High dose subcutaneous unfractionated heparin for prevention of venous thromboembolism in overweight neurocritical care patients

Thromboembolic prevention and anticoagulant therapy during the COVID-19 pandemic: updated clinical guidance from the anticoagulation forum

Thromboembolism is a common and deadly consequence of COVID-19 infection for hospitalized patients. Based on clinical evidence pre-dating the COVID-19 pandemic and early observational reports, expert consensus and guidance documents have strongly encouraged the use of prophylactic anticoagulation for patients hospitalized for COVID-19 infection. More recently, multiple clinical trials and larger observational studies have provided evidence for tailoring the approach to thromboprophylaxis for patients with COVID-19. This document provides updated guidance for the use of anticoagulant therapies in patients with COVID-19 from the Anticoagulation Forum, the leading North American organization of anticoagulation providers. We discuss ambulatory, in-hospital, and post-hospital thromboprophylaxis strategies as well as provide guidance for patients with thrombotic conditions who are considering COVID-19 vaccination.

Comparison of Chemical and Mechanical Prophylaxis of Venous Thromboembolism in Non-surgical Mechanically Ventilated Patients

To compare the efficacy of mechanical and chemical prophylaxis in non-surgically mechanically ventilated patients in terms of reduction in mortality and length of hospital stay.

A total of 200 patients admitted to intensive care units (ICUs) were recruited retrospectively. Half participants received mechanical prophylaxis and half received chemical prophylaxis. Patients with medical diseases with age 18 years or above, both genders, Pakistani nationals, receiving mechanical ventilation for more than 48 hours or receiving subcutaneous low molecular weight (LMW) heparin or subcutaneous unfractionated heparin were included. Cases who undergone surgery and were then admitted to ICU, those who received both mechanical and chemical therapies, and patients who received anticoagulant treatment before admission to ICU were excluded from the study. The patient’s age, gender, length of stay in ICU, and mortality were recorded in each group. Chi-square test was used to compare categorical data and Student t-test for continuous variables.

The mean age was 55.51±8.37 years. The males were 108(54%) and females were 92(46%). The mortality rate was higher in the mechanical prophylaxis group (49%) than chemical (31%) statistically significantly (P=0.014). Similarly, the length of hospital stay was also higher in the mechanical prophylaxis group (7.27±0.897 days) than chemical (6.67±1.045) statistically (P<0.001).

Chemical prophylaxis can reduce mortality and length of hospital stay more effectively than mechanical prophylaxis in ICUs admitted patients.

Drug dosing in the critically ill obese patient: a focus on medications for hemodynamic support and prophylaxis

Medications used for supportive care or prophylaxis constitute a significant portion of drug utilization in the intensive care unit. Evidence-based guidelines are available for many aspects of supportive care but drug doses listed are typically for patients with normal body habitus and not morbid obesity. Failure to account for the pharmacokinetic changes that occur with obesity can lead to an incorrect dose and treatment failure or toxicity. This paper is intended to help clinicians design initial dosing regimens in critically ill obese patients for medications commonly used for hemodynamic support or prophylaxis. A detailed literature search of medications used for supportive care or prophylaxis listed in practice guidelines was conducted with an emphasis on obesity, pharmacokinetics and dosing. Relevant manuscripts were reviewed and strategies for dosing are provided. For medications used for hemodynamic support, a similar strategy can be used as in non-obese patients. Similarly, medications for stress ulcer prophylaxis do not need to be adjusted. Anticoagulants for venous thromboembolism prophylaxis, on the other hand, require an individualized approach where higher doses are necessary.

Safety of High-Dose Unfractionated Heparin for Prophylaxis of Venous Thromboembolism in Hospitalized Obese Patients

BACKGROUND

Optimal dosing of unfractionated heparin (UFH) for thromboprophylaxis in the obese patient population is uncertain because of their high-risk, prothrombotic state and a complexity of pharmacokinetic considerations. Literature on the appropriateness of the use of a higher dose UFH regimen remains unclear and inconsistent.

OBJECTIVE

To evaluate the safety of the use of 7500 units every 8 hours (high-dose) of subcutaneous UFH compared with the use of 5000 units every 8 hours (standard-dose) of subcutaneous UFH for thromboprophylaxis in obese patients (defined as BMI ≥30 kg/m²).

METHODS

In a retrospective cohort study, 326 adult patients were included, with a BMI ≥30 kg/m², who were admitted to a large, urban academic medical center between September 1, 2015, and September 1, 2018. Patients received either high-dose or standard-dose UFH for at least 48 hours. The primary end point was the incidence rate of bleeding events, defined as a ≥2-g/dL fall in hemoglobin level or receipt of transfusion of 2 or more units of packed red blood cells (pRBCs) from the start of the UFH order.

RESULTS

The incidence rate of bleeding was significantly higher in those who received high-dose UFH (43%) compared with those who received standard-dose UFH (29%; P = 0.008). No significant difference was found between venous thromboembolism event rates.

CONCLUSION AND RELEVANCE

High-dose UFH was associated with an increased bleeding event rate compared with standard-dose UFH in patients with a BMI ≥30 kg/m². This raises safety concerns about the appropriateness of utilizing this regimen in this population.

Safety and Efficacy of High-Dose Unfractionated Heparin Versus High-Dose Enoxaparin for Venous Thromboembolism Prevention in Morbidly Obese Hospitalized Patients

BACKGROUND

Venous thromboembolism is a cause of morbidity and mortality in hospitalized patients, and morbid obesity increases this risk. Various prophylaxis dosing strategies have been investigated. However, it is unclear if high-fixed dose enoxaparin or high-fixed dose unfractionated heparin thromboprophylaxis is optimal for minimizing the incidence of major bleeding and reducing hospital-acquired venous thromboembolism.

METHODS

A single-center retrospective observational study was conducted in hospitalized patients who were morbidly obese (body mass index ≥40 kg/m²) and who received either high-fixed dose enoxaparin (40 mg every 12 hours) or unfractionated heparin (7500 units every 8 hours) for venous thromboembolism prophylaxis. Co-primary outcomes included incidence of major bleeding and venous thromboembolism diagnosed during hospitalization. Predictors of major bleeding were evaluated by multivariable regression.

RESULTS

In the 305 patients included (n = 190 unfractionated heparin, n = 115 enoxaparin), the incidence of major bleeding was significantly higher in the unfractionated heparin group (odds ratio [OR] 1.85, 95% confidence interval [CI] 1.07-3.13; P = 0.025), with no significant difference in the incidence of venous thromboembolism diagnosed during hospitalization. The only independent predictors of major bleeding were intensive care acuity (OR 3.32, 95% CI 1.91-5.78; P <0.001) and selection of unfractionated heparin rather than enoxaparin for venous thromboembolism prophylaxis (OR 2.16, 95% CI 1.22-3.82; P = 0.008).

CONCLUSION

High-fixed dose unfractionated heparin for venous thromboembolism prophylaxis may lead to a higher risk of major bleeding events compared with high-fixed dose enoxaparin in patients who are morbidly obese.

Analysis of venous thromboembolism in neurosurgical patients undergoing standard versus routine ultrasonography

Routine screening of high-risk asymptomatic trauma or surgical patients for venous thromboembolism (VTE) is controversial. Studies suggest against screening while others recognize that some patients at high risk may benefit. The purpose of this pilot study is to evaluate the benefit of routine screening using doppler ultrasonography for the early detection of deep venous thrombosis (DVT) in post-operative neurosurgical patients. This was a quasi-experimental study at a major academic tertiary care medical center. A total of 157 adults underwent cranial or spinal surgical interventions from March through August 2017 and received either standard screening (n = 104) versus routine ultrasonography screening (n = 53). There was no significant difference in incidence of DVT between the two groups: 11 (11%) in the standard screening group versus 5 (9%) in the routine screening group, p = 0.823. Upper and lower extremity ultrasonography was performed in 43 (41%) of the standard screening group versus 53 (100%) in the routine screening group, p < 0.001. DVT was identified in nearly one of every 6 ultrasonography screenings in the standard screening group versus 27 ultrasonography screenings required to identify one DVT in the routine screening group. There were the same number of screenings for upper extremity ultrasonography, but they did not yield or detect DVT; instead only superficial, untreatable, DVTs were reported. Total cost to diagnose one DVT, including screening and labor, averaged $13,664 in the standard group versus $56,525 in the routine group. Routine screening in neurosurgical patients who received VTE prophylaxis was not associated with lower incidence of VTE and mortality attributed to PE. Thus, routine screening may not be cost effective to prevent complications from DVT incidence.

Anti-Xa activity by weight in critically ill patients receiving unfractionated heparin for venous thromboembolism prophylaxis

PURPOSE

This study compared anti-Xa activity in critically ill patients receiving UFH for VTE prophylaxis between two weight groups (<100 kg vs ≥100 kg).

METHODS

This prospective, observational study included critically ill patients on UFH 5000 or 7500 units every 8 h. A peak and trough anti-Xa activity assay was ordered for each patient at steady state. Goal peak anti-Xa activity was 0.1-0.3 units/mL.

RESULTS

From March 2017 to June 2018, 75 patients were enrolled with 44 in the <100 kg group and 31 in the ≥100 kg group. There was no significant difference in the percentage of patients with peak anti-Xa activity within goal range between patients <100 kg and ≥ 100 kg (55.3% vs 35.7%, p = 0.12). The odds ratio for achieving peak anti-Xa activity within goal range as weight-based dose increased was 1.03 (95% CI 0.99-1.07). No differences were found in trough anti-Xa activity, VTE, bleeding, length of stay, or death.

CONCLUSIONS

Though only one-third of patients ≥100 kg had peak anti-Xa activity within goal range, no significant difference was found between the weight groups. Additional prospective studies with adequate sample sizes are warranted to further investigate appropriate weight-based dosing of UFH in critically ill patients.

Venous Thromboembolism Prophylaxis: A Narrative Review With a Focus on the High-Risk Critically Ill Patient

Venous thromboembolism (VTE) is a major health concern associated with significant morbidity and mortality. Critically ill patients are at an increased risk of VTE compared to general medical patients due to unique risk factors: prolonged immobilization, invasive lines and devices, certain medications, and acquired thrombophilia. Furthermore, VTE in the critically ill is associated with increased duration of mechanical ventilation, increased length of intensive care unit and hospital stay, and a trend toward increased mortality. Clinical practice guidelines therefore recommend VTE prophylaxis with either subcutaneous heparin or low-molecular-weight heparin for all critically ill patients without contraindication. Yet, many patients will develop VTE despite appropriate pharmacologic prophylaxis, which has led to interest in risk-stratifying critically ill patients for more aggressive prophylaxis strategies. Recent research identified patients at highest risk of failure of thromboprophylaxis and provided insight into the pathophysiologic mechanisms. Obesity and the receipt of vasopressors are 2 risk factors consistently identified in observational studies; further clinical data support decreased absorption of anticoagulant administered via the subcutaneous route as the likely mechanism behind thromboprophylaxis failure in these patient populations. Several studies have investigated novel thromboprophylaxis strategies to circumvent pharmacokinetic limitations in patients who are obese or on vasopressors: increased fixed-dose, weight-based subcutaneous, or continuous intravenous infusion of a prophylactic dose of anticoagulant has shown promise in limited studies; however, the results have yet to demonstrate superiority compared to current standard-of-care. This review discusses observational studies identifying patients at risk of thromboprophylaxis failure and critiques clinical studies evaluating novel thromboprophylaxis strategies in high-risk, critically ill patients with a focus on their limitations. Future studies are currently being conducted that will provide further guidance into the appropriate use of individualized thromboprophylaxis.

Efficacy of standard dose unfractionated heparin for venous thromboembolism prophylaxis in morbidly obese and non-morbidly obese critically Ill patients

To determine the efficacy of standard dose unfractionated heparin (UFH) for venous thromboembolism (VTE) prophylaxis in critically ill morbidly obese patients. Retrospective single-center observational cohort study in a single tertiary teaching hospital intensive care units (ICUs) in Multiparameter Intelligent Monitoring in Intensive Care II Clinical Database. Patients 18 years or older, admitted to the ICU, and received either UFH 5000 units subcutaneously twice daily or UFH 5000 units three times daily for VTE prophylaxis between 2001 and 2008 were included. Total 243 patients in the BMI ≥ 40 kg/m² group and 2813 patients in the BMI < 40 kg/m² group were identified. There was no difference in VTE incidence between the two groups. However, a strong linear association was found showing as BMI increased so did the rate of VTE incidence. Morbidly obese patients had longer hospital (17 vs. 14 days, P = 0.016) and ICU length of stay (10 vs. 8 days, P = 0.007). After controlling Padua score, logistic regression analysis revealed the odds of VTE increased by a factor of 1.026 for each one-unit increase in BMI. Additionally, having a BMI ≥ 40 kg/m² was associated with a greater likelihood of VTE incidence in males (OR 3.92) but not in females. In patients treated with standard dose UFH, morbid obesity does not increase VTE risk overall. However, BMI has a strong linear relationship with VTE incidence and morbid obesity is more likely associated with greater hospital and ICU length of stay.

Low-Dose versus Therapeutic Range Intravenous Unfractionated Heparin Prophylaxis in the Treatment of Patients with Severe Aneurysmal Subarachnoid Hemorrhage After Aneurysm Occlusion

BACKGROUND

While prophylaxis with intravenous unfractionated heparin (UFH) can effectively prevent venous thromboembolism (VTE) during the neurocritical care of patients with severe aneurysmal subarachnoid hemorrhage (aSAH), the risk for intracranial bleeding complications might increase. Owing to this therapeutic dilemma, the UFH administration regimen in this critical patient population remains highly controversial.

METHODS

We performed a retrospective analysis of patients with severe aSAH (Fisher grade 3-4) receiving either low-dose (activated partial thromboplastin time [aPTT] <40 seconds) or therapeutic range (aPTT 50-60 seconds) UFH during intensive care unit (ICU) treatment after complete surgical/endovascular aneurysm occlusion. The primary outcome was the rate of bleeding/VTE complications and the investigation of potential risk factors.

RESULTS

This study series comprised 410 patients with aneurysmal SAH (aSAH), with a mean age of 54.7 ± 12.6 years, a male:female ratio of 1:2.2, and aSAH-associated intracerebral hemorrhage (ICH) in 33.2%. After complete aneurysm occlusion, 112 patients (27.3%) received therapeutic dose UFH and 298 patients (72.7%) received low-dose UFH. VTE events occurred in 5.4% of the low-dose UFH cohort and in 6.3% of the therapeutic dose UFH cohort, with no significant differences in the rate and severity of VTE events. However, an increase in initial SAH-associated ICH was significantly (P = 0.007) more frequent in the therapeutic dose cohort (18.8% vs. 3.4%). Heparin-induced thrombocytopenia (HIT) was the sole risk factor for VTE (P < 0.001), and both an aPTT ≥50 seconds under UFH administration (P = 0.007) and the initial presence of SAH-associated ICH (P = 0.035) were significant risk factors for intracranial bleeding complications.

CONCLUSIONS

Even in high-risk neurocritical patients with severe SAH and prolonged ICU treatment, low-dose UFH-administration for VTE prophylaxis is equally effective as therapeutic UFH administration and carries a lower risk of bleeding complications.

Assessment of the Relationship between Body Mass Index and Incidence of Venous Thromboembolism in Hospitalized Overweight and Obese Patients

STUDY OBJECTIVE

To assess whether a positive linear association exists between body mass index (BMI) and incidence of venous thromboembolism (VTE) in overweight and obese hospitalized patients.

DESIGN

Single-center retrospective observational cohort study.

SETTING

Large academic tertiary care medical center.

PATIENTS

A total of 1452 adults hospitalized between January 1, 2013, and December 31, 2014, who weighed more than 100 kg and had a BMI of 25 kg/m² or greater on admission, and received heparin subcutaneously for VTE prophylaxis. Patients were categorized into four subgroups based on World Health Organization BMI classification: overweight (141 patients), obese class I (305 patients), obese class II (324 patients), and obese class III (682 patients).

MEASUREMENTS AND MAIN RESULTS

The primary outcome was occurrence of VTE in each subgroup; all-cause mortality and length of hospital stay were secondary outcomes. A linear trend test did not show an association between occurrence of VTE and BMI of 25 kg/m² or greater. VTE occurred in 7 (5%) of 141 patients in the overweight group, 5 (2%) of 305 in the obese class I group, 8 (3%) of 324 in the class II group, and 18 (3%) of 682 in the class III group (p=0.573). In addition, no linear association was noted between all-cause mortality or length of hospital stay and BMI of 25 kg/m² or greater. Overall mortality was 10% (146/1452 patients). Ten deaths (7%) occurred in the overweight group, 45 (15%) in the obese class I group, 38 (12%) in the obese class II group, and 53 (8%) in the obese class III group (p=0.067). The median length of hospital stay was 5 days (interquartile range 3-9, p=0.122) for all patients.

CONCLUSION

In overweight and obese hospitalized patients who weighed more than 100 kg and had a BMI of 25 kg/m² or greater, the incidence of VTE did not increase incrementally with increasing severity of obesity.

Impact of practice change in reducing venous thromboembolism in neurocritical overweight patients: 2008-2014

Publications regarding early initiating venous thromboembolism (VTE) prophylaxis have been available since the early 1990s. These recommendations became available in current guidelines on and after 2012. The purpose of this study is to review the practice change in reducing the incidence of VTE in brain injury patients from 2008 to 2014. This was a single-center, retrospective, observational, cohort study. Data was extracted from our data base that included patients over 100 kg from January 2008 to August 2014. Included were all patients admitted with a primary diagnosis of acute brain and spinal injury to neurocritical care unit. Clinical endpoints examined were incidence of bleeding and VTE. A total of 509 patients who met the inclusion criteria were divided into two groups: The previous group (n = 212) included patients from 2008 to 2010, and the recent group (n = 297) included patients from 2011 to 2014. The time for initiating VTE prophylaxis from admission was (median, IQR) 73 h (37-140) vs. 34 h (20-46); p < 0.01. There were no differences in major and minor bleeding complications. Discontinuation of VTE prophylaxis for association with progressive bleeding was not documented in any of the study patients. The incidence of VTE was 10 % (22/212) vs. 5 % (15/297); p = 0.02. In hospital LOS in days was 16 (10-26) vs. 7 (4-15); P < 0.01. In multivariable logistic regression analysis, only the time of the initiation VTE prophylaxis after admission was significantly associated with the occurrence of VTE (median, IQR) 70 h (37-158) vs. 36 h (20-63); OR 1.004, 95 % CI 1.001-1.007; P < 0.01. In this 6-year review of data, early initiation of VTE prophylaxis has decreased the incidence of VTE without clinically documented bleeding complications.

Antifactor Xa levels vs. activated partial thromboplastin time for monitoring unfractionated heparin. A pilot study

WHAT IS KNOWN AND OBJECTIVES

The two most common methods for monitoring unfractionated heparin (UFH) infusion are the activated partial thromboplastin time (aPTT) and the antifactor Xa heparin assay (anti-Xa). The purpose of this study is to compare the performance of an aPTT protocol vs. an anti-Xa protocol in adult patients as defined by the time to reach therapeutic range, the percentage of time the values were within the goal range and the number of times laboratory monitoring was conducted. We then analysed the discordance between paired values of anti-Xa and aPTT.

METHODS

This was a single-centre prospective cohort pilot study conducted from 1 September 2013 to 31 May 2014.

RESULTS

Eighty-five patients were treated with UFH infusion, aPTT monitoring (n = 48), anti-Xa monitoring (n = 37). The number of times aPTT and anti-Xa values were ordered was (median, IQR) 14 (2-34) vs 7 (2-76); P = 0·23. The time to reach therapeutic range in hours was (mean, SD) 22 (20) aPTT vs 15 (13) anti-Xa; P = 0·08. Therapeutic range (>50-100% of the time) was achieved in only 5 (10%) patients in the aPTT group vs. 21 (57%) in the anti-Xa group; P < 0·01. Supratherapeutic values (>50-100%) were observed in 38 (78%) patients in the aPTT group vs. 14 (38%) in the anti-Xa group; P < 0·01. The discordance between aPTT and anti-Xa was evaluated using 234 paired values from 37 patients. There was discordance between anti-Xa and aPTT values 57% of the time. Two patients had bleeding complications requiring blood transfusion or discontinuation of post-pilot protocol.

WHAT IS NEW AND CONCLUSION

Utilizing an anti-Xa protocol to monitor heparin infusion showed favourable results compared with utilizing an aPTT protocol by maintaining values within the therapeutic goal range. The most common discordant pattern in our study was a disproportionate prolongation of aPTT to anti-Xa values. Patients with discordant values presenting with high aPTT to normal anti-Xa values may have an increased risk of bleeding complications.

Safety and Efficacy of High-Dose Unfractionated Heparin for Prevention of Venous Thromboembolism in Overweight and Obese Patients

STUDY OBJECTIVE

To determine the safety and efficacy of high-dose subcutaneous unfractionated heparin (UFH) for prevention of venous thromboembolism (VTE) in overweight and obese patients.

DESIGN

Single-center retrospective observational cohort study.

SETTING

Large academic tertiary care medical center.

PATIENTS

A total of 1335 adults who weighed more than 100 kg on admission and received either subcutaneous UFH 7500 units every 8 hours (751 patients [high-dose group]) or 5000 units every 8 hours (584 patients [low-dose group]) for VTE prophylaxis during their hospitalization between January 1, 2013, and August 31, 2014.

MEASUREMENTS AND MAIN RESULTS

The incidences of VTE and bleeding complications were assessed in each group. Each group was further divided into four groups based on their body mass index (BMI): overweight (BMI 25-29.9 kg/m(2) ), obese class I (BMI 30-34.9 kg/m(2) ), obese class II (BMI 35-39.9 kg/m(2) ), and obese class III (BMI ≥ 40 kg/m(2) ). The incidence of VTE was similar for patients in the high-dose group versus those in the low-dose group for all BMI categories. Bleeding complications were significantly higher for patients in the high-dose group. The proportion of patients with at least a 2-g/dl hemoglobin drop from admission was higher in patients in the high-dose groups in obese classes II and III: obese class II, 46 (30%) of 152 patients in the high-dose group versus 30 (18%) of 171 patients in the low-dose group (p<0.01); obese class III, 109 (25%) of 432 patients in the high-dose group versus 31 (12%) of 249 patients in the low-dose group (p<0.01). In addition, the proportion of patients who received at least 2 units of packed red blood cell transfusion was significantly higher in patients in the high-dose group who were in obese class III: 47 (11%) of 432 in the high-dose group versus 13 (5%) of 249 in the low-dose group (p<0.01).

CONCLUSION

Administering a higher dose of heparin to patients weighing more than 100 kg may not impart additional efficacy in reducing the incidence of VTE. However, it may increase the risk for bleeding.

Efficacy and Safety of High-Dose Subcutaneous Unfractionated Heparin Prophylaxis for the Prevention of Venous Thromboembolism in Obese Hospitalized Patients

BACKGROUND

Obese patients experience a higher risk of venous thromboembolism (VTE) than their nonobese counterparts, which may warrant a more aggressive approach to thromboprophylaxis in this population.

OBJECTIVE

The purpose of this study was to compare rates of nosocomial VTE in obese patients treated with high-dose versus conventional-dose subcutaneous unfractionated heparin sodium (UFH) for thromboprophylaxis.

METHODS

A retrospective, single-center, cohort study was conducted to evaluate obese, adult, hospitalized patients admitted between April 2011 and April 2014 who received heparin 5,000 or 7,500 units subcutaneously every 8 hours for thromboprophylaxis. The primary outcome assessed the rate of nosocomial VTE in obese patients treated with high-dose heparin (7,500 units subcutaneously q 8 h) versus conventional-dose heparin (5,000 units subcutaneously q 8 h). Additionally, a secondary outcome assessed safety by quantifying bleeding events.

RESULTS

Nosocomial VTE occurred in 2/196 (1.02%) patients who received high-dose heparin thromboprophylaxis and in 5/2,182 (0.23%) patients who received conventional-dose heparin (p = .05). Bleeding occurred in 0/196 (0%) patients in the high-dose heparin group and in 2/2,182 (0.09%) patients in the conventional-dose heparin group (p = .67). All bleeding events were minor.

CONCLUSIONS

This study failed to demonstrate a statistically significant reduction in the rate of nosocomial VTE in obese patients who received high-dose heparin thromboprophylaxis. Despite receiving a higher heparin dose, no increased risk of bleeding was observed in the high-dose group. Further investigation is needed to identify the optimal heparin dose for thromboprophylaxis in obese patients.