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Adult Circulatory Support

Blood Product Utilization with Left Ventricular Assist Device Implantation: A Decade of Statewide Data

Quader, Mohammed*; LaPar, Damien J.; Wolfe, Luke*; Ailawadi, Gorav; Rich, Jeffrey; Speir, Alan§; Fonner, Clifford; Kasirajan, Vigneshwar*; Investigators for the Virginia Cardiac Surgery Quality Initiative

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doi: 10.1097/MAT.0000000000000345
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Abstract

Cardiac surgery procedures account for up to 15% of total blood products used from the national blood supply and 80% of which is used by 20% of cardiac surgery patients.1 Blood transfusion with cardiac surgery has been associated with increased risk of sepsis, stroke,2–5 right ventricle dysfunction,6 mortality,2,4,7–9 higher cost of care,3 and immune modulation.10 The latter is particularly important for patients awaiting heart transplantation (HTx) where allo-sensitization would lead to prolonged wait times and possibly graft failure. In an effort to reduce blood transfusions within cardiac surgery, the Society of Thoracic Surgeons (STS) and Society of Cardiovascular Anesthesiologists have established a task force to identify patients at high risk for blood transfusions (older age, low preoperative hematocrit, nonelective surgery, and patients undergoing complex surgical procedures) and recommended measures to reduce blood utilization.1 After their recommendations, many cardiac surgery centers developed blood conservation protocols resulting in a decrease in overall utilization of blood products11; however this trend was not studied in patients undergoing left ventricular assist device (LVAD) implantation. Unlike data on coronary artery bypass surgery (CABG), literature on blood transfusion associated with LVAD implantation is limited.3,9 We elected to conduct a comprehensive analysis of more than a decade of multi-institutional STS data in the state of Virginia for individual blood component and overall blood transfusion rates with LVAD implantation. In addition, we compared the blood product usage in the first half of the study compared with the latter half, a reflection of newly implemented blood conservation protocols in the state.

Materials and Methods

The Virginia Cardiac Surgery Quality Initiative (VCSQI) is a voluntary group of 18 hospitals (six LVAD implantation centers) and 14 cardiac surgery practices representing 99% of the cardiac surgery procedures performed in the State of Virginia. VCSQI collects certified STS data quarterly from each center and compares patients’ outcomes with the primary objective of identifying quality improvement opportunities. The current study is exempt from Institutional Review Board review at each participating center as it represents a secondary analysis of the VCSQI’s deidentified data.

We analyzed data on primary LVAD implantation for long-term circulatory support on all patients aged >18 years who had surgery performed between July 1, 2004 and June 30, 2014. Patients undergoing LVAD exchange were excluded from the study. After discussions at multiple quarterly meetings (2007–2008), VCSQI members developed and adopted a blood conservation protocol where blood transfusion triggers are set at a hematocrit of 18 on cardiopulmonary bypass (CPB) machine and 21 after the surgery. Details of the protocol are reported earlier.3 Based on the approximate timing of adoption of blood conservation protocols, the study duration was divided into two halves: 2004–2009 and 2010–2014. We analyzed blood transfusion data by usage of any blood products, individual components of blood products, and the quantity of blood products used during and after LVAD surgery. Statistical analyses were performed using SAS 9.4 (SAS Institute, Cary, NC). All tests were two-tailed and assumed a significance level of 0.05. For univariate comparisons, the Wilcoxon Rank test was used to compare continuous variables and Fisher’s Exact test was used to compare categorical variables. Multivariate logistic regression with stepwise selection was used to identify independent predictors of intraop blood product use.

Results

Between July 2004 and June 2014, 666 LVADs were implanted for long-term circulatory support. Blood transfusion data was missing in three patients and they were excluded from analysis. The mean age of patients was 54.5 ± 12.6 years and 77% were male. Among the different LVADs implanted (Table 1), the most frequently implanted LVAD was Thoratec HeartMate II (Thoratec Corporation, Pleasanton, CA). The number of LVADs implanted steadily increased over time. Left ventricular assist devices were implanted as bridge-to-transplantation in 74.2% of patients, destination therapy in 23.5%, and bridge to recovery in 2.3%. Overall postoperative mortality was 13.2%.

Table 1.
Table 1.:
Left Ventricle Assist Devices Implanted in Study Population

Over the decade, use of any blood products with LVAD surgery ranged from a low of 83% in year 2013 to a high of 100% in year 2008 with a mean of 92 ± 5.3% for the entire study duration (Figure 1). Intraoperative and postoperative blood product use was 71.8% and 73%, respectively. Only 7.4% of patients did not receive any blood products. Individual blood products transfused during surgery consisted of plasma (60%), platelets (56%), red blood cells (RBCs; 44.3%), and cryoprecipitate (32%); postoperatively, RBC use was more frequent (68%). The average units of blood products transfused with LVAD implantation ranged from a low of 15.3 ± 18.9 units in year 2012 to a high of 34.4 ± 30.5 units in year 2006 (Figure 1). Mean units of individual blood components transfused per LVAD implantation were RBC 8 ± 11, plasma 6.2 ± 7.8, platelets 2.6 ± 3.8, and cryoprecipitate 1 ± 1.9.

Figure 1.
Figure 1.:
Blood transfusion with left ventricular assist device implantation.

Distribution of patients in the first (2004–2009) and second (2010–2014) halves of study was uneven, with 153 (23%) LVADs implanted in the first half compared with 510 (77%) in the second half. Demographics and the majority of preoperative morbidities were comparable between the two study durations with the following exceptions Table 2. Patients in the second half of the study had higher BMI and history of hypertension. Greater numbers of patients in the second half of study were taking aspirin before surgery (60.2% vs. 48.6%, p = 0.01). For both of the study halves, LVAD designation for a majority of patients at the time of surgery was bridge-to-transplantation, and continuous flow LVAD was implanted in more than 90% of patients. Preoperative intraaortic balloon pump (IABP) use was more frequent in the first half of study (33.9% vs. 17.6%, p < 0.0001), whereas ECMO support was used only in the second half of study (2.9% vs. 0%, p = 0.02).

Table 2.
Table 2.:
Preoperative Patient Characteristics

Compared with the first half, in second half of the study there were more elective LVAD implantations (23% vs. 7.9%) and fewer emergent surgeries (7.4% vs. 21.7%, p < 0.0001; Table 3). The incidence of reoperative procedures and concomitant valve surgery at the time of LVAD implantation was comparable in two study halves.

Table 3.
Table 3.:
Operative and Outcomes Variables

The percentage of patients receiving any blood components during or after the LVAD surgery was 95.4% and 91.1% (p = 0.12), for the first and second halves of the study, respectively (Table 4). In the second half, a significantly lower percentage of patients were given any blood products intraoperatively (66.8% vs. 88.2%, p < 0.0001). The decrease in usage of blood products was noted for all blood components. The mean number of units of any blood components used intraoperatively in the second half was significantly lower (5.7 ± 8.3 vs. 9.7 ± 10.9, p < 0.0001). Postoperative blood product usage by study halves did not differ significantly (Table 4).

Table 4.
Table 4.:
Blood Product Utilization Data

By multivariable analysis, preoperative factors predictive of blood transfusions in LVAD patients were lower hematocrit, lower BMI, reoperative surgery, need for IABP, and nonelective surgery (Table 5). By univariable analysis, urgent and emergent surgeries were the only preoperative risk factors associated with higher mortality (p < 0.0001), and no risk factors were significantly associated with mortality by multivariable analysis. By univariable analysis, both intraoperative and postoperative quantities of blood transfusions were associated with mortality (p = 0.05). However, this association did not attain statistical significance by multivariable analysis.

Table 5.
Table 5.:
Risk Factors for Intraop Blood Product Transfusion by Multivariate Logistic Regression Analysis

Postoperative outcomes are summarized in Table 3. Any postoperative morbidity was noted in 75.8% of patients in the first half and 75% of patients in the second half. Of the individual postoperative morbidities, only the incidence of postoperative pneumonia was less in the second half of study (9.7% vs. 15%, p = 0.07). Length of stay after LVAD surgery was significantly shorter in the second half (25.4 ± 20.9 days vs. 37.5 ± 32.3 days, p < 0.0001). Operative mortality was 13.2% for the entire cohort and did not differ significantly between the two study halves.

Discussion

With identification and acknowledgement of risks associated with blood transfusion during cardiac surgery, concerted efforts were undertaken by institutions and surgeons over the past decade to limit the use of blood products with cardiac surgery. Our study examined the outcomes of such efforts in patients undergoing LVAD implantation in the state of Virginia. For the entire study duration 92 ± 5.3% of patients with LVAD implantation received blood transfusions in the perioperative period, ranging from 83% to 100% by year. Almost equal percentages of patients received blood intraoperatively (72%) and postoperatively (73%), and only 7.4% of patients did not receive any blood products. Although the overall percentage of patients receiving blood transfusions with LVAD implantation remained similar between the two halves of the study duration, the quantity of blood products transfused decreased significantly in the second half of study.

Blood transfusion practice varies significantly between institutions and was studied more frequently for CABG than for any other cardiac surgery procedures.3,8,12 The reported usage of blood products with CABG varied by institution from 27% to 92%12 and by gender 50–100% for men and 72–100% for women.8 In a randomized trial of Transfusion Requirements After Cardiac Surgery (TRACS), 502 patients were assigned to either liberal transfusion (maintain hematocrit of >30) or restrictive transfusion (for a hematocrit of <24) groups. The transfusion requirements were significantly less in the restrictive transfusion population (47% vs. 78%), but there were no observe differences in 30 day morbidity or mortality.13 In the same study, the number of blood units transfused directly correlated with clinical complications and operative mortality. Data on blood product transfusion rates with LVAD surgeries is limited. The two main multi-institution studies on the currently used LVADs reported transfusion of more than 2 units of pack red blood cell (PRBC) at 53%14 and any PRBC transfusion at 81%.15 Neither of the aforementioned studies presented the percentage or amount of non-PRBC blood products transfused. A more recent report from a single institution reported 93% of patients receiving any kind of blood products with LVAD surgery,9 similar to our study findings of 92%.

The STS task force identified six high-risk patient and procedure characteristics that are associated with increased likelihood of receiving blood transfusion with cardiac surgery: advanced age, low preoperative RBC volume, preoperative antiplatelet or antithrombotic drugs, reoperative or complex procedures, emergency operations, and noncardiac patient comorbidities.1 The foremost noncardiac patient comorbidity was heart failure, which was identified as an independent risk factor for blood transfusion in multiple studies.16–18 Patients requiring LVAD support such as our study cohort shared several of these risk factors. In addition, the majority of patients with advanced heart failure require preoperative anticoagulation as observed in 58% of our study patients, which adds to the complexity of LVAD surgery. Reoperative surgery, another risk factor for blood transfusion was present in 19% of our patients. Re-exploration for bleeding is a common event (30%) after LVAD implantation.9,14,15 We observed this problem in 22% of patients. Another factor contributing to the higher blood transfusion rates is urgent and emergent surgeries, which was observed in 81% of our patients. These factors individually and in combination have contributed to the high overall blood transfusion rate in our study.

Blood conservation protocols were adopted at many cardiac surgery institutions after the STS task force recommendations, with a noticeable decline in the amount of blood products transfused in the past few years.11 We reported a similar decrease in blood transfusion rates with primary CABG surgery in the state of Virginia.3 Because the same institutions that demonstrated fewer blood transfusions with primary CABG surgery were also VCSQI’s LVAD implantation centers, we elected to separate the study data into halves to find whether similar blood conservation practices applied to LVAD implantation surgery. Compared with the first half of the study, the amount of blood products transfused declined significantly in the second half, primarily from less intraoperative blood products usage. Because the STS data does not capture reasons for blood transfusions, we can only speculate the possible reasons for this observation. All the centers implanting LVADs have blood conservation protocols that are team oriented. This multidisciplinary approach to LVAD patient care where multiple team members contribute to the decision-making regarding blood transfusion limits the bias associated with individual decisions. Another factor relate to the higher frequency of CF-LVADs implanted in later half of study compared with more pulsatile devices implanted in the first half, which are known to be associated with more bleeding risks and blood transfusions.15,19 Prevalence of reoperation was relatively low in our study, especially in the second half (21%), compared with published reports of 30% with LVAD implantation.14,15 Our better reoperation rates, especially in the second half of study are possibly related to higher frequency of HM II implantations and improved surgical techniques with higher volume of LVAD implantations. Finally, centers implanting LVADs employ patient point-of-care (POC) testing and deficient coagulation factor directed therapy, which is known to decrease blood loss and transfusions. We believe multiple factors were involved in reducing the amount of blood transfused in the second half of the study. Otherwise, besides fewer emergent procedures in the second half of the study, the actual identified risk factors for blood transfusion with LVAD implantation such as use of antiplatelet agents, anticoagulant use, ECMO support, and reoperative surgery were more frequent, which should have resulted in more blood transfusions.

Further efforts to limit transfusions with LVAD implantation are needed in the future. Recommendations suggested by the STS task force1 such as identification and management of preoperative antiplatelet and anticoagulant drug therapy, autologous blood preservation in operating room, use of cell-saver circuits, minimized CPB circuits, normovolemic hemodilution, modified ultrafiltration, and use of fibrinolytic agents are routinely practiced in the operating rooms.20 Additional blood conservation measures described in the literature include erythropoietin and iron supplementation for patients with low preoperative hematocrit,21 autologous blood donation,22 and desmopressin (DDAVP) for patients with platelet dysfunction. Another opportunity to reduce blood transfusions is to increase the threshold for RBC transfusion on CPB; however, it is to be noted that there is no well-defined safe low hematocrit on CPB. Studies have shown that nadir hematocrit on CPB circuit is associated with increased complications.16,23,24 Those patients on antiplatelet agents such as clopidogrel, aspirin benefit from stopping the medication 5–7 days before surgery.1 In addition, lysine analog antifibrinolytic agents are well established in reducing intraoperative blood loss.25 In situations of intractable nonsurgical bleeding, factor VIIa was effective in reducing RBC transfusion with cardiac surgery.26 Prothrombin complex concentrate (PCC) is a mixture of vitamin K-dependent coagulation factors (factor II VII IX X, protein C and S). In a randomized trial, PCC was found to reverse the Coumadin effect more effectively and with less bleeding compared with fresh frozen plasma.27 Another novel method that has been shown to decrease bleeding and transfusion requirements is POC testing. This involves targeting blood product therapy according to specific coagulation abnormalities as identified in a timely fashion, such as immediately after reversal of protamine in the operating room. Thromboelastography is one such POC testing and was found to decrease platelet and fresh frozen plasma transfusion rates.28

With these preoperative, operative and postoperative modalities available to reduce blood transfusions with LVAD implantation, major blood conservation would come from employing a combination of initiatives in a comprehensive multidisciplinary approach. This approach was effective within the VCSQI with primary CABG operations3 and was similarly demonstrated by 25 Ontario surgery programs.29

Study Limitations

This is a retrospective analysis of prospectively collected standard STS data. Over the long study span there have been significant changes in the LVAD design and indications for mechanical circulatory support. This could have influenced the blood product utilization in the two halves of our study. Reasons for blood product transfusion are not captured in the STS data and the driving factors behind the use of blood products such as blood loss, a set threshold of hemoglobin level for transfusion, hemodynamic instability or surgeon’s preference is unknown. Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) profile, which is considered to be a better measure of LVAD patients’ acuity of illness, is not available in STS data for analysis. The postoperative follow-up of patients is limited to 30 days or to the index hospitalization. Despite these limitations, our collective multi-institutional statewide database allowed us to pool a large number of LVAD patients’ data on blood product used, enabling a meaningful statistical analysis.

Conclusions

More than 90% of patients undergoing LVAD implantation received blood transfusion. Over the 10 years of study, the percentage of patients receiving blood transfusions remained unchanged; however, quantities of blood components transfused in the operating room decreased significantly in the second half of the study. Blood transfusions were associated with increased mortality by univariable analysis but not in the multivariable model. Concerted efforts should be made in a multidisciplinary team approach to further reduce the blood transfusions associated with LVAD implantation.

References

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Keywords:

Blood transfusion; LVAD; Blood conservation

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