.01) markers. Gene expression analysis revealed that constant and cyclic hyperoxia exposure differently activates oxidative stress, nuclear factor kappa B, Notch, and peroxisome proliferator-activated receptor pathways.

CONCLUSIONS

Extreme hyperoxia exposure induces inflammation, apoptosis and cell death in HUVECs. Although our findings cannot be transferred to clinical settings, results suggest that hyperoxia exposure may cause vascular injury that could play a role in determining perioperative outcome.