How I manage major hemorrhage.

Acute hemorrhage can be a life-threatening emergency that is complex in its management and affects many patient populations. The last 15 years has seen the introduction of comprehensive massive hemorrhage protocols, wider use of viscoelastic testing, new coagulation factor products, and the publication of robust randomized controlled trials in diverse bleeding patient populations. Although gaps continue to exist in the evidence-base for several aspects of patient care, there is now sufficient evidence to allow for an individualized hemostatic response based on the type of bleeding and specific hemostatic defects. We present three clinical cases that highlight some of the challenges in acute hemorrhage management, focusing on the importance of inter-professional communication, rapid provision of hemostatic resuscitation, repeated measures of coagulation, immediate administration of tranexamic acid, and prioritization of surgical or radiologic control of hemorrhage. This article provides a framework for the clear and collaborative conversation between the bedside clinical team and the consulting hematologist to achieve prompt and targeted hemostatic resuscitation. In addition to providing consultations on the hemostatic management of individual patients, the hematology service must be involved in setting hospital policies for the prevention and management of patients with major hemorrhage.

Reconsidering Routine Repeat Group and Screens During Pregnancy-Personalizing Pregnancy Care.

The group and screen (G&S) are performed in early pregnancy to identify clinically significant antibodies (CSA) that may necessitate fetal monitoring for hemolysis/anemia or affect RhIg eligibility. Guidelines vary, including differences between RhD-positive and negative patients, but typically, the G&S is repeated at 28 weeks, and sometimes pre-delivery. We reviewed data showing a low risk (0.01%-0.43%) of detecting a new CSA in late gestation (late alloimmunization) and the risk of late alloimmunization causing severe hemolysis/anemia is even lower at <0.01%. Routinely repeating a G&S at 28 weeks and delivery may not be necessary for healthy, low-risk pregnancies.

Effect of Convalescent Plasma on Organ Support-Free Days in Critically Ill Patients With COVID-19: A Randomized Clinical Trial.

IMPORTANCE: The evidence for benefit of convalescent plasma for critically ill patients with COVID-19 is inconclusive. OBJECTIVE: To determine whether convalescent plasma would improve outcomes for critically ill adults with COVID-19. DESIGN, SETTING, AND PARTICIPANTS: The ongoing Randomized, Embedded, Multifactorial, Adaptive Platform Trial for Community-Acquired Pneumonia (REMAP-CAP) enrolled and randomized 4763 adults with suspected or confirmed COVID-19 between March 9, 2020, and January 18, 2021, within at least 1 domain; 2011 critically ill adults were randomized to open-label interventions in the immunoglobulin domain at 129 sites in 4 countries. Follow-up ended on April 19, 2021. INTERVENTIONS: The immunoglobulin domain randomized participants to receive 2 units of high-titer, ABO-compatible convalescent plasma (total volume of 550 mL ± 150 mL) within 48 hours of randomization (n = 1084) or no convalescent plasma (n = 916). MAIN OUTCOMES AND MEASURES: The primary ordinal end point was organ support-free days (days alive and free of intensive care unit-based organ support) up to day 21 (range, -1 to 21 days; patients who died were assigned -1 day). The primary analysis was an adjusted bayesian cumulative logistic model. Superiority was defined as the posterior probability of an odds ratio (OR) greater than 1 (threshold for trial conclusion of superiority >99%). Futility was defined as the posterior probability of an OR less than 1.2 (threshold for trial conclusion of futility >95%). An OR greater than 1 represented improved survival, more organ support-free days, or both. The prespecified secondary outcomes included in-hospital survival; 28-day survival; 90-day survival; respiratory support-free days; cardiovascular support-free days; progression to invasive mechanical ventilation, extracorporeal mechanical oxygenation, or death; intensive care unit length of stay; hospital length of stay; World Health Organization ordinal scale score at day 14; venous thromboembolic events at 90 days; and serious adverse events. RESULTS: Among the 2011 participants who were randomized (median age, 61 [IQR, 52 to 70] years and 645/1998 [32.3%] women), 1990 (99%) completed the trial. The convalescent plasma intervention was stopped after the prespecified criterion for futility was met. The median number of organ support-free days was 0 (IQR, -1 to 16) in the convalescent plasma group and 3 (IQR, -1 to 16) in the no convalescent plasma group. The in-hospital mortality rate was 37.3% (401/1075) for the convalescent plasma group and 38.4% (347/904) for the no convalescent plasma group and the median number of days alive and free of organ support was 14 (IQR, 3 to 18) and 14 (IQR, 7 to 18), respectively. The median-adjusted OR was 0.97 (95% credible interval, 0.83 to 1.15) and the posterior probability of futility (OR <1.2) was 99.4% for the convalescent plasma group compared with the no convalescent plasma group. The treatment effects were consistent across the primary outcome and the 11 secondary outcomes. Serious adverse events were reported in 3.0% (32/1075) of participants in the convalescent plasma group and in 1.3% (12/905) of participants in the no convalescent plasma group. CONCLUSIONS AND RELEVANCE: Among critically ill adults with confirmed COVID-19, treatment with 2 units of high-titer, ABO-compatible convalescent plasma had a low likelihood of providing improvement in the number of organ support-free days. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT02735707.

Complications of a severe autoimmune hemolytic anemia crisis: transfusional iron overload and gangrenous cholecystitis.

BACKGROUND: Evans syndrome is a rare autoimmune disorder that is defined by the simultaneous or sequential presence of two or more cytopenias without an obvious underlying precipitating cause. Evans syndrome usually follows a chronic relapsing and remitting course and is quite rare, making it difficult to evaluate in clinical studies. CASE REPORT: A 66-year-old male patient with a 17-year history of Evans syndrome presented with fulminant autoimmune hemolytic anemia (AIHA). He presented with a markedly elevated C-reactive protein (CRP; 46 mg/L [normal, 0-5 mg/L]) before onset of a decrease in hemoglobin. He required the transfusion of 20 units of red blood cells while awaiting response to aggressive immunosuppressive therapy including high-dose corticosteroids, intravenous immunoglobin therapy, and rituximab. He achieved a complete hematologic response. RESULTS: His postdischarge course was complicated by acute cholecystitis requiring laparoscopic cholecystectomy. In addition, his transfusional iron overload requiring 16 phlebotomies to reduce his ferritin level from 4933 µg/L to 326 µg/L, with phlebotomies ongoing every 2 weeks to achieve a ferritin level of less than 100 µg/L. CONCLUSION: Neither transfusional iron overload nor acute cholecystitis are well-recognized complications of a severe episode of AIHA. An elevated CRP has been recently recognized as an important prognostic marker in patients with immune thrombocytopenic purpura and this case suggests a need to evaluate its utility in AIHA.

Cardiac stress biomarkers after red blood cell transfusion in patients at risk for transfusion-associated circulatory overload: a prospective observational study.

BACKGROUND: Transfusion-associated circulatory overload (TACO) is a leading cause of serious reactions. In regard to TACO, little is known regarding biomarkers as a predictor, their most informative timing, or thresholds of significance or differentiation from other reactions. STUDY DESIGN AND METHODS: In this study of inpatients at risk for TACO (age ≥ 50 years) receiving 1 red blood cell unit, cardiac biomarkers, brain natriuretic peptide (BNP), N-terminal pro-BNP (NT-proBNP), and high-sensitivity troponin were measured at baseline, 6 to 12 hours (except troponin) posttransfusion, and 18 to 24 hours posttransfusion. Primary outcome was a critical increase in biomarkers (>1.5-fold increase and supranormal) at 18 to 24 hours. RESULTS: Fifty-one patients were analyzed; 29% had cardiovascular disease, 73% had one or more cardiac risk factors, and 50% took cardiac or antihypertensive therapies. Although eight (16%) developed an increase in systolic pressure of at least 30 mmHg and four (8%) reported dyspnea and/or cough, none had TACO. At baseline, BNP level was more than 100 ng/L in 59% and NT-proBNP was more than 300 pg/mL in 83%. A total of 25% had a BNP critical increase, 33% had a NT-proBNP critical increase, and 2% had a troponin critical increase at 18 to 24 hours. Overall, 38% had at least one biomarker critical increase and NT-proBNP/BNP concordance was 84%. An increase in the NT-proBNP (>1.5-fold increase and >300 pg/mL) at 18 to 24 hours was the commonest biomarker change. CONCLUSIONS: An increase of the NT-proBNP at 18 to 24 hours may be the preferred surrogate marker for identifying a patient experiencing physiologic difficulty in handling the volume challenge. Larger studies are needed to clarify the risk of TACO for a given pretransfusion biomarker profile and the correlation between TACO and increase in biomarkers after transfusion.

Red Cell Transfusion-Associated Hemolysis in Cardiac Surgery: An Observational Cohort Study.

BACKGROUND: Red cell viability is impaired during storage, resulting in excess hemolysis during storage and after transfusion. As a result, transfusions may oversaturate the hemoglobin clearance pathways, resulting in cell-free hemoglobin and iron toxicity in susceptible patients, such as those undergoing cardiac surgery with cardiopulmonary bypass. To explore this hypothesis, we assessed the relationship of red cell transfusions with cell-free hemoglobin and transferrin saturation levels in a consecutive cohort of cardiac surgical patients. METHODS: Laboratory measures of hemolysis were obtained in consecutive cardiac surgical patients 15 to 30 minutes after bypass. Multivariable regression models controlling for important confounders were constructed to determine the independent relationship of red cell transfusions during bypass with cell-free hemoglobin and transferrin saturation levels post-bypass, analyzed as continuous variables (linear regression) and categorized at the 90th percentiles (logistic regression). RESULTS: Of the 543 included patients, 82 (15.1%) received red cell transfusions during bypass (median 1; interquartile range 1-2 units). Cell-free hemoglobin was detected in all patients (mean 11.3; standard deviation ± 9.3; 90th percentile 18 µmol/L), and transferrin saturations were relatively high (mean 41 ± 19%; 90th percentile 66%). After controlling for confounders, transfusions were not associated with cell-free hemoglobin (P > .25 in linear and logistic regression) but were directly associated with transferrin saturation levels (P < .001 in linear and logistic regression). Transfused patients had a 6.2-fold (95% confidence interval: 2.4-16.1) risk-adjusted increase in the odds of having high (>66%) transferrin saturation levels. CONCLUSIONS: The findings support the hypothesis that transfusion-related adverse events may be in part caused by the excessive hemolysis of transfused red cells, which can lead to acute iron overload and related toxicity. This suggests that strategies aimed at avoiding or mitigating transfusion-related acute iron overload may improve the safety of red cell transfusions.

A retrospective observational study of leucoreductive strategies to manage patients with acute myeloid leukaemia presenting with hyperleucocytosis.

Acute myeloid leukaemia (AML) patients with hyperleucocytosis have higher early mortality, lower complete remission (CR) and overall survival (OS). Whether different pre-induction leucoreduction strategies can improve outcome is unknown. A single centre retrospective cohort study was conducted on AML patients with a white blood cell count (WBC) >100 × 10(9) /l between 1987 and 1997, and on all AML patients between 1998 and 2006, to determine (a) the effect of four different leucoreductive strategies (leukapheresis, hydroxycarbamide, leukapheresis and hydroxycarbamide or no pre-induction leucoreduction) on early (day 28) mortality, CR, and OS; and (b) whether a high presenting WBC remains a negative predictor of OS in patients surviving induction (first 28 d). In the 1998-2006 cohort (n = 702), higher WBC was associated with higher early mortality and lower OS but its effects were greatly diminished in patients who survived the first 28 d (Hazard Ratio 1·094 vs. 1·002). A WBC of 34·1 × 10(9) /l had the highest sensitivity (75·6%) and specificity (67·4%) for early mortality. None of the four leucoreduction strategies differed significantly in early mortality, CR, or OS in patients with WBC>100 × 10(9) /l (n = 166). The number of leucostatic signs was a significant predictor of early mortality (P < 0·0001) and OS (P = 0·0007). The results suggest that AML patients with hyperleucocytosis should be induced, if eligible, without pre-induction leucoreduction.

Making thawed universal donor plasma available rapidly for massively bleeding trauma patients: experience from the Pragmatic, Randomized Optimal Platelets and Plasma Ratios (PROPPR) trial.

BACKGROUND: The Pragmatic, Randomized Optimal Platelets and Plasma Ratios (PROPPR) trial was a randomized clinical trial comparing survival after transfusion of two different blood component ratios for emergency resuscitation of traumatic massive hemorrhage. Transfusion services supporting the study were expected to provide thawed plasma, platelets, and red blood cells within 10 minutes of request. STUDY DESIGN AND METHODS: At the 12 Level 1 trauma centers participating in PROPPR, blood components transfused and delivery times were tabulated, with a focus on universal donor (UD) plasma management. The adequacy of site plans was assessed by comparing the bedside blood availability times to study goals and the new American College of Surgeons guidelines. RESULTS: Eleven of 12 sites were able to consistently deliver 6 units of thawed UD plasma to their trauma-receiving unit within 10 minutes and 12 units in 20 minutes. Three sites used blood group A plasma instead of AB for massive transfusion without complications. Approximately 4700 units of plasma were given to the 680 patients enrolled in the trial. No site experienced shortages of AB plasma that limited enrollment. Two of 12 sites reported wastage of thawed AB plasma approaching 25% of AB plasma prepared. CONCLUSION: Delivering UD plasma to massively hemorrhaging patients was accomplished consistently and rapidly and without excessive wastage in high-volume trauma centers. The American College of Surgeons Trauma Quality Improvement Program guidelines for massive transfusion protocol UD plasma availability are practicable in large academic trauma centers. Use of group A plasma in trauma resuscitation needs further study.

Transfusion of plasma, platelets, and red blood cells in a 1:1:1 vs a 1:1:2 ratio and mortality in patients with severe trauma: the PROPPR randomized clinical trial.

IMPORTANCE: Severely injured patients experiencing hemorrhagic shock often require massive transfusion. Earlier transfusion with higher blood product ratios (plasma, platelets, and red blood cells), defined as damage control resuscitation, has been associated with improved outcomes; however, there have been no large multicenter clinical trials. OBJECTIVE: To determine the effectiveness and safety of transfusing patients with severe trauma and major bleeding using plasma, platelets, and red blood cells in a 1:1:1 ratio compared with a 1:1:2 ratio. DESIGN, SETTING, AND PARTICIPANTS: Pragmatic, phase 3, multisite, randomized clinical trial of 680 severely injured patients who arrived at 1 of 12 level I trauma centers in North America directly from the scene and were predicted to require massive transfusion between August 2012 and December 2013. INTERVENTIONS: Blood product ratios of 1:1:1 (338 patients) vs 1:1:2 (342 patients) during active resuscitation in addition to all local standard-of-care interventions (uncontrolled). MAIN OUTCOMES AND MEASURES: Primary outcomes were 24-hour and 30-day all-cause mortality. Prespecified ancillary outcomes included time to hemostasis, blood product volumes transfused, complications, incidence of surgical procedures, and functional status. RESULTS: No significant differences were detected in mortality at 24 hours (12.7% in 1:1:1 group vs 17.0% in 1:1:2 group; difference, -4.2% [95% CI, -9.6% to 1.1%]; P = .12) or at 30 days (22.4% vs 26.1%, respectively; difference, -3.7% [95% CI, -10.2% to 2.7%]; P = .26). Exsanguination, which was the predominant cause of death within the first 24 hours, was significantly decreased in the 1:1:1 group (9.2% vs 14.6% in 1:1:2 group; difference, -5.4% [95% CI, -10.4% to -0.5%]; P = .03). More patients in the 1:1:1 group achieved hemostasis than in the 1:1:2 group (86% vs 78%, respectively; P = .006). Despite the 1:1:1 group receiving more plasma (median of 7 U vs 5 U, P < .001) and platelets (12 U vs 6 U, P < .001) and similar amounts of red blood cells (9 U) over the first 24 hours, no differences between the 2 groups were found for the 23 prespecified complications, including acute respiratory distress syndrome, multiple organ failure, venous thromboembolism, sepsis, and transfusion-related complications. CONCLUSIONS AND RELEVANCE: Among patients with severe trauma and major bleeding, early administration of plasma, platelets, and red blood cells in a 1:1:1 ratio compared with a 1:1:2 ratio did not result in significant differences in mortality at 24 hours or at 30 days. However, more patients in the 1:1:1 group achieved hemostasis and fewer experienced death due to exsanguination by 24 hours. Even though there was an increased use of plasma and platelets transfused in the 1:1:1 group, no other safety differences were identified between the 2 groups. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT01545232.

Plasma: indications, controversies, and opportunities.

Plasma is overused as a blood product worldwide; however, data supporting appropriate use of plasma is scant. Its most common utilization is for treatment of coagulopathy in actively bleeding patients; it is also used for coagulation optimization prior to procedures with specific coagulation profile targets. A baseline literature review in PUBMED and Google Scholar was done (1 January 2000 to 1 June 2023), utilizing the following search terms: plasma, fresh frozen plasma, lyophilized plasma, indications, massive transfusion protocol, liver disease, warfarin reversal, cardiothoracic surgery, INR < 2. An initial review of the titles and abstracts excluded all articles that were not focused on transfusional medicine. Additional references were obtained from citations within the retrieved articles. This narrative review discusses the main indications for appropriate plasma use, mainly coagulation factor replacement, major hemorrhage protocol, coagulopathy in liver disease, bleeding in the setting of vitamin K antagonists, among others. The correlation between concentration of coagulation factors and INR, as well as the proper plasma dosing with its volume being weight-based, is also discussed. A high value approach to plasma utilization is supported with a review of the clinical situations where plasma is overutilized or unnecessary. Finally, a discussion of novel plasma products is presented for enhanced awareness.

Beta-Amyloid Related Neurodegenerative and Neurovascular Diseases: Potential Implications for Transfusion Medicine.

Cerebral amyloid angiopathy (CAA) is a progressive cerebrovascular and neurodegenerative disorder that is caused by the aberrant accumulation of soluble beta-amyloid isoforms in the small vessel walls of the cerebral and cerebellar cortices and the leptomeninges. Vascular beta-amyloid deposition increases vulnerability to intracerebral hemorrhage (ICH). Clinically, CAA can be the underlying cause of up to half of spontaneous lobar ICHs and can also present with convexity subarachnoid hemorrhage, transient focal neurologic episodes and progressive cognitive decline leading to dementia. The majority of CAA is sporadic, with increasing prevalence with age and often coexists with Alzheimer's Disease (AD). Genetic and iatrogenic etiologies are rare. Cases of CAA and AD have been linked to the use of cadaveric pituitary hormone and later life iatrogenic CAA has also been described following early-life neurosurgical procedures with cadaveric dura grafts. Together these data suggest a capacity of beta-amyloid transmissibility. A recent study found that in over 1 million transfusion recipients from donors who later developed (i) >1 ICH or (ii) one ICH event and dementia, had an elevated risk of developing future ICH. Considering prior reports of transfusion associated variant-Creutzfeldt Jakob Disease in humans and in vivo evidence in sheep, coupled with emerging data supporting beta-amyloid's prion-like properties, raises the question of whether CAA could be transmissible by blood transfusion. This would also have implications for screening, especially in an era of emerging plasma biomarkers of cerebral amyloidosis. Given the public health concerns raised by this biologically plausible question, there is a need for future studies with well-characterized definitions - and temporal ascertainment - of CAA exposure and outcomes to examine whether CAA is transfusion-transmissible, and, if so, with what frequency and timing of onset.

Utilization of frozen plasma in Ontario: a provincewide audit reveals a high rate of inappropriate transfusions.

BACKGROUND: Frozen plasma (FP) is frequently transfused inappropriately, an intervention that results in risk without benefit for the patient. To better understand current utilization practices in our region, we undertook a provincewide prospective audit to evaluate the clinical indications and appropriateness of FP transfusion. STUDY DESIGN AND METHODS: All hospitals in the Canadian province of Ontario with transfusion medicine services were invited to participate in a 5-day audit of FP utilization. FP dose, indication, and clinical patient data were collected for each transfusion request. Indications for FP transfusions were independently adjudicated as appropriate, inappropriate, or indeterminate based on predefined criteria. RESULTS: Seventy-six (49%) of 155 invited hospitals participated in the audit, which included 573 requests for 2012 units of FP. A total of 559 transfusions (1909 units) were administered. Of 573 requests, 164 (28.6%) were deemed inappropriate most often because: 1) they were administered to patients with an international normalized ratio below 1.5 or 2) they were administered in absence of bleeding or emergency surgery. The most frequent indications for FP transfusions were before surgery and warfarin reversal. Overall, patients admitted to the clinical areas of surgery, internal medicine, and the emergency department represented the largest users of FP, but this varied by hospital type (community vs. academic). The most frequently requested doses of FP were 2 and 4 units. CONCLUSION: This point-prevalence hospital audit revealed that transfusion of FP is frequently inappropriate. Focusing on reducing the two most common reasons for inappropriate FP transfusions could lead to a significant improvement in FP utilization.

Plasma transfusion for patients with severe hemorrhage: what is the evidence?

The following review will detail the current knowledge in massive hemorrhage with regard to the pathophysiology of the coagulation disturbance, the role of plasma, the role of alternatives to plasma, and the clinical value of having a massive transfusion protocol. The coagulation disturbance in trauma patients is more than just the result of consumption of clotting factors at sites of injury and dilution from the infusion of intravenous fluids and red blood cells (RBCs). Even before substantial amounts of fluid resuscitation and RBC transfusion, one-quarter of trauma patients already have abnormal coagulation variables. There is an apparent role for the activation of protein C, hypofibrinogenemia, and fibrin(gen)olysis in the coagulation disturbance after trauma and massive hemorrhage. None of these three disturbances would be completely mitigated by the use of plasma alone, suggesting that there may be an opportunity to improve care of these patients with alternative strategies, such as fibrinogen concentrates and antifibrinolytics. Despite numerous retrospective cohort studies evaluating 1:1 plasma to RBC formula-driven resuscitation, the overall clinical value of this approach is unclear. Studies have even raised concerns regarding a potential increase in morbidity associated with this approach, particularly for patients overtriaged to 1:1 where a massive transfusion is unlikely. We also do not have sufficient evidence to recommend either goal-directed therapy with thromboelastography or early use of fibrinogen replacement, with either cryoprecipitate or fibrinogen concentrates. We have high-quality data that argue against the role for recombinant Factor VIIa that should prompt removal of this strategy from existing protocols. In contrast, we have high-level evidence that all bleeding trauma patients should receive tranexamic acid as soon as possible after injury. This therapy must be included in hemorrhage protocols. If we are to improve the care of massively bleeding patients on a firm scientific ground, we will need large-scale randomized trials to delineate the role of coagulation replacement and the utility of laboratory monitoring. But even until these trials are completed, it is clear that a massive transfusion protocol is needed in all hospitals that manage bleeding patients, to ensure a prompt and coordinated response to hemorrhage.

Acute kidney injury after cardiac surgery: focus on modifiable risk factors.

BACKGROUND: Acute kidney injury (AKI) after cardiac surgery is a major health issue. Lacking effective therapies, risk factor modification may offer a means of preventing this complication. The objective of the present study was to identify and determine the prognostic importance of such risk factors. METHODS AND RESULTS: Data from a multicenter cohort of 3500 adult patients who underwent cardiac surgery at 7 hospitals during 2004 were analyzed (using multivariable logistic regression modeling) to determine the independent relationships between 3 thresholds of AKI (>25%, >50%, and >75% decrease in estimated glomerular filtration rate within 1 week of surgery or need for postoperative dialysis) with death rates, as well as to identify modifiable risk factors for AKI. The 3 thresholds of AKI occurred in 24% (n=829), 7% (n=228), and 3% (n=119) of the cohort, respectively. All 3 thresholds were independently associated with a >4-fold increase in the odds of death and could be predicted with several perioperative variables, including preoperative intra-aortic balloon pump use, urgent surgery, and prolonged cardiopulmonary bypass. In particular, 3 potentially modifiable variables were also independently and strongly associated with AKI. These were preoperative anemia, perioperative red blood cell transfusions, and surgical reexploration. CONCLUSIONS: AKI after cardiac surgery is highly prevalent and prognostically important. Therapies aimed at mitigating preoperative anemia, perioperative red blood cell transfusions, and surgical reexploration may offer protection against this complication.

Reducing redundant creatine kinase testing in cardiac injury.

BACKGROUND: Creatine kinase (CK) testing in the setting of suspected cardiac injury is commonly performed yet rarely provides clinical value beyond troponin testing. We sought to evaluate and reduce CK testing coupled with troponin testing by 50% or greater. METHODS: We performed root cause analysis to study prevailing processes and patterns of CK testing. We developed new institutional guidelines, removed CK from high-volume paper and electronic order bundles and conducted academic detailing for departments with highest ordering frequency. We evaluated consecutive patients at Sunnybrook Health Sciences Centre between 1 January 2018 and 31 March 2020 who had either a CK or troponin level measured. We prespecified successful implementation as a reduction of 50% in total CK orders and a decrease in the ratio of CK-to-troponin tests to one-third or less. We retained additional data beyond our study period to assess for sustained reductions in testing. RESULTS: Total CK tests decreased over the study period from 3963 to 2111 per month, amounting to a 46.7% reduction (95% CI 33.2 to 60.2; p<0.001) equalling 61 fewer tests per hospital day. Troponin testing did not significantly change during the intervention. Ratio of CK-to-troponin tests decreased from 0.91 to 0.49 (p<0.001). The reduction coincided with changes to order-sets, was observed across all clinical units and was sustained during additional months beyond the study period. These reductions in testing resulted in a projected annual cost savings of C$28 446. CONCLUSIONS: We demonstrate that a low-cost and feasible quality improvement initiative may lead to significant reduction in unnecessary CK testing and substantial savings in healthcare costs for patients with suspected cardiac injury.