Risk for excessive anticoagulation during hemodialysis is associated with type of vascular access and bedside coagulation testing: Results of a cross-sectional study

Background

Recommendations and practice patterns for heparin dosing during hemodialysis show substantial heterogeneity and are scantly supported by evidence. This study assessed the variability in unfractionated heparin (UFH) dosing during hemodialysis and its clinical and biological anticoagulatory effects, and identified explanatory factors of heparin dosing.

Methods

Cross-sectional study assessing UFH dosing, coagulation tests - activated partial thromboplastin time (aPTT) and activated clotting time (ACT) before dialysis start, 1 h after start and at treatment end (4 h) - and measurement of residual blood compartment volume of used dialyzers.

Results

101 patients, 58% male, with a median dialysis vintage of 33 (6-71) months received hemodialysis using a total UFH dose of 9,306 ± 4,079 (range 3,000-23,050) IU/session. Use of a dialysis catheter (n = 56, 55%) was associated with a 1.4 times higher UFH dose (p < 0.001) irrespective of prior access function. aPTT increased significantly more than ACT both 1 h and 4 h after dialysis start, independent of the dialysis access used. 53% of patients with catheter access and ACT ratio < 1.5, 1 h after dialysis start had simultaneous aPTT ratios > 2.5. Similar findings were present at 1 h for patients with AVF/AVG and at dialysis end for catheter use. No clinically significant clotting of the extracorporeal circuit was noted during the studied sessions. Dialyzer's blood compartment volume was reduced with a median of 9% (6-20%) without significant effect of UFH dose, aPTT or ACT measurements and vascular access type.

Conclusion

UFH dose adaptations based on ACT measurements frequently result in excessive anticoagulation according to aPTT results. Higher doses of UFH are used in patients with hemodialysis catheters without evidence that this reduces dialyzer clotting.

Dialyzer Performance During Hemodialysis Without Systemic Anticoagulation Using a Heparin-Grafted Dialyzer Combined With a Citrate-Enriched Dialysate: Results of the Randomized Crossover Noninferiority EvoCit Study

RATIONALE & OBJECTIVE

The EvoCit study was designed to evaluate performance of a heparin-grafted dialyzer during hemodialysis with and without systemic anticoagulation.

STUDY DESIGN

Randomized, crossover, noninferiority trial. Noninferiority was defined as a difference of≤10% for the primary outcome.

SETTING & PARTICIPANTS

Single hemodialysis center; 26 prevalent patients treated with 617 hemodialysis sessions.

INTERVENTIONS

Hemodialysis using a heparin-grafted dialyzer combined with a 1.0mmol/L citrate-enriched dialysate ("EvoCit") without systemic anticoagulation compared with hemodialysis performed with a heparin-grafted dialyzer with systemic heparin ("EvoHep"). Patients were randomly allocated to a first period of 4 weeks and crossed over to the alternative strategy for a second period of 4 weeks.

OUTCOMES

The primary end point was the difference in Kt/V_urea between EvoCit and EvoHep. Secondary end points were urea reduction ratio, middle molecule removal, treatment time, thrombin generation, and reduction in dialyzer blood compartment volume.

RESULTS

The estimated difference in Kt/V_urea between EvoCit and EvoHep was-0.03 (95% CI, -0.06 to-0.007), establishing noninferiority with mean Kt/V_urea of 1.47±0.05 (SE) for EvoCit and 1.50±0.05 for EvoHep. Noninferiority was also established for reduction ratios of urea and β₂-microglobulin. Premature discontinuation of dialysis was required for 4.2% of sessions among 6 patients during EvoCit and no sessions during EvoHep. Effective treatment time was 236±5 minutes for EvoCit and 238±1 minutes for EvoHep. Thrombin generation was increased and there was greater reduction in dialyzer blood compartment volume after treatments with EvoCit compared with EvoHep.

LIMITATIONS

The effects of avoiding systemic anticoagulation on clinical outcomes were not evaluated.

CONCLUSIONS

EvoCit is noninferior to EvoHep with respect to solute clearance but results in a greater number of shortened treatments, more membrane clotting, and greater thrombin generation TRIAL REGISTRATION: Registered at ClinicalTrials.gov with study number NCT03887468.

P1054COMBINING A HEPARIN-GRAFTED DIALYZER WITH A CITRATE ENRICHED DIALYSATE OFFERS ADEQUATE HEMODIALYSIS EFFICACY AVOIDING SYSTEMIC ANTICOAGULATION: RESULTS OF THE NON-INFERIORITY RANDOMIZED EVOCIT STUDY

Background and Aims

The combined use of a heparin-grafted membrane with a citrate enriched dialysate is an effective hemodialysis strategy with low circuit clotting rates while avoiding systemic anticoagulation. Whether this technique results in dialysis efficacy that is non-inferior to regular hemodialysis using systemic anticoagulation has not been investigated up to now.

Method

Prevalent hemodialysis (n=26) patients were recruited for a randomized crossover non-inferiority trial powered at &gt;90% to detect a prespecified non-inferiority threshold of 10% spKt/Vurea (NCT03887468). Hemodialysis using a heparin-grafted dialyzer in combination with a 1.0 mmol/L citrate enriched dialysate (“evocit”) was compared to hemodialysis using a heparin-grafted dialyzer, systemic unfractionated heparin and regular bicarbonate-based dialysate (“evohep”). Each treatment arm lasted 4 weeks with a 3x4hours weekly hemodialysis regimen. All sessions were standardized with fixed blood- and dialysate flow rates. Biological analyses were done during midweek sessions. The primary endpoint was spKt/Vurea. Secondary endpoints included alternative adequacy markers, premature treatment termination, retransfusion failure and loss of total cell volume of the dialyzer after dialysis.

Results

A total of 617 hemodialysis sessions were performed: 307 sessions according to evocit and 310 sessions according to evohep protocol. Mean spKt/Vurea was 1.45±0.25 for evocit sessions and 1.50±0.26 for evohep sessions. In a paired analysis, mean of the difference in spKt/Vurea between both study arms was 0.05 with a 95%CI of 0.012-0.098 (p=0.01), the upper bound of the estimate lying within the prespecified non-inferiority threshold (i.e. &lt;0.15).

Processed blood volume was 75.4±3L vs 75.8±1.5L and online Kt was 47.3±5L vs 48.3±4L for all evocit and evohep sessions respectively. Urea reduction rate (RR) was 71.3±5.7 vs 72.3±5.8, bèta2microglobulin RR 37.1±8 vs 37.9±8 and myoglobin RR 30.9±9.8 vs 34.5±12.5 for midweek evocit and evohep sessions respectively. Circuit thrombosis leading to premature treatment end occurred in 13/307 (4.23%) of evocit sessions in 6/26 patients but in none of the evohep sessions (p=0.03). Treatment time of evocit sessions complicated with circuit thrombosis (n=13) was reduced with 36 minutes (IQR 20-46 minutes) without impact on effective treatment times overall (236±12 vs 238±4 minutes for evocit and evohep sessions respectively). Retransfusion failure occurred in 3/307 (0.98%) of evocit sessions and none of the evohep sessions. Dialyzers’ total cell volume was reduced with 17% (IQR 11-33%) and 9% (IQR 6-17%) (p&lt;0.0001) after evocit and evohep sessions respectively.

Conclusion

Hemodialysis avoiding systemic anticoagulation using a heparin-grafted dialyzer with a citrate enriched dialysate is an adequate technique for maintenance hemodialysis offering spKt/Vurea results within recommended dose, and is not inferior to standard hemodialysis using systemic anticoagulation with heparin in terms of spKt/Vurea.

Circuit clotting complications occurred at low frequency during evocit sessions and did not have clinically significant repercussions on dialysis efficacy.

Traveling waves in a spring-block chain sliding down a slope

Traveling waves are studied in a spring slider-block model. We explicitly construct front waves (kinks) for a piecewise-linear spinodal friction force. Pulse waves are obtained as the matching of two traveling fronts with identical speeds. Explicit formulas are obtained for the wavespeed and the wave form in the anticontinuum limit. The link with localized waves in a Burridge-Knopoff model of an earthquake fault is briefly discussed.

Successful Pretreatment Using Plasma Exchange before Thyroidectomy in a Patient with Amiodarone-Induced Thyrotoxicosis

INTRODUCTION

Amiodarone, used for the management of tachyarrhythmias, is associated with both hypothyroidism and thyrotoxicosis. Total thyroidectomy is an effective procedure for promptly reducing circulating thyroid hormone levels. It has been proposed in patients who have severe amiodarone-induced thyrotoxicosis (AIT) or are refractory to medical therapy, or when such therapy is contraindicated. Therapeutic plasma exchange (TPE) may be considered as a pretreatment for restoring a euthyroid state preoperatively, thereby reducing a patient's symptoms and the potential perioperative risk associated with thyrotoxicosis.

CASE REPORT

We describe the case of a 62-year-old man with type 2 AIT who presented with severe unremitting thyrotoxicosis after 8 weeks of medical therapy with glucocorticosteroids, thiamazole, and potassium perchlorate. Given the severity of his presentation, a total thyroidectomy was indicated. TPE was performed preoperatively and was successful in rapidly restoring euthyroidism. This dramatically improved the patient's symptoms which had been suggestive of ischemic heart disease. Subsequently, the patient underwent total thyroidectomy under general anesthesia without any major complications.

CONCLUSION

TPE is successful in rapidly restoring a clinical and biochemical euthyroid state, and may be used to decrease the perioperative risks associated with thyroidectomy in patients with life-threatening thyrotoxicosis or in cases refractory to medical treatment.

Categorization of neural excitability using threshold models

A classification of spiking neurons according to the transition from quiescence to periodic firing of action potentials is commonly used. Nonbursting neurons are classified into two types, type I and type II excitability. We use simple phenomenological spiking neuron models to derive a criterion for the determination of the neural excitability based on the afterpotential following a spike. The crucial characteristic is the existence for type II model of a positive overshoot, that is, a delayed after depolarization, during the recovery process of the membrane potential. Our prediction is numerically tested using well-known type I and type II models including the Connor, Walter, & McKown (1977) model and the Hodgkin-Huxley (1952) model.

Synchronization and desynchronization of neural oscillators

We have used continuous and discrete-time versions of a neural oscillator model to analyze how various types of synaptic connections between oscillators affect synchronization and desynchronization phenomena. First, we present a synthesis of the mathematical properties of both neural oscillator versions. Then, we show that the choice of parameters leads to a relationship between the two versions. Finally, we achieve the coupling of two oscillators in order to study how synaptic connections affect the phase lag. With this in mind, we state some of the results for the continuous-time model. The second part of this paper deals with the behavior of neural networks comprising connected oscillators, which involves looking at the conditions for desynchronization of a totally synchronized oscillator net. Such a study has been carried out both for a fully and for a sparsely connected network. This leads to the observation that some architectures enable proper desynchronization when the size of the network is large. While searching for the conditions for desynchronization, we have discovered that a macroscopic description of the network is sometimes possible. To conclude, we discuss the advantages and the limitations of this macroscopic approach.