Cardiothoracic Surgical Patients Research Articles

Postoperative Delirium in a Substudy of Cardiothoracic Surgical Patients in the BAG-RECALL Clinical Trial

Postoperative delirium in the intensive care unit (ICU) is a frequent complication after cardiac or thoracic surgery and is associated with increased morbidity and mortality. In this single-center substudy of the BAG-RECALL trial (NCT00682825), we screened patients after cardiac or thoracic surgery in the ICU twice daily for delirium using the Confusion Assessment Method for the ICU. The primary outcome was the incidence of delirium in patients who had been randomized to intraoperative Bispectral Index (BIS)-guided and end-tidal anesthetic concentration-guided depth of anesthesia protocols. As a secondary analysis, a Bayesian stochastic search variable selection strategy was used to rank a field of candidate risk factors for delirium, followed by binary logistic regression. Of 310 patients assessed, 28 of 149 (18.8%) in the BIS group and 45 of 161 (28.0%) in the end-tidal anesthetic concentration group developed postoperative delirium in the ICU (odds ratio 0.60, 95% confidence interval, 0.35-1.02, P= 0.058). Low average volatile anesthetic dose, intraoperative transfusion, ASA physical status, and European System for Cardiac Operative Risk Evaluation were identified as independent predictors of delirium. A larger randomized study should determine whether brain monitoring with BIS or an alternative method decreases delirium after cardiac or thoracic surgery. The association between low anesthetic concentration and delirium is a surprising finding and could reflect that patients with poor health are both more sensitive to the effects of volatile anesthetic drugs and are also more likely to develop postoperative delirium. Investigation of candidate methods to prevent delirium should be prioritized in view of the established association between postoperative delirium and adverse patient outcomes.

Prevalence of Vitamin D Deficiency Prior to Cardiothoracic Surgery

Vitamin D deficiency is one of the most common chronic medical conditions in the world and also prevalent in Australia. A growing body of evidence suggests that low vitamin D also has adverse effects on cardiovascular health, including coronary risk factors and adverse cardiovascular outcomes such as myocardial infarction, cardiac failure and stroke. There is some evidence suggesting that a greater proportion of people with cardiovascular disease have low vitamin D compared to the general population. We examined the prevalence of vitamin D deficiency and insufficiency in elective cardiothoracic surgical patients presenting to the Alfred Hospital in Melbourne, Australia and compared this to recent Victorian statistics for people of the same age group. Consecutive adult elective cardiothoracic surgical patients listed for either coronary artery bypass graft surgery or heart valve repair or replacement surgery attending The Alfred Hospital, Melbourne between July 2011 and October 2012 were invited to participate. This ensured that patients were enrolled over all four seasons. Fasting serum samples were taken on the day of surgery, immediately after admission. Eighty volunteers participated in the study. Of the group, 40% were due to have coronary artery bypass graft surgery, 35% valve surgery and 25% a combination of the two; 74% reported having hypertension, 69% hyperlipidaemia, 26% diabetes and 39% had a BMI >30 kg/m(2). Test results revealed that 92.5% of patients had Vitamin D levels < 75 nmol/L, 67.5% had levels < 60 nmol/L, 52.5% had levels between 30-59 nmol/L and 15% had levels < 30 nmol/L. Inadequate vitamin D levels were found in 80% of obese patients (BMI > 30 kg/m(2)) compared to 59% of non-obese patients. Based on our small screening study, a substantial proportion of elective cardiothoracic surgical patients have less than optimal serum vitamin D3 levels prior to surgery. We found two-thirds of patients had serum vitamin D levels below 60 nmol/L, placing them at higher risk of falls. This finding is of concern as these patients would have received multiple consultations with various medical practitioners prior to hospital admission and yet their inadequate vitamin D status remained. Failing to identify patients with low vitamin D and correcting it with supplementation places older adults at unnecessary risk, especially of falls, which are associated with a high risk of mortality. In an ageing population with CVD, vitamin D status needs to be assessed and any inadequacy corrected. Whether low vitamin D status prior to cardiac surgery affects post-surgery outcomes, is another issue which deserves future investigation.

Percutaneous Tracheostomy Can be Safely Performed in Patients with Uncorrected Coagulopathy after Cardiothoracic Surgery

It is a common situation after cardiothoracic surgery that a tracheostomy is required for patients who are coagulopathic or on therapeutic anticoagulation. We present our results of percutaneous tracheostomy with uncorrected coagulopathy. Between 2007 and 2012, a total of 149 patients in our Cardiothoracic Surgical Intensive Care Unit underwent percutaneous tracheostomy using the Ciaglia Blue Rhino system (Cook Medical, Bloomington, IN USA). The patients were divided into coagulopathic (platelets, ≤50,000; international normalized ratio of prothrombin time, ≥1.5; and/or partial thromboplastin time, ≥50) and noncoagulopathic groups. Coagulopathy, if present before percutaneous tracheostomy, was not routinely corrected. A total of 75 patients (49%) were coagulopathic. Twenty-one patients (14%) had two or more criteria. The coagulopathic patients had a lower platelet count [108 (106) vs 193 (111) (thousands), P < 0.001], with the lowest of 10; higher international normalized ratio of prothrombin time [1.7 (0.6) vs 1.2 (0.1), P < 0.001], with the highest of 5.3; longer partial thromboplastin time [40 (13) vs 33 (7) seconds, P < 0.001], with the longest of 85; and higher total bilirubin [4.6 (7.3) vs 1.9 (3.3) mg/dL, P = 0.005]. Patient demographics and comorbidities were comparable between the groups. No patients had overt bleeding. One coagulopathic patient (1.3%) had clinical oozing treated with packing, as opposed to zero in the noncoagulopathic patients (P = 1.00). There were no patients with posttracheostomy mediastinitis or late tracheal stenosis. Uncorrected coagulopathy and therapeutic anticoagulation did not increase bleeding risk for percutaneous tracheostomy in our cardiothoracic surgical patients.

Evaluation of a Model for Glycemic Prediction in Critically Ill Surgical Patients

We evaluated a neural network model for prediction of glucose in critically ill trauma and post-operative cardiothoracic surgical patients. A prospective, feasibility trial evaluating a continuous glucose-monitoring device was performed. After institutional review board approval, clinical data from all consenting surgical intensive care unit patients were converted to an electronic format using novel software. This data was utilized to develop and train a neural network model for real-time prediction of serum glucose concentration implementing a prediction horizon of 75 minutes. Glycemic data from 19 patients were used to “train” the neural network model. Subsequent real-time simulated testing was performed in 5 patients to whom the neural network model was naive. Performance of the model was evaluated by calculating the mean absolute difference percent (MAD%), Clarke Error Grid Analysis, and calculation of the percent of hypoglycemic (≤70 mg/dL), normoglycemic (>70 and <150 mg/dL), and hyperglycemic (≥150 mg/dL) values accurately predicted by the model; 9,405 data points were analyzed. The models successfully predicted trends in glucose in the 5 test patients. Clark Error Grid Analysis indicated that 100.0% of predictions were clinically acceptable with 87.3% and 12.7% of predicted values falling within regions A and B of the error grid respectively. Overall model error (MAD%) was 9.0% with respect to actual continuous glucose modeling data. Our model successfully predicted 96.7% and 53.6% of the normo- and hyperglycemic values respectively. No hypoglycemic events occurred in these patients. Use of neural network models for real-time prediction of glucose in the surgical intensive care unit setting offers healthcare providers potentially useful information which could facilitate optimization of glycemic control, patient safety, and improved care. Similar models can be implemented across a wider scale of biomedical variables to offer real-time optimization, training, and adaptation that increase predictive accuracy and performance of therapies.

A Model to Create an Efficient and Equitable Admission Policy for Patients Arriving to the Cardiothoracic ICU*

To develop queuing and simulation-based models to understand the relationship between ICU bed availability and operating room schedule to maximize the use of critical care resources and minimize case cancellation while providing equity to patients and surgeons. Retrospective analysis of 6-month unit admission data from a cohort of cardiothoracic surgical patients, to create queuing and simulation-based models of ICU bed flow. Three different admission policies (current admission policy, shortest-processing-time policy, and a dynamic policy) were then analyzed using simulation models, representing 10 yr worth of potential admissions. Important output data consisted of the "average waiting time," a proxy for unit efficiency, and the "maximum waiting time," a surrogate for patient equity. A cardiothoracic surgical ICU in a tertiary center in New York, NY. Six hundred thirty consecutive cardiothoracic surgical patients admitted to the cardiothoracic surgical ICU. None. Although the shortest-processing-time admission policy performs best in terms of unit efficiency (0.4612 days), it did so at expense of patient equity prolonging surgical waiting time by as much as 21 days. The current policy gives the greatest equity but causes inefficiency in unit bed-flow (0.5033 days). The dynamic policy performs at a level (0.4997 days) 8.3% below that of the shortest-processing-time in average waiting time; however, it balances this with greater patient equity (maximum waiting time could be shortened by 4 days compared to the current policy). Queuing theory and computer simulation can be used to model case flow through a cardiothoracic operating room and ICU. A dynamic admission policy that looks at current waiting time and expected ICU length of stay allows for increased equity between patients with only minimum losses of efficiency. This dynamic admission policy would seem to be a superior in maximizing case-flow. These results may be generalized to other surgical ICUs.

A Diagnosis of Heparin-Induced Thrombocytopenia with Combined Clinical and Laboratory Methods in Cardiothoracic Surgical Intensive Care Unit Patients

A Diagnosis of Heparin-Induced Thrombocytopenia with Combined Clinical and Laboratory Methods in Cardiothoracic Surgical Intensive Care Unit Patients

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Introduction: The risk for development of severe sepsis or septic shock (SS/SS) is a great concern in the cardiothoracic surgery patient population. The Surviving Sepsis Campaign has recommended sepsis bundles that have been shown to reduce mortality in patients with SS/SS. Our group has previously shown that using an early sepsis initiative in the surgical population as a whole has significant benefit; however, there is little data looking at the particularly vulnerable cardiothoracic surgery cohort. Hypothesis: We believe that implementation of an early sepsis initiative will improve outcomes in the cardiothoracic surgery patient population. Methods: A retrospective review of 460 patients receiving the diagnosis of SS/SS after undergoing cardiothoracic surgery during hospital admission from November of 2003 through December of 2009 was conducted at an academic medical center. Mortality, length of hospital stay (LOS), intensive care unit (ICU) days, and ventilator days were calculated for the pre-intervention (November 2003-December 2005, N=148) and post-intervention (January 2006-December 2009, N=312) groups. Statistical analysis was conducted using T-test for continuous variables and chi-squared analysis for categorical variables. A p-value of 0.05 or less was considered significant. Results: The in hospital mortality rate slightly decreased from 16.22% to 15.70% after implementation of the early sepsis initiative (p=0.892). LOS was reduced from a mean of 31.66 ± 34.38 days to 24.12 ± 25.12 days (p=0.018). ICU days decreased from 22.24 ± 35.80 days to 13.29 ± 23.71 days (p=0.008). Ventilator days were reduced from 16.71 ± 28.88 days to 9.03 ± 11.77 days (p=0.005). Conclusions: The results demonstrate that the implementation of early best practice sepsis initiative leads to significant reduction in hospital LOS, ICU days, and ventilator days in the cardiothoracic surgical patient population. However, there was not a significant decrease in mortality. This is in contrast to the larger surgical population, in which significant mortality benefit has been observed. There is a great need for additional studies in reducing mortality in the SS/SS cardiothoracic surgery cohort.

A Diagnosis of Heparin-Induced Thrombocytopenia With Combined Clinical and Laboratory Methods in Cardiothoracic Surgical Intensive Care Unit Patients

*Department of Anesthesiology, †Transfusion Medicine, and ‡Department of Critical Care Medicine, Emory University, Atlanta, GA.

Recognition of heparin-induced thrombocytopenia and initiation of argatroban therapy after cardiothoracic surgery in the intensive care unit

Patients recovering from cardiothoracic surgery are known to be at increased risk of heparin-induced thrombocytopenia. Postoperatively, if heparin-induced thrombocytopenia is suspected, heparin is discontinued immediately and an alternative anticoagulant, such as the direct thrombin inhibitor argatroban, is administered. Current data regarding the safety and efficacy of argatroban in the postoperative cardiothoracic surgical patient in the intensive care setting are limited. Data were collected retrospectively from January 1, 2007, to December 31, 2010, from patients tested for antiplatelet factor 4/heparin antibodies on clinical suspicion of heparin-induced thrombocytopenia after cardiothoracic surgery. We evaluated the use of argatroban as a therapeutic agent for the postoperative treatment of suspected heparin-induced thrombocytopenia by comparing thrombotic and bleeding events, platelet dynamics, antiplatelet factor 4/heparin antibody titer, and clinical probability score between patients who did and did not receive argatroban. Eighty-seven patients were included; 47 patients (54%) were treated with argatroban, and 40 patients (46%) were not treated with argatroban. There was no association between argatroban therapy and bleeding, mortality, length of stay, or pretreatment thrombotic events. Among all patients, antiplatelet factor 4/heparin antibody titer and clinical probability score were higher in patients treated with argatroban. Clinical suspicion of heparin-induced thrombocytopenia as detected by clinical probability score and thrombotic complications should prompt immediate cessation of heparin and initiation of an alternative anticoagulant such as argatroban. The results from this study demonstrate that argatroban should be considered without increased risk for adverse events, including bleeding, in the cardiothoracic intensive care unit after surgery.

Strategies for longitudinal follow-up of patients with pediatric and congenital cardiac disease

Meaningful evaluation of the quality of medical and surgical care must include longitudinal follow-up. Long-term evaluation of the outcomes of patients undergoing cardiothoracic operations is a professional responsibility for all who provide care to these patients. Over the past decade, a substantial body of literature has been published related to the potential transformation of short-term clinical registries into platforms for longitudinal follow-up. This transformation will ultimately result in a higher quality of care for all cardiothoracic surgical patients by facilitating outcomes analysis, quality improvement, and clinical and longitudinal comparative effectiveness research on a national and international level. Several potential strategies will allow longitudinal follow-up to be conducted with clinical registries: (1) Linking with Administrative Data; (2) Linking with National Death Registries, such as the Social Security Death Master File (SSDMF) and the National Death Index (NDI); (3) Linking to other Clinical Registries; and (4) Creating Clinical Longitudinal Follow-up Modules. The purpose of this review article is to summarize the current state of the art of strategies for the longitudinal follow-up of patients with pediatric and congenital cardiac disease.

Preparation of the senior medical student for integrated surgery training: Significant impact of a competency-based course

Introduction As initiatives to broadly implement integrated training programs for surgery proceed, senior medical students (SMS) will need to be better prepared. Consequently, it is imperative that we prepare students to more effectively care for patients upon residency matriculation. Using cardiothoracic training as a model for integrated programs, we developed a course with a focus on cardiothoracic topics and examined its efficacy in preparing SMS for the management of cardiothoracic patients. Methods 22 SMS matched into surgical residencies completed a 4-week, competency-based, preparatory course incorporating didactics, simulation, skills labs, and covering areas essential for care of cardiothoracic surgical patients. Knowledge base, skill acquisition, and readiness were measured through written tests, performance examinations, and confidence self-assessments (5-point Likert scale). T-tests were used for pre- and post-course comparisons (alpha=0.05). Results Pre-course, students possessed significant measured anxiety related to both cognitive and technical skills needed for management of cardiothoracic patients. Cardiothoracic topics were ranked most important by the students, yet were the curricular areas of most substantial weakness. Measured confidence rose significantly (Table). Students demonstrated significant gains in knowledge base on the written test[mean pre-test score, 54.9%; post-test 86.4% (p ⁎ 4.18Emergent post-op events4.911.553.64 ⁎ 4.36Chest tubes, CVCs, art lines4.182.094.09 ⁎ 4.18Post-op cardiothoracic pts4.411.733.14 ⁎ 3.90Surgical critical care4.412.093.45 ⁎ 3.59Ventilators/ABGs4.252.463.89 ⁎ 3.80Post-op fluid mgmt4.272.363.95 ⁎ 3.95Post-op transplants4.321.592.82 ⁎ 3.50Bronchoscopy/endoscopy3.811.822.55 ⁎ 2.77⁎P Conclusions SMS have significant baseline deficits in skills necessary for seamless matriculation into integrated cardiothoracic surgery residencies. This study demonstrates the efficacy of a competency-based, preparatory course in significantly improving task-specific confidence, knowledge base, and technical proficiency. Further, these findings have broader implications for how we effectively prepare SMS for the transition to integrated surgical training programs.

A Diagnosis of Heparin-Induced Thrombocytopenia with Combined Clinical and Laboratory Methods in Cardiothoracic Surgical Intensive Care Unit Patients

Diagnosing postoperative heparin-induced thrombocytopenia (HIT) in cardiothoracic surgical patients is complicated because of the profound thrombocytopenia that occurs with cardiopulmonary bypass (CPB). CPB predisposes patients to develop a frequent incidence of antibodies directed against platelet factor 4 (PF4)/heparin complexes and HIT. The sensitivity of readily available antibody immunoassays is high, but specificity is quite low. The use of both a clinical probability score and rapid laboratory immunoassay has been shown to increase specificity, which is of particular importance in the CPB setting. Prompt diagnosis is crucial because cessation of heparin and treatment with alternative anticoagulation can reduce the risk of thromboembolic events. We retrospectively reviewed records from cardiothoracic surgical patients whose serum was tested with both the serotonin release assay (SRA) and the PF4/heparin immunoassay from January 2007 through December 2010. We assigned a high, intermediate, or low clinical "4Ts" probability score that quantifies thrombocytopenia, timing of platelet decrease, and thrombotic complications in each patient. We then compared the clinical score and the PF4/heparin immunoassay against the "gold standard" diagnostic test, the SRA. The sensitivity and specificity for PF4/heparin optical density >0.40 were 100% and 26%, respectively. Sensitivity and specificity for the diagnosis of HIT with a combination of PF4/heparin optical density >0.40 and high/intermediate 4Ts score were 100% and 70%, respectively. The negative predictive value was 100% for low 4Ts score. We demonstrated that the use of the 4Ts clinical score combined with the PF4/heparin immunoassay for HIT diagnosis increases the sensitivity and specificity of HIT testing compared with the PF4/heparin immunoassay alone. Furthermore, with an intermediate 4Ts score and positive PF4/heparin antibody test, a confirmatory platelet activation assay such as the SRA is necessary. Physicians treating patients after cardiothoracic surgery should recognize the need for an antibody test and confirmation with a platelet activation assay with even moderate clinical probability of HIT.

Iron studies and red cell transfusion in cardiothoracic and orthopaedic surgical patients: a retrospective audit at a tertiary hospital

Preoperative diagnosis and treatment of anaemia are important to minimize adverse postoperative outcomes. This audit reviewed red cell transfusion practice, degree of anaemia, iron deficiency anaemia (IDA) and chronic disease or anaemia of inflammation (AI) in cardiothoracic and orthopaedic surgical patients who had available iron studies. A total of 178 consecutive cardiothoracic and orthopaedic surgical patients with available iron studies were retrospectively reviewed. Of patients, 36·5% had preoperative iron studies. However, 63·2% males and 45·3% females with postoperative iron studies presented with anaemia; 38·5% patients with preoperative iron studies had AI; 21·5% IDA; 23·1% normal. For patients with iron studies requested within the first two postoperative intervals (≤ 5 days and 6 ≤ 10 days) 73·8% and 63·6%, respectively, had AI; few had classical IDA or were normal, and 51·5% patients transfused postsurgery had a discharge Hb ≥ 110 g/l. Restricting the discharge Hb to 90 or 100 g/l may have eliminated postsurgical transfusion in 14·8-42·6% patients. Iron studies were more commonly requested postoperatively despite many being anaemic at admission. A higher proportion of patients with postoperative iron studies had AI, and few had classical IDA or normal iron parameters, suggesting a transient inflammatory effect of surgery. This may mask underlying IDA or normal iron parameters and affect treatment. Preadmission assessment, including iron status, should be emphasized allowing diagnosis and correction of presurgical anaemia with treatment modalities other than red cell transfusion. In the postsurgical setting, consideration of a restrictive transfusion regimen sufficient to alleviate a patient's clinical symptoms would ensure that this valuable resource is appropriately used.

Changes in B-Type Natriuretic Peptide During Ventilator Weaning in Cardiothoracic Surgical Patients Admitted to a Long-term Acute Care Facility

PURPOSE: The purpose of this study is to evaluate the role of B-type natriuretic peptide (BNP) levels during the weaning process in cardiothoracic surgical (CTS) patients admitted to an Atlanta LTAC requiring prolonged mechanical ventilation.

Outcomes of Cardiothoracic Surgical Patients Admitted to a Long-term Acute Care Facility

Outcomes of Cardiothoracic Surgical Patients Admitted to a Long-term Acute Care Facility

S3-Leitlinie zur intensivmedizinischen Versorgung herzchirurgischer Patienten

Hemodynamic monitoring and adequate volume therapy, as well as treatment with positive inotropic drugs and vasopressors are the basic principles of postoperative intensive care treatment of patients after cardiothoracic surgery. The goal of these S3 guidelines is to evaluate the recommendations with respect to evidence-based medicine and to define therapy goals for monitoring and therapy. In context with the clinical situation the evaluation of the different hemodynamic parameters allows the development of a therapeutic concept and the definition of target criteria to evaluate the effect of treatment.Up to now there have only been guidelines for subareas of postoperative treatment of cardiothoracic surgical patients, such as the use of pulmonary artery catheters or transesophageal echocardiography.The German Society for Thoracic and Cardiovascular Surgery and the German Society for Anesthesiology and Intensive Care Medicine made an approach to ensure and improve the quality of postoperative intensive care medicine after cardiothoracic surgery by the development of S3 consensus-based treatment guidelines.The goal of these guidelines is to assess the available monitoring methods with respect to indications, procedures, predication, limits, contraindications and risks for use. The differentiated therapy of volume replacement, positive inotropic support and vasoactive drugs, the therapy with vasodilatators, inodilatators and calcium sensitizers and the use of intra-aortic balloon pumps will also be addressed.These guidelines have been developed following the recommendations for the development of guidelines by the Association of the Scientific Medical Societies in Germany (AWMF). The presented key messages of the guidelines were approved after two consensus meetings under the moderation of the AWMF.

Treatment of irradiated poststernotomy sternal nonunion with autologous stem cell–impregnated bone matrix and sternal plating

Sternal wound complications are an infrequent but significant cause of postoperative morbidity for cardiothoracic surgical patients. Sternal nonunion occurs in fewer than 1% of patients after median sternotomy, but it represents a challenging clinical problem because it is often associated with chronic pain of debilitating magnitude. Affected patients are often treated with debridement and sternal rewiring, which requires reexploration of the mediastinum. We describe the case of a patient successfully treated with an autologous stem cell–seeded bone matrix and sternal plating for chronic manubrial nonunion in a postsurgical, irradiated sternum.

A QUALITY IMPROVEMENT INITIATIVE TO REDUCE THE AMOUNT OF BLOOD DRAWN BY RESPIRATORY THERAPISTS IN THE CARDIOTHORACIC INTENSIVE CARE UNIT

PURPOSE: Analyses of arterial blood gases (ABG) are essential in the postoperative phase of cardiothoracic (CT) surgery. With the current trend toward blood management (a program to reduce the need for transfusion of blood and/or blood products in selected surgery populations), we are attempting to decrease the amount of blood drawn from our CT surgical patients. The amount of blood required for analysis with current instrumentation (Radiometer ABL800) is nominally 165 microliters.

Applications of statins in cardiothoracic surgery: more than just lipid-lowering

Statins exert several actions in cardiothoracic surgical procedures besides lipid-lowering. In patients undergoing coronary artery bypass grafting (CABG), statins improve bypass graft patency, perioperative as well as long-term mortality rates. In addition, statins reduce the number of postoperative complications and clinical events, revascularization rates and postoperative hospital stay (as well as associated costs). Furthermore, they are protective against de novo atrial fibrillation and renal dysfunction following CABG. In cardiac transplantation, statins decrease cardiac allograft vasculopathy and cardiac rejection rates. They are also associated with a significant reduction in mortality rates in cardiac transplant patients. According to the results of a meta-analysis, statins are associated with one life saved for every 8.5 heart transplant recipients treated for 1 year. Alternatively, routine statin treatment in cardiac transplant patients might have the potential to save 471 lives each year among the 4000 heart transplantation operations performed worldwide. The results from several studies suggest that statins may also play a role in heart valve surgery, lung transplantation, pulmonary resection and thoracic aortic aneurysm repair. Statin use is safe and cost-effective. Despite the multiple beneficial effects of statin therapy, there is evidence suggesting that a large percentage of cardiothoracic surgical patients are suboptimally treated with respect to statins. Risk management in these patients should be improved to reduce cardiovascular morbidity and mortality rates.

Systemic Anticoagulant Effect of Low-Dose Subcutaneous Unfractionated Heparin as Determined Using Thrombelastography

In an observational study using heparinase-modified thrombelastography, we investigated the percentage of elective cardiothoracic surgical patients receiving low-dose unfractionated heparin (5000 IU 12 hourly subcutaneously) who had a demonstrable systemic heparin effect. Blood samples were obtained at induction from 40 adult elective cardiothoracic surgical patients who had received 5000 IU unfractionated heparin subcutaneously within six hours. Simultaneous kaolin and heparinase-modified thrombelastographies were run on all samples. Fourteen patients (35%; 95% CI: 20 to 50%) had a demonstrable heparin effect (defined as a kaolin thrombelastography R time >25% longer than the heparinase-modified control). Their mean +/- SD kaolin thrombelastography R time was 13.6 +/- 5.9 minutes (normal range 4 to 8 minutes) vs. 7.1 +/- 2.0 minutes for the heparinase-modified controls. In 10 patients the thrombelastography R times were >50% longer and in four patients >100% longer than their respective heparinase-modified controls. In a post hoc analysis, there was little correlation between the extent of the prolongation and patient age (r = 0.02), weight (r = -0.31), preoperative creatinine (r = -0.17), or time since administration of heparin (r = 0.14). These results indicate that about one third of patients who have received low-dose unfractionated heparin subcutaneously within six hours have a demonstrable heparin effect. The potential for this effect should be considered if central neural blockade is planned.