Factors influencing intraoperative blood loss in orthognathic surgery

Abstract

This retrospective study aimed to identify factors of importance for intraoperative blood loss relative to total blood volume in patients undergoing orthognathic surgery. The study included 356 patients treated consecutively at a Danish university hospital between 1 January 2010 and 31 December 2012. Inclusion criteria were (1) patient age ≥18 years and (2) patient undergoing a three-piece Le Fort I osteotomy, a bilateral sagittal split osteotomy, or a combination of the two. The patient-specific relative blood loss was calculated as a percentage by dividing the intraoperative blood loss by the estimated preoperative total blood volume, and then correlated with body mass index (BMI), age, sex, operating time, and treatment modality in a multivariate stepwise regression analysis. Operating time ( P < 0.001), BMI ( P < 0.001), and treatment modality ( P < 0.001) had a significant impact on relative blood loss; no significant effect of age or sex was observed. The coefficient of determination of relative blood loss was R 2 = 0.34. In conclusion, this study introduces relative blood loss as a patient-specific measure of intraoperative blood loss. Average relative blood loss in this patient sample was 6.5%. Extensive surgery, a prolonged operating time, and reduced BMI significantly increase the intraoperative relative blood loss in patients undergoing orthognathic surgery.

Orthognathic surgery is generally considered a safe and routine surgical procedure with few intraoperative complications. Although rare, severe and fatal blood loss in relation to orthognathic surgery has been reported, often in relation to iatrogenic injury of major vessels in the surgical field. A systematic review suggests that mean blood loss during orthognathic surgery is approximately 400 ml. Factors known to influence intraoperative blood loss are the operating time, sex, weight, the surgical procedure, type of anesthesia, and surgeon’s experience. Studies have focused on the continuous measurement of haemoglobin and thromboelastography as predictors of intraoperative blood loss.

Despite extensive research in the field, studies have so far investigated single factors of importance for intraoperative blood loss. Increasing knowledge of the various interplays between these factors may provide a broader understanding of intraoperative blood loss. This would improve preoperative patient information and assist staff in the planning and performance of surgical procedures.

Previous research has investigated absolute blood loss, rather than blood loss in relation to the blood volume of the individual patient. The present study introduces the patient-specific measure of relative blood loss, which is calculated as a percentage by dividing the intraoperative blood loss by the estimated preoperative total blood volume. This patient-specific measure may more accurately describe the acceptable level of blood loss. Furthermore, measurement of the relative blood loss is easy and requires few resources.

The existing literature does not include a comprehensive multivariate analysis of the predictive factors influencing intraoperative blood loss. The aim of the present study was to identify factors of importance for intraoperative relative blood loss in a group of patients undergoing orthognathic surgery.

Materials and methods

This retrospective study included a total of 356 patients treated consecutively between 1 January 2010 and 31 December 2012 at a university hospital in Denmark. Inclusion criteria were the following: (1) patient age ≥18 years; (2) a surgical procedure involving a three-piece Le Fort I osteotomy, or a bilateral sagittal split osteotomy (BSSO), or a combination of the two. The patients were divided into three groups according to the surgical procedure performed for further analysis. No patients were treated with anticoagulants as home medication before surgery.

Preoperative procedures

Patients were diagnosed with jaw discrepancies necessitating surgical correction of the mandible, the maxilla, or both. All patients had an individual treatment plan drawn up in advance in cooperation with an orthodontist and a surgeon. Full fixed appliances were applied to align the arches and create sufficient space for sectioning of the maxilla. The day before surgery, surgical splints were controlled and a full preoperative evaluation was made by an anaesthesiologist with emphasis on general health (American Society of Anesthesiologists (ASA) classification). Two hours before surgery, the patients received 3500 IU of low-molecular-weight heparin, tinzaparin, as a prophylactic anticoagulant (Innohep; Leo Pharma, Ballerup, Denmark) and 1 g of paracetamol (Pamol; Takeda Pharma, Hobro, Denmark), in accordance with the general recommendations of the department of clinical biochemistry.

Anaesthesia

Hypotensive general anaesthesia was administered intravenously by a combination of remifentanil (Ultiva; GlaxoSmithKline Pharma, London, UK) and propofol (Diprivan; AstraZeneca, London, UK), with the addition of sevoflurane inhalation (Baxter, Deerfield, Illinois, USA) on indication. Nasotracheal intubation was used for all patients, and surgical gauze was packed around the tube in the oropharynx. After induction of anaesthesia, local anaesthesia (lidocaine–adrenalin 1%; AstraZeneca, London, UK) was administered in the surgical field; 10 ml was used in single jaw procedures and 20 ml in double jaw procedures. Preoperatively, all patients received intravenous administration of 40 mg methylprednisolone sodium succinate (SoluMedrol; Pfizer, New York City, New York, USA), 1000 mg metronidazole (Actavis, Parsippany-Troy Hills, New Jersey, USA), and 1500 mg cefuroxime (Actavis). If surgery exceeded 3 h, an additional dose of cefuroxime (1500 mg) was administered as routine. Patients allergic to penicillin were given 600 mg clindamycin (Stragen Pharma, Geneva, Switzerland).

Surgical procedures

The BSSO procedure for the mandible was performed according to the Obwegeser technique, with the Hunsuck and Epker modifications. For the maxilla, a standardized three-piece Le Fort I osteotomy was performed according to the technique of Bell et al. The major palatine arteries were routinely preserved. In the case of haemorrhage, identifiable vessel ligation or cauterization was performed. Surgical splints were used in all patients and the final splint was rigidly fixed. In cases of bimaxillary surgery, the Arnett principles were applied, and wires for skeletal anchorage were inserted in the anterior nasal spine and the mandibular symphysis.

Surgery was performed by senior staff assisted by oral and maxillofacial surgery residents. The total operating time was recorded and intraoperative blood loss was measured by subtracting saline used for rinsing from the total volume collected in the suction device.

Formulae used

Patient-specific estimated blood volume (EBV) was calculated as follows:

<SPAN role=presentation tabIndex=0 id=MathJax-Element-1-Frame class=MathJax style="POSITION: relative" data-mathml='EBV(ml)=Weight(kg)×Average blood volume(ml/kg)’>EBV(ml)=Weight(kg)×Average blood volume(ml/kg)EBV(ml)=Weight(kg)×Average blood volume(ml/kg)
EBV ( ml ) = Weight ( kg ) × Average blood volume ( ml/kg )

The reference value for average blood volume was 75 ml/kg for men and 65 ml/kg for women.

Patient-specific relative blood loss (RBL %) was calculated as follows:

<SPAN role=presentation tabIndex=0 id=MathJax-Element-2-Frame class=MathJax style="POSITION: relative" data-mathml='RBL(%)=intraoperative blood loss(ml)estimated blood volume(ml)×100′>RBL(%)=intraoperative blood loss(ml)estimated blood volume(ml)×100RBL(%)=intraoperative blood loss(ml)estimated blood volume(ml)×100
RBL ( % ) = intraoperative blood loss ( ml ) estimated blood volume ( ml ) × 100
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Dec 15, 2017 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Factors influencing intraoperative blood loss in orthognathic surgery
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