Temperature effects on haemostasis in whole blood from ticagrelor- and aspirin-treated patients with acute coronary syndrome

Effect of hypothermia on haemostasis and bleeding risk: a narrative review

It must be remembered that clinically important haemostasis occurs in vivo and not in a tube, and that variables such as the number of bleeding events and bleeding volume are more robust measures of bleeding risk than the results of analyses.

In this narrative review, we highlight trauma, surgery, and mild induced hypothermia as three clinically important situations in which the effects of hypothermia on haemostasis are important. In observational studies of trauma, hypothermia (body temperature <35°C) has demonstrated an association with mortality and morbidity, perhaps owing to its effect on haemostatic functions. Randomised trials have shown that hypothermia causes increased bleeding during surgery. Although causality between hypothermia and bleeding risk has not been well established, there is a clear association between hypothermia and negative outcomes in connection with trauma, surgery, and accidental hypothermia; thus, it is crucial to rewarm patients in these clinical situations without delay. Mild induced hypothermia to ≥33°C for 24 hours does not seem to be associated with either decreased total haemostasis or increased bleeding risk.

Bleeding Complications After Cardiac Arrest and Targeted Temperature Management, a Post Hoc Study of the Targeted Temperature Management Trial

Target Temperature Management (TTM) is standard care following out of hospital cardiac arrest (OHCA). The aim of the study was to evaluate if treatment temperature (33°C or 36°C) or other predefined variables were associated with the occurrence of bleeding in the TTM study. This study is a predefined, post hoc analysis of the TTM trial, a multinational randomized controlled trial comparing treatment at 33°C and 36°C for 24 hours after OHCA with return of spontaneous circulation. Bleeding events from several locations were registered daily. The main outcome measure was occurrence of any bleeding during the first 3 days of intensive care. Risk factors for bleeding, including temperature allocation, were evaluated. Complete data were available for 722/939 patients. Temperature allocation was not associated with bleeding either in the univariable (p = 0.95) or in the primary multivariable analysis (odds ratio [OR] 0.95; 95% confidence interval [CI] 0.64-1.41, p = 0.80). A multiple imputation model, including all patients, was used as a sensitivity analysis, rendering similar results (OR 0.98; 95% CI 0.69-1.38, p = 0.92). Factors associated with bleeding were increasing age, female sex, and angiography with percutaneous coronary intervention (PCI) within 36 hours of cardiac arrest (CA) in both the primary and the sensitivity analysis. TTM at 33°C, when compared to TTM at 36°C, was not associated with an increased incidence of bleeding during the first 3 days of intensive care after CA. Increasing age, female gender, and PCI were independently associated with any bleeding the first 3 days after CA.

Dose-response effects of omega-3 on platelet aggregation: an observational study

OBJECTIVE

This study aimed to evaluate the dose-response effects of supplemental omega-3 fatty acids on platelet function in healthy volunteers.

METHODS

Twelve healthy volunteers ingested a normal supplemental dose of 1260 mg omega-3 fatty acids daily for 5 days, followed by a high dose of 2520 mg daily for another 5 days. Multiple electrode aggregometry (MEA) with four different agonists was used to measure platelet aggregation before and after the normal- and high-dose regimes. In vitro spiking using physiological doses of omega-3 fatty acids was also performed to determine whether MEA is capable of detecting a platelet-inhibiting effect due to omega-3 fatty acids.

RESULTS

There were no differences in platelet aggregation measured by the MEA assay in healthy volunteers after intake of either the normal or high dose of omega-3 fatty acids. In the in vitro experiment, a platelet-inhibiting effect of omega-3 fatty acids was shown by an arachidonic acid agonist in MEA .

CONCLUSIONS

Supplemental omega-3 fatty acids do not evoke their positive health effects through inhibition of platelet aggregation measurable with MEA.

The value of Sonoclot detection technology to guide the clinical medication of the perioperative anticoagulation and antiplatelet therapy in patients with acute myocardial infarction undergoing emergent PCI

The value of Sonoclot detection technology to guide the clinical medication of the perioperative anticoagulation and antiplatelet therapy in patients with acute myocardial infarction (AMI) undergoing emergent percutaneous coronary intervention (PCI) was estimated. One hundred and twenty-eight patients were randomly divided into control group and observation group with 64 cases in each group. Control group adopted routine blood coagulation indexes, including prothrombin time, activated partial thromboplastin time, fibrinogen and plasma thrombin time, platelet count and platelet aggregation turbidity analysis; observation group adopted Sonoclot detection technology, including activated clotting time, coagulation rate and platelet function. Anticoagulant therapy selected was of low molecular weight heparin calcium perioperatively, intraoperative unfractionated heparin, and clopidogrel (75 mg) combined with aspirin enteric-coated tablets (100 mg) as antiplatelet drugs. The therapy was administered in accordance with blood coagulation results. The blood coagulation time, postoperative creatine kinase isoenzyme MB, cardiac troponin I and B-type natriuretic peptide levels in the observation group are significantly lower than those in the control group (P<0.05) though the operating time and specifications of the stenting did not show any significant difference (P>0.05). The incidence of recurrent myocardial infarction, microembolism, acute and subacute thrombosis and bleeding events in the observation group are significantly lower than those in the control group (P<0.05). In the control group, there is no difference in the coagulation indexes of the patients with thrombosis events or bleeding events or no event (P>0.05). Whereas, in the observation group, there is significant difference in coagulation indexes of the patients with thrombosis events or bleeding events or no event (P<0.05). In conclusion, Sonoclot detection technology instructs emergent PCI treatment in AMI patients to shorten the detection time of blood coagulation, reduce the degree of myocardial injury, reduce the incidence of perioperative thrombosis and bleeding events. Furthermore, it has great value in guiding the clinical medication of anticoagulation and antiplatelet therapy.

Comparison of citrated and fresh whole blood for viscoelastic coagulation testing during elective neurosurgery

BACKGROUND

Previous viscoelastic haemostatic tests studies have often indicated a hypercoagulative test signal with citrated blood, which could influence clinical decision makings.

PURPOSE

The aim of this study was to compare fresh and citrated whole blood using two non-automated viscoelastic ROTEM and Sonoclot tests. Our hypothesis was that citrated blood would demonstrate a hypercoagulative response in this setting, not tested before.

METHODS

Perioperative viscoelastic coagulation changes were evaluated with a ROTEM and Sonoclot in 38 patients undergoing elective brain tumor surgery. The citrated samples were recalcified with CaCl₂. Wilcoxon nonparametric-paired tests and Bland-Altman plots were performed to compare the fresh and citrated blood analyses.

RESULTS

The citrated blood showed a hypercoagulative response in ROTEM NATEM-clot formation time and α-angle, Sonoclot-clot rate and platelet function, as compared to fresh blood (p<0.0001).

CONCLUSIONS

Fresh whole blood may theoretically reflect in vivo haemostasis more closely than citrated analyses, which indicated a hypercoagulative response as compared to the fresh whole blood analyses Bland-Altman plots also indicated that ROTEM reference ranges in patients undergoing brain surgery should be redefined. Future studies must establish the correlation between viscoelastic test results using fresh or citrate anticoagulated blood and clinical outcomes, such as bleeding, transfusion or reoperation for postoperative haematoma.

Influence of temperature on thromboelastometry and platelet aggregation in cardiac arrest patients undergoing targeted temperature management

BACKGROUND

Coagulation can be visualised using whole blood coagulation analyses such as thromboelastometry and platelet aggregation tests; however, the role of temperature in the analyses is ambiguous. The aim was to examine whether temperature influences the whole blood coagulation tests.

METHODS

We included 40 patients treated with targeted temperature management (33 ± 1 °C) after out-of-hospital cardiac arrest. The blood samples were obtained on hypothermia and normothermia. Each blood sample was analysed simultaneously at 33 °C and 37 °C by thromboelastography (ROTEM®) employing the assays EXTEM®, INTEM®, FIBTEM® and HEPTEM®, and by Multiplate®Analyzer, using COLtest®, ADPtest®, ASPItest® and TRAPtest® as agonists. Data on antithrombotic drugs were collected systematically from medical records, and data were analysed using repeated measurement analysis of variance (ANOVA).

RESULTS

The ROTEM® analyses showed increased clotting time, lower maximum velocity and increased time to maximum velocity (all p values <0.02) when performed at 33 °C compared with 37 °C, irrespective of the patients being hypothermic (median 33.1 °C) or normothermic (median 37.5 °C). However, EXTEM® time to maximum velocity showed no difference between the analyses performed at 33 °C and 37 °C when the patients were hypothermic (p = 0.83). No differences were found in maximum clot firmness (all p values >0.09) analysed at 33 °C and 37 °C, independent of the body temperature. In the hypothermic blood sample, no difference was found when using the COLtest®, ASPItest® or TRAPtest® to compare platelet aggregation analysed at 33 °C and 37 °C (all p values >0.19), but platelet aggregation was significantly higher using the ADPtest® (p < 0.001) when analysed at 33 °C. In the normothermic blood sample, the TRAPtest® showed no difference (p = 0.73) when performed at 33 °C; however, significantly lower aggregation was found using the COLtest® and ASPItest® (all p values <0.001), while a higher aggregation at 33 °C was found using the ADPtest® (p = 0.003).

CONCLUSION

ROTEM® analyses seemed not to be dependent on body temperature but showed a slower initiation of coagulation when analysed at 33 °C compared with 37 °C. The Multiplate®Analyzer results were dependent on the temperature used in the analyses and the body temperature. In whole blood coagulation tests, the temperature used in the analyses should be kept at 37 °C irrespective of the patient's body temperature being 33 °C or 37 °C.

Efficacy of enteral ticagrelor in hypothermic patients after out-of-hospital cardiac arrest

Introduction

Delivery of crushed ticagrelor via a nasogastric tube is a widely spread off-label use in unconscious patients following out-of-hospital cardiac arrest (OHCA). Notwithstanding the importance of a potent dual antiplatelet therapy in these patients, the efficacy of crushed ticagrelor after OHCA has not been established yet.

Methods

In a prospective, single-center, observational trial, 38 consecutive MI patients after OHCA were included. 27 patients (71.1 %) underwent mild induced hypothermia. The primary outcome was platelet inhibition at 24h measured by impedance aggregometry.

Results

There was sufficient platelet inhibition in most patients after OHCA. In all hypothermic patients, there was an adequate platelet inhibition by ticagrelor at 24 h (p < 0.001). 15 patients (39.5 %) had significant gastroesophageal reflux and one patient with significant reflux had inadequate platelet inhibition at 24 h. There were no stent thrombosis or recurrent atherothrombotic events in these patients.

Conclusion

Administration of crushed ticagrelor via a nasogastric tube reliably inhibited platelet function in vitro and in vivo regardless of the presence of hypothermia in MI patients. Thus, platelet inhibition can be reliably achieved in MI patients during neuroprotective hypothermia following OHCA.