In the presence of normal haemostasis, the incidence of spinal haematoma and paraplegia associated with epidural/spinal is extremely low and similar in incidence to the spontaneous occurence of this complication. However, partial or complete haemostatic failure from any cause or combination of causes produces a spectrum of risk, negligible in the case of low dose aspirin, and very high (>1%) in fully heparinised patients (1, 2, 3). In obstetrics, impairment of platelet or coagulation system function is common in conditions such as pre-eclampsia or sepsis and care is needed to exclude all such possibilities before assessing the risk of spinal haematoma following neuraxial blockade (Chapter 72).
Aspirin:
The useful anti-thrombotic effects of aspirin are due to its inhibition of platelet cyclooxygenase as well as other platelet and non-platelet pathways (4, 5). Although a single 600mg aspirin dose increases bleeding time (initially by 50%) for the platelet life span (one week) (6), this minor degree of haemostatic impairment is compatible with safe epidural outcome. Support for this view is the absence of any reports of aspirin induced spinal haematoma cases following epidural or spinal, and case series of neuraxial blockade in the presence of aspirin without incident (7, 8). Measurement of bleeding time is not recommended in view of the fact that no consistent relationship exists between bleeding time and bleeding tendency (9).
Heparin:
High dose, unfractionated heparin.
Unfractionated heparin in high dose (1500 to 2500 IU/hr) significantly increases the risk of clinically important haemorrhage (10) and is contraindicated prior to epidural/spinal.
Low dose, unfractionated heparin.
A single dose of unfractionated heparin (5000 IU) given subcutaneously does not alter laboratory coagulation parameters but may increase wound haematoma rate. Repeated doses can cause thrombocytopenia in a small proportion of patients after several days. An exaggerated bleeding tendency can be expected when low dose heparin occurs in the presence of liver failure or is used in combination with other drugs acting on the coagulation system. Under normal circumstances, however, the risk of spinal bleeding after epidural/spinal is acceptably low (11, 12) .
Fractionated heparins.
Fractionated (low molecular weight) heparins (LMWHs) were introduced in the expectation that the incidence of bleeding complications would be reduced. However, it is likely that the different LMWHs each have different specific modes of action. This, together with variations in dose schedules, may explain the differing incidences of bleeding complications and the sometimes paradoxical increase in bleeding when compared to unfractionated heparin (13, 14). In any case, the difference is small and, in combination with neuraxial blockade, LMWHs in low dose are associated with minimal risk (15).
References:
1. Brem SS, Hafler DA, Van Uitert RL, Ruff RL, Reichert V: Spinal subarachnoid hematoma a hazard of lumbar puncture resulting in reversible paraplegia. N Engl J Med 1981;304:1020
2. Owens EL, Kasten GW, Hessel EA: Spinal subarachnoid hematoma after lumbar puncture and heparinsation: a case report, review of the literature and discussion of anesthetic implications. Anesth Analg 1986;65:1201-1207
3. Rao L, El-Etr AA: Anti-coagulation following placement of epidural and subarachnoid catheters: an evaluation of neurological sequelae. Anesthesiology 1981; 55:618-620
4. Buchanan MR, Rischke JA, Hirsh J: Aspirin inhibits platelet function independent of the acetylation of cyclooxygenase. Thromb Res 1982; 25:363-373
5. Loew D, Vinazzer A: Dose dependent influence of acetylsalicylic acid on platelet functions and plasmatic coagulation factors. Haemostasis 1976:5:239-249
6. Harker LA, Slichter S J: The bleeding time as a screening test for evaluation of platelet function. N Engl J Med 1972; 287:155-159
7. Benzon HT, Brunner EA, Vaisrub N: Bleeding time and nerve blocks after aspirin. Reg Anaesth 1984; 9:86-89
8. Horlocker TT, Wedel DJ, Schroeder DR, Rose SH, Elliott BA, McGregor DG, Wong GY: Preoperative antiplatelet therapy does not increase the risk of spinal hematoma associated with regional anesthesia. Anesth Analg 1995; 80:303-309
9. Rodgers RPC, Levin J: A critical reappraisal of the bleeding time. Semin Thromb Hemost 16:1-19, 1990
10. Green D, Lee MY, Ito VY, Cohn T, Press J, Filbrandt PR, VadenBerg WC, Yarkony GM, Meyer PR: Fixed vs adjusted dose heparin in the prophylaxis of thromboembolism in spinal cord injury. JAMA 1988; 260:1255-1258
11. Vandermeulen EP, Van Aken H, Vermylen J: Anticoagulants and spinal-epidural anesthesia. Anesth Analg 1994; 79:1165-77
12. Wille-Jorgensen P, Jorgensen LN, Rasmussen LS: Lumbar regional anaesthesia and prophylactic anticoagulant therapy - is the combination safe? Anaesthesia 1991:46:623-627
13. Kakkar VV, Cohen AT, Edwardson RA, Philips MJ, Coopere D J, Das SK. Low molecular weight versus standard heparin for prevention of venous thromboembolism after major abdominal surgery. Lancet 341;259-165, 1993
14. Bergqvist D, Lindblad B, Matzsch T: Low molecular weight heparin for thromboprophylaxis and epidural/spinal anaesthesia is there a risk? Acta Anaesthesiol Scand 36;605-709, 1992
15. Wolf H. Experience with regional anaesthesia in patients receiving low molecular weight heparins. Sem Thromb Hemost 19 (suppl 1); 152-154, 1993