Idiopathic scoliosis is a common deformity of the spinal column, with orthomorphia surgery being its essential treatment. The preparation of graft bed (including decortication and V-osteotomy of small articular process) and the thoracoplasty require that a great amount of cancellous bone tissues be bitten away and the vertebral lamina surface be decorticated, causing heavy bleeding. In order to avoid the need of transfusion of a great amount of allogeneic blood and to minimize transfusion complications like allergic reactions, the spread of hepatitis and AIDS, immune suppression and complications associated with heavy transfusion[3-4], our department carried out, based on intraoperative controlled hypotension performed in all the patients both in the experimental group and the control group, autologous blood collection on the patients in the experimental group, including preoperative autologous blood deposit and intraopertive autologous blood salvage.
Significance of controlled hypotension
Scoliosis orthomorphia surgery is associated with heavy blood loss, ranging from 800 mL to 4 100 mL as reported by literature[5-6]; by contrast, results of this study showed the blood loss in the control group was 400-1 000 (867±161) mL and that in the experimental group was 350-1 400 (842±376) mL. As can be seen, controlled hypotension has the potential to reduce bleeding and provide a clearer surgical field, quite beneficial for the performance of surgical procedures. Nevertheless, the application of controlled hypotension presents certain risk to vital organs. It can lead to unexplained reduced blood capacity and vasoconstriction in the course of surgery, anemia, hidden coronary artery diseases, or sudden hemorrhage and tension pneumothorax which make patients susceptible to myocardial ischemia or cardiac arrest. Furthermore, controlled hypotension may also lead to insufficient local blood supply to the optic nerves, greatly increasing the possibility of unilateral or complete visual impairment[7-8]. Therefore, in the process of controlled hypotension, when blood oozing in the surgical field has been obviously reduced, it is not proper to further lower the blood pressure for a “bloodless surgical field”, otherwise, blood perfusion of the vital organs will become insufficient. Study of Shear et al[9] have showed that a blood pressure level lower than 55-65 mm Hg after controlled hypotension would affect blood perfusion of the brain and cause corresponding complications.
Application of autologous blood transfusion
Transfusion of preoperative deposited blood is limited for patients who will undergo selected surgery, including:
①patients who have good preoperative general conditions not requiring emergent operation; ②patients whose intraoperative blood loss and postoperative blood transfusion needs are predictable; ③patients whose blood type is rare; ④patients with a past history of adverse reactions associated with allogeneic blood transfusion; ⑤patients who refuse allogeneic blood transfusion because of religious belief; ⑥in areas with allogeneic blood shortage. According to American Association of Blood Bank (AABB), the pre-collection concentration of hemoglobin should be higher than 110 g/L and that of hemocrit should be higher than 0.33. Blood collection volume per session shall not exceed (450±45) mL, or 12% of the circulating blood volume; for patients whose weight is less than 50 kg, the blood collection volume should be less than 8 mL per kg body weight. Blood collection should be started 1 week before surgery, with an inter-session interval not less than 3 days, and the time of the last collection session should precede the surgery at least 72 hours. The patients undergoing preoperative autologous blood deposit require supplementation of iron, an essential element for production of red blood cells. As routine, patients were given erythropoietin and oral ferrous sulfate tablets. Blood collection went smooth in all the patients without any adverse reactions. Current technology only allows the autologous blood to be preserved for 3 weeks, and in addition patients are prone to experience decline of preoperative hemoglobin and hematocrit after blood collection, therefore, it is impossible to collect a great volume of autologous blood. In this sense, autologous blood transfusion cannot completely replace the extensive clinical application of allogeneic blood transfusion.
The intraoperative autologous blood salvage procedures involved the use of a blood recovering system to suction the oozing blood from the wound into a blood reservoir with heparin added during blood suctioning for anticoagulation purpose, the processing of the recovered blood by centrifugation and washing, and then the reinfusion of the salvaged red blood cells into the patients. As the recovery rate of blood from surgical field was 60%-80% and the recovery rate of red blood cells from the blood processing procedure was 60%-70%, intra-operative autologous blood reinfusion was not necessary for patients in whom the blood loss volume was less than 500 mL. In addition, because the washing process removes free hemoglobin, blood potassium, fibrin degradation products, platelet activation and degradation products, complement activation products, micro-thrombus, and cell and tissue fragments, transfusion of washed red blood cells alone may lead to coagulation disorders. Tawes et al[10] believed that platelets and clotting factors in the washed blood are markedly decreased, thus re-infusing plenty autologous blood is likely to dilute the blood and cause clotting disorders, consequently leading to bleeding tendency. Li et al[11] suggested that the appropriate autologous blood transfusion volume should be within 3 000 mL, and if the volume exceeds 4 000 mL, infusion of fresh frozen plasma is warranted. Autologous blood reinfusion has been increasingly used in clinics. There have been studies[12-14] demonstrated that autologous blood reinfusion not only raised postoperative hemoglobin level, reduces occurrence of SIRs and infection, but also increases serum CK-MB level, playing a certain role in myocardial cell repairing. As regards the cost of blood transfusion, transfusion in the control group cost averagely 3 450 Chinese Yuan (1 650- 6 000 Chinese Yuan, a standard cost in Chongqing, China), while the transfusion cost in the experimental group averaged at 2 250 Chinese Yuan (160 -5 290 Chinese Yuan) which included the preoperative autologous blood deposit cost 160 Chinese Yuan, the intra-operative blood salvage cost 1 000 Chinese Yuan and the allogeneic blood transfusion cost (if any). The transfusion costs between the two groups were significantly different, indicating autologous blood reinfusion can promise a great relief of financial burden.
Therefore, it is concluded that in patients who undergo idiopathic scoliosis orthomorphia surgery, controlled hypotension combined with autotransfusion not only promises milder intraoperative bleeding, less allogeneic blood transfusion, minimized transfusion-related complications and absence of blood-borne diseases, but also avoids wasting the autologous blood, which is especially meaningful for patients with RH negative blood type, reducing financial burden to patients. Controlled hypotension combined with autotransfusion is of high value in idiopathic scoliosis orthomorphia.
