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We would like to report the case of a 23-year-old primigravida woman with von Willebrand's disease (VWD). Our local consultant haematologist notified us of her when she was 36 weeks gestation. Apart from her von Willebrand's disease she was apparently fit and healthy and was enjoying an uncomplicated pregnancy. Her laboratory results were as follows: von Willebrand factor antigen (vWF:Ag) 28% and Ricof level 42%. On the basis of these results, the haematologist suggested that an experienced anaesthetist could perform epidural analgesia safely as her risk of bleeding into the epidural space was minimal. We, along with our colleagues, were not sure of the validity of this advice and were unfamiliar with these laboratory results. We therefore decided to determine the significance of the haematological investigations performed in patients with VWD and clarify the risk of bleeding associated with regional analgesia. We felt that anaesthetists need to be aware of this disease and have an understanding of how it is investigated in order to make valued judgements in the use of regional techniques in the presence of possible abnormal haemostasis.

Von Willebrand's disease is an inherited haematological disorder where there is a deficiency of von Willebrand's factor (vWF). In type I VWD there is a reduction in the amount of vWF in the blood, in type 2 VWD normal levels of vWF are found but it is functionally abnormal, and in type 3 VWD there is a severe deficiency in levels of vWF. VWF is required for platelet adhesion to damaged endothelium during the formation of the platelet plug. It is also the carrier protein for factor VIII. Deficiency of vWF leads to prolonged bleeding times and patients usually present with abnormal bleeding conditions such as menorrhagia or epistaxis

The haematological investigations are used in VWD to determine both the quantity and functional capacity of vWF in the patient's plasma. The amount of vWF is determined by measuring the vWF:Ag level, whereas the Ricof level is a measure of its functional activity. The vWF:Ag level in the plasma can be assayed directly and compared to a reference curve of standard dilutions so that a level > 50% is normal. Ricof levels are determined by adding a sample of the patient's plasma to normal platelets and then adding the antibiotic ristocetin. Ristocetin reacts with vWF and the platelet membrane to induce platelet aggregation. This interaction requires the presence of a functional unit of the vWF known as the ristocetin cofactor. Ristocetin-induced aggregation follows a dose–response curve dependent upon the amount of functional vWF present. Thus, a ‘normal’ Ricof level is quoted as > 50%. Ristocetin does not agglutinate the platelets in many patients with VWD due to the absence of the ristocetin cofactor. Thus in VWD the Ricof level is often reduced. If the Ricof level is above 30% the risk of bleeding is not thought to be increased; however, when below this level, especially if the level is < 10%, there is a significant risk of bleeding.

There does not seem to be any consensus on the Ricof level that is safe for regional anaesthesia (Giangrande PLF, Oxford Haemophilia Centre, personal communication). We could only find one case report in the literature that described the use of an epidural in a patient with VWD. This obstetric patient had a Ricof level of 10% and vWFAg level of 35%. The use of an epidural was uneventful [1].

Fortunately, our patient had an uneventful delivery and did not require our assistance. However, as a precaution we arranged for desmopressin to be available on the delivery suite in the event of a postpartum haemorrhage (PPH). Women with VWD are at increased risk of PPH as the level of vWF falls rapidly following delivery. Desmopressin is used therapeutically to boost the level of vWF production in vivo.

We would be interested to hear the experience of other anaesthetists in the management of patients with VWD and at what Ricof level they regard regional anaesthesia to be safe.

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