Transfusion of standard-issue packed red blood cells induces pulmonary vasoconstriction in critically ill patients after cardiac surgery-A randomized, double-blinded, clinical trial

Monitoring of Levosimendan Administration in Patients with Pulmonary Hypertension Undergoing Cardiac Surgery and Effect of Two Different Dosing Schemes on Hemodynamic and Echocardiographic Parameters

INTRODUCTION

The perioperative management of patients with pulmonary hypertension (PH) undergoing cardiac surgery represents one of the most challenging clinical scenarios. This fact mainly depends on the relationship existing between PH and right ventricular failure (RVF). Levosimendan (LS) is an inodilator that might be an effective agent in the treatment of PH and RVF. The aim of this study was to examine the impact of the duration of cardiopulmonary bypass (CPB) on the therapeutic drug monitoring of LS and to evaluate the effect of preemptive administration of LS on perioperative hemodynamic and echocardiographic parameters in cardiac surgical patients with preexisting PH.

MATERIALS AND METHODS

In this study, LS was administered in adult patients undergoing cardiac surgery before CPB in order to prevent exacerbation of preexisting PH and subsequent right ventricular dysfunction. Thirty cardiac surgical patients with preoperatively confirmed PH were randomized to receive either 6 μg/kg or 12 μg/kg of LS after the induction of anesthesia. The plasma concentration of LS was measured after CPB. In this study, a low sample volume was used combined with a simple sample preparation protocol. The plasma sample was extracted by protein precipitation and evaporated; then, the analyte was reconstituted and detected using specific and sensitive bioanalytical liquid chromatography with mass spectrometry (LC-MS/MS) methodology. The clinical, hemodynamic, and echocardiographic parameters were registered and evaluated before and after the administration of the drug.

RESULTS

A fast bioanalytical LC-MS/MS methodology (a run time of 5.5 min) was developed for the simultaneous determination of LS and OR-1896, its main metabolite in human plasma. The LC-MS/MS method was linear over a range of 0.1-50 ng/mL for LS and 1-50 ng/mL for its metabolite OR-1896. Measured plasma concentrations of LS were inversely related to the duration of CPB. LS administration before CPB during cardiac surgery was effective in reducing pulmonary artery pressure and improving hemodynamic parameters after CPB, with a more pronounced and durable effect of the drug at the dose of 12 μg/kg. Additionally, administration of LS at a dose of 12 μg/kg in cardiac surgical patients with PH before CPB improved right ventricular function.

CONCLUSION

LS administration decreases pulmonary artery pressure and may improve right ventricular function in patients with PH undergoing cardiac surgery.

Autologous red blood cell transfusion does not result in a more profound increase in pulmonary capillary wedge pressure compared to saline in critically ill patients: A randomized crossover trial

Background and Objectives

Transfusion‐associated circulatory overload (TACO) is a major cause of severe transfusion‐related morbidity. Transfusion of red blood cells (RBCs) has been shown to induce hydrostatic pressure overload. It is unclear which product‐specific factors contribute. We set out to determine the effect of autologous RBC transfusion versus saline on pulmonary capillary wedge pressure (PCWP) change.

Materials and Methods

In a randomized crossover trial, patients who had undergone coronary bypass surgery were allocated to treatment post‐operatively in the intensive care unit with either an initial 300 ml autologous RBC transfusion (salvaged during surgery) or 300 ml saline infusion first, followed by the other. Primary outcome was the difference in PCWP change. Secondary outcome measures were the difference in extra‐vascular lung water index (EVLWI) and pulmonary vascular permeability index (PVPI).

Results

Change in PCWP was not higher after autologous RBC transfusion compared to saline (ΔPCWP 0.3 ± 0.4 vs. 0.1 ± 0.4 mmHg). ΔEVLWI and ΔPVPI were significantly decreased after autologous RBC transfusion compared to saline (ΔEVLWI −1.6 ± 0.6 vs. 0.2 ± 0.4, p = 0.02; ΔPVPI −0.3 ± 0.1 vs. 0.0 ± 0.1, p = 0.01). Haemodynamic variables and colloid osmotic pressure were not different for autologous RBC transfusion versus saline.

Conclusion

Transfusion of autologous RBCs did not result in a more profound increase in PCWP compared to saline. RBC transfusion resulted in a decrease of EVLWI and PVPI compared to saline. Our data suggest that transfusing autologous RBCs may lead to less pulmonary oedema compared to saline. Future studies with allogeneic RBCs are needed to investigate other factors that may mediate the increase of PCWP, resulting in TACO.

The impact of a PDA on tissue oxygenation and haemodynamics following a blood transfusion in preterm infants

BACKGROUND

To examine the impact of PRBC transfusion on pulmonary vascular resistance (PVR), systemic vascular resistance and myocardial function using echocardiography and cerebral and splanchnic tissue oxygenation using near-infrared spectroscopy (NIRS) in premature babies with and without a PDA.

METHODS

A prospective observational study of premature infants born <1500 g in receipt of PRBC transfusions beyond 10 days of age. Echocardiography and NIRS monitoring were performed at baseline, during the transfusion and 24 h after transfusion.

RESULTS

Thirty infants with a median gestation of 26.4 [24.8-28.0] weeks were enrolled. Ten infants had a PDA. Following transfusion, a significant decrease in PVR markers occurred in all infants. Right ventricular (RV) function increased following transfusion in the PDA closed group only. Cerebral oxygen saturation increased following transfusion in all infants. Babies in the PDA open group had significantly lower splanchnic oxygen saturations at baseline compared to the PDA closed group which persisted over the study period and were unaltered by transfusion.

CONCLUSIONS

PRBC transfusion lowers PVR irrespective of PDA status. Those with a PDA demonstrated a lack of improvement in RV function and splanchnic oxygenation highlighting the impact a PDA has on the neonatal circulation.

IMPACT

The presence or absence of the PDA imposes differential effects on splanchnic oxygenation during red blood cell (PRBC) transfusion in the premature population. This is the first study to assess the impact of the PDA on splanchnic oxygenation via near-infrared spectroscopy (NIRS) during red blood cell transfusion in premature neonates. New insights have been found into the impact of PRBC transfusion on pulmonary vascular resistance, right ventricular function, cerebral and splanchnic oxygenation in the presence and absence of a PDA and emphasises the ongoing impact of ductal patency on gut oxygenation.

Transfusion thresholds for guiding red blood cell transfusion

BACKGROUND

The optimal haemoglobin threshold for use of red blood cell (RBC) transfusions in anaemic patients remains an active field of research. Blood is a scarce resource, and in some countries, transfusions are less safe than in others because of inadequate testing for viral pathogens. If a liberal transfusion policy does not improve clinical outcomes, or if it is equivalent, then adopting a more restrictive approach could be recognised as the standard of care.  OBJECTIVES: The aim of this review update was to compare 30-day mortality and other clinical outcomes for participants randomised to restrictive versus liberal red blood cell (RBC) transfusion thresholds (triggers) for all clinical conditions. The restrictive transfusion threshold uses a lower haemoglobin concentration as a threshold for transfusion (most commonly, 7.0 g/dL to 8.0 g/dL), and the liberal transfusion threshold uses a higher haemoglobin concentration as a threshold for transfusion (most commonly, 9.0 g/dL to 10.0 g/dL).

SEARCH METHODS

We identified trials through updated searches: CENTRAL (2020, Issue 11), MEDLINE (1946 to November 2020), Embase (1974 to November 2020), Transfusion Evidence Library (1950 to November 2020), Web of Science Conference Proceedings Citation Index (1990 to November 2020), and trial registries (November 2020). We  checked the reference lists of other published reviews and relevant papers to identify additional trials. We were aware of one trial identified in earlier searching that was in the process of being published (in February 2021), and we were able to include it before this review was finalised.

SELECTION CRITERIA

We included randomised trials of surgical or medical participants that recruited adults or children, or both. We excluded studies that focused on neonates. Eligible trials assigned intervention groups on the basis of different transfusion schedules or thresholds or 'triggers'. These thresholds would be defined by a haemoglobin (Hb) or haematocrit (Hct) concentration below which an RBC transfusion would be administered; the haemoglobin concentration remains the most commonly applied marker of the need for RBC transfusion in clinical practice. We included trials in which investigators had allocated participants to higher thresholds or more liberal transfusion strategies compared to more restrictive ones, which might include no transfusion. As in previous versions of this review, we did not exclude unregistered trials published after 2010 (as per the policy of the Cochrane Injuries Group, 2015), however, we did conduct analyses to consider the differential impact of results of trials for which prospective registration could not be confirmed.   DATA COLLECTION AND ANALYSIS: We identified trials for inclusion and extracted data using Cochrane methods. We pooled risk ratios of clinical outcomes across trials using a random-effects model. Two review authors independently extracted data and assessed risk of bias. We conducted predefined analyses by clinical subgroups. We defined participants randomly allocated to the lower transfusion threshold as being in the 'restrictive transfusion' group and those randomly allocated to the higher transfusion threshold as being in the 'liberal transfusion' group.

MAIN RESULTS

A total of 48 trials, involving data from 21,433 participants (at baseline), across a range of clinical contexts (e.g. orthopaedic, cardiac, or vascular surgery; critical care; acute blood loss (including gastrointestinal bleeding); acute coronary syndrome; cancer; leukaemia; haematological malignancies), met the eligibility criteria. The haemoglobin concentration used to define the restrictive transfusion group in most trials (36) was between 7.0 g/dL and 8.0 g/dL.  Most trials included only adults; three trials focused on children. The included studies were generally at low risk of bias for key domains including allocation concealment and incomplete outcome data. Restrictive transfusion strategies reduced the risk of receiving at least one RBC transfusion by 41% across a broad range of clinical contexts (risk ratio (RR) 0.59, 95% confidence interval (CI) 0.53 to 0.66; 42 studies, 20,057 participants; high-quality evidence), with a large amount of heterogeneity between trials (I² = 96%). Overall, restrictive transfusion strategies did not increase or decrease the risk of 30-day mortality compared with liberal transfusion strategies (RR 0.99, 95% CI 0.86 to 1.15; 31 studies, 16,729 participants; I² = 30%; moderate-quality evidence) or any of the other outcomes assessed (i.e. cardiac events (low-quality evidence), myocardial infarction, stroke, thromboembolism (all high-quality evidence)). High-quality evidence shows that the liberal transfusion threshold did not affect the risk of infection (pneumonia, wound infection, or bacteraemia). Transfusion-specific reactions are uncommon and were inconsistently reported within trials. We noted less certainty in the strength of evidence to support the safety of restrictive transfusion thresholds for the following predefined clinical subgroups: myocardial infarction, vascular surgery, haematological malignancies, and chronic bone-marrow disorders.

AUTHORS' CONCLUSIONS

Transfusion at a restrictive haemoglobin concentration decreased the proportion of people exposed to RBC transfusion by 41% across a broad range of clinical contexts. Across all trials, no evidence suggests that a restrictive transfusion strategy impacted 30-day mortality, mortality at other time points, or morbidity (i.e. cardiac events, myocardial infarction, stroke, pneumonia, thromboembolism, infection) compared with a liberal transfusion strategy. Despite including 17 more randomised trials (and 8846 participants), data remain insufficient to inform the safety of transfusion policies in important and selected clinical contexts, such as myocardial infarction, chronic cardiovascular disease, neurological injury or traumatic brain injury, stroke, thrombocytopenia, and cancer or haematological malignancies, including chronic bone marrow failure.  Further work is needed to improve our understanding of outcomes other than mortality. Most trials compared only two separate thresholds for haemoglobin concentration, which may not identify the actual optimal threshold for transfusion in a particular patient. Haemoglobin concentration may not be the most informative marker of the need for transfusion in individual patients with different degrees of physiological adaptation to anaemia. Notwithstanding these issues, overall findings provide good evidence that transfusions with allogeneic RBCs can be avoided in most patients with haemoglobin thresholds between the range of 7.0 g/dL and 8.0 g/dL. Some patient subgroups might benefit from RBCs to maintain higher haemoglobin concentrations; research efforts should focus on these clinical contexts.

Impact of anemia on outcomes in on-pump coronary artery bypass surgery patients

Aim    To study the contribution of preoperative anemia to the prognosis of adverse clinical events (mortality, complications, transfusion) in patients with ischemic heart disease (IHD) after myocardial revascularization in the conditions of artificial circulation.Material and methods    This retrospective cohort study included 1 133 patients with IHD who had undergone isolated myocardial revascularization in the conditions of artificial circulation in 2019. The primary endpoints were mortality and a composite endpoint that included, in addition to mortality, cases of acute coronary syndrome, heart, respiratory and renal failure, neurological deficit, and infectious complications. The secondary endpoints were duration of artificial ventilation of more than 12 h, duration of stay in the resuscitation and intensive care unit (RICU) of more than one day, and duration of postoperative inpatient treatment of more than 7 days. Results    Preoperative anemia was found in 196 (17.3 %) patients. The anemia was not associated with mortality but increased the risk of the composite endpoint, prolonged artificial ventilation, stay in RICU for more than one day, and red blood cell transfusion. Despite the absence of a relationship between red blood cell transfusion and mortality, the use of transfusion was associated with increased risks of the composite endpoint and prolonged stay in the RICU and hospital.Conclusion    Preoperative anemia is a risk factor for adverse outcomes of myocardial revascularization in the conditions of artificial circulation. Timely treatment of preoperative anemia may improve outcomes of the treatment.

Human glycocalyx shedding: Systematic review and critical appraisal

BACKGROUND

The number of studies measuring breakdown products of the glycocalyx in plasma has increased rapidly during the past decade. The purpose of the present systematic review was to assess the current knowledge concerning the association between plasma concentrations of glycocalyx components and structural assessment of the endothelium.

METHODS

We performed a literature review of Pubmed to determine which glycocalyx components change in a wide variety of human diseases and conditions. We also searched for evidence of a relationship between plasma concentrations and the thickness of the endothelial glycocalyx layer as obtained by imaging methods.

RESULTS

Out of 3,454 publications, we identified 228 that met our inclusion criteria. The vast majority demonstrate an increase in plasma glycocalyx products. Sepsis and trauma are most frequently studied, and comprise approximately 40 publications. They usually report 3-4-foldt increased levels of glycocalyx degradation products, most commonly of syndecan-1. Surgery shows a variable picture. Cardiac surgery and transplantations are most likely to involve elevations of glycocalyx degradation products. Structural assessment using imaging methods show thinning of the endothelial glycocalyx layer in cardiovascular conditions and during major surgery, but thinning does not always correlate with the plasma concentrations of glycocalyx products. The few structural assessments performed do not currently support that capillary permeability is increased when the plasma levels of glycocalyx fragments in plasma are increased.

CONCLUSIONS

Shedding of glycocalyx components is a ubiquitous process that occurs during both acute and chronic inflammation with no sensitivity or specificity for a specific disease or condition.

Colloid osmotic pressure of contemporary and novel transfusion products

Background and Objectives

Colloid osmotic pressure (COP) is a principal determinant of intravascular fluid homeostasis and a pillar of fluid therapy and transfusion. Transfusion‐associated circulatory overload (TACO) is a leading complication of transfusion, and COP could be responsible for recruiting additional fluid. Study objective was to measure COP of blood products as well as investigate the effects of product concentration and storage lesion on COP.

Materials and Methods

Three units of each product were sampled longitudinally. COP was measured directly as well as the determinants thereof albumin and total protein. Conventional blood products, that is red blood cell (RBC), fresh‐frozen plasma (FFP) and platelet concentrates (PLTs), were compared with their concentrated counterparts: volume‐reduced RBCs, hyperconcentrated PLTs, and fully and partially reconstituted lyophilized plasma (prLP). Fresh and maximally stored products were measured to determine changes in protein and COP. We calculated potential volume load (PVL) to estimate volume recruited using albumin's water binding per product.

Results

Colloid osmotic pressure varies widely between conventional products (RBCs, 1·9; PLTs, 7·5; and FFP, 20·1 mmHg); however, all are hypooncotic compared with human plasma COP (25·4 mmHg). Storage lesion did not increase COP. Concentrating RBCs and PLTs did not increase COP; only prLP showed a supraphysiological COP of 47·3 mm Hg. The PVL of concentrated products was lower than conventional products.

Conclusion

Colloid osmotic pressure of conventional products was low. Therefore, third‐space fluid recruitment is an unlikely mechanism in TACO. Concentrated products had a lower calculated fluid load and may prevent TACO. Finally, storage did not significantly increase oncotic pressure of blood products.

Old, older, the oldest: red blood cell storage and the potential harm of using older red blood cell concentrates

PURPOSE OF REVIEW

Over the last decades, clinical studies have suggested that transfusion of red blood cells (RBCs) might negatively impact patient outcomes. Even though large randomized clinical trials did not show differences in mortality when transfusing fresh versus standard-issue RBC units, data imply that RBCs at the very end of storage could elicit negative effects.

RECENT FINDINGS

Certain alterations of RBCs during cold storage -- such as an increase of potassium and lactate in the storage solution -- have been discovered a century ago. In recent years, proteomic and metabolomic studies have shed more light into pathophysiological changes of RBCs during storage and have helped to specify the definition of old blood. These advancements are now utilized to increase the quality of stored RBCs and devise therapeutic strategies (e.g. nitric oxide, haptoglobin, or reduction of the iron load) when transfusing old blood.

SUMMARY

Further research to improve the quality of RBC units and to study populations potentially at risk is warranted. Until the question whether transfusion of old blood is detrimental for specific patient populations has been answered, a deliberate use of RBC transfusion should be implemented.

Volume incompliance and transfusion are essential for transfusion-associated circulatory overload: a novel animal model

BACKGROUND

Transfusion‐associated circulatory overload (TACO) is the predominant complication of transfusion resulting in death. The pathophysiology is poorly understood, but inability to manage volume is associated with TACO, and observational data suggest it is different from simple cardiac overload due to fluids. We developed a two‐hit TACO animal model to assess the role of volume incompliance (“first‐hit”) and studied whether volume overload (“second‐hit”) by red blood cell (RBC) transfusion is different compared to fluids (Ringer's lactate [RL]).

MATERIALS AND METHODS

Male adult Lewis rats were stratified into a control group (no intervention) or a first hit: either myocardial infarction (MI) or acute kidney injury (AKI). Animals were randomized to a second hit of either RBC transfusion or an equal volume of RL. A clinically relevant difference was defined as an increase in left ventricular end‐diastolic pressure (ΔLVEDP) of +4.0 mm Hg between the RBC and RL groups.

RESULTS

In control animals (without first hit) LVEDP was not different between infusion groups (Δ + 1.6 mm Hg). LVEDP increased significantly more after RBCs compared to RL in animals with MI (Δ7.4 mm Hg) and AKI (Δ + 5.4 mm Hg), respectively. Volume‐incompliant rats matched clinical TACO criteria in 92% of transfused versus 25% of RL‐infused animals, with a greater increase in heart rate and significantly higher blood pressure.

CONCLUSION

To our knowledge, this is the first animal model for TACO, showing that a combination of volume incompliance and transfusion is essential for development of circulatory overload. This model allows for further testing of mechanistic factors as well as therapeutic approaches.