Individualised flow-controlled ventilation reduces applied mechanical power and improves ventilation efficiency in a porcine intra-abdominal hypertension model.

BACKGROUND: Aim of this study was to evaluate feasibility and effects of individualised flow-controlled ventilation (FCV), based on compliance guided pressure settings, compared to standard of pressure-controlled ventilation (PCV) in a porcine intra-abdominal hypertension (IAH) model. The primary aim of this study was to investigate oxygenation. Secondary aims were to assess respiratory and metabolic variables and lung tissue aeration. METHODS: Pigs were randomly assigned to FCV (n = 9) and PCV (n = 9). IAH was induced by insufflation of air into the abdomen to induce IAH grades ranging from 0 to 3. At each IAH grade FCV was undertaken using compliance guided pressure settings, or PCV (n = 9) was undertaken with the positive end-expiratory pressure titrated for maximum compliance and the peak pressure set to achieve a tidal volume of 7 ml/kg. Gas exchange, ventilator settings and derived formulas were recorded at two timepoints for each grade of IAH. Lung aeration was assessed by a computed tomography scan at IAH grade 3. RESULTS: All 18 pigs (median weight 54 kg [IQR 51-67]) completed the observation period of 4 h. Oxygenation was comparable at each IAH grade, but a significantly lower minute volume was required to secure normocapnia in FCV at all IAH grades (7.6 vs. 14.4, MD - 6.8 (95% CI - 8.5 to - 5.2) l/min; p < 0.001). There was also a significant reduction of applied mechanical power being most evident at IAH grade 3 (25.9 vs. 57.6, MD - 31.7 (95% CI - 39.7 to - 23.7) J/min; p < 0.001). Analysis of Hounsfield unit distribution of the computed tomography scans revealed a significant reduction in non- (5 vs. 8, MD - 3 (95% CI - 6 to 0) %; p = 0.032) and poorly-aerated lung tissue (7 vs. 15, MD - 6 (95% CI - 13 to - 3) %, p = 0.002) for FCV. Concomitantly, normally-aerated lung tissue was significantly increased (84 vs. 76, MD 8 (95% CI 2 to 15) %; p = 0.011). CONCLUSIONS: Individualised FCV showed similar oxygenation but required a significantly lower minute volume for CO2-removal, which led to a remarkable reduction of applied mechanical power. Additionally, there was a shift from non- and poorly-aerated lung tissue to normally-aerated lung tissue in FCV compared to PCV.

Interleukin-6 Levels During Normothermic Machine Perfusion Impact Postreperfusion Hemodynamics of Liver Graft Recipients: A Prospective Single-center Observational Study.

BACKGROUND: Hemodynamic instability after liver graft reperfusion increases recipient morbidity after liver transplantation. The etiologies of hemodynamic disturbances appear to be multifactorial and are poorly understood. Normothermic machine perfusion (NMP) provides an opportunity to analyze graft quality prior to transplantation. In the present study, we aim to investigate the influence of interleukin-6 (IL-6) levels during NMP on postreperfusion hemodynamics of the recipient. METHODS: Consecutive NMP-liver transplants at a single-center were prospectively analyzed. Perfusate samples were collected at the beginning, after 6 h, and at the end of perfusion and analyzed for IL-6 levels. Mean arterial pressure (MAP) and catecholamine consumption during surgery were recorded. IL-6 levels at the end of NMP were correlated to donor and perfusion characteristics as well as changes in MAP and catecholamine requirements during the anhepatic and reperfusion phase. RESULTS: IL-6 perfusate measurements were assessed in 77 livers undergoing NMP and transplantation. Donor age, sex, cold ischemic time, and NMP time did not correlate with IL-6 levels. Perfusates of donation after circulatory death grafts showed higher IL-6 levels at the end of NMP than donation after brain death grafts. However, IL-6 levels at the end of NMP correlated with catecholamine requirements and MAP in the reperfusion phase. Per log10 increase in IL-6 levels, an increase of 42% points in administered catecholamine dose was observed, despite MAP being decreased by 3.6% points compared to baseline values. CONCLUSIONS: IL-6 levels may be a predictor for recipient hemodynamic instability during liver reperfusion. Larger studies are needed to confirm this finding.

Flow-controlled versus pressure-controlled ventilation in cardiac surgery with cardiopulmonary bypass - A single-center, prospective, randomized, controlled trial.

STUDY OBJECTIVE: Multifactorial comparison of flow-controlled ventilation (FCV) to standard of pressure-controlled ventilation (PCV) in terms of oxygenation in cardiac surgery patients after chest closure. DESIGN: Prospective, non-blinded, randomized, controlled trial. SETTING: Operating theatre at an university hospital, Austria. PATIENTS: Patients scheduled for elective, open, on-pump, cardiac surgery. INTERVENTIONS: Participants were randomized to either individualized FCV (compliance guided end-expiratory and peak pressure setting) or control of PCV (compliance guided end-expiratory pressure setting and tidal volume of 6-8 ml/kg) for the duration of surgery. MEASUREMENTS: The primary outcome measure was oxygenation (PaO2/FiO2) 15 min after intraoperative chest closure. Secondary endpoints included CO2-removal assessed as required minute volume to achieve normocapnia and lung tissue aeration assessed by Hounsfield unit distribution in postoperative computed tomography scans. MAIN RESULTS: Between April 2020 and April 2021 56 patients were enrolled and 50 included in the primary analysis (mean age 70 years, 38 (76%) men). Oxygenation, assessed by PaO2/FiO2, was significantly higher in the FCV group (n = 24) compared to the control group (PCV, n = 26) (356 vs. 309, median difference (MD) 46 (95% CI 3 to 90) mmHg; p = 0.038). Additionally, the minute volume required to obtain normocapnia was significantly lower in the FCV group (4.0 vs. 6.1, MD -2.0 (95% CI -2.5 to -1.5) l/min; p < 0.001) and correlated with a significantly lower exposure to mechanical power (5.1 vs. 9.8, MD -5.1 (95% CI -6.2 to -4.0) J/min; p < 0.001). Evaluation of lung tissue aeration revealed a significantly reduced amount of non-aerated lung tissue in FCV compared to PCV (5 vs. 7, MD -3 (95% CI -4 to -1) %; p < 0.001). CONCLUSIONS: In patients undergoing on-pump, cardiac surgery individualized FCV significantly improved oxygenation and lung tissue aeration compared to PCV. In addition, carbon dioxide removal was accomplished at a lower minute volume leading to reduced applied mechanical power.

COVID-19 Pandemic Did not Influence Number of Oncologic and Emergency Surgeries: A Retrospective Cohort Study from a Tertiary Hospital in Austria.

BACKGROUND: Many articles described a massive decline in surgical procedures during the COVID-19 pandemic waves. Especially the reduction in oncologic and emergency procedures led to the concern that delays and cancelling surgical activity might lead to a substantial increase in preventable deaths. METHODS: Overall numbers and types of surgery were analysed in a tertiary hospital in Austria during the winter period (October-April) from 2015/16 to 2021/22. The half-years 2019/20, 2020/21 and 2021/22 were defined as pandemic half-years and were compared with the mean results of the previous, four, pre-pandemic half-years. RESULTS: A reduction was found for overall numbers and elective surgeries during 2019/20 (4.62%; p < 0.0001 and 12.14; p < 0.0001 respectively) and 2021/22 (14.94%; p < 0.0001 and 34.27; p < 0.0001 respectively). Oncologic surgery increased during 2021/22 (- 12.59%; p < 0.0001) and remained unchanged during the other periods. Emergency surgeries increased during 2019/20 (- 6.97%; p < 0.0001) and during 2021/22 (- 9.44%; p < 0.0001) and remained unchanged during 2020/21. CONCLUSIONS: The concern that the pandemic led to a decrease in oncologic and emergency surgeries cannot be supported with the data from our hospital. A flexible, day-by-day, resource allocation programme with central coordination adhering to hospital resilience recommendations may have helped to adapt to the impact of the COVID-19 pandemic during the first three pandemic half-years.

Improved ventilation efficiency due to continuous gas flow compared to decelerating gas flow in mechanical ventilation: results of a porcine trial.

In pressure-controlled ventilation (PCV), a decelerating gas flow pattern occurs during inspiration and expiration. In contrast, flow-controlled ventilation (FCV) guarantees a continuous gas flow throughout the entire ventilation cycle where the inspiration and expiration phases are simply performed by a change of gas flow direction. The aim of this trial was to highlight the effects of different flow patterns on respiratory variables and gas exchange. Anesthetized pigs were ventilated with either FCV or PCV for 1 h and thereafter for 30 min each in a crossover comparison. Both ventilation modes were set with a peak pressure of 15 cmH2O, positive end-expiratory pressure of 5 cmH2O, a respiratory rate of 20/min, and a fraction of inspired oxygen at 0.3. All respiratory variables were collected every 15 min. Tidal volume and respiratory minute volume were significantly lower in FCV (n = 5) compared with PCV (n = 5) animals [4.6 vs. 6.6, MD -2.0 (95% CI -2.6 to -1.4) mL/kg; P < 0.001 and 7.3 vs. 9.5, MD -2.2 (95% CI -3.3 to -1.0) L/min; P = 0.006]. Notwithstanding these differences, CO2-removal as well as oxygenation was not inferior in FCV compared with PCV. Mechanical ventilation with identical ventilator settings resulted in lower tidal volumes and consecutive minute volume in FCV compared with PCV. This finding can be explained physically by the continuous gas flow pattern in FCV that necessitates a lower alveolar pressure amplitude. Interestingly, gas exchange was comparable in both groups, which is suggestive of improved ventilation efficiency at a continuous gas flow pattern.NEW & NOTEWORTHY This study examined the effects of a continuous (flow-controlled ventilation, FCV) vs. decelerating (pressure-controlled ventilation, PCV) gas flow pattern during mechanical ventilation. It was shown that FCV necessitates a lower alveolar pressure amplitude leading to reduced applied tidal volumes and consequently minute volume. Notwithstanding these differences, CO2-removal as well as oxygenation was not inferior in FCV compared with PCV, which is suggestive of improved gas exchange efficiency at a continuous gas flow pattern.

Individualised flow-controlled ventilation versus pressure-controlled ventilation in a porcine model of thoracic surgery requiring one-lung ventilation: A laboratory study.

BACKGROUND: Flow-controlled ventilation (FCV) enables precise determination of dynamic compliance due to a continuous flow coupled with direct tracheal pressure measurement. Thus, pressure settings can be adjusted accordingly in an individualised approach. OBJECTIVE: The aim of this study was to compare gas exchange of individualised FCV to pressure-controlled ventilation (PCV) in a porcine model of simulated thoracic surgery requiring one-lung ventilation (OLV). DESIGN: Controlled interventional trial conducted on 16 domestic pigs. SETTING: Animal operating facility at the Medical University of Innsbruck. INTERVENTIONS: Thoracic surgery was simulated with left-sided thoracotomy and subsequent collapse of the lung over a period of three hours. When using FCV, ventilation was performed with compliance-guided pressure settings. When using PCV, end-expiratory pressure was adapted to achieve best compliance with peak pressure adjusted to achieve a tidal volume of 6 ml kg -1 during OLV. MAIN OUTCOME MEASURES: Gas exchange was assessed by the Horowitz index (= P aO 2 /FIO 2 ) and CO 2 removal by the P aCO 2 value in relation to required respiratory minute volume. RESULTS: In the FCV group ( n  = 8) normocapnia could be maintained throughout the OLV trial despite a significantly lower respiratory minute volume compared to the PCV group ( n  = 8) (8.0 vs. 11.6, 95% confidence interval, CI -4.5 to -2.7 l min -1 ; P  < 0.001), whereas permissive hypercapnia had to be accepted in PCV ( P aCO 2 5.68 vs. 6.89, 95% CI -1.7 to -0.7 kPa; P  < 0.001). The Horowitz index was comparable in both groups but calculated mechanical power was significantly lower in FCV (7.5 vs. 22.0, 95% CI -17.2 to -11.8 J min -1 ; P  < 0.001). CONCLUSIONS: In this porcine study FCV maintained normocapnia during OLV, whereas permissive hypercapnia had to be accepted in PCV despite a substantially higher minute volume. Reducing exposure of the lungs to mechanical power applied by the ventilator in FCV offers a possible advantage for this mode of ventilation in terms of lung protection.

Impact of COVID-19 on elective, emergency and oncological surgery during the first and the second wave in a tertiary university hospital : Have we learned the lessons?

BACKGROUND: The COVID-19 pandemic caused an important reduction in surgical activities during the first wave. Aim of this retrospective time-trend analysis was to examine whether also during the second wave in fall and winter 2020/2021 surgical interventions decreased. METHODS: Absolut numbers and types of surgeries in a tertiary university hospital during the second COVID-19 wave in fall/winter 2020/2021 were collected from the surgical planning software and compared with the same time frame over the last 5 years. In a second step, the reduction of surgical interventions during the second wave was compared with the reduction of surgical procedures during the first wave in spring 2020 at the same hospital. RESULTS: Despite a higher 7­day incidence of COVID-19 infection and a higher number of patients needing ICU treatment during the second wave, the reduction of surgical interventions was 3.22% compared to 65.29% during the first wave (p < 0.0001). Elective surgical interventions decreased by 88.63% during the first wave compared to 1.79% during the second wave (p < 0.0001). Emergency and oncological interventions decreased by 35.17% during the first wave compared to 5.15% during the second wave (p : 0.0007) and 47.59% compared to 3.89% (p < 0.0001), respectively. Surgical activity reduction in our institution was less pronounced despite higher occupancy of ICU beds during the second COVID-19 wave in fall/winter 2020/2021. CONCLUSION: Better understanding of the disease, adequate supply of disposables and improved interdisciplinary day by day management of surgical and ICU resources may have contributed to this improvement.

CPR with restricted patient access using alternative rescuer positions: a randomised cross-over manikin study simulating the CPR scenario after avalanche burial.

BACKGROUND: The aim of this manikin study was to evaluate the quality of cardiopulmonary resuscitation (CPR) with restricted patient access during simulated avalanche rescue using over-the-head and straddle position as compared to standard position. METHODS: In this prospective, randomised cross-over study, 25 medical students (64% male, mean age 24) performed single-rescuer CPR with restricted patient access in over-the-head and straddle position using mouth-to-mouth ventilation or pocket mask ventilation. Chest compression depth, rate, hand position, recoil, compression/decompression ratio, hands-off times, tidal volume of ventilation and gastric insufflation were compared to CPR with unrestricted patient access in standard position. RESULTS: Only 28% of all tidal volumes conformed to the guidelines (400-800 ml), 59% were below 400 ml and 13% were above 800 ml. There was no significant difference in ventilation parameters when comparing standard to atypical rescuer positions. Participants performed sufficient chest compressions depth in 98.1%, a minimum rate in 94.7%, correct compression recoil in 43.8% and correct hand position in 97.3% with no difference between standard and atypical rescuer positions. In 36.9% hands-off times were longer than 9 s. CONCLUSIONS: Efficacy of CPR from an atypical rescuer position with restricted patient access is comparable to CPR in standard rescuer position. Our data suggest to start basic life-support before complete extrication in order to reduce the duration of untreated cardiac arrest in avalanche rescue. Ventilation quality provided by lay rescuers may be a limiting factor in resuscitation situations where rescue ventilation is considered essential.

Impact of COVID-19 Related Lockdown on the Frequency of Acute and Oncological Surgeries-Lessons Learned From an Austrian University Hospital.

Innsbruck Medical University Hospital, Austria, provides the highest level of care for a region of approximately 1.8 million people. During the early COVID-19 outbreak in spring 2020 surgical activity was drastically reduced with the prime goal of preserving hospital capacities, especially intensive care beds. We conducted a retrospective analysis of surgical activities performed at Innsbruck Medical University Hospital during the lockdown period from March 15 to April 14, 2020 and compared these activities to the same period during the previous 5 years. Total surgical activity was reduced by 65.4% compared to the same period during the previous 5 years (p < 0.001); elective surgeries were reduced by 88.7%, acute surgeries by 35.3% and oncological surgeries by 47.8% compared to the previous 5 years (all p < 0.001). This dramatic decrease in acute and oncological surgeries can most likely be ascribed to the fact that many patients avoided health care facilities because of the strict stay-at-home policy and/or the fear of contracting SARS-CoV-2 in the hospital. In view of future waves, the population should be encouraged to seek medical help for acute symptoms and to attend cancer screening programs.

Adrenaline improves regional cerebral blood flow, cerebral oxygenation and cerebral metabolism during CPR in a porcine cardiac arrest model using low-flow extracorporeal support.

BACKGROUND: The effects of adrenaline on cerebral blood vessels during cardiopulmonary resuscitation (CPR) are not well understood. We developed an extracorporeal CPR model that maintains constant low systemic blood flow while allowing adrenaline-associated effects on cerebral vasculature to be assessed at different mean arterial pressure (MAP) levels independently of the effects on systemic blood flow. METHODS: After eight minutes of cardiac arrest, low-flow extracorporeal life support (ECLS) (30 ml/kg/min) was started in fourteen pigs. After ten minutes, continuous adrenaline administration was started to achieve MAP values of 40 (n = 7) or 60 mmHg (n = 7). Measurements included intracranial pressure (ICP), cerebral perfusion pressure (CePP), laser-Doppler-derived regional cerebral blood flow (CBF), cerebral regional oxygen saturation (rSO2), brain tissue oxygen tension (PbtO2) and extracellular cerebral metabolites assessed by cerebral microdialysis. RESULTS: During ECLS without adrenaline, regional CBF increased by only 5% (25th to 75th percentile: -3 to 14; p = 0.2642) and PbtO2 by 6% (0-15; p = 0.0073) despite a significant increase in MAP to 28 mmHg (25-30; p < 0.0001) and CePP to 10 mmHg (8-13; p < 0.0001). Accordingly, cerebral microdialysis parameters showed a profound hypoxic-ischemic pattern. Adrenaline administration significantly improved regional CBF to 29 ± 14% (p = 0.0098) and 61 ± 25% (p < 0.001) and PbtO2 to 15 ± 11% and 130 ± 82% (both p < 0.001) of baseline in the MAP 40 mmHg and MAP 60 mmHg groups, respectively. Importantly, MAP of 60 mmHg was associated with metabolic improvement. CONCLUSION: This study shows that adrenaline administration during constant low systemic blood flow increases CePP, regional CBF, cerebral oxygenation and cerebral metabolism.

A randomized trial comparing the Ambu® Aura-i™ and the Ambu® Aura Gain™ laryngeal mask as conduit for tracheal intubation in children.

BACKGROUND: The Ambu Aura Gain is a newer second-generation supraglottic airway device designed for fibreoptic bronchoscopy (FOB)-guided tracheal intubation. METHODS: 57 patients between 18 months and six years of age were randomized to receive either the Ambu Aura-I (N.=29) or the Ambu Aura Gain (N.=28). Primary endpoint was the time for intubation. Secondary endpoints were the time and number of attempts for device insertion, the feasibility of FOB-guided intubation, the oropharyngeal leak pressure (OLP) the fibreoptic grade of laryngeal view and possible complications. RESULTS: No difference was found in the time for intubation, the time for device insertion or the fibreoptic grade of laryngeal view. First-attempt device insertion was successful in all (N.=28) patients with Aura Gain (100%) and in 27 (97%) with Aura-i. In the Aura-i group one insertion failed. A significant difference in successful intubation was seen between the Aura-i and the Aura Gain (79% vs. 100%, respectively, P=0.0011). Also found was a significant difference in the mean OLP (SD) between the Ambu Aura-i and the Ambu Aura Gain (18 [3] vs. 20 [3] cmH2O, respectively; mean difference [MD] 2 cmH2O; P=0.005). CONCLUSIONS: The Ambu Aura Gain served as a reliable device for FOB-guided tracheal intubation. Even if the time for intubation, when intubation was possible did not differ, the Aura-i showed only 79% intubation success, making it a doubtful device for FOB-guided tracheal intubation in cases of emergency and severe hypoxemia in small children.

Resolution of biliary stricture after living donor liver transplantation in a child by percutaneous trans-hepatic cholangiography and drainage: a case report.

INTRODUCTION: Intra-hepatic cholestasis arising from biliary strictures is a frequent complication in pediatric patients after liver transplantation. Minimally invasive procedures such as percutaneous drainage placement and balloon dilation are the preferred diagnostic and therapeutic modalities. CASE PRESENTATION: We report the case of a 12-month-old Caucasian boy with biliary atresia who was initially treated with hepatoportoenterostomy. In the following months, he developed biliary cirrhosis, accompanied by cystic bile retention, recurrent bile duct infections and malabsorption. Six months after the initial surgical intervention, he underwent living donor liver transplantation. Within two months, the hepatico-jejunostomy became occluded leading to progressive intra-hepatic cholestasis. Under sonographic guidance, external drainage of bile was accomplished by percutaneous trans-hepatic cholangiography and drainage. In total, our patient underwent 12 interventions under general anesthesia until balloon dilatation of the hepatico-jejunostomy was successfully performed. Finally, our patient's general condition improved and he gained weight. CONCLUSIONS: Minimally invasive techniques are preferred to surgical revisions and justify even multiple attempts. Interventions under general anesthesia, though not without risks, are still reasonable. Co-operation with parents and multidisciplinary approach to complication management by the involved surgeon, radiologist, pediatrician and anesthesiologist are important.