Transfusion of standard-issue packed red blood cells induces pulmonary vasoconstriction in critically ill patients after cardiac surgery—A randomized, double-blinded, clinical trial
Transfusion of standard-issue packed red blood cells induces pulmonary vasoconstriction in critically ill patients after cardiac surgery-A randomized, double- blinded, clinical trial
Joanna Baron-StefaniakID 0 1
Gerda C. Leitner 1
Nina K. I. Ku? ntzel 0 1
Elias L. Meyer 1
Michael J. Hiesmayr 0 1
Roman Ullrich 0 1
David M. Baron 0 1
0 Department of Anaesthesia, Intensive Care Medicine and Pain Medicine, Medical University of Vienna , Vienna , Austria , 2 Department of Blood Group Serology and Transfusion Medicine, Medical University of Vienna , Vienna , Austria , 3 Section for Medical Statistics, Center for Medical Statistics , Informatics, and Intelligent Systems , Medical University of Vienna , Vienna , Austria
1 Editor: Iratxe Puebla, Public Library of Science , UNITED KINGDOM
Experimental and volunteer studies have reported pulmonary vasoconstriction during transfusion of packed red blood cells (PRBCs) stored for prolonged periods. The primary aim of this study was to evaluate whether transfusion of PRBCs stored over 21 days (standardissue, siPRBCs) increases pulmonary artery pressure (PAP) to a greater extent than transfusion of PRBCs stored for less then 14 days (fresh, fPRBCs) in critically ill patients following cardiac surgery. The key secondary aim was to assess whether the pulmonary vascular resistance index (PVRI) increases after transfusion of siPRBCs to a greater extent than after transfusion of fPRBCs.
Data Availability Statement: All relevant data are
within the paper and its Supporting Information
Funding: The authors received no specific funding
for this work.
Competing interests: The authors have declared
that no competing interests exist.
The study was performed as a single-center, double-blinded, parallel-group, randomized
clinical trial. Leukoreduced PRBCs were transfused while continuously measuring
hemodynamic parameters. Systemic concentrations of syndecan-1 were measured to assess
glycocalyx injury. After randomizing 19 patients between January 2014 and June 2016, the study
was stopped due to protracted patient recruitment.
Of 19 randomized patients, 11 patients were transfused and included in statistical analyses.
Eight patients were excluded prior to transfusion, 6 patients received fPRBCs (10?3 storage
days), whereas 5 patients received siPRBCs (33?4 storage days). The increase in PAP (7
?3 vs. 2?2 mmHg, P = 0.012) was greater during transfusion of siPRBCs than during
transfusion of fPRBCs. In addition, the change in PVRI (150?89 vs. -4?37 dyn s cm-5 m2, P =
0.018) was greater after transfusion of siPRBCs than after transfusion of fPRBCs. The
increase in PAP correlated with the change of systemic syndecan-1 concentrations at the
end of transfusion (R = 0.64,P = 0.034).
Although this study is underpowered and results require verification in larger clinical trials,
our findings suggest that transfusion of siPRBCs increases PAP and PVRI to a greater
extent than transfusion of fPRBCs in critically ill patients following cardiac surgery.
Glycocalyx injury might contribute to pulmonary vasoconstriction associated with transfusion of
Current transfusion practice allows for storage of packed red blood cells (PRBCs) up to 42
days, with the oldest compatible PRBC unit being assigned for transfusion (standard-issue
PRBCs, siPRBCs). Observational studies indicate that transfusion of PRBCs stored for
prolonged periods increases the risk of kidney injury and infection, and prolongs the length of
hospital stay and time to extubation in patients undergoing cardiac surgery [
Furthermore, a meta-analysis in this patient population revealed that transfusion of stored PRBCs
increases mortality risk [
]. In contrast, recent randomized controlled trials suggest that
transfusion of siPRBCs does not negatively affect survival in a general population of hospitalized
], in critically ill patients [
], or in patients following cardiac surgery [
Experimental and volunteer studies, however, reported a pulmonary vasoconstrictor effect
of PRBCs stored for prolonged periods [
]. Baron et al. demonstrated that transfusion of
PRBCs stored for 40 days transiently increases pulmonary artery pressure (PAP) and
pulmonary vascular resistance (PVR) in lambs [
]. This pulmonary vasoconstrictor effect of stored
PRBCs was potentiated by endothelial dysfunction induced by inhibition of nitric oxide (NO)
synthesis  or hemorrhagic shock [
]. Furthermore, Berra et al. showed that transfusion of
autologous PRBCs stored for 40 days increases PAP in obese adults with endothelial
]. We hypothesized that transfusion of stored PBRCs but not fresh PRBC would induce
pulmonary vasoconstriction in critically patients following cardiac surgery.
Reduced NO synthesis by endothelial cells is a key characteristic of endothelial dysfunction,
which is commonly diagnosed in patients undergoing cardiac surgery [
]. Several studies
have associated the reduction of NO bioavailability with scavenging of NO by free hemoglobin
]. This effect was suggested as a central mechanism for vasoconstriction after
transfusion of stored PRBCs [
]. However, additional factors might contribute to reduced
bioavailability of NO. Blood transfusion induces degradation of the endothelial glycocalyx
layer , which functions as a mechanical sensor and transducer used to regulate NO
production by endothelial cells [
]. An injury of the glycocalyx during transfusion might further
reduce NO bioavailability and potentiate the vasoconstrictor effects of PRBCs in patients with
endothelial dysfunction. Furthermore, macrophage migration inhibitory factor (MIF), a
mediator of the innate inflammatory response, has been associated with pulmonary
]. As transfusion of stored PRBCs induces innate inflammatory response,
transfusionrelated secretion of MIF might contribute to the pulmonary vasoconstrictor effects of stored
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In this study we evaluated whether transfusion of PRBCs stored for more than 21 days
(standard issue PRBCs, siPRBCs) would increase PAP and subsequently PVR to a greater
extent than transfusion of PRBCs stored for less then 14 days (fresh PRBCs; fPRBCs) in
critically ill patients following cardiac surgery. In addition, we assessed glycocalyx injury and
release of MIF into serum after transfusion of fPRBCs and siPRBCs.
This study was performed as a double-blinded, parallel-group, randomized clinical trial at the
General Hospital of Vienna in accordance with the ethical standards stated in the Declaration
of Helsinki. The CONSORT (Consolidated Standards of Reporting Trials) guidelines were
used to guide the preparation of this article. Ethical approval for this study (reference number
1239/2013) was provided by the Ethical Committee of the Medical University of Vienna,
Vienna, Austria. The study was registered at clinicaltrials.gov (NCT02050230) on January 17,
2014. Written informed consent was obtained from each patient before enrollment. Patients
were screened for enrollment from January 2014 until June 2016.
Patients ( 18 years) admitted to an intensive care unit (ICU) after cardiac surgery with a
pulmonary arterial catheter in place and requiring transfusion of one PRBC unit as standard care
were eligible for inclusion. Transfusion trigger was a Hb below 8 mg/dl. Exclusion criteria
were ongoing hemodynamic support with adrenaline or continuous infusion of more than
0.2 ?g kg-1 min-1 noradrenaline, immediate need of transfusing 2 or more PRBC units, and
administration of inhaled NO, prostacycline, or systemic phosphodiesterase inhibitors within
24 hours prior to inclusion.
According to the definition of a full analysis set defined by ICH E9 we excluded 8 patients,
who were randomized without receiving treatment, in our case transfusion. Since no data
were obtained and recorded for these patients, they were handled the same way as individuals
not enrolled in the study.
Study design, randomization and blinding
Patients were randomly assigned to receive transfusion of 1 unit of PRBCs stored <14 days
(fPRBCs) or 1 unit of PRBCs stored for 21?42 days (siPRBCs). Packed red blood cells were
leukoreduced and stored in saline-adenine-glucose-mannitol solution. Standard-issue PRBCs
were handled as ?first in, first out?, meaning that the oldest compatible unit from the blood
bank was assigned for transfusion.
Allocation of PRBCs was performed at the Department of Blood Group Serology and
Transfusion Medicine. The allocation list was generated using a computer-based random
number generator (Randomizer, Social Psychology Network, Middletown, CT). Sequentially
numbered envelopes with concealed allocation to respective study groups were prepared using
a randomization ratio of 1:1. After an order for a PRBC unit was made by a study investigator
at the ICU, a member of the Department of Blood Group Serology and Transfusion Medicine
opened the concealed enveloped and prepared an appropriate PRBC unit for the randomized
patient according to the assigned study group. The product number and expiration date were
concealed, and the PRBC unit was sent to the ICU via pneumatic tube transport. At the ICU, a
study investigator collected the PRBC unit, performed a bed-side test, and initiated and
supervised the transfusion. Duration of transfusion was standardized to 15 minutes in all patients.
The study investigators, study participants, the ICU team, and the statisticians performing the
analysis remained blinded to treatment allocation status until final statistical analysis.
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The PAP, mean arterial pressure (Infinity Delta, Draeger, Luebeck, Germany), and cardiac
output (Vigilance II monitor, Edwards Lifescience, Irvine, CA, USA) were monitored
continuously. Indices of pulmonary vascular resistance (PVRI) and systemic vascular resistance
(SVRI) and the cardiac index were calculated using standard formulas. Hemodynamic
parameters were recorded prior to transfusion at baseline (BL), immediately following transfusion
(time point T15), and at 60 minutes after initiation of transfusion (T60). To assess whether
hemodynamic parameters at T15 and T60 differed from baseline, values recorded at T15 and
T60 were subtracted from those at baseline (?15 and ?60, respectively).
Blood sampling and measurements
Arterial blood samples were collected at baseline, at T15, and at T60. In addition, samples were
collected from the transfusion line of each PRBC unit immediately after transfusion. Blood
samples were analyzed for standard laboratory parameters including leukocytes, platelets,
bilirubin, lactate dehydrogenase, creatine kinase, creatinine, alkaline phosphatase, aspartate
aminotransferase, and alanine aminotransferase at the central laboratory. Additionally, arterial
blood samples were analyzed for blood Hb concentrations, pH, lactate, glucose, sodium, and
potassium using an ABL800 Flex blood gas analyzer (Radiometer Medical, Copenhagen,
Denmark). Furthermore, arterial and PRBC samples were centrifuged for 10 minutes at 1000 g and
4?C. Supernatants were stored at -80?C until analysis.
Glycocalyx injury was assessed by measuring concentrations of syndecan-1 (SDC), a
marker of glycocalyx degradation, in serum and in supernatants of PRBC units [
addition, concentrations of the pro-inflammatory cytokine MIF were measured in serum and in
supernatants of PRBC units. Concentrations of SDC and MIF were measured with
enzymelinked immunosorbent assays (ELISA) according to the manufacturer?s protocol (R&D
Systems, Minneapolis, MN, USA). Furthermore, blood samples and supernatants of PRBC units
were analyzed for concentrations of free Hb at the central laboratory. The changes in systemic
concentrations of SDC, MIF, and free Hb between baseline and T15 (?15) were calculated by
subtracting the concentrations at T15 from those at baseline.
Sample size and study termination
Based on previous studies [
] we estimated that PAP would increase by 1?4 mmHg during
transfusion of fPRBCs and by 4?4 mmHg during transfusion of siPRBCs. Using a two-group
t-test with a 0.05 two-sided significance level, a sample size of 29 in each group was calculated
to have 80% power to detect a difference in means of 3 mmHg assuming a common standard
deviation of 4 mmHg. Taking into account an expected drop-out rate of 10%, we planned to
include 64 patients in the study.
Despite a precise calculation of sample size based on previous data, we experienced
unexpected protraction in patient recruitment after study initiation. Reasons for protracted patient
recruitment were a reduced used of pulmonary arterial catheters in cardiac surgery
implemented in 2014 at our institution, and a quick removal of pulmonary arterial catheters at the
ICU when patients were stable following surgery. Furthermore, the concept of patient blood
management was implemented at our department starting in 2014. A restrictive postoperative
transfusion policy and the use of autologous transfusions devices during surgery resulted in a
significant reduction of PRBCs transfused. These unforeseen developments markedly delayed
realization and finalization of the study, which led the investigators to terminate the study in
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The primary endpoint was the increase in PAP during transfusion of PRBCs (?15 PAP) with
the increase in PVRI during transfusion of PRBCs (?15 PVRI) as the key secondary end point.
Welch?s t-tests was performed to analyze whether ?15 PAP and ?15 PVRI during transfusion
of fPRBCs differed from those during transfusion of siPRBCs. Additionally, an ANCOVA
using the baseline value as a covariate was computed and results were compared to those of the
Secondary endpoints: Differences in all other measured hemodynamic parameters among
groups were assessed using Welch?s t-tests. Concentrations of SDC, MIF and free Hb in serum
and in the supernatant of PRBCs were analyzed with Welch?s t-tests to compare differences
between groups. Correlations between ?15 PAP and ?15 of SDC, MIF and free Hb in serum
and supernatants of PBRCs were calculated using Pearson?s correlation coefficient. Asymptotic
95% confidence intervals for correlation coefficients were calculated using Fisher?s
Data at any study level were obtained and recorded only for randomized and transfused
patients, but not for randomized patients who were not transfused. Hence, these individuals
were not included in analyses. A value of P<0.05 was considered statistically significant. All
Pvalues cited in the manuscript are derived from Welch?s t-tests, while P-values derived from
ANCOVAS are reported in the supporting material only. Calculated P-values for secondary
endpoints serve only descriptive purposes, hence no multiple testing corrections were applied.
Statistical analysis was performed using SPSS 23 (SPSS Inc., Chicago, IL, USA) and R 3.3.2.
Nineteen patients were randomized between January 2014 and June 2016, of which 7 patients
were not transfused and excluded prior to study procedures and measurements (Fig 1). One
patient developed a severe adverse event due to a hemolytic reaction (from which she fully
recovered) and was excluded from analysis. Eleven patients completed the study and were
included in the final analysis.
Of the patients included in the analysis, 6 patients received fPRBCs, whereas 5 patients
received siPRBCs. Mean storage duration was 10?3 days for fPRBCs and 33?4 days for
siPRBCs. Characteristics and demographic data of study participants and performed surgical
procedures are depicted in Table 1. Baseline laboratory parameters of both groups are listed in
Primary and key secondary endpoint
The increase in PAP (?15 PAP) was greater during transfusion of siPRBCs than during
transfusion of fPRBCs (P = 0.012, 95% CI for difference in means [-7.86; -1.41]; Fig 2A and
Table 2). In addition, the increase in PVRI (?15 PVRI) was greater during transfusion of
siPRBCs than during transfusion of fPRBCs (P = 0.016, 95% CI for difference in means [-272;
-37]; Fig 2B and Table 2). Correspondingly, results of ANCOVA demonstrate a greater
increase in PAP and PVRI after transfusion of siPRBCs than after transfusion of fPRBCs (S2
The PAP increased from 24?3 mmHg at BL to 31?3 mmHg at T15 (P = 0.039) after
transfusion of siPRBCs, but did not change after transfusion of fPRBC (29?5 mmHg at BL vs. 31?6
mmHg at T15, P = 0.651, Table 2). The PVRI values did not differ in patients receiving
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Fig 1. Study participation flow diagram. Abbreviations: PAC, pulmonary artery catheter; Hb, hemoglobin; ICU, intensive care unit; SAE, serious adverse
event; PRBCs, packed red blood cells.
siPRBCs (257?101 dyn s cm-5 m2 at BL vs. 407?169 dyn s cm-5 m2 at T15 (P = 0.276), or those
receiving fPRBCs (394?144 dyn s cm-5 m2 at BL vs. 390?162 dyn s cm-5 m2 at T15, P = 0.989,
Changes in PAP and PVRI for ?60 did not differ among groups (Table 3). The increase in
SVRI (?15 SVRI) was greater during transfusion of siPRBCs than during transfusion of
fPRBCs (P = 0.005). Furthermore, changes in cardiac index and mean arterial pressure for ?15
and ?60, and SVRI for ?60 did not differ among groups. Changes in hemodynamic
parameters between baseline and T15 are depicted in S2 Table.
Concentrations of SDC in the supernatant of fPRBCs and siPRBCs were below the
detection limit of the ELISA kit. Concentrations of MIF in the supernatant of fPRBCs did not differ
significantly from those in the supernatant of siPRBCs (158?115 vs. 521?436 ng/ml,
respectively, P = 0.137). Similarly, concentrations of free Hb in the supernatant of fPRBCs units did
not differ from those in the supernatant of siPRBCs (76?33 vs. 165?114 mg/dl, P = 0.158). No
correlations were found between the increase in PAP (?15 PAP) and the concentrations of
MIF (R = 0.26, 95% CI [-0.40; 0.74]) and free Hb (R = 0.22, 95% CI [-0.44; 0.72]) in the
supernatant of PRBCs.
The increase in PAP (?15 PAP) positively correlated with the increase of systemic SDC
concentrations (?15 SDC; R = 0.64, 95% CI [0.06; 0.90]). The increase in PAP during
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In this double-blinded, randomized clinical study we investigated whether transfusion of
PRBCs induces pulmonary vasoconstriction in critically ill patients following cardiac surgery.
The study was terminated due to protracted patient recruitment and remained underpowered.
In the 11 critically ill patients included in the study, transfusion of siPRBCs increased PAP and
PVRI to a greater extent than transfusion of fPRBCs. Additionally, SVRI increased after
transfusion of siPRBCs, but not after transfusion of fPRBCs. Mean arterial pressure and cardiac
output did not differ among groups. Furthermore, the increase in PAP was associated with an
increase in concentrations of SDC, a marker of glycocalyx injury.
In a volunteer study, Berra et al. confirmed that transfusion of stored PRBCs increases PAP
in obese individuals with endothelial dysfunction. Because transfusion of stored PRBCs did
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Fig 2. Changes in pulmonary arterial pressure and pulmonary vascular resistance index at 15 minutes after initiation of transfusion. Change in (A)
pulmonary arterial pressure (? PAP) and (B) pulmonary vascular resistance index (? PRVI) at 15 minutes after initiation of transfusion in patients receiving
fresh packed red blood cells (fresh PRBCs, white bars) or standard-issue packed red blood cells (standard-issue PRBCs, grey bars). Black dots represent
respective changes in individual patients. P-values indicate differences among patients receiving fresh PRBCs and standard-issue PRBCs.
not alter cardiac output, Berra et al. suggested that the increase in PAP was mediated by an
increase in PVR caused by pulmonary vasoconstriction. The investigators reported an
estimated PAP, which was calculated from the pulmonary artery acceleration time measured by
transthoracic ultrasound [
]. In our study we measured the PAP directly using pulmonary
artery catheters. Similarly to the findings reported by Berra et al. we found a greater increase in
PAP and PVRI after transfusion of siPRBCs than after transfusion of fPRBCs. Additionally,
the cardiac output remained unchanged in both groups. Although our results have to be
interpreted with caution due to the small patient number included in this study, our findings
support the assumption by Berra et al. that the increase in PAP after transfusion of stored PRBCs
is caused by pulmonary vasoconstriction. However, the findings require verification in larger
In addition to pulmonary vasoconstriction, siPRBCs induced systemic vasoconstriction in
our patients. These data are in agreement with findings by Risbano et al [
]. The authors
transfused healthy volunteers with autologous leukopheresed PRBCs. Transfusion of PRBCs
stored for 42 days decreased acetylcholine-dependent forearm blood flows to a greater extent
than transfusion of PRBCs stored for 5 days. Similarly, Rezoagli and co-authors reported a
transient increase in both pulmonary and systemic vascular resistances in patients developing
hemolysis after cardio-pulmonary bypass [
]. These results indicate systemic vasoconstriction
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with significant impairment of endothelial function after transfusion of PRBCs stored for
prolonged periods or prolonged periods of cardio-pulmonary bypass.
Endothelial dysfunction occurs in disorders including hypertension, diabetes, and
], and has been shown to augment vasoconstriction after transfusion of stored
PRBCs in mice [
], in lambs [
], and in humans [
]. All patients included in our study
suffered from disorders associated with endothelial dysfunction. Thus, it is likely that endothelial
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dysfunction was present in individuals included in our study. Reduced bioavailability of NO is
one of the key characteristics of endothelial dysfunction. In healthy individuals, the glycocalyx
functions as a mechanical sensor and transducer used to regulate NO production by
endothelial cells [
]. Experimental studies have demonstrated that removal of glycocalyx components
reduces cellular NO production upon mechanical stimuli [
]. In humans, Larsen et al.
suggested that blood transfusion induces degradation of the endothelial glycocalyx layer after
measuring elevated concentrations of SDC following blood transfusion . Syndecan-1 is
generally acknowledged as a marker of endothelial glycocalyx injury. In our study, the increase
in PAP after transfusion of PRBCs positively correlated with systemic SDC concentrations.
Based on this finding we speculate that glycocalyx injury might play a key role in the
mechanism behind pulmonary vasoconstriction associated with transfusion of stored PRBCs.
Several studies associated the reduction of NO bioavailability with scavenging of NO by
free Hb. Hemolysis increases during storage of PRBCs, and the host?s systemic concentrations
of free Hb increase after transfusion of stored PRBCs [
]. Free Hb rapidly reacts with
NO to form methemoglobin and nitrate, resulting in NO consumption [
]. In addition,
hemolysis decreases NO bioavailability by releasing arginase-1, an enzyme converting arginine
to ornithine [
]. Arginase-1 reduces concentrations of arginine, which is a substrate for
NO synthesis. In our study, free Hb concentrations in serum did not differ among groups. The
low number of patients included most likely explains the lack of statistical significance.
The pro-inflammatory cytokine MIF has previously been linked to pulmonary
vasoconstriction. Clinical studies demonstrated elevated MIF concentration in patients suffering from
pulmonary hypertension [
]. Animal studies showed that antibodies directed against MIF
reversed hypoxia-induced pulmonary hypertension in mice and in rats [
Zhang et al. reported that MIF has no direct vasoconstrictor effects in the pulmonary
circulation, the authors demonstrated that MIF potentiated pulmonary vasoconstriction pre-evoked
by phenylephrine [
]. In our study, we were unable to confirm an association between MIF
and pulmonary vasoconstriction after transfusion of stored blood. Concentrations of MIF in
the supernatant of fPRBCs and siPRBCs did not differ significantly due to the limited patient
Current clinical practice is to transfuse the oldest compatible unit available at the blood
bank. Some clinical studies investigating the effects of storage duration of PRBCs had only
small differences in storage durations among groups. A strength of our study is the marked
difference in storage duration of PRBCs (10?3 vs. 33?4 days). Furthermore, the inserted
pulmonary arterial catheter allowed direct measurement of PAP and calculation of PVR.
There are several limitations to our study. A major limitation is the low number of included
patients. During preparation of the study protocol in 2012, sample size calculation yielded that
inclusion of 29 patients per group would allow to detect a significant difference in PAP with a
power of 80%. However, after initiating the study in 2014, we experienced protracted patient
recruitment starting from 2015. One reason for protracted patient inclusion was a reduced use
of pulmonary arterial catheters in cardiac surgery enforced at our cardiac anesthesiology
department since 2014. In addition, our hospital implemented the concept of patient blood
management in 2014, which is a multidisciplinary approach focusing on reducing blood
transfusions. In particular, anesthesiologists started to adhere to a restrictive transfusion policy in
the postoperative phase and to use autologous cell salvage devices during surgery. These
unforeseen developments made it impossible to achieve the planned patient number within a
reasonable time frame. Therefore, we decided to stop the study in June 2016 and perform
analysis with the included patients.
Of note, this low number of included and analyzed patients resulted in an underpowered
study. With respect to scientific studies, low power means that the chance of discovering
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effects that are genuinely true is low [
]. Results from underpowered studies are at greater
risk of being false negative than results from adequately powered studies. In addition, when
underpowered studies discover true effects, the found effects might be inflated, resulting in a
phenomenon called winner?s curse [
]. Thus, although statistic analysis yielded significant
results in our study, the results should be interpreted as indefinite or unproven and require
verification in larger studies.
Another limitation is that the absolute PAP values after transfusion did not differ between
groups, and the increase in PAP was transient and not detectable within 60 minutes after
transfusion. As a consequence, we were unable to answer whether the increase of PAP and
PVR after transfusion of stored blood is clinically relevant and could translate into adverse
pulmonary and cardiac events. Larger clinical trials are required to clarify whether an increase in
PAP and PVR after transfusion of stored blood influences outcomes in patients following
cardiac surgery. Furthermore, as only one unit of PRBCs was transfused, transfusion of multiple
PRBC units might potentiate the increase in PAP and PVR and thus negatively affects
outcome. In addition, we tried to identify new molecules potentially contributing to pulmonary
vasoconstriction after transfusion of stored blood, but the limited number of samples analyzed
does not allow us to draw significant conclusion from our results. In addition, we did not
focus on pathomechanisms described in previous experimental settings. Thus, other possible
noxious effects of stored PRBC transfusions mediated by iron, microparticles, protein
oxidation, or lipid peroxidation of the erythrocyte membrane were not assessed in our study.
In conclusion, the results of this study suggest that transfusion of siPRBCs might increase
PAP and PVRI to a greater extent than transfusion of fPRBCs in patients admitted to the ICU
following cardiac surgery.
S1 CONSORT checklist. Checklist of information required for reporting a randomised
S1 Table. Laboratory values of study participants prior to transfusion. Data are depicted as
mean?standard deviation. Abbreviations: PRBCs, packed red blood cells.
S2 Table. Results of ANCOVA for the increase within 15 minutes during transfusion as
the dependent variable. Abbreviations: ANCOVA, analysis of co-variance; CI, cardiac index;
FHB, free hemoglobin; MAP, mean arterial pressure; PAP, pulmonary arterial pressure;
PRBC, packed red blood cells; PVRI, pulmonary vascular resistance index; SVRI, systemic
vascular resistance index.
S1 Dataset. Complete anonymized dataset of the study population. Abbreviations: AH,
arterial hypertension; AS, aortic stenosis; AVR, aortic valve replacement; CABG, coronary
artery bypass graft; CAD, coronary artery disease; CMP, cardiomyopathy; COPD, chronic
obstructive pulmonary disease; FHB, free hemoglobin; GERD, gastro-esophageal reflux
disease; HLP, hyperlipidemia; HR, heart rate; MAP, mean arterial pressure; MVR, mitral valve
replacement; NIDDM, non insulin-dependent diabetes mellitus; PAP, pulmonary arterial
pressure; PEEP, positive end-expiratory pressure; PVRI, pulmonary vascular resistance index;
RBC, red blood cells; SVRI, systemic vascular resistance index.
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S1 Study Protocol. English translation of the study protocol.
S2 Study Protocol. Original German version of the study protocol.
The authors thank Professor Warren M. Zapol for critical review of the manuscript.
Conceptualization: Joanna Baron-Stefaniak, Gerda C. Leitner, Elias L. Meyer, Michael J.
Hiesmayr, Roman Ullrich, David M. Baron.
Data curation: Joanna Baron-Stefaniak, Nina K. I. Ku?ntzel, Elias L. Meyer, David M. Baron.
Formal analysis: Joanna Baron-Stefaniak, Elias L. Meyer, David M. Baron.
Funding acquisition: Roman Ullrich, David M. Baron.
Investigation: Joanna Baron-Stefaniak, Gerda C. Leitner, David M. Baron.
Methodology: Joanna Baron-Stefaniak, Gerda C. Leitner, Nina K. I. Ku?ntzel, Elias L. Meyer,
Michael J. Hiesmayr, David M. Baron.
Project administration: David M. Baron.
Resources: Roman Ullrich, David M. Baron.
Software: Joanna Baron-Stefaniak.
Supervision: Roman Ullrich, David M. Baron.
Validation: Joanna Baron-Stefaniak, David M. Baron.
Visualization: Joanna Baron-Stefaniak, David M. Baron.
Writing ? original draft: Joanna Baron-Stefaniak, David M. Baron.
Writing ? review & editing: Joanna Baron-Stefaniak, Gerda C. Leitner, Elias L. Meyer,
Michael J. Hiesmayr, Roman Ullrich, David M. Baron.
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