title: Thromboelastography (TEG®) demonstrates that tinzaparin 4500 international units has no detectable anticoagulant activity after caesarean section.
abstract: BACKGROUND
  Low molecular weight heparin is routinely used for thromboprophylaxis in pregnancy and the puerperium. Consensus guidelines recommend waiting 10-12h after administration of a thromboprophylactic dose of low molecular weight heparin before performing a neuraxial block or removing an epidural catheter. Thromboelastography (TEG®) has been reported to be sensitive to the effects of enoxaparin 4h after administration. The purpose of this study was to use TEG to examine coagulation changes in the first 10h after a thromboprophylactic dose of tinzaparin in an attempt to ratify the current consensus guidelines about timing of neuraxial blockade and epidural catheter removal.
  
  
  METHODS
  Twenty-four women who had undergone caesarean delivery and were classified as low or intermediate risk of thrombosis were recruited. Blood samples were taken before subcutaneous administration of tinzaparin 4500IU, and at 4, 8 and 10h post-dose. Standard TEG analyses were performed using plain and heparinase cuvettes and samples were also sent for laboratory anti-Xa assay. Thromboelastograph profiles were analysed for a low molecular weight heparin effect.
  
  
  RESULTS
  Analysis revealed no significant differences in R time, K time, alpha angle or maximum amplitude between plain and heparinase samples at any time point. Apart from a small statistically significant (P=0.033) decrease in maximum amplitude of 2.8% (95% CI 0.3 to 5.4%) at 4h, there were no significant changes in coagulation for any TEG parameter. Anti-Xa levels were virtually undetectable in all patients over the 10h period (median 0.00U/mL; range 0.00-0.13U/mL).
  
  
  CONCLUSIONS
  A thromboprophylactic dose of tinzaparin 4500IU had little detectable effect on coagulation as assessed by TEG and anti-Xa assay. These findings support consensus guidelines which state that it is acceptable to perform neuraxial blockade or remove an epidural catheter 10-12h after a thromboprophylactic dose of tinzaparin. Rather than suggesting a lack of anticoagulant activity, the findings indicate that TEG may not have the sensitivity to detect a tinzaparin effect when this dose is used in this patient group.
authors.affiliation: Department of Obstetric Anaesthesia, Queen Charlotte's and Chelsea Hospital, London, UK. Electronic address: sarah.griffiths3@nhs.net.
authors.forename: S
authors.initials: S
authors.lastname: Griffiths
authors.affiliation: Department of Obstetric Anaesthesia, Queen Charlotte's and Chelsea Hospital, London, UK.
authors.forename: C
authors.initials: C
authors.lastname: Woo
authors.affiliation: Department of Obstetric Anaesthesia, Queen Charlotte's and Chelsea Hospital, London, UK.
authors.forename: V
authors.initials: V
authors.lastname: Mansoubi
authors.affiliation: Department of Obstetric Anaesthesia, Queen Charlotte's and Chelsea Hospital, London, UK.
authors.forename: A
authors.initials: A
authors.lastname: Riccoboni
authors.affiliation: Department of Obstetric Anaesthesia, Queen Charlotte's and Chelsea Hospital, London, UK.
authors.forename: A
authors.initials: A
authors.lastname: Sabharwal
authors.affiliation: Department of Obstetric Anaesthesia, Queen Charlotte's and Chelsea Hospital, London, UK.
authors.forename: S
authors.initials: S
authors.lastname: Napier
authors.affiliation: Department of Anaesthesia, University Hospital of South Manchester, Manchester, UK.
authors.forename: M
authors.initials: M
authors.lastname: Columb
authors.affiliation: Department of Haematology, Hammersmith Hospital, London, UK.
authors.forename: M
authors.initials: M
authors.lastname: Laffan
authors.affiliation: Department of Obstetric Anaesthesia, Queen Charlotte's and Chelsea Hospital, London, UK.
authors.forename: G
authors.initials: G
authors.lastname: Stocks
mesh_terms: D000328:Adult; D000925:Anticoagulants / Q000494:pharmacology*; D002585:Cesarean Section; D005260:Female; D006495:Heparin, Low-Molecular-Weight / Q000494:pharmacology*; D006801:Humans; D008875:Middle Aged; D011183:Postoperative Complications / Q000517:prevention & control*; D011247:Pregnancy; D013916:Thrombelastography / Q000379:methods*; D000078222:Tinzaparin; D055815:Young Adult
chemical_list: D000925:Anticoagulants; D006495:Heparin, Low-Molecular-Weight; D000078222:Tinzaparin
keywords: Low molecular weight heparin; TEG; Thromboelastography; Tinzaparin