Normal coagulation is important to the obstetric anaesthetist for two reasons: firstly because of the potential risk of spinal haematoma following regional analgesia and anaesthesia, and secondly because of the risk of antepartum and postpartum haemorrhage.
Problems and special considerations
In general terms, increased bleeding may arise from defects in the function of:
• Blood vessels - e.g. caused by severe infections, metabolic disease (such as hepatic failure, renal failure) or congenital structural abnormalities.
• Platelets - caused by reduced numbers (e.g. thrombocytopenia, disseminated intravascular coagulation (DIC)) or impaired function (e.g. antiplatelet drugs).
• The coagulation system - caused by congenital disorders (e.g. haemophilia, von Willebrand’s disease), acquired coagulation factor dysfunction (e.g. anticoagulant therapy, hepatic failure, vitamin K deficiency, DIC) or increased fibrinolysis.
Management options
Specific disorders should be managed according to the underlying pathology and in conjunction with haematologists. In the absence of a known or potential haemostatic disorder that may be suggested by eliciting a history, coagulation studies are not generally indicated as screening tools in healthy parturients. It has been suggested that regional blockade can be performed as long as the activated partial thromboplastin time ratio (APTTR) or international normalised ratio (INR) is less than 1.5, although this is controversial. Symptoms of excessive bruising or bleeding should be sought, since they may signify increased risk of bleeding in borderline cases.
In recent years, more research has been directed at establishing the usefulness of point- of-care coagulation tests such as thromboelastography/thromboelastometry (TEG/ ROTEM) in the assessment of coagulation status in pregnant women. Information provided by these techniques may aid decision making in major obstetric haemorrhage, especially as part of a validated transfusion protocol algorithm. Other tools such as platelet function analysis have been described, but their role in clinical practice is yet to be established.
Increasing numbers of women are presenting in pregnancy taking anticoagulant therapy. Whereas full anticoagulation is a contraindication to regional analgesia and anaesthesia, it should be possible to time regional analgesia and anaesthesia for prophylactic regimens. Low-dose aspirin is generally felt to pose minimal risk, although the numbers of mothers who have been studied (receiving both aspirin and regional blockade) are small considering the rarity of the outcome (spinal haematoma). Other antiplatelet drugs are less commonly used in pregnancy, and experience with them is limited.
Prophylactic heparin (especially low-molecular-weight heparin) has been associated with spinal haematoma in non-pregnant patients who receive regional analgesia and anaesthesia, although many of these cases have been associated with relatively large doses in high-risk patients. The risk of therapeutic levels of heparin activity following a supposedly prophylactic dose in pregnancy is unknown. In addition, heparin pharmacokinetics are altered in pregnancy and larger doses are required than in non-pregnant patients, so data from series in which standard (non-pregnant) doses of heparin were used may be misleading. It must be remembered that the duration of action of these agents may be prolonged in women with renal dysfunction.
Most obstetric anaesthetists would follow the guidelines recommended for non-preg- nant patients, as shown in Table 106.1. In particular cases where the risks of general anaesthesia are increased (e.g. obesity, cardiac disease), regional anaesthesia may still represent a safer option than general anaesthesia, even within these time limits.
Key points
• Specific coagulation disorders should be managed with the involvement of haematologists.
• Low-dose aspirin therapy is considered to represent minimal risk.
• The risks and benefits of regional analgesia and anaesthesia should be considered for women who are receiving prophylactic heparin therapy. In general, guidelines prohibiting regional blockade or catheter removal within certain periods of heparin administration should be followed.
Further reading
Association of Anaesthetists of Great Britain and Ireland; Obstetric Anaesthetists’ Association;
Regional Anaesthesia UK. Regional anaesthesia and patients with abnormalities of coagulation. Anaesthesia 2013; 68: 966-72.
Gonzalez-Fiol A, Eisenberger A. Anesthesia implications of coagulation and anticoagulation during pregnancy. Semin Perinatal 2014; 38: 370-7.
Katz D, Beilin Y. Disorders of coagulation in pregnancy. Br J Anaesth 2015; 115: ii75-88.
Pacheco LD, Costantine MM, Saade GR, et al. von Willebrand disease and pregnancy: a practical approach for the diagnosis and treatment. Am J Obstet Gynecol 2010; 203: 194-200.
Table 106.1 Relative risk of neuraxial blockade in obstetric patients with abnormalities of coagulation
|
Risk factor |
Normal risk |
Increased risk |
High risk |
Very high risk |
|||
|
LMWH - prophylactic dose |
> 12 h |
6-12 h |
< 6 h |
< 6 h |
|||
|
LMWH - therapeutic dose |
> 24 h |
12-24 h |
6-12 h |
||||
|
UFH - infusion |
Stopped > 4 h and APTTR < 1.4 |
APTTR above norma range |
|||||
|
UFH - prophylactic bolus dose |
Last given > 4 h |
Last given < 4 h |
|||||
|
NSAID + aspirin |
Without LMWH |
With LMWH dose 12-24 h |
With LMWH dose < 12 h |
||||
|
Warfarin |
INR < 1.4 |
INR < 1.4-1.7 |
INR < 1.7- 2.0 |
INR > 2.0 |
|||
|
General anaesthesia |
Starved, not in labour, antacids given |
Full stomach or in labour |
|||||
|
Pre-eclampsia |
Platelets > 100х 109/l Within 6 h of block |
Platelets 75-100 x 109/l (stable) and normal coagulation tests |
Platelets 75-100 x 109/l (decreasing) and normal coagulation tests |
Platelets < 75 x 109/l or abnormal coagulation tests with indices > 1.5 or HELLP syndrome |
|||
|
Idiopathic thrombocytopenia |
Platelets > 75 x 109/l within 24 h of block |
Platelets 50-75 x 109/l |
Platelets 20-50 x 109/l |
Platelets < 20 x 109/l |
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|
Intrauterine fetal death |
FBC and coagulation tests normal within 6 h of block |
No clinical problems but no investigation results available |
With abruption or overt sepsis |
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|
Cholestasis |
INR < 1.4 within 24 h |
No other clinical problems but no investigation results available |
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APTTR, activated partial thromboplastin time ratio; FBC.ful blood count; HELLP, haemolysis, elevated liver enzymes and low platelet count; I NR, international normalised ratio;
LMWH, low-molecular-weight heparin; NSAID, non-steroidal anti-inflammatory drug; UFH, unfractionated heparin.
Reproduced with permission from Association of Anaesthetists of Great Britain and Ireland, Obstetric Anaesthetists' Association and Regional Anaesthesia UK. Regiona anaesthesia and patients with abnormalities of coagulation. Anaesthesia 2013; 68: 966-72.