Thromboprophylaxis In Elective Neurosurgery

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The high incidence ofVTE in neurosurgery patients makes the use of thromboprophylaxis mandatory.2,18 Even a small intracranial bleed might have devastating consequences and therefore a rational throm-boprophylactic strategy incorporating both mechanical and pharmacological measures is essential. These measures are often simple such as ensuring that the patient is well hydrated and mobile and that unnecessary arterial and venous cannulae are avoided. The use of mechanical measures, such as, intermittent pneumatic compression (IPC) and graduated compression stockings (CS) help reduce throm-botic risk by minimising reducing venous stasis and dilation. In addition local fibrinolysis is stimulated with a reduction in plasminogen activator inhibitor and an increase in circulating endogenous tissue plasminogen activator. IPC appears to be highly effective at preventing DVT in neurosurgery patients with an average risk reduction of 68% compared with controls (Fig. 4). Although one study revealed

Fig. 4 Intermittent pneumatic compression is highly effective at preventing deep vein thrombosis in neurosurgical patients.

that CS alone was as effective as the CS and the IPC combination, concerns about the efficacy of CS alone have been raised. Two large prophylaxis studies have compared the use of CS alone, with a combination of CS and LMWH started within 24 hours postoperatively. With CS alone DVT rates were 26% and 33%, respectively, improving to 19% and 17% using combined prophylaxis. However, we must be cautious about preoperative or early postoperative LMWH prophylaxis in craniotomy patients, as intracranial haemorrhage rates in randomised trials were 2.1% for postoperative LMWH and 1.1% for mechanical prophylaxis or no prophylaxis. Most bleeds occurred within the first two days after surgery. Furthermore, in a meta-analysis examining VTE prevention in neurosurgery, all forms of bleeding were twice as common in those receiving LMWH postoperatively as opposed to mechanical measures (6.1% versus 3.0%; p = 0.02).

In summary, IPC with or without CS is currently recommended for VTE prevention in patients undergoing intracranial neurosurgery. In high-risk neurosurgery patients, a combination of mechanical prophylaxis and pharmacological prophylaxis may be considered. If used, LMWH or low dose UFH should be given postoperatively. The former is more convenient and has a lower incidence of side effects such as heparin induced thrombocytopenia. Individual circumstances and assurance of secure postoperative haemostasis will determine the timing of commencement of prophylaxis. If the patient is at a high bleeding risk, for instance, due to recent ingestion of anti-platelet drugs, pharmacological prophylaxis may be withheld and commenced later in the postoperative course. In patients weighing less than 90 kg, the dose of LMWH should not exceed 40 mg of enoxa-parin or dalteparin 5000 units, daily. On occasion, use of smaller doses or split dosing can diminish bleeding risk. Extended thromboprophylaxis should be considered in high-risk patients, including those with malignancy, thrombophilia, and prolonged immobility. The use of surveillance duplex ultrasonography may also enable early detection of a DVT. There is no role for anti-platelet agents, such as, aspirin in prophylaxis of venous thromboembolism.

Patients with acute spinal cord injury have high VTE rates, with symptomatic DVT and PE rates of 15% and 5%, respectively.2 PE remains the third most common cause of death in these patients.

Mechanical measures alone are insufficient, and pharmacological measures must be instituted. LMWH is more effective than low dose or adjusted dose UFH in this setting, but initiation must be delayed if there is evidence of perispinal haematoma. Patients with spinal cord injury remain at risk of thrombosis for at least three months, particularly if the injury is complete. Extended thromboprophylaxis would be indicated using LMWH or warfarin aiming for a target INR of 2.5.

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