|Year : 2022 | Volume
| Issue : 1 | Page : 62-67
An audit on transfusion of blood products based on clinical judgment in patients undergoing cardiac surgery
Joseph Punnoose Paarel1, Vinay Rao2, Anand Ganesh1, Sukesh Nair3, Sathish kumar Dharmalingam1, Ben Babu Kurien1, Raj Sahajanandan1
1 Department of Anaesthesia, Christian Medical College Hospital, Vellore, Tamil Nadu, India
2 Department of Cardiovascular and Thoracic Surgery, Christian Medical College Hospital, Vellore, Tamil Nadu, India
3 Department of Clinical Pathology, Christian Medical College Hospital, Vellore, Tamil Nadu, India
|Date of Submission||22-Apr-2021|
|Date of Decision||13-Jun-2021|
|Date of Acceptance||09-Nov-2021|
|Date of Web Publication||23-Mar-2022|
Dr. Ben Babu Kurien
Assistant Professor, Department of Anaesthesia,Christian Medical College Hospital, Vellore, Tamil Nadu
Source of Support: None, Conflict of Interest: None
Background: Transfusion of blood and blood products is strongly associated with increased morbidity and mortality in cardiovascular surgery. This includes transfusion-related acute lung injury, transfusion-associated circulatory overload, renal injury, anaphylactic reactions to blood products, and sepsis. Transfusion of blood products based on the clinician's judgment often results in excessive transfusion. Research suggests that the use of point-of-care (POC) coagulation tests coupled to algorithm-based management decrease transfusion requirements in cardiac surgery.
Objectives: To determine abnormal thromboelastograph (TEG) values among patients who received blood products based on clinical judgment and to determine if a POC coagulation test could have resulted in reduced transfusion rates in these patients.
Methods: A total of 45 cardiac surgical patients who received blood products during a 3 months period were included in the audit. Coagulation profile and TEG were sent before transfusion for all patients. Data were entered using EPIDATA software. Descriptive analysis was used to define the data. The Fisher exact test was used to assess differences between groups for categorical variables.
Results: The R time was abnormal in 4.4% of patients, the Alpha angle was abnormal in 51.1% of patients, maximum amplitude was abnormal in 2.2% of patients, and there was no evidence of fibrinolysis on TEG in these patients.
Conclusion: Clinical judgment about the need for blood transfusion had poor correlation with dynamic tests of coagulation. A POC test-based algorithm would have avoided a significant amount of blood product transfusion both in terms of choice of therapy and the dose of component used.
Keywords: Blood product transfusion, cardiopulmonary bypass, coagulation, cryoprecipitate, fresh-frozen plasma, thromboelastography
|How to cite this article:|
Paarel JP, Rao V, Ganesh A, Nair S, Dharmalingam Sk, Kurien BB, Sahajanandan R. An audit on transfusion of blood products based on clinical judgment in patients undergoing cardiac surgery. Indian Anaesth Forum 2022;23:62-7
|How to cite this URL:|
Paarel JP, Rao V, Ganesh A, Nair S, Dharmalingam Sk, Kurien BB, Sahajanandan R. An audit on transfusion of blood products based on clinical judgment in patients undergoing cardiac surgery. Indian Anaesth Forum [serial online] 2022 [cited 2022 Oct 3];23:62-7. Available from: http://www.theiaforum.org/text.asp?2022/23/1/62/340484
| Introduction|| |
Inadequate surgical hemostasis and abnormality in the coagulation system are the main attributable causes of abnormal bleeding following cardiac surgery. The multifactorial nature of coagulation disorders after cardiopulmonary bypass (CPB), along with the delay of laboratory data complicates clinical management, and treatment is often empirical based on clinical judgment. Inappropriate use of blood products in cardiac surgical patients has important adverse health and economic consequences. Excessive bleeding after CPB is an important cause of patient morbidity and mortality., Transfusion of blood products to treat excessive hemorrhage may expose the patient to additional risks like acute lung injury (ALI), transfusion reactions and increased expenditure.
The use of routine coagulation tests to guide therapy and treatment of excessive bleeding has been shown to reduce the need for transfusion of blood products. However, the use of traditional tests of coagulation after bypass (prothrombin time [PT], partial thromboplastin time [PTT], international normalized ratio, and platelet count) have several issues, notably their inability to test platelet function, and the delay in receiving results (high turnaround time) from the laboratory. Thromboelastometry is a method of analyzing whole blood coagulation which assesses the interaction of platelets and the plasma coagulation system and their ability to form a functional clot. This can be done as a point of care (POC) test or in the lab.
Often, the decision to transfuse fresh-frozen plasma (FFP) and platelets depends on the clinician's judgment or institutional practice. We felt that the experienced senior surgeon's judgment of the surgical site bleeding was more accurate than the junior surgeons. This was supported by a study by Dixon et al. who concluded that the surgeon is an independent risk factor for postoperative bleeding and transfusion.
We proposed this audit to analyze the clinician's judgment for transfusion of blood products against the therapy suggested by thromboelastographic tests. Our objectives were, first, to determine the incidence of abnormal thromboelastograph (TEG) values among patients who received blood products during cardiac surgery and, second, to determine whether POC coagulation tests (TEG), if available, could have reduced the transfusion of blood products.
| Methods|| |
After obtaining approval form the institutional Review Board, and written informed consent, 310 adult patients above the age of 18 years, who underwent cardiac surgery, were recruited into the study [Table 1]. The data of 45 patients who received transfusion of blood products during surgery were included in the audit [Table 2]. Patients with preexisting coagulation abnormalities and those who underwent emergency surgeries were excluded from the study [Figure 1].
Basic demographic details and preoperative medication history, as well as prior coagulation disorders, were documented for all patients before surgery. Baseline blood investigations were done routinely for all patients. These included hemoglobin, platelet count, prothrombin time PT, activated PTT (aPTT) [Table 3].
A sample of the patient's blood was sent to the blood bank for crossmatch on the previous day of surgery. All the patients received a standard anesthetic regimen (balanced anesthesia). CPB was conducted with Medtronic oxygenator at a flow of 75–150 ml/m2. The CPB circuit was primed with Ringer Lactate and plasmalyte. Heparin was administered to patients as follows: Initial Bolus dose of 400 units/kg and an oxygenator priming dose of 2500 units. Additional Heparin of 100–200 units/kg was given when activated clotting time (ACT) is <450 s. All patients underwent retrograde autologous priming and anterograde autologous priming as part of blood conservation strategy guided by the Society of thoracic surgeons (STS) 2011 guidelines. All patients received tranexamic acid 20 mg/kg followed by an infusion of 4 mg/kg/h to a maximum of 50 mg/kg. After discontinuation of CPB, a thorough assessment of the entire pericardial cavity to rule out any surgical bleed was done by the senior surgeon. If any they are repaired and only then was the initial Protamine Sulfate dose at a ratio of 1:1/unit of heparin administered. Before the aortic decannulation and separation from CPB, the residual blood was transfused back to the patient and protamine administration was completed. Heparin neutralization was regarded as adequate if the post protamine ACT value was <140 s. Additional protamine (0.1–0.2:1) was added if ACT >140 s, after ensuring that the temperature >36°C, pH >7.3, Hb >7.5 g% and ionized calcium level was >1 mmol/L. Adequacy of hemostasis was reassessed at this point and the decision of transfusion of blood products was taken if there was no surgical cause of bleeding and there was generalized oozing with no clot formation. We did not use a cell saver as we rarely had significant residual volume after both anterograde and retrograde priming as well as it was an additional economic burden for the consumables.
Patients who were transfused blood products, based on clinical judgment due to the presence of generalized ooze-type (microvascular) bleeding in the surgical field or absence of visible clots were included in the audit. Once the decision to transfuse blood products was made, a blood sample was taken from the patient to test for coagulation studies, before transfusion. The sample was tested for platelet count, PT, aPTT, fibrinogen and TEG. Our institution does not have a POC testing for TEG in the OR complex. The blood sample collected in 3.2% citrated vacutainer (BD Vacutainer® sodium citrate tubes) was sent to the central clinical pathology laboratory located in the adjacent block. The test was performed by trained personnel in a TEG analyser (TEG Haemoscope, 5000, USA) and activated using tissue factor (TF). TF was prepared by dilution of Prothrombin time Innovin reagent (Dade Behring, Newark, DE, USA) at 1:2000 dilution, modified from the method described by Sørensen et al. Thirty μl of TF was added to 500 μl of citrated blood. After mixing, 320 μl of the blood was added to the cup, followed by 20 μl of 0.2 M calcium chloride and test was initiated.
TEG parameters included reaction time (R), K time (K), alpha angle (α), maximum amplitude, lysis index (LY 30%): clot lysis (percentage decrease in amplitude 30 min post-MA). The reference range for TEG variables is 3–8 min for R time, 1–3 min for K time, 55°–78° for α angle, 51–69 mm for MA, 0%–8% for lysis 30.
The “turnaround time” of the test included the time taken for transport of samples (10 min), the time taken to initiate the test (5–45 min depending on whether the TEG machine was occupied with other patient samples) and another 10–15 min for the initial R and K time to be reported from the laboratory (overall 30–45 min). An additional 20–25 min is needed for the release of thawed FFP from the blood bank. Unless the dynamic tests (TEG/ROTEM) is available as POC, it takes about 45–60 min to transfuse an appropriate blood product. The high turnaround time and fact that the surgical causes for bleeding are found in only about 50% of cases and coagulopathy play a major and correctable cause of bleeding after cardiac surgery are the possible reasons for empirical transfusion.
| Results|| |
During the study period, 45 patients who required transfusion of blood products satisfied the inclusion criteria for the study.
The different parameters of TEG measured among 45 patients in the audit who received transfusion of blood products showed the following results:
- R time was abnormal in 4.4% of patients
- Alpha angle was abnormal in 51.1% of patients
- MA was abnormal in 2.2% of patients
- Ly30 was normal in all patients.
The 45 patients included in the study received a total of 98 units of FFP's, 115 units of platelet-rich concentrate (PRC), and 26 units of cryoprecipitate based on clinician judgement [Figure 2].
|Figure 2: Total amount of blood products transfused among the 45 patients. FFP = Fresh frozen plasma; PRC = Platelet rich concentrate|
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Analysis of patients who received blood products showed that [Table 4]:
|Table 4: Comparison among patients who received blood products and those with abnormal thromboelastograph values, along with correlation between static and dynamic tests|
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- R time was normal in 43 out of 45 (95.6%) of patients. Twenty five out of these 45 patients (55%) received 3 units of FFP
- Alpha angle was abnormal in 23 out of 45 patients (51.1%). However, 36 patients received PRC's based on clinician judgment. All these patients had normal MA values
- Among the four patients who were transfused cryoprecipitate, only one patient had alpha angle value below normal
- The TEG done in all the 45 patients did not show any fibrinolysis.
| Discussion|| |
Cardiac surgery is one of the leading consumers of blood and blood products. The hemostatic problems associated with cardiac surgery and the use of CPB are multifactorial, ranging from preoperative coagulopathy due to drugs, hemodilution due to circuit priming, systemic heparinization, hypothermia, thrombocytopenia, and platelet functional abnormalities secondary to CPB and fibrinolysis triggered by shed mediastinal blood.
Conventional laboratory tests are not useful in the setting of cardiac surgery due to its long turnaround time of 45–60 min. An additional 30 min is required for transportation of the sample to the lab and initiation of the test. Hence, dynamic tests of hemostasis, especially done as a POC testing with a turnaround time of 15–30 min are employed to guide transfusion practices in many centers It is imperative that Indian centres performing cardiac, trauma, obstetric and liver surgeries should have TEG/ROTEM as a POC test in the OR complex.
In the absence of the availability of dynamic tests like TEG and ROTEM, the decision to transfuse blood and products are often taken empirically by the primary surgeon and anesthetist, based on their experience and clinical judgment. The transfusion practices guided by the empirical judgment of the clinician has been proven to result in unwarranted use of blood and blood products, leading to increased risk to patients due to unnecessary exposure to allogeneic blood products, Complex surgical procedures (double valve replacement with tricuspid annuloplasty) are associated with prolonged aortic cross-clamp and CPB duration. The presence of multiple suture lines (e.g., Bentall operation), redo surgeries with significant adhesions, patients on aspirin or low-molecular-weight heparin preoperatively, preoperative thrombocytopenia is considered at high risk for perioperative blood product transfusion. All these factors in varying combinations influenced the surgical team to request for empirical blood products where the turnaround time to release the thawed FFP and platelets was about 30 min from the time of the request. However, if the decision making is based on laboratory-based dynamic or static coagulation test, the turnaround time is about 75–90 min.
In our audit, among the 45 patients included in the study, a total of 98 units of FFP were transfused based on the clinician's decision. The R time was abnormal (more than 10 min) in 4.4% of patients. Among patients who received at least 3 units of FFP, 92% had normal R-value. If POC testing was available, the transfusion of FFP would not have been indicated in 41 out of 45 patients (91.2%). Furthermore, FFP was not administered based on dosage as per weight. All patients received an arbitrary volume, of around 10–15 ml/kg. Hence, the use of dynamic testing would have resulted in decreased transfusion rates for FFP. Our results were in sharp contrast with the findings of Meesters et al. who found that FFP transfusion based on anesthetists judgment was accurate in 95% of cases. While we agree that clinical judgment is important, rational use of blood products is crucial considering the limited availability and associated risks. Our results show that the clinician's decision is subjective yet a multidisciplinary assessment and POC test based protocols are the need of the hour in every cardiac surgical centers to provide optimal care as per the latest concept of patient blood management in cardiac surgery.
Forty-four out of 45 patients (97.8%) had a normal value of MA (48-75 mm). However, 36 out of the 45 patients received PRC. One patient with abnormal value for MA was transfused 3 units of PRC along with 3 units of FFP, despite his R-value and K value being within normal limits. In the presence of dynamic testing-based algorithms, platelet transfusion could have been avoided in 35 out of the 36 patients (97.2%). However, platelet count was below 1,00,000/cu mm in 42.2% of patients, necessitating transfusion if the patient was clinically bleeding. The correlation between MA and platelet count was poor. This could be overcome using platelet mapping TEG as a POC test. The other alternative is to use FIBTEM of ROTEM which will detect hypofibrinogenemia as the cause of low Maximum clot firmness (MCF) value. Reduced alpha angle suggestive of hypofibrinogenemia and thrombocytopenia was seen in (51.1%) of patients. Even though only 23 out of 45 patients had a decreased alpha angle, 36 patients (80%) received PRC transfusions, utilizing a total of 103 units of PRC. Only 4 out of the 45 patients received cryoprecipitate transfusion. Of the 23 patients who had a reduced alpha angle value, only seven patients (31.8%) had hypofibrinogenemia defined as <150 mg/dl, showing poor correlation between static and dynamic tests. Among these seven patients with low alpha value and hypofibrinogenemia, only one patient received both PRC and cryoprecipitate transfusion. All other patients were transfused FFP and PRC. Out of four patients who received cryoprecipitate, only 1 (25%) patient had low alpha angle value. Seventy five percent of patients who received cryoprecipitate had normal alpha angle value. Ly30 was observed to be normal in all 45 study patients. This could be partly explained by the shorter bypass time (mean CPB time was 110 min) and prophylactic use of antifibrinolytics in all patients other than elective coronary artery bypass graft.
This study was conducted as an audit of the transfusion practises for blood products among patients undergoing cardiac surgery. We did not quantify intraoperative packed-cell transfusions which could result in coagulation abnormality leading to product administration. This study was not designed as an interventional study to determine the need for transfusion based on the POC test. The impact of transfusion on outcomes like ALI, mechanical ventilation, duration of intensive care unit stay, re-exploration and economic burden to the patient, which are major concerns with transfusions, was not studied. We did not assess the influence of predictive factors for transfusion like preoperative hemoglobin, CPB and cross-clamp time, ejection fraction and preoperative low platelet counts. The unavailability of TEG as a POC testing in the operation room was a major limitation.
| Conclusion|| |
Our audit concluded that clinical judgment about the need for blood transfusion, though necessary, had poor correlation with dynamic tests of coagulation. If POC testing was available, appropriate products can be arranged as soon as residual heparin is reversed and adequacy of hemostasis was assessed. The overall time would have been reduced by nearly 30 min. Availability of a POC test-based algorithm would have avoided a significant amount of blood product transfusion both in terms of choice of therapy and the dose of the component.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3], [Table 4]