Development of a risk prediction model for transfusion in carotid endarterectomy and demonstration of cost-saving potential by avoidance of "type and screen"

Systematic review highlights high risk of bias of clinical prediction models for blood transfusion in patients undergoing elective surgery

BACKGROUND

Blood transfusion can be a lifesaving intervention after perioperative blood loss. Many prediction models have been developed to identify patients most likely to require blood transfusion during elective surgery, but it is unclear whether any are suitable for clinical practice.

STUDY DESIGN AND SETTING

We conducted a systematic review, searching MEDLINE, Embase, PubMed, The Cochrane Library, Transfusion Evidence Library, Scopus, and Web of Science databases for studies reporting the development or validation of a blood transfusion prediction model in elective surgery patients between January 1, 2000 and June 30, 2021. We extracted study characteristics, discrimination performance (c-statistics) of final models, and data, which we used to perform risk of bias assessment using the Prediction model risk of bias assessment tool (PROBAST).

RESULTS

We reviewed 66 studies (72 developed and 48 externally validated models). Pooled c-statistics of externally validated models ranged from 0.67 to 0.78. Most developed and validated models were at high risk of bias due to handling of predictors, validation methods, and too small sample sizes.

CONCLUSION

Most blood transfusion prediction models are at high risk of bias and suffer from poor reporting and methodological quality, which must be addressed before they can be safely used in clinical practice.

An update on red blood cell transfusion in non-cardiac thoracic surgery

BACKGROUND

The aim of this study was to evaluate risk factors for red blood cell (RBC) transfusion in non-cardiac thoracic surgery.

METHODS

All patients undergoing non-cardiac thoracic surgery in a single tertiary referral center between January and December 2021 were eligible for this study. Data on blood requests and perioperative RBC transfusion were retrospectively analyzed.

RESULTS

A total of 379 patients were included, of whom 275 (72.6%) underwent elective surgery. The overall RBC transfusion rate was 7.4% (elective cases: 2.5%, non-elective cases: 20.2%). Patients with lung resections required transfusion in 2.4% of the cases versus 44.7% in patients undergoing surgery for empyema. In multivariable analysis, empyema (P=0.001), open surgery (P<0.001), low preoperative hemoglobin (P=0.001), and old age (P=0.013) were independent risk factors for RBC transfusion. The best predictor of blood transfusion was preoperative hemoglobin with a cut-off value <10.4 g/dL (sensitivity 82.1%, specificity 86.3%, area under the curve 0.882).

CONCLUSIONS

The rate of RBC transfusion in current non-cardiac thoracic surgery is low, especially in elective lung resections. In urgent cases and open surgery, transfusion rates remain high, particularly in empyema cases. Preoperative requesting of RBC units should be tailored to patient-specific risk factors.

Cost-effectiveness of routine type and screens in select urological surgeries

PURPOSE

To evaluate the cost-effectiveness of obtaining a preoperative type and screen (T/S) for common urologic procedures.

METHODS

A decision tree model was constructed to track surgical patients undergoing two preoperative blood ordering strategies as follows: obtaining a preoperative T/S versus not doing so. The model was applied to the National (Nationwide) Inpatient Sample (NIS) data, from January 1, 2006 to September 30, 2015. Cost estimates for the model were created from combined patient-level data with published costs of a T/S, type and crossmatch (T/C), a unit of pRBC, and one unit of emergency-release transfusion (ERT). The primary outcome was the incremental cost per ERT prevented, expressed as an incremental cost-effectiveness ratio (ICER) between the two preoperative blood ordering strategies. A cost-effectiveness analysis determined the ICER of obtaining preoperative T/S to prevent an emergency-release transfusion (ERT), with a willingness-to-pay threshold of $1,500.00.

RESULTS

A total of 4,113,144 surgical admissions from 2006 to 2015 were reviewed. The overall transfusion rate was 10.54% (95% CI, 10.17-10.91) for all procedures. The ICER of preoperative T/S was $1500.00 per ERT prevented. One-way sensitivity analysis demonstrated that the risk of transfusion should exceed 4.12% to justify preoperative T/S.

CONCLUSION

Routine preoperative T/S for radical prostatectomy (rate = 3.88%) and penile implants (rate = .91%) does not represent a cost-effective practice for these surgeries. It is important for urologists to review their institution T/S policy to reduce inefficiencies within the preoperative setting.

Selective type & screen for elective colectomy based on a transfusion risk score may generate substantial cost savings

BACKGROUND

Preoperative type and screen are currently recommended for all patients undergoing colectomy. We aimed to identify risk factors for transfusion and define a low-risk cohort of patients undergoing colectomy in whom type and screen may be safely avoided.

METHODS

We identified all patients undergoing elective colectomy in the National Surgical Quality Improvement Project-Targeted Colectomy files from 2012 to 2016. Patients transfused preoperatively and those undergoing other concurrent major abdominal procedures were excluded. We compared patients who received blood transfusion on the day of surgery to those who did not. Half of the cohort was randomly selected for development of a points-based model predicting blood transfusion on the day of surgery. This model was then validated using the remaining patients.

RESULTS

Of 61,964 patients undergoing colectomy, 3128 (5%) patients were transfused with 1290 (2.1%) occurring on the day of surgery. Preoperative anemia was the strongest predictor of blood transfusion on the day of surgery. Among patients with hematocrit > 35%, day of surgery transfusion risk was 0.8%; 99% of patients with hematocrit > 35% had a score 20 or less. Selective type and screen for patients with score ≤ 20 or hematocrit > 35% would avoid type and screen in 91% and 81% of patients, respectively.

CONCLUSION

Transfusion following elective colectomy is rare and can be accurately predicted by preoperative patient characteristics. Selective type and screen based on these parameters have the potential to prevent operative delays and lower cost.

A Multi-Centre, Single-Arm Clinical Study to Confirm Safety and Performance of PuraStat®, for the Management of Bleeding in Elective Carotid Artery Surgery

Anastomotic bleeding in vascular surgery can be difficult to control. Patients, in particular those undergoing carotid surgery, have often been started on treatment with dual antiplatelet agents and receive systemic heparinization intraoperatively. The use of local hemostatic agents as an adjunct to conventional methods is widely reported. 3-D Matrix's absorbable hemostatic material RADA16 (PuraStat®), is a fully synthetic resorbable hemostatic agent. The aim of this study is to confirm the safety and performance of this agent when used to control intraoperative anastomotic bleeding during carotid endarterectomy (CEA). A prospective, single-arm, multicenter study involving 65 patients, undergoing CEA, in whom the hemostatic agent was applied to the suture line after removal of arterial clamps. Patients were followed up at 24 h, discharge, and one month after surgery. Time to hemostasis was measured as the primary endpoint. Secondary endpoints included hemostasis efficacy and safety outcomes, blood loss, intraoperative and postoperative administration of blood products, and incidence of reoperation for bleeding. A total of 65 cases (51 male and 14 female) undergoing CEA, utilizing patch reconstruction (90. 8%), eversion technique (6.1%), and direct closure (3.1%) were analyzed. All patients received dual antiplatelet therapy preoperatively and were administered systemic intravenous heparin intraoperatively, as per local protocol. The mean time to hemostasis was 83 s ± 105 s (95% CI: 55-110 s). Primary hemostatic efficacy was 90.8%. The mean volume of product used was 1.7 mL ± 1.1 mL. Hemostasis was achieved with a single application of the product in 49 patients (75.3%). Two patients required a transfusion of blood products intraoperatively. There were no blood product transfusions during the postoperative period. The intraoperative mean blood loss was 127 mL ± 111.4 mL and postoperatively, the total mean drainage volume was 49.0 mL ± 51.2 mL. The mean duration of surgery was 119 ± 35 min, and the mean clamp time was 35 min 12 s ± 19 min 59 s. In 90.8% of patients, there was no presence of hematoma at 24 h postoperatively. Three returned to theatre due to bleeding (2 in the first 24 h), however, none of these cases were considered product related. Overall, there were no device-related serious adverse events (SAE) or unanticipated device-related SAEs reported. Use of the hemostatic agent PuraStat® is associated with a high rate of hemostatic efficacy (90.8%) and a short time to hemostasis. The safety of the product for use on vascular anastomoses has been demonstrated.

External Validation of Risk Prediction Models to Improve Selection of Patients for Carotid Endarterectomy

BACKGROUND AND PURPOSE

The net benefit of carotid endarterectomy (CEA) is determined partly by the risk of procedural stroke or death. Current guidelines recommend CEA if 30-day risks are <6% for symptomatic stenosis and <3% for asymptomatic stenosis. We aimed to identify prediction models for procedural stroke or death after CEA and to externally validate these models in a large registry of patients from the United States.

METHODS

We conducted a systematic search in MEDLINE and EMBASE for prediction models of procedural outcomes after CEA. We validated these models with data from patients who underwent CEA in the American College of Surgeons National Surgical Quality Improvement Program (2011-2017). We assessed discrimination using C statistics and calibration graphically. We determined the number of patients with predicted risks that exceeded recommended thresholds of procedural risks to perform CEA.

RESULTS

After screening 788 reports, 15 studies describing 17 prediction models were included. Nine were developed in populations including both asymptomatic and symptomatic patients, 2 in symptomatic and 5 in asymptomatic populations. In the external validation cohort of 26 293 patients who underwent CEA, 702 (2.7%) developed a stroke or died within 30-days. C statistics varied between 0.52 and 0.64 using all patients, between 0.51 and 0.59 using symptomatic patients, and between 0.49 to 0.58 using asymptomatic patients. The Ontario Carotid Endarterectomy Registry model that included symptomatic status, diabetes, heart failure, and contralateral occlusion as predictors, had C statistic of 0.64 and the best concordance between predicted and observed risks. This model identified 4.5% of symptomatic and 2.1% of asymptomatic patients with procedural risks that exceeded recommended thresholds.

CONCLUSIONS

Of the 17 externally validated prediction models, the Ontario Carotid Endarterectomy Registry risk model had most reliable predictions of procedural stroke or death after CEA and can inform patients about procedural hazards and help focus CEA toward patients who would benefit most from it.

Development of a preoperative risk score predicting allogeneic red blood cell transfusion in children undergoing spinal fusion

BACKGROUND

Children undergoing spinal fusion often receive blood products. The goal of this study was to develop a preoperative score to help physicians identify those who are at risk of allogeneic red blood cell (RBC) transfusion.

STUDY DESIGN AND METHODS

This retrospective study of children undergoing spinal fusion in the ACS-NSQIP Pediatric database (2016-2019) aimed at identifying risk factors associated with allogeneic RBC transfusion. Univariable logistic regression and multivariable logistic regression were performed using preoperative patient characteristics and aided in the creation of a simplified scoring system.

RESULTS

Out of 13,929 total patients, 2990 (21.5%) were transfused. We created a risk score based on 10 independent predictors of transfusion: age, sex, race, weight < 3rd percentile, American Society of Anesthesiologists physical status classification, cardiac risk factors, hematologic disease, preoperative anemia, deformity type, and number of spinal levels to be fused. Patients in both the training and testing cohorts were assigned a score ranging from 0 (lowest risk) to 21 (highest risk). The developed transfusion risk score showed 77% accuracy in distinguishing patients who did not receive a transfusion during or soon after surgery (AUROC 0.7736 [95% CI, 0.7619-0.7852]) in the training cohort and 77% accuracy (AUROC 0.7732 [95% CI, 0.7554-0.7910]) in the testing cohort.

DISCUSSION

Our score, based on routinely available preoperative data, accurately estimates the risk of allogeneic RBC transfusion in pediatric patients undergoing spinal fusion. Future studies will inform whether patient blood management interventions targeted to high-risk patients can help reduce the need for transfusion and improve outcomes.

A preoperative risk score for transfusion in infrarenal endovascular aneurysm repair to avoid type and cross

OBJECTIVE

Preoperative type and cross are often routinely ordered before elective endovascular aneurysm repair (EVAR), but the cost of this practice is high, and transfusion is rare. We therefore aimed to stratify patients by their risk of transfusion to identify a cohort in whom a type and screen would be sufficient.

METHODS

We queried the targeted vascular module of the National Surgical Quality Improvement Program (NSQIP) for all elective EVARs from 2011 to 2015. We included only infrarenal aneurysms and excluded ruptured aneurysms and patients transfused within 72 hours preoperatively. Two-thirds of the cases were randomly assigned to a model derivation cohort and one third to a validation cohort. We created and subsequently validated a risk model for transfusion within the first 24 hours of surgery (including intraoperatively), using logistic regression.

RESULTS

Between 2011 and 2015, there were 4875 patients who underwent elective infrarenal EVAR, only 221 (4.5%) of whom received a transfusion within 24 hours of surgery. The frequency of transfusion during the study period declined monotonously from 6.5% in 2011 to 3.2% in 2015. The factors independently associated with transfusion were preoperative hematocrit <36% (odds ratio [OR], 3.4 [95% confidence interval, 2.1-5.4]; P < .001), aortic diameter (per centimeter increase: OR, 1.2 [1.03-1.4]; P = .02), preoperative dependent functional status (OR, 2.5 [1.1-5.5]; P = .03), and chronic obstructive pulmonary disease (OR, 1.7 [1.04-2.9]; P = .04). A risk prediction model based on these criteria produced a C statistic of 0.69 in the prediction cohort and 0.76 in the validation cohort and a Hosmer-Lemeshow goodness of fit of 0.62 and 0.14, respectively. A score of <3 of 9, corresponding to a <5% probability of transfusion, would avoid preoperative type and cross in 86% of patients. Of the 4203 patients (86%) with a hematocrit >36%, only 6 (0.1%) had a risk score of >3.

CONCLUSIONS

Perioperative transfusion for EVAR is becoming increasingly uncommon and is predicted well by a transfusion risk score or simply a hematocrit of <36%. Application of this risk score would avoid unnecessary type and cross in the majority of patients, leading to significant savings in both time and cost.

Multifactorial risk index for prediction of intraoperative blood transfusion in endovascular aneurysm repair

BACKGROUND

In some institutions, the current blood ordering practice does not discriminate minimally invasive endovascular aneurysm repair (EVAR) from open procedures, with consequent increasing costs and likelihood of blood product wastage for EVARs. This limitation in practice can possibly be addressed with the development of a reliable prediction model for transfusion risk in EVAR patients. We used the American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP) database to create a model for prediction of intraoperative blood transfusion occurrence in patients undergoing EVAR. Afterward, we tested our predictive model on the Vascular Study Group of New England (VSGNE) database.

METHODS

We used the ACS NSQIP database for patients who underwent EVAR from 2011 to 2013 (N = 4709) as our derivation set for identifying a risk index for predicting intraoperative blood transfusion. We then developed a clinical risk score and validated this model using patients who underwent EVAR from 2003 to 2014 in the VSGNE database (N = 4478).

RESULTS

The transfusion rates were 8.4% and 6.1% for the ACS NSQIP (derivation set) and VSGNE (validation) databases, respectively. Hemoglobin concentration, American Society of Anesthesiologists class, age, and aneurysm diameter predicted blood transfusion in the derivation set. When it was applied on the validation set, our risk index demonstrated good discrimination in both the derivation and validation set (C statistic = 0.73 and 0.70, respectively) and calibration using the Hosmer-Lemeshow test (P = .27 and 0.31) for both data sets.

CONCLUSIONS

We developed and validated a risk index for predicting the likelihood of intraoperative blood transfusion in EVAR patients. Implementation of this index may facilitate the blood management strategies specific for EVAR.

Preoperative anemia is associated with mortality after carotid endarterectomy in symptomatic patients

OBJECTIVE

Preoperative anemia and blood transfusions are associated with worse outcomes after surgery. However, the impact of preoperative anemia and transfusions on outcomes after carotid endarterectomy (CEA) is unknown.

METHODS

CEA patients from 2011 to 2015 in the American College of Surgeons National Surgical Quality Improvement Program Targeted Vascular module were compared by the presence of preoperative anemia (hematocrit <36%) after stratification by symptom status. Multivariable analysis accounted for differences in baseline characteristics. We included an interaction term in our multivariable model to assess whether the effect of anemia differed significantly between patients who received a perioperative transfusion and those who did not, with 30-day mortality as our primary outcome.

RESULTS

Of 16,068 patients, 6734 (42%) were symptomatic, of whom 1500 (22%) had anemia. Of the 9334 asymptomatic patients, 1935 (21%) had anemia. Both symptomatic and asymptomatic anemic patients were more likely to be transfused perioperatively compared with nonanemic patients, with 7.0% vs 0.4%, and 5.8% vs 0.7% (both P < .001). Among symptomatic patients, those with anemia compared with those without had a higher rate of 30-day mortality (2.5% vs 0.7%; P < .001). After adjustment, anemic symptomatic patients had a higher 30-day mortality risk (odds ratio [OR], 3.1; 95% confidence interval [CI], 1.9-5.0; P < .001) compared with nonanemic symptomatic patients. In addition, in symptomatic patients, we found a significant interaction between anemia and perioperative transfusion on the outcome of 30-day mortality (P = .004), with a higher risk in perioperatively transfused symptomatic patients with anemia (OR, 7.8; 95% CI, 3.4-18.0; P < .001) than in symptomatic patients with anemia who did not receive a perioperative transfusion (OR, 2.3; 95% CI, 1.4-3.9; P = .002). In asymptomatic patients, anemic and nonanemic patients had comparable 30-day mortality rates (0.9% vs 0.6%; P = .2). After adjustment, anemia was not associated with 30-day mortality in asymptomatic patients (OR, 1.0; 95% CI, 0.5-2.0; P = .9), nor did we identify an interaction between anemia and perioperative transfusion in asymptomatic patients (P = .1). Patients who received a preoperative transfusion had a higher 30-day mortality rate than anemic patients not receiving preoperative transfusion in both symptomatic (n = 31, 9.7% vs 2.5%; P = .04) and asymptomatic patients (n = 21, 9.5% vs 0.9%; P = .02).

CONCLUSIONS

Preoperative anemia is a risk factor for 30-day mortality after CEA in symptomatic patients but not in asymptomatic patients. These results should be factored into the selection of symptomatic patients for CEA and dissuade treatment of asymptomatic patients scheduled for CEA who need a preoperative transfusion.