Management of Haemostasis in Spine Surgery

Blood loss in spine surgery is an underestimated problem. It is an important concern in the performance of spinal surgery, not only in major deformity surgery but also in less extensive fusion procedures. The degree of blood loss varies enormously and is related to the complexity of the procedure, duration of surgery and co-morbid conditions. Extensive blood loss leads to greater transfusion needs and serious consequences for the patient’s haemodynamic equilibrium, and can cause devastating neurological damage because of the vicinity of major and highly fragile neurological structures. It is important to reduce bleeding in spine surgery in terms of the surgeon as well as the patient: reduced bleeding allows a better view of the surgical field, thereby increasing the surgeon’s control and shortening surgery time, which further decreases bleeding. This article will summarise the main haemodynamic and pharmacological techniques used to reduce bleeding in spine surgery.

Methods to Reduce Bleeding in Spine Surgery
Blood-sparing techniques can be divided into two groups: they aim at either decreasing the bleeding itself or decreasing the need for homologous transfusion. Several blood-sparing techniques are available to surgeons who treat complex spinal disorders; these techniques include haemodynamic methods and pro-haemostatic methods used either systemically or locally. Inhibiting fibrinolysis with antifibrinolytics offers evidence of bleeding prevention. Topical agents combining collagen, thrombin and fibrin have successfully demonstrated bleeding control. This article reviews the clinical effectiveness of several treatments of surgical wound management in spinal surgery.

Controlled Hypotensive Anaesthesia
Controlled hypotension has been shown to reduce blood loss and improve operating conditions during orthopaedic surgery. It is frequently advocated for spinal surgery, alone or in combination with haemodilution, and promising results have been published since the early 1970s.^1–8

The mechanism underlying decreased blood loss through controlled hypotension is still unclear. The effect on blood extravasation depends not only on local blood flow, but also on the relationship between blood pressure and vascular resistance. Lee et al. measured blood flow in paraspinal muscles during spine surgery under administration of two hypotensive drugs. Although there were similar degrees of hypotension and blood loss with both drugs, they found different values for local blood flow. ⁹ The effects on blood flow in the epidural venous plexuses¹⁰ as well as on blood pressure itself ¹¹ have been hypothesised to be an important variable. In spinal fusion, bleeding is mainly associated with bone decortication. Some authors report that blood loss is not influenced by a decrease in arterial pressure, but essentially by venous pressure.¹² Brodsky et al. found that blood flow was more strongly correlated to surgery duration than to blood pressure.¹² Kakiushi observed a correlation of intraoperative blood pressure to intraosseous but not arterial pressure in thoracic vertebral bodies.¹³

It has been shown that hypotensive anaesthesia does not decrease transfusion requirements compared with normotensive anaesthesia in scoliosis surgery.¹⁴ However, Malcolm-Smith and McMaster showed a 58% reduction in total blood loss for patients with idiopathic scoliosis. ¹⁵ Although hypotensive anaesthesia may lead to complications¹⁶ and is contraindicated in some patients with hypertension or ischaemic disorders, the safety risk in spinal surgery is difficult to quantify. The risk of neurological damage in addition to direct injury may be worsened by ischaemic complications.^17,18 The effect on spinal cord function during scoliosis surgery has also been questioned.¹ However, although electrophysiological monitoring may detect temporary alterations, hypotensive anaesthesia does not appear to increase the risk of neurological damage.¹⁹ Hypotensive anaesthesia can be safely combined with acute normovolaemic haemodilution. ²⁰ Acute normovolaemic haemodilution is widely used in spine surgery with favourable results in both fusion surgery^20–22 and scoliosis surgery.^23–25 Combined application of acute normovolaemic haemodilution and pre-operative autologous blood transfusion in spinal fusion patients eliminated the use of homologous blood transfusion.²⁶

Many drugs have been used over time: anaesthetic agents,²⁷ calcium (Ca) channel blockers,²⁸ beta blockers,²⁹ nitroglycerin, nitroprusside ^30,31 and opioids. ³² As all of these drugs are administered intravenously and are associated with different side effects, Namazi proposed using a transdermal nitroglycerin preparation for the reduction of peri-operative bleeding. ³³