Short-term mild hyperventilation on intracranial pressure, cerebral autoregulation, and oxygenation in acute brain injury patients: a prospective observational study

Current guidelines suggest a target of partial pressure of carbon dioxide (PaCO2) of 32-35 mmHg (mild hypocapnia) as tier 2 for the management of intracranial hypertension. However, the effects of mild hyperventilation on cerebrovascular dynamics are not completely elucidated. The aim of this study is to evaluate the changes of intracranial pressure (ICP), cerebral autoregulation (measured through pressure reactivity index, PRx), and regional cerebral oxygenation (rSO2) parameters before and after induction of mild hyperventilation. Single center, observational study including patients with acute brain injury (ABI) admitted to the intensive care unit undergoing multimodal neuromonitoring and requiring titration of PaCO2 values to mild hypocapnia as tier 2 for the management of intracranial hypertension. Twenty-five patients were included in this study (40% female), median age 64.7 years (Interquartile Range, IQR = 45.9-73.2). Median Glasgow Coma Scale was 6 (IQR = 3-11). After mild hyperventilation, PaCO2 values decreased (from 42 (39-44) to 34 (32-34) mmHg, p < 0.0001), ICP and PRx significantly decreased (from 25.4 (24.1-26.4) to 17.5 (16-21.2) mmHg, p < 0.0001, and from 0.32 (0.1-0.52) to 0.12 (-0.03-0.23), p < 0.0001). rSO2 was statistically but not clinically significantly reduced (from 60% (56-64) to 59% (54-61), p < 0.0001), but the arterial component of rSO2 (ΔO2Hbi, changes in concentration of oxygenated hemoglobin of the total rSO2) decreased from 3.83 (3-6.2) μM.cm to 1.6 (0.5-3.1) μM.cm, p = 0.0001. Mild hyperventilation can reduce ICP and improve cerebral autoregulation, with minimal clinical effects on cerebral oxygenation. However, the arterial component of rSO2 was importantly reduced. Multimodal neuromonitoring is essential when titrating PaCO2 values for ICP management.

Video vs. direct laryngoscopy for adult surgical and intensive care unit patients requiring tracheal intubation: a systematic review and meta-analysis of randomized controlled trials

OBJECTIVE

This systematic review and meta-analysis aimed to determine whether a specific videolaryngoscopy technique is superior to standard direct laryngoscopy using a Macintosh blade to reduce the risk of difficult intubation in surgical and intensive care unit patients.

MATERIALS AND METHODS

We identified all randomized controlled trials comparing videolaryngoscopes (VLSs) to direct laryngoscopy in the Cochrane Central Register of Controlled Trials, MEDLINE, and EMBASE (from inception to April 2020). The primary outcome was difficult intubation in adult surgical and intensive care unit patients. Secondary outcomes were successful intubation at the first attempt, airway trauma, sore throat, hoarseness, hypoxia, and mortality.

RESULTS

We included 97 randomized controlled trials to evaluate 12775 patients. A high risk of bias was found in at least 50% of the included studies for each outcome. VLSs reduced the risk of difficult intubation compared to direct Macintosh laryngoscopy (RR 0.48, 95% CI from 0.35 to 0.65). VLSs increased the rate of successful intubation at the first attempt when compared to direct Macintosh laryngoscopy (RR 1.03, 95% CI from 1.00 to 1.07). Lower risks of airway trauma were found with VLSs (RR 0.69, 95% CI from 0.55 to 0.86). A decreased risk of hoarseness was associated with the use of VLSs (RR 0.67, 95% CI from 0.54 to 0.83). In addition, VLSs did not significantly reduce the risk of hypoxia compared with direct laryngoscopy (RR 0.83, 95% CI from 0.60 to 1.16).

CONCLUSIONS

In this systematic review and meta-analysis, we found that the use of VLSs reduced the risk of difficult intubation and slightly increased the ratio of successful intubation at the first attempt among adult patients.

Erratum to: 36th International Symposium on Intensive Care and Emergency Medicine: Brussels, Belgium. 15-18 March 2016

[This corrects the article DOI: 10.1186/s13054-016-1208-6.].

The application of esophageal pressure measurement in patients with respiratory failure

This report summarizes current physiological and technical knowledge on esophageal pressure (Pes) measurements in patients receiving mechanical ventilation. The respiratory changes in Pes are representative of changes in pleural pressure. The difference between airway pressure (Paw) and Pes is a valid estimate of transpulmonary pressure. Pes helps determine what fraction of Paw is applied to overcome lung and chest wall elastance. Pes is usually measured via a catheter with an air-filled thin-walled latex balloon inserted nasally or orally. To validate Pes measurement, a dynamic occlusion test measures the ratio of change in Pes to change in Paw during inspiratory efforts against a closed airway. A ratio close to unity indicates that the system provides a valid measurement. Provided transpulmonary pressure is the lung-distending pressure, and that chest wall elastance may vary among individuals, a physiologically based ventilator strategy should take the transpulmonary pressure into account. For monitoring purposes, clinicians rely mostly on Paw and flow waveforms. However, these measurements may mask profound patient-ventilator asynchrony and do not allow respiratory muscle effort assessment. Pes also permits the measurement of transmural vascular pressures during both passive and active breathing. Pes measurements have enhanced our understanding of the pathophysiology of acute lung injury, patient-ventilator interaction, and weaning failure. The use of Pes for positive end-expiratory pressure titration may help improve oxygenation and compliance. Pes measurements make it feasible to individualize the level of muscle effort during mechanical ventilation and weaning. The time is now right to apply the knowledge obtained with Pes to improve the management of critically ill and ventilator-dependent patients.

Performance of different PEEP valves and helmet outlets at increasing gas flow rates: a bench top study

BACKGROUND

Aim of the paper was to assess the performance of different expiratory valves and the resistance of helmet outlet ports at increasing gas flow rates.

METHODS

A gas flow-meter was connected to 10 different expiratory peep valves: 1 water-seal valve, 4 precalibrated fixed PEEP valves and 5 adjustable PEEP valves. Three new valves of each brand, set at different pressure levels (5-7.5-10-12.5-15 cmH(2)O, if available), were tested at increasing gas flow rates (from 30 to 150 L/min). We measured the pressure generated just before the valves. Three different helmets sealed on a mock head were connected at the inlet port with a gas flow-meter while the outlet was left clear. We measured the pressure generated inside the helmet (due to the flow-resistance of the outlet port) at increasing gas flow rates.

RESULTS

Adjustable valves showed a variable degree flow-dependency (increasing difference between the measured and the expected pressure at increasing flow rates), while pre-calibrated valves revealed a flow-independent behavior. Water seal valve showed low degree flow-dependency. The pressures generated by the outlet port of the tested helmets ranged from 0.02 to 2.29 cmH(2)O at the highest gas flow rate.

CONCLUSION

Adjustable PEEP valves are not suggested for continuous-flow CPAP systems as their flow-dependency can lead to pressures higher than expected. Precalibrated and water seal valves exhibit the best performance. Different helmet outlet ports do not significantly affect the pressure generated during helmet CPAP. In order to avoid iatrogenic complications gas flow and pressure delivered during helmet CPAP must always be monitored.

Long-term extracorporeal membrane oxygenation with minimal ventilatory support: a new paradigm for severe ARDS?

Pulmonary tuberculosis can lead to acute respiratory distress syndrome (ARDS) which is associated with high mortality. We report the case of a patient with pulmonary tuberculosis and severe ARDS (PaO2/FiO2<100 mmHg) who was initially managed with advanced up-to-date treatments (protective ventilation and extracorporeal membrane oxygenation, ECMO) but failed to improve. After a month of failure and the development of bilateral pneumothoraces, we drastically changed our therapeutic strategy: we maximized ECMO support to maintain oxygenation, we greatly reduced ventilation pressures and we left the pneumothoraces undrained. From then on, the patient improved and he eventually survived. This case suggests that ECMO permits large reductions in lung inflation and ventilation to rest the lungs, while maintaining acceptable oxygenation. The combination of ECMO and markedly attenuated ventilation strategy may be effective in cases of severe ARDS.

Management of acute respiratory complications from influenza A (H1N1) infection: experience of a tertiary-level Intensive Care Unit

BACKGROUND

The novel influenza A (H1N1) pandemic was associated with an epidemic of critical illness.

METHODS

We describe the clinical profiles of critically ill patients with severe complications due to microbiologically confirmed pandemic influenza A (H1N1) infection admitted to a medical ICU in Monza, Italy, over a 6-month period.

RESULTS

From August 2009 to January 2010, 19 patients (13 adults and 6 children) required ICU admission. Nine subjects were referred to our hospital from other ICUs. In all patients, with the exception of a case of severe septic shock, the cause of ICU admission was acute respiratory failure. Other nonpulmonary organ failures were common. A trial of non-invasive ventilation was attempted in 13 cases and was successful in four of them. The majority of the patients required invasive mechanical ventilation. In the 7 most severely hypoxemic patients, we applied veno-venous ECLS, with a very high rate of success. The median ICU stay was 9 days (range 1-78 days). Sixteen out of 19 (84%) patients survived.

CONCLUSION

In the majority of our patients, critical illness caused by pandemic influenza A (H1N1) was associated with severe hypoxemia, multiple organ failure, requirement for mechanical ventilation and frequent use of rescue therapies and ECLS support.

Implications of ICU triage decisions on patient mortality: a cost-effectiveness analysis

Introduction

Intensive care is generally regarded as expensive, and as a result beds are limited. This has raised serious questions about rationing when there are insufficient beds for all those referred. However, the evidence for the cost effectiveness of intensive care is weak and the work that does exist usually assumes that those who are not admitted do not survive, which is not always the case. Randomised studies of the effectiveness of intensive care are difficult to justify on ethical grounds; therefore, this observational study examined the cost effectiveness of ICU admission by comparing patients who were accepted into ICU after ICU triage to those who were not accepted, while attempting to adjust such comparison for confounding factors.

Methods

This multi-centre observational cohort study involved 11 hospitals in 7 EU countries and was designed to assess the cost effectiveness of admission to intensive care after ICU triage. A total of 7,659 consecutive patients referred to the intensive care unit (ICU) were divided into those accepted for admission and those not accepted. The two groups were compared in terms of cost and mortality using multilevel regression models to account for differences across centres, and after adjusting for age, Karnofsky score and indication for ICU admission. The analyses were also stratified by categories of Simplified Acute Physiology Score (SAPS) II predicted mortality (< 5%, 5% to 40% and >40%). Cost effectiveness was evaluated as cost per life saved and cost per life-year saved.

Results

Admission to ICU produced a relative reduction in mortality risk, expressed as odds ratio, of 0.70 (0.52 to 0.94) at 28 days. When stratified by predicted mortality, the odds ratio was 1.49 (0.79 to 2.81), 0.7 (0.51 to 0.97) and 0.55 (0.37 to 0.83) for <5%, 5% to 40% and >40% predicted mortality, respectively. Average cost per life saved for all patients was $103,771 (€82,358) and cost per life-year saved was $7,065 (€5,607). These figures decreased substantially for patients with predicted mortality higher than 40%, $60,046 (€47,656) and $4,088 (€3,244), respectively. Results were very similar when considering three-month mortality. Sensitivity analyses performed to assess the robustness of the results provided findings similar to the main analyses.

Conclusions

Not only does ICU appear to produce an improvement in survival, but the cost per life saved falls for patients with greater severity of illness. This suggests that intensive care is similarly cost effective to other therapies that are generally regarded as essential.

A case of ARDS associated with influenza A - H1N1 infection treated with extracorporeal respiratory support

After the first outbreak identified in Mexico in late March 2009, influenza A sustained by a modified H1N1 virus ("swine flu") rapidly spread to all continents. This article describes the first Italian case of life-threatening ARDS associated with H1N1 infection, treated with extracorporeal respiratory assistance (venovenous extracorporeal membrane oxygenation [ECMO]). A 24-year-old, previously healthy man was admitted to the Intensive Care Unit (ICU) of the local hospital for rapidly progressive respiratory failure with refractory impairment of gas exchange unresponsive to rescue therapies (recruitment manoeuvres, pronation and nitric oxide inhalation). An extracorporeal respiratory assistance (venovenous ECMO) was performed. It allowed a correction of the respiratory acidosis and made possible the transportation of the patient to the ICU (approximately 150 km from the first hospital). A nasal swab tested positive for H1N1 infection and treatment with oseltamivir was started. The chest computed tomography scan showed bilateral massive, patchy consolidation of lung parenchyma; lab tests showed leukopenia, elevated CPK levels and renal failure. The patient required high dosages of norepinephrine for septic shock and continuous renal replacement therapy. The clinical course was complicated by Pseudomonas aeruginosa superinfection, treated with intravenous and aerosolised colistin. ECMO was withheld after 15 days, while recovery of renal and respiratory function was slower. The patient was discharged from the ICU 34 days after admission. In this case, ECMO was life-saving and made the inter-hospital transfer of the patient possible.

Prolonged extracorporeal membrane oxygenation therapy for severe acute respiratory distress syndrome in a child affected by rituximab-resistant autoimmune hemolytic anemia: a case report

INTRODUCTION

Autoimmune hemolytic anemia in children younger than 2 years of age is usually characterized by a severe course, with a mortality rate of approximately 10%. The prolonged immunosuppression following specific treatment may be associated with a high risk of developing severe infections. Recently, the use of monoclonal antibodies (rituximab) has allowed sustained remissions to be obtained in the majority of pediatric patients with refractory autoimmune hemolytic anemia.

CASE PRESENTATION

We describe the case of an 8-month-old Caucasian girl affected by a severe form of autoimmune hemolytic anemia, which required continuous steroid treatment for 16 months. Thereafter, she received 4 weekly doses of rituximab (375 mg/m(2)/dose) associated with steroid therapy, which was then tapered over the subsequent 2 weeks. One month after the last dose of rrituximab, she presented with recurrence of severe hemolysis and received two more doses of rrituximab. The patient remained in clinical remission for 7 months, before presenting with a further relapse. An alternative heavy immunosuppressive therapy was administered combining cyclophosphamide 10 mg/kg/day for 10 days with methylprednisolone 40 mg/kg/day for 5 days, which was then tapered down over 3 weeks. While still on steroid therapy, the patient developed an interstitial pneumonia with Acute Respiratory Distress Syndrome, which required immediate admission to the intensive care unit where extracorporeal membrane oxygenation therapy was administered continuously for 37 days. At 16-month follow-up, the patient is alive and in good clinical condition, with no organ dysfunction, free from any immunosuppressive treatment and with a normal Hb level.

CONCLUSIONS

This case shows that aggressive combined immunosuppressive therapy may lead to a sustained complete remission in children with refractory autoimmune hemolytic anemia. However, the severe life-threatening complication presented by our patient indicates that strict clinical monitoring must be vigilantly performed, that antimicrobial prophylaxis should always be considered and that experienced medical and nursing staff must be available, to deliver highly specialized supportive salvage therapies, if necessary, during intensive care monitoring.

The use of helmets to deliver non-invasive continuous positive airway pressure in hypoxemic acute respiratory failure

Non-invasive continuous positive airway pressure (CPAP) is a useful tool for managing patients with acute respiratory failure. The head helmet is a relatively novel interface that is as effective as the traditionally employed face-mask in delivering CPAP and can possibly be characterized as better for the patient's tolerance and, consequently, a longer duration of treatment. This review focuses on the main properties of the helmet and the issues related to its use, as shown by the physiological and bench studies. Clinical experience, both personal and reported in the literature, for the treatment of both cardiogenic and non-cardiogenic pulmonary edema is reviewed as well.

Glottic-modulated lung ventilation during continuous transtracheal gas insufflation: an experimental study

We investigated a new method of pulmonary ventilation that included a minitracheostomy, a reverse thrust catheter to deliver continuous flow of gas to the carina, and a threshold valve to avoid lung overinflation. In six lightly sedated healthy sheep, at a continuous flow of 5, 10, or 15 L/min and a threshold valve of 5, 10, 15, or 20 cm H(2)O, we observed a novel respiratory pattern that was characterized either by active lung inflation followed by passive and prolonged inspiratory hold (mixed pattern) or by an absence of all active inspiratory effort and only passive inflation of the lungs (passive pattern). We correlated airway pressure changes with direct visualization of the glottic opening through a fiberoptic bronchoscope. We measured airway pressures at the level of the carina, the subglottic level, and in the pleural space, and respiratory events were monitored through inductive plethysmography. An increase in continuous flow, threshold valve, or both resulted in 1) an increase in glottic breathing; 2) a decrease in respiratory rate, with a decrease in inspiratory pleural pressure excursion; or 3) an increased inspiratory/expiratory ratio and mean airway pressure. During transtracheal gas insufflation, as in this study, a novel respiratory pattern evolved that was modulated by the glottis, accompanied by a decreased effort of breathing; coughing and swallowing remained, and vocalization remained unimpaired.

Intratracheal pulmonary ventilation keeps tracheal tubes clean without impairing mucociliary transport

BACKGROUND

Intratracheal pulmonary ventilation (ITPV) is a form of tracheal gas insufflation through a reverse thrust catheter that facilitates expiration and enhances CO2 removal. Tracheas of sheep mechanically ventilated for 3 days with gas delivered through the reverse-thrust catheter remained free of secretions, without suctioning. It was hypothesized that: 1) The expiratory flow from the lungs, combined with continuous cephalad flow from the reverse-thrust catheter keeps endotracheal tubes clean; and 2) tracheal mucus velocity is not impaired by ITPV.

METHODS

A model trachea connected to a test lung and to a ventilator, via an 8-mm endotracheal tube, was used. Inspiratory and expiratory peak flow velocities and the movement of mucus in the model trachea and in the endotracheal tube were measured during conventional mechanical ventilation and ITPV. Tracheal mucus velocity was measured radiographically, using tantalum discs as markers, in seven intubated sheep ventilated for one hour with volume-controlled ventilation, and with ITPV. One millilitre Evans Blue dye was introduced into the trachea, to visualize mucus transport into the endotracheal tube.

RESULTS

Peak expiratory flow velocity exceeded peak inspiratory flow velocity by 100% during ITPV. During volume-controlled ventilation, flow velocities were equal. During ITPV, there was slow, then rapid cephalad movement of mucus in the model trachea, 0.5 cm distal to the tip of the endotracheal tube, the velocity increasing once mucus entered the endotracheal tube. During volume-controlled ventilation, no movement of mucus was found. Baseline tracheal mucus velocity was equal during volume-controlled ventilation and ITPV. Secretions stained with Evans Blue dye entered the endotracheal tube and were rapidly expelled from within the endotracheal tubes during ITPV; only traces of mucus were found in two sheep during volume-controlled ventilation.

CONCLUSION

The enhanced expiratory flow during ITPV expels secretions from the endotracheal tube through entraining of mucus at the tip of the endotracheal tube. Tracheal mucus velocity is not influenced by ITPV.

Computerised tomography scan imaging in acute respiratory distress syndrome

Computerised tomography (CT) is being used with increasing frequency in acute respiratory distress syndrome (ARDS) patients. This brief review will discuss some of the clinical insights that a CT scan can offer. A large number of CT scan studies have provided new insights into the pathophysiology of ARDS and of mechanical ventilation, and are particularly focused on the recruitment-derecruitment phenomenon. To this end, newer fast CT scan technology promises a dynamic, rather than a static view of lung ventilation.

Permissive hypercapnia

The term permissive hypercapnia defines a ventilatory strategy for acute respiratory failure in which the lungs are ventilated with a low inspiratory volume and pressure. The aim of permissive hypercapnia is to minimize lung damage during mechanical ventilation; its limitation is the resulting hypoventilation and carbon dioxide (CO2) retention. In this article we discuss the rationale, physiologic implications, and implementation of permissive hypercapnia. We then review recent clinical studies that tested the effect of various approaches to permissive hypercapnia on the outcome of patients with acute respiratory failure.

Reverse-thrust ventilation in hypercapnic patients with acute respiratory distress syndrome. Acute physiological effects

Techniques of tracheal gas insufflation (TGI) have been shown to enhance CO(2) clearance efficiency in mechanically ventilated patients with acute respiratory distress syndrome (ARDS). Clinical studies have explored the effects of such techniques only at moderate intratracheal gas flow rates, with TGI superimposed to mechanical ventilation in a continuous fashion, or synchronized to the expiratory phase of the duty cycle. We examined the effects of intratracheal pulmonary ventilation (ITPV), delivering the entire tidal volume (VT) in the proximity of the tracheal carina, with all the gas flow supplied continuously through a reverse-thrust catheter (RTC). A potential limitation in the application of TGI is dynamic hyperinflation. Therefore, in a subgroup of patients, we also evaluated the effects of ITPV on end-expiratory lung volume (EELV) by respiratory inductive plethysmography (RIP). Eleven patients with ARDS under volume-cycled mechanical ventilation were subsequently switched to ITPV at the same baseline respiratory rate, I:E ratio, and VT. At the same minute volume, Pa(CO(2)) decreased from 70 +/- 12.3 to 59 +/- 9.5 mm Hg, with a percent reduction of 15 +/- 4% (range from 10 to 20%). The CO(2) decrease was greater in patients with higher baseline Pa(CO(2)) levels (DeltaPa(CO(2)) = 0.29 x Pa(CO(2)) - 9.48, r = 0.95). During transition from mechanical ventilation to ITPV, tracheal positive end-expiratory pressure (PEEP(tr)) decreased with a correspondent decrease in EELV. Both were restored by increasing the PEEP at the ventilator by 3.6 +/- 2.0 cm H(2)O. These data suggest that in patients with ARDS ITPV effectively reduces dead space ventilation and the employment of the RTC may limit or avoid dynamic hyperinflation.