Asian Cardiovasc Thorac Ann 2002;10:16-19
© 2002 Asia Publishing EXchange Pte Ltd
Transfusion for Coagulopathy After Heart Surgery: Efficacy of Laboratory Studies
Timothy S Hall, MD,
Alan J Skoultchi, MD
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Division of Cardiothoracic Surgery University of California at San Francisco San Francisco, California, USA The Robert Wood Johnson Medical School New Brunswick, New Jersey, USA
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Timothy S Hall, MD Tel: 1 415 476 3503 Fax: 1 415 840 0269 email: hallt{at}surgery.ucsf.edu Division of Cardiothoracic Surgery, University of California at San Francisco, 533 Parnassus Avenue, U-119, San Francisco CA 94143-1267, USA.
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ABSTRACT
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Limited information exists regarding transfusions specifically for coagulopathy following cardiac surgery and the value of pre- and postoperative coagulation tests. Procedures (86% coronary bypass, 7.5% valve, and 6.5% combined valve and bypass) on 478 patients were reviewed; 101 patients (21%) were transfused for postoperative coagulopathy. Compared to those not transfused, patients with coagulopathy were significantly older and smaller, and they had more combined valve procedures, emergency operations, and preoperative heparin treatment as well as longer crossclamp and bypass times. Three preoperative tests showed significant differences in the coagulopathy group: activated clotting time, partial thromboplastin time, and antithrombin-III level. Four postoperative tests showed significant differences between the groups: prothrombin time, partial thromboplastin time, fibrinogen level, and fibrin split products at 10 dilutions. Patient characteristics and pre- and postoperative testing can identify patients at high risk of transfusion specifically related to coagulopathy.
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INTRODUCTION
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Bleeding problems have occurred since the introduction of cardiopulmonary bypass (CPB), as Gibbon1 and other authors have noted.2–7 Data regarding transfusion specifically for coagulopathy are limited. When the issues of cost effectiveness and resource utilization are considered, the use of routine coagulopathy screening has been questioned and the value of postoperative studies has been reviewed.8 This study was undertaken to identify preoperative indicators of coagulopathy following open heart surgery and to assess the usefulness of pre- and postoperative coagulopathy screening.
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PATIENTS AND METHODS
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A retrospective review was undertaken of the records of 478 adult patients who underwent cardiac surgery in a university hospital. Coagulopathy-related transfusions were defined as transfusions of fresh frozen plasma, platelets, or cryoprecipitate for ongoing bleeding. The need for transfusion was determined intraoperatively by the quantity of bleeding based on clinical judgment, and postoperatively on chest tube output, according to standard guidelines.9 None of the patients required reexploration. Patients with a preoperative history of bleeding problems or abnormal bleeding tests were excluded. The variables evaluated were age, gender, procedure, heparin dosage, body surface area, CPB time, aortic crossclamp time, preoperative renal function, preoperative anticoagulant medications, preoperative intraaortic balloon pumping, protamine dosage, prior open heart procedures, post-operative inotropic support, postoperative blood loss, transfusions, length of postoperative hospital stay, complications, and mortality. In all patients, preoperative heparin was discontinued prior to transport to the operating room. Warfarin was routinely discontinued 5 days before the procedure. Patients on aspirin were continued on their medication until the day of surgery.
Invasive monitoring (Swan-Ganz and radial artery catheters) was set up and a narcotic-based anesthetic was administered. A median sternotomy was performed in all cases. A loading dose of heparin 300 U•kg-1 was given intravenously. The activated clotting time (ACT) was maintained above 400 seconds during CPB, with additional heparin as necessary. Roller pumps and membrane oxygenators were used in all cases. The CPB circuit was primed with 2 L of crystalloid solution. Intraoperatively, red blood cell salvage was accomplished by scavenging and reinfusion using a cell saver (Haemonetics, Braintree, MA, USA) and hemoconcentration. Intermittent cold blood cardioplegia (1:4 dilution) was employed for myocardial protection. All patients were exposed to moderate hemodilution (hematocrit, 19% to 27%) and hypothermia (34°C to 25°C) with rewarming to temperatures above 35°C. Protamine was administered intravenously after the discontinuance of CPB, equal to the weight of administered heparin. If the ACT remained elevated following the initial dose of protamine, an additional intravenous dose of 50 mg was given.
The reliability of data retrieval was assessed by an internal audit of the database. All information was garnered following appropriate Institutional Review Board approval. Group comparisons were made with Fisher's exact test for categorical variables, and with analysis of variance (ANOVA), Student's t test, and Tukey's post-hoc test for continuous variables. The mean and 95% confidence limits (CL) were calculated. A significance level of p 
0.05 was used. Hospital mortality was defined as death during the same admission, regardless of duration or cause.
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RESULTS
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Of the 478 patients studied, 86% had undergone coronary bypass surgery, 7.5% had valve surgery, and 6.5% had combined valve and coronary bypass surgery. The mean age was 64.2 years. Preoperative intravenous heparin was given to 27.5% of patients, and 9.4% were classified as emergency cases. Transfusion of platelets, fresh frozen plasma, or cryoprecipitate was required for coagulopathy in 101 patients (21%). The chest tube drainage at 24 hours reflected the increased bleeding due to coagulopathy; for patients requiring coagulopathy-related transfusion, the mean chest tube drainage at 24 hours was 1,004 mL (95% CL, 905 to 1,102 mL) compared to 756.6 mL (95% CL, 725.6 to 778.6 mL) in patients not transfused (p 0.0001). Patients requiring coagulopathy-related transfusion had a mean age of 68.7 years (95% CL, 66.7 to 70.0 years) compared to 62.95 years (95% CL, 61.9 to 64.0 years) in patients not transfused (p 0.0001). Small patients were more likely to require coagulopathy-related transfusions; the mean body surface area of transfused patients was 1.83 m2 (95% CL, 1.79 to 1.88 m2) compared to 1.92 m2 (95% CL, 1.90 to 1.94 m2) in the other patients (p 0.0006).
Of the patients on intravenous heparin preoperatively, 65.6% were transfused for coagulopathy compared to 34.4% of the others (p 0.002). Among patients who were hemodynamically unstable and required preoperative intraaortic balloon pumping, a greater percentage received coagulopathy-related transfusions (54% versus 45.6%) than those who did not require balloon pumping (p 0.007). Of the patients requiring preoperative inotropic support, 85% received coagulopathy-related transfusions, which was significantly higher than the 17% of patients not on inotropics (p 0.0002). The type of operation was related to the need for transfusions due to coagulopathy: 19% of coronary bypass cases and 20% of valve cases required transfusion for coagulopathy compared to 48% of patients undergoing combined valve and coronary procedures (p 0.004). The mean aortic crossclamp time was 94 minutes (95% CL, 87 to 101 minutes) in patients transfused for coagulopathy compared to 72.9 minutes (95% CL, 70.2 to 75.6 minutes) in patients not transfused (p 0.0001). As expected, the CPB time reflected this difference; the mean CPB time was 150.1 minutes (95% CL,140.3 to 160 minutes) in those requiring transfusion for coagulopathy, compared to 114 minutes (95% CL, 110.3 to 117.7 minutes) in the other patients (p 0.0001).
Several preoperative and postoperative tests showed differences in patients who received transfusions, as shown in Table 1
. In addition, the fibrin split products were elevated postoperatively in patients requiring coagulopathyrelated transfusions: 16% were positive at 1–10 dilutions compared to 5.3% of patients not transfused; 5% of transfused patients were positive at 1–40 dilutions compared to 0.5% of those not requiring transfusions (p 0.001 by Fisher's exact test, p = 0.004 by the chi-squared test, respectively). Postoperative platelet counts were not helpful in identifying patients requiring postoperative coagulopathy-related transfusions; the mean platelet count was 124.6 x 103/cm3 (95% CL, 115.4–133.8 x 103/cm3) in those transfused versus 133.9 x 103/cm3 (95% CL, 129.0–138.8 x 103/cm3) in those not transfused (p 0.08).
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Table 1. Differences Between 101 Patients Transfused for Coagulopathy After Heart Surgery and 377 Patients Not Transfused
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DISCUSSION
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This study found that smaller, older, and hemodynamically unstable patients exposed to longer and more complex procedures were more likely to have received transfusions specifically for coagulopathy. The limitations of this study were that it was not a prospectively controlled clinical trial with strict transfusion guidelines based on clotting factors rather than clinical judgment. This group was selected to exclude patients bleeding from surgical causes (requiring reexploration). Dacey and colleagues10 found a similar difference in patient characteristics in terms of age, body size, and CPB time in a study on reexploration for postoperative hemorrhage. However, they did not report how many reoperations were for surgical sources of bleeding. In contrast to the results of Omari and colleagues11 our study found that preoperative heparin treatment was related to increased risk of excessive postoperative bleeding.
The finding that preoperative ACT, prothrombin time, and partial thromboplastin time were different in patients who developed coagulopathy is of significance in that the current guidelines for normalizing the coagulation levels preoperatively are vague, with recommendations to lower the international normalized ratio to less than 2.25.12 Our data suggest these guidelines should be more restrictive. Supporting this approach, Despotis and colleagues13 also demonstrated that reoperation and concomitant valve and coronary procedures were additional risks for post-operative coagulopathy in their study on point-of-care coagulation testing. We demonstrated no benefit in measuring preoperative bleeding times, in contrast to Khuri and colleagues14 who reported that preoperative bleeding times correlated with postoperative blood loss at 2 hours. On the other hand, the postoperative studies of coagulation were significantly different in patients requiring transfusions for coagulopathy. This is consistent with other studies using a number of different testing devices that demonstrated efficacy in detecting coagulopa-thy in postoperative patients, and disagreeing with Gravlee and colleagues8 on the use of these studies.11,15–17
After reviewing our findings, we stopped testing pre-operative fibrinogen levels and bleeding times. The antithrombin-III level reflected use of preoperative heparin and was otherwise of no value; hence it was also eliminated from the preoperative coagulation profile. We continue to measure prothrombin time, partial thromboplastin time, and ACT preoperatively. For high-risk patients (> 75 years old, < 1.8 m2 in body surface area, emergencies, hemodynamically unstable, or those exposed to CPB times > 180 minutes), the standard postoperative bleeding profiles are drawn. A postoperative coagulation profile is otherwise drawn on a selective basis. This study has allowed a reduction of unnecessary blood testing by targeting a high-risk group, thereby decreasing the postoperative studies in routine patients. In addition, newer technologies that may further decrease the need for postoperative transfusions for coagulopathy can now be applied to this specific patient group.
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ABSTRACT
INTRODUCTION
