CHAPTER 23. Haemorrhagic diseases
Purpura (usually due to platelet defects) and clotting defects are the main causes of haemorrhagic disorders.
INVESTIGATION OF A HISTORY OF EXCESSIVE BLEEDING
A careful history (Box 23.1) is absolutely essential and is as important as the blood tests.
• Results of previous dental operations? Have simple extractions led to prolonged bleeding?
• Has bleeding persisted for more than 24 hours?
• Has admission to hospital ever been necessary for dental bleeding?
• Have other operations or injuries caused prolonged bleeding?
• Is there a family history of prolonged bleeding?
• Are anticoagulants or other drugs being taken?
• Is there any medical cause such as leukaemia or liver disease?
• Does the patient carry a warning card or hospital letter about bleeding tendencies?
Most of the severe haemorrhagic diseases, such as haemophilia, are hereditary and a positive family history should be carefully evaluated. Bleeding for up to 24 hours after an extraction is usually due to local causes or a minor defect of haemostasis manageable by local measures. More prolonged bleeding is significant. Even a mild haemophiliac can bleed for weeks after a simple extraction.
Signs of anaemia and purpura should be looked for. Examination of the mouth shows how any operation should be planned. In the case of haemophilia, all essential extractions should be carried out at a single operation with factor VIII cover. Radiographs should be taken to anticipate possible difficulties with the extractions.
Details of investigations are decided by the haematologists, but summarised in Box 23.2.
• Haemoglobin level and blood picture
• Assessment of haemostatic function, particularly the
Prothrombin time (expressed as the INR)
Activated partial thromboplastin time (APTT)
• Blood grouping and cross-matching
It is essential to look for anaemia. It is an almost inevitable result of repeated bleeding and worsened by any further bleeding as a result of surgery. Anaemia increases the risks of general anaesthesia and should be treated before any surgery. Anaemia is also an essential feature of some haemorrhagic diseases, particularly acute leukaemia.
Blood grouping is required as transfusions may be needed before operation to improve haemostasis or afterwards, if blood loss is severe.
Purpura is typically the result of platelet disorders (Box 23.3) and relatively rarely caused by vascular defects. The bleeding time is prolonged but clotting functions are normal. An exception is von Willebrand’s disease, where there is an associated deficiency of a clotting factor.
• Idiopathic thrombocytopenic purpura
• Connective-tissue diseases (especially SLE)
• Acute leukaemias
• HIV infection
• Von Willebrand’s disease
• Corticosteroid treatment
• Ehlers–Danlos syndrome
• Hereditary haemorrhagic telangiectasia
Purpura (bleeding into the skin or mucous membranes, causing petechiae or ecchymoses or ‘spontaneous bruising’) also causes prolonged bleeding after injury or surgery. Unlike haemophilia, haemorrhage immediately follows the trauma but, usually, bleeding in purpura ultimately stops spontaneously as a result of normal coagulation.
Many women will say that they bruise easily, but such bruises are usually only a few millimetres across. The most informative test of platelet function is the bleeding time, supplemented as necessary by tests of platelet aggregations and adhesion. Deficiency of platelets (fewer than 100 000/mm 3) is termed thrombocytopenia, but spontaneous bleeding is uncommon until the count falls below 50 000/mm 3.
A typical site of oral purpura is the palate where the posterior border of a denture presses into the mucosa. Excessive gingival bleeding or blood blisters are other signs (Fig. 23.1).
Idiopathic thrombocytopenic purpura
The immediate cause is IgG autoantibodies which bind to platelets. The number of platelets in the peripheral blood is greatly reduced.
The disease may affect children or young adult women and the first sign may be profuse gingival bleeding or post-extraction haemorrhage. More often there is spontaneous bleeding into the skin.
Thrombocytopenic purpura frequently responds, at least in the short term, to corticosteroids which can be used for urgently needed surgery. Long-term use of corticosteroids is associated with their usual hazards. Some cases resolve spontaneously, but persistent cases may respond to splenectomy. However, 10–20% of cases are unresponsive to any form of treatment and, now that haemophilia is a manageable disease, such cases have become one of the most troublesome of the haemorrhagic diseases. For operative treatment, transfusions of platelet concentrates can be given, but immunosuppressive drugs may also have to be given to prevent platelet destruction by antibodies. As with other platelet disorders, aspirin and other anti-inflammatory analgesics should be avoided.
Autoimmune thrombocytopenia can complicate HIV infection and can be an early sign. Purpuric patches in the mouth, particularly in a young male, should suggest this possibility and also need to be distinguished from oral Kaposi’s sarcoma by tests of haemostasis and, if necessary, biopsy.
Many drugs, particularly aspirin, interfere with platelet function (Box 23.4). Others act as haptens and cause immune destruction of platelets or suppress marrow function causing pancytopenia (aplastic anaemia) of which purpura is typically an early sign. The most frequent cause of aplastic anaemia in Britain has been phenylbutazone.
• Thiazide diuretics
• Quinine and quinidine
Other drugs affecting thrombus formation include the anti-platelet drugs, such as clopidogrel, and glycoprotein inhibitors. These drugs may affect the activated partial prothrombin time and may complicate major surgical procedures.
Fibrinolytic drugs, such as streptokinase, used in the acute treatment of myocardial infarction are potential causes of bleeding tendencies so that dental surgery is possibly hazardous.
Tropical infections are increasingly brought into Britain on aircraft. Fortunately, the viral haemorrhagic fevers have not been brought here. They include Ebola, Lassa fever, Congo Crimea haemorrhagic fever – there was an epidemic of the last recently in Afghanistan.
Bleeding from every orifice is the main feature of these diseases and probably first starts from the gingival margins. Platelet dysfunction is the main cause and the mortality is high.
Scurvy is the only cause of vitamin deficiency-related bleeding. It is now of little more than historical interest. The defect is in the impaired connective tissue support for blood vessels together with a platelet disorder due to vitamin C deficiency.
Gingival bleeding is typically the first sign. The gingivae become engorged and swollen and, as mentioned earlier, the disease was so severe among the Crusaders that the Christian knights had to have their grossly swollen gingivae cut back to enable them to eat.