Background
In the Fluid Expansion as Supportive Therapy (FEAST) trial, African children with shockrandomized to early rapid fluid resuscitation (20 to 40 ml/kg boluses) with normalsaline or 5% human albumin had a 3.3% increased absolute risk of death by 48 hourscompared with no-bolus controls [
1]. Followingpublication, commentary papers, letters and discussion groups have speculated on reasonsfor this surprising result [
2‐
7], given that bolus resuscitation is the gold standard forshock-management in well-resourced countries (albeit based on weak levels of evidence)[
8].
FEAST was a pragmatic trial conducted in African hospitals without ventilationfacilities. It included children with shock caused by a heterogeneous group ofconditions including sepsis [
9] and malaria[
10] but excluded those withgastroenteritis and severe malnutrition [
11].Consistency of adverse outcome was shown over all sites and in all possible subgroups,with no benefit of boluses observed for any working diagnosis [
1], for any definition of shock [
7,
12‐
14], or presence or absence of anemia or under-nutrition. Asreasons for harm caused by boluses remained unclear, we undertook further analyses toexplore possible mechanisms and modes of death in children randomized to bolusresuscitation versus control. We hypothesized that boluses may cause excess deaths fromneurological or respiratory events, particularly those relating to fluid overload. Weexplored the effect of boluses on 48-hour mortality according to signs and symptoms atenrolment (presentation syndrome, PS); predominant clinical syndrome in each patientprior to death (terminal clinical event, TCE); and changes in vital signs, measuredprospectively at pre-specified times.
Methods
Trial design and population
The methods and the outcome of the trial have been reported in detail [
1]. In brief, children, aged 60 days to 12 years, withsevere febrile illness (classed as impaired consciousness (prostration or coma)and/or respiratory distress (increased work of breathing) plus clinical evidence ofimpaired perfusion (one of capillary refill time >2 seconds, lower limbtemperature gradient, weak radial pulse volume or severe tachycardia) at six centersin Kenya, Tanzania and Uganda were enrolled into two strata according to systolicblood pressure [
1]. Stratum A included 3,141children without severe hypotension who were randomized to immediate bolus of 20ml/kg (increased to 40 ml/kg after protocol amendment [
1]) of 5% albumin (albumin-bolus: 1,050 children) or 0.9%saline (saline-bolus: 1,047 children), or no-bolus (control, maintenance fluids 4ml/kg/hour: 1,044 children). The saline-bolus and albumin-bolus arms, but not thecontrol arm, received an additional 20 ml/kg bolus at one hour if impaired perfusionpersisted. In all three arms, further 40 ml/kg boluses of study fluid (saline for thecontrol arm) were only prescribed beyond one hour if severe hypotension developed(see definition below). Stratum B included 29 children with FEAST entry criteria plussevere hypotension (defined as systolic blood pressure <50 mmHg if <12 months;<60 mmHg if 1 to 5 years; <70 mmHg if > 5 years) who were randomized toalbumin or saline boluses of 40 to 60 ml/kg only. The primary endpoint was 48-hourmortality. Children with severe malnutrition, gastroenteritis, trauma, surgery orburns were excluded.
Baseline and follow-up data collection
Trial clinicians completed a structured clinical case report form at admission. Avenous blood sample was taken for immediate biochemical analyses with a handheldblood analyzer (iSTAT, Abbott Laboratories, Abbott Park, IL, USA), hemoglobin wasmeasured with HemOcue (Ängelholm, Sweden), glucose and lactate were measuredwith an On-Call glucometer and a Lactate Pro meter respectively and HIV antibodytesting. Blood smears for malaria parasites were prepared for immediate reading andsubsequent quality control. Standardized clinical reviews were conducted at 1, 4, 8,24 and 48 hours including vital signs and hemodynamic monitoring. A working clinicaldiagnosis was recorded at 48 hours as well as history of prior neurodevelopmentalprogress and any pre-admission neurological deficits. Children were managed ongeneral pediatric wards; mechanical ventilation (other than short-term 'bag-and-mask'support) was not available. Basic infrastructural support for emergency care as wellas oxygen saturation and automatic blood pressure monitors were provided for eachsite. All trial patients received intravenous antibiotics, antimalarial drugs (forthose with falciparum malaria) and intravenous maintenance fluids (2.5 to 4ml/kg/hour as per national guidelines) until the child was able to retain oralfluids. Antipyretics, anticonvulsants and treatment for hypoglycemia (blood sugar<2.5 mmol/l) were administered according to nationally agreed protocols. Childrenwith a hemoglobin level <5 g/dl were transfused with 20 ml/kg of whole blood over4 hours.
Assignment of presentation syndrome and terminal clinical event
Prior to and throughout the trial, clinical staff received onsite training in triageand emergency life support management to optimize case recognition, implementsupportive management and ensure protocol adherence. Throughout the hospitaladmission, severe adverse events were reported immediately and clinical features ofpulmonary edema and raised intracranial pressure, and evidence of hypovolemia andallergic events were actively solicited. An independent clinician removed allreferences to randomized arm or fluid management prior to review by the EndpointReview Committee (ERC), which included an independent chair (JE), five independentpediatricians (experienced in high dependency care and/or working in Africa), andcenter principal investigators. The ERC had access to 'blinded' clinical narratives,bedside vital observations (below), iSTAT results (baseline, 24 hours), microbiology,malaria and HIV status, and concomitant treatments. They adjudicated (blind torandomized arm) on whether fatal and non-fatal events could be related to bolusinterventions and the main causes of death [
1]. In addition, the ERC chairperson and another non-center ERCmember reviewed all deaths occurring within 48 hours; using pre-specified criteria,they stratified all children by presentation syndrome (PS) and classified thepredominant clinical mode of death (TCE).
Presentation syndromes definitions
Severe shock or acidosis presentationwas any one of blood lactate>5 mmol/l [
8], base excess >-8 mmol/l[
10]; World Health Organization shockdefinition (all of cold hands or feet; capillary refill time >3 seconds; weak andfast pulse) [
14] or moderate hypotension(systolic blood pressure (SBP) 50 to 75 mmHg in children aged <12 months, 60 to 75mmHg in children aged 1 to 5 years, and 70 to 85 mmHg in children aged >5years).
Respiratory presentation
hypoxia (oxygen saturation <92% measured by pulse oximetry) [
15] plus one of history of cough, chest indrawingor crepitations [
16].
Neurological presentation
coma or seizures at or immediately preceding hospital admission [
16].
Terminal clinical event syndrome definitions
Cardiogenic/cardiovascular collapse
signs of shock at the point of demise - severe tachycardia or bradycardia plus oneof prolonged capillary refill time >2 seconds, cold peripheries or low SBP. Ifhypoxia was also present then this mode of TCE was a consensus view among ERCmembers, that circulatory failure was deemed to be the primary problem.
Respiratory
Ongoing or development of hypoxia (PaO2 <90%) with chest signs(crepitations or indrawing). Primary cause of death assigned as pneumonia and/orinvolving possible pulmonary edema.
Neurological
Possible raised intracranial pressure (high SBP or relative bradycardia) or, inchildren with severely reduced conscious level (Blantyre Coma Score ≤2[
17]), focal neurological signs,abnormal pupil response to light or posturing at the point of demise.
Children whose deaths were unwitnessed were assigned 'unknown' TCE.
Analysis
The analysis focused on children in stratum A, in which 86% of deaths occurred within48 hours. Stratum B (mortality 62% (18 out of 29)) was not included because allchildren received boluses [
1]. Albumin- andsaline-bolus arms were combined, as mortality was very similar in both. Allcomparisons between combined bolus and control arms were performed according tointention-to-treat, and all statistical tests were two-sided.
PS prevalence was described by randomized arm and 48-hour mortality was compared byrandomized arm within each PS. Forest plots were constructed to show comparisonsbetween arms for 48-hour mortality according to PS and all individual features ofeach PS. Hazard ratios for the comparison between bolus and no-bolus arms wereestimated for different levels of oxygen saturation and hemoglobin from Coxproportional hazard models, with a single indicator for treatment group, the level ofthe parameter and an interaction between treatment group and parameter. Competingrisks methods were used to estimate cumulative incidence curves and sub-hazard ratiosto compare the two treatment groups in terms of TCEs [
18].
Oxygen saturation, axillary temperature, heart rate, respiratory rate, SBP, glucosevalues and a composite measure of shock or impaired perfusion (defined as any of thefollowing: capillary refill time >2 seconds, lower limb temperature gradient, weakradial pulse volume or severe tachycardia (<12 months, >180 bpm; 1 to 5 years,>160 bpm; >5 years, >140 bpm)) were summarized for survivors over time (atbaseline, 1, 4, 8, 24 and 48 hours) with box and whisker plots and bar charts.Treatment groups were compared in terms of mortality after one hour, conditional onchanges in shock and hypoxia parameters 1-hour post-randomization. Our analysesfocused only on early changes where the number of deaths was similar acrossrandomized arms; thereafter, because of excess deaths in bolus arms, results would besubject to survivorship bias.
Ethics statement
Ethics Committees of Imperial College London, Makerere University Uganda, MedicalResearch Institute, Kenya and National Medical Research Institute, Tanzania approvedthe protocol.
Discussion
In this paper, we have explored possible mechanisms for the excess death rate amongchildren randomized to receive rapid boluses of 20 to 40 ml/kg of 5% albumin or 0.9%saline fluid resuscitation compared with no-bolus controls. We found no evidence thatexcess 48-hour mortality associated with boluses differed by type of PS, by individualconstituent components of each syndrome, or by baseline hemoglobin level. Remarkably, inevery subgroup we examined, there was consistent evidence of harm by boluses.Paradoxically, the syndromes where most concern has been expressed over trial inclusion(respiratory or neurological alone and/or less severe shock criteria) not only had lowermortality overall, but also tended to have smaller differences between bolus andcontrol, although care must be taken with interpretation of smaller subgroups. The onlyexception was hypoxia, present in a quarter of children at admission, which surprisinglyappeared to be associated with significantly less harm from boluses. There appears to beno good rationale for this finding, which could have occurred by chance.
Even though this trial was conducted in settings with limited resources and no access tointensive care, the conduct of the trial complied to the highest standards of goodclinical practice including adherence to intervention strategy and completeness offollow-up, 100% source document monitoring and the robust and blinded methodology fordetermining PS and TCE. An intention-to-treat analysis with no need for imputation formissing data minimized the likelihood of bias and underpinned the magnitude andimportance of the unexpected findings of the trial and further analyses.
Noteworthy is that, consistent with global clinical experience, we observed a superiorresolution of impaired perfusion by one hour in the bolus arms compared with the controlarm. However, importantly, this did not translate into a superior outcome when comparedwith children with continued impaired perfusion: in both cases, boluses resulted inhigher mortality. Mortality excess with boluses among children with and without hypoxiaat baseline occurred to a similar extent irrespective of oxygen saturation status at onehour. Although de novo development of hypoxia at one hour was more common inthe bolus arms, it was not associated with a significant increase in 48-hour mortality -suggesting that, if fluid boluses were causing pulmonary edema (and hypoxia), this wasnot a unifying mechanism for increased mortality from boluses. Moreover, there waslittle evidence that fluid overload was the mechanism for excess deaths with bolusesfrom our analyses of neurological or respiratory TCEs. Overall, cardiovascular collapsewas the main TCE and contributed most substantially to the excess mortality in the bolusarms compared to control, peaking at 2 to 11 hours post-bolus. Whilst it is possiblethat subtle effects of fluid overload on the lungs or brain could have been missed, ourfindings do not lend support to this hypothesis, particularly as the ERC review processwas blind to randomization and used pre-specified TCE definitions.
A limitation of our trial was that we were unable to undertake invasive or point-of-carecontinuous monitoring to provide greater insight into TCEs, as in high-income intensivecare settings. However, the availability of patient-centered variables from our bedsideobservations and laboratory data from most children at baseline has enabled furthercharacterization of the trial participants into clinically relevant presentations (PS)in the context of where the trial was conducted. It has provided a more in-depthunderstanding of the spectrum of clinical groupings of children enrolled in the trialand the degree of adverse outcome fluid boluses had in these groups. Our bedsideobservations at pre-defined times following randomization, as well as adjudication ofcause of death by the ERC, blind to randomized arm and using pre-specified criteria(TCE), provide more speculative data but remain informative because they are largelyoperator-independent. These methodologies are central to the internal validity of ouranalysis, which sought to minimize systematic bias.
Whereas initial improvement in circulatory status following bolus resuscitation isconsistent with global clinical experience [
8,
12,
19], the observation of excesssubsequent cardiovascular collapse and excess mortality, even in the early responders,was only made possible because of exemplary adherence to randomized allocation, and in atrial protocol in which further boluses were given to only (very few) childrendeveloping severe hypotension [
12]. Thepossibility that fluid resuscitation lead to hemodilution [
20,
21] in already anemic children, reducingoxygen delivery to the myocardium [
22] andleading to ischemia and cardiac dysfunction, is largely ruled out by the lack ofheterogeneity in the TCEs by hemoglobin level, and by the analysis showing excess harmwith fluids across the whole range of hemoglobin values. These findings challenge thepresumption that early and rapid reversal of shock by fluid resuscitation translatesinto longer-term survival benefits [
8,
23,
24] in settings where intensive carefacilities are not available. They do raise a possibility that rapid fluid resuscitationmay cause adverse effects on vascular hemodynamics and myocardial performance, drivingthe requirement for inotropic and pressor support. Rapid restoration of microcirculatoryperfusion may come at the expense of requiring other components of the sepsis bundle,including inotropes and ventilation. This possibility could be explored in futureclinical and preclinical research examining the natural history of shock in patientsmanaged by maintenance only (as in the control arm) and with fluid boluses.
Adverse effects of hyperchloremia, at the doses given in this trial, remaincontroversial [
25‐
29].Intriguingly, the most deleterious effects of boluses were in those patients with severeacidosis at baseline, the group with the least
a priori equipoise regarding thepotential benefits of fluid resuscitation - lending support to the notion of adverseeffects of the resuscitation fluids on acid-base equilibrium. Alternatively, this mayindicate lethal reperfusion injury [
30] or asurge of cytokines [
31] in cases with advancedshock. As previously suggested [
1], shock may bean adaptive, time-dependent response sustaining children through a prolonged periodprior to hospital admission - only to die within hours of reperfusion.
Whatever the explanation, these findings raise important questions about thepathophysiological mechanisms of shock and goal-directed management, questioning whetherthe protocol-driven requirement for inotropes and vasoactive drugs has been driven, inpart, by aggressive fluid challenge [
12]. The2008 Surviving Sepsis Campaign Guidelines, informed by a modified Delphi process, gradedthe pediatric recommendation (20 ml/kg boluses over 5 to 10 minutes up to 60 ml/kg) as2C, indicating a weak recommendation with low quality of evidence. The pediatric studieson which these recommendations were based included only two retrospective, observationalstudies of initial resuscitation volume on the outcome of children with putative sepsisfrom a single tertiary referral center, involving 34 and 91 children respectively[
19,
24]. Theinclusion criteria for both studies were children who survived to intensive care unitadmission, but were inotrope-dependent and had pulmonary arterial catheters
insitu. Higher initial fluid boluses and early shock reversal in 9 and 24 childrenin the two respective studies were associated with improved global outcome. However, thestudy design and the patient population had major limitations in terms of survivorshipbias and external validity to other settings. Other sources of evidence that werereferenced to inform fluid resuscitation guidelines include dengue shock. We suggestthese are largely irrelevant to the management of sepsis, because shock as acomplication of dengue occurs 7 to 10 days after fever defervescence, secondary to grossintravascular leakage leading to vomiting, abdominal pain, increasingly tenderhepatomegaly, narrow pulse pressure and hemoconcentration [
32]. The American College of Critical Care Medicine guideline,and similar guidelines, nevertheless have been adopted by many countries worldwide wherepoint-of-care testing and intensive care facilities are available and are considered tobe best practice. These are now being recommended as standards of care for resource-poorsettings [
33,
34];indicating that the FEAST trial had limited generalizability because the adverse effectsof fluid boluses were largely confined to children with malaria and/or anemia[
33]. The data presented in the originalmanuscript [
1], subsequence correspondence[
7] and this detailed sub-analysisdefinitely counter this interpretation. A recent systematic review assessing theevidence base for fluid resuscitation in the treatment of children with shock due tosepsis or severe infection found only 13 pediatric trials. Whilst the majority of allrandomized evidence to date comes from the FEAST trial, they recommended thatimplementation of simple algorithms for children managed at hospitals with limitedresources to ensure identification of children who maybe potentially be harmed by fluidboluses [
35]. The findings we report here raisequestions over the rates, volumes and types of solutions recommended in pediatricresuscitation protocols, most of which remain untested in clinical trials.
Acknowledgements
The study group would like to thank the children and families who participated in thetrial and the other members of the trial management group (listed below). We wouldalso like to thank Professor Rinaldo Bellomo for helpful comments on an earlierdraft.
The study was supported by a grant (G0801439) from the Medical Research Council,United Kingdom (provided through the MRC DFID concordat). Baxter Healthcare Sciencesdonated the resuscitation fluids (5% albumin and 0.9% saline). The funders (MedicalResearch Council) and Baxter Healthcare Sciences had no role in study design, datacollection and analysis, decision to publish, or preparation of the manuscript.
FEAST Management Group: KEMRI-Wellcome Trust Clinical Trials Facility, Kilifi,Kenya: Kathryn Maitland (Chief Principal Investigator (PI)), Mukami J. Mbogo(Trial Manager), Gilbert Ogetii; Malaria Consortium, Kampala, Uganda: JamesTibenderana, Lilian Akello, Moses Waweru; Data Management Group: NaomiWaithira, Trudie Lang, Roma Chilengi, Greg Fegan; Medical Research CouncilClinical Trials Unit, London, UK: Abdel Babiker (Trial Statistician),Elizabeth Russell (statistician), Margaret Thomason, Diana Gibb; ImperialCollege, London: Michael Levin.
Centers: Uganda: Mulago National Referral Hospital, Kampala: Sarah Kiguli(Chief PI Uganda), Robert O. Opoka (PI), Mariam Namutebi (Study Site Coordinator;SSC), Daniel Semakula, Ahmed Ddungu, Jalia Serwadda. Soroti Regional ReferralHospital: Charles Engoru (PI), Denis Amorut (SSC), Vincent Okuuny, RonaldWokulira, Moses Okiror, Steven Okwi; Mbale Regional Referral Hospital: PeterOlupot-Olupot (PI), Paul Ongodia (SCC), Julius Nteziyaremye, Martin Chebet, ConneliusMbulalina, Tony Ssenyondo, Anna Mabonga, Emmanuela Atimango; St. Mary's Hospital,Lacor: Richard Nyeko (PI), Benedict Otii (SSC), Sarah Achen, Paska Lanyero,Ketty Abalo, Paul Kinyera. Kenya: Kilifi District Hospital: SamuelO. Akech (PI), Molline Timbwa (SSC), Ayub Mpoya, Mohammed Abubakar, Mwanamvua Boga,Michael Kazungu. Tanzania: Teule Designated District Hospital, Muheza: George Mtove (PI), Hugh Reyburn (Co-PI), Regina Malugu (SSC), Ilse C EHendriksen, Jacqueline Deen, Selemani Mtunguja.
Pediatric Emergency Triage Assessment and Treatment training team: Hans-JorgLang, Mwanamvua Boga, Natalie Prevatt, Mohammed Shebe, Jackson Chakaya, JaphethKarisa.
Endpoint Review Committee: Jennifer Evans (Chair), Diana Gibb, JaneCrawley, Natalie Young; Serious adverse events reviewers: BernadetteBrent, Ayub Mpoya.
Competing interests
The authors declare that they have no competing interests.
Authors' contributions
KM conceived the trial and participated in the design of the sub-study and wrote thefirst draft of the manuscript; ECG participated in the design of the study and performedthe statistical analysis; JAE chaired the ERC, and participated in the design of thestudy and the writing of the manuscript; SK coordinated the clinical trial withinUganda, and participated in the design of the sub-study and writing of the manuscript;PO was a member of ERC, and participated in the design of the study and writing of themanuscript; SOA was a member of the ERC, and participated the design of the study andwriting of the manuscript; ROO was a member of the ERC, and participated in the datacollection and interpretation of data; CE participated in the coordination of the study,was a member of the ERC, and participated in the data collection and interpretation ofdata; RN participated in the coordination of the study and was a member of the ERC, andparticipated in the data collection and interpretation of data; GM participated in thecoordination of the study, was a member of the ERC, and participated in the datacollection and interpretation of data; HR participated in the design of the study andwriting of the manuscript; BB carried out the independent review of serious adverseevents and was involved in the writing of the manuscript; JN was involved in thecoordination of data collection and interpretation; AM carried out the independentreview of serious adverse events and was involved in the writing of the manuscript; NPparticipated in the training of study clinicians and coordination of data collection anddata interpretation; CMD participated in the data collection and interpretation of data;DS participated in the data collection and interpretation of data; AD participated inthe data collection and interpretation of data; VO participated in the data collectionand interpretation of data; RW participated in the data collection and interpretation ofdata; MT participated in the training of study clinicians, data collection andinterpretation of data; BO participated in the data collection and interpretation ofdata; ML participated the design of the study and writing of the manuscript; JCparticipated in the design of the study, the ERC and writing of the manuscript, AGBparticipated in the design of the study and performed the statistical analysis, DMGparticipated in the design of the study, the ERC and writing of the manuscript. Allauthors read and approved the final manuscript.