Identifying Optimal Initial Infusion Rates for Unfractionated Heparin in Morbidly Obese Patients

Anticoagulant Therapy in Patients Undergoing Acute Pulmonary Embolism Interventions

Catheter-based interventions and surgical embolectomy represent alternatives to systemic fibrinolysis for patients with high-risk pulmonary embolism (PE) or those with intermediate-high-risk PE who deteriorate hemodynamically. They are indicated when systemic fibrinolysis is contraindicated or ineffective, or if obstructive shock is imminent. Extracorporeal membrane oxygenation can be added to reperfusion therapies or used alone for severe right ventricular dysfunction and cardiogenic shock. These advanced therapies complement but do not replace anticoagulation, which remains the cornerstone in PE management. This review summarizes the evidence and shares practical recommendations for the use of anticoagulant therapy before, during, and after acute PE interventions.

Clinical guidance for unfractionated heparin dosing and monitoring in critically ill patients

INTRODUCTION

Unfractionated heparin is a widely used anticoagulant in critically ill patients. It has a well-established safety profile and remains an attractive option for clinicians due to its short half-life and reversibility. Heparin has a unique pharmacokinetic profile, which contributes to significant inter-patient and intra-patient variability in effect. The variability in anticoagulant effect combined with heparin's short half-life mean close monitoring is required for clinical efficacy and preventing adverse effects. To optimize heparin use in critically ill patients, effective monitoring assays and dose adjustment strategies are needed.

AREAS COVERED

This paper explores the use of heparin as an anticoagulant and optimal approaches to monitoring in critically ill patients.

EXPERT OPINION

Conventional monitoring assays for heparin dosing have significant limitations. Emerging data appear to favor using anti-Xa assay monitoring for heparin anticoagulation, which many centers have successfully adopted as the standard. The anti-Xa assay appears have important benefits relative to the aPTT for heparin monitoring in critically ill patients, and should be considered for broader use.

Gerinnungsdiagnostik im klinischen Alltag – Teil 2

Während bei einer Vitamin-K-Antagonisten-Therapie die Therapieüberwachung (International Normalized Ratio [INR]) obligat ist, gilt dies für direkte orale Antikoagulanzien (DOAK) oder niedermolekulares Heparin (NMH) nur in ausgewählten klinischen Szenarien. Bei DOAK steht die Bestimmung von Tal- und Spitzenspiegeln des Medikaments im Plasma im Vordergrund, bei NMH die Anti-Xa-Aktivität. Der Zeitpunkt der Probenabnahme in Relation zur Einnahme ist für die Bewertung essenziell. Eine neu aufgetretene Thrombozytopenie im Rahmen stationärer Behandlungen ist häufig. Einordnung der Grunderkrankung, Tag des Auftretens sowie Erfassung medikamentöser Einflüsse und ihrer Dynamik ermöglichen oft die Eingrenzung der Ursache. Die Thrombophilietestung nach venöser Thromboembolie wird aufgrund fehlender therapeutischer Konsequenz zunehmend seltener durchgeführt. Ein Antiphospholipidsyndrom darf aber nicht übersehen werden, da sowohl die Therapiedauer als auch die Wahl des Antikoagulans davon abhängen.

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.

Review of Medical Therapies for the Management of Pulmonary Embolism

Traditionally, the management of patients with pulmonary embolism has been accomplished with anticoagulant treatment with parenteral heparins and oral vitamin K antagonists. Although the administration of heparins and oral vitamin K antagonists still plays a role in pulmonary embolism management, the use of these therapies are limited due to other options now available. This is due to their toxicity profile, clearance limitations, and many interactions with other medications and nutrients. The emergence of direct oral anticoagulation therapies has led to more options now being available to manage pulmonary embolism in inpatient and outpatient settings conveniently. These oral therapeutic options have opened up opportunities for safe and effective pulmonary embolism management, as more evidence and research is now available about reversal agents and monitoring parameters. The evolution of the pharmacological management of pulmonary embolism has provided us with better understanding regarding the selection of anticoagulants. There is also a better understanding and employment of anticoagulants in pulmonary embolism in special populations, such as patients with liver failure, renal failure, malignancy, and COVID-19.

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 Time to Therapeutic Anticoagulation and Associated Outcomes in Critically Ill, Obese Patients With Pulmonary Embolism Receiving Unfractionated Heparin

BACKGROUND

Delays in time to therapeutic activated partial thromboplastin time (aPTT) have been associated with poor outcomes in patients with acute pulmonary embolism (PE).

OBJECTIVE

To investigate the relationship between time to therapeutic anticoagulation and in-hospital mortality in critically ill, obese patients with acute PE.

METHODS

This study examined 204 critically ill patients with a body mass index (BMI) ≥30 kg/m² receiving unfractionated heparin (UFH) for PE treatment. Patients achieving therapeutic anticoagulation within 24 hours of UFH initiation (early) were compared to those in >24 hours (delayed). Additional end points included 30-day mortality, median time to therapeutic aPTT, proportion of therapeutic and supratherapeutic aPTT values, hemodynamic deterioration, thrombolytic therapy after UFH initiation, length of stay, and bleeding.

RESULTS

No difference in in-hospital or 30-day all-cause mortality was seen (odds ratio [OR]: 1.33, confidence interval [CI]: 0.647-2.72; OR: 1.003, CI: 0.514-1.96). Patients in the early group had a greater proportion of therapeutic aPTT values (66.7% vs 50%, P < .001) and higher percentage of supratherapeutic aPTT values (20.9% vs 11.3%, P < .001); however, no increase in clinically significant bleeding was evident (15.2% vs 10.9%, P = .366).

CONCLUSION

In this population, a shorter time to therapeutic aPTT was not associated with improved survival.

Anticoagulation at the extremes of body weight: choices and dosing

INTRODUCTION

The landscape of therapeutic anticoagulation has changed dramatically over the past decade, with availability of direct oral anticoagulants (DOACs), which inhibit factor Xa or thrombin. However, the optimal anticoagulant agent and dosing strategy for patients at both extremes of body weight has not been established for any anticoagulant, including DOACs, vitamin K antagonists (VKA), and the various heparin options. Areas covered: This paper reviews available evidence to assist clinicians in prescribing of anticoagulation therapy at the extremes of body weight. Expert commentary: There are limited data to guide prescribing of all available anticoagulants at the extremes of weight and further research regarding efficacy and safety outcomes in these groups is required. Laboratory monitoring to guide dosing of traditional anticoagulants provides reassurance of 'predictable' efficacy. In contrast agents that are not routinely monitored by laboratory testing provide greater challenges. For example, underweight patients are at risk of receiving higher drug exposures of DOACs, whereas the use of fixed dose DOACs in obese patients may be associated with lower drug exposures.

Peri-operative management of overweight and obese children and adolescents

Obesity has become endemic, even in children. Systemic complications associated with obesity include metabolic syndrome, cardiovascular disease, and respiratory compromise. These comorbidities require adequate investigation, targeted optimisation, and, if surgery is required, specific management during the peri-operative period. Specific peri-operative strategies should be used for paediatric patients who are overweight or obese to prevent postoperative complications, and optimising the respiratory function during surgery is particularly crucial. This Review aims to provide up-to-date information on peri-operative management for physicians who are caring for children and adolescents (usually younger than 18 years) who are overweight or obese undergoing surgery, including bariatric surgery. We have particularly focussed on the physiological consequences of obesity-namely, obstructive sleep apnoea, respiratory compromise, and pharmacological considerations.

Argatroban dosing in obesity

PURPOSE

Obesity is associated with significant alterations in pharmacokinetic and pharmacodynamic properties. The use of weight based anticoagulants such as argatroban may put obese patients at an increased risk of hemorrhagic events. The purpose of this study was to evaluate argatroban dosing requirements in obese vs non-obese patients.

METHODS

This single-center, retrospective cohort study included patients ≥18 years with suspected HIT, treated with argatroban for ≥12 h. Patients were stratified by body mass index (BMI) into obese (BMI > 30 kg/m²) and non-obese (BMI ≤ 30 kg/m²) groups. The primary outcome was the median maintenance dose required to achieve two consecutive therapeutic activated partial thromboplastin times.

RESULTS

A total of 121 patients were included. The median BMI in the obese vs non-obese groups was 35.8 vs 24.05 kg/m² (p < .0001). Although statistically significant, there was no clinically significant difference in median maintenance argatroban dose in obese versus non-obese patients (1 vs 1 μg/kg/min; p = .01). In-hospital major bleeding and in-hospital thrombosis also did not differ between the two groups.

CONCLUSION

Obese patients require similar median argatroban maintenance doses when compared to non-obese patients. Based on these results argatroban should be dosed using actual body weight regardless of BMI.

Identifying optimal heparin management during cardiopulmonary bypass in obese patients: A prospective observational comparative study

BACKGROUND

The heparin regimen providing anticoagulation during cardiopulmonary bypass (CPB) is usually adapted to total body weight (TBW), but may be inaccurate in obese patients in whom TBW exceeds their ideal body weight.

OBJECTIVES

The objective is to compare the effects of heparin injection based on TBW on haemostatic parameters between obese and nonobese patients during cardiac surgery and to calculate the optimal heparin regimen.

DESIGN

Prospective comparative study.

SETTING

University hospital.

PATIENTS

Two groups of 50 patients (BMI≥ or <30 kg m) were included in the study over a 9-month period in 2013. The study started on 27 February 2013.

INTERVENTIONS

An unfractionated heparin (UFH) bolus of 300 IU kg TBW was injected before initiation of CPB followed by additional doses (50 to 100 IU kg) to maintain a target activated coagulation time (ACT) of at least 400 s.

MAIN OUTCOME MEASURES

ACT and plasma heparin concentration were measured at different time points after initiation of, and weaning from CPB.

RESULTS

Obese patients received higher initial and total doses of heparin (P < 0.0001). Plasma heparin concentrations were significantly higher in obese patients at each time point (P < 0.001) and reached very high values after the initial bolus (5.90 vs. 4.48 IU ml, P < 0.0001). The relationship between plasma heparin concentration and ACT after the initial bolus was not linear and followed an asymptotic regression curve. Haemoglobin concentration decreased intraoperatively to a greater extent in the obese group (P < 0.001). No significant differences in postoperative bleeding or global transfusion requirements were observed.

CONCLUSION

The standard heparin regimen based on TBW in obese patients during CPB results in excessive plasma heparin concentrations and a significant intraoperative decrease in haemoglobin concentration. ACT monitoring was not accurate in identifying this excess dosage. An initial bolus of 340 IU kg ideal body weight would achieve a heparin concentration of 4.5 IU ml, similar to that observed in nonobese patients. Further investigations are warranted to confirm this heparin regimen.

Relation Between TRCA Complication Rates and Peak ACT Levels Stratified According to the BMI Tertiles

We evaluated the efficacy and safety of the fixed dose of 5000 IU unfractionated heparin (UFH) represented as peak activated clotting time (ACT) according to the body mass index (BMI) tertiles in patients undergoing diagnostic transradial coronary angiography (TRCA). A total of 422 patients were included in the present study, 84 in the normal weight group, 218 in the overweight group, and the 120 in the grades 1 and 2 obesity groups. Radial artery occlusion (RAO) was observed in 29 (6.8%) patients and the hematoma was observed in 43 (10.1%) patients. The rate of RAO and hematoma did not differ across the BMI tertiles ( P = .749 and P = .066). Also, peak ACT and procedure duration did not differ between the study groups ( P = .703 and P = .999). The only independent predictor of hematoma was sheath/radial artery diameter ( P = .011) and the independent predictors for RAO were peak ACT, sheath/radial artery diameter, and procedure duration ( P = .001, P = .028, and P < .001, respectively). In conclusion, a fixed dose of 5000 IU UFH is safe and effective regardless of the BMI in diagnostic TRCA procedure.

Relation Between End-Procedural Activated Clotting Time Values and Radial Artery Occlusion Rate With Standard Fixed-Dose Heparin After Transradial Cardiac Catheterization

Although heparin administration has reduced the incidence of radial artery occlusion (RAO) during the transradial coronary angiography (TRCA), the effective activated clotting time (ACT) value for guiding unfractionated heparin dosing in patients undergoing TRCA is unknown. Four hundred thirty-two patients who were scheduled for elective TRCA were enrolled in our prospective study. All the patients received a standard dose of 5,000 IU unfractionated heparin. Anticoagulation level was assessed by ACT measurements that were taken at the end of the procedure just before the sheath removal. The day after TRCA, all patients were evaluated by color Doppler ultrasound to detect RAO. RAO was found in 29 patients (6.7%). A median ACT of 205 seconds in the RAO group and 265 seconds in the radial artery patent group were detected (p <0.001). Mean procedure duration was significantly longer in the RAO group than in the radial artery patent group (18.55 ± 9.80 vs 11.24 ± 7.07 minutes, p <0.001). There was a negative correlation between end-procedural ACT and procedure duration (r = -0.117, p = 0.015). In multivariate analysis, end-procedural ACT (odds ratio 0.981, 95% confidence interval [CI] 0.972 to 0.989, p <0.001), procedure duration (odds ratio 1.076, 95% CI, 1.037 to 1.116, p <0.001), and radial artery diameter (odds ratio 0.240, 95% CI 0.063 to 0.907, p = 0.035) were found as independent predictors of RAO. In conclusion, shorter end-procedural ACT levels, longer procedural duration, and smaller radial arterial diameter were independently associated with RAOs after TRCA with standard-dose heparin. In prolonged procedures, ACT-based heparin dosing may be useful to overcome RAO.

Biochemical characterization of a factor X activator protein purified from Walterinnesia aegyptia venom

Factor X of blood coagulation cascade can be activated by both intrinsic and extrinsic activating complex, trypsin and some kind of snake venom. A factor X activator protein is reported in Elapidae snake venom. The aim of this study was to evaluate biochemical properties of factor X activator protein because of its prospective application in biochemical research and therapeutics. Crude venom was fractionated on a HPLC system Gold 126/1667 using a combination of Protein PAK 125 and Protein PAK 60 Columns. Molecular weight was determined using SDS-PAGE. Walterinnesia aegyptia venom was fractionated into several protein peaks, but procoagulant and factor X activation activity coexisted into peak no.6. It appeared as single band on native PAGE and molecular weight was 60,000 ± 3. Purified up to 37-fold over crude venom. It shortened recalcification time, effect was dose-dependent and strictly Ca(2++)-dependent. Factor X activator seems to be able to activate factor X specifically because it showed no activation activity on human prothrombin, plasminogen, or protein C. It did not hydrolyze factor Xa substrate S-2222, thrombin substrate S-2238, plasmin substrate S-2251 or S-2302 and kalikrein substrate S-2266. It did not hydrolyze synthetic ester benzoyl arginine ethyl ester. Procoagulant activity was completely inhibited by irreversible serine protease inhibitors phenylmethylsulphonyl fluoride and N-p-tosylphenylalanine chloromethyl ketone. This study illustrates that factor X activator from W. aegyptia is though different in many aspects from factor X activators of Viperidae and Crotalidae venoms, but shows several properties identical to factor X activators from Elapidae venoms.

Development of a pharmacist-driven protocol for automatic medication dosage adjustments in obese patients

PURPOSE

A hospital protocol utilizing automatic dosage adjustments and pharmacist consultations to optimize the use of certain medications in obese patients is described.

SUMMARY

After conducting a literature search focused on medication dosing in obese patients, pharmacists at a large community hospital developed a list of commonly ordered medications appropriate for inclusion in a pharmacy-driven institutional protocol for automatic medication dosage adjustment in adult patients with obesity. Evidence-based recommendations on initial dosing of eight antimicrobials and two anticoagulant agents according to weight and renal function were formulated. Under the protocol, pharmacists receive electronic alerts regarding protocol-eligible patients during initial order verification and automatically adjust medication dosages as appropriate. For patients prescribed anticoagulants at specified dosage levels, clinical pharmacists consult with prescribers to help ensure safe and effective initial and ongoing therapy. Multidisciplinary educational initiatives were conducted prior to protocol implementation. During two designated three-week postimplementation data collection periods, pharmacists received a total of 372 protocol-eligible medication orders. Pharmacists adjusted a total of 149 dosages and verified an additional 183 dosages consistent with the protocol as originally ordered. Clinical pharmacy consults were completed for 10-15% of patients, with laboratory monitoring ordered in 25-30% of those cases (all patients were found to have appropriate test values). There have been no documented adverse drug reactions in patients whose medication dosages were adjusted per protocol.

CONCLUSION

Pharmacists implemented weight- and renal function-based dosage adjustments for obese patients in 40% of evaluated protocol-eligible cases to achieve 89% compliance with the protocol. Heparin and cefazolin were the medications most likely to require obesity-related dosage adjustments.

Unfractionated heparin dosing for therapeutic anticoagulation in critically ill obese adults

PURPOSE

Research evaluating unfractionated heparin (UFH) dosing in obese critically ill populations is limited. This study aimed to determine optimal weight-based and total therapeutic infusion rates of UFH in this population.

METHODS

This retrospective cohort study compared adults on UFH infusions in intensive care units from May 2011 through October 2013 across 3 weight strata: 95 to 104 kg (control), 105 to 129 kg (high weight), and greater than or equal to 130 kg (higher weight). Primary outcomes included total and weight-based infusion rates for therapeutic anticoagulation.

RESULTS

To achieve therapeutic activated partial thromboplastin times, higher weight patients had higher mean infusion rates compared with control (2017 vs 1582 U/h; P = .002). Mean weight-based therapeutic infusion rate was lower in the higher weight group compared with control (13.1 vs 15.8 U kg(-1) h(-1); P = .008). Post hoc analyses indicated mean weight-based infusion rate to achieve therapeutic anticoagulation was 15 U kg(-1) h(-1) in patients less than 165 kg and 13 U kg(-1) h(-1) in patients greater than 165 kg.

CONCLUSIONS

Patients greater than or equal to 130 kg have lower weight-based heparin requirements compared with patients 95 to 104 kg. This difference appears to be driven by patients greater than 165 kg. Patients greater than 165 kg have lower weight-based heparin requirements, whereas patients from 105 to 164 kg have weight-based requirements similar to a normal-weight patient population. Initiating heparin at appropriate weight-based doses for obese patients may optimize anticoagulation.

Influence of Body Mass Index on the Activated Clotting Time Under Weight-Based Heparin Dose

BACKGROUND

Activated clotting time (ACT) has been successfully applied during percutaneous coronary intervention (PCI) to monitor the extent of thrombin inhibition and anti-coagulation from unfractionated heparin (UFH) aiming to reduce the incidence of thrombotic adverse events and hemorrhagic complications. And this investigation was to explore the influence of body mass index (BMI) on ACT in patients received weight-based dose of UFH during PCI treatment.

METHODS

78 male patients undergoing coronary angiography or PCI treatment with a mean age of 63.86 ± 6.89 years were enrolled in this study. The patients were statistically divided into four quartiles according to their BMI. The ACT values were recorded as ACT0 , ACT5 , ACT10 , ACT30 and ACT60 , respectively. Taking the preoperative ACT0 as reference, and the differences of the other ACT values with ACT0 was indicated as ΔACTs. ACT values peaked at 5 min in 33.33% of the patients, 10 min in 51.33% of the patients and 30 min in 15.34% of the patients, respectively.

RESULTS

In addition, significant differences were found in overall maximum post-UFH ACT values among all BMI quartiles. UFH doses per blood volume were significantly different among the BMI quartiles, showing a positive association with BMI quartiles; further evidence revealed that the areas under the ΔACT-time curves increased gradually from quartile I to quartile IV. The proportions of ACT60 > 250 s and ACT60 > 300 s were found to be positively correlated with the increased BMI at 60 min after heparin loading.

CONCLUSIONS

The results of our study have shown that a standardized dosing nomogram that uses the actual body weight to calculate the heparin doses may result in UFH overdose for patients with higher BMI compared to patients with lower BMI.

Comparison of heparin dosing based on actual body weight in non-obese, obese and morbidly obese critically ill patients

Background:

Obesity is endemic in the United States and obese patients are at increased risk of thromboembolism but little data are available for dosing unfractionated heparin (UFH). We evaluated the relationship between obesity and UFH efficacy during critical illness by examining UFH infusions in non-obese, obese, and morbidly obese critically ill patients.

Materials and Methods:

Retrospective review of UFH infusions in non-obese, obese, and morbidly obese critically ill patients. Heparin was initiated without a bolus at 16 units/kg/h or 12 units/kg/h in obese and morbidly obese patients. Demographics, UFH dosage/therapy duration, laboratory values, and bleeding events were reviewed for patients receiving UFH for >24 h. Steady state (SS) was defined as the dosage that resulted in three consecutive activated partial thromboplastin times (aPTT) within target range.

Results:

Sixty-two patients were analyzed including 21 non-obese (mean body mass index (BMI) 24.2 ± 2.3); 21 obese (BMI 34.1 ± 3.1); and 20 morbidly obese (mean BMI 55.3 ± 13.7). Patients had otherwise similar demographics. Although 92% had at least one therapeutic aPTT, only 55% of patients reached SS. Six patients developed minor bleeding, but no major hemorrhagic complications. The dosing of heparin based on actual body weight (units/kg/h) and time to first therapeutic aPTT was similar between groups, but dose was statistically higher at steady state in the non-obese (16.3 ± 5.3 non-obese, 11.6 ± 5.5 obese and 11.1 ± 1.2 obese, P = 0.01) with similar times to steady state.

Conclusions:

Dosing of UFH in morbidly obese and obese critically ill patients based on actual body weight and a reduced initial dose was associated with similar time to first therapeutic aPTT and steady state.

Delayed efficient anticoagulation with heparin in patients with a weight of 110 kg and more treated for acute coronary syndrome

OBJECTIVE

The use of a weight-based nomogram is considered as standard care for prescribing appropriate doses of unfractionated heparin (UFH). Because of the need for multiple other medications that may affect bleeding and that clinical data have relied on similar dosing algorithms, maximum initial bolus and infusion rates have been suggested (capped initial dose). Whether these weight-based heparin nomograms properly address therapeutic dosing in obese patients remains questionable.

DESIGN AND METHODS

Thirty patients treated for acute coronary syndrome and weighing ≥110 kg were retrospectively compared with 90 controls (three groups of 30 patients, weighting 50-69.9, 70-89.9, or 90-109.9 kg), all treated with UFH, July 2008 to April 2009. The primary end point was the time required to obtain a threshold activated partial thromboplastin time (aPTT).

RESULTS

Mean time to achieve threshold aPTT was longer for obese patients weighing ≥110 kg than for controls (31.47 vs. 12.89 hours; P < 0.0001). At 24 hours, 63% of obese patients weighing ≥110 kg had not reached threshold aPTT vs. 7% of controls (P < 0.0001). However, threshold infusion rate did not differ between weight categories (13.0 vs. 13.1 U/kg/h; P = NS) and approximated the initial infusion rate recommended by nomograms without applying the dose cap (12 U/kg/h).

CONCLUSIONS

Adequate anticoagulation time doubled in patients weighing ≥110 kg, suggesting that these patients were not receiving appropriate heparin doses initially to achieve threshold aPTT rapidly. Using initial infusion rate recommended by a nomogram without capping for total body weight is suggested as acceptable in this study. This approach should be further evaluated in a prospective study.

Evaluation of weight-based dosing of unfractionated heparin in obese children

OBJECTIVE

To determine whether pediatric patients with obesity receiving weight-based dosages of unfractionated heparin (UFH) exhibit an enhanced response when dosed by actual body weight compared with nonobese patients as assessed primarily by the frequency of supratherapeutic anticoagulation. Secondary measures included UFH doses associated with therapeutic anticoagulation.

STUDY DESIGN

This single-institution retrospective case-matched study included children with and without obesity, matched on a 1:1 basis, who received a weight-based continuous infusion of UFH. Therapeutic monitoring values were defined for activated partial thromboplastin time (aPTT) level (70-101 seconds) and anti-activated factor X (Xa) level (0.35-0.7 U/mL).

RESULTS

The study included 50 children. The percentage of patients with supratherapeutic anticoagulation at any point in the study, as measured by either aPTT or anti-Xa level, was similar in the obese and nonobese groups (76% vs 72%; P = 1.0). However, compared with patients without obesity, those with obesity received a lower mean starting dose (17.4 vs 20.2 U/kg/hour; P = .013) and a lower mean maintenance dose (19.1 vs 24.3 U/kg/hour; P = .033) to achieve stable therapeutic monitoring test values. There was no difference in mean initial post-UFH aPTT between the 2 groups, but the mean initial anti-Xa level was higher in the obese group (0.45 vs 0.29 U/mL; P = .045).

CONCLUSION

Compared with children without obesity, those with obesity who received actual body weight-based continuous UFH infusions did not exhibit a higher frequency of supratherapeutic anticoagulation, but did require lower dosages to achieve comparable anticoagulation. Our results highlight recognized discrepancies between aPTT and anti-Xa monitoring assays.

How one academic medical center has managed potency changes with unfractionated heparin

The United States Pharmacopeia recently changed the standards for unfractionated heparin (UFH) resulting in reduction in potency by about 10 %. Despite the reduction in potency, no new recommendations for UFH dosing were recommended. A retrospective review was conducted on patients receiving UFH and at least one activated partial thromboplastin time (aPTT) after start of infusion. Patients receiving UFH prior to April 2010 were collected as old UFH potency patients versus those receiving UFH after May 1st, 2010 were defined as new UFH potency patients. The primary endpoint was time to a therapeutic aPTT. Secondary endpoints included the number venous thrombotic events (VTE) and bleeding events during hospitalization through 30 days post discharge. Thrombotic events were defined as acute coronary syndrome, ischemic stroke, and VTE. Bleeding was defined in accordance with the GUSTO bleeding scale. A total of 359 patients were included for evaluation, 181 in the old UFH group and 178 in the new UFH group. The primary endpoint was similar between groups with an average time of 18.8 ± 25.4 versus 20.8 ± 22.2 h in the old and new UFH groups respectively (p = 0.092). Patients receiving old UFH and an initial bolus had higher aPTTs (96.6 ± 43.7 s) than those receiving new UFH and an initial bolus (76.7 ± 34.5 s) (p = 0.003). There was no difference found between groups in regards to bleeding or thrombotic events during hospitalization or through 30 days. In patients receiving UFH, dosed per the institutions' nomogram, no clinically significant outcomes were found between the old and new UFH potencies.

Drug-nutrient interactions: a broad view with implications for practice

The relevance of drug?nutrient interactions in daily practice continues to grow with the widespread use of medication. Interactions can involve a single nutrient, multiple nutrients, food in general, or nutrition status. Mechanistically, drug?nutrient interactions occur because of altered intestinal transport and metabolism, or systemic distribution, metabolism and excretion, as well as additive or antagonistic effects. Optimal patient care includes identifying, evaluating, and managing these interactions. This task can be supported by a systematic approach for categorizing interactions and rating their clinical significance. This review provides such a broad framework using recent examples, as well as some classic drug?nutrient interactions. Pertinent definitions are presented, as is a suggested approach for clinicians. This important and expanding subject will benefit tremendously from further clinician involvement.

Polypharmacy and food-drug interactions among older persons: a review

Polypharmacy is generally defined as the use of 5 or more prescription medications on a regular basis. The average number of prescribed and over-the-counter medications used by community-dwelling older adults per day in the United States is 6 medications, and the number used by institutionalized older persons is 9 medications. Almost all medications affect nutriture, either directly or indirectly, and nutriture affects drug disposition and effect. This review will highlight the issues surrounding polypharmacy, food-drug interactions, and the consequences of these interactions for the older adult.

Heparin Dosing in Obese Pediatric Patients in the Cardiac Catheterization Laboratory

Background:

Unfractionated heparin (UFH) dosing may need to be adjusted when used in obese patients. The prevalence of pediatric obesity is increasing and, to our knowledge, no data exist to determine the effect of obesity on UFH therapy in children.

Objective:

To determine whether obese pediatric patients who receive a weight-based dose of UFH in the cardiac catheterization laboratory exhibit an enhanced response compared with those of normal body habitus.

Methods:

The records of pediatric patients who underwent a cardiac catheterization procedure from September 2006 to September 2010 at Texas Children's Hospital were reviewed. Patients were included if they had received a bolus dose of UFH during their procedure, and had pre- and post-UFH bolus activated clotting time (ACT) values determined. Patients were identified as obese if their body mass index (BMI) was at the 95th percentile or more for age and sex and were matched by age, sex, and catheterization procedure to a control group of patients with a BMI lower than the 95th percentile. Differences in demographic, UFH, and ACT variables were compared between obese and nonobese paired groups.

Results:

Seventy-eight patients (39 obese) met study criteria; 46 (58.9%) patients were male. The primary catheterization procedure was radiofrequency ablation (n = 32). There was no statistically significant difference in the mean (SD) dose per kilogram of UFH administered (72.3 [24.9] vs 63.6 [23.6] units/kg; p = 0.12) and no statistically significant difference in the time after the UFH bolus that the ACT was measured (52 [26] vs 56 [26] minutes; p = 0.59) between the 2 groups. No statistically significant difference was noted in the percent change in ACT after UFH bolus in obese compared to nonobese pediatric patients (196% [106] vs 165% [97]; p = 0.17).

Conclusions:

No significant difference in response to UFH was identified in obese pediatric patients compared to nonobese pediatric patients as measured by ACT in the cardiac catheterization laboratory.