Time to Target Anti-Xa Level in Obese Vs Nonobese Patients Using an Adjusted Body Weight Heparin Infusion Protocol for the Treatment of Venous Thromboembolism

BACKGROUND

Unfractionated heparin (UFH) is a first-line option for the acute treatment of venous thromboembolism (VTE). Weight-based dosing protocols have demonstrated a decreased time to therapeutic anticoagulation, however, there are limited data on their utilization in obese patients, including the type of weight used.

OBJECTIVE

The purpose of this study was to determine equivalency in time to reach target antifactor-Xa (anti-Xa) for obese and nonobese patients using the same adjusted body weight (AdjBW)-based UFH infusion protocol.

METHODS

This was a single-center retrospective study of patients aged 18 years or older receiving an infusion of UFH for the treatment of VTE. The primary outcome was the median time to first target anti-Xa. Secondary outcomes included the percentage of first anti-Xa levels at 6 hours that were within, below, or above the target range and the median time to the second consecutive anti-Xa level within the target range. The safety outcome of evidence of major bleed was also evaluated.

RESULTS

Of the 166 patients assessed (75 obese and 91 nonobese), there was no observed difference in median time to first target anti-Xa in obese vs nonobese patients when using an AdjBW UFH protocol (12.45 vs 13.03 hours, P = 0.49). The percentage of patients achieving a target anti-Xa at first evaluation did not differ between obese and nonobese groups (32.0% vs 34.07%, P = 0.78). A total of 14 patients across groups experienced evidence of major bleed, with no observed difference between obese and nonobese groups (8.00% vs 8.89%, P = 0.84).

CONCLUSIONS AND RELEVANCE

There was no observed difference in median time to first target anti-Xa in obese vs nonobese patients when using an AdjBW heparin infusion protocol, with no observed difference in evidence of major bleed. Our findings support the use of AdjBW in weight-based UFH dosing.

Evaluation of unfractionated heparin therapy for venous thromboembolism using adjusted body weight in elderly or higher weight patients

The use of weight-based unfractionated heparin (UFH) infusions is the standard of care in hospital management of venous thromboembolism (VTE). Initial dosing strategies for UFH in older adults and higher body weight patients remain uncertain given differences in pharmacokinetics and concerns for over-anticoagulation. Methods: This was a single-center, retrospective, pre-post study involving older adults aged ≥ 65 years and patients weighing ≥ 100 kg with suspected or confirmed VTE to determine if the use of adjusted body weight (AdjBW)-based UFH regimens improves time to therapeutic anti-Xa levels compared to total body weight (TBW)-based regimens Patients received weight-based UFH infusions, dosed according to either TBW or AdjBW, to target a therapeutic anti-Xa level. Each cohort consisted of 40 patients, stratified by whether they met age or weight criteria to ensure equal representation of elderly and higher body weight patients between cohorts. The median time to therapeutic anti-Xa levels was shorter in the AdjBW group compared to the TBW group (13.6 h versus 20.9 h; point estimate 5.3 h (95% CI 0.2 to 9.9)). This finding was driven by those aged ≥ 65 years and those who received a bolus dose at the start of the infusion. Among older adults and higher weight adults with suspected or confirmed VTE, the use of AdjBW to guide heparin infusion initiation was associated with shorter time to therapeutic anti-Xa levels. This finding driven by the older adult sample and the subgroup analyses did not find a statistically significant difference in time to therapeutic anti-Xa levels in higher body weight patients aged less than 65 years.

Anticoagulation approach in morbid obesity: a comprehensive review on venous thromboembolism management

Obesity is a recognized risk factor for venous thromboembolism (VTE), associated with distinct challenges in managing anticoagulation therapy. There is still limited evidence regarding the impact of extreme body weight on the pharmacokinetics, pharmacodynamics, efficacy, and safety of various anticoagulant medications. To our knowledge, this is the first comprehensive review to address both prophylactic and therapeutic anticoagulant dosages specifically for managing VTE in patients with a body mass index (BMI) ≥40 kg/m2 or weight ≥120 kg. Our aim was to synthesize the findings of relevant studies alongside the latest recommendations on anticoagulation in this unique population. We gathered and analyzed data on all classes of anticoagulants available for VTE management, including vitamin K antagonists (VKAs), unfractionated heparin (UFH), low-molecular-weight heparin (LMWH), fondaparinux, and direct oral anticoagulants (DOACs), offering insights into their efficacy and safety profiles. Additionally, we explored special subpopulations of morbidly obese patients, such as those with cancer, renal dysfunction, or those undergoing bariatric surgery, recognizing the nuanced therapeutic challenges they present. The current evidence for anticoagulant therapy in morbidly obese patients with VTE is evidently insufficient, underscoring the need for a tailored approach and meticulous monitoring to achieve an optimal therapeutic balance.

Clinical decision making under uncertainty: a bootstrapped counterfactual inference approach

BACKGROUND

Learning policies for decision-making, such as recommending treatments in clinical settings, is important for enhancing clinical decision-support systems. However, the challenge lies in accurately evaluating and optimizing these policies for maximum efficacy. This paper addresses this gap by focusing on two key aspects of policy learning: evaluation and optimization.

METHOD

We develop counterfactual policy learning algorithms for practical clinical applications to suggest viable treatment for patients. We first design a bootstrap method for counterfactual assessment and enhancement of policies, aiming to diminish uncertainty in clinical decisions. Building on this, we introduce an innovative adversarial learning algorithm, inspired by bootstrap principles, to further advance policy optimization.

RESULTS

The efficacy of our algorithms was validated using both semi-synthetic and real-world clinical datasets. Our method outperforms baseline algorithms, reducing the variance in policy evaluation by 30% and the error rate by 25%. In policy optimization, it enhances the reward by 1% to 3%, highlighting the practical value of our approach in clinical decision-making.

CONCLUSION

This study demonstrates the effectiveness of combining bootstrap and adversarial learning techniques in policy learning for clinical decision support. It not only enhances the accuracy and reliability of policy evaluation and optimization but also paves avenues for leveraging advanced counterfactual machine learning in healthcare.

Comparison of Different Weight Scalars to Dose Sugammadex for the Reversal of Neuromuscular Blockade in Morbidly Obese Patients: A Systematic Review

This systematic review was conducted to evaluate the optimal weight scalar to dose sugammadex in a morbidly obese (MO) patient population (BMI≥40 kg/m2). The primary outcome was recovery time from moderate neuromuscular blockade (NMB) or deep NMB. Secondary outcomes included time to extubation and incidence of postoperative residual curarization (PORC). Eight randomized controlled trials (RCTs) involving 645 participants were included. The different dose scalars included were total body weight (TBW), ideal body weight (IBW), 20% corrected body weight (CBW) and 40% CBW). A dose of 2 mg/kg of sugammadex based on 40% CBW and a 4 mg/kg dose of sugammadex based on 40% CBW provide a reliable and timely reversal of moderate and deep NMB respectively in the MO patients.

Emergency Department Management of Acute Venous Thromboembolism in Patients With Obesity With Intravenous Unfractionated Heparin and Anti-Xa Monitoring

BACKGROUND

Unfractionated heparin (UFH) remains a frequently utilized agent in the emergency department (ED) for management of acute venous thromboembolism (VTE). While various protocols of UFH dosing have been proposed for patients with obesity, the optimal dosing and monitoring strategy is unclear.

OBJECTIVE

This study aims to compare the time to the first therapeutic anti-Xa level in obese acute VTE patients following the use of either total body weight (TBW) or adjusted body weight-based (AdjBW) dosing of UFH in the ED, and to analyze the impact of different dosing strategies on patient outcomes.

METHODS

Inclusion criteria included adult patients with a BMI > 30 kg/m², and suspected VTE managed with UFH per institutional protocol utilizing a bolus dose followed by maintenance infusion and anti-Xa monitoring. The primary outcome was time to the first therapeutic anti-Xa level in the group dosed per TBW compared with the group dosed per AdjBW. Safety outcomes included incidence of bleeding events, protamine administration, and mortality.

RESULTS

There were 32 patients included in the study. Patients dosed per TBW achieved a median time to first therapeutic anti-Xa level of 14.5 hours compared with 15 hours in the AdjBW group (P = .613). The median therapeutic UFH infusion rate was 16 units/kg/hr in the TBW group compared with 13.5 units/kg/hr in the AdjBW group (P < .001). Safety outcomes were not significantly different between groups.

CONCLUSION

Patients presenting to the ED with acute VTE may be managed with UFH using either a TBW or AdjBW dosing strategy.

Optimizing Robotic Hysterectomy for the Patient Who Is Morbidly Obese with a Surgical Safety Pathway

STUDY OBJECTIVE

Obesity is a growing worldwide epidemic, and patients classified as obese undergoing gynecologic robotic surgery are at increased risk for surgical complications. This study aimed to evaluate the feasibility and outcomes of a surgical safety protocol known as the High BMI [Body Mass Index] Pathway (HBP) for patients with BMI ≥40 kg/m² undergoing planned robotic hysterectomy. Our primary outcome was the rate of all-cause perioperative complications in patients undergoing surgery with the use of the HBP.

DESIGN

A retrospective cohort study.

SETTING

An academic teaching hospital.

PATIENTS

A total of 138 patients classified as morbidly obese (BMI ≥40 kg/m²) undergoing robotic hysterectomy.

INTERVENTIONS

The HBP was developed by a multidisciplinary team and was instituted on January 1, 2016, as a quality improvement project. Patients classified as morbidly obese undergoing robotic hysterectomy after this date were compared with consecutive historical controls.

MEASUREMENTS AND MAIN RESULTS

Seventy-two patients underwent robotic hysterectomies on the HBP and were compared with 66 controls. There were no differences in age, BMI, blood loss, number of comorbidities, or cancer diagnosis. Since the implementation of the HBP, there has been a decrease in anesthesia time (-57.0 minutes; p = .001) and total operating room time (-47.0 min; p = .020), as well as lower estimated blood loss (median 150 mL [interquartile range 100-200] vs 200 mL [interquartile range 100-300]; p = .002) and reduction in overnight hospital admissions (33.3% vs 63.6%; p <.001). In the HBP group, there were fewer all-cause complications (19.4% vs 37.9%; p = .023) and infectious complications (8.3% vs 33.3%; p = .001), and there was no increase in the readmission rates (p = .400). In multivariable analysis, the HBP reduced all-cause complications (odds ratio 0.353; p = .010) after controlling for the covariate (total time in the operating room).

CONCLUSION

The HBP is a feasible method of optimizing the outcome for patients classified as morbidly obese undergoing major gynecologic surgery. Initiation of the HBP can lead to decreased anesthesia and operating times, all-cause complications, and overnight hospital admissions without increasing readmission rates.

Thromboelastometry, Thromboelastography, and Conventional Tests to Assess Anticoagulation During Extracorporeal Support: A Prospective Observational Study

Optimal anticoagulation monitoring in patients with extracorporeal membrane oxygenation (ECMO) is fundamental to avoid hemorrhagic and thromboembolic complications. Besides conventional coagulation tests, there is growing interest in the use of viscoelastic hemostatic assays (VHA), in particular of tromboelastography (TEG). Evidence on the use of rotational thromboelastometry (ROTEM) is lacking in this setting. The aim of the study was to evaluate ROTEM as a tool for assessing hemostasis during ECMO, by comparing it to TEG and conventional coagulation assays. We conducted a prospective, observational, single-center study on adult patients on ECMO support anticoagulated with unfractioned heparin (UFH). Kaolin reaction time (R, min) for TEG and INTEM clotting time (CT, sec) for ROTEM were analyzed and compared with conventional coagulation tests. In the study period, we included 25 patients on ECMO support (14 V-A and 11 V-V); 84 data points were available for the analysis. Median UFH infusion rate was 15 [11-18] IU/min/kg. Median values for activated partial thromboplastin time (aPTT) ratio, Kaolin TEG R time, and INTEM CT were 1.44 [1.21-1.7], 22 [13-40] min, and 201 [183-225] sec, respectively. INTEM CT (ROTEM) showed a moderate correlation with standard coagulation tests (R2 = 0.34 and 0.3 for aPTT and activated clotting time (ACT), respectively, p < 0.001). No significant correlation was found between INTEM CT and Kaolin R time (R2 = 0.01). Further studies are needed to identify an appropriate anticoagulation target for ROTEM during ECMO.

Continuous Renal Replacement Therapy in Venovenous Extracorporeal Membrane Oxygenation: A Retrospective Study on Regional Citrate Anticoagulation

Systemic infusion of unfractionated heparin (UFH) is the standard anticoagulation technique for continuous renal replacement therapy (CRRT) during extracorporeal membrane oxygenation (ECMO), but often fails to avoid CRRT circuit clotting. The aim of this study was to assess, in patients undergoing CRRT during venovenous ECMO (vv-ECMO), the efficacy and safety of adding regional citrate anticoagulation (RCA) for CRRT circuit anticoagulation (RCA + UFH group) compared with the sole systemic heparin anticoagulation (UFH group). We performed a retrospective chart review (2009-2018) of patients treated with CRRT during ECMO. We evaluated filter life span, rate of CRRT circuit clotting, and coagulation parameters. The incidence of citrate anticoagulation-related complications was recorded. Forty-eight consecutive adult patients underwent CRRT during vv-ECMO in the study period. The incidence of CRRT circuit clotting was lower in the RCA + UFH group (11% vs. 38% in the UFH group, p < 0.001). Log-rank survival analysis demonstrated longer circuit lifetime for RCA + UFH group. No complication ascribable to citrate anticoagulation was recorded. Regional citrate anticoagulation resulted a feasible, safe, and effective technique as additional anticoagulation for CRRT circuits during ECMO. Compared with systemic heparinization only, this technique allowed to reduce the rate of CRRT circuit clotting.

Toward Optimal Heparin Dosing by Comparing Multiple Machine Learning Methods: Retrospective Study

Background

Heparin is one of the most commonly used medications in intensive care units. In clinical practice, the use of a weight-based heparin dosing nomogram is standard practice for the treatment of thrombosis. Recently, machine learning techniques have dramatically improved the ability of computers to provide clinical decision support and have allowed for the possibility of computer generated, algorithm-based heparin dosing recommendations.

Objective

The objective of this study was to predict the effects of heparin treatment using machine learning methods to optimize heparin dosing in intensive care units based on the predictions. Patient state predictions were based upon activated partial thromboplastin time in 3 different ranges: subtherapeutic, normal therapeutic, and supratherapeutic, respectively.

Methods

Retrospective data from 2 intensive care unit research databases (Multiparameter Intelligent Monitoring in Intensive Care III, MIMIC-III; e–Intensive Care Unit Collaborative Research Database, eICU) were used for the analysis. Candidate machine learning models (random forest, support vector machine, adaptive boosting, extreme gradient boosting, and shallow neural network) were compared in 3 patient groups to evaluate the classification performance for predicting the subtherapeutic, normal therapeutic, and supratherapeutic patient states. The model results were evaluated using precision, recall, F1 score, and accuracy.

Results

Data from the MIMIC-III database (n=2789 patients) and from the eICU database (n=575 patients) were used. In 3-class classification, the shallow neural network algorithm performed the best (F1 scores of 87.26%, 85.98%, and 87.55% for data set 1, 2, and 3, respectively). The shallow neural network algorithm achieved the highest F1 scores within the patient therapeutic state groups: subtherapeutic (data set 1: 79.35%; data set 2: 83.67%; data set 3: 83.33%), normal therapeutic (data set 1: 93.15%; data set 2: 87.76%; data set 3: 84.62%), and supratherapeutic (data set 1: 88.00%; data set 2: 86.54%; data set 3: 95.45%) therapeutic ranges, respectively.

Conclusions

The most appropriate model for predicting the effects of heparin treatment was found by comparing multiple machine learning models and can be used to further guide optimal heparin dosing. Using multicenter intensive care unit data, our study demonstrates the feasibility of predicting the outcomes of heparin treatment using data-driven methods, and thus, how machine learning–based models can be used to optimize and personalize heparin dosing to improve patient safety. Manual analysis and validation suggested that the model outperformed standard practice heparin treatment dosing.

Unfractionated heparin dosing in obese patients

Background The effect of obesity on the pharmacokinetics and pharmacodynamics of unfractionated heparin is not clearly understood, therefore to reduce the risk of bleeding, maximal dose (capped) nomograms are often used. This can lead to inadequate anticoagulation and increased mortality and morbidity. In Queensland, Australia, statewide nomograms recommend total-body-weight-based dosing, with capped initial bolus and maintenance doses. Objective To determine if current practices for unfractionated heparin dosing leads to inadequate anticoagulation in obese patients. Setting Princess Alexandra Hospital, Queensland, Australia. Method A retrospective audit of unfractionated heparin dosing in 200 patients divided into cohorts of; < 100 kg (defined as non-obese), 100-124.9 kg, 125-150 kg and > 150 kg, Main outcomes measured Mean maintenance doses in U/h and U/kg/h required to achieve two consecutive therapeutic activated partial thromboplastin times' and the corresponding time to achieve this endpoint. Results The mean ± standard deviation maintenance doses required to achieve two consecutive therapeutic activated partial thromboplastin times' in U/h were 1229 ± 316, 1673 ± 523, 2031 ± 596 and 2146 ± 846, and in U/kg/h were 16 ± 4.1, 15.1 ± 4.8, 14.9 ± 4.2 and 11.6 ± 4.2 for the weight cohorts respectively. The median time (inter-quartile range) to therapeutic activated partial thromboplastin times' for obese patients was 39 (21.5-56) h. Conclusions Our results suggest inadequate dosing in obese patients. We recommend the use of larger absolute doses (U/h) of nfractionated heparin but reduced uncapped total body weight-based doses-(U/kg/h) as patient weight increases.

Unfractionated heparin infusion for treatment of venous thromboembolism based on actual body weight without dose capping

Controversy exists regarding the use of dose capping of weight-based unfractionated heparin (UFH) infusions in obese and morbidly obese patients. The primary objective of this study was to compare time to first therapeutic activated partial thromboplastin time (aPTT) in hospitalized patients receiving UFH for acute venous thromboembolism (VTE) among three body mass index (BMI) cohorts: non-obese (< 30 kg/m2), obese (30–39.9 kg/m2), and morbidly obese (⩾ 40 kg/m2). In this single-center, retrospective cohort study, patients were included if they ⩾ 18 years of age, had a documented VTE, and were on an infusion of UFH for at least 24 hours. Weight-based UFH doses were calculated using actual body weight. A total of 423 patients met the inclusion criteria, with 230 (54.4%), 146 (34.5%), and 47 (11.1%) patients in the non-obese, obese, and morbidly obese cohorts, respectively. Median times to therapeutic aPTT were 16.4, 16.6, and 17.1 hours in each cohort. Within 24 hours, the cumulative incidence rates for therapeutic aPTT were 70.7% for the non-obese group, 69.9% for the obese group, and 61.7% for the morbidly obese group (obese vs non-obese: HR = 1.02, 95% CI: 0.82–1.26, p = 0.88; morbidly obese vs non-obese: HR = 0.87, 95% CI: 0.62–1.21, p = 0.41). There was no significant difference in major bleeding events between BMI groups (obese vs non-obese, p = 0.91; morbidly obese vs non-obese, p = 0.98). Based on our study, heparin dosing based on actual body weight without a dose cap is safe and effective.

Evaluation of an Unfractionated Heparin Pharmacy Dosing Protocol for the Treatment of Venous Thromboembolism in Nonobese, Obese, and Severely Obese Patients

Background: Despite large interpatient variability in dose response, heparin is utilized for treatment of venous thromboembolism (VTE). Current data on the optimal heparin dosing in obese patients are conflicting. Objective: The objective was to evaluate the time and dose required to achieve a therapeutic activated partial thromboplastin time (aPTT) in nonobese, obese, and severely obese patients using a pharmacist-directed heparin dosing protocol. Methods: This was a retrospective cohort study in a single-center community hospital inpatient setting. Adult patients receiving heparin for VTE treatment from July 1, 2013, to July 31, 2015, were evaluated. Patients were categorized into 3 groups: nonobese (BMI < 30 kg/m2), obese (BMI = 30-39.9 kg/m2), and severely obese (BMI ≥ 40 kg/m2). Data on height, weight, initial bolus dose, initial infusion rate, time to therapeutic aPTT, and therapeutic infusion rate were collected. Dosing body weight (DBW) was utilized for patients 20% over their ideal body weight (IBW). The primary outcome was time to therapeutic aPTT. Results: Analysis included 298 patients. Median times to therapeutic aPTT (hours:minutes) in the nonobese, obese, and severely obese were 15:00 (interquartile range [IQR] = 8:05-23:21), 15:40 (IQR = 9:22-25:10), and 15:22 (IQR = 7.54-23:40), respectively ( P = 0.506). There was no difference in bleeding among the nonobese (14%), obese (13.9%), or severely obese groups (7.9%; P = 0.453). No adverse thrombotic events occurred during hospitalization. Conclusion: Using a DBW for heparin dosing in patients 20% over their IBW resulted in similar times to therapeutic aPTT and adverse events in the nonobese, obese, and severely obese.