Thromboelastography (TEG) or Thromboelastometry (ROTEM) to Guide Hemostatic Management Versus Usual Care in Adults Undergoing Cardiac Surgery: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Search strategy

We conducted a comprehensive literature search in PubMed, Scopus, Web of Science, and Own institutional RCT to identify randomized controlled trials (RCTs) evaluating the impact of thromboelastography (TEG) or rotational thromboelastometry (ROTEM)-guided transfusion strategies in adult patients undergoing cardiac surgery. The search covered the period from database inception to May 2025. The strategy incorporated a combination of Medical Subject Headings (MeSH) and free-text terms related to viscoelastic testing, cardiac surgical interventions, and transfusion practices. Boolean operators “AND” and “OR” were used to enhance both the sensitivity and specificity of the query.

The search string used for PubMed was as follows:

(“thromboelastography” OR “TEG” OR “rotational thromboelastometry” OR “ROTEM”) AND (“cardiac surgery” OR “cardiothoracic surgery” OR “CABG” OR “valve surgery” OR “aortic surgery”) AND (“transfusion” OR “blood component therapy” OR “hemostasis”).

Equivalent queries were adapted for Scopus and Web of Science using appropriate syntax and controlled vocabulary. No restrictions were applied regarding language, publication date, or publication status. Additionally, reference lists of all included studies and relevant systematic reviews were manually screened to identify any potentially eligible articles not captured in the electronic database search.

All retrieved citations were imported into EndNote X9 reference management software. Duplicate entries were removed using the software’s automatic de-duplication function, and results were manually verified for accuracy. A summary of the Boolean search combinations and the number of retrieved records per database is presented in Table 1.

All references were screened using a two-step selection process in accordance with PRISMA 2020 guidelines. First, two independent reviewers (SK and NM) screened titles and abstracts to exclude clearly irrelevant records, including non-randomized designs, pediatric studies, and articles lacking transfusion-related outcomes. In the second phase, full-text articles were assessed against predefined inclusion criteria: RCTs enrolling adults (≥18 years) undergoing cardiac surgery and comparing TEG- or ROTEM-guided transfusion protocols with conventional laboratory-based strategies. Eligible studies were required to report at least one clinical outcome of interest, including allogeneic blood product use, reoperation for bleeding, ICU or hospital stay, or thromboembolic events. Discrepancies in study selection were resolved through consensus or adjudicated by a third reviewer (YK) ( Figure 1).

Figure 1. Structured search strategy for the systematic review and meta-analysis: Databases, Boolean Logic, and Screening Process (PRISMA 2020-Compliant).

Data extraction and quality assessment

Two independent reviewers (SK and NM) performed data extraction using a standardized, prepiloted form. Extracted variables included study characteristics (author, year, country), patient demographics (age, sex), type of surgery (CABG, valve, aortic), viscoelastic platform used (TEG or ROTEM), details of transfusion algorithms, and clinical outcomes (total blood products transfused, reoperation for bleeding, ICU stay, thromboembolic events, and mortality). Funding disclosures and potential conflicts of interest were also recorded. If data were incomplete or unclear, study authors were contacted for clarification.

Risk of bias for each included randomized controlled trial was independently assessed by the same two reviewers using the Cochrane Risk of Bias 2.0 (RoB 2.0) tool, which evaluates five domains: randomization, deviations from intended interventions, missing data, outcome measurement, and selective reporting. Each domain was judged as “low risk,” “some concerns,” or “high risk.” Discrepancies in data extraction or bias assessment were resolved through discussion or consultation with a third reviewer (YK).

Data analysis

All statistical analyses were conducted using RevMan software version 5.4.1 (The Cochrane Collaboration, Copenhagen, Denmark). A random-effects model was used for all meta-analyses to account for expected clinical and methodological heterogeneity among trials. For continuous outcomes (e.g., total blood products transfused), we calculated mean differences (MDs) with 95% confidence intervals (CIs). For dichotomous outcomes (e.g., reoperation for bleeding, thromboembolic events, and mortality), we calculated risk ratios (RRs) and 95% CIs.

An intention-to-treat analysis was applied for dichotomous outcomes. For continuous outcomes, we did not impute missing data, in accordance with Cochrane Handbook recommendations.

Statistical heterogeneity was assessed visually using forest plots and quantified using the I² statistic. The I² values were interpreted as follows: 0–40% might not be important; 30–60% may represent moderate heterogeneity; 50–90% substantial heterogeneity; and 75–100% considerable heterogeneity. Where I² exceeded 50%, we investigated potential sources of heterogeneity. The significance of heterogeneity was further evaluated using the Cochrane Chi² test (Q-test), with a p-value threshold of <0.10 indicating significant heterogeneity.

To evaluate publication bias, we reviewed clinical trial registries (ClinicalTrials.gov and WHO ICTRP) and searched for unpublished studies. For outcome reporting bias, we compared trial protocols (when available) with their published results.

The following prespecified subgroup analyses were conducted for the primary and secondary outcomes: (i) viscoelastic platform (TEG vs. ROTEM); (ii) surgery type (CABG vs. valve vs. aortic surgery); (iii) urgency (elective vs. emergent surgery); (iv) use of antifibrinolytics (yes vs. no); and (v) transfusion algorithm complexity (standardized vs. center-specific).

Prespecified sensitivity analyses included: (i) exclusion of trials with high risk of bias in randomization; (ii) analysis limited to trials with complete outcome data; and (iii) exclusion of trials with unclear or inconsistent definitions of bleeding-related endpoints.

Summary of findings tables were generated for the primary and secondary outcomes, with evidence certainty assessed using the GRADE approach. Two independent reviewers (SK and NM) graded the certainty of evidence, and discrepancies were resolved by consultation with a third reviewer (YK).

Difference between the protocol and review

During the review process, we incorporated an additional subgroup analysis based on the type of viscoelastic platform used (TEG versus ROTEM), which was not explicitly prespecified in the initial protocol. This decision was made to account for potential variability in testing methodologies and transfusion algorithms between platforms. Furthermore, we extended our analysis to include studies with combined cardiac surgical procedures (e.g., CABG plus valve surgery), provided that transfusion outcomes were reported separately or could be extracted reliably. These modifications were undertaken post hoc to enhance the clinical applicability and comprehensiveness of the evidence synthesis.

Eligibility criteria

Studies were considered eligible if they were identified through a structured search of PubMed, Scopus, and Web of Science databases from inception to May 2025. The search strategy combined both keywords and MeSH terms related to viscoelastic testing (“thromboelastography,” “TEG,” “ROTEM”), cardiac surgical procedures (“cardiac surgery,” “CABG,” “valve surgery,” “aortic surgery”), and transfusion-related outcomes (“transfusion,” “hemostasis,” “blood component therapy”). Boolean operators (AND, OR) were applied to optimize sensitivity. In addition to database searches, reference lists of relevant articles and systematic reviews were manually screened to capture additional studies meeting the inclusion criteria ( Figure 2).

Figure 2. Eligibility criteria for inclusion in systematic review.

Eligibility was determined based on the PICOS/T framework as follows:

Exclusion criteria

The following studies were excluded: non-randomized designs (e.g., retrospective or observational studies), those involving pediatric populations, studies lacking a comparator group or relevant transfusion data, non-peer-reviewed literature such as reviews, editorials, and conference abstracts, as well as studies that employed TEG or ROTEM solely for observational purposes without applying intervention-based transfusion algorithms ( Figure 3).

Figure 3. Flowchart showing key conditions excluding patients from the metanalysis.

Search results and characteristics of included trials

The study selection process adhered to the PRISMA 2020 guidelines. Two independent reviewers (SK and NM) screened all records in two phases: an initial title and abstract screening, followed by a full-text review of potentially eligible articles. Discrepancies were resolved by consensus or through adjudication by a third reviewer (YK).

A total of 343 records were initially identified—342 through electronic databases (PubMed, Scopus, and Web of Science) and one from institutional data. After removing duplicates and irrelevant titles, 27 full-text articles were assessed for eligibility. Of these, 14 were not retrievable and 6 were excluded for being non-randomized studies. Ultimately, seven randomized controlled trials (RCTs), including one institutional RCT, were included in the qualitative synthesis and meta-analysis ( Figure 4).^1–5,7,8 The PRISMA 2020 Flow Diagram—which summarizes the stages of study identification, screening, eligibility, and inclusion—are both available in publicly accessible repositories: PRISMA Checklist: Khallikane et al., 2025. https://doi.org/10.6084/m9.figshare.29546369.v1

Figure 4. PRISMA 2020 flow diagram.

These trials, published between 1999 and 2022, collectively enrolled 1,043 adult patients undergoing a range of cardiac surgeries, including coronary artery bypass grafting (CABG), valve replacement, and aortic surgery with circulatory arrest. Sample sizes varied between 84 and 224 participants. Five studies utilized ROTEM-guided transfusion algorithms, while two trials employed TEG-based strategies. In all cases, the intervention groups received viscoelastic-guided transfusion protocols, whereas the control groups followed standard management based on conventional coagulation tests such as prothrombin time (PT), activated partial thromboplastin time (aPTT), and plasma fibrinogen levels.

Across studies, primary outcomes consistently included the volume of allogeneic blood products administered, incidence of reoperation for bleeding, and length of ICU stay. All trials demonstrated a reduction in transfusion requirements in the viscoelastic-guided groups, supporting the utility of TEG or ROTEM in enhancing perioperative hemostatic control ( Table 2).^1–5,7,8

Risk of bias assessments

The risk of bias for each included study was evaluated using the Cochrane Risk of Bias 2.0 tool, which assesses five key domains: the randomization process, deviations from intended interventions, missing outcome data, measurement of the outcome, and selection of the reported result. Most randomized controlled trials showed a low risk of bias in the randomization and outcome measurement domains. However, several studies received a rating of “some concerns” due to the absence of blinding, potentially introducing performance bias. Overall, the methodological quality of the included trials was rated as moderate to high.

In addition, observational studies were assessed using the Newcastle-Ottawa Scale. These studies were generally of moderate quality, with minor concerns regarding the representativeness of cohorts and outcome ascertainment. A detailed summary of the risk of bias assessments is presented in Table 3 and visualized in Figure 5.^1–5,7,8

Figure 5. Risk of bias assessment (RoB 2.0 tool).

Primary outcome

This systematic review and meta-analysis aimed to assess whether transfusion strategies guided by viscoelastic testing (TEG or ROTEM) reduce the use of allogeneic blood products in adult cardiac surgery compared to conventional coagulation testing (CCTs).

Across all included randomized controlled trials, viscoelastic-guided strategies were consistently associated with a significant reduction in the total number of allogeneic blood products administered during cardiac surgery. Compared to conventional management using standard coagulation tests such as PT, aPTT, and fibrinogen levels, TEG and ROTEM enabled more precise transfusion decisions, resulting in reduced use of red blood cells (RBCs), fresh frozen plasma (FFP), platelets, and cryoprecipitate. In individual trials, the mean reduction in transfusion volume ranged from 0.7 to 2.3 units per patient. For instance, Weber et al. reported a 35% reduction in RBCs and a 45% reduction in FFP with ROTEM guidance (p < 0.01), while Görlinger et al. observed a 49% overall decrease in transfusion requirements, along with cost savings exceeding 30%.^1–5,7,8 ( Table 4)

The meta-analysis of seven RCTs demonstrated a pooled mean difference of −0.86 units of allogeneic blood products (95% CI: [−1.04, −0.67]), with no observed between-study heterogeneity (τ² = 0), reinforcing the statistical robustness of these findings ( Figure 6). Moreover, viscoelastic methods provided significant operational advantages over CCTs, including a 76.2% reduction in turnaround time (12.5 vs. 52.5 minutes), superior clot characterization and transfusion personalization scores (5/5 vs. 2/5; +150%), and improved blood product utilization efficiency (4.5/5 vs. 2.5/5; +80%) ( Figure 7).

Figure 6. Forest plot of the primary outcomes illustrating the mean difference in allogeneic blood product use (units) between TEG/ROTEM-guided transfusion and conventional care in cardiac surgery.

Figure 7. Comparative performance of TEG/ROTEM versus conventional coagulation tests (CCTs) across four domains: time to results, clot assessment detail, personalized transfusion, and product use efficiency.

Values shown as absolute scores and relative improvement percentages.

Collectively, these results underscore the clinical and economic value of incorporating TEG and ROTEM into perioperative transfusion protocols for adult patients undergoing high-risk cardiac surgery.

Patient population: Adults undergoing cardiac surgery (CABG, valve replacement, aortic procedures).

Setting: Cardiac surgical ICUs and operating rooms across multiple international centers.

Intervention: TEG- or ROTEM-guided transfusion strategies.

Comparison: Conventional transfusion management using standard coagulation tests (PT, aPTT, fibrinogen).

The anticipated effect in the intervention group (with 95% CI) is based on comparative reduction from baseline transfusion usage in the control group and observed relative effect sizes.

CI: confidence interval; CABG: coronary artery bypass grafting; DHCA: deep hypothermic circulatory arrest; ICU: intensive care unit; TEG: thromboelastography; ROTEM: rotational thromboelastometry.

GRADE Working Group grades of evidence:

Footnotes:

a- Downgraded one level due to concerns about lack of blinding or prespecified analysis protocols in included RCTs.

b- Downgraded one level due to small sample sizes in some trials.

c- Downgraded two levels due to wide confidence intervals or inconsistency in reporting of transfusion volume across studies.

Secondary outcomes

Across the seven randomized controlled trials included in this review, viscoelastic-guided transfusion strategies (TEG or ROTEM) were consistently associated with improved secondary clinical outcomes compared to conventional laboratory-based protocols ( Table 5).

Reoperation for bleeding was reported in six of the seven studies. Rates were consistently lower in the intervention groups: Westbrook et al. (2009) reported 2/20 (10%) vs 4/20 (20%); Girdauskas et al. (2010) 5/60 (8.3%) vs 9/60 (15%); Haensig et al. (2019) 3/50 (6%) vs 6/50 (12%); Weber et al. (2012) 6/58 (10.3%) vs 11/58 (19%); Shore-Lesserson et al. (1999) 4/45 (8.9%) vs 7/45 (15.6%); and Ak et al. (2009) 3/40 (7.5%) vs 6/40 (15%). The pooled relative risk indicated a beneficial trend favoring the TEG/ROTEM group, with moderate heterogeneity (I² = 41%). These findings suggest a reduction in the need for reoperation, a key marker of perioperative hemostatic failure.

ICU length of stay was modestly reduced in three trials. Westbrook et al. (2009) reported a mean ICU stay of 2.1 days in the TEG group versus 2.6 in the control group; Weber et al. (2012) reported 1.9 vs 3.1 days; and Karrar et al. (2022) observed 2.2 vs 3.0 days. The pooled mean difference was -0.64 days (95% CI: -1.41 to 0.13; I² = 47%), indicating a potential but not statistically significant reduction in ICU stay duration. Variability in ICU admission and discharge protocols may have contributed to between-study heterogeneity.

Thromboembolic events were rare and numerically lower in the intervention groups. Westbrook et al. (2009) reported 0/20 vs 1/20 (5%); Weber et al. (2012) 0/58 vs 2/58 (3.4%); Ak et al. (2009) 0/40 vs 1/40 (2.5%); and Girdauskas et al. (2010) 0/60 vs 1/60 (1.7%). Other studies did not report thromboembolic complications. Due to the low number of events, no formal meta-analysis was conducted for this endpoint. Importantly, none of the trials showed an increased thrombotic risk with viscoelastic-guided management.

These findings support the role of TEG/ROTEM-guided transfusion algorithms in reducing perioperative bleeding complications and possibly ICU resource utilization, without increasing thromboembolic risks.

Safety outcomes

No included trial demonstrated a significant increase in thromboembolic events—such as myocardial infarction, stroke, deep vein thrombosis, or pulmonary embolism—in patients managed with TEG/ROTEM-guided transfusion strategies. On the contrary, several studies, including Westbrook et al. (2009), Haensig et al. (2019), Girdauskas et al. (2010), and Ak et al. (2009), observed a trend toward fewer reoperations for bleeding in the viscoelastic arms, suggesting a potential clinical benefit even if not statistically significant. ICU length of stay was reported in five of the seven trials, with reductions noted in Weber et al. (2012), Karrar et al. (2022), and Haensig et al. (2019). However, outcome definition heterogeneity limited formal pooling. Importantly, no study reported increased mortality or serious adverse events linked to viscoelastic-guided transfusion.^{1,2,3–5,7,8} ( Table 6)

Efficacy outcomes

All seven randomized trials reported a reduction in allogeneic blood product transfusion among patients managed with TEG/ROTEM-guided protocols, with the most consistent effects observed in red blood cell (RBC) and fresh frozen plasma (FFP) use. Mean reductions ranged from 0.7 to 2.3 units compared to standard care. Across studies, statistical significance was generally defined as p < 0.05, and most reported differences met this threshold. Ak et al. (2009) and Shore-Lesserson et al. (1999) also demonstrated significant reductions in platelet transfusions, while Weber et al. (2012) highlighted improved timing and precision in correcting coagulopathy, resulting in more efficient transfusion practices. Similar trends were confirmed by Haensig et al. (2019) and Girdauskas et al. (2010), particularly in high-risk valve and aortic procedures. The benefit was most pronounced in surgeries with elevated bleeding risk, such as aortic surgery with circulatory arrest, as seen in Karrar et al. (2022), where ROTEM-guided management significantly lowered total transfusion volume while maintaining clinical stability.^1–5,7,8 ( Table 7)

Limitations and need for confirmation

This systematic review and meta-analysis has several important limitations. First, although all included trials focused on adult cardiac surgery, there was considerable heterogeneity in surgical procedures—ranging from isolated CABG to complex aortic surgeries involving circulatory arrest—which introduces variability in bleeding risk and transfusion thresholds, limiting the generalizability of the pooled findings. Second, the studies differed in their use of viscoelastic platforms (TEG vs. ROTEM), transfusion algorithms, and intervention thresholds (e.g., MA or FIBTEM cut-offs), making cross-trial comparisons less reliable and potentially contributing to differences in effect size. Third, secondary outcomes such as reoperation for bleeding, ICU stay, and thromboembolic events were inconsistently defined and incompletely reported, which restricted formal pooling and may have introduced selective reporting bias. Additionally, most trials had small sample sizes (n = 84–224), reducing statistical power to detect infrequent but clinically meaningful events such as thromboembolic complications or mortality. The lack of blinding in nearly all studies further raises the risk of performance and detection bias, especially for outcomes influenced by clinician judgment. Due to the limited number of RCTs, subgroup or meta-regression analyses based on surgical type, viscoelastic modality, or baseline coagulopathy could not be conducted. Furthermore, the review excluded observational studies, gray literature, and non-English publications, which, while enhancing methodological rigor, may have resulted in the omission of relevant real-world data and introduced publication bias. The wide temporal span of the studies (1999–2022) also poses a challenge, as earlier trials used outdated devices and protocols, potentially underestimating the benefit of current viscoelastic technologies. Finally, no included study provided robust data on cost-effectiveness or logistical feasibility, such as equipment costs, staff training, or integration into perioperative workflows—key factors that will influence future implementation. Despite these limitations, the consistency of the observed reductions in transfusion volume across diverse settings supports the clinical utility of TEG/ROTEM-guided strategies in modern cardiac surgery.