Red blood cell transfusion results in adhesion of neutrophils in human endotoxemia and in critically ill patients with sepsis.

BACKGROUND: Red blood cell (RBC) transfusion is associated with adverse effects, which may involve activation of the host immune response. The effect of RBC transfusion on neutrophil Reactive Oxygen Species (ROS) production and adhesion ex vivo was investigated in endotoxemic volunteers and in critically ill patients that received a RBC transfusion. We hypothesized that RBC transfusion would cause neutrophil activation, the extent of which depends on the storage time and the inflammatory status of the recipient. STUDY DESIGN AND METHODS: Volunteers were injected with lipopolysaccharide (LPS) and transfused with either saline, fresh, or stored autologous RBCs. In addition, 47 critically ill patients with and without sepsis receiving either fresh (<8 days) or standard stored RBC (2-35 days) were included. Neutrophils from healthy volunteers were incubated with the plasma samples from the endotoxemic volunteers and from the critically ill patients, after which priming of neutrophil ROS production and adhesion were assessed. RESULTS: In the endotoxemia model, ex vivo neutrophil adhesion, but not ROS production, was increased after transfusion, which was not affected by RBC storage duration. In the critically ill, ex vivo neutrophil ROS production was already increased prior to transfusion and was not increased following transfusion. Neutrophil adhesion was increased following transfusion, which was more notable in the septic patients than in non-septic patients. Transfusion of fresh RBCs, but not standard issued RBCs, resulted in enhanced ROS production in neutrophils. CONCLUSION: RBC transfusion was associated with increased neutrophil adhesion in a model of human endotoxemia as well as in critically ill patients with sepsis.

Diagnosis and outcome of acute respiratory failure in immunocompromised patients after bronchoscopy.

OBJECTIVE: We wished to explore the use, diagnostic capability and outcomes of bronchoscopy added to noninvasive testing in immunocompromised patients. In this setting, an inability to identify the cause of acute hypoxaemic respiratory failure is associated with worse outcome. Every effort should be made to obtain a diagnosis, either with noninvasive testing alone or combined with bronchoscopy. However, our understanding of the risks and benefits of bronchoscopy remains uncertain. PATIENTS AND METHODS: This was a pre-planned secondary analysis of Efraim, a prospective, multinational, observational study of 1611 immunocompromised patients with acute respiratory failure admitted to the intensive care unit (ICU). We compared patients with noninvasive testing only to those who had also received bronchoscopy by bivariate analysis and after propensity score matching. RESULTS: Bronchoscopy was performed in 618 (39%) patients who were more likely to have haematological malignancy and a higher severity of illness score. Bronchoscopy alone achieved a diagnosis in 165 patients (27% adjusted diagnostic yield). Bronchoscopy resulted in a management change in 236 patients (38% therapeutic yield). Bronchoscopy was associated with worsening of respiratory status in 69 (11%) patients. Bronchoscopy was associated with higher ICU (40% versus 28%; p<0.0001) and hospital mortality (49% versus 41%; p=0.003). The overall rate of undiagnosed causes was 13%. After propensity score matching, bronchoscopy remained associated with increased risk of hospital mortality (OR 1.41, 95% CI 1.08-1.81). CONCLUSIONS: Bronchoscopy was associated with improved diagnosis and changes in management, but also increased hospital mortality. Balancing risk and benefit in individualised cases should be investigated further.

The effect of red blood cell transfusion on iron metabolism in critically ill patients.

BACKGROUND: Anemia of inflammation (AI) has a high prevalence in critically ill patients. In AI, iron metabolism is altered, as high levels of inflammation-induced hepcidin reduce the amount of iron available for erythropoiesis. AI is treated with red blood cell (RBC) transfusions. The effect of RBC transfusion on iron metabolism during inflammatory processes in adults is unknown. We investigated the effect of RBC transfusion on iron metabolism in critically ill patients. METHODS: In a prospective cohort study in 61 critically ill patients who received 1 RBC unit, levels of iron variables were determined before, directly after, and 24 hours after transfusion in septic and nonseptic patients. RESULTS: Serum iron levels were low and increased after transfusion (p = 0.02). However, RBC transfusion had no effect on transferrin saturation (p = 0.14) and ferritin levels (p = 0.74). Hepcidin levels increased after RBC transfusion (p = 0.01), while interleukin-6 levels decreased (p = 0.03). In septic patients, RBC transfusion induced a decrease in haptoglobin levels compared to baseline, which did not occur in nonseptic patients (p = 0.01). The effect of RBC transfusion on other iron variables did not differ between septic and nonseptic patients. CONCLUSION: Transfusion of a RBC unit transiently increases serum iron levels in intensive care unit patients. The increase in hepcidin levels after transfusion can further decrease iron release from intracellular storage making it available for erythropoiesis. RBC transfusion is associated with a decrease in haptoglobin levels in septic compared to nonseptic patients, but did not affect other markers of hemolysis.

Hyperoxia does not affect oxygen delivery in healthy volunteers while causing a decrease in sublingual perfusion.

OBJECTIVE: To determine the human dose-response relationship between a stepwise increase in arterial oxygen tension and its associated changes in DO2 and sublingual microcirculatory perfusion. METHODS: Fifteen healthy volunteers breathed increasing oxygen fractions for 10 minutes to reach arterial oxygen tensions of baseline (breathing air), 20, 40, 60 kPa, and max kPa (breathing oxygen). Systemic hemodynamics were measured continuously by the volume-clamp method. At the end of each period, the sublingual microcirculation was assessed by SDF. RESULTS: Systemic DO2 was unchanged throughout the study (Pslope  = .8). PVD decreased in a sigmoidal fashion (max -15% while breathing oxygen, SD18, Pslope  = .001). CI decreased linearly (max -10%, SD10, Pslope  < .001) due to a reduction in HR (max -10%, SD7, Pslope  = .009). There were no changes in stroke volume or MAP. Most changes became apparent above an arterial oxygen tension of 20 kPa. CONCLUSIONS: In healthy volunteers, supraphysiological arterial oxygen tensions have no effect on systemic DO2 . Sublingual microcirculatory PVD decreased in a dose-dependent fashion. All hemodynamic changes appear negligible up to an arterial oxygen tension of 20 kPa.

Respiratory Viruses in Invasively Ventilated Critically Ill Patients-A Prospective Multicenter Observational Study.

OBJECTIVES: The presence of respiratory viruses and the association with outcomes were assessed in invasively ventilated ICU patients, stratified by admission diagnosis. DESIGN: Prospective observational study. SETTING: Five ICUs in the Netherlands. PATIENTS: Between September 1, 2013, and April 30, 2014, 1,407 acutely admitted and invasively ventilated patients were included. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Nasopharyngeal swabs and tracheobronchial aspirates were collected upon intubation and tested for 14 respiratory viruses. Out of 1,407 patients, 156 were admitted because of a severe acute respiratory infection and 1,251 for other reasons (non-severe acute respiratory infection). Respiratory viruses were detected in 28.8% of severe acute respiratory infection patients and 17.0% in non-severe acute respiratory infection (p < 0.001). In one third, viruses were exclusively detected in tracheobronchial aspirates. Rhinovirus and human metapneumovirus were more prevalent in severe acute respiratory infection patients (9.6% and 2.6% vs 4.5 and 0.2%; p = 0.006 and p < 0.001). In both groups, there were no associations between the presence of viruses and the number of ICU-free days at day 28, crude mortality, and mortality in multivariate regression analyses. CONCLUSIONS: Respiratory viruses are frequently detected in acutely admitted and invasively ventilated patients. Rhinovirus and human metapneumovirus are more frequently found in severe acute respiratory infection patients. Detection of respiratory viruses is not associated with worse clinically relevant outcomes in the studied cohort of patients.

Vitamin C: should we supplement?

PURPOSE OF REVIEW: Hypovitaminosis C and vitamin C deficiency are very common in critically ill patients due to increased needs and decreased intake. Because vitamin C has pleiotropic functions, deficiency can aggravate the severity of illness and hamper recovery. RECENT FINDINGS: Vitamin C is a key circulating antioxidant with anti-inflammatory and immune-supporting effects, and a cofactor for important mono and dioxygenase enzymes. An increasing number of preclinical studies in trauma, ischemia/reperfusion, and sepsis models show that vitamin C administered at pharmacological doses attenuates oxidative stress and inflammation, and restores endothelial and organ function. Older studies showed less organ dysfunction when vitamin C was administered in repletion dose (2-3 g intravenous vitamin C/day). Recent small controlled studies using pharmacological doses (6-16 g/day) suggest that vitamin C reduces vasopressor support and organ dysfunction, and may even decrease mortality. SUMMARY: A short course of intravenous vitamin C in pharmacological dose seems a promising, well tolerated, and cheap adjuvant therapy to modulate the overwhelming oxidative stress in severe sepsis, trauma, and reperfusion after ischemia. Large randomized controlled trials are necessary to provide more evidence before wide-scale implementation can be recommended.

Making sense of early high-dose intravenous vitamin C in ischemia/reperfusion injury.

This article is one of ten reviews selected from the Annual Update in Intensive Care and Emergency Medicine 2018. Other selected articles can be found online at https://www.biomedcentral.com/collections/annualupdate2018 . Further information about the Annual Update in Intensive Care and Emergency Medicine is available from http://www.springer.com/series/8901 .

Effects of hyperoxia on vascular tone in animal models: systematic review and meta-analysis.

BACKGROUND: Arterial hyperoxia may induce vasoconstriction and reduce cardiac output, which is particularly undesirable in patients who already have compromised perfusion of vital organs. Due to the inaccessibility of vital organs in humans, vasoconstrictive effects of hyperoxia have primarily been studied in animal models. However, the results of these studies vary substantially. Here, we investigate the variation in magnitude of the hyperoxia effect among studies and explore possible sources of heterogeneity, such as vascular region and animal species. METHOD: Pubmed and Embase were searched for eligible studies up to November 2017. In vivo and ex vivo animal studies reporting on vascular tone changes induced by local or systemic normobaric hyperoxia were included. Experiments with co-interventions (e.g. disease or endothelium removal) or studies focusing on lung, brain or fetal vasculature or the ductus arteriosus were not included. We extracted data pertaining to species, vascular region, blood vessel characteristics and method of hyperoxia induction. Overall effect sizes were estimated with a standardized mean difference (SMD) random effects model. RESULTS: We identified a total of 60 studies, which reported data on 67 in vivo and 18 ex vivo experiments. In the in vivo studies, hyperoxia caused vasoconstriction with an SMD of - 1.42 (95% CI - 1.65 to - 1.19). Ex vivo, the overall effect size was SMD - 0.56 (95% CI - 1.09 to - 0.03). Between-study heterogeneity (I2) was high for in vivo (72%, 95% CI 62 to 85%) and ex vivo studies (86%, 95% CI 78 to 98%). In vivo, in comparison to the overall effect size, hyperoxic vasoconstriction was less pronounced in the intestines and skin (P = 0.03) but enhanced in the cremaster muscle region (P < 0.001). Increased constriction was seen in vessels 15-25 µm in diameter. Hyperoxic constriction appeared to be directly proportional to oxygen concentration. For ex vivo studies, heterogeneity could not be explained with subgroup analysis. CONCLUSION: The effect of hyperoxia on vascular tone is substantially higher in vivo than ex vivo. The magnitude of the constriction is most pronounced in vessels ~ 15-25 µm in diameter and is proportional to the level of hyperoxia. Relatively increased constriction was seen in muscle vasculature, while reduced constriction was seen in the skin and intestines.

Hemodynamic effects of acute hyperoxia: systematic review and meta-analysis.

BACKGROUND: In clinical practice, oxygen is generally administered to patients with the intention of increasing oxygen delivery. Supplemental oxygen may, however, cause arterial hyperoxia, which is associated with hemodynamic alterations. We performed a systematic review and meta-analysis of the literature to determine the effect of hyperoxia on central hemodynamics and oxygen delivery in healthy volunteers and cardiovascular-compromised patients. METHODS: PubMed and EMBASE were searched up to March 2017. Studies with adult humans investigating changes in central hemodynamics or oxygen delivery induced by acute normobaric hyperoxia were included. Studies focusing on lung, retinal, or brain parameters were not included. We extracted subject and oxygen exposure characteristics, indexed and unindexed values for heart rate, stroke volume, cardiac output, mean arterial pressure (MAP), systemic vascular resistance, and oxygen delivery during normoxia and hyperoxia. For quantitative synthesis of the data, a random-effects ratio of means (RoM) model was used. RESULTS: We identified 33 studies with 42 datasets. Study categories included healthy volunteers (n = 22 datasets), patients with coronary artery disease (CAD; n = 6), heart failure (HF; n = 6), coronary artery bypass graft (CABG; n = 3) and sepsis (n = 5). Hyperoxia (arterial oxygen tension of 234-617 mmHg) reduced cardiac output (CO) by 10-15% in both healthy volunteers (-10.2%, 95% confidence interval (CI) -12.9% to -7.3%) and CAD (-9.6%, 95% CI -12.3% to -6.9%) or HF patients (-15.2%, 95% CI -21.7% to -8.2%). No significant changes in cardiac output were seen in CABG or septic patients (-3%). Systemic vascular resistance increased remarkably in patients with heart failure (24.6%, 95% CI 19.3% to 30.1%). In healthy volunteers, and those with CAD and CABG, the effect was smaller (11-16%) and was virtually absent in patients with sepsis (4.3%, 95% CI -3.2% to 12.3%). No notable effect on MAP was found in any group (2-3%). Oxygen delivery was not altered by hyperoxia. Considerable heterogeneity existed between study results, likely due to methodological differences. CONCLUSIONS: Hyperoxia may considerably decrease cardiac output and increase systemic vascular resistance, but effects differ between patient categories. Heart failure patients were the most sensitive while no hemodynamic effects were seen in septic patients. There is currently no evidence supporting the notion that oxygen supplementation increases oxygen delivery.

Low Transmission of Airway Pressures to the Abdomen in Mechanically Ventilated Patients With or Without Acute Respiratory Failure and Intra-Abdominal Hypertension.

PURPOSE: Intra-abdominal pressure, measured at end expiration, may depend on ventilator settings and transmission of intrathoracic pressure. We determined the transmission of positive intrathoracic pressure during mechanical ventilation at inspiration and expiration into the abdominal compartment. METHODS AND RESULTS: We included 9 patients after uncomplicated cardiac surgery and 9 with acute respiratory failure. Intravesical pressures were measured thrice (reproducibility of 1.8%) and averaged, at the end of each inspiratory and expiratory hold maneuvers of 5 seconds. Transmission, the change in intra-abdominal over intrathoracic pressures from end inspiration to end expiration, was about 8%. End-expiratory intra-abdominal pressure was lower than "total" intra-abdominal pressure over the entire respiratory cycle by 0.34 cm H2O. It was 0.73 cm H2O higher than "true" intra-abdominal pressure over the entire respiratory cycle, taking transmission into account. The percentage error was 3% for total and 10% for true pressure. Results did not differ among patients with or without acute respiratory failure and decreased respiratory compliance or between those with (≥12 mm Hg, n = 5) or without intra-abdominal hypertension. CONCLUSIONS: Transmitted airway pressure only slightly affects intra-abdominal pressure in mechanically ventilated patients, irrespective of respiratory compliance and baseline intra-abdominal pressure values. End-expiratory measurements referenced against atmospheric pressure may suffice for clinical practice.