Discard volume necessary for elimination of heparin flush effect on thromboelastography

Abstract

Heparin is commonly used to prevent obstruction of indwelling arterial catheters with blood clots. It is known to affect the outcomes of analysis of coagulation parameters with thromboelastography (TEG); therefore, it has been recommended to neutralize its effect with heparinase. However, heparinase may also neutralize the effect of low molecular weight heparin and endogenous heparinoids present in critically ill patients and thus yields unreliable results. The aim of this study was to evaluate the minimal discard blood volume needed to eliminate the effect of heparin flush on TEG parameters without the use of heparinase. Ten patients with indwelling arterial catheter were included in the study. Coagulation parameters were evaluated with kaolin-activated TEG. Blood samples were obtained after discarding 1, 2, 3, 4, 5 or 10 ml of blood to eliminate the effect of heparin. We investigated the influence of the discard volume on time until the first detectable clot (R), speed of clot development (alpha angle), maximal amplitude of the measured clot and time to maximal amplitude of the measured clot. We found an increase in coagulation (reflecting the heparin elimination) with the increasing discard volume between 1 and 4 ml. This was obvious from an increase in alpha angle and maximal amplitude of the measured clot and a decrease in R and time to maximal amplitude of the measured clot (P < 0.001). However, values obtained after discarding 4, 5 and 10 ml of blood did not differ markedly. To obtain valid information about TEG parameters, it is necessary to discard volume of at least 4 ml of blood (i.e., five times the volume of catheter dead space).

Utility of thromboelastography and/or thromboelastometry in adults with sepsis: a systematic review

“…CFT, alpha and MCF did not differ between groups. Lysis index had best accuracy for diagnosis sepsis.Altmann [48]Prospective observationalSeptic shock (n = 16), severe sepsis (n = 7), SIRS (n = 10)ROTEM0, 12, 24, 48 h after inclusionNoneAll parameters within reference values.Durila [49]Prospective observationalSevere sepsis (n = 44)TEGNot statedINR, APTT, fibrinogen, ATAll parameters within reference values.Adamzik [9]Prospective observationalSepsis (n = 98)ROTEMWithin 24 hours of diagnosisINR39% of sepsis patients had normal CFT, MCF, and α angle, values in 61% with pathologic variable showed broad distribution Hypocoagulable profile associated with increased mortality (OR 4.1; 95% CI 1.4-11.9).Cortegiani (abstract) [51]Prospective observationalSevere sepsis (n = 31), postoperative (n = 31)TEGWithin 12 hours of diagnosisNoneSepsis patients had lower α angle, other TEG parameters did not differ.Brenner [54]Prospective observationalSeptic shock (n = 30), major surgery (n = 30), healthy volunteers (n = 30)ROTEMSepsis: at diagnosis, 24 h, 4, 7, 14, 28 daysProthrombin index, factor levels, IL-6, TNF-αIn sepsis patients, majority of ROTEM analysis within reference values; however, sepsis patients with DIC showed more hypocoagulable traces compared with those without DIC were more hypercoagulable Compared with surgical and healthy controls fibrinolysis was impaired in sepsis patients.Durila [53]Prospective observationalPostsurgical esophagectomy (n = 38), of these, nine developed sepsis.TEGMorning of surgery and daily day 1-6 post operativeAPTT, INR, CRP, lactate, IL-6, procalcitonin, AT, D-dimerOn postoperative day 6, sepsis patients had higher lysis index compared with SIRS patients. Overall TEG not helpful in discriminating sepsis from SIRSMassion [52]Prospective cohortSeptic shock (n = 39)ROTEMAdmission to day 7APTT, PT, Thrombin generation, factor levels, AT, protein CFibrinolysis was decreased (increased lysis indexes), associated with hypocoagulation in conventional coagulation tests (decreased protein C and AT).…”

“…Of the included studies, 11 [9, 10, 41, 43, 44, 48–51, 53, 54] used the sepsis and SIRS criteria defined by the Society of Critical Care Medicine Consensus Conference [55]. Seven studies used TEG [10, 39, 40, 42, 49, 51, 53], and 11 used ROTEM [9, 41, 43–48, 50, 52, 54]. …”

“…In five studies, all TEG/ROTEM measurements in sepsis were within reference values [44, 46, 48, 49, 54]. These studies included a total of 176 sepsis and severe sepsis patients.…”

“…Interestingly, TEG/ROTEM failed to detect coagulopathy in two observational studies, whereas conventional coagulation assays were outside normal ranges [44, 49]. In 44 sepsis patients, mean INR, D-dimer, and fibrinogen levels were increased, whereas mean TEG values were not [49].…”

Heparinase‐modified thromboelastography can result in a fibrinolytic pattern

“…We recommend careful interpretation of such samples in the context of the patients' clinical condition or the elimination of the requirement for heparinase by not using heparin in the catheter flush system or discarding the first aspirated volume to eliminate the added heparin [6].…”