Introduction

Epidural haematoma is a complication of spinal surgery, with an incidence rate of approximately 0.1–3% [1,2,3,4]. Most epidural haematoma are asymptomatic and require no treatment [5,6,7]. However, on rare occasions, the conditions of epidural haematoma could become clinically evident and require immediate operation. Pain around the wound and/or the innervated area is the predominant initial symptom. The haematoma could cause compression of the spinal cord or nerve roots, leading to neurological consequences, such as urinary and fecal incontinency, motor and sensory loss [8]. We define such conditions as symptomatic spinal epidural haematoma (SSEH); and if not treated timely, irreversible neurological sequelea may occur.

Because of the rarity of the SSEH, are were only limited reports investigating the risk factors of the development of SSEH after spinal surgery [1, 4, 7, 9, 10]. The risk factors include: advanced age (> 60 years old), use of pre-operative non-steroidal anti-inflammatories, high alcohol consumption (> 10 units/week), history of spinal surgery, pre-operative coagulation disorder, Rh-positive blood type, insertion of drain, multi-segmental operation, intra-operative hemoglobin <100 g/L, blood loss >1 L, and an international normalized ratio > 2.0 within the first 48 hours post-surgery. Most of these factors are uncontrollable. In this study, we carried out a detailed review of 11 cases that developed post-operative SSEH, aiming to explore if any other controllable clinical parameters are associated with SSEH; practical measures for the prevention of SSEH were also discussed.

Patients and methods

We retrospectively reviewed 4,457 cases that underwent spinal surgery in two medical centres between November 2009 and November 2012. Among the 4,457 cases, 11 developed post-operative SSEH. Demographic and clinical information was collected, including age, gender, medical history, coagulation function, blood type, surgical site, number of segments operated, intra-operative blood loss, peri-operative medication, drainage use, onset time and symptoms of SSEH, imaging features, SSEH symptom duration before haematoma evacuation, findings during re-operation, management and recovery results. Neurological state was assessed by using the American Spinal Injury Association (ASIA) grading system at the following time points: before and immediately after initial operation, before and two weeks after haematoma evacuation, the last follow-up.

The 11 SSEH cases included six male and five female patients. The age was from 21 to 82 years old (Table 1). The mean follow-time was 9.2 months (ranging from 3 to 16 months) (Table 2). All 11 cases had normal coagulation function, positive Rh blood type and had used post-operative drainage. The average blood loss was 972.7 ± 666.5 ml, and the mean number of segments operated was 2.18 ± 1.33. The first operation was performed for the following medical conditions: spine fracture for trauma (1 case), deformity (3 cases), degenerative diseases (6 cases), and angioma in spinal canal (1 case). All of the patients underwent posterior spinal surgery, except one case in which a combined procedure was performed. The sites of operation were: 18.2% cervical (2 cases), 9.1% cervicothoracic (1 case), 9.1% thoracic (1 case), 18.2% thoracolumbar (2 cases), 45.5% lumbar (5 cases). Tables 1 and 2 show the details of the cases.

Table 1 Patient profile
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Table 2 Symptoms, symptom duration before haematoma evacuation and neurologic function
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Statistical analysis of the associations between clinical parameters and recovery was performed using SPSS Statistics 17.0 (Chicago, IL, USA). Independent sample t-test was used to compare the SSEH symptom duration between the complete recovery group and incomplete recovery/no improvement group. Mann-Whitney U-test was used to compare the neurological state at different time points between the two groups.

Results

Symptoms of SSEH

Neurological impairment was observed in patients with SSEH. All but one patient had the impairment emerge in bilateral lower limbs. Urinary or fecal incontinence was reported in three patients (27.3%). New deficits or deterioration of neurological function were found in all 11 cases (100%). Pain around the wound area occurred in two cases (18.2%), and radiating pain occurred in one patient (9.1%).

Medical history and findings during haematoma evacuation

Case number 6 had small volume platelet with a history of chronic lymphocytic leukemia, indicating a higher chance of haemorrhage. Six cases were administered with low molecular weight heparin (LMWH) post-surgery, and two of them developed SSEH after removal of the drain tube (3–4 days after surgery), suggesting the occurrence of re-bleeding after the drain tube was removed.

There were nine cases with SSEH developed before the drain tube was removed (average 10.0 ± 8.3 h after surgery), and uncoagulated blood was found during the haematoma evacuation, indicating an inadequate drainage. During the second operation, uncoagulated blood spewed out in eight cases, indicating the high blood pressure in the haematoma.

MRI findings

MRI examinations were performed in seven cases before haematoma evacuation. The typical manifestations of the haematoma were: heterogeneous hyperintense/isointense signal in T2-weighted images (Figs. 1 and 3) or isointense/slightly hyperintense signal in T1-weighted images (Figs. 2 and 3). The dural sac and spinal cord were compressed.

Fig. 1
figure 1

A 43-year-old male, who suffered from L4/5 spondylolisthesis, was administered with low molecular weight heparin (LMWH) post-operatively for thromboprophylaxis. He complained of progressive motor and sensory dysfunction in bilateral lower limbs on the third day after the drain tube was removed (case number 1). T2-weighted image showed lumbar epidural haematoma which had heterogeneous isointense signal. The superficial area in the wound was hyperintense. The dural sac was compressed

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Fig. 2
figure 2

A 82-year-old male who had small volume platelets with a history of chronic lymphocytic leukemia. He complained of progressive motor and sensory deterioration in his lower limb 5 hours after resection of the epidural angioma in the cervicothoracic spinal canal (case number 6). The T1-weighted image showed epidural haematoma, which had isointense or slightly hyperintense signal. The spinal cord was compressed

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Fig. 3
figure 3

A 62-year-old female who had lumbar spinal stenosis. She complained of progressive motor and sensory dysfunction in her lower limb 24 hours after the operation on L2-S1 laminectomy and fusion. MRI showed a huge haematoma and a compression on the dural sac

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Treatment and outcome

In this cohort, SSHE was treated either conservatively (by suction drainage or sucking with a syringe) or by a second operation. Two cases, case numbers 2 and 3, were treated conservatively. The second operation was performed on the other nine cases to evacuate haematoma. Closed drainage container without vacuum was used postoperatively in case number 2, and the patient developed SSEH three hours after operation. His symptoms vanished after continuous suction drainage was used instead. Continuous suction drainage was used in case number 3, and the patient developed SSEH four hours after surgery. Syringe was used to aspirate 30 mL of uncoagulated blood, and the symptoms disappeared afterwards.

We defined a complete recovery as neurological state recovered to the state immediately after the first operation. In this cohort, six patients recovered completely, three incompletely, and two had no improvement (the neurological state at the final follow-up visit was the same as the state before haematoma evacuation) (Table 3). In the group of complete recovery, the mean time of symptom duration was 5.58 ± 10.02 hours before the haematoma evacuation, and the ASIA grades of the patients were D (n = 4) and C (n = 2). In the groups of incomplete recovery and no improvement, the mean time of symptom duration before haematoma evacuation was 61.50 ± 126.65 hours. Before haematoma evacuation, the ASIA grades were C (n = 4) and B (n = 1). We compared the symptom duration and ASIA grading of different time points between the complete and incomplete/no improvement groups. Statistical analyses showed significant differences of ASIA grading before haematoma evacuation, suggesting mild nerve injury at the initial state is more likely to have complete recovery (Table 3).

Table 3 The relationships of symptom duration and ASIA grading between complete and incomplete/no improvement groups
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Discussion

It was reported that the incident rate of spinal epidural haematoma after spinal surgery was 0.1–3% [1,2,3,4]. The incident rate of the present cohort was 0.25%, a relatively lower rate than reported. Although the occurrence of SSEH is rare, if patients are not treated timely and properly, the neurological sequella could be devastating. Therefore, it is important to have preventive measures, proper diagnosis and treatments as early as possible.

Causes of SSHE development

Clotting disorder

Case number 6 had small volume platelets and a history of chronic lymphocytic leukemia, indicating a higher risk of clotting dysfunction. Others had no predisposing factors for blood clotting disorder.

Six patients were administered with LMWH post-operatively for thromboprophylaxis, and two of them developed SSEH after the drain was removed (3–4 days after initial operation). The development of haematoma may be attributed to the use of LMWH. Although, it was reported that the well-controlled use of anticoagulant and drainage were not associated with the increased risk of post-operative spinal epidural haematoma, the accurate control of anticoagulant effect may be difficult to achieve due to individual differences that may affect bioavailability and pharmacodynamics of drugs [1, 9, 11]. In addition, patients might have lower concentration of coagulation factors and platelets due to massive liquid infusion/transfusion during operation. The change in internal body environment (e.g. lowering of body temperature and acidosis) will also affect the normal coagulation process.

There is no clear consensus on thromboprophylaxis after spinal surgery [12]. Guidelines published by the Seventh American College of Chest Physicians (ACCP) Conference recommended that only patients with risk factors need thromboprophylaxis management. The risk factors include: age ≥ 60 years, BMI ≥30 kg/m2, genetic thrombophilia, history of VTE, anterior or combined procedure, thoracic/lumbar/sacral procedure. Among the six patients who received LMWH in this study, only two patients had the above risk factors: one was ≥60 years old and the other one underwent a combined anterior and posterior procedure. The reduced use of LMWH may help to lower the likelihood of SSEH development. It is worth noting that mechanical prophylaxis or early ambulation were proposed for thromboprophylaxis management [13, 14], which could also be taken into consideration. A report showed that the use of mechanical prophylaxis, pneumatic compression stocking, could reduce the incidence of deep venous thrombosis and pulmonary embolism in spinal surgery [15]. Indeed the National Institute for Care and Excellence (NICE) guideline recommends mechanical prophylaxis for patients with spinal injury. The guidance outlines certain risk factors of bleeding, and if such criteria are met, LMWH should be used.

Fluctuations of blood pressure

Coughing, sneezing or experience of severe pain during wake-up from general anaesthesia may result in fluctuations of blood pressure, causing re-bleeding [16]. Patients with high blood pressure, atherosclerosis, diabetes mellitus or hypoproteinemia are more likely to have re-bleeding after surgery. Extra caution is required when moving, turning over, or extubating such patients.

Incomplete hemostasis during initial surgery

Case number 6 was found to have active bleeding at the muscular layer during haematoma evacuation. During the initial surgery, the injured vessels had stopped bleeding temporarily with compression by retractor and gauze. This patient has small volume platelet, and re-bleeding was likely to occur. It is also possible that some other sites of bleeding were not noticed before suturing, or vessels were damaged during suturing [17]. It is therefore important to ensure no active bleeding before closure.

Inadequate drainage

Nine cases in this study developed SSEH before the drainage tube was removed. And seven of them were found to have haematoma of uncoagulated blood. Obstruction of drainage tubes should be the primary reason for the SSEH. When internal bleeding occurs, blood clots formed could block the drainage tube. Some surgeons are fond of placing a block of gelatin sponge on the dural and placing the tube on the sponge. This practice may lead to an inadequate drainage, as the debris from the gelatin sponge may block the tube. In addition, folding or compression of the tube, for example, via clots formed around the tube, could also lead to inadequate drainage. To mitigate the risk, some surgeons suggested placing two tubes on both sides of the wound, so that there is at least one functional drainage tube when the other one is compressed or obstructed.

The material and internal diameter of the tube are important factors which influence the effect of drainage. The tube that has a large internal diameter and is not easily compressed is recommended. If the tube was mostly obstructed by clot, a drainage tube with a coating of anticoagulants may help.

The outflow suction of the drains is created by connecting the tube to a vacuum device, like a deformable grenade-shaped container. It is important to maintain the negative pressure inside the device; otherwise, a positive pressure could be formed along with the continuous internal bleeding.

Although the use of drains is controversial, with the potential for infection [18, 19], no obvious evidence was found to support such association in the present study. Indeed a prospective randomization trial showed no significant difference in the rates of infection in patients with or without a drain placed after complicated spinal surgery [20]. It is clear, however, that protocols should be optimized to minimize chance of wound contamination, e.g. limiting duration of drains [19].

Diagnosis and treatment of SSEH

It is important to diagnose SSEH in an early stage. SSEH should be considered if the following happened [16, 21, 22]: severe pain of the wound with blood oozing or swelling, unexplainable sensor and/or motor dysfunction after open spinal operation (e.g. deteriorating or new neurologic signs or symptoms) or pain in the innervated area, progressive deterioration of neurologic dysfunction.

To confirm the diagnosis of SSEH, the following examinations could be performed [21, 23,24,25,26]: re-examination of haematology, blood chemistry, and coagulation tests; MRI scan to determine the location and volume of the haematoma, and whether the dural sac or spinal cords were compressed. To avoid prolonged compression of the spinal cord, confirmation with MRI scan should be performed as soon as possible if the likelihood of SSEH is high [6, 26]. Some studies, however, suggested that the use of post-operative MRI have a high false-positive rate for diagnosis of SSEH [4, 27]. Therefore, in addition to imaging, it is important for the surgeons to carefully monitor the physical signs and patients’ symptoms.

Once the SSEH is confirmed, check if there is any blockage in the drainage tube; take out some stitches to allow the release of pressure from haematoma ooze; patients with no improvement after the above measures, or patients with severe symptoms or progressive deterioration will need re-operation to clear the haematoma and stop the internal bleeding.

Nursing personnel also plays an important role in early detection of SSEH. The nurse’s prompt recognition and reporting of neurological symptoms of SSEH has been shown to help achieve a positive clinical outcome [28]. It is therefore important to have post-operative nursing personnel aware of the risk factors, clinical presentation and the need for rapid treatment.

Factors that influence the neurologic recovery

We found larger differences in symptom duration before haematoma evacuation between complete and incomplete/no improvement recovery groups. Although the differences were not statistically significant, the finding suggested that the earlier the haematoma was evacuated, the better neuro-function recovery was obtained. Patients with lower grade of damaged neuro-function before haematoma evacuation recovered better after treatment (P<0.05), suggesting it is the major factor associated with prognosis, while the duration of haematoma compression is relatively less important. This is in accordance with other reports that recovery of neurologic injury is related to the severity of the initial neurologic injury [29]. As such, it was once a controversy as to whether emergency operation was needed for traumatic spinal cord injury with vertebral fracture. However, nowadays early decompression is most recommended [30,31,32]. It is believed that patients with both shorter symptom duration and less severity of neurologic injury would recover better [4, 8], since continuous bleeding in the wound occurring after the onset of SSEH may lead to increasing pressure and further neurologic injury.

The present study is limited by its retrospective nature and small case number. Since development of SSEH after spinal surgery is very rare and catastrophic, it may not be possible to conduct a formal prospective case-control clinical study. We reviewed a relatively large data set from two medical centres over several years, but we could not find a large cohort size for evaluation, as the occurrence of SSEH is very rare.

In conclusion, post-operative bleeding in the wound and inadequate drainage are the key factors related to the formation of spinal epidural haematoma. It is important to pay attention to every step of the operation to prevent occurrence of SSEH. Since the sequelae of SSEH is devastating, it should be diagnosed as early as possible, and confirmatory tests should be done when progressive neurological deterioration occurs in the innervated area. Severity of the neurologic state before haematoma evacuation is the major factor associated with recovery. Therefore, once SSEH is diagnosed, the nerve compression should be relieved at once to prevent progression of neurologic injury.